Dual layer DVD Burners (DVD9)?

[rhuala2]

Curiousities about DVD9:

1. Are there any 2 layer (DVD9) burners out there yet? If not will there be anytime soon? Is this something maybe Hollywood will never let the public have as we could then make perfect 1 DVD to 1 DVD backups of all dual layer DVD's?

2. Would this require special media. Can 2 layers be burned onto regular DVD-R's or are the commercial DVD's special?

3. How does dual layer burning work anyways? Anyone have have brief URL explaining this maybe?

Thanks.

rhuala

[LanceSteel]

Curiousities about DVD9:

1. Are there any 2 layer (DVD9) burners out there yet? If not will there be anytime soon? Is this something maybe Hollywood will never let the public have as we could then make perfect 1 DVD to 1 DVD backups of all dual layer DVD's?

2. Would this require special media. Can 2 layers be burned onto regular DVD-R's or are the commercial DVD's special?

3. How does dual layer burning work anyways? Anyone have have brief URL explaining this maybe?

In short...

1. No, there are none and I've never heard anyone talk about making one.

2. Yes, special media would be required.

3. It doesn't. You can't burn dvd-9's. They commercially press dual layered disks.

[BJ_M]

not anything hollywood doing to prevent you from having one --- just physics ...

you cant get a laser to go through one die layer to burn a second die layer without it screwing up the first die layer ... the die is to fragle and never fixated enough.

you could always buy your own pressing machine if you really want dual layer disks 9and a bunch of other equipment) -- i thik it would run about $500,000 for the bottom quality --

CD and DVD discs are made by first moulding using stampers produced during mastering and then metallising and lacquering (CD) or bonding (DVD). The steps are:

Injection moulding of the clear polycarbonate discs using a hydraulic moulding machine
Metallising to create an aluminium reflective surface
Lacquering to protect the reflective surface of CDs ready for printing
Bonding of 2 substrates to produce a DVD disc
Printing of the disc label on top of the lacquer.

[BJ_M]

Producing DVD Discs
All DVD discs comprise two substrates each 0.6mm thick and moulded separately. The replication process varies somewhat for the different formats. DVD-5 and DVD-10 were the first to be manufactured. DVD-9 has proved to be considerably more difficult due to the different metallisation and bonding requirements.
DVD-5 & DVD-10
For DVD-5 discs, the active substrate is metalised and then bonded with the blank, non-metalised substrate. For DVD-10, both substrates are metalised.


DVD-9
For DVD-9 discs two metalisation layers are required, one being semi-reflective, using gold or silicon. Parameters such as tilt, bonding layer transparency etc are more severe for DVD-9. Also the layer 1 aluminium layer must be uniform in thickness to avoid jitter.


Injection Moulding
Optical grade polycarbonate is first 'baked' to remove any moisture and is injection moulded in a high pressure moulding machine (press) using the stamper mounted in the mould fixed to the press. This mould is in two parts and provides a cavity which ensures that perfectly moulded discs are produced with the correct dimensions every time. One half of the mould contains the stamper (to form the pits) while the other half contains the mirror block to ensure a smooth surface.
The hydraulic press applies a force to the two halves of the mould which are closed. Molten polycarbonate is then injected into the cavity and held in place by the applied pressure while the disc cools and solidifies. During cooling the centre hole is punched. After cooling, the press opens and the pressed disc is transferred by robot arms to a conveyor to allow the disc to cool before the next stage. The centre hole with sprue (formed by the injected polycarbonate) is discarded or re-cycled.

Successful moulding of CDs which meet the CD specification, requires stable processes with the machines setup correctly. Moulding parameters which can affect the resultant CD include stamper geometry, mould temperature, polycarbonate temperature, compression force and cycle time.

Cycle times for injection moulding of CDs have decreased substantially and are now around 3 seconds for the latest presses and moulds.

DVD moulding is similar to CD moulding but with some important differences.

Two pressings are needed for each final DVD disc
Each half disc (substrate) is 0.6mm thick instead of 1.2mm
The thinner disc also requires different moulding parameters, such as a shorter injection time and higher mould temperature.
Redesigned or new moulding machines are needed with injection compression where the mould is kept slightly apart until most of the polycarbonate has been injected.
Cycle times tend to be longer than for CDs.
The quality of the final disc, including tilt and jitter, is critically dependent on the moulding process.

Metallising
The polycarbonate discs after moulding are transparent, so need to be covered by a mirror surface to reflect the laser light, to allow the pits to be read.
The active surface of each disc is coated with aluminium by sputtering. Sputtering requires the transparent polycarbonate discs to be transferred to the sputtering chamber which is then quickly evacuated of any remaining air and filled with argon gas. The argon ions are attracted to the aluminium target by the use of a high voltage. As the ions strike the target, particles of aluminium are ejected and are deposited onto the CD surface.

The two DVD substrates are each metallised in the same way, but layer 0 of a DVD-9 is metallised with gold, silver or silicon to achieve a semi-reflective layer instead of aluminium. DVD-5s, DVD-10s and layer 1 of DVD-9s are usually metallised using aluminium.

Modern metallisers are capable of cycle times of under 2 seconds allowing them to be used in duolines where one metalliser can handle the output from two moulding machines. The fastest metallisers can achieve cycle times of about 1.5 seconds.

Lacquering
The aluminium layer on each CD is then protected by a lacquer which is spread as a liquid evenly across the surface of the disc by spin coating. The centrifugal force created by spinning the disc ensures that the lacquer covers the whole disc in an even layer.
It is important that the lacquer overlaps the aluminium therefore sealing it from the elements. If left exposed, aluminium will start to oxidise within a few days.

The lacquer is cured by ultra-violet (UV) light producing a hard protective surface. The discs are then ready for printing.

Lacquering involves two steps in the spin-coating process, lacquer deposition and spin-off. Cycle times of under 2 seconds are normally achieved by either splitting the two steps into two stations or using two spin coating stations.



DVD discs do not need to be lacquered as the reflective layers are protected by the two substrates which are used to make a DVD.

DVD Bonding
Bonding is necessary for DVD as these discs comprise two substrates that need to be bonded together. It is one of the most difficult parts of the DVD replication process. A number of possible solutions have been developed.
Hot melt bonding is the method used for Laserdiscs where the two substrates just need to be glued together. It is also suitable for single layer (single or double sided) DVDs. The process is simple and relatively inexpensive, but tends now to be replaced by UV bonding.
Radical UV Cured bonding is suitable for dual layer discs because it is transparent. It involves coating one or both of the substrates with a UV cured resin similar to normal lacquer, but with suitable optical and mechanical characteristics.
Cationic UV Bonding involves screen printing the resin over both substrates, curing each with UV light and then pushing the discs together. This method is not suitable for dual layer discs as the resin used is opaque.
Radical UV Cured bonding is the most widely used as it is compatible with all DVD formats. DVD-9 bonding is particularly difficult as the bonding layer must

be of uniform thickness within close tolerances
be optically transparent with no defects such as bubbles
not introduce tilt outside the DVD specification

[defense]

LOL...do you have your answer now Rhuala? If only my posts would be answered with such detail. Very interesting detail that goes into making those DVD'S.

[donpedro]

Wow !!! Thanks for enlighting me....