Photo-curable ink composition

1. A photo-curable ink composition, comprising:

colorant, water, photo-initiator, UV curable polyurethane dispersions and hydrophobic radiation-curable monomers;

wherein the UV curable polyurethane dispersions and the hydrophobic radiation-curable monomers form a non-aqueous phase in the ink composition, the non-aqueous phase in the ink composition representing from about 20 wt % to about 50 wt % of the total weight of the ink composition.

2. The photo-curable ink composition of claim 1 wherein the UV curable polyurethane dispersions are present in an amount representing from about 1 wt % to about 25 wt % of the total weight of the ink composition.

3. The photo-curable ink composition of claim 1 wherein the UV curable polyurethane dispersions are water-dispersible (meth)acrylated polyurethane.

4. The photo-curable ink composition of claim 1 wherein the hydrophobic radiation-curable monomers are acrylate monomers or vinyl monomers.

5. The photo-curable ink composition of claim 1 wherein the hydrophobic radiation-curable monomers are selected from the group consisting of vinyl caprolactam, hexanediol diacrylate, trimethylolpropane triacrylate and propoxylated neopentyl glycol diacrylate.

6. The photo-curable ink composition of claim 1 , wherein the composition contains water in an amount ranging from about 10 wt % to about 80 wt % by total weight of the ink composition.

7. The photo-curable ink composition of claim 1 , wherein the ink composition further contains a water-soluble or water-miscible organic solvent.

8. The photo-curable ink composition of claim 1 , wherein the ink composition further contains one or more additives selected from the group consisting of surfactant, dispersing agent, UV stabilizer, de-foaming agent, rheology modifiers and biocides.

9. A photo-curable ink composition, comprising:

colorant, water, photo-initiator, UV curable polyurethane dispersions and hydrophobic radiation-curable monomers;

wherein the UV curable polyurethane dispersions and the hydrophobic radiation-curable monomers form a non-aqueous phase in the ink composition, and the hydrophobic radiation-curable monomers are vinyl caprolactam.

10. A method for forming a printed article, comprising:

providing a photo-curable ink composition containing water, colorant, photo-initiator, UV curable polyurethane dispersions and hydrophobic radiation-curable monomers, wherein the UV curable polyurethane dispersions and the hydrophobic radiation-curable monomers form a non-aqueous phase in the ink composition, the non-aqueous phase in the ink composition representing from about 20 wt % to about 50 wt % of the total weight of the ink composition;

providing a media substrate;

projecting of stream of droplets of said photo-curable ink composition onto the media substrate; and

applying photo energy to the ink composition once printed on the media substrate, said photo energy having a frequency and energy level suitable for curing the photo-curable ink composition.

11. The method for forming a printed article of claim 10 , wherein the projection of stream of droplets of ink composition, onto the media substrate, is done via a piezoelectric printhead.

12. An inkjet printing system, comprising:

a media substrate;

at least one photo-curable ink composition comprising colorant, water, photo-initiator, UV curable polyurethane dispersions and hydrophobic radiation-curable monomers, wherein the UV curable polyurethane dispersions and the hydrophobic radiation-curable monomers form a non-aqueous phase in the ink composition, the non-aqueous phase in the ink composition representing from about 20 wt % to about 50 wt % of the total weight of the ink composition; and

a photo energy source configured to apply photo energy to said ink composition once printed on a substrate, said photo energy having a frequency and energy level suitable for curing the photo-curable ink composition.

13. The inkjet printing system of claim 12 , wherein the photo energy source is a UV light source.

14. A method for preparing photo-curable ink composition, comprising:

providing in combination colorant, water, photo-initiator, UV curable polyurethane dispersions and hydrophobic radiation-curable monomers;

subjecting the combination to conditions under which the ink composition becomes substantially uniform, thereby forming from the UV curable polyurethane dispersions and the hydrophobic radiation-curable monomers a non-aqueous phase in the ink; and

subjecting the combination to filtration.