POROUS POLYOLEFIN FILM, PROCESS FOR PRODUCING THE SAME, AND USE THEREOF

摘要

A porous polyolefin film which is highly permeable to air and moisture and combines an extremely high overall-light transmittance with an extremely high tear strength. The porous polyolefin film is produced, for example, by stretching in at least a uniaxial direction in an areal stretch ratio of 1.1 to 1.5 an unstretched polyolefin film made of a resin composition comprising 100 parts by weight of a polyolefin, 50 to 150 parts by weight of an inorganic filler having a 50%-median diameter as measured by the light scattering method of from 2 mu m to 7 mu m , excluding 7 mu m, and 2 to 20 parts by weight of a polyolefin wax. It has a moisture permeability of 1,000 g/m<2>•24 hr or higher, an overall-light transmittance of 65% or higher, and a tear strength of 0.6 N or higher.