| 摘要 |
PURPOSE:To obtain a base film for a high-density magnetic recording medium having an excellent running characteristic, durability and head touch by forming the base film in such a manner that projections having <=0.1mum height exist at 10<5>-10<9> pieces in average for each 1mm<2>. CONSTITUTION:This base film consisting of a polyimide film characterized by the presence of the proejections having <=0.1mum height at 10<5>-10<9> in average for each 1mm<2>. The polyimide is preferably the polyimide of which the diamine component consists of >=30mol% paraphenylene diamine and 0-70mol% diamonodiphenyl ether and the acid dihydride component consists of a biphenyl tetracarboxylic dihydride and pyromellitic dihydride. The surface projections can be formed by forming fine reggedness of an casting belt and transferring the ruggedness to the film surface and the finer control of the ruggedness is possible with a method for dispersing pulverous inorg. particles of Al2O3, TiO2, Fe, etc. in a polyimide soln. The height of the surface projections is preferably 40-300Angstrom and the projections are preferably 10<5>-10<9> pieces for each 1mm<2> surface. |
