Substrate material for high speed optical discs
View Patent ↗This invention relates to the use of polycarbonate for the production of an optical recording medium in which secure high speed operation, a transcriptability of the pit/groove structure of >85% and sufficient disc flatness can be achieved and the polycarbonate is based on bisphenol A and the polycarbonate contains a release agent in an amount less than 2000 ppm.
1. A method of producing a substrate for optical discs which comprises utilizing polycarbonate that can sustain the high rotation speed test at 24000 RPM for at least 30 minutes without failure due to disc breakage and wherein the optical disc has a transcriptability of the pit/groove structure of >85% wherein the polycarbonate
(i) has a relative solution viscosity of 1.210 to 1.285,
(ii) contains a release agent in an amount less than 2000 ppm and
(iii) contains biphenol A.
2. The method according to claim 1 , wherein the polycarbonate has a relative solution viscosity of 1.220 to 1.285.
3. The method according to claim 1 , wherein the polycarbonate has a relative solution viscosity of 1.230 to 1.270.
4. The method according to claim 1 , wherein the polycarbonate contains less than 1000 ppm release agent.
5. The method according to claim 1 , wherein the polycarbonate contains less than 500 ppm release agent.
6. The method according to claim 1 , wherein the release agent is glycerin mono stearate or glycerin mono palmitate or mixtures thereof.
7. The method according to claim 1 , wherein the transcriptability is more than 90%.
8. A substrate for an optical medium made of polycarbonate having a relative solution viscosity of 1.210 to 1.285 that can sustain 24000 RPM on a spin stand for at least 30 minutes without failure due to disc breakage and wherein the polycarbonate is based on bisphenol A and the polycarbonate contains a release agent in an amount less than 2000 ppm.
9. An optical medium made of the substrate according to claim 8 .