Liquid platemaking with laser engraving
View Patent ↗A method of making a relief image printing element from a liquid photopolymer composition is described. The method includes the steps of (1) casting a liquid photopolymer layer onto a cover sheet and at least substantially simultaneously placing a hacking sheet onto the liquid photopolymer layer; (2) preliminarily exposing the liquid photopolymer layer to actinic radiation to create at least one island of solid photopolymer in the liquid photopolymer layer where it is desirable to laser engrave a relief image; (3) reclaiming uncured liquid photopolymer from the relief image printing element; (4) processing the at least one island of solid photopolymer to remove uncured liquid photopolymer; (5) exposing the at least one island of solid photopolymer to actinic radiation to fully cure the islands of solid photopolymer; and (6) laser engraving the at least one island of solid photopolymer to produce the relief image therein.
1. A method of making a relief image printing element from a liquid photopolymer composition, the method comprising the steps of, in order:
a) casting a liquid photopolymer layer onto a cover sheet and at least substantially simultaneously placing a backing sheet onto the liquid photopolymer layer;
b) preliminarily exposing the liquid photopolymer layer to actinic radiation to create at least one island of solid photopolymer in the liquid photopolymer layer where it is desirable to laser engrave a relief image;
c) recovering and reclaiming uncured liquid photopolymer from the relief image printing element for reuse;
d) processing the at least one island of solid photopolymer to remove residual traces of uncured liquid photopolymer remaining on the relief image printing element after step c);
e) exposing the at least one island of solid photopolymer to actinic radiation to fully cure the at least one island of solid photopolymer; and
f) laser engraving the at least one island of solid photopolymer to produce the relief image therein.
2. The method according to claim 1 , wherein the laser for engraving the at least one island of cured photopolymer operates in the infrared or near infrared range.
3. The method according to claim 1 , wherein the step of preliminarily exposing the liquid photopolymer layer to actinic radiation to create at least one island of photopolymer includes back exposing the liquid photopolymer layer to create a floor layer in the relief image printing element.
4. The method according to claim 1 , wherein the step of recovering and reclaiming uncured liquid photopolymer comprises using an air knife or a squeegee to remove the uncured liquid photopolymer from the relief image printing element.
5. The method according to claim 1 , wherein the processing step comprises dry blotting, or using soap and a water wash, to remove the uncured photopolymer from the printing element.
6. The method according to claim 1 , further comprising the step of detacking the photopolymer resin layer prior to the laser engraving step.
7. The method according to claim 1 , further comprising the step of washing debris off of the engraved surface of the relief image printing element after step f).
8. The method according to claim 1 , comprising the step of detacking the photopolymer resin layer after the laser engraving step.
9. The method according to claim 1 , wherein the backing sheet and the cover sheet are transparent.
10. The method according to claim 1 , wherein the step of preliminarily exposing the liquid photopolymer layer to actinic radiation creates multiple islands of solid photopolymer in the liquid photopolymer layer where it is desirable to laser engrave the relief image.
11. The method according to claim 3 , wherein the step of preliminarily exposing the liquid photopolymer layer to actinic radiation to create at least one island of photopolymer and the step of back exposing the liquid photopolymer layer to create the floor layer take place at least substantially simultaneously.