| abstract |
The present invention provides a microporous membrane excellent in balance of temperature characteristics, shrinkage characteristics, permeability, and strength, thereby realizing a separator for a nonaqueous electrolyte secondary battery with high performance and excellent safety, and a nonaqueous electrolyte A secondary battery. A microporous film made of polyolefin, characterized in that the difference between the closed shrinkage temperature in the TD direction and the maximum shrinkage temperature measured by TMA is 7.2° C. or more, and the difference between the closed shrinkage rate in the TD direction and the maximum shrinkage rate is less than 25%, When the film thickness is 16 μm, the puncture strength is 400 gf or more, and when the film thickness is 16 μm, the ratio of puncture strength to air resistance is 2.0 to 4.0 (gf/(sec/100cc)). |