Image forming method, and image formed matter

1. An image forming method, comprising:

applying a pre-treatment liquid, capable of aggregating a water-dispersible colorant, onto a surface of a coating layer on a surface of a support of a recording medium,

jetting an inkjet ink onto the surface of the coating layer, onto which the pre-treatment liquid has been applied, thereby forming an image, and

applying or jetting a post-treatment liquid onto the surface of the coating layer, onto which the inkjet ink has been jetted, thereby forming a transparent protective layer on the coating layer,

wherein the inkjet ink comprises the water-dispersible colorant, a water-soluble organic solvent, a surfactant, a penetrant, and water,

an amount of pure water transferred into the coating layer on the surface of the recording medium is from 1 mL/m 2 to 10 mL/m 2 measured at a contact time of 100 ms with a dynamic scanning liquid absorptometer, and

the pre-treatment liquid comprises a water-soluble aliphatic organic acid.

2. The image forming method of claim 1 , wherein a number of carbon atoms of the water-soluble aliphatic organic acid is from 2 to 6.

3. The image forming method of claim 1 ,

wherein the water-soluble aliphatic organic acid comprises at least one compound of a formula selected from the group consisting of Formulae (I), (II), and (III):

wherein R 1 is a hydrogen atom or a methyl group substituted by a hydroxyl group or carboxyl group and

R 2 is a methyl group or a methyl group substituted by a hydroxyl group or carboxyl group;

wherein n is an integer of from 0 to 4; and

wherein n is an integer of from 0 to 4.

4. The image forming method of claim 1 , wherein the pre-treatment liquid further comprises a water-soluble organic monoamine compound.

5. The image forming method of claim 4 , wherein the water-soluble organic monoamine compound comprises at least one compound of a formula selected from the group consisting of Formulae (IV) and (V):

wherein R 3 , R 4 , and R 5 are each independently a hydrogen atom, an alkoxy group comprising from 1 to 4 carbon atoms, an alkyl group comprising from 1 to 8 carbon atoms, a hydroxyethyl group, or a hydroxypropyl group,

with the proviso that R 3 , R 4 , and R 5 are not all hydrogen atoms and

wherein R 6 is a hydroxymethyl group;

R 7 is a methyl group, an ethyl group, or a hydroxymethyl group; and

R 8 is a hydrogen atom, an alkyl group comprising from 1 to 4 carbon atoms, or a hydroxymethyl group.

6. The image forming method of claim 1 , wherein a static surface tension of the pre-treatment liquid is 30 mN/m or lower.

7. The image forming method of claim 1 , wherein the water-dispersible colorant is a pigment, and the pigment comprises an anionic self-dispersible pigment, a pigment coated with an anionic resin, or both.

8. The image forming method of claim 1 , wherein a static surface tension of the inkjet ink is 30 mN/m or lower.

9. The image forming method of claim 1 , wherein the post-treatment liquid comprises a thermoplastic resin.

10. The image forming method of claim 9 , wherein the thermoplastic resin is a water-dispersible resin with a glass transition temperature (Tg) of −30° C. or higher and a minimum film forming temperature (MFT) of 50° C. or lower.

11. The image forming method of claim 10 , wherein the water-dispersible resin is at least one resin selected from the group consisting of an acrylic resin, a styrene-acrylic resin, a urethane resin, an acryl-silicone resin, and a fluorine resin.

12. The image forming method of claim 1 , wherein a dry adhesion amount of the post-treatment liquid to the recording medium is from 0.5 g/m 2 to 10 g/m 2 .

13. The image forming method of claim 1 , further comprising:

heating the recording medium, onto which the post-treatment liquid has been applied or jetted, at 100° C. to 150° C. by a heating unit, thereby thermally fixing the inkjet ink on the recording medium.

14. The image forming method of claim 1 , wherein a wet coating amount of the pre-treatment liquid applied to the surface of the coating layer is from 0.1 g/m 2 to 30.0 g/m 2 .

15. The image forming method of claim 14 , wherein the wet coating amount of the pre-treatment liquid applied to the surface of the coating layer is from 0.2 g/m 2 to 10.0 g/m 2 .

16. The image forming method of claim 1 , wherein the water-soluble aliphatic acid comprises an organic acid comprising a sulfo group.

17. The image forming method of claim 16 , wherein the water-soluble aliphatic acid comprises taurine.

18. The image forming method of claim 1 , wherein the water-soluble organic solvent comprises a polyhydric alcohol, a polyhydric alcohol alkyl ether, a polyhydric alcohol aryl ether, a nitrogen-containing heterocyclic compound, an amide, an amine, a sulfur-containing compound, propylene carbonate, ethylene carbonate, or a mixture thereof.

19. The image forming method of claim 1 , wherein an equilibrium water content of the water-soluble organic solvent is 30% by mass or more at 23° C. and 80% relative humidity.