Treatment of release layer and inkjet ink formulations
Aqueous inkjet ink formulations comprising a solvent including water and a co-solvent, a water soluble or water dispersible polymeric resin and a colorant, and a method for facilitating the use of such an aqueous inkjet ink in an indirect printing system in which the ink is jetted onto a hydrophobic release layer of an intermediate transfer member before having the solvent removed therefrom and being transferred to a substrate, wherein prior to the jetting of the ink the release layer is brought into contact with an aqueous solution of a positively charged polymeric chemical agent. Other aspects are also described.
1. A printed ink image on a substrate comprising a water-soluble or water-dispersible polymeric resin, and for which at least one of the following is true:
(a) the image has an X-Ray Photoelectron Spectroscopy (XPS) peak at 402.0±0.4 eV;
(b) the image has on its outer surface distal to the substrate a polymeric chemical agent containing at least 1 wt. % of one or more chargeable nitrogen atoms and having at least one of
(1) a positive charge density of at least 3 meq/g of chemical agent and an average molecular weight of at least 250 and
(2) a molecular weight of at least 10,000;
(c) the ratio of the surface concentration of nitrogen at the outer surface of the image distal to the substrate to the bulk concentration of nitrogen within the image is at least 1.2:1;
(d) the surface concentration of secondary amines, tertiary amines, and/or an ammonium group at the image surface distal to the substrate exceeds their respective bulk concentrations at a depth of at least 30 nanometers below the surface.
2. A printed ink image of claim 1 wherein the image has on its outer surface said polymeric chemical agent, the polymeric chemical agent having a positive charge density of at least 3 meq/g and an average molecular weight of at least 5,000.
3. The printed ink image of claim 1 , wherein the polymeric chemical agent has an average molecular weight of at least 800.
4. The printed ink image of claim 1 wherein the charge density of the polymeric chemical agent is at least 6 meq/g of chemical agent.
5. The printed ink image of claim 1 wherein the polymeric chemical agent is selected from the group consisting of linear polyethylene imine, branched polyethylene imine, modified polyethylene imine, poly(diallyldimethylammonium chloride), poly(4-vinylpyridine), polyallylamine, a vinyl pyrrolidone-dimethylaminopropyl methacrylamide co-polymer, a vinyl caprolactam-dimethylaminopropyl methacryamide hydroxyethyl methacrylate copolymer, a quaternized copolymer of vinyl pyrrolidone and dimethylaminoethyl methacrylate with diethyl sulfate a guar hydroxypropyltrimonium chloride, and a hydroxypropyl guar hydroxypropyltrimonium chloride.
6. The printed ink image of claim 1 , wherein a surface concentration of nitrogen at the surface distal to the substrate exceeds a bulk concentration of nitrogen within the bulk of the ink image, the bulk concentration being measured at a depth of at least 30 nanometers below the ink image surface distal to the substrate, and the ratio of the surface concentration to the bulk concentration is at least 1.1 to 1.
7. The printed ink image of claim 6 , wherein the bulk concentration is measured at a depth of at least 3-50 nm from the ink image surface distal to the substrate.
8. The printed ink image of claim 1 , wherein the ratio of the surface concentration of nitrogen at the outer surface of the image distal to the substrate to the bulk concentration of nitrogen within the image is at least 1.3:1.
9. The printed ink image of claim 8 , wherein the ratio of the surface concentration of nitrogen at the outer surface of the image distal to the substrate to the bulk concentration of nitrogen within the image is at least 1.5:1.
10. The printed ink image of claim 9 , wherein the ratio of the surface concentration of nitrogen at the outer surface of the image distal to the substrate to the bulk concentration of nitrogen within the image is at least 1.75:1.
11. The printed ink image of claim 10 , wherein the ratio of the surface concentration of nitrogen at the outer surface of the image distal to the substrate to the bulk concentration of nitrogen within the image is at least 2:1.1.
12. The printed ink image of claim 11 , wherein the ratio of the surface concentration of nitrogen at the outer surface of the image distal to the substrate to the bulk concentration of nitrogen within the image is at least 3:1.
13. The printed ink image of claim 12 , wherein the ratio of the surface concentration of nitrogen at the outer surface of the image distal to the substrate to the bulk concentration of nitrogen within the image is at least 5:1.
14. The printed ink image of claim 3 , wherein the polymeric chemical agent has a positive charge density of at least 3 meq per g of chemical agent and an average molecular weight of at least 1,000.
15. The printed ink image of claim 14 , wherein the polymeric chemical agent has a positive charge density of at least 3 meq per g of chemical agent and an average molecular weight of at least 1,300.
16. The printed ink image of claim 15 , wherein the polymeric chemical agent has a positive charge density of at least 3 meq per g of chemical agent and an average molecular weight of at least 1,700.
17. The printed ink image of claim 16 , wherein the polymeric chemical agent has a positive charge density of at least 3 meq per g of chemical agent and an average molecular weight of at least 2,000.
18. The printed ink image of claim 17 , wherein the polymeric chemical agent has a positive charge density of at least 3 meq per g of chemical agent and an average molecular weight of at least 2,500.
19. The printed ink image of claim 1 , wherein the image has on its outer surface said polymeric chemical agent, the polymeric chemical agent having a positive charge density of at least 6 meq/g and an average molecular weight of at least 1,000.
20. The printed ink image of claim 1 , wherein
(a) the image has an X-Ray Photoelectron Spectroscopy (XPS) peak at 402.0±0.4 eV;
(b) the image has on its outer surface distal to the substrate a polymeric chemical agent containing at least 1 wt. % of one or more chargeable nitrogen atoms and having
(1) a positive charge density of at least 3 meq/g of chemical agent and an average molecular weight of at least 250 and
(2) a molecular weight of at least 10,000;
(c) the ratio of the surface concentration of nitrogen at the outer surface of the image distal to the substrate to the bulk concentration of nitrogen within the image is at least 1.2:1;
(d) the surface concentration of secondary amines, tertiary amines, and/or an ammonium group at the image surface distal to the substrate exceeds their respective bulk concentrations at a depth of at least 30 nanometers below the surface.