Infra-red absorbing dyes:- Explained in brief
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Infra-red absorbing dyes:-
The recording of data on a disc, light energy is absorbed by an i.r.-absorbing dye contained in a polymer film coating such as poly(methymethacrylate). The laser causes the latter to melt locally and form micro-pits. These pits can subsequently be read by a lower energy laser beam. The dyes used in this connection depend on the emission wave-length of the laser, generally absorbing in the 650-800 nm region. They include phthalocyanine derivatives and cyanine dyes as shown in Table.
Conventional cyanines have poor light fastness. The introduction of a cyclic ring system, however, as a central part of the chromophoric chain gives useful i.r. dyes. They are applied in conjuction with a dithiol or o-phenylenediamine metal complex acting as a singlet oxygen quencher to inhibit the photo-oxidation of the polymer medium.
