PURPOSE: To improve handling property, running property and durability and also basic characteristics such as high strength, high heat resistance, etc., and thereby to attain higher-density recording by using a biaxially oriented composite film which is constructed of layers A and B having different structures and different average particle sizes, etc.
CONSTITUTION: A biaxially oriented composite film prepared by laminating a layer A constituted of polyethylene-2,6-naphthalate containing a germanium compound or the like and a layer B containing inactive particulates. The layer A has a surface structure having a wind-wrought pattern, contains the inactive particulates of an average particle size (x:μm) less than 0.3μm in the amount (y:wt.%) of addition satisfying y<0.12-0.4x and has a surface of a roughness 5nm or below. The layer B contains particles of 0.01-1wt.% of which the average particle size is 0.1-1wt.%, and has a surface of which the roughness is 25nm or below.
OKUBO KENICHI
FUKADA KAZUYOSHI
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