Biaxially oriented laminated polyester film

摘要

A biaxially oriented laminated polyester film comprising a first polyester surface layer having (a1) a central line average roughness RaA of 1 to 7.9 nm, (b1) a 10-points average roughness RZA of 15 to 400 nm and (c1) an RZA/RaA ratio of 11 - 51, and a second polyester surface layer having (a2) a central line average roughness RaB which is greater than RaA and is 5 to 40 nm, (b2) a 10-points average roughness RZB of 75 to 600 nm and (c2) an RZB/RaB ratio of 20 or less, and satisfying the relationship between the first polyester surface layer and the second polyester surface layer, which is represented by the following expressions, $$ $ This\; biaxially\; oriented\; laminated\; polyester\; film\; is\; excellent\; in\; lubricity,\; high-speed\; take-up\; properties,\; processability\; and\; electromagnetic\; characteristics\; when\; used\; for\; a\; magnetic\; film,\; and\; is\; particularly\; useful\; as\; a\; base\; film\; for\; a\; magnetic\; recording\; medium.\mathop{\mathrm{image}}$$$