A coloured organic
compound that increases the sensitivity of photographic emulsions
to a wider range of light frequencies
Cyanine was used for the first CDR discs and was specified as the standard in the Orange Book specification. A metal-stablized cyanine compound is more frequently used today because it is more durable. These CDR discs can be identified by either an emerald green or cobalt blue color, depending on if the reflective layer is gold or silver, respectively.
When the recording laser heats the dye, the chemical composition is altered so that when the disc is read, the dye will allow less light to pass through, effectively simulating a "pit" on the recorded CD.
Many people believe that cyanine discs are better suited for a wider range of recording speeds and writing techniques than discs containing other dyes. The only problem with cyanine dye discs is that since they are more sensitive, there is the possibility that data could be lost after long exposures to light.
The estimated lifetime for cyanine dye discs is only about 20 years, but that increases to 70 years for metal stabilized cyanine dye compounds. However, phthalocyanine dye discs have been estimated to last around 100 years.