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

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

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

[0002] Inkjet printers are not only used for home use, but are also widely used in industrial applications due to the trend toward smaller print runs, and in recent years, the business has expanded to include textile applications and flexible packaging. Among these, yellow ink is an important core 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 systems in addition to having coloring power and lightfastness.

[0003] As a yellow pigment for yellow ink, C.I. Pigment Yellow 180 (hereinafter referred to as "Y180"), a type of benzimidazolone yellow pigment, has attracted attention from the viewpoint of achieving both coloring strength and lightfastness. Patent Document 1 listed below is an example of the use of Y180 in an inkjet ink. Patent Document 1 describes the use of a pigment derivative (amine salt, ammonium salt, or monovalent metal salt) of Y180 or other pigment containing a sulfonic acid group together with a benzimidazolone yellow pigment such as Y180.

[0004] Japanese Patent Application Laid-Open No. 2002-220557

[0005] The present inventors have investigated conventional pigment compositions containing Y180, such as those described in Patent Document 1, and have found that they do not have sufficient storage stability or dispersion stability when used in inkjet inks. 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 inkjet aqueous pigment inks.

[0006] As a result of extensive research aimed at solving the above problems, the present inventors have discovered the use of a derivative of Y180 having a specific zeta potential and solubility parameter, and have completed the present invention. The mechanism of the present invention is as follows.

[0007] Because the Y180 pigment has highly hydrophilic functional groups and bonding moieties in its molecular structure, it tends to have high water wettability and good initial dispersion. However, it is believed 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, we believe it is important to increase the resin adsorption using a derivative. Generally, particles with a high absolute value of zeta potential are considered to have high dispersion stability due to electrostatic repulsion. In this invention, however, dispersion stability is improved by using a derivative with a low absolute value of zeta potential. This is because, to achieve the dispersion stability effect of the derivative, the derivative must be adsorbed onto the pigment particle surface, and derivatives with a high absolute value of zeta potential cannot be densely adsorbed onto the pigment particle surface due to electrostatic repulsion. Furthermore, pigment particles with a small aspect ratio can achieve even higher dispersion stability. Pigment particles with a large aspect ratio and low dispersion stability have an elongated, rod-like shape. Furthermore, because Y180 pigment particles grow by stacking through π-π stacking, the short axis plane of the rod-shaped particles inevitably becomes the π-stacking plane. In water, π-π stacking is the dominant force that causes derivatives to adhere to pigment particles, with the π-stacking surfaces of the short axis being the sites of derivative adsorption. Pigment particles with a large aspect ratio have poor dispersion stability due to the large area of ​​the long axis that does not adsorb derivatives. Pigment particles with a small aspect ratio have a high area ratio of the short axis that adsorbs derivatives, resulting in a strong dispersion stabilization effect from the derivatives. For pigment particles with a small aspect ratio, the distance between the two short axis surfaces within the same pigment particle is short due to the small aspect ratio, and the influence between the short axis surfaces is significant. As mentioned above, electrostatic repulsion of the derivative itself can hinder the adsorption of derivatives to pigment particles. Therefore, when attempting to adsorb a derivative with a high absolute value of zeta potential to particles with a small aspect ratio, electrostatic repulsion occurs between the two short axis surfaces within the same pigment particle, resulting in insufficient effectiveness. Therefore, it is presumed 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, pigments with a small aspect ratio have a larger area ratio of the minor axis plane, making it easier for the derivative to adsorb, but the highly hydrophilic Y180 also easily adsorbs water, and even if the derivative does adsorb once, the water inhibits this, causing poor dispersion stability. Furthermore, derivatives with a large solubility parameter have a high affinity for water, which increases the effect of inhibiting adsorption to the pigment, and also strengthens the interaction between the pigment and water, making them more likely to cause poor dispersion. Therefore, it is speculated that using 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 relates to: "Item 1. A pigment composition comprising 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. Item 2. The pigment composition according to Item 1, in which the aspect ratio of the C.I. Pigment Yellow 180 is 1.0 to 2.0. Item 3. The pigment composition according to Item 1 or 2, in which the derivative is a derivative of C.I. Pigment Yellow 180. Item 4. The pigment composition according to any one of Items 1 to 3, in which the derivative has a sulfonic acid group. Item 5. The pigment composition according to any one of Items 1 to 4, in which 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 inkjet ink, comprising the pigment composition according to any one of Items 1 to 5. Item 7. An aqueous inkjet pigment ink, comprising the pigment composition according to any one of Items 1 to 5."

[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 aqueous inkjet inks.

[0011] The present invention will be described in detail below. In the present invention, Y180 does not simply mean the compound represented by the following Chemical Formula 1, but means a pigment constituted by said compound. The concept of said pigment includes not only its crystalline structure but also the primary particles formed by aggregation or aggregation of said particles, and further the physical properties of the aggregation or aggregation resulting from the surface condition, 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. Such a derivative is generally called a pigment derivative (synergist). In addition to the pigment such as Y180 and the derivative, the pigment composition of the present invention may also contain other solid components such as a resin to improve dispersibility.

[0013] (Pigment) Y180, CAS No. 77804-81-0, 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]

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

[0016] The aspect ratio of 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, aggregation of pigment particles can be reduced, resulting in a smaller particle size and excellent dispersion stability and storage stability when used as an aqueous pigment dispersion or ink for inkjet inks.

[0017] The primary particle minor diameter of 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 reduced, resulting in excellent print density (OD) when used as an aqueous pigment dispersion for inkjet ink or ink.

[0018] The major axis, aspect ratio, and minor axis of the primary particles in Y180 are preferably within the above-mentioned 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 using an electron microscope or the like and averaging the lengths measured for, for example, 100 particles.

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

[0020] The specific treatment involves, for example, using 200 to 1,000 parts by mass of an inorganic salt per 100 parts by mass of the pigment (crude pigment) and performing milling while heating in the presence of a solvent (solvent salt milling). By performing milling while heating in the presence of a solvent, the crystallinity of the pigment can be improved while the primary particle size falls within a specific range.

[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 inorganic salts can be easily obtained by finely grinding a conventional inorganic salt. The amount of inorganic salt used is, for example, 200 to 1,000 parts by mass, preferably 300 to 800 parts by mass, per 100 parts by mass of the pigment. From the viewpoint of miniaturizing the pigment particles, a larger amount of inorganic salt is preferable, but in the present invention, the above range is preferable from the viewpoint of achieving a balance with the degree of crystallinity.

[0022] As the solvent, it is preferable to use an organic solvent capable of suppressing crystal growth. 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 these, diethylene glycol (DEG) is particularly preferred because it can be heated to an appropriate temperature and has excellent wettability with the pigment. The amount of solvent used is, for example, 10 to 500 parts by mass, preferably 50 to 300 parts by mass, per 100 parts by mass of the pigment in order to achieve an appropriate viscosity during grinding.

[0023] The above-mentioned solvent salt milling is carried out by charging the pigment, inorganic salt, and a solvent that does not dissolve them into a kneader and kneading them therein. Examples of kneaders that can be used in this process include a kneader, a trimix, and a mix muller. The heating temperature during the solvent salt milling is, for example, 50 to 100°C, and preferably 60 to 90°C. The heating temperature can be changed as appropriate using a temperature control device provided in the kneader. The time for which the solvent salt milling is carried out is, for example, 2 to 10 hours, and 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 specifically, C.I. 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, 185, and 213. Furthermore, dyes and pigments other than the above yellow pigments may be contained. In the pigment composition of the present invention, Y180 preferably accounts for 50% by mass or more, more preferably 60% by mass or more, of the total pigments.

[0025] The content of the pigment in the pigment composition (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] The resin (dispersion resin) for improving the dispersibility may be a copolymer resin such as a styrene-(meth)acrylic acid copolymer, a styrene-maleic acid copolymer, a diisobutylene-maleic acid copolymer, or a vinylnaphthalene-(meth)acrylic acid polymer, a urethane resin, a surfactant, etc. The content of these dispersion resins is, for example, 3 to 30 parts by weight, and preferably 5 to 20 parts by weight, per 100 parts by weight of the pigment such as Y180.

[0027] (Derivative) The zeta potential of the 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, the derivative can be easily adsorbed to the Y180 pigment, thereby improving the dispersion stability of the pigment composition. The zeta potential can be measured by electrophoretic light scattering measurement (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, affinity with the Y180 pigment is high, and as a result, an increase in viscosity over time in the pigment composition can be suppressed, and storage stability can be improved. The solubility parameter (SP) can be determined by mixing the derivative with a solvent such as acetone, whose solubility parameter is known, and measuring the SP value of the mixed solution when the pigment is completely wetted.

[0029] Examples of the derivative include derivatives having a pigment structure such as C.I. 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 C.I. Pigment Yellow 180 (Y180) are preferred because of their excellent dispersion stability and storage stability when used as 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 derivative may have an acid group such as a carboxylic acid group, a hydroxyl group, or a sulfonic acid group, but it is preferable that the derivative has a sulfonic acid group. ３H, or a group consisting of an organic compound having a sulfo group substituted on the carbon skeleton (-RSO ３ In the present invention, the sulfonic acid group is represented by —SO ３ It is preferably a group represented by H. The number of sulfonic acid groups (average number of substituents) possessed by the 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 derivative may contain both or either a compound having one sulfonic acid group introduced into the same molecule (mono-substituted compound) and a compound having two sulfonic acid groups introduced into the same molecule (di-substituted compound). The molar ratio of the mono-substituted compound to the di-substituted compound (SN ratio (di-substituted compound / mono-substituted compound)) in the derivative 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 groups is within the above range, the dispersion stability and storage stability of Y180 are improved. The average number of substituents on the sulfonic acid groups and the SN ratio of the derivative can be calculated from the area ratio of each compound in liquid chromatography.

[0032] To introduce sulfonic acid groups into a derivative such as Y180, for example, a sulfonating agent such as fuming sulfuric acid, concentrated sulfuric acid, or chlorosulfuric acid may be allowed to act on 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 adjust the zeta potential to 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 one of these metal ions. Aluminum is preferred from the viewpoints of economy and performance.

[0035] If necessary, other pigment derivatives (synergists) may be used as the derivatives. 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 different types of these derivatives can also be used in combination.

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

[0037] (Aqueous pigment dispersion for inkjet ink) The aqueous pigment dispersion for inkjet 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 may contain other components such as a dispersant as necessary.

[0038] The aqueous pigment dispersion for inkjet inks may contain a water-soluble organic solvent together with water as the 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 glycols, and lactams such as N-methyl-2-pyrrolidone. These organic solvents can 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 an inkjet ink is, for example, about 0 to 60%, and preferably 0 to 45%, and the remainder other than the pigment dispersion for an inkjet ink (non-volatile components) is almost entirely water.

[0040] [Inkjet Water-Based Pigment Ink] The inkjet water-based 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 Y180. 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, C.I. 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, 185, 213, etc. Furthermore, dyes or pigments other than the above yellow pigments may be contained. Furthermore, when mixing yellow pigments or dyes other than Y180, there are no particular limitations on the mixing method. The pigment composition may be mixed in the inkjet ink as a pigment composition, or the pigment dispersion ...

[0041] The inkjet water-based pigment ink may contain additives as needed. 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 ink concentration of the water-based pigment ink may also be adjusted by adding water or a water-soluble organic solvent.

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

[0043] The viscosity (25°C) of the inkjet aqueous pigment ink is preferably 1 to 30 mPa·s, more preferably 2 to 20 mPa·s, from the viewpoint of improving the storage stability of the ink. The pH of the inkjet aqueous pigment ink is, for example, 7.0 or higher, preferably 7.5 or higher, 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 lower, preferably 10.0 or lower.

[0044] The inkjet aqueous 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. Inkjet recording devices include continuous jet types (charge control types, spray types, etc.) and on-demand types (piezo type, thermal type, electrostatic suction type, etc.), and the aqueous pigment ink of the present invention can be used with any of these types.

[0045] The present invention will be described in further 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. 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, aqueous inkjet 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 these examples, "parts" and "%" mean "parts by weight" and "% by weight" unless otherwise specified.

[0046] (Preparation Example 1) [Synthesis of PY180SA-1] 50 parts of C.I. Pigment Yellow 180 (manufactured by DIC Corporation) was added to 750 parts of 95% sulfuric acid (manufactured by 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 1000 g of ice water to precipitate. The mixture was stirred for 30 minutes, filtered, and washed with 5% saline to obtain a wet cake of C.I. Pigment Yellow 180 sulfonic acid (PY180SA-1). The wet cake was dried at 90 ° C., and the resulting 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 above, except that the amount of C. I. 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 above, except that the sulfuric acid concentration was 98%, the amount of C.I. 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 above, except that the sulfuric acid concentration was 98%, the amount of C.I. 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 above, except that the sulfuric acid concentration was 98%, the amount of C.I. 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 above, 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 PY180SA-1 wet cake (solid content 23.4%) prepared in Preparation Example 1 above was added to 1,000 parts of water, and the temperature was raised to 80°C with stirring. After the wet cake lumps disappeared, the pH was adjusted to 12.0-12.5 with a 25% aqueous sodium hydroxide solution, and the mixture was stirred for 30 minutes. 36 parts of aluminum sulfate 14-18 hydrate (manufactured by Kanto Chemical Co., Inc.) was added and the mixture was stirred for 60 minutes. After filtration and washing with water, a wet cake of C.I. Pigment Yellow 180 sulfonic acid aluminum salt (PY180SA-Al-1) was obtained. The wet cake was dried at 90°C, and the resulting solid was pulverized using 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 above, 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 a 1% aqueous sodium hydroxide solution and stirred for 30 minutes. 15 parts of triethanolamine (manufactured by Kanto Chemical Co., Ltd.) was added and stirred for 60 minutes. After filtration and washing with water, a wet cake of triethanolamine salt of C.I. Pigment Yellow 180 sulfonic acid (PY180SA-TA) was obtained. The wet cake was dried at 90°C, and the resulting solid was pulverized using a juicer mixer to obtain PY180SA-TA.

[0059] (Preparation Example 14) [Synthesis of PY180SA Analog] 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 was added. While maintaining the temperature at 5°C or below by adding ice, 18.1 parts of 40% aqueous sodium nitrite solution was 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 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 was added and dissolved to obtain a coupler component. The volume 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. After adding the coupler component dropwise to adjust the pH to 6.0, the diazo component was added dropwise at a constant rate. The coupler component was added dropwise simultaneously with the diazo solution to prevent the presence of excess diazonium salt in the acetic acid solution, and coupling was carried out 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 approximately 3 hours while ice or 5% sodium hydroxide solution was added periodically to maintain the temperature at 20°C and the pH at 6.0 during coupling, and the mixture was then heated to 90°C and maintained for 1 hour. The resulting wet cake, which was then filtered and washed with water, was dried at 90°C. The resulting solid was pulverized using a juicer mixer to obtain a PY180SA analog.

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

[0061] (Production Example 1) [Synthesis of Pigment (Y180)] 225 parts of 1,2-bis(2-aminophenoxy)-ethane were dispersed in 3,300 parts of water, followed by the addition of 538.5 parts of 35% hydrochloric acid. While maintaining the temperature at 5°C or below with ice, 337 parts of 40% aqueous sodium nitrite solution were added dropwise to prepare a diazo component. Next, 455 parts of 5-acetoacetylamino-benzimidazolone were dispersed in 3,400 parts of water, followed by the addition of 595 parts of 25% aqueous sodium hydroxide solution to dissolve the dispersion, yielding a coupler component. The diazo component and coupler component were prepared by adding water and ice to adjust the liquid volumes to 6,500 parts and 4,500 parts, respectively. 30.6 parts of 90% acetic acid were added to 6,500 parts of water, and the temperature of the solution was adjusted to 20°C. The coupler component was then added dropwise to adjust the pH to 6.0, after which the diazo component was started to be added dropwise at a constant rate. To prevent the presence of excess diazonium salt in the acetic acid solution, the dropwise addition of the coupler component was started simultaneously with the dropwise addition of the diazo solution, and coupling was carried out while adjusting the pH of the acetic acid solution to 6.0 by adjusting the dropwise addition rate of the coupler component. The coupling was completed in about 3 hours while ice or 5% sodium hydroxide solution was added from time to time 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 there for 1 hour. The resulting wet cake, which was then filtered and washed with water, was dried at 90°C. The resulting solid was pulverized in 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 to maintain the internal temperature at 80°C to 100°C, followed by grinding for 5 hours. The ground pigment composition was poured into warm water at 50°C, stirred, and thoroughly reslurried, then filtered and washed with water. The resulting wet cake was dried at 90°C. The resulting solid was pulverized using a juicer mixer to obtain a powder.

[0063] [Zeta Potential Measurement] The zeta potential of the derivative was measured using the following method. The obtained evaluation results are shown in Table 1. The 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 in 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 in the Bransonic M2800-J. The prepared measurement solution was injected into a 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 measurement range (10,000 to 50,000 cps), the measurement continued. If it was outside the appropriate range, the concentration of the measurement sample was adjusted to bring it within the appropriate range before measurement. The measurement conditions using the ELSZ-2000Z were as follows: Measurement was repeated three times, and the average value was used as the zeta potential of the measurement sample in water. [Measurement conditions] Measurement temperature: 25°C Measurement wait time: 300 seconds Pinhole: 50 Number of accumulations: 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: 51 mA Lorentz fit: 1 peak Zeta potential conversion formula: Smoluchows

[0064]

[0065] [Measurement of Solubility Parameter] The solubility parameter of the pigment and derivative was measured using the following method. The obtained 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 pigment or derivative was added as a measurement sample, and after stirring for 1 minute, the amount of acetone when the entire pigment or derivative had 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]

[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 pigment compositions. 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 is without being treated in the mixer.

[0068] [Preparation of Aqueous Inkjet 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 weight) was added as a dispersing resin, 0.4 g of a 25% by weight aqueous potassium hydroxide solution, 1.0 g of isopropyl alcohol, and 22.8 g of ion-exchanged water were added to make the total amount of aqueous pigment dispersion 30.0 g. 1 mm glass beads were then added to the aqueous pigment dispersion, and the mixture was dispersed for 90 minutes using a paint conditioner. Subsequently, ion-exchanged water was added to adjust the nonvolatile content to 15% by weight. 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, thereby preparing an aqueous inkjet ink.

[0069] The initial viscosity, rate of change, and viscosity evaluation results for each of the resulting aqueous inkjet 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]

[0072]

[0073] [SNR Measurement] The SNR of the derivative 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 using a shaker (product name "VORTEX-GENIE2", manufactured by Scientific Industries). Subsequently, the mixture was mixed for 1 hour at 130 rpm while maintaining the temperature at 25 ° C. using a thermostatic shaker (product name "PERSONAL-11", manufactured by Taitec Co., Ltd.). Thereafter, the measurement sample was filtered through a 0.45 μm filter (manufactured by ADVANTECH) and dispensed into a 2 mL sample bottle, which was then placed in the Agilent 1100 and measured. The peak detected at retention times of 11.4 to 12.4 is the di-substituted product, and the peak detected at retention times of 14.7 to 14.9 is the mono-substituted product. The S / N ratio was calculated from these HPLC area values ​​according to the following formula. The HPLC measurement conditions were as follows, and measurements were repeated twice, with the average value being used as the S / N ratio of the measurement sample. [Calculation formula] S / N ratio = area value of di-substituted product / area value of mono-substituted product [HPLC measurement conditions] Column: C18 U120 S3 (Φ4.6 mm × 100 mm, 3 μm) Eluent 1: 30 mM ammonium acetate Eluent 2: methanol Gradient (1 / 2): 90 / 10 (up to 3 minutes), 0 / 100 (up to 40 minutes), 90 / 10 (up to 50 minutes) Flow rate: 1.0 mL / min Oven: 50°C Wavelength: 400 nm Injection volume: 1.0 μL

[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, and then the viscosity was measured in the same manner. The storage stability was determined from the change in viscosity (viscosity ratio) before heating. (Evaluation criteria) ◎: Rate of change less than 120% ○: Rate of change 120% or more but less than 140% △: Rate of change 140% or more but less than 200% ×: Rate of change 200% or more

[0075] [Dispersed Average Particle Size] The initial particle sizes in Table 4 above were measured using the following method. Measurements were performed using a particle size distribution analyzer (product name "Nanotrac Wave II", manufactured by Microtrac Bell Co., Ltd.), and the average dispersed particle size Mv was calculated. After the dispersion was left to stand in a thermostatic chamber at 70°C for one week, Mv was calculated using the same method, and storage stability was determined from the change in Mv before heating (Mv ratio). (Evaluation criteria) ◎: Initial particle size less than 200nm and change rate less than 150% ○: Initial particle size less than 200nm and change rate 150% to less than 200% △: Initial particle size less than 200nm and change rate 200% to less than 250% ×: Initial particle size 200nm or more, or change rate 250% or more

[0076] As can be seen from Table 3 above, the pigment compositions of the present invention (Examples 1-9), which use a derivative of Y180 pigment having a zeta potential of -20 mV or more but less than 0 mV and a solubility parameter of 21 or less, have a smaller rate of change in viscosity than Comparative Examples 1-10. Furthermore, 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 size than Comparative Examples 1-10. This demonstrates that the pigment compositions of the present invention have excellent dispersion stability and storage stability when used in aqueous inkjet 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 having a zeta potential of -20 mV or more and less than 0 mV and a solubility parameter of 21 or less, 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. 2. The pigment composition according to claim 1, wherein said derivative is a derivative of C.I. Pigment Yellow 180.

3. The pigment composition according to claim 1 or 2, wherein the derivative has a sulfonic acid group.

4. The pigment composition according to claim 3, wherein the molar ratio of mono-substituted to di-substituted sulfonic acid groups in the derivative (SN ratio (di-substituted / mono-substituted)) is 0.1 or more.

5. 3. The pigment composition according to claim 1, 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.

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

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