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More on media Longevity... LONG!



For those of you who are RECMGMT-L regulars, this is a duplicate, but
for rest of you, I hope you find this of some value. I'm not on this
list, but thanks to Peter... I get "cut in" to some topics
occasionally.

Larry
***************************************
I know we started getting into this issue over the past week and I
have to agree with Bill's comments about "it's not the media, it's
the technology that READS IT you need to be concerned about"... with
that said though, for those of us that ARE concerned about the media
and how well (and accurately) it captures information for however
long there will be devices available to read it, I'd like to offer
the following sources of further information:


From Maxell's Website, http://www.maxell-data.com/focus/index.htm :

What actually makes a Maxell CD-R appear green, gold or blue?

The color of a specific type of CD-R disc depends on the dye material in the
recording layer used by the manufacturer. This dye color can alter in
appearance when different reflector coatings are applied (gold or silver).

Three types of dyes utilized in today's CD-R's are:

Cyanine:

This dye is actually blue in color. When combined with a gold reflective layer
Cyanine discs appear green in color. If a silver reflector is
applied, the discs
appear light blue in color. A major advantage of Cyanine based discs is that
they work with a wider range of laser powers, making them more compatible
among several different brands of writers. This is due to the fact that Cyanine
has a greater sensitivity to light than other dyes. This
characteristic also affects
their longevity. These discs have a life span of 50 plus years. The majority of
Maxell CD-R media sold in the U.S. is Cyanine based.

Pthalocyanine: This dye is actually yellow-green in color. When combined
with a gold reflector the discs appear gold or greenish gold in color.
Pthalocyanine dye is a newer dye that has less sensitivity to light.
Resulting in a
life span of up to 100 years. However, less light sensitivity can sometimes be
an issue when it comes to working with certain manufacturer's writers. Maxell
CD-R media manufactured in Mexico is Pthalocyanine based.

Azo: Mitsubishi Chemical Company manufactures this dye. Azo discs usually
use a silver reflective layer that give the data side of the disc a
deep blue color.
This dye has been used in other optical recording products in the past. Some
early formulations of Azo dyes had difficulty writing at higher speeds.
Longevity for Azo based discs should be in the 100-year range. Maxell has
never produced an Azo based CD-R.


As a further level of detail on the subject, I suggest you take a
look at this article from Dana Parker on the differences between the
types of CDs and their respective life spans:
http://www.cd-info.com/CDIC/History/Commentary/Parker/stcroix.html

In part, (to whet your appetite) the article offers this:

"It is not quite so cut-and-dried as "phthalocyanine discs last longer,
so they are better". There are far too many CD-R users who, from
long experience, swear by cyanine media as staunchly as you and
others do by phthalocyanine. As it turns out, they have good reason
to do so. Allow me to shed some light as well as heat on the subject."

"CD recordable technology is a complex and convoluted subject. There
are many factors that come into play when recording a disc: the rate of
spin, the formula of the dye, the ambient temperature, the internal
temperature, the age of the media, the power and wavelength of the laser,
the spacing and size of the marks on the media relative to the speed of the
disc, to name but a very few. Media manufacturers are constantly adjusting
the myriad factors of disc production, including but certainly not limited to
the formula of the dye polymer. CD-R media must combine the properties of
compatibility, writability, readability, and data longevity. To say
that a certain
dye formula or brand of media is inherently better than another based
exclusively on one of these properties is not only simplistic, it is
misleading."

And as a final offering, from the same site as above:
http://www.cd-info.com/CDIC/Technology/CD-R/Media/Longevity.html

"One of the primary applications for CD-Recordable is archiving. To
consider CD-R a viable medium for this purpose, obviously some data
on the reliability and expected lifespan of discs is required by those
responsible for preserving important information. CD-R is a new
technology,however, and estimating lifespans expected to be many
decades for a medium that is less than fifteen years old requires
sophisticated accelerated aging techniques and rigorous testing
methodologies whose results may not be easy to interpret."
--
Lawrence Medina
Sr. Records Administrator
Lawrence Livermore National Lab
925.422.7628
medina9@llnl.gov

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