 |
 |
The reason why phthalocyanine dye cannot be used in DVD-Rs is that the wavelength of the laser used to burn DVDs is smaller than that used for CD-Rs, and the dye doesn't respond to (absorb) this wavelength. -----Original Message----- From: Richard L. Hess [mailto:[log in to unmask]] Sent: Saturday, March 25, 2006 5:59 PM Subject: Re: Further thoughts on the new CLIR report. DVDs At 08:45 PM 3/25/2006, steven c wrote: >Question for the technically knowledgeable... > >Since CD's and DVD's are (AFAIK) more or less the "same animal" and >operate by pressing (or "burning") pits into the surface of a plastic >disc, why should there be any difference in the lifespan of the two? > >Do the littler "holes" fill themselves up more rapidly? There is one major difference in construction. The CD has the delicate top layer that is the reflective layer covered with lacquer. The DVD's reflective layer is in the middle and the two discs are bonded together. That bond is a source of concern. The CD-Rs that seem to fare best in tests use phthalocyanine dye. I think Joe Iraci pointed out that the DVDs do not use that dye. That could contribute to the lower life expectancy. I don't know why phthalocyanine dye cannot be used in DVD-Rs, but apparently it cannot. The gold DVD-Rs from MAM-A, by the way, are only 4x while almost everyone is shipping silver 8x and perhaps faster. Cheers, Richard Tape Restoration Seminar: MAY 9-12, 2006; details at Web site. Richard L. Hess email: [log in to unmask] Aurora, Ontario, Canada (905) 713 6733 1-877-TAPE-FIX Detailed contact information: http://www.richardhess.com/tape/contact.htm