Ink-jet printing method
The present invention provides a method of inkjet printing comprising the following steps, in order: (i) providing a hybrid inkjet ink comprising an organic solvent, a radiation-curable material, a photoinitiator and optionally a colorant; (ii) printing the ink on to a substrate; (iii) pinning the ink by exposing the ink to actinic radiation at a dose of 1-200 mJ/cm 2 ; (iv) evaporating at least a portion of the solvent from the ink; and (v) exposing the ink to additional actinic radiation to cure the ink.
1. A method of inkjet printing comprising the following steps, in order:
(i) providing a hybrid inkjet ink comprising an organic solvent, a radiation-curable material, a photoinitiator and optionally a colorant;
(ii) printing the ink on to a substrate;
(iii) pinning the ink by exposing the ink to actinic radiation at a dose of 1-200 mJ/cm 2 , and wherein said actinic radiation does not fully cure said ink;
(iv) evaporating at least a portion of the solvent from the ink; and
(v) exposing the ink to additional actinic radiation to cure the ink.
2. A method as claimed in claim 1 , wherein ink comprises at least 30% by weight of organic solvent based on the total weight of the ink.
3. A method as claimed in claim 1 , wherein the ink comprises less than 5% by weight of water based on the total weight of the ink.
4. A method as claimed in claim 1 , wherein the radiation-curable material is present in an amount of 2 to 65% by weight based on the total weight of the ink.
5. A method as claimed in claim 1 , wherein the radiation-curable material comprises a radiation-curable oligomer.
6. A method as claimed in claim 1 , wherein the ink contains less than 20% by weight of radiation-curable material having a molecular weight of less than 450, based on the total weight of the ink.
7. A method as claimed in claim 1 , wherein the photoinitiator is a radical photoinitiator.
8. A method as claimed in claim 1 , wherein the inkjet ink is a component of an inkjet ink set.
9. A method as claimed in claim 1 , wherein the inkjet ink is printed using a piezo drop-on-demand printhead.
10. A method as claimed in claim 1 , wherein the source of actinic radiation is a UV source selected from a mercury discharge lamp, an LED, a flash lamp, a UV fluorescent lamp and combinations thereof.
11. A method as claimed in claim 1 , wherein the ink is jetted at less than 35° C.
12. A method as claimed in claim 1 , wherein, in step (iii), the dose is 1-100 mJ/cm 2 .
13. A method as claimed in claim 1 , wherein step (iii) is initiated within 5 seconds of impact of the ink onto the substrate.
14. A method as claimed in claim 1 , wherein the solvent is evaporated by heating the printed ink.
15. A method as claimed in claim 1 , wherein the printing is performed on a roll-to-roll printer or flat-bed printer.