Orient Chemical Industries, Ltd.

Toshiyuki Nagasawa

Sohko Itoh

Tetsuji Kihara

Kazuo Goda

Nobuyuki Murai

Yoichi Ueda

Aiko Okamura

Disclosed is an aqueous pigment ink composition comprising at least water and carbon black, wherein a surface oxygen content of said carbon black is not less than 0.07 in atom-numeral ratio based on carbon atom measured by an X-ray photoelectron spectroscopic method, and a combined value of a surface carboxyl group carbon content and a surface hydroxyl group carbon content of said carbon black, the both being measured by an X-ray photoelectron spectroscopic method, is not less than 0.5%. The aqueous pigment ink composition realizes smooth printing with an ink jet nozzle, and smooth writing with a fine pen tip and it has sufficient density. Further, the recorded traces obtained by using the ink composition is excellent in water resistance.

Aqueous pigment ink composition

The present invention provides an aqueous black ink composition for a writing board which hardly causes thickening, coagulation of the pigment, decreasing of writing density due to sedimentation, clogging in a penpoint, and break in writing. The aqueous black ink composition comprises water, the oxidized carbon black obtained by oxidizing carbon black using hypohalogenous acid and/or salt thereof, a film forming agent, and a release agent.

Aqueous black ink composition for writing board

An aqueous pigment ink composition comprising an oxidized carbon black obtained by wet-oxidation of a carbon black using a hypohalous acid and/or salt thereof, and a water-soluble cationic polymer or oligomer in an aqueous medium. The aqueous pigment ink composition of the present invention does not cause clogging in a nozzle when used for ink jet recording, enables smooth writing from a narrow pen tip, and provides a recorded image excellent in water resistance and light resistance and excellent in density and hue.

Disclosed is an aqueous pigment ink composition comprising water and oxidized carbon black dispersed stably in the water, wherein said oxidized carbon black is obtained by oxidizing carbon black using hypohalous acid and/or salt thereof and wherein at least a part of an acidic group existing on the surface of said oxidized carbon black associates with an amine compound to form an ammonium salt. The aqueous pigment ink composition realizes smooth printing with ink jet nozzle, and smooth writing with fine pen tip and it has sufficient density. Further, the recorded traces obtained by using the ink composition is excellent in water resistance.

The present invention provides a process for producing aqueous pigment ink which forms a black matrix having high optical density, excellent flatness of a film and low conductivity, and imparts high resolution power to a color filter. The process comprises the steps of:

Process of producing aqueous pigment ink

Water-based pigment ink having high concentration which provides excellent jetting stability when using for ink-jet printer and provides excellent writing stability when using for fine-point pen was provided. The water-based pigment ink comprises water and carbon black, wherein said carbon black has a surface active hydrogen content of not less than 1.5 mmol/g.

Water-based pigment ink and process for producing the same

A writing board ink composition comprises a medium formed of a lower alcohol solvent which contains an alcohol-soluble polymer, a scraping (erasing) agent, a surfactant and a diketopyrrolopyrrole pigment having a median Stokes diameter (ultrafine particle size) of not more than 0.2 .mu.m and represented by the following formula ##STR1## R.sup.1 and R.sup.2 independently represent an unsubstituted phenyl or naphthyl group of a non-water-solubilizing substituent substituted phenyl or naphthyl group, and R.sup.3 and R.sup.4 independently represent hydrogen or a non-water-solubilizing substituent. The writing board ink composition remains stable for a long time while in pens even when the resin content (alcohol-soluble polymer) is such that unclear writing and scrapability reduction (loss of scrapability or erasability) can be avoided, since the pigment of ultrafine particle size is fast to lower alcohol solvents.

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Yawata, Japan

Toshiyuki Nagasawa