BIAXIALLY STRETCHED POLYESTER FILM AND METHOD FOR MANUFACTURING THE SAME

摘要

PROBLEM TO BE SOLVED: To provide a biaxially stretched polyester film excellent in the adhesive strength between constituent layers, low in cost, excellent in barrier properties and generating no problem in disposal and reproduction. SOLUTION: The biaxially stretched polyester film consists of a base layer B comprising 80 wt.% or more of a thermoplastic polyester, at least one outer layer B and a metal or ceramic layer provided on the outer layer A. The outer layer A comprises a copolymer or a mixture of the copolymer and a homopolymer and consists of 90-98 wt.% of an ethylene/2,6-naphthalate unit, 10 wt.% or less of an ethylene terephthalate unit and 10 wt.% or less of an alicyclic or aromatic diol and/or a dicarboxylic acid. The thickness of the outer layer is larger than 0.7μm and below 25% of the total thickness of the film. The Tg2 of the polyester film is higher than Tg2 of the base layer and lower than Tg2 of the outer layer A.