Method for making a lithographic printer plate precursor
View Patent ↗A method for making a lithographic printing plate precursor is disclosed comprising the steps of a. providing a lithographic printing plate precursor including a support having a hydrophilic surface or which is provided with a hydrophilic layer, a photopolymerizable coating comprising a photopolymerizable composition, and an overcoat layer comprising a water soluble low molecular weight acid, wherein said overcoat layer has a surface pH-value ranging between 1 to 6; b. image-wise exposing the precursor; c. optionally heating the exposed precursor; d. processing the obtained precursor by applying a gum solution and optionally brushing the precursor, and/or by mounting the precursor on a plate cylinder of a lithographic printing press and rotating the plate cylinder while feeding dampening liquid and/or ink to the coating. The printing plate obtained after imaging and processing in an off-press configuration with a gum solution or in an on-press configuration with fountain solution and ink shows an improved roll-up performance in the start-up of a printing process on a printing press.
1. A method for making a lithographic printing plate precursor comprising the steps of:
(a) providing a lithographic printing plate precursor including a support having a hydrophilic surface or which is provided with a hydrophilic layer, a photopolymerizable coating comprising a photopolymerizable composition including a polymerizable monomer or oligomer including an ethylenically unsaturated compound having at least one terminal ethylenic group and a polymerization initiator and an overcoat layer comprising a water soluble low molecular weight acid, wherein said overcoat layer has a surface pH-value ranging between 1 to 6;
(b) image-wise exposing the precursor;
(c) optionally heating the exposed precursor; and
(d) processing and gumming the obtained precursor by applying a gum solution including at least one surface protective compound and optionally brushing the precursor, thereby removing at least part of the coating at non-exposed areas and gumming the plate in a single step;
wherein the processing and gumming step is carried out in a gumming station which comprises a first and at least a second gumming unit.
2. The method according to claim 1 , wherein the gum solution has a pH ranging between 5.5 and 8.
3. The method according to claim 1 , wherein the surface pH-value ranges between 2.5 to 5.95.
4. The method according to claim 2 , wherein the surface pH-value ranges between 2.5 to 5.95.
5. The method according to claim 1 , wherein the surface pH-value ranges between 3.5 to 5.80.
6. The method according to claim 2 , wherein the surface pH-value ranges between 3.5 to 5.80.
7. The method according to claim 1 , wherein before the processing and gumming step the precursor is treated in a prewashing station by applying water or an aqueous solution to the coating.
8. The method according to claim 2 , wherein before the processing and gumming step the precursor is treated in a prewashing station by applying water or an aqueous solution to the coating.
9. The method according to claim 1 , wherein the photopolymerizable composition comprises a binder having at least one monomeric unit having an anionic group in the side chain.
10. The method according to claim 1 , wherein the anionic group is an acid or a salt of an acid, said acid being selected from a carboxylic acid, a sulphonic acid, a phosphonic acid, a phosphoric acid or a phenolic acid.
11. The method according to claim 10 , wherein the salt of the acid is an amine salt.