Method for producing liquid composition, and inkjet recording method

Abstract

To provide a method for producing a liquid composition which can improve dispersion stability of a pigment in a liquid composition formed by mixing two or more kinds of different crystal type copper phthalocyanine blue pigments for obtaining desired color reproducibility.SOLUTION: There is provided a method for producing a liquid composition which contains at least two kinds of pigments of a first pigment and a second pigment having different crystal structures, among pigments selected from an α type copper phthalocyanine blue, a β type phthalocyanine blue, and a ε type copper phthalocyanine blue. The method for producing the liquid composition includes: a mixing step of obtaining a pigment mixture of the first pigment and the second pigment; and a dispersion step of dispersing the pigment mixture into a dispersion medium using a resin.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for producing a liquid composition and an ink-jet recording method. [Background technology]

[0002] In recent years, inkjet recording methods have been used to record business documents using plain paper as a recording medium and photographic images using glossy paper as a recording medium, and the frequency of use has increased dramatically. As color materials used when recording images using inkjet recording methods, pigments have become mainstream due to their high fastness. However, when ink containing pigments as color materials is used, the range of color reproducibility is inferior to when ink containing dyes as color materials is used. Therefore, it is becoming mainstream to use pigments that have been pulverized to a primary particle diameter of about 20 nm to 100 nm to be finely divided. There are many methods for pulverizing pigments, but wet kneading pulverization such as solvent salt milling and dry pulverization are widely used (Patent Document 1).

[0003] On the other hand, various combinations of pigments have been proposed to obtain the desired color reproducibility. Copper phthalocyanine blue organic pigments, which are mainly used in the blue region, include reddish blue α-type crystals, greenish blue β-type crystals, and reddish blue ε-type crystals. Nevertheless, from the viewpoint of vividness, β-type copper phthalocyanine blue organic pigments are widely used (Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6393257 [Patent Document 2] Japanese Patent Application Publication No. 11-143130 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when only β-type copper phthalocyanine blue is used as an ink in the blue region as proposed in the past, the desired hue may not be obtained. Therefore, a method of obtaining the desired color reproducibility by mixing two different crystal types is considered. However, when a plurality of liquid compositions in which a pigment is dispersed in a liquid medium are mixed, the dispersion stability of the pigment in the liquid composition after mixing may be lower than the dispersion stability of the pigment in each liquid composition before mixing. As a result of the study by the present inventors, it was confirmed that the dispersion stability is significantly lowered when liquid compositions in which copper phthalocyanine blue pigments of different crystal types, in particular those having a primary particle diameter of 50 nm or less, are mixed.

[0006] Therefore, an object of the present invention is to provide a method for producing a liquid composition capable of improving the dispersion stability of a liquid composition in which two or more copper phthalocyanine blue pigments having different crystal forms are mixed in order to obtain a desired color reproducibility. Another object of the present invention is to provide an inkjet recording method using the liquid composition obtained by the above-mentioned production method. [Means for solving the problem]

[0007] That is, according to the present invention, there is provided a method for producing a liquid composition containing at least two pigments, a first pigment and a second pigment, which have different crystal structures from each other and are selected from α-type copper phthalocyanine blue, β-type copper phthalocyanine blue, and ε-type copper phthalocyanine blue, the method for producing a liquid composition comprising: a mixing step of obtaining a pigment mixture of the first pigment and the second pigment; and a dispersing step of dispersing the pigment mixture in a dispersion medium using a resin. Effect of the Invention

[0008] According to the present invention, there can be provided a method for producing a liquid composition capable of improving the dispersion stability of a liquid composition in which two or more copper phthalocyanine blue pigments having different crystal forms are mixed in order to obtain a desired color reproducibility. Furthermore, according to the present invention, there can be provided an inkjet recording method using the liquid composition obtained by the above-mentioned production method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The present invention will be described in more detail below with reference to preferred embodiments. In the present invention, when the compound is a salt, the salt is present in the ink in the form of dissociation into ions, but for convenience, it is expressed as "containing a salt." In addition, water-based ink for inkjet printing may be simply referred to as "ink." Physical property values ​​are values ​​at room temperature (25°C) unless otherwise specified.

[0010] Copper phthalocyanine blue exhibits homogeneous crystals, and has crystal structures such as α-type, β-type, γ-type, δ-type, and ε-type. The lattice constant and tilt angle of these crystal structures are determined by crystal structure analysis using X-ray diffraction, and the crystal type is defined by the measured value of the diffraction angle with respect to the diffraction plane and the interplanar spacing. In particular, in α-type copper phthalocyanine blue, the Bragg angles 2θ determined by X-ray diffraction spectrum are 6.8°, 7.4°, 26.6°, and 27.5°. The Bragg angles 2θ of β-type copper phthalocyanine blue are 7.0°, 9.0°, and 23.7°, and the Bragg angles 2θ of ε-type copper phthalocyanine blue are 7.6°, 9.2°, and 23.0°.

[0011] In addition, the color of copper phthalocyanine blue varies depending on the crystal type. α-type copper phthalocyanine blue shows reddish blue, β-type copper phthalocyanine blue shows greenish blue, and ε-type copper phthalocyanine blue shows reddish blue. Therefore, in order to obtain the desired color reproducibility, the present inventors have attempted to prepare a liquid composition in which a pigment is dispersed in a liquid medium and to mix a plurality of liquid compositions with different crystal types. However, when a plurality of liquid compositions in which a pigment is dispersed in a liquid medium are mixed, the dispersion stability of the pigment in the liquid composition after mixing may be lower than the dispersion stability of the pigment in each liquid composition before mixing. The present inventors speculate that this is because the pigment of one crystal type peels off the dispersant of the pigment of the other crystal type by mixing the liquid compositions prepared individually, resulting in a decrease in stability.

[0012] Based on the above results, the present inventors attempted to prepare a liquid composition by mixing copper phthalocyanine blues having different crystal types when dispersing a pigment in a liquid medium. As a result, it was found that a liquid composition obtained by mixing copper phthalocyanine blues having multiple crystal types among α-type, β-type, and ε-type, and then dispersing the pigment mixture in a dispersion medium using a resin, had excellent dispersion stability of the pigment.

[0013] Furthermore, the present inventors considered that when a mixture of pigments with different crystal types is prepared by salt milling, which is generally used as a method for controlling the particle size and surface condition of pigments, the surface condition of the pigments will be equivalent and the dispersion stability will be increased. Therefore, the present inventors prepared a pigment mixture containing pigments with different crystal types by salt milling, and prepared a liquid composition in the same manner as above. As a result, it was found that the dispersion stability of the pigments in the obtained liquid composition was further improved.

[0014] <Method of producing liquid composition> One embodiment of the present invention relates to a method for producing a liquid composition containing at least two pigments, a first pigment and a second pigment, which are selected from α-type copper phthalocyanine blue, β-type copper phthalocyanine blue, and ε-type copper phthalocyanine blue and have different crystal structures. The method for producing the liquid composition includes a mixing step of obtaining a pigment mixture of the first pigment and the second pigment, and a dispersing step of dispersing the pigment mixture in a dispersion medium using a resin. Each step and each material used will be described in detail below.

[0015] [Mixing process] The method for producing a liquid composition includes a mixing step of obtaining a pigment mixture of a first pigment and a second pigment (hereinafter, these may be collectively referred to simply as "pigments"). The ratio (mass %) of the amount of the first pigment used to the total amount of the first pigment and the second pigment used is preferably 10% by mass or more and 90% by mass or less, and more preferably 30% by mass or more and 70% by mass or less. The ratio (mass %) of the amount of the second pigment used to the total amount of the first pigment and the second pigment used is preferably 10% by mass or more and 90% by mass or less, and more preferably 30% by mass or more and 70% by mass or less.

[0016] An example of a method for mixing pigments is a dry grinding method. For example, a method using a mixing blade type mixer (e.g., Mixmuller manufactured by Sinto Kogyo) in which a mixing container is provided with a stirring blade and the powders to be mixed (first and second pigments) are stirred and mixed by the stirring blade can be mentioned. Another example is a method using a container rotation type mixer (e.g., V-type mixer manufactured by Seishin Enterprise Co., Ltd.) in which a mixing container is rotatably provided and the powders to be mixed (first and second pigments) are stirred and mixed by rotating the mixing container. As a method for obtaining a pigment mixture of the first and second pigments, it is preferable to carry out the following kneading step using a solvent salt milling method, which is a wet grinding method.

[0017] (Kneading process) The mixing step preferably includes a kneading step by a salt milling method in which a mixture containing a first pigment, a second pigment, a water-soluble inorganic salt, and an organic solvent is kneaded to obtain a kneaded product. By using a pigment mixture of the first pigment and the second pigment obtained through a kneading step by the salt milling method, the dispersion stability of the pigment in the liquid composition is further improved, and good dispersion stability can be obtained even under severer conditions.

[0018] The above-mentioned salt milling method is also called a solvent salt milling method because an organic solvent is used in addition to a pigment and a water-soluble inorganic salt. The solvent salt milling method is a method in which a mixture containing pigments (first pigment and second pigment), a water-soluble inorganic salt, and an organic solvent is kneaded using a kneading device while compressing the mixture by applying a load to the mixture.

[0019] As the kneading device, for example, a batch type, a continuous type, a normal pressure type, a pressurized type, and a reduced pressure type can be used, and a device that applies a load to the contents to compress and knead can be preferably used. In addition, a kneading device equipped with a material input section such as a kneading kettle and a hopper, and an agitation section such as an agitation blade, an agitation blade, a blade, a screw, and a roll for agitating the materials can be preferably used. Specific examples of the kneading device include kneading devices such as a kneader, a roll mill, a ball mill, an attritor, a sand mill, a planetary mixer, and a continuous uniaxial kneader. An example of the planetary mixer is Trimix (trade name) manufactured by Inoue Seisakusho. An example of the continuous uniaxial kneader is Miracle KCK (trade name) manufactured by Asada Iron Works. Among the kneading devices listed above, it is preferable to use a planetary mixer.

[0020] The mixing ratio of the pigment, the water-soluble inorganic salt, and the organic solvent in the kneading step is preferably the following ratio based on the total amount of the first pigment and the second pigment. The amount of the water-soluble inorganic salt used in the kneading step is preferably 3.0 times or more and 20.0 times or less, and more preferably 5.0 times or more and 10.0 times or less, in terms of mass ratio to the total amount of the first pigment and the second pigment. The amount of the organic solvent used in the kneading step is preferably 0.5 times or more and 5.0 times or less, and more preferably 1.0 times or more and 3.0 times or less, in terms of mass ratio to the total amount of the first pigment and the second pigment. Furthermore, as described later, the water-soluble inorganic salt may contain moisture, so in the kneading step, a small amount of water may be contained in the mixture containing the pigment, the water-soluble inorganic salt, and the organic solvent. The mass of water in the kneading step is preferably 0.5 mass% or more and 3.0 mass% or less, in terms of mass ratio to the mass of the water-soluble inorganic salt.

[0021] In the kneading step, the order of kneading the materials is preferably such that the pigment and the organic solvent are kneaded first, and then the water-soluble inorganic salt is kneaded while mixing them. The kneading temperature in the kneading step is preferably 0° C. or higher and 150° C. or lower, and more preferably 25° C. or higher and 90° C. or lower. The kneading time in the kneading step is preferably 1 hour or higher and 10 hours or lower, and more preferably 2 hours or higher and 8 hours or lower.

[0022] The average primary particle size of the first pigment and the second pigment before the mixing step is preferably 1 μm or less, more preferably 500 nm or less. In addition, the difference in the average primary particle size of the first pigment and the second pigment is preferably 100 nm or less. From the viewpoint of improving color development performance, the average primary particle size of the pigment mixture of the first pigment and the second pigment after the mixing step, preferably after the mixing step including the kneading step, is preferably 50 nm or less. Furthermore, in order to further improve the dispersion stability of the pigment, it is preferable that 90% or more of the pigment particles have a pigment particle size that differs from the average primary particle size by 20% or less.

[0023] The average primary particle size of each pigment, such as the first pigment, the second pigment, and the pigment mixture, can be measured by the following method. The pigment is observed under a scanning electron microscope (SEM) and an image of the pigment particles is taken at a magnification of 200,000 times. The particle sizes of 100 random pigment particles are visually measured and the arithmetic average is calculated, and this average value can be regarded as the average primary particle size.

[0024] (Pigments) A first pigment and a second pigment are used as the pigment. Both the first pigment and the second pigment are copper phthalocyanine blue pigments selected from α-type copper phthalocyanine blue, β-type copper phthalocyanine blue, and ε-type copper phthalocyanine blue. However, the first pigment and the second pigment are copper phthalocyanine blue pigments having different crystal structures (α-type, β-type, ε-type). Therefore, in the method for producing the liquid composition, two or more (two or three) types of copper phthalocyanine blue pigments selected from the group consisting of α-type copper phthalocyanine blue, β-type copper phthalocyanine blue, and ε-type copper phthalocyanine blue are used.

[0025] Specific examples of copper phthalocyanine blue pigments include CI Pigment Blue 15:1, CI Pigment Blue 15:2, CI Pigment Blue 15:3, and CI Pigment Blue 15:4. From the viewpoints of color development and dispersion stability, it is preferable to use at least two or more of these copper phthalocyanine blue pigments.

[0026] (Water-soluble inorganic salts) The water-soluble inorganic salt used in the kneading process utilizes its high hardness to crush the pigment in the kneading process, contributing to the refinement of the primary particles of the pigment. The water-soluble inorganic salt is not particularly limited as long as it is an inorganic salt that dissolves in water. Specific examples of the water-soluble inorganic salt include sodium chloride, potassium chloride, sodium sulfate, zinc chloride, calcium chloride, magnesium chloride, and mixtures of two or more of these. Among these, it is preferable to use sodium chloride from the viewpoint of cost.

[0027] The particle size of water-soluble inorganic salts is the cumulative 50% particle size (median particle size; D 50 ) is 1 μm or more and 250 μm or less, and the cumulative 95% particle size (D 95 ) is preferably 500 μm or less. When a particularly fine pigment is desired, it is preferable that the water-soluble inorganic salt used as the grinding aid is also fine. Specifically, the cumulative 50% particle diameter (D 50 ) is 1 μm or more and 100 μm or less, and the cumulative 95% particle size (D 95 ) is 200 μm or less.

[0028] Water-soluble inorganic salt D 50 and D. 95 The value can be measured using an optical microscope. Specifically, the particle diameters of 500 water-soluble inorganic salts are measured using an optical microscope, and D is calculated from the volume-based particle size distribution. 50 and D. 95 The water-soluble inorganic salts used in the examples described below were also measured by the above-mentioned measurement method. 50 and D. 95 asked for.

[0029] The water content is also important as a quality of the water-soluble inorganic salt. Standard salt for industrial use usually contains 1.0% by mass or more of water. From the viewpoint of suppressing the broadening of the particle size distribution of the finely divided pigment and easily adjusting the average primary particle size of the pigment to the range of 10 nm to 100 nm, the water content of the water-soluble inorganic salt is preferably 3.0% by mass or less, and more preferably 1.5% by mass or less.

[0030] (Organic solvent) The organic solvent used in the kneading process is intended to moisten the mixture of pigment and water-soluble inorganic salt and make it into a dough (a mass formed by kneading) of appropriate hardness. This makes it easier to apply a strong load to the kneaded mixture, increasing the grinding effect and promoting the fineness of the pigment.

[0031] The organic solvent is not particularly limited, and water-soluble organic solvents such as alcohols, glycols, and ethers are preferred. Specific examples of the water-soluble organic solvent include 2-(methoxymethoxy)ethanol, 2-butoxyethanol, 2-(isopentyloxy)ethanol, 2-(hexyloxy)ethanol, diethylene glycol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol, triethylene glycol monomethyl ether, liquid polyethylene glycol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, low molecular weight polypropylene glycol, aniline, pyridine, tetrahydrofuran, dioxane, methanol, ethanol, isopropanol, n-propanol, isobutanol, n-butanol, ethylene glycol, propylene glycol, propylene glycol monomethyl ether acetate, ethyl acetate, isopropyl acetate, acetone, methyl ethyl ketone, dimethylformamide, dimethyl sulfoxide, and N-methylpyrrolidone. The water-soluble organic solvents may be used alone or in combination of two or more as necessary. Among them, it is preferable to use water-soluble organic solvents having high viscosity such as ethylene glycol, diethylene glycol, and polyethylene glycol.

[0032] [Other steps] The above-mentioned kneading step can provide a kneaded product containing the first pigment, the second pigment, a water-soluble inorganic salt, an organic solvent, and the like. In the method for producing a liquid composition, when a kneaded product containing the first pigment, the second pigment, a water-soluble inorganic salt, an organic solvent, and the like is obtained, it is preferable to carry out a purification step for removing the water-soluble inorganic salt and the organic solvent from the kneaded product. Examples of the purification step include a method in which the kneaded product and a liquid medium such as water are stirred and mixed, the water-soluble inorganic salt and the organic solvent in the kneaded product are dissolved in the liquid medium, and then the water-soluble inorganic salt and the organic solvent are removed by filtration or centrifugation. Furthermore, a pigment composition containing a pigment mixture in which the amount of liquid content such as water is adjusted using a dryer or the like can be obtained, and a dried pigment mixture can also be obtained.

[0033] [Dispersion process] The method for producing a liquid composition includes a dispersing step in which the pigment mixture of the first pigment and the second pigment obtained in the above-mentioned mixing step is dispersed in a dispersion medium using a resin. Through the dispersion step, a liquid composition containing the pigment mixture (the first pigment and the second pigment), a resin, and a dispersion medium can be obtained. In this method for producing a liquid composition, a resin (resin dispersant) is used as a dispersant for dispersing the pigment mixture in the dispersion medium. The pigment mixture in the dispersion step is preferably a pigment mixture of the first pigment and the second pigment obtained through the above-mentioned kneading step by the salt milling method.

[0034] As the dispersion medium, it is preferable to use an aqueous medium such as water that can be used in the ink described below, and it is more preferable to use water. By using a liquid medium such as water as the dispersion medium, it is possible to obtain a pigment dispersion as a liquid composition, that is, a dispersion of a pigment mixture, preferably an aqueous dispersion of a pigment mixture. It is also possible to obtain an ink as a liquid composition, and in this case, it is preferable to first obtain an aqueous dispersion of the pigment mixture, and then use the aqueous dispersion of the pigment mixture to prepare an aqueous ink.

[0035] When a pigment dispersion is obtained as a liquid composition, the content (mass %) of the pigment mixture in the pigment dispersion is preferably 1.0 mass % or more and 50.0 mass % or less, and more preferably 5.0 mass % or more and 30.0 mass % or less, based on the total mass of the pigment dispersion.

[0036] The resin used as the dispersant is not particularly limited, but a resin capable of stably dispersing the above-mentioned pigment mixture in a dispersion medium by the action of an anionic group can be suitably used. Examples of the resin used as the dispersant include styrene-acrylic acid copolymer, styrene-acrylic acid-acrylic acid alkyl ester copolymer, styrene-maleic acid copolymer, styrene-maleic acid-acrylic acid alkyl ester copolymer, styrene-methacrylic acid copolymer, styrene-methacrylic acid-acrylic acid alkyl ester copolymer, styrene-maleic acid half ester copolymer, vinylnaphthalene-acrylic acid copolymer, vinylnaphthalene-maleic acid copolymer, styrene-maleic anhydride-maleic acid half ester copolymer, and benzyl methacrylate-methacrylic acid copolymer, as well as salts of these copolymers. The resin may be used alone or in combination of two or more.

[0037] The weight average molecular weight of the resin used as the dispersant is preferably 1,000 to 30,000, more preferably 3,000 to 15,000. The weight average molecular weight of the resin can be a value calculated based on standard polystyrene measured using gel permeation chromatography (GPC). The acid value (mgKOH / g) of the resin can be a value measured by a potentiometric titration device using a potassium hydroxide-methanol titrant. The amount of the resin used is preferably 10% by mass to 50% by mass with respect to the amount of the pigment used.

[0038] A method for dispersing the pigment mixture of the first pigment and the second pigment in a dispersion medium using a resin can be performed using a dispersing device, such as an ultrasonic homogenizer, a high-pressure homogenizer, a paint shaker, a ball mill, a sand mill, a sand grinder, a Dyno Mill, a Dispermat, an SC Mill, a spike mill, a Nanomizer, an agitator mill, and a planetary mill.

[0039] The liquid composition obtained by the above-mentioned method for producing a liquid composition can be suitably used in any application requiring a coloring function. Examples of such applications include paints, printing inks, colored molded products, toners for developing electrostatic images, color filters for liquid crystal display devices, and inkjet inks. Among these, aqueous inkjet inks are preferred.

[0040] <Inkjet recording method> The liquid composition obtained by the above-mentioned method for producing a liquid composition is preferably used in an inkjet recording method in which an ink is ejected from an inkjet recording head to record an image on a recording medium. Specifically, in this inkjet recording method, an ink containing the liquid composition obtained by the above-mentioned method for producing a liquid composition can be used. Examples of the method for ejecting the ink include a method for ejecting the ink by applying mechanical energy to the ink and a method for ejecting the ink by applying thermal energy to the ink. The ink containing the liquid composition can provide a remarkable effect, particularly when used in an inkjet recording method that utilizes thermal energy.

[0041] <Ink> Next, an ink containing the liquid composition obtained by the above-mentioned method for producing a liquid composition will be described. When preparing this ink, it is preferable to use the above-mentioned pigment dispersion as the liquid composition, and it is more preferable to prepare the ink by blending the pigment dispersion, an aqueous medium, and other additives used as necessary.

[0042] (Colorant) The ink contains the liquid composition obtained by the above-mentioned method for producing a liquid composition, and therefore contains a pigment mixture of the first pigment and the second pigment as a coloring material. The content (mass %) of the pigment mixture in the ink is preferably 0.1 mass % or more and 15.0 mass % or less, and more preferably 1.0 mass % or more and 10.0 mass % or less, based on the total mass of the ink.

[0043] (aqueous medium) The ink is preferably an aqueous ink containing at least water as an aqueous medium. For the ink, water or an aqueous medium that is a mixed solvent of water and a water-soluble organic solvent can be used. As the water, deionized water (ion-exchanged water) is preferably used. The content (mass %) of water in the ink is preferably 40.0 mass % or more and 95.0 mass % or less, and more preferably 50.0 mass % or more and 95.0 mass % or less, based on the total mass of the ink.

[0044] Examples of water-soluble organic solvents that can be contained in the ink include alkyl alcohols having 1 to 4 carbon atoms, amides, ketones, ketoalcohols, ethers, polyalkylene glycols, glycols, alkylene glycols having an alkylene group with 2 to 6 carbon atoms, polyhydric alcohols, alkyl ether acetates, alkyl ethers of polyhydric alcohols, nitrogen-containing compounds, and sulfur-containing compounds. One or more of these water-soluble organic solvents can be used as necessary. The content (mass%) of the water-soluble organic solvent in the liquid composition is preferably 3.0% by mass or more and 50.0% by mass or less, and more preferably 3.0% by mass or more and 40.0% by mass or less, based on the total mass of the liquid composition.

[0045] (Other additives) In addition to the above-mentioned components, the ink may contain, as necessary, water-soluble organic compounds that are solid at room temperature, such as polyhydric alcohols such as trimethylolpropane and trimethylolethane, urea derivatives such as urea, ethyleneurea, and hydantoins, and sugars. Furthermore, the ink may contain, as necessary, various additives, such as surfactants, pH adjusters, rust inhibitors, preservatives, antifungal agents, antioxidants, reduction inhibitors, evaporation promoters, chelating agents, and water-soluble resins.

[0046] <Ink cartridges> When the ink described above is used in an inkjet recording method, an ink cartridge can be used. The ink cartridge includes the ink described above and an ink storage section that stores the ink. Furthermore, the ink cartridge may be configured to include an ink storage section and a recording head. EXAMPLES

[0047] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples without departing from the gist of the invention. "Parts" and "%" used to describe the amounts of components are based on mass unless otherwise specified.

[0048] <Measurement of primary particle size> The average primary particle diameter of the pigment was determined by taking an image of the pigment particles magnified 200,000 times using an SEM (product name "S-4800", manufactured by Hitachi High-Technologies Corporation), measuring the particle diameters of 100 random particles by visual inspection, and calculating the arithmetic average to calculate the number average primary particle diameter.

[0049] <Measurement of pigment crystal type> The crystal type of the produced pigment was measured by X-ray spectroscopy (trade name "D8 ADVANCE", manufactured by BRUKER).

[0050] <Preparation of pigment> (Pigment 1) β-type copper phthalocyanine blue (product name "Hostaperm Blue B2G-D", manufactured by Clariant) 1 part, D 50 Ten parts of sodium chloride having a particle size of 100 μm or less and two parts of diethylene glycol were used. These materials were charged in a planetary mixer (product name "Trimix", manufactured by Inoue Seisakusho) and kneaded at 0 to 40° C. for 8 hours to obtain a kneaded product. After kneading, the kneaded product was removed from the planetary mixer and placed in a container containing 100 parts of water, and after stirring for 1 hour, the kneaded product was repeatedly filtered and washed with water to obtain a copper phthalocyanine blue pigment having an average primary particle size of 50 nm (hereinafter referred to as "Pigment 1"). When the obtained Pigment 1 was subjected to X-ray spectroscopy, the crystal type of Pigment 1 was found to be α type.

[0051] (Pigment 2) A copper phthalocyanine blue pigment having an average primary particle size of 50 nm (hereinafter referred to as "Pigment 2") was obtained by carrying out the same operation as for Pigment 1, except that the kneading temperature was changed to 60 to 100°C. X-ray spectroscopy of the obtained Pigment 2 revealed that the crystal type of Pigment 2 was β type.

[0052] <Preparation of Pigment Mixture> (Pigment Mixture 1-4) The components (pigment A and pigment B) shown in Table 1 were mixed in the component ratios (unit: parts) shown in Table 1, and mixed powders of pigment mixtures 1 to 4 were obtained using a V-type container rotary mixer (product name "V-type mixer", manufactured by Seishin Enterprises) by a dry method. In addition to the above-mentioned pigments 1 and 2, the following copper phthalocyanine blue pigment was also used. α-type copper phthalocyanine blue (product name "Chromofine Blue 5108", manufactured by Dainichi Seika Chemicals Co., Ltd.) β-type copper phthalocyanine blue (product name "Cyanine blue 3463", manufactured by Dainichi Seika Chemicals Co., Ltd.) ε-type copper phthalocyanine blue (product name "FASTOGEN BLUE AE-8", manufactured by DIC)

[0053] TIFF2025079353000001.tif43170

[0054] (Pigment Mixture 5) β-type copper phthalocyanine blue (product name "Hostaperm Blue B2G-D", manufactured by Clariant) 1 part, D 50 is 250μm, D 95 10 parts of sodium chloride with a particle size of 425 μm and 2 parts of diethylene glycol were used. These materials were charged in a planetary mixer (trade name "Trimix", manufactured by Inoue Seisakusho) and kneaded for 4 hours at 40 to 60 ° C. by a solvent salt milling method to obtain a kneaded product. After kneading, the kneaded product was taken out of the planetary mixer and placed in a container containing 100 parts of water, and after stirring for 1 hour, the kneaded product was repeatedly filtered and washed with water to obtain a pigment composition with an average primary particle size of 100 nm. When the obtained pigment composition was subjected to X-ray spectroscopy, it was found to be a pigment mixture (hereinafter referred to as "pigment mixture 5") in which the crystal types were mixed in a ratio of α type and β type in a 1:1 ratio. The ratio of α type to β type was calculated from the ratio of the intensity of the peak characteristic of α type copper phthalocyanine blue appearing at a Bragg angle 2θ = 7.4 ° in X-ray spectroscopy measured with CuKα rays to the intensity of the peak characteristic of β type copper phthalocyanine blue appearing at 2θ = 9.0 °.

[0055] (Pigment Mixture 6) β-type copper phthalocyanine blue (product name "Hostaperm Blue B2G-D", manufactured by Clariant) 1 part, ε-type copper phthalocyanine blue 0.05 parts, D 50 is 250μm, D 9510 parts of sodium chloride with a particle size of 425 μm and 2 parts of diethylene glycol were used. These materials were charged in a planetary mixer (trade name "Trimix", manufactured by Inoue Seisakusho) and kneaded for 4 hours at 60 to 80 ° C. by a solvent salt milling method to obtain a kneaded product. After kneading, the kneaded product was taken out of the planetary mixer and placed in a container containing 100 parts of water, and after stirring for 1 hour, the kneaded product was repeatedly filtered and washed with water to obtain a pigment composition with an average primary particle size of 100 nm. When the obtained pigment composition was subjected to X-ray spectroscopy, it was found to be a pigment mixture (hereinafter referred to as "pigment mixture 6") in which the crystal types were mixed in a ratio of β type and ε type in a 1:1 ratio. The ratio of β type to ε type was calculated from the ratio of the intensity of the peak characteristic of β type copper phthalocyanine blue appearing at a Bragg angle of 2θ = 9.0 ° in X-ray spectroscopy measured with CuKα rays to the intensity of the peak characteristic of ε type copper phthalocyanine blue appearing at 2θ = 7.6 °.

[0056] (Pigment Mixture 7) A pigment composition having an average primary particle size of 100 nm was obtained by carrying out the same operation as in Pigment Mixture 6, except that β-type copper phthalocyanine blue was replaced with α-type copper phthalocyanine blue (trade name "PVFastBlue A2R", manufactured by Clariant). When the obtained pigment composition was subjected to X-ray spectroscopy, it was found to be a pigment mixture in which the crystal types were a 1:1 mixture of α-type and ε-type (hereinafter referred to as "Pigment Mixture 7"). The ratio of α-type to ε-type was calculated from the ratio of the intensity of the peak characteristic of α-type copper phthalocyanine blue appearing at a Bragg angle of 2θ=7.4° in X-ray spectroscopy measured using CuKα rays to the intensity of the peak characteristic of ε-type copper phthalocyanine blue appearing at 2θ=9.2°.

[0057] (Pigment Mixture 8) A pigment composition having an average primary particle size of 100 nm was obtained by carrying out the same operation as for pigment mixture 5, except that the amount of sodium chloride was changed to 5 parts and the kneading time was changed to 24 hours. When the obtained pigment composition was subjected to X-ray spectroscopy measurement, it was found to be a pigment mixture in which the crystal types were a 1:1 mixture of α-type and β-type (hereinafter referred to as "pigment mixture 8").

[0058] (Pigment Mixture 9) A pigment composition having an average primary particle size of 100 nm was obtained by carrying out the same operation as for Pigment Mixture 5, except that the amount of sodium chloride was changed to 15 parts and the kneading time was changed to 2 hours. X-ray spectroscopy of the obtained pigment composition revealed that it was a pigment mixture in which the crystal types were a 1:1 mixture of α-type and β-type (hereinafter referred to as "Pigment Mixture 9").

[0059] (Pigment Mixture 10) Sodium chloride, D 50 is 60μm, D 95 A pigment composition having an average primary particle size of 50 nm was obtained by carrying out the same operation as in Pigment Mixture 5, except that sodium chloride having an average primary particle size of 120 μm was used. When the obtained pigment composition was subjected to X-ray spectroscopy measurement, it was found to be a pigment mixture in which the crystal types were a 1:1 mixture of α-type and β-type (hereinafter referred to as "Pigment Mixture 10").

[0060] <Preparation of pigment dispersion> (Pigment Dispersion 1-13) The components (unit: parts) shown in Table 2 were mixed to obtain a mixture. The resin aqueous solution shown in Table 2 is an aqueous solution of the resin used as a dispersant. Specifically, a styrene-acrylic acid copolymer with an acid value of 100 mgKOH / g was neutralized with potassium hydroxide in an amount equivalent to the acid value, and dissolved in ion-exchanged water to obtain an aqueous solution with a resin (solid content) content of 10.0%. The above mixture was placed in a batch-type vertical sand mill (manufactured by Imex), filled with 150 parts of zirconia beads with a diameter of 0.3 mm, and dispersed for 5 hours while cooling with water. After that, coarse particles were removed by centrifugation to obtain each pigment dispersion with a pigment content of 16.0% and a resin (solid content) content of 4.0%.

[0061] TIFF2025079353000002.tif107170

[0062] <Ink Preparation> The components (unit: parts) shown in Table 3 were mixed and thoroughly stirred, and then pressure filtered through a microfilter (manufactured by Fujifilm) with a pore size of 2.5 μm to prepare each ink. The surfactant used was "Acetylenol E100" (manufactured by Kawaken Fine Chemicals). The preservative used was "PROXEL GXL(S)" (manufactured by Arch Chemicals Japan).

[0063] TIFF2025079353000003.tif88170

[0064] <Storage stability of ink> Each ink was placed in a sealed container made of polytetrafluoroethylene and left at room temperature (15 to 25°C) for one month to carry out a storage test. The viscosity was measured before and after the storage test, and the change rate of the ink viscosity = (viscosity of the ink after the storage test) / (viscosity of the ink before the storage test) was calculated, and the storage stability of the ink was evaluated according to the evaluation criteria shown below. The closer the change rate of the ink viscosity is to 1.0, the higher the storage stability of the ink. In this example, in the following evaluation criteria, "A", "B", and "C" were defined as acceptable levels, and "D" was defined as an unacceptable level. The evaluation results are shown in Table 4. A: The rate of change in ink viscosity was less than 1.1. B: The rate of change in ink viscosity was 1.1 or more and less than 1.2. C: The rate of change in ink viscosity was 1.2 or more and less than 1.5. D: The rate of change in ink viscosity was 1.5 or more.

[0065] TIFF2025079353000004.tif82170

[0066] In addition, in Example 8, the evaluation result of the ink storage stability was A, but it was thought that the processing time was longer than in the examples that had the same evaluation result.

[0067] The disclosure of this embodiment includes the following methods. (Method 1) A method for producing a liquid composition containing at least two pigments, a first pigment and a second pigment, which have different crystal structures and are selected from α-type copper phthalocyanine blue, β-type copper phthalocyanine blue, and ε-type copper phthalocyanine blue, comprising the steps of: a mixing step of obtaining a pigment mixture of the first pigment and the second pigment; a dispersing step of dispersing the pigment mixture in a dispersion medium using a resin; A method for producing a liquid composition comprising the steps of: (Method 2) The method for producing a liquid composition according to Method 1, wherein the mixing step includes a kneading step by a salt milling method in which a mixture containing the first pigment, the second pigment, a water-soluble inorganic salt, and an organic solvent is kneaded to obtain a kneaded mixture. (Method 3) The method for producing a liquid composition according to Method 2, wherein the amount of the water-soluble inorganic salt used in the kneading step is 5.0 times or more and 10.0 times or less in terms of mass ratio to the total amount of the first pigment and the second pigment used. (Method 4) The method for producing a liquid composition according to any one of Methods 1 to 3, wherein the average primary particle diameter of the pigment mixture is 50 nm or less. (Method 5) An inkjet recording method for recording an image on a recording medium by ejecting ink from an inkjet recording head, comprising the steps of: 5. An ink-jet recording method, wherein the ink contains a liquid composition obtained by the method for producing a liquid composition according to any one of Methods 1 to 4.

Claims

1. A method for producing a liquid composition containing at least two pigments, a first pigment and a second pigment, which are different in crystal structure from each other and are selected from α-type copper phthalocyanine blue, β-type copper phthalocyanine blue, and ε-type copper phthalocyanine blue, comprising: a mixing step of obtaining a pigment mixture of the first pigment and the second pigment; a dispersing step of dispersing the pigment mixture in a dispersion medium using a resin; A method for producing a liquid composition comprising the steps of:

2. The method for producing a liquid composition according to claim 1 , wherein the mixing step includes a kneading step by a salt milling method in which a mixture containing the first pigment, the second pigment, a water-soluble inorganic salt, and an organic solvent is kneaded to obtain a kneaded product.

3. The method for producing a liquid composition according to claim 2 , wherein the amount of the water-soluble inorganic salt used in the kneading step is 5.0 times or more and 10.0 times or less in terms of mass ratio to the total amount of the first pigment and the second pigment used.

4. The method for producing a liquid composition according to claim 1 , wherein the average primary particle size of the pigment mixture is 50 nm or less.

5. An inkjet recording method for recording an image on a recording medium by ejecting ink from an inkjet recording head, comprising: An ink jet recording method, comprising the step of: forming an ink containing a liquid composition obtained by the method for producing a liquid composition according to claim 1 .

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