Metal Optical Recording Dyes

The key component of the optical recording system is the recording medium, which is marked in one step and read in another step with a laser beam. Many materials have been considered for the purpose, including metal-films, organic dyes, dye-loaded polymers, metal-loaded polymers, discontinuous metal films, thermal coloration systems and bilayers (1-19). Tellurium- and gold-based optical disks have been the most widely studied materials to date. 

Infrared dyes include indoleninecyanines and azulenium compounds, both of which are used in optical recording materials.46 Other examples are metal (Mn, Fe, Co, Cd, Al, Cu, Pd)-complexed phthalocyanines, quinones, quinonoids, and imminium and diiminium compounds (Fig. 13.37). 

The preparation of optical recording elements having recording layers containing mixtures of metallized formazan, (I), and cyanine dyes, (II), is provided (3). 

A variety of organic-polymeric-based materials have been investigated for optical recording, including dyes (pigments), dye (pigment)-polymer composites, dye-polymer solutions, and polymer-metal-layered or particulate structures. In all instances, the light absorption function is provided by the dye or metal, and the polymer serves the role of binder and film former. 

There are no clear advantages in terms of functional performance between the two classes of dyes, except that phthalocyanines are generally more light stable but tend to be more expensive to synthesize and modify. Phthalocyanine dyes are not suitable for DVD-R media, since the main chromophore cannot readily be modified to produce a sufficiently large hypsochromic shift. Other dyes potentially suitable for DVD-R include metal azo complexes, quinophthalones, and diphenyl-methanes. The cyanine dyes are particularly useful as they can be readily modified to tailor the optical absorbance requirements for all current optical disk recording applications.199... 

Coumarin-linked benzo-47/-l-thia-2,4-diazine 1,1-dioxides 283, where X is a cryptand or crown ether, have been studied for their potential in measuring metal cation concentrations <1998EPP861843>. 3,4-Dialkylated benzo-477-l-thia-2,4-diazine 1,1-dioxides 284 are useful as couplers in the formation of photographic dyes <2002JPP2002318441>. Bis(3-substituted-47/-benzo-l-thia-2,4-diazine 1,1-dioxides) such as 285 are useful as materials in the recording layers of optical disks that use lasers in the 300-900 nm range <2006JPP2006076209>. 

The modified images of the interface are shown in Fig. 3.4 superimposed upon the capacitance curve recorded during the optical measurement At positive potentials (images A and B), fluorescence from both dye molecules are quenched because of the proximity of the surfactant and metal. At potentials negative of -... 

In addition, the surface should be free of contaminating particles and occlusions that would interfere with the information retrieval process. A typical ablative-mode optical disk has the structure shown in Figme 16.14. The substrate is an optically transparent material such as polycarbonate, PMMA, polyfethylene terephthalate), or polyfvinyl chloride) topped by a subbing layer to provide an optically smooth surface for the recording layer. A metal reflector (typically aluminum) is then incorporated next to a transparent dielectric medium such as poly(a-methyl styrene) and, finally, the absorbing layer where the information pits are created is added. The latter can be a metal-polymer composite (silver particles in a gel) or a dye molecule dispersed in a polymer matrix such as squaryllium dyes, which act as infrared absorbers for GaAs lasers, typically... 

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