Gel particles, ink composition and production method thereof, photosensitive composition, and image forming method

1. An ink composition for ink jet comprising:

gel particles which have a polymerizable group, and a three-dimensional crosslinked structure including at least one bond selected from a urethane bond and a urea bond, and enclose a photopolymerization initiator; and

water.

2. The ink composition for ink jet according to claim 1 , wherein the photopolymerization initiator includes at least one of a carbonyl compound or an acylphosphine oxide compound.

3. The ink composition for ink jet according to claim 1 , wherein the gel particles have a hydrophilic group on the surfaces.

4. The ink composition for ink jet according to claim 3 , wherein the hydrophilic group is at least one type selected from a group having a polyether structure, a carboxylic acid group, and a salt of a carboxylic acid group.

5. The ink composition for ink jet according to claim 1 , wherein the gel particles further enclose a polymerizable monomer.

6. The ink composition for ink jet according to claim 1 , wherein the gel particles further enclose a sensitizer.

7. The ink composition for ink jet according to claim 1 , further comprising a polymerizable compound in the outer portion of the gel particles.

8. The ink composition for ink jet according to claim 1 , further comprising a photopolymerization initiator in the outer portion of the gel particles.

9. The ink composition for ink jet according to claim 1 , wherein the total solid content amount of the gel particles is 50% by mass or greater with respect to the total solid content of the ink composition for ink jet.

10. The ink composition for ink jet according to claim 1 , wherein the volume average particle diameter of the gel particles is from 0.01 μm to 10.0 μm.

11. A production method of the ink composition for ink jet according claim 1 , comprising:

obtaining an emulsion by mixing and emulsifying any one oil phase component selected from an oil phase component including a photopolymerization initiator, a tri- or higher functional isocyanate compound, a polymerizable monomer, and an organic solvent, an oil phase component including a photopolymerization initiator, a tri- or higher functional isocyanate compound having a polymerizable group, and an organic solvent, and an oil phase component including a photopolymerization initiator, a tri- or higher functional isocyanate compound having a polymerizable group, a polymerizable monomer, and an organic solvent, with an aqueous phase component including water; and

gelling the above emulsion by heating.

12. The production method of the ink composition for ink jet according to claim 11 , wherein the tri- or higher functional isocyanate compound is an isocyanate compound derived from at least one type selected from isophorone diisocyanate, hexamethylene diisocyanate, trimethyl hexamethylene diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, m-xylylene diisocyanate, and dicyclohexylmethane-4,4′-diisocyanate.

13. The production method of the ink composition for ink jet according to claim 11 , wherein the oil phase component or the aqueous phase component further comprises a surfactant.

14. An image forming method, comprising:

applying the ink composition for ink jet according to claim 1 to a recording medium by ink jet method; and

irradiating the ink composition for ink jet applied to the recording medium with active energy rays.

15. The ink composition for ink jet according to claim 1 , wherein the three-dimensional crosslinked structure has a structure of a reaction product of water and a tri- or higher functional isocyanate compound represented by General Formula (2) below:

wherein, in General Formula (2); X represents a (l+m+n) valent organic group; l, m, and n are each independently 0 or greater; l+m+n is 3 or greater; Y 1 , Y 2 , and Y 3 each independently represent O, S, or NH; R 1 , R 2 , and R 3 each independently represent an alkylene group which may have a substituent having 1 to 20 carbon atoms, a cycloalkylene group which may have a substituent having 1 to 20 carbon atoms, or an arylene group which may have a substituent having 1 to 20 carbon atoms.

16. The ink composition for ink jet according to claim 1 , wherein the three-dimensional crosslinked structure has a structure of a reaction product of water, a monoether of polyethylene oxide, and a tri- or higher functional isocyanate compound represented by General Formula (2) below:

wherein, in General Formula (2); X represents a (l+m+n) valent organic group; l, m, and n are each independently 0 or greater; l+m+n is 3 or greater; Y 1 , Y 2 , and Y 3 each independently represent O, S, or NH; R 1 , R 2 , and R 3 each independently represent an alkylene group which may have a substituent having 1 to 20 carbon atoms, a cycloalkylene group which may have a substituent having 1 to 20 carbon atoms, or an arylene group which may have a substituent having 1 to 20 carbon atoms.

17. The production method of the ink composition for ink jet according to claim 11 , wherein the tri- or higher functional isocyanate compound is a tri- or higher functional isocyanate compound represented by General Formula (2) below:

wherein, in General Formula (2); X represents a (l+m+n) valent organic group; l, m, and n are each independently 0 or greater; l+m+n is 3 or greater; Y 1 , Y 2 , and Y 3 each independently represent O, S, or NH; R 1 , R 2 , and R 3 each independently represent an alkylene group which may have a substituent having 1 to 20 carbon atoms, a cycloalkylene group which may have a substituent having 1 to 20 carbon atoms, or an arylene group which may have a substituent having 1 to 20 carbon atoms.