From: Patent Tactics, George Brock-Nannestad
Hello,
Andrew Hamilton wrote:
> Excellent question.
----- well, not quite. I used my gut reaction concerning photoresist
("protecting part of a surface against etching when after exposure it is
dumped in an etching bath"), and it turns out it does not work in the case of
CD manufacture. The proof lies in the fact that the glass disc may be reused.
The pits are indeed only formed in the photoresist. The only fact I got right
was that a glass surface is so fine that it will even support CD manufacture.
Kind regards,
George
Why not photo-admittance? Well, they don't
> call it that, but they do use it, too...
> Wiki has a page on CD glass mastering and explains that there are two
> kinds of photoresist (positive or negative) that can be washed away,
> after laser developing, but there is also
> NPR (non-photoresist) glass mastering, which uses an organic polymer
> dye as the laser-beam target layer. This dye layer is deeper than a
> pit, much the same as the lacquer layer, on a blank destined for
> vertical or stereo cutting, is deeper than the most deep, intentional
> embossing (gouge?). The pitch on a CompuDisk or Zuma is set to
> avoid hitting the bedrock of the supporting layer, whereas I believe
> that the photoresist layer, in the former-mentioned CD glass
> mastering method, is washed away clean down to the substrate - unlike
> a well-cut lacquer. Fortunately, the CD player is only trying to
> make a variable strobe light display, rather than musical wiggles...
> at that point in the chain.
>
>
> Andrew
>
>
>
>
>
>
> On Jan 23, 2011, at 7:49 AM, George Brock-Nannestad wrote:
>
> > From: Patent Tactics, George Brock-Nannestad
> >
> >
> > ----- are they not etched into the glass afterwards? What is the
> > photoresist
> > resistant against?
> >
> > George
> >
> >
> >> Regarding CDs, the pits are in a thin photoresist layer that is
> >> spun onto
> >> the glass substrate.
> >>
> >> Jerry
> >> Media Sciences, Inc.
> >>
> >>> -----Original Message-----
> >>> From: Association for Recorded Sound Discussion List
> >>> [mailto:[log in to unmask]] On Behalf Of George Brock-
> >>> Nannestad
> >>> Sent: Saturday, January 22, 2011 6:09 PM
> >>> To: [log in to unmask]
> >>> Subject: Re: [ARSCLIST] How many 78s to the Matrix
> >>>
> >>> From: Patent Tactics, George Brock-Nannestad
> >>>
> >>>
> >>> Hello,
> >>>
> >>> Stewart Goodeman wrote [quote]:
> >>>
> >>> I know in 1943, when they recorded the Rodgers and Hart
> >>>> revival of "A Connecticut Yankee" they actually used glass.
> >>>>
> >>>
> >>> ----- just to avert any confusion: glass means that the disc that
> >>> supported
> >>> the layer that the cut was made in was made of glass. The layer
> >>> could
> >> have
> >>> been lacquer, or it could have been wax, both were used. It has been
> >>> thought
> >>> that glass was a cheap substitute for aluminum that was the most
> >>> used
> >>> material for lacquer mastering discs, due to other uses for aluminum
> >>> during
> >>> the war. But in fact, the quality of the cut in glass-based discs
> >>> was
> >>> better
> >>> than for aluminum, because the surface of glass was much smoother.
> >>>
> >>> This is very different from the use of glass in the manufacture
> >>> of CDs;
> >>> here
> >>> the pits are really represented in the glass as a stage of
> >>> manufacture.
> >>>
> >>> Kind regards,
> >>>
> >>>
> >>> George
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