Stability, Care and Handling of Microforms, Magnetic Media and Optical Disks

Article excerpt

PART 3. OPTICAL DISKS

MEDIA OVERVIEW

Optical storage technology uses lasers to record information by selectively altering the light reflectance characteristics of a given medium. The alteration may be accomplished in various ways: by forming microscopic pits or bubbles in the medium's surface (ablative recording), by fusing two metallic layers to create a reflective alloy (dual alloy recording), by altering an organic dye material (dye-based recording), by changing the direction of light reflected from a magnetizable surface (magneto-optical recording), by inducing crystalline-to-amorphous transitions (phase-change recording), or by other means. Regardless of method, a "playback" laser detects the alterations and decodes (reads) the recorded information. The playback laser typically operates at lower power or a different wavelength than the laser that is used for recording.

As their most attractive and important characteristic, optical storage media support very high areal recording densities. Manufacturers of magnetic storage devices and media have steadily increased their recording densities from 10,000 bits per square inch in the early 1960s to the more than 60 million bits per square inch supported by new products; optical storage media, by contrast, routinely record hundreds of millions of bits per square inch. They consequently offer much higher storage capacities than magnetic media of comparable size. For libraries and other information-intensive work environments, optical disks offer sufficient capacity to store huge quantities of character-coded text, computer data bases, graphic images, and audio signals, thereby permitting the implementation of large-scale electronic information systems. When automated jukebox retrieval units are utilized, optical disk installations can provide unattended access to hundreds of billions or even trillions of bytes of data.

Areal density aside, optical and magnetic media support similar applications; any computer, audio, or video information that can be recorded on magnetic tapes or magnetic disks can be stored on optical media, and vice versa. While all magnetic media support direct recording, however, optical disks are available in read/write and read-only varieties. Read/ write optical disks, as their name suggests, resemble their magnetic counterparts in supporting both recording and playback of machine-readable information. Read-only optical disks, in contrast, have no direct recording capabilities; they are limited to playback of prerecorded information generated by a mastering and replication process described below. Depending on the equipment configuration employed in a specific situation and the application in which they are used, optical disks may contain computer-generated data, video images, and/or audio signals. Depending on the disk format, the information itself may be encoded in either digital or analog form, the former being the most common. The following discussion surveys the most important types of optical disks, emphasizing physical and recording characteristics that can have an impact on media stability, care, and handling.

Read/Write Media

Read/write optical media, as noted above, support direct recording of machine-readable information. Such media are purchased blank, although they may be pregrooved or contain some prerecorded control signals. Like their magnetic counterparts, they can accept information from various sources. This report emphasizes optical disks, the most widely encountered read/write optical media and the only ones for which library applications have been reported. Optical cards and optical tapes, described briefly below, offer interesting capabilities that may eventually lead to library-related implementations, but installations to date have consisted mainly of field trials, demonstration projects, and highly customized systems.

Optical cards, also known as optical memory cards and optical digital data cards, were introduced in the early 1980s as compact, portable storage media for microcomputer configurations. The technology is discussed by Cory (1990), Drexler (1981, 1982, 1983), Hosaka (1988), Toyota et al. (1990), and Urrows and Urrows (1989). Optical cards are the size and thickness of a credit card (approximately 2.1 by 3.4 by 0.03 inches). They are coated on one side with a reflective strip of optical recording material. Their leading manufacturer is Drexler Technology Corporation, the developer of the LaserCard brand of optical memory cards and the Drexon optical recording material employed by such cards. Two Japanese companies, Canon Incorporated and Optical Memory Card Business Corporation, also manufacture optical memory cards under licenses obtained from Drexler Technology. Other Japanese manufacturers have experimented with alternative optical memory cards, but such products have not been commercialized. The ISO/IEC 11693 and ISO/IEC 11694 standards delineate the physical characteristics, optical properties, recording methods, and other attributes of optical memory cards.

Optical memory cards are available in read-only and read/write versions. The latter are more common; like certain optical disks described below, they are not erasable media. First-generation optical memory cards provided 2.86 megabytes of formatted capacity. Drexler Technology introduced a 4.2-megabyte LaserCard in 1993. While their manufacturers emphasize the advantages of portability and reliability, widespread adoption of optical memory cards has been impeded by the limited availability of reader/writer equipment for microcomputer installations. Until recently, such equipment could be purchased only in limited quantities, but it is now being manufactured by several Japanese companies. LaserCard Systems Corporation, a subsidiary of Drexler Technology, offers complete optical memory card systems, including reader/writers, software, and documentation. To date, the principal applications for optical memory cards have involved medical information. Examples are described in many publications, including Bouldin and Haddock (1990), Brown (1989), De Martino (1993), Demetriades and Gomez (1990), Guibert and Gamache (1993), Horie et al. (1992), Nishibori and Shiina (1990), Price-Francis (1993), Shoda et al. (1990), Siedband et al. (1990), and Uythof (1993). Optical memory cards have also been used for equipment maintenance records, cashless funds transfers, transaction processing, and as personal identification media in computer-controlled security and access systems.

As its name suggests, an optical tape is a ribbon of film coated with an optical recording material. Its mass storage potential has been discussed for many years in journal articles and conference papers. Examples include Arai et al. (1995), Dancygier (1987), Gopalaswamy et al, (1994), Lee et al. (1978), Narahara et al. (1993), Neubert et al. (1989), Schmitt and Lee (1979), and Strandjord et al. (1992). Currently, only one company, EMASS, sells an optical tape recording system. Originally developed by Creo Products, it stores one terabyte of information on a 12-inch reel of optical tape. The tape measures 35 millimeters wide by 880 meters (approximately 2,400 feet) long. It is described by Gelbart (1990) and Spencer (1988, 1990). Optical tapes in other formats have been demonstrated in prototype versions only.

Read/write optical disks, the focal point of this discussion, are available in write-once and rewritable varieties. Write-once optical disks are sometimes described as WORM media; the acronym variously stands for Write Once Read Many or Write Once Read Mostly. Such media are not erasable. Once information is recorded in a given area of a write-once optical disk, that area cannot be reused. With rewritable optical disks, in contrast, the contents of previously recorded media segments can be deleted or overwritten with new information. Like their magnetic counter-parts, rewritable optical disks are reusable.

Like magnetic tapes and diskettes, optical disks are removable storage media. With Compact Discs, video disks, and certain digital video disk (DVD) products as notable exceptions, optical disks are encapsulated in plastic cartridges that protect their information-bearing surfaces during loading, removal, or other media handling. Depending on the system, read/write optical disks may permit single-sided or double-sided recording. Double-sided media are the most common type, even though the majority of optical disk drives are single-sided devices that require a mounted cartridge to be removed and turned over to access information recorded on the other side.

Most read/write optical disks are designed to store digitally coded, computer-processible information. Write-once and rewritable optical disks are typically categorized by size, as determined by platter diameters. For computer applications, optical disks are available in sizes ranging from 3.5 inches (90 millimeters) to 14 inches (356 millimeters). Intermediate sizes are 12 inches (300 millimeters), 5.25 inches (130 millimeters), and 4.75 inches (120 millimeters). Fourteen-inch and 12-inch optical disks are considered large-format optical storage products. They are principally intended for mainframe and minicomputer installations with voluminous storage requirements. Storage capacities of the newest models range from 12 gigabytes to 25 gigabytes per optical disk cartridge. Earlier models, no longer being manufactured, stored two gigabytes to 10 gigabytes. Storage capacities of 5.25-inch optical disks have increased from 200 megabytes per cartridge in the mid-1980s to 2.6 gigabytes per cartridge for the newest products. A migration path, defined by the Optical Storage Technology Association, specifies a doubling of media capacities every two to three years. 5.25-inch optical disks with 5.2 gigabytes of storage capacity are expected by the end of this decade. Compact Disc-Recordable (CD-R) and Compact Disc-Rewritable (CD-RW) are read/write optical disk products in the Compact Disc product family. CD-R products are write-once media, while CD-RW media are erasable and reusable. Both measure 4.75 inches in diameter and can store 540 megabytes to 660 megabytes, depending on the type of medium selected. Unlike other read/write optical disks, CD-R and CD-RW media are not encapsulated in protective cartridges. The newest 3.5-inch optical disks can store 640 megabytes per cartridge. Older models stored as little as 128 megabytes. Regardless of capacity, 3.5-inch optical disks are available in rewritable versions only.

Read-Only Media

Read-only optical disks, as previously noted, contain prerecorded information. Intended for electronic publishing applications, such disks are produced by a mastering and replication process. Computer-generated information, video images, or audio signals to be recorded on read-only optical disks are organized, edited, and otherwise prepared for submission to a production facility, which produces a master disk from which individual copies are generated by injection molding or some other process. In most cases, one or more test media are produced initially for customer evaluation. If the test media are judged to be satisfactory, a multi-copy production run is initiated. The copies, which are purchased by or distributed to libraries and other organizations, have no recordable properties. They are read by playback devices that have no recording mechanisms.

Video disks, Compact Discs, and DVD media are examples of read-only optical disks. Video disks store analog television images, accompanied by analog stereo signals. Introduced in 1978, read-only video disks were the first optical storage products to be successfully commercialized. They are available in 12-inch and eight-inch sizes. The 12-inch version can store 54,000 still-video images or 60 minutes of full-motion television with stereo audio on each of two sides. Eight-inch video disks can store 24,000 still-video images or 13.5 minutes of full-motion television and stereo audio per side. During the 1980s, several companies developed special production techniques that could store digitally coded, computer-processible data on read-only video disks. While several library-oriented information products were offered on such digital video disks, they have since been supplanted by CD-ROM systems.

Compact Disc (CD) is the collective designation for a group of interrelated optical storage formats and products that are based on technology developed during the 1970s and 1980s by Sony and Philips. Introduced in the 1980s, the most widely encountered type of Compact Disc is a rigid plastic platter that measures 4.75 inches in diameter. Its developmental history and technical characteristics are discussed in many publications, including Carasso et al. (1982) and Pohlmann (1988, 1989). A 3.5-inch (90-millimeter) version was introduced in 1987, but it is rarely encountered in library applications. Size aside, the various Compact Disc formats are categorized by the type of information they contain. For library applications, the two most important examples are Compact Disc-Digital Audio (CD-DA), which stores digitally encoded audio signals, and Compact Disc-Read Only Memory (CD-ROM), which stores computer-processible information. CD-ROM is the read-only counterpart of the CD-R and CD-RW formats described above.

DVD, originally known as the Digital Video Disk and later as the Digital Versatile Disk, is the compatible successor to Compact Discs and a replacement for analog video disks. DVD technology, products, and applications are discussed in a growing number of publications. Examples include Herther (1996), Immink (1996), Kobori (1997), Mimura (1997), Parker (1997), Pushic (1997), Rong et al. (1996), Terao et al. (1997), Verhoeven (1996), Wilkinson (1997), and Yamada (1997). Like Compact Discs, DVD media measure 4.75 inches in diameter. In its initial configuration, DVD technology stores approximately 130 minutes of full-motion video, digitally encoded on read-only media. Prerecorded movies in that format, along with DVD players, became commercially available in 1997. DVD-ROM, a format for computer-processible information, has a storage capacity of 4.7 gigabytes. At the time of this writing, some microcomputer manufacturers had begun incorporating DVD drives into their desktop and notebook models, but few DVD-ROM information products were commercially available and no library-oriented DVD-ROM products had been announced. Presumably, DVD-ROM will prove attractive for large reference data bases, such as Medline, that are currently distributed on multiple CD-ROMs. Recordable DVD formats-variously described as DVD-R, DVD-RAM, and DVD-E-have also been announced. At the time of this writing, evaluation units were available to systems integrators and other resellers. Widespread commercial availability is expected in 1998.

RECORDING TECHNOLOGY

Like their magnetic counterparts, read/write optical storage media consist of three components: (1) a recording material that is capable of absorbing laser light, converting it to thermal energy, and producing localized, detectable reflectivity transformations in areas irradiated by the laser; (2) a substrate or base material on which the recording material is coated; and (3) one or more additional layers designed to protect the recording material, compensate for substrate deficiencies, and/or facilitate the detection of reflectivity transformations when recorded information is played back. Read-only optical disks, as described above, are created by a mastering and replication process. Copies of Compact Discs, video disks, and DVD media purchased by libraries contain prerecorded information and have no recordable coating, although their substrates and other components can have a significant impact on media stability, care, and handling. The following discussion of optical recording technology emphasizes write-once and rewritable optical disk systems, although some points may also apply to optical cards and optical tapes.

Write-Once Media

Laboratory experiments with optical recording materials date from the 1970s. Write-once optical disk drives and media became commercially available in the early 1980s. Most of the optical disk drives and media being sold today are fourth- or fifth-generation products. Though not as widely analyzed as the principles of magnetic recording, the general characteristics of write-once optical recording technology are described in many monographs, journal articles, and conference papers. Examples, which vary considerably in technical detail, include Bell (1980, 1983), Cornet (1983), Croucher and Hopper (1987), Edwards (1987), Emmelius et al. (1989), Freese et al. (1982), Goldstein (1982), Gravesteijn (1988, 1989), Gravesteijn and Van der Veen (1984), Gravesteijn et al. (1987), Hecht (1982), Suh (1985), and Thomas (1987, 1988). At various times, five different write-once recording technologies have been utilized in commercially available optical disk systems. Several of them have been discontinued in recent years, although drives that employ discontinued processes remain in service and the media must be stored until their contents are no longer needed. All five technologies use lasers to record information by altering the reflectivity characteristics of a thermally sensitive material:

1. One of the most widely publicized approaches to write-once optical recording employs a thin film of tellurium coated on a platter-shaped substrate. In most cases, the tellurium is alloyed with other materials, such as selenium or lead, to enhance stability. A highly focused laser selectively irradiates areas of the recording material. The laser's energy is converted to heat, creating microscopic pits in the tellurium alloy-a process that is termed "ablation" or "ablative recording." In computer applications, the microscopic pits represent the one bits in digitally coded data; to represent the zero bits, spaces are left in areas where pits might otherwise have been formed. The recorded information is read by a laser and optical pickup mechanism that detects differences in the reflectivity characteristics of the pits and spaces. During the 1980s, half a dozen suppliers of optical storage products employed ablative recording. Most of those products have been discontinued, although many ablated media remain in storage. Philips LMS is the only remaining manufacturer of optical disk drives and media that use ablative recording technology.

2. Dye-based optical recording materials are variously described as dye-polymer, dye-in-polymer, or organic dye binder media. They feature a transparent polymer that contains an infrared-absorbing dye. The recording material is coated on a plastic, platter-shaped substrate. In some cases, a reflective metal layer is deposited between the substrate and the recording material. Information is recorded by a laser that operates at the dye's absorption wavelength. The laser's energy is converted to heat, forming pits or bumps with detectable reflectivity characteristics. As with the tellurium thin films described above, the pits or bumps typically represent the one bits in digitally coded data; zero bits are represented by spaces. Dye-based technology is currently employed by Compact Disc-Recordable (CD-R) products. Mischke et al. (1996) and Ypma (1996) discuss CD-R media characteristics and manufacturing processes. Other dye-based optical disk drives and media, available in the 1980s and early 1990s, have been discontinued.

3. Phase-change recording materials consist of tellurium and/or selenium compounds alloyed with small quantities of other metals. Initially, these compounds exist in either a crystalline or an amorphous state. A laser records information by heating selected areas of the recording layer until its glass transition temperature is reached. A crystalline-to-amorphous or amorphous-to-crystalline transition occurs in the heated areas, accompanied by a change in their reflectivity characteristics. In the write-once variant of phase-change recording, the transition is irreversible. Phase-change recording is utilized in 14-inch WORM optical disks manufactured by Eastman Kodak and in 5.25-inch PD disks manufactured by Matsushita and others. Other WORM phase-change systems have been4 discontinued. In the future, recordable DVD systems are expected to utilize phase-change technology. As discussed below, phase-change technology is also available in a rewritable implementation.

4. In the thermal bubble approach to write-once optical recording, heat from a highly focused laser beam evaporates a polymer layer to selectively form bubbles or bumps in a thin film composed of precious metals, such as gold or platinum. The bubbles open to form pits that reveal a reflective underlayer. Areas with the exposed underlayer typically represent the one bits in digitally coded data, while unexposed areas represent the zero bits. Thermal bubble recording has been used in WORM drives and media marketed by ATG.

5. Dual-alloy write-once optical recording media consist of two metal alloys coated as thin films on a platter-shaped plastic substrate. One of the alloys is composed of tellurium and bismuth, the other of selenium and antimony. The recording material is layered, the tellurium-bismuth alloy being surrounded by two layers of selenium-antimony. All layers are covered by a protective seal. To record the one bits in digitally coded information, a laser fuses the three layers, creating a four-element layer with detectable alterations in reflectivity. Zero bits are represented by unfused layers. Dual-alloy technology is utilized in 12-inch WORM drives and media manufactured by Sony Corporation.

Rewritable Media

Rewritable optical disks and drives have been commercially available in the United States since 1988, although various prototype models were demonstrated in the early 1980s. With their ability to accommodate changing data and text files, rewritable optical disks broaden the scope of optical storage applications. More versatile than WORM disks, they offer an alternative, complement, or supplement to magnetic recording media in a variety of computer applications. The history and characteristics of rewritable optical recording technology and materials are surveyed by Bate (1987), Bell (1986), Bennett (1988), Bernede (1992), Connell (1986), Engler (1990), Freese (1988), Mansuripur et al. (1985), Urrows and Urrows (1990), and Van Uijen (1985), among many others.

The most widely encountered rewritable optical disks are based on magneto-optical (MO) recording, also termed thermo-magneto-optical (TMO) recording. As its name suggests, magneto-optical recording is a hybrid process. Information is stored magnetically but recorded and read by a laser. Magneto-optical disks are actually multilayered magnetic disks. Their glass or plastic substrates are coated with an active recording layer that combines iron with selected rare-earths and transition metals (RETMs). Rare-earths is the collective name for a group of chemical elements with atomic numbers 21, 39, and 57-71. Examples encountered in magneto-optical recording include terbium, neodymium, dysprosium, and gadolinium. Rare-earths are actually abundant in the earth's crust, but they were initially discovered in very rare minerals, hence their name. Transition metals are elements with atomic numbers 22-28, 40-46, and 72-78. Examples encountered in magneto-optical recording include cobalt, platinum, titanium, chromium, and zirconium. Iron (atomic number 26) is also considered a transition metal. Many of the rare-earths and transition metals are described as "lanthanide series elements" because they follow Lanthanum (atomic number 57) in the periodic table.

A magneto-optical recording layer is typically surrounded by additional layers that provide protection against contaminants and facilitate playback of recorded information. On an unrecorded magneto-optical disk, all particles have the same magnetic orientation. To record information, a highly focused laser beam heats a spot on the disk until its Curie temperature is reached, causing a loss of the disk's initial magnetic direction as explained in Part 2 of this report. An electromagnet then generates a magnetic field to orient the particles in the desired direction. The magnetic particles assume the desired orientation as the recording material cools below its Curie temperature.

Retrieval of information recorded on magneto-optical media depends on the Kerr effect; when read by a laser and pickup mechanism, recorded areas of a magneto-optical disk will rotate reflected light in a clockwise or counterclockwise direction to play back the one and zero in its digitally coded data. Since the 1980s, research publications on magneto-optics have far outnumbered those dealing with other optical recording technologies. Representative works include Balasubramanian (1992), Bartholomeusz (1989), Buschow (1988, 1989), Crasemann et al. (1989), Fujii and Tokunaga (1997), Cadetsky et al. (1996), Gau (1989), Greidanus (1990), Greidanus and Bas Zeper (1990), Creidanus et al. (1989), Hansen (1990), Hansen and Heitmann (1989), Hatwar et al. (1997), Hirokane et al. (1994), Izumi et al. (1994), Kaneko et al. (1994), Kant and Barez (1996), Kim et al. (1995), Kryder (1985, 1990), Kugiya et al. (1995), Mansuripur (1987, 1995), McGahan and Woollam (1989), Owa et al. (1994), Shen (1996), and Wang et al. (1997).

Magneto-optical technology is used in rewritable optical disk drives manufactured by more than a dozen companies, including Hewlett-Packard, Fujitsu, Maxoptix, and Sony. Such drives are available in 3.5-inch and 5.25-inch form factors. While magneto-optical media are rewritable, they can be enclosed in specially designed cartridges that inhibit erasure when used in designated drives. In that packaging, magneto-optical disks have emerged as popular WORM products. Multifunctional optical disk drives can accept 5.25-inch magneto-optical media in either rewritable or WORM cartridges.

Matsushita introduced the first rewritable optical drives and media based on phase-change technology in 1990. As described above, phase-change materials are utilized by certain write-once optical disk systems. They record information by changing areas of an optical disk from a crystalline to an amorphous state, or vice versa. In the write-once variant of phase-change recording, the transition is irreversible. The reversible properties of tellurium alloys have been recognized for several decades, however; Matsushita demonstrated a prototype version of a rewritable phase-change optical disk drive as early as 1983. Commercial versions have been available for almost a decade. They use lasers of different wavelengths to switch areas of an optical disk between crystalline and amorphous states. The technology is explained by Akiyama et al. (1995), Chen and Rubin (1989), Chen et al. (1985, 1986), Gravesteijn (1989), Iwasaki et al. (1992, 1993), Rubin and Chen (1989), Situ et al. (1989), Van der Poel et al. (1986), and Yamazaki et al. (1993).

Matsushita's 5.25-inch rewritable optical disk drives that employed phase-change technology could not compete with magneto-optical products, which are available from many suppliers. Recently, however, phase-change recording has reemerged as a technology for Compact Disc-Rewritable (CD-RW) drives and media, as well as for future recordable DVD products. Ongoing research on phase-change technology is discussed in a growing number of journal articles, conference papers, and technical reports. Examples include Akahira et al. (1995), Chiba et al. (1995), Jacobs and Duchateau (1997), Jasionowski (1991), Hiratsune et al. (1995, 1996), Nishimura et al. (1995), Ohno et al. (1991), Ohta et al. (1995, 1996), Okada et al. (1995), Okuda and Matsushita (1996), Okuda et al. (1992), Rong et al. (1996), Shinotsuka et al. (1997), and Terao et al. (1997). CD-RW technology is discussed by Coombs et al. (1994), Iwasaki (1997), Iwasaki et al. (1995), Kageyama et al. (1996), Kim et al. (1997)

Other rewritable optical storage technologies, including a rewritable implementation of the dye-polymer media described above, have been demonstrated in prototype versions, but they have not been commercialized.

Read-Only Media

As described above, the read-only optical disks purchased by libraries are non-recordable copies produced by a mastering and replication process. With Compact Discs and DVD media, a laser creates a glass master that is used to produce metal stampers. Disk copies are produced from the stampers, usually by injection molding; hot plastic is quickly injected into a cavity formed by two stampers, then cooled. Video disks are produced by photopolymerization; a liquid lacquer, poured into a mould, is cured by exposure to ultraviolet light.

Regardless of the manufacturing process employed, read-only optical disks consist of a thin reflective metal layer and protective coating that rest on a plastic substrate. With Compact Discs and DVD media, the substrate material is polycarbonate (PC). Video disk substrates are typically constructed of polymethyl methacrylate (PMMA). The reflective layer may be composed of gold, silver, platinum, or other metals. The protective overcoat is a layer of acrylic or lacquer. Disk production processes are described by Armstrong (1987), Kloosterboer and Lippits (1986), Legierse (1987), Lippits and Melis (1986), Mayr (1987), McCrary (1988), Reynolds and Halliday (1987), and Van Rijsewijk et al. (1982), among others.

Read-only optical video disks are dual-sided media. They are constructed, in effect, of two disks bonded together with their metal layers adjoining. In such configurations, the PMRA substrates serve as transparent protective surfaces through which the recorded information is read. In contrast, Compact Discs and DVD media contain information on one side only. The other side usually contains a label printed in one or more colors. The label occupies all or part of the medium's non-recorded surface. Video disks are usually labeled on both sides. The labels, which resemble those used for vinyl phonograph records, are affixed to a small area in the center of the disk that is not used for recorded information.

STABILITY OF RECORDED INFORMATION

As with the magnetic tapes discussed in Part 2 of this report, read/write optical disks are often described in advertisements and manufacturers' product literature as archival media. The description is typically employed in the data processing sense, where "to archive" means to transfer inactive data from a relatively expensive online storage device-typically, a hard drive-to a presumably less expensive removable medium for offline storage. Historically, magnetic tape has been the most been the most widely used medium for such data archiving applications. Since optical disk cartridges can be removed from their drives for offline storage, they offer an alternative to magnetic tape in such situations. In fact, magnetic tape replacement-sometimes termed "optical archiving"-is one application for optical storage technology. Typical systems and installations are described by Davis (1987), Ferebee and Kibler (1989), Francis (1988), Green (1988), Hume (1988), Keele (1988), Osterlund (1987), and Ramsay (1988). With their high storage capacities, optical disks permit dramatic consolidations of magnetic tape collections with resulting simplification of storage requirements. A 2.6-gigabyte, 5.25-inch magneto-optical disk, for example, can store the equivalent of 14 reels of nine-track magnetic tape recorded at 6,250 bits per inch. Such consolidation is particularly important where archived media are stored in vaults or other expensive space, including commercial storage facilities that charge by the amount of space occupied.

In the case of research-type information maintained by libraries and related organizations, the term "archival"-as discussed above-implies permanence; an archival medium will retain its original information-bearing characteristics indefinitely. Optical storage's potential for permanent preservation of large quantities of computer-processible information, video images, or audio signals in library-related applications has been widely discussed since the early 1980s, when the Library of Congress initiated pilot projects to examine the use of write-once optical disk and video disks for preservation and reference purposes. Those projects are described in many publications, including Criswell (1983), Dean (1983), Nugent (184), Parker (1985), Price (1984, 1985, 1986), and Welsh (1987). Among preservation specialists, there has been much discussion of image-based optical disk systems as alternatives to microfilm.

Despite this interest, the archival properties of optical disks have not been demonstrated. The only national or international standard that addresses the issue of optical disk stability is ANSI/NAPM IT9.21, Life Expectancy of Compact Disc Read Only Memory (CD-ROM)-Method for Estimating, Based on Effects of Temperature and Relative Humidity. Published in 1996, it describes accelerated aging tests for determining the storage life of CD-ROM, a type of read-only optical disk. It does not specify the life expectancy of CD-ROM media, however. At the time of this writing, there were no published standards for the permanence of information recorded on read/write optical disks, and there is no indication that such media are suitable for permanent preservation of important library materials.

Information contained in published studies and manufacturers' product literature suggests that optical storage media are less stable than the paper documents and microfilm that comprise the majority of library collections. As defined in preceding sections of this report, stability denotes the extent to which a given storage medium retains physical characteristics and chemical properties appropriate to its intended purpose. Over time, optical disks undergo significant chemical and physical changes that will eventually render them unsuitable for accurate recording of new information and retrieval of previously recorded information. Such changes may be induced by environmental effects or by defects associated with media manufacturing. Optical disks, like magnetic tapes and diskettes, are also subject to physical damage through improper media handling. The following discussion examines each of these factors.

Environmental Effects

Many of the read/write optical storage technologies described above utilize media composed of metallic thin films. Magneto-optical recording materials, for example, include various combinations of rare-earths and transition metals. Some write-once optical disks are based on tellurium alloys, as are rewritable phase-change media. As a group, the metallic thin films employed in optical recording are susceptible to oxidation resulting from exposure to air. Over time, oxidation promotes pinhole formation and other forms of corrosion that can significantly alter the reflectivity, transmissiveness, signal-to-noise ratio, pit formation characteristic, bit-error frequencies, and other recording and playback properties of read/write optical media.

Oxidation and corrosion are aging mechanisms that significantly shorten the useful lifetimes of read/write optical media. These effects are well documented in journal articles, conference papers, technical reports, and other published sources. Their degradative impact is beyond dispute. Because read/write optical disks have been commercially available for less than two decades, information about their long-term interactions with environmental conditions is not based on direct observation. Instead, it relies on accumulated knowledge about the chemical behavior of materials used in optical recording-tellurium, for example, was discovered in the late eighteenth century-plus the results of accelerated aging tests performed in research laboratories. While specific methodologies vary, accelerated aging tests expose optical recording media to extremely hot and humid storage conditions for predetermined but relatively brief periods of time. Degradative changes in the recording media are noted, and mathematical models are used to predict the amount of time required for comparable changes to occur in ordinary storage environments. Test concepts, lifetime models, and measurement techniques applicable to accelerated aging of optical media are discussed by Clover (1984), Croll (1991), Manns (1986), Nikles and Forbes (1991), Podio (1991, 1992), Podio et al. (1990), Scheinert (1984), and Spruijt (1984). As discussed elsewhere in this report, accelerated aging tests are also employed to estimate the useful lifetimes of microfilm and magnetic media.

As noted above, degradative environmental effects are extensively documented in published studies of optical recording technology. Milch and Tasaico (1980) were among the first to confirm the oxidation-related aging of tellurium-based write-once storage media exposed to various temperature and humidity conditions. Lee and Ceiss (1983) likewise reported the degradation of tellurium thin films by oxidation, supplemented by weight loss associated with the formation of unidentified volatile products. Based on accelerated aging tests conducted at Philips, Lou (1981) noted that degradation of tellurium-based WORM disks, judged by bit-error measurements, is primarily the result of electrochemical corrosion attributable to high humidity. The adverse effects of temperature and humidity on magneto-optical media are likewise widely acknowledged. Among the many published studies of this subject, Bernstein and Gueugnon (1985), Birecki et al. (1985), and Heitman et al. (1985) cite oxidation of rare-earths and transition metals as the principal cause of aging in magneto-optical media. Rare-earths such as terbium, for example, are easily oxidized. Tejedor and Fernandez (1986) found that oxidation of terbium-ferrite thin films caused significant changes in magnetization, coercivity, and other properties that affect recording and playback. Miller et al. (1988) found that exposure of terbium-ferrite-cobalt to high temperatures initiates an oxidation process that significantly alters their magneto-optical characteristics. Following a series of accelerated aging experiments at high humidity, Okada et al. (1989) reported various types of bit errors in magneto-optical disks manufactured by NEC. Katayama et al. (1988) reported reduced recording sensitivity and lower coercivity over time in magneto-optical media manufactured by Sharp Corporation; the reductions were accelerated at higher temperatures, which typically intensify environmental degradation of computer media. Maeda et al. (1989) reported decreased playback stability in terbium-ferrite-cobalt disks over time.

As explained by Aisenberg and Stein (1981), Maeno and Kobayashi (1990), and others, the oxidation resistance and longevity of optical storage media can be improved by protective coatings-sometimes described as "passivation layers"-and by improvements in optical recording materials themselves. To enhance the stability of write-once and rewritable optical recording media, most manufacturers employ some type of protective encapsulation or barrier coating. Misaki et al. (1989) and Ohkubo et al. (1990) describe the benefits of silicon-based protective coatings for magneto-optical disks. Miyazaki et al. (1987) report on Fujitsu's experiments with silicon dioxide coated on terbium-ferrite-cobalt disks. Aratani et al. (1985, 1987) discuss the oxidation-inhibiting effects of an aluminum nitride overcoat applied to terbium-ferrite and terbium-ferrite-cobalt disks. The aluminum overcoat suppressed pinhole formation in disks exposed to a corrosive solution. Similar results are reported by Asano et al. (1987), Hartmann et al. (1986), Kobayashi and Kawamura (1987), Lee et al. (1990), Wang et al. (1987), and Watanabe et al. (1987). Sato et al. (1985) and McIntire and Hatwar (1989) found that a protective coating of aluminum nitride above and below the magneto-optical recording layer provided greater corrosion resistance than a single overcoat. Wright et al. (1987) contend that an aluminum overlayer prevents loss of coercivity in magneto-optical recording media exposed to high temperatures for long periods of time.

The information-bearing side of a Compact Disc has a polycarbonate overcoat for scratch protection. As discussed by Best and Prime (1993), the label side is coated with a thin acrylic lacquer for corrosion protection. Most read-only Compact Discs have an aluminum reflective layer that is vulnerable to environmental degradation. If the acrylic coating does not completely cover all edges of a Compact Disc, oxidation can attack the reflective layer. The resulting damage, which was widely publicized in the late 1980s, has been variously described as "CD rot" or "laser rot." It It is discussed by Marshall (1991) and Marshall and Voerdisch (1990). The problem also occurs with video disks. Since the early 1990s, it has been successfully addressed by improved manufacturing processes. As a complicating factor, however, scratches can penetrate a Compact Disc's acrylic coating, exposing the medium's reflective layer. Flexing of media, a greater concern with 12-inch video disks than with Compact Discs, can also cause cracks in the acrylic coating. Further, as discussed by Day (1989) some media labels contain chemically active inks that can damage the aluminum reflective layer. Most optical disk manufacturers, however, deny using corrosive inks, but recordable Compact Discs are labeled by their users not their manufacturers. As a precaution, CD-R manufacturers increasingly apply a single hard coating to both media surfaces. The coating protects recorded information against scratches, accidental tears, fingerprints, and spilled liquids, while providing a suitable surface for labeling.

The stability of corrosion-prone thin films, such as tellurium and terbium, can be improved by alloying them with oxidation-resistant materials. (Broadly defined, an alloy is a combination of two or more metals.) Researchers have long confirmed the stability-enhancing properties of such alloyed optical recording materials. Ahn et al. (1981), for example, reported that the corrosion resistance and useful lifetimes of tellurium-based optical storage media can be increased by the addition of various metals, including boron, silicon, chromium, aluminum, rhodium, and phosphorus. In cyclic climate tests, Markvoort et al. (1983) reported that tellurium alloys proved far more resistant to environmental degradation when compared to pure tellurium films. Lee (1983, 1983a) found that the addition of small amounts of selenium, bismuth, and germanium significantly enhanced the stability of tellurium. Herd et al. (1982) and Terao et al. (1983) likewise indicate that tellurium-selenium alloys resist oxidation. Terao et al. (1987) found that the addition of a selenium layer to tellurium thin films completely inhibited oxidation at extreme temperatures and relative humidities, while the addition of a small amount of lead or other metallic elements inhibited cracking, Hatwar and Majumdar (1988), and Majumdar and Hatwar (1989), Tanaka and Imamura (1985), and Tanaka et al. (1985) contend that the addition of platinum suppresses pinhole formation in magneto-optical thin films composed of terbium, iron, and cobalt. Similar advantages are claimed for other titanium, beryllium, indium, boron, gadolinium, and other metals. These magneto-optical alloys are discussed in many research reports. Examples include Abe and Gomi (1990) Iijima (1987), Iijima and Hatakeyama (1987), Kobayashi et al. (1985, 1987, 1987a), Matsushima et al. (1987), Niihara et al. (1988), Tada et al. (1986), Tokushima et al. (1980), and Yan et al. (1990).

As explained above, write-once and rewritable optical recording materials may be coated onto glass or plastic substrates; the latter, as previously noted, include polycarbonate and occasionally, polymethyl methacrylate (PMMA). As discussed by Inui et al. (1987), Kaempf (1987), Leuschke (1989), and Smith (1981), the most important characteristics of optical disk substrates include reliability, environmental stability, accurate mechanical and optical capabilities, and suitability for fine pattern fabrication. Chen et al. (1983) analyze the relationship between optical disk substrates and media noise. Proponents of glass substrates cite their superior uniformity, optical clarity, mechanical stability, scratch resistance, freedom from warping, resistance to moisture absorption, and ability to withstand high temperatures. Advocates of plastic substrates emphasize economic advantages associated with high-volume production.

Studies by Choe and Walser (1990), Heitmann et al. (1987), Naoe et al. (1988), Yoshida (1984), and others indicate a relationship between substrate characteristics, coating deposition processes, and potential for oxidation and corrosion of optical recording layers. Lee (1983) and Lee and Wieder (1983) report that tellurium thin films typically oxidize uniformly, but localized degradation can occur at the site of initial defects in glass and PMMA substrates. The problem was judged to be more common with PMMA substrates, which have a higher rate of manufacturing defects than their glass counterparts. Yamamoto and Yamada (1988) report that optical recording materials coated on glass substrates proved less vulnerable to oxidation than media based on polycarbonate substrate, since polycarbonate materials tend to absorb moisture. Reflecting this observation, manufacturers who offer a choice of glass or polycarbonate disks typically claim greater stability for their glass products.

Shrawagi et al. (1984) found that bit errors in tellurium-coated optical disks were largely the result of microscopic pits, surfaced roughness, and other defects in uncoated substrates. A study of magneto-optical disks by Takeda et al. (1989) indicated that microscopic defects in polycarbonate substrates were the main cause of pinhole formation. Farrow and Marinero (1990) found that substrate defects promote the interaction of moisture with magneto-optical recording materials, thereby contributing to pitting-like corrosion. Moribe et al. (1988) indicate that many substrate defects are attributable to stamper residues and dust. Bartholomeusz and Hatwar (1989) contend that deposition processes that produce dense, featureless coatings can minimize the adverse effects of substrate irregularities. Shieh et al. (1988, 1989) found that moderate air pressure during coating produces dense, smooth coatings that improve the oxidation resistance of magneto-optical thin films. Ito and Naoe (1990) likewise emphasize the relationship between dense, uniform coatings and media stability.

Read-only optical disks, as described above, invariably use plastic substrates-polycarbonate for Compact Discs and DVD and PMMA for video disks. Most magneto-optical drives similarly require polycarbonate media; glass media, an option in the early 1990s, is rarely supported by newer drives. The adverse effects of temperature and moisture on poly-carbonate materials are reviewed in numerous publications, including Bair et al. (1978), Hill et al. (1990), Nakada et al. (1987), Narkis et al. (1984, 1985), Ram et al. (1985), Ricco and Smith (1990), Trznadel and Kryszewski (1988), and Yee et al. (1988). Forms of potential degradation include,internal cracking, swelling, shrinkage, changes in tensile strength, and formation of water-filled pockets, any of which can alter the substrate's optical characteristics. Anecdotal evidence, reflected in letters to the editors of consumer audio magazines, suggests that play-ability problems with Compact Discs are not unusual, and many librarians can confirm this based on first-hand experience with audio Compact Discs and CD-ROMs. On the other hand, Burton (1990) reports that an apartment fire caused no damage to an entire collection of 150 Compact Discs, although their plastic containers had melted and required replacement.

Experiments by Sato et al. (1987) indicate that polycarbonate is generally preferable to PMRA, which has a greater tendency to absorb moisture. The impact of temperature and humidity on physical degradation of PMMA materials is documented in numerous journal articles and conference papers. Examples include Cheng et al. (1990, 1990a), Crissman and McKenna (1990), Drotning and Roth (1989), Mijovic et al. (1989), Peppas et al. (1988), and Yianakopoulos (1990). As discussed by Isailovic (1985), PMMA substrates can also experience cold flow problems. When PMMA disks are placed on an uneven surface, their shape may be altered in a manner that can adversely affect playback of recorded information.

Regardless of substrate material, injection-molded disks are formed and cooled so rapidly that stresses and strains may be molded into them. In warm office areas, Compact Discs and video disks may soften slightly, relieving the stresses and strains but distorting the media's shape. Where optical disks are stacked on top of one another, such distortions may be aggravated by pressure. As discussed by Crawford (1988), read-only optical disks are also subject to surface contamination from stamper residues, as well as from dust, vaporized chemicals, and other airborne particles in the production facility. During metallization and the application of protective layers, such surface contaminants may be overcoated, producing bubbles or bumps that can render portions of the disk unplayable. The overcoated particles may become dislodged during use, forming pinholes and diminishing reflectivity in areas where the metallized coating has flaked away. While such contamination problems are minimized by quality-assurance procedures and the stringent clean room conditions discussed by Schicht (1985), they are not entirely eliminated.

Media Wear

In advertisements and other promotional literature, manufacturers of read/write optical storage media depict their products-with considerable justification-as more durable than the magnetic recording materials with which they compete in various information management applications. In particular, proponents of optical storage note that the use of lasers for "contactless" recording and playback eliminates the possibility of damaging head crashes and diminishes the potential for media wear. Compact Discs and video disks offer similar advantages over video- and audiotapes, which are subject to degradative wear. Compared to vinyl phonograph records, audio Compact Discs are not eroded by repeated playing.

In many respects, optical media manufacturers' claims of greater durability are justified. With write-once optical disks, for example, playback of previously recorded information is a non-destructive process. The information can presumably be read an unlimited number of times without media wear. Rewritable optical disks, however, are engineered for a specific number of recording, erasure, and retrieval incidents. For magneto-optical disks coated on plastic substrates, most manufacturers claim a duty cycle of one million write, erase, or read operations. Manufacturers of optical disks with glass substrate claim a duty cycle of 10 million write, erase, or read operations. To put these numbers in perspective, a rewritable optical disk engineered for one million write, erase, or read cycles could be utilized continuously for approximately 280 hours with one such operation being performed each second.

As previously discussed, read/write optical disks are removable media. They are stored offline, on shelves or in autochangers, until required for recording or reference, at which time they are loaded into an appropriate drive. Some optical media manufacturers specify a limit, typically 10,000 incidents, for cartridge loading and removal. That limit should not prove constraining in most library applications; performed four times per day, for example, 10,000 cartridge loading operations would require seven years to complete.

Erasure

Magneto-optical recording, as described above, relies on a combination of lasers and magnetism. They are consequently subject to accidental or malicious erasure of information as described in Part 2 of this report. As a precaution, media manufacturers typically recommend that magneto-optical disks not be exposed to magnetic fields exceeding 600 oersteds. As previously noted, magnets exceeding that strength can be purchased in hardware stores or other retail outlets. Because magnetism plays no role in other optical disks technologies, the information they contain is unaffected by magnetic fields. Accidental or malicious erasure of information is impossible. Unlike magnetic tapes, optical media are not subject to print-through effects.

Lifetime Estimates

As discussed in preceding sections, the stability of information recorded on optical disks is principally imperiled by time-dependent degradation attributable to environmentally induced changes in the chemical and physical characteristics of optical storage media. Such rechanges can have a significant impact on reflectivity, bit error rates, and other media properties that affect reliable recording and playback. Unfortunately, generalizations about the lifespans of optical storage media are complicated by several factors:

1. Optical storage is not a monolithic product group. Read/write optical disk drives and media, as previously explained, employ a variety of write-once and rewritable technologies. Each involves different recording materials, processes, and equipment. Optical disks may be composed of metallic alloys, metal/polymer combinations, or dye-based materials. Class or plastic substrates may be utilized. Information may be recorded by forming microscopic pits, bubbles, or bumps; by diffusion of dyes; by crystalline-to-amorphous transitions; by fusing metallic layers; or through a combination of heat and magnetism. A report prepared for the National Archives and Records Administration by the National Research Council (1986) estimates that over 190,000 different combinations of optical storage media characteristics and recording processes are possible. While some optical recording processes, devices, and media have been discontinued since the 1980s, much variety remains,

2. Specific implementations of a given optical recording technology vary from manufacturer to manufacturer. The magneto-optical disks of different manufacturers, for example, feature different formulations of recording materials. Manufacturers of tellurium-based write-once optical disks and phase-change media similarly employ different alloys, each optimized for use in a specific drive.

3. Optical storage media have been in existence for a relatively short time. Write-once optical disks, as previously noted, were introduced in North America in 1983; rewritable optical disks have been commercially available since 1988. Among read-only optical disks, video disks date from the late 1970s and Compact Discs from the early 1980s. Suh (1986) reports that optical disks created in a laboratory environment have shown little degradation in 10 years of storage, but, given the comparative newness of optical recording media, lifetime estimates based on accelerated aging models cannot be confirmed by experience with working media.

4. In their specification sheets and other product literature, some manufacturers of optical storage media provide lifetime estimates that are based, as discussed above, on accelerated aging tests. Details about accelerated life testing are seldom provided, although manufacturers' claims may be based on studies presented in journal articles, conference papers, or other publications. It is often difficult, however, to relate such published studies to specific products, since accelerated aging tests may be performed during the product development stage on laboratory disks rather than commercially available media.

5. As a further concern, most accelerated aging tests have been performed by the media manufacturers themselves. There is no reason to believe them incorrect, but independent research studies that might replicate their methods and confirm their conclusions have been few in number and limited in scope. Makino (1989) reports on accelerated aging tests performed on selected magneto-optical media by the Japanese Standard Committee for Optical Digital Data Disk. Podio (1991, 1992) and Podio et al. (1990) describe a study of optical disk life expectancy conducted for the National Archives and Records Administration (NARA) by the National Institute of Standards and Technology (NIST). The study, which initially planned to evaluate multiple 12-inch WORM disks, was ultimately limited to one product manufactured by Sony. The 12-inch WORM drives that utilize those Sony media have since been discontinued. In a study conducted by the British Library, Winterbottom (1995) found that optical disks remained usable after three years in storage. Parker and Starrett (1996) discuss the nature and importance of CD-R testing. Leek (1995) surveys CD-R longevity studies.

With these cautionary notes in mind, the following discussion surveys current research and manufacturers' claims for stability of optical disks that utilize specific recording technologies. Published studies are cited where pertinent.

Manufacturers of write-once optical storage media often provide separate lifetime estimates for recording stability and playback stability. Recording stability, sometimes termed "shelf stability" or "shelf life," denotes the period of time during which a given optical disk permits the reliable recording of new information in previously unused areas of the disk. Manufacturers of write-once optical disks typically claim a useful recording life of five years from the medium's manufacturing date, regardless of the specific optical recording technology employed. Playback stability, sometimes termed "storage stability," denotes the period of time during which previously recorded information can be reliably retrieved from a given optical disk. With write-once optical disks, playback stability is longer than shelf stability. With rewritable optical disks, manufacturers' claims are identical for shelf stability and playback stability; to be useful, rewritable media must presumably provide continuing support for recording of new information as well as retrieval of previously recorded information.

For both write-once and rewritable optical disks, stability periods vary with the recording technology employed. The stability of magneto-optical recording materials is discussed in many of the research reports cited above, as well as by Arimune et al. (1985, 1987), Birecki et al. (1985a), Carcia et al. (1988), Freese et al. (1985), Grundy et al. (1987), Higgins and Oesterreicher (1987), Jacobs et al. (1984, 1984a), Katayama et al. (1988), Kobori et al. (1986), Luborsky et al. (1985), Maeda et al. (1989), McDaniel and Finkelstein (1991), Numata et al. (1988), Okada et al. (1989), Sekiya et al. (1988), Usherwood et al. (1996), Watanabe et al. (1989), Yardy et al. (1990), and Zhang et al. (1991). Manufacturers' technical specification sheets cite useful lifespans of 20 to 40 years for magneto-optical disks, with 30 years being a typical stability claim. Various published studies support such claims. Based on bit-error analysis following accelerated aging tests, for example, Okazaki et al. (1989) estimated a useful life of at least 25 years for magneto-optical disks stored in an office environment.

Manufacturers of tellurium-based write-once optical disks for ablative recording variously claim a useful storage life of 10 to 40 years. Published reports of accelerated aging tests performed in the early 1980s indicated a useful life of at least 10 years for reliable playback of information recorded on such media. Kanazawa et al. (1984) and Kitani and Tsunoda (1984), for example, cite storage stability exceeding 10 years for the first generation of write-once optical disks manufactured by Hitachi. Blom and Lou (1984), Lou (1981), Markvoort et al. (1983, 1984), and Vriens et al. (1983) report similar findings for tellurium-based optical disks manufactured by Philips. Since the late 1980s, manufacturers of such media have claimed a useful life of 30 to 40 years. The increased longevity is attributed to improved tellurium alloys, media designs, and manufacturing methods.

Studies by Chung et al. (1984), Cornet (1983), and Freese et al. (1982) claim playback stability of at least 10 years for the write-once optical disks that employ thermal-bubble technology. Manufacturers claim a useful life of 30 years for new thermal bubble media. Based on accelerated aging tests, Nakane et al. (1985, 1986) report playback stability of at least 30 years for the dual-alloy 12-inch WORM disks manufactured by Sony. Since 1988, Sony has been claiming playback stability of 100 years for such media, although it has not documentated that claim in journal articles, conference papers, or other published studies. Accelerated aging tests reported in the previously cited study by Podio (1991, 1992) estimated a stable life span of 57 to 121 years for Sony's 12-inch WORM media. Unfortunately, the test results are of academic interest; as noted above, Sony has discontinued its 12-inch WORM drives.

The stability of dye-based write-once optical recording materials is discussed by Kay et al. (1984), Nikles et al. (1989), Oba et al. (1986), and Pearson (1986). During the 1980s, manufacturers of dye-based WORM media claimed playback stability of 15 to 30 years for their optical disks. For the most part, those products have been discontinued, although some dye-based WORM drives remain in use and many dye-based disks are in storage. As previously discussed, CD-R media are now the most widely encountered examples of dye-based optical disks. At its web site (www.osta.org), the Optical Storage Manufacturers Association reports that manufacturers of CD-R media claim playback stability of 75 to 200 years for their products. These claims are typically based on a measurement known as the block error rate (BLER), which denotes the number of errors detected in a given Compact Disc within a 10-second period.

All Compact Disc drives are equipped with error correction circuitry that compensates for defects within a given medium and reads information as it was originally recorded. If the BLER is too high, however, a Compact Disc drive's error correction capabilities will be over-whelmed. As specified in the previously cited ANSI/NAPM IT9.21 standard, a Compact Disc is judged to be at the end of its stable life when the block error rate equals 220. Recognizing that the life span of any given Compact Disc cannot be predicted with certainty, ANSI/NAPM IT9.21 defines the standardized life expectancy (SLE) as the minimum life span that can be expected for 95 percent of Compact Discs with a 95-percent confidence level.

ANSI/NAPM IT9.21 is limited to read-only Compact Discs, including CD-ROMs and audio Compact Discs. It specifically excludes recordable media, but CD-R manufacturers employ BLER measurements when estimating the life expectancy of their products. CD-R test methods are discussed by Steenbergen and Van Dorp (1996). Howe (1994) considers differences in error characteristics for CD-R and CD-ROM. Most manufacturers of C-R media assume a maximum acceptable block error rate (BLERmax) of 50, which is more conservative than the ANSI/NAPM IT9.21 specification. Lifetime estimates based on BLERmax50 measurements assume that CD-R media will be stored in darkness at 25 degrees Celsius (77 degrees Fahrenheit) with a relative humidity of 40 percent. In its product literature, Eastman Kodak suggests that a longer stable life may be achieved if CD-R media are stored at cooler temperatures; 10 degrees Celsius (50 degrees Fahrenheit) is specifically mentioned. Eastman Kodak claims playback stability exceeding 200 years for CD-R media stored in controlled storage and 100 years for CD-R media stored in an office environment. Kodak's CD-R media, which feature a gold reflective layer, are discussed by Zimmer (1993). Lifetime estimates for CD-R media are provided at some manufacturers' web sites. Examples include www.kodak.com, www.imation.com, www.mitsuigold. com, www.plasmon.com, www.tdkonline.com, and www.verbatimcorp.com.

The stability of phase-change optical recording materials, including results of accelerated aging tests, are discussed by Jiang and Okuda (1991), Ohta et al. (1990), Suzuki et al. (1994), Tamaru and Amano (1992), and Terao et al. (1989). Matsushita claims playback stability of 10 years for the rewritable phase-change disks used in its Panasonic drives and 15 years for write-once phase-change disks. Other manufacturers claim longer life expectancies for write-once phase-change media. Eastman Kodak, for example, claims playback stability of 30 years for the phase-change media used in its 14-inch WORM drives. Plasmon Data Systems claims playback stability of 50 years for the platinum-based WORM disks it manufactures for use in Panasonic drives. Results of Plasmon's accelerated aging tests are reported by Storey et al. (1988). Manufacturers of CD-RW media, which utilize rewritable phase-change technology, claim playback stabilities up to 50 years.

Stability claims for read-only optical disks vary. Long life spans are possible; Yamaguchi et al. (1991) describe an experimental CD-ROM with an estimated stable life of 300 years. The ANSI/NAPM IT9.21 standard, as discussed above, specifies test methods for read-only Compact Discs based on block error rate measurements. There are no comparable test methods for video disks or emerging DVD products. Most manufacturers indicate that Compact Discs and video disks will be playable for at least 25 years. Some CD-ROM manufacturers claim life expectancies up to 100 years for their newest media, which are less vulnerable to damaging oxidation than their predecessors. As discussed by Oudard (1991), multi-decade and even century-long life spans are confidently predicted for read-only Compact Discs with gold reflective layers. Compared to the aluminum reflective layer employed in conventional Compact Discs, gold offers superior resistance to oxidation.

Lifetime estimates may not be significant for CD-ROM data bases, which are often updated by replacement media at predetermined intervals. Similarly, software distributed on CD-ROM is often updated by new releases. Libraries adding audio Compact Discs and video disks to their collections, however, may expect those materials to remain playable for many years. Because read-only optical disks are produced in multiple copies by a mastering process, any given disk will not represent the only copy of valuable information. If a problem arises with a library's copy of a Compact Disc or video disk, a new copy can be purchased-assuming, of course, that the desired title is still available for sale.

LIBRARY GUIDELINES

As with the microforms and magnetic media discussed in Parts 1 and 2 of this report, libraries must develop formalized procedures for the storage, care, and handling of read/write and read-only optical disks. By controlling the conditions under which such disks are maintained and used, properly implemented guidelines can minimize the potential for media damage and increase the likelihood that optical recordings of computer-processible information, video images, or audio signals will remain useful for their intended purposes. The following discussion presents recommendations for the management of optical disks in four areas: (1) the selection of media with characteristics appropriate to their intended purposes; (2) the creation of an appropriate storage environment for optical media; (3) handling procedures and precautions to minimize the potential for physical damage to optical media; and (4) equipment-related considerations. The recommendations are based on guidelines presented in various published and unpublished sources, including technical specification sheets and other documentation provided by media manufacturers.

Media Selection

A systematic approach to the management of optical disks for computer, video, or audio recording begins with the selection of media appropriate to their intended purposes. Certain characteristics of optical recording media can have a significant impact on their storage, care, and handling. In selecting optical disks for specific applications, libraries should consider the following points:

1. Through the late 1980s, optical disk users had little choice but to purchase media from optical disk drives manufacturers. At that time, many optical disks were proprietary products, and drive manufacturers were the sole sources for procurement of compatible media. Since the early 1990s, however, standards have been developed for certain types of unrecorded optical disks, and alternative procurement sources have become available for the most popular optical disk formats. CD-R and 5.25-inch magneto-optical disks, in particular, are available from many suppliers, including mail-order companies that offer optical media at substantial discounts. For best results, optical recording media must be selected for quality rather than price. Cochrane (1996) notes that variations in CD-R media have a greater impact on system compatibility and performance than variations in CD-R drives. For use in write-once and rewritable drives, libraries should purchase high-quality optical media from known manufacturers. Brand-name media produced by established companies are typically constructed of high-quality materials. They are subject to strict quality control procedures and have low error rates. As with magnetic tapes and diskettes, libraries should avoid media of uncertain origin and potentially marginal quality.

2. Optical disks selected for a given library application should comply fully with specifications established by the manufacturer of the equipment on which the disks will be recorded and played. Such fully compliant media are sometimes described as "qualified" or "certified" for use in a given drive.

3. Libraries should restrict purchases of prerecorded Compact Discs and video disks to reliable information publishers and other well established procurement sources. Where long retention of information is an important consideration, libraries should consider purchasing gold Compact Discs. An increasing selection of audio Compact Disc titles and a few CD-ROM products are available, at admittedly premium prices, on gold media. As noted above, gold provides superior oxidation resistance for enhanced media stability.

4. As discussed by Watson et al. (1997), a study conducted by Doculabs for the Special Interest Group on CD Applications and Technology (SIGCAT) concluded that gold CD-R media, also described as "gold and gold" disks, offer superior longevity and performance when compared to green CD-R media, which is described as "green and gold." The gold media employ phthalocyanine as their dye-based recording material, while green media use a cyanine dye. Phthalocyanine media, which were first offered by Mitsui Toatsu Chemicals and Eastman Kodak, are now produced by other CD-R manufacturers. The Doculabs/SIGCAT study can be accessed online at www.sigcat.org. Other CD-R compatibility studies have been conducted by the Optical Storage Technology Association and by a consortium of Japanese CD-R manufacturers known as the Orange Book Study Group. These studies are summarized by Bennett (1997), Martin and Hyon (1995), and Williams (1997). The Optical Storage Technology Association study can be accessed at www.osta.org. As discussed by Parker (1997a), CD-R compatibility is complicated by poorly calibrated recorders, software variations, and older CD-ROM drives used as playback devices.

5. Read/write optical disks that are intended to record computer, video, or audio information for long-term storage should be recently manufactured, purchased new, and used as soon as possible after purchase. Lifetime estimates cited by optical disk manufacturers and others begin with a disk's manufacturing date, not the date when information was recorded. Recycled media-that is, rewritable optical disks previously used for computer, video, or audio recording-should not be used for long-term storage copies. Prior to use, unrecorded optical disks should be stored under conditions specified by the manufacturer.

6. For very important information to be retained on write-once or rewritable optical disks, two or more long-term storage copies should be created. To provide the greatest protection against the possibility of defective media, optical disks from different manufacturing lots should be utilized for each of the copies.

7. As discussed in the preceding section, the playback stability of write-once and rewritable optical disks varies with the recording technology and other factors. Some types of optical disks, as delineated above, have longer estimated lifespans than others. Where media longevity is more important than storage capacity or fast retrieval responsiveness, libraries may prefer CD-R to magneto-optical disks. CD-R drives are slower and provide less online capacity than magneto-optical models, but CD-R media have longer life spans than magneto-optical disks. In the past, some manufacturers of 5.25-inch magneto-optical disks offered a choice of glass or plastic substrates. Glass substrates are typically more stable than their plastic counterparts, which tend to absorb moisture. The newest magneto-optical drives, however, support plastic media exclusively.

As a complicating factor introduced in Part 2 of this report, read/write and read-only optical disks, like magnetic tapes and diskettes, are designed for use with specific hardware and, in the case of computer-processible information, specific systems and application software. The service life of optical disk equipment will invariably prove shorter than the stable life spans of the media themselves. While a given optical disk may retain playback stability for several decades or longer, there is no historical precedent for computer storage peripherals remaining in service for that length of time. Most optical disk drives are engineered for a maximum service life of 10 years, but the frequency of repair and high maintenance costs associated with aging equipment will typically necessitate replacement before that time. The availability of new models with improved cost-performance characteristics, coupled with changing application requirements, also encourages replacement of computer storage peripherals at relatively short intervals-within five years or less in many cases.

The continued utility of a given optical disk may be adversely affected by changes in equipment specifications and recording formats that can render previously recorded media unplayable. Some optical disk formats have evolved through three or four generations, and continuing refinements can be expected. As previously noted, the defined migration path for 5.25-inch magneto-optical disks calls for a doubling of media capacity at two-to-three-year intervals. Similarly, DVD-RAM media will be the next generation of recordable Compact Discs. To facilitate the transition from one generation of products to the next, manufacturers of new optical disk drives may offer backward compatibility for reading purposes; that is, new drives can retrieve information from media recorded by predecessor models in a given manufacturer's product line. While such backward compatibility is customary, there is no guarantee that it will be continued for all future products developed by a given manufacturer. On the contrary, the history of computer storage peripherals suggests that, at best, backward compatibility is limited to two or three generations. Eventually, support for older media is phased out. As an example, the GD 1001, a 12-inch optical disk drive introduced in the early 1980s, provided a double-sided recording capacity of two gigabytes per WORM cartridge. Two successor drives-the GD 6001, introduced in 1989, and the GD 9001, introduced in 1991-offered much higher media capacities, but they could also read media recorded by the GD 1001. The product line's backward compatibility was limited to three generations, however; the GD 9001/S, a fourth-generation model introduced in 1992, could not read media recorded by the first-generation CD 1001 media. Such disks will be unreadable when the installed base of compatible drives passes out of service.

Product discontinuations pose additional problems. Since the early 1980s, manufacturers of optical disk drives and media have discontinued certain models or entire product lines without providing replacements or migration paths. All 15 WORM drives listed by Saffady (1992) as commercially available in the early 1990s have been discontinued; in 12 cases, the manufacturer provided no successor products for backward compatibility with previously recorded media. Fujitsu, Hitachi, Mitsubishi, Philips LMS, Pioneer, Ricoh, and Toshiba have discontinued the 5.25-inch WORM drives they introduced in the mid-to-late 1980s. Philips LMS continues to manufacture 12-inch WORM drives, but its second- and third-generation products, which have been introduced since 1990, are not compatible with the company's earliest model. Sony has discontinued its 12-inch WORM product line, although it continues to manufacture 5.25-inch magneto-optical drives and media. In 1997, Matsushita discontinued the phase-change optical disk drives that it had sold under the Panasonic brand name. Several optical disk manufacturers, including Optimem and Optotech, have ceased operation entirely.

Software changes, as previously discussed, can likewise pose significant compatibility problems for previously recorded media. To minimize the adverse impact of hardware and software dependence, libraries prefer paper or microfilm for long-term storage copies, relying on optical disks for reference copies.

Storage and Handling

Optical storage media, like their magnetic counterparts, can be damaged by improper storage conditions and careless handling. As discussed above, hot and/or humid storage conditions promote oxidation and corrosion of read/write optical disks composed of metallic thin films. Specially designed alloys and passivation layers retard such media degradation, but they cannot prevent it. Read-only and read/write optical disk substrates are likewise adversely affected by high temperatures and relative humidities. While optical disks are more resistant to wear than magnetic tapes or diskettes, they can be damaged by rough handling. Most read/write optical disks, as previously noted, are encapsulated in plastic cartridges to protect their recording surfaces from scratches, skin oils, fingerprints, dust, and other contaminants. Read-only optical disks, as well as CD-R and CD-RW media, are not enclosed in cartridges; their information-bearing surfaces are exposed during loading, unloading, and other handling. Such disks are coated to protect against scratches, as described above, but they are not impervious to damage. Audio Compact Discs, video disks, and other optical media that circulate to library users are particularly vulnerable to uncontrolled use environments and rough handling.

The potential for damage to optical disks can be minimized or eliminated, however, by strict adherence to the handling procedures and precautions outlined in the following discussion. The recommendations presented here are based on manufacturers' recommendations and various published guidelines. They apply equally to working and storage copies of optical disks:

1. Ideal temperature and humidity conditions for long-term storage of optical media are not defined by national or international standards. The formulation of all-encompassing storage specifications for optical disks is complicated by many factors, including the various combinations of recording technologies and media utilized by write-once, rewritable, and read-only optical disk systems. Manufacturers' product specifications typically indicate the environmental conditions under which their optical disk drives and media will operate reliably. With few exceptions, optical disk systems are engineered for use in ordinary office environments. Acceptable operating temperatures cited in product literature for read/write optical disk drives range from 10 to 60 degrees Celsius (50 to 140 degrees Fahrenheit), with a maximum gradient of 10 to 20 degrees Celsius (50 to 68 degrees Fahrenheit) per hour. Relative humidities can range from 10 to 80 percent, with a maximum gradient of 10 to 20 percent per hour. A broader range of environmental conditions is specified for media storage-minus 10 degrees to plus 50 degrees Celsius (16 to 122 degrees Fahrenheit), with a relative humidity of 10 to 90 percent. These manufacturers' recommendations are so permissive as to be meaningless. They are obviously less stringent than the long-term storage specifications presented in the preceding discussion of magnetic media. Given that high temperature and high humidity promote oxidation, a cool, dry storage environment cannot be harmful to optical disks, but it is uncertain whether it is helpful. The previously cited stability tests for CD-R media assume storage conditions of 25 degrees Celsius (77 degrees Fahrenheit) with 40 percent relative humidity, but published reports and manufacturers' product literature do not indicate whether the life spans of other optical storage media can be extended by comparably tight environmental controls.

2. Based on the manufacturers' recommendations cited above, optical disks require minimal climate controls to attain life spans that equal or exceed those of magnetic media maintained in very tightly controlled environments. For medium-term storage of computer information, video images, or audio recordings within the limits permitted by specific media, librarians may consequently prefer optical disks to magnetic tapes or diskettes.

3. Given the moisture-absorbing tendencies of polycarbonate and PMMA materials, optical disks with plastic substrates should not be stored or used in humid areas. Extreme temperatures should likewise be avoided. Optical disks should never be stored in direct sunlight, placed near radiators, or otherwise exposed to intense heat sources. When optical disks are placed on top of their drives, they are exposed to both heat and dust. Where libraries circulate Compact Discs or other optical media, borrowers should be advised not to leave them in cars during winter or summer months.

4. Dust and debris will adversely affect the performance of read/write and read-only optical disks. Storage and work areas should consequently be cleaned regularly. To minimize scattering of dust particles and other potentially harmful contaminants, proper housekeeping habits, as outlined in the preceding discussion of magnetic media, must be observed.

5. As previously described, most read/write optical disks are encapsulated in plastic cartridges to protect their recording surfaces against careless handling and minimize exposure to airborne debris. Contact with such media should be limited to their protective housings. Optical disk cartridges should be lifted by their edges and handled gently. Recording surfaces should never be touched. The cartridge shutter, which exposes the recording surface when an optical disk is mounted in an appropriate drive, should never be retracted manually.

6. Because optical disk cartridges are not hermetically sealed, dust particles may enter through small openings. Such particles can affect a disk's optical characteristics and damage drive mechanisms. To remove debris, several manufacturers offer cleaning kits for use with read/write optical media. Such cleaning kits, which typically include solutions and cloths, should always be used in strict conformity with manufacturers' directions and only with those media for which they are specifically designed.

7. Because they are not housed in protective cartridges, the information-bearing surfaces of Compact Discs and video disks are exposed to rough handling and contaminants. To guard against the damaging effects of skin oils and fingerprints, contact with information-bearing surfaces should be avoided. Compact Discs and video disks should be handled by their outer edges. Compact Discs are typically packaged in plastic containers popularly termed "jewel boxes." Video disks are packaged in cardboard sleeves similar to those employed by phonograph records. To prevent scratches and minimize exposure to potentially abrasive airborne debris, Compact Discs and video disks should be kept in their containers when not in use. Dust should be cleared from these containers prior to removing the disks.

8. CD-R media may be damaged by exposure to light. Their dye layers can fade, with a resulting reduction of contrast that impairs retrieval of recorded information. CD-R media should be stored in jewel boxes or other containers when not in use, and the containers should be kept in closed cabinets. Light stability is not an issue with other dye-based optical disks, which are encapsulated in plastic cartridges that protect them from light. CD-R media, as previously described, are not housed in cartridges.

9. Martin (1993) notes that readability problems can often be resolved by cleaning Compact Discs. Dust can be removed from Compact Discs and video disks with a soft, lint-free cloth by wiping them in a circular motion from the center to the outer edges. Dust should always be removed from disks prior to use. Several manufacturers offer cleaning kits for Compact Discs. Such kits should always be used in strict conformity with their manufacturers' directions. Conventional household cleaners should never be used with read-only optical disks; they contain solvents that can damage a disk's protective overcoat.

10. Food, spilled liquids, and smoke particles can contaminate or otherwise damage optical media. Eating, drinking, and smoking should consequently be prohibited in all areas where optical disks are used or stored. Boiling water or otherwise creating water vapors must likewise be avoided.

11. Do not squeeze or otherwise apply pressure to optical disk cartridges. Do not place books or other heavy objects on top of them. Care must be taken to avoid bending Compact Discs and video disks when removing them from or inserting them into their containers. Read/write and read-only optical disks should not be stacked horizontally on tables or desktops. To prevent warpage, they should be shelved in a vertical, upright position. Several companies offer special storage units for optical disk cartridges, Compact Discs, and video disks.

12. Information recorded on most optical disks is unaffected by magnetic fields. Magneto-optical disks are an exception; they are subject to accidental erasure through inadvertent exposure to magnetic fields of sufficient coercivity. While the danger of accidental erasure is often exaggerated, permanent magnets and other objects that generate magnetic fields must be prohibited in areas where magneto-optical media will be stored or used. To avoid inadvertent exposure to magnetic fields in transit, a distance of three inches should be maintained between magneto-optical disks and the sides of transport containers. As previously noted, specially designed transit cases are available for this purpose.

13. Bar codes or other adhesive labels should never be affixed to the nonrecorded site of Compact Discs. Such labels may contain solvents that can damage a disk's protective coating and reflective metal layer. For the same reason, permanent markers should not be used to label such disks. Markers with water-soluble ink are acceptable, however. Some companies offer CD-R media that are designed for ink jet or thermal transfer labels, but a misaligned label can put a Compact Disc out of balance when it is spinning at high speed. Further, removal of an adhesive label can damage a Compact Disc's protective coating. Ballpoint pens or other writing instruments with sharp points should never be used to label Compact Discs. They can damage a medium's protective coating.

14. Equipment operators, librarians, or others responsible for the care and handling of optical disks should visually inspect each medium prior to use or on return from circulation. Unusual conditions should be reported for corrective action. Examples of such conditions include damage to the protective cartridges of read/write optical media; scratches or other physical damage to Compact Discs and video disks; and excessive amounts of dust or other debris on media or containers. Suspect disks should be tested immediately for usability. In the case of write-once and rewritable media, a new copy should be made of any disk that appears to be physically or chemically damaged.

15. Optical disks that contain valuable information intended for long-term storage should be used as infrequently as possible, since each use subjects media to possible damage from improperly adjusted equipment or careless handling. One or more working copies should be made to satisfy reference requirements.

16. To facilitate the early detection of problems, optical disks in long-term storage should be inspected annually or at shorter intervals. The inspection should involve a visual examination of the medium and its housing, followed by retrieval or playback of recorded information. In a large collection of optical storage media, examination of individual disks may prove prohibitively time-consuming. In such situations, a portion of the collection can be sampled. Alternatively, one or more control media containing test signals can be created. Such control media should be created on the same system, from the same recording materials, and with the same recording characteristics as information-bearing media. The control media should be inspected for usability and physical damage on a regular basis-annually or at shorter intervals. If permanent errors are detected in one or more control disks, the entire collection must be examined.

17. To overcome limitations associated with the non-archival nature of optical recording materials, the contents of read/write optical disks can be copied onto new media at intervals shorter than the estimated life spans of the original disks. Used regularly and repeatedly, such periodic copying can extend the life of recorded information indefinitely. For convenient information transfer, a dual-drive optical recording system is recommended. Given the high storage capacity of write-once and rewritable optical disks, librarians are cautioned that a considerable amount of time may be required to copy the contents of a single disk.

Equipment Considerations

The performance of read/write and read-only optical disks is dependent on and affected by the equipment on which given media will be used for recording and/or playback:

All equipment must be in proper operating condition. Defective equipment should be repaired immediately and not used until repairs are completed. Preventive maintenance procedures recommended by the equipment's manufacturer should be enforced.

Where applicable, machine components should be cleaned regularly in a manner specified by the equipment manufacturer.

Optical disks should not be mounted on or loaded into equipment until they are ready for recording or playback. Optical disks should be removed from their drives immediately after use.

Some computer peripherals, such as printers, generate debris. Optical disks and drives should be located as far away from such devices as is practical.

REFERENCES

Abe, M. and M. Gomi. 1990. Magneto-optical recording on garnet films. Journal of Magnetism and Magnetic Materials 84 (3): 222-28.

Adelstein, P. 1976. A progress report: ANSI activities on stability of processed diazo and vesicular films. Journal of Micrographics 9 (4): 99-101.

Adelstein, P. 1984. Medium term, long term, and archival properties of photographic materials. In Proceedings of the National Bureau of Standards/National Security Agency Workshop on Standardization Issues for Optical Digital Data Disk (OD3) Technology. Washington, D.C.: National Bureau of Standards, 136-39.

Adelstein, P. 1986. Status of permanence standards. Journal of Imaging Technology 12 (1): 52-56.

Adelstein, P. and J. McCrea. 1965. Permanence of processed Estar polyester base photographic films. Photographic Science and Engineering 9 (3): 305-313.

Adelstein, P. and J. McCrea. 1977. Dark image stability of diazo films. Journal of Applied Photographic Engineering 3 (3): 173-78.

Adelstein, P. et al. 1981. Stability of processed polyester base photographic films. Journal of Applied Photographic Engineering 7 (6): 160-67.

Adelstein, P. et al. 1991. Hydrogen peroxide test to evaluate redox blemish formation on processed microfilm. Journal of Imaging Technology 17 (3): 91-98.

Adelstein, P. et al. 1992. Stability of cellulose ester base photographic film: I. Laboratory testing procedures. SMPTE Journal 101 (5): 336-46.

Adelstein, P. et al. 1992a. Stability of cellulose ester base photographic film: II. Practical storage considerations. SMPTE Journal 101 (5): 347-53.

Adelstein, P. et al. 1995. Stability of cellulose ester base photographic film: III. Measurement of film degradation. SMPTE Journal 104 (5): 281-91.

Adelstein, P. et al. 1995a. Stability of cellulose ester base photographic film: IV. Behavior of nitrate base film. SMPTE Journal 104 (6): 359-69.

Adelstein, P. et al. 1995b. Stability of cellulose ester base photographic film; V. Recent findings. SMPTE Journal 104 (7): 439-47.

Adelstein, P. 1996. Standards on the permanence of recording materials. In Proceedings of the SPIE, vol. CR61. Bellingham, Wash.: SPIE, 155-75.

Aisenberg, S. and M. Stein. 1981. Corrosion-resistant optical storage media. IBM Technical Disclosure Bulletin 24 (1A): 303-4.

Akahira, N. et al. 1995. High density recording on phase change optical disks. In Proceedings of the SPIE, vol. 2514. Bellingham, Wash.: SPIE, 294-301.

Akashi, G. 1982. The development of metal powder for magnetic recording. In Ferrites: Proceedings of the ICF3, Third International Conference on Ferrites. Dordrecht, The Netherlands: Reidel, 548-52.

Akiyama, T. et al. 1995. New disk structure for million cycle overwritable phase change optical disk. Optical Review 2 (2): 100-102.

Ali, I. et al. 1989. Stability of chromium dioxide particles in aqueous media. Colloid and Polymer Science 267 (3): 255-61.

Allen, N. et al. 1987. Degradation of historic cellulose triacetate cinematographic film: The vinegar syndrome. Polymer Degradation and Stability 19 (4): 379-87.

Allen, N. et al. 1988. Acid-catalysed hydrolytic degradation of historic cellulose triacetate cinematographic film: The vinegar syndrome. In Proceedings of the Fifteenth Water-Borne and Higher-Solids Coating Symposium. Hattiesburg, Miss.: University of Southern Mississippi, 94-103.

Allen, N. et al. 1988a. Degradation of cellulose triacetate cinematographic film: Prediction of archival life. Polymer Degradation and Stability 23 (1): 43-50.

Amemiya, M. et al. 1980. Formation and magnetic properties of gamma ferric-oxide particles surface modified with crystallized cobalt-ferrite. IEEE Transactions on Magnetics 16 (1): 17-19.

Anderson, M. and V. Wagner. 1964. Stability of vesicular microfilm images. Photographic Science and Engineering 14 (2): 353-58,

Anderson, S. and D. Kopperl (1993). Limitations of accelerated image stability testing. Journal of Imaging Science and Technology 37 (4): 363-73.

Anoikina, T. et al. 1996. Archivability of metal-based flexible media. In Proceedings of the Symposium on Critical Factors in Localized Corrosion II. Pennington, N.J.: Electrochemical Society, 175-87.

Anoikina, T. et al. 1996a. Microscopic studies of corrosion phenomena in metal evaporated metal particle flexible media. IEEE Transactions on Magnetics 32 (5): 4016-18.

Aoyama, S. et al. 1991. The behavior of lauric acid lubricant in a magnetic coating layer and its effect on mechanical properties of magnetic media. IEEE Transactions on Magnetics 27 (2): 791-94.

Aoyama, S. et al. 1993. Surface chemical properties of cobalt modified gamma ferric oxide magnetic particles. Journal of Materials Science 28 (16): 4451-55.

Arai, K. et al. 1995. New tracking method using crosstalk signals for an optical tape recording system. In Proceedings of the SPIE, vol. 2514. Bellingham, Wash.: SPIE, 144-52,

Aratani, K. et al. 1985. Magnetic and magneto-optic properties of Tb-FeCo-Al films. Journal of Applied Physics 57 (8): 3903-3905.

Aratani, K. et al. 1987. Aging changes of some properties of amorphous TbFeAl thin films as magneto-optical recording medium. IEEE Translation Journal on Magnetics in Japan 2 (5): 393-94.

Arimune, H. et al. 1985. Environmental stability of the magneto-optic medium. IEEE Translation Journal on Magnetics in Japan 1 (3): 337-38.

Arimune, H. et al. 1987. Thermal stability and reliability of magneto-optical media with periodic structures. IEEE Translation Journal on Magnetics in Japan 2 (3): 401-3.

Armstrong, P. 1987. Premastering and mastering. In CD ROM: Optical Publishing. Redmond, Wash.: Microsoft Press, 217-26.

Arroyo, J. et al. 1994. Electrochemical evaluation of the effect of binder additives on iron corrosion. Journal of Applied Physics 75 (10): 5568-70.

Asano, K. et al. 1996. The magnetic switching volume of cobalt-modified iron oxides and its application to improved video properties. Journal of Magnetism and Magnetic Materials 155 (1-3): 107-9.

Asano, M. et al. 1987. Magneto-optical recording media with new protective films. IEEE Transactions on Magnetics 23 (5): 2620-22.

Auweter, H. et al. 1990. Chromium dioxide particles for magnetic recording. IEEE Transactions on Magnetics 26 (1): 66-68.

Avedon, D. 1972. Microfilm permanence and archival quality standards. Special Libraries 63 (12): 586-88.

Avedon, D. 1978. Archival quality and performance of microfilm. IMC Journal 1 (1): 12-14.

Avedon, D. and A. DeVilliers. 1979. Microfilm permanence and archival quality. Journal of the American Society for Information Science 30 (2): 100-102.

Bagg, T. 1976. Evaluation of Transparent Electro-Photographic Film and Camera System. Washington, D.C.: National Bureau of Standards.

Bair, H. et al. 1978. Water sorption of polycarbonate and its effect on the polymer's dielectric behavior. Journal of Applied Physics 49 (10): 4976-84.

Baker, M. and A. Bezur. 1996. Micro-ATR analysis of polyurethane binders in museum videotape collections: Natural aging reactions in archive tapes. Polymer Preprints 37 (2): 180-81.

Balasubramanian, K. 1992. Materials and design issues of multilayer magneto-optical thin-film media for optical recording. Optical Engineering 31 (12): 2674-86.

Ballou, H. and J. Rather, 1955. Microfilm and microfacsimile publications. Library Trends 4 (2): 182-94.

Barger, M. et al. 1983. Gilding and sealing daguerrotypes. Photographic Science and Engineering 27 (4): 141-46.

Bartholomeusz, B. 1989. Thermo-magnetic marking of rare-earth transition-metal thin films. Journal of Applied Physics 65 (1): 262-68.

Bartholomeusz, B. and T. Hatwar. 1989. Modeling studies of rare earth-transition metal optical recording media in relation to experiment. Thin Solid Film 181 (2): 115-28.

Basile, G. et al. 1980. An empirical correlation between print through values and magnetic characteristics of chromium dioxide powders. IEEE Transactions on Magnetics 16 (1): 59-61.

Bate, G. 1987. Materials challenges in metallic, reversible, optical recording media: A review. IEEE Transactions on Magnetics 23 (1): 151-61.

Batis-Landoulsi, H. and P. Vergnon. 1983. Magnetic moment of gamma ferric oxide microcrystals: Morphological and size effect. Journal of Materials Science 18 (11): 3399-3403.

Beeman, D. 1975. Micrographic standards for containers (cartridges and cassettes) for 16mm roll microfilm. Journal of Micrographics 9 (3): 51-54.

Behr, M. and J. Osborn. 1981. Technique for measuring dynamically the dimensional stability of a flexible magnetic storage disk. IEEE Transactions on Magnetics 17 (6): 2748-50.

Bell, A. 1980. Optical disks for information storage. Nature 287 (6): 583-85.

Bell, A. 1983. Optical data storage technology: Status and prospects. Computer Design 22 (1): 133-38.

Bell, A. 1986. Materials for reversible optical storage. In IEE Colloquium on Optical Mass Storage. London: IEE, 5/1-5.

Bennett, H. 1997. CD-R media, readers, and writers. EMedia Professional 10 (9): 30-35.

Bennett, M. 1988. Rewritable optical technology and applications. In Proceedings of the Fifth Annual Conference on Optical Information Systems. London: Meckler, 221-28.

Berkowitz, A. et al. 1985. Microstructure, relaxation, and print-through in gamma ferric oxide particles. Journal of Applied Physics 57 (8): 3928-30.

Bernede, J. 1992. Materials for erasable optical disks. Materials Chemistry and Physics 32 (2): 189-95.

Bernstein, G. 1972. Why 24x/48x? Journal of Micrographics 5 (3): 295-300.

Bernstein, P. and C. Gueugnon. 1985. Properties of amorphous rare earth-transition metal thin films for magneto-optical recording. IEEE Transactions on Magnetics 21 (5): 1613-17.

Berry, B. and W. Pritchet. 1988. Elastic and viscoelastic behavior of a magnetic recording tape. IBM Journal of Research and Development 32 (5): 882-94.

Bertram, H. and A. Eshel. 1980. Recording Media Archival Attributes. Redwood City, Calif.: Ampex Corporation, Advanced Technology Division. (Available from the National Technical Information Service as report no. AD/A088 187/0)

Bertram, H. and E. Cuddihy. 1982. Kinetics of the humid aging of magnetic recording tape. IEEE Transactions on Magnetics 18 (5): 993-99.

Bertram, H. et al. 1980. The print-through phenomenon. Journal of the Audio Engineering Society 28 (10): 690-705.

Best, M. and R. Prime. 1993. Characterization and control of cure of polymer coating on optical disks. In Proceedings of the SPIE, vol. 1774. Bellingham, Wash.: SPIE, 169-80.

Bhushan, B. 1996. Tribology and Mechanics of Magnetic Storage Devices. New York: Springer-Verlag.

Bhushan, B. and D. Khatavkar. 1995. Role of tape abrasivity on friction, wear, staining and signal degradation in audio tapes. Wear 190 (1): 16-27.

Bhushan, B. and D. Khatavkar. 1996. Role of water vapor on the wear of the MnZn ferrite heads sliding against magnetic tapes. Wear 202 (1): 30-34.

Bhushan, B. and F. Hahn. 1995. Stains on magnetic tape heads. Wear 184 (2): 193-202.

Bhushan, B. and J. Lowry. 1994. Friction and wear of particulate and ME magnetic tapes sliding a Mn-Zn ferrite head in a linear mode. IEEE Transactions on Magnetics 30 (6): 4176-78.

Bhushan, B. and J. Lowry. 1995. Friction and wear studies of various head materials and magnetic tapes in a linear mode accelerated test using a new nano-scratch wear measurement technique. Wear 190 (1): 1-15.

Bhushan, B. and J. Monahan. 1995. Accelerated friction and wear studies of various particulate and thin-film magnetic tapes against tape path materials in pure sliding and rotary/sliding modes. Tribology Transactions 38 (2): 329-41.

Bhushan, B. and S. Patton. 1994. Friction and wear of ultrahigh-density magnetic tapes. Journal of Applied Physics 75 (19): 5771-73.

Bhushan, B. and V. Koinkar. 1995. Microtribology of metal particle, barium ferrite and metal evaporated magnetic tapes. Wear 181 (1): 360-70.

Bhushan, B. et al. 1984. Friction in magnetic tapes: II. Role of physical properties. ASLE Transactions 27 (2): 89-100.

Binkley, R. 1936. Manual on Methods of Reproducing Research Materials. Ann Arbor: Edwards Brothers, 1936.

Birecki, H. et al. 1985. Magnetooptic quadrilayer reliability and performance. In Proceedings of the SPIE, vol. 529. Bellingham, Wash.: SPIE, 19-24.

Birecki, H. et al. 1985a. Reliability and performance of magnetooptic recording media. In Digest of Papers-COMPCON Spring 85: Technological Leverage, A Competitive Necessity. Los Alamitos, Calif.: IEEE Computer Society Press, 83-85.

Blagev, A. and S. Hirz. 1992. Effect of surface properties on cobalt modification of iron oxides. IEEE Transactions on Magnetics 28 (5): 2382-84.

Blom, G. and D. Lou. 1984. Archival life of telurium-based materials for optical recording. Journal of the Electrochemical Society 131 (1): 146-51.

Blumentritt, B. 1979. Annealing of polyethylene terephthalate-film-based magnetic recording media for improved dimensional stability. IBM Journal of Research and Development 23 (1): 56-65.

Bottoni, G. 1995. Magnetization stability and interactions in particulate recording media. Materials Chemistry and Physics 42 (1): 45-50.

Bottoni, G. et al. 1990. Influence of the Co-doping of iron oxides on magnetic particle interactions. IEEE Transactions on Magnetics 26 (5): 1885-87.

Bouldin, E. and R. Haddock. 1990. Applications of an optical memory card as a portable medical record. In Proceedings of the SPIE, vol. 1248. Bellingham, Wash.: SPIE, 196-203.

Bowmer, T. et al. 1988. Characterization and hydrolysis of magnetic tapes. Polymer Preprints 29 (2): 258-59.

Bradshaw, R. and B. Bhushan. 1984. Friction in magnetic tapes: III. Role of chemical properties. ASLE Transactions 27 (3): 207-19.

Bradshaw, R. and S. Falcone. 1988. Polyester-polyurethane interactions with chromium dioxide. Polymer Preprints 29 (2): 266-67.

Bradshaw, R. and T. Reid. 1991. Archival stability of IBM 3480/3490 cartridge tapes. IEEE Transactions on Magnetics 27 (5): 4388-95.

Bradshaw, R. et al. 1986. Chemical and mechanical performance of flexible magnetic tape containing chromium dioxide. IBM Journal of Research and Development 30 (2): 203-16.

Brandt, E. 1984. Mechanistic studies of silver image stability: I. Redox chemistry of oxygen and hydrogen peroxide at clean and at adsorbate-covered silver electrodes. Photographic Science and Engineering 28 (1): 1-12.

Brandt, E. 1984a. Mechanistic studies of silver image stability: II. Iodide absorption on silver in the presence of thiosulfate and the influence of adsorbed iodide on the catalytic properties of silver toward hydrogen peroxide. Photographic Science and Engineering 28 (1): 13-19.

Brandt, E. 1987. Mechanistic studies of image stability: III. Oxidation of silver from vantage point of corrosion theory. Journal of Imaging Science 31 (5): 199-207.

Bray, A. and C. Corley. 1994. 3M DC6150 data cartridge archival storage integrity estimation via accelerated life testing. In Proceedings of the Annual Reliability and Maintainability Symposium (RAMS). New York: IEEE, 105-9.

Brems, K. 1988. The archival quality of film bases. SMPTE Journal 97 (12) 991-93.

Broadhurst, R. 1976. An Investigation of the Effects of Exposure to Light on Diazo Microfilm. Hatfield, England: National Reprographic Centre for Documentation.

Brown, D. et al. 1984. Hydrolysis of crosslinked polyester polyurethanes. In Proceedings of the ACS Division of Polymeric Materials Science and Engineering, vol. 51. Washington, D.C.: American Chemical Society, 155-61.

Brown, D. et al. 1984a. Predictions of Long-Term Stability of Polyester-Based Recording Media. Gaithersburg, Md.: National Bureau of Standards, NBSIR 84-2988.

Brown, D. et al. 1986. Predictions of Long-Term Stability of Polyester-Based Recording Media. Gaithersburg, Md.: National Bureau of Standards, NBSIR 86-3474.

Brown, J. 1989. A new computer memory for biology and medicine using the laser card. Computers in Biology and Medicine 19 (6): 375-83.

Bruneau J. et al. 1997. Optical properties of phase change materials for optical recording. In 1997 Optical Data Storage Topical Meeting ODS: Conference Digest. New York: IEEE, 104-5.

Burton, G. 1990. Disaster (almost). Stereo Review 55 (11): 101-3.

Buschow, K. 1988. Magneto-optical properties of alloys and intermetallic compounds. In Ferromagnetic Materials: A Handbook on the Properties of Magnetically Ordered Substances. Amsterdam: North-Holland Physics Publishing, 493-595.

Buschow, K. 1989. Magneto-optical recording materials. Journal of Less-Common Metals 155 (2): 307-18.

Calmes, A. 1987. To archive and preserve: A media primer. Inform 1 (5): 14-17, 33.

Camras, M. 1988. Magnetic Recording Handbook. New York: Van Nostrand Reinhold.

Carasso, M. et al. 1982. Compact disc digital audio system. Philips Technical Review 40 (1): 151-55.

Carcia, P. et al. 1988. Stability of Te-Cu amorphous alloy thin films for optical recording. Journal of Applied Physics 64 (4): 1671-78.

Chacko, A. et al. 1993. Studies into the chemical and physical processes limiting the archival lifetime of metal particle tape: 1. Use of electron paramagnetic resonance spin probe techniques. In Proceedings of the ACS Division of Polymeric Materials Science and Engineering, vol. 69. Washington, D.C.: ACS Books and Journals Division, 335-36.

Chen, H. et al. 1984. Advances in properties and manufacturing of chromium dioxide. IEEE Transactions on Magnetics 20 (1): 24-26.

Chen, M. and K. Rubin. 1989. Progress of erasable phase-change materials. In Proceedings of the SPIE, vol. 1078. Bellingham, Wash.: SPIE, 150-56.

Chen, M. et al. 1983. Characterization of optical recording disk noise. In Proceedings of the SPIE, vol. 420. Bellingham, Wash.: SPIE, 306-12.

Chen, M. et al. 1985. Reversibility and stability of tellurium alloys for optical data storage. Applied Physics Letters 49 (9): 734-36.

Chen, M. et al. 1986. Compound materials for reversible, phase-change optical storage. Applied Physics Letters 49 (9): 502-4.

Cheng, W. et al. 1990. Mechanical behaviour of poly methyl methacrylate: 1. Tensile strength and fracture toughness. Journal of Materials Science 25 (4): 1917-23.

Cheng, W. et al. 1990a. Mechanical behaviour of poly methyl methacrylate: 2. The temperature and frequency effects on fatigue crack propogation behaviour. Journal of Materials Science 25 (4): 1924-30.

Chhabra, V. et al. 1996. Preparation of ultrafine high density gamma ferric oxide using aerosol OT microemulsions and its characterization. Colloid and Polymer Science 273 (10): 939-46.

Chiba, K. et al. 1989. Metal evaporated tape for high band 8mm video system. IEEE Transactions on Consumer Electronics 35 (3): 421-28.

Chiba, R. et al. 1995. Phase-change optical disks compatible with a two-wavelength laser beam. Applied Optics 34 (32): 7588-96.

Ching-Shan, J. et al. 1994. Degradation of passivated iron particles in humid atmospheres. IEEE Transactions on Magnetics 30 (6): 4065-67.

Choe, G. and R. Walser. 1990. Effect of bias sputtering on stability of amorphous Th sub 32 Fe sub 68 compositionally-modulated thin films. Journal of Applied Physics 67 (9): 5316-18.

Chubachi, R. and N. Tamagawa. 1984. Characteristics and applications of metal tape. IEEE Transactions on Magnetics 2 (1): 45-47.

Chung, C. et al. 1984. Stability of 3M DRAW optical recording media. In Topical Meeting on Optical Data Storage: Technical Digest. Washington, D.C.: Optical Society of America, 1/1-4.

Clover, J. 1984. Measurement techniques and standards: Thin film technology. In Proceedings of the National Bureau of Standards/National Security Agency Workshop on Standardization Issues for Optical Digital Data Disk (OD3) Technology. Washington, D.C.: National Bureau of Standards, 176-77.

Cochrane, K. 1996. Is there a CD-R media problem? CD-ROM Professional 9 (2): 52-61.

Comstock, D. et al. 1974. Dropout identification and cleaning methods for magnetic tape. Journal of the Audio Engineering Society 22 (7): 511-19.

Connell, G. 1986. Magneto-optics and amorphous metals: An optical storage revolution. Journal of Magnetism and Magnetic Materials 53 (3): 1561-66.

Coombs, J. et al. 1994. A CD-compatible erasable disc. In Proceedings of the SPIE, vol. 2338.Bellingham, Wash.: SPIE, 94-106.

Cope, O. 1982. Diazo and vesicular microfilm technologies. Journal of Applied Photographic Engineering 8 (5): 190-99.

Cornet, J. 1983. Deformation recording process in polymer-metal bilayers and its use for optical storage. In Proceedings of the SPIE, vol. 420. Bellingham, Wash.: SPIE, 86-95.

Corradi, A. et al. 1982. Cobalt-modified iron oxides: A critical review based on new experimental data. In Ferrites: Proceedings of the ICF3, Third International Conference on Ferrites. Dordrecht, The Netherlands: Reidel, 526-31.

Corradi, A. et al. 1984. Print-through, erasability, playback losses: Different phenomena from the same roots. IEEE Transactions on Magnetics 20 (5): 760-62.

Corradi, A. et al. 1987. Reversible coercivity vs. temperature losses in activated cobalt adsorbed iron oxides. IEEE Transactions on Magnetics 23 (1): 48-52.

Corradi, A. et al. 1989. On the stability properties of new semidoped/ stabilized cobalt modified recording oxides. Crystalline Properties and Preparations 27 (2): 875-79.

Cory, C. 190. Implementing optical card technologies. Optical Information Systems 10 (1): 44-52.

Crandall, T. et al. 1987. Improved quality chromium dioxide particles. IEEE Transactions on Magnetics 23 (1): 36-38.

Crasemann, J. et al. 1989. Thermo-magnetic switching on rare-earth transition-metal alloy magneto-optic disks. Journal of Applied Physics 66 (3): 1273-78.

Crawford, B. 1988. Pitfalls of CD manufacturing. Microcontamination 6 (1): 39-42.

Crissman, J. and G. McKenna. 1990. Physical and chemical aging in PMMA and their effects on creep and creep rupture behavior. Journal of Polymer Science, Part B 28 (9): 1463-73.

Criswell, L. 1983. Serials on optical disks: A Library of Congress pilot program. Library Hi Tech 1 (3): 17-21.

Croll, M. 1991. The life expectancy of optical recording. Image Technology 73 (4): 134-38, 142.

Croucher, M. and M. Hopper. 1987. Materials for optical disks. Chemtech 17 (3): 426-33.

Cuddihy, E. 1976. Hygroscopic properties of magnetic recording tape. IEEE Transactions on Magnetics 12 (2): 126-35.

Cuddihy, E. 1980. Aging of magnetic recording tape. IEEE Transactions on Magnetics 16 (4): 558-65.

Cuddihy, E. 1983. Chemical aging mechanism of magnetic recording tape. In Organic Coatings and Applied Polymer Science Proceedings, vol. 48. Washington, D.C.: American Chemical Society, 422-26.

Cuddihy, E. 1984. Chemical aging mechanism of magnetic recording tape. In Tribology and Mechanics of Magnetic Storage Systems: ASPE Special Publication 16. Park Ridge, Ill.: ASLE, 21-26.

Cullity, B. 1972. Introduction to Magnetic Materials. Reading, Mass.: Addison-Wesley Publishing Company.

Dancygier, M. 1987. Magnetic properties of TbFe amorphous alloys deposited on Kapton: Optical tape feasibility. IEEE Transactions on Magnetics 23 (5): 2608-10.

Davis, D. 1987. Optical archiving: Where are we now and where do we go from here? Optical Information Systems 7 (1): 66-71.

Davison, G. 1961. Microcards and microfiches: History and possibilities. Library Association Record 63 (1): 69-78.

Davison, P. et al. 1968. Ageing of magnetic tape: A critical bibliography and comparison of literature sources. Computer Journal 11 (3): 241-46.

Day, R. 1989. Where's the rot? A special report on CD longevity. Stereo Review 54 (4): 23-24.

Dean, J. 1983. Advances in preservation technology and library binding. Serials Review 9 (3): 95-97.

De Martino, A. 1993. The laser card: A challenge for physicians. In Patient Care with Computers and Cards: Fifth Global Congress on Patient Cards and Computerization of Health Records. Newton, Mass.: Medical Records Institute, 33-35.

Demazeau, G. et al. 1979. Materials for magnetic recording derived from chromium dioxide. Materials Research Bulletin 14 (1): 121-26.

Demazeau, G. et al. 1980. New magnetic materials derived from chromium dioxide. IEEE Transactions on Magnetics 16 (1): 9-10.

Demetriades, J. and E. Gomez. 1990. Optical patient card prototype within the Department of Veterans Affairs. UG Quarterly 20 (1): 109-12.

Deng, M. et al. 1992. Acicular gamma ferric-oxide particles surface-coated with barium ferrite. IEEE Transactions on Magnetics 28 (5): 2385-87.

Djalali, A. et al. 1991. Study of the stability of metal particle data recording tapes. Journal of the Electrochemical Society 138 (9): 2504-9.

Dodson, S. 1985. Microfilm: Which film type, which application? Microform Review 14 (2): 87-94, 96-98.

Dorfman, H. 1993. Diazo duplicating microfilm. International Journal of Micrographics and Optical Technology 11 (2): 69-75.

Drago, F. and W. Lee. 1984. Stability and restoration of image on Kodak professional duplicating film/4168. Journal of Imaging Technology 19 (3): 113-18.

Drago, F. and W. Lee. 1986. Review of the effects of processing on the image stability of black-and-white silver materials. Journal of Imaging Technology 12 (1): 57-64.

Drexler, J. 1981. Drexon optical memory media or laser recording and archival data storage. Journal of Vacuum Science and Technology 18 (1): 87-91.

Drexler, J. 1982. Laser card for compact optical data storage system. In Proceedings of the SPIE, vol. 329. Bellingham, Wash.: SPIE, 61-68.

Drexler, J. 1983. The Drexon product family for laser recording and digital data storage: A status report. In Proceedings of the SPIE, vol. 420. Bellingham, Wash.: SPIE, 57-59.

Drotning, W. and E. Roth. 1989. Effects of moisture on the thermal expansion of polymethylmethacrylate. Journal of Materials Science 24 (9): 3137-40.

Dupont, J. 1986. Microform film stock, a Hobson's choice: Are librarians getting the worst of both worlds? Library Resources and Technical Services 30 (1): 79-83.

Edge, M. et al. 1991. Aspects of poly(ethylene terephthalate) degradation for archival life and environmental degradation. Polymer Degradation and Stability 32 (2): 131-53.

Edge, M. et al. 1992. Methods for predictive stability testing of archival polymers: A preliminary assessment of cellulose triacetate based motion picture film. Polymer Degradation and Stability 35 (2): 147-55.

Edge, M. et al. 1993. Degradation of magnetic tape: Binder oxidation studies. European Polymer Journal 29 (8): 1031-35.

Edge, M. et al. 1993a. Degradation of magnetic tape: Support and binder stability. Polymer Degradation and Stability 39 (2): 207-14.

Edwards, I. 1987. Optical storage developments: Write-once media. Electronic and Optical Publishing 7 (1): 16-20.

Eiling, A. et al. 1986. Magnetic and storage properties of co-modified pigments. IEEE Transactions on Magnetics 22 (5): 741-43.

Emmelius, M. et al. 1989. Materials for optical data storage. Angewandte Chemie: International Edition in English 28 (11): 1445-71.

Engler, E. 1990. Advanced materials for reversible optical storage. Advanced Materials 2 (4): 166-73.

Farrow, M. and E. Marinero. 1990. Corrosion processes in magneto-optic films. Journal of the Electrochemical Society 137 (3): 808-14.

Feldman, L. 1981. Discoloration of black-and-white photographic prints. Journal of Applied Photographic Engineering 7 (1): 1-9.

Ferebee, M. and J. Kibler. 1989. The earth radiation budget experiment optical disk archival system. Optical Information Systems 9 (1): 1-9.

Fernandez, A. and A. Moya, 1993. Estudio de la contaminacion microbiana en microfichas durante el proceso de microfilmacion [A study of microbial contamination of microfiche during the microfilming process]. Ciencias de la Informacion 24 (2): 110-15.

Fernandez, A. and A. Moya. 1993a. Estudio de la contaminacion microbiana en microfichas conservadas en el Instituto de Historia de Cuba [Study of microbial contamination on microfiche stored at the Institute of History of Cuba]. Clencias de la Informacion 24 (2): 116-20.

Fischer, G. et al. 1993. Aging effects of metal evaporated tapes. IEEE Transactions on Magnetics 29 (6): 3757-59.

Fisher, R. et al. 1982. Magnetic characteristics of gamma ferric oxide dispersions. IEEE Transactions on Magnetics 18 (6): 1098-1100.

Flanders, P. 1986. Remanence loss in gamma ferric-oxide tapes as related to reptation, viscosity, and print-through. IEEE Transactions on Magnetics 22 (3): 145-48.

Flanders, P. and M. Sharrock. 1987. An analysis of time-dependent magnetization and coercivity and of their relationship to print-through in recording tapes. Journal of Applied Physics 62 (7): 2918-28.

Fleischer, C. et al. 1996. Film as a composite material. MRS Bulletin 21 (7): 14-19.

Flower, P. 1992. Reference applications of color microfiche: The world in the palm of your hand. Microform Review 21 (2): 62-66.

Folcarelli, R. et al. 1982. The Microform Connection: A Basic Guide for Libraries. New York: Bowker.

Fowkes, F. et al. 1988. Surface and colloid chemical studies of gamma iron oxides for magnetic memory media. Colloids and Surfaces 29 (3): 243-61.

Francis, B. 1988. PC back-up's optical understudy. Datamation 34 (25): 57-60.

Green, I. 1988. The new face of C-O-M: Arkive IV/CRS. Optical Information Systems 8 (2): 84-85.

Greenberg, H. et al. 1977. Dimensional stability of floppy disks. IEEE Transactions on Magnetics 13 (5): 1397-99.

Greidanus, F. 1990. Status and future of magneto-optical disk drive technologies. Philips Journal of Research 45 (1): 19-34.

Greidanus, F. and W. Bas Zeper. 1990. Magneto-optical storage materials. MRS Bulletin 15 (4): 31-39.

Greidanus, F. et al, 1989. Thermomagnetic writing in thin Co/Pt layered structures. Applied Physics Letters 54 (24): 2481-83.

Grundy, P. et al. 1987. Stability and microstructural phenomena in RE-TM films for thermo-magneto-optic recording. IEEE Transactions on Magnetics 23 (5): 2632-34.

Guibert, H. and A. Gamache. 1993. Optical memory card applicability for implementing a portable medical record. Medical Informatics 18 (3): 271-78.

Gunn, M. 1978. Document microphotography in colour. British Journal of Photography 10 (1): 121-25.

Gunn, M. 1979. Colour microforms and their application to the visual arts. Microform Review 8 (3): 187-92.

Gunn, M. 1985. Current developments in colour microform technology. Microform Review 14 (1): 21-23.

Gunther, A. 1962. Microphotography in the library. UNESCO Bulletin for Libraries 14 (1): 1-22.

Habib, P. and J. Plumadore. 1974. A new microelectrophotographic system. Journal of Micrographics 7 (1): 249-54.

Hadad, A. and P. Pizzo. 1992. Effect of Temperature, Humidity, and Silicon Content on the Oxidation of Fine Iron Particles. In Symposium on Corrosion of Electronic and Magnetic Materials. ASTM Special Publication No. 1148. Philadelphia: ASTM, 53-67.

Hadfield, D. 1989. Magnetic materials in the third millenium. Materials and Design 10 (5): 222-30.

Haines, R. 1981. Chromium dioxide magnetic media. IBM Technical Disclosure Bulletin 24 (3): 1648.

Han, D. and Z. Yang. 1995. Remanence properties of substituted Ba-ferrite particles for high density magnetic recording. IEEE Transactions on Magnetics 31 (3): 2351-54.

Hansen, P. 1990. Magneto-optical recording materials and technologies. Journal of Magnetism and Magnetic Materials 83 (1): 6-12.

Hansen, P. and H. Heitmann. 1989. Media for erasable magneto-optic recording. IEEE Transactions on Magnetics 25 (6): 4390-4404.

Hartmann, M. et al. 1986. Improvement of corrosion resistance of GdTbFe by metal coatings. IEEE Transactions on Magnetics 22 (5): 943-45.

Hatwar, T. and D. Majumdar. 1988. Oxidation and corrosion resistance of TbFeCoPt alloy films. IEEE Transactions on Magnetics 24 (6): 2449-51.

Hatwar, T. et al. 1997. High-performance Co/Pt multilayer magneto-optical disk using ultrathin seed layers. Journal of Applied Physics 81 (8): 3839-41.

Hawken, W. 1966. Copying Methods Manual. Chicago: American Library Association.

Hayama, F. et al. 1982. Formation of cobalt-epitaxial iron oxides and their magnetic properties. In Ferrites: Proceedings of the ICF3, Third International Conference on Ferrites. Dordrecht, The Netherlands: Reidel, 521-25.

Hecht, J. 1982. Lasers store a wealth of data. High Technology 2 (3): 60-67.

Heitmann, H. et al. 1985. Amorphous rare earth-transition metal films for magneto-optical storage. Journal of Physics 46 (6): 9-18.

Heitmann, H. et al. 1987. Influence of preparation conditions on magnetic properties and aging behavior of rf diode sputtered GdTbCo films. Journal of Applied Physics 61 (8): 3331-33.

Hempstock, M. and J. Sullivan. 1996. Study of the mechanical and magnetic performance of metal evaporated tape. Journal of Magnetism and Magnetic Materials 155 (1-3): 323-28.

Henn, R. and D. Wiest. 1963. Microscopic spots in processed microfilm: Their nature and prevention. Photographic Science and Engineering 7 (5): 253-61.

Henn, R. and D. Wiest. 1965. Microscopic spots in processed microfilm: The effect of iodide. Photographic Science and Engineering 9 (3): 167-73.

Henn, R. and D. Wiest. 1965a. A gold protective treatment for microfilm. Photographic Science and Engineering 9 (6): 378-84.

Henn, R. and D. Wiest. 1966. Properties of gold-treated microfilm images. Photographic Science and Engineering 10 (1): 15-22.

Herd, S. et al. 1982. Structural changes in Se-Te bilayers by laser writing. Journal of Applied Physics 53 (5): 3520-22.

Hertel, D. et al. 1989. On the image quality of diazo materials. Journal of Photographic Science 37 (2): 44-48.

Herther, N. 1996. DVD: Taking the compact disc to new heights of power and function. Online 20 (5): 89-92, 94, 97-98.

Herzog, D. 1979. Description of a dry silver film tactical laser beam recorder. In Proceedings of the SPIE, vol. 200. Bellingham, Wash.: Society of Photo-Optical Instrumentation Engineers, 25-43.

Herzog, D. and L. Dobbins. 1983. Performance comparisons of electrophotographic, dry silver, and wet processed recording media exposed with gas laser and laser diode light sources for image recording. In Proceedings of the SPIE: The International Society for Optical Engineering, vol. 390. Bellingham, Wash.: SPIE, 149-54.

Hibst, H. 1988. Magnetic pigments for recording information. Journal of Magnetism and Magnetic Materials 74 (2): 193-202.

Higgins, B. and H. Oesterreicher. 1987. Properties and stability of Nd sub 2/Fe sub 14/B particles. IEEE Transactions on Magnetics 23 (1): 92-93.

Hill, A. et al. 1990. The effects of physical aging in polycarbonate. Journal of Polymer Science, Part B 28 (3): 387-405.

Hiller, D. 1978. High coercivity chromium dioxide. Journal of Applied Physics 49 (3): 1821-22.

Hiratsuka, H. et al. 1980. Material requirements for highly durable magnetic recording tape. Transactions of the Institute of Electronics and Communication Engineers of Japan, Section E 63 (6): 480-81.

Hiratsune, A. et al. 1995. New phase-change rewritable optical recording film having well suppressed material flow for repeated rewriting. Applied Physics Letters 66 (18): 2312-14.

Hiratsune, A. et al. 1996. High-density recording on a phase-change optical disk with suppression of material flow and recording-mark shape-deformation. Japanese Journal of Applied Physics, Part 135 (1B): 346-49.

Hirokane, J. et al. 1994. Recording characteristics of a magneto-optical super-resolution disk. In Proceedings of the SPIE, vol. 2338. Bellingham, Wash.: SPIE, 301-4.

Hoagland, A. and J. Monson. 1991. Digital Magnetic Recording. New York: John Wiley and Sons.

Horie, M. et al. 1992. Health information system using optical memory cards: The Isehara experience. In MEDINFO 92: Proceedings of the Seventh World Congress on Medical Informatics. Amsterdam: North Holland Publishing, 359-61.

Hosaka, H. 1988. Advances in magnetic and optical recording card. Journal of the Institute of Television Engineering of Japan 42 (4): 365-68.

Hosokawa, S. et al. 1985. Influence of storage conditions on magnetic tape life and its improvement. Transactions of the Institute of Electronic and Communications Engineering of Japan 68C (12): 1053-59.

Hourdajian, A. 1995. Hybrid color micro-imaging. In Final Program and Advance Printing of Papers, IS&T's Forty-Eighth Annual Conference: Imaging on the Information Superhighway. Springfield, Va.: Society for Imaging Science and Technology, 133-35.

Howe, D. 1994. CD error characterization; differences between CD-ROM and writable CD. In Proceedings of the SPIE, vol. 2338. Bellingham, Wash.: SPIE, 2-5.

Hubbell, D. et al. 1976. Methods for testing image stability of colour photographic products. Photographic Science and Engineering 11 (5): 295-305.

Huisman, H. 1984. Degradation of polyurethanes in organic solvents. In Organic Coatings, Science and Technology, vol. 6. New York: Marcel Dekker, 167-86.

Hume, A. 1988. The file-motel: An incremental backup system for Unix. In Proceedings of the Summer 1988 USENIX Conference. Berkeley, Calif.: USENIX Association, 61-72.

Huynh, T. and G. Thomas. 1989. Characterization of barium ferrite recording materials. In Proceedings of the MRS International Meeting on c Advanced Materials: Microstructure-Property Relationships in Magnetic Materials. Pittsburgh: Materials Research Society, 229-31,

Iijima, T. 1987. Highly stable indium alloyed TbFe amorphous films for ic magneto-optic memory. Applied Physics Letters 50 (25): 1835-37.

Iijima, T. and I. Hatakeyama. 1987. Stability properties of indium doped TbFe amorphous films for magneto-optic memory applications. IEEE Transact-ions on Magnetics 23 (5): 2626-28.

Imaoka, Y. et al. 1978. Characteristics of cobalt absorbed iron oxide tapes. IEEE Transactions on Magnetics 14 (5): 649-54.

Imaoka, Y. et al. 1982. Advances in magnetic recording media: From maghemite and chromium dioxide to cobalt adsorbed gamma ferric oxide. In Ferrites: Proceedings of the ICF3, Third International Conference on Ferrites. Dordrecht, The Netherlands: Reidel, 516-20.

Immink, K. 1996. The digital versatile disc (DVD): System requirements and channel coding. SMPTE Journal 105 (8): 483-89.

Inaba, H. et al. 1993. The advantages of the thin magnetic layer of a metal particulate tape. IEEE Transactions on Magnetics29 (6): 3607-12.

Inui, T. et al. 1987. Development of optical disk substrates. Sharp Technical Journal (37): 77-81.

Isailovic, J. 1985. Videodisc and Optical Memory Systems. Englewood Cliffs, N.J.: Prentice-Hall.

Isesaka, K. et al. 1989. The application of high-coercivity cobalt iron oxide tape for digital video recording. SMPTE Journal 98 (3): 168-72.

Isurugi, M. et al. 1989. Influence of surface roughness on durability of Co-Cr perpendicular magnetic recording media. IEEE Translation Journal on Magnetics in Japan 4 (1): 3-9.

Ito, H. and M. Naoe. 1990. Preparation of highly stable TbFeCo thin films by plasma-free sputtering at high rate. IEEE Transactions on Magnetics 26 (1): 181-83.

Ito, J. et al. 1990. Characteristics of S-VHS tape. IEEE Transactions on Magnetics 26 (1): 87-90.

Iwano, H. et al. 1994. Method for measuring the stability of silver images to aerial oxidation and the image stabilization by a thiol. Journal of Imaging Science and Technology 38 (2): 140-44.

Iwasaki, H. 1997. CD-rewritable and future disc technology. In 1997 Optical Data Storage Topical Meeting: Conference Digest. New York: IEEE, 9-10.

Iwasaki, H. et al. 1992. Completely erasable phase change optical disk. Japanese Journal of Applied Physics, Part 1 31 (2B): 461-65.

Iwasaki, H. et al. 1993. Completely erasable phase change optical disc: II. Application of Ag-In-Sb-Te mixed phase-system for rewritable compact disc compatible with CD-velocity and double CD-velocity. Japanese Journal of Applied Physics, Part 1 32 (11B): 5241-47.

Iwasaki, H. et al. 1995. CD-erasable (CD-E) disc technology. In Proceedings of the SPIE, vol. 2514. Bellingham, Wash.: SPIE, 200-201.

Izumi, H. et al. 1994. Magneto-optical disk techniques for high-data-density recording. Fujitsu Scientific and Technical Journal 30 (2): 224-31.

Jacobs, B. 1985. Thin film requirements for optical recording. Vacuum 35 (4): 445-46.

Jacobs, B. and J. Cuchateau. 1997. Improved high-density phase-change recording. Japanese Journal of Applied Physics, Part 1 36 (1B): 491-94.

Jacobs, B. et al. 1984. Aging characteristics of amorphous magneto-optic recording media. Applied Optics 23 (22): 3979-82.

Jacobs, B. et al. 1984a. Aging characteristics of amorphous magneto-optical recording media. In Topical Meeting on Optical Data Storage: Technical Digest. Washington, D.C.: Optical Society of America, 4/1-4.

Jakubovics, J. 1987. Magnetism and Magnetic Materials. London: Institute of Metals.

Jasionowski, A. 1991. Using phase-change technology with direct overwrite in a multifunction optical disk drive. Optical Information Systems 11 (1): 4-8.

Jiang, F. and M. Okuda. 1991. The effect of doping on the erasure speed and stability of reversible phase-change optical recording films. Japanese Journal of Applied Physics 30 (1): 97-100.

Jordan, L. et al. 1972. Chromium dioxide audio cassette tape. Journal of the Audio Engineering Society 20 (1): 2-6.

Jorgensen, F. 1995. The Complete Handbook of Magnetic Recording, 4th ed. Blue Ridge Summit, Penn.: TAB Books.

Kaempf, G. 1987. Special polymers for data memories. Polymer Journal 19 (2): 257-68.

Kageyama, Y. et al. 1996. Compact disc erasable (CD-E) with Ag-In-Sb-Te phase change recording material. Japanese Journal of Applied Physics, Part 1. 35 (1): 500-501.

Kampf, J. et al. 1994. Investigation of the archivability of metal evaporated tape. In Proceedings of the Third International Symposium on Corrosion and Reliability of Electronic Materials and Devices. Pennington, N.J.: Electrochemical Society, 318-26.

Kanazawa, Y. et al. 1984. Development of large capacity optical disk. In Proceedings of the SPIE, vol. 490. Bellingham, Wash.: SPIE, 12-19.

Kaneda, Y. 1997. Tribology of metal-evaporated tape for high-density magnetic recording. IEEE Transactions on Magnetics 33 (2): 1058-68.

Kaneko, M. et al. 1994. IRISTER: Magneto-optical disk for mgnetically induced super-resolution. Proceedings of the IEEE 82 (4): 544-53.

Kant, R. and F. Barez. 1996. The writing process in magneto-optical recording. In Inter-Society Conference on Thermal Phenomena in Electronic Systems. New York: IEEE, 321-28.

Karten, H. 1984. How durable are your disks? Very. Canadian Business 57 (9): 257-68.

Kartuzhanski, A. 1978. The problem of aging in non-silver photography. In Papers from the 1978 International Congress of Photographic Science. Washington, D.C.: SPSE, 21.

Katayama, H. et al. 1988. Recording sensitivity and lifetime estimate of a magneto-optical disk., IEEE Translation Journal on Magnetics in Japan 3 (2): 126-31.

Kawamata, T. et al. 1984. Study for wear resistance and abrasivity of magnetic recording tape. Transactions of the Institute of Electronic and Communications Engineering of Japan 67C (2): 227-34.

Kawana, T. et al. 1995. Advanced metal evaporated tape. IEEE Transactions on Magnetics 31 (6): 2865-70.

Kawana, T. et al. 1996. Archival stability of metal evaporated tape. Journal of Magnetism and Magnetic Materials 155 (1-3): 273-75.

Kay, D. et al. 1984. Experimental measurements on long-term IR readout of data recorded in organic optical storage media. In Topical Meeting on Optical Data Storage: Technical Digest. Washington, D.C.: Optical Society of America, 2/1-3.

Keele, R. 1988. Optical storage: Terabytes online for IBM mainframes. In Proceedings of the SPIE, vol. 899. Bellingham, Wash.: SPIE, 262-71.

Ker, N. 1986. Preparing your archives for the next 20,000 years. International Journal of Micrographics and Video Technology 5 (3): 223-25.

Ker, N. 1987. Gold toning the Domesday Book gives better than archival performance. Microform Review 16 (4): 300-303.

Kim, K. et al. 1990. Magnetic media durability: A systems approach. IEEE Transactions on Magnetics 26 (1): 159-64.

Kim, M. et al. 1997. CD-rewritable optical disks with enhanced media cyclability. In 1997 Optical Data Storage Topical Meeting: Conference Digest. New York: IEEE, 100-101.

Kim, Y. et al. 1995. High density magneto-optical disk suitable for short wavelength recording. In Proceedings of the SPIE, vol. 2514. Bellingham, Wash.: SPIE, 171-75.

Kitani, H. and Y. Tsunoda. 1984. Large-capacity optical disk files. Hitachi Review 33 (3): 109-14.

Kitaori, N. and T. Maeda. 1991. Changes in characteristics of magnetic tape composed of mixtures of chromium dioxide and metal particles. IEICE Transactions 74 (5): 1314-16.

Klaus, E. and B. Bhushan. 1986. Study of the Stability of Magnetic Tape Lubricants. ASLE Special Publication SP-21. Park Ridge, Ill.: ASLE.

Klaus E. and B. Bhushan. 1988. Effects of inhibitors and contaminants on the stability of magnetic tape lubricants. Tribology Transactions 31 (2): 276-81.

Kloosterboer, J. and G. Lippits. 1986. Replication of video discs using photopolymerization: Process design and study of network formation. Journal of Imaging Science 30 (4): 177-83.

Kobayashi, M. and K. Kawamura. 1988. High corrosion resistant magneto-optical recording disk. Oki Technical Review 55 (131): 33-38.

Kobayashi, M. et al. 1985. Improvements in corrosion resistance of Tb-Fe thin films. In Topical Meeting on Optical Data Storage: Digest of Technical Papers. Washington, D.C.: Optical Society of America, 2/1-4.

Kobayashi, M. et al. 1987. High-corrosion-resistant magneto-optical recording media using TbFeCoTi films. Applied Physics Letters 50 (23): 1694-95.

Kobayashi, M. et al. 1987a. Corrosion resistance of magneto-optical recording media. IEEE Translation Journal on Magnetics in Japan 2 (5): 404-5.

Kobori, H. 1997. DVD-RAM technology: First generation and future prospects. In 1997 Optical Data Storage Topical Meeting: Conference Digest. New York: IEEE, 11-12.

Kobori, H. et al. 1986. 130mm diameter magneto-optic disc memory. Journal of the Institute of Television Engineers of Japan 40 (6): 535-60.

Kojima, T. et al. 1982. Study of the wear mechanism of magnetic head by passing of magnetic tapes. Transactions of the Institute of Electronics and Communication Engineers of Japan, Section E 65 (4): 224.

Kopperl, D. 1988. Use of Arrhenius testing to determine thiosulphate tolerance in silver halide black-and-white materials. Journal of Photographic Science 36 (3): 63.

Kopperl, D. and J. Huttemann. 1986. Effect of residual thiosulfate ion on the image stability of microfilms. Journal of Imaging Technology 12 (4): 173-80.

Kopperl, D. et al. 1982. A method to predict the effect of residual thiosulfate content on the long-term image stability characteristics of radiographic films. Journal of Applied Photographic Engineering 8 (2): 83-89.

Kopperl, D. et al. 1988. Use of Arrenhius testing to determine thiosulphate tolerance in silver halide black-and-white materials. Journal of Photographic Science 36 (2): 40-42.

Kopperl, D. et al. 1992. Use of Arrhenius testing to evaluate the thiosulfate tolerance of black-and-white aerial film. Journal of Imaging Science and Technology 36 (1): 42-45.

Kryder, M. 1985. Magneto-optic recording technology. Journal of Applied Physics 57 (8): 3913-18.

Kryder, M. 1990. Advances in magneto-optic recording technology. Journal of Magnetism and Magnetic Materials 83 (1): 1-5.

Kugiya, F. et al. 1995. Future technology trends on magneto-optical recording. IEICE Transactions on Electronics E78-C (11): 1499-1508.

Kurtilla, K. 1977. Dry silver film stability. Journal of Micrographics 10 (3): 113-17.

Lee, L. 1978. Everything you wanted to know about updatables but had no one to ask. Journal of Micrographics 12 (11): 187-97.

Lee, L. 1979. Are updatables archival? IMC Journal 2 (2): 7-11.

Lee, T. 1990. Selection of lubricants for metal evaporated tape. IEEE Transactions on Magnetics 26 (1): 171-73.

Lee, T. and P. Papin. 1982. Analysis of dropouts in video tapes. IEEE Transactions on Magnetics 18 (6): 1092-94.

Lee, T. et al. 1978. Development of thermoplastic photoconductor tape for optical recording. Applied Optics 17 (4): 2802-11.

Lee, T. et al. 1987. Stability studies of iron particle. IEEE Transactions on Magnetics 23 (5): 2880-82.

Lee, W. 1983. The stability of thin tellurium and tellurium alloy films for optical data storage. Thin Solid Films 108 (3): 353-63.

Lee, W. 1983a. Thin Te and Te alloy films for optical data storage. In Proceedings of the SPIE, vol. 420. Bellingham, Wash.: SPIE, 265-72.

Lee, W. and C. Bard. 1987. The stability of Kodak professional motion picture film bases. Image Technology 69 (12): 518-21.

Lee, W. and R. Geiss. 1983. Degradation of thin tellurium films. Journal of Applied Physics 54 (3): 1351-57.

Lee, W. and H. Weider. 1983. The stability of Te and Te-alloy films for optical data storage. In Topical Meeting on Optical Data Storage. Washington, D.C.: Optical Society of America, 3/1-4.

Lee, W. et al. 1984. Toner treatments for photographic images to enhance image stability. Journal of Imaging Technology 19 (3): 119-26.

Lee, Z. et al. 1990. Enhancement and corrosion resistance improvement by A1N and ALSiN films. Journal of Applied Physics 67 (9): 5340.

Leek, M. 1995. A look at CD-recordable media longevity studies: Will a good disc last forever? CD-ROM Professional 8 (11): 102-10.

Legierse, P. 1987. Mastering technology and electroforming for optical disc systems. Transactions of Metal Finishing 65 (1): 13-17.

Lekawat, L. et al. 1993. Annealing study of the erasability of high energy tapes. IEEE Transactions on Magnetics 29 (6): 3628-30.

Lekawat, L. et al. 1993a. Erasure and noise study in barium-ferrite tape media. Journal of Applied Physics 73 (10): 6719-21.

Leuschke, C. 1989. Polycarbonate for optical applications. Kunststoffe 79 (10): 77.

Lippits, G. and G. Melis. 1986. High precision replication of Laservision video discs using UV-curable coatings. In Integration of Fundamental Polymer Science and Technology. London: Elsevier Applied Science Publishers, 663-68.

Lou, D. 1981. The archival stability of tellurium films for optical information storage. Journal of the Electrochemical Society 128 (3): 699-701.

Lowman, C. 1972. Magnetic Recording. New York: McGraw-Hill.

Luborsky, F. et al. 1985. Stabilty of amorphous transition metal-rare earth films for magneto-optic recording. IEEE Transactions on Magnetics 21 (5): 1618-23.

Ludwig, M. et al. 1993. Relationship between the morphology of maghemite and the properties of magnetic tapes. Chemometrics and Intelligent Laboratory Systems 18 (2): 221-27.

Luitjens, S. et al. 1996. Metal evaporated tape: State of the art and prospects. Journal of Magnetism and Magnetic Materials 155 (1-3): 261-65.

Maeda, M. et al. 1989. Study on readout stability of TbFeCo magneto-optical disks. IEEE Transactions on Magnetics 25 (5): 3539-41.

Maediger, C. et al. 1984. Analysis of signal statistics and drop-out behavior of magnetic tapes. IEEE Transactions on Magnetics 20 (5): 765-67.

Maeno, Y. and M. Kobayashi. 1990. Fabrication of magnetic films for magneto-optical recording disk. Fujitsu 39 (6): 321-28.

Maestro, P. et al. 1982. New improvements of chromium-dioxide-related magnetic recording materials. IEEE Transactions on Magnetics 18 (5): 1000-1003.

Majumdar, D. and T. Hatwar. 1989. Effects of platinum and zirconium on the oxidation behavior of FeThCo. Journal of Vacuum Science and Technology 7 (4): 2673-77.

Makino, H. 1989. Reliability test of magneto-optical disks. Japanese Journal of Applied Physics 28 (3): 97-100.

Mallinson, J. 1988. On the preservation of human- and machine-readable records. Information Technology and Libraries 7 (1): 19-23.

Mallinson, J. 1993. The Foundations of Magnetic Recording. Boston: Academic Press.

Mallinson, J. and S. Gavrel. 1986. Preserving machine-readable archival records for the millennia. Archivaria (22): 147-55.

Manns, B. 1986. Optical disk testing system. In Proceedings of the SPIE, vol. 695. Bellingham, Wash.: SPIE, 306-9.

Mansuripur, M. 1987. Magnetization reversal, coercivity, and the process of thermomagnetic recording in thin films of amorphous rare earth transition metal alloys. Journal of Applied Physics 61 (4): 1580-87.

Mansuripur, M. 1995. The Physical Principles of Magneto-Optical Recording. Cambridge: Cambridge University Press.

Mansuripur, M. et al. 1985. Erasable optical disks for data storage: Principles and applications. Industrial and Engineering Chemistry: Product Research and Development 24 (1): 80-84.

Markvoort, J. et al. 1983. Aging properties of optical non-erasable disks. In Proceedings of the SPIE, vol. 420. Bellingham, Wash.: SPIE, 134-40.

Markvoort, J. et al. 1984. Mechanical, environmental and accelerated ageing tests on OML disks. In Topical Meeting on Optical Data Storage: Technical Digest. Washington, D.C.: Optical Society of America, 4/1-3.

Marshall, M. 1991. Compact disc's "indestructibility": Myth and maybe. OCLC Micro 7 (1): 20-23.

Marshall, M. and G. Voedisch. 1990. Compact discs: Permanence and irretrievability may be synonymous in libraries as well as in Roget's. In National Online Meeting Proceedings. Medford, N.J.: Learned Information, pp. 249-54.

Martin, M. 1993. Compact disc media evaluation: what do we know about disc quality. CD-ROM Professional 6 (2): 74-77.

Martin, M. and J. Hyon. 1995. Results of CD-R media study. In Proceedings of the SPIE, vol. 2514. Bellingham, Wash.: SPIE, 55-61.

Materazzi, A. 1978. Archival Stability of Microfilm: A Technical Review. Washington, D.C.: U.S. Government Printing Office.

Mathur, M. et al. 1992. A detailed study of the environmental stability of metal particle tapes. IEEE Transactions on Magnetics 28 (5): 2362-64.

Matick, R. 1977. Computer Storage Systems and Technology. New York: John Wiley and Sons.

Matshushima, M. et al. 1987. Aging properties of amorphous GdTbFeCo magnetic films and the effect of other elements added to them. IEEE Translation Journal on Magnetics in Japan 2 (5): 399-400.

Mayr, M. 1987. High vacuum equipment for compact disc coating. Metal Finishing 85 (1): 37-39.

McCamy, C. 1964. Inspection of Processed Photographic Record Films for Aging Blemishes, NBS Handbook 96. Washington, D.C.: National Bureau of Standards.

McCamy, C. and C. Pope. 1965. Current research on preservation of archival records on silver-gelatin type microfilm in roll form. Journal of Research of the National Bureau of Standards 69A (5): 385-95.

McCamy, C. and C. Pope. 1970. Redox blemishes: Their causes and prevention. Journal of Micrographics 3 (6): 165-70.

McCrary, L. 1988. Sputtering technology for CD manufacturing. Optical Information Systems 8 (3): 118-19.

McDaniel, T. and B. Finkelstein. 1991. Magnetization stability in the magneto-optical readout of TbFeCo disks. Journal of Applied Physics 69 (8): 4954-56.

McDonald, P. 1988. Color microforms: New possibilities. Microform Review 17 (3): 146-49.

McGahan, W. and J. Woollam. 1989. Magnetooptics of multilayer systems. Applied Physics Communications 9 (1): 1-25.

McIntire, G. and T. Hatwar. 1989. The corrosion protection behaviour of aluminum nitride and silicon dioxide coatings on magneto-optical media. Corrosion Science 29 (7): 811-21.

Mee, C. 1986. The Physics of Magnetic Recording. Amsterdam: North-Holland Publishing.

Mee, C. and E. Daniel. 1995. Magnetic Recording Technology, 2nd ed. New York: McGraw-Hill.

Meichle, L. and R. Victora. 1992. Temperature dependence of coercivity at recording frequencies: Barium ferrite versus oxide. IEEE Transactions on Magnetics 28 (6): 3393-97.

Meyer, A. 1983. Silver dye-bleach colour microfilm. Journal of Applied Photographic Engineering 9 (4): 117-20.

Meyers, W. 1975. Laser micrographic recording on non-silver halide media. Journal of Micrographics 8 (4): 265-73.

Middleton, B. et al. 1996. Models of metal evaporated tape. Journal of Magnetism and Magnetic Materials 155 (1-3): 26-72.

Mijovic, J. et al. 1989. Physical aging in polymethyl methacrylate/polystyrene-co-acrylon itrile blends: Enthalpy relaxation. Polymer Engineering and Science 29 (22): 1604-10.

Milch, A. and P. Tasaico. 1980. The stability of tellurium films in moist air: A model for atmospheric corrosion. Journal of the Electrochemical Society 127 (4): 884-91.

Miller, D. et al. 1988. XPS oxidation study of TbFeCo films. Applied Surface Science 35 (1): 153-63.

Mimura, H. 1997. DVD-Video format. In Digest of Papers: COMPCON Spring 97, Forty-Second IEEE Computer Society International Conference Proceedings. Los Alamitos, Calif.: IEEE Computer Society Press, 291-94.

Misaki, H. et al. 1989. Hydrogen-containing SiCN protective films for magneto-optical media. IEEE Transactions on Magnetics 25 (5): 4030-32.

Mischke, W. et al. 1996. Manufacturing CD-R media. In Proceedings of the SPIE, vol. 2931. Bellingham, Wash.: SPIE, 43-51.

Mitton, D. et al. 1993. An XPS and AES study of the ageing of cobalt oxide-nickel metal-evaporated tape. Surface and Interface Analysis 20 (1): 36-42.

Miyazaki, M. et al. 1987. A new protective film for magneto-optical TbFeCo media. Journal of Applied Physics 61 (8): 3326-28.

Mochizuki, K. and I. Sato. 1986. Friction and wear characteristics of flexible disk media. Transactions of the Institute of Electronic and Communications Engineering of Japan 69E (4): 450-51.

Montuori, T. 1974. Testing recently processed microfilm for archival stability. Journal of Micrographics 8 (2): 79-82.

Morgan, D. 1979. Dry silver materials for laser printing applications. In Proceedings of the SPIE, vol. 169. Bellingham, Wash.: Society of Photo-Optical Instrumentation Engineers, 105-11.

Morgan, D. 1982. Dry silver imaging: New advances and applications. Electro-Optical Systems Design 14 (9): 41-44.

Morgan, D. 1982a. Dry silver process for imaging. Electro-Optical Systems Design 14 (8): 59-62.

Morgan, D. 1987. New capabilities with dry silver recording materials. Journal of Imaging Technology 13 (1): 4-7.

Mori, T. 1985. Progress of magnetic recording materials. BKSTS Journal 67 (9): 526-29.

Moribe, M. et al. 1988. Bit-error reduction in magneto-optical disks. In Proceedings of the SPIE, vol. 899. Bellingham, Wash.: SPIE, 88-92.

Morrison, F. and J. Corcoran. 1992. Accelerated life testing of metal particle tape. In International Broadcasting Convention, IBC92. IEE Conference Publication No. 358. Stevenage, England: IEE, 107-11. Mottice, R. and M. Schreiber. 1969. New method for residual thiosulfate analysis. Journal of Micrographics 3 (6): 38-45.

Nakada, M. et al. 1987. Change in birefringence in polycarbonate substrates under operating environments. Japanese Journal of Applied Physics 26 (4): 95-98.

Nakamae, K. et al. 1996. Lifetime expectancy of polyurethane binder as magnetic recording media. International Journal of Adhesion and Adhesives 16 (4): 277-83.

Nakane, Y. et al. 1985. Principle of laser recording mechanism by forming an alloy in the trilayer of thin metallic films. In Proceedings of the SPIE, vol. 529. Bellingham, Wash.: SPIE, 76-82.

Nakane, Y. et al. 1986. Optical write-once disk subsystem with higher data integrity. Journal of the Institute of Television Engineers of Japan 40 (6): 508-13.

Narahara, T. et al. 1993. A new tracking method for helical scanning optical tape recorder. Japanese Journal of Applied Physics 32 (11): 5421-27.

Narkis, M. et al. 1984. Hot water aging of polycarbonate. Engineering and Science 24 (3): 211-17.

Narkis, M. et al. 1985. Water effects on polycarbonate. Polymer Communications 26 (11): 339-42.

Naruse, H. et al. 1996. Advanced metal evaporated tape for consumer digital VCRs. IEEE Transactions on Consumer Electronics 42 (3): 851-59.

Nasuta, A. 1981. Floppy disk and magnetic tape cassette magnetic field susceptibility. In IEEE International Symposium on Electromagnetic Compatibility. New York: IEEE, 208-10.

National Research Council. 1986. Preservation of Historical Records. Washington, D.C.: National Academy Press.

Neubert, S. et al. 1989. Use of magnetic tape as an optical storage media. In Proceedings of the SPIE, vol. 1018. Bellingham, Wash.: SPIE, 102-8.

Niihara, T. et al. 1988. High corrosion-resistant magneto-optical film on a new plastic substrate. IEEE Transactions on Magnetics 24 (6): 2437-42.

Nikles, D. and C. Forbes. 1991. Accelerated aging studies for polycarbonate optical disk substrates. In Proceedings of the SPIE, vol. 1499. Bellingham, Wash.: SPIE, 39-41.

Nikles, D. et al. 1989. Accelerated aging studies for organic optical data storage media. In Proceedings of the SPIE, vol. 1078. Bellingham, Wash.: SPIE, 43-50.

Nikumbh, A. 1990. Magnetic properties and Mossbauer spectra of gamma ferric oxide and doped gamma ferric oxide. Journal of Materials Science 25 (8): 3773-79.

Nikumbh, A. et al. 1992. Electrical and magnetic properties of gamma ferric-oxide synthesized from ferrous tartarate one and half hydrate. Journal of Magnetism and Magnetic Materials 114 (1-2): 27-34.

Nishibori, M. and S. Shiina. 1990. An automated data conversion and entry system for the medical optical card. In Biomedical Engineering Perspectives: Health Care Technologies for the 1990s and Beyond: Proceedings of the Annual Conference on Engineering in Medicine and Biology. Piscataway, N.J.: IEEE, 1262-63.

Nishikawa, Y. et al. 1989. Anti-corrosion thin protective film for vacuum deposited Co-Ni-O layers. Fuji Film: Research and Development (34): 130-32.

Nishimura, K. et al. 1995. High density recording using phase change optical disk. In Proceedings of the SPIE, vol. 2514. Bellingham, Wash.: SPIE, 319-28.

Nouchi, N. et al. 1991. Corrosion analysis for Co-Ni-O film adopted as the magnetic layer of metal evaporated tape. IEEE Translation Journal on Magnetics in Japan 6 (4): 274-83.

Nowak, R. 1988. Cibachrome Micrographic: Ein archivbestaendiger Farbfilm [Cibachrome Micrographic: A color film with archival properties). ABI-Technik 8 (4): 1-6.

Nugent, W. 1984. Applications of digital optical disks in library preservation and reference. International Journal of Micrographics and Video Technology 3 (1): 59-61.

Numata, T. et al. 1988. Stability of magnetic properties of magnetooptical TbFe films. IEEE Translation Journal on Magnetics in Japan 3 (6): 498-99.

Oba, H. et al. 1986. Organic dye materials for optical recording media. Applied Optics 25 (22): 4023-26.

Ohkubo, K. et al. 1990. Effects of dielectric layers on TbFeCo magneto-optical disk. IEEE Translation Journal on Magnetics in Japan 5 (1): 68-78.

Ohno, E. et al. 1991. Erasable compact disk utilizing phase change material and multi-pulse recording method. In Proceedings of the SPIE, vol. 1499. Bellingham, Wash.: SPIE, 171-79.

Ohta, T. et al. 1990. Accelerated aging studies for phase change type disc media. In Proceedings of the SPIE, vol. 1316. Bellingham, Wash.: SPIE, 367-43.

Ohta, T. et al. 1995. High-density phase-change optical recording. Optoelectronics: Devices and Technologies 10 (3): 361-80.

Ohta, T. et al. 1996. Evolution of the phase-change optical disk into the multimedia era. In Proceedings of the SPIE, vol. 2931. Bellingham, Wash.: SPIE, 7-12.

Okada, M. et al. 1989. Bit error analysis for magneto-optical disks under accelerated aging condition. NEC Research and Development (94): 49-56.

Okada, M. et al. 1995. High-density phase-change optical disk with a Si reflective layer. In Proceedings of the SPIE, vol. 2514. Bellingham, Wash.: SPIE, 329-37.

Okamoto, K. et al. 1996. Advanced metal particles technologies for magnetic tapes. Journal of Magnetism and Magnetic Materials 155 (1-3): 60-66.

Okazaki, H. et al. 1989. A theoretical analysis for media life estimation using error rate. In Proceedings of the SPIE, vol. 1078. Bellingham, Wash.: SPIE, 51-58.

Okazaki, Y. et al. 1992. Estimating the archival life of metal particulate tape. IEEE Transactions on Magnetics 28 (5): 2365-67.

Okuda, M. and T. Matsushita. 1996. Size and electron-hole pair effects on the melting of phase change optical materials. In Proceedings of the SPIE, vol. 2931. Bellingham, Wash.: SPIE, 2-6.

Okuda, M. et al. 1992. Discussion on the mechanism of reversible phase change optical recording. Japanese Journal of Applied Physics, Part 1 31 (2B): 466-70.

Onodera, S. et al. 1996. Materials for magnetic-tape media. MRS Bulletin 21 (9): 35-41.

Onodera, S. et al. 1996a. The archival stability of metal evapoated tape for consumer digital VCRs. Journal of Applied Physics 79 (8): 4875-77.

Osaki, H. 1996. Tribology of videotapes. Wear 200 (1-2): 244-51.

Osterlund, S. 1987. Optical archiving systems. DEC Professional 6 (6): 66-69.

Otoma, S. 1994. Effects of Cr and Ti additions on wear resistance and magnetic properties of Fe-Al-Si alloy. Journal of the Japan Institute of Metals 58 (4): 455-60.

Oudard, D. 1991. The evolution of Century Disc archival technology. CD-ROM Professional 4 (6): 42, 44, 46.

Owa, H. et al. 1994. Advances in magneto-optical super-resolution for very high density MO recording. In Proceedings of the SPIE, vol. 2338. Bellingham, Wash.: SPIE, 296-300.

Ozawa, K. 1988. Friction and wear of magnetic heads sliding against magnetic tapes. Junkatsu 33 (7): 520-25.

Pan, T. et al. 1996. Magnetic properties and microstructure of evaporated Co oxide tape media. Journal of Magnetism and Magnetic Materials 155 (1-3): 309-11.

Parker, D. 1997. DVD-ROM: Who needs it, who will use it, and how? EMedia Professional 10 (1): 26-37.

Parker, D. 1997a. Reading a new CD-R media market: How do you differentiate a commodity product? EMedia Professional 10 (9): 38-47.

Parker, D. and R. Starrett. 1996. Testing, testing ... CD-R. CD-ROM Professional 9 (2): 32-46.

Parker, E. 1985. The Library of Congress non-print optical disk pilot program. Information Technology and Libraries 4 (4): 289-92.

Parker, M. et al. 1992. Magnetic and magneto-photoellipsometric evaluation of corrosion in metal-particle media. IEEE Transactions on Magnetics 28 (5): 2368-70.

Parker, M. et al. 1996. Mossbauer effect study of metal particle tape stability. Journal of Magnetism and Magnetic Materials 162 (1): 122-30.

Patton, S. and B. Bhushan. 1995. Effect of interchanging tapes and head contour on the durability of metal evaporated, metal particle and barium ferrite magnetic tapes. Tribology Transactions 38 (4): 801-10.

Patton, S. and B. Bhushan. 1996. Friction and wear of metal particle, barium ferrite and metal evaporated tapes in rotary head recorders. Transactions of the ASME: Journal of Tribology 118 (1): 21-32.

Patton, S. and B. Bhushan. 1997. Environmental effects on the streaming mode performance of metal evaporated and metal particle tapes. IEEE Transactions on Magnetics 33 (4): 2513-30.

Pearson, J. 1986. Polymeric optical disk recording media. CRC Critical Review of Solid State and Material Science 13 (1): 1-26.

Peppas, N. et al. 1988. Polydimethacrylates for laser videodisc applications. In Proceedings of the ACS Division of Polymeric Materials Science and Engineering, vol. 59. Washington, D.C.: American Chemical Society, Books and Journals Division, 1219.

Podio, F. 1991. Development of a Testing Methodology to Predict Optical Disk Life Expectancy Values. Report No. NIST/SP 500/200. Washington, D.C.: National Institute of Standards and Technology.

Podio, F. 1992. Research on methods for determining optical disk media life expectancy estimates. In Proceedings of the SPIE, vol. 1663. Bellingham, Wash.: SPIE, 447-55.

Podio, F. et al. 1990. Standardization of testing methods for optical disk media characteristics and related activities at NIST. Optical Information Systems 10 (4): 174-78.

Pohlmann, K. 1988. The compact disc formats: Technology and applications. Journal of the Audio Engineering Society 36 (4): 250-58.

Pohlmann, K. 1989. The Compact Disc: A Handbook of Theory and Use. Madison, Wisc: A-R Editions.

Pope, C. 1969. Simplified method for determining residual thiosulfate in processed microfilm. Photographic Science and Engineering 13 (5): 278-79.

Pope, C. 1971. A new method of determining residual thiosulfate in processed photographic film. Journal of Research of the National Bureau of Standards 75C (1): 19-22.

Price, J. 1984. The optical disk pilot program at the Library of Congress. Videodisc and Optical Disk 4 (6): 424-32.

Price, J. 1985. Optical disks and demand printing research at the Library of Congress. Information Services and Use 5 (1): 3-20.

Price, J. 1986. Optical disk pilot program at the Library of Congress. In Impact of New Information Technology on International Library Cooperation: Essen Symposium 8-11, September 1986. Essen, Germany: Essen University Library, 179-87.

Price-Francis, S. 1993. The optical card as a portable medical record. In Patient Care with Computers and Cards: Fifth Global Congress on Patient Cards and Computerization of Health Records. Newton, Mass.: Medical Records Institute, pp. 10-13.

Pundsack, A. et al. 1984. Applications of Xerox dry microfilm (XDM), a camera-speed, high resolution, nonsilver film with instant, dry development. Journal of Imaging Technology 10 (5): 190-96.

Pushic, D. 1997. DVD and the replicator: Can we really make those things. Emedia Professional 10 (1): 38-49.

Ram, A. 1988. Archival preservation of photographic films: A perspective. Polymer Degradation and Stability 29 (1): 3-29.

Ram, A. and J. McCrea. 1988. Stability of processed cellulose ester photographic films. SMPTE Journal 97 (6): 474-83.

Ram, A. and E. Potter. 1970. Stability of vesicular microfilm images. Photographic Science and Engineering 14 (4): 283-88.

Ram, A. et al. 1985. Life expectation of polycarbonate. Polymer Engineering and Science 25 (9): 535-40.

Ram, A. et al. 1989. Image stability of processed Kodak Dacomatic DL film. Journal of Imaging Technology 15 (4): 169-77.

Ram, A. et al. 1991. Simulated aging of processed cellulose triacetate motion picture films. Image Technology 73 (4): 124-30.

Ram, A. et al. 1994. Effects and prevention of the "vinegar syndrome." Journal of Imaging Science and Technology 38 (3): 249-61.

Ramsay, N. 1988. Using optical disk in non-image applications. Optical Information Systems 8 (4): 164-68.

Reilly, J. et al. 1988. Stability of black-and-white photographic images, with special reference to microfilm. Microform Review 17 (5): 270-78.

Reilly, J. et al. 1988a. When clouds obscure silver film's lining. Inform 2 (8): 16-20, 37-39.

Reilly, J. et al. 1991. Polysulfide treatment for microfilm. Journal of Imaging Technology 17 (3): 99-107.

Reilly, J. et al. 1994. Protection of microform images against oxidation. Journal of Imaging Science and Technology 38 (4): 326-32.

Renwick, W. and A. Cole. 1971. Digital Storage Systems. London: Chapman and Hall.

Reynolds, G. and J. Halliday. 1987. Compact disc processing. In Sound Recording Practice, 3rd ed. Oxford: Oxford University Press, 440-52.

Rhoads, J. 1976. Letter to P. Z. Adelstein. Journal of Applied Photographic Engineering 2 (2): 64.

Ricco, T. and T. Smith. 1990. Rate of physical aging of polycarbonate at a constant tensile strain. Journal of Polymer Science, Part B 28 (4): 513-20.

Richter, H. 1993. Media requirements and recording physics for high density magnetic recording. IEEE Transactions on Magnetics 29 (5): 2185-2201.

Richter, H. and R. Veitch. 1995. Advances in magnetic tapes for high density information storage. IEEE Transactions on Magnetics 31 (6): 2883-88.

Richter, H. and R. Veitch. 1996. MP tape for high density digital recording. Journal of Magnetism and Magnetic Materials 155 (1-3): 80-82.

Righetti, B. et al. 1984. Study on latent image stability: Latensifying effect of temperature. Journal of Photographic Science 32 (3): 89-92.

Rong, A. et al. 1996. Thermal-induced phase-change ODS and photo-excited bistable state-change DVD-RAM. In Proceedings of the SPIE, vol. 2890. Bellingham, Wash.: SPIE, 74-81.

Rong, A. et al. 1996a. International standards of optical disks and DVD-RAM technology. In Proceedings of the SPIE, vol. 2931. Bellingham, Wash.: SPIE, 108-13.

Rouyer, P. 1992. Humidity control and the preservation of silver gelatin microfilm. Microform Review 21 (2): 74-76.

Rubin, K and M. Chen. 1989. Progress and issues of phase-change erasable optical recording media. Thin Solid Films 181 (2): 129-39.

Saffady, W. 1985. Micrographics. 2nd ed. Littleton, Colo.: Libraries Unlimited.

Saffady, W. 1990. Micrographic Systems. Silver Spring, Md.: Association for Information and Image Management.

Saffady, W. 1992. Optical Storage Technology 1992: A State of the Art Report. Westport, Conn.: Meckler.

Salantrie, F. 1973. Dry silver technology. Modern Lithography 41 (4): 23-26.

Sato, M. et al. 1985. Magneto-optical memory disk using plastic substrate. IEEE Translation Journal on Magnetics in Japan 1 (5): 637-38.

Sato, M. et al. 1987. Reliability of magneto-optical memory disks. IEEE Translation Journal on Magnetics in Japan 2 (5): 395-96.

Sato, T. and T. Kitamura. 1985. Structure of metal evaporated tape. IEEE Translation Journal on Magnetics in Japan 1 (6): 765-76.

Sawada, Y. et al. 1992. Synthesis and magnetic properties of ultrafine iron particles prepared by pyrolysis of carbonyl iron. Japanese Journal of Applied Physics, Part 1 31 (12A): 3858-61.

Scheinert, P. 1984. Accelerated life testing--optical media. In Proceedings of the National Bureau of Standards/National Security Agency Workshop on Standardization Issues for Optical Digital Data Disk (OD3) Technology. Washington, D.C.: National Bureau of Standards, 178-81.

Schelble, J. 1993. Stabilization of oleic acid in audio tapes. Journal of Magnetism and Magnetic Materials 120 (1-3): 122-24.

Schicht, H. 1985. Clean room technology: The concept of total environmental control for advanced industries. Vacuum 35 (10): 485-91.

Schmitt, F. and T. Lee. 1979. Developments in thermoplastic tape for optical recording. In Proceedings of the SPIE, vol. 177. Bellingham, Wash.: SPIE, 89-96.

Schmitt, W. 1993. Erasability of Co-modified iron oxide tapes. Journal of Magnetism and Magnetic Materials 120 (1-3): 100-102.

Schreiber, M. 1971. Technical note: New residual thiosulfate test methods. Journal of Micrographics 5 (3): 53.

Schreiber, W. 1974. A laser dry silver facsimile system. TAPPI 54 (4): 91-93.

Schwab, E. et al. 1993. Cobalt-modified iron oxides with improved aging stability. Journal of Magnetism and Magnetic Materials 120 (1-3): 43-47.

Sekiya, M. et al. 1988. Effect of Ti and In/sub 2/0/sub 3/ layers on stability of TbFeCo magneto-optical media on a polycarbonate substrate. IEEE Transactions on Magnetics 24 (6): 2787-89.

Shareck, M. et al. 1977. 3M and Kodak dry silver recording materials for laser imagery transmission application. In Proceedings of the SPIE, vol. 123. Bellingham, Wash.: Society of Photo-Optical Instrumentation Engineers, 61-66.

Sharrock, M. and L. Carlson. 1995. Application of barium ferrite particles in advanced recording media. IEEE Transactions on Magnetics 31 (6): 2871-76.

Sharrock, M. and R. Bodnar. 1985. Magnetic materials for recording: An overview with special emphasis on particles. Journal of Applied Physics 57 (8): 3919-24.

Shen, D. 1996. Garnet films for magneto-optical recording. In Proceedings of the SPIE, vol. 2931. Bellingham, Wash.: SPIE, 19-24.

Shephard, J. 1972. Dry silver film technology. In Proceedings of the Twenty-First Annual Conference and Exposition of the National Micrographics Association. Silver Spring, Md.: National Micrographics Association, 88-92.

Shephard, J. 1982. Early dry silver technology at 3M. Journal of Applied Photographic Engineering 8 (5): 210-12.

Shieh, H. et al. 1988. Microstructure and stability of RF-diode sputtered GdTbFeCo thin films. Journal of Applied Physics 63 (8): 3627-29.

Shinotsuka, M. et al. 1997. Potentiality of the Ag-In-Sb-Te phase change recording material for high density erasable optical discs. Japanese Journal of Applied Physics, Part 1 36 (1B): 536-38.

Shoda, J. et al. 1990. Evaluation of optical memory card system for patient records. In Proceedings of the SPIE, vol. 1348. Bellingham, Wash.: SPIE, 536-44.

Shrawagi, S. et al. 1984. Defect measurements in digital optical disks. Journal of Vacuum Science and Technology 2 (2): 346-49.

Siebert, H. 1984. Video tapes in head abrasion tests: Tape types affect lifetime. Funkschau (17): 54-57.

Sides, P. et al. 1994. Investigation of the archivability of metal particle tape. IEEE Transactions on Magnetics 30 (6): 4059-64.

Siedband, M. et al. 1990. Optical data card for medical imaging. In Proceedings of the SPIE, vol. 1248. Bellingham, Wash.: SPIE, 204-9.

Simmons, R. 1989. The effect of media properties on the longitudinal recording performance of particulate barium ferrite media. IEEE Transactions on Magnetics 25 (5): 4051-53.

Simmons, R. 1990. Remanence and longitudinal recording properties of advanced particulate media and metal thin-film media. IEEE Transactions on Magnetics 26 (1): 93-96.

Situ, H. et al. 1989. Mechanism of transformations in phase-change optical recording media. Journal of Non-Crystalline Solids 113 (1): 88-93.

Smith, L. et al. 1986. Prediction of the Long Term Stability of Polyester-Based Recording Media. Gaithersburg, Md.: National Bureau of Standards.

Spaulding, C. 1978. Kicking the silver habit. American Libraries 9 (12): 653-59.

Speliotis, D. 1987. Barium ferrite magnetic recording media. IEEE Transactions on Magnetics 23 (1): 25-28.

Speliotis, D. 1987a. Distinctive characteristics of barium ferrite media. IEEE Transactions on Magnetics 23 (5): 3143-45.

Speliotis, D. 1987b. Digital recording performance of Ba-ferrite media. Journal of Applied Physics 61 (8): 3878-80.

Speliotis, D. 1990. Corrosion of particulate and thin film media. IEEE Transactions on Magnetics 26 (1): 124-26.

Speliotis, D. 1990a. Corrosion of particulate and thin film media. IEEE Transactions on Magnetics 26 (1): 124-26.

Speliotis, D. 1995. Performance of metal particle and barium ferrite tapes in high density recording applications. IEEE Transactions on Magnetics 31 (6): 2877-82.

Speliotis, D. 1996. Advanced metal particle and barium ferrite tapes. Journal of Magnetism and Magnetic Materials 155 (1-3): 83-85.

Speliotis, D. and J. Judge. 1991. Magnetic and thermomagnetic analysis of metal evaporated tape. Journal of Applied Physics 69 (8): 5157-59.

Speliotis, D. and K. Peter. 1991. Corrosion study of metal particle, metal film, and Ba-ferrite tape. IEEE Transactions on Magnetics 27 (6): 4724-26.

Speliotis, D. and K. Peter. 1993. High density digital recording on 4mm metal particle Ba-ferrite tapes. Journal of Magnetism and Magnetic Materials 120 (1-3): 28-32.

Spencer, K. 1988. Terabyte optical tape recorder. In Digest of Papers: Ninth IEEE Symposium on Mass Storage Systems. Washington, D.C.: IEEE Computer Society Press, 144-46.

Spencer, K. 1990. Optical tape recorder: Easy data handling at less cost. Photonics Spectra 24 (2): 115-16.

Spruijt, L. 1984. Recorded media: Data life. In Proceedings of the National Bureau of Standards/National Security Agency Workshop on Standardization Issues for Optical Digital Data Disk Technology. Washington, D.C.: National Bureau of Standards, 149-61.

Steenbergen, C. and R. Van Dorp. 1996. Testing of CD-recordable discs. In Proceedings of the SPIE, vol. 2931. Bellingham, Wash.: SPIE, 192-97.

Steinberg, C. 1986. Video tape recording 1935-1996: A perspective and prospective view. In International Conference on the History of Television: From Early Days to the Present. London: IEE, 109-13.

Steinberg, G. 1987. Tribology of magnetic media and its relation to media failure. IEEE Transactions on Magnetics 23 (1): 115-17.

Stephenson, A. and J. Shao. 1993. The angular dependence of the remanent coercivity of gamma ferric oxide "tape" particles. IEEE Transactions on Magnetics 29 (1): 7-10.

Stevens, R. 1971. The microform revolution. Library Trends 19 (2): 370-95.

Storey, P. et al. 1988. Environmental evaluation of rugged and long-life write-once optical disks. In Proceedings of the SPIE, vol. 899. Bellingham, Wash.: SPIE, 226-32.

Stosich, M. 1990. Archival revival: Problems and solutions in long-term tape performance. Audio 74 (11): 61-67.

Strandjord, A. et al. 1992. Flexible storage medium for write-once optical tape. In Proceedings of the SPIE, vol. 1663. Bellingham, Wash.: SPIE, 362-71.

Suh, S. 1985. Writing process in ablative optical recording. Applied Optics 24 (4): 868-74.

Suh, S. 1986. Optical recording in multilayer Bi/Se thin films. In Proceedings of the SPIE, vol. 695. Bellingham, Wash.: SPIE, 16-19.

Sullivan, J. 1996. The tribology of flexible magnetic recording media: Journal of Magnetism and Magnetic Materials 155 (1-3): 312-17.

Suzuki, M. et al. 1994. Stability of phase-change optical disks produced by a pass-through type sputtering system. In Proceedings of the SPIE, vol. 2338. Bellingham, Wash.: SPIE, 211-21.

Suzuki, S. et al. 1981. Coercivity and unit particle size of metal pigment. IEEE Transactions on Magnetics 17 (6): 3017-19.

Suzuki, S. et al. 1984. Performance of metal pigment tapes with 600-700 Oe coercivity. IEEE Transactions on Magnetics 20 (1): 39-41.

Suzuki, T. 1992. Orientation and angular dependence of magnetic properties for Ba-ferrite tapes. IEEE Transactions on Magnetics 28 (5): 2388-90.

Suzuki, T. et al. 1993. Ba ferrite 8mm data tapes. Journal of Magnetism and Magnetic Materials 120 (1-3): 25-27.

Tada, J. et al. 1986. Significant improvement of magnetic properties and corrosion resistance in evaporated Co-Ni recording media. IEEE Transactions on Magnetics 22 (5): 343-45.

Tagami, K. and Y. Motomura. 1994. Critical issues on pass-wear durability for CoCr perpendicular flexible disks. Journal of Magnetism and Magnetic Materials 134 (2-3): 370-75.

Takeda, Y. et al. 1989. Pin-hole failure analysis of plastic-based magneto-optical disk. In ISFTA 89. Materials Park, Ohio: ASM International, 223-29.

Tamaru, N. and N. Amano. 1992. Data reliability evaluation of flexible optical disk system using accelerated test of dust density. Applied Optics 31 (35): 7464-70.

Tanaka, S. and N. Imamura. 1985. The effect of noble metals on oxidation resistance of TbFe. Japanese Journal of Applied Physics 2 (5): 375-76.

Tanaka, S. et al. 1987. Improvement of lifetimes of magneto-optical disks by alloying various elements. IEEE Translation Journal on Magnetics in Japan 2 (5): 397-98.

Taubes, E. 1979. Color microfilming of large documents. Journal of Micrographics 12 (3): 285-88.

Taubes, E. 1984. Color microfilming of documents. Journal of Imaging Technology 10 (4): 165-68.

Taylor, C. 1981. Certified "acid free" microfiche envelopes. Journal of Micrographics 14 (12): 40.

Tejedor, M. and A. Fernandez. 1986. Effect of the oxidation of the magnetic properties of vacuum evaporated Tb-Fe thin films. Journal of Magnetism and Magnetic Materials 59 (1): 28-32.

Terao, M. et al. 1983. The resistance of oxidation of Te-Se recording films. In Topical Meeting on Optical Data Storage. Washington, D.C.: Optical Society of America, 2/1-4.

Terao, M. et al. 1987. Oxidation resistance of Pb-Te-Se optical recording film. Journal of Applied Physics 62 (3): 1029-34.

Terao, M. et al. 1989. Effect of transition metal addition to a Ge-Sb-Te phase-change optical recording film. Optoelectronics: Devices and Technologies 4 (2): 223-34.

Terao, M. et al. 1997. High performance phase change media for DVD-RAM. In 1997 Optical Data Storage Topical Meeting ODS: Conference Digest. New York: IEEE, 27-29.

Thomas, G. 1987. Thin films for optical recording applications. Journal of Vacuum Science and Technology, Part A 5 (6): 1965-66.

Thomas, G. 1988. Future trends in optical recording. Philips Technical Review 44 (2): 51-57.

Thurlow, J. 1990. The debut of dry silver color. Computer Graphics Review 5 (2): 40-42.

Tobin, V. et al. 1988. Magnetization time decay in chromium dioxide tape. IEEE Transactions on Magnetics 24 (6): 2880-82.

Tokuoka, Y. et al. 1982. The formation of iron particles and their magnetic properties. In Ferrites: Proceedings of the ICF3, Third International Conference on Ferrites. Dordrecht, The Netherlands: Reidel, 553-55.

Tokushima, T. et al. 1989. Improvement of environmental stability by doping beryllium in TbFeCo magnetooptical recording media. IEEE Transactions on Magnetics 25 (1): 687-91.

Tomago, A. et al. 1985. Metal-evaporated video tape. National Technical Report 31 (6): 899-907.

Tomago, A. et al. 1985a. Effects of the surface configuration of magnetic layers on durability against mechanical stress. IEEE Transactions on Magnetics 21 (5): 1524-26.

Toyota, K. et al. 1990. A new optical card requiring no preformatting. In Proceedings of the SPIE, vol. 1316. Bellingham, Wash.: SPIE, 345-55.

Trznadel, M. and M. Kryszewski. 1988. Shrinkage and related relaxation of internal stresses in oriented glassy polymers. Polymer 29 (3): 418-25.

Uehori, T. et al. 1978. Magnetic properties of iron-cobalt alloy particles for magnetic recording media. IEEE Transactions on Magnetics 1 (5): 852-54.

Urrows, H. and E. Urrows. 1989. The future of transactional card technologies. Optical Information Systems 10 (1): 14-27.

Urrows, H. and E. Urrows. 1990. Erasable-rewritables now and promised: Introductory notes. Optical Information Systems 10 (1): 14-27.

Usherwood, T. et al. 1996. A computer modelling approach to predicting the long term thermal stability of Co-Pd magnetic multilayers. Journal of Magnetism and Magnetic Materials 162 (2-3): 383-90.

Ustinov, V. and Y. Shepelyov. 1989. Storage life of video recordings on modern magnetic tapes. Radio and Television 39 (4): 35-39.

Utyhof, B. 1993. A national care card concept: Cooperation and competition. In Patient Care with Computers and Cards: Fifth Global Congress on Patient Cards and Computerization of Health Records. Newton, Mass.: Medical Records Institute, pp. 98-99.

Van Bogart, J. 1994. NML Media Stability Studies, Final Report. Minneapolis: National Media Laboratory.

Van Bogart, J. 1995. Magnetic Tape Storage and Handling: A Guide for Libraries and Archives. Minneapolis: National Media Laboratory.

Van der Poel, C. et al. 1986. Phase-change optical recording in TeSeSb alloys. Journal of Applied Physics 59 (6): 1819-21.

Van Rijsewijk, H. et al. 1982. Manufacture of Laser Vision video discs by a photopolymerization process. Philips Technical Review 40 (10): 287-97.

Van Uijen, C. 1985. Reversible optical recording: Phase-change media and magneto-optics. In Proceedings of the SPIE, vol. 529. Bellingham, Wash.: SPIE, 2-5.

Veaner, A. 1975. Microfilm and the library: A retrospective. Drexel Library Quarterly 11 (1): 3-16.

Veaner, A. 1979. Permanence: A view from and to the long range. Microform Review 8 (1): 75-77.

Veaner, A. 1982. Practical microform materials for libraries: Silver, diazo, vesicular. Library Resources and Technical Services 26 (4): 306-8.

Verhoeven, J. 1996. Prospects of DVD. In Proceedings of the SPIE, vol. 2931. Bellingham, Wash.: SPIE, 98-107.

Verry, H. 1952. Micro-opaques. Aslib Proceedings 4 (3): 153-62.

Vincett, P. 1983. Xerox dry microfilm: A versatile camera-film and information-recording medium. Journal of Applied Photographic Engineering 9 (1): 38-44.

Vincett, P. et al. 1985. XDM: Photography updated. Chemtech 15 (3) 160-67.

Vriens, L. et al. 1983. Ablative optical recording in Te-alloy films. In 1983 SID International Symposium: Digest of Technical Papers. Los Angeles: Society for Information Display, 52-53.

Waghorne, R. and H. Lewis. 1984. The effect of tape integrity and tape cleaning on drop-out performance. In Fifth International Conference on Video and Data Recording. London: IERE, 63-65.

Wang, R. et al. 1997. Magnetic field modulated direct overwrite with pulsed laser irradiation for TbFeCo magneto-optical disks. Optical Engineering 36 (9): 2513-16.

Wang, Y. et al. 1987. The annealing effect and the origin of perpendicular anisotropy in amorphous GdTbFe film. Journal of Magnetism and Magnetic Materials 66 (1): 84-90.

Wassell, J. Illini fighting redox. Inform 4 (5): 26-30.

Watanabe, N. et al. 1989. Studies of long term aging effects on the magneto-optic properties of amorphous Tb-Fe films. In Materials for Magneto-Optic Data Storage Symposium. Pittsburgh: Materials Research Society, 239-44.

Watanabe, Y. et al. 1987. Magnetooptical disk with alumina based oxide layer. IEEE Transactions on Magnetics 23 (5): 2623-25.

Watson, J. et al. 1997. The debate over green vs. gold CD-R media. Inform 11 (9): 12-16, 18-19.

Weick, B. and B. Bhushan. 1996. Relationship between dynamic mechanical behavior, transverse curvature, and wear of magnetic tapes. Wear 202 (1): 17-29.

Weir, T. 1988. 3480 Class Tape Cartridge Drives and Archival Data Storage: Technology Assessment Report. National Archives Technical Information Paper No. 4. Washington, D.C.: National Archives and Records Administration.

Wellwood, J. 1987. Magnetic Thin Film Recording Media. UK Patent No. GB2186293A, Thorn EMI.

Welsh, W. 1987. International cooperation in preservation of library materials. Collection Management 9 (2): 119-31.

Wheeler, J. 1983. Long-term storage of videotape. SMPTE Journal 92 (6): 650-54.

White, R. 1985. Introduction to Magnetic Recording. New York: IEEE Press.

Wilkinson, R. 1997. DVD mastering using dye polymer media. In 1997 Optical Data Storage Topical Meeting: Conference Digest. New York: IEEE, 90-91.

Williams, B. 1970. Miniaturized Communications. London: Library Association.

Williams, L. 1997. Do you need to test your CD-R discs? Tape-Disc Business 11 (1): 23-27.

Williamson, M. 1991. 3480 Type Tape Cartridge: Potential Data Storage Risks and Care and Handling Procedures to Minimize Risks. Gaithersburg, Md.: National Institute of Standards and Technology.

Winterbottom, D. 1995. Data Demonstrator System to Monitor Optical Disk Deterioration: Results and Analysis of Tests from August 1991 to September 1994. BLRD Report 6218. British Library, Research and Development Department.

Witherell, F. 1984. Surface and near-surface chemical analysis of cobalt-treated iron oxide. IEEE Transactions on Magnetics 20 (5): 739-41.

Wolf, D. 1987. Update on updatables, 1986: The technologies and role of updateable micrographic record systems; image stability tests. IMC Journal 23 (1): 44-49.

Xie, Y. and B. Bhushan. 1996. Fundamental wear studies with magnetic particles and head cleaning agents used in magnetic tapes. Wear 202 (1): 3-16.

Xu, J. et al. 1997. Effect of temperature and humidity on the friction and wear of magnetic tape. Wear 203 (3): 642-47.

Yamada, H. 1997. DVD overview. In Digest of Papers: COMPCON Spring 97, Forty-second IEEE Computer Society International Conference Proceedings. Los Alamitos, Calif.: IEEE Computer Society Press, 287-90.

Yamaguchi, H. et al. 1991. Extremely durable CD-ROM with novel structure. In Proceedings of the SPIE, vol. 1499. Bellingham, Wash.: SPIE, 29-38.

Yamamoto, M. and I. Yamada. 1988. Bit error characteristics in magneto-optical disk. IEEE Translation Journal on Magnetics in Japan 3 (9): 683-93.

Yamamoto, Y. et al. 1990. Study of corrosion stability in metal particulate media. IEEE Transactions on Magnetics 26 (5): 2098-2100.

Yamamoto, Y. et al. 1992. Storage stability of professional video metal tapes. In International Broadcasting Convention, IBC92. IEE Conference Publication No. 358. Stevenage, England: IEE, 12-26.

Yamazaki, H. et al. 1993. Overwrite repeatability of GeSbTe phase-change-type optical disk media. Advanced Materials 5 (3): 214-16.

Yan, B. et al. 1990. The effect of terbium and gadolinium composition on the corrosion resistance of sputtered GdTbFeCo thin films. Journal of Applied Physics67 (9): 5310-12.

Yardy, R. et al. 1990. Read stability of magneto-optical storage. In Proceedings of the SPIE, vol. 1316. Bellingham, Wash.: SPIE, 106-16.

Yashiro, T. et al. 1987. Effects of barium ferrite particles added to VHS tapes. IEEE Transactions on Magnetics 23 (1): 100-102.

Yee, A. et al. 1988. Strain and temperature accelerated relaxation in polycarbonate. Journal of Polymer Science, Part B 26 (12): 2463-83.

Yianakopoulos, G. et al. 1990. Influence of physical aging processes on electrical properties of amorphous polymers. IEEE Transactions on Electrical Insulation 25 (4): 693-701.

Yokoyama, H. et al. 1992. Barium ferrite particulate tapes for high-band 8 mm VCR. IEEE Transactions on Magnetics 28 (5): 2391-93.

Yoshida, T. 1984. Summary of media life. In Proceedings of the National Bureau of Standards/National Security Agency Workshop on Standardization Issues for Optical Digital Data Disk (OD3) Technology. Washington, D.C.: National Bureau of Standards, 182-83.

Ypma, G. 1996. Manufacturing of CD-recordable discs. In Proceedings of the SPIE, vol. 2931. Bellingham, Wash.: SPIE, 57-61.

Zagami, R. 1986. The engineering aperture card. Journal of Information and Image Management 19 (8): 30-34.

Zhang, S. et al. 1991. Preparation and stability of NdDyFeCoTi magneto-optical amorphous films. Journal of Applied Physics 69 (8): 5994-96.

Zimmer, L. 1993. Going beyond the gold: Kodak writable media. CD-ROM Professional 6 (6): 30-33.

Oops!

An unknown error has occurred. Please click the button below to reload the page. If the problem persists, please try again in a little while.