Lithographic printing members for use with laser-discharge imaging

Abstract

Lithographic printing plates suitable for imaging by means of laser devices that emit in the near-infrared region. Laser output either ablates one or more plate layers or physically transforms a surface layer, in either case resulting in an imagewise pattern of features on the plate. The image features exhibit an affinity for ink or an ink-abhesive fluid that differs from that of unexposed areas.

What is claimed is: 
     
       1. A lithographic printing member directly imageable by laser discharge, the member comprising: a. a topmost first layer which is polymeric; and   b. a thin metal layer underlying the first layer; and   c. a substrate underlying the metal layer; wherein   d. the metal layer is formed of a material which is subject to ablative absorption of imaging infrared radiation and the first layer is not; and   e. the first layer .Iadd.exhibits an affinity for an abhesive fluid for ink .Iaddend.and the substrate .[.exhibit different affinities for at least one printing liquid selected from the group consisting of ink and an abhesive fluid for ink.]. .Iadd.exhibits an affinity for ink.Iaddend..   
     
     
       2. The member of claim 1 wherein the metal is tintanium. 
     
     
       3. The member of claim 1 wherein the metal is selected from the group consisting of alloys of titanium, aluminum, alloys of aluminum, nickel, iron and chromium. 
     
     
       4. The member of claim 1 wherein the metal is deposited to a thickness of less than 200 Å. 
     
     
       5. The member of claim 1 wherein the metal is deposited to an optical density ranging from 0.2 to 1.0. 
     
     
       6. The member of claim 1 wherein the metal is deposited to an optical density of 2.5 or less. 
     
     
       7. The member of claim .[.1.]. .Iadd.22 .Iaddend.wherein the first layer is oleophobic. .[.8. The member of claim 7 wherein the first layer is a 
     
     
        silicone chemical species..].9. The member of claim .[.8.]. .Iadd.22 .Iaddend.wherein the silicone is anchored to the metal layer by means of a silane adhesion promoter. .[.10. The member of claim 1 wherein the first 
     
     
        layer is hydrophobic..].11. The member of claim .[.10.]. .Iadd.1 .Iaddend.wherein the first layer is a polyvinyl alcohol chemical species. 
     
     
         2. The member of claim 11 wherein the polyvinyl alcohol is anchored to 
     
     
        the metal layer by means of a titanate adhesion promoter. 13. The member of claim 1 wherein the first layer is anchored to the metal layer by means 
     
     
        of an adhesion promoter. 14. The member of claim 1 wherein the substrate comprises first and second surfaces, at least one of which has means to 
     
     
        improve adhesion. 15. The member of claim 1 wherein the substrate comprises first and second surfaces, at least one of which has means to 
     
     
        reduce static buildup. 16. The member of claim 1 wherein the substrate comprises first and second surfaces, the first has means to improve 
     
     
        adhesion and the second surface has means to reduce static buildup. 17. The member of claim 1 further comprising an antireflective layer 
     
     
        between the metal and first layers. 18. The member of claim 1 wherein the 
     
     
        substrate is laminated to a metal support. .Iadd.19.  The member of claim 1 wherein the substrate comprises a material that reflects imaging radiation. .Iaddend..Iadd.20. The member of claim 19 wherein the material is IR-reflective barium sulfate. .Iaddend..Iadd.21. The member of claim 20 wherein the substrate comprises a polyester polymer within which the barium sulfate is dispersed. .Iaddend..Iadd.22. A lithographic printing member directly imageable by laser discharge, the member comprising: a. a topmost first layer which is formed of an addition-cured silicone;   b. a thin metal layer underlying the first layer and formed of titanium or an alloy thereof; and   c. a substrate underlying the metal layer; wherein   d. the metal layer is subject to ablative absorption of imaging infrared radiation and the first layer is not; and   e. the first layer and the substrate exhibit different affinities for at least one printing liquid selected from the group consisting of ink and an abhesive fluid for ink. .Iaddend..Iadd.23. The member of claim 22 wherein the metal is deposited to a thickness of less than 200 Å. .Iaddend..Iadd.24. The member of claim 22 wherein the metal is deposited to an optical density ranging from 0.2 to 1.0. .Iaddend..Iadd.25. The member of claim 22 wherein the metal is deposited to an optical density of 2.5 or less. .Iaddend..Iadd.26. The member of claim 22 wherein the substrate comprises first and second surfaces, at least one of which has means to improve adhesion. .Iaddend..Iadd.27. The member of claim 22 wherein the substrate comprises first and second surfaces, at least one of which has means to reduce static buildup. .Iaddend..Iadd.28. The member of claim 22 wherein the substrate comprises first and second surfaces, the first has means to improve adhesion and the second surface has means to reduce static buildup. .Iaddend..Iadd.29. The member of claim 22 further comprising an antireflective layer between the metal and first layers. .Iaddend..Iadd.30. The member of claim 22 wherein the substrate is laminated to a metal support. .Iaddend..Iadd.31. The member of claim 22 wherein the substrate comprises a material that reflects imaging radiation. .Iaddend..Iadd.32. The member of claim 31 wherein the material is IR-reflective barium sulfate. .Iaddend..Iadd.33. The member of claim 32 wherein the substrate comprises a polyester polymer within which the barium sulfate is dispersed. .Iaddend.