Patent ID: 7999059

Claim:
An optical film, comprising an ester-based polymer comprising a repeating unit represented by formula (I): wherein A and B each represent a substituent, a and b represent the number of the substituents A and the number of the substituents B, respectively, each of which is an integer of 0 to 4, A and B each independently represent hydrogen, halogen, an alkyl group of 1 to 6 carbon atoms, or a substituted or unsubstituted aryl group, R1 and R2 each independently represent a straight-chain or branched alkyl group of 1 to 10 carbon atoms or a substituted or unsubstituted aryl group, R3 to R6 each independently represent a hydrogen atom, a halogen atom, a straight-chain or branched alkyl group of 1 to 6 carbon atoms, a cycloalkyl group of 5 to 10 carbon atoms, or a substituted or unsubstituted aryl group (provided that at least one of R3 to R6 is not a hydrogen atom), n represents an integer of 2 or more; and wherein in formula (I), R1 is a methyl group, and R2 is a straight-chain or branched alkyl group of 2 to 4 carbon atoms.