| 摘要 |
PROBLEM TO BE SOLVED: To provide a biaxially oriented film, containing a thermoplastic acrylic polymer having a ring structure in the main chain, that has characteristics suitable for an optical film such as a high film strength, a low staining property and few appearance defects, etc., while maintaining low birefringence and heat resistance. SOLUTION: This biaxially oriented film includes the thermoplastic acrylic polymer having the ring structure in the main chain, and satisfies the following conditions: (A) an in-plane phase difference value (Re) is≤5 nm; (B) an absolute value of a thickness-directional phase difference value (Rth) is≤5 nm; (C) a glass transition temperature (Tg) is≥110°C; (D) a content of the thermoplastic acrylic polymer having the ring structure in the main chain is≥93 wt.%; and (E) a number of times of folding in an MIT folding endurance test is≥500. Preferably, a content of a structural unit derived from an aromatic vinyl monomer in the biaxially oriented film is≤5 wt.%. COPYRIGHT: (C)2010,JPO&INPIT
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