Curable resin composition, water-soluble ink composition, ink set, and image-forming method

1. A curable resin composition comprising:

fine particles;

a polymerizable compound having an ethylenic unsaturated group;

a water soluble photopolymerization initiator having a betaine structure; and

water,

wherein the betaine structure of the photopolymerization initiator is represented by at least one of Formulae (1) to (3) described below,

in Formulae (1) to (3), each of R 1 and R 2 independently represents an alkyl group, L 1 represents a single bond or a divalent linking group, and L 2 represents a divalent linking group.

2. The curable resin composition according to claim 1 ,

wherein the photopolymerization initiator having a betaine structure has any of a benzophenone skeleton, a thioxanthone skeleton, a thiochromanone skeleton, a biimidazole skeleton, an α-aminoacetophenone skeleton, an α-hydroxyacetophenone skeleton, or a benzyl ketal skeleton.

3. The curable resin composition according to claim 1 ,

wherein the fine particles are pigments or resin particles.

4. A water-soluble ink composition comprising the curable resin composition according to claim 1 .

5. The water-soluble ink composition according to claim 4 ,

wherein the fine particles are pigments.

6. The water-soluble ink composition according to claim 4 ,

wherein at least one of the polymerizable compound having an ethylenic unsaturated group is a bi- or more functional (meth)acrylamide compound.

7. An ink set comprising:

the water-soluble ink composition according to claim 4 ; and

an acidic ink composition containing an acidic compound having a molecular weight in a range of 50 to 200 and pKa in water in a range of 1 to 5.

8. An image-forming method comprising:

supplying an acidic ink composition onto a recording medium; and

supplying the water-soluble ink composition according to claim 4 onto the acid-treated recording medium to form an image.

9. The image-forming method according to claim 8 ,

wherein, in the supplying the water-soluble ink composition step, the ink is supplied by an ink jet method.

10. The curable resin composition according to claim 1 ,

wherein the photopolymerization initiator has a degree of solubility in water that the photopolymerization initiator is fully dissolved at room temperature when 3 mass % of aqueous solution thereof is prepared.

11. A curable resin composition comprising:

fine particles;

a polymerizable compound having an ethylenic unsaturated group;

a water soluble photopolymerization initiator having a betaine structure; and water,

wherein the photopolymerization initiator is a compound represented by following Formula (A), (B), (C), (D), (E), (F) or (G),

in Formulae (A) to (G),

each of R a1 , R a2 , R b1 to R b6 , R c1 , R c2 , R e1 and R e2 independently represents a substituent;

each of R d1 and R d2 independently represents a hydrogen atom or a substituent;

R d1 and R d2 may be bonded to each other so as to form a ring;

each of n1 and n2 independently represents an integer of 0 to 5, and each of n3 and n4 independently represents an integer of 0 to 4, n1+n2 is in a range of 1 to 10, and n3+n4 and n3+n5 are in a range of 1 to 8; and

any one of R a1 and R a2 in Formulae (A), (B), and (C), R b1 to R b6 in Formula (D), R a1 , R c1 , R c2 , R d1 , and R d2 in Formula (E), R a1 , R c1 , and R c2 in Formula (F), R a1 , R a2 , R e1 , and R e2 in Formula (G) is a substituent having a betaine structure.