Claims
- 1. A method for obtaining a lithographic printing surface comprising the steps of:a) image-wise or information-wise exposing to radiation a thermally convertible lithographic printing precursor comprising: i) a hydrophilic lithographic base; and ii) a radiation sensitive coating on a surface of said hydrophilic lithographic base, said coating comprising: (1) uncoalesced particles of a hydrophobic thermoplastic polymer; (2) an inorganic salt that is substantially soluble in an aqueous medium, said salt being present in a concentration sufficient to allow the removal of said coating by said aqueous medium in areas of said coating that are not exposed to said radiation; and (3) a converter substance capable of converting radiation into heat; and b) developing said exposed thermally convertible lithographic printing precursor with an aqueous medium in order to remove the unexposed areas of said coating.
- 2. A method according to claim 1 wherein said radiation is one of visible light and infra-red.
- 3. A method according to claim 2 wherein said radiation has a wavelength in the range of 700-1,100 nm.
- 4. A method according to claim 3 wherein said hydrophobic thermoplastic polymer is a member of at least one of the following groups of polymers: polystyrene, polymers of substituted polystyrene, polyethylene, poly(meth)acrylates, polyvinylchloride, polyurethanes, polyesters, polyacrylonitrile, and copolymers thereof.
- 5. A method according to claim 1 wherein said converter substance is at least one of carbon black, a pigment, and a dye.
- 6. A method according to claim 1 wherein said converter substance is an infrared absorbing dye.
- 7. A method according to claim 1 wherein said inorganic salt is a metal salt.
- 8. A method according to claim 1 wherein said inorganic salt is an alkali metal salt.
- 9. A method according to claim 1 wherein said hydrophilic lithographic base is one of a metallized plastic sheet, a treated aluminum plate, a sleeve-less printing press cylinder, and a printing press cylinder sleeve and a flexible support having thereon a cross-linked hydrophilic layer.
- 10. A method according to claim 9 wherein said sleeve-less printing press cylinder and said printing press cylinder sleeve are seamless.
- 11. A method according to claim 9 wherein the surface of said lithographic base is anodized aluminum.
- 12. A method according to claim 9 wherein said aluminum plate is grained.
- 13. A method according to claim 12 wherein said aluminum plate is anodized.
- 14. A method according to claim 1 wherein at least one laser is used for said image-wise or information-wise exposing.
- 15. A method according to claim 1 wherein said image-wise or information-wise exposing is performed while said thermally convertible lithographic printing precursor is mounted on a printing press, said mounting being one of fixed and removable.
- 16. A method according to claim 1 wherein said radiation sensitive coating is applied to said hydrophilic lithographic base while said hydrophilic lithographic base is mounted on a printing press, said mounting being one of fixed and removable.
- 17. A method according to claim 1 wherein said developing of an image-wise or information-wise exposed thermally convertible lithographic printing precursor is performed while said precursor is mounted on a printing press, said mounting being one of fixed and removable.
- 18. A method according to claim 1 wherein said coating comprises more than one layer.
- 19. A method according to claim 18 wherein said converter substance is present in the same layer as said uncoalesced particles of hydrophobic thermoplastic polymer.
- 20. A method according to claim 1 wherein said concentration of inorganic salt is between 2-50% by weight relative to the weight of said hydrophobic thermoplastic polymer.
- 21. A method according to claim 1 wherein said concentration of inorganic salt is between 10-40% by weight relative to the weight of said hydrophobic thermoplastic polymer.
- 22. A method according to claim 1 wherein said inorganic salt is selected from the group consisting of sodium acetate, lithium acetate, potassium carbonate, sodium carbonate, sodium metasilicate and sodium phosphate.
- 23. A method according to claim 1 wherein the amount of said hydrophobic thermoplastic polymer in said coating is in the range of 20-95% by weight of said coating.
- 24. A method according to claim 1 wherein the amount of said hydrophobic thermoplastic polymer in said coating is in the range of 50-85% by weight of said coating.
- 25. A method according to claim 1 wherein said aqueous medium is fountain solution.
CROSS-REFERENCE TO RELATED APPLICATION
This application is related to our co-pending U.S. patent application entitled “Thermally Convertible Lithographic Printing Precursor,” Ser. No. 09/745,548, filed Dec. 26, 2000.
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