Patent ID: 8741399

Claim:
A birefringent film, comprising an aromatic polyester having a repeating unit represented by the following general formula (1): wherein A(s), B(s), C(s), and D(s) are each a substituent, and each independently represent a group selected from a halogeno group, a linear or branched alkyl group which has 1 to 6 carbon atoms and may have a substituent, and an aryl group which may have a substituent; a, b, c, and d are each the substitution number of the corresponding A(s), B(s), C(s), or D(s); a and b each represent an integer of 0 to 4; c and d each represent an integer of 0 to 3; R1 represents a hydrogen atom, or a linear or branched alkyl group which has 1 to 10 carbon atoms and may have a substituent; R2 represents a linear or branched alkyl group which has 2 to 10 carbon atoms and may have a substituent; R3to R6each independently represent a group or atom selected from a hydrogen atom, a halogeno group, a linear or branched alkyl group which has 1to 6carbon atoms and may have a substituent, and an aryl group which may have a substituent; and l and m each represent an integer of 2or more.