| 摘要 |
PROBLEM TO BE SOLVED: To obtain a film roll having a good winding style even if a film is taken up at a high speed by forming the surface average roughness at a specific cut-off value on a surface provided with a magnetic layer, surface waving index and the number of coarse projections to specific values. SOLUTION: The film consisting essentially of polyester is so formed that cut-off value of the surface provided with at least the magnetic layer is 0.08 and at this time the surface average roughness Ra is <=15 nm, the surface waving index is >=2.0 to <=20 and the number of the coarse projections of a height above 500 nm is <=10 per 1 mm<2> , by which the polyester film for magnetic recording media is obtd. The roughness and surface waving of the film are confined within the prescribed ranges and the coarse projections are decreased as far as possible in such a manner, by which the polyester film having the output characteristics, traveling property and winding style necessary for the base film of the magnetic recording media of a digital recording type, etc., is obtd. |
