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CD-R Questions

Postby Albinoni on Mon Feb 03, 2003 11:37 am

1.Anybody here know which brand CD-R supports or has the most gold
reflective layer ? I know Kodak use real gold for their CD-R's.

2. Black reflective CD-R's. I read a review on this some where but not
quite sure where. Though did read that these black reflective CD-R's
produce excellent sound quality. Was in my local store last week and
did see a pack of 10 Imation black CD-R's but due to the fact of them
being seal, I could not see the back layer, though the front was all black
with the Imation Logo on it.
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Postby Han on Mon Feb 03, 2003 12:15 pm

1. Slower speed media have more gold in its dye. Older, true MITSUI media, labeled as Reference CD-R, have the best gold reflective layer.

2. I'm sceptical to these CDs. I've seen today Memorex ones, unfortunately also sealed. Personally, I wouldn't recommend them. Gold or silvergold reflective layer is proven to be the best for CD-R technology.
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Postby cfitz on Mon Feb 03, 2003 3:06 pm

Gold, the metallic element Au, is not in the dye itself but rather in the reflective layer. So saying that older media have more gold in the dye is inaccurate. Older media may have thicker gold reflective layers, but the amount of gold in the dye is the same - zero.

As far as the desirability of a gold reflective layer, the truth is that silver, at the infrared wavelengths used for burning and reading CDs, has better optical properties than gold, including higher reflectivity. So everything else being equal, a disc with a silver reflective layer will be easier to read than one with a gold reflective layer. The advantage of gold (ignoring the flim-flam of way-out audiophiles who insist it has a more "natural" sound) is that it is a noble element, and thus more resistant to corrosion and oxidation due to the dye and any air that makes it to the reflective layer. This gives the disc a (theoretically) longer lifetime, making it a good choice for long-term archive applications.

Finally, keep in mind that just because a disc looks gold doesn't mean it has a gold reflective layer. Manufacturers have been known to add coloring to their discs to make them look gold, hoping that this will increase the perceived value to consumers. The gold versions of Mitsui and (formerly) Kodak are two examples of discs that do have genuine gold reflective layers.

As for the black CD-Rs, they are just gimmicks in my opinion. First, the black has nothing to do with the reflective layer or the dye. The reflective layer is the same standard silver and the dye is the same standard cyanine or phthalocyanine as used in regular discs. The black is only a coloring added to the polycarbonate substrate, and is really just for appearance. Second, although the claim has been made that black coloring reduces unwanted reflections and thus improves overall writing and reading performance, this doesn’t make any sense. If the black coloring really did attenuate reflections from stray laser output, then it would equally attenuate the main laser beam, and that’s no way to improve writing and reading performance. At best, I would say the black CDs are simply an option for those who like the visual appeal. At worst I would say that the black coloring may actually absorb some of the laser power and thus make the discs harder to write and read.

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Postby Han on Mon Feb 03, 2003 3:57 pm

Thanks for the profound explanation, cfitz. I'm aware that dye consists of only azo, cyanine or phthalocyanine. But it doesn't make sense why Mitsui advertises its media, which have in fact a silver reflective layer, as SilverGold discs with golden dye...
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Postby jase on Mon Feb 03, 2003 8:30 pm

I was under the impression that, whilst (genuine) gold media does contain at least some of the gold element, the silver discs don't contain silver. Whilst some silver discs *may* have better reflective properties than gold, this is not always the case.

As for the black-bottomed media, of course it is a gimmick. It was initially introduced by a number of small, rather low-grade Taiwanese manufacturers (King Pro Mediatek and Lead Data being two) who saw a niche for discs that, with a label stuck on top, would look like genuine Playstation 1 discs. For some bizarre reason, people have picked up on these media is somehow offering better quality. Bunkum, is what I say. They're no better than any other coloured-bottom media (you get the rainbow-coloured discs from Ritek and Prodisc among others). The "pure silver"/"diamond" media was produced for similar reasons, as were the truly appalling Duradisc media "Made in USA" which were coloured the same purple as the Playstation 2 discs.
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Postby cfitz on Mon Feb 03, 2003 8:53 pm

Han wrote:I'm aware that dye consists of only azo, cyanine or phthalocyanine.

Then I guess your statement "Slower speed media have more gold in its dye" was simply a typo. But it doesn't hurt to clear it up for those who aren't aware.

Han wrote:But it doesn't make sense why Mitsui advertises its media, which have in fact a silver reflective layer, as SilverGold discs with golden dye...

That is just history and marketing, and based solely on the visual appearance of the dye. When Mitsui first developed phthalocyanine dye its competitor was Taiyo Yuden's cyanine dye. Cyanine dye against a gold reflective layer looks green, while the very light phthalocyanine dye against a gold reflective layer looks gold (this is primarily just the gold reflective layer showing through the mostly transparent phthalocyanine). Thus, calling phthalocyanine "gold/golden dye" made sense - that is what it looked like, particularly in comparison to cyanine dye. Add in the bonus marketing cachet of "gold" and the fact that "gold" is a heck of a lot easier to say and spell than "phthalocyanine", and it is easy to see why Mitsui went with "golden dye" as the casual nomenclature.

Even after silver reflective layers became common, the name "golden dye" stuck because it was already established and because phthalocyanine against a silver reflective layer does have a gold tinge to its very light-green hue.

It is also probably worth noting that while phthalocyanine is commonly referred to as both “gold dye” and “golden dye”, on official Mitsui web sites only the phrase “golden dye” is used. I may be reading too much into subtle twists of the language, but presumably this is to avoid running afoul of truth-in-advertising statutes. Mitsui is quite aware that phthalocyanine contains no actual gold, and “Gold dye” would imply the actual presence of the element Au in the dye while “golden dye” can be defended as just an adjectival phrase describing only the color.

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Postby cfitz on Mon Feb 03, 2003 9:06 pm

jase wrote:I was under the impression that, whilst (genuine) gold media does contain at least some of the gold element, the silver discs don't contain silver. Whilst some silver discs *may* have better reflective properties than gold, this is not always the case.

Pressed CDs use aluminum as the reflective layer, but aluminum is too reactive to be in contact with the organic dye layers of CD-Rs and would soon corrode if it was, so "silver" CD-Rs use a silver alloy reflective layer. I don't know the exact composition of this silver alloy, but it does contain the element Ag.

As for the reflectivity advantage of silver over gold, while it is a fact that silver has better reflectivity (just like silver has better conductivity), the advantage isn't terribly significant. It is on the order of a couple of percent. But my main goal in mentioning that silver has better optical characteristics was to debunk the idea that a gold reflective layer imbues a CD-R with superior characteristics. Again, the only advantage of a (true) gold reflective layer is improved long-term archival stability.

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Postby Han on Tue Feb 04, 2003 12:25 pm

cfitz wrote:
Han wrote:I'm aware that dye consists of only azo, cyanine or phthalocyanine.

Then I guess your statement "Slower speed media have more gold in its dye" was simply a typo.

You could say I've used a more common phrase. :wink: The other day I was reading an article describing the whole procedure of making high speed CDR media and was quite surprised that these media have much thiner dye. Under that impression I wrote that slower speed media have more gold in its dye. - If you look closer, you'll indeed see that these discs are more transparent...
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Postby cfitz on Tue Feb 04, 2003 1:16 pm

Han wrote:You could say I've used a more common phrase. :wink: The other day I was reading an article describing the whole procedure of making high speed CDR media and was quite surprised that these media have much thiner dye. Under that impression I wrote that slower speed media have more gold in its dye. - If you look closer, you'll indeed see that these discs are more transparent...

I'm not deliberately trying to be difficult, but I would cite this as an example of why the reflective layer ought not be referred to as "dye". Because of your mixing of the terms, when you say, "(I) was quite surprised that these media (high speed CD-R) have much thinner dye", I don't know what you mean anymore. Is it the actual organic dye layer that is thinner, or the metallic reflective layer? It would make sense, at least on one level, for the organic dye layer to be thinner. For a given laser output power, at high speeds less total energy can be delivered to each "pit" than at lower speeds, so switching to a thinner dye layer with its concomitant lower thermal mass makes sense.

But then you go on to state that "these discs are more transparent", which leads me to think you are still referring to the metallic reflective layer when you say the "dye" is thinner. Why? Because the organic dyes are pretty much transparent to visible light anyway, and any increased transparency that you see when looking through the disc is primarily due to a thinner metallic reflective layer. I'm sure you know in your head what you mean, but to me it isn't clear when reading your words.

I'm not aware that referring to the reflective layer as "dye" is common. Maybe it is and I've just never seen it done before. But if it is, then I think we should lead the charge against such confusing nomenclature. Particularly in these forums where we are trying to reduce confusion, not increase it. :wink:

By the way, do you have a link to that article?

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Postby Han on Tue Feb 04, 2003 1:42 pm

Sorry for not being more precise. When I say dye, I actually mean it, and when I say reflective layer, I mean that too. I should corroborate my observations also with thinner reflective layer.

It bothers me quite a bit that companies, in order to keep the minimal profit, are reducing both - thickness of dye and reflective layer.

The article is in our local monthly paper. I guess I'd have to translate it for you to understand it... :wink:
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Postby cfitz on Tue Feb 04, 2003 2:19 pm

Han wrote:Sorry for not being more precise. When I say dye, I actually mean it, and when I say reflective layer, I mean that too. I should corroborate my observations also with thinner reflective layer.

Okay, gotcha. My tired brain comprehends now. :wink:

Han wrote:It bothers me quite a bit that companies, in order to keep the minimal profit, are reducing both - thickness of dye and reflective layer.

I have to agree with you there, although it isn't anything new. I remember the first time, many years ago, when I realized I could see right through a pressed CD. What a shock! And that particular one had such a thin reflective layer that I didn't even have to hold it up to the light to see through it. I could just set it down on my textbook and read the page underneath. :o :(

You don't need much thickness to reflect all the light, since a the surface penetration of an electromagnetic wave into a metal is extremely shallow, but there are limits, and some of these reflective layers seem to be pushing them.

The article is in our local monthly paper. I guess I'd have to translate it for you to understand it... :wink:

Hmmm. Too bad. They don't have an online version, I suppose, since it is a small local paper. But then again they probably got the article from another source, since it is a small local paper. Any chance they listed the prime source?

By the way, when you say translate, do you mean to electronic format or to English? If it is the latter, I wasn't aware you spoke another language.

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Postby Han on Tue Feb 04, 2003 3:39 pm

cfitz wrote:They don't have an online version, I suppose, since it is a small local paper. But then again they probably got the article from another source, since it is a small local paper. Any chance they listed the prime source?

The computer magazine (sorry again for saying "local paper") isn't that small and the source is its own. It so happens that they visited our first local factory, which recently started a massive CD-R production...

cfitz wrote:By the way, when you say translate, do you mean to electronic format or to English? If it is the latter, I wasn't aware you spoke another language.

To English. My mother tongue is Slovenian. :wink:
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Postby cfitz on Tue Feb 04, 2003 3:46 pm

Han wrote:It so happens that they visited our first local factory, which recently started a massive CD-R production...

Do they offer tours? That would be interesting to see.

Han wrote:My mother tongue is Slovenian. :wink:

Well, no one would ever know it based on your flawless English. Did you learn English as a child?

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Postby Han on Tue Feb 04, 2003 4:00 pm

cfitz wrote:
Han wrote:It so happens that they visited our first local factory, which recently started a massive CD-R production...

Do they offer tours? That would be interesting to see.

I guess they do, but they won't tell you all the "secrets".

cfitz wrote:Well, no one would ever know it based on your flawless English. Did you learn English as a child?

I'm trying my best, thanks. I learnt English in primary and secondary school (8 years total). I also took private German lessons and then learnt it in secondary school as secondary foreign language. But I didn't like it much, so I'm quite embarrassed I can't read/write it with confidence.
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Postby cfitz on Tue Feb 04, 2003 4:14 pm

Han wrote:I'm trying my best, thanks. I learnt English in primary and secondary school (8 years total). I also took private German lessons and then learnt it in secondary school as secondary foreign language. But I didn't like it much, so I'm quite embarrassed I can't read/write it with confidence.

Well, I don't know about your German, but your English is just fine. I wish I could speak Japanese as well as you speak English. But, alas, that will never be. (I started too late and am too lazy to study hard enough... :oops: :( )

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Postby dodecahedron on Tue Feb 04, 2003 5:58 pm

cfitz wrote:
Han wrote:My mother tongue is Slovenian. :wink:

Well, no one would ever know it based on your flawless English. Did you learn English as a child?

cfitz

ha!
i knew it!

just the other day you wrote that your regional settings were Slovenian :wink: 8)

btw, i sencond cfitz'c compliments to your English, Han.
One Ring to rule them all, One Ring to find them,
One Ring to bring them all and in the darkness bind them
In the land of Mordor, where the Shadows lie
-- JRRT
M.C. Escher - Reptilien
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Postby Gary Kokkin on Tue Feb 04, 2003 6:24 pm

Han Wrote :
"I'm sceptical to these CDs. I've seen today Memorex ones, unfortunately also sealed. Personally, I wouldn't recommend them. Gold or silvergold reflective layer is proven to be the best for CD-R technology"

Memorex black discs not able burn on label's speed at all .
In my tests in CDR label speed 40x burn @ 16x ! using Liteon 48125W
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Postby Action Jackson on Wed Feb 05, 2003 8:21 pm

I've used some Black Smart Buy 32x CDR. Burnt fine at 40x on a 52x LiteON.

I've also tried some of the E3 Works 24x "Vinyl" look CDR's. They work okay too.

One thing I noticed is that I cannot see the color change that would normally be associated with other non-black CDR's.
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Postby jase on Wed Feb 05, 2003 8:54 pm

One thing I noticed is that I cannot see the color change that would normally be associated with other non-black CDR's.


That's because it's hidden by the coloured plastic, the dye used is standard phthalocyanine.

Given that the polycarbonate is partially opaque to red light (by definition -- a black surface is so coloured because it absorbs most light rather than reflecting it) I'm surprised these discs work at all TBH.
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Postby cfitz on Wed Feb 05, 2003 11:44 pm

jase wrote:Given that the polycarbonate is partially opaque to red light (by definition -- a black surface is so coloured because it absorbs most light rather than reflecting it) I'm surprised these discs work at all TBH.

The laser used for CD-R recording is an infrared laser, of course, so just because the disc is partially opaque to visible light doesn't necessarily mean it is opaque to the laser as well. However, the 780-790 nm wavelength of CD-R lasers isn't all that far outside of the 400-700 nm visible light spectrum, so it's hard to believe the CD-R laser doesn't suffer at least somewhat.

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