Dic Corporation

Dainippon Ink and Chemicals, Incorporated

Tomoyuki Uezono

Satoshi Idemura

Kenji Sugo

A production method of an aqueous pigment dispersion liquid of the present invention includes: a kneading step of kneading a mixture including (a) C. I. pigment violet 23, (b) a styrene-acrylic acid-based copolymer with an acid value of 50 to 300 mgKOH/g, (c) an alkali metal hydroxide, (d) water, and (e) a wetting agent, thereby producing a colored, kneaded material; and a dispersion step of dispersing the pigmented, kneaded material in an aqueous medium by using a dispersing machine with media, wherein the mass ratio of (b)/(a) in the kneading step is within a range of 0.15 to 0.45, the mass ratio of (d)/(a) in the first half of the kneading step is within a range of 0.04 to 0.42, and the change in viscosity of materials to be dispersed in the dispersion step is 10% or lower.

Aqueous pigment dispersion liquid and ink-jet recording ink

The present invention is to provide an orange ink composition for inkjet recording high in color saturation and gloss, while having long storage stability and jet stability, and also to provide an aqueous pigment dispersion mainly composing the ink composition. The aqueous pigment dispersion which contains a styrene-acrylic acid copolymer containing 60% by mass or more of styrene-based monomer units with respect to total monomer components and having an acid value of 130 to 200 and a weight-average molecular weight of 6,000 to 40,000, an alkali metal hydroxide, a wetting agent and C. I. Pigment Red 168 is excellent in storage stability and high in gloss. Further, an ink composition for inkjet recording mainly composing the aqueous pigment dispersion reflects an excellent dispersibility of the aqueous pigment dispersion, thereby having a favorable jettability and excellent light fastness.

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Ageo, Japan

Tomoyuki Uezono