BIAXIALLY ORIENTED LAMINATED POLYESTER FILM FOR MAGNETIC RECORDING MEDIUM

摘要

PURPOSE:To obtain a polyester film capable of ensuring superior output characteristics and superior running durability of a magnetic face as a film for a metallic thin film type magnetic recording medium especially requiring high performance by imparting a laminated structure to a film for a magnetic recording medium and regulating the particle content of a layer of the film, the relation between the thickness of the layer and the particle diameter, and the distribution of height of protrusions. CONSTITUTION:This laminated polyester film consists of at least two layers A, B. The ratio of the thickness t mum of the top layer A of this film to the average particle diameter d mum of inert particles contained in the layer A is 0.5-20 and the particle content of the layer A is 0.02-1.5wt.%. The number of protrusions each having >0.035mum height from a flat face is <=0.75% of the total number of all protrusions existing on the surface of the layer A and the total reflection Raman crystallization index of the surface of the layer A is <=20cm<-1>.