| 摘要 |
PROBLEM TO BE SOLVED: To provide a biaxially stretched polyester film having excellent tear rectilinearity and tear strength while holding dynamic characteristics, aroma retention, heat resistance, oil resistance, low moisture absorption and, especially, dimensional stability under dry and moist heat environment required in a food packaging material. SOLUTION: The biaxially stretched polyester film comprises a mixture consisting of 90-70 weight % of a crystalline polyester resin (A) containing 80 mol% or more of terephthalic acid and 10-30 weight % of block copolyester (B) consisting of a crystal segment with a melting point of 170 deg.C or higher and a soft polymer with a melting or softening point of 100 deg.C or lower and a molecular weight of 400-8,000 and is excellent in tear rectilinearity in a machine direction and characterized by that a ratio of tear strength in a machine direction to that in the direction crossing the machine direction at a right angle is 0.7 or more.
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