Patent ID: 8426054

Claim:
A laminated porous film, comprising: a porous membrane layer (A layer) having a thickness of 10 μm or greater; and a non-woven fabric layer (B layer) having a fiber diameter of 1 μm or less; wherein: a ratio (AP 1 /AP 2 ) of an air permeability after heating (AP 1 ) to an air permeability prior to heating (AP 2 ), in a heat test in which the film is placed for three minutes in an oven heated to a temperature of from 150° C. to 200° C., is 10 or greater; the air permeability prior to heating (AP 2 ) is from 10 to 10,000 sec/100 ml; the non-woven fabric layer (B layer) comprises a thermoplastic resin (b) as a main constituent; and the thermoplastic resin (b) comprises at least one member selected from the group consisting of polyfluorinated vinylidenes, polyacrylonitriles, aramides, polyimides, polyamide imides, polyacrylonitriles, polyacrylates, celluloses, polyazomethines, polyacetylenes, and polypyrroles.