Pigment composition, aqueous pigment dispersion for inkjet ink, and aqueous pigment ink

Abstract

The purpose of the present invention is to provide a pigment composition having excellent storage stability and dispersion stability and especially suitably applicable for aqueous pigment inks for IJ.　Specifically, a pigment composition of the present invention contains C.I. Pigment Yellow 180 and a derivative having a zeta potential of -20 mV or more and less than 0 mV and a solubility parameter of 21 or less.　It is preferable that the aspect ratio of the C.I. Pigment Yellow 180 is 1.0-2.0.　It is preferable that the derivative is a derivative of C.I. Pigment Yellow 180.　It is preferable that the derivative has a sulfonic acid group.　It is preferable that the trivalent metal in the trivalent metal salt of the derivative is at least one selected from the group consisting of iron, chromium, cobalt, and aluminum.

Description

[Technical field]

[0001] The present invention relates to a pigment composition containing CI Pigment Yellow 180, and an aqueous pigment dispersion for inkjet (hereinafter referred to as "IJ") ink and an aqueous pigment ink containing the same. [Background technology]

[0002] Inkjet printers are not only used for home use, but are also widely used for industrial purposes due to the trend towards smaller print runs, and in recent years the business has expanded to include textile and soft packaging applications. Among these, yellow ink is important as a central ink along with cyan, magenta, and black. In recent years, water-based inks have become the mainstream ink used in inkjet printers, and the pigments used in these inks are required to be easily dispersible in water-based inks in addition to having coloring power and light resistance.

[0003] As a yellow pigment for yellow ink, CI Pigment Yellow 180 (hereinafter referred to as "Y180"), a type of benzimidazolone yellow pigment, has been attracting attention from the viewpoint of achieving both coloring strength and lightfastness. An example of using Y180 in an inkjet ink is the following Patent Document 1. Patent Document 1 describes the use of a pigment derivative (amine salt, ammonium salt, or monovalent metal salt) of Y180 or the like containing a sulfonic acid group together with a benzimidazolone yellow pigment such as Y180. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2002-220557 A DISCLOSURE OF THEINVENTION [Problem to be solved by the invention]

[0005] The present inventors have studied conventional pigment compositions containing Y180, such as those described in Patent Document 1, and have found that the storage stability and dispersion stability of the pigment composition when made into an inkjet ink are insufficient. Therefore, an object of the present invention is to provide a pigment composition that is excellent in storage stability and dispersion stability and is particularly suitable for use in an inkjet water-based pigment ink. [Means for solving the problem]

[0006] As a result of intensive research to solve the above problems, the present inventors have found that a derivative having a specific zeta potential and solubility parameter can be used for Y180, and have completed the present invention. The mechanism of the present invention is as follows.

[0007] Since the Y180 pigment has a highly hydrophilic functional group and a bond in its molecular structure, it has a tendency to have high wettability in water and good initial dispersion. However, it is presumed that water inhibits the interaction between the pigment and the resin over time, causing the pigment to aggregate and resulting in poor dispersion stability. Therefore, it was considered important to increase the resin adsorption degree using a derivative. Generally, particles with a large absolute value of zeta potential are said to have high dispersion stability due to electrostatic repulsion, but in the present invention, the dispersion stability is improved by using a derivative with a small absolute value of zeta potential. This is because, in order to obtain the effect of dispersion stability by the derivative, the derivative needs to be adsorbed on the pigment particle surface, and a derivative with a large absolute value of zeta potential cannot be densely adsorbed on the pigment particle surface due to electrostatic repulsion. In addition, by making the pigment particles have a small aspect ratio, even higher dispersion stability can be obtained. Pigment particles with a large aspect ratio and low dispersion stability have a long and slender rod-like shape. In addition, since the Y180 pigment particles grow by piling up by π-π stacking, the short axis surface of the rod-shaped particle inevitably becomes the π-stacking surface. In water, π-π stacking is a strong force that causes the derivative to adhere to the pigment particles, and the π-stacking surface of the short axis is the site where the derivative adheres. Pigment particles with a large aspect ratio have poor dispersion stability because the long axis surface that does not adsorb the derivative is wide, while pigment particles with a small aspect ratio have a high area ratio of the short axis surface that adsorbs the derivative, so the dispersion stability effect of the derivative is strongly exerted. Regarding pigment particles with a small aspect ratio, when considering the distance between the two short axis surfaces within the same pigment particle, the distance is close due to the small aspect ratio, and the influence between the short axis surfaces is large. As mentioned above, when the derivative adheres to the pigment particle, the electrostatic repulsion of the derivative itself can be an obstacle, so if a derivative with a large absolute value of the zeta potential is attempted to be adsorbed to a particle with a small aspect ratio, the effect of electrostatic repulsion occurs between the two short axis surfaces within the same pigment particle, and sufficient effect cannot be obtained. Therefore, it is speculated that by combining particles with a small aspect ratio and particles with a small absolute value of the zeta potential, the electrostatic repulsion of the derivative is minimized and the adsorption of the derivative to the pigment particles is maximized, resulting in a Y180 pigment composition with specifically high dispersion stability.

[0008] As mentioned above, in pigments with a small aspect ratio, the area ratio of the short axis plane increases, making it easier for derivatives to adsorb, but the highly hydrophilic Y180 also easily adsorbs water, and even if the derivative is once adsorbed, the water inhibits it, causing poor dispersion stability. In addition, derivatives with a large solubility parameter have a high affinity between the derivative and water, which increases the effect of inhibiting adsorption to the pigment, and the interaction between the pigment and water is strengthened, making them more likely to cause poor dispersion. Therefore, it is speculated that the use of a derivative with a small solubility parameter will suppress the release of the derivative from the pigment and further weaken the interaction between water and the pigment, resulting in a Y180 pigment composition with high dispersion stability.

[0009] That is, the present invention is "Item 1. A pigment composition comprising CI Pigment Yellow 180 and a derivative having a zeta potential of -20 mV or more and less than 0 mV and a solubility parameter of 21 or less. Item 2. The pigment composition according to Item 1, wherein the CI Pigment Yellow 180 has an aspect ratio of 1.0 to 2.0. Item 3. The pigment composition according to item 1 or 2, wherein the derivative is a derivative of CI Pigment Yellow 180. Item 4. The pigment composition according to any one of Items 1 to 3, wherein the derivative has a sulfonic acid group. Item 5. The pigment composition according to any one of Items 1 to 4, wherein the derivative is a salt of a trivalent metal, and the trivalent metal is at least one selected from the group consisting of iron, chromium, cobalt, and aluminum. Item 6. An aqueous pigment dispersion for ink-jet ink, comprising the pigment composition according to any one of items 1 to 5. Item 7. A water-based pigment ink for ink-jet recording, comprising the pigment composition according to any one of items 1 to 5. Effect of the Invention

[0010] The pigment composition of the present invention exhibits little change in viscosity or particle size over time and has excellent dispersion stability and storage stability, making it suitable for use in water-based inkjet inks. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The present invention will be described in detail below. In the present invention, Y180 does not simply mean a compound represented by the following [Chemical Formula 1], but means a pigment composed of the compound. The pigment is a concept that includes not only the crystal structure, but also the primary particles formed by aggregation or assembly of the crystal structure, and further the physical properties of the aggregates and aggregates resulting from the surface state, etc.

[0012] [Pigment composition] The pigment composition of the present invention contains Y180 and a derivative having a zeta potential of -20 mV or more and less than 0 mV and a solubility parameter of 21 or less. Generally, such a derivative is called a pigment derivative (synergist). The pigment composition of the present invention may contain other solid components such as a resin for improving dispersibility in addition to the pigment such as Y180 and the derivative.

[0013] (Pigments) Y180 is CAS No. 77804-81-0 and is a yellow pigment represented by the following chemical formula: The pigment composition of the present invention only needs to contain Y180 as a colorant, and may contain pigments or dyes other than Y180 as long as the effects of the present invention are not impaired.

[0014] [ka]

[0015] Y180 can be obtained by coupling 5-acetoacetylamino-benzimidazolone with the bisdiazonium salt solution obtained by diazotizing 1,2-bis(2-aminophenoxy)-ethane in the presence of a strong acid under ice-cooling conditions, and then adding an aqueous solution of sodium nitrite.

[0016] The aspect ratio of the above Y180 is preferably 1.0 to 2.0, more preferably 1.0 to 1.9, and even more preferably 1.0 to 1.8. When the aspect ratio is within this range, the aggregation of pigment particles can be reduced, resulting in a small particle size, and excellent dispersion stability and storage stability when used as an aqueous pigment dispersion liquid / ink for IJ inks.

[0017] The primary particle minor diameter in the above Y180 is, for example, 30 to 100 nm, preferably 30 to 80 nm, and more preferably 30 to 50 nm. When the primary particle minor diameter is within this range, the particle diameter of the pigment in the dispersion or ink can be made small, resulting in excellent print density (OD) when used as an aqueous pigment dispersion for IJ ink or ink.

[0018] The major axis, aspect ratio and minor axis of the primary particles in Y180 are preferably within the above ranges, for example, 30 to 150 nm, preferably 30 to 100 nm, and more preferably 30 to 80 nm. The minor axis and major axis of the primary particles and the aspect ratio calculated from these can be determined by observing the primary particles of the pigment with an electron microscope or the like, and averaging the lengths measured for, for example, 100 particles.

[0019] The Y180 in the present invention may be a conventional synthetic product obtained by adding an aqueous solution of sodium nitrite to 1,2-bis(2-aminophenoxy)-ethane in the presence of a strong acid under ice-cooling conditions, and subjecting the bisdiazonium salt solution obtained by the diazotization reaction to coupling with 5-acetoacetylamino-benzimidazolone, or may be a commercially available product such as "SYMULER FAST YELLOW BY 2000GT" (manufactured by DIC Corporation), but it is preferable to produce it by further carrying out a specific treatment.

[0020] The specific treatment is, for example, to use 200 to 1000 parts by mass of inorganic salt per 100 parts by mass of pigment (crude pigment) and perform grinding while heating in the presence of a solvent (solvent salt milling). By performing grinding while heating in the presence of a solvent, it is possible to set the primary particle size within a specific range while improving the crystallinity of the pigment.

[0021] As the inorganic salt, a water-soluble inorganic salt can be suitably used, and it is preferable to use inorganic salts such as sodium chloride, potassium chloride, and sodium sulfate. It is more preferable to use an inorganic salt having an average particle size of 0.5 to 50 μm. Such an inorganic salt can be easily obtained by finely grinding a normal inorganic salt. The amount of the inorganic salt used is, for example, 200 to 1000 parts by mass, preferably 300 to 800 parts by mass, per 100 parts by mass of the pigment. From the viewpoint of making the pigment particles finer, the more the inorganic salt, the better, but in the present invention, the above range is preferable from the viewpoint of balancing with the degree of crystallinity.

[0022] As the solvent, it is preferable to use an organic solvent capable of suppressing crystal growth, and as such an organic solvent, a water-soluble organic solvent can be suitably used, for example, diethylene glycol (DEG), glycerin, ethylene glycol, propylene glycol, liquid polyethylene glycol, liquid polypropylene glycol, 2-(methoxymethoxy)ethanol, 2-butoxyethanol, 2-(isopentyloxy)ethanol, 2-(hexyloxy)ethanol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol, triethylene glycol monomethyl ether, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, dipropylene glycol, dipropylene glycol monomethyl ether, etc. can be used. Among them, diethylene glycol (DEG) is particularly preferable because it can be heated to a moderate temperature and has excellent wettability with the pigment. The amount of the solvent used is, for example, 10 to 500 parts by mass, preferably 50 to 300 parts by mass, relative to 100 parts by mass of the pigment in terms of obtaining a moderate viscosity during grinding.

[0023] The above-mentioned grinding (solvent salt milling) is carried out by feeding the pigment, the inorganic salt, and a solvent that does not dissolve them into a kneading machine and kneading them therein. As the kneading machine, for example, a kneader, a trimix, a mix muller, etc. can be used. The heating temperature during grinding (solvent salt milling) is, for example, 50 to 100°C, preferably 60 to 90°C. The heating temperature can be appropriately changed by a temperature control device provided in the kneading machine. The time for grinding (solvent salt milling) is, for example, 2 to 10 hours, preferably 3 to 8 hours.

[0024] The pigment composition of the present invention may contain a yellow pigment or dye other than Y 180. Examples of such yellow pigments include azo-based, disazo-based, azomethine-based, anthraquinone-based, quinophthalone-based, benzimidazolone-based, isoindoline-based, quinacridone-based, and perinone-based pigments, and more specifically, CI Pigment Yellow 1, 2, 3, 12, 13, 14, 16, 17, 20, 23, 24, 34, 35, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 116, 117, 118, 119, 120, 1 , 53, 55, 73, 74, 75, 81, 83, 86, 93, 95, 97, 98, 100, 101, 104, 108, 109, 110, 114, 117, 120, 125, 128, 129, 137, 138, 139, 147, 148, 150, 151, 153, 154, 155, 166, 168, 185, 213, etc. Also, dyes and pigments other than the above yellow pigments may be contained. In the pigment composition of the present invention, Y180 is preferably 50 mass% or more of the total pigments, more preferably 60 mass% or more.

[0025] The content of the pigment in the pigment composition (the total content when two or more types are contained) is, for example, 50 to 99 mass %, preferably 60 to 98 mass %, and more preferably 70 to 98 mass %.

[0026] As the resin (dispersion resin) for improving the dispersibility, copolymer resins such as styrene-(meth)acrylic acid copolymers, styrene-maleic acid copolymers, diisobutylene-maleic acid copolymers, vinylnaphthalene-(meth)acrylic acid polymers, urethane resins, surfactants, etc. The content of these dispersion resins is, for example, 3 to 30 parts by weight, preferably 5 to 20 parts by weight, based on 100 parts by weight of the pigment such as Y180.

[0027] (derivative) The zeta potential of the above derivative is -20 mV or more and less than 0 mV, preferably -18 mV or more and less than 0 mV, and more preferably -16 mV or more and less than 0 mV. When the zeta potential is in this range, it can be easily adsorbed to the Y180 pigment, and as a result, the dispersion stability in the pigment composition can be improved. The zeta potential can be measured by electrophoretic light scattering measurement method (laser Doppler method) using a zeta potential / particle size / molecular weight measurement system (product name ELSZ-2000ZS; manufactured by Otsuka Electronics Co., Ltd.) or the like.

[0028] The solubility parameter (SP) of the derivative is 21 or less, preferably 20 or less. When the solubility parameter (SP) is in this range, the affinity with the Y180 pigment is high, and as a result, the increase in viscosity over time in the pigment composition can be suppressed, and the storage stability can be improved. The solubility parameter (SP) can be determined by mixing the derivative with a solvent such as acetone, which has a known solubility parameter, and measuring the SP value of the mixed solution when the pigment is completely wetted.

[0029] Examples of the derivatives include derivatives having a pigment structure such as CI Pigment Yellow 1, 2, 3, 12, 13, 14, 16, 17, 20, 23, 24, 34, 35, 37, 53, 55, 73, 74, 75, 81, 83, 86, 93, 95, 97, 98, 100, 101, 104, 108, 109, 110, 114, 117, 120, 125, 128, 129, 137, 138, 139, 147, 148, 150, 151, 153, 154, 155, 166, 168, 180, 185, and 213. Among these, derivatives of CI Pigment Yellow 180 (Y180) are preferred because of their excellent dispersion stability and storage stability when used in a pigment composition. Y180 in the above derivative is a yellow pigment (CAS No. 77804-81-0) represented by the chemical formula described above for the pigment.

[0030] The above derivative may have an acid group such as a carboxylic acid group, a hydroxyl group, or a sulfonic acid group, and preferably has a sulfonic acid group. The sulfonic acid group is a group represented by -SO3H, or a group consisting of an organic compound in which a sulfo group is substituted on a carbon skeleton (-RSO3H; R is a carbon skeleton that is an alkyl group or an aryl group). In the present invention, the sulfonic acid group is preferably a group represented by -SO3H. The number of sulfonic acid groups (average number of substituents) possessed by the above derivative is, for example, 1 to 4, preferably 1 to 3, and more preferably 1 to 2. When the number of sulfonic acid groups (average number of substituents) is within the above range, the dispersion stability and storage stability of Y180 are improved.

[0031] The above derivatives may contain both or either of a compound having one sulfonic acid group introduced in the same molecule (mono-substitution) and a compound having two sulfonic acid groups introduced in the same molecule (di-substitution). The molar ratio of the mono-substituted to di-substituted derivatives (SN ratio (di-substituted / mono-substituted)) is, for example, 0.1 or more, preferably 0.1 to 30.0, and more preferably 0.5 to 5.0. When the SN ratio of the sulfonic acid group is within the above range, the dispersion stability and storage stability of Y180 are improved. The average number of sulfonic acid substituents and the SN ratio of the above derivatives can be calculated from the area ratio of each compound in liquid chromatography.

[0032] To introduce sulfonic acid groups into derivatives such as Y180, for example, a sulfonating agent such as fuming sulfuric acid, concentrated sulfuric acid, or chlorosulfuric acid may be applied to the derivative. The number of sulfonic acid groups can be adjusted by controlling reaction conditions such as sulfuric acid concentration, pigment content, reaction temperature, and reaction time. The pigment content here refers to the weight ratio of Y180 to sulfuric acid (pigment charge amount / sulfuric acid charge amount).

[0033] The sulfuric acid concentration is, for example, 92 to 100% by weight, preferably 92 to 98% by weight, and more preferably 95 to 98% by weight. The pigment content is, for example, 0.04 to 0.08, preferably 0.04 to 0.07, and more preferably 0.05 to 0.07. The reaction temperature is, for example, 5 to 30°C, preferably 5 to 20°C, and more preferably 10 to 20°C. The reaction time is, for example, 0.5 to 5 hours, preferably 0.5 to 4 hours, and more preferably 1 to 4 hours.

[0034] The derivative is preferably a trivalent metal salt. Examples of trivalent metals in the trivalent metal salt include iron, chromium, cobalt, aluminum, gallium, indium, and thallium. Among them, at least one selected from the group consisting of iron, chromium, cobalt, and aluminum is preferred from the viewpoint of the ability to set the zeta potential in an appropriate range and practicality. The trivalent metal salt is a compound in which the hydrogen atom (H) of the sulfonic acid group is substituted with these metal ions. Aluminum is preferred from the viewpoints of economy and performance.

[0035] The above derivatives may be used with pigment derivatives (synergists) other than those mentioned above, if necessary. Examples of such derivatives include pigment derivatives that have a pigment skeleton and have a substituent added to the pigment skeleton. Specifically, azo pigment derivatives, disazo pigment derivatives, azomethine pigment derivatives, anthraquinone pigment derivatives, quinophthalone pigment derivatives, benzimidazolone pigment derivatives, isoindoline pigment derivatives, quinacridone pigment derivatives, and perinone pigment derivatives can be used. Examples of the derivative moiety include a hydroxyl group, a carboxylic acid group, and a sulfonic acid group. Two or more of these derivatives of different types can also be used in combination.

[0036] The content of the derivative (total content when two or more types are included) is, for example, 0.5 to 30 parts by weight, preferably 1.0 to 20 parts by weight, and more preferably 2.0 to 15 parts by weight, relative to 100 parts by weight of the pigment such as Y180. The content of the derivative in the pigment composition (total content when two or more types are included) is, for example, 0.5 to 30% by mass, preferably 1.0 to 20% by mass, and more preferably 2.0 to 15% by mass. When the content of the derivative is within this range, the adsorption effect of the derivative to the pigment can be set to an appropriate range, and as a result, the dispersion stability and storage stability of the pigment composition can be improved.

[0037] (Water-based pigment dispersion for IJ ink) The aqueous pigment dispersion for an IJ ink of the present invention is not particularly limited as long as it contains the pigment composition of the present invention and a solvent for dispersing it, but it may contain other components such as a dispersant as necessary.

[0038] The aqueous pigment dispersion for IJ ink may use a water-soluble organic solvent together with water as a solvent. Examples of such water-soluble organic solvents include alcohols such as methanol, ethanol, propanol, isopropanol, n-butanol, isobutanol, 1,2-hexanediol, and 1,6-hexanediol, ketones such as acetone and methyl ethyl ketone, polyalkylene glycols such as ethylene glycol, diethylene glycol, and propylene glycol, alkyl ethers of polyalkylene glycol, and lactams such as N-methyl-2-pyrrolidone. These organic solvents may be used alone or in combination of two or more.

[0039] The content of the water-soluble organic solvent in the total mass of the aqueous pigment dispersion for IJ ink is, for example, about 0 to 60%, and preferably 0 to 45%, and the remainder other than the pigment dispersion for IJ ink (non-volatile components) is almost entirely water.

[0040] [Water-based pigment ink for inkjet printing] The IJ aqueous pigment ink of the present invention is not particularly limited as long as it contains the pigment composition and solvent of the present invention, but may contain a yellow pigment or dye other than Y 180. Examples of such yellow pigments include azo-based, disazo-based, azomethine-based, anthraquinone-based, quinophthalone-based, benzimidazolone-based, isoindoline-based, quinacridone-based, and perinone-based pigments, and specifically, CI Pigment Yellow 1, 2, 3, 12, 13, 14, 16, 17, 20, 23, 24, 34, 35, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, , 53, 55, 73, 74, 75, 81, 83, 86, 93, 95, 97, 98, 100, 101, 104, 108, 109, 110, 114, 117, 120, 125, 128, 129, 137, 138, 139, 147, 148, 150, 151, 153, 154, 155, 166, 168, 185, 213, etc. In addition, dyes and pigments other than the above yellow pigments may be contained. In addition, when mixing yellow pigments and dyes other than Y180, there is no particular limitation on the mixing method. They may be mixed as a pigment composition at the stage of producing an aqueous pigment dispersion, or they may be mixed as a pigment dispersion at the stage of producing an IJ aqueous pigment ink. In the aqueous pigment ink for IJ ink of the present invention, Y180 is preferably 10% by mass or more of the total pigments, more preferably 20% by mass or more.

[0041] The IJ aqueous pigment ink may contain additives as necessary. Examples of additives include preservatives, pH adjusters, chelating agents, rust inhibitors, water-soluble UV absorbers, water-soluble polymer compounds, antioxidants, water-dispersible resins, and surfactants. Examples of surfactants include anionic, cationic, nonionic, amphoteric, silicone-based, and fluorine-based surfactants. The aqueous pigment ink may further contain water or a water-soluble organic solvent to adjust the ink concentration.

[0042] The content of the additives in the total mass of the IJ water-based pigment ink (total amount when two or more types are included) is about 0 to 30%, preferably 0 to 15%. The content of the pigment in the water-based pigment ink is, for example, 1 to 15% by mass, preferably 2 to 10% by mass.

[0043] The viscosity (25°C) of the inkjet water-based pigment ink is preferably 1 to 30 mPa·s, and more preferably 2 to 20 mPa·s, from the viewpoint of improving the storage stability of the ink. The pH of the water-based pigment ink is, for example, 7.0 or more, and preferably 7.5 or more, from the viewpoint of further improving the storage stability of the ink. Furthermore, from the viewpoints of component resistance and skin irritation, the pH is, for example, 11.0 or less, and preferably 10.0 or less.

[0044] The inkjet water-based pigment ink of the present invention can be loaded into a known inkjet recording device and ejected as ink droplets onto a recording medium to record an image, etc. IJ recording devices include continuous ejection types (charge control types, spray types, etc.) and on-demand types (piezo type, thermal type, electrostatic suction type, etc.), and the water-based pigment ink of the present invention can be used in any of these types. EXAMPLES

[0045] The present invention will be described in more detail below using examples and comparative examples. Derivatives were synthesized by the methods described in Preparation Examples 1 to 15 below, and pigments were synthesized by the methods described in Production Examples 1 and 2 below. Pigment compositions were prepared using these derivatives and pigments by the methods described in Examples 1 to 9 and Comparative Examples 1 to 10 below. Furthermore, water-based IJ inks for evaluation were prepared from these pigment compositions, and these inks were evaluated. The evaluation results are as shown in Tables 3 and 4 below. In the examples, "parts" and "%" mean "parts by weight" and "% by weight" unless otherwise specified.

[0046] (Preparation Example 1) [Synthesis of PY180SA-1] 50 parts of CI Pigment Yellow 180 (DIC Corporation) was added to 750 parts of 95% sulfuric acid (Kanto Chemical Co., Ltd.) (pigment content 0.067) at 10°C or less. The mixture was heated to 15°C and stirred for 2 hours, then poured into 1000g of ice water to precipitate. The mixture was stirred for 30 minutes, filtered, and washed with 5% saline to obtain a wet cake of CI Pigment Yellow 180 Sulfonic Acid (PY180SA-1). The wet cake was dried at 90°C, and the obtained solid was pulverized with a juicer mixer to obtain PY180SA-1.

[0047] (Preparation Example 2) [Synthesis of PY180SA-2] A wet cake was obtained in the same manner as in Preparation Example 1, except that the amount of CI Pigment Yellow 180 was changed to 45 parts and the reaction time was changed to 1 hour.

[0048] (Preparation Example 3) [Synthesis of PY180SA-3] A wet cake was obtained in the same manner as in Preparation Example 1, except that the sulfuric acid concentration was 98%, the amount of CI Pigment Yellow 180 was 40 parts, the reaction temperature was 10° C., and the reaction time was 1 hour.

[0049] (Preparation Example 4) [Synthesis of PY180SA-4] A wet cake was obtained in the same manner as in Preparation Example 1, except that the sulfuric acid concentration was 98%, the amount of CI Pigment Yellow 180 was 45 parts, the reaction temperature was 10° C., and the reaction time was 2.5 hours.

[0050] (Preparation Example 5) [Synthesis of PY180SA-5] A wet cake was obtained in the same manner as in Preparation Example 1, except that the sulfuric acid concentration was 98%, the amount of CI Pigment Yellow 180 was 45 parts, the reaction temperature was 20° C., and the reaction time was 1 hour.

[0051] (Preparation Example 6) [Synthesis of PY180SA-6] A wet cake was obtained in the same manner as in Preparation Example 1, except that the sulfuric acid concentration was changed to 98% and the reaction time was changed to 4 hours.

[0052] (Preparation Example 7) [Synthesis of PY180SA-Al-1] 41 parts of the wet cake of PY180SA-1 (solid content 23.4%) prepared in Preparation Example 1 was added to 1000 parts of water, and the temperature was raised to 80°C while stirring. After the wet cake lumps disappeared, the pH was adjusted to 12.0-12.5 with 25% aqueous sodium hydroxide solution, stirred for 30 minutes, and 36 parts of aluminum sulfate 14-18 hydrate (manufactured by Kanto Chemical Co., Ltd.) was added and stirred for 60 minutes. After filtration and washing with water, a wet cake of CI Pigment Yellow 180 sulfonic acid aluminum salt (PY180SA-Al-1) was obtained. The wet cake was dried at 90°C, and the obtained solid was pulverized with a juicer mixer to obtain PY180SA-Al.

[0053] (Preparation Example 8) [Synthesis of PY180-SA-Al-2] A powder was obtained in the same manner as in Preparation Example 7, except that the wet cake used was changed to PY180SA-2.

[0054] (Preparation Example 9) [Synthesis of PY180-SA-Al-3] A powder was obtained in the same manner as in Preparation Example 7, except that the wet cake used was changed to PY180SA-3.

[0055] (Preparation Example 10) [Synthesis of PY180-SA-Al-4] A powder was obtained in the same manner as in Preparation Example 7, except that the wet cake used was changed to PY180SA-4.

[0056] (Preparation Example 11) [Synthesis of PY180-SA-Al-5] A powder was obtained in the same manner as in Preparation Example 7, except that the wet cake used was changed to PY180SA-5.

[0057] (Preparation Example 12) [Synthesis of PY180-SA-Al-6] A powder was obtained in the same manner as in Preparation Example 7, except that the wet cake used was changed to PY180SA-6.

[0058] (Preparation Example 13) [Synthesis of PY180SA-TA] 10 parts of PY180SA prepared in Preparation Example 1 above was added to 200 parts of 1% aqueous sodium hydroxide solution and stirred for 30 minutes. 15 parts of triethanolamine (Kanto Chemical Co., Ltd.) was added and stirred for 60 minutes. After filtration and washing with water, a wet cake of triethanolamine salt of CI Pigment Yellow 180 sulfonic acid (PY180SA-TA) was obtained. The wet cake was dried at 90°C, and the obtained solid was pulverized with a juicer mixer to obtain PY180SA-TA.

[0059] (Preparation Example 14) [Synthesis of PY180SA analogues] 12 parts of 1,2-bis(2-aminophenoxy)-ethane were dispersed in 72 parts of water, and then 28.9 parts of 35% hydrochloric acid were added. While ice was added to keep the temperature below 5°C, 18.1 parts of 40% aqueous sodium nitrite solution were added dropwise to prepare a diazo component. 11.6 parts of potassium 4-(acetoacetylamino)benzenesulfonate were dissolved in 150 parts of water, and the entire amount of the solution was added dropwise to the diazo component at a constant rate. Next, 13.7 parts of 5-acetoacetylamino-benzimidazolone were dispersed in 218 parts of water, and then 17.7 parts of 25% aqueous sodium hydroxide solution were added and dissolved to obtain a coupler component. The amount of the coupler component was adjusted to 500 parts by adding water and ice. 1.6 parts of 90% acetic acid were added to 660 parts of water, and the temperature of this solution was adjusted to 20°C. The coupler component was added dropwise to adjust the pH to 6.0, and then the diazo component was started to be added dropwise at a constant rate. In order to prevent the presence of excess diazonium salt in the acetic acid solution, the drop of the coupler component was started simultaneously with the drop of the diazo solution, and the coupling was performed while adjusting the pH of the acetic acid solution to 6.0 by adjusting the drop rate of the coupler component. The coupling was completed in about 3 hours while adding ice or 5% sodium hydroxide solution at appropriate times to maintain the temperature at 20°C and the pH at 6.0 during the coupling, and then heated to 90°C and held for 1 hour. The wet cake obtained after filtration and washing with water was dried at 90°C. The obtained solid was pulverized with a juicer mixer to obtain a PY180SA analogue.

[0060] (Preparation Example 15) [Synthesis of PY180SA-Al analogue] 41.8 parts of wet cake of PY180SA analog (solid content 23.9%) was added to 158.2 parts of water, and the temperature was raised to 80°C while stirring. Next, the pH was adjusted to 12.0-12.5 with 25% aqueous sodium hydroxide solution, and the mixture was stirred for 30 minutes. 36 parts of aluminum sulfate 14-18 hydrate (Kanto Chemical Co., Ltd.) was added and the mixture was stirred for 60 minutes. After filtration and washing with water, a wet cake of PY180SA-Al analog was obtained. The wet cake was dried at 90°C, and the obtained solid was pulverized with a juicer mixer to obtain PY180SA-Al analog.

[0061] (Production Example 1) [Synthesis of Pigment (Y180)] 225 parts of 1,2-bis(2-aminophenoxy)-ethane was dispersed in 3300 parts of water, 538.5 parts of 35% hydrochloric acid was added, and ice was added to keep the temperature below 5°C, while 337 parts of 40% aqueous sodium nitrite solution was added dropwise to prepare a diazo component. Next, 455 parts of 5-acetoacetylamino-benzimidazolone was dispersed in 3400 parts of water, and 595 parts of 25% aqueous sodium hydroxide solution was added to dissolve, to obtain a coupler component. The diazo component and coupler component were adjusted to 6500 parts and 4500 parts of liquid by adding water and ice, respectively. 30.6 parts of 90% acetic acid was added to 6500 parts of water, and the temperature of this solution was adjusted to 20°C. After the coupler component was added dropwise to adjust the pH to 6.0, the diazo component was started to be added dropwise at a constant rate. In order to prevent excess diazonium salt from being present in the acetic acid solution, the coupler component was added dropwise at the same time as the diazo solution was added dropwise, and coupling was performed while adjusting the pH of the acetic acid solution to 6.0 by adjusting the drop rate of the coupler component. The coupling was completed in about 3 hours while ice or 5% sodium hydroxide solution was added at appropriate times to maintain the temperature at 20°C and the pH at 6.0 during coupling, and then the mixture was heated to 90°C and held for 1 hour. The wet cake obtained after filtration and washing with water was dried at 90°C. The obtained solid was pulverized with a juicer mixer to obtain Y180 pigment.

[0062] (Production Example 2) [Grinding treatment of pigment (Y180)] 500 parts of the yellow powder of Y180 pigment obtained in Production Example 1, 2500 parts of salt, and 500 parts of diethylene glycol were charged into a 15 L Trimix (TM; manufactured by Inoue Seisakusho Co., Ltd.), and the temperature was adjusted so that the internal temperature was maintained at 80°C to 100°C, followed by grinding for 5 hours. The ground pigment composition was poured into 50°C warm water, stirred, and thoroughly reslurried, filtered, washed with water, and the resulting wet cake was dried at 90°C. The resulting solid was pulverized with a juicer mixer to obtain a powder.

[0063] [Zeta potential measurement] The zeta potential of the derivative was measured by the following method. The obtained evaluation results are shown in Table 1. Zeta potential was measured using a zeta potential, particle size and molecular weight measurement system (product name "ELSZ-2000Z", manufactured by Otsuka Electronics Co., Ltd.). First, 5 mg of the measurement sample and 5 mL of pure water were weighed into a 30 mL sample bottle and dispersed for 15 minutes using an ultrasonic cleaner (product name "Bransonic M2800-J", manufactured by Yamato Scientific Co., Ltd.). Next, 100 μL of the measurement sample dispersion and 10 mL of pure water were weighed into a 30 mL sample bottle and dispersed for 1 minute using Bransonic M2800-J. The measurement solution prepared was injected into the flow cell unit, the cell was installed in the ELSZ-2000Z, and the scattering intensity was confirmed. If the scattering intensity was within the appropriate range for measurement (10,000 to 50,000 cps), the measurement was continued. If it was outside the appropriate range, the concentration of the measurement sample was adjusted so that it was within the appropriate range before measurement. The measurement conditions using the ELSZ-2000Z were as follows. Measurements were repeated three times, and the average value was used as the zeta potential of the measurement sample in water. [Measurement conditions] Measurement temperature: 25℃ Measurement waiting time: 300 seconds Pinhole: 50 Number of times: 10 Cell measurement positions: 0.70 / 0.35 / 0.00 / -0.35 / -0.70 Applied voltage: Fixed Applied voltage (fixed): 60 Applied voltage waveform type: Auto Constant current: 51mA Lorentz fit: 1peak Zeta potential conversion formula: Smoluchows

[0064] [Table 1]

[0065] [Measurement of solubility parameters] The solubility parameters of the pigments and derivatives were measured by the following method. The evaluation results are shown in Table 2. 50 ml of pure water and X ml of acetone were added to a 100 ml beaker and gently stirred with a stirrer. 0.1 g of a pigment or derivative was added as a measurement sample, and after stirring for 1 minute, the amount of acetone when the entire amount of the pigment or derivative was sunk was taken as X. The solubility parameter (δm) was calculated according to the following formula. δm=(50×δw+X×δa) / (50+X) δw=23.43 δa=9.75

[0066] [Table 2]

[0067] (Examples 1-9 and Comparative Examples 1-10) 20 parts of the pigment obtained in Production Example 2 and 0.6 parts of PY180SA-Al-1 were added to a mixer (product name "LAB MILL", manufactured by Osaka Chemical Co., Ltd.), and blending for 10 seconds was repeated three times to obtain a pigment composition. For Examples 2-9 and Comparative Examples 1-10, pigment compositions were obtained in the same manner as in Example 1 using the pigments and derivatives shown in Tables 3 and 4 below. Note that for Comparative Examples 1, 5, 7, and 9, each pigment was used as it was without being treated in the mixer.

[0068] [Preparation of water-based IJ ink for evaluation] To 4.0 g of the pigment composition obtained above, 1.8 g of a styrene-(meth)acrylic acid copolymer (acid value: 167, active ingredient 45% by mass) was added as a dispersing resin, 0.4 g of a 25% by mass potassium hydroxide aqueous solution, 1.0 g of isopropyl alcohol, and 22.8 g of ion-exchanged water were added to make the total amount of the aqueous pigment dispersion 30.0 g. Then, 1 mm glass beads were added to the aqueous pigment dispersion, and the mixture was dispersed for 90 minutes using a paint conditioner. After that, ion-exchanged water was added to adjust the dispersion to a non-volatile content of 15% by mass. To 9.6 g of this aqueous pigment dispersion, 0.2 g of Surfynol 465 (manufactured by Nissin Chemical Industry Co., Ltd.), 2.3 g of glycerin, 1.7 g of triethylene glycol, 1.4 g of 2-pyrrolidone, 0.8 g of 1,2-hexanediol, and 14.0 g of ion-exchanged water were added to make the total amount 30.0 g, to prepare an aqueous IJ ink.

[0069] The initial viscosity, rate of change, and viscosity evaluation results for each of the resulting water-based IJ inks for evaluation are shown in Table 3, and the initial particle size, rate of change, and particle size evaluation results are shown in Table 4. The pigments shown in Tables 3 and 4 below are as follows.

[0070] Pigments PY180-A: Pigment obtained in Production Example 1 PY180-B ‥ Pigment obtained in Production Example 2 PY180-C Product name: TONER YELLOW HG (manufactured by Clariant Japan Co., Ltd.) PY180-D Product name: PV FAST YELLOW HG01 (manufactured by Clariant Japan Co., Ltd.)

[0071] [Table 3]

[0072] [Table 4]

[0073] [SN ratio measurement] The SN ratio of the derivatives was calculated using liquid chromatography (product name "Agilent 1100", manufactured by Agilent Technologies, Inc.). First, 5 mg of the measurement sample and 10 mL of dimethyl sulfoxide (manufactured by Kanto Chemical Co., Ltd.) were weighed into a 30 mL sample bottle and mixed for 10 seconds with a shaker (product name "VORTEX-GENIE2", manufactured by Scientific Industries Co., Ltd.). Next, the mixture was mixed for 1 hour at 130 rpm while maintaining 25 °C with a thermostatic shaker (product name "PERSONAL-11", manufactured by Taitec Co., Ltd.). After that, the measurement sample was filtered with a 0.45 μm filter (manufactured by ADVANTECH Co., Ltd.) and divided into 2 mL sample bottles, which were then placed in the Agilent 1100 and measured. The peak detected at retention times of 11.4 to 12.4 is the disubstituted product, and the peak detected at retention times of 14.7 to 14.9 is the monosubstituted product. The SN ratio was calculated from the area values ​​of these HPLC measurements according to the following formula. The HPLC measurement conditions were as follows. The measurement was repeated twice, and the average value was used as the SN ratio of the measurement sample. [Calculation formula] SN ratio = area value of 2-substituted bodies / area value of 1-substituted bodies [HPLC measurement conditions] Column: C18 U120 S3 (Φ4.6mm×100mm, 3μm) Eluent 1: 30mM ammonium acetate Eluent 2: Methanol Gradient (1 / 2): 90 / 10 (~3 minutes) 0 / 100(~40 minutes) 90 / 10(~50 minutes) Flow rate: 1.0mL / min Oven: 50°C Wavelength: 400nm Injection volume: 1.0μL

[0074] [Viscosity measurement] The initial viscosity in Table 3 above was measured by the following method. Measurement was performed using an E-type viscometer TV-25 (manufactured by Toki Sangyo Co., Ltd.) at 20° C. and 30 rpm. The dispersion was left to stand in a thermostatic chamber at 70° C. for one week, after which the viscosity was measured in the same manner, and the storage stability was determined from the change in viscosity before and after heating (viscosity ratio). (judgment criteria) ◎: Change rate less than 120% ○: Change rate is 120% or more but less than 140% △: Change rate is 140% or more but less than 200% ×: Change rate 200% or more

[0075] [Dispersion average particle size] The initial particle size in Table 4 above was measured by the following method. The average dispersed particle diameter Mv was calculated by measuring with a particle size distribution analyzer (product name "Nanotrac WaveII", manufactured by Microtrack Bell Co., Ltd.). After leaving the dispersion liquid in a thermostatic chamber at 70°C for one week, Mv was calculated in the same manner, and the storage stability was determined from the change in Mv before heating (Mv ratio). (judgment criteria) ◎: Initial particle size less than 200 nm and rate of change less than 150% ○: Initial particle size less than 200 nm and change rate 150% to less than 200% △: Initial particle size less than 200 nm and rate of change between 200% and 250% ×: Initial particle size 200 nm or more or rate of change 250% or more

[0076] As can be seen from Table 3 above, the pigment compositions of the present invention (Examples 1-9) using a derivative with a zeta potential of -20 mV or more and less than 0 mV and a solubility parameter of 21 or less for the Y180 pigment have a smaller rate of change in viscosity than Comparative Examples 1-10. Also, as can be seen from Table 4 above, the pigment compositions of the present invention (Examples 1-9) have a smaller rate of change in particle diameter than Comparative Examples 1-10. This shows that the pigment compositions of the present invention have excellent dispersion stability and storage stability when used in aqueous IJ inks.

Claims

1. A pigment composition comprising C.I. Pigment Yellow 180 having an aspect ratio of 1.0 to 2.0 and a derivative, The derivative is C.I. Pigment Yellow 180 having a sulfonic acid group, 【Chemistry 1】 The compound includes a compound selected from the group consisting of compounds represented by The zeta potential of the derivative is −20 mV or more and less than 0 mV; The solubility parameter of the derivative is 21 or less; The solubility parameter is calculated from the following formula, in which 0.1 g of a derivative is added to a mixture of 50 ml of pure water and X ml of acetone, and the amount of acetone at which the entire amount of the derivative sinks after stirring for 1 minute is X: δm=(50×δw+X×δa) / (50+X) δw=23.43 δa=9.75 the molar ratio of mono- to di-substituted sulfonic acid groups in the derivative (signal-to-noise ratio (di-substituted / mono-substituted)) is 0.1 to 30.0; The pigment composition has a content of the derivative of 0.5 to 10 parts by weight based on 100 parts by weight of the C.I. Pigment Yellow 180.

2. the derivative is a salt of a trivalent metal, 2. The pigment composition according to claim 1, wherein the trivalent metal is at least one selected from the group consisting of iron, chromium, cobalt, and aluminum.

3. An aqueous pigment dispersion for ink-jet ink, comprising the pigment composition according to claim 1 or 2.

4. An aqueous pigment ink for inkjet recording, comprising the pigment composition according to claim 1 or 2.

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