AQUEOUS INK-JET INK, RECORDING UNIT USING THE SAME, AND INK-JET RECORDING METHOD

PROBLEM TO BE SOLVED: To provide an aqueous ink for ink-jet recording, which restrains a resin from being stuck to the surface of a discharge nozzle to get wet easily with the aqueous ink and makes slight the changes of the surface properties of the surface of the discharge nozzle so that the destabilization of a discharging direction of the aqueous ink is restrained. SOLUTION: The aqueous ink for ink-jet recording can be used in an ink-jet recording apparatus in which an ink droplet is discharged from the discharge nozzle of a recording head, the surface of which nozzle is not made water-repellent, according to a recording signal and recording is performed on a material to be recorded with the discharged ink droplet. The aqueous ink for ink-jet recording contains a pigment, a water-soluble resin and a surfactant and is characterized in that the surface tension value of a mixed solution, which contains the same pigment, water-soluble resin and surfactant as those of the aqueous ink for ink-jet recording, satisfies the following expression (1): [[surface tension value (mN/m2) of mixed solution of pigment in ink and aqueous resin]-[surface tension value (mN/m2) of mixed solution of pigment in ink, aqueous resin, and surfactant]]/[[surface tension value (mN/m2) of mixed solution of pigment in ink and aqueous resin]-[surface tension value (mN/m2) of surfactant solution at critical micelle concentration]]>0.6 and the adhesion energy of a mixed aqueous solution, the surface tension value of which is adjusted to 40 mN/m2and contains the surfactant and purified water, to the surface of the discharge nozzle is ≥3.5 mJ/m2. COPYRIGHT: (C)2010,JPO&INPIT