Patent ID: 7704597
Filing Date: 2010-04-27
Classification: H01M,Y02E,Y10T

Abstract:
1. A porous film comprising a crosslinked material of a resin composition containing (a) 1-50% by weight of polynorbornene, (b) 1-50% by weight of a thermoplastic elastomer, and (c) 5-98% by weight of an ultra-high molecular polyolefin resin having a weight average molecular weight exceeding 500,000, the porous film stretched in a machine direction (MD) and a transverse direction (TD), wherein the film has a peak of shrinkage force in the TD at a temperature region of a shutdown temperature of the film or higher, and the shrinkage force as measured at the peak is 63 N/cm 2 or lower, wherein the MD stretch ratio/the TD stretch ratio is from 1.5 to 3.5.