Positive working heat-sensitive lithographic printing plate precursor
View Patent ↗A positive working heat-sensitive lithographic printing plate precursor is disclosed which comprises a support having a hydrophilic surface and a coating, provided on the hydrophilic surface, wherein the coating comprises a spacer particle comprising aluminum hydroxide or aluminum oxide and having an average particle size larger than 0.3 μm, for improving the scuff-mark resistance of the coating. Furthermore, the coating comprises an infrared light absorbing agent, an oleophilic resin soluble in an aqueous alkaline developer and a developer resistant means.
1. A positive working heat-sensitive lithographic printing plate precursor comprising a support having a hydrophilic surface and a coating provided on the hydrophilic surface, said coating comprising:
(a) an infrared light absorbing agent,
(b) an oleophilic resin soluble in an aqueous alkaline developer,
(c) a developer resistance means; and
(d) spacer particles,
wherein said spacer particles comprise aluminum hydroxide or aluminum oxide and have an average particle size larger than 0.4 μm, wherein the coating has a surface and the average particle size is selected so that a portion of a plurality of the spacer particles extend beyond the surface of the coating, and wherein the amount of said particles in the coating is between 5 and 200 mg/m 2 .
2. A positive working heat-sensitive lithographic printing plate precursor according to claim 1 wherein said particle size is between 0.5 μm and 20 μm.
3. A positive working heat-sensitive lithographic printing plate precursor according to claim 2 , wherein said coating has a layer thickness comprised between 0.6 g/m 2 and 2.8 g/m 2 .
4. A positive working heat-sensitive lithographic printing plate precursor according to claim 3 , wherein said coating comprises at least two layers and wherein said spacer particles are present in at least one of the layers of the coating.
5. A positive working heat-sensitive lithographic printing plate precursor according to claim 4 , wherein said developer resistance means is a polymer comprising siloxane or perfluoroalkyl units.
6. A positive working heat-sensitive lithographic printing plate precursor according to claim 1 wherein said particle size is between 1 μm and 7 μm.
7. A positive working heat-sensitive lithographic printing plate precursor according to claim 6 , wherein said coating has a layer thickness comprised between 0.6 g/m 2 and 2.8 g/m 2 .
8. A positive working heat-sensitive lithographic printing plate precursor according to claim 1 wherein said coating has a layer thickness comprised between 0.6 g/m 2 and 2.8 g/m 2 .
9. A positive working heat-sensitive lithographic printing plate precursor according to claim 1 wherein said coating comprises at least two layers and wherein said spacer particles are present in at least one of the layers of the coating.
10. A positive working heat-sensitive lithographic printing plate precursor according to claim 5 , wherein said developer resistance means is a polymer comprising siloxane or perfluoroalkyl units.
11. A positive working heat-sensitive lithographic printing plate precursor according to claim 1 wherein said developer resistance means is a polymer comprising siloxane or perfluoroalkyl units.
12. A stack comprising a plurality of positive working heat-sensitive lithographic printing plate precursors, according to claim 1 , wherein adjacent plate precursors are separated by an interleave.
13. A package comprising a stack according to claim 12 .
14. A process for improving the scuff-mark resistance of a positive working heat-sensitive lithographic printing plate precursor comprising providing a support having a hydrophilic surface and applying onto the hydrophilic surface of the support a coating comprising:
(a) an infrared light absorbing agent,
(b) an oleophilic resin soluble in an aqueous alkaline developer,
(c) a developer resistance means; and
(d) spacer particles,
wherein said spacer particles comprise aluminum hydroxide or aluminum oxide and have an average particle size larger than 0.4 μm, wherein the coating has a surface and the average particle size is selected so that a portion of a plurality of the spacer particles extend beyond the surface of the coating, and wherein the amount of said particles in the coating is between 5 and 200 mg/m 2 .