Developing method for laser sensitive lithographic printing plate
OwnerGary Ganghui Tenginventor
Life of this patent
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Abstract
A method of developing a laser sensitive lithographic printing plate is described. The plate comprises on a substrate a photosensitive layer soluble or dispersible in ink and/or fountain solution and capable of hardening upon exposure to a laser. The plate is exposed with a laser and deactivated under a safe light or in the dark, and then on-press developed with ink and/or fountain solution preferably under white light. Alternatively, the plate is developed off press with ink and/or fountain solution, or with an organic solvent-based or oil-based liquid or paste and/or an aqueous solution, and then mounted on press for lithographic printing.
Claims20
A method of lithographically printing images on a receiving medium, comprising in order:
- (a) providing a lithographic plate comprising (i) a substrate, and (ii) a photosensitive layer soluble or dispersible in and on-press removable with ink and/or fountain solution, and capable of hardening upon exposure to a laser having a wavelength selected from 200 to 1200 nm;
- wherein said photosensitive layer exhibits an affinity or aversion substantially opposite to the affinity or aversion of said substrate to at least one printing liquid selected from the group consisting of ink and an adhesive fluid for ink;
- (b) exposing the plate with said laser according to digital imaging information to cause hardening of the photosensitive layer in the exposed areas;
- (c) contacting said exposed plate off press with ink and/or fountain solution, or with an organic solvent-based or oil-based liquid or paste and/or an aqueous solution, to remove the photosensitive layer in the non-hardened areas;
- and
- (d) mounting said developed plate on a lithographic press to lithographically print images from said plate to the receiving medium;
- (e) wherein said steps (a) to (c) are performed with the plate under lightings (including darkness) that will not cause hardening of the photosensitive layer, and said step (d) is performed under a lighting that will cause hardening of the photosensitive layer.
A method of lithographically printing images on a receiving medium, comprising in order:
- (a) providing within a light-tight cassette a lithographic plate comprising on a hydrophilic substrate an oleophilic photosensitive layer comprising a polymeric binder, a free radical polymerizable monomer, a free radical initiator, and a sensitizing dye;
- said photosensitive layer being soluble or dispersible in and on-press removable with ink and/or fountain solution, and capable of hardening upon exposure to a laser having a wavelength selected from 200 to 1200 nm;
- (b) feeding said plate from said cassette to an exposure device to imagewise expose the plate with said laser to cause hardening of the photosensitive layer in the exposed areas;
- (c) automatically transferring said exposed plate to an off-press developing device to contact with ink and/or fountain solution, or with an organic solvent-based or oil-based liquid or paste and/or an aqueous solution, to remove the photosensitive layer in the non-hardened areas;
- and
- (d) mounting said developed plate on a lithographic press to lithographically print images from said plate to the receiving medium;
- (e) wherein said plate is shielded with light-tight covers all the time in said steps (a) to (c) until it has been developed, and is open to white room light in said step (d).
A method of lithographically printing images on a receiving medium, comprising in order:
- (a) providing within a light-tight cassette a lithographic plate comprising on a hydrophilic substrate an oleophilic photosensitive layer comprising a polymeric binder, a free radical polymerizable monomer, a free radical initiator, and a sensitizing dye;
- said photosensitive layer being soluble or dispersible in ink and/or fountain solution and capable of hardening upon exposure to a laser having a wavelength selected from 200 to 1200 nm;
- (b) feeding said plate from said cassette to an exposure device to imagewise expose the plate with said laser to cause hardening of the photosensitive layer in the exposed areas;
- (c) automatically transferring said exposed plate to a deactivating device to contact said exposed plate with an aqueous solution containing a deactivating agent to deactivate the photosensitive layer;
- and
- (d) mounting said deactivated plate on a lithographic press to contact said plate with ink and/or fountain solution to remove the photosensitive layer in the non-hardened areas and to lithographically print images from said plate to the receiving medium;
- (e) wherein said plate is shielded with light-tight covers all the time in said steps (a) to (c) until it has been deactivated, and is open to white room light in said step (d).
Dependencies are inferred from the claim text.