An aqueous ink for ink jet containing a self-dispersible pigment, a compound represented by General Formula (I): ##STR00001##
where in General Formula (I) each R1 independently represents a hydrogen atom or an alkyl group.

An aqueous ink for ink jet containing a self-dispersible pigment, a compound represented by General Formula (I): ##STR00001##
where in General Formula (I) each R1 independently represents a hydrogen atom or an alkyl group.

An ink is provided. The ink includes a quinacridone pigment and an organic solvent having a solubility parameter of from 9.00 to 11.80 in an amount of from 30% to 60% by mass of total mass of the ink. Both a viscosity change rate and a particle diameter change rate of the ink, before and after the ink is heated at 80 C. for 4 weeks in a sealed state, are in the range of from 5% to 1%.

The present invention provides an aqueous pigment dispersion including at least a pigment, colloidal silica, bio-nanofibers having an average diameter of 1 nm to 100 nm and an aspect ratio of 100 or more, an anionic group-containing organic polymer compound, and also provides an aqueous ink. The bio-nanofibers are preferably cellulose nanofibers or chitosan nanofibers, and the ratio between the pigment, the colloidal silica, and the bio-nanofibers preferably satisfies (1) colloidal silica/pigment=1/100 to 20/100 or (2) colloidal silica/bio-nanofibers=1/2 to 10/1 and (3) bio-nanofibers/pigment=1/100 to 15/100.

The present invention provides an aqueous pigment dispersion including at least a pigment, colloidal silica, bio-nanofibers having an average diameter of 1 nm to 100 nm and an aspect ratio of 100 or more, an anionic group-containing organic polymer compound, and also provides an aqueous ink. The bio-nanofibers are preferably cellulose nanofibers or chitosan nanofibers, and the ratio between the pigment, the colloidal silica, and the bio-nanofibers preferably satisfies (1) colloidal silica/pigment=1/100 to 20/100 or (2) colloidal silica/bio-nanofibers=1/2 to 10/1 and (3) bio-nanofibers/pigment=1/100 to 15/100.

Provided is an ink set including black ink and color ink, in which the black ink contains carbon black having a carboxyl group on a surface thereof, a resin particle having a carboxyl group on a surface thereof, betaine, an alkali ion, and water, the alkali ion contains a potassium ion, a sodium ion, and an organic alkali compound, and a content of the potassium ion is the largest among the alkali ions.

Provided is an ink set including black ink and color ink, in which the black ink contains carbon black having a carboxyl group on a surface thereof, a resin particle having a carboxyl group on a surface thereof, betaine, an alkali ion, and water, the alkali ion contains a potassium ion, a sodium ion, and an organic alkali compound, and a content of the potassium ion is the largest among the alkali ions.

This invention pertains to aqueous inkjet inks containing self-dispersing pigments. The self-dispersing pigments are modified with multivalent cations.

This invention pertains to aqueous inkjet inks containing self-dispersing pigments. The self-dispersing pigments are modified with multivalent cations.

The invention provides a tablet having a powdered or soft surface on which a dry-ink film of information for improving identifiability of the tablet is printed, and provides an ink for inkjet printers.