| abstract |
With the conventional coating technique, it has been difficult to form a porous layer having a uniform thickness on a polyolefin microporous membrane, which is a wide and thin film. The present invention provides a polyolefin microporous membrane suitable for forming a porous layer with little unevenness in thickness, and a battery separator suitable for increasing the capacity of a battery. A polyolefin microporous membrane having a fluctuation of 1 MPa or less in the width direction of the F25 value, a thickness of 3 μm or more, less than 7 μm, and a width of 100 mm or more (here, the F25 value refers to the load when the test piece is elongated by 25% using a tensile tester. It represents the value divided by the cross-sectional area of the test piece) |