Patent ID: 7753515
Filing Date: 2010-07-13
Classification: C09D

Abstract:
1. An ink set, which is an ink set (A) constituted by a plurality of aqueous inks (a) and used together with an aqueous ink (B) containing a water-insoluble coloring material, wherein each of the plurality of aqueous inks (a) constituting the ink set (A) contains a water-soluble dye as a coloring material and at least one water-soluble organic solvent(s) serving as a poor solvent for the water-insoluble coloring material contained in the aqueous ink (B), wherein the total sum of the content(s) (mass %) of the at least one water-soluble organic solvent(s) contained in each of the plurality of aqueous inks (a) constituting the ink set (A) and serving as a poor solvent for the water-insoluble coloring material contained in the aqueous ink (B) is three times or more the content (mass %) of the water-insoluble coloring material contained in the aqueous ink (B), wherein at least one of the at least one water-soluble organic solvent(s) contained in each of the plurality of aqueous inks (a) constituting the ink set (A) and serving as a poor solvent for the water-insoluble coloring material contained in the aqueous ink (B) has a vapor pressure at 20° C. that is lower than the vapor pressure of water at 20° C. and is selected from polyethylene glycol having average molecular weight of 200, polyethylene glycol having average molecular weight of 600, 1,5-pentanediol, 2-pyrrolidone, and 1,2,6-hexanetriol, wherein the water-insoluble coloring material contained in the aqueous ink (B) is a pigment to the surface of which at least one selected from a group consisting of —COOM1, —SO wherein the water-soluble dye has an anionic group, and wherein the at least one water-soluble organic solvent(s) contained in each of the plurality of aqueous inks (a) constituting the ink set (A) and serving as a poor solvent for the water-insoluble coloring material contained in the aqueous ink (B) is capable of causing aggregation of the water-insoluble coloring material contained in the aqueous ink (B) on a recording medium, the aggregation being caused by reducing a charge amount of the water-insoluble coloring material, making a dispersion of the water-insoluble coloring material unstable.