| 摘要 |
PURPOSE:To obtain the titled film superior in smoothness and lubricity, high in density, by limiting average refractive index and biaxial orientation degree in specified ranges and lowering surface roughness to not over a specified value. CONSTITUTION:The present polyester film is biaxially stretched to orient the polymer molecules biaxially, and its average refractive index n and its face orientation degree DELTAP satisfy inequalities and equations I and II, and its average surface protuberance height is <=15nm. As a result, it is distinguished in electrical characteristics, and excellent in smoothness and lubricity, and suitable for use in magnetic recording materials capable of high density recording, such as video magnetic tape, magnetic video disc, and floppy disc. |
