Method of making a heat-sensitive lithographic printing plate
View Patent ↗A method of making a lithographic printing plate is disclosed which comprises the steps of (1) providing a lithographic printing plate precursor comprising (i) a support having a hydrophilic surface or which is provided with a hydrophilic layer and (ii) a coating provided thereon which comprises hydrophobic thermoplastic polymer particles; (2) exposing the precursor to IR-light or heat, thereby inducing coalescence of the thermoplastic polymer particles at exposed areas of the coating; (3) applying a hydrophilic protective layer on the coating; and then, (4) while the precursor is mounted on a print cylinder of a printing press, developing the precursor by supplying an aqueous dampening liquid and/or ink to said precursor while rotating said print cylinder whereby the coating and the hydrophilic protective layer are removed from the support on the non-exposed areas. According to the above method, the hydrophilic protective layer can be applied by coating a solution by means a spray nozzle or a jet nozzle and wherein the applied hydrophilic protective layer improves clean-out in an on-press development.
1. A method of making a lithographic printing plate comprising the steps of
(a) providing a lithographic printing plate precursor comprising (i) a support having a hydrophilic surface or which is provided with a hydrophilic layer and (ii) a coating provided thereon which comprises hydrophobic thermoplastic polymer particles;
(b) exposing the precursor to IR-light or heat, thereby inducing coalescence of the thermoplastic polymer particles at exposed areas of the coating;
(c) applying a hydrophilic protective layer on the coating without completely removing the coating on the non-exposed areas;
(d) mounting the precursor on a print cylinder of a printing press; and
(e) developing the precursor by supplying an aqueous dampening liquid and/or ink to said precursor while rotating said print cylinder whereby the coating and the hydrophilic protective layer are removed from the support on the non-exposed areas,
wherein step (c) is carried out afier step (b) and before step (d).
2. The method according to claim 1 , wherein said hydrophilic protective layer comprises a hydrophilic polymer and/or a surfactant.
3. The method according to claim 2 , wherein said hydrophilic polymer comprises anionic groups or non-ionic groups.
4. The method according to claim 2 , wherein said hydrophilic polymer is a polymer or copolymer of polyvinylalcohol, poly(meth)acrylic acid, polystyrene sulphonic acid, poly(meth)acrylamide, polyhydroxyethyl(meth)acrylate, polyvinylmethylether, polyvinylpyrrolidone, polysaccharide, gelatine, arabic gum, alginic acid or salts thereof.
5. The method according to claim 2 , wherein said surfactant is an anionic or non-ionic surfactant.
6. The method according to claim 1 , wherein said hydrophilic protective layer is applied by coating a solution comprising a hydrophilic polymer and/or a surfactant by means of a spray nozzle or a jet nozzle.
7. The method according to claim 6 , wherein said jet nozzle is an ink jet nozzle or a valve jet nozzle.
8. The method according to claim 1 , wherein said hydrophilic protective layer has a layer thickness of at least 0.2 g/m 2 .
9. The method according to claim 1 , wherein said hydrophobic thermoplastic particles comprise a copolymer of styrene and at least 5 mole % of a nitrogen-containing monomer.
10. The method according to claim 1 , wherein the coating further comprises a compound which is capable of converting infrared light into heat, and wherein the exposure step is performed by exposing the precursor to infrared light.
11. The method according to claim 2 , wherein said hydrophilic protective layer is applied by coating a solution comprising a hydrophilic polymer and/or a surfactant by means of a spray nozzle or a jet nozzle.
12. The method according to claim 3 , wherein said hydrophilic protective layer is applied by coating a solution comprising a hydrophilic polymer and/or a surfactant by means of a spray nozzle or a jet nozzle.
13. The method according to claim 4 , wherein said hydrophilic protective layer is applied by coating a solution comprising a hydrophilic polymer and/or a surfactant by means of a spray nozzle or a jet nozzle.
14. The method according to claim 5 , wherein said hydrophilic protective layer is applied by coating a solution comprising a hydrophilic polymer and/or a surfactant by means of a spray nozzle or a jet nozzle.
15. The method according to claim 2 , wherein said hydrophilic protective layer has a layer thickness of at least 0.2 g/m 2 .
16. The method according to claim 3 , wherein said hydrophilic protective layer has a layer thickness of at least 0.2 g/m 2 .
17. The method according to claim 4 , wherein said hydrophilic protective layer has a layer thickness of at least 0.2 g/m 2 .
18. The method according to claim 5 , wherein said hydrophilic protective layer has a layer thickness of at least 0.2 g/m 2 .
19. The method according to claim 6 , wherein said hydrophilic protective layer has a layer thickness of at least 0.2 g/m 2 .
20. The method according to claim 7 , wherein said hydrophilic protective layer has a layer thickness of at least 0.2 g/m 2 .
21. The method according to claim 2 , wherein said hydrophobic thermoplastic particles comprise a copolymer of styrene and at least 5 mole % of a nitrogen-containing monomer.
22. The method according to claim 3 , wherein said hydrophobic thermoplastic particles comprise a copolymer of styrene and at least 5 mole % of a nitrogen-containing monomer.
23. The method according to claim 4 , wherein said hydrophobic thermoplastic particles comprise a copolymer of styrene and at least 5 mole % of a nitrogen-containing monomer.
24. The method according to claim 5 , wherein said hydrophobic thermoplastic particles comprise a copolymer of styrene and at least 5 mole % of a nitrogen-containing monomer.
25. The method according to claim 6 , wherein said hydrophobic thermoplastic particles comprise a copolymer of styrene and at least 5 mole % of a nitrogen-containing monomer.
26. The method according to claim 7 , wherein said hydrophobic thermoplastic particles comprise a copolymer of styrene and at least 5 mole % of a nitrogen-containing monomer.
27. The method according to claim 8 , wherein said hydrophobic thermoplastic particles comprise a copolymer of styrene and at least 5 mole % of a nitrogen-containing monomer.
28. The method according to claim 2 , wherein the coating further comprises a compound which is capable of converting infrared light into heat, and wherein the exposure step is performed by exposing the precursor to infrared light.
29. The method according to claim 3 , wherein the coating further comprises a compound which is capable of converting infrared light into heat, and wherein the exposure step is performed by exposing the precursor to infrared light.
30. The method according to claim 4 , wherein the coating further comprises a compound which is capable of converting infrared light into heat, and wherein the exposure step is performed by exposing the precursor to infrared light.
31. The method according to claim 5 , wherein the coating further comprises a compound which is capable of converting infrared light into heat, and wherein the exposure step is performed by exposing the precursor to infrared light.
32. The method according to claim 6 , wherein the coating further comprises a compound which is capable of converting infrared light into heat, and wherein the exposure step is performed by exposing the precursor to infrared light.
33. The method according to claim 7 , wherein the coating further comprises a compound which is capable of converting infrared light into heat, and wherein the exposure step is performed by exposing the precursor to infrared light.
34. The method according to claim 8 , wherein the coating further comprises a compound which is capable of converting infrared light into heat, and wherein the exposure step is performed by exposing the precursor to infrared light.
35. The method according to claim 9 , wherein the coating further comprises a compound which is capable of converting infrared light into heat, and wherein the exposure step is performed by exposing the precursor to infrared light.