Patent ID: 6534150
Filing Date: 2003-03-18
Classification: B29C,B29K,B32B,Y10T

Abstract:
A stretched film of a thermoplastic resin, comprising:(A) a stretched film base layer containing 40 to 85 wt % of a thermoplastic resin and 60 to 15 wt % of a first inorganic fine powder or a first organic fine powder; and (B) a stretched film surface layer which is provided on at least one surface of said stretched film base layer and which contains 30 to 90 wt % of a thermoplastic resin and 70 to 10 wt % of a second inorganic fine powder or a second organic fine powder having an average particle size smaller than that of the first inorganic fine powder or the first organic fine powder contained in the stretched film base layer; (C) a back layer comprising 30 to 70 wt % of a thermoplastic resin and 70 to 30 wt % of a third inorganic fine powder having a surface finished by hydrophilic treatment or a third organic fine powder having a surface finished by hydrophilic treatment; wherein said back layer is provided on the surface of the stretched film base layer opposite to the stretched film surface layer; wherein said stretched film of said thermoplastic resin has a porosity of 5 to 60%; wherein said porosity is expressed by formula (1) Ï 0-Ï 1Ï 0Ã—100(1)wherein &rgr;0 is a true density of the stretched film of the thermoplastic resin; wherein said true density is almost equal to a density of the film before stretching; and wherein &rgr;1 is a density of the stretched film of the thermoplastic resin.