BIAXIALLY ORIENTED FILM

摘要

A biaxially oriented polyethylene naphthalate copolymer film, characterized in that: (1) the film is made substantially of a polyethylene naphthalate copolymer comprising 90 to 99.9 mole % (based on the total of the repeating units) of ethylene 2,6-naphthalate units and containing an isophthalic acid component or a decalin-2,6-dicarboxylic acid component in an amount of 0.1 to 10 mole % based on the total of the dicarboxylic acid components, (2) the Young's moduli of the film in the lengthwise and widthwise directions are each 500 kg/mm2 or above, (3) the plane orientation coefficient of the film is 0.230 to 0.275, and (4) the density thereof is 1.350 g/cm3 or above.