Optical disk substrate

摘要

An optical disk substrate is disclosed, which is molded from a terpolymer composed of (A) an aromatic vinyl monomer, (B) cyclohexylmaleimide, and (C) at least one compound selected from the group consisting of (meth)acrylonitrile, isobornyl (meth)acrylate and cyclohexyl (meth)acrylate, with the cyclohexyl maleimide being copolymerized in an amount of from 5 to 60 wt % of said terpolymer. The optical disk substrate exhibits high heat resistance, low water absorption and low birefringence.