BIAXIALLY ORIENTED POLYESTER FILM AND FLEXIBLE DISK

摘要

A biaxially oriented polyester film having a difference in refractive index between front and back surfaces thereof of 0 to 0.002, a degree of heat shrinkage at 105 DEG C for 30 min under no load of 0 to 0.6 %, a Young's modulus of 4609 Mpa (470 kg/mm<2>) or more, a difference between the maximum and the minimum of Young's modulus in a surface of a film of 981 Mpa (100 kg/mm<2>) or less, a mean roughness in a central line of a film of 2 to 10 nm and a static friction coefficient of 0.55 or less. A flexible disk having excellent electromagnetic conversion characteristics can be provided by forming adhesive layers on both surfaces of the film and forming magnetic layers on the adhesive layers.