Method for producing laminated porous film, and laminated porous film

摘要

The present invention produces a laminated porous film which improves the stability of an aqueous dispersion of a metal oxide without lowering battery characteristics, while having high binding properties and excellent heat resistance. This laminated porous film exhibits excellent characteristics when used as a separator for batteries. This laminated porous film is produced by forming a porous coating layer on at least one outer surface of a resin porous film, which is formed of a single layer or a laminate of a plurality of layers, by applying a coating liquid that contains a metal oxide, a resin binder and a volatile acid thereto and drying the applied coating liquid. The coating liquid is prepared so that the difference between the pH (pH1) of the coating liquid and the pH (pH2) of the coating layer is not less than 2.

主权项

1. A method of producing a laminated porous film comprising a porous coating layer formed on a porous resin film consisting of a single layer or a laminate of a plurality of layers by applying a coating solution containing a metal oxide, a resin binder, and a volatile acid to at least one outer surface of said porous resin film and drying said coating solution to obtain a dried coating layer on at least one outer surface of said porous resin film,
wherein: a pH (pH1) of said coating solution is so adjusted that a difference between said pH (pH1) of said coating solution and a pH (pH2) of said dried coating layer is not less than 2, determining pH2 is carried out by dripping a droplet of ion exchange water on a pH test paper, rubbing the pH test paper against the dried coating layer, and analyzing the pH test paper to determine pH2.