Abstract: The invention relates to a biaxially oriented polyester film which has three layers and which, together with very good electromagnetic properties compared with prior art films, has improved abrasion properties. The two sides of the film are built up from at least one base layer B and, applied to this base layer, outer layers A and C, where these outer layers have a defined number of elevations of defined height. The invention also relates to a process for producing the film and to its use as magnetic tape film.

Abstract: The invention relates to a biaxially oriented polypropylene film which has good processing performance and, after it has been metallized or oxidically coated, is a very good barrier to oxygen, and which is composed of at least a base layer, wherein the planar orientation delta p of the film is greater than 0.0138.

Abstract: The invention relates to a three-layer, biaxially oriented polyester film which has better abrasion properties than prior art films, together with very good electromagnetic properties. The structure on the two sides of the film in composed of at least one base layer B and, applied to this base layer, outer layers A and C, wherein the outer layer A has a roughness gas flow greater than 1000 sec and less than 2000 sec, and the outer layer C has a roughness profile gas flow of less than 600 sec. The invention further relates to a process for producing the film, and to its use as a magnetic tape film.

Abstract: The invention relates to a biaxially oriented polyester film which, after metallization, has low oxygen permeation and good adhesion to the metallization, and is composed of at least one base layer B and, applied to this base layer, at least one layer A, where this layer A i) has, per mm2 of film surface, a number N of elevations whose respective heights h and diameters d are correlated by the following equations: log N/mm2<Ah−Bh*log h/&mgr;m, 0.05 &mgr;m<h<1.0 &mgr;m  (1) wherein Ah=1.4; Bh=2.5 log N/mm2<Ad−Bd*log d/&mgr;m, 0.2 &mgr;m<d<10.0 &mgr;m  (2) wherein Ad=3.4; Bd=2.4 and ii) has a copolyester coating derived from isophthalic acid and a sulfomonomer.