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At 09:49 AM 7/7/2005 +0200, George Brock-Nannestad wrote:

>----- several persons responded - apparently correctly - that there are no
>adhesives used in the lamination process for CDs. However, for the CD-R to be
>able to tolerate handling, there has to be adhesion between the various
>layers. If the strength in the interface between layers (adhesion) or in the
>material internally (cohesion) is not sufficient for the purpose, then the
>laminate separates. That could potentially be the case in the phthalocyanine
>layer that separates the polycarbonate from the metallization. I have no
>reports of such a thing happening, but on the other hand, very few people
>have first-hand experience of phthalocyanine as a house building material. I
>have myself _unsuccessfully_ tried the Scotch-tape test (using a high-grade
>tape) to separate the polycarbonate sheet from the deposits.

I believe there is some misunderstanding here, but a valid point is
adjacent to the one being made.

There is no phthalocyanine "layer"; the dye (phthalocyanine or another) is
contained in a region of the polycarbonate - my assumption is that it is
suspended in the plastic.

However, there is a substantial issue of adhesion of the acrylic lacquer to
the metallizing. Potential faults are not only peeling of the lacquer but
also perfusion of oxygen through it, particularly about the edge. While the
metal/lacquer interface itself is not significant, integrity of the metal
surface is essential to reading the disc (pressed or recorded) and its
exposure means failure.


Mike
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