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