Patent ID: 8592071

Claim:
A laminated porous film comprising: at least two porous layers consisting of a first layer and a second layer laminated thereon, wherein said first layer consists of a composition containing a β crystal nucleating agent and a mixed resin comprising a polypropylene resin and a resin whose crystal fusion peak temperature is lower than that of said polypropylene resin and is from 100° C. to 150° C. in a mixing mass ratio of propylene resin to resin whose crystal fusion peak temperature is lower than that of said polypropylene resin of 20:80 to 80:20; and said second layer is a heat-resistant layer consisting of a resin composition whose crystal fusion peak temperature is higher than that of a resin composition of said first layer and not less than 200° C.; said laminated porous film has a β activity and/or a β crystal generation power; a shut down temperature of the laminated porous film at which pores of the porous layer are closed is set to a range of from 100° C. to 160° C., a break down temperature of the laminated porous film at which the laminated porous film breaks is not less than 200° C., and a pin puncture strength of the laminated porous film is not less than 1.5 N.