Biaxially oriented polyester film

摘要

The present invention relates to a biaxially oriented polyester film comprising a polyester containing 0.001 to 3.0% by weight of porous spherical silica particles and having a degree of deformation of said porous spherical silica particles of 1.2 to 5.0, which polyester film is obtained from extruding and biaxially stretching said polyester containing said porous spherical silica particles having an average particle size of 0.3 to 15 mu m, a sphericity ratio defined by the following equation (1) of 0.90 to 1.0 and a particle size distribution factor defined by the following equation (2) of 1.2 to 2.5. $where\; d10\; and\; d90\; are\; particle\; diameters\; (\; mu\; m)\; at\; 10\%\; and\; 90\%,\; respectively,\; based\; on\; the\; total\; volume\; when\; the\; integrated\; volume\; of\; the\; group\; of\; particles\; was\; measured\; from\; the\; larger-diameter\; particle\; side.$