Biaxially oriented polyester film for magnetic recording media containing theta or mixed alpha plus gamma aluminum oxide and inert organic particles

摘要

A biaxially oriented polyester film for magnetic recording media, which comprises: (A) 0.05 to 1.0% by weight of theta -aluminum oxide or mixed ( alpha + gamma ) aluminum oxide having an average particle diameter in the range of from 0.02 to 0.3 mu m and a specific surface area in the range of from 50 to 120 m2/g, and (B) 0.01 to 1.5 % by weight of inert organic particles having an average particle diameter which is in the range of from 0.1 to 1.5 mu m and greater than the average particle diameter of the aluminum oxide.