| 摘要 |
PROBLEM TO BE SOLVED: To obtain a porous film which exhibits an excellent performance as a solid-liq. separation film or as a battery diaphragm by selecting a film which comprises crosslinked polyvinylidene fluoride or a copolymer contg. crosslinked polyvinylidene fluoride and of which the min.-pore-size layer has a specified average pore size. SOLUTION: A porous film comprising polyvinylidene fluoride or a copolymer contg. at least 50 wt.% polyvinylidene fluoride is irradiated with a radiation energy such as an electron beam or 7-rays to give a crosslinked porous vinylidene fluoride resin film. Thus obtd. crosslinked porous film is characterized in that it has a thickness of 1-500 μm, a porosity of 10-95%, and a gel fraction of 10-80 wt.%, that it has a film structure wherein both the surface and the inside have three-dimensional network structures, a film structure wherein at least one surface is denser than other parts and the inside has a three- dimensional network structure, or a film structure wherein at least one surface is denser than the other parts and the inside has large pores and a three- dimensional network structure, and that the average pore size of the min.- pore-size layer is 0.05-5 μm. |
