| 摘要 |
PURPOSE:To obtain a film excellent in slidability, chipping resistance during high-speed winding of a tape into a cassette and scratch resistance by adding specified colloidal silica particles to a biaxially oriented polyester film and specifying the formed protrusions. CONSTITUTION:A film prepared by adding 0.001-0.5wt.% heat-resistant polymer particles having a mean particle diameter of 0.03-1.5mum and 0.05-2.0wt.% colloidal silica particles having a rate of separate particles of 80% or above and a mean particle diameter of 0.30mum or below, wherein the distribution curve of the protrusions formed by these particles on the film surface in the range of a height (x:mum) of 0.05mum or above and the number (y: /mm<2>) of 30/mm<2> or above satisfies formula A, and the change ( muK) in the coefficient of friction in travelling of the film is below 0.15. In the formula, x is the height (mum) from the reference level; and y is the number (/mm<2>) of protrusions counted when they are cut to the height x. |
