The replication process for DVD is essentially the same as
that for CD,
except with much closer tolerances and some extra steps. There
are also some
differences in replication depending on the type of DVD disc
being made:
DVD-5, DVD-9, DVD-10 or DVD-18.
All DVD discs are made of two parts, each half the thickness
of a CD. The
two parts are bonded together, producing a disc as thick as a
CD. Thus, two
pressings are needed to make one complete disc. DVD-5 and DVD-9
discs, which
have data on only one side, consist of one part with data and
one blank
part.
As in CD replication, DVD replication begins with Glass mastering.
This uses
a flat glass disc covered with photo-resist material. As the
disc spins, a
laser beam modulated according to the information on the DLT
tape or DVD-r
"writes" the data onto the disc by creating chemically
etched pits. By
electroplating, a metal negative to the glass disc is produced;
very similar
to the CD stamper.
This metal stamper is then placed in molding presses. Melted
plastic is
poured over the stamper and allowed to cool. (As compared with
a CD, DVD
discs need a shorter plastic-injection time and a higher molding
temperature.)
The disc is then finished by applying the reflective layer, protective
lacquer, and a label. DVD-9 and DVD-18 discs contain data in
two layers; one
of the layers is semi-reflective, allowing the playback laser
to read the
data on both layers in sequence. Both layers are read by a laser
from the
same side.
From this point on it is the same as in CD; the discs are
printed with your
design and automatically packed with the DVD wrap and booklet
into the
traditional Amaray case. It is then boxed and delivered to you
for sale.
