| abstract |
The present invention provides: a polyolefin microporous membrane suited for providing a uniform thickness of porous layer; and a battery separator comprising the polyolefin microporous membrane provided with a uniform thickness of porous layer, and suited for increasing battery capacity. The battery separator comprises a polyolefin microporous membrane whereof the variation width of an F25 value in the length direction is 1 MPa or less, and, on at least one surface thereof, a porous layer containing a fluorine resin and an inorganic particle and having an average thickness T(ave) of 1 to 5 μm. (Here, F25 value represents the value from the division, by the test piece cross section, of the load value when the test piece has been stretched 25% using a tensile tester.) |