CD/R TECHNOLOGY

A recordable CD, or CD/R, is far more complicated than a standard replicated CD. It contains 4 or 5 layers of material (the label coating is not found on all CD/R's):

• The Polycarbonate Layer is similar to that used in replicated CD's. A replicated CD, however, contains a series of pits and lands generated during the mastering process and based specifically on the data provided by the customer. The polycarbonate layer of a CD/R does not contain these pits and lands but instead contains a shallow groove (or pregroove) that is used for timing and tracking.
• The Dye Surface varies by manufacturer. There are currently three popular dyes used for CD/R's: Cyanine (including Metal-Stabilized Cyanine), Phthalocyanie, and AZO.
• The Reflective Layer is comprised of either gold or silver. Yes, this is REAL gold or REAL silver, but it exists in such small amounts that it would not be worth the effort to extract it!
• The Lacquer Layer protects the Reflective Layer.
• The Label Coating is present on some discs, and is also referred to by some manufacturers as the data shield. Most agree that this coatings primary benefit is that it will accept printing from inkjet printers. There are several competing formulas that are used to create this surface, each designed for a different print engine.

The disc has a spiral track onto which the data is written. This is preformed during the manufacturing process. This ensures that the recorder follows the same spiral path as a conventional CD. CD/Rs are written from the center (the hub) of the disc outward. Instead of pressing a CD with indentations (like a CD-ROM), a CD/R writes data to a disc by using its lasers to physically "burn" pits into the organic dye. When heated beyond a certain temperature, the area that was "burned" becomes opaque and reflects less light than the areas that have not been "burned". A CD/Rs "burned" and "unburned" areas represent the pits and lands of a standard CD. This is why a recorded CD can be played in a regular CD Player.

CD/R, like DVD and CD-ROM, are 120mm in diameter and 1.2mm thick. They generally come in 800-megabyte format, equal to approximately 80 minutes of audio. CD/R is a Write Once/Read Many (WORM) storage disc. However, you cannot erase what has been written to the disc. You may leave the session "open" (not recording on the entire CD) and go back and add more to it later. By doing this though, you run the risk of the disc not reading on all players.

CD/R Dyes

There are currently three competing organic dye polymers that are used to manufacture recordable CD's (CD-R). To date there has been no conclusive proof that any of these dye polymers are superior. Manufacturers (and some customers), however, have preferences based on a variety of factors including perceptions, personal (or secondhand) experience, and cost.

CYANINE (including METAL-STABILIZED CYANINE

This is the original dye polymer used in the Orange Book specification for recordable media. Discs using this type of dye can be identified by the emerald green or cobalt blue. (The dye itself is blue, but will appear different based on the material used for the reflective layer. A gold reflective layer will produce the green while a silver reflective layer will produce the blue).

When the recording laser heats the dye the chemical composition is altered and the dye will allow less light to pass through, effectively simulating a "pit" on a replicated CD.

Many involved in this industry believe that Cyanine discs are better suited for a wider range of recording speeds and writing techniques. In particular, TDK claims that it's metal-stabilized cyanine discs were formulated to produce better quality with a wider range of CD-R burners (TDK can handle 6.5 mW +/- 1.0 mW while phthalocyanine can only handle 5.5 mW +/- 0.5 mW) The argument against cyanine dyes is in it's native state cyanine is extremely sensitive to light and that there is the possibility that data could be lost after long exposures to light. This is not to say that data will be lost overnight; the proponents of the other dye types instead claim that the cyanine dye will hold data for only 20 years (70 for metal stabilized), while other types will last longer.

PHTHALOCYANINE (pronounced thal-o-sy-a-nene)

This dye (almost a clear yellow-green) produces discs that appear gold or greenish gold. We presume that this is based on a gold reflective layer and that a silver reflective layer would produce a silver or greenish-yellowish silver disc.

When the recording laser heats the phthalocyanine dye it causes it to melt. As it melts the polycarbonate layer below the dye expands to fill the gap. This melted "blob" effectively diffuses the light enough to resemble the pits on a replicated CD.

The estimated life of phthalocyanine discs is pegged at 100 years.

AZO

This formulation was developed by Mitsubishi and is offered in the US by Verbatim. It is easily recognized by it's deep blue color, partially caused by it's unique silver alloy reflective layer. There is not an abundant source of information on this disc, which is surprising considering that it is a price leader and is currently one of the products most requested by our customers. The manufacturer claims that it has a data life of 100 years.