MICROPOROUS POLYETHYLENE MEMBRANE, ITS PRODUCTION METHOD, AND BATTERY SEPARATOR

摘要

A microporous polyethylene membrane made of a polyethylene resin having a ratio (mass-average molecular weight/number-average molecular weight) of 5 to 300 and comprising 1% or more by mass of ultra-high-molecular-weight polyethylene having a mass-average molecular weight of 7x105 or more, the microporous polyethylene membrane comprising (a) a coarse-structure layer having an average pore diameter of more than 0.04 mum, which is formed on at least one surface, and (b) a dense-structure layer having an average pore diameter of 0.04 mum or less, an area ratio of the coarse-structure layer to the dense-structure layer in a membrane cross section being 0.1 to 0.8.