MICROPOROUS POLYOLEFIN FILM WITH A THERMALLY STABLE POROUS LAYER AT HIGH TEMPERATURE

摘要

PURPOSE: A microporous polyolefin film for a secondary battery is provided to improve the transparency of a film by playing a filler as a role of beads forming pores by forming pores on the interface of polypropylene and filler. CONSTITUTION: A microporous polyolefin film for a secondary battery is characterized in that: an intermediate layer includes a polypropylene 20-80 weight% with a melting temperature 150°C or more and a filler 80-20 weight% with a melting temperature 140°C or more; the total content of the filler and polypropylene within the intermediate layer are 60 weight% or more; and the both surface layer includes polyethylene and at least one surface is polyethylene of 70 weight% or more.