Processless lithographic printing plate

• US 20020132187A1
• Filed: 11/19/2001
• Published: 09/19/2002
• Est. Priority Date: 11/21/2000
• Status: Active Grant

• Current Assignee: Agfa Graphics Nv (Agfa-Gevaert N.V.)
• Original Assignee: Agfa-Gevaert N.V.
• Inventors: Van Damme, Marc, Sap, Wim
• Granted Patent: US 6,620,573 B2
• Time in Patent Office: Days
• US Class Current: 430/273.1
• CPC Class Codes: B41C 1/1033 by laser or spark ablation
• CPC Class Codes: Y10S 430/145 Infrared
• CPC Class Codes: Y10S 430/146 Laser beam

Abstract

A negative-working heat-sensitive material for making a lithographic printing plate by direct-to-plate recording is disclosed which comprises in the order given a lithographic base having a hydrophilic surface, an oleophilic imaging layer and a cross-linked hydrophilic upper layer, characterize in that the oleophilic imaging layer comprises at least one transition metal complex of an organic acid. Materials according to the invention are characterized by an increased run length and can be used as a printing plate immediately after exposure.

Claims

1. A negative-working heat-sensitive material for making a lithographic printing plate by direct-to-plate recording, the material comprising in the order given a lithographic base having a hydrophilic surface, an oleophilic imaging layer and a cross-linked hydrophilic upper layer, characterized in that said oleophilic imaging layer comprises at least one transition metal complex of an organic acid.

2. A material according to claim 1 wherein the transition metal is chromium.

3. A material according to claim 1 wherein the oleophilic imaging layer has a dry coating weight between 0.1 and 0.75 g/m².

4. A material according to claim 1 wherein the oleophilic imaging layer comprises a heat-sensitive binder.

5. A material according to claim 1 wherein the oleophilic imaging layer comprises carbon black or graphite as IR-absorbing compound.

6. A material according to claim 1 wherein the cross-linked hydrophilic upper layer comprises oxides or hydroxides of beryllium, magnesium, aluminum, silicon, gadolinium, germanium, arsenic, indium, tin, antimony, tellurium, lead, bismuth, titanium or a transition metal.

7. A material according to claim 1 wherein the lithographic base is a grained and anodized aluminum support or a flexible support provided with a cross-linked hydrophilic base layer.

8. A material according to claim 1 wherein the cross-linked hydrophilic upper layer has a dry thickness between 0.3 and 5 μ

m.

9. A direct-to-plate method of making a lithographic printing plate comprising the steps of

(i) providing a material according to any of the preceding claims;

(ii) image-wise exposing the material to an infrared laser beam having an intensity higher than 0.1 mW/μ

m²;

(iii) contacting the material with fountain solution and ink.

10. A method according to claim 9 wherein, before or after step (ii), the material is mounted on a cylinder of a printing press.