Abstract: The present invention provides (I) a dry-stretched microporous membrane and a separator for an electric storage device excellent in balance among the required performances such as product safety, charge/discharge characteristics, dimension stability, energy cost, consideration to the environment, etc., (II) a separator for an electric storage device superior in product safety obtained by controlling a puncture depth of a microporous membrane comprised in the separator for an electric storage device, or/and (III) a dry-stretched microporous membrane and a separator for an electric power storage device excellent in product safety realized by controlling a porosity and a puncture strength of a thin microporous membrane.

Abstract: The present invention provides (I) a dry-stretched microporous membrane and a separator for an electric storage device excellent in balance among the required performances such as product safety, charge/discharge characteristics, dimension stability, energy cost, consideration to the environment, etc., (II) a separator for an electric storage device superior in product safety obtained by controlling a puncture depth of a microporous membrane comprised in the separator for an electric storage device, or/and (III) a dry-stretched microporous membrane and a separator for an electric power storage device excellent in product safety realized by controlling a porosity and a puncture strength of a thin microporous membrane.

Abstract: A microporous film having at least one of the following properties: unrestrained MD shrinkage, when the film is baked unrestrained at 90° C. for 1 hour, of 2% or more; unrestrained MD shrinkage, when the film is baked unrestrained at 105° C. for 1 hour, of 2.5% or more; MD restrained growth, when measured using the MD restrained growth test, of less than or equal to 0.2%; rebound or recovery of 5% or greater when measured by the compressibility test; a max compression greater than or equal to 18% when measured by the compressibility test; swelling in DEC when measured according to the swelling in DEC test of 0.95% or less; the film exhibits a round-shaped, not a slit-shaped opening when subjected to the puncture test; the lamellae of the film have a thickness no greater than 250 nm; a normalized puncture strength above 350 g/16 micron; and having higher modulus and lower elongation before break of less than 40% in the machine direction.