A biaxially oriented film which is made substantially of (1) a polyethylene naphthalate copolymer comprising an ethylene naphthalate unit in an amount of 92 to 99.5 mol% based on all recurring units and at least one copolymer component selected from the group consisting of (a) a glycol having a fluorene skeleton in the molecule, (b) p-hydroxymethylbenzoic acid, (c) p-hydroxyethoxybenzoic acid and (d) p-hydroxyethoxyethoxybenzoic acid in an amount of 0.5 to 8 mol% based on the total of all dicarboxylic acid components, and which has (2) Young's moduli in both longitudinal and transverse directions of 500 kg/mm2 or more and (3) a delamination resistance of 10 % or less in terms of fold line whitening ratio.
Since this biaxially oriented film of the present invention is excellent in delamination resistance, curling resistance, mechanical strength, color and transparency, it is of great value as a base film for a photo film.
一种双向拉伸薄膜,它主要由以下物质制成:(1)聚
萘二
甲酸乙二醇酯共聚物,其中
萘二
甲酸乙二醇酯单元的含量为 92 至 99.5摩尔%,至少有一种共聚组分选自以下组别:(a)分子中含有
芴骨架的
乙二醇,(b)对羟甲基
苯甲酸,(c)对羟乙氧基
苯甲酸和(d)对羟乙氧基乙氧基
苯甲酸,其含量为0.(2)纵向和横向的杨氏模量均大于或等于 500 kg/mm2,(3)抗分层性(折线白化率)小于或等于 10%。
由于本发明的这种双向拉伸薄膜在抗分层性、抗卷曲性、机械强度、颜色和透明度方面都非常出色,因此作为照相胶片的基膜具有很高的价值。