| 摘要 |
PURPOSE:To make it possible to reduce the double refraction of an optical disc by decreasing the photoelastic constant of an aromatic polycarbonate, by forming the disc from an aromatic polycarbonate copolymer obtained by copolymerizing two specified bisphenols through carbonate bonds. CONSTITUTION:This optical disc is formed from an aromatic polycarbonate copolymer obtained by copolymerizing 97-3mol% 2,2-bis(3,5-dimethyl-4- hydroxydiphenyl)propane with 3-97mol% 2,2-bis(4-hydroxy-3-tert-butylphenyl) propane through carbonate bonds. It is preferable that the viscosity-average MW of said copolymer is 13,000-50,000.
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