Kao Corporation

Azusa Kuroda

Yuta Matsumoto

Kazuki Watanabe

Tsuyoshi Egawa

Kazuki Ishida

The present invention relates to a water-based ink containing a pigment (A), a water-soluble organic solvent (C), a surfactant (D) and water, in which a content of water in the water-based ink is not less than 40% by mass and not more than 65% by mass, a boiling point of the water-soluble organic solvent (C) is not higher than 230&#xb0; C., and a content of a high-boiling point organic solvent having a boiling point of not lower than 250&#xb0; C. in the water-based ink is not more than 4% by mass, and the surfactant (D) contains a silicone-based surfactant (d-1) and an acetylene glycol-based surfactant (d-2) which satisfy the following conditions 1 and 2: Condition 1: [(content of component (d-1))/(content of component (C))]&#xd7;100=0.15 to 4; and Condition 2: [(content of component (d-2))/(content of component (C))]&#xd7;100=0.35 to 1.65. In accordance with the present invention, it is possible to form ink dots having a complete circular shape and produce a printed material that is excellent in solid image fillability, image quality and rub fastness even when printed on a low-liquid absorbing printing medium.

Water-based ink

The present invention relates to an ink-jet printing method of overprinting a first ink and a second ink on a low-liquid absorbing printing medium, in which the first ink and the second ink are respectively in the form of a water-based ink containing a colorant (A), a polymer (B), an organic solvent (C) and water, and satisfy the following formulae (1) and (2), said ink-jet printing method including the steps of forming characters or images using at least one ink as the first ink, and then forming a background image using the second ink such that the background image is superimposed on at least a part of the characters or images formed by the first ink: [T&#x2212;T]&#x3c;0 mN/m (1); and [V&#x2212;V]&#x2265;1.0 mPa&#xb7;s (2) wherein Tis the static surface tension of the second ink; Tis the static surface tension of the first ink; Vis the viscosity of the second ink as measured at 32&#xb0; C.; and Vis the viscosity of the first ink as measured at 32&#xb0; C. According to the method of the present invention, it is possible to obtain good printed characters or images that are excellent in uniformity of solid image printing and suffer from less intercolor bleeding.

Inkjet recording method

The present invention relates to an ink-jet printing method that is capable of obtaining good printed characters or images which are free of occurrence of white lines or streaks irrespective of irradiation with an active energy ray. The present invention provides an ink-jet printing method including the steps of ejecting at least one ink A selected from the group consisting of a black ink and chromatic inks onto a low-liquid absorbing printing medium and then ejecting a white ink thereonto, in which the ink A contains at least one pigment selected from the group consisting of a black pigment and chromatic pigments, and a polymer dispersant containing a constitutional unit derived from a polyalkylene glycol (meth)acrylate; and the white ink contains titanium oxide and a polymer dispersant containing a constitutional unit derived from a polyalkylene glycol (meth)acrylate.

The present invention relates to an ink-jet printing method that is capable of obtaining good printed characters or images which are free of thermal deformation of a low-liquid absorbing printing medium as well as occurrence of mottling or color bleeding. The present invention provides an ink-jet printing method including the step of printing characters or images on a low-liquid absorbing printing medium using an ink-jet printing apparatus equipped with an ink-jet print head that is capable of ejecting water-based inks onto the low-liquid absorbing printing medium, in which the water-based inks each contain a colorant (A), an organic solvent (C) and water; the ink-jet printing apparatus is loaded with the two or more kinds of water-based inks which are different in static surface tension from each other; the printing medium is heated to a temperature of from 30 to 75&#xb0; C.; and the water-based inks are ejected in the sequential order from the water-based ink having a higher static surface tension.

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Wakayama, Japan

Azusa Kuroda