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Disc Construction

Last Update: 16/04/2007

CD Construction

A Compact Disc is made up of four layers. The first layer is the thickest and easiest to repair. However, the other three layers combined (reflective foil, lacquer, and graphic) are only as thin as a human hair and offer little or no protection of the data beneath them. You can see the different layers as shown in figure 1.

1. Bottom Polycarbonate Layer

First, data is stamped on the top side of a plastic disc creating millions of “on’s” and “off’s” or zeros and ones. On recordable CD’s, data can be burnt in at different levels within the plastic disc, for multi-session recording. Please note that recordable CDs have a much thinner layer due to the manufacturers name printed on this layer.

2. Foil Layer

Second, a micro thin layer of aluminium (copper, silver or gold on higher quality CDs) is applied to the top of the CDs covering the data. This layer reflects the laser beam back through the lastic disc, allowing the stamped
data to be read.

3. Lacquer Layer

Third, lacquer is dripped onto the disc and spun at a high speed to create a thin layer of sealant or the foil layer. This seals in the foil layer, but offers little or no protection for the foil or the data beneath.

4. Label Layer

Finally, a layer of ink is screened onto the lacquer layer for dynamic graphic and/or sales impact. (Recordable CDs don’t have this layer).

DVD CONSTRUCTION

A Digital Versatile Disc, like a Compact Disc is made up of four layers, however unlike a CD a DVD has its data layer in the middle of the disc sandwiched between to polycarbonate layers. So unlike a CD a DVD is more resistant to label side scratches. This construction method also allows data to be read from both sides of the disc, however because of the reduced amount of plastic either side of the data, DVD's can only be repaired half the amount of time as a CD.

1. Bottom Polycarbonate Layer

First, data is stamped on the top side of a plastic disc creating millions of “on’s” and “off’s” or zeros and ones.

2. Foil Layer

Second, a micro thin layer of aluminium (copper, silver or gold on higher quality CDs) is applied to the top of the CDs covering the data. This layer reflects the laser beam back through the plastic disc, allowing the stamped
data to be read.

3. Top Polycarbonate Layer

Third. the second or top plastic coating over the foil layer is added and the foil is encased in the middle.

4. Label Layer

Finally, a layer of ink is screened onto the lacquer layer for dynamic graphic and/or sales impact. (Recordable CDs don’t have this layer).