Ink composition comprising cationic, water-soluble resin

An ink set consisting of a black ink, a yellow ink, a cyan ink, and a magenta ink, said black, yellow, cyan, and magenta inks each independently consisting essentially of an alkali-soluble colorant, a water-soluble organic solvent, water, cationic water-soluble resin, a base which is a hydroxide of an alkali metal or an alkaline earth metal and, optionally, one or more of a nonionic water-soluble resin and an assistant selected from the group consisting of a penetration accelerator, a viscosity modifier, a surface tension modifier, a hydrotropy agent, a humectant, a pH adjustor, an antimold, a chelating agent, a preservative and a rust preventive;

• the cationic, water-soluble resin consisting of repeating units represented by the following formula (I):
• where R1 and R2 which may be the same or different represent a C1-5 alkyl group, and
• n is 0, 1, or 2,
• wherein the alkali-soluble colorant for the black ink is selected from the group of dyes consisting of C.I. Direct Black 19, 35, 154, 168, 171, and 195 and C.I. Food Black 2
• the alkali-soluble colorant for the yellow ink is selected from the group of dyes consisting of C.I. Direct Yellow 50, 55, 86, 132, 142, and 144 and C.I. Acid Yellow 23
• the alkali-soluble colorant for the cyan ink is selected from the group of dyes consisting of C.I. Direct Blue 86, 87 and 199 and C.I. Blue 9 and 249,
• the alkali soluble colorant for the magenta ink is selected from the group of dyes consisting of C.I. Direct Red 9 and 227, C.I. Acid Red 52 and 289, and dyes represented by the following structural formula (II):
• wherein R3 and R4 represent a hydrogen atom, a C1-5 alkyl group, or a phenoxy group or a derivative thereof, a triazine ring or a derivative thereof, a carboxyl group or a salt thereof, or a sulfonyl group or a derivative thereof;
• X represents a hydrogen or halogen atom;
• and
• Y1 and Y2 which may be same or different represent an alkali metal atom, ammonium or a C1-5 alkylammonium.

An ink composition comprising an alkali-soluble colorant, a water-soluble organic solvent, water, and a cationic, water-soluble resin,

• the cationic, water-soluble resin consisting of repeating units represented by the following formula (I):
• wherein R1 and R2 which may be the same or different represent a hydrogen atom or a C1-5 alkyl group, provided that R1 and R2 do not simultaneously represent a hydrogen atom;
• and
• n is 1.

An ink set comprising a black ink, a yellow ink, a cyan ink, and a magenta ink, said black, yellow, cyan, and magenta inks each independently comprising an alkali-soluble colorant, a water-soluble organic solvent, water, and a cationic, water-soluble resin,

• the cationic, water-soluble resin consisting of repeating units represented by the following formula (I):
• wherein R1 and R2 which may be the same or different represent a C1-5 alkyl group, and
• n is 1,
• the black ink comprising a colorant selected from the group of dyes consisting of C.I. Direct Black 19, 35, 154, 168, 171, and 195 and C.I. Food Black 2,
• the yellow ink comprising a colorant selected from the group of dyes consisting of C.I. Direct Yellow 50, 55, 86, 132, 142, and 144 and C.I. Acid Yellow 23,
• the cyan ink comprising a colorant selected from the group of dyes consisting of C.I. Direct Blue 86, 87, and 199 and C.I. Acid Blue 9 and 249,
• the magenta ink comprising a colorant selected from the group of dyes consisting of C.I. Direct Red 9 and 227, C.I. Acid Red 52 and 289, and dyes represented by the following structural formula (II):
• wherein R3 and R4 represent a hydrogen atom, a C1-5 alkyl group, an aryl group, a C1-5 alkoxy group, or a phenoxy group or a derivative thereof, a triazine ring or a derivative thereof, a carboxyl group or a salt thereof, or a sulfonyl group or a derivative thereof;
• X represents a hydrogen or halogen atom;
• and
• Y1 and Y2 which may be the same or different represent an alkali metal atom ammonium, or a C1-5 alkylammonium.