This is a type of dye
used for various applications (including enamels
, printing inks
, and plastics
), but it is especially well known as the recording medium in CDR discs
The dye (almost a clear yellow-green) produces discs that appear gold or greenish gold, depending on the reflective layer: gold for gold reflective layers, and greenish-yellow for silver reflective layers.
The recording laser melts the dye, causing the polycarbonate layer below to expand and fill the gap creating a pit where light will be diffused when the disc is read.
Phthalocyanine dye discs are expected to last longer than cyanine dye discs. The estimated maximum life of phthalocyanine discs is about 100 years.