| abstract |
Provided is a multi-layered porous film which includes a functional layer having a controlled thickness in a length-wise direction thereof and which is suitable as a separator for batteries. The multi-layered porous film includes a base film, and a functional layer containing both an inorganic filler and a binder resin, the functional layer being formed on the base film, wherein a difference between a maximum basis weight and a minimum basis weight of the multi-layered porous film in a length-wise direction thereof is equal to or smaller than 2 grams/m 2 , the basis weight being measured every 100 meters interval. The separator fabricated by cutting a film roll comprised of a multi-layered porous film into pieces each having a given length has small lot-based fluctuation in quality, and makes it possible to fabricate a battery having a small fluctuation in quality. |