BIAXIALLY ORIENTED POLYETHYLENE TEREPHTHALATE FILM

摘要

PURPOSE: To obtain the optimum film as base film of a magnetic tape for a digital video which is inexpensive and moreover, better in electromagnetic changing characteristic with higher resistance to cutting in a production process and in a VTR. CONSTITUTION: This film comprises polyester containing ethyleneterephthalate 85mol% or more in a repeated unit. Total thickness of the film is 3-8μm, an elastic modulus B across the wmdth thereof us 600kg/mm<2> or more and a difference B-A from the elastic modulus A along the length thereof 100kg/mm<2> or the like. The surface roughness (Ra) of at least one side of the film is up to 0.1nm and the film is used as support body of a painted type magnetic recording medium for a digital video with the sum of the thickness of a coated layer being below 2μm.