To provide a biaxially oriented polyester film which has good dimensional stability at the time of processing of the film and is excellent in the coating processing properties of a magnetic layer in particular at the time of processing of a magnetic tape, traveling durability when adapted to the production of the magnetic tape, storage stability and electromagnetic conversion characteristics.
The biaxially oriented polyester film is characterized in that the heat-shrinkage factor in the width direction thereof under a 100°C/30 min condition is -0.4-0%, a crystal size χc in the thickness direction thereof is 50-80 Å, the modulus of elasticity Ym in the longitudinal direction of the film is 6-15 GPa, and the ratio Ym/Yt of the modulus of elasticity Ym in the longitudinal direction and the modulus of elasticity Yt in the width direction is 1.2-2.5.
COPYRIGHT: (C)2004,JPO&NCIPI
Takuji Higashioji
Tetsuya Tsunekawa
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