Article written by John Zois (DVD Bits Editor) on 29-Oct-2000
Photography and design by Tully Rosen

REPLICATION

Once the nickel master is ready, rapid replication of DVDs can begin. The nickel master, which is manufactured to exacting tolerances, is loaded into an injection moulding press designed for DVD replication. The moulding press compresses a molten resin (polycarbonate) into the cavity that the nickel master is located to form the disc. This process happens repeatedly, producing a DVD every 4.95 seconds, with a total of 40,000 DVDs per day made by the three machines.

 The disc at this stage has all the information from the master pressed into it but is still unplayable. It is then transported into a vacuum metalising chamber to be coated with the reflective layer that a home DVD player can read.

Because DVD discs hold so much information (8.7 GB) the DVD discs are replicated in halves (CD 1.20mm, DVD 0.60mm) and at this stage the discs are very unstable and need to be bonded together.

BONDING

The bonding process of DVD manufacturing is the most important part of the disc replication. It is at this stage that the two DVD half discs are joined forming the finished replica.

To do this the discs are joined using a specially designed machine for DVD bonding.

Resin is applied to layer 1 and then it gets joined with layer 0. They then get placed into a spinner bowl, the resin gets spun out due to centrifugal force and spreads evenly through the surface. The interesting thing is, that the resin not only has to bind the two layers together, but must also allow the laser to pass through it to read layer 1. At the same time it also serves to protect the aluminium layer from oxidisation.

The joined disc then goes under a UV lamp and gets cured . To ensure the bonding was successful, the disc is quickly inspected with a special camera that checks the reflectivity of the gold and aluminium layers. If any imperfections are found the disc is immediately put on a “bad spindle”.

While all this may sound somewhat simple, there are hundreds of parameters that are set from an  LCD screen on the machine controlling everything from the thickness of the resin, down to the tilt on the disc and the centrifugal force created by the spinning.

TEST LAB

 This is one of the two rooms (the other being the board room) in the entire plant where you can actually watch a DVD play on a normal DVD player and television. However the purpose of the testing here is not to judge how good the video and audio transfer is but rather to test the functionality of the interactive menus and other such things. Therefore there is no giant screen or THX sound system here.

 Apart from the human visual and aural testing done in this room there are also a number of equipment that electrically check the entire surface of the disc and look for abnormalities in the electrical signal. Abnormalities would render the disc unplayable on DVD players. This testing is essential in order to satisfy worldwide standard and testing procedures and ensures only suitable product reaches the marketplace. In addition it also serves as a useful tool to judge the effect new implementations in the manufacturing process have on the percentage of defective discs.

Finally, this room, apart for serving as the test lab for DVDs it's also the gallery of some of the DVDs that PMI has produced. Glancing on the walls you notice many familiar DVDs. On one side of the wall there is a gallery of the early discs that PMI produced (e.g Seven, La Boheme etc) while on another side there is a large selection of new release discs including a few like Men In Black etc that PMI are particularly proud of.