BIAXIALLY ORIENTED POLYESTER FILM

摘要

PURPOSE:To provide a biaxially oriented polyester film wherein damages on the surface of the film during high speed process occur seldom and damages on the magnetic face occur seldom when used as a magnetic tape. CONSTITUTION:A biaxially oriented polyester film wherein 0.01-3wt.% particle A consisting of an oxide of an element of the fifth or the sixth period in the periodical table of elements with a mean primary particle diameter of at least 0.0017mum and at most 0.3mum and a mean degree of aggregate of 2-100 are incorporated and at the same time, 0.01-2.0wt.% inert particle B with a mean primary particle diameter of at least 0.3mum and at most 2.0 P are incorporated and the heat shrinkage in the longer direction of the film is at most 2.0% and the number of projections on one face of the film is 1,000/mm<2> or larger and the mean carvature radius of the projections is 0.3-3.0mum.