BIAXIALLY ORIENTED POLYESTER FILM FOR CAPACITOR

摘要

PROBLEM TO BE SOLVED: To provide a biaxially oriented polyester film suitable for a capacitor dielectric body which is capable of enhancing a capacitor much in electrostatic capacity keeping high breakdown voltage characteristics. SOLUTION: A film has physical properties where film thickness (t) is 2.5μm or below through a weight method, a deviation in thicknessΔt/t in the lengthwise direction of the film is 0.15 or below, and the average grain diameter (d) 50 (μm) of particles which are the largest in average grain diameter of particles contained in the film and the thickness (t) of the film are so set as to satisfy a formula (1). 0.5t<=d50<=1.0t...(1).