Kao Corporation

Daiki Kawata

Masashi Inoue

Hirotaka Takeno

Yuki Wakabayashi

Tomoaki Il

Inoue Masashi

Tomoaki Ii

The present invention relates to a water-based ink containing at least pigment-containing water-insoluble crosslinked polymer particles (A), a polymer emulsion (B) and water, in which a water-insoluble crosslinked polymer constituting the crosslinked polymer particles (A) is obtained by subjecting a polymer that contains a constitutional unit derived from a carboxylic acid monomer having an acid value of not less than 200 mgKOH/g and a constitutional unit derived from a hydrophobic monomer, to crosslinking reaction with an epoxy compound, and a polymer constituting the polymer emulsion (B) contains a constitutional unit derived from a carboxylic acid monomer and a constitutional unit derived from a hydrophobic monomer. The water-based ink of the present invention is excellent in ejection stability and fastness of the printed characters or images while maintaining good optical density.

Aqueous ink

The present invention relates to [1] a water-based ink containing water-insoluble polymer particles (A), an organic solvent (B) and water, in which a polymer constituting the water-insoluble polymer particles (A) is in the form of a crosslinked polymer; the organic solvent (B) contains a polyhydric alcohol ether; and a rate of change in viscosity of the organic solvent (B) as calculated according to the formula (1) is not more than 140%, and [2] a printing method of printing characters or images on a printing medium using the water-based ink described in the above [1], in which a water absorption of the printing medium per a unit surface area thereof as measured by contacting the printing medium with pure water for 100 milliseconds is not less than 0 g/mand not more than 10 g/m.

The present invention provides a water-based ink for ink-jet printing which is excellent in ejection stability and storage stability, in particular, excellent in quick-drying fixing properties and image uniformity when printing characters or images on a low-water absorbing recording medium, and an image forming method using the water-based ink. The present invention relates to [1] a water-based ink for ink-jet printing, including a pigment, a water-insoluble polymer, an organic solvent (C) and water, in which the organic solvent (C) includes diethylene glycol isopropyl ether (DEGPE) and an organic solvent (c2) having a 1-octanol/water partition coefficient that is smaller than that of DEGPE; a total content of the pigment, the water-insoluble polymer and DEGPE in the water-based ink is not less than 5.0% by mass; and a value obtained by multiplying a total content of the pigment and the water-insoluble polymer in the water-based ink by a content of DEGPE in the water-based ink is from 10 and 300; and [2] an image forming method including the steps of mounting a container filled with the water-based ink to an ink-jet printing apparatus equipped with an ink ejecting means; and ejecting the ink onto a recording medium having a water absorption of from 0 to 10 g/mas measured by contacting with pure water for 100 ms to print characters or images thereon.

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Wakayama, Japan

Daiki Kawata