| abstract |
A biaxially oriented laminate polyester film fornmagnetic recording medium, which is a laminate filmncomprising a base layer (A) formed of a polyester resinnand a coating layer (B) which exists on one surface ofnthe base layer (A) and contains a binder resin, addednfine particles and a surfactant, wherein the base layern(A) is a biaxially oriented film which substantiallyncontains no fine particles added or contains 0.001 ton0.1 % by weight of added fine particles having annaverage particle diameter of 0.005 to 0.3 µm, thencoating layer (B) has a surface having a central planenroughness (SRa) of 5 nm or less, the surface of thencoating layer (B) has protrusions having a majorndiameter of 0.05 µm or more in a density of 80,000npieces/mm 2 or less and has extra-large protrusions havingna major diameter of 10 µm or more in a density of 20npieces/cm 2 or less. Further, a thin film layer (C) maynbe further laminated on a surface on the side of thenbase layer (A) of the laminate polyester film which sidenis not in contact with the coating layer (B). n According to the present invention, there isnprovided a biaxially oriented laminate polyester filmnuseful as a base film for a magnetic recording mediumnwhich has excellent running durability andnelectromagnetic conversion characteristics and is almostnfree from drop-out. |