| 摘要 |
PURPOSE:To obtain an optical disk substrate reduced in the double refraction to oblique incidence and also reduced in the quantity of electrification under high speed rotation by forming the optical disk substrate from an aromatic polycarbonate copolymer having surface resistivity of below 1X10<10>OMEGA. CONSTITUTION:An optical disk substrate is constituted of an aromatic polycar bonate copolymer having surface resistivity of below 1X10<10>OMEGA, pref., about 7.5X10<7>-2X10<9>OMEGA. The aromatic polycarbonate copolymer is prepared by the carbonate bonding of 4, 4 '-dihydroxy-2,2,2-triphenylethane 55-75mol% and 1, 1'-bis(4-hydroxyphenyl)-m-disopropylbenzene 45-25mol%. This aromatic polycar bonate copolymer is characterized by that double refraction at the time of oblique incidence is 2.5-3.0X10<-4>, surface resistivity is below 1X10<10>OMEGA, the quan tity of esterification before rotation is below 50mV and the quantity of electrifi cation after high speed rotation of 3600rpm is below 180mV. |
