| abstract |
A microporous polyolefin film having a crystallinity of 65 to 85%, a content ratio of lamellar crystals of 30 to 85% relative to the total amount of crystals, crystal lengths of 5 to 50 nm and non-crystal lengths of 3 to 30 nm as measured by DSC; and a microporous polyolefin film having crystal sizes of 12.5 to 13.5 nm and a crystallinity of 64 to 68% as measured by X-ray diffraction. |