Toshiba have presented recording and readout results of their proposed
HD DVD-R DL, the company's new double layer HD DVD-R disc with a
capacity of 30 GB, at the ISOM/ODS '05 event.
The International Symposium on Optical Memory and Optical Data Storage
was held this year (July 10-14) at the Hyatt Regency in Waikiki
Honolulu, Hawaii.
Toshiba revealed details of the prototype, following a press meeting
in May 2005, at which the company only showed its playback signals.
Along with the development of an organic dye for the recording layer,
the company also established a manufacturing process requiring lower
costs than the previous DVD-R DL manufacturing process.
To make an HD-DVD disc double-layered, the company needed to reduce
the thickness of the Ag reflection layer, located close to the optical
head so thatthe laser beam can reach the other layer (Layer 0) more
easily. However, the thinner the Ag reflection layer gets, which also
works as a heat sink, the weaker its heat releasing effects become;
and therefore the larger the heat interferences between recorded marks
grow. Toshiba overcame these problems with an organic dye with good
heat conductivity, newly developed in conjunction with raw material
manufacturers. This dye is a low to high polarity dye, which increases
reflection when exposed.
Conventional 2P (photopolymer) process is used to form the middle
layer. In existing double layer DVD-R media, disposable polyolefin
stampers are used to transcribe the recording layer's concavities and
convexities onto the photopolymer. Toshiba has employed 0.6 mm-thick,
polycarbonate injection molded stampers instead of the polyolefin
stampers. As a result, polycarbonate once used in stampers can be
reused as alternative dummy substrates.
The Blu-Ray Response
At the same time, Philips showcased the latest developments and
results of its research work on behalf of the rival Blu-Ray camp. The
Philips research team announced their successfull testing on BD-R
(Blu-Ray Recordable) recording procedures.
Unlike the BD-RE (Blu-Ray Rewritable) disc which is based on the
phase-change layer technology, and alternatively to the use of a dye
layer, Philips proposed the usage of a Cu/ Si bilayer to be applied as
the recording medium in a write-once Blu-ray Disc (BD-R).
The write process basically comprises the formation of a CuSi alloy
containing 25?30 at. % Si, while any excess Si is left behind as
unreacted film. Auger analyses of the laser-written layers indicate
that recording consists primarily of the diffusion of Si into Cu.
The results coming from Philips labs indicate that this technology
offers adequate results in terms of disc readability and high
recording speeds. The very low jitter levels of typically 4%, proved
to be achievable with equally thick films of Cu and Si as recording
medium.
Philips has successfully tested first recordings on Cu/Si bilayer BD-R
media at 1x-7x speeds (25GB, single layer). Note that 7x BD-R speed
equals 10x for DVD and 30x for CD. The results indicate that the
shortest possible recording time was given at a rotational speed fixed
at 10800 rpm, which is equal to 200 km/h! At the same time, the linear
velocity at 7x is aproximatelly 35m/sec. To make things clear, this
means that 25GB of data can be recorded at 7x in just 14 minutes.
The most suitable writing strategy for 7x recording, according to
Philips, should be the so-called "Castle Write Strategy". Hence, for
speeds of 1X-2X it will use the improved (n-1) writing strategy and
for 4X - 7X the Castle writing strategy just mentioned.
"Arguing with anonymous strangers on the Internet is a sucker's game
because they almost always turn out to be -- or to be indistinguishable from
-- self-righteous sixteen-year-olds possessing infinite amounts of free time."
- Neil Stephenson, _Cryptonomicon_
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