STAGES IN THE MANUFACTURE OF A COMPACT DISC

The content of your master CD is re-transcribed using an industrial recorder (called an LBR, Laser Beam Recorder) on to a plate of polished glass covered with a photo-sensitive resin. A 10 nm layer of silver is then vaporised on to the surface of the glassmaster. This evens out the roughness in the surface of the plate due to the burning of the data by the LBR. The quality of the disc encoding is then carefully checked, using special equipment.

2. Galvanisation
The glassmaster (whose layer of silver acts as a cathode) is then dipped in an electrolytic bath which contains the anode in the form of a block of nickel. When an electric current passes, nickel atoms are torn from the anode and are deposited on the cathode forming a homogeneous layer of nickel. Once the desired thickness has been reached, the nickel disc is removed from the glass plate, which involves the destruction of the information on the surface of the glassmaster. The nickel disc thus formed, called the stamper or father, contains the mirror image of the binary encoding which was on the glassmaster. As a security measure, a copy is made from this (a mother), which can be used to produce back-up sub-masters (for long runs).

3. Injection / pressing
Once it has been cut to the correct size and its surface polished, the stamper is mounted in an industrial press, into which polycarbonate is injected, in order to obtain a transparent disc which already contains the binary encoding of your master on one of its surfaces. Polycarbonate was chosen for its transparency properties, optical purity and constant refraction index.

4. Metallisation / printing
A 40-50 nm layer of aluminium is then deposited on the encoded surface of the disc, to reflect the laser beam from the CD player. A protective varnish is then applied to the aluminium, using a centrifugal process. It only remains to print a visual (label) on the disc, using screen or offset printing, to complete the industrial manufacturing process.