Prev: Another Laptop to TV question
Next: Dim backlight in XP on Gateway laptop
From: bob on 5 Jan 2008 21:24
I was just wondering why DVD companies don't put a clear scratch-

resistant coating on the bottom of DVDs. This would help keep the
DVD

from getting scratched. It would be like Scotch tape.

From: RobertVA on 6 Jan 2008 02:32
bob(a)coolgroups.com wrote:
> I was just wondering why DVD companies don't put a clear scratch-
>
> resistant coating on the bottom of DVDs. This would help keep the
> DVD
>
> from getting scratched. It would be like Scotch tape.
>

Then the coating would get scratched and you wouldn't have gained
anything. The adhesive of peel off layers could interfere with the laser
or leave residue behind. The polycarbonate plastic that disks are made
of is a fairly hard plastic anyway.

Check you audio/video retailer for polishing kits (might NOT be at
places like the supermarket or chain pharmacy). Some sell manually
operated kits that are less expensive than either the motorized or hand
cranked kits.

What you really have to worry about is the much thinner lacquer coating
on the TOP of single sided optical media. If damage (chemical from a
solvent based marking pen or mechanical from ball points or other
objects) penetrates that, the aluminum reflective layer corrodes.

Use the center hole release button in storage cases that are equipped
with them to reduce the chance of cracking.
From: VanguardLH on 6 Jan 2008 02:43
<bob(a)coolgroups.com> wrote in message
news:a5fb58f6-7b93-4bfc-8140-a5c00d28638c(a)21g2000hsj.googlegroups.com...
>I was just wondering why DVD companies don't put a clear scratch-
> resistant coating on the bottom of DVDs. This would help keep the
> DVD
> from getting scratched. It would be like Scotch tape.


They already do. In fact it is an extremely thick coating. It is
almost as thick as the disc itself.

The data is not recorded on the bottom (lens-facing) side of the disc.
The data is record in pits or bubbles on the TOP side. That is the
side just under the label. That is the side that you write on. That
is the side which if scratched through will permanently destroy the
data on that disc.

From: Paul on 6 Jan 2008 02:52
bob(a)coolgroups.com wrote:
> I was just wondering why DVD companies don't put a clear scratch-
>
> resistant coating on the bottom of DVDs. This would help keep the
> DVD
>
> from getting scratched. It would be like Scotch tape.
>

I thought this document was neat. It covers a bit about the
various kinds of optical media.

http://www.memorex.com/downloads/whitepapers/WhitePaper_Labeling_Optical_Media_Jul07.pdf
From: kony on 6 Jan 2008 04:38
On Sun, 6 Jan 2008 01:43:15 -0600, "VanguardLH"
<VanguardLH(a)mail.invalid> wrote:

><bob(a)coolgroups.com> wrote in message
>news:a5fb58f6-7b93-4bfc-8140-a5c00d28638c(a)21g2000hsj.googlegroups.com...
>>I was just wondering why DVD companies don't put a clear scratch-
>> resistant coating on the bottom of DVDs. This would help keep the
>> DVD
>> from getting scratched. It would be like Scotch tape.
>
>
>They already do. In fact it is an extremely thick coating. It is
>almost as thick as the disc itself.

Not really a coating, it is the body of the disc, the
polycarbonate platter upon which it's all built.



>
>The data is not recorded on the bottom (lens-facing) side of the disc.
>The data is record in pits or bubbles on the TOP side. That is the
>side just under the label. That is the side that you write on. That
>is the side which if scratched through will permanently destroy the
>data on that disc.

You are thinking of a CD not a DVD. A CD has the metal
layer set on top of the polycarbonate disc then a coating
over the metal layer. A DVD has a bottom layer of
polycarbonate, a metal layer (or dye then the layer if a
writable disc), then an adhesive and top polycarbonte layer.

In the case of DL DVD, there's just a spacer and 2nd metal
layer (plus dye if recordable) before the adhesive and top
polycarbonate layer.

While I'm not certain of it, I believe the reason for this
difference has to do with focal length to read the smaller
pits on a DVD, that it's better to keep them closer to the
bottom for this purpose though a top layer is still added
for protection and to maintain a thickness enough for
acceptible rigidity.
 |  Next  |  Last
Pages: 1 2 3
Prev: Another Laptop to TV question
Next: Dim backlight in XP on Gateway laptop