| 摘要 |
PURPOSE:To obtain a polyester film which, when used as a magnetic recording medium, can show improved running property, especially, under high-humidity and high-temperature conditions without detriment to its electromagnetic transduction characteristics, by forming a biaxially oriented polyester film satisfying specified conditions concerning characteristic values. CONSTITUTION:A polyester film which is a biaxially oriented film based on a polyester and simultaneously satisfies the following equations: (1) 0.2<=D<=2.0, (2) sigma<=0.4 and (3) 1.1<=pi<=6, wherein D (unit:mum) is the modal diameter of the surface protrusions on at least either surface and sigma is the principal variance of the surface protrusion diameters and phi is the variance ratio. It is preferable that this film satisfies the condition: the max. value of a running parameter DELTAmuk<=0.005. |
