The manufacturing process of a digital versatile disc (DVD) is parallel to that of a compact disc (CD) and it is manufactured in standard diameters of 4.7 and 3.1 inches. However, DVD is a dual-substrate disc and the manufacturing process involves the connection of two halves of the disc so that a flat, uniform disc with an equivalent thickness to a CD can be formed.
Injection Molding
The formation of the polycarbonate plastic substrate of the disc is the first step in the manufacturing process. Polycarbonate, which is a synthetic thermoplastic resin that softens when heated, is melted and emptied into a cast. A molding stamper is impressed upon the cast under quite a lot of tons of pressure so that tiny indentations can be created to hold the data on a DVD.
Sputtering
Sputtering is used to apply an organic dye recording layer by spin coating and the plastic mold goes through a metallizer which will apply a layer of thin, reflective metal that is usually silver, silver alloy or gold. As soon as last touches have been put on the two sides of the DVD, they are joined together by hot melting or electrochemical processes. In a single-sided DVD, a dummy side is bonded to the recording side and it comprises a blank polycarbonate substrate, probably coated with a layer of metal for aesthetic purposes.
Rewritable DVD
There is more complexity in the manufacturing process of a rewritable DVD+/-RW or DVD-RAM disc compared to a recordable DVD+/-R disc because data can be rewritten as many times as possible. Rewritable DVD formats make use of an alloy of tellurium, germanium and antimony, in different proportions, as a recording layer. The capability of the alloy to change phases between a crystalline and non-crystalline state makes it possible to rewrite a rewritable DVD. The alloy is sputtered onto the disc in its non-crystalline or amorphous state so that the recording layer is returned to its crystalline state through the use of a powerful laser device referred to as an initializer.
Finishing
Finally, the exterior of the recording side is coated with a transparent material, like silicon-based lacquer, in order to give it a protective coating against scratches, fingerprints, dust and corrosion. Screen printing can be used to apply additional decoration on the surface of the DVD in order to make it more attractive for users and also to indicate its content.
