We present results of the feasibility study on photoaddressable polymers (PAPs) applied to optical disc systems. PAPs represent a new class of organic rewritable materials that exhibit a huge signal birefringence (Δ
n) at the readout wavelength. By optimizing the disc structure and the readout optics, the signal amplitude is proved to be sufficient for the optical disc systems. A low noise profile and sharp recording profile led to a maximum carrier-to-noise ratio (C/N) of 58 dB and a clear eye-pattern. They also showed a potential for multi-level recording, since the recording was dominated by a pure photon mode.
A principle focus of this book is the classification of dyes by chemical structure. This is certainly not the only possible classification scheme for dyes: ordering by application properties, e.g., naming according the substrate to be dyed is another alternative. Neither of these two categories can be used with the exclusion of the other one, and overlap is often inevitable. Nevertheless, for this book it was decided to make the chemical structure of dyes the main sorting system. This chapter is devoted to the chemical chromophores of dyes, but the term ªchromophoreº is used here in a somewhat extended manner that also considers dye classes such those as based on cationic, di-and triarylcarbonium, and sulfur compounds, and metal complexes.The two overriding trends in traditional colorants research for many years have been improved cost-effectiveness and increased technical excellence. Improved cost-effectiveness usually means replacing tinctorially weak dyes such as anthraquinones, until recently the second largest class after the azo dyes, with tinctorially stronger dyes such as heterocyclic azo dyes, triphendioxazines, and benzodifuranones. This theme will be pursued throughout this chapter, in which dyes are discussed by chemical structure.During the last decade, the phenomenal rise in high-tech industries has fuelled the need for novel high-tech (functional) dyes having special properties. These hi-tech applications can bear higher costs than traditional dye applications, and this has facilitated the evaluation and use of more esoteric dyes (see Chapter 6).
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