Lithographic printing plate

Abstract

An improved lithographic printing plate which comprises (a) a substrate with (b) a substantially planar porous metal coating on at least one surface of the substrate and (c) a light-sensitive coating on the porous metal coating on the substrate. The substrate (a) can be made by a process for forming a substantially planar porous metal coating on a substrate which comprises thermal spraying of the metal on the substrate to form a porous metal coating on the substrate, rolling the sprayed coating to render it substantially planar and in the process close the pores, and the removing part of the surface to improve planarity and to reopen the surface-connected pores. The metal to be sprayed may be in the form of a wire, powder or molten metal mass and be selected from the group consisting of aluminum, zinc, tin, copper, nickel, or their alloys. Preferably, the substrate is selected from the gorup consisting of steel, aluminum, aluminized or galvanized steel, tin plate, and plastic. The spraying is preferably conducted in a non-oxidizing or reducing atmosphere. Preferably, the coating on the substrate is subjected to cold rolling. Most preferably, the rolling is conducted so as to reduce the coating thickness to approximately half of its original thickness. The substantially planar porous metal coated substrates are particularly desirable because of the 'tooth' for the light-sensitive coating provided by the pores of the metal coating on the substrate. The novel lithographic printing plates may be either presensitized or 'wipe-on' lithographic printing plates.