A magenta pigment dispersant can include a mixture of quinacridones including a first quinacridone including two nitrogen- and aromatic-containing pendant groups and a second quinacridone with one nitrogen- and aromatic-containing pendant group.

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This fine particle production method involves a dissolving step in which a stirrer having a rotating stirring blade is used to dissolve at least one type of fine particle raw material in a solvent to obtain a fine particle raw material solution, and a precipitation step in which the fine particle raw material solution and at least one type of precipitation solvent for precipitating the fine particle raw material from the fine particle raw material solution are introduced between at least two treatment surfaces which are arranged oppositely one another, can move closer to and farther apart from one another, and at least one of which can rotate relative to the other, and the fine particle raw material solution and the at least one type of precipitation solvent are mixed in a thin film fluid formed between the at least two treatment surfaces, and the fine particles are precipitated. The stirring energy is determined by the stirring time conditions of the stirrer, the circumferential velocity conditions of the stirring blade, and the temperature conditions of the fine particle raw material solution, and in the dissolving step, the stirring energy is varied by changing at least one of the aforementioned conditions, and by changing the stirring energy, the degree of crystallization and the crystal form of the fine particles obtained in the precipitation step are controlled.

Disclosed herein are compositions (e.g., pigment dispersions or ink compositions such as inkjet ink compositions) comprising at least one quinacridone magenta pigment and at least one synergist selected from compounds (A) and (B) having the following structures, wherein each n is an integer independently ranging from 1 to 4, and R.sub.1-R.sub.3 are each independently selected from H, CH.sub.3, Cl, and F, ##STR00001##

A method for producing an aqueous pigment dispersion liquid, including: a kneading step of kneading a mixture of a quinacridone pigment (a), a pigment derivative (b), an organic high-molecular compound having an anionic group (c), a basic compound (d), and an acetylene glycol surfactant (e) in a closed kneader to prepare a pigment-kneaded material having a solid content in the range of 50% to 80% by mass; and a step of diluting the pigment-kneaded material with an aqueous medium. A method for producing a water-based ink for ink jet recording, including a step of diluting the aqueous pigment dispersion liquid with an aqueous medium.

There is provided a technique for producing a quinacridone solid solution pigment, the technique making it possible to obtain a quinacridone solid solution pigment which produces a colored product having high chroma and a bluish hue, more preferably which has controlled particle diameters. Specifically, a method for producing a quinacridone solid solution pigment, the method including a crude quinacridone solid solution production step of subjecting a diarylaminoterepththalic acid and a dialkylarylaminoterephthalic acid to a co-cyclization reaction in polyphosphoric acid, thereby obtaining a water-containing crude quinacridone solid solution containing a solid solution of an unsubstituted quinacridone and a 2,9-dialkylquinacridone, the solid solution containing water, a drying step of drying the water-containing crude quinacridone solid solution to reduce the water content to less than 1% and obtain a powdery, crude quinacridone solid solution, and a pigmentation step of heating the powdery, crude quinacridone solid solution in a liquid medium that cannot dissolve the crude quinacridone solid solution.

There is provided a technique for producing a quinacridone solid solution pigment, the technique making it possible to obtain a quinacridone solid solution pigment which produces a colored product having high chroma and a bluish hue, more preferably which has controlled particle diameters. Specifically, a method for producing a quinacridone solid solution pigment, the method including a crude quinacridone solid solution production step of subjecting a diarylaminoterepththalic acid and a dialkylarylaminoterephthalic acid to a co-cyclization reaction in polyphosphoric acid, thereby obtaining a water-containing crude quinacridone solid solution containing a solid solution of an unsubstituted quinacridone and a 2,9-dialkylquinacridone, the solid solution containing water, a drying step of drying the water-containing crude quinacridone solid solution to reduce the water content to less than 1% and obtain a powdery, crude quinacridone solid solution, and a pigmentation step of heating the powdery, crude quinacridone solid solution in a liquid medium that cannot dissolve the crude quinacridone solid solution.

There is provided a technique for producing a quinacridone solid solution pigment, the technique making it possible to obtain a quinacridone solid solution pigment which produces a colored product having high chroma and a bluish hue, more preferably which has controlled particle diameters. Specifically, a method for producing a quinacridone solid solution pigment, the method including a crude quinacridone solid solution production step of subjecting a diarylaminoterepththalic acid and a dialkylarylaminoterephthalic acid to a co-cyclization reaction in polyphosphoric acid, thereby obtaining a water-containing crude quinacridone solid solution containing a solid solution of an unsubstituted quinacridone and a 2,9-dialkylquinacridone, the solid solution containing water, a drying step of drying the water-containing crude quinacridone solid solution to reduce the water content to less than 1% and obtain a powdery, crude quinacridone solid solution, and a pigmentation step of heating the powdery, crude quinacridone solid solution in a liquid medium that cannot dissolve the crude quinacridone solid solution.

An example of an inkjet ink composition includes a pigment, a dispersion synergist, a metal oxide, a polar solvent and water. The pigment is selected from the group consisting of a quinacridone and a phthalocyanine. The dispersion synergist has a structure of the pigment substituted with at least one solubilizing moiety selected from the group consisting of an ionic moiety, a non-ionic moiety, and a combination thereof.

A black inkjet ink composition includes a carbon black pigment; a dispersion synergist having an aromatic structure substituted with at least one solubilizing moiety selected from the group consisting of an ionic moiety, a non-ionic moiety, and a combination thereof; a polar solvent; and water. A method for making the black inkjet ink composition and a printing method using the same is also disclosed.

An object to be achieved by the present, invention is to provide a quinacridone pigment having hue that is yellowish and clear and having excellent storage stability, wherein the quinacridone pigment can be advantageously used in an ink-jet ink and the like. Provided is a quinacridone solid solution pigment comprising at least C. I. Pigment Violet 19 and C. I. Pigment Red 122, wherein the ratio of a diffraction peak intensity at a diffraction angle 2 of 14.80.2 to a diffraction peak intensity at a diffraction angle 2 of 11.90.2 is 1.20 or less, as measured by X-ray diffractometry with respect to the quinacridone solid solution pigment.