JP4835896B2 - Aqueous pigment dispersion for inkjet ink and inkjet ink composition - Google Patents

Description

  The present invention relates to an aqueous dispersion of an organic pigment and an inkjet ink composition using the same.

Conventionally, an ink-jet ink in which a color material is dissolved or dispersed in a liquid medium containing water as a main component has been used. In these inks, when the coloring material is a dye, water resistance and light resistance after printing are difficult, and it is difficult to apply to outdoor use.
On the other hand, an ink composition using a colorant as a pigment having excellent light resistance is widely used in black ink using carbon black.

However, in order to form a multicolor image by using an aqueous ink composition in which an organic pigment, particularly a chromatic organic pigment is dispersed, for inkjet recording, the coloring power of the inkjet ink is good. It is important to have a hue that forms an image with good color reproducibility in combination with inks of different colors, and various pigments having different hues have been studied for inkjet recording.
Pigment Yellow 3, 12, 13, 14, 17, 24, 34, 35, 37, 42, 53, 55, 74, 81, 83, 95, 97, 98, 100, 101, yellow inkjet ink Many pigments are being studied, including 104, 108, 109, 110, 117, 120, 138, 147, 151, 153, 180, 181. However, not many ink jet inks can be used favorably.

The water-based inkjet ink composition in which these yellow organic pigments are dispersed has the advantage that the pigment is finely crushed and the coarseness that causes the ejection failure of the inkjet in order to obtain the practicality equivalent to or higher than that of the dye ink. There is no need for particles to be present in the ink, and long-term ejection stability and storage stability similar to those of dye-based inks are required. However, in normal applications, even if it is a yellow pigment having excellent hue and coloring power and no problem in use, when used as an inkjet ink, dispersibility, storage stability and ejection stability are insufficient. Therefore, there are many cases where it cannot be used.
In addition, since many yellow pigments tend to cause a decrease in light resistance, the optimum pigment cannot always be determined only from the hue immediately after image formation. Further, depending on the pigment, the primary particles become large due to crystal growth during synthesis, and the transparency of color development is deteriorated or the ink ejection property is deteriorated. For this reason, depending on the pigment used, it is necessary to consider the use of a dispersion aid in the ink composition (see Patent Document 1, Patent Document 2, Patent Document 3, and Patent Document 4).

Thus, in a yellow inkjet ink composition, it is extremely difficult to select a yellow pigment that completely satisfies all of coloring power, hue, light resistance, storage stability, and the like, and a good balance of properties among the above properties. It is used for inkjet inks by selecting pigments and compensating for defects with ink blending and manufacturing methods.
For example, C.I. I. Pigment Yellow 74 has been reported to improve light resistance by adding a styrene (meth) acrylic acid-based water-soluble resin (see Patent Document 5).
For example, C.I. I. Pigment Yellow 128 is used in combination with Pigment Yellow 110 and has a wide range of color reproducibility (see Patent Document 6).
For example, C.I. I. Pigment Yellow 93 is used together with a styrene acrylic acid copolymer and an acetylene glycol compound to improve ejection properties and storage stability (see Patent Document 7).


Among these properties, dispersibility and storage stability are particularly important because they directly affect ink ejection and storage stability at a high pigment concentration is necessary for good color reproducibility.

For this reason, various dispersants and dispersion methods have been studied in order to improve the dispersibility and storage stability of the aqueous pigment dispersion.
For example, terpolymers of acrylic acid, styrene, and α-methylstyrene are used to improve the stable discharge from inkjet ink nozzles containing azo organic pigments and improve the water resistance of printed images (Patent Literature). 8).
For example, it is described that 0.01 to 5% by weight of a polymer having a carboxyl group having an acid value of 50 to 700 or a polymer having a carboxyl group salt is contained, and styrene-maleic anhydride, styrene-anhydride A hydrolyzate of maleic acid or a salt or ester thereof is used (see Patent Document 9).
For example, a solid kneaded material is prepared by kneading a high viscosity together with a pigment, a basic compound, a resin, and a wetting agent using a styrene acrylic resin, and an aqueous pigment dispersion for an inkjet recording ink composition having good storage stability. As the styrene acrylic resin, those having a monomer composition ratio of styrene / methacrylic acid / acrylic acid = 77/13/10 (mass ratio) and a mass average molecular weight of 3000 to 50000 are used (Patent Literature). 10).

In order to realize the storage stability and ejection stability equivalent to dye inks while taking advantage of the pigment's coloring power and water resistance, first select a yellow pigment with a well-balanced characteristic and optimal dispersion for the pigment. It is important to give excellent dispersibility and storage stability by combining the resins.
However, many resin dispersants, including the above, only describe the general theory of resins as dispersants that can be used in inkjet inks and aqueous pigment dispersions, and each resin dispersant is applied to yellow pigments. There is no suggestion about the selection of the optimal yellow pigment.
By selecting the optimal combination of yellow pigment and resin dispersant and optimizing the composition, molecular weight, blending, etc. of the resin dispersant for the applied pigment, it is a yellow aqueous solution with extremely excellent storage stability and dispersibility. Pigment dispersions can be made. However, such a detailed examination has not yet been made for each yellow pigment, and a well-balanced aqueous pigment dispersion having excellent dispersibility and storage stability while satisfying coloring power, light resistance, and color reproducibility. Is desired.
In particular, aqueous pigment dispersions used for thermal jet ink jet inks preferably have excellent storage stability during high-temperature storage, but such excellent storage stability while satisfying coloring power, light resistance, and color reproducibility. No yellow ink-jet ink composition exhibiting properties has been found.
JP-A-10-158555 JP 2001-98200 A Japanese Patent Laid-Open No. 7-126546 JP 2003-253188 A JP-A-11-199811 JP 2001-81369 A JP 2002-226738 A JP-A-8-253716 JP-A-9-157564 Japanese Patent Laid-Open No. 2003-226832

  An object of the present invention is an aqueous pigment dispersion using a yellow pigment, which has good dispersibility and storage stability, and has a good balance of coloring power, light resistance, water resistance, and discharge stability. It is to provide an aqueous pigment dispersion capable of forming an inkjet ink. Furthermore, an object of the present invention is to provide an aqueous pigment dispersion capable of forming a thermal jet type ink-jet ink having the above-mentioned various performances, good storage stability at high temperatures, and good ejection stability.

The inventors studied suitable combinations of yellow pigments and dispersion resins, and further, among the physical properties and compounding compositions of the dispersion resins, factors that are the main factors for the properties to be realized of inkjet inks and aqueous pigment dispersions. The inventors of the present invention have reached the present invention after elucidating them and conducting studies to optimize them.
The present invention relates to C.I. I. An aqueous pigment dispersion for inkjet inks containing Pigment Yellow 74, a styrene acrylic resin having an acid value of 100 to 250, and a basic compound,
The styrene acrylic resin contains at least a styrene monomer unit, an acrylic acid monomer unit, and a methacrylic acid monomer unit as its constituent monomer units, and the ratio of the styrene monomer units to the total amount of all monomer units is 50% by mass or more. And the sum of styrene monomer units, acrylic acid monomer units and methacrylic acid monomer units is 95% by mass or more based on the total amount of all monomer units, and the weight average molecular weight of the resin is 7,000 to 15,000. An aqueous pigment dispersion for ink-jet inks is provided.

The aqueous pigment dispersion of the present invention has a good coloring power and color reproducibility. I. By using a combination of Pigment Yellow 74 and a styrene acrylic resin having an acid value of 100 to 250 and adding a basic compound thereto, dispersibility and storage stability are achieved while taking advantage of the coloring power and color reproducibility of the pigment. A water-based pigment dispersion having a good property balance capable of producing an ink-jet ink having excellent properties and light resistance was able to be produced. Since the monomer selection of the styrene acrylic resin and the composition of the styrene acrylic resin have been optimized for Pigment Yellow 74, the storage stability of the aqueous pigment dispersion is extremely good and the storage stability during high-temperature storage is also excellent. A good thermal jet type ink-jet ink can be produced.
That is, since the styrene acrylic resin has a high content of hydrophobic styrene monomer, it adsorbs well on the pigment surface of Pigment Yellow 74 and coats the pigment surface to prevent an increase in the particle size of the pigment which tends to aggregate. At the same time, the styrene acrylic resin imparted with the dispersibility by the addition of the basic compound is uniformly dispersed in the aqueous medium while including the pigment. The inventors have optimized the balance of the hydrophobic component and the hydrophilic component of the styrene acrylic resin with respect to Pigment Yellow 74 to obtain an aqueous pigment dispersion having good coloring power, dispersibility, and storage stability. It was. It was confirmed that the ink-jet ink containing the aqueous pigment dispersion as a main component has good water resistance due to a large amount of the styrene-based monomer and also has an effect of increasing the printing density at the same time.

  Furthermore, the present invention provides an inkjet ink composition containing the aqueous pigment dispersion for inkjet ink as a main component.

  The aqueous pigment dispersion of the present invention is excellent in storage stability, and the ink jet ink mainly composed of the aqueous pigment dispersion has a good balance of properties, and is excellent in storage stability, ejection stability, light resistance, and coloring power. In addition, by using the ink composition, it is possible to print a high-quality image having excellent water resistance with little bleeding on plain paper or the like. Furthermore, stable ejection can be obtained even when used in a thermal jet printer.

  Hereinafter, the aqueous pigment dispersion of the present invention and the inkjet ink composition using the same will be described in detail.

C.I. which is a yellow pigment used in the present invention. I. Pigment Yellow 74 is excellent in the hue balance of high transparency and secondary color tone as a process color emphasized during full color printing, and can be used as a suitable yellow pigment for inkjet ink compositions.
C. I. Pigment Yellow 74 can be used in the pigment dispersion of the present invention regardless of the form of dry powder, granule, paste, water-containing slurry, etc. In order to affect the dispersion state of the liquid, the volume average particle size in the aqueous pigment dispersion is preferably 0.5 μm or less, and more preferably 0.2 μm or less.

If the dispersibility, storage stability and clearness of hue are not impaired, C.I. I. Other pigments can be used in combination with Pigment Yellow 74. Examples of pigments that can be used in combination include various azo lake pigments, insoluble monoazo pigments, insoluble disazo pigments, condensed azo pigments and other azo pigments, anthraquinone pigments, thioindigo pigments, perinone pigments, perylene pigments, quinacridone pigments, isoindolinone pigments, and quinophthalone pigments. In addition, condensed polycyclic pigments such as isoindolinone pigments can be used.
In selecting the type of pigment, there is a demand for color tone and the like, and the pigment is not necessarily limited to the examples given here.

The styrene acrylic resin used in the aqueous pigment dispersion of the present invention contains a styrene monomer unit, an acrylic acid monomer unit, and a methacrylic acid monomer unit as essential components. Furthermore, the ratio of the styrene monomer unit included as an essential component to the total amount of all monomer units must be 50% by mass or more, and the total of the styrene monomer unit, the acrylic acid monomer unit, and the methacrylic acid monomer unit is the total monomer unit. It is necessary to be 95% by mass or more based on the total amount.
The styrene acrylic resin used in the aqueous pigment dispersion of the present invention has a good adsorptivity to the hydrophobic pigment surface because the ratio of the styrene monomer units to the total amount of all monomer units is 50% by mass or more. C. is a pigment. I. It can be effectively adsorbed on the surface of Pigment Yellow 74. If it is less than 50% by mass, the adsorption to the pigment surface tends to be insufficient, and the storage stability of the aqueous pigment dispersion tends to be lowered. In addition, there is a tendency that the image recording density of the inkjet ink prepared from the aqueous pigment dispersion when printing on paper such as plain paper is lowered, and the print quality is likely to be lowered. Furthermore, the water resistance of the inkjet ink tends to decrease. Further, the total content of the styrene monomer units is further increased by increasing the total content of the styrene monomer units by making the total of the styrene monomer units, acrylic acid monomer units, and methacrylic acid monomer units 95% by mass or more based on the total amount of all monomer units, Since the acid value of 250 can be secured, the dispersibility is further improved.

Examples of the styrene monomer unit include alkyl styrene such as styrene, α-methyl styrene, β-methyl styrene, 2,4-dimethyl styrene, α-ethyl styrene, α-butyl styrene, α-hexyl styrene, 4-chloro Examples thereof include halogenated styrene such as styrene and 3-bromostyrene, and further 3-nitrostyrene, 4-methoxystyrene, vinyltoluene and the like, and styrene is preferable.
The styrene acrylic resin used in the aqueous pigment dispersion of the present invention includes various derivatives having a vinyl group copolymerized with the styrene monomer and the (meth) acrylic acid monomer in addition to the styrene monomer and the (meth) acrylic acid monomer. Can be used in combination.

The various derivatives having vinyl groups that can be used include methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, stearyl acrylate. Benzyl acrylate, p-tolyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate , Octyl methacrylate, stearyl methacrylate, benzyl methacrylate, p-tolyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, cyclohexyl methacrylate, dimethyl maleate, male Monoethyl acid, diethyl maleate, di-n-butyl maleate, bis (2-ethylhexyl) maleate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl hexanoate, vinyl benzoate, vinyl stearate, vinyl acrylate, Unsaturated esters such as vinyl methacrylate, allyl acetate, allyl propionate, allyl n-butyrate, allyl heptanoate, allyl phenoxyacetate, allyl methacrylate; acrylamide, N, N-dimethylacrylamide, N-isopropylacrylamide, Unsaturated amides such as Nt-butylacrylamide, N- (butoxymethyl) acrylamide, methacrylamide, N-[(3-dimethylamino) propyl] methacrylamide; acrylonitrile, methacrylonitrile, 3-hydroxypropiyl Unsaturated tolyls such as nitriles; unsaturated ethers such as ethyl vinyl ether, propyl vinyl ether, n-butyl vinyl ether, t-butyl vinyl ether, cyclohexyl vinyl ether, 2-ethylhexyl vinyl ether, ethylene glycol vinyl ether, di (ethylene glycol) divinyl ether And heterocyclic vinyl compounds such as 2-vinylpyridine, 4-vinylpyridine, N-vinylcarbazole, N-vinylpyrrolidone, and the like. The selection of copolymerizable monomer components is not necessarily limited to the examples given here.
Here, the (meth) acrylic acid monomer includes an acrylic acid monomer and a methacrylic acid monomer.

In the composition of the styrene acrylic resin, the styrene monomer unit is preferably in the range of 60 to 90% by mass, more preferably 70 to 80% by mass.
Furthermore, the total of hydrophilic monomer units other than acrylic acid and methacrylic acid is preferably 2% by mass or less of the total amount of all monomer units, and most preferably does not contain substantially. Here, “substantially free of hydrophilic monomer” means that the amount is much less than the amount that affects the properties of the copolymer resin by the hydrophilic monomer, and indicates about 0.5% by mass or less. And
As the hydrophilic monomer whose use is limited for the styrene acrylic resin of the present invention, a hydrophilic substituent such as a hydroxyl group, a sulfone group, an amino group, a quaternary ammonium group or the like is included in the chemical structure of the monomer. In addition, those containing repeating units of ethylene oxide and propylene oxide can be mentioned. The resin substantially free of these hydrophilic monomers further improves the water resistance of the inkjet printed image immediately after printing.

The styrene acrylic resin used in the aqueous pigment dispersion of the present invention is produced by copolymerization by using the above monomer units in a lump or divided. For the synthesis of the resin, known methods such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method, and an emulsion polymerization method can be employed.
More specifically, for example, in the solution polymerization method, a monomer component is mixed in various solvents as necessary, a compound such as a radical reaction initiator is added, and the reaction temperature is controlled, whereby a resin by copolymerization is obtained. Can be manufactured. The reaction is usually performed at a temperature of 20 to 100 ° C. for 1 to 10 hours under an inert gas atmosphere as necessary. In addition to the solvents, monomer species and initiator species to be used, depending on the polymerization degree of the resin. Reaction conditions are selected. After the polymerization reaction, it can be concentrated and isolated from the reaction solution by reprecipitation, solvent distillation or the like.

The molecular weight of the resin is an important factor for the inkjet application of the present invention, and a weight average molecular weight of 7,000 to 15,000 is selected. This is because C.I. I. When Pigment Yellow is used for the pigment, if the molecular weight exceeds 15,000, the viscosity at the time of preparation of the aqueous pigment dispersion tends to be high, which tends to affect the ejection of inkjet ink, particularly thermal inkjet ejection. Because. This is because if the molecular weight is less than 7,000, the dispersion stability of the target pigment particles tends to decrease.
Here, the weight average molecular weight is a value measured by a GPC (gel permeation chromatography) method, and is a value converted to a molecular weight of polystyrene used as a standard substance. The weight average molecular weight of the resin used in the present invention was measured by the following apparatus and conditions.
Liquid delivery pump: Shimadzu Corporation brand name “LC-9A”, System controller: Shimadzu Corporation brand name “SIL-6B”, Autoinjector: Shimadzu Corporation brand name “SIL-6B”, detector: Shimadzu Product name “RID-6A” manufactured by Seisakusho Co., Ltd. Data processing software: Product name “Sic480II Data Station” manufactured by System Instruments. Column: Hitachi Chemical Co., Ltd., trade name “GL-R400 (guard column)” + “GL-R440” + “GL-R450” + “GL-R400M”, elution solvent: THF, elution volume: 2 ml / min, column Temperature: 35 ° C.

  The acid value of the resin of the present invention is 100 to 250, preferably 100 to 200. This is because when the acid value is set higher than 250, C.I. I. Since the amount of the hydrophobic component that is preferentially adsorbed on the surface of Pigment Yellow 74 is reduced, the resin coating with the styrene acrylic resin is difficult to be performed, and the dispersibility of the aqueous pigment dispersion tends to be reduced. If it is set lower, the effect of improving the dispersibility due to neutralization by the acid value base component is diminished, so that the dispersibility of the aqueous pigment dispersion also tends to decrease.

  The glass transition point of the aqueous pigment dispersion of the present invention is preferably 90 ° C. or higher, and more preferably in the range of 100 to 150 ° C. A temperature of 90 ° C. or higher is preferable because it is easy to obtain a good balance between ejection stability, storage stability, and print quality. It is particularly suitable when used as a thermal jet type ink jet ink.

  In the aqueous pigment dispersion liquid of the present invention, C.I. I. Although the dispersibility and storage stability of Pigment Yellow 74 are improved, the following general formula (1) or (2)

（１）
（式中、Ｒ１、Ｒ２、Ｒ３は各々独立的に、水素原子、メチル基、メトキシ基、エトキシ基、クロル基を表し、Ｒ４はメチル基またはメトキシ基を表す。）

(1)
(Wherein R1, R2, and R3 each independently represents a hydrogen atom, a methyl group, a methoxy group, an ethoxy group, or a chloro group, and R4 represents a methyl group or a methoxy group.)

（２）
（式中、Ｒ１、Ｒ２、Ｒ３は各々独立的に、水素原子、メチル基、メトキシ基、エトキシ
基、クロル基を表し、Ｒ５およびＲ６は各々独立的に水素原子、メチル基、エチル基、メトキシ基、エトキシ基、水酸基を表し、Ｒ７およびＲ８は、 −ＮＨ−Ｙ−ＳＯ_３Ｈで表される基または水酸基を表し、Ｒ７とＲ８のうち少なくとも一方は−ＮＨ−Ｙ−ＳＯ_３Ｈで表される基であり、Ｙはエチレン基、フェニレン基、ナフタレン基を表し、Ｚは下記一般式（３）

(2)
(Wherein R1, R2, and R3 each independently represent a hydrogen atom, a methyl group, a methoxy group, an ethoxy group, or a chloro group, and R5 and R6 each independently represent a hydrogen atom, a methyl group, an ethyl group, or a methoxy group) group, an ethoxy group, a hydroxyl group, tables in R7 and R8, -NH-Y-SO represents a group or a hydroxy group represented by ₃ H, at least one of the R7 and R8 -NH-Y-SO ₃ H Y represents an ethylene group, a phenylene group, or a naphthalene group, and Z represents the following general formula (3)

（３）
で示される２価の連結基の一つを表す。）
で表される、スルホン酸基含有アセト酢酸アリールアミド系モノアゾ化合物を分散助剤として用いることが好ましい。前記化合物はＣ．Ｉ．ピグメントイエロー７４と同様のアセト酢酸アリールアミド構造を有しており、イエロー７４への吸着性が良好で、かつイオン性の置換基であるスルホン酸基の親水性により水性顔料分散液の安定性を向上させる。

(3)
1 represents a divalent linking group represented by )
It is preferable to use a sulfonic acid group-containing acetoacetic acid arylamide monoazo compound represented by The compound is C.I. I. It has the same acetoacetic acid arylamide structure as CI Pigment Yellow 74, has good adsorptivity to Yellow 74, and the hydrophilicity of the sulfonic acid group that is an ionic substituent improves the stability of the aqueous pigment dispersion. Improve.

  These sulfonic acid group-containing acetoacetic acid arylamide-based azo compounds introduce a sulfone group by acting a sulfonating agent such as fuming sulfuric acid, concentrated sulfuric acid, chlorosulfuric acid or the like on the base skeleton compound, or a base having a sulfone group is diazonium. After forming a salt, it can be synthesized by a diazo coupling reaction with an acetoacetic acid arylamide coupler. In any method, when a sulfonic acid group-containing acetoacetic acid arylamide azo compound is obtained by synthesis, it is preferable that by-products and unreacted substances are reduced by adjusting reaction conditions. These can be removed by refining to the extent that they do not significantly affect the properties of the aqueous pigment dispersion of the present invention. However, from the viewpoint of ease of operation and cost, there is a method through a diazo coupling reaction with a base having a sulfone group. preferable.

  As the sulfonic acid group-containing acetoacetic acid arylamide azo compound of the present invention, those represented by the above general formula (1) or (2) can be used, but the following general formula (7)

（７）
（式中、Ｒ１、Ｒ２、Ｒ３は各々独立的に、水素原子、メチル基、メトキシ基、エトキシ基、クロル基を表す。）
の化合物を用いることが好ましい。
特にＲ１がオルトメトキシ基、Ｒ２、Ｒ３が水素原子である場合、水性顔料分散液から調製されたインクジェットインクの普通紙上の濃度と耐久性において優れた性能が発揮される。

(7)
(In the formula, R1, R2, and R3 each independently represent a hydrogen atom, a methyl group, a methoxy group, an ethoxy group, or a chloro group.)
It is preferable to use this compound.
In particular, when R1 is an orthomethoxy group and R2 and R3 are hydrogen atoms, excellent performance is exhibited in the density and durability of the inkjet ink prepared from the aqueous pigment dispersion on plain paper.

  The amount of the sulfonic acid group-containing acetoacetic acid arylamide azo compound of the present invention is C.I. I. It is preferable to use it as a small component with respect to CI Pigment Yellow 74. I. Printed matter of inkjet ink prepared from the aqueous pigment dispersion of the present invention that the mass ratio of CI Pigment Yellow 74 and the sulfonic acid group-containing acetoacetic acid arylamide azo compound is in the range of 80:20 to 99: 1 From the viewpoint of the hue, color development, and stability of the accelerated deterioration test in a heating environment.

  C. I. Mass ratio of CI Pigment Yellow 74 to sulfonic acid group-containing acetoacetic acid arylamide azo compound, (Yellow 74 / azo compound) is less than 80/20, and ratio of sulfonic acid group-containing acetoacetic acid arylamide azo compound Increases, the C.I. I. Pigment Yellow 74 tends to interfere with color development, (Yellow 74 / Azo compound) is greater than 99/1, and is prepared from an aqueous pigment dispersion when the proportion of sulfonic acid group-containing acetoacetic arylamide azo compound is reduced. It is difficult to recognize the effect on the stability of the accelerated deterioration test under the heating environment of the inkjet ink.

（４）
（式中Ｒ４はメチル基またはメトキシ基を表す。）
で表される一般式（１）のベース及び／又は一般式（５）

（５）
（式中Ｒ５およびＲ６は各々独立的に水素原子、メチル基、エチル基、メトキシ基、エトキシ基、水酸基を表し、Ｒ７とＲ８のうち少なくとも一方は−ＮＨ−Ｙ−ＳＯ３Ｈで表される基であり、Ｙはエチレン基、フェニレン基、ナフタレン基を表し、Ｚは上記一般式（３）で示される２価の連結基の一つを表す。）
で表される一般式（２）のベースによって構成されるジアゾニウム塩と化学式（６）

（６）
で示されるカップラーを用いて行われることが好ましい。 When the sulfonic acid group-containing acetoacetic acid arylamide azo compound of the present invention is synthesized by a diazo coupling reaction, C.I. I. In the same system as the synthesis of Pigment Yellow 74, C.I. I. The diazo coupling reaction can be performed simultaneously with the diazo coupling reaction of CI Pigment Yellow 74. For example, a sulfonic acid group-containing acetoacetic acid arylamide azo compound can be prepared by carrying out mixed coupling with a sulfonic acid group-containing base during the synthesis of an azo pigment by an azo coupling reaction.
In this way, C.I. I. Since the same coupler as used in the synthesis of Pigment Yellow 74 is used, the affinity between the sulfonic acid group-containing acetoacetic acid arylamide compound and the pigment is high, and the effect of improving the pigment dispersion stability is great.
In the mixed coupling of the present invention, the C.I. I. Pigment Yellow 74 and a sulfonic acid group-containing acetoacetic acid arylamide azo compound were synthesized from 4-nitro-o-anisidine and general formula (4).

(4)
(Wherein R4 represents a methyl group or a methoxy group.)
Base of general formula (1) and / or general formula (5)

(5)
(Wherein R5 and R6 each independently represents a hydrogen atom, a methyl group, an ethyl group, a methoxy group, an ethoxy group, or a hydroxyl group, and at least one of R7 and R8 is a group represented by -NH-Y-SO3H. Y represents an ethylene group, a phenylene group, or a naphthalene group, and Z represents one of the divalent linking groups represented by the general formula (3).
A diazonium salt constituted by the base of the general formula (2) represented by the chemical formula (6)

(6)
It is preferable to carry out using the coupler shown by these.

  In the present invention, the C.I. I. When Pigment Yellow 74 and a sulfonic acid group-containing acetoacetic acid arylamide azo compound are synthesized in the same system, each compound is used in a mixed state as an azo pigment composition, and each needs to be isolated separately. There is no. In this case, C.I. I. The mass ratio between CI Pigment Yellow 74 and the sulfonic acid group-containing acetoacetic acid arylamide-based azo compound can be considered as the mass ratio of the present invention, with the theoretical amount generated by each synthesis.

  C. of the present invention. I. The ratio of the coloring material containing CI Pigment Yellow 74 and the sulfonic acid group-containing acetoacetic acid arylamide azo compound to the styrene acrylic resin used as the dispersant is preferably coloring material / resin = 1 / 0.1 to 1 / It is preferable to select from the range of 2. Furthermore, it is more preferable that the color material / resin is in the range of 1 / 0.1 to 1/1 in order to sufficiently exhibit the coloring ability of the color material.

Since the resin used in the aqueous pigment dispersion of the present invention contains a carboxyl group derived from acrylic acid and methacrylic acid, stable dispersion in water can be obtained by neutralization with a basic compound.
Examples of basic compounds used for such purposes include alkali metal hydroxides and low molecular organic amine compounds. In particular, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and alcohol amines such as triethanolamine, diethanolamine, and methyldiethanolamine can be dispersed and stored stably when an aqueous pigment dispersion is prepared into an inkjet ink. In view of the decap characteristics of the ink jet printer, the water resistance of the printed matter, and the like. Among these basic compounds, alkali metal hydroxides typified by potassium hydroxide and sodium hydroxide are particularly preferable from the viewpoint of ejection stability of the inkjet ink because they contribute to lowering the viscosity of the pigment dispersion.

  When performing neutralization with a basic component, it is preferable to use a basic component having a neutralization rate of 50 to 130% with respect to the acid value of the styrene acrylic resin of the present invention. Use of a basic component having a sum ratio is more preferable from the viewpoint of pH control of the pigment dispersion and the inkjet ink composition using the pigment dispersion.

In the present invention, the neutralization rate is a numerical value represented by the following formula.
Neutralization rate (%) = ((mass of basic compound (g) × 56 × 1000) / (resin acid value × equivalent of basic compound × resin amount (g))) × 100

In order to produce the aqueous pigment dispersion of the present invention, the C.I. I. Pigment Yellow A mixture containing the styrene acrylic resin, the basic compound, and water is prepared, and dispersion is performed with a dispersing device to prepare an aqueous dispersion.
As a method for dispersing the pigment, a known dispersing device can be used. Examples thereof include an ultrasonic homogenizer, a paint shaker, a ball mill, a sand mill, a sand grinder, a dyno mill, a disper mat, an SC mill, a spike mill, and a nanomizer. In the case of using a medium as a disperser, beads for grinding such as glass, zirconia, alumina, and plastic can be used.

In the step of dispersing the pigment, a water-soluble organic solvent may be added as necessary. Examples of such water-soluble organic solvents include, for example, methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, isobutyl alcohol, etc. 4 alkyl alcohols; amides of dimethylformamide and dimethylacetamide; ketones or ketoalcohols such as acetone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane; N-methyl-2pyrrolidone and 1,3 dimethyl-2 -Nitrogen-containing heterocyclic ketones such as imidazodinone; polyalkylene glycols such as polyethylene glycol and polypropylene glycol; ethylene glycol, propylene glycol, butylene glycol, triethylene glycol Alkylene glycols containing 2 to 6 carbons in alkylene groups such as coal, 1,2,6 hexanetriol, thiodiglycol, hexylene glycol, diethylene glycol, etc .; glycerin; ethylene glycol methyl ether, diethylene glycol (ethyl) methyl ether And lower alcohol ethers of polyhydric alcohols such as triethylene glycol (ethyl) methyl ethers.
These wetting agents can be used alone or in combination of two or more. These humectants also serve as humectants and anti-drying agents in aqueous pigment dispersions and inkjet inks. Therefore, they have a high boiling point, low volatility, high surface tension, and a boiling point of 170 ° C. or higher, more preferably 200 ° C. or higher. Polyhydric alcohols that are liquid at room temperature are preferred, and glycols such as diethylene glycol and triethylene glycol are more preferred.
The amount of water-soluble organic solvent added varies depending on the resin. I. 300 mass% or less is preferable with respect to the sum total of the pigment yellow 74 and an acetoacetic acid arylamide type azo compound, and it is more preferable that it is the range of 200 mass% or less.

In the production of the aqueous pigment dispersion of the present invention, among the components contained in the aqueous pigment dispersion, C.I. I. Pigment Yellow 74, a sulfonic acid group-containing acetoacetic acid arylamide-based azo compound, and a styrene acrylic resin-containing mixture having a high solid content ratio are kneaded in advance with high viscosity to more efficiently produce an aqueous dispersion. May be.
At this time, the basic compound may be added in the dispersion process after kneading, but the dispersion process in water can be further facilitated by adding from the kneading process. It is preferable to add a wetting agent during the kneading process because the resin is easily swelled and the kneading can proceed more effectively and efficiently.
Of the water-soluble organic solvents, polyhydric alcohols can be suitably used as the wetting agent.

  The concentration of each component in the aqueous pigment dispersion of the present invention can be appropriately selected within a concentration range in which the intended inkjet ink can be prepared. In preparing an inkjet ink in a later step using an aqueous pigment dispersion, the concentration range of the azo pigment in the aqueous pigment dispersion of the present invention is preferably 2 to 25% by mass in consideration of work efficiency and cost. -20 mass% is further more preferable. The concentration of the sulfonic acid group-containing acetoacetic acid arylamide azo compound, styrene acrylic resin, and basic component in the aqueous pigment dispersion of the present invention is appropriately selected within the ratio to the content of the azo pigment.

In order to produce an aqueous ink composition for inkjet recording using the aqueous pigment dispersion of the present invention as a main component, the pigment concentration and viscosity may be adjusted, and various additives may be added.
These various components to be added can be selected from known compounds applicable to inkjet inks. Such various compounds include viscosity modifiers, penetrants, surfactants, pH adjusters, anti-drying agents, antiseptic / antifungal agents, chelating agents, ultraviolet absorbers, antioxidants, antifoaming agents, kogation Examples include inhibitors.

  The penetrant can be used to adjust the penetrability of the inkjet ink into the recording medium and the dot diameter on the recording medium. Examples of water-soluble organic solvents that exhibit penetrability include lower alcohols such as ethanol and isopropyl alcohol, ethylene oxide adducts of alkyl alcohols such as ethylene glycol hexyl ether and diethylene glycol butyl ether, and propylene oxide adducts of alkyl alcohols such as propylene glycol propyl ether. Etc.

  Surfactants can be used to adjust the surface tension of ink-jet inks, control ejection stability and paper penetration during printing, and adjust ink-jet ink bleed and set-off and drying speed. . Specifically, known anionic, cationic, nonionic and amphoteric surfactants can be used.

  The pH adjuster controls the pH of the aqueous pigment dispersion or inkjet ink, but in addition to the basic components constituting the aqueous pigment dispersion of the present invention, various acidic and basic compounds can be used as necessary. It is.

  The anti-drying agent is used for reducing the occurrence of concentration change and precipitation / precipitation due to clogging of nozzles of water-based pigment dispersion and ink-jet ink, and water evaporation. Specifically, ethylene glycol, diethylene glycol, propylene glycol, 1,3-propanediol, triethylene glycol, polyethylene glycol, glycerin, tetraethylene glycol, dipropylene glycol, 1,2-hexanediol, 2, 4, 6- Polyhydric alcohols such as hexanetriol are preferred.

  Antiseptic / antifungal agents are used to reduce spoilage and ejection failure due to mold and bacteria on aqueous pigment dispersions and inkjet inks. Specifically, sodium dehydroacetate, sodium benzoate, sodium pyridinethione-1-oxide, zinc pyridinethione-1-oxide, 1,2-benzisothiazolin-3-one, 1-benzisothiazolin-3-one An amine salt or the like is used.

  The aqueous pigment dispersion of the present invention can be suitably used for well-known conventional inkjet inks such as a piezo method and a thermal method, through blending of various additives and adjusting the concentration, etc. Very stable ink ejection is possible in the printer. In particular, stable ejection can be obtained even for thermal ink jet inks, which have a great influence on the ejection characteristics of ink properties.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited by a following example. In the description of the following examples, “part” means “part by mass” unless otherwise specified.

(Preparation of resin solution)
10 parts of MEK in 10 parts of resin consisting of styrene (77 parts), acrylic acid (10 parts), methacrylic acid (13 parts), acid value = 150 mgKOH / g, weight average molecular weight 7,500, glass transition point 107 ° C. After adding 1.07 parts of sodium hydroxide and 60 parts of purified water and stirring, MEK was distilled under reduced pressure (70 ° C., 150 Pa) to obtain a resin solution (D-1) containing a solid content of 22% by mass. .
MEK 10 parts, hydroxylation 10 parts resin consisting of styrene (77 parts), acrylic acid (10 parts), methacrylic acid (13 parts), acid value = 150 mg KOH / g, weight average molecular weight 11500, glass transition point 107 ° C. After adding 1.5 parts of potassium and 60 parts of purified water and stirring, MEK was distilled under reduced pressure (70 ° C., 150 Pa) to obtain a resin solution (D-2) containing 22% by mass of solid content.
MEK 10 parts, hydroxylation 10 parts resin consisting of styrene (77 parts) / acrylic acid (10 parts) / methacrylic acid (13 parts), acid value = 150 mg KOH / g, weight average molecular weight 5000, glass transition point 107 ° C. After adding 1.07 parts of sodium and 60 parts of purified water and stirring, MEK was distilled under reduced pressure (70 ° C., 150 Pa) to obtain a resin solution (D-3) containing 22% by mass of solid content.
MEK 10 parts, hydroxylation 10 parts resin consisting of styrene (77 parts) / acrylic acid (10 parts) / methacrylic acid (13 parts), acid value = 150 mg KOH / g, weight average molecular weight 20000, glass transition point 107 ° C. After adding 1.07 parts of sodium and 60 parts of purified water and stirring, MEK was distilled under reduced pressure (70 ° C., 150 Pa) to obtain a resin solution (D-4) containing 22% by mass of solid content.
Resin comprising styrene (45 parts), methyl methacrylate (32 parts), acrylic acid (10 parts), methacrylic acid (13 parts), acid value = 150 mgKOH / g, weight average molecular weight 12000, glass transition point 109 ° C. After 10 parts of MEK, 1.5 parts of potassium hydroxide and 60 parts of purified water were added to 10 parts and stirred, MEK was distilled under reduced pressure (70 ° C., 150 Pa) to obtain a resin solution containing 22% by mass of solid content (D -5) was obtained.

(Synthesis Example 1)
(Synthesis of yellow pigment composition Y-1)
(Synthesis of diazotized liquid)
To a mixed solution of 700 parts of water and 315 parts of 35% hydrochloric acid, 181.4 parts of 4-nitro-o-anisidine and 68.8 parts of the following compound (8) were added and stirred. After cooling by adding 600 parts of ice, Then, 188 parts of 46.8% sodium nitrite aqueous solution was added, and the mixture was stirred at 10 ° C. or lower for 1 hour to eliminate excess nitrous acid with sulfamic acid, followed by filtration to obtain a diazotized liquid.

（８）

(8)

(Synthesis of coupler liquid)
Dissolve 100 parts of sodium acetate in 8900 parts of water, add 256.7 parts of o-acetoacetanisidide, add 185 parts of 30% sodium hydroxide and dissolve, and adjust to pH 6 by adding 80% acetic acid dropwise. A coupler solution was obtained.

(Coupling reaction)
The diazotized solution was dropped into the coupler solution at 25 ° C. and reacted, and then aged at 90 ° C. for 30 minutes. Further, filtration, washing with water, drying and pulverization yielded 495 parts of a yellow pigment composition (Y-1).
This yellow pigment composition (Y-1) is C.I. I. Pigment Yellow 74, R1 is a methoxy group, R2, R3, R5, and R6 are hydrogen atoms, R7 and R8 are —NH—CH ₂ CH ₂ —SO ₃ H, and Z is —SO ₂ — linked in Pigment Yellow 74 and General Formula (2) It is calculated that the acetoacetic acid arylamide azo compound (9), which is a group, is present in a mass ratio of 81:19.

（９）

(9)

(Synthesis Example 2) (Synthesis of Yellow Pigment Composition Y-2)
The same as Synthesis Example 1 except that the addition amount of 4-nitro-o-anisidine was 185.5 parts, and 45.3 parts of the following compound (10) was used instead of 68.8 parts of the compound (8). As a result, 472 parts of a yellow pigment composition (Y-2) were obtained.

（１０）
この黄色顔料組成物（Ｙ−２）はＣ．Ｉ．ピグメントイエロー７４と、一般式（２）においてＲ１がメトキシ基、Ｒ２、Ｒ３が水素原子、Ｒ５、Ｒ６がメチル基、Ｒ７が−ＮＨ−ＣＨ_２ＣＨ_２−ＳＯ_３Ｈ、Ｒ８が水酸基、Ｚが−ＣＨ_２−連結基、であるアセト酢酸アリールアミド系アゾ化合物（１１）とが、質量比８７：１３の割合で存在すると計算される。

(10)
This yellow pigment composition (Y-2) is C.I. I. Pigment Yellow 74, R1 is a methoxy group, R2 and R3 are hydrogen atoms, R5 and R6 are methyl groups, R7 is —NH—CH ₂ CH ₂ —SO ₃ H, R8 is a hydroxyl group, and Z is It is calculated that the acetoacetic acid arylamide azo compound (11) which is —CH ₂ — linking group is present in a mass ratio of 87:13.

（１１）

(11)

(Synthesis Example 3) (Synthesis of Yellow Pigment Composition Y-3)
(Synthesis of Compound 13)
In a mixed solution of 400 parts of water and 58.4 parts of 35% hydrochloric acid, 83.2 parts of the following compound (12) was added and stirred. After adding 500 parts of ice and cooling, a 46.8% aqueous sodium nitrite solution was cooled. 26 parts were added, and the mixture was stirred at 10 ° C. or lower for 1 hour to eliminate excess nitrous acid with sulfamic acid, followed by filtration to obtain a diazotized liquid.

（１２）
一方、水１２００部に３０％苛性ソーダ７６部を加えた液にｏ−クロロアセトアセトアニリド３８部を添加して溶解させた後、８０％酢酸を滴下してｐＨを６に調整してカップラー液とした。
上記カップラー液にジアゾ化液を２５℃で滴下し、６０分間攪拌して反応させた後、８０℃で３０分間熟成させた。ろ過、水洗して固形分３６．５％の化合物（１３）のペースト２６４部を得た。

(12)
On the other hand, after adding 38 parts of o-chloroacetoacetanilide to a solution obtained by adding 76 parts of 30% caustic soda to 1200 parts of water, 80% acetic acid was added dropwise to adjust the pH to 6 to obtain a coupler solution. .
The diazotized solution was added dropwise to the coupler solution at 25 ° C., and the mixture was stirred for 60 minutes to react and then aged at 80 ° C. for 30 minutes. Filtration and washing with water gave 264 parts of a compound (13) paste having a solid content of 36.5%.

（１３）

(13)

(Synthesis of diazotized liquid)
In a mixed solution of 700 parts of water and 315 parts of 35% hydrochloric acid, 197.6 parts of 4-nitro-o-anisidine and 3,3′-dimethyl-4,4′-diaminobiphenyl-6,6′-disulfonic acid Add 9 parts, stir, add 600 parts of ice, cool, add 188 parts of 46.8% sodium nitrite aqueous solution, stir at 10 ° C. or less for 1 hour, and eliminate excess nitrous acid with sulfamic acid. Then, it filtered and it was set as the diazotization liquid.

(Synthesis of coupler liquid)
Dissolve 100 parts of sodium acetate in 8900 parts of water, add 256.7 parts of o-acetoacetanisidide, add 185 parts of 30% sodium hydroxide and dissolve, and adjust to pH 6 by adding 80% acetic acid dropwise. A coupler solution was obtained.

(Coupling reaction)
After the diazotization solution was dropped into the coupler solution at 25 ° C. and reacted, 264 parts of the previously synthesized paste of the compound (13) was added and aged at 80 ° C. for 30 minutes with stirring. Further, filtration, washing with water, drying and pulverization yielded 470 parts of a yellow pigment composition (Y-3).
This yellow pigment composition (Y-3) is C.I. I. Pigment Yellow 74 and general formula (2), R1 is a chloro group, R2 and R3 are hydrogen atoms, R5 and R6 are methyl groups, R7 is —NH—Y—SO ₃ H (where Y is a phenylene group), R8 Is an acetoacetic acid arylamide azo compound (13) wherein Z is a —CH ₂ — linking group, and in general formula (1), R 1 is a methoxy group, R 2 and R 3 are hydrogen atoms, and R 4 is a methyl group It is calculated that compound (14) is present in a ratio of 83: 12: 5.

（１３）

(13)

（１４）

(14)

(Synthesis Example 4) (Synthesis of Yellow Pigment Composition Y-4)
The addition amount of 4-nitro-o-anisidine was 168.2 parts, and the same procedure as in Synthesis Example 1 was performed except that 12.4 parts of the compound (12) was used instead of 68.8 parts of the compound (8). As a result, 470 parts of a yellow pigment composition (Y-4) were obtained.
This yellow pigment composition (Y-4) is C.I. I. Pigment Yellow 74, R1 is a methoxy group, R2 and R3 are hydrogen atoms, R5 and R6 are methyl groups, R7 is -NH-C6H4-SO3H, R8 is a hydroxyl group, and Z is a -CH2- linking group in the structural formula (2) The acetoacetic acid arylamide azo compound (15) is calculated to be present at a mass ratio of 96: 4.

（１５）

(15)

(Synthesis Example 5) (Synthesis of Yellow Pigment Composition Y-5)
446 parts of a yellow pigment composition (Y-5) were obtained in the same manner as in Synthesis Example 1 except that 22.4 parts of 4-aminotoluene-3-sulfonic acid was used instead of 68.8 parts of compound (8). It was.
This yellow pigment composition (Y-5) is C.I. I. It is calculated that Pigment Yellow 74 and the low molecular weight acetoacetic acid arylamide azo compound (16) are present in a mass ratio of 90:10, unlike the compounds represented by the general formulas (1) and (2).

（１６）

(16)

Example 1
Commercially available C.I. I. 10 parts of Pigment Yellow 74 (trade name “Fast Yellow 7410” manufactured by Sanyo Color Co., Ltd.), 18.2 parts of Resin Solution (D-1), 20 parts of diethylene glycol, 18.5 parts of purified water, and zirconia beads 400 having a diameter of 1.25 mm Then, the mixture was shaken for 4 hours using a paint shaker (trade name “Test Disperser No. 488” manufactured by Toyo Seiki Seisakusho Co., Ltd.) to obtain an aqueous pigment dispersion (A).

(Example 2)
An aqueous pigment dispersion (B) was obtained in the same manner as in Example 1 except that the resin solution (D-1) in Example 1 was replaced with the resin solution (D-2).

Example 3
C. of Example 1 I. An aqueous pigment dispersion (C) was obtained in the same manner as in Example 1, except that 10 parts of Pigment Yellow 74 was replaced with 10 parts of the yellow pigment composition (Y-1) obtained in Synthesis Example 1.

Example 4
C. of Example 1 I. An aqueous pigment dispersion (D) was obtained in the same manner as in Example 1, except that 10 parts of Pigment Yellow 74 was replaced with 10 parts of the yellow pigment composition (Y-2) obtained in Synthesis Example 2.

(Example 5)
C. of Example 1 I. Pigment Yellow 74 and 10 parts are replaced with 10 parts of the yellow pigment composition (Y-3) obtained in Synthesis Example 3, and 18.2 parts of the resin solution (D-1) is 18.2 parts of the resin solution (D-2). An aqueous pigment dispersion (E) was obtained in the same manner as in Example 1, except that

(Example 6)
C. of Example 1 I. Pigment Yellow 74 and 10 parts are replaced with 10 parts of the yellow pigment composition (Y-4) obtained in Synthesis Example 4, and 18.2 parts of the resin solution (D-1) is 18.2 parts of the resin solution (D-2). An aqueous pigment dispersion (F) was obtained in the same manner as in Example 1 except that

(Example 7)
C. of Example 1 I. Pigment Yellow 74 and 10 parts are replaced with 10 parts of the yellow pigment composition (Y-5) obtained in Synthesis Example 5, and 18.2 parts of the resin solution (D-1) is 18.2 parts of the resin solution (D-2). An aqueous pigment dispersion (G) was obtained in the same manner as in Example 1 except that

(Comparative Example 1)
C. of Example 1 I. Pigment Yellow 74, 10 parts of C.I. I. Pigment Yellow 93 (trade name “Chromophthal Yellow 3GNP” manufactured by Ciba Specialty Chemicals) was used in the same manner as in Example 1 except that 10 parts were used to obtain an aqueous pigment dispersion (H).

(Comparative Example 2)
C. of Example 1 I. Pigment Yellow 74, 10 parts of C.I. I. Pigment Yellow 147 (trade name “Chromoval Yellow AGR” manufactured by Ciba Specialty Chemicals) was used in the same manner as in Example 1 except that 10 parts were used to obtain an aqueous pigment dispersion (I).

(Comparative Example 3)
C. of Example 1 I. Pigment Yellow 74, 10 parts of C.I. I. An aqueous pigment dispersion (J) was obtained in the same manner as in Example 1 except that Pigment Yellow 128 (trade name “Chromophthal Yellow 8GN” manufactured by Ciba Specialty Chemicals Co., Ltd.) was replaced with 10 parts.

(Comparative Example 4)
An aqueous pigment dispersion (K) was obtained in the same manner as in Example 3 except that 18.2 parts of the resin solution (D-1) of Example 3 was replaced with 18.2 parts of the resin solution (D-3). It was.

(Comparative Example 5)
An aqueous pigment dispersion (L) was obtained in the same manner as in Example 3 except that 18.2 parts of the resin solution (D-1) of Example 3 was replaced with 18.2 parts of the resin solution (D-4). It was.

(Comparative Example 6)
An aqueous pigment dispersion (M) was obtained in the same manner as in Example 3, except that 18.2 parts of the resin solution (D-1) of Example 3 was replaced with 18.2 parts of the resin solution (D-5). It was.

  The compositions of Examples 1 to 7 and Comparative Examples 1 to 6 are shown in Table 1.

  Examples 1 to 7 and Comparative Examples 1 to 6 having the above compositions were evaluated by the following test methods.

(Dispersibility test)
The volume average particle diameters of the aqueous pigment dispersions obtained in Examples 1 to 7 and Comparative Examples 1 to 6 were measured by a trade name “Microtrac UPA-150” manufactured by Leeds & Northrop. The results are shown in Table 2.

(Storage stability promotion test)
Examples 1 to 7 and Comparative Examples 1 to 6 comprising 33.3 parts of an aqueous pigment dispersion, 8 parts of triethylene glycol monobutyl ether, and 58.7 parts of purified water were blended for a storage stability acceleration test, The container was sealed in a glass container and heated at 70 ° C. for 1 week, and changes in viscosity and particle size distribution before and after heating were measured. The viscosity was measured by the product name “TVE-20L” manufactured by Tokimec. The results are shown in Table 2.

  The aqueous pigment dispersions of Examples 1 to 6 have small changes in viscosity due to heating and small changes in volume average particle diameter, and good dispersibility and storage stability. In particular, the aqueous pigment dispersions of Examples 3 to 6 are preferable because they maintain the initial small volume average particle diameter after heating. In Example 7, the volume average particle diameter increases after heating, but does not exceed 200 μm and there is no increase in viscosity, so there is no problem in ink ejection. In Comparative Examples 3 and 4, a slight increase in the volume average particle diameter is observed, but the viscosity is increased by 10% or more compared to the Examples, and the viscosity may increase with time. is there. In Comparative Example 1, Comparative Example 2, Comparative Example 5, and Comparative Example 6, either increase in viscosity or precipitation occurs, and both dispersibility and storage stability are low.

(Piezo jet discharge characteristics test)
After adding and mixing 10 parts of glycerin, 5 parts of propylpropylene glycol, and 65 parts of purified water to 20 parts of the aqueous pigment dispersions obtained in Examples 1 to 7 and Comparative Examples 1 to 6, respectively, using a 0.5 μm membrane filter. It filtered and it was set as the water-based pigment inkjet ink for an initial discharge test.
A part of this ink-jet ink was sealed in a glass container, and a temperature cycle of 4 hours at 70 ° C. and 4 hours at −20 ° C. was repeated four times to obtain an ink jet ink for ejection stability test after the temperature cycle was performed.
Using these two types of ink-jet inks, a piezo-type ink-jet printer (trade name “EM-900C” manufactured by Epson Corporation) was used to perform a printing test on a product name “4024 paper” manufactured by Xerox Corporation. The evaluation results are shown in Table 3.

(Light resistance test)
Using the aqueous pigment inkjet ink prepared for the initial discharge test from the aqueous pigment dispersions of Examples 1 to 7 and Comparative Examples 1 to 6, a solid print image was prepared on a trade name “4024 paper” manufactured by Xerox Corporation. The color difference ΔE was measured with the product name “colorimetric color difference sigma 80” manufactured by Nippon Denshoku Co., Ltd. before and after the light resistance test for 100 hours with the Heraeus brand name “SUNTEST CPS” xenon lamp. . The evaluation results are shown in Table 3.

(Water resistance test)
Using the aqueous pigment inkjet ink prepared for the initial discharge test from the aqueous pigment dispersions of Examples 1 to 7 and Comparative Examples 1 to 6, a text print image on a product name “4024 paper” manufactured by Xerox Co., Ltd. was prepared. Immediately after the printing of the image, it was gently immersed in purified water at room temperature for 1 hour, and the image of the wet printed image was visually observed. In the printed materials of Examples 1, 2, 6 and Comparative Example 5, no bleeding was observed, and in the printed materials of Examples 3 to 5, a slightly yellowish spread was observed in the periphery of the image. The evaluation results are shown in Table 3.

(Coloring power test)
Similarly, solid image printing was performed on a product name “4024 paper” manufactured by Xerox Co., Ltd. using a piezo inkjet printer (trade name “EM-900C” manufactured by Epson Corporation), and the visual coloring power was compared. The image of the ink prepared from the aqueous pigment dispersion obtained from Examples 1 to 6 has a sufficient image density compared with the printing result of the yellow dye ink mounted on the trade name “EM-900C” manufactured by Epson Corporation. Obtained. The evaluation results are shown in Table 3.

(Thermal inkjet ejection characteristics test)
In the aqueous pigment dispersions obtained in Examples 1 to 7 and Comparative Examples 1 to 6, 3 parts of glycerin, 8 parts of triethylene glycol monobutyl ether, 8 parts of 2-pyrrolidinone, manufactured by Air Products Co., Ltd. After 0.2 parts of Surfynol 420 "and 60.8 parts of purified water were added and mixed, the mixture was filtered through a 1 μm membrane filter to obtain an aqueous pigment inkjet ink for a thermal inkjet discharge test. Next, this inkjet ink is mounted on the Canon brand name “thermal inkjet printer BJ360”, and 20 sheets of continuous discharge, gradation pattern and solid printing are performed on commercially available inkjet paper and A4 glossy paper made by Seiko Epson. A test was conducted. Further, the remaining part of the ink is sealed in a glass container, heated for 2 weeks in an environment of 70 ° C., and then subjected to a printing test with a product name “thermal ink jet printer BJ360” manufactured by Canon Inc. Ejection stability test after heating Went. A continuous 20-sheet, gradation pattern and solid print were performed on commercially available paper for exclusive use of ink jet and A4 size Hikarizawa paper manufactured by Seiko Epson Corporation.
The aqueous pigment ink-jet inks obtained from Examples 1 to 7 are stable, high-quality images that can be stably ejected, do not cause ink stains even if the printing surface is touched immediately after printing, and are less distorted. was gotten. The aqueous pigment ink-jet inks obtained from Comparative Examples 1 to 6 were not stably ejected and did not recover even after several printer cleaning operations. The evaluation results are shown in Table 3.

Table 3 Piezojet and thermal jet printing tests and results of light resistance and water resistance evaluation

The evaluation criteria are as follows.
Piezo jet ejection characteristics / thermal jet ejection characteristics
A: Good discharge, uniform image; B: Substantially good discharge, image uniformity recovered by cleaning operation; Δ: Discharge defective; X: Discharge abnormal, disordered, not recovered by cleaning operation.
Coloring power ◎: better than yellow dye ink; ○: almost equivalent; Δ: slightly inferior light resistance ◎: ΔE is 0 to 1; ○: ΔE is 2 to 5
Water resistance ◎: Extremely good (no bleeding); ○: Good (with slight bleeding);
Δ: Inferior (with bleeding)
* 1 Discharge was slightly unstable at the beginning of writing and the image was inferior in uniformity. Recovery by printer head cleaning operation.
* 2 Unevenness in image quality was caused, resulting in unstable ejection and poor uniformity. There was an image strikethrough.

  In this way, C.I. I. Pigment Yellow 74 is a pigment that can be applied to a well-balanced aqueous pigment ink-jet ink excellent in coloring power, storage stability, and ejection stability by using a styrene acrylic resin having a specific structure and a basic compound. A dispersion is obtained. The ink-jet ink has excellent ejection stability when applied to an ink-jet printer including a thermal method, and can obtain a high print quality. Furthermore, by using a sulfonic acid group-containing acetoacetic acid arylamide compound having a specific structure in combination, an ink-jet ink having further excellent characteristics can be obtained.

Claims (7)

C. I. Styrene-acrylic resins Pigment Yellow 74 and an acid value of 100 to 250, a basic compound, and to prepare a mixture containing water, a manufacturing method of the ink-jet ink aqueous pigment dispersion for performing dispersion by dispersing device, wherein The styrene acrylic resin contains at least a styrene monomer unit, an acrylic acid monomer unit, and a methacrylic acid monomer unit as its constituent monomer unit, and the ratio of the styrene monomer unit to the total amount of all monomer units is 50% by mass or more. The total of the styrene monomer unit, the acrylic acid monomer unit, and the methacrylic acid monomer unit is 95% by mass or more based on the total amount of all the monomer units, and the weight average molecular weight of the resin is 7,000 to 15,000. Oh I, and in distributed by the distribution device,
The following general formula (1) or (2)

(1)

(Wherein R1, R2 and R3 each independently represents a hydrogen atom, a methyl group, a methoxy group, an ethoxy group or a chloro group, R4 represents a methyl group or a methoxy group, and R5 and R6 each independently represent Represents a hydrogen atom, a methyl group, an ethyl group, a methoxy group, an ethoxy group, or a hydroxyl group, R7 and R8 represent a group or a hydroxyl group represented by -NH-Y-SO3H, and at least one of R7 and R8 is -NH -Y-SO3H is a group, Y represents an ethylene group, a phenylene group, or a naphthalene group, and Z represents one of divalent linking groups represented by the following general formula (3).

(3)

Method of manufacturing an inkjet ink aqueous pigment dispersion characterized that you added in represented by a sulfonic acid group-containing acetoacetic acid arylamide-based azo compound.   The method for producing an aqueous pigment dispersion for inkjet ink according to claim 1, wherein the styrene acrylic resin is made into a resin solution by previously adding a basic compound and water. C. above. I. The method for producing an aqueous pigment dispersion for inkjet ink according to claim 1 or 2 , wherein the mass ratio of CI Pigment Yellow 74 to the sulfonic acid group-containing acetoacetic acid arylamide azo compound is in the range of 80:20 to 99: 1. . C. above. I. Pigment Yellow 74 and sulfonic acid group-containing acetoacetic acid arylamide-based azo compound are synthesized with 4-nitro-o-anisidine and general formula (4) at the time of synthesis by azo coupling reaction.

(4)
(Wherein R4 represents a methyl group or a methoxy group.)
Base of general formula (1) and / or general formula (5)

(5)
(Wherein R5 and R6 each independently represents a hydrogen atom, a methyl group, an ethyl group, a methoxy group, an ethoxy group, or a hydroxyl group, and at least one of R7 and R8 is a group represented by -NH-Y-SO3H. Yes, Y represents an ethylene group, a phenylene group, or a naphthalene group, and Z represents one of the divalent linking groups represented by the general formula (3).
A diazonium salt constituted by the base of the general formula (2) represented by the chemical formula (6)

(6)
The method for producing an aqueous pigment dispersion for inkjet ink according to any one of claims 1 to 3, which is synthesized by mixing and coupling with a coupler represented by formula ( 1) . The method for producing an aqueous pigment dispersion for inkjet ink according to any one of claims 1 to 4 , wherein the sulfonic acid group-containing acetoacetic acid arylamide azo compound is represented by the following general formula (7).

(7)
(In the formula, R1, R2, and R3 each independently represent a hydrogen atom, a methyl group, a methoxy group, an ethoxy group, or a chloro group.) Inkjet ink composition containing as a main component jet recording aqueous pigment dispersion obtained by the production method of the ink-jet ink aqueous pigment dispersion according to claim 1-5. The inkjet ink composition according to claim 6 , wherein the inkjet ink composition is used in a thermal jet type inkjet printer.