Porous material for fuel cell electrolyte membrane, method for producing the same, electrolyte membrane for solid polymer fuel cell, membrane electrode assembly (MEA), and fuel cell

A method for producing a porous material for a fuel cell electrolyte membrane, wherein the porous material has a multi-layer structure consisting of at least one strength auxiliary layer and at least one high porosity layer, the at least one strength auxiliary layer being provided inside and/or on a surface of the at least one high porosity layer, the method comprising:

• stretching at least one dense polymer film for the at least one strength auxiliary layer;
• laminating the stretched dense polymer film for the at least one strength auxiliary layer, and another dense polymer film for the at least one high porosity layer;
• and subjecting the laminate to another stretching, wherein the at least one strength auxiliary layer has a dense portion and through holes, and the at least one high porosity layer has a sponge-like bicontinuous structure, and, wherein an average diameter of pores of the at least one strength auxiliary layer is 0.01 to 10 μm, different from an average diameter of pores of the at least one high porosity layer, and larger than a largest through-hole diameter of the at least one high porosity layer.