Ink set and printing method
An ink set includes a water-based coloring ink and a water-based coating liquid having an acting of aggregating the water-based coloring ink, wherein a dynamic surface tension value at 25° C. at a surface life of 100 ms of the water-based coating liquid is smaller than a dynamic surface tension value at 25° C. at a surface life of 100 ms of the water-based coloring ink, a difference between the dynamic surface tension value at 25° C. at a surface life of 100 ms of the water-based coating liquid and the dynamic surface tension value at 25° C. at a surface life of 100 ms of the water-based coloring ink is 5 mN/m or more and 20 mN/m or less, and the dynamic surface tension value at 25° C. at a surface life of 100 ms of the water-based coating liquid is within a range of 20 to 30 mN/m.
1. An ink set, comprising: a water-based coloring ink and a water-based coating liquid having an acting of aggregating the water-based coloring ink, wherein
the water-based coloring ink comprises water in a range of 50% by mass to 90% by mass, a pigment in a range of 0.5% by mass to 10% by mass, a water-soluble solvent in a range of 5% by mass to 49% by mass, and a resin in a range of 1% by mass to 10% by mass, the water-based coloring ink may further comprise a surface conditioner, and the resin in the water-based coloring ink comprises a self-dispersible urethane resin,
the water-based coating liquid comprises water in a range of 50% by mass to 90% by mass, a water-soluble solvent in a range of 5% by mass to 49% by mass, and a resin in a range of 0.005% by mass to 15% by mass, wherein
the water-based coating liquid comprises an amine compound selected from the group consisting of N-methyldiethanolamine, N-ethyldiethanolamine, N,N-dimethylethanolamine, and N,N-diethylethanolamine,
the water-based coating liquid optionally comprises a surface conditioner,
the water-soluble solvent in the water-based coating liquid comprises a diol compound and/or a glycol ether compound, and
the resin in the water-based coating liquid comprises a water-soluble polymer having a cation,
a dynamic surface tension value at 25° C. at a surface life of 100 ms of the water-based coating liquid is smaller than a dynamic surface tension value at 25° C. at a surface life of 100 ms of the water-based coloring ink,
a difference between the dynamic surface tension value at 25° C. at a surface life of 100 ms of the water-based coating liquid and the dynamic surface tension value at 25° C. at a surface life of 100 ms of the water-based coloring ink is 7 mN/m or more and 20 mN/m or less, and
the dynamic surface tension value at 25° C. at a surface life of 100 ms of the water-based coating liquid is within a range of 20 to 30 mN/m.
2. The ink set according to claim 1 , wherein the water-based coating liquid comprises the water in a range of 50% by mass to 90% by mass, the water-soluble solvent in a range of 5% by mass to 35% by mass, and the resin in a range of 0.005% by mass to 5% by mass.
3. The ink set according to claim 1 , wherein the water-based coloring ink comprises polyether urethane resin particles and/or polyester urethane resin particles.
4. The ink set according to claim 1 , wherein the water-based coating liquid comprises a polyether-modified silicone-based surface conditioner.
5. The ink set according to claim 1 , wherein the water-based coloring ink comprises a polyether-modified silicone-based surface conditioner.
6. The ink set according to claim 1 , wherein
a static surface tension at 25° C. of the water-based coating liquid is within a range of 20 to 25 mN/m, and a static surface tension at 25° C. of the water-based coloring ink is within a range of 20 to 50 mN/m, and
the static surface tension at 25° C. of the water-based coating liquid is smaller than the static surface tension at 25° C. of the water-based coloring ink, and a difference therebetween is 3 mN/m or more and 15 mN/m or less.
7. The ink set according to claim 1 , wherein
an acid value (A) of the self-dispersible urethane resin is within a range of 5 to 60, and
a ratio (A:B) of the acid value (A) of the self-dispersible urethane resin to a cation degree (B) of the water-soluble polymer is within a range of 10:1 to 1:1.
8. The ink set according to claim 1 , wherein the water-based coating liquid comprises a water-soluble polymer having a quaternary ammonium cation, and a proportion of the water-soluble polymer having a quaternary ammonium cation in the resin included in the water-based coating liquid is within a range of 50% by mass or more.
9. The ink set according to claim 1 , wherein a pH of the water-based coating liquid is within a range of 7.01 to 10.0.
10. The ink set according to claim 1 , wherein
the water-based coating liquid and the water-based coloring ink comprise the amine compound,
a content of the amine compound in the water-based coating liquid is 0.1 to 2.0% by mass, and
a content of the amine compound in the water-based coloring ink is 0.1 to 2.0% by mass.
11. A printing method in which a print layer is formed on a substrate by an inkjet printer provided with the ink set according to claim 1 , comprising:
ejecting the water-based coating liquid from a print head to land coating droplets on the substrate; and
ejecting the water-based coloring ink from the print head to land ink droplets on the coating liquid to form the print layer.
12. The printing method according to claim 11 , further comprising: drying the print layer with hot air.
13. The printing method according to claim 11 , further comprising: drying the print layer with hot air at 70 to 130° C.
14. The printing method according to claim 11 , wherein the substrate is a non-absorbent substrate or a poorly absorbable substrate.
15. The printing method according to claim 11 , wherein the water-based coloring ink is composed of a plurality of water-based coloring inks, and the water-based coloring ink that first lands on the coating liquid has a lowest dynamic surface tension at 25° C. at a surface life of 100 ms among the plurality of water-based coloring inks.