Microporous film, and method for producing same

Abstract

Provided is a microporous film which has a surface A and a surface B opposite to the surface A. In one embodiment, the microporous film has a ratio (FB/FA) of a dynamic friction coefficient FB of the surface B to a dynamic friction coefficient FA of the surface A of 1.2 to 20. In another embodiment, the microporous film is a single layer having a thickness of 3-18 μm, a number NA of pores on the surface A is 10-100/μm2, a number NB of pores on the surface B is 20-200/μm2, and NA/NB is 0.2-0.96. In addition, a total area SA of pores on the surface A is 0.02-0.5 μm2/μm2, a total area SB of pores on the surface B is 0.01-0.3 μm2/μm2, and SA/SB is 1.1-10. Furthermore, in another embodiment, a number WB of protrusion-like bodies on the surface B is 0.2-1000/100 μm2.

Dependencies are inferred from the claim text.