| 摘要 |
PROBLEM TO BE SOLVED: To obtain a composition, which is excellent in transferability of signals from a stamper, is small in warpage when molded as a substrate and has a small refractive index in a vertical direction of a molded substrate, by compounding a specified amount of polystyrene glycol having a specified molecular weight in an aromatic polycarbonate resin having a specified molecular weight. SOLUTION: 0.2 to 50 pts.wt. of polystyrene glycol having a molecular weight of 300 to 10,000 is compounded in 100 pts.wt. of an aromatic polycarbonate resin having a viscosity-average molecular weight of 10,000 to 23,000. The aromatic polycarbonate resin should preferably be composed of structural units of formula I, and should more preferably be composed of a polycarbonate resin prepared from 2,2-bis(4-hydroxyphenyl)propane(bisphenol A). In the formula, R1 and R2 independently represent H, 1-6C alkyl or phenyl; and R3 and R4 independently represent H, 1-6C alkyl or halogen. The composition is used as a substrate for optical disk and particularly, as a substrate for high density optical disk.
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