Editing CD-R (section)

=== Dyes ===
{{anchor|dyes}}
There are three basic formulations of dye used in CD-Rs:
# [[Cyanine]] dye CD-Rs were the earliest ones developed, and their formulation is [[patent]]ed by [[Taiyo Yuden]]. CD-Rs based on this dye are mostly green in color. The earlier models were very chemically unstable and this made cyanine-based discs unsuitable for archival use; they could fade and become unreadable in a few years. Many manufacturers like Taiyo Yuden use proprietary chemical additives, typically a metal atom bonded to the cyanine molecule,<ref>{{cite web |title=Archival Lifespan of TDK CD-R |url=https://www.cdrom2go.com/archival-lifespan-of-tdk-cd-r |website=cdrom2go.com |publisher=US Digital Media |access-date=12 March 2022}}</ref> to make more stable cyanine discs ("metal-stabilized Cyanine", "Super Cyanine"). Older cyanine dye-based CD-Rs, as well as all the hybrid dyes based on cyanine, are very sensitive to UV-rays and can become unreadable after only a few days if they were exposed to direct sunlight. Although the additives used have made cyanine more stable, it is still the most sensitive of the dyes in UV rays (showing signs of degradation within a week of direct sunlight exposure). A common mistake users make is to leave the CD-Rs with the "clear" (recording) surface upwards, in order to protect it from scratches, as this lets the sun hit the recording surface directly.
# [[Phthalocyanine]] dye CD-Rs are usually silver, gold, or light green. The patents on phthalocyanine CD-Rs are held by [[Mitsui]] and [[Ciba Specialty Chemicals]]. Phthalocyanine is a natively stable dye (has no need for stabilizers) and CD-Rs based on this are often given a rated lifetime of hundreds of years. Unlike [[cyanine]], phthalocyanine is more resistant to UV rays, and CD-Rs based on this dye show signs of degradation only after two weeks of direct sunlight exposure.{{Clarify|date=April 2014}}{{Citation needed|date=April 2014}} However, phthalocyanine is more sensitive than cyanine to writing laser power calibration, meaning that the power level used by the writing laser has to be more accurately adjusted for the disc in order to get a good recording; this may erode the benefits of dye stability, as marginally written discs (with higher correctable error rates) will lose data (i.e. have uncorrectable errors) after less dye degradation than well-written discs (with lower correctable error rates).
# [[Azo dye]] CD-Rs are dark blue in color, and their formulation is patented by [[Mitsubishi Chemical Corporation]]. Azo dyes are also chemically stable, and Azo CD-Rs are typically rated with a lifetime of decades. Azo is the most resistant dye against UV light and begins to degrade only after the third or fourth week of direct sunlight exposure. More modern implementations of this kind of dye include Super Azo which is not as deep blue as the earlier Metal Azo. This change of composition was necessary in order to achieve higher writing speeds.

There are many hybrid variations of the dye formulations, such as [[Formazan]] by [[Kodak]] (a hybrid of cyanine and phthalocyanine).

Many manufacturers have added additional coloring to disguise their unstable cyanine CD-Rs in the past, so the formulation of a disc cannot be determined based purely on its color. Similarly, a gold reflective layer does not guarantee the use of phthalocyanine dye. The quality of the disc is also not only dependent on the dye used, it is also influenced by sealing, the top layer, the reflective layer, and the polycarbonate. Simply choosing a disc based on its dye type may be problematic. Furthermore, correct power calibration of the laser in the writer, as well as correct timing of the laser pulses, stable disc speed, and so on, is critical to not only the immediate readability but the longevity of the recorded disc, so for archiving it is important to have not only a high-quality disc but a high-quality writer. In fact, a high-quality writer may produce adequate results with medium-quality media, but high-quality media cannot compensate for a mediocre writer, and discs written by such a writer cannot achieve their maximum potential archival lifetime.