IMPROVED BIAXIALLY ORIENTED COPOLYESTER FILM FOR MAGNETIC RECORDING MEDIA

摘要

Disclosed herein is a biaxially oriented mono- or multilayer copolyester film wherein the two surfaces of the film have different surface roughness, characterized in that at least one layer essentially consists of PENBB and the first surface of the film has large protrusions with a diameter of 0.2 to 2 mu m and the second surface has either no protrusions or small protrusions with a diameter smaller than those of the large protrusions on the first surface. PENBB as mentioned herein is a copolyester containing units of formula (I).___________________________________________