| 摘要 |
PURPOSE:To obtain the titled film having a smooth surface and excellent abrasion resistance and protrusion deformation resistance, by extruding a mixture of a poly(tetramethylene glycol) component with a poly(butylene tetraphthalate) and/or poly(butylene isophthalate) component. CONSTITUTION:A polyester of an intrinsic viscosity >=0.40, obtained by mixing a poly(tetramethylene glycol) component (a) with a poly(butylene terephthalate) and/or poly(butylene isophthalate) component (b) so that the relationships of formulas I-III [wherein A is the wt% of component (a) based on the polyester film and B is the wt% of component (b) based on the polyester film] may be simultaneously satisfied is melt-extruded at 280-300 deg.C to obtain a film. This film is cooled to 70 deg.C or below, stretched in the lengthwise and crosswise directions at an area draw ratio >=4 and heat-treated at 120-250 deg.C to obtain a biaxially stretched polyester film for magnetic recording media, having a centerline average roughness of 0.003-0.023mum. |
