Pigment py155, and pigment dispersion and ink comprising same

Abstract

One embodiment of the present invention provides a C.I. pigment yellow 155 in which a ratio ((A) / (B)) of a maximum diffraction intensity (A) of a diffraction peak at a diffraction angle 2θ=10.0±0.2° to an average diffraction intensity (B) of diffraction peaks at a diffraction angle 2θ=8.0-8.5° is 6.0-28.0 in a CuKα characteristic X-ray diffraction spectrum. [The maximum diffraction intensity (A) is an intensity of the highest diffraction peak among diffraction peaks located at a diffraction angle 2θ=10.0±0.2° in a CuKα characteristic X-ray diffraction spectrum, and the average diffraction intensity (B) is a value obtained by dividing the total of diffraction peak intensities as measured in the range of 2θ = 8.0–8.5° by the number of diffraction peaks.]

Description

Pigment PY155, Pigment Dispersion Containing the Same, and Ink

[0001] The present invention relates to a pigment PY155 having a predetermined X-ray diffraction peak intensity ratio, a pigment dispersion containing the same, and an ink.

[0002] Conventionally, pigments have been mainly used for coloring inks, paints, toners, rubbers, and plastics, mass coloring of synthetic fibers, pigment printing, cosmetics, etc. Among these, printing applications such as inks play an important role in industry. For example, gravure inks, flexo inks, etc. are widely used for the purpose of imparting beauty and functionality to printed substrates such as flexible packaging films. In recent years, with the spread of inkjet printers, there has been an increasing expectation for the development of inkjet inks with more excellent performance.

[0003] Inkjet printers are not only used for home use, but also widely deployed for industrial use in response to the trend of smaller print runs, and in recent years, the business has expanded to textile applications and flexible packaging applications for packages. The pigments used in such inks are required to have performance such as coloring power, lightfastness, and easy dispersibility.

[0004] For example, C.I. Pigment Yellow 155 (hereinafter also referred to as "PY155"), which is a yellow pigment excellent in various properties such as lightfastness, heat resistance, and solvent resistance, is used in a wide range of fields such as paints, inks, and plastics, and is also used in digital applications such as inkjet inks and toners (for example, Patent Document 1). The high fastness of PY155 is considered to be due to the intramolecular hydrogen bonding of the hydrazone structure, carbonyl group, and ester bond of the PY155 molecule, and the PY155 molecules stacking while taking a planar structure to form a strong crystal structure. On the other hand, this also causes a problem that the interaction between particles increases, and the dispersibility of the pigment in the dispersion medium decreases. When the dispersibility is low, the dispersed particle diameter of the pigment in the dispersion medium becomes large, and as a result, the viscosity becomes high.

[0005] Japanese Patent Application Laid-Open No. 2020-059844

[0006] Given the above background, there is a need for PY155 with even more desirable properties. The present invention aims to provide PY155 with excellent properties such as dispersibility.

[0007] As a result of diligent research, the inventors have found that PY155 having a predetermined X-ray diffraction peak intensity ratio exhibits excellent properties such as dispersibility. The present invention is, for example, as follows: [1] C. I. Pigment Yellow 155, in which the ratio ((A) / (B)) of the maximum diffraction intensity (A) of the diffraction peak at a diffraction angle of 2θ = 10.0 ± 0.2° to the average diffraction intensity (B) of the diffraction peaks at a diffraction angle of 2θ = 8.0 to 8.5° in the CuKα characteristic X-ray diffraction spectrum is 6.0 to 28.0: [Here, the maximum diffraction intensity (A) is the intensity of the largest diffraction peak among the diffraction peaks located at a diffraction angle of 2θ = 10.0 ± 0.2° in the CuKα characteristic X-ray diffraction spectrum; the average diffraction intensity (B) is the value obtained by summing up all the diffraction peak intensities measured in the range of diffraction angles 2θ = 8.0 to 8.5° in the CuKα characteristic X-ray diffraction spectrum and dividing it by the number of diffraction peaks measured]. [2] The ratio of the maximum diffraction intensity (A) to the average diffraction intensity (C) of the diffraction peaks at diffraction angles 2θ = 23.0 to 24.0° ((A) / (C)) is 9.0 to 27.0, as described in [1] C.I. Pigment Yellow 155: [Here, the average diffraction intensity (C) is the value obtained by summing up all the diffraction peak intensities measured in the range of diffraction angles 2θ = 23.0 to 24.0° in the CuKα characteristic X-ray diffraction spectrum and dividing it by the number of diffraction peaks measured]. [3] BET specific surface area is 50 m ２[1] or [2] C.I. Pigment Yellow 155, wherein the amount is 1 / g or more. [4] C.I. Pigment Yellow 155, wherein the pH is 7.0 or less, wherein the amount is 1 / g

[11] A method for producing C.I. Pigment Yellow 155 according to any one of [1] to [5], comprising: (1) a solvent salt milling step of kneading raw material PY155 together with a metal salt and a solvent; and (2) an acid treatment step of mixing the product obtained in step (1) with an acidic compound and stirring.

[12] C.I. Pigment Yellow 155 according to any one of [1] to [5], produced by a method comprising: (1) a solvent salt milling step of kneading raw material PY155 together with a metal salt and a solvent; and (2) an acid treatment step of mixing the product obtained in step (1) with an acidic compound and stirring.

[13] C.I. Pigment Yellow 155 according to the method in

[11] or the method in

[12] , wherein the metal salt is sodium chloride or sodium sulfate.

[14] The acidic compound is sulfuric acid, hydrogen halide, or nitric acid, the method according to

[11] or

[13] or the C.I. pigment yellow 155 according to

[12] or

[13] .

[15] The solvent salt milling step is carried out at a temperature of 50 to 150°C for 1 to 24 hours, the method according to any one of

[11] ,

[13] , or

[14] or the C.I. pigment yellow 155 according to any one of

[12] to

[14] .

[0008] According to the present invention, it is possible to provide PY155 with excellent properties such as dispersibility.

[0009] Figure 1 shows the CuKα characteristic X-ray diffraction spectrum of PY155 (Example 1). Figure 2 shows the CuKα characteristic X-ray diffraction spectrum of PY155 (Example 2). Figure 3 shows the CuKα characteristic X-ray diffraction spectrum of PY155 (Example 3). Figure 4 shows the CuKα characteristic X-ray diffraction spectrum of PY155 (Example 4). Figure 5 shows the CuKα characteristic X-ray diffraction spectrum of PY155 (Example 5). Figure 6 shows the CuKα characteristic X-ray diffraction spectrum of PY155 (Comparative Example 1). Figure 7 shows the CuKα characteristic X-ray diffraction spectrum of PY155 (Comparative Example 2).

[0010] Embodiments of the present invention will be described in detail below. In this specification, "raw material PY155" means PY155 as a raw material before being subjected to the solvent salt milling process, and descriptions such as "PY155 of the present invention," "PY155 according to the embodiment," and "PY155 after treatment" mean PY155 according to the present invention after being subjected to the solvent salt milling process and the acid treatment process. In cases where it is clear from the context which meaning is intended, it may simply be written as "PY155."

[0011] According to one embodiment, in the CuKα characteristic X-ray diffraction spectrum, the PY155 of the present invention has a ratio ((A) / (B)) of 6.0 to 28.0 of the maximum diffraction intensity (A) of the diffraction peak at a diffraction angle of 2θ = 10.0 ± 0.2° to the average diffraction intensity (B) of the diffraction peaks at a diffraction angle of 2θ = 8.0 to 8.5°. Here, the maximum diffraction intensity (A) is the intensity of the largest diffraction peak among the diffraction peaks located at a diffraction angle of 2θ = 10.0 ± 0.2° in the CuKα characteristic X-ray diffraction spectrum. The average diffraction intensity (B) is the value obtained by summing all the diffraction peak intensities measured in the range of diffraction angles 2θ = 8.0 to 8.5° in the CuKα characteristic X-ray diffraction spectrum and dividing it by the number of diffraction peaks measured.

[0012] As a result of diligent research, the inventors have found that PY155 having the predetermined X-ray diffraction peak intensity ratio described above exhibits excellent dispersibility when used as a pigment dispersion or ink. X-ray diffraction (XRD) is a method for obtaining crystal structure information of a sample from its X-ray diffraction pattern. A crystal, which is the target of evaluation by XRD, is a state in which the atoms and molecules constituting a substance are arranged repeatedly in three dimensions. PY155 particles can take on a crystal structure in which PY155 molecules are arranged in an ordered manner, but the size of this crystal state (crystallinity) depends on the manufacturing method.

[0013] When PY155 is dispersed in a dispersion medium, the PY155 particles remain suspended within the medium at a constant distance from each other. If the crystallinity of PY155 is low, the PY155 molecules located on the surface of the PY155 particles become unstable, resulting in higher surface energy. Consequently, a strong force acts to aggregate the PY155 particles in order to reduce their surface energy. In other words, if the crystallinity of PY155 is low, the particle size of the dispersed PY155 in the pigment dispersion increases, and as a result, the viscosity of the pigment dispersion tends to increase. On the other hand, if the crystallinity of PY155 is too high, the PY155 particles themselves are large, which in turn increases the particle size of the dispersed PY155 in the pigment dispersion. As a result, the viscosity of the pigment dispersion increases.

[0014] In contrast, the PY155 of the present invention has a predetermined X-ray diffraction peak intensity ratio, which reduces the size of dispersed particles in the pigment dispersion, achieving high dispersibility and resulting in the excellent effect of lower viscosity of the pigment dispersion. Using such PY155 as a pigment in inkjet ink also has the advantage of preventing clogging of the nozzle head of an inkjet printer.

[0015] The following describes in detail the components, manufacturing methods, physical properties, and applications of PY155, pigment dispersions, inks, toners, etc., according to the embodiment. In this application, PY155 does not simply mean a compound having the structure shown below, but also a pigment composed of said compound. The concept of said pigment includes not only substances characterized by their crystalline structure, but also substances characterized by the physical properties of aggregates and / or aggregates arising from the primary particles formed by aggregation and / or aggregation of said pigment, and further from the surface state of said pigment.

[0016] [Pigments] [1] C. I. Pigment Yellow 155 (PY155) PY155 is a yellow pigment and contains, as a main component, a compound represented by the following structural formula. The following compound is an azo-hydrazo tautomer and may contain both the azo (-N=N-) and hydrazo (>N-NH-) forms. Pigment PY155 may also contain components other than the following compounds, to the extent that they do not impair the effects of the present invention.

[0017] The PY155 according to the embodiment is characterized by having a predetermined X-ray diffraction peak intensity ratio. Firstly, the PY155 according to the embodiment has a ratio ((A) / (B)) of 6.0 to 28.0 of the maximum diffraction intensity (A) of the diffraction peak at a diffraction angle of 2θ = 10.0 ± 0.2° to the average diffraction intensity (B) of the diffraction peak at a diffraction angle of 2θ = 8.0 to 8.5°. The ratio (A) / (B) is preferably 8.0 to 27.5, and more preferably 10.0 to 27.0.

[0018] Here, the maximum diffraction intensity (A) is the intensity of the largest diffraction peak located at the diffraction angle 2θ = 10.0 ± 0.2° in the CuKα characteristic X-ray diffraction spectrum. The average diffraction intensity (B) is the sum of all diffraction peak intensities measured in the diffraction angle range 2θ = 8.0 to 8.5° in the CuKα characteristic X-ray diffraction spectrum, divided by the number of measured diffraction peaks. For example, if the X-ray diffraction intensity is measured every 2θ = approximately 0.026°, there will be 19 measurement points in the diffraction angle range 2θ = 8.0 to 8.5°. The average diffraction intensity (B) is obtained by summing the 19 diffraction peak intensities at these measurement points and dividing the result by the number of measurement points, 19 (if there is no diffraction peak at a measurement point, a diffraction peak intensity of 0 is added, and finally divided by the number of measurement points, 19).

[0019] Secondly, in the embodiment of PY155, the ratio ((A) / (C)) of the maximum diffraction intensity (A) to the average diffraction intensity (C) of the diffraction peaks at the diffraction angle 2θ = 23.0 to 24.0° in the CuKα characteristic X-ray diffraction spectrum is preferably 9.0 to 27.0. The ratio (A) / (C) is more preferably 11.0 to 27.0, and particularly preferably 13.0 to 26.9. Here, the average diffraction intensity (C) is the value obtained by summing up all the diffraction peak intensities measured in the diffraction angle range 2θ = 23.0 to 24.0° in the CuKα characteristic X-ray diffraction spectrum and dividing it by the number of diffraction peaks measured. For example, if the X-ray diffraction intensity is measured every 2θ = approximately 0.026°, there will be 38 measurement points in the diffraction angle range 2θ = 23.0 to 24.0°. The average diffraction intensity (C) is obtained by summing up the diffraction peak intensities of all 38 measurement points and dividing the result by the number of measurement points, which is 38.

[0020] Furthermore, the diffraction peaks in the diffraction angle range 2θ = 8.0 to 8.5° used to calculate the average diffraction intensity (B), and the diffraction peaks in the diffraction angle range 2θ = 23.0 to 24.0° used to calculate the average diffraction intensity (C), are both thought to originate from amorphous components and background components (such as scattering by the sample being measured).

[0021] The maximum diffraction intensity (A) is preferably 2000 or higher, more preferably 2000 to 5000, and particularly preferably 2500 to 4500 or 2100 to 4100. The average diffraction intensity (B) is preferably 300 or lower, more preferably 100 to 300, and particularly preferably 125 to 250. The average diffraction intensity (C) is preferably 210 or lower, more preferably 110 to 210, and particularly preferably 145 to 210. By having each diffraction intensity within the above range, when PY155 is used as a pigment dispersion, the dispersed particle size becomes smaller, and higher dispersibility is achieved. The X-ray diffraction spectrum can be measured by the method described in the examples below.

[0022] The average aspect ratio (major diameter / minor diameter) of PY155 according to the embodiment is preferably 1.0 to 1.8, more preferably 1.1 to 1.7, and particularly preferably 1.2 to 1.6, from the viewpoint of suppressing aggregation of pigments. The average particle diameter (minor diameter) of PY155 according to the embodiment is preferably 10 to 80 nm, more preferably 15 to 60 nm, and particularly preferably 20 to 50 nm, from the viewpoint of reducing the dispersed particle diameter. Furthermore, the average particle diameter (major diameter) of PY155 according to the embodiment is preferably a value such that the average value of the average aspect ratio and minor diameter falls within the above range, but is preferably 10 to 100 nm, more preferably 20 to 80 nm, and particularly preferably 30 to 70 nm. The average particle diameter (major diameter, minor diameter) can be measured by image analysis using an electron microscope, as described in the examples below, and the average aspect ratio can be calculated by the formula "average particle diameter (major diameter) / average particle diameter (minor diameter)".

[0023] The specific surface area (BET specific surface area) of PY155 according to this embodiment is preferably 50 m², from the viewpoint of reducing the dispersed particle size. ２ / g or more, more preferably 50 to 100 m ２ / g, particularly preferably 50 to 80 m ２The value is / g. Because the specific surface area is within the above range, the dispersed particle size tends to be smaller when PY155 according to the embodiment is used as an ink. The BET specific surface area can be measured using a fully automatic specific surface area measuring device, as described in the examples below.

[0024] The pH of PY155 according to the embodiment is preferably 7.0 or less, more preferably 3.0 to 7.0, and particularly preferably 4.0 to 6.0, from the viewpoint of viscosity when used as a pigment dispersion or ink. In pigment dispersions and inks, viscosity decreases when the interaction between pigment particles is small. When the pH of PY155 according to the embodiment is acidic, protons are released from the surface of the PY155 particles, causing the particle surface to become negatively charged, and electrostatic repulsion occurs between the PY155 particles, resulting in a decrease in viscosity, which is preferable. When the pH is within the above range, the viscosity tends to be even lower when PY155 according to the embodiment is used as a dispersion or ink. The pH can be measured by the method described in JIS K 5101-17-1:2004, as described in the examples below.

[0025] In the embodiment of PY155, the calcium (Ca) content is preferably 80.0 ppm or less, 60.0 ppm or less, 40.0 ppm or less, 30.0 ppm or less, or 20.0 ppm or less, from the viewpoint of reducing the dispersed particle size. A lower Ca content in PY155 is preferable. When the Ca content is within the above range, the viscosity tends to be lower when PY155 in the embodiment is used as a dispersion or ink, and in particular, the dispersed particle size tends to be smaller in the ink. Here, Ca refers to a concept that includes Ca atoms and Ca ions, and originates from the materials (such as water) used in the manufacturing process.

[0026] When a large amount of Ca is present in PY155, it dissolves when a dispersion medium is added, canceling out the negative charge on the surface of the PY155 particles. As a result, the electrostatic repulsion between PY155 particles disappears, and it is thought that the size of the dispersed particles in the dispersion increases. Therefore, to reduce the size of the dispersed particles and improve dispersibility, it is preferable to have a low Ca content in PY155. The Ca content can be measured using an energy-dispersive X-ray fluorescence analyzer PANlytical Epsilon 5 (manufactured by Spectris), as described in the examples below.

[0027] [2] PY155 manufacturing method PY155 according to the embodiment can be manufactured by a method comprising: (1) a solvent salt milling step of kneading raw material PY155 together with a metal salt and a solvent; and (2) an acid treatment step of mixing and stirring the product obtained in step (1) with an acidic compound. According to another embodiment, a method for manufacturing PY155 is provided, comprising: (1) a solvent salt milling step of kneading raw material PY155 together with a metal salt and a solvent; and (2) an acid treatment step of mixing and stirring the product obtained in step (1) with an acidic compound.

[0028] (Solvent Salt Milling Process) Solvent salt milling is a method of mechanically grinding pigment particles while mixing them with a metal salt and a solvent. As the raw material PY155, commercially available products can be used, or products synthesized by known methods may be used (for example, Japanese Patent Application Publication No. 11-202558).

[0029] The metal salt is not particularly limited, but from an economic standpoint, sodium chloride, sodium sulfate, etc., are preferred. The amount of metal salt used is preferably 100 to 2000 parts by mass, more preferably 200 to 1000 parts by mass, and particularly preferably 400 to 900 parts by mass or 400 to 800 parts by mass, per 100 parts by mass of raw material PY155. Using the metal salt in such amounts is preferable from the viewpoint of dispersion particle size and viscosity when PY155 according to the embodiment is used as a pigment dispersion or ink. As the solvent, an organic solvent is preferred, such as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, etc. The amount of solvent used is preferably 50 to 500 parts by mass, more preferably 75 to 250 parts by mass, per 100 parts by mass of raw material PY155. Using the solvent in such amounts is preferable from the viewpoint of dispersion particle size and viscosity when PY155 according to the embodiment is used as a pigment dispersion or ink.

[0030] The processing temperature (grinding temperature) and processing time (grinding time) in the solvent salt milling process can be set as appropriate. From the viewpoint of dispersion particle size and viscosity when PY155 according to the embodiment is used as a pigment dispersion or ink, the processing is preferably carried out at a temperature of 50 to 150°C, more preferably 75 to 120°C, particularly preferably 80 to 100°C or 90 to 100°C for 1 to 24 hours, more preferably 3 to 10 hours, and particularly preferably 5 to 7 hours. The solvent salt milling process can be carried out using a kneader (double-arm type kneader (capacity 2L, manufactured by Yoshida Seisakusho)), planetary mixer, Trimix (manufactured by Inoue Seisakusho), Super Mixer (manufactured by Kawata), Miracle KCK (manufactured by Asada Tekko), etc.

[0031] (Acid Treatment Process) The acid treatment process involves adding the kneaded material obtained in the solvent salt milling process (1) described above to a solvent together with an acidic compound and treating it. The acidic compound is not particularly limited, but sulfuric acid, hydrogen halides, nitric acid, etc. are preferred. Hydrogen chloride is preferred as the hydrogen halide. The amount of acidic compound used is preferably 1 to 150 parts by mass, more preferably 5 to 100 parts by mass, and particularly preferably 10 to 75 parts by mass, per 100 parts by mass of the raw material PY155. Using the acidic compound in such an amount is preferable from the viewpoint of dispersion particle size and viscosity when PY155 according to the embodiment is used as a pigment dispersion or ink.

[0032] A solvent may be used in the acid treatment process, and water is preferred as the solvent from an economic standpoint. The amount of solvent used is preferably 1,000 to 100,000 parts by mass, more preferably 2,000 to 50,000 parts by mass, and particularly preferably 3,000 to 6,000 parts by mass, per 100 parts by mass of the raw material PY155. Using such an amount of solvent is preferable from the viewpoint of the dispersion particle size and viscosity when used as a pigment dispersion or ink.

[0033] The treatment temperature and treatment time in the acid treatment process can be set as appropriate. From the viewpoint of dispersion particle size and viscosity when the PY155 according to the embodiment is used as a pigment dispersion or ink, the treatment is preferably carried out at a temperature of 0 to 100°C, more preferably 30 to 90°C, for 0.1 to 24 hours, and more preferably 0.5 to 8 hours. The acid treatment process can be carried out using any reaction tank and stirring blade. After the acid treatment process, the obtained PY155 may be washed with water as needed. From the viewpoint of washing away impurities, the amount of water used during washing is preferably 1,000 to 100,000 parts by mass, more preferably 5,000 to 60,000 parts by mass, and particularly preferably 10,000 to 30,000 parts by mass, per 100 parts by mass of the raw material PY155.

[0034] (Other Processing) PY155 after the acid treatment process may be further dried and / or pulverized as needed. Drying can be performed using a box-type forced-air dryer, band dryer, vacuum dryer, freeze vacuum dryer, spin flash dryer, spray dryer, etc. When using a box-type forced-air dryer, the drying temperature is preferably 60 to 150°C, more preferably 70 to 140°C, and particularly preferably 80 to 130°C, from the viewpoint of sufficiently volatilizing moisture. The drying time is preferably 2 to 100 hours, more preferably 5 to 50 hours, and particularly preferably 10 to 30 hours, from the viewpoint of sufficiently volatilizing moisture. Pulverization can be performed using a roller mill, jet mill, hammer mill, pin mill, attritor, bead mill, cutter mill, etc. Other processing can be performed by setting appropriate methods and conditions to obtain PY155 having the desired crystal structure.

[0035] [Pigment Dispersion] According to another embodiment of the present invention, a pigment dispersion is provided comprising PY155 according to the above-described embodiment and a dispersion medium. In the pigment dispersion, PY155 according to the embodiment exists in a dispersed state in the dispersion medium. As the dispersion medium, any material commonly used in the art that can disperse a pigment composition can be appropriately selected and used, for example, an aqueous dispersion medium. The aqueous dispersion medium is, for example, water, and specifically, pure water or ultrapure water such as ion-exchanged water, ultrafiltered water, reverse osmosis water, or distilled water can be used. The dispersion medium is preferably used in a range of 35% to 75% by mass, and more preferably in a range of 45% to 65% by mass, based on the total amount of the pigment dispersion. Mixing can be carried out by a method commonly used in the art, for example, a mixing method using a dispenser. The mixed state of the pigment dispersion is not particularly limited. The PY155 according to the embodiment is preferably contained in a ratio of 5% to 30% by mass, and more preferably in a ratio of 10% to 20% by mass, based on 100% by mass of the pigment dispersion.

[0036] The pigment dispersion may further contain a dispersant. Such a dispersant can be any dispersant that has the effect of dispersing PY155 according to the embodiment, and examples include copolymers (e.g., block copolymers, random copolymers, and graft copolymers) consisting of at least two monomers selected from the group consisting of monomers such as styrene and its derivatives, vinylnaphthalene and its derivatives, aliphatic alcohol esters of α,β-ethylenically unsaturated carboxylic acids, acrylic acid and its derivatives, maleic acid and its derivatives, itaconic acid and its derivatives, fumaric acid and its derivatives, vinyl acetate, vinyl alcohol, vinylpyrrolidone, and acrylamide.

[0037] The amount of dispersant added is preferably 0.5 to 10% by mass, more preferably 1 to 5% by mass, as solid content, based on 100% by mass of the pigment dispersion. The pigment dispersion may also contain additives other than the dispersant, such as preservatives, pH adjusters, water-soluble polymer compounds, water-dispersible resins, and surfactants. The amount of other additives added is preferably 0 to 30% by mass, more preferably 0 to 15% by mass, based on 100% by mass of the pigment dispersion.

[0038] The viscosity (initial) of the pigment dispersion (especially the pigment dispersion for inkjet ink) is preferably 1 to 80 mPa·s, more preferably 2 to 50 mPa·s, and most preferably 3 to 20 mPa·s, from the viewpoint of obtaining a beautiful printed image. The viscosity of the pigment dispersion can be measured by the method described in the examples below.

[0039] The volume-average dispersed particle diameter (Mv) of the pigment dispersion (particularly the pigment dispersion for inkjet ink) is preferably 80 to 280 nm, more preferably 90 to 250 nm, and most preferably 100 to 190 nm, from the viewpoint of preventing nozzle clogging of the inkjet head. The volume-average dispersed particle diameter (Mv) of the pigment dispersion can be measured by the method described in the examples below.

[0040] [Ink] The pigment dispersion according to the embodiment can be used, for example, in the production of ink. Thus, according to one embodiment, an ink containing the above-described pigment dispersion is provided. The pigment dispersion may be used as ink as it is, or additional components may be added to the pigment dispersion to form ink. The type of ink is not particularly limited, and examples include gravure ink, flexo ink, and inkjet ink. Among them, inkjet ink is preferred in terms of cost efficiency and the ability to print on various materials.

[0041] The ink is produced by adding and mixing a dispersion medium and additives commonly used in the art to the above-described pigment dispersion. The dispersion medium for ink is not particularly limited, and examples include those similar to the dispersion media described in the pigment dispersion. The mixing method is also not particularly limited, and it can be mixed by a method commonly used in the art. Examples of mixing methods using dispersers such as bead mills, ultrasonic homogenizers, high-pressure homogenizers, paint shakers, ball mills, roll mills, sand mills, sand grinders, dyno mills, dispermatts, SC mills, and nanomizers can be mentioned.

[0042] The ink may contain additives commonly used in the art as necessary. Examples of such additives include binders, surfactants, waxes, wetting agents (drying inhibitors), penetrants, preservatives, viscosity modifiers, pH adjusters, chelating agents, plasticizers, antioxidants, ultraviolet absorbers, and the like.

[0043] As the binder, for example, an acid-modified polypropylene resin can be used. As the acid-modified polypropylene resin, a resin obtained by modifying polypropylene with one or more acidic compounds can be used, and it is preferable to use a resin having a polypropylene-derived skeleton (polypropylene skeleton) and a functional group derived from an acidic compound. An ink containing an acid-modified polypropylene resin can suppress the occurrence of mottling and white streaks in the printed matter even when printed on a recording medium that does not absorb or hardly absorbs the solvent in the ink.

[0044] As the surfactant, for example, anionic surfactants, nonionic surfactants, cationic surfactants, amphoteric surfactants and the like can be used. Among these, from the viewpoint of being easily able to suppress the occurrence of streak-like printing defects, it is preferable to use an anionic surfactant or a nonionic surfactant. The content of the surfactant is preferably 0.1 to 2.0% by mass, more preferably 0.5 to 2% by mass, and still more preferably 0.8 to 1.6% by mass with respect to the total amount of the ink. The ink containing the surfactant in such an amount has good wettability of the ejected droplets on the surface of the printing object, is likely to have sufficient wet spreading on the printing object, and is easily able to obtain the effect of preventing the occurrence of streak-like printing defects.

[0045] As the wax, for example, polyethylene wax oxide and the like can be used. By using an ink containing polyethylene wax oxide, a printed matter excellent in image fastness can be obtained.

[0046] The wetting agent can be used for the purpose of preventing the drying of the ink at the ejection nozzles of the inkjet head. As the wetting agent, it is preferable to use one that is miscible with water and can obtain the effect of preventing the clogging of the ejection ports of the inkjet head. For example, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol having a molecular weight of 2000 or less, propylene glycol, dipropylene glycol, tripropylene glycol, isopropylene glycol, isobutylene glycol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, meso-erythritol, pentaerythritol, glycerin and the like can be mentioned. The content of the wetting agent is preferably 3 to 50% by mass with respect to the total amount of the ink in terms of being able to balance the ease of drying of the ink on the recording medium and preventing the sticking of the ink inside the inkjet head.

[0047] Penetrating agents include lower alcohols such as ethanol and isopropyl alcohol; and glycol monoethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl butyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monopropyl ether, triethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, tripropylene glycol monopropyl ether, and tripropylene glycol monobutyl ether.

[0048] The ratio of the additive to the total mass of the ink according to the embodiment (the total amount if two or more additives are included) is preferably 0 to 30% by mass, more preferably 0 to 15% by mass. It is preferable that the PY155 according to the embodiment is contained in an amount of 1 to 10% by mass, and more preferably 3 to 6% by mass, per 100% by mass of ink.

[0049] The pH of the ink according to this embodiment is, for example, 7.0 or higher, preferably 7.5 or higher, from the viewpoint of further improving the storage stability of the ink. Also, from the viewpoint of material resistance and skin irritation, the pH is, for example, 11.0 or lower, preferably 10.0 or lower.

[0050] The viscosity (initial) of the ink (especially inkjet ink) is preferably 1.0 to 9.0 mPa·s, more preferably 2.0 to 8.0 mPa·s, and most preferably 3.0 to 7.0 mPa·s, from the viewpoint of obtaining a beautiful printed image. The viscosity of the ink can be measured by the method described in the examples below.

[0051] The volume-average dispersed particle diameter (Mv) of the ink (especially inkjet ink) is preferably 80 to 280 nm, more preferably 90 to 250 nm, and most preferably 100 to 180 nm, from the viewpoint of preventing nozzle clogging of the inkjet head. The volume-average dispersed particle diameter (Mv) of the ink can be measured by the method described in the examples below.

[0052] When the ink according to the embodiment is used as an inkjet ink, it can be loaded into a known inkjet recording device and ejected as ink droplets onto a recording medium to record images, etc. Inkjet recording devices include continuous ejection type (charge-controlled type, spray type, etc.) and on-demand type (piezo type, thermal type, electrostatic attraction type, etc.), but the ink according to the embodiment can be used with any of these types.

[0053] Furthermore, a toner containing PY155 according to the embodiment is also provided. The toner is a micro-sized powder used in laser printers and copiers, in which color particles are attached to electrostatically charged plastic particles, and PY155 according to the embodiment can be used as the color particles. The toner can be manufactured by methods commonly used in the art (for example, Japanese Patent Application Publication No. 2023-091995).

[0054] The present invention will be described in detail below with reference to examples, but the content of the present invention is not limited thereto. [1] Synthesis of C.I. Pigment Yellow 155 (raw material PY155)

[0055] [Preparation Example 1: Preparation of PY155-C1] 104.5 parts by mass of dimethyl aminoterephthalate was added to a mixture of 70 parts by mass of water, 111.5 parts by mass of glacial acetic acid, and 150 parts by mass of 30% hydrochloric acid while stirring, and the mixture was stirred for 4 hours. An ice bath was attached, and the suspension was cooled to 0°C by adding 100 parts by mass of ice. 150 parts by mass of 23.5% sodium nitrite aqueous solution (35.25 parts by mass as sodium nitrite) was added to the suspension, and the mixture was stirred for 1 hour while maintaining a temperature of 5°C or lower with ice. Next, an aqueous sulfamic acid solution was added to decompose the excess nitrite. 5 parts by mass of activated carbon was added, and the mixture was stirred for 30 minutes. The residue was then removed by filtration to obtain a diazo solution.

[0056] Separately, 93.1 parts by mass of a 30% by mass sodium hydroxide aqueous solution was added to 500 parts by mass of water and cooled to 10°C. 69.0 parts by mass of 1,4-bis(acetoacetylamino)benzene was added, and the resulting mixture was stirred for about 30 minutes. Next, 5.0 parts by mass of activated carbon was added and stirred for 30 minutes, and the solution was filtered. 400 parts by mass of water, 400 parts by mass of ice, 73.5 parts by mass of glacial acetic acid, and 53.2 parts by mass of a 30% by mass sodium hydroxide aqueous solution were added to the filtrate over 30 minutes to obtain a coupler solution.

[0057] The coupler solution obtained above was stirred at room temperature, and the diazo solution obtained above was added dropwise to the coupler solution over 2 hours. Next, the reaction mixture was heated to 40°C and stirred for 1 hour, then heated to 60°C and stirred for another hour, and finally heated to 80°C and stirred for 1 hour. The reaction mixture was filtered through a Nutsche filter and washed with 20,000 parts by mass of water. The resulting filtrate was dried in a forced-air dryer at 120°C for 14 hours, ground, and obtained PY155-C1.

[0058] [Preparation Example 2: Preparation of PY155-C2] 104.5 parts by mass of dimethyl aminoterephthalate was added to a mixture of 70 parts by mass of water, 111.5 parts by mass of glacial acetic acid, and 150 parts by mass of 30% hydrochloric acid while stirring, and the mixture was stirred for 4 hours. An ice bath was attached, and the suspension was cooled to 0°C by adding 100 parts by mass of ice. 150 parts by mass of 23.5% sodium nitrite aqueous solution (35.25 parts by mass as sodium nitrite) was added to the suspension, and the mixture was stirred for 1 hour while maintaining a temperature of 5°C or lower with ice. Next, an aqueous sulfamic acid solution was added to decompose the excess nitrite. 5 parts by mass of activated carbon was added, and the mixture was stirred for 30 minutes. The residue was then removed by filtration to obtain a diazo solution.

[0059] Separately, 93.1 parts by mass of a 30% by mass sodium hydroxide aqueous solution was added to 500 parts by mass of water and cooled to 10°C. 69.0 parts by mass of 1,4-bis(acetoacetylamino)benzene was added, and the resulting mixture was stirred for about 30 minutes. Next, 5.0 parts by mass of activated carbon was added and stirred for 30 minutes, and the solution was filtered. 400 parts by mass of water, 400 parts by mass of ice, 73.5 parts by mass of glacial acetic acid, and 53.2 parts by mass of a 30% by mass sodium hydroxide aqueous solution were added to the filtrate over 30 minutes to obtain a coupler solution.

[0060] The coupler solution obtained above was stirred at 40°C, and the diazo solution obtained above was added dropwise to the coupler solution over 2 hours. The mixture was then stirred for 1 hour, the temperature was raised to 60°C and stirred for another hour, and finally the temperature was raised to 80°C and stirred for another hour. The reaction mixture was filtered through a Nutsche filter and washed with 20,000 parts by mass of water. The resulting filtrate was dried in a forced-air dryer at 120°C for 14 hours, ground, and obtained PY155-C2.

[0061] [Example 1] (Solvent Salt Milling Process) 100 parts by mass of PY155-C1 obtained in Preparation Example 1, 500 parts by mass of sodium chloride, and 111 parts by mass of diethylene glycol were charged into a double-arm kneader (capacity 2 L, manufactured by Yoshida Seisakusho), and the mixture was ground at 95°C for 7 hours to obtain a kneaded product.

[0062] (Acid Treatment Process) Next, 4545.7 parts by mass of pure water and 17.1 parts by mass of 98% sulfuric acid aqueous solution (16.8 parts by mass of sulfuric acid per 100 parts by mass of PY155-C1) were charged into a 15L enamel tank (manufactured by AS ONE) and mixed, and the kneaded mixture obtained above was added thereto. The mixture was heated to 60°C, stirred for 4 hours, filtered, and washed with 20,000 parts by mass of pure water.

[0063] (Drying and Grinding Process) The obtained filtrate was dried at 120°C for 14 hours using a box-type forced-air dryer (forced-air constant-temperature dryer: Windy Oven WFO-520W, manufactured by Tokyo Rikakikai Co., Ltd.), and then ground using a grinder (LAB MILL, manufactured by Osaka Chemical Co., Ltd.) under the conditions of a large grinding cup and a grinding time of 15 seconds to obtain PY155-1.

[0064] - Production of pigment dispersion for inkjet ink (IJ dispersion) 12.82 g of styrene-acrylic copolymer aqueous solution (resin content 43.7% by mass, manufactured by DIC Corporation), 88.66 g of pure water, 3.74 g of 25% by mass potassium hydroxide aqueous solution, and 6.78 g of isopropyl alcohol were placed in a 250 mL poly bottle (wide-mouth bottle, manufactured by Teraoka Corporation), and the mixture was shaken for 10 minutes in a paint shaker (manufactured by Toyo Seiki Seisakusho Co., Ltd.) to prepare the resin solution.

[0065] Next, 16.00 g of the resin solution obtained above, 4.00 g of PY155-1, and 100 g of zirconia beads (YTZ balls, φ0.5 mm, manufactured by Nikkatoh) were placed in a 100 mL poly bottle (wide-mouth bottle, manufactured by Teraoka Co., Ltd.), and the mixture was shaken for 90 minutes using a paint shaker (manufactured by Toyo Seiki Seisakusho Co., Ltd.). Then, 12.00 g of pure water was added, and after mixing by hand, the zirconia beads were separated using a mesh, and the dispersed intermediate was placed in a 100 mL poly bottle (wide-mouth bottle, manufactured by Teraoka Co., Ltd.). This was aged for one week in a constant temperature bath at 70°C (multi-safety type dryer MSO-45TPH, manufactured by Futaba Chemical Co., Ltd.) to obtain an IJ dispersion.

[0066] - Manufacturing of inkjet ink (IJ ink) 37.80 g of glycerin, 6.00 g of 1,2-hexanediol, and 99 g of pure water were placed in a 250 mL poly bottle (wide-mouth bottle, manufactured by Teraoka Co., Ltd.) and mixed by hand to prepare a mixed solvent. Next, 9.60 g of the IJ dispersion prepared above and 20.40 g of the mixed solvent prepared above were placed in a 100 mL poly bottle and mixed by hand to obtain IJ ink.

[0067] [Example 2] PY155-2 was produced in the same manner as in Example 1, except that the conditions for the solvent salt milling process and the acid treatment process were changed to the conditions shown in Table 1. In the acid treatment process, 35% by mass hydrochloric acid was used. Then, the IJ dispersion and IJ ink were produced in the same manner as in Example 1.

[0068] [Example 3] PY155-3 was produced in the same manner as in Example 1, except that the conditions for the solvent salt milling process and the acid treatment process were changed to the conditions shown in Table 1. In the acid treatment process, 60% by mass nitric acid was used. Then, the IJ dispersion and IJ ink were produced in the same manner as in Example 1.

[0069] [Example 4] PY155-4 was produced in the same manner as in Example 1, except that the conditions for the solvent salt milling process and the acid treatment process were changed to the conditions shown in Table 1. In the acid treatment process, 98% by mass sulfuric acid was used. Then, the IJ dispersion and IJ ink were produced in the same manner as in Example 1.

[0070] [Example 5] PY155-5 was produced in the same manner as in Example 1, except that the conditions for the solvent salt milling process and the acid treatment process were changed to the conditions shown in Table 1. In the acid treatment process, 35% by mass hydrochloric acid was used. Then, the IJ dispersion and IJ ink were produced in the same manner as in Example 1.

[0071] [Comparative Example 1] PY155-A was produced in the same manner as in Example 1, except that the conditions for the solvent salt milling process and the acid treatment process were changed to the conditions shown in Table 1. In the acid treatment process, 98% by mass sulfuric acid was used. Then, an IJ dispersion and an IJ ink were produced in the same manner as in Example 1.

[0072] [Comparative Example 2] PY155-C1, which is the raw material PY155, was used as PY155-B. Then, an IJ dispersion and IJ ink were manufactured in the same manner as in Example 1.

[0073] The PY155, IJ dispersions, and IJ inks obtained in Examples 1-5 and Comparative Examples 1 and 2 were evaluated for the items listed in Table 2. The measurement methods for each item in Table 2 are as follows: (1) Measurement items for PY155 (X-ray diffraction measurement) The CuKα characteristic X-ray diffraction spectrum of PY155 was measured using a powder X-ray diffractometer (X'Pert PRO MPD, manufactured by PANALYtical) under the following conditions: X-ray source: CuKα rays Tube current: 40 mA Tube voltage: 45 kV Scanning range: 2θ = 4° to 35°

[0074] Figures 1 to 7 show the CuKα characteristic X-ray diffraction spectra of PY155 obtained in Examples 1 to 5 and Comparative Examples 1 and 2, respectively. Table 2 shows the values ​​of the maximum diffraction intensity (A), average diffraction intensity (B), average diffraction intensity (C), (A) / (B), and (A) / (C) calculated from these spectra. In Table 2, the maximum diffraction intensity (A) is the intensity of the largest diffraction peak among the diffraction peaks located at the diffraction angle 2θ = 10.0 ± 0.2°. The average diffraction intensity (B) is the value obtained by summing all the diffraction peak intensities measured in the diffraction angle range 2θ = 8.0 to 8.5° in the CuKα characteristic X-ray diffraction spectrum and dividing it by the number of diffraction peaks measured. Since the X-ray diffraction intensity was measured every 2θ = approximately 0.026°, there were 19 measurement points in the diffraction angle range 2θ = 8.0 to 8.5°. The average diffraction intensity (B) was calculated by summing up the diffraction peak intensities of all 19 measurement points and dividing the result by the number of measurement points, which was 19.

[0075] The average diffraction intensity (C) is calculated by summing up all diffraction peak intensities measured in the CuKα characteristic X-ray diffraction spectrum within the diffraction angle range of 2θ = 23.0 to 24.0° and dividing the sum by the number of diffraction peaks measured. Since the X-ray diffraction intensity was measured at intervals of approximately 0.026° of 2θ, there were 38 measurement points within the diffraction angle range of 2θ = 23.0 to 24.0°. The average diffraction intensity (C) was calculated by summing up the 38 diffraction peak intensities at these measurement points and dividing the result by the number of measurement points, which is 38.

[0076] (pH) The pH of PY155 was measured according to the method described in JIS K 5101-17-1:2004. (BET specific surface area) For 200 mg of PY155, the BET specific surface area was calculated by measuring the amount of gas (nitrogen) adsorbed using the single-point method with a fully automated specific surface area analyzer Macsorb HM model-1208 (manufactured by Mountec Co., Ltd.). (Ca content) The Ca content was measured using an energy-dispersive X-ray fluorescence analyzer PANlytical Epsilon 5 (manufactured by Spectris).

[0077] (Average Particle Size) The particle size (major and minor diameters) was measured as follows: 5 mg of C.I. Pigment Yellow 155 was added to 4 mL of cyclohexanone and dispersed for 10 minutes using an ultrasonic cleaner (product name "Bransonic M2800-J", manufactured by Yamato Scientific Co., Ltd.). The resulting dispersion was dropped onto a mesh (collodion membrane attached, 200 mesh, manufactured by Nisshin EM Co., Ltd.) to prepare a measurement sample. The measurement sample was photographed using an electron microscope (product name "JEM-1400Flash", manufactured by JEOL Ltd.), and the major and minor diameters of 100 primary pigment particles in the resulting photograph were measured using ImageJ (image processing software), and the average value (arithmetic mean) was calculated.

[0078] (Average Aspect Ratio) The average aspect ratio was calculated as "average of major axis / average of minor axis".

[0079] (2) Measurement items for IJ dispersion and IJ ink (Viscosity) The viscosity of the IJ dispersion or IJ ink was measured using an E-type viscometer TV-25 (manufactured by Toki Sangyo Co., Ltd.) at 20°C and 30 rpm.

[0080] (Volume-average dispersed particle size; Mv) 0.5 mL of IJ dispersion or IJ ink was diluted with 100 g of pure water, and the volume-average dispersed particle size (referred to simply as "particle size" in Table 2) was measured by analyzing the Cumulants method using a table-cell type nanoparticle size distribution and dispersion evaluation system VASCO (Solvent:Water, DTC:UP, manufactured by CORDOUAN Technologies). The results are shown in Table 2 below.

[0081] Table 2 shows that when PY155 is used in Examples 1 to 5, both the inkjet dispersion and the inkjet ink have small dispersed particle sizes and low viscosity. Using such inks enables cleaner printing, and the small dispersed particle size also prevents clogging of the inkjet printer nozzle head.

[0082] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents.

Claims

1. In the CuKα characteristic X-ray diffraction spectrum, the ratio ((A) / (B)) of the maximum diffraction intensity (A) of the diffraction peak at a diffraction angle of 2θ = 10.0 ± 0.2° to the average diffraction intensity (B) of the diffraction peaks at a diffraction angle of 2θ = 8.0 to 8.5° is 6.0 to 28.0 for C. I. Pigment Yellow 155: [Here, the maximum diffraction intensity (A) is the intensity of the largest diffraction peak among the diffraction peaks located at a diffraction angle of 2θ = 10.0 ± 0.2° in the CuKα characteristic X-ray diffraction spectrum; the average diffraction intensity (B) is the value obtained by summing all the diffraction peak intensities measured in the range of diffraction angles 2θ = 8.0 to 8.5° in the CuKα characteristic X-ray diffraction spectrum and dividing it by the number of diffraction peaks measured].

2. The ratio of the maximum diffraction intensity (A) to the average diffraction intensity (C) of the diffraction peaks at a diffraction angle 2θ = 23.0 to 24.0° ((A) / (C)) is 9.0 to 27.0, as described in claim 1: [Here, the average diffraction intensity (C) is the value obtained by summing up all the diffraction peak intensities measured in the diffraction angle 2θ = 23.0 to 24.0° in the CuKα characteristic X-ray diffraction spectrum and dividing it by the number of diffraction peaks measured].

3. BET specific surface area is 50 m² ２ C.I. Pigment Yellow 155 according to claim 1 or 2, wherein the amount is 1 / g or more.

4. C.I. Pigment Yellow 155 according to any one of claims 1 to 3, wherein the pH is 7.0 or less.

5. C.I. Pigment Yellow 155 according to any one of claims 1 to 4, wherein the Ca content is 20 ppm or less.

6. A pigment dispersion comprising C.I. Pigment Yellow 155 according to any one of claims 1 to 5 and a dispersion medium.

7. The pigment dispersion according to claim 6, further comprising a dispersant.

8. The pigment dispersion according to claim 6 or 7, wherein the volume-average dispersed particle diameter (Mv) is 100 to 190 nm.

9. An ink comprising the pigment dispersion according to any one of claims 6 to 8.

10. A toner comprising C.I. Pigment Yellow 155 as described in any one of claims 1 to 5.

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