I came across an interesting plastics industry article from 1998 that was discussing the challenges of producing the quality polycarbonates needed to manufacturer DVDs. While it was obviously a reference to pressed DVD-ROMs, the same general information could just as easily be applied to the yet-undeveloped DVD-R, DVD-RW, DVD+R, DVD+RW, DVD-R DL and DVD+R DL formats.
These were listed as the challenges
Quote:
Physical Attributes- Consistent pellet geometry
- Minimal fines and chaff
- Minimal particulates
- Optical homogeneity
- Low birefringence
- Meets impact requirements
Chemical Attributes- Low polymerization by-products
- Minimal additives
- Narrow molecular weight distribution
- Low glass transition temperature
Processing Attributes- No clouding, sticking, or staining
- Good color with low yellowness index
- A robust processing window
- Fast cycling
- Consistent viscosity
- Minimal, uniform static charge on substrate surface
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It's a safe assumption that the low-grade pressed and recordable discs we see probably fail at attaining the quality needed to produce quality in-spec blanks and metal DVD-ROMs. These two platters can be just as important as the glues/bonding, the DVD dyes and the silver or gold foils. Bad materials will usually equal a bad disc.
URL: plasticstoday.com/articles/meeting-new-molding-challenges-dvds
For archival purposes, a printout of the article is also attached below as a PDF.
