Patent ID: 6258442
Filing Date: 2001-07-10
Classification: C08J,C08L,G11B,Y10S,Y10T

Abstract:
A biaxially oriented polyester film for a magnetic recording medium, which comprises an aromatic polyester resin composition comprising:(A) an aromatic polyester;(B) 0.01 to 0.3 wt % of silicone resin particles(a) which can be obtained by polymerizing a silane compound containing trialkoxysilane represented by the following formula (1):R.sup.1 Si(OR.sup.2).sub.3 (1)wherein R.sup.1 is an alkyl group having 1 to 6 carbon atoms or a phenyl group and R.sup.2 is an alkyl group having 1 to 4 carbon atoms,in the presence of a surfactant and water and contain at least 80 wt % of recurring units represented by the following formula (2):R.sup.1 SiO.sub.3/2 (2)wherein R.sup.1 is the same as defined above,(b) which are substantially spherical, and(c) which have an average particle diameter of 0.1 to 1.0 .mu.m; and(C) 0.05 to 1.0 wt % of other inert fine particles having an average particle diameter, smaller than that of the above silicone resin particles, of 0.01 to 0.5 .mu.m,wherein said silicone resin particles are substantially spherical with a volume shape coefficient of 0.4 to 0.52, and have particle diameter 3 times or more the average particle diameter at a density of 30 or less per million particles.