CD Mediacting - Fabrication, duplication, burning, pressing CD DVD Vinyl HD DVD Blu-ray

A CD-R is made up of several layers, as follows:

The substrate which is the polycarbonate injected disc (plastic material). This is the base element of the CD-R, to which the other components are applied. The disc must be perfectly homogeneous, so that the beam of the laser reader that passes over it and reads the it does not deviate.

The colorant or dye is an organic substance which is applied to the surface of the substrate and which allows the recording of the information in binary format. Actually, this colorant blackens under the effect of the heat from the recorderâ€™s laser beam, which creates more or less reflective areas for the beam on the CD player.

There are three types of organic colorants:

Phthalocyanine is the organic colorant with the best reflectivity compared to the two other types of compound and therefore has the best compatibility with all types of recorders and players on the market. It is characterised by a gold reflection on the surface of the CD-R.
The organic colorant with a cyanine base gives a greenish tinge to CD-Rs. The quality, as well as the life span of this type of media is quite low in comparison to those using phthalocyanine. The reflection of the light is weaker, given the colour of the colorant and the encoding quality (laser recording) is less precise.
Virgin CDs based on metal azo are blue in colour and use a silver reflective layer to ensure good reflectivity, in spite of the colour of their organic colorant. As in the case of cyanine, the stability of the colorant is less than for phthalocyanine technology, with a higher recording error rate (Bler) and as a result a more limited life span.

The gold or silver reflective layer is deposited on top of the dye in a vacuum. This allows the laser beam which reads the CD to be reflected. To reduce production costs and increase the reflectivity of the layer, silver has gradually replaced gold as the base material for the reflective layer. It is nevertheless clear that the life span of a CD-R with a silver layer is less than that of one with a gold layer.

A coat of varnish is then applied over the reflective layer to protect it against humidity and oxidation.

Where archiving or medical CD-Rs are concerned, a very hard varnish is applied to the face read by the laser beam to protect the disc against scratches and accidental marks which can permanently alter the playback of recorded data.

Finally, a visual (text, logos, description of the CDâ€™s content) is screen or offset printed on the CDâ€™s surface.

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