I think back in the early 80's Sony/Philips estimated 50-100 year life for CD's. And given at that moment in time, they stored 650MB reliable, quite a feat. I doubt there are any other storage media from the 80's that is still bit perfect readable en mass. Tape (6250bps) was supposed to be annually wound/rewound to maintain integrity. I don't have any so don't know if they are still readable. I do however have a ton of cd's most collected during the 80's and lived thru multiple summers/winters in cars that had cd players in the 90's & 00's. Of course now cars use thumbdrives. But I doubt the thumb drives I have created will last 40 years with no errors. I am still impressed with the engineering that went into the CD at that moment in time. Sure, data rate of 1.4 mega bits per second is trivial today, but back then non-trivial. Philips did a great job given the practical limits of the day.
The glass masters were used as part of the molding tool, and the poly carbonate was injected against it, that was my impression.
So I made the above statement.
Thanks for enlightening me.
Just what was the tool material for the actual tool, as in the patterned part?
So I made the above statement.
Thanks for enlightening me.
Just what was the tool material for the actual tool, as in the patterned part?
The only controversial thing I've heard was at the end of the 80s, when a company was premature age testing CDs from the Nimbus DADC pressing plant in Austria. They supposedly found a flaw with the aluminum layer being prone to oxidation. As I grew up in Germany, I have many of these CDs from that plant. All of them read perfectly after all these years. Goes to show you the scientists and engineers aren't always right.
The glass master, which contains the bit pattern, is used to create a metal stamper.
First the glass master is metalized by a sputtering process, and then it is electroplated with nickel to grow the stamper.
The stamper is then separated from the glass master as a thin metal disc.
In the process the bit pattern has transferred to the stamper.
One glass master can make several stampers, and each stamper can make about 100K discs before it wears out.
This stamper is mounted in the stationary side of the mold cavity into which molten poly-carbonate is injected under pressure.
The resulting poly-carbonate disc now contains the bit pattern and is then sputtered with aluminum to form the reflective layer.
Next, this layer is covered with a protective lacquer that is cured by UV.
Now the CD is done except for printing and packaging.
DVDs are similar but a little more complex due the two layers.
First the glass master is metalized by a sputtering process, and then it is electroplated with nickel to grow the stamper.
The stamper is then separated from the glass master as a thin metal disc.
In the process the bit pattern has transferred to the stamper.
One glass master can make several stampers, and each stamper can make about 100K discs before it wears out.
This stamper is mounted in the stationary side of the mold cavity into which molten poly-carbonate is injected under pressure.
The resulting poly-carbonate disc now contains the bit pattern and is then sputtered with aluminum to form the reflective layer.
Next, this layer is covered with a protective lacquer that is cured by UV.
Now the CD is done except for printing and packaging.
DVDs are similar but a little more complex due the two layers.
The glass surface is coated with a photo sensitive resist material.
Then the bit pattern burned into the resist with a laser.
Then cured and metalized as above.
I don't think the glass actually gets etched, it just serves as a very smooth, flat substrate to build on.
Our facility was not large enough to have our own mastering equipment so we just purchased the service from a stamper house.
I did visit and see the whole mastering process a few times and it is quite interesting.
Then the bit pattern burned into the resist with a laser.
Then cured and metalized as above.
I don't think the glass actually gets etched, it just serves as a very smooth, flat substrate to build on.
Our facility was not large enough to have our own mastering equipment so we just purchased the service from a stamper house.
I did visit and see the whole mastering process a few times and it is quite interesting.
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Oh, I thought the glass was actually etched, probably using hydrofluoric acid.
Somewhat disappointed by learning it´s only a mechanical substrate.
Somewhat disappointed by learning it´s only a mechanical substrate.
Well, sorry, but, that is a very crucial step of the whole process.
A famous mastering engineer told me that a record label sent digital files (if he told me, I don't recall if they were on PMCDs or Sony 1630 Pro Video Cassettes) of the same album to five different CD pressing plants. The test pressings from all five sounded different, and two engineers ranked them the same.
They researched and researched and decided that the "sources of variability" (to get all W. Edwards Deming for a bit) were the lasers at the glass-mastering stage. Supposedly, and this is where I begin to get skeptical, the label impounded the best glass-mastering laser and reserved it for the most important albums only, so it would not wear out on nothingburger records, my word not his.
The Crystal DIsc process uses a glass substrate and then a stamper, it appears from their website, presses (but does not injection-mold) a blob of proprietary plastic which then is cured under pressure and light. I am told the process for each Crystal Disc takes hours.
amb,
john
Electro formed nickel...used in complex parabolic profiles for torch reflectors as well, biggest use seems to be screen printing screens.
The vacuum coating process is done at low pressures, almost total vacuum, so it takes time to go to full vacuum, then the sputtering is done, and pressure brought up to normal, IIRC.
That will take time.
The vacuum coating process is done at low pressures, almost total vacuum, so it takes time to go to full vacuum, then the sputtering is done, and pressure brought up to normal, IIRC.
That will take time.
There was a Swiss company called Satis Vacuum, they were among the makers of vacuum coating machines.
I have not checked their website, they may have many competitors, check them out if you are curious, similar process is used for the coatings on sunglasses and sports goggles.
Another application is the anti reflective and anti scratch coatings on spectacle lenses, hard coatings can be done by other methods as well.
I have not checked their website, they may have many competitors, check them out if you are curious, similar process is used for the coatings on sunglasses and sports goggles.
Another application is the anti reflective and anti scratch coatings on spectacle lenses, hard coatings can be done by other methods as well.