Pigment dispersion liquid, ultraviolet curable inkjet ink, and printed film

Abstract

To provide pigment dispersion in which pigment is finely dispersed at low viscosity even in a case where monomers of a relatively small SP value is contained, and which has excellent storage stability, and is useful as a raw material for preparing ultraviolet-curable type inkjet ink.SOLUTION: Pigment dispersion contains monomers whose SP value is 7.0 to 10.5 and resin-treated pigment, where the resin-treated pigment is obtained by adding a specified quantity of resin A having a constitutional unit (ii) expressed by a general formula (3) to a mixture containing organic pigment of magenta color and pigment derivative expressed by a general formula (1), and by depositing resin B. (M denotes sodium atom or the like; E denotes organic pigment skeleton; R3 denotes H or the like; R4 denotes methyl group or the like; R5 denotes methyl group or the like; C denotes O or NH; D denotes ethylene group or propylene group; X denotes Cl or the like).SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a pigment dispersion, an ultraviolet curable inkjet ink, and a printed film.

Background Art

[0002] The inkjet printing method is a printing method that does not require a plate and can print an image on demand by data output from a personal computer. In the inkjet printing method, water-based inkjet ink, solvent-based inkjet ink, ultraviolet curable inkjet ink, and the like are used. When using solvent-based inkjet ink, there is concern that the organic solvent in the discharged ink may impose a burden on the environment. For this reason, water-based inkjet ink using water as a solvent and ultraviolet curable inkjet ink that substantially does not contain volatile components and all components become a coating film are widely used in industrial applications.

[0003] Among them, a printing method using ultraviolet curable inkjet (hereinafter also referred to as "UVIJ") ink, which does not require a drying process and can obtain an image with excellent durability, is being studied for industrial applications such as sign displays, packaging, and printing on plastic containers. The printing method using UVIJ ink has shifted from the conventional single-pass printing to high-speed printing that can eject from a line head at once and print a large-area image at once. And there is a need for UVIJ ink that can cope with such high-speed printing.

[0004] UVIJ ink is prepared by blending a pigment dispersion liquid using an ultraviolet curable monomer as a liquid medium, an oligomer, a photoinitiator, and the like. As the hues of UVIJ ink, in addition to the three primary colors of cyan, magenta, and yellow, there are black and white, and complementary colors such as green, orange, and blue. And for the preparation of each color of UVIJ ink, a pigment dispersion liquid containing pigments of each color is used. In order to stably eject from the recording head, and to prepare an ink in which the pigments are finely dispersed and have a low viscosity, a pigment dispersion liquid in which the pigments are finely dispersed, the pigments are less likely to aggregate even after storage, and the viscosity is stable is required. And various pigment dispersion liquids having such characteristics have been studied (Patent Documents 1 to 6). An ink in which the pigments are finely dispersed, have a low viscosity, and the dispersion state of the pigments is stably maintained has good ejection properties from the recording head, can record an image with clear dots, and furthermore, can also cope with the above-mentioned high-speed printing.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, when attempting to finely disperse the pigment, the increase in surface energy makes the pigment prone to aggregation. As a result, problems such as an increase in the viscosity of the pigment dispersion during storage, an increase in the particle size of the pigment, etc. occur, leading to the problem of a decrease in the storage stability of the pigment dispersion. Also, to achieve a reduction in the viscosity of the pigment dispersion containing a UV-curable monomer, pigment, and pigment dispersant and fine dispersion of the pigment, a long dispersion process is required, resulting in problems such as an increase in cost and energy consumption.

[0007] Furthermore, the type of UV-curable monomer is selected and used according to the substrate to be coated. For this reason, it is necessary to separately prepare pigment dispersions corresponding to the types of UV-curable monomers, and there may be a case where the number of types of pigment dispersions to be prepared increases. Also, when transporting pigment dispersions containing various monomers, there are various regulations, and there are also problems such as an increase in cost and energy consumption.

[0008] By the way, in recent years, the biomass conversion of inkjet inks has been promoted. Among them, using a monomer derived from biomass as a monomer to be blended in UVIJ inks and the like is one of the useful methods for improving the biomass conversion rate of inks. However, for example, isobornyl acrylate (IBXA), which is a monofunctional monomer derived from biomass, has a relatively small SP value (SP value: 8.34). And when using a monomer with such a small SP value, compared with the case of using a monomer with a large SP value, it may take a long time to disperse the pigment. Furthermore, it may be difficult to enhance the color development of an image recorded with a UVIJ ink prepared using a pigment dispersion containing a monomer with a small SP value.

[0009] The present invention has been made in view of such problems of the prior art, and the problem to be solved is to provide a pigment dispersion useful as a raw material for preparing a UV-curable inkjet ink, which has a low viscosity, fine dispersion of the pigment, and excellent storage stability even when containing a monomer with a relatively small SP value.

[0010] Another object of the present invention is to provide an ultraviolet-curable inkjet ink that uses the above pigment dispersion liquid, has a low viscosity, fine dispersion of pigments, excellent storage stability, and is capable of forming a printed film excellent in color developability and adhesion to a substrate. Further, an object of the present invention is to provide a printed film excellent in color developability and adhesion to a substrate, which is formed using the above ultraviolet-curable inkjet ink.

Means for Solving the Problems

[0011] That is, according to the present invention, there is provided a pigment dispersion liquid shown below. [1] It contains a monomer having an SP value of 7.0 to 10.5 and a resin-treated pigment dispersed in the monomer. The resin-treated pigment is a mixture containing 100 parts by mass of a magenta organic pigment, 5 to 20 parts by mass of a dye derivative represented by the following general formula (1), and water, and contains 40 to 80% by mass of a structural unit (i) represented by the following general formula (2), 3 to 30% by mass of a structural unit (ii) represented by the following general formula (3), and 1 to 57% by mass of other structural units (iii). It is obtained by adding 25 to 60 parts by mass of a liquid resin A at room temperature having a number average molecular weight of 10,000 to 30,000 and precipitating a resin B in which at least a part of the structural unit (ii) is converted into a structural unit (iv) represented by the following general formula (4). The addition amount of the resin A is such that the amount of the quaternary ammonium salt in the following general formula (3) is 1.45 to 1.80 molar equivalents with respect to the amount of the sulfonic acid ion in the following general formula (1). Pigment dispersion liquid.

[0012] TIFF0007717043000001.tif32170 (In the above general formula (1), M represents a lithium atom, a sodium atom, or a potassium atom, and E represents an organic dye skeleton)

[0013] TIFF0007717043000002.tif41170(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 a number from 20 to 100 representing the average number of repeating units, and p represents an arbitrary number of repetitions)

[0014] TIFF0007717043000003.tif43170(In the general formula (3), R3 represents a hydrogen atom or a methyl group, R4 each independently represents 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 an arbitrary number of repetitions)

[0015] TIFF0007717043000004.tif37170(In the general formula (4), R3 represents a hydrogen atom or a methyl group, R4 each independently represents 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 an arbitrary number of repetitions)

[0016] [2] The pigment dispersion liquid according to [1], wherein the organic dye skeleton represented by E in the general formula (4) is a quinacridone dye skeleton. [3] The pigment dispersion liquid according to [1] or [2], wherein the structural unit (iii) is a structural unit derived from α-methylstyrene. [4] The pigment dispersion liquid according to any one of [1] to [3], wherein the structural unit (iii) contains a structural unit (iii-1) represented by the following general formula (5).

[0017] TIFF0007717043000005.tif41170(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)

[0018] [5] The monomer is an ultraviolet-curable monomer, and the pigment dispersion according to any one of [1] to [4] above, which is used in an ultraviolet-curable inkjet ink.

[0019] Further, according to the present invention, an ultraviolet-curable inkjet ink and a printed film shown below are provided. [6] An ultraviolet-curable inkjet ink containing the pigment dispersion according to [5] above. [7] A printed film which is a cured product of the ultraviolet-curable inkjet ink according to [6] above.

Advantages of the Invention

[0020] According to the present invention, even when a monomer having a relatively small SP value is contained, a pigment dispersion useful as a raw material for preparing an ultraviolet-curable inkjet ink, in which the viscosity is low, the pigment is finely dispersed, and the storage stability is excellent, can be provided.

[0021] Further, according to the present invention, an ultraviolet-curable inkjet ink using the above pigment dispersion, in which the viscosity is low, the pigment is finely dispersed, the storage stability is excellent, and the color developability and adhesion to a substrate are excellent, can be provided. Furthermore, according to the present invention, a printed film having excellent color developability and adhesion to a substrate, which is formed using the above ultraviolet-curable inkjet ink, can be provided.

Embodiments for Carrying Out the Invention

[0022] <Pigment Dispersion> Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments. One embodiment of the pigment dispersion of the present invention contains a monomer having an SP value of 7.0 to 10.5 and a resin-treated pigment dispersed in the monomer. Hereinafter, the details of the pigment dispersion of this embodiment will be described.

[0023] (Resin-treated pigment) The resin-treated pigment is manufactured by the manufacturing method shown below. That is, the manufacturing method of the resin-treated pigment has a step of adding 25 to 60 parts by mass of resin A to a mixture containing 100 parts by mass of a magenta organic pigment, 5 to 20 parts by mass of a dye derivative represented by the following general formula (1), and water. Resin A has 40 to 80% by mass of a structural unit (i) represented by the following general formula (2), 3 to 30% by mass of a structural unit (ii) represented by the following general formula (3), and 1 to 57% by mass of other structural units (iii), and its number average molecular weight is 10,000 to 30,000, and it is a resin that is liquid under room temperature conditions. In the above step, by adding resin A to the mixture containing the organic pigment, the dye derivative, and water, a resin B in which at least a part of the structural unit (ii) in resin A is converted into a structural unit (iv) represented by the following general formula (4) is precipitated to obtain a resin-treated pigment. And the addition amount of resin A to the mixture in the above step is an amount such that the amount of the ammonium salt in the following general formula (3) is 1.45 to 1.80 molar equivalents with respect to the amount of the sulfonic acid ion in the following general formula (1).

[0024] TIFF0007717043000006.tif32170 (In the above general formula (1), M represents a lithium atom, a sodium atom, or a potassium atom, and E represents an organic dye skeleton) TIFF0007717043000007.tif41170 (In the above 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 a number from 20 to 100 representing the average number of repeating units, and p represents an arbitrary number of repetitions) TIFF0007717043000008.tif43170(In the general formula (3), R3 represents a hydrogen atom or a methyl group, R4 each independently represents 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 an arbitrary number of repetitions) TIFF0007717043000009.tif37170(In the general formula (4), R3 represents a hydrogen atom or a methyl group, R4 each independently represents 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 an arbitrary number of repetitions)

[0025] [Organic Pigment] As the organic pigment, a magenta organic pigment is used. Examples of the magenta organic pigment include azo pigments, quinacridone pigments, dioxazine pigments, anthraquinone pigments, perinone pigments, diketopyrrolopyrrole pigments, perylene pigments, anthraquinone pigments, dianthraquinonyl pigments, etc. In addition, composites such as mixed crystals and solid solution pigments of different pigments can also be used.

[0026] As the organic pigment, an organic pigment used in inkjet inks is preferred, and C.I. Pigment Red 122, 177, 192, 202, 207, 209, 254, 255, 264, 296; C.I. Pigment Violet 19, 23, 29; etc. are more preferred. The content of the organic pigment in the pigment dispersion is preferably 2 to 50% by mass.

[0027] Organic pigments are usually in particulate form. The number average particle diameter (primary particle diameter) of the particulate organic pigment is preferably 150 nm or less. By using an organic pigment having a number average particle diameter of 150 nm or less, the optical density, chroma, color developability, and printing quality of the recorded image can be improved, and clogging of the recording head can be prevented and good ejection can be achieved. The number average particle diameter of the organic pigment can be measured, for example, using an electron microscope, a light scattering particle size distribution meter, or the like.

[0028] [Dye derivative] The dye derivative is a compound in which an anion of a sulfonic acid group is bonded to an organic dye skeleton, represented by the following general formula (1). In the 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 because it is likely to strongly adsorb to the organic pigment. The resin B having a structural unit (iv) having a counter ion derived from the dye derivative is insoluble in a liquid medium such as water or an organic solvent. Then, it adsorbs to the organic pigment and introduces an anion of a sulfonic acid group, and is difficult to desorb from the adsorbed organic pigment, and the organic pigment can be stably finely dispersed in the liquid medium.

[0029] TIFF0007717043000010.tif32170 (In the general formula (1), M represents a lithium atom, a sodium atom, or a potassium atom, and E represents an organic dye skeleton)

[0030] In the 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, and a diketopyrrolopyrrole dye skeleton. Among them, in the general formula (4), the organic dye skeleton represented by E is preferably a quinacridone dye skeleton. In the general formula (1), M is a lithium atom, a sodium atom, or a potassium atom, and among them, a sodium atom or a potassium atom is preferable. When M in the general formula (1) is a lithium atom, it may be difficult to dissociate in water. The anion of the sulfonic acid may be bonded to one organic dye skeleton represented by E, or may be bonded to two or more.

[0031] Examples of the dye derivative having an azo dye skeleton include compounds represented by the following formulas (A) and (B).

[0032] TIFF0007717043000011.tif91170

[0033] Examples of the dye derivative having an anthraquinone dye skeleton include compounds represented by the following formulas (C) and (D).

[0034] TIFF0007717043000012.tif134170

[0035] Examples of the dye derivative having a quinacridone dye skeleton include compounds represented by the following formulas (E) and (F).

[0036] TIFF0007717043000013.tif90170

[0037] Examples of dye derivatives having a diketopyrrolopyrrole dye skeleton include compounds represented by the following formula (G).

[0038] TIFF0007717043000014.tif51170

[0039] [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).

[0040] TIFF0007717043000015.tif41170 (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).

[0041] TIFF0007717043000016.tif43170(In general formula (3), R3 represents a hydrogen atom or a methyl group, R4 each independently represents 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 an arbitrary number of repetitions)

[0042] Constituent unit (i) is a constituent unit derived from a macromonomer having a polyalkylene glycol chain. When constituent unit (i) is dissolved in a dispersion medium such as an ultraviolet curable monomer, it causes steric hindrance between particles and repels them, enabling the organic pigment to be stably dispersed in the dispersion medium over a long period of time. Also, by containing a large amount of the polyalkylene glycol chain, resin A can be made liquid under room temperature conditions.

[0043] Since the average number of repeating units represented by n in general formula (2) is a number from 20 to 100, the molecular weight of the macromonomer is within the range of 880 to 5,800.

[0044] Examples of the macromonomer 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; reaction products of (meth)acryloyloxyethyl isocyanate with polyethylene glycol monomethyl ether, polyethylene glycol polypropylene glycol monobutyl ether, etc.; reaction products of (meth)acryloyloxyethyl isocyanate with polyethylene glycol monomethyl ether monoamine, polyethylene glycol polypropylene glycol monomethyl ether monoamine; reaction products of (meth)acrylic acid, (meth)acrylic acid chloride, (meth)acrylic anhydride with polyethylene glycol monomethyl ether monoamine, polyethylene glycol polypropylene glycol monomethyl ether monoamine; and the like. Among them, water-insoluble monomers are preferred, and macromonomers containing 50 mol% or more of polypropylene glycol in the glycol chain are preferred, and monomers containing 70 mol% or more are more preferred.

[0045] The structural unit (ii) is a monomer having a quaternary ammonium base with an anion of chlorine, bromine, or iodine as a counter ion. By having the structural unit (ii), the resin A is hydrophilic and soluble in water. When the dye derivative represented by the 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, and the counter ion of the quaternary ammonium base in the resin A becomes the anion of the sulfonic acid group of the dye derivative. As a result, a resin B is produced in which at least a part of the structural unit (ii) is converted into the structural unit (iv) represented by the general formula (4).

[0046] In a state where the anions of sulfonic acid groups in the pigment derivative are adsorbed on the organic pigment, resin A is converted into resin B, and the converted resin B is adsorbed on at least a part of the surface of the organic pigment, and the organic pigment will be surface-treated. Resin A, which had an affinity for water and was dissolved with the structure of structural unit (ii), becomes insoluble in water due to the sulfonate ions of the pigment derivative becoming counterions with the halide ions, and precipitates on the pigment surface while undergoing desalting and ion exchange. Then, due to the solubility and steric repulsion of structural unit (i), the dispersibility of the organic pigment is maintained in a good state over a long period of time.

[0047] Examples of the monomer constituting structural unit (ii) include (meth)acryloyloxyethyltrimethylammonium chloride, (meth)acryloyloxyethyldiethylmethylammonium chloride, (meth)acryloyloxyethylbenzyldimethyl chloride, (meth)acryloyloxyethylbenzyldiethyl chloride, (meth)acryloyloxyethyltrimethylammonium bromide, (meth)acryloyloxyethyldiethylmethylammonium bromide, (meth)acryloyloxyethylbenzyldimethyl bromide, (meth)acryloyloxyethylbenzyldiethyl bromide, (meth)acryloyloxyethyltrimethylammonium iodide, (meth)acryloyloxyethyldiethylmethylammonium iodide, (meth)acryloyloxyethylbenzyldimethyl iodide, (meth)acryloyloxyethylbenzyldiethyl iodide, (meth)acryloylaminopropyltrimethylammonium chloride, (meth)acryloylaminopropylbenzyltrimethylammonium chloride, (meth)acryloylaminopropyldiethylmethylammonium chloride, (meth)acryloylaminopropylbenzyldiethyl chloride, (meth)acryloylaminopropyldibutylmethyl chloride, (meth)acryloylaminopropylbenzyldibutylammonium chloride, etc.

[0048] Other structural unit (iii) is a structural unit that can be linked to structural units (i) and (ii). As the monomer constituting structural unit (iii), conventionally known monomers capable of radical polymerization can be used. Examples of the monomer constituting structural unit (iii) include (meth)acrylic acid-based monomers such as (meth)acrylic acid and (meth)acrylate; vinyl monomers such as styrene, vinyltoluene, vinylpyridine, vinylcaprolactone, vinylimidazole, α-methylstyrene, and vinyl acetate; and the like. Among them, α-methylstyrene is preferred because it is easy to adjust the molecular weight and control the polymerization.

[0049] Structural unit (iii) preferably includes structural unit (iii-1) represented by the following general formula (5).

[0050] TIFF0007717043000017.tif41170(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)

[0051] Examples of the monomer constituting structural unit (iii-1) include dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylamide, diethylaminoethylpropyl (meth)acrylamide, dibutylaminopropyl (meth)acrylamide, and the like.

[0052] 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. Here, the total of structural units (i) to (iii) is 100% by mass. When the proportion of structural unit (i) is less than 40% by mass, steric hindrance becomes insufficient and the dispersibility of the organic pigment decreases. On the other hand, when the proportion of structural unit (i) exceeds 80% by mass, since the macromonomer has a high molecular weight, the polymerizable groups at the ends become dilute and tend to remain without polymerization.

[0053] When the proportion of structural unit (ii) is less than 3% by mass, the amount of the binding dye derivative decreases and the adsorption part of the organic pigment becomes small. As a result, resin B detaches from the organic pigment during dispersion or storage, and the dispersion stability decreases. On the other hand, when the proportion of structural unit (ii) exceeds 30% by mass, the amount of the binding dye derivative increases, and the pigment dispersibility decreases or the pigment aggregates. In addition, since many dye derivatives are introduced, the hue of the dye derivative is likely to appear.

[0054] The number average molecular weight of resin A is 10,000 to 30,000, preferably 12,000 to 24,000. The "number average molecular weight (Mn)" in this specification means the number average molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC). When the number average molecular weight of resin A is less than 10,000, the dispersibility of the pigment decreases, and thickening of the pigment dispersion, sedimentation of the pigment, etc. may occur. On the other hand, when the number average molecular weight of resin A exceeds 30,000, the polymerization time may become long or the process may become complicated in order to obtain a high molecular weight, and the viscosity of the pigment dispersion may become excessively high.

[0055] Resin A is a resin that is liquid under room temperature (25°C) conditions. When treating a pigment with a resin that is solid under room temperature conditions to obtain a dry powder, it is necessary to dissolve the solid resin in a liquid medium when dispersing it in the liquid medium. As a result, it takes time for the dispersion, and "lumps" may be formed due to incomplete dissolution of the resin. In contrast, when using liquid Resin A under room temperature conditions, the resin quickly becomes compatible with the liquid medium, and the desired resin-treated pigment can be easily obtained.

[0056] Resin A can be synthesized by a conventionally known method. For example, a conventionally known radical polymerization method; a polymerization method using a chain transfer agent such as thiol to adjust the molecular weight; a living radical polymerization method that can make the molecular weight of the main chain more uniform and can form an A-B block copolymer depending on the addition method, specifically, an atom transfer radical polymerization method (ATRP method), a reversible addition-fragmentation chain transfer polymerization method (RAFT method), a nitroxide method (NMP method), an organic tellurium method (TERP method), an iodine transfer polymerization method (ITP method), a reversible transfer catalyst polymerization method (RTCP method), a reversible catalyst-mediated polymerization method (RCMP method), etc. of living radical polymerization methods; can be used for synthesis.

[0057] The polymerization may be either thermal polymerization or photopolymerization, and an azo-based radical generator, a peroxide-based radical generator, a photosensitizer, etc. may be added to the polymerization reaction system. The polymerization form may be any of solvent-free, solution polymerization, and emulsion polymerization, and solution polymerization is particularly preferred. In the production method of the present invention, when mixing an organic pigment, a dye derivative, and Resin A in water, a water-soluble organic solvent can be used. Therefore, since Resin A obtained by the polymerization reaction can be used as it is without isolation, it is preferable to synthesize Resin A by solution polymerization in a water-soluble organic solvent. Examples of the water-soluble organic solvent include lower alcohols, polyhydric alcohols, glycols, glycol ethers, glycol esters, amides, sulfoxides, and ureas. Note that Resin A obtained by the polymerization reaction may be isolated.

[0058] [Method for Producing Resin-Treated Pigment] To a mixture containing 100 parts by mass of an organic pigment, 5 to 20 parts by mass of a pigment derivative, and water, 25 to 60 parts by mass of resin A is added and mixed. As a result, the counter ion (X - ) of the quaternary ammonium salt in structural unit (ii) and the cation (M + ) in the pigment derivative form a salt that desorbs (deposits salt), and through ion exchange, at least a part of structural unit (ii) is converted into structural unit (iv) represented by the following general formula (4), generating resin B. Since the generated resin B is substantially insoluble in water, it is considered to precipitate and adsorb and deposit on the surface of at least a part of the pigment. Thereby, the target resin-treated pigment in which resin B is adsorbed and deposited on the surface of at least a part of the pigment can be obtained.

[0059] TIFF0007717043000018.tif37170 (In the above general formula (4), R3 represents a hydrogen atom or a methyl group, R4 each independently represents 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 an arbitrary number of repetitions)

[0060] The mixture containing the organic pigment, the pigment derivative, and water can further contain a water-soluble organic solvent as needed. 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; carbonate solvents such as ethylene carbonate; and the like.

[0061] It is preferable that resin B is uniformly adsorbed and deposited on the surface of the primary particles of the organic pigment. Therefore, the organic pigment used when preparing the mixture may be a powdery dry product, but is preferably in the state 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 made into fine primary particles by stirring. The amount of the organic pigment in the mixture is preferably 1 to 10% by mass.

[0062] The pigment derivative may be adsorbed in advance on the surface of the organic pigment. The sulfonic acid group in the pigment derivative may be a free acid that is not neutralized, but it is advisable to add an aqueous solution of an alkali metal hydroxide or the like before adding resin A to form a salt. It is preferable to thoroughly mix and stir the mixture (aqueous slurry) containing the organic pigment, the pigment derivative, and water to finely disperse the particles of the organic pigment.

[0063] The liquidity of the mixture when adding resin A is preferably neutral to alkaline, and more preferably within the range of pH 6.5 to 9.5. If the liquidity of the mixture is acidic, resin B may be difficult to form (difficult to precipitate). Also, when resin A has an amino group, the amino group is likely to be ionized, so resin B is less likely to precipitate and may be difficult to filter during post-treatment. On the other hand, if the liquidity of the mixture is strongly alkaline (for example, above pH 9.5), resin B may be difficult to precipitate in water. Also, when resin A has an acidic group, the acidic group is likely to be ionized, so resin B is less likely to precipitate and may be difficult to filter during post-treatment. After adding resin A to the mixture to precipitate resin B, in order to facilitate filtration, it is preferably heated to 80°C or lower, more preferably 60°C or lower, and then filtered.

[0064] After washing the solid content obtained by filtering the mixture, and drying and pulverizing it as necessary, the target resin-treated pigment can be obtained. The temperature during drying is preferably 150°C or lower, more preferably 110°C or lower. When pulverizing the solid content, if it is pulverized too finely, there is a possibility that the particles will easily fuse due to the heat during pulverization. Even a coarse particle size such as 100 mesh pass can be sufficiently used.

[0065] The amount of the dye derivative with respect to 100 parts of the organic pigment is 5 to 20 parts by mass, preferably 6 to 15 parts by mass, and more preferably 6.5 to 10 parts by mass. If it is less than 5 parts by mass, since the amount of the dye derivative is small, resin B is likely to desorb from the particle surface of the organic pigment, and the dispersion stability decreases. On the other hand, if it exceeds 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.

[0066] The addition amount of resin A is 25 to 60 parts by mass with respect to 100 parts by mass of the organic pigment, preferably 25 to 45 parts by mass, and more preferably 30 to 45 parts by mass. If it is less than 25 parts by mass, the resin content is insufficient and the dispersion stability decreases. On the other hand, if it exceeds 60 parts by mass, the viscosity of the dispersion may become excessively high.

[0067] The amount (addition amount) of resin A added to the mixture is such that the amount of the quaternary ammonium salt in the following general formula (3) is 1.45 to 1.80 molar equivalents, preferably 1.50 to 1.70 molar equivalents, with respect to the amount of sulfonic acid ions in the general formula (1). If the amount of the quaternary ammonium salt is too small, the amount of the desorbed salt is small, and the amount of the precipitated resin B is insufficient. For this reason, it becomes difficult to sufficiently coat the organic pigment, and the viscosity of the pigment dispersion obtained by dispersing it in a monomer having a small SP value becomes excessively high, or aggregates are generated. On the other hand, if the amount of the quaternary ammonium salt is too large, due to the influence of the excessive remaining quaternary ammonium salt, the viscosity of the obtained pigment dispersion becomes excessively high, or filtration becomes difficult.

[0068] [Resin B] Resin B preferably contains 35 to 70% by mass of structural unit (i) represented by the following general formula (2), other structural units (iii), and 10 to 50% by mass of structural unit (iv) represented by the following general formula (4).

[0069] TIFF0007717043000019.tif41170(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 from 20 to 100, and p represents an arbitrary number of repetitions)

[0070] TIFF0007717043000020.tif37170(In the general formula (4), R3 represents a hydrogen atom or a methyl group, R4 each independently represents 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 an arbitrary number of repetitions)

[0071] In Resin B, the proportion of structural unit (i) is preferably 35 to 70% by mass, more preferably 40 to 65% by mass. Also, in Resin B, the proportion of structural unit (iv) is preferably 10 to 50% by mass, more preferably 15 to 45% by mass. Note that the total of all structural units is 100% by mass. If the proportion of structural unit (i) is less than 35% by mass, the amount of the polyalkylene glycol chain becomes insufficient and the steric repulsion is somewhat insufficient, which may reduce the dispersion stability. If the proportion of structural unit (iv) is less than 10% by mass, the amount of the dye derivative in the formulation during production becomes less than 5% by mass, and the adsorption amount onto the organic pigment is somewhat insufficient, which may reduce the dispersion stability. On the other hand, if it exceeds 50% by mass, the amount of the dye derivative becomes excessive, so the hue is likely to change and the water resistance may decrease.

[0072] Resin B may further have a structural unit (ii) represented by the following general formula (3). In Resin B, the total content of the structural unit (ii) and the structural unit (iii) is preferably 0.5 to 60% by mass. Hereinafter, for convenience, the "structural unit (ii)" and the "structural unit (iii)" are also collectively referred to as the "structural unit (v)". That is, the structural unit (v) is a structural unit containing the structural unit (iii) in Resin A and the structural unit (ii) remaining without ion exchange.

[0073] TIFF0007717043000021.tif43170(In the general formula (3), R3 represents a hydrogen atom or a methyl group, R4 each independently represents 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 an arbitrary number of repetitions)

[0074] In the resin-treated pigment, the amount of Resin B relative to 100 parts by mass of the organic pigment is preferably 30 to 70 parts by mass, and more preferably 30 to 50 parts by mass. If the amount of Resin B is less than 30 parts by mass relative to 100 parts by mass of the organic pigment, the dispersion stability may become insufficient. On the other hand, if the amount of Resin B exceeds 70 parts by mass relative to 100 parts by mass of the organic pigment, the viscosity of the pigment dispersion may increase excessively. Also, since Liquid Resin A is used under room temperature conditions, it may fuse due to heat during grinding or during storage.

[0075] (Monomer) The monomer is a component used as a liquid medium for dispersing the resin-treated pigment. The SP value of the monomer is 7.0 to 10.5, preferably 8.0 to 10.0. As described above, the pigment dispersion of the present embodiment contains a resin-treated pigment produced by a predetermined method, particularly using a quaternary ammonium salt in a specific amount (molar equivalent) relative to the amount of sulfonic acid ions. Therefore, while containing the above monomer with a relatively small SP value, the pigment is finely dispersed with a low viscosity and has excellent storage stability.

[0076] If the SP value of the monomer is less than 7.0, it becomes difficult to disperse the resin-treated pigment, and the viscosity of the resulting pigment dispersion becomes excessively high, and aggregates are likely to occur. On the other hand, if the SP value of the monomer exceeds 10.5, the viscosity of the resulting pigment dispersion becomes excessively high, and the dispersion stability of the pigment decreases. In the pigment dispersion, the mass ratio of the organic pigment to the monomer is preferably organic pigment: monomer = 2:98 to 50:50.

[0077] The "SP value" in this specification is the Hildebrand solubility parameter (SP value: δ) calculated from the Hansen solubility parameter (HSP value). The HSP value is a value calculated using the Y-MB method in HSPiP (version 5.4.03) software, and the dispersion force term (δ D ), the polarity term (δ P ), and the hydrogen bond term (δ H ) consist of three components. The relationship between the HSP value and the SP value is represented by the formula: δ 2 =δ D 2 +δ P 2 +δ H 2 .

[0078] As the monomer, it is preferable to use an ultraviolet curable monomer. By using an ultraviolet curable monomer as the liquid medium and dispersing the resin-treated pigment in the liquid medium, a pigment dispersion used for preparing an ultraviolet curable inkjet (UVIJ) ink can be obtained.

[0079] As the ultraviolet curable monomer, a conventionally known monomer that cures by irradiating ultraviolet rays can be used. The ultraviolet curable monomer may usually be a monofunctional monomer having one reactive group or a polyfunctional monomer having two or more reactive groups. Furthermore, a photocurable oligomer or a photocurable polymer having an ultraviolet curable group may be used in combination.

[0080] Examples of monofunctional monomers include radically polymerizable monomers such as isobornyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, trimethylcyclohexyl (meth)acrylate, t-butyl (meth)acrylate, isodecyl (meth)acrylate, (2-methyl-2-ethyl-1,3-dioxolan-4-ylmethyl) (meth)acrylate, methyl 2-(allyloxymethyl)acrylate, cyclic trimethylolpropane formal (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, etc. Among them, those containing an acrylate skeleton with good ultraviolet curability are preferred.

[0081] Examples of polyfunctional monomers and photocurable oligomers include 1,9-nonanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, tripropylene glycol di(meth)acrylate, etc. Among them, those containing an acrylate skeleton with good ultraviolet curability are preferred.

[0082] Examples of photocurable polymers include those having a plurality of radically 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 epoxy resin.

[0083] In a general oil-based pigment dispersion, the dispersant adsorbs to the pigment through an ionic bond between the acidic group of the pigment and the basic group of the resin used as the dispersant. Therefore, when using a highly polar monomer (compounds having an amide bond such as acryloylmorpholine, vinylpyrrolidone, vinylcaprolactone, etc.; ether-based compounds such as acryloyloxyethyl vinyl ether, etc.) as the ultraviolet curable monomer, the ionic bond is easily dissociated and the dispersant is desorbed from the pigment, and the dispersibility of the pigment is likely to decrease. On the other hand, in the case of the above-mentioned resin-treated pigment used in the pigment dispersion of the present invention, since an organic dye skeleton is introduced into the resin B adsorbed on the pigment, the resin B is strongly adsorbed to the pigment and does not easily desorb. Furthermore, since the constitutional unit (iv) is also difficult to dissolve in a highly polar monomer, the dispersion stability of the pigment can be maintained at a high level.

[0084] (Other components) The pigment dispersion and the UVIJ ink described later may further contain various additives. Examples of the additives include polymerization inhibitors, surfactants, antioxidants, ultraviolet absorbers, light stabilizers, leveling agents, thickeners, viscosity modifiers, preservatives, fungicides, dyes, waxes, fillers, acid generators, and alkali generators. Examples of the polymerization inhibitors include phenolic compounds such as p-methoxyphenol, t-butylcatechol, di-t-butylparacresol, hydroquinone monomethyl ether, 3,5-di-t-butyl-4-hydroxytoluene, 2,2'-methylenebis(4-methyl-6-t-butylphenol); quinone compounds such as p-benzoquinone; amine compounds such as p-benzylaminophenol, di-β-naphthyl paraphenylenediamine, phenylhydroxylamine, diethylhydroxylamine; oxime compounds such as quinonedioxime, cyclohexanone oxime; sulfur compounds such as phenothiazine; etc. A photoinitiator may be premixed in the pigment dispersion.

[0085] The composition of the pigment dispersion can be arbitrarily set. Taking a specific example, in the pigment dispersion, it is preferable that the resin-treated pigment is 5 to 30% by mass, the polymer dispersant is 0.5 to 30% by mass, and the monomer is 40 to 94.5% by mass. Further, in the pigment dispersion, it is more preferable that the resin-treated pigment is 10 to 25% by mass, the polymer dispersant is 1 to 25% by mass, and the monomer is 60 to 90% by mass.

[0086] (Method for producing pigment dispersion) The pigment dispersion can be prepared according to a conventionally known method. For example, a mixture of a monomer, a resin-treated pigment, a polymer dispersant, etc. is prepared, and an organic solvent is added as necessary. The pigment dispersion can be obtained by performing a dispersion treatment using a paint shaker, a ball mill, an attritor, a sand mill, a horizontal media mill, a colloid mill, a roll mill, etc. The concentration of the pigment can be adjusted by adding a monomer to the obtained pigment dispersion. Further, other additives may be added as necessary. Furthermore, it is preferable to remove coarse particles by treatment with a centrifuge or a filter.

[0087] In order to make the number average particle diameter (particle size distribution) of the pigment within a desired range, the following methods are adopted: using small-sized grinding media; increasing the filling rate of the grinding media; lengthening the dispersion treatment time; slowing down the discharge rate; classifying with a filter, a centrifuge, etc. after grinding; etc. The viscosity of the pigment dispersion at 25°C is preferably 3 to 100 mPa·s.

[0088] <UV curable inkjet ink and printed film> One embodiment of the ultraviolet-curable inkjet ink (UVIJ ink) of the present invention contains the aforementioned pigment dispersion using an ultraviolet-curable monomer. And one embodiment of the printed film of the present invention is a cured product of this UVIJ ink. The UVIJ ink of this embodiment is an ink for inkjet in which an organic pigment is finely dispersed, using an ultraviolet-curable monomer as a liquid medium. The UVIJ ink of this embodiment is an ink that takes into account an environment that substantially does not contain volatile components, and the components applied to the recording medium are cured by irradiated ultraviolet light to form an image (printed film).

[0089] In addition to the aforementioned pigment dispersion, the UVIJ ink of this embodiment may further contain, for example, a photoinitiator, an ultraviolet-curable polymer, and various additives described above. As the photoinitiator, a photo radical polymerization initiator or a photo cationic polymerization initiator can be used. Among them, it is preferable to use a photo radical polymerization initiator. Examples of the photoinitiator include benzophenone-based photoinitiators, thioxanthone-based photoinitiators, ketooxime ester-based photoinitiators, and acylphosphine oxide-based photoinitiators. The content of the photoinitiator in the UVIJ ink is preferably 3 to 12% by mass. If the content of the photoinitiator is less than 3% by mass, curing defects may easily occur. On the other hand, if the content of the photoinitiator exceeds 12% by mass, the photoinitiator may remain or coloring may occur due to the photoinitiator.

[0090] After mixing the above components and stirring well, the target UVIJ ink can be obtained by filtering with a filter or the like. 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.

[0091] When the UVIJ ink of the present invention is used, an image which is a printed film excellent in durability such as high color density, high color developability, adhesion, and abrasion resistance can be recorded (printed) on various base materials by an inkjet recording method. Examples of the base material (recording medium) include paper, printing paper, photographic glossy paper, plastic film, fabric, ceramics, and metal.

Examples

[0092] Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to these examples. In addition, "parts" and "%" in the examples and comparative examples are based on mass unless otherwise specified.

[0093] <Synthesis of Resin A> (Synthesis Example 1: Resin A-1) Into a reaction vessel, 156 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 mgKOH / g, molecular weight converted from hydroxyl value 2,160, polystyrene-reduced number average molecular weight 3,400 measured by GPC (THF-GPC) using tetrahydrofuran (THF) as a developing solvent), 5.2 parts of α-methylstyrene (MSt), 10 parts of methyl methacrylate (MMA), and 35.5 parts of dimethylaminoethyl methacrylate (DMAEMA) were added, and the mixture was stirred while flowing nitrogen and heated to 75°C. 5 parts of 2,2'-azobis(isobutyric acid) dimethyl (V-601) (trade name "V-601", manufactured by Fujifilm Wako Pure Chemical Corporation) was added, and after polymerization for 8 hours, the mixture was cooled to obtain a precursor solution of the resin. A part was sampled, and the solid content of the precursor solution measured at 180°C using an infrared moisture meter was 50.1%, confirming that almost all the polymerization had occurred. The amine value of the precursor measured by a potentiometric automatic titrator using a 0.1 mol / L isopropanolic hydrochloric acid solution was 85.1 mgKOH / g. When the precursor solution was added to water, it became turbid and a white viscous substance precipitated. That is, the generated resin precursor was insoluble in water.

[0094] 10 parts of benzyl chloride and 10 parts of MPG were placed in a separate container, and a precursor solution was further added under room temperature conditions. After stirring for 1 hour, the mixture was heated to 80 °C and reacted for 5 hours to obtain a viscous resin A-1 solution with some turbidity. The solid content of the resin A-1 solution sampled and measured was 52.0%. Also, the solid content (resin A-1) was a viscous liquid under room temperature conditions. The number average molecular weight (Mn) of resin A-1 in terms of polystyrene, measured by GPC (DMF-GPC) using a 0.1 mmol / L lithium bromide dimethylformamide (DMF) solution as the developing solvent, was 9,600, and the molecular weight distribution (PDI = weight average molecular weight / number average molecular weight) was 1.90. In DMF-GPC, almost no peak of MAC was detected, indicating that most of MAC was introduced into resin A-1. The amine value of resin A-1 was 50.1 mgKOH / g, showing that 35 mol% of the amino groups in the precursor were quaternized, that is, the quaternization rate was 35 mol%. The amount of quaternary salt contained in 1 g of resin A-1 was calculated to be 0.470 mmol. In the obtained resin A-1, the proportion of structural unit (i) was 59.5%, the proportion of structural unit (ii) was 13.3%, and the proportion of structural unit (iii) was 27.2%. When the solution of resin A-1 was added to water, it dissolved in water without forming insoluble matter.

[0095] Details of the obtained resin A-1 are shown in Table 1.

[0096] TIFF0007717043000022.tif104170

[0097] <Manufacture of Resin-Treated Pigment> (Production Example 1: Resin-Treated Pigment 1) Into a beaker, 340 parts of an aqueous paste (purity: 29.4%) of C.I. Pigment Red 122 (PR122) (trade name: "6111T", manufactured by Dainichi Seika Kogyo Co., Ltd.) and 1,600 parts of ion-exchanged water were placed, and the mixture was stirred at 2,000 revolutions using a disper to obtain an aqueous slurry. 173.3 parts of an aqueous solution of sodium monophthalimidomethylated quinacridone monosulfonic acid (MSPQNa) (purity: 3%, pH 8.9, a transparent red solution) represented by formula (F) was added to the aqueous slurry, and the mixture was stirred at 2,000 revolutions for 2 hours. When the stirred aqueous slurry was spotted on filter paper, the pigment was deposited on the filter paper, and bleeding due to MSPQNa occurred around the pigment, and the back side of the filter paper was bled red. Also, the pH of the aqueous slurry became 7.2.

[0098] Into another container, 57.7 parts of a solution of Resin A-1 and 57.7 parts of ion-exchanged water were placed and mixed to obtain a uniform mixture. The obtained mixture was gradually added to the aqueous slurry. When the aqueous slurry was spotted on filter paper, no bleeding or penetration occurred. After heating to 60 °C and stirring for 30 minutes, the mixture was filtered and washed with ion-exchanged water. After drying at 80 °C for 24 hours using a dryer, the mixture was pulverized using a pulverizer to obtain 124.9 parts of a resin-treated pigment 1. The yield was 92.4%, and the nonvolatile content measured after drying at 120 °C was 99.3%. At least a part of the constitutional unit (ii) in Resin A was converted to the constitutional unit (iv), and Resin B derived from Resin A was formed. The amount of the quaternary ammonium salt (DMQ) relative to the amount of sulfonic acid ions was 1.57 molar equivalents. Also, the amount of Resin B relative to 100 parts of the pigment was 34.7 parts. In the formed Resin B, the ratio of the constitutional unit (i) was 51.4%, the ratio of the constitutional unit (iv) was 20.9%, and the ratio of the constitutional unit (v) (the total of the constitutional unit (ii) and the constitutional component (iii)) was 27.7%.

[0099] (Production Examples 2 and 3: Resin-Treated Pigments 2 and 3) Resin-treated pigments 2 and 3 were obtained in the same manner as in Production Example 1 described above, except that the formulations shown in Table 2 were used. Details of the obtained resin-treated pigments are shown in Table 2.

[0100] TIFF0007717043000023.tif104170

[0101] <Manufacture of Pigment Dispersion for UVIJ Ink> (Example 1: Pigment Dispersion 1) 19.3 parts of resin-treated pigment 1 and 80.7 parts of isobornyl acrylate (IBXA, SP value: 8.34) were placed in a resin container. 400 parts of zirconia beads with a diameter of 0.5 mmφ were further added, sealed, and dispersed using a paint shaker. The zirconia beads were separated and removed to obtain Pigment Dispersion 1 for UVIJ Ink. The viscosity (initial viscosity) of Pigment Dispersion 1 measured using an E-type viscometer under the conditions of 60 rpm and 25 °C was 28.9 mPa·s. The number average particle diameter (initial number average particle diameter) of the pigment in Pigment Dispersion 1 measured using a dynamic light scattering particle size distribution meter was 112 nm.

[0102] A storage test was conducted by storing the obtained Pigment Dispersion 1 at 60 °C for 1 week. The ratio of the viscosity after the storage test (viscosity retention rate) based on the initial viscosity was 96%. Also, the ratio of the number average particle diameter of the pigment after the storage test (particle diameter retention rate) based on the initial number average particle diameter was 99%.

[0103] A filtration test was carried out by filtering 30 g of Pigment Dispersion 1 obtained using a filter with a holding particle diameter of 5 μm (product name "PF-050", manufactured by ADVANTEC) at a load pressure of 0.04 MPa. When the filterability was evaluated according to the evaluation criteria shown below, it was evaluated as "○". [Evaluation Criteria for Filterability] ○: The entire amount passed through the liquid, and the filtration time was good. △: The entire amount passed through the liquid. ×: Little liquid passed through, and clogging occurred.

[0104] (Examples 2 to 4, Comparative Examples 1 to 3: Pigment Dispersions 2 to 7) Except for using the formulation shown in Table 3, pigment dispersions 2 to 7 for UVIJ ink were obtained in the same manner as in Example 1 described above. The details of the obtained pigment dispersions are shown in Table 3. In Table 3, "PEA" is phenoxyethyl acrylate (SP value: 9.5), and "ACMO" is acryloyl morpholine (SP value: 10.9).

[0105] TIFF0007717043000024.tif106170

[0106] <Manufacture of UVIJ Ink> (Example 5: UVIJINK-M-1) 18 parts of pigment dispersion 1, 53.5 parts of PEA, 19 parts of acryloyloxyethoxyethyl vinyl ether (VEEA, manufactured by Nippon Shokubai Co., Ltd.), 5 parts of photoinitiator 1 (trade name "Lucirin TPO", manufactured by BASF), and 4.5 parts of photoinitiator 2 (trade name "Irgacure 819", manufactured by BASF) were mixed. After thorough stirring, it was filtered through a 5 μm filter to obtain UVIJ ink (UVIJINK-M-1). The viscosity of the obtained ink and the number average particle diameter of the pigment were measured. The results are shown in Table 4. Also, the above-mentioned storage test was conducted in which the obtained ink was put into a brown sample bottle and stored at 60°C for 1 week. Then, the ratio of the viscosity after the storage test to the initial viscosity (viscosity retention rate), and the ratio of the number average particle diameter of the pigment after the storage test to the initial number average particle diameter (particle diameter retention rate) were calculated. The results are shown in Table 4.

[0107] (Examples 6 to 8, Comparative Examples 4 to 6: UVIJINK-M-2 to 7) Except for using the formulation shown in Table 4, UVIJ inks (UVIJINK-M-2 to 7) were obtained in the same manner as in Example 5 described above. The details of the obtained UVIJ inks are shown in Table 4.

[0108] <Manufacture and Evaluation of UV-Cured Coating Film (Printing Film)> Using an automatic bar coater, UVIJ ink was applied onto a PET film with a thickness of 100 μm so that the film thickness became 6 μm to form a coating film. Next, the formed coating film was cured using a UV curing device to form a UV-cured coating film (printing film).

[0109] (1) Reflectance density Using a colorimeter (trade name "i1PRO", manufactured by X-Rite), the reflectance density (average value of values measured 10 times while changing the position) of the formed UV-cured coating film was measured. Then, the reflectance density of the UV-cured coating film was evaluated according to the evaluation criteria shown below. The results are shown in Table 4. [Evaluation criteria for reflectance density] ◎: The reflectance density was 1.15 or more and less than 1.20. ○: The reflectance density was 1.10 or more and less than 1.15. △: The reflectance density was 1.05 or more and less than 1.10.

[0110] (2) Glossiness Using a surface gloss meter (trade name "micro-tri-gloss", manufactured by BYK), the glossiness at 20° (average value of values measured 7 times while changing the position) of the formed UV-cured coating film was measured. Then, the glossiness of the UV-cured coating film was evaluated according to the evaluation criteria shown below. The results are shown in Table 4. [Evaluation criteria for glossiness] ◎: The glossiness was 135 or more and less than 140. ○: The glossiness was 130 or more and less than 135. △: The glossiness was 125 or more and less than 130.

[0111] (3) Adhesion Using an automatic bar coater, UVIJ ink was applied onto a PET film with a thickness of 250 μm so that the film thickness became 6 μm to form a coating film. Then, the formed coating film was cured using a UV curing apparatus to form a UV-cured coating film (printed film). Then, an adhesion test by the cross-cut method in accordance with JIS standards (JIS K 5600-5-6) was carried out, and the adhesion of the UV-cured coating film was evaluated according to the evaluation criteria shown below. The results are shown in Table 4. [Evaluation criteria for adhesion] 0: There was no peeling in any of the grid cells. 1: There was small peeling at the intersections of the cuts, and the area affected by the cross-cut part was less than 5%. 2: Peeling occurred at the cut edges or intersections, and the affected area was more than 5% and less than 15%. 3: Peeling occurred significantly along the cut edges, and the affected area was more than 15% and less than 35%. 4: Peeling occurred significantly along the cut edges, and the affected area was more than 35% and less than 65%. 5: The degree of peeling exceeded the evaluation of "4".

[0112] TIFF0007717043000025.tif144170

Industrial Applicability

[0113] The pigment dispersion of the present invention is useful as a raw material for preparing an ultraviolet curable inkjet ink, and monomers derived from biomass can be actively used.

Claims

1. Comprising a monomer with an SP value of 7.0 to 10.5 and a resin-treated pigment dispersed in the monomer, wherein the resin-treated pigment is obtained by adding 25 to 60 parts by mass of a liquid resin A at room temperature, which has a number average molecular weight of 10,000 to 30,000, to a mixture containing 100 parts by mass of a magenta organic pigment, 5 to 20 parts by mass of a dye derivative represented by the following general formula (1), and water, and having 40 to 80% by mass of a structural unit (i) represented by the following general formula (2), 3 to 30% by mass of a structural unit (ii) represented by the following general formula (3), and 1 to 57% by mass of other structural units (iii), and precipitating a resin B in which at least a part of the structural unit (ii) is converted into a structural unit (iv) represented by the following general formula (4), wherein the addition amount of the resin A is an amount such that the amount of the quaternary ammonium salt in the following general formula (3) is 1.45 to 1.80 molar equivalents with respect to the amount of the sulfonic acid ion in the following general formula (1). A pigment dispersion. (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, R １ represents a hydrogen atom or a methyl group, 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 repetitions.) (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 an arbitrary 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. The pigment dispersion according to claim 1, wherein the organic dye skeleton represented by E in the general formula (4) is a quinacridone dye skeleton.

3. The pigment dispersion according to claim 1, wherein the structural unit (iii) is a structural unit derived from α-methylstyrene.

4. The pigment dispersion according to claim 3, 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)

5. wherein the monomer is an ultraviolet curable monomer, and the pigment dispersion according to any one of claims 1 to 4 is used in an ultraviolet curable inkjet ink.

6. An ultraviolet curable inkjet ink containing the pigment dispersion according to claim 5.

7. A printed film which is a cured product of the ultraviolet curable inkjet ink according to claim 6.

Images