| abstract |
The embodiment according to the present disclosure provides a method of manufacturing a composite film. This method includes: subjecting a porous substrate containing a thermoplastic resin to a heat treatment at a temperature T which satisfies the Formula: Tg+60° C.≦temperature T≦Tm (wherein Tg represents a glass transition temperature (° C.) of the thermoplastic resin; and Tm represents a melting point (° C.) of the thermoplastic resin); coating a coating liquid containing at least a resin and a solvent on one surface or both surfaces of the porous substrate, which has been subjected to the heat treatment, to form a coating layer, with a tensile stress in a machine direction in the porous substrate adjusted to be within a range in which an elongation of the porous substrate is 2% or less; and solidifying the coating layer to obtain a composite film including the porous substrate and a porous layer containing at least the resin formed on one surface or both surfaces of the porous substrate. |