| 摘要 |
PROBLEM TO BE SOLVED: To provide a digital video tape having good durability and a little dropout number and to provide a polyester film for a magnetic recording medium which is suitable for the production of the tape. SOLUTION: This polyester film has minute surface projections of 10 to 50 nm height on one surface. The density of the minute surface projections having 10 to 50 nm height is 1×106 to 1×108 pieces/mm2. When the film is left to stand at 30 deg.C room temp. for 30 days, the number of polyester oligomers having >=0.5μm diameter crystallized on the one surface of the film is <=500 pieces/mm2. In this method, any polyester which can form a high strength film by orientation of molecules can be used, and the polyester is preferably polyethylene terephthalate or polyethylene-2,6-naphthalate containing ethylene terephthalate or ethylene naphthalate by >=80% of the structural component. |
