Claims
- 1. A thermally convertible lithographic printing precursor developable using an aqueous medium, said printing precursor comprising:(a) a hydrophilic lithographic base; (b) a radiation sensitive coating on a surface of said base, said coating comprising: (i) uncoalesced particles of a hydrophobic thermoplastic polymer; (ii) an inorganic salt that is substantially soluble in said aqueous medium, said salt being present in said coating 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 (iii) a converter substance capable of converting said radiation into heat.
- 2. A thermally convertible lithographic printing precursor as in claim 1, wherein said radiation is one of visible light and infra-red.
- 3. A thermally convertible lithographic printing precursor as in claim 2, wherein said radiation has a wavelength in the range of 700-1,100 nm.
- 4. A thermally convertible lithographic printing precursor according to claim 1, 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 thermally convertible lithographic printing precursor according to claim 1, wherein said converter substance is at least one of carbon black, a pigment, and a dye.
- 6. A thermally convertible lithographic printing precursor according to claim 1, wherein said converter substance is an infrared absorbing dye.
- 7. A thermally convertible lithographic printing precursor according to claim 1, wherein said inorganic salt is a metal salt.
- 8. A thermally convertible lithographic printing precursor according to claim 1, wherein said inorganic salt is an alkali metal salt.
- 9. A thermally convertible lithographic printing precursor 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 thermally convertible lithographic printing precursor as in claim 9, wherein said sleeve-less printing press cylinder and said printing press cylinder sleeve are seamless.
- 11. A thermally convertible lithographic printing precursor as in claim 9 wherein the surface of said lithographic base is anodized aluminum.
- 12. A printing precursor according to claim 9 wherein said aluminum plate is grained.
- 13. A thermally convertible lithographic printing precursor according to claim 1, wherein said coating comprises two or more layers.
- 14. A printing precursor according to claim 13 wherein said converter substance is present in the same layer as said uncoalesced particles of hydrophobic thermoplastic polymer.
- 15. A printing precursor 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.
- 16. A printing precursor 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.
- 17. A printing precursor 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.
- 18. A printing precursor 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.
- 19. A printing precursor 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.
- 20. A printing precursor 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 “Method for obtaining a lithographic printing surface,” Ser. No. 09/745,520, filed Dec. 26, 2000.
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