Patent ID: 7601295

Claim:
A method for producing a filter comprising a sintered sheet of a non-woven cloth of a metal fiber to be installed in a liquid passage, the method comprising steps of: preparing the sintered sheet with a web-shaped laminated structure, the sintered sheet comprising a first non-woven layer constituted of a first metal fiber with a predetermined average wire diameter inside the sintered sheet and second non-woven layers constituted of a second metal fiber with an average wire diameter greater than the predetermined average wire diameter and forming both surfaces of the sintered sheet, wherein the first non-woven layer and the second non-woven layer are directly bonded with each other; rolling the sintered sheet after preparing the sintered sheet; and electrolytic polishing the sintered sheet after said rolling step, with the sintered sheet serving as an anode, by arranging two electrodes serving as a cathode at positions opposed to the second non-woven layers so that an etching rate of the first metal fiber is less than that of the second metal fiber.