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Warping Blu-ray Discs Could Damage Players?!

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Warping Blu-ray Discs Could Damage Players?!

Postby Ian on Tue Sep 05, 2006 10:25 am

Personally, I think this is just Toshiba slinging mud at Blu-ray but you never know.

http://lifestyle.hexus.net/content/item ... 639&page=2

HEXUS.lifestyle: But in just raw data storage, Blu-ray is going to be better as it holds more data.
Jim Armour: Looking at the numbers on a bit of paper, you’d think so, but what you need to do is look at the Blu-ray discs and players first, before you make a decision. Let’s go back to the disc construction for a second. HD DVD uses a sandwich method which helps to combat disc warping. Blu-ray doesn’t. It uses a single plastic substrate layer, then adds on the recording material and then top it all off with a very hard Zircon layer. This means that when the disc expands to get hot, it will warp downwards as that Zircon layer isn’t going to budge.

HEXUS.lifestyle: But that’s a uniform direction of warping? Surely as long as you’re ready for it, it won’t make any difference?
Jim Armour: You’d think so, wouldn’t you? But now we have to go back to the lens. Blu-ray uses a 0.85 Numerical Aperture and, with their recording layer just 0.1mm below the disc surface, they’ve got to get the lens very close to the disc surface to be able to focus it tightly enough to give them a 25GB storage capacity. So now you’ve got a Blu-ray lens sitting somewhere between 0.1 and 0.3 millimetres from a disc coated with a substance almost as tough as diamond which, when it warps, can only warp downwards, towards the lens. Guess what happens when you run Zircon over glass at 2000rpm? Sure, your data will be safe but you’re going to need a new Blu-ray lens.

HEXUS.lifestyle: So the Blu-ray system has a built in flaw that could mean you get through Blu-ray players quicker than you do discs?
Jim Armour: It would appear so, yes. The other thing to remember is that Blu-ray discs are very expensive to produce when compared to HD DVD discs, mostly because of the construction methods needed to place the recording layer at the optimum distance from the lens so they can get 25GB of storage space. HD DVD takes a more sensible and robust route, chosen from a combination of factors – disc warping, disc durability, focal point of the laser etc. Plus, the use of better Codecs mean that HD DVD doesn’t even need as much storage space as Blu-ray to achieve the same high-quality video. The lower disc production costs reflect this, too.
"Blu-ray is just a bag of hurt." - Steve Jobs
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Postby dolphinius_rex on Tue Sep 05, 2006 12:08 pm

Yeah... I find this a little hard to swallow. Actually, the first thing that comes to mind after reading that is "oh good, Bluray won't have the same BONDING ISSUES that DVD suffers from".
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Postby MonsterMan on Tue Sep 05, 2006 5:46 pm

If that zircon layer is so strong, wouldn't it (help) prevent warping? :-k
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Postby dolphinius_rex on Tue Sep 05, 2006 5:55 pm

MonsterMan wrote:If that zircon layer is so strong, wouldn't it (help) prevent warping? :-k


Yeah, that's the theory... I think that's TDK's part in the whole BluRay scheme of things, but I'm not 100% sure.

On the whole, I'm been pretty unimpressed with the longevity of DVD media. Time and time again it's been shown that CD-Rs are longer lasting (when properly made) then DVDR media (also when properly made). CD-Rs, like BluRay are not made with sandwhiched layers, and also can get pretty darn hot when read/burned at full speed, or for any length of time.
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Postby MonsterMan on Tue Sep 05, 2006 6:02 pm

Is the zircon layer then part of TDKs improved "armor plating" that's on the surface of the Blu-Ray discs?
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Postby dolphinius_rex on Tue Sep 05, 2006 6:18 pm

MonsterMan wrote:Is the zircon layer then part of TDKs improved "armor plating" that's on the surface of the Blu-Ray discs?


That's what I'm guessing, but it's just a guess.

EDIT:
Looking here, I'd have to say the layer is specifically used for cases where expansion is caused due to heat:
http://www.nasatech.com/Briefs/Jun98/LEW16393.html
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Postby MonsterMan on Tue Sep 05, 2006 6:50 pm

In other words Toshiba's full of it :D
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Postby dolphinius_rex on Tue Sep 05, 2006 7:10 pm

MonsterMan wrote:In other words Toshiba's full of it :D


Certainly seems that way! :roll:

Why is it that whenever I see a PRO HDDVD article, it makes sure to point out problems with BluRay technology... but whenever I read a BluRay article, it's focused more on the BluRay technology itself?

Or maybe that's just the impression I'm left with afterwards, and I'm forgetting the other stuff?
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Postby dodecahedron on Wed Sep 06, 2006 1:53 am

while i'm no expert at material strength etc., it would seem to me that it the top layer is zirconium and that doesn't expand, and the lower layer is polycarbonate that expands (when heated), the disc would warp up.
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Postby pika2000 on Wed Sep 06, 2006 3:21 am

Hmm, so much for confidence in higher capacity optical media. Regardless of it being HD-DVD or bluray, when 2nd tier manufactures start making the disc, I don't think this will matter, since they all are probably going to be crappy in the first place. We will just have more expensive coasters.
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Postby dolphinius_rex on Wed Sep 06, 2006 3:59 am

dodecahedron wrote:while i'm no expert at material strength etc., it would seem to me that it the top layer is zirconium and that doesn't expand, and the lower layer is polycarbonate that expands (when heated), the disc would warp up.


Hrm... that seems to follow yeah. Because if the lower layer was SHRINKING and the upper layer was staying the same, then the upper layer would be pulled down in an 'n' shape. So if the upper layer is smaller then the lower layer, it should be pulled into a 'u' shape.

I'm sure if I remembered just a LITTLE more of my Physics 11 I would be able to make a diagram showing this mathematically. I'm sure Cfitz or MediumRare could do that though :wink:
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Postby dodecahedron on Wed Sep 06, 2006 5:41 am

maybe something like this ?
Attachments
warp.PNG
when the lower layer becomes longer than the upper layer
warp.PNG (1.26 KiB) Viewed 1663 times
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