| 摘要 |
PURPOSE:To obtain a film capable of satisfying both of a surface property and runnability, by a method wherein the surface of one of the layers of the film has specific RPA (center line depth) and the surface of the other layer thereof has specific RPB (center line depth) and specific RaB (center line average roughness) and projections each having a height of a specific value or more. CONSTITUTION:A film composed of aromatic polyamide and aromatic polyimide consists of two layers A, B and the surface of the layer A provided with a magnetic layer has RPA of 10-200Angstrom and, when RPA is smaller than 10Angstrom , surface becomes excessively smooth and is easily damaged at the time of the preparation of a magnetic recording medium and, contrarily, when RPA is larger than 200Angstrom , an electromagnetic conversion characteristic becomes inferior. With respect to the surface properties of the layer B (called a B-surface) on a side provided with no magnetic layer, it is necessary that RPB is within a range of formula (1) and, when RPB is smaller than RPA+50, the B-surface is too smooth to contribute to the improvement in the runnability of the film and, when RPB is larger than 1500Angstrom , runnability is well but the smoothness of the film or magnetic layer is lost. The RaB of the B-surface is 20-200Angstrom and it is necessary that 30 or more projections having a height of 50Angstrom or more are present per 1mm. |
