| 摘要 |
PURPOSE:To reduce drop-out and to enhance slit aptitude, by containing a specific amount of specific particles having a specific particle size in polyester and limiting the crystallization coefficient of the surface layer of a polyester film to a specific range. CONSTITUTION:The inert particle contained in the polyester of a polyester film is a flocculated particulate material of particles having a primary particle size of 10-100mum and a pref. average particle size of 20-80mum and the average particle size thereof is 500-1,500mum, pref., 700-1,200mum. The crystallization coefficient of the surface layer of the polyester film must be within a range of 0.50-0.70, pref., 0.55-0.67. This polyester film is used as a magnetic recording base film for a magnetic tape and a magnetic disk excellent in running property, especially running property and abrasion resistance under a high temp. and high humidity condition and generating no drop-out. |
