Biaxially oriented polypropylene film, metalized film, and film capacitor

Abstract

Disclosed is a biaxially oriented polypropylene film which has projections on both surfaces of the film. The most common height (PhZ) of the projections among the projections on each surface is 100 nm or more but less than 400 nm on each surface, and the number of projections (Pc) per 0.1 mm2 of each surface is 150 projections or more but less than 500 projections on each surface. The biaxially oriented polypropylene film is easily processed into an element, and provides a capacitor that has high withstand voltage and excellent squealing characteristics when processed into a capacitor.

Description

technical field [0001] This invention relates to biaxially oriented polypropylene films suitable for capacitor applications. More specifically, it relates to a biaxially oriented acrylic film that is easy to process as an element, and can obtain a capacitor with high withstand voltage and low squeeling when processed into a capacitor. Hereinafter, the characteristics of such a biaxially oriented propylene film are respectively referred to as device processability, voltage resistance, and squealing characteristics. Background technique [0002] Polypropylene films are widely used for electrical applications due to reasons such as excellent electrical characteristics. Among them, the development as a dielectric material in capacitor applications is remarkable. In recent years, demands for miniaturization and cost reduction have been strong, and the thickness reduction of the dielectric film has been progressing. In addition, the requirements for withstand voltage characteri...

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Problems solved by technology

[0008] However, in the mechanical and chemical methods, the roughness density is low, and in the method of stretching the β-crystal sheet, coarse protrusions are likely to be generated.

Moreover, the film whose surface is roughened by these methods has the following problems: the gap between the film layers becomes uneven, and corona discharge is likely to occur when an AC voltage is applied at the portion where the gap is enlarged due to the coarse protrusion, and the life of the capacitor is reduced. Moreover, the vibration characteristics deteriorate, etc.

[0018] However, only optimizing the thermal shrinkage stress value at 120°C in the longitudinal direction and the heat-sealing strength can suppress the occurrence of squealing characteristics and corona discharge, but the adhesion between the films is too high, so the capacitor's Safety cannot be ensured sufficiently, and high withstand voltage characteristics cannot be obtained

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