Method of developing a heat-sensitive lithographic printing plate precursor with a gum solution
View Patent ↗A method of making a lithographic printing plate includes the steps of: providing a lithographic printing plate precursor including (i) a support having a hydrophilic surface or which is provided with a hydrophilic layer and (ii) a coating provided thereon which includes hydrophobic thermoplastic polymer particles; exposing the coating to heat, thereby inducing coalescence of the thermoplastic polymer particles at exposed areas of the coating; and developing the precursor by applying a gum solution to the coating, thereby removing non-exposed areas of the coating from the support. According to the above method, the plate precursor can be developed and gummed in a single step.
1. A method of making a lithographic printing plate comprising the steps of:
(a) providing a lithographic printing plate precursor including (i) a support having a hydrophilic surface or which is provided a hydrophilic layer and (ii) a coating provided thereon which includes polymer particles and a compound which is capable of converting infrared light into heat, wherein the polymer particles include a copolymer having at least 5 wt. % of a nitrogen-containing monomeric unit;
(b) exposing the coating to infrared light, and
(c) developing the precursor by applying a gum solution to the coating, thereby removing non-exposed areas of the coating from the support.
2. A method according to claim 1 , wherein the copolymer includes styrene as a further monomeric unit.
3. A method according to claim 1 , wherein the nitrogen-containing monomeric unit is (meth)acrylonitrile.
4. A method according to claim 1 , wherein the copolymer is poly(styrene-acrylonitrile).
5. A method according to claim 1 , wherein the coating further includes a contrast dye or pigment which provides a visible image after development.
6. A method according to claim 1 , wherein the lithographic printing plate precursor is not mounted on a printing press during step (c).
7. A method according to claim 1 , wherein the gum solution has a pH between 5 and 8.
8. A method according to claim 1 , wherein the gum solution includes a surface protective compound and, after the developing step, a layer having 0.05 to 20 g/m 2 of the surface protective compound remains on the lithographic printing plate.
9. A method according to claim 8 , wherein the surface protective compound is a hydrophilic film-forming polymer.
10. A method according to claim 8 , wherein the surface protective compound is a surfactant.