Abstract: A water-based ink includes: a dye; water; an acidic preservative; and at least one of a surfactant and a penetrant. The acidic preservative preferably includes at least one selected from the group consisting of a polyvalent unsaturated fatty acid, a polyvalent unsaturated fatty acid salt, dehydroacetic acid, and a dehydroacetate. A content of the acidic preservative in the water-based ink is preferably 0.3% by mass to 6.0% by mass relative to a total mass of the water-based ink. The surfactant preferably includes an acetylene-based surfactant. The penetrant preferably includes at least one selected from the group consisting of an alkylene diol and a glycol ether compound.

Abstract: A water-based ink for inkjet recording, includes: a pigment; water; and an acidic preservative. The pigment is preferably a self-dispersing pigment. The acidic preservative preferably includes at least one selected from the group consisting of a polyvalent unsaturated fatty acid, a polyvalent unsaturated fatty acid salt, dehydroacetic acid, and a dehydroacetate. A content of the acidic preservative in the water-based ink is preferably 0.5% by mass to 5.0% by mass relative to a total mass of the water-based ink. The water-based ink preferably further includes a surfactant. The water-based ink preferably further includes a penetrant which includes at least one selected from the group consisting of 1,2-hexanediol, 3-methyl-1,5-pentanediol, and triethylene glycol-n-butyl ether (BTG).

Abstract: A first ink composition includes: water; a water-soluble organic solvent; and a color developing agent. The color developing agent includes a pH indicator. The water-soluble organic solvent includes at least one water-soluble organic solvent having a SP value of 16 or less and 11 or more. An amount of the water-soluble organic solvent having a SP value of 16 or less and 11 or more in the first ink composition is 15 wt % or more. A second ink composition includes: water; a water-soluble organic solvent; and a color developing agent. The color developing agent includes a pH indicator. The water-soluble organic solvent includes at least one water-soluble organic solvent having a SP value of 16 or less. An amount of the water-soluble organic solvent having a SP value of 16 or less in the second ink composition is 15 wt % or more. The second ink composition is a water-based ink for ink-jet recording.

Abstract: A first ink composition includes: water; a water-soluble organic solvent; and a color developing agent. The color developing agent includes a pH indicator. The water-soluble organic solvent includes at least one water-soluble organic solvent having a SP value of 16 or less and 11 or more. An amount of the water-soluble organic solvent having a SP value of 16 or less and 11 or more in the first ink composition is 15 wt % or more. A second ink composition includes: water; a water-soluble organic solvent; and a color developing agent. The color developing agent includes a pH indicator. The water-soluble organic solvent includes at least one water-soluble organic solvent having a SP value of 16 or less. An amount of the water-soluble organic solvent having a SP value of 16 or less in the second ink composition is 15 wt % or more. The second ink composition is a water-based ink for ink-jet recording.

Abstract: An erasable ink set includes: an erasable ink; and an erasing time adjuster which is stored separately from the erasable ink and is capable of adjusting an erasing time of the erasable ink. The erasable ink includes a color developing agent including a pH indicator, water, and at least one selected from the group consisting of a first water-soluble organic solvent and a first surfactant. The erasing time adjuster includes water and at least one selected from the group consisting of a second water-soluble organic solvent and a second surfactant.

Abstract: A water-based ink for ink-jet recording includes dyes and water. The dyes include a blue dye having a hue angle of 220° to 280°; a yellow dye having a hue angle of 70° to 120°; and a copper phthalocyanine dye. A mass ratio (C/B) of a content (C) of the copper phthalocyanine dye to a content (B) of the blue dye in an entire amount of the water-based ink is equal to or more than 0.5, and a total content of the dyes in the entire amount of the water-based ink is equal to or more than 6% by mass.

Abstract: A water-based ink for ink-jet recording includes: a solid solution of a quinacridone pigment including C.I. Pigment Violet 19 and C.I. Pigment Red 122; an azo pigment including C.I. Pigment Red 176; and water.

Abstract: A water-based ink for ink-jet recording includes: water; a solid solution pigment composed of at least a first pigment and a second pigment; and a non-solid solution pigment which is the same as the first pigment. An image L*60 of the first pigment has the highest chromaticness C* among those of pigments composing the solid solution pigment, the image L*60 having lightness L* which is closest to 60 among a plurality of solid images recorded on a recording paper by using one of aqueous dispersions containing the pigments composing the solid solution pigment at a same solid content concentration, respectively, while changing recording duty at every 5% in a range of 0% to 100%.

Abstract: A water-based ink for ink-jet recording, includes: a solid solution of a quinacridone pigment including C.I. Pigment Violet 19 and C.I. Pigment Red 202, an azo pigment including C.I. Pigment Red 150, and water.

Abstract: A water-based ink set for ink-jet recording includes: a water-based yellow ink containing water and a yellow dye having a blending amount in an entire amount of the water-based yellow ink of 2 to 3% by weight, the water-based yellow ink having a hue angle of 45° to 65°; a water-based magenta ink containing water and a magenta dye having a blending amount in an entire amount of the water-based magenta ink of 2 to 3% by weight, the water-based magenta ink having a hue angle of 340° to 360° or 0° to 5°; a water-based cyan ink containing water and a cyan dye having a blending amount in an entire amount of the water-based cyan ink of 2 to 3% by weight, the water-based cyan ink having a hue angle of 200° to 230°; and a water-based black ink containing water and a black dye having a blending amount in an entire amount of the water-based black ink of 6 to 7.5% by weight.

Abstract: There is provided a water-based ink for ink-jet recording including: water; a self-dispersible black pigment; and a resin-dispersed pigment of which hue angle is in a range of 180° to 270° and of which sedimentation velocity in the water-based ink is slower than sedimentation velocity of the self-dispersible black pigment in the water-based ink. A ratio (R/S) of a solid content weight (R) of the resin-dispersed pigment to a solid content weight (S) of the self-dispersible black pigment in the water-based ink is in a range of 0.26 to 0.80.

Abstract: There is provided a water-based ink for ink-jet recording including: water; a self dispersible black pigment of which mean particle diameter is not less than 140 nm; and a resin-dispersed pigment which is a copper phthalocyanine-based pigment and of which sedimentation velocity in the water-based ink is slower than sedimentation velocity of the self-dispersible black pigment in the water-based ink.

Abstract: A water-based ink for ink-jet recording includes dyes and water. The dyes include a blue dye having a hue angle of 220° to 280°; a yellow dye having a hue angle of 70° to 120°; and a copper phthalocyanine dye. A mass ratio (C/B) of a content (C) of the copper phthalocyanine dye to a content (B) of the blue dye in an entire amount of the water-based ink is equal to or more than 0.5, and a total content of the dyes in the entire amount of the water-based ink is equal to or more than 6% by mass.

Abstract: A water-based ink set for ink-jet recording includes: a water-based yellow ink containing a yellow pigment, a resin dispersant, and water; a water-based magenta ink containing a magenta pigment, a resin dispersant, and water; a water-based cyan ink containing a cyan pigment, a resin dispersant, and water; and a water-based black ink containing self-dispersible carbon black and water. At least one water-based color ink selected from the group consisting of the water-based yellow ink, the water-based magenta ink, and the water-based cyan ink further contains a dye. The self-dispersible carbon black has an average particle size of 120 to 170 nm.

Abstract: A water-based ink set for ink-jet recording includes: a water-based yellow ink containing water and a yellow dye having a blending amount in an entire amount of the water-based yellow ink of 2 to 3% by weight, the water-based yellow ink having a hue angle of 45° to 65°; a water-based magenta ink containing water and a magenta dye having a blending amount in an entire amount of the water-based magenta ink of 2 to 3% by weight, the water-based magenta ink having a hue angle of 340° to 360° or 0° to 5°; a water-based cyan ink containing water and a cyan dye having a blending amount in an entire amount of the water-based cyan ink of 2 to 3% by weight, the water-based cyan ink having a hue angle of 200° to 230°; and a water-based black ink containing water and a black dye having a blending amount in an entire amount of the water-based black ink of 6 to 7.5% by weight.

Abstract: There is provided a water-based ink for ink-jet recording including: a self-dispersible pigment of which mean particle diameter is not less than 130 nm; a resin-dispersed pigment; and water; wherein the mean particle diameter of the self-dispersible pigment is in a range of 1.5 times to 3 times mean particle diameter of the resin-dispersed pigment.

Abstract: There is provided a water-based ink for ink-jet recording including: water; a self-dispersible black pigment; and a resin-dispersed pigment of which hue angle is in a range of 180° to 270° and of which sedimentation velocity in the water-based ink is slower than sedimentation velocity of the self-dispersible black pigment in the water-based ink. A ratio (R/S) of a solid content weight (R) of the resin-dispersed pigment to a solid content weight (S) of the self-dispersible black pigment in the water-based ink is in a range of 0.26 to 0.80.

Abstract: There is provided a water-based ink for ink-jet recording including: water; a self dispersible black pigment of which mean particle diameter is not less than 140 nm; and a resin-dispersed pigment which is a copper phthalocyanine-based pigment and of which sedimentation velocity in the water-based ink is slower than sedimentation velocity of the self-dispersible black pigment in the water-based ink.

Abstract: A water-based ink set for ink-jet recording includes: a water-based yellow ink containing a yellow pigment, a resin dispersant, and water; a water-based magenta ink containing a magenta pigment, a resin dispersant, and water; a water-based cyan ink containing a cyan pigment, a resin dispersant, and water; and a water-based black ink containing self-dispersible carbon black and water. At least one water-based color ink selected from the group consisting of the water-based yellow ink, the water-based magenta ink, and the water-based cyan ink further contains a dye. The self-dispersible carbon black has an average particle size of 120 to 170 nm.

Abstract: A water-based ink for ink-jet recording includes a colorant, water, a surfactant, and a compound represented by the following formula (1). In the formula (1), R is an alkyl ether group or an alkyl ester group in which a number of carbon atoms of a main chain is not less than 6, and each of an alkyl group of the alkyl ether group and an alkyl group of the alkyl ester group is in a straight chain form or a branched chain form.