Abstract: An ink jet recording head, includes a nozzle array of nozzle flow paths; ink ejection orifices communicating with the nozzle flow paths; heaters in the nozzle flow paths; and ink with which the head is filled. The ink contains a coloring material, an acetylene glycol-based surfactant, and water, the surfactant containing one or more kinds of an acetylene glycol or an ethylene oxide adduct thereof, an average addition number of moles of ethylene oxide of the whole surfactant being 3 to 7. The ink has a viscosity of 1.5 mPa·s to 3.0 mPa·s. The head is a line type head having an opening area of each ink ejection orifice of 100 ?m2 to 350 ?m2, a total number of nozzles of 1,200 or more, and a length of the nozzle array of 2 inches or more, and the head is driven at a frequency of 1 kHz to 10 kHz.

Abstract: An ink jet recording ink including a pigment; water; and water-soluble compounds. The pigment comprises a resin-dispersed pigment dispersed with a (meth)acrylate-based random copolymer having an acid value of 100-160 mgKOH/g. The water-soluble compounds include at least ethylene urea and a water-soluble compound having a hydrophilicity-hydrophobicity coefficient defined by the following equation (A) of 0.37 or less The total content of the water-soluble compounds is 22-50 mass % with respect to the total amount of the ink The content of the ethylene urea is 11.0 mass % or more with respect to the total amount of the ink, and the proportion of the amount of the ethylene urea in the total amount of the water-soluble compounds is 50% by mass or less, Hydrophilicity-hydrophobicity coefficient=((water activity value of 20% aqueous solution)?(molar fraction of water in 20% aqueous solution))/(1?(molar fraction of water in 20% aqueous solution))??Equation (A).

Abstract: An ink-jet recording ink set includes: an ink (I) containing a dye D1, a compound C1 represented by the following formula and having a U+V of S1, and water; and an ink (II) containing a dye D2, a compound C2 represented by the following formula and having a U+V of S2, and water in which in case that a surface tension ?L1 (mN/m) of an evaluation liquid L1 obtained by adding, to a 5 mass % aqueous solution of the dye D1, a compound C3 in an amount corresponding to 1 mass % of the aqueous solution, and a surface tension ?L2 (mN/m) of an evaluation liquid L2 obtained by adding, to a 5 mass % aqueous solution of the dye D2, the compound C3 in an amount corresponding to 1 mass % of the aqueous solution satisfy a relationship of ?L1??L2?10 (mN/m), the S1 and the S2 satisfy a relationship of 2?S2?S1?7.

Abstract: An ink jet recording ink including a pigment; water; and water-soluble compounds. The pigment comprises a resin-dispersed pigment dispersed with a (meth)acrylate-based random copolymer having an acid value of 100-160 mgKOH/g. The water-soluble compounds include at least ethylene urea and a water-soluble compound having a hydrophilicity-hydrophobicity coefficient defined by the following equation (A) of 0.37 or less The total content of the water-soluble compounds is 22-50 mass % with respect to the total amount of the ink The content of the ethylene urea is 11.0 mass % or more with respect to the total amount of the ink, and the proportion of the amount of the ethylene urea in the total amount of the water-soluble compounds is 50% by mass or less, Hydrophilicity-hydrophobicity coefficient=((water activity value of 20% aqueous solution)?(molar fraction of water in 20% aqueous solution))/(1?(molar fraction of water in 20% aqueous solution)) ??Equation (A).

Abstract: An ink jet recording ink including a coloring material; water; and three kinds of water-soluble compounds. The content of the water is 70 mass % or more with respect to the total amount of the ink. Each water-soluble compound has a molecular weight of 80 or more and is a liquid compound having a vapor pressure at 20° C. of 5 Pa or less or a solid compound, and at least one kind of the water-soluble compounds is a solid compound. In case that the water-soluble compounds are mixed at a ratio at which the water-soluble compounds are incorporated into the ink to provide a mixture, a 40% aqueous solution of the mixture has a water activity value of 0.88-0.91 and a viscosity of 3.3 mPa·s or less. The total content of the water-soluble compounds in the ink is 20-25 mass % with respect to the total amount of the ink.

Abstract: An ink jet recording head, including: a nozzle array of nozzle flow paths; ink ejection orifices communicating with the nozzle flow paths; heaters in the nozzle flow paths; and ink with which the head is filled, the ink containing a coloring material, an acetylene glycol-based surfactant, and water, the surfactant containing one or more kinds of an acetylene glycol or an ethylene oxide adduct thereof, an average addition number of moles of ethylene oxide of the whole surfactant being 3 to 7, the ink having a viscosity of 1.5 mPa·s to 3.0 mPa·s, the head comprising a line type head having an opening area of each ink ejection orifice of 100 ?m2 to 350 ?m2, a total number of nozzles of 1,200 or more, a length of the nozzle array of 2 inches or more, and the head being driven at a frequency of 1 kHz to 10 kHz.

Abstract: An ink-jet recording ink set includes: an ink (I) containing a dye D1, a compound C1 represented by the following formula and having a U+V of S1, and water; and an ink (II) containing a dye D2, a compound C2 represented by the following formula and having a U+V of S2, and water in which in case that a surface tension ?L1 (mN/m) of an evaluation liquid L1 obtained by adding, to a 5 mass % aqueous solution of the dye D1, a compound C3 in an amount corresponding to 1 mass % of the aqueous solution, and a surface tension ?L2 (mN/m) of an evaluation liquid L2 obtained by adding, to a 5 mass % aqueous solution of the dye D2, the compound C3 in an amount corresponding to 1 mass % of the aqueous solution satisfy a relationship of ?L1??L2?10 (mN/m), the S1 and the S2 satisfy a relationship of 2?S2?S1?7.