|The CD-R drive writes onto a special compact disc that has a gold layer instead of the familiar silvery aluminum layer inside audio compact discs. However, the disc can be only written once. When information is recorded onto the disc, a layer of organic dye is altered and can never be changed.
The basic phthalocyanine (gold) formulation is patented by Mitsui Toatsu Chemicals (MTC) of Japan, and is licensed to other phthalocyanine media manufacturers.
These discs are generally referred to as "high speed" discs, and will usually work better at 2x writing speed.
Discs which are darker green on the bottom use cyanine as the recording dye. Gold discs use phthalocyanine dye. The more common blue discs usually use Azo dye.
A metal-stabilized cyanine dye formulation has been developed that showed excellent overall performance. As more manufacturers develop this technology, the difference between the performance of pthalocyanine and cyanine media is vanishing.