| abstract |
A biaxially oriented film formed from a intimate mixture comprising (I) an aromatic polyester, (II) 0.005 to 1.0% by weight, based on the aromatic polyester, of fine particles of a silicone resin having (a) a composition represented by the following formula (A) RxSiO2-x/2 (A) wherein R represents a hydrocarbon group having 1 to 7 carbon atoms, and x is a number of from 1 to 1.2, (b) a volume shape factor (f), represented by the following formula (B), of more than 0.4 but not exceeding pi /6 f=V/D3 (B) wherein V is the average volume ( mu m3) of the particles and D is the average maximum particle diameter ( mu m) of the particle, and (c) an average particle diameter of 0.3 to 4 mu m. The film optionally contains (III) 0.005 to 1% by weight, based on the aromatic polyester, of inert fine particles having an average particle diameter of 0.01 to 1 mu m but being smaller than the average particle diameter of the silicone resin particles. The film is useful for a base film on a magnetic recording medium. |