| 摘要 |
A method for the production of biaxially stretched polyester film. The method comprises the steps of: adding cubic calcium carbonate particles of calcite structure satisfying the following conditions at any stage of polyester preparation, so as to prepare polyester resin: d25/d75<2.00(1) 0.7</=d50</=1.50(2) a:b:c=1:(1 DIFFERENCE 1.5):(1 DIFFERENCE 1.5)(3) wherein d25, d50 and d75 are the diameters ( mu m) of particles when the accumulated weights of the particles are on the order of 25, 50 and 75% of the total weight of the particles, respectively, and a, b, c are width, length and height of the cubic calcium carbonate particles and the shortest one among a, b and c is set a=1; and applying melt-extrusion to the polyester resin. The biaxially stretched copolyester film provided is superior in travelling capacity as well as abrasion resistance and scratch resistance, so that it is useful for magnetic recording media.
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