JP2006096777A - Aqueous pigment dispersion for inkjet ink and inkjet ink composition - Google Patents

Abstract

An inkjet ink using a yellow pigment, which is excellent in dispersion stability, storage stability and ejection stability, has a good coloring power, and can obtain a high-quality and high water-resistant printed image. An inkjet ink that can be produced, and a yellow aqueous pigment dispersion that can produce the inkjet ink are provided.
An aqueous pigment dispersion comprising an acetoacetate arylamide azo pigment, a sulfonic acid group-containing acetoacetate arylamide azo compound having a specific structure, a styrene acrylic resin, and a basic compound, comprising styrene The acrylic resin contains 50% by mass or more of a styrene monomer unit and an acrylic acid monomer unit and a methacrylic acid monomer unit in which the sum of the styrene monomer units is 95% by mass or more of the total amount of all monomer units. An aqueous pigment dispersion having a weight average molecular weight of 3,000 to 30,000 is provided.

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 color developability of each pigment is good, It is important to form an image with good color reproducibility by combining with ink compositions of other colors, and various pigments having different hues have been studied for inkjet recording.
An aqueous inkjet ink composition in which an organic pigment is dispersed is required to finely disperse and stabilize the pigment until coarse particles that are disadvantageous for inkjet ejection are not present in the ink. Further, it is required that the long-term storage stability similar to that of the dye-based ink is achieved and there is no change in the physical properties of the ink.
Moreover, in the pigment dispersion used in the ink-jet ink composition, the pigment is remarkably miniaturized as compared with a normal paint, and therefore, there is a strong tendency that the coloring power is inferior and chroma and the like are not easily produced. For this reason, in order to maintain the printing density, it is necessary to increase the concentration of the pigment contained in the ink-jet ink composition, which causes the dispersion to become more unstable.

Thus, in order to produce a pigment-based ink composition for ink jet recording, it is necessary to produce an aqueous pigment dispersion in which pigment fine particles having excellent coloring power are stably dispersed while maintaining a concentration above a certain value. is there. However, the dispersion instability factors of finely divided pigments are various, and the factors differ depending on the pigments used. Therefore, it is not easy to improve the dispersion stability of a specific pigment.
Especially for yellow pigments, light resistance is likely to decrease, so pigments with excellent coloring power and light resistance must be selected. In addition, primary particles tend to be large and opaque due to the growth of crystals insolubilized during synthesis. Many are unsuitable for inkjet applications. Accordingly, it has been more difficult to obtain a pigment dispersion for inkjet ink having good dispersion stability and high practicality.

  For example, azo pigments, which are typical organic pigments that obtain abundant hues from yellow to red, have good color developability when used in ink jet recording inks, but they do not necessarily have sufficient storage stability when pulverized. I could not say. In particular, an acetoacetic acid arylamide azo pigment has high coloring power and saturation, and an ink composition for ink jet recording containing this pigment forms an ink set with good color reproduction together with an ink composition composed of pigments of other colors. However, there was a problem in stability when the aqueous pigment dispersion was produced.

For this reason, various dispersing agents and dispersion methods have been studied in order to realize storage stability when pulverized and to obtain stable ejection from a fine nozzle. In particular, the technique using a resin as a dispersant is highly effective in stabilizing the dispersion of pigments.
For example, for the purpose of improving the stability of the dispersion, a method in which pigment particles are coated with a resin by a phase inversion emulsification method has been proposed. Styrene monomer 60 to 90 mol%, acrylic acid monomer 5 to 15 mol%, methacrylic acid monomer 5 A styrene acrylic resin having a monomer blending ratio of ˜25 mol% is used (see Patent Document 1). However, when used as an inkjet recording ink in a region where the pigment concentration is high, the long-term storage stability is not always satisfactory.

The styrene acrylic resin having a high content of the styrene monomer unit gives a printed image with good water resistance, but in order to obtain a better dispersion, a styrene acrylic resin having a styrene monomer unit of 50% by mass or more and water An aqueous pigment dispersion obtained by dispersing a resin aqueous solution containing sodium oxide, carbon black, and a wetting agent that causes the resin to swell but does not completely dissolve when mixed in an amount four times that of the styrene acrylic resin. Is obtained (Patent Document 2). In addition, an aqueous pigment dispersion for an inkjet recording ink composition having good storage stability by preparing a solid kneaded material by kneading with high viscosity together with a pigment, a basic compound, a resin, and a wetting agent using a styrene acrylic resin. As a styrene acrylic resin, 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 is used (patent) Reference 3).
However, the optimum composition of the resin used as the dispersant differs depending on the chemical structure of the pigment, the treatment method, the surface condition, etc., and it is necessary to adjust the resin composition used for each pigment. In particular, the application resin for the acetoacetic acid arylamide-based azo pigment has not been sufficiently studied, and good long-term storage stability has not been obtained. In particular, the storage stability under high-temperature storage, which is important for thermal ink jet inks, was insufficient.

On the other hand, as another method for improving the dispersion stability, it is a monoazo pigment that improves the particle size stability and storage stability by using a compound having a similar structure as a dispersion aid together with the pigment used as the main component. (See Patent Documents 4 and 5), however, depending on the composition of the ink-jet ink using a water-soluble solvent, satisfactory properties are not always obtained in the accelerated storage stability test at high temperatures. .
Further, it has been pointed out that an azo compound having a triazine skeleton is an effective pigment dispersant for dispersion of an azo pigment in a non-aqueous vehicle (see Patent Document 6). There is no description about the liquid.
In image recording pigment compositions, an azo compound having a triazine skeleton has been proposed as a pigment dispersant (see Patent Document 7). However, even when the present pigment dispersant is used, when the ink-jet ink is designed in a region where the pigment concentration is high, the long-term storage stability is not always satisfactory.
As described above, the method using a structure similar to an azo pigment as a dispersion aid has a certain effect in improving dispersibility, but it cannot be said that the long-term storage stability is sufficient. In order to further improve the dispersion stabilizing effect of these dispersion aids, it is necessary to examine the combination of the above-described dispersants with the resin.
However, for such an azo pigment and an aqueous pigment dispersion for inkjet inks in which a compound having a structure similar to that of the azo pigment is used as a dispersion aid, investigation of a resin as a suitable dispersant is insufficient. This has not been done for acetoacetic acid arylamide azo pigments.
JP-A-8-183920 JP 2002-256201 A Japanese Patent Laid-Open No. 2003-226832 JP-A-10-158555 JP 2001-98200 A Japanese Patent Laid-Open No. 7-126546 JP 2003-253188 A

  An object of the present invention is a highly water-resistant ink-jet ink suitable for water-based ink-jet inks using organic pigments, excellent in dispersion stability and ejection stability, and capable of obtaining high-quality printing, and pigment dispersion as a raw material thereof. To provide liquid. It is a further object of the present invention to provide an inkjet ink that can obtain stable ejection in a thermal on-demand inkjet printer.

  The present invention is an aqueous pigment dispersion containing an acetoacetic acid arylamide azo pigment, a sulfonic acid group-containing acetoacetic acid arylamide azo compound, a styrene acrylic resin, and a basic compound, the sulfonic acid group The acetoacetic acid arylamide-based azo compound contains the following general formula (1)

（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。）
または下記一般式（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, and R4 represents a methyl group or a methoxy group.)
Or the following general formula (2)

（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、
かつ前記スチレンアクリル系樹脂は、５０質量％以上のスチレン系モノマー単位と、前記スチレンモノマー単位との総和が全モノマー単位の総量の９５質量％以上となるアクリル酸モノマー単位及びメタクリル酸モノマー単位を含有し、７，０００〜３０，０００の重量平均分子量を有することを特徴とする水性顔料分散液を提供する。

(3)
1 represents a divalent linking group represented by )
Represented by
The styrene acrylic resin contains 50% by mass or more of styrene monomer units and an acrylic acid monomer unit and a methacrylic acid monomer unit in which the sum of the styrene monomer units is 95% by mass or more of the total amount of all monomer units. And an aqueous pigment dispersion having a weight average molecular weight of 7,000 to 30,000.

  The acetoacetic acid arylamide azo pigment used in the aqueous pigment dispersion of the present invention has good color development and light resistance. On the other hand, a sulfonic acid group-containing acetoacetic acid arylamide azo compound having a structure of formula (1) or formula (2) is adsorbed on the surface of the azo pigment, thereby suppressing crystal growth of the azo pigment and preventing aggregation. To do. At the same time, the styrene acrylic resin in the aqueous pigment dispersion that has been given dispersibility by the addition of a basic compound is uniformly dispersed in the aqueous medium and is efficiently adsorbed to the surface of the azo pigment. This is coated to prevent aggregation of the azo pigment.

  Furthermore, the present invention provides an inkjet ink composition containing the aqueous pigment dispersion for inkjet ink as a main component. The inkjet ink composition of the present invention contains 50% by mass or more of styrene monomer units in the styrene acrylic resin to be used, and the printed image can maintain good water resistance due to its hydrophobicity. Further, by using such a styrene acrylic resin, the printed image of the present invention can realize a high image density.

  The aqueous pigment dispersion of the present invention is excellent in dispersion stability and storage stability. In addition, the inkjet ink composition containing the aqueous pigment dispersion as a main component is excellent in ejection stability, and by using the ink composition, a high-quality image excellent in water resistance with little bleeding on plain paper or the like. You can print out.

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

  The acetoacetic acid arylamide azo pigments used in the present invention have low solubility in water as a general property of azo pigments, and are used for coloring materials such as yellow and red.

  The acetoacetate arylamide azo pigments that can be used are not particularly defined, and examples thereof include acetoacetate arylamide monoazo pigments, acetoacetate arylamide disazo pigments, and condensed disazo pigments that are excellent in color development. These can be used as chromatic color pigments such as red and yellow, and generally can be specified by specifying color, chemical structure, etc. in a color index. In particular, an acetoacetic acid arylamide monoazo pigment is excellent in yellow color development and is suitable as the pigment of the present invention.

  Specific examples of usable acetoacetic acid arylamide azo pigments include C.I. I. Pigment yellow 1, C.I. I. Pigment yellow 3, C.I. I. Pigment yellow 4, C.I. I. Pigment yellow 5, C.I. I. Pigment yellow 6, C.I. I. Pigment yellow 65, C.I. I. Pigment yellow 73, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 97, C.I. I. Pigment yellow 98, C.I. I. Pigment yellow 116, C.I. I. Pigment Orange 1 and the like are benzimidazolone-based insoluble azo pigments such as C.I. I. Pigment yellow 120, C.I. I. Pigment yellow 151, C.I. I. Pigment yellow 154, C.I. I. Pigment yellow 180, C.I. I. Pigment Orange 36 and the like include C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. Pigment yellow 95, C.I. I. And CI Pigment Yellow 155.

  In particular, C.I. I. Pigment Yellow 74 is excellent in the hue balance of a secondary color as a process color that is important during full color printing and a hue with high transparency, and can be used as a suitable yellow pigment for an inkjet ink composition.

  These azo pigments can be used in the pigment dispersion of the present invention regardless of the form of dry powder, granules, paste, hydrous slurry, etc. In order to affect the dispersion state of the dispersion, 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.

  In particular, among the azo pigments, the acetoarylamide monoazo pigment represented by the following general formula (4) also has a highly transparent hue and a secondary color tone balance as a process color that is important in full-color printing. It is excellent and can be used as a suitable yellow pigment for inkjet ink compositions. Among them, in the general formula (4), R9 is a methoxy group, R10 is a nitro group, R11 is an orthomethoxy group, R12 and R13 are hydrogen atoms, C.I. I. Pigment Yellow 74 can be used as a suitable yellow pigment because of its light resistance and coloring power.

（４）
（式中、Ｒ９及びＲ１０は互いに相違する水素原子、塩素原子、ニトロ基、メチル基又はメトキシ基を表し、Ｒ１１、Ｒ１２、Ｒ１３は各々独立的に、水素原子、塩素原子、メチル基、メトキシ基、エトキシ基表す。）

(4)
(Wherein R9 and R10 represent different hydrogen atoms, chlorine atoms, nitro groups, methyl groups or methoxy groups, and R11, R12 and R13 each independently represent a hydrogen atom, chlorine atom, methyl group, methoxy group) Represents an ethoxy group.)

Further, other pigments can be used in combination as long as the stability of dispersion and the clearness of hue are not impaired. 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 request for color tone and the like, and the pigment is not necessarily limited to the examples given here.

  In the aqueous pigment dispersion of the present invention, those represented by the following general formula (1) or (2) are used as the sulfonic acid group-containing acetoacetic acid arylamide monoazo compound.

（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。）

(3)
1 represents a divalent linking group represented by )

  These sulfonic acid group-containing acetoacetic acid arylamide type azo compounds are introduced with a sulfonating agent such as fuming sulfuric acid, concentrated sulfuric acid, chlorosulfuric acid or the like on the base skeleton compound, or the 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 materials 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 (4)

（４）
（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。特にアセト酢酸アリールアミドアゾ化合物をＣ．Ｉ．ピグメントイエロー７４のごとき、不溶性モノアゾ顔料から選択した場合、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。

(4)
(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, an acetoacetic acid arylamide azo compound is selected from C.I. I. When selected from insoluble monoazo pigments such as CI Pigment Yellow 74, the ink jet ink prepared from the aqueous pigment dispersion exhibits excellent performance in terms of concentration and durability on plain paper.

  The amount of the sulfonic acid group-containing acetoacetate arylamide azo compound of the present invention is preferably used as a minor component with respect to the acetoacetate arylamide azo pigment mainly used. The hue of the printed matter of the ink-jet ink prepared from the aqueous pigment dispersion of the present invention is such that the mass ratio of the sulfonic acid group-containing acetoacetic acid arylamide-based azo compound is in the range of 80:20 to 99: 1. This is preferable from the viewpoints of color development and the stability of the accelerated deterioration test in a heating environment.

  The mass ratio (b) / (c) between the acetoacetic acid arylamide azo pigment (b) and the sulfonic acid group-containing acetoacetic acid arylamide azo compound (c) is less than 80/20, and the sulfonic acid group-containing aceto Increasing the proportion of the acetic acid arylamide azo compound (c) tends to hinder the original color development of the azo pigment, and (b) / (c) is greater than 99/1, and the sulfonic acid group-containing aryl acetoacetate When the ratio of the amide-based azo compound (c) is reduced, it is difficult to recognize the effect on the stability of the accelerated deterioration test in the heating environment of the inkjet ink prepared from the aqueous pigment dispersion.

In the case where the sulfonic acid group-containing acetoacetic acid arylamide azo compound of the present invention is synthesized by a diazo coupling reaction, in the same system as the synthesis of the acetoacetic acid arylamide azo pigment mainly used in the aqueous pigment dispersion, The diazo coupling reaction can be performed simultaneously with or before or after the diazo coupling reaction of the azo pigment. 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, the same coupler as used in the synthesis of acetoacetate arylamide azo pigments is used, so the affinity between the sulfonic acid group-containing acetoacetate arylamide compounds and the pigment is high, and the pigment dispersion stability is improved. Great effect.

  In the present invention, when the azo pigment (b) and the sulfonic acid group-containing acetoacetic acid arylamide azo compound are synthesized in the same system, each compound is used as an azo pigment composition in a mixed state. There is no need to isolate each separately. In this case, the mass ratio between the acetoacetic acid arylamide azo pigment (b) and the sulfonic acid group-containing acetoacetic acid arylamide azo compound (c) has a theoretical amount generated by each synthesis, It can be considered as the mass ratio of the present invention.

The styrene acrylic resin used in the aqueous pigment dispersion of the present invention can contain various components as monomer components, but contains at least 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 can adsorb effectively on the surface of the hydrophobic pigment because the ratio of the styrene monomer units to the total amount of all monomer units is 50% by mass or more. . 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. Further, there is a tendency that the image recording density at the time of printing on the paper such as plain paper of the inkjet ink prepared from the aqueous pigment dispersion liquid, and the print quality tends to be lowered. Furthermore, the water resistance of the inkjet ink tends to decrease. Further, the dispersion stability is further improved by setting the sum of the styrene monomer unit, acrylic acid monomer unit, and methacrylic acid monomer unit to 95% by mass or more based on the total amount of all monomer units.

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 mass%, more preferably 70 to 80 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
The hydrophilic monomer whose use is restricted for the styrene acrylic resin of the present invention includes, in addition to hydrophilic substituents such as hydroxyl group, sulfone group, amino group, and quaternary ammonium group in the chemical structure of the monomer. And those containing repeating units of ethylene oxide and propylene oxide. 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. 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 30,000 is selected. This is because if the molecular weight exceeds 30,000, 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. Further, 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 is measured by the following apparatus and conditions.
General benefit pump: LC-9A, System controller: SIL-6B, Autoinjector: SIL-6B, Detector: RID-6A Data processing software: Sic480II data station (manufactured by System Instruments).
Column: GL-R400 (guard column) + GL-R440 + GL-R450 + GL-R400M (manufactured by Hitachi Chemical Co., Ltd.), elution solvent: THF, elution volume: 2 ml / min, column temperature: 35 ° C.

  The acid value of the resin of the present invention is preferably in the range of 100 to 250, more preferably 100 to 200. This is because when the acid value is set higher than 250, the amount of hydrophobic components that are preferentially adsorbed on the pigment surface decreases, so that the resin coating with the styrene acrylic resin is difficult to be carried out, and the dispersibility of the aqueous pigment dispersion is reduced. If it is set lower than 100, the effect of improving the dispersibility by neutralization with an acid-valued 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. A temperature of 90 ° C. or higher is preferable because it is easy to obtain a good balance between discharge, stability, and print quality.

  The ratio of the color material containing the acetoacetic acid arylamide azo pigment of the present invention and the sulfonic acid group-containing acetoacetic acid arylamide azo compound and the styrene acrylic resin used as the dispersant is determined by the dispersion stability of the pigment particles and the aqueous The ink jet ink prepared from the pigment dispersion is appropriately selected depending on the ejection and printing characteristics. Preferably, the mass ratio between the color material and the resin is preferably selected in the range of color material / resin = 1 / 0.1 to 1/2. 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.

In particular, since the resin used in the aqueous pigment dispersion of the present invention contains carboxyl groups derived from acrylic acid and methacrylic acid, it is considered that stable dispersion can be obtained in water 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 used when an aqueous pigment dispersion is prepared into an inkjet ink. This is preferable from the standpoint of decap characteristics of the printer and water resistance of the printed matter. Among these basic compounds, alkali metal hydroxides typified by potassium hydroxide dispersion sodium hydroxide contribute to lowering the viscosity of the pigment dispersion and are particularly preferable from the viewpoint of ejection stability of the inkjet ink.

  When neutralizing with a basic component, it is preferable to use 50 to 130% of the basic component with respect to the acid value of the styrene acrylic resin of the present invention. It is further preferable from the viewpoint of pH control of the pigment dispersion and the inkjet ink composition using the same.

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

To produce the aqueous pigment dispersion of the present invention, the acetoacetic acid arylamide azo pigment, the sulfonic acid group-containing acetoacetic acid arylamide azo compound, the styrene acrylic resin, the basic compound, and water are contained. An aqueous dispersion is prepared by preparing a mixture to be dispersed and performing dispersion using a dispersion apparatus. As a dispersion method, a known method can be used.
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 addition amount of the water-soluble organic solvent varies depending on the resin, but is preferably 300% by mass or less, more preferably 200% by mass or less based on the pigment.

In the production of the aqueous pigment dispersion of the present invention, among the components contained in the aqueous pigment dispersion, an acetoacetic acid arylamide azo pigment, a sulfonic acid group-containing acetoacetic acid arylamide azo compound, and a styrene acrylic resin The aqueous dispersion may be more efficiently produced by kneading a mixture containing a high solid content ratio in advance with high viscosity.
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 in proportion to the content of the azo pigment.

  The portion corresponding to the water content of the aqueous pigment dispersion of the present invention includes, in addition to the azo pigment, sulfonic acid group-containing acetoacetate arylamide azo compound, styrene acrylic resin and basic component, from the aqueous pigment dispersion. This is a portion excluding various components added as necessary.

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 are preferably selected from components applicable to inkjet inks because the aqueous pigment dispersion of the present invention is used as a base material for inkjet inks. Such various components include viscosity modifiers, penetrants, surfactants, pH adjusters, anti-drying agents, antiseptic / antifungal agents, chelating agents, UV absorbers, antioxidants, antifoaming agents, kogation Examples include inhibitors. These various additives may be handled as components having a plurality of functions.

  The penetrant is a characteristic necessary for adjusting 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 permeability 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.

  The surfactant adjusts the surface tension of the ink-jet ink, controls the ejection stability and the paper permeability during printing, and affects the ink-jet ink bleeding, 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 are used as necessary. Can be used.

  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 thus obtained should be suitably used for known and commonly used inkjet inks such as piezo method and thermal method after blending various additives and adjusting the concentration. Therefore, very stable ink ejection is possible in each type of printer.

  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)
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 7500, 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-1) 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 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 45000, 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.

  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, 10 parts of MEK, 1.5 parts of potassium hydroxide and 60 parts of purified water were added and stirred, MEK was distilled under reduced pressure (70 ° C., 150 Pa) to obtain a resin solution containing 22% by mass of solids ( 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 (5) 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.

（５）

(5)

(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 (6), which is a group, is present in a mass ratio of 81:19.

（６）

(6)

(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 (7) was used instead of 68.8 parts of the compound (5). As a result, 472 parts of a yellow pigment composition (Y-2) were obtained.

（７）
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（８）とが、質量比８７：１３の割合で存在すると計算される。

(7)
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 (8) which is —CH ₂ — linking group is present in a mass ratio of 87:13.

（８）

(8)

(Synthesis Example 3) (Synthesis of Yellow Pigment Composition Y-3)
(Synthesis of Compound 10)
In a mixed solution of 400 parts of water and 58.4 parts of 35% hydrochloric acid, 83.2 parts of the following compound (9) was added and stirred. After adding 500 parts of ice and cooling, a 46.8% aqueous sodium nitrite solution was added. 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.

（９）
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（１０）のペースト２６４部を得た。

(9)
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 (10) paste having a solid content of 36.5%.

（１０）

(10)

(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 liquid was dropped into the coupler liquid at 25 ° C. and reacted, 264 parts of the paste of the compound (10) 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 (10) in which 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 (11) is present in a ratio of 83: 12: 5.

（１０）

(10)

（１１）

(11)

(Synthesis Example 4) (Synthesis of Yellow Pigment Composition Y-4)
The amount of 4-nitro-o-anisidine added was 168.2 parts, and yellow was prepared in the same manner as in Synthesis Example 1 except that 12.4 parts of compound (9) was used instead of 68.8 parts of compound 5 above. 470 parts of 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 (12) is calculated to be present at a mass ratio of 96: 4.

（１２）

(12)

(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 (5). It was.
This yellow pigment composition (Y-5) is C.I. I. It is calculated that Pigment Yellow 74 and an acetoacetic acid arylamide azo compound (13) different from the present invention are present in a mass ratio of 90:10.

（１３）

(13)

(Synthesis Example 6) (Synthesis of Yellow Pigment CI Pigment Yellow 74)
The yellow pigment C.I. was prepared in the same manner as in Synthesis Example 1 except that the amount of 4-nitro-o-anisidine added was 201.6 parts and the addition of compound 1 was omitted. I. Pigment Yellow 74 was obtained.

Example 1
10 parts of the yellow pigment composition (Y-1) obtained in Synthesis Example 1, 18.2 parts of the resin solution (D-1), 20 parts of diethylene glycol, 18.5 parts of purified water, 400 parts of 1.25 mm diameter zirconia beads After that, the mixture was shaken for 4 hours using a paint shaker (Test Disperser No. 488, manufactured by Toyo Seiki Seisakusho Co., Ltd.) to obtain an aqueous pigment dispersion (I).

(Example 2)
Aqueous pigment dispersion was carried out in the same manner as in Example 1 except that 10 parts of the yellow pigment composition (Y-1) of Example 1 were replaced with 10 parts of the yellow pigment composition (Y-2) obtained in Synthesis Example 2. Liquid (II) was obtained.

(Example 3)
10 parts of the yellow pigment composition (Y-1) of Example 1 was 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) was replaced with the resin solution. (D-2) An aqueous pigment dispersion (III) was obtained in the same manner as in Example 1 except that 18.2 parts were used.

Example 4
10 parts of the yellow pigment composition (Y-1) of Example 1 was 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) was replaced with the resin solution. (D-2) An aqueous pigment dispersion (IV) was obtained in the same manner as in Example 1 except that 18.2 parts were used.

(Comparative Example 1)
10 parts of the yellow pigment composition (Y-1) of Example 1 was 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) was replaced with the resin solution. (D-2) An aqueous pigment dispersion (V) was obtained in the same manner as in Example 1 except that 18.2 parts were used.

(Comparative Example 2)
10 parts of the yellow pigment composition (Y-1) of Example 1 obtained in Synthesis Example 6 were obtained. I. In the same manner as in Example 1 except that 18.2 parts of the resin solution (D-1) was replaced with 18.2 parts of the resin solution (D-2) instead of 10 parts of Pigment Yellow 74, an aqueous pigment dispersion liquid (VI) was obtained.

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

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

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

(Initial stability test)
The volume average particle diameters of the aqueous pigment dispersions obtained in Examples 1 to 4 and Comparative Examples 1 to 5 were measured with Microtrac UPA-150 (manufactured by Leeds & Northrop). The results are shown in Table 1.

(Heating stability promotion test)
Examples 1 to 4 and Comparative Examples 1 to 5 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 results are shown in Table 1.

(Printing 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 4 and Comparative Examples 1 to 5, respectively, using a 0.5 μm membrane filter It filtered and it was set as the aqueous pigment inkjet ink for printing tests.
A part of this ink-jet ink was sealed in a glass container, and a temperature cycle of 70 ° C. for 4 hours and −20 ° C. for 4 hours was repeated four times to obtain an ink-jet ink for stability test.
These two types of ink-jet inks were subjected to a printing test on Xerox 4024 paper using a piezo-type ink-jet printer (EM-900C manufactured by Epson Corporation).

(Light resistance)
Using the aqueous pigment inkjet ink prepared for the printing test from the aqueous pigment dispersions of Examples 1 to 4 and Comparative Examples 1 and 2, solid print images were prepared on Xerox 4024 paper. The color difference ΔE was measured with a colorimetric color difference sigma 80 manufactured by Nippon Denshoku Co., Ltd. before and after the light resistance test for 100 hours with the xenon lamp. The evaluation results are shown in Table 2.

(Water resistance and image bleeding)
Text printing images on 4024 paper manufactured by Xerox Co., Ltd. were prepared using aqueous pigment inkjet inks prepared for printing tests from the aqueous pigment dispersions of Examples 1 to 4 and Comparative Examples 1 and 2. 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. No blur is observed in the printed materials of Example 4 and Comparative Example 2, while in the printed materials of Examples 1 to 3, a slight yellowish spread is observed in the periphery of the image, and in the printed material of Comparative Example 1, the color spread is further increased. Was observed as a large bleed. The evaluation results are shown in Table 2.

Table 2 Results of printing test, light resistance and water resistance evaluation

Print quality A: Good discharge, uniform image; Δ: Discharge poor; X: Discharge abnormal, disordered Light resistance ○: No difference in evaluation samples.
Water resistance (bleeding) ◎: Good (no bleeding); ○: Good (slight bleeding); △: Inferior (bleeding)
* 1 Discharge was unstable at the beginning of writing and the image was inferior in uniformity.
* 2 Discharge was unstable at the beginning of writing and the image was inferior in uniformity.
* 3 Discharge was unstable at the beginning of writing and the image was inferior in uniformity.
* 4 Unevenness in image quality was caused, resulting in unstable ejection and poor uniformity.

(Thermal inkjet discharge test)
In the aqueous pigment dispersions obtained in Examples 1 to 3, 3 parts of glycerin, 8 parts of triethylene glycol monobutyl ether, 8 parts of 2-pyrrolidinone, 0.2 parts of surfactant Surfynol 420 (manufactured by Air Products) Then, 60.8 parts of purified water was added and mixed, and then filtered through a 1 μm membrane filter to obtain an aqueous pigment inkjet ink (Ic) for inkjet recording. Next, this ink-jet ink was mounted on a thermal ink-jet printer BJ360 (manufactured by Canon Inc.), and continuous printing, gradation printing and solid printing of 20 sheets were performed on commercially available ink-jet exclusive paper and A4 gloss paper made by Seiko Epson. Even if the printing surface was touched immediately after printing, ink smear did not occur, and a smooth, high-quality image was obtained with little disturbance in the printed image.

  In the aqueous pigment dispersion and the ink-jet ink composition of the present invention, the styrenic monomer used in the present invention is a factor that achieves both the discharge stability and the ink physical property stability and can obtain a high print quality on plain paper. When a resin with many units is used as a dispersant, the molecular weight of the azo compound having an ionic substituent such as a sulfonic acid group is increased to some extent, and the hydrophobic contribution by the aromatic component is large. In addition, it is considered that an azo compound containing a sulfonic acid group used in the examples works advantageously. Furthermore, since the sulfonic acid group-containing acetoacetic acid arylamide azo compound and the azo pigment are obtained by azo coupling with a similar acetoacetic acid arylamide coupler, the affinity with the pigment is high and the pigment dispersion is stable. This is thought to be a major effect in improving the performance.

In addition, in the low molecular weight sulfonic acid group-containing acetoacetic acid arylamide-based azo compound as in Comparative Example 1, in addition to water resistance and bleeding of a single color printing result, secondary color expression in which other color inks immediately after printing overlap, Deterioration in print quality is likely to occur. In contrast, an aqueous pigment dispersion and an inkjet ink composition comprising an azo pigment, a specific sulfonic acid group-containing acetoacetic acid arylamide azo compound having a higher molecular weight, a specific resin and a basic compound used in the present invention In this case, such deterioration in print quality is not induced.
According to the aqueous pigment dispersion for ink-jet ink of the present invention, excellent printing can be achieved with respect to an on-demand type ink-jet printer in which a large amount of heat energy is applied to the ink and the heat energy is applied to eject ink droplets from the orifice. A highly reliable ink-jet ink capable of obtaining quality can be obtained. This is because, in addition to the combination of the sulfonic acid group-containing acetoacetic acid arylamide azo compound and the azo pigment of the present invention, a high degree of dispersion stability due to the specific styrene acrylic acid resin contributes.

Thus, (a) water, (b) an azo pigment, (c) a sulfonic acid group-containing acetoacetic arylamide azo compound having a specific structure, (d) a styrene acrylic resin having a specific structure, and (e) a base In the aqueous pigment dispersion and the ink-jet ink composition of the present invention comprising a functional compound, both ejection stability and ink physical property stability are compatible, and a high print quality can be obtained on plain paper.

Claims (9)

Aqueous pigment dispersion for inkjet ink comprising an acetoacetate arylamide azo pigment, a sulfonic acid group-containing acetoacetate arylamide azo compound, a styrene acrylic resin, and a basic compound, wherein the sulfonic acid group-containing acetoacetate The arylamide azo compound is represented by the following general formula (1) or (2):

(1)

(2)
(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)

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. Yes, 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 30,000. An aqueous pigment dispersion characterized by being in the range of The aqueous pigment dispersion for inkjet ink according to claim 1, wherein the calculated glass transition point of the styrene acrylic resin is 90 ° C or higher. The aqueous pigment dispersion for inkjet ink according to claim 1 or 2, wherein the acetoacetic acid arylamide azo pigment is represented by the following general formula (4).

(4)
(Wherein R9 and R10 represent different hydrogen atoms, chlorine atoms, nitro groups, methyl groups or methoxy groups, and R11, R12 and R13 each independently represent a hydrogen atom, chlorine atom, methyl group, methoxy group) Represents an ethoxy group.) 4. The mass ratio of the acetoacetic acid arylamide azo pigment to the sulfonic acid group-containing acetoacetic acid arylamide azo compound is in the range of 80:20 to 99: 1. 5. Aqueous pigment dispersion for inkjet ink. The acetoacetic acid arylamide azo pigment is C.I. I. The aqueous pigment dispersion for inkjet ink according to claim 1, which is CI Pigment Yellow 74. A sulfonic acid group-containing acetoacetic acid arylamide-based azo compound is synthesized by performing mixed coupling with a sulfonic acid group-containing base during the synthesis of the acetoacetic acid arylamide-based azo pigment by an azo coupling reaction. 6. The aqueous pigment dispersion for inkjet ink according to any one of 5 above. The aqueous pigment dispersion for inkjet ink according to any one of claims 1 to 6, wherein the sulfonic acid group-containing acetoacetic acid arylamide azo compound is represented by the following general formula (5).

(5)
(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.) An inkjet ink composition comprising the aqueous pigment dispersion for inkjet inks according to claim 1 as a main component. The inkjet ink composition according to claim 8, wherein the inkjet ink composition is used for a thermal jet type inkjet printer.