ROLL OF MICROPOROUS FILM AND PROCESS FOR PRODUCTION THEREOF

A microporous membrane winding includes a microporous membrane wound around a core. The core has an outer diameter of 5 inches or greater, and has an outer surface with a surface roughness of 3.0 µm or less. A microporous membrane that is excellent in thickness uniformity and is favorably used as a separator for a lithium-ion secondary battery can be obtained from the microporous membrane winding.