PURPOSE: To obtain a biaxially oriented polyester film excellent in chipping resistance, lubricity, clutch resistance, molding workability, etc., by dispersing a specified amount of spherical silica particles specified in the average particle diameter and particle diameter ratio in a polyester.
CONSTITUTION: Spherical silica particles having an average particle diameter of 0.3W4μm and a particle diameter ratio (major diameter/minor diameter) of 1W1.2 and, preferably, a relative standard deviation represented by the formula of 0.5 or below are prepared. 1W4wt.% these spherical silica particles are dispersed in a polyester (e.g., polyethylene terephthalate). This polyester is formed into a film, which is biaxially oriented to obtain the purpose biaxially oriented polyester film. The obtained film can be used suitably as a base film for videotapes, computers, etc.
HASEGAWA KINJI
HAMANO HISASHI
KATO HIDEO
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