| 摘要 |
PROBLEM TO BE SOLVED: To provide a high-quality polyester film which has improved qualities such as durability of the film surface and gives a magnetic recording medium excellent in output-characteristics, surface durability. SOLUTION: This biaxial oriented polyester film has, at least one side of it, a surface which has the number of peakings whose height is at least 3 nm of 3×106-1×108/mm2, the number of peakings whose height is at least 50 nm of not more than 1×104/mm2, a three-dimensional surface roughness Ra of 1-10 nm and the ratio, Ry/Ra, of the maximum height, Ry, to the three- dimensional surface roughness, Ra, of 10-100.
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