Composition sensitive to radiation in electromagnetic spectrum ranges for printing purposes, printing plate comprising said composition, use of said composition and image development process

A method for preparing a printing plate comprising, providing a lithographic printing plate, the printing plate comprising a pre-treated aluminum substrate;

• applying a composition to a surface of the printing plate, the composition comprising:
• (a) a mixture of binding polymers;
• (b) an ethylenically unsaturated compound;
• (c) one or more compounds capable of forming free radicals in a selected region of the spectrum;
• (d) a sensitizer;
• (e) a dye;
• and
• (f) an adhesion promoter,
• wherein said mixture of binding polymers comprises polyvinyl acetal polymers and acrylic polymers and a weight ratio between the polyvinyl acetal and the acrylic polymer ranges from 3:1 to 1:3, and wherein said dye is selected from the group consisting of pthalocyanin blue and a preparation of dye blue in polyvinyl butyral containing 50% dye, and wherein
• after exposure to radiation and after being subjected to a an aqueous developing solution, when dried, forms a film, wherein the pre-treatment of the aluminum substrate comprises:
• (a) degreasing and deoxidizing the aluminum surface by the action of an alkaline substance, (b) electrochemical treatment, (c) anodization treatment, (d) washing with deionized water, and (e) treating the aluminum surface with a solution of polyvinyl phosphonic acid.

A lithographic printing plate comprising (1) a pre-treated hydrophilic aluminum substrate, wherein the pre-treatment of the aluminum substrate comprises:

• (a) degreasing and deoxidizing the aluminum surface by the action of an alkaline substance, (b) electrochemical treatment, (c) anodization treatment, (d) washing with deionized water, and (e) treating the aluminum surface with a solution of polyvinyl phosphonic acid;
• (2) a first layer of adhesion promoter solution applied isolated on the surface of the treated aluminum substrate;
• (3) a second layer sensitive to Ultraviolet, Violet, or Infrared radiations of the electromagnetic radiation composed of a photosensitive composition, applied on the aluminum substrate;
• and
• (4) a third layer applied on the second layer, impermeable to air oxygen, and wherein said photosensitive composition comprises:
• (a) a mixture of binding polymers;
• (b) an ethylenically unsaturated compound;
• (c) one or more compounds capable of forming free radicals in a selected region of the spectrum;
• (d) a sensitizer;
• (e) a dye;
• and
• (f) an adhesion promoter,
• wherein said mixture of binding polymers comprises polyvinyl acetal polymers and acrylic polymers and a weight ratio between the polyvinyl acetal and the acrylic polymer ranges from 3:1 to 1:3, and wherein said dye is selected from the group consisting of pthalocyanin blue and a preparation of dye blue in polyvinyl butyral containing 50% dye.