METHOD OF FORMING LAMINATED POROUS FILM

摘要

PROBLEM TO BE SOLVED: To provide a method of forming a porous film having not only a breakdown property (BD) of a polypropylene-based resin but a shutdown property (SD) to secure the safety of a battery.

SOLUTION: A laminated non-porous film-like substance comprises at least two layers including a layer (PP layer) of a thermoplastic resin composition containing a polypropylene-based resin having β-activity and/or β-crystal generation power and a layer (SD layer) that is shut down at a lower temperature than the PP layer and prepared by using a thermoplastic resin composition containing the thermoplastic resin whose peak value of a crystalline melting temperature is lower than that of the polypropylene-based resin. A large number of fine pores each having communication in a thickness direction are formed by stretching the laminated non-porous film-like substance.

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