Patent ID: 7829175

Claim:
A white, biaxially oriented polyester film, which has a base layer (B) and has at least one outer layer (A), where a) the base layer (B) comprises, as sole whitener, a concentration of from 5 to 25% by weight of barium sulfate, and b) the outer layer (A) comprises, as sole whitener, a concentration of from 5 to 25% by weight of barium sulfate having a median diameter in the range from 0.1 to 5 μm, and also comprises from 0.01 to 4% by weight of antiblocking agent whose median diameter (d 50 value) is from 2 to 8 μm, wherein said film exhibits a Berger whiteness greater than 70 and the average roughness of the outer layer (A) is from 40 to 150 nm.