| abstract |
A polyolefin microporous membrane suitable for providing a porous layer exhibiting less variation in thickness and having a width not less than 100 mm, wherein a variation range of an F25 value in the width direction is not greater than 1 MPa, wherein the F25 value is a value obtained by dividing a load at 25% elongation of a sample piece using a tensile testing machine by a cross-sectional area of the sample piece. |