| abstract |
A polyolefin microporous membrane has a microporous structure with a small pore size and a highly superior air permeability and the like. The polyolefin microporous membrane includes at least a first layer and a second layer, wherein the first layer is composed of a first polyolefin resin containing polyethylene, wherein the second layer is composed of a second polyolefin resin containing polyethylene and polypropylene, and wherein the polyolefin microporous membrane satisfies (I) and (II); and the like. (I) The polyolefin microporous membrane has an air resistance of from 10 to 200 sec/100 ml. (II) The polyolefin microporous membrane has a bubble point pore size of from 5 to 35 nm. |