| 摘要 |
A biaxially oriented film of a polyethylene-2,6-naphthalenedicarboxylate, which (1) has a Young's modulus of at least 600 kg/mm<2> in the transverse direction and a Young's modulus of at least 500 kg/mm<2> in the longitudinal direction, the Young's modulus in the transverse direction being greater than the Young's modulus in the longitudinal direction, (2) satisfies the following relationships between an elongation ST (%) in the transverse direction per kg/mm<2> of a load at 120 DEG C and the Young's modulus YT (kg/mm<2>) in the transverse direction, <MATH> when YT is at least 1,200 kg/mm<2>, and <MATH> when YT is greater than 1,200 kg/mm<2>, and (3) has a heat shrinkage percentage of 0.1 % or less in the longitudinal direction when heat-treated under no load at 70 DEG C for 1 hour. This film is almost free from a dimensional change in the transverse direction and is excellent in lubricity and durability and is useful as a base film for a magnetic recording medium capable of high-density recording for a long time. |
