| 摘要 |
PROBLEM TO BE SOLVED: To provide a polyethylene naphthalate copolymer suited for photographic films excellent in all of delamination resistance, restorability from curl, mechanical strengths, hue and transparency and to provide a biaxially oriented film. SOLUTION: This invention provides a polyethylene naphthalate copolymer comprising an acid component based on naphthalenedicarboxylic acid and a glycol component based on ethylene glycol and containing 0.5-5 mol.%, based on the total acid component, fluorene compound having an esterifiable functional group as a comonomer in the glycol component and at most 3 mol.%, based on the total acid component, diethylene glycol component and a base film for a photographic film made from this copolymer and being excellent in curling resistance and delamination resistance. |
