Patent ID: 7223451

Claim:
A uni- or bi-axially oriented film (A) which comprises a polymer or polymer mixture containing a recurring unit represented by the following formula (I): wherein R 1 to R 8 are each independently a member selected from the group consisting of hydrogen atom, halogen atom, hydrocarbon group having 1 to 6 carbon atoms and hydrocarbon-O— group having 1 to 6 carbon atoms, and X is represented by the following formula (1)-1: wherein R 30 and R 31 are each independently a halogen atom or alkyl group having 1 to 3 carbon atoms, and n and m are each independently an integer of 0 to 4, each of the polymer and the polymer mixture containing the recurring unit represented by the above formula (I) in an amount of more than 30 mol % and up to 60 mol % based on the total of all the recurring units of the polymer or polymer mixture and having a glass transition temperature of 165° C. or higher, (B) which has a heat shrinkage factor when it is heated at 90° C. for 500 hours under no load of 0.1% or less obtained by heat setting after stretching, and (C) which satisfies the following formula (1): 1 ≦R (450)/ R (550)≦1.06 (1) wherein R(450) and R(550) are retardations within the film plane at wavelengths of 450 nm and 550 nm, respectively.