| abstract |
Provided is a composite membrane substrate comprising a polyolefin microporous membrane that, even without undergoing hydrophilic treatment beforehand, has favorable permeability to aqueous solutions with a high concentration of moisture and relatively high surface free energy, and allows for favorable packing of a hydrophilic resin compound into the pores. The composite membrane substrate comprises a polyolefin microporous membrane and is for supporting a hydrophilic resin compound within the pores of the microporous membrane, wherein: the average pore size is 1 to 50 nm, the porosity is 50% to 78%, and the membrane thickness is 1 to 12 μm; and, if a mixed solution (volume ratio 1/2) of ethanol and water is dripped onto the surface of the polyolefin microporous membrane that has not been subjected to hydrophilic treatment, then the contact angle θ1 between the liquid droplet and the surface at 1 second after dripping is 0° to 90°, the contact angle θ2 between the liquid droplet and the surface at 10 minutes after dripping is 0° to 70°, and the percentage change in contact angle ((θ1-θ2)/θ1× 100) is 10-50%. |