POROUS POLYPROPYLENE FILM AND PRODUCTION METHOD THEREFOR

摘要

This invention is a porous polypropylene film, in which the number of such portions where the quantity of light transmitted through each portion is not smaller than 5 times the average quantity of light transmitted through the film is 0.5 portion or less per 1 m 2 . The porous polypropylene film has a high porosity and excellent production characteristics, and when used as a separator in an electrical storage device, has excellent quality and few defects that could negatively impact battery performance. Using the porous polypropylene film, an electrical storage device can be produced having a suppressed occurrence of self-discharge and heating due to shorts.