Compact disks

Budgeting. These changes in the storage and retrieval of chemical information requite that Hbraries and information centers now consider not only what should be purchased but also what monies should be allocated for the purchase of information in nonprint formats such as CD-ROMs (compact disk read-only memory) and on-line databases. Coupled with this is budgeting for the cost of hardware and software to enable the rapid and cost-effective deHvery of needed information (15). The geometric increase in sources, both printed and on-line, has increased the role of information speciaHst as an expert in the deHvery of chemical information. Retrieval from increasingly diverse and complex sources becomes the paramount issue for searchers of chemical Hterature in the 1990s. 

CD-ROM not erasablenot rewritable technology identical with audio compact disk (CD-DA) substrate and information layer from polycarbonate (PC)... 

CD-ROM disks are nearly identical to the weU-known compact disk-digital audio (CD-DA short CD). The information on a CD-ROM is stamped in the form of clearly defined pits on the disk surface during the disk s manufacture, using injection mol ding or injection stamping techniques. A metal stamper transfers the digital information to the disk s surface. 

Fig. 1. Compact disk geometry (a) CD-ROM, sector detail (1) (b) CD-DA, geometry of the tracks (grooves).

The CD-I (compact disk-interactive) is a low cost alternative to the CD-ROM for the entertainment industry. CD-I is a subset of the CD-ROM standard data format. It allows the digital storage of data, audio, and video information in a form that permits rapid interaction with a computer. CD-I is compatible to CD-ROM and to CD-AD 0 = 120 mm. The definition of the CD-I format is put down in the Green Book (Philips/Sony). 

CD-V (compact disk-video) is premolded for both video and digital music 0 = 305 mm oi0 = 203 mm. There is also a videocHp version (0 = 120 mm) for 22 min CD audio and 5 min of video information. CD-VEP (video extended play) 0 = 200 mm, is recorded on both sides, whereas for CD-VLP (video long play) 0 = 200 mm, one- or two-sided recording can be selected max. 60 min video/side. 

Polycarbonates. Currently, all audio CDs (CD-AD), all CD-ROM, and the biggest fraction of substrate disks for WORM and EOD worldwide are manufactured from a modified bisphenol A—polycarbonate (BPA-PC) (3). In 1991, some 1.3 x 10 compact disks were produced, equivalent to an annual amount of about 35,000 t BPA-PC. WORM and EOD disks are manufactured mainly from BPA-PC for sizes of 5.25 in. and below, and glass for larger form factors (eg, 12 in.), partially also from BPA-PC, and in some cases from aluminum or from cross-linked polymers (epoxy resins) (190). 

Fig. 24. Birefringence (path difference) of a compact disk, made from CD-modified BPA polycarbonate (191). Q, max value Q, min value (—), mean value.

Other Polymers. Besides polycarbonates, poly(methyl methacrylate)s, cycfic polyolefins, and uv-curable cross-linked polymers, a host of other polymers have been examined for their suitabiUty as substrate materials for optical data storage, preferably compact disks, in the last years. These polymers have not gained commercial importance polystyrene (PS), poly(vinyl chloride) (PVC), cellulose acetobutyrate (CAB), bis(diallylpolycarbonate) (BDPC), poly(ethylene terephthalate) (PET), styrene—acrylonitrile copolymers (SAN), poly(vinyl acetate) (PVAC), and for substrates with high resistance to heat softening, polysulfones (PSU) and polyimides (PI). 

Consumer Products. Laser-based products have emerged from the laboratories and become familiar products used by many millions of people in everyday circumstances. Examples include the supermarket scaimer, the laser printer, and the compact disk. The supermarket scanner has become a familiar fixture at the point of sale in stores. The beam from a laser is scaimed across the bar-code marking that identifies a product, and the pattern of varying reflected light intensity is detected and interpreted by a computer to identify the product. Then the information is printed on the sales sHp. The use of the scanner can speed checkout from places like supermarkets. The scanners have usually been helium—neon lasers, but visible semiconductor lasers may take an impact in this appHcation. 

The compact disk player has become a very widespread consumer product for audio reproduction. The information is stored along tracks on the disk in the form of spots of varying reflectivity. The laser beam is focused on a track on the surface of the disk, which is rotated under the beam. The information is recovered by detecting the variations in the reflected light. The compact disk offers very high fideHty because there is no physical contact with the disk. This appHcation has usually employed a semiconductor laser source operating at a wavelength of around 780 nm. Tens of millions of such compact disk players are produced worldwide every year. 

A total of 15,000—17,000 t of resin is used aimuaHy. Polycarbonate also has many technical uses in instmment panels and devices, especiaHy for membrane switches and insulators. Optical quaHty polycarbonate is the only suitable material for the compact disk market. Since their introduction in 1983, compact disks have shown explosive growth in the consumption of polycarbonate, with utiHty for audio, video, and computer appHcations. Consumption of optical quaHty resin more than doubled between 1988 and 1992, and as of 1995 accounted for about 20,000 t of annual production. 

Other apphcatioas for 4-/ f2 -octylpheaol iaclude chaia termination of polycarboaates (54). The properties of low molecular weight polycarboaates used ia injection-molding apphcatioas to form compact disks are enhanced when the polymer is termiaated usiag 4-/ f2 -octylphenoL... 

The relevance of photonics technology is best measured by its omnipresence. Semiconductor lasers, for example, are found in compact disk players, CD-ROM drives, and bar code scaimers, as well as in data communication systems such as telephone systems. Compound semiconductor-based LEDs utilized in multicolor displays, automobile indicators, and most recendy in traffic lights represent an even bigger market, with approximately 1 biUion in aimual sales. The trend to faster and smaller systems with lower power requirements and lower loss has led toward the development of optical communication and computing systems and thus rapid technological advancement in photonics systems is expected for the future. In this section, compound semiconductor photonics technology is reviewed with a focus on three primary photonic devices LEDs, laser diodes, and detectors. Overviews of other important compound semiconductor-based photonic devices can be found in References 75—78. 

A.nnual Survey of Manufactures, Geographic Area Series, 1987 Economic Censuses compact disk, Vol. 1, Release IE, Data User Services... 

A very useful catalog for chromatographic products and information relating to chromatography (from gas chromatography to biochromatography) is that produced by Merck, called the ChromBook and the associated compact disk, ChromCircle. 

Toys and games, personal compact disk or cassette players, tape recorders... 

ASCE American Society of Civil CD compact disk (disc)... 

Schmidt, L. B., et al., Injection Molding of Polycarbonate Compact Disks Relationship between Process Conditions, Birefringence, Block Error Rate, SPE-ANTEC, 1992. 

Calculate the radius of the cavity formed by three circular disks of radius r that lie in a dose-packed planar arrangement. Check your answer experimentally by using three compact disks and measuring the radius of the cavity that they form. 

Optoelectronic devices are found in numerous consumer products such as television, compact-disk players, laser communications, laser printers, radar detectors, cellular telephones, direct-broad-cast television, and many others. Many of these applications were developed in Japan and that country is still prominent in the field. 

The present chapter will focus on the practical, nuts and bolts aspects of this particular CA approach to modeling. In later chapters we will describe a variety of applications of these CA models to chemical systems, emphasizing applications involving solution phenomena, phase transitions, and chemical kinetics. In order to prepare readers for the use of CA models in teaching and research, we have attempted to present a user-friendly description. This description is accompanied by examples and hands-on calculations, available on the compact disk that comes with this book. The reader is encouraged to use this means to assimilate the basic aspects of the CA approach described in this chapter. More details on the operation of the CA programs, when needed, can be found in Chapter 10 of this book. 

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