| abstract |
A high-quality biaxially oriented polyester film having improved mechanical properties such as Young's modulus and dimensional stability and a method for producing the same are provided. SOLUTION: A polyester (A) and a polymer containing, as constituent units, a phosphonic acid residue represented by the structural formula (1) and a dihydric phenol residue represented by the structural formula (2) in the molecule ( And B) containing a biaxially oriented polyester film. R 1 : organic group X 1 : O, S or Se (However, two or more phosphonic acid residues having different R 1 or X 1 may be contained in the polymer.) R 2 , R 3 : H, NO 2 , a halogen atom or an aliphatic or aromatic group having 1 to 20 carbon atoms, p and q: integers and 0 ≦ p + q ≦ 8 Y 1 : O, S, alkylene group, etc. . [Selection diagram] None |