Optical data storage media

In general, the commercially used optical data storage media deposit the information on disks or cards (two-dimensional data deposition. Table 1). Data storage systems, which store data in three and more dimensions are being developed. 

Copolymers nd Blends of PC. Numerous co- and terpolymers as well as polymer blends of BPA-PC have been developed and their suitabihty as substrate materials for optical data storage media has been tested (Table 8) (195). From these products, three lines of development have been chosen for closer examination. 

By the sol-gel-process, inorganic glassy and hybrid polymeric materials are accessible at comparatively low temperatures [1], Therefore, organic molecules or dyes can easily be incorporated into the oxide matrix. This combination is especially attractive for the development of the following devices optical filters, solid-state lasers, optical switches, nonlinear optical laser hosts, optical data storage media, and photoconductive devices and films [2]. 

These dyes are used predominandy as photographic spectral sensitizers, but some years ago a new application in optical data storage media was found. Compound 10 dyes paper in brilliant pink shades [6] ... 

Optical data storage media fall into three main classes [26] (Figure 6.9). Read only media comprise the CD in its audio and CD-ROM formats and DVD, also of the CD format but having about six to ten times the data capacity of a CD-ROM, depending upon whether one or two recording layers are used. These read only media are mainly dedicated to entertainment. As seen from Figure 6.9, the systems which use organic dyes are WORM (write-once-read-many), CD-R, and DVD-R. 

Figure 6.9 General classes of optical data storage media...

M. Irie, Advances in photochromic materials for optical data storage media, Jpn. J Appl. Rhys. 28, Suppl. 3, 215-219(1989). 

M. Irie, Photochromic diarylethenes for optical data storage media, Mol. Cryst. Liq. 227, 263-270 (1993). 

Cyclic oligomeric formals, (IV), characterized by a lowered water absorption were prepared by Wehrmann [4] and blended with polycarbonates for use in optical data storage media. Copolyformals, (V), were prepared by the author [5] and also used in optical data storage media applications. 

Pham VP, Galstian T, Granger A, Lessard R. 1997. Novel azo dye doped poly(methyl methacrylate) films as optical data storage media. Jpn J Appl Physt 36 (part 1 B) 429 438. 

Nematic and smectic side-chain LCP are suitable as optical data storage media. A particular technique is the heat-mode recording technique [75], By locally heating, an optical scattering center is generated. However, heat-mode recording has the disadvantages of slow response time and low resolution [19],... 

Pham, V.P. Galstyan, T. Granger, A. Lessard, R.A. (1997). Novel Azo Dye-Doped Poly(methyl methacrylate) Films as Optical Data Storage Media. Jpn. J. Appl. Phys., 1997,36,429 8. 

Modulation of Optical Properties of New Photosensitive Polymers 3-D Optical Data Storage Media... 

Recently polymer photonic crystal materials have been applied as optical data storage media. An optically active, core-shell latex colloidal crystal with dye-labeled polymer cores was atmealed into a material with a periodic array of fluorescent particles in an optically inert matrix. A two-photon laser scanning microscope was used to write information to, and read from, the material leading to increased optical storage density over conventional materials [133]. 

Now, what is the role of structure in optical materials. A lens can be used as a magnifying glass due to its specific shape. It is the exact distribution of black, white or colors that turns a sheet of paper into a tax declaration form, a love letter, or any other document. On this scale, each stmctural element such as a printed letter is typically perceived individually and has its own clearly defined significance. This can apply to smaller scales, too in optical data storage media, the information of one bit is represented by the reflection properties of a well-defined area of typically submicrometer size. 

Consumer products such as optical data storage media and appliances, is the major user of polycarbonate with 29% of total world consumption, followed by electrical and electronics with 24.9%, industrial 18.8% and automotive 16.5%. Other markets , comprising packaging, medical optical lenses and sports equipment, with 10.8% of total consumption, account for the remainder. 

This section examines the growing use of engineering plastics in consumer products. The main areas of application are domestic appliances, power tools, sports equipment, houseware, cookware and optical data storage media. 

In 2002, total polycarbonate consumption in consumer product maikets amounted to 497,000 tonnes compared with 358,000 tonnes in 1999. World consumption of polycarbonate in consumer products has increased substantially in recent years, mainly due to growth in the optical data storage market. China and Western Europe have been the fastest growing maikets for optical data storage media since 1999. 

A growing amount of polycarbonate is used for manufacture of optical data storage media such as CDs, CD-ROMs and DVDs. Optical data storage media contain microscopically small items of information, which need to be read without any errors if possible, even under critical ambient conditions. Only a polymer offering high transparency and dimensional stability, coupled with an extremely high reproduction accuracy and dimensional stability, will be a suitable substrate material. 

PMMA is used in optical data storage media such as CDs and DVDs. Substrates made from PMMA provide an optimised balance of high-flow characteristics and heat resistance. They also have good optical characteristics such as high light transmission and low birefringence. 

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