CYTOP has excellent transmission (>95% for a 200um coat) all the way out to 200nm wavelengths. I'd suggest using it as a coating over your glass to prevent stress concentration of PCB on the glass. Here's a link to the data sheet which includes the transmission curve as well as all the relevant optical, mechanical, and thermal properties:
http://www.bellexinternational.com/products/cytop/pdf/cytop-catalog.pdf -Marc
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> To: Homebrew_PCBs@yahoogroups.com
> From: dj@...
> Date: Mon, 16 Aug 2010 17:40:55 -0400
> Subject: Re: [Homebrew_PCBs] UV: alternatives to glass?
>
>
>
> Hmm... my UV box is single-sided at the moment, are you suggesting
> putting the PCB on a rubber membrane, then the film, then glass - and
> letting the vacuum pull the rubber UP to the glass? That might be
> tricky to get air-tight...
>
>