Definition
The DLT is now used to cut a glass master, and make stamping discs.
A check disc is then made from the stamper. Once you the client approve
the check disc, then thousands of copies will be mass-produced.
Other services provided at this stage are serialising the discs. Or
putting other custom information in the BCA (Burst Cutting Area)
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Seamless integration between the authoring and replication stages.
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More Information
DVD disc replication is similar to the process used for CD replication
although DVD discs require much more stringent manufacturing tolerances,
and also require a bonding step that is not required by CD replication.
A check disc is provided, which is essentially a limited run version
of the final disc.
Check discs are indispensable; especially if your project is a dual
layer disc, don’t skip this stage! Even though you can break the
discs into smaller parts on DVD-R’s, you cannot thoroughly test
layer changes and full navigation.
There are eight basic steps in the DVD replication process:
1. Physical Formatting. In the physical formatting step the disc image
stored on the DLT tape or DVD-R is converted into a bit stream suitable
for use with a Laser Beam Recorder (LBR). The original disc image undergoes
sector formatting, scrambling (if CSS encryption is required), generation
of the proper error correction codes, interleaving, and finally 8/16
modulation and synchronisation. There is a common misconception that
the pits on a DVD disc represent individual data bits. Individual pits
are simply parts of the 8/16 modulated signal created in this step.
When a disc is read by the laser in a DVD-Video player or DVD-ROM drive,
individual data bits are reconstructed through a process of 8/16 demodulation,
deinterleaving, error detection and correction, and finally unscrambling
(if CSS encryption was used)
2. Glass Mastering. The bit stream from the Physical Formatting is sent
to a Laser Beam Recorder which uses a laser to write the information
onto a 240 mm Soda-Lime Glass Master with a 100nm photo resist coating.
The laser writes information to the glass master by burning away the
photo resist coating on some of the areas of the discs, and leaving
the coating intact on others. After completion of the recording session
of the glass master is developed using a Sodium Metasilicate developing
solution. This developing process creates a master disc that has the
required “pits and tracks” of the DVD disc to be manufactured.
3. Metallisation. A thin layer of metal is applied to the developed
glass master to provide a conductive layer for the electroplating process.
4. Electroplating. A layer of Nickel Sulfamate onto the metallised glass
master then makes a 305 micrometer thick stamper. This stamper has a
mirror image of the pits and tracks stored on the glass master. Since
individual stampers can only be used a finite number of times before
they wear out, additional stampers can be made from the glass master
as required. In some cases additional stampers will be made to support
high volume DVD title needs to be replicated simultaneously on multiple
replication lines.
- Silkscreen. Application of coloured ink to the label side of the disc.
- Offset printing. Greater definition than silkscreen, and better balance control for the disc.
- Pit art. A stamper that embosses a graphic design into the back substrate.
