| abstract |
PURPOSE:To form a biaxially oriented polyester film having excellent surface flatness, slip properties, and anti-scraping characteristics, by compounding an arom. polyester and porous fine silica particles having a spherical shape close to a real sphere, a small particle size and a large specific surface area, molding the mixture into a film and drawing biaxially the film. CONSTITUTION:This biaxially oriented polyester film is formed by molding a dense mixture of an arom. polyester [1] and 0.005-4wt.% spherical porous fine silica particles [2] based on the wt. of the arom. polyester having a particle size ratio (a) defined by the radio of the max. diameter to the min. diameter, of 1.0-1.2, a mean particle size (b) of 0.01-4mum and a specific surface area (c) measured by the BET method of 70m<2>/g or larger. The said spherical porous fine silica particles are obtd. by, e.g., treating zeolite (Na2O.2SiO2.Al2O3.nH2O) with an acid to dissolve and remove the alumina component. |