Patent ID: 8114550

Claim:
A reinforced electrolyte membrane for a fuel cell which is reinforced by a porous membrane, comprising: void portions in a joining portion between the surface of the porous membrane and/or pore surface and the electrolyte for buffering swelling when water is contained, the void portions being obtained by a first process including adding a component which elutes by hydrolysis to an electrolyte membrane in advance, and making the component elute from the electrolyte membrane during hydrolysis; or a second process including introducing a functional group which can form an imide group onto the surface of the porous membrane, dipping the porous membrane on which the functional group has been introduced in a melted F-type electrolyte precursor, and providing an ion exchange group by hydrolyzing the F-type electrolyte precursor and wherein the void portions are 1 to 10% by volume of the total electrolyte membrane.