Optical disk substrate, optical disk and aromatic polycarbonate resin

An optical disk substrate formed substantially of an aromatic polycarbonate resin from an aromatic dihydroxy component containing at least 20 mol % of 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane,

• wherein:
• (A) the aromatic polycarbonate resin has a specific viscosity of 0.2 to 0.5 when measured in a solution of 0.7 g of the aromatic polycarbonate resin in 100 ml of methylene chloride at 20.degree. C.,
• (B) the aromatic polycarbonate resin shows a water absorption percentage, defined in the present specification, of 0.2% by weight or less,
• (C) the aromatic polycarbonate resin has an oligomer content, measured by the method defined in the present specification, of 10% or less, and
• (D) the number of undissolved particles having a diameter of 0.5 .mu.m or greater is 25,000 pieces or less per g of the polycarbonate resin, and the number of undissolved particles having a diameter of 1 .mu.m or greater is 500 pieces or less per g of the polycarbonate resin when the aromatic polycarbonate is measured in a methylene chloride solution.