| abstract |
A first microporous layer forming at least both surface layers and at least one second microporous layer formed between both surface layers, wherein the first layer has a ratio of ultra high molecular weight polyethylene having a weight average molecular weight of 1 x 10 6 or more to 8 Wherein the second layer contains a second polyethylene resin having a ratio of the ultrahigh molecular weight polyethylene of 7% by mass or less, wherein the pore distribution curve obtained by the mercury porosimetry has at least two Peak, and the total thickness of the first and second layers is 100%, and the total thickness of the first layer is 15 to 60%.n n n n Battery, separator, polyolefin, polypropylene, polyethylene, porous, fine |