| 摘要 |
PROBLEM TO BE SOLVED: To provide a polyolefin microporous membrane having a dense membrane structure and good permeation characteristics together with low shrinkage at a high temperature, making initial battery performance compatible with cycle performance, and suitable as a separator for a secondary battery such as lithium ion secondary battery excellent also in safety, and to provide a method for producing the membrane. SOLUTION: This polyolefin microporous membrane has water permeability/air permeability balance of 0.8×10<SP>-3</SP>-1.7×10<SP>-3</SP>and a bubble point of >0.5 MPa and <1.0 MPa. This method for producing the membrane comprises not less than three times stretching in transverse direction (TD) before extraction as indispensable process and after the extraction, stretching at least in machin direction (MD) is performed. COPYRIGHT: (C)2005,JPO&NCIPI |
