Method for producing resin-treated pigment, resin-treated pigment, pigment dispersion, and ultraviolet-curable inkjet ink

Abstract

To provide a method for simply producing a resin-treated pigment where a pigment is finely dispersed with low viscosity, that is excellent in storage stability and enables preparation of a pigment dispersion applicable to various monomers, with less energy consumption.SOLUTION: A method for producing a resin-treated pigment includes adding 30-60 pts.mass of a resin A having 3-30 mass% of a constitutional unit (ii) represented by general formula (3) to a mixture containing 100 pts.mass of an organic pigment, 5-20 pts.mass of a pigment derivative, and water, precipitating a resin B in which at least a part of the constitutional unit (ii) has been converted into the constitutional unit (iv) represented by general formula (4), and obtaining a resin-treated pigment. In the general formulae, R3 represents a hydrogen atom, R4 represents a methyl group, R5 represents a methyl group, C represents O or NH, D represents an ethylene group or a propylene group, X represents a chlorine atom, and q and r represent arbitrary repeating numbers.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a resin-treated pigment, a resin-treated pigment, a pigment dispersion, and an ultraviolet-curable inkjet ink. [Background technology]

[0002] Inkjet printing is a printing method that does not require a printing plate and allows images to be printed on demand by outputting data from a personal computer. Inkjet printing uses aqueous inkjet inks, solvent-based inkjet inks, ultraviolet-curable inkjet inks, and the like. When solvent-based inkjet inks are used, there are concerns that the organic solvents released from the ink may place a burden on the environment. For this reason, aqueous inkjet inks that use water as a solvent and ultraviolet-curable inkjet inks that are substantially free of volatile components and in which all components form a coating film are widely used in industrial applications.

[0003] In particular, printing methods using ultraviolet-curable inkjet (hereinafter also referred to as "UVIJ") inks, which do not require a drying process and can produce highly durable images, are being considered for industrial applications such as printing on sign displays, packaging, and plastic containers. Printing methods using UVIJ inks are shifting from conventional single-pass printing to high-speed printing, which allows large-area images to be printed in one go by ejecting ink from a line head. Therefore, UVIJ inks that can support such high-speed printing are required.

[0004] UVIJ inks are prepared by blending a pigment dispersion containing a UV-curable monomer as a liquid medium, an oligomer, a photoinitiator, and other ingredients. UVIJ ink hues include the three primary colors of cyan, magenta, and yellow, as well as black and white, and complementary colors such as green, orange, and blue. Each UVIJ ink is prepared using a pigment dispersion containing the corresponding pigment. To prepare an ink that can be stably ejected from a print head, has finely dispersed pigments, and is low in viscosity, a pigment dispersion is required in which the pigments are finely dispersed, are resistant to aggregation even after storage, and have stable viscosity. Various pigment dispersions with these properties have been investigated (Patent Documents 1 to 6). Inks with finely dispersed pigments, low viscosity, and a stable pigment dispersion are easily ejected from a print head, can print images with clear dots, and are also compatible with the high-speed printing described above. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-282758 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-2528 [Patent Document 3] Japanese Patent Application Laid-Open No. 2014-145053 [Patent Document 4] Japanese Patent Application Laid-Open No. 2001-288386 [Patent Document 5] Japanese Patent Application Laid-Open No. 2003-321628 [Patent Document 6] Japanese Patent Application Laid-Open No. 2008-285677 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when attempting to finely disperse a pigment, the pigment is more likely to aggregate due to an increase in surface energy. As a result, problems such as an increase in the viscosity of the pigment dispersion during storage and an increase in the pigment particle size occur, resulting in problems such as a decrease in the storage stability of the pigment dispersion. Furthermore, achieving low viscosity and fine dispersion of the pigment in a pigment dispersion containing a UV-curable monomer, a pigment, and a pigment dispersant requires a long dispersion process, which poses problems such as increased costs and energy consumption.

[0007] Furthermore, the type of UV-curable monomer is selected depending on the substrate to be coated. Therefore, it is necessary to prepare a pigment dispersion liquid for each type of UV-curable monomer individually, which may result in a large number of pigment dispersion liquids being prepared. In addition, there are various regulations when transporting pigment dispersion liquids containing various monomers, and there are also issues such as increased costs and energy consumption.

[0008] The present invention has been made in view of the problems associated with the prior art, and an object of the present invention is to provide a method for simply producing, with less energy consumption, a resin-treated pigment in which the pigment is finely dispersed at low viscosity, has excellent storage stability, and is capable of preparing a pigment dispersion that is applicable to various monomers.

[0009] Another object of the present invention is to provide a resin-treated pigment that has low viscosity, finely dispersed pigments, and excellent storage stability, and that can be used to prepare pigment dispersions that are applicable to various monomers; a pigment dispersion for an ultraviolet-curable inkjet ink that uses this resin-treated pigment; and an ultraviolet-curable inkjet ink. [Means for solving the problem]

[0010] That is, according to the present invention, there is provided the following method for producing a resin-treated pigment. [1] A method for producing a resin-treated pigment, comprising the steps of: adding 30 to 60 parts by mass of a resin A that is liquid at room temperature and contains 40 to 80% by mass of structural units (i) represented by general formula (2) below, 3 to 30% by mass of structural units (ii) represented by general formula (3) below, and 1 to 57% by mass of other structural units (iii), and having a number average molecular weight of 10,000 to 30,000, to a mixture containing 100 parts by mass of an organic pigment, 5 to 20 parts by mass of a dye derivative represented by general formula (1) below, and water; and precipitating a resin B in which at least a portion of the structural units (ii) have been converted to structural units (iv) represented by general formula (4) below, thereby obtaining the resin-treated pigment.

[0011] TIFF0007742805000001.tif25169 (in the general formula (1), M represents a lithium atom, a sodium atom, or a potassium atom, and E represents an organic dye skeleton)

[0012] TIFF0007742805000002.tif33170 (in the general formula (2), R represents a hydrogen atom or a methyl group, R1 represents a hydrogen atom or a methyl group, R2 represents a hydrogen atom, a methyl group, or a butyl group, A represents O or NH, B represents an ethylene group or a methylethylene group, X represents O, NHCOO, or NHCONH, n represents the average number of repeating units and is a number of 20 to 100, and p represents an arbitrary number of repeating units)

[0013] TIFF0007742805000003.tif37170 (in the general formula (3), R3 represents a hydrogen atom or a methyl group; R4s each independently represent a methyl group, an ethyl group, or a propyl group; R5 represents a methyl group or a benzyl group; C represents O or NH; D represents an ethylene group or a propylene group; X represents a chlorine atom, a bromine atom, or an iodine atom; and q represents any number of repeating groups.)

[0014] TIFF0007742805000004.tif38170 (in the general formula (4), R3 represents a hydrogen atom or a methyl group; R4s each independently represent a methyl group, an ethyl group, or a propyl group; R5 represents a methyl group or a benzyl group; C represents O or NH; D represents an ethylene group or a propylene group; E represents an organic dye skeleton; and r represents any number of repeating units.)

[0015] [2] The method for producing a resin-treated pigment according to [1] above, wherein the structural unit (iii) comprises a structural unit (iii-1) represented by the following general formula (5):

[0016] TIFF0007742805000005.tif36170 (in the general formula (5), R3 represents a hydrogen atom or a methyl group, C represents O or NH, D represents an ethylene group or a propylene group, R4 each independently represents a methyl group, an ethyl group, or a propyl group, and s represents an arbitrary number of repetitions)

[0017] The present invention also provides the following resin-treated pigment.

[0018] [3] A resin-treated pigment comprising an organic pigment and 35 to 70 parts by mass of resin B relative to 100 parts by mass of the organic pigment, wherein resin B contains 35 to 70% by mass of a structural unit (i) represented by the following general formula (2), other structural unit (iii), and 10 to 50% by mass of a structural unit (iv) represented by the following general formula (4), and may further contain a structural unit (ii) represented by the following general formula (3), and the total content of structural units (ii) and (iii) in resin B is 0.5 to 60% by mass.

[0019] TIFF0007742805000006.tif33170 (in the general formula (2), R represents a hydrogen atom or a methyl group, R1 represents a hydrogen atom or a methyl group, R2 represents a hydrogen atom, a methyl group, or a butyl group, A represents O or NH, B represents an ethylene group or a methylethylene group, X represents O, NHCOO, or NHCONH, n is a number of 20 to 100 representing the average number of repeating units, and p represents an arbitrary number of repeating units).

[0020] TIFF0007742805000007.tif37170 (in the general formula (3), R3 represents a hydrogen atom or a methyl group; R4s each independently represent a methyl group, an ethyl group, or a propyl group; R5 represents a methyl group or a benzyl group; C represents O or NH; D represents an ethylene group or a propylene group; X represents a chlorine atom, a bromine atom, or an iodine atom; and q represents any number of repeating groups.)

[0021] TIFF0007742805000008.tif38170 (in the general formula (4), R3 represents a hydrogen atom or a methyl group; R4s each independently represent a methyl group, an ethyl group, or a propyl group; R5 represents a methyl group or a benzyl group; C represents O or NH; D represents an ethylene group or a propylene group; E represents an organic dye skeleton; and r represents any number of repeating units.)

[0022] [4] The resin-treated pigment according to [3], wherein the organic dye skeleton represented by E in the general formula (4) is an azo dye skeleton, an anthraquinone dye skeleton, a quinacridone dye skeleton, a phthalocyanine dye skeleton, a diketopyrrolopyrrole dye skeleton, or an isoindoline dye skeleton. [5] The resin-treated pigment according to [3] or [4], wherein the structural unit (iii) is a structural unit derived from α-methylstyrene.

[0023] Furthermore, according to the present invention, there are provided the following pigment dispersion and ultraviolet-curable inkjet ink. [6] A pigment dispersion for ultraviolet-curable inkjet ink, comprising an ultraviolet-curable monomer and the resin-treated pigment according to any one of [3] to [5] above dispersed in the ultraviolet-curable monomer. [7] An ultraviolet-curable inkjet ink containing the pigment dispersion liquid described in [6] above. [Effects of the Invention]

[0024] According to the present invention, it is possible to provide a method for simply producing a resin-treated pigment with less energy consumption, which has low viscosity, finely dispersed pigments, excellent storage stability, and is capable of preparing pigment dispersions that are applicable to various monomers.

[0025] Furthermore, according to the present invention, it is possible to provide a resin-treated pigment that has low viscosity, finely dispersed pigments, has excellent storage stability, and is capable of preparing a pigment dispersion that is applicable to various monomers; a pigment dispersion for an ultraviolet-curable inkjet ink that uses this resin-treated pigment; and an ultraviolet-curable inkjet ink. DETAILED DESCRIPTION OF THE INVENTION

[0026] <Resin-treated pigment and its manufacturing method> Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments. The resin-treated pigment of the present invention contains an organic pigment and 35 to 70 parts by mass of resin B per 100 parts by mass of the organic pigment. Resin B contains 35 to 70% by mass of structural unit (i) represented by the following general formula (2), other structural unit (iii), and 10 to 50% by mass of structural unit (iv) represented by the following general formula (4), and may further contain structural unit (ii) represented by the following general formula (3). The total content of structural unit (ii) and structural unit (iii) in resin B is 0.5 to 60% by mass.

[0027] The resin-treated pigment can be produced by the following production method. Specifically, the method for producing the resin-treated pigment of the present invention includes the step of adding 30 to 60 parts by mass of resin A to a mixture containing 100 parts by mass of an organic pigment, 5 to 20 parts by mass of a dye derivative represented by the following general formula (1), and water. Resin A is a resin that is liquid at room temperature and has a number-average molecular weight of 10,000 to 30,000, and contains 40 to 80% by mass of structural units (i) represented by the following general formula (2), 3 to 30% by mass of structural units (ii) represented by the following general formula (3), and 1 to 57% by mass of other structural units (iii). In the above step, resin A is added to a mixture containing the organic pigment, the dye derivative, and water, thereby precipitating resin B, in which at least a portion of the structural units (ii) in resin A have been converted to structural units (iv) represented by the following general formula (4), thereby obtaining the resin-treated pigment.

[0028] TIFF0007742805000009.tif25169 (in the general formula (1), M represents a lithium atom, a sodium atom, or a potassium atom, and E represents an organic dye skeleton)

[0029] TIFF0007742805000010.tif33170 (in the general formula (2), R represents a hydrogen atom or a methyl group, R1 represents a hydrogen atom or a methyl group, R2 represents a hydrogen atom, a methyl group, or a butyl group, A represents O or NH, B represents an ethylene group or a methylethylene group, X represents O, NHCOO, or NHCONH, n represents the average number of repeating units and is a number of 20 to 100, and p represents an arbitrary number of repeating units).

[0030] TIFF0007742805000011.tif37170 (in the general formula (3), R3 represents a hydrogen atom or a methyl group; R4s each independently represent a methyl group, an ethyl group, or a propyl group; R5 represents a methyl group or a benzyl group; C represents O or NH; D represents an ethylene group or a propylene group; X represents a chlorine atom, a bromine atom, or an iodine atom; and q represents any number of repeating groups.)

[0031] TIFF0007742805000012.tif38170 (in the general formula (4), R3 represents a hydrogen atom or a methyl group; R4s each independently represent a methyl group, an ethyl group, or a propyl group; R5 represents a methyl group or a benzyl group; C represents O or NH; D represents an ethylene group or a propylene group; E represents an organic dye skeleton; and r represents any number of repeating units.)

[0032] (organic pigments) Conventionally known organic pigments can be used as the organic pigment. Examples of the organic pigment include azo pigments, phthalocyanine pigments, quinacridone pigments, benzimidazolone pigments, isoindolinone pigments, isoindoline pigments, dioxazine pigments, anthraquinone pigments, quinophthalone pigments, perinone pigments, diketopyrrolopyrrole pigments, perylene pigments, anthraquinone pigments, dianthraquinonyl pigments, anthrapyrimidine pigments, anthanthrone pigments, indanthrone pigments, flavanthrone pigments, and pyranthrone pigments. Carbon materials such as carbon black can also be used. Furthermore, composites such as mixed crystallized products of different pigments and solid solution pigments can also be used.

[0033] As the organic pigment, organic pigments used in inkjet inks are preferred, and more preferred are CI Pigment Blue 15:3, 15:4, 15:6, 60; CI Pigment Green 7, 36, 58; CI Pigment Red 122, 177, 192, 202, 207, 209, 254, 255, 264, 296; CI Pigment Violet 19, 23, 29; CI Pigment Yellow 74, 139, 150, 151, 155, 180, 181, 185; Pigment Orange 43, 64, 71, 73; Pigment Black 7; and the like.

[0034] Organic pigments are usually particulate. The number-average particle diameter (primary particle diameter) of particulate organic pigments is preferably 150 nm or less. Using an organic pigment with a number-average particle diameter of 150 nm or less can improve the optical density, saturation, color development, and print quality of the recorded image, while preventing clogging of the recording head and enabling good ejection. The number-average particle diameter of the organic pigment can be measured using, for example, an electron microscope or a light-scattering particle size distribution analyzer.

[0035] (dye derivatives) The dye derivative is a compound represented by the following general formula (1) in which an anion of a sulfonic acid group is bonded to an organic dye skeleton. In general formula (1), it is preferable that the organic dye skeleton represented by E has a structure equivalent to or similar to that of the organic pigment, as this facilitates strong adsorption to the organic pigment. Resin B, which has structural unit (iv) with a counter ion derived from the dye derivative, is insoluble in liquid media such as water or organic solvents. It then adsorbs to the organic pigment, introducing an anion of a sulfonic acid group, and is difficult to detach from the adsorbed organic pigment, allowing the organic pigment to be stably finely dispersed in the liquid medium.

[0036] TIFF0007742805000013.tif25169 (in the general formula (1), M represents a lithium atom, a sodium atom, or a potassium atom, and E represents an organic dye skeleton)

[0037] In general formula (1), examples of the organic dye skeleton represented by E include an azo dye skeleton, an anthraquinone dye skeleton, a quinacridone dye skeleton, a phthalocyanine dye skeleton, a diketopyrrolopyrrole dye skeleton, and an isoindoline dye skeleton. In general formula (1), M is a lithium atom, a sodium atom, or a potassium atom, and is preferably a sodium atom or a potassium atom. When M is a lithium atom in general formula (1), dissociation in water may be difficult. One sulfonic acid anion may be bonded to the organic dye skeleton represented by E, but two or more may be bonded.

[0038] Examples of the dye derivative having an azo dye skeleton include compounds represented by the following formulas (A) and (B).

[0039] TIFF0007742805000014.tif86170

[0040] Examples of the dye derivative having an anthraquinone dye skeleton include compounds represented by the following formulas (C) and (D).

[0041] TIFF0007742805000015.tif129170

[0042] Examples of the dye derivative having a quinacridone dye skeleton include compounds represented by the following formulas (E) and (F).

[0043] TIFF0007742805000016.tif87170

[0044] Examples of the dye derivative having a phthalocyanine dye skeleton include compounds represented by the following formulas (G) and (H).

[0045] TIFF0007742805000017.tif134170

[0046] Examples of the dye derivative having a diketopyrrolopyrrole dye skeleton include compounds represented by the following formula (I).

[0047] TIFF0007742805000018.tif45170

[0048] Examples of dye derivatives having an isoindoline dye skeleton include compounds represented by the following formula (J).

[0049] TIFF0007742805000019.tif55170

[0050] (Resin A) Resin A has a structural unit (i) represented by the following general formula (2), a structural unit (ii) represented by the following general formula (3), and another structural unit (iii).

[0051] TIFF0007742805000020.tif33170 (in the general formula (2), R represents a hydrogen atom or a methyl group, R1 represents a hydrogen atom or a methyl group, R2 represents a hydrogen atom, a methyl group, or a butyl group, A represents O or NH, B represents an ethylene group or a methylethylene group, X represents O, NHCOO, or NHCONH, n represents the average number of repeating units and is a number of 20 to 100, and p represents an arbitrary number of repeating units).

[0052] TIFF0007742805000021.tif37170 (in the general formula (3), R3 represents a hydrogen atom or a methyl group; R4s each independently represent a methyl group, an ethyl group, or a propyl group; R5 represents a methyl group or a benzyl group; C represents O or NH; D represents an ethylene group or a propylene group; X represents a chlorine atom, a bromine atom, or an iodine atom; and q represents any number of repeating groups.)

[0053] The structural unit (i) is derived from a macromonomer having a polyalkylene glycol chain. The structural unit (i) dissolves in a dispersion medium such as a UV-curable monomer, creating steric hindrance between particles, causing repulsion, and enabling the organic pigment to be stably dispersed in the dispersion medium for a long period of time. Furthermore, the inclusion of a large amount of polyalkylene glycol chains allows the resin A to be liquid at room temperature.

[0054] In general formula (2), the average number of repeating units represented by n is a number from 20 to 100, and therefore the molecular weight of the macromonomer is within the range of 880 to 5,800.

[0055] Examples of macromonomers constituting the structural unit (i) include polyethylene glycol mono(meth)acrylate, polyethylene glycol monomethyl mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, polyethylene glycol polypropylene glycol mono(meth)acrylate, polyethylene glycol polypropylene glycol monobutyl(meth)acrylate, a reaction product of (meth)acryloyloxyethyl isocyanate with polyethylene glycol monomethyl ether, polyethylene glycol polypropylene glycol monobutyl ether, etc., a reaction product of (meth)acryloyloxyethyl isocyanate with polyethylene glycol monomethyl ether monoamine, polyethylene glycol polypropylene glycol monomethyl ether monoamine, a reaction product of (meth)acrylic acid, (meth)acrylic acid chloride, (meth)acrylic anhydride with polyethylene glycol monomethyl ether monoamine, polyethylene glycol polypropylene glycol monomethyl ether monoamine, etc. Among these, water-insoluble monomers are preferred, and macromonomers containing 50 mol% or more of polypropylene glycol in the glycol chain are preferred, with monomers containing 70 mol% or more being more preferred.

[0056] The structural unit (ii) is a monomer having a quaternary ammonium base with a chlorine, bromine, or iodine anion as a counter ion. The presence of the structural unit (ii) makes the resin A soluble in water. When the dye derivative represented by general formula (1) and the resin A are mixed in water, an anion exchange reaction occurs, and the salt formed by the alkali metal ion and the halide ion is eliminated. The counter ion of the quaternary ammonium base in the resin A becomes the anion of the sulfonic acid group of the dye derivative. This results in the production of a resin B in which at least a portion of the structural unit (ii) is converted to the structural unit (iv) represented by general formula (4).

[0057] With the anions of the sulfonic acid groups in the dye derivative adsorbed to the organic pigment, resin A is converted to resin B, and the converted resin B adsorbs to at least a portion of the surface of the organic pigment, thereby surface-treating the organic pigment. Resin A, which was water-soluble and compatible due to the structure of structural unit (ii), becomes insoluble in water when the sulfonic acid ions of the dye derivative become counterions to the halide ions, and precipitates on the pigment surface while undergoing desalting and ion exchange. The solubility and steric repulsion of structural unit (i) then allow the organic pigment to maintain good dispersibility for an extended period of time.

[0058] Examples of monomers constituting the structural unit (ii) include (meth)acryloyloxyethyl trimethylammonium chloride, (meth)acryloyloxyethyl diethylmethylammonium chloride, (meth)acryloyloxyethyl benzyl dimethyl chloride, (meth)acryloyloxyethyl benzyl diethyl chloride, (meth)acryloyloxyethyl trimethylammonium bromide, (meth)acryloyloxyethyl diethylmethylammonium bromide, (meth)acryloyloxyethyl benzyl dimethyl bromide, (meth)acryloyloxyethyl benzyl diethyl bromide, (meth)acryloyloxyethyl trimethylammonium iod ... benzyl dimethyl bromide Examples thereof include (meth)acryloyloxyethyl diethylmethylammonium iodide, (meth)acryloyloxyethyl benzyl dimethyl iodide, (meth)acryloyloxyethyl benzyl diethyl iodide, (meth)acryloylaminopropyl trimethylammonium chloride, (meth)acryloylaminopropyl benzyl trimethylammonium chloride, (meth)acryloylaminopropyl diethylmethylammonium chloride, (meth)acryloylaminopropyl benzyl diethyl chloride, (meth)acryloylaminopropyl dibutylmethyl chloride, and (meth)acryloylaminopropyl benzyl dibutylammonium chloride.

[0059] The other structural unit (iii) is a structural unit that can be linked to the structural units (i) and (ii). Conventionally known radically polymerizable monomers can be used as the monomer that constitutes the structural unit (iii). Examples of the monomer that constitutes the structural unit (iii) include (meth)acrylic acid-based monomers such as (meth)acrylic acid and (meth)acrylate; and vinyl monomers such as styrene, vinyl toluene, vinyl pyridine, vinyl caprolactone, vinyl imidazole, α-methyl styrene, and vinyl acetate. Of these, α-methyl styrene is preferred because it is easy to adjust the molecular weight and control the polymerization.

[0060] The structural unit (iii) preferably includes a structural unit (iii-1) represented by the following general formula (5).

[0061] TIFF0007742805000022.tif36170 (in the general formula (5), R3 represents a hydrogen atom or a methyl group, C represents O or NH, D represents an ethylene group or a propylene group, R4 each independently represents a methyl group, an ethyl group, or a propyl group, and s represents an arbitrary number of repetitions)

[0062] Examples of monomers that constitute the structural unit (iii-1) include dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylamide, diethylaminoethylpropyl (meth)acrylamide, and dibutylaminopropyl (meth)acrylamide.

[0063] In resin A, the proportion of structural unit (i) is 40 to 80% by mass, preferably 50 to 70% by mass, the proportion of structural unit (ii) is 3 to 30% by mass, preferably 5 to 20% by mass, and the proportion of structural unit (iii) is 1 to 57% by mass. The total of structural units (i) to (iii) is 100% by mass. If the proportion of structural unit (i) is less than 40% by mass, steric hindrance becomes insufficient, resulting in reduced dispersibility of organic pigments. On the other hand, if the proportion of structural unit (i) is more than 80% by mass, the macromonomer has a high molecular weight, so the terminal polymerizable groups become diluted and are more likely to remain unpolymerized.

[0064] If the proportion of structural unit (ii) is less than 3% by mass, the amount of dye derivative bonded decreases, resulting in fewer adsorption sites for the organic pigment. This causes resin B to detach from the organic pigment during dispersion or storage, resulting in reduced dispersion stability. On the other hand, if the proportion of structural unit (ii) is more than 30% by mass, the amount of dye derivative bonded increases, resulting in reduced pigment dispersibility and pigment aggregation. Furthermore, since a large amount of dye derivative is introduced, the hue of the dye derivative is more likely to appear.

[0065] The number-average molecular weight of resin A is 10,000 to 30,000, preferably 12,000 to 24,000. In this specification, "number-average molecular weight (Mn)" refers to the number-average molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC). If the number-average molecular weight of resin A is less than 10,000, the dispersibility of the pigment may decrease, resulting in increased viscosity of the pigment dispersion or sedimentation of the pigment. On the other hand, if the number-average molecular weight of resin A exceeds 30,000, the polymerization time may be prolonged or the process may become complicated in order to achieve a high molecular weight, and the viscosity of the pigment dispersion may become excessively high.

[0066] Resin A is a liquid resin at room temperature (25°C). If a pigment is treated with a solid resin at room temperature to produce a dry powder, the solid resin must be dissolved in the liquid medium before it can be dispersed in the liquid medium. This takes time to disperse, and the resin may not dissolve completely, forming "lumps." In contrast, if Resin A, which is liquid at room temperature, is used, the resin quickly becomes compatible with the liquid medium, making it easy to obtain the desired resin-treated pigment.

[0067] Resin A can be synthesized by a conventionally known method, such as a conventionally known radical polymerization method, a polymerization method in which the molecular weight is adjusted using a chain transfer agent such as thiol, or a living radical polymerization method that can more uniformly adjust the molecular weight of the main chain and can produce an AB block copolymer by the addition method, specifically, living radical polymerization methods such as atom transfer radical polymerization (ATRP), reversible addition-fragmentation chain transfer polymerization (RAFT), nitroxide (NMP), organotellurium (TERP), iodine transfer polymerization (ITP), reversible transfer catalyzed polymerization (RTCP), and reversible catalyst-mediated polymerization (RCMP).

[0068] The polymerization may be either thermal polymerization or photopolymerization, and an azo-based radical generator, a peroxide-based radical generator, a photosensitizer, or the like may be added to the polymerization reaction system. The polymerization method may be solventless, solution polymerization, or emulsion polymerization, with solution polymerization being preferred. In the production method of the present invention, a water-soluble organic solvent can be used when mixing the organic pigment, the dye derivative, and resin A in water. Therefore, resin A obtained by the polymerization reaction can be used as is without isolation, and therefore it is preferable to synthesize resin A by solution polymerization in a water-soluble organic solvent. Examples of water-soluble organic solvents include lower alcohols, polyhydric alcohols, glycols, glycol ethers, glycol esters, amides, sulfoxides, and ureas. Resin A obtained by the polymerization reaction may also be isolated.

[0069] (Method of manufacturing resin-treated pigment) In the method for producing a resin-treated pigment of the present invention, 30 to 60 parts by mass of resin A is added to a mixture containing 100 parts by mass of an organic pigment, 5 to 20 parts by mass of a dye derivative, and water, and mixed. This allows the counter ion (X - ) and the cation in the dye derivative (M + ) is released (desalted), and at the same time, ion exchange is performed to produce a resin B in which at least a portion of the structural units (ii) are converted to structural units (iv) represented by general formula (4). Because the produced resin B is insoluble in water, it precipitates and is adsorbed and deposited on at least a portion of the surface of the pigment. This allows the production of the desired resin-treated pigment in which resin B is adsorbed and deposited on at least a portion of the surface of the pigment.

[0070] TIFF0007742805000023.tif38170 (in the general formula (4), R3 represents a hydrogen atom or a methyl group; R4s each independently represent a methyl group, an ethyl group, or a propyl group; R5 represents a methyl group or a benzyl group; C represents O or NH; D represents an ethylene group or a propylene group; E represents an organic dye skeleton; and r represents any number of repeating units.)

[0071] The mixture containing the organic pigment, the coloring matter derivative, and water may further contain a water-soluble organic solvent, if necessary. Examples of the water-soluble organic solvent include alcohols such as methanol, ethanol, and isopropanol; glycols such as ethylene glycol, propylene glycol, polyethylene glycol, polypropylene glycol, diethylene glycol butyl ether, and triethylene glycol dimethyl ether; glycerin; amide solvents such as dimethylformamide, dimethylacetamide, and N-methylpyrrolidone; urea solvents such as tetramethylurea; and carbonate solvents such as ethylene carbonate.

[0072] It is preferable that resin B is uniformly adsorbed and deposited on the surface of the primary particles of the organic pigment. For this reason, the organic pigment used in preparing the mixture may be a dried powder, but is preferably in the form of an aqueous paste. In the case of an aqueous paste, since it is not dried, even if the organic pigment forms secondary particles, the cohesive force is weak, and it can be easily converted into fine primary particles by stirring. The amount of organic pigment in the mixture is preferably 1 to 10% by mass.

[0073] The dye derivative may be pre-adsorbed onto the surface of the organic pigment. The sulfonic acid group in the dye derivative may be an unneutralized free acid, but it is preferable to form a salt by adding an aqueous solution of an alkali metal hydroxide or the like before adding resin A. It is preferable to thoroughly mix and stir a mixture containing the organic pigment, dye derivative, and water (aqueous slurry) to finely disperse the organic pigment particles.

[0074] The pH of the mixture when resin A is added is preferably neutral to alkaline, and more preferably within the range of pH 6.5 to 9.5. If the mixture is acidic, resin B may be difficult to form (precipitate). Furthermore, if resin A has an amino group, the amino group is easily ionized, making it difficult for resin B to precipitate and filtration during post-treatment. On the other hand, if the mixture is strongly alkaline (e.g., pH greater than 9.5), resin B may be difficult to precipitate in water. Furthermore, if resin A has an acidic group, the acidic group is easily ionized, making it difficult for resin B to precipitate and filtration during post-treatment. After resin A is added to the mixture to precipitate resin B, the mixture is preferably heated to a temperature of preferably 80°C or less, more preferably 60°C or less, before filtration to facilitate filtration.

[0075] The mixture is filtered, the resulting solids are washed, and then dried and pulverized as necessary to obtain the desired resin-treated pigment. The drying temperature is preferably 150°C or less, and more preferably 110°C or less. If the solids are pulverized too finely, the heat generated during pulverization may cause the particles to fuse together. Even particles with a coarse particle size, such as passing through a 100-mesh screen, can be used satisfactorily.

[0076] The amount of the dye derivative per 100 parts of the organic pigment is 5 to 20 parts by mass, preferably 6 to 18 parts by mass. If the amount is less than 5 parts by mass, the amount of the dye derivative is so small that resin B is likely to detach from the particle surface of the organic pigment, resulting in reduced dispersion stability. On the other hand, if the amount is more than 20 parts by mass, the hue of the dye derivative may affect the hue of the organic pigment, and the viscosity of the dispersion may become excessively high.

[0077] The amount of resin A added is 30 to 60 parts by mass, preferably 35 to 55 parts by mass, per 100 parts by mass of the organic pigment. If the amount is less than 30 parts by mass, the resin content will be insufficient, resulting in reduced dispersion stability. On the other hand, if the amount is more than 60 parts by mass, the viscosity of the dispersion may become excessively high. Furthermore, the amount of quaternary ammonium salt in resin A relative to the amount of sulfonate ions in the dye derivative is preferably 1 to 2 molar equivalents, more preferably 1.1 to 1.8 molar equivalents.

[0078] (Resin B) Resin B contains 35 to 70 mass % of the structural unit (i) represented by general formula (2), other structural units (iii), and 10 to 50 mass % of the structural unit (iv) represented by the following general formula (4).

[0079] TIFF0007742805000024.tif38170 (in the general formula (4), R3 represents a hydrogen atom or a methyl group; R4s each independently represent a methyl group, an ethyl group, or a propyl group; R5 represents a methyl group or a benzyl group; C represents O or NH; D represents an ethylene group or a propylene group; E represents an organic dye skeleton; and r represents any number of repeating units.)

[0080] In Resin B, the proportion of structural unit (i) is 35 to 70 mass%, preferably 40 to 65 mass%, and the proportion of structural unit (iv) is 10 to 50 mass%, preferably 15 to 45 mass%. The total of all structural units is taken as 100 mass%. If the proportion of structural unit (i) is less than 35 mass%, the amount of polyalkylene glycol chain becomes insufficient, resulting in insufficient steric repulsion and reduced dispersion stability.

[0081] If the proportion of structural unit (iv) is less than 10% by mass, the amount of dye derivative in the formulation during production will be less than 5% by mass, resulting in insufficient adsorption to the organic pigment and reduced dispersion stability.On the other hand, if it exceeds 50% by mass, the amount of dye derivative will be excessive, which may result in a change in hue and reduced water resistance.

[0082] Resin B may further contain a structural unit (ii) represented by general formula (3). The total content of structural units (ii) and (iii) in Resin B is 0.5 to 60 mass%. Hereinafter, for convenience, "structural unit (ii)" and "structural unit (iii)" will also be collectively referred to as "structural unit (v)". In other words, structural unit (v) is a structural unit containing structural unit (iii) in Resin A and structural unit (ii) that remains without ion exchange.

[0083] In the resin-treated pigment, the amount of resin B per 100 parts by mass of the organic pigment is 35 to 70 parts by mass, preferably 40 to 60 parts by mass. If the amount of resin B is less than 35 parts by mass per 100 parts by mass of the organic pigment, the dispersion stability will be insufficient. On the other hand, if the amount of resin B is more than 70 parts by mass per 100 parts by mass of the organic pigment, the viscosity of the pigment dispersion prepared using this resin-treated pigment may increase excessively. Furthermore, since resin A is used in a liquid state under room temperature conditions, it may fuse due to heat during grinding or during storage.

[0084] <Pigment dispersion for UV-curable inkjet (UVIJ) ink> The resin-treated pigment described above can be dispersed in a liquid medium to produce a pigment dispersion for preparing ink. Furthermore, inkjet inks and the like can be prepared using this pigment dispersion. Conventional organic solvents can be used as the liquid medium. In particular, a pigment dispersion for UVIJ ink can be obtained by using a UV-curable monomer as the liquid medium and dispersing the resin-treated pigment in the UV-curable monomer. That is, the pigment dispersion for UVIJ ink of the present invention contains a UV-curable monomer and the resin-treated pigment described above dispersed in the UV-curable monomer.

[0085] As the UV-curable monomer, a conventionally known monomer that cures upon irradiation with UV light can be used. The UV-curable monomer may generally be a monofunctional monomer having one reactive group, or a polyfunctional monomer having two or more reactive groups. Furthermore, a photo-curable oligomer or photo-curable polymer having a UV-curable group may be used in combination.

[0086] Examples of monofunctional monomers include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, trimethylcyclohexyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentenyl (meth)acrylate, adamantyl (meth)acrylate, adamantylmethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 2-hydroxypropyl (meth)acrylate. Examples of the radical polymerizable monomer include propyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, glycidyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, polyethylene glycol mono(meth)acrylate, polyethylene glycol monomethyl ether (meth)acrylate, 2-ethoxyethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, allyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, (3-ethyloxetan-3-yl)methyl (meth)acrylate, an adduct of phthalic anhydride and 2-hydroxyethyl (meth)acrylate, acryloylmorpholine, N-vinylpyrrolidone, and N-vinylcaprolactam. Among these, those containing an acrylate skeleton with good UV curability are preferred.

[0087] Examples of polyfunctional monomers and photocurable oligomers include vinyloxyethoxyethyl (meth)acrylate, neopentyl glycol di(meth)acrylate, ethylene glycol di(meth)acrylate, poly(n=2 or more) ethylene glycol di(meth)acrylate, polypropylene glycol (n=2 or more) di(meth)acrylate, polybutylene glycol (n=2 or more) di(meth)acrylate, 2,2-bis(4-(meth)acryloxyethoxyphenyl)propane, 2,2-bis(4-(meth)acryloxydiethoxyphenyl)propane, trimethylolpropane diacrylate, bis(2-( Epoxy poly(meth)acrylates such as epoxy di(meth)acrylates obtained by reacting bisphenol A diepoxy with (meth)acrylic acid, 1,Urethane tri(meth)acrylate obtained by reacting 2-hydroxyethyl (meth)acrylate with a trimer of 6-hexamethylene diisocyanate, urethane di(meth)acrylate obtained by reacting isophorone diisocyanate with 2-hydroxypropyl (meth)acrylate, urethane hexa(meth)acrylate obtained by reacting isophorone diisocyanate with pentaerythritol tri(meth)acrylate, urethane di(meth)acrylate obtained by reacting dicyclohexyl diisocyanate with 2-hydroxyethyl (meth)acrylate, dicyclo Examples of suitable poly(meth)acrylates include urethane di(meth)acrylates obtained by reacting 2-hydroxyethyl (meth)acrylate with a urethane reaction product of hexyl diisocyanate and poly(n=6-15)tetramethylene glycol; polyester (meth)acrylates obtained by reacting trimethylolethane with succinic acid and (meth)acrylic acid; and polyester poly(meth)acrylates obtained by reacting trimethylolpropane with succinic acid, ethylene glycol, and (meth)acrylic acid. Among these, those containing an acrylate skeleton with good UV curability are preferred.

[0088] Examples of photocurable polymers include those having multiple radical polymerizable groups, such as (meth)acryloyloxy groups, at the terminals or side chains of polymers such as poly(meth)acrylate, polyurethane, polyester, polyamide, polyimide, and polyepoxy resin.

[0089] In typical oil-based pigment dispersions, the dispersant is adsorbed to the pigment through ionic bonds between the acidic groups of the pigment and the basic groups of the resin used as the dispersant. Therefore, when highly polar monomers (compounds with amide bonds such as acryloylmorpholine, vinylpyrrolidone, and vinylcaprolactone; ether-based compounds such as acryloyloxyethyl vinyl ether, etc.) are used as UV-curable monomers, the ionic bonds easily dissociate, causing the dispersant to detach from the pigment, resulting in a decrease in pigment dispersibility. In contrast, in the case of the resin-treated pigment used in the pigment dispersion of the present invention, an organic dye skeleton is introduced into the resin B adsorbed to the pigment, so that the resin B is firmly adsorbed to the pigment and does not easily detach. Furthermore, because the structural unit (iv) is not easily soluble in highly polar monomers, the pigment dispersion stability can be maintained at a high level.

[0090] The pigment dispersion and the UVIJ ink described below may further contain various additives. Examples of additives include polymerization inhibitors, surfactants, antioxidants, UV absorbers, light stabilizers, leveling agents, thickeners, viscosity modifiers, preservatives, antifungal agents, dyes, waxes, fillers, acid generators, and alkali generators. Examples of polymerization inhibitors include phenolic compounds such as p-methoxyphenol, t-butylcatechol, di-t-butyl-p-cresol, hydroquinone monomethyl ether, 3,5-di-t-butyl-4-hydroxytoluene, and 2,2'-methylenebis(4-methyl-6-t-butylphenol); quinone compounds such as p-benzoquinone; amine compounds such as p-benzylaminophenol, di-β-naphthyl-p-phenylenediamine, phenylhydroxylamine, and diethylhydroxylamine; oxime compounds such as quinonedioxime and cyclohexanoneoxime; and sulfur compounds such as phenothiazine. A photoinitiator may be previously blended into the pigment dispersion.

[0091] The composition of the pigment dispersion can be set as desired. A specific example is preferably a pigment dispersion containing 5 to 30% by mass of resin-treated pigment, 0.5 to 30% by mass of polymer dispersant, and 40 to 94.5% by mass of UV-curable monomer. More preferably, the pigment dispersion contains 10 to 25% by mass of resin-treated pigment, 1 to 25% by mass of polymer dispersant, and 60 to 90% by mass of UV-curable monomer.

[0092] The pigment dispersion can be prepared according to a conventional method. For example, a mixture of a UV-curable monomer, a resin-treated pigment, a polymeric dispersant, and the like is prepared, and an organic solvent is added as needed. The pigment dispersion can be obtained by dispersing the mixture using a paint shaker, ball mill, attritor, sand mill, horizontal media mill, colloid mill, roll mill, or the like. The pigment concentration can be adjusted by adding a UV-curable monomer to the obtained pigment dispersion. Other additives may also be added as needed. Furthermore, it is preferable to remove coarse particles by processing using a centrifuge or filter.

[0093] To achieve the desired number average particle size (particle size distribution) of the pigment, various techniques can be employed, such as using small-sized grinding media, increasing the packing density of the grinding media, lengthening the dispersion time, slowing the discharge speed, and classifying the particles after grinding using a filter or centrifuge. The viscosity of the pigment dispersion at 25°C is preferably 3 to 100 mPa·s.

[0094] <Ultraviolet-curable inkjet (UVIJ) ink> The UVIJ ink of the present invention contains the aforementioned pigment dispersion for UVIJ ink, and is an inkjet ink containing a finely dispersed organic pigment in a liquid medium of a UV-curable monomer. The UVIJ ink of the present invention is an environmentally friendly ink that contains substantially no volatile components, and forms an image by curing the components applied to a recording medium when exposed to UV light.

[0095] In addition to the pigment dispersion described above, the UVIJ ink of the present invention may further contain, for example, a photopolymerization initiator, an ultraviolet-curable polymer, and the various additives described above. Photopolymerization initiators include photoradical polymerization initiators and photocationic polymerization initiators. Among these, photoradical polymerization initiators are preferred. Examples of photoinitiators include benzophenone-based photopolymerization initiators, thioxanthone-based photopolymerization initiators, ketoxime ester-based photopolymerization initiators, and acylphosphine oxide-based photopolymerization initiators. The content of the photopolymerization initiator in the UVIJ ink is preferably 3 to 12% by mass. If the photopolymerization initiator content is less than 3% by mass, poor curing may occur. On the other hand, if the photopolymerization initiator content exceeds 12% by mass, residual photopolymerization initiator may remain or coloration may occur due to the photopolymerization initiator.

[0096] The desired UVIJ ink can be obtained by mixing the above components, thoroughly stirring, and then filtering the mixture. The surface tension of the UVIJ ink at 25°C is preferably 15 to 45 mN / m, and more preferably 20 to 40 mN / m.

[0097] The UVIJ ink of the present invention can be used to record (print) images on various substrates by inkjet recording, forming a printed film with high saturation, excellent color development, adhesion, abrasion resistance, and other durability. Examples of substrates (recording media) include paper, photographic paper, glossy photographic paper, plastic film, fabric, ceramics, and metal. [Example]

[0098] The present invention will be specifically described below based on examples, but the present invention is not limited to these examples. In the examples and comparative examples, "parts" and "%" are by mass unless otherwise specified.

[0099] <Synthesis of Resin A (1)> (Synthesis Example 1: Resin A-1) A reaction vessel was charged with 100 parts of propylene glycol monomethyl ether (MPG), 100 parts of propylene glycol monomethacrylate (MAC) (trade name "Blemmer PP-2000" manufactured by NOF Corporation, hydroxyl value 26 mg KOH / g, molecular weight calculated from the hydroxyl value 2,160, number average molecular weight in terms of polystyrene measured by GPC (THF-GPC) using tetrahydrofuran (THF) as a developing solvent 3,400), 7.5 parts of α-methylstyrene (MSt), 10 parts of methyl methacrylate (MMA), and 33.5 parts of dimethylaminoethyl methacrylate (DMAEMA). The mixture was stirred under a nitrogen stream and heated to 75 °C. Five parts of 2,2'-azobis(isobutyrate) dimethyl (V-601) (trade name "V-601" manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were added, polymerized for 8 hours, and then cooled to obtain a resin precursor solution. A portion of the precursor solution was sampled and measured at 180°C using an infrared moisture meter. The solids content was 58.5%, confirming that most of the polymer had polymerized. The amine value of the precursor was measured using a potentiometric automatic titrator with a 0.1 mol / L 2-propanol hydrochloric acid solution and was 79.1 mg KOH / g. When the precursor solution was added to water, the solution became cloudy and a white viscous substance precipitated. This means that the resulting resin precursor was insoluble in water.

[0100] In a separate container, 13.5 parts of benzyl chloride and 13.5 parts of MPG were placed, and the precursor solution was added at room temperature. After stirring for 1 hour, the mixture was heated to 80°C and reacted for 5 hours, resulting in a slightly turbid, viscous solution of resin A-1. A portion of the resin A-1 solution was sampled and measured to have a solids content of 58.0%. The solids (resin A-1) were a viscous liquid at room temperature. The polystyrene-equivalent number-average molecular weight (Mn) of resin A-1 was measured by GPC (DMF-GPC) using a 0.1 mmol / L lithium bromide solution in dimethylformamide (DMF) as the developing solvent. The molecular weight distribution (PDI = weight-average molecular weight / number-average molecular weight) was 1.88. Almost no MAC peak was detected by DMF-GPC, indicating that most of the MAC was incorporated into resin A-1. The amine value of Resin A-1 was 36.3 mg KOH / g, indicating that 50 mol% of the amino groups in the precursor were quaternized, i.e., the quaternization rate was 50 mol%. The amount of quaternary salt contained in 1 g of Resin A-1 was calculated to be 0.648 mmol. In the obtained Resin A-1, the proportion of structural unit (i) was 60.8%, the proportion of structural unit (ii) was 18.4%, and the proportion of structural unit (iii) was 20.8%. When a solution of Resin A-1 was added to water, it dissolved in water without producing any insoluble matter.

[0101] (Synthesis Examples 2 and 3: Resins A-2 and A-3) Resins A-2 and A-3 were obtained in the same manner as in Synthesis Example 1 above, except that the amount of benzyl chloride used was the amount shown in Table 1. The physical properties of the obtained Resins A-2 and A-3 are shown in Table 1. Both Resins A-2 and A-3 were viscous liquids at room temperature. Furthermore, almost no MAC peak was detected by DMF-GPC.

[0102] TIFF0007742805000025.tif111170

[0103] <Synthesis of macromonomer> (Reference synthesis example 1) A reaction vessel was charged with 100.0 parts (0.05 mol) of polypropylene glycol polyethylene glycol monomethyl ether monoamine (polypropylene glycol (PO) / polyethylene glycol (PE) molar ratio = 26 / 6, amine value 28.0 mg KOH / g, molecular weight calculated from the amine value 2,004) and stirred at room temperature for 10 minutes to homogenize. A dropping funnel was charged with 7.75 parts (0.05 mol) of 2-isocyanatoethyl methacrylate (MOI) (trade name "Karends MOI" manufactured by Showa Denko K.K.). The reaction mixture was then added dropwise over 30 minutes to yield the macromonomer MAC-1. A portion of the reaction solution was sampled and analyzed by infrared spectroscopy (IR), confirming the near complete disappearance of the absorption of the isocyanate group derived from the MOI and the formation of urea bonds. The amine value of MAC-1 was 0.1 mg KOH / g, confirming the near completion of the reaction between the amino and isocyanate groups. MAC-1 is a macromonomer in which a methacryloyl group is bonded to one end of polypropylene glycol / polyethylene glycol (PPG / PEG), and corresponds to the macromonomer that forms the structural unit (i) represented by general formula (2). The Mn of MAC-1 measured by THF-GPC was 3,400.

[0104] (Reference synthesis example 2) MAC-2, a macromonomer in which a methacryloyl group is bonded to one end of PPG, was obtained in the same manner as in Reference Synthesis Example 1, except that polypropylene glycol monobutyl ether (hydroxyl value: 18.7 mg KOH / g, molecular weight calculated from the hydroxyl value: 3,000) was used instead of polyethylene glycol propylene glycol monomethyl ether monoamine, and 1 mL of a 1% diethylene glycol dimethyl ether solution of tin dilaurate was added and reacted at 80°C for 10 hours. MAC-2 corresponds to the macromonomer that forms the structural unit (i) represented by general formula (2). The Mn of MAC-2 measured by THF-GPC was 4,500.

[0105] (Reference comparative synthesis example 1) HMAC-1, a macromonomer in which a methacryloyl group is bonded to one end of a PPG / PEG copolymer, was obtained in the same manner as in Reference Synthesis Example 1 above, except that polyethylene glycol propylene glycol monomethyl ether monoamine (PO / PE (molar ratio) = 9 / 1, amine value 93.5 mg KOH / g, molecular weight calculated from the amine value 600) was used instead of polyethylene glycol propylene glycol monomethyl ether monoamine. This HMAC-1 does not fall under the category of macromonomers that form the structural unit (i) represented by general formula (2). The Mn of HMAC-1 measured by THF-GPC was 940.

[0106] <Synthesis of Resin A (2)> (Synthesis Example 4: Resin A-4) A reaction vessel was charged with 100 parts of MPG, 110 parts of MAC-1, 5 parts of MSt, 25 parts of MMA, 10 parts of DMAEMA, and 6 parts of V-601. Polymerization was carried out in the same manner as in Synthesis Example 1 to obtain a resin precursor solution. The solids content of the resulting precursor solution was 60.5%, confirming that the polymerization was almost complete. The amine value of the precursor was 23.8 mg KOH / g. Next, a mixture of 8.0 parts of benzyl chloride and 8.0 parts of MPG was added to the precursor solution, and the reaction was carried out in the same manner as in Synthesis Example 1 to obtain a solution of Resin A-4. The solids content of the solution of Resin A-4 was 60.1%, and the solids (Resin A-4) were a viscous liquid at room temperature. The Mn of Resin A-4 was 13,000, the PDI was 2.1, and no MAC-1 peak was observed. The amine value of Resin A-4 was 0.02 mg KOH / g, and the quaternization rate was approximately 100 mol%. The amount of quaternary salt contained in 1 g of resin A-4 was calculated to be 0.402 mmol. In the obtained resin A-4, the proportion of structural unit (i) was 69.6%, the proportion of structural unit (ii) was 11.4%, and the proportion of structural unit (iii) was 19.0%. When a solution of resin A-4 was added to water, it dissolved in water without producing any insoluble matter.

[0107] (Synthesis Example 5, Comparative Synthesis Examples 1 and 2: Resins A-5, HA-1, and HA-2) Resins A-5, HA-1, and HA-2 were obtained in the same manner as in Synthesis Example 4, except for the formulations shown in Table 2. The physical properties of the obtained resins A-5, HA-1, and HA-2 are shown in Table 2.

[0108] TIFF0007742805000026.tif166170

[0109] (Comparative synthesis example 3: Resin HA-3) A reaction vessel was charged with 74.7 parts of MPG, 0.6 parts of iodine, 3.3 parts of V-601, 5.4 parts of MMA, 5.4 parts of butyl methacrylate, 5.4 parts of 2-ethylhexyl methacrylate, 17.8 parts of polyethylene glycol monomethyl ether methacrylate (molecular weight 200), and 0.1 parts of N-iodosuccinimide. The mixture was heated to 60°C and reacted for 5 hours to obtain a solution of polymer block A. The Mn of polymer block A was 5,000 and the PDI was 1.23. The solids content of polymer block A was 33.5%, and the polymerization rate was approximately 100%. Next, 2.7 parts of DMAEMA and 3.4 parts of benzyl methacrylate were added, and the mixture was reacted at 60°C for 4 hours. The mixture was cooled to room temperature, 2.1 parts of benzyl chloride was added, and the mixture was stirred for 1 hour. After that, the mixture was reacted at 80°C for 3 hours to obtain a solution of resin HA-3, an AB block type resin. The solids content of the resin HA-3 solution was 38.0%. The Mn of resin HA-3 was 7,100, and the PDI was 1.42. The peak of polymer block A in the GPC chart shifted to the higher molecular weight side, suggesting that it was an AB block resin. The amine value of resin HA-3 was 0.1 mg KOH / g, and the quaternization rate was approximately 100 mol%. The amount of quaternary salt contained in 1 g of resin HA-3 was calculated to be 4.01 mmol. Resin HA-3 was soluble in water. Polymer block A, which constitutes resin HA-3, is a solvent-soluble chain, and polymer block B is a chain containing a quaternary base. Polymer block B undergoes ion exchange with the sulfonate ion of the dye derivative, introducing the dye skeleton into polymer block B, resulting in a resin-treated pigment.

[0110] (Reference Comparative Synthesis Example 2: Solid of Resin A-4) 1 L of hexane was placed in a 3 L beaker and stirred, and 100 parts of the solution of Resin A-4 obtained in Synthesis Example 4 was added to separate a highly viscous liquid Resin A-4. The hexane was removed by decantation, and the resulting Resin A-4 was placed in a tray. After 24 hours of air drying at room temperature to thoroughly remove the hexane, the resin was placed in a dryer at 60°C for 24 hours to obtain a viscous liquid resin. The non-volatile content of the resulting resin at 120°C was 99.0%. This is the solid form of Resin A-4 obtained in Synthesis Example 4.

[0111] <Production of resin-treated pigments> Example 1 A beaker was charged with 285.7 parts of CI Pigment Blue 15:3 (PB-15:3) (product name "3463," Dainichiseika Color & Chemicals Mfg. Co., Ltd.) aqueous paste (35% purity) and 1,714 parts of ion-exchanged water, and the mixture was stirred at 2,000 rpm using a disper to obtain an aqueous slurry. 200 parts of an aqueous solution of copper phthalocyanine monosulfonate sodium salt (MSPCNa) represented by formula (G) (2.5% purity, pH 8.9, clear blue solution) was added to the aqueous slurry, and the mixture was stirred at 2,000 rpm for 2 hours. After stirring, the aqueous slurry was spotted onto filter paper. The pigment was deposited on the filter paper, and the MSPCNa bled around the pigment, resulting in a blue bleed on the back of the filter paper. The pH of the aqueous slurry was 7.8.

[0112] In a separate container, 66.6 parts of resin A-4 solution and 66.6 parts of ion-exchanged water were mixed to obtain a uniform mixture. The resulting mixture was gradually added to the water slurry. When the water slurry was spotted on filter paper, no bleeding or bleed-through occurred. The mixture was heated to 60°C and stirred for 1 hour, then filtered and washed with ion-exchanged water. The mixture was dried at 100°C for 24 hours using a dryer and then pulverized using a pulverizer to obtain 144 parts of resin-treated pigment CX-001. The yield was 98.0%, and the nonvolatile content measured after drying at 120°C was 99.8%. At least a portion of the structural unit (ii) in resin A was converted to structural unit (iv), forming resin B derived from resin A. The amount of resin B per 100 parts of pigment was 46.8 parts. In the formed resin B, the proportion of structural unit (i) was 59.4%, the proportion of structural unit (iv) was 21.4%, and the proportion of structural unit (v) (total of structural unit (ii) and structural unit (iii)) was 19.2%.

[0113] (Example 2, Comparative Examples 1 to 3) Resin-treated pigments CX-002 and HCX-001 to 003 were obtained in the same manner as in Example 1 above, except that the types of "resins used" shown in Table 3 were used. Details of the obtained resin-treated pigments are shown in Table 3.

[0114] TIFF0007742805000027.tif78170

[0115] Examples 3 to 5 Resin-treated pigments BX-001, MX-001, and YX-001 were obtained in the same manner as in Example 1, except for the formulation shown in Table 4. Details of the obtained resin-treated pigments are shown in Table 4. The meanings of the abbreviations in Table 4 are as follows: PB-7: CI Pigment Black 7 (product name "Special Black 350", manufactured by Orion Engineered Carbons) PR-122: CI Pigment Red 122 (product name "6111", manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.) PY-155: CI Pigment Yellow 155 (product name "INKJET YELLOW 4GC", manufactured by Clariant) ·MSQNa: Sodium quinacridone monosulfonate (compound represented by formula (E)) ·MSTDATNa: Sodium anthraquinone cyanur monosulfonate (compound represented by formula (C))

[0116] TIFF0007742805000028.tif113170

[0117] (Examples 6 to 9, Comparative Example 4) Resin-treated pigments MX-002 to 005 and HMX-001 were obtained in the same manner as in Example 4 above, except that the formulation shown in Table 5 was used. The details of the obtained resin-treated pigments are shown in Table 5. In Table 5, "MSPQNa" is sodium monophthalimidomethylated quinacridone monosulfonate (compound represented by formula (F)).

[0118] TIFF0007742805000029.tif120170

[0119] (Production of Pigment Dispersion for UVIJ Ink) (Example 10) Into a resin container, 22.0 parts of resin-treated pigment CX-001 and 78.0 parts of phenoxyethyl acrylate (PEA) as a dispersion medium were put. After stirring for 1 hour using a disper, 300 parts of zirconia beads with a diameter of 0.5 mmφ were put in and sealed, and dispersion treatment was carried out for 30 minutes using a scandex. After separating and removing the zirconia beads, coarse particles were removed through a 0.5 μm filter, and UVIJ-C-01, a pigment dispersion for UVIJ ink, was obtained. The viscosity of UVIJ-C-01 measured using an E-type viscometer under the conditions of 60 rpm and 25 °C was 25.6 mPa·s. The number average particle diameter of the pigment in UVIJ-C-01 measured using a dynamic light scattering type particle size distribution meter was 95.6 nm. Also, a storage test of storing the obtained UVIJ-C-01 at 60 °C for 1 week was carried out. The viscosity of UVIJ-C-01 after the storage test was 23.6 mPa·s, and the number average particle diameter of the pigment was 95.4 nm.

[0120] (Examples 11 to 13) Pigment dispersions for UVIJ inks, UVIJ-B-01, M-01, and Y-01, were obtained in the same manner as in Example 10, except that 20.2 parts of resin-treated pigment BX-001, 21.6 parts of MX-001, and 22.4 parts of YX-001 were used instead of resin-treated pigment CX-001. The physical properties of the obtained pigment dispersions are shown in Table 6.

[0121] TIFF0007742805000030.tif58170

[0122] (Examples 14 to 16) UVIJ-C-02 to UVIJ-C-04, pigment dispersions for UVIJ inks, were obtained in the same manner as in Example 10, except that 22.0 parts of resin-treated pigment CX-002 was used instead of resin-treated pigment CX-001, and the dispersion time using Scandex was set to the time shown in Table 7. The physical properties of the obtained pigment dispersions are shown in Table 7.

[0123] TIFF0007742805000031.tif63170

[0124] (Comparative Examples 5 to 7) HUVIJ-C-01 to HUVIJ-C-03, which are pigment dispersions for UVIJ inks, were obtained in the same manner as in Example 10, except that the types of resin-treated pigments shown in Table 8 were used. The physical properties of the obtained pigment dispersions are shown in Table 8.

[0125] TIFF0007742805000032.tif58170

[0126] In Comparative Example 7, when the dispersion time was set to 180 minutes, the viscosity of the resulting pigment dispersion was 35.6 mPa s and the number-average particle size of the pigment was 100.1 nm. Furthermore, the viscosity and number-average particle size of the resulting pigment dispersion did not change significantly after a storage test, confirming that it was a good pigment dispersion. However, it was found that a long dispersion time was necessary to obtain a good pigment dispersion, as described above.

[0127] (Examples 17 to 28, Comparative Examples 8 to 10) Except for using the resin-treated pigments and monomers (dispersion media) of the types shown in Tables 9 to 11, pigment dispersions UVIJ-M-02 to 13 and HUVIJ-M-01 to 03 for UVIJ ink were obtained in the same manner as in Example 10 described above. The physical properties, etc. of the obtained pigment dispersions are shown in Tables 9 to 11. In Tables 9 to 11, "BzA" is benzyl acrylate, and "ACMO" is acryloyl morpholine.

[0128] (Comparative Examples 11 to 13) Also, 15 parts of PR-122, 5 parts of monophthalimidomethylated quinacridone monosulfonic acid (MSQ) (the free acid of the compound represented by formula (F)), and 40 parts of the solid of resin A-4 obtained in Reference Comparative Synthesis Example 2 were put into a resin container. Further, monomers (dispersion media) of the types shown in Table 11 in an amount such that the pigment content was 15% were added, and dispersion treatment was carried out in the same manner as in Example 10 described above to obtain pigment dispersions HUVIJ-M-04 to 0 as for UVIJ ink. The physical properties, etc. of the obtained pigment dispersions are shown in Table 11.

[0129] TIFF0007742805000033.tif94170

[0130] TIFF0007742805000034.tif94170

[0131] TIFF0007742805000035.tif97170

[0132] <Manufacture of UVIJ Ink> (Examples 29 to 32) 18 parts each of UVIJ-C-01, UVIJ-B-01, UVIJ-M-01, and UVIJ-Y-01, 53.5 parts of PEA, 19 parts of acryloyloxyethoxyethyl vinyl ether, 5 parts of photopolymerization initiator 1 (trade name "Lucirin TPO" manufactured by BASF), and 4.5 parts of photopolymerization initiator 2 (trade name "Irgacure 819" manufactured by BASF) were mixed. After thorough stirring, the mixture was filtered through a 5 μm filter to obtain UVIJ inks of various colors (UVIJ INK-C, B, M, and Y). The viscosity and number-average particle size of the pigment of each ink were measured. The results are shown in Table 12. The inks were then placed in brown sample bottles and stored at 60°C for one week, as described above, to undergo the storage test. After the storage test, the viscosity and number-average particle size of the pigment of each ink were measured. The results are shown in Table 12.

[0133] TIFF0007742805000036.tif75170

[0134] The resulting UVIJ ink was filled into a cartridge and installed in an inkjet printer (product name "EB100", manufactured by Konica Minolta). Using this inkjet printer, a solid image was printed continuously for one hour on polyethylene terephthalate (PET) film. The printing was smooth without clogging the recording head. Furthermore, the resulting image was free of streaks or distortion, demonstrating good ejection stability.

[0135] The image obtained using a UV lamp was exposed to ultraviolet light to obtain a print sample. After cutting the print sample into a grid pattern using a cutter, an adhesion (fixation) test was conducted in which cellophane tape was applied and then quickly peeled off. As a result, the print sample did not peel off at all, demonstrating good adhesion to the film. Furthermore, instead of the PET film, images were printed in the same manner using vinyl chloride film and surface-treated polypropylene film, and the film was exposed to ultraviolet light to obtain print samples. A similar adhesion (fixation) test was then conducted, and the print sample did not peel off at all, demonstrating good adhesion to the film. [Industrial Applicability]

[0136] The resin-treated pigment produced by the production method of the present invention is useful as a pigment dispersion for preparing an ultraviolet-curable inkjet ink.

Claims

1. A mixture containing 100 parts by mass of an organic pigment, 5 to 20 parts by mass of a dye derivative represented by the following general formula (1), and water, Adding 30 to 60 parts by mass of a resin A that is liquid at room temperature and has a number average molecular weight of 10,000 to 30,000, and contains 40 to 80% by mass of structural units (i) represented by the following general formula (2), 3 to 30% by mass of structural units (ii) represented by the following general formula (3), and 1 to 57% by mass of other structural units (iii), A method for producing a resin-treated pigment, comprising a step of precipitating a resin B in which at least a portion of the structural unit (ii) has been converted to a structural unit (iv) represented by the following general formula (4), thereby obtaining a resin-treated pigment: (In the general formula (1), M represents a lithium atom, a sodium atom, or a potassium atom, and E represents an organic dye skeleton.) (In the general formula (2), R represents a hydrogen atom or a methyl group, and R １ represents a hydrogen atom or a methyl group, and R ２ represents a hydrogen atom, a methyl group, or a butyl group; A represents O or NH; B represents an ethylene group or a methylethylene group; X represents O, NHCOO, or NHCONH; n is a number from 20 to 100 representing the average number of repeating units; and p represents an arbitrary number of repeating units. (In the general formula (3), R ３ represents a hydrogen atom or a methyl group, and R ４ each independently represents a methyl group, an ethyl group, or a propyl group; R ５ represents a methyl group or a benzyl group, C represents O or NH, D represents an ethylene group or a propylene group, X represents a chlorine atom, a bromine atom, or an iodine atom, and q represents any number of repetitions. (In the general formula (4), R ３ represents a hydrogen atom or a methyl group, and R ４ each independently represents a methyl group, an ethyl group, or a propyl group; R ５ represents a methyl group or a benzyl group, C represents O or NH, D represents an ethylene group or a propylene group, E represents an organic dye skeleton, and r represents an arbitrary number of repetitions.

2. 2. The method for producing a resin-treated pigment according to claim 1, wherein the structural unit (iii) includes a structural unit (iii-1) represented by the following general formula (5): (In the general formula (5), R ３ represents a hydrogen atom or a methyl group, C represents O or NH, D represents an ethylene group or a propylene group, and R ４ each independently represents a methyl group, an ethyl group, or a propyl group, and s represents an arbitrary number of repetitions.

3. An organic pigment and 35 to 70 parts by mass of resin B per 100 parts by mass of the organic pigment, The resin B contains 35 to 70 mass% of a structural unit (i) represented by the following general formula (2), other structural units (iii), and 10 to 50 mass% of a structural unit (iv) represented by the following general formula (4), and may further contain a structural unit (ii) represented by the following general formula (3): The resin-treated pigment, wherein the total content of the structural units (ii) and (iii) in the resin B is 0.5 to 60 mass %. (In the general formula (2), R represents a hydrogen atom or a methyl group, and R １ represents a hydrogen atom or a methyl group, and R ２ represents a hydrogen atom, a methyl group, or a butyl group; A represents O or NH; B represents an ethylene group or a methylethylene group; X represents O, NHCOO, or NHCONH; n is a number from 20 to 100 representing the average number of repeating units; and p represents an arbitrary number of repeating units. (In the general formula (3), R ３ represents a hydrogen atom or a methyl group, and R ４ each independently represents a methyl group, an ethyl group, or a propyl group; R ５ represents a methyl group or a benzyl group, C represents O or NH, D represents an ethylene group or a propylene group, X represents a chlorine atom, a bromine atom, or an iodine atom, and q represents any number of repetitions. (In the general formula (4), R ３ represents a hydrogen atom or a methyl group, and R ４ each independently represents a methyl group, an ethyl group, or a propyl group; R ５ represents a methyl group or a benzyl group, C represents O or NH, D represents an ethylene group or a propylene group, E represents an organic dye skeleton, and r represents an arbitrary number of repetitions.

4. 4. The resin-treated pigment according to claim 3, wherein the organic dye skeleton represented by E in the general formula (4) is an azo dye skeleton, an anthraquinone dye skeleton, a quinacridone dye skeleton, a phthalocyanine dye skeleton, a diketopyrrolopyrrole dye skeleton, or an isoindoline dye skeleton.

5. 5. The resin-treated pigment according to claim 3, wherein the structural unit (iii) is a structural unit derived from α-methylstyrene.

6. an ultraviolet-curable monomer; A pigment dispersion for ultraviolet-curable inkjet ink, comprising: the resin-treated pigment according to claim 3 or 4 dispersed in the ultraviolet-curable monomer.

7. An ultraviolet-curable inkjet ink containing the pigment dispersion liquid according to claim 6.

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