Patent ID: 7947411

Claim:
A method of producing a membrane and electrode assembly produced by sandwiching a polymer electrolyte membrane between a pair of catalyst layers, wherein there is produced a membrane and electrode assembly comprising a catalyst layer in which the volume of fine pores with a diameter of 1.0 μm or smaller in terms of cylinder approximation for fine pores evaluated by the mercury intrusion method is increased toward the polymer electrolyte membrane (the inside) from the surface of the catalyst layer (the outside), the method comprising: dispersing particles carrying a catalyst material and a polymer electrolyte in a solvent to produce a catalyst ink; applying the catalyst ink onto a substrate selected from a gas diffusion layer and a transfer sheet to form a coating film, drying the coating film to remove the solvent in the coating film and to form a catalyst layer, a step of giving a temperature to the opposite side of the substrate of the coating film higher than a temperature to the face of the coating film on the substrate side in the thickness direction of the coating film when the coating film formed on the substrate is dried to remove the solvent; and joining the catalyst layer formed on the substrate to the polymer electrolyte membrane.