COMPOSITE FILM, ITS MANUFACTURING METHOD, AND SEPARATOR FOR BATTERY USING THE SAME OR FILTER

摘要

PROBLEM TO BE SOLVED: To provide a composite film which can be used as a high quality separator in which a coating layer itself is not liable to heat melt in a field of a chemical battery such as a lithium cell or the like, and which can be used as a filter not liable to lower a performance even when the film is contacted with a high temperature chemical for a long time even in a field of a separate film, and to provide a method for manufacturing the same. SOLUTION: The composite film comprises a coating layer made of a porous material (B) of a heat resistant polymer on at least one surface of a polyolefin microporous film (A) in such a manner that a mean pore size of the porous material (B) is larger than a maximum pore size of the microporous film (A). The method for manufacturing the composite film comprises a step of coating a heat resistant polymer substance solution or precursor solution on at least one surface of the film (A), a step of contacting the coating surface with their poor solvent to phase separate the solution, and a step of forming a coating layer made of the porous material (B) of the heat resistant polymer substance by heating and drying the phase separated surface.