LAYERED POROUS FILM AND NONAQUEOUS-ELECTROLYTE SECONDARY BATTERY

摘要

Provided is a layered porous film which includes a functional layer having a controlled longitudinal-direction thickness and which is suitable as a separator for batteries. The layered porous film comprises a base film and, formed on a surface thereof, a functional layer comprising an inorganic filler and a binder resin. When the layered porous film is examined for basis weight at intervals of 100 m in the length direction, the difference between the maximum basis weight and the minimum basis weight is 2 g/m2 or less. Separators obtained by cutting a film roll constituted of the layered porous film into a given length are reduced in lot-to-lot variation, and hence are effective in diminishing quality fluctuations in batteries produced using said separators.