Patent ID: 8288038

Claim:
A separator for a non-aqueous electrolyte secondary battery, comprising: at least one porous layer X including a polyolefin, a porosity of said porous layer X being 35% or more and 65% or less, said porous layer X having a dynamic hardness DH of 1000 or more when the load to an indenter reaches 12 kgf/cm 2 , said polyolefin including a high density polyethylene and a low density polyethylene, the amount of the high density polyethylene being 40 wt % or more relative to a total of the low density polyethylene and the high density polyethylene, the specific gravity of the low density polyethylene being 0.93 or less and the specific gravity of the high density polyethylene being 0.94 or more, wherein, in a pore size distribution of said porous layer X measured with a mercury porosimeter, a ratio of pores having a pore size of 0.02 Î¼m or more and 0.2 Î¼m or less is 30-75 vol % relative to a total pore volume.