There are two primary layers on CDR media. One is the reflective layer. The other is referred to as the dye or recording layer. These layers are applied to a polycarbonate plastic disk. To aid in understanding these layers, a word on how the CD reading and recording processes work will help clarify what the reflective layer and the dye layer are all about. A CD-ROM drive or a CD player has a small laser in the drive that is used to read or play the CD. This laser is precisely aimed at the bottom surface of the disk and moves across the disk from track to track as it reads or plays it. A sensor in the drive picks up the laser's light as it is reflected off of the disk. The data or audio content of the disk is recorded in a binary data format. This is a scheme where data is represented in a pattern of ones and zeros. The reflected light is different for a one versus a zero. The drive's electronics detect this difference in the reflected light and reproduces the ones and zeros pattern just as it is on the CD.

When a CDR disk is manufactured, the reflective layer and the dye layer are applied. These layers are applied to the top of the plastic disk, not the bottom as is sometimes thought. The dye layer goes on first and the reflective layer is applied on top of the dye layer. Usually a lacquer layer is applied but this is only to protect the reflective layer from being easily scratched or damaged. A CDR recorder has a more powerful laser than does a CD-ROM drive or CD player. The purpose of this stronger laser is to enable it to record onto the CDR disk. This process is often referred to as "burning" a CD. This term is used because the heat of the laser actually creates tiny deformations of the dye layer during the recording process. Each deformation represents a bit of recorded data. As the disk spins in the CDR recorder, the laser is turned off and on to correspond to the ones and zeros that represent the data or bit pattern of the information that is being recorded. These tiny deformations are to alter the amount of light that is reflected from the reflective layer when the disk is subsequently played on a CD-ROM drive or CD player. This difference in reflection represents the pattern of ones and zeros that make up the recorded data.

So now, let's take a look at media colors. First, let's discuss the reflective layer. The ideal reflective layer should be one that reflects the maximum amount of the laser's light in the CD-ROM drive or player in which the disk will be played. Additionally, it shouldn't shift the color of the laser's light. Any color shift reduces the readability of the disk because the sensor in a drive or player may not recognize the altered reflected light. The wavelength of the laser's light isn't visible to the human eye, however we still refer to it as color; it is just a color that we can't see. A technical problem existed when CDR media was initially developed. In order to resist the heat of the recorder's laser, the reflective layer had to be made of metal. Shiny plastic film for example couldn't be used because the recording process would damage it and destroy the reflective properties required for the reflective layer. At that time, silver wasn't suitable because it oxidized (tarnish) and this changed the reflective characteristics and made silver unreliable for use as the reflective layer. Gold worked well because it doesn't oxidize. This made it the material of choice for the reflective layer.

Gold wasn't without its problems though. Since it is golden in color, it shifts the color of the laser light. This created a readability problem in some players. They weren't able to reliably read the disks because of the color shift. The read sensors in some of these drives weren't designed to cope with this color shift. They were designed to read silver colored pressed CDs, not gold CDR media. More recently, major technological advancements have been made that allow silver to be used as the reflective layer. Actually, it isn't pure silver that is used. It is a silver alloy containing other metals that make it no longer subject to oxidation and the problems that causes. An analogy could be made to iron versus stainless steel. Iron easily rusts when exposed to moisture and air. However, when certain other metals are added to iron, an alloy is formed which won't rust at all even though the primary content of stainless steel is iron. Because these silver alloys don't cause a color shift when used as the reflective layer on CDR media, the media manufacturers have almost entirely converted to the use of silver alloys for the reflective layer.

Some users are of the opinion that gold media is better because gold is more valuable than silver or other misguided ideas. But that isn't the case. Gold jewelry may be more valuable than silver but intrinsic value isn't the issue in this case. The real question is; which material is best suited for the application. The technical jury says silver alloy is. The only case where gold media is preferred is for use in some older recorders that were designed before the widespread use of silver media. These recorders were designed to deal with the gold color shift problem and they don't always handle silver media reliably. Most of these recorders are no longer in use due to obsolescence in other respects as well.

There are two materials that are primarily used for the dye layer (also know as the recording layer). These are cyanine, which is light blue and pthalocyanine, which is nearly colorless. Both are organic compounds. There is no cyanide in either of them as is sometimes mistakenly thought. These materials were chosen for their predictable and uniform performance. You may be thinking; what about green dye, I used to buy gold media that was green on the bottom. Actually it isn't green it's blue. It only appears to be green because it looks green when viewed with the gold reflective layer behind it. Gold plus blue equals green. Remember the color shift that the gold reflective layer causes. In this case, you are seeing it with your own eye. The dye layer must uniformly alter the reflection of light from the reflective layer when bits are recorded by "burning" tiny spots on the dye layer. Drive to drive variations in laser power as well as different recording speeds are considerations that must be accommodated if the recorded disk is to be reliably played in a CD-ROM drive or CD player.

Technological advancements in CDR media technology have blurred the distinction between the two materials with respect to which is "better". The media manufacturers have developed proprietary dye layer formulations that are much more reliable and predictable than either cyanine or pthalocyanine were in earlier media manufacturing processes. Each media manufacturer can build their case about their product's virtues; however, from the user's perspective it is difficult to separate the sales pitches from the facts. Buying high quality Grade A media from a reliable source is a safe bet with current technology media. As far as IO Products is concerned, if it isn't premium Grade A media, we don't sell it. Whether the user's choice is silver/light blue media or silver/silver media is more an issue of their color preference than one of functional reliability.

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