| 摘要 |
PROBLEM TO BE SOLVED: To have high strengths lengthwise and widthwise and realize a favorable frictional resistance and slipperiness by a method wherein the lengthwise Young's modulus of a film and the ratio of the lengthwise static friction coefficient of the film to its widthwise static friction coefficient are set to have specified values. SOLUTION: The lengthwise Young's modulus of a film is set to be 5-10 GPa. The ratio of the lengthwise static friction coefficient of the film to its widthwise static friction coefficientμsMD/μsTD is set to be 1.05-1.25. In order to realize respective desired surface roughnesses on respective surfaces, a lamination structure consisting of two layers or more is employed under the condition that the surface roughnesses of the respective surfaces are respectively set to be 0.008μm or more and 0.005μm or less in order to preferably reconcile the outputting characteristics and slipperiness of the film used for a magnetic tape. As the polyester film, a polyethylene terephthalate, a polybutylene naphthalate, a polybutylene terephthalate, a polyethylene naphthalate and their copolymer or the like is preferable. These repeating units of 100 or more and intrinsic viscosities of 0.6 dl/g or more are preferable.
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