Method of making corrosion resistant metallic plates particularly useful as lithographic plates and the like

Abstract

Abstract In a process for making lithographic plates which includes a step for forming on metallic plates a protective layer or film which additionally provides a hydrophilic film on at least one surface thereof and in the course of which the metallic plates are placed in contact with water at diverse steps of the process, the improvement consisting in using purified water. The metallic plates initially take preferably the form of a continuous web of an appropriate metal, such as aluminum, which is successively: cleaned by suitable detergent, rinsed in purified water, provided with a protective layer or film, rinsed again in purified water, and coated with a sensitizing diazo resin or the like. The metallic plates are provided with a protective layer or film by dipping in a solution of a soluble silicate in purified water at a predetermined temperature, or alternately, the metallic plates may have a protective layer electrolytically formed thereon, the electrolyte consisting of a solution of sodium silicate in purified water. The use of purified water, which is basically tap water which has been de-ionized, de-chlorinated, de-gasified, and which is free of solid particles, in the diverse steps of the process prevents the formation of ''''black spots'''' on the surface of the plates provided with a photosensitive coating of diazo resin or the like.

Inventors

• 👤 E Casson

Bibliographic Details