LAMINATED POROUS FILM, SEPARATOR FOR NONAQUEOUS ELECTROLYTE SECONDARY BATTERY, AND NONAQUEOUS ELECTROLYTE SECONDARY BATTERY

摘要

PROBLEM TO BE SOLVED: To provide a laminated porous film having excellent air permeability and strength while maintaining high heat resistance even when further wall thinning is achieved, and having excellent characteristics when used as a separator for a nonaqueous electrolyte secondary battery.SOLUTION: A laminated porous film has a coating layer (II layer) including a filler (a) and a resin binder (b) disposed on at least one surface of a polyolefin resin porous film (I layer) and has a thickness of 23 μm or thicker. In the laminated porous film, the thickness of the coating layer (II layer) occupying in the whole thickness of the laminated porous film is 10% or more but 45% or less, and the piercing strength per thickness of the laminated porous film is 5 gf/μm or more, and a rate of increase of air permeability of the laminated porous film relative to the air permeability of the polyolefin resin porous film (I layer) is 5% or more but 35% or less.