| 摘要 |
PURPOSE:To obtain a porous film, having excellent balance between physical properties in the MD and TD directions as well as tear strength and containing extremely homogeneous fine pores, by melt extrusion molding a filler-containing polyolefin resin and biaxially drawing the resultant film. CONSTITUTION:A porous olefinic resin film, obtained by extrusion melt molding a filler-containing polyolefin resin composition and biaxially drawing the resultant film, having 25-50% voids (V), satisfying the formulas V=(Dsm-Dfm)/ DsmX100(%) (Dsm is the density of the raw material polyolefin resin composition; Dfm is the apparent density of the film) and 1.5<=X<=4 and X=(a/b+d/C+f/e) [a is the tensile strength (kg/25mm) in MD; b is the tensile strength (kg/25mm) in TD; c is the tensile elongation (%) in MD; d is the tensile elongation (%) in TD; e is the tear strength in MD; f is the tear strength in TD; MD is the running direction of the film; TD is the perpendicular direction], through-hole type pores having 0.01-3mu average pore diameter and >=500g/m<2>.24hr moisture permeability and exhibiting <=50mu thickness. |
