| 摘要 |
A biaxially oriented polyester film for a high-density magnetic recording medium, particularly a high-density magnetic recoding medium of linear recording system, which has high strength in longitudinal and transverse directions, excellent dimensional stability in a crosswise direction and is flat and excellent in output characteristics and a process for producing the same. The biaxially oriented film is made from polyethylene-2,6-naphthalate and has a Young's modulus in a longitudinal direction of 8 GPa or more, a Young's modulus in a transverse direction of 6 GPa or more, a temperature expansion coefficient in the transverse direction (alphat) of -5x10-6/° C. to +12x10-6/° C., a humidity expansion coefficient in the transverse direction (alphah) of 5x10-6/%RH to 12x10-6/%RH and a thermal shrinkage factor in the transverse direction at 105° C. of -0.5 to +1.5%
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