Ink composition and inkjet recording method

Abstract

Provided is an ink composition which comprises a water-insoluble coloring agent, a dispersing agent, a resin A, a resin B, and water, in which the resin A is obtained through polymerization of at least a C1-C4 alkyl methacrylate and a C2-C6 alkyl acrylate, and the resin B is obtained through polymerization of at least a styrene-based monomer and divinyl benzene. In addition, the present invention provides: an inkjet-recording method in which the ink composition is used; a recording medium to which the ink composition is attached; and an inkjet printer comprising a container filled with the ink composition.

Description

Technical Field

[0001] The present invention relates to an ink composition, an inkjet recording method using the ink composition, a recording medium to which the ink composition is attached, and an inkjet printer equipped with a container filled with the ink composition.

Background Art

[0002] An inkjet printing method using an inkjet printer is known as one of the typical color printing methods. In this inkjet method, printing is performed by generating small droplets of ink and attaching them to a recording medium such as paper.

[0003] In recent years, the application of the inkjet printing method for industrial use has been progressing. The colorants contained in inkjet inks are roughly classified into water-soluble colorants and water-insoluble colorants. Among them, water-insoluble colorants typified by pigments generally have superior various fastnesses compared to water-soluble colorants. Therefore, industrial inkjet inks often contain water-insoluble colorants. On the other hand, water-insoluble colorants generally have inferior color development properties compared to water-soluble colorants. Against such a background, there is a strong demand for industrial inks that contain water-insoluble colorants and are excellent in color development and glossiness.

[0004] Examples of the base materials used for industrial applications include various papers, fibers, films, etc., and there is a tendency to diversify. Among those base materials, there are also many ink non-absorbent base materials or ink poorly absorbent base materials (hereinafter, also collectively referred to as "ink non-·poorly absorbent base materials"). As the ink used when printing on such ink non-·poorly absorbent base materials, non-aqueous solvent inks, curable inks, etc. are known.

[0005] However, non-aqueous solvent inks and curable inks contain high levels of volatile organic compounds (VOCs), raising safety concerns for the natural environment and living organisms. Therefore, there is a strong demand for water-based inks that can print on non-absorbent and poorly absorbent substrates. Water-based inks have a composition that minimizes VOCs and contain water-insoluble colorants and dispersants. Furthermore, water-based inks generally contain resins, waxes, etc., to improve scratch resistance and solvent resistance. Such water-based inks have a high solid component content, making them extremely prone to drying and generating solid matter upon drying. When printing on non-absorbent or poorly absorbent substrates, these solid components form a film, improving adhesion to the substrate and scratch resistance. Therefore, the stronger the film formed by these solid components, the more desirable it is for the printed material.

[0006] Furthermore, when printing on non-ink-absorbing or poorly absorbing substrates, scratch resistance is required in addition to adhesion to the substrate and abrasion resistance. Non-ink-absorbing or poorly absorbing substrates are generally at a disadvantage in terms of adhesion and abrasion resistance because they have poor ink absorption. Therefore, it is desirable to further strengthen the coating with solid components to improve scratch resistance as well.

[0007] On the other hand, ink drying can also occur during long-term storage, or in high-temperature or low-humidity environments. When ink filled in an inkjet printer dries, solid matter forms in the nozzles or ink channels of the inkjet head, causing clogging. When clogging occurs in the inkjet head, stable ink ejection becomes impossible, leading to a decrease in the quality of recorded images. Furthermore, the frequency of the inkjet head becoming unusable increases, which is a major problem. For this reason, there is a strong demand for inkjet heads that can be easily cleaned even if solid matter forms inside them. However, since the improvement of adhesion, abrasion resistance, and scratch resistance through the formation of the aforementioned film is inversely related to the ability to be easily cleaned, a water-based ink that satisfies both effects has not yet been proposed. For these reasons, methods such as equipping the nozzle of industrial inkjet heads with cap components to prevent ink drying have been proposed. However, even with these measures, it is still extremely difficult to completely prevent ink drying.

[0008] Patent documents 1 to 8 describe resin emulsions or resin particle dispersions, and ink compositions containing them. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] International Publication No. 2015 / 147192 [Patent Document 2] Japanese Patent Publication No. 2000-34432 [Patent Document 3] Japanese Patent Publication No. 2000-336292 [Patent Document 4] Japanese Patent Publication No. 2009-191133 [Patent Document 5] Japanese Patent Publication No. 2013-213210 [Patent Document 6] Japanese Patent Publication No. 2017-141388 [Patent Document 7] International Publication No. 2021 / 006211 [Patent Document 8] Patent No. 6833339 [Patent Document 9] International Publication No. 2013 / 115071 [Overview of the project] [Problems that the invention aims to solve]

[0010] The present invention aims to provide an ink composition that exhibits good color development and glossiness, as well as excellent scratch resistance and washability; an inkjet recording method using the ink composition; a recording medium to which the ink composition is attached; and an inkjet printer comprising a container filled with the ink composition. [Means for solving the problem]

[0011] The following embodiments are specific means for solving the above problems. <1> It contains a water-insoluble coloring agent, a dispersant, resin A, resin B, and water. The resin A is a resin obtained by polymerizing at least C1-C4 alkyl methacrylate and C2-C6 alkyl acrylate. An ink composition in which the resin B is a resin obtained by polymerizing at least a styrene monomer and divinylbenzene. <2> The resins A and B are resins obtained by polymerizing a reactive emulsifier having a radically polymerizable double bond in its molecule. <1> The ink composition described above. <3> The reactive emulsifier is a reactive emulsifier having an anionic group in its molecule. <2> The ink composition described above. <4> The aforementioned anionic group is a salt of a sulfate ester group. <3> The ink composition described above. <5> Furthermore, it contains a water-soluble organic solvent. <1> ~ <4> An ink composition according to any one of the items. <6> An inkjet recording method of performing recording by ejecting droplets of the ink composition according to any one of <1> to <4> onto a recording medium by an inkjet printer according to a recording signal. <7> The inkjet recording method according to <6>, wherein the recording medium is a recording medium having an ink receiving layer. <8> The inkjet recording method according to <6>, wherein the recording medium is a recording medium having no ink receiving layer. <9> The inkjet recording method according to any one of <6> to <8>, wherein the inkjet printer is a line head type inkjet printer. <10> A recording medium to which the ink composition according to any one of <1> to <4> is attached. <11> The recording medium according to <10>, wherein the recording medium is a recording medium selected from a recording medium having an ink receiving layer and a recording medium having no ink receiving layer. <(12)> An inkjet printer including a container filled with the ink composition according to any one of <1> to <4>. <(13)> The inkjet printer according to <(I2)>, wherein the inkjet printer is a line head type inkjet printer.

Advantages of the Invention

[0012] According to the present invention, it is possible to provide an ink composition having good color development property and glossiness, excellent scratch resistance and detergency, an inkjet recording method using the ink composition, a recording medium to which the ink composition is attached, and an inkjet printer including a container filled with the ink composition.

Embodiments for Carrying Out the Invention

[0013] <Ink Composition> The ink composition according to this embodiment contains a water-insoluble colorant, a dispersant, resin A, resin B, and water. Resin A is a resin obtained by polymerizing at least C1-C4 alkyl methacrylate and C2-C6 alkyl acrylate, and resin B is a resin obtained by polymerizing at least a styrene-based monomer and divinylbenzene. Hereinafter, the components contained in the ink composition according to this embodiment will be described in detail. Each of the components described below may be used alone or in combination of two or more.

[0014] [Water-insoluble colorant] The above water-insoluble colorant means a colorant having a solubility in water at 25°C of usually 3 g / L or less, preferably 2 g / L or less, more preferably 1 g / L or less.

[0015] Examples of the water-insoluble colorant include pigments, disperse dyes, and solvent dyes. Representative examples thereof include colorants selected from C.I.Pigment, C.I.Disperse, and C.I.Solvent.

[0016] Examples of the pigment include inorganic pigments, organic pigments, extender pigments, etc.

[0017] Examples of the inorganic pigment include carbon black, metal oxides, metal hydroxides, metal sulfides, metal ferrocyanides, metal chlorides, etc.

[0018] Examples of the carbon black include thermal black, acetylene black, oil furnace black, gas furnace black, lamp black, gas black, and channel black. Among these, furnace black, lamp black, acetylene black, channel black, etc. are preferable. Various types of carbon black can be easily obtained from Columbian Carbon, Cabot, Degussa, Mitsubishi Chemical Corporation, etc.

[0019] Examples of organic pigments include soluble azo pigments, insoluble azo pigments, insoluble diazo pigments, condensed azo pigments, phthalocyanine pigments, quinacridone pigments, isoindolinone pigments, dioxazine pigments, perylene pigments, perinone pigments, thioindigo pigments, anthraquinone pigments, and quinophthalone pigments.

[0020] Specific examples of organic pigments include, for example, CIPigment Yellow 1, 2, 3, 12, 13, 14, 16, 17, 24, 55, 73, 74, 75, 83, 93, 94, 95, 97, 98, 108, 114, 128, 129, 138, 139, 150, 151, 154, 180, 185, 193, 199, 202; CIPigment Red CIPigment Blue 1,2,3,15,15:1,15:2,15:3,15:4,15:6,16,22,25,60,66,80;CIPigment Violet 19,23,29,37,38,50;CIPigment Orange 13,16,68,69,71,73;CIPigment Green 7, 36, 54;CIPigment Black Examples include: 1; and others.

[0021] Examples of extender pigments include silica, calcium carbonate, talc, clay, barium sulfate, and white carbon. These extender pigments are often used in combination with inorganic or organic pigments to improve the fluidity of the powder.

[0022] Furthermore, as a water-insoluble colorant, self-dispersing pigments can also be used, in which the surface of the pigment particles is chemically treated to impart self-dispersion properties.

[0023] Examples of disperse dyes include CIDispers Yellow 9, 23, 33, 42, 49, 54, 58, 60, 64, 66, 71, 76, 79, 83, 86, 90, 93, 99, 114, 116, 119, 122, 126, 149, 160, 163, 165, 180, 183, 186, 198, 200, 211, 224, 226, 227, 231, 237; CIDispers Red 60, 73, 88, 91, 92, 111, 127, 131, 143, 145, 146, 152, 153, 154, 167, 179, 191, 192, 206, 221, 258, 283; CIDispers Orange Examples include 9, 25, 29, 30, 31, 32, 37, 38, 42, 44, 45, 53, 54, 55, 56, 61, 71, 73, 76, 80, 96, 97; CIDispers Violet 25, 27, 28, 54, 57, 60, 73, 77, 79, 79:1; CIDispers Blue 27, 56, 60, 79:1, 87, 143, 165, 165:1, 165:2, 181, 185, 197, 202, 225, 257, 266, 267, 281, 341, 353, 354, 358, 364, 365, 368; etc.

[0024] Furthermore, water-insoluble colorants can also be water-insoluble copolymers colored with water-soluble colorants. Examples of water-insoluble copolymers include polyesters, dispersants, and resins, which will be discussed later.

[0025] Examples of water-soluble colorants include direct dyes, acid dyes, food dyes, basic dyes, reactive dyes, vat dyes, and soluble vat dyes. Representative examples of these colorants include dyes selected from CIDirect, CIAcid, CIFood, CIBasic, CIReactive, CIVat, and CISolubilised Vat, respectively.

[0026] Furthermore, the copolymer used in a water-insoluble copolymer colored with a water-soluble coloring agent and the copolymer used as a dispersant, for example, may be the same copolymer or different copolymers. When the same copolymer is used, the copolymer colored with the water-soluble coloring agent and the copolymer not colored with the water-soluble coloring agent correspond to the water-insoluble coloring agent and the dispersant, respectively.

[0027] Among these water-insoluble colorants, pigments are preferred, and pigments selected from CIPigment are more preferred.

[0028] The content of the water-insoluble colorant in the total mass of the ink composition according to this embodiment is usually 1 to 30% by mass, preferably 1 to 15% by mass, and more preferably 2 to 10% by mass.

[0029] [Dispersant] Examples of dispersants include copolymers composed of at least two monomers selected from monomers such as styrene and its derivatives; vinylnaphthalene and its derivatives; aliphatic alcohol esters of α,β-ethylenically unsaturated carboxylic acids; (meth)acrylic acid and its derivatives; maleic acid and its derivatives; itaconic acid and its derivatives; fumaric acid and its derivatives; vinyl acetate, vinyl alcohol, vinylpyrrolidone, acrylamide, and their derivatives (preferably at least one of which is a hydrophilic monomer). Examples of hydrophilic monomers include monomers that retain a carboxyl group after polymerization, such as acrylic acid and methacrylic acid.

[0030] Examples of such copolymers include styrene-(meth)acrylic acid copolymer, styrene-(meth)acrylic acid-(meth)acrylic acid ester copolymer, (meth)acrylic acid ester-(meth)acrylic acid copolymer, polyethylene glycol (meth)acrylate-(meth)acrylic acid copolymer, and styrene-maleic acid copolymer. Among these, styrene-(meth)acrylic acid copolymer, styrene-(meth)acrylic acid-(meth)acrylic acid ester copolymer, (meth)acrylic acid ester-(meth)acrylic acid copolymer, and polyethylene glycol (meth)acrylate-(meth)acrylic acid copolymer are preferred, styrene-(meth)acrylic acid copolymer, styrene-(meth)acrylic acid-(meth)acrylic acid ester copolymer, and (meth)acrylic acid ester-(meth)acrylic acid copolymer are more preferred, (meth)acrylic acid ester-(meth)acrylic acid copolymer is even more preferred, and methacrylic acid ester-methacrylic acid copolymer is particularly preferred. Examples of copolymer types include block copolymers, random copolymers, and graft copolymers. These copolymers may also be in the form of salts.

[0031] In this specification, the term "(meth)acrylic" is used to include both "acrylic" and "methacrylic." The same applies to "(meth)acrylate," etc.

[0032] Dispersants can be synthesized or obtained commercially.

[0033] As copolymers obtained by synthesis, for example, the AB block copolymer disclosed in International Publication No. 2013 / 115071 is preferred. The monomer constituting the A block of the AB block polymer disclosed in International Publication No. 2013 / 115071 is at least one monomer selected from (meth)acrylic acid and linear or branched C4 alkyl (meth)acrylate, with at least one monomer selected from methacrylic acid and n-butyl methacrylate being preferred, and more preferably a combination of these two monomers. Furthermore, the monomer constituting the B block of the AB block polymer disclosed in International Publication No. 2013 / 115071 is at least one monomer selected from benzyl methacrylate and benzyl acrylate, with benzyl methacrylate being preferred. Specific examples of AB block polymers include the block copolymers disclosed in Synthesis Examples 3 to 8 of International Publication No. 2013 / 115071.

[0034] Examples of commercially available dispersants include Joncyrl 62, 67, 68, 678, and 687 (styrene-acrylic copolymers manufactured by BASF); Movinyl S-100A (modified vinyl acetate copolymer manufactured by Japan Coating Resin Co., Ltd.); and Julimar AT-210 (polyacrylic acid ester copolymer manufactured by Toagosei Co., Ltd.).

[0035] The mass-average molecular weight (Mw) of the dispersant is typically 3,000 to 50,000, preferably 7,000 to 25,000. The mass-average molecular weight of the dispersant can be measured by gel permuration chromatography (GPC). Specifically, the measurement can be performed using an HLC-8320GPC (manufactured by Tosoh Corporation) as the GPC instrument, two TSK gel Super Multipore HZ-H columns (manufactured by Tosoh Corporation, inner diameter 4.6 mm × 15 cm), tetrahydrofuran as the eluent, and TSK Standard (manufactured by Tosoh Corporation) as the standard sample.

[0036] The acid value of the dispersant is typically 50-300 mgKOH / g, preferably 80-275 mgKOH / g, and more preferably 80-250 mgKOH / g.

[0037] The dispersant can be used in a mixed state with the water-insoluble colorant. Alternatively, it can be used with part or all of the surface of the water-insoluble colorant coated with the dispersant. Or, both of these states may be used in combination.

[0038] The ink composition according to this embodiment is preferably prepared by first preparing a dispersion containing a water-insoluble colorant and a dispersant, and then mixing it with other components. Known methods can be used to prepare the dispersion.

[0039] One example of a method for preparing a dispersion is the phase inversion emulsification method. Specifically, a dispersant is dissolved in an organic solvent such as 2-butanone, and an aqueous solution of a neutralizing agent is added to prepare an emulsion. A water-insoluble coloring agent is added to the resulting emulsion and dispersed. The desired dispersion can be obtained by removing the organic solvent and some of the water from the liquid obtained in this way under reduced pressure. Dispersion can be performed using, for example, a sand mill (bead mill), roll mill, ball mill, paint shaker, ultrasonic disperser, microfluidizer, etc. As an example, when using a sand mill, beads with a particle size of about 0.01 to 1 mm can be used, and the bead packing rate can be appropriately set to perform dispersion. The dispersion obtained in the above way may be subjected to operations such as filtration and centrifugation. This operation can standardize the particle size of the particles contained in the dispersion. If foaming occurs during the preparation of the dispersion, a very small amount of a known defoaming agent such as a silicone-based or acetylene glycol-based defoaming agent may be added.

[0040] Other methods for preparing dispersions include acid precipitation, interfacial polymerization, in-situ polymerization, liquid curing coating, coacervation (phase separation), liquid drying, melt-dispersion-cooling, air suspension coating, and spray drying.

[0041] Among these preparation methods, phase inversion emulsification, acid precipitation, and interfacial polymerization are preferred.

[0042] The average particle size (D50) of the water-insoluble colorant in the dispersion is typically 300 nm or less, preferably 30 to 280 nm, more preferably 40 to 270 nm, and even more preferably 50 to 250 nm. The average particle size (D90) of the water-insoluble colorant is typically 400 nm or less, preferably 350 nm or less, and more preferably 300 nm or less. A lower limit of 100 nm or more is preferred. The average particle size (D10) of the water-insoluble colorant is typically 10 nm or more, preferably 20 nm or more, and more preferably 30 nm or more. A higher limit of 100 nm or less is preferred. The particle size of the water-insoluble colorant can be measured using laser light scattering.

[0043] The content of the dispersant in the total mass of the ink composition according to this embodiment is typically 0.5 to 6.0% by mass, preferably 0.5 to 4.0% by mass, and more preferably 1.0 to 4.0% by mass.

[0044] [Resin A] Resin A is a resin (polymer) obtained by polymerizing at least C1-C4 alkyl methacrylate and C2-C6 alkyl acrylate. That is, resin A contains at least C1-C4 alkyl methacrylate units and C2-C6 alkyl acrylate units as constituent monomer units. By using such resin A, the VOC component in the ink composition can be reduced, and the storage stability and redispersibility of the ink composition tend to be further improved. Examples of resin A include block copolymers, random copolymers, and graft copolymers, with random copolymers being preferred. Resin A may also be in the form of a salt. Resin A can be synthesized by known methods.

[0045] Examples of C1-C4 alkyl methacrylates include those with a linear alkyl portion, such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, and n-butyl methacrylate; those with a branched alkyl portion, such as isopropyl methacrylate, isobutyl methacrylate, and t-butyl methacrylate; and those with a cyclic alkyl portion, such as cyclopropyl methacrylate and cyclobutyl methacrylate. Among these, those with a linear alkyl portion are preferred, C1-C3 alkyl methacrylates with a linear alkyl portion are more preferred, and methyl methacrylate is even more preferred.

[0046] Examples of C2-C6 alkyl acrylates include those with a linear alkyl portion, such as ethyl acrylate, n-propyl acrylate, n-butyl acrylate, n-pentyl acrylate, and n-hexyl acrylate; those with a branched alkyl portion, such as isopropyl acrylate, isobutyl acrylate, isopentyl acrylate, and isohexyl acrylate; and those with a cyclic alkyl portion, such as cyclobutyl acrylate, cyclopentyl acrylate, and cyclohexyl acrylate. Among these, those with a linear alkyl portion are preferred, C2-C6 alkyl acrylates with a linear alkyl portion are more preferred, and butyl acrylate is even more preferred.

[0047] Resin A may be a resin obtained by polymerizing C1-C4 alkyl methacrylate and C2-C6 alkyl acrylate, as well as other monomers (1) such as C2-C4 unsaturated alkyl methacrylate, methacrylic acid, and sodium styrene sulfonate. The other monomers (1) may be used individually or in combination of two or more.

[0048] Examples of C2-C4 unsaturated alkyl methacrylates include vinyl methacrylate, allyl methacrylate, and 3-methyl-3-butynyl methacrylate. Among these, C3 unsaturated alkyl methacrylates are preferred, and allyl methacrylate is more preferred.

[0049] Table 1 below shows a guideline for the range of amounts to be used for C1-C4 alkyl methacrylate (preferably methyl methacrylate), C2-C6 alkyl acrylate (preferably butyl acrylate), and other monomers (1). It is preferable to adjust the monomer mixture consisting of C1-C4 alkyl methacrylate, C2-C6 alkyl acrylate, and other monomers (1) within the range shown in Table 1 so that the total amount is 100 parts by mass. The values ​​in Table 1 are in "parts by mass," and the abbreviations have the following meanings. MC1-4: C1-C4 alkyl methacrylate AC2-6: C2-C6 alkyl acrylate

[0050] [Table 1]

[0051] Resin A is preferably a resin obtained by polymerizing all of the following as other monomers (1): C2-C4 unsaturated alkyl methacrylate (preferably allyl methacrylate), methacrylic acid, and sodium styrene sulfonate. In this case, the amount of C2-C4 unsaturated alkyl methacrylate used is preferably 0.5 to 2.0 parts by mass, more preferably 0.7 to 2.0 parts by mass, and even more preferably 0.7 to 1.8 parts by mass, per 100 parts by mass of the total amount of the monomer mixture. The amount of methacrylic acid used is preferably 5.0 to 12.0 parts by mass, more preferably 6.0 to 12.0 parts by mass, and even more preferably 6.0 to 11.0 parts by mass, per 100 parts by mass of the total amount of the monomer mixture. The amount of sodium styrene sulfonate used is preferably 0.1 to 1.0 parts by mass, more preferably 0.3 to 1.0 parts by mass, and even more preferably 0.3 to 0.8 parts by mass, per 100 parts by mass of the total amount of the monomer mixture.

[0052] Resin A can be synthesized or obtained commercially. When synthesizing resin A, it is preferable to use a reactive emulsifier together with the above monomer mixture. By using a reactive emulsifier, an emulsion of resin A can be obtained. When preparing the ink composition according to this embodiment, it is preferable to use such an emulsion of resin A.

[0053] Reactive emulsifiers are emulsifiers that have a radically polymerizable double bond in their molecule. The number of radically polymerizable double bonds is usually one. As for the reactive emulsifier, anionic-type reactive emulsifiers that have an anionic group in their molecule are preferred. Such anionic-type reactive emulsifiers are sometimes referred to as "reactive anionic surfactants," etc. Examples of anionic groups include sulfonic acid groups, sulfonate groups, sulfate ester groups, phosphate groups, phosphate ester groups, nitrate ester groups, carboxyl groups, and salts thereof. Among these, sulfonic acid groups, sulfonate groups, sulfate ester groups, and salts thereof are preferred, and salts of sulfate ester groups are more preferred. Examples of salts include ammonium salts and alkali metal salts (e.g., sodium salts, potassium salts, etc.).

[0054] Among reactive emulsifiers, ethylenically unsaturated monomers having a group selected from sulfonic acid groups, sulfonate groups, sulfate ester groups, phosphate groups, phosphate ester groups, and salts thereof are preferred.

[0055] Specific examples of reactive emulsifiers include ammonium polyoxyalkylene alkenyl ether sulfate, ammonium ether sulfate, phosphate esters, bis(polyoxyethylene polycyclic phenyl ether) methacrylate sulfate, sodium sulfoethyl methacrylate, alkoxy polyethylene glycol maleate, and salts thereof. Specific examples of reactive emulsifiers include sodium alkylallyl sulfosuccinate (Sanyo Chemical Industries, Ltd., Eleminor JS-20), dipotassium alkenylsuccinate (Kao Corporation, Latemul ASK), polyoxyethylene alkylpropenylphenyl ether sulfate (Daiichi Kogyo Seiyaku Co., Ltd., Aqualon HS-10), α-[1-[(allyloxy)methyl]-2-(nonylphenoxy)ethyl]-ω-polyoxyethylene sulfate (ADEKA Corporation, Adekaria Soap SE series such as Adekaria Soap SE-10N), and polyoxyethylene-1-(allyloxymethyl)alkyl ether sulfate ammonium salt (Daiichi Kogyo Seiyaku Co., Ltd., Aqualon KH-1025, etc.). Examples include the KH series), styrene sulfonates (manufactured by Tosoh Finechem Co., Ltd., spinomer NaSS), α-[2-[(allyloxy)-1-(alkyloxymethyl)ethyl]-ω-polyoxyethylene sulfate (manufactured by ADEKA Corporation, Adekaria Soap SR series such as Adekaria Soap SR-1025), sulfate salts of polyoxyethylene polyoxybutylene (3-methyl-3-butenyl) ether (manufactured by Kao Corporation, Latemul PD-104), and ammonium salts of sulfated products of oxirane polyadducts of {C10-C14 branched chain alkanol and 1-(allyloxy)-2,3-epoxypropane}, mainly composed of [({α-[2-(allyloxy)-1-({C10-C14 alkyloxy}methyl)ethyl]-ω-hydroxypoly(n=1~100)(oxyethylene)}].Among these, the ammonium salt of the sulfated product of the reaction product of {C10-C14 branched chain alkanol and 1-(allyloxy)-2,3-epoxypropane}, mainly composed of {α-[2-(allyloxy)-1-({C10-C14 alkyloxy}methyl)ethyl]-ω-hydroxypoly(n=1~100)(oxyethylene)} is preferred.

[0056] The amount of reactive emulsifier used when synthesizing resin A is not particularly limited. As a guideline for the amount used, it is usually 0.1 to 10% by mass, preferably 0.3 to 5% by mass, more preferably 0.5 to 3% by mass, and even more preferably 1 to 3% by mass, relative to the total mass of the above monomer mixture. By using the reactive emulsifier within the above range, resin A can be synthesized stably, the average particle size of resin A can be controlled within a suitable range, and the viscosity of the resin A emulsion can be adjusted within a suitable range.

[0057] The average particle size of resin A is typically 10 to 500 nm, preferably 20 to 200 nm, more preferably 25 to 150 nm, and even more preferably 30 to 130 nm. By setting the average particle size to the range of 10 to 500 nm, clogging of the inkjet head and re-aggregation of resin A tend to be suppressed.

[0058] The glass transition temperature (Tg) of resin A is typically 10 to 65°C, preferably 20 to 60°C, more preferably 30 to 55°C, and even more preferably 40 to 50°C. The acid value of resin A is typically 20 to 85 mg KOH / g, preferably 30 to 80 mg KOH / g, more preferably 40 to 75 mg KOH / g, and even more preferably 50 to 70 mg KOH / g.

[0059] The insolubility of resin A in tetrahydrofuran is typically 60-100%, preferably 70-80%. This degree of insolubility allows for control of the average molecular weight of resin A and tends to result in a resin free from unreacted monomers and other impurities.

[0060] In the total mass of the ink composition according to this embodiment, the lower limit of the content of resin A (in terms of solid content) is usually 0.1% by mass, preferably 0.2% by mass, more preferably 0.3% by mass, and the upper limit is usually 10% by mass, preferably 7% by mass, more preferably 6% by mass, and even more preferably 5% by mass.

[0061] [Resin B] Resin B is a resin (polymer) obtained by polymerizing at least styrene monomers and divinylbenzene. That is, resin B contains at least styrene monomer units and divinylbenzene units as constituent monomer units. By using such resin B, the abrasion resistance of the ink composition tends to be improved while maintaining the storage stability of the ink composition. Examples of resin B include block copolymers, random copolymers, and graft copolymers, with random copolymers being preferred. Resin B may also be in the form of a salt. Resin B can be synthesized by known methods.

[0062] Styrene monomers are compounds in which a substituent containing an ethylenically unsaturated bond is attached to a monocyclic aromatic ring, and may further have substituents such as halogen atoms (fluorine, chlorine, bromine, etc.); alkyl groups (methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl, octyl, etc.); nitro groups; amino groups; hydroxyl groups; sulfo groups; carboxyl groups; etc. The alkyl groups as substituents may further be substituted with halogen atoms or the like. Examples of styrene monomers include styrene, p-fluorostyrene, m-fluorostyrene, 2,3,4,5,6-pentafluorostyrene, p-chlorostyrene, o-chlorostyrene, m-chlorostyrene, p-bromostyrene, o-bromostyrene, m-bromostyrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 1-ethyl-2-vinylbenzene, 3-(trifluoromethyl)styrene, 4-isopropenyltoluene, 4-t-butylstyrene, 4-n-octylstyrene, 2,4,6-trimethylstyrene, 4-vinylbiphenyl, 4-vinylbenzoic acid, 4-vinylbenzoic acidamine, and o-vinylbenzyl Examples include lucianides, m-vinylbenzyl cyanides, 4-methoxystyrene, 2-vinylphenylacetic acid, 1-(1-ethoxyethoxy)-4-vinylbenzene, 4-t-butoxystyrene, 4-vinylbenzoate methyl, 4-vinylphenyl acetate, 4-(trifluoromethyl)styrene, 4-(chloromethyl)styrene, 4-fluoro-α-methylstyrene, p-nitrostyrene, p-aminostyrene, m-aminostyrene, trimethyl(4-vinylphenyl)silane, trimethoxy(4-vinylphenyl)silane, diphenyl(4-vinylphenyl)phosphine, 3-vinylphenylboric acid, 4-vinylphenylboric acid, and sodium styrenesulfonate. Among these, styrene, α-methylstyrene, and sodium styrenesulfonate are preferred because they exhibit good reactivity during polymerization and excellent stability of resin particles, with styrene and sodium styrenesulfonate being more preferred.

[0063] Examples of divinylbenzenes include 1,2-divinylbenzene, 1,3-divinylbenzene, and 1,4-divinylbenzene.

[0064] Resin B may be a resin obtained by polymerizing styrene monomers and divinylbenzene with other monomers (2) such as acrylic acid, methacrylic acid, and n-dodecyl mercaptan. The other monomers (1) may be used individually or in combination of two or more.

[0065] Table 2 below shows a guideline for the range of amounts to be used for styrene monomers, divinylbenzene, and other monomers (2). It is preferable to adjust the amount of the monomer mixture consisting of styrene monomers, divinylbenzene, and other monomers (2) within the range shown in Table 2 so that the total amount is 100 parts by mass. The values ​​in Table 2 are in "parts by mass," and the abbreviations have the following meanings. STM: Styrene monomer DVB: Divinylbenzene

[0066] [Table 2]

[0067] Resin B is preferably a resin obtained by polymerizing styrene and sodium styrenesulfonate as styrene monomers. In this case, the amount of styrene used is preferably 27.5 to 53.8 parts by mass, more preferably 29.5 to 51.0 parts by mass, and even more preferably 33.3 to 49.0 parts by mass, per 100 parts by mass of the total amount of the monomer mixture. The amount of sodium styrenesulfonate used is preferably 0.1 to 1.0 parts by mass, more preferably 0.3 to 1.0 parts by mass, and even more preferably 0.3 to 0.8 parts by mass, per 100 parts by mass of the total amount of the monomer mixture.

[0068] Furthermore, it is preferable that resin B is a resin obtained by polymerizing all of the other monomers (2): acrylic acid, methacrylic acid, and n-dodecyl mercaptan. In this case, the amount of acrylic acid used is preferably 0.5 to 2.5 parts by mass, more preferably 0.7 to 2.5 parts by mass, and even more preferably 0.7 to 2.3 parts by mass, per 100 parts by mass of the total amount of the monomer mixture. The amount of methacrylic acid used is preferably 0.5 to 3.0 parts by mass, more preferably 0.7 to 3.0 parts by mass, and even more preferably 0.7 to 2.8 parts by mass, per 100 parts by mass of the total amount of the monomer mixture. The amount of n-dodecyl mercaptan used is preferably 0.1 to 1.0 parts by mass, more preferably 0.3 to 1.0 parts by mass, and even more preferably 0.3 to 0.8 parts by mass, per 100 parts by mass of the total amount of the monomer mixture.

[0069] Resin B can be synthesized or obtained commercially. When synthesizing resin B, it is preferable to use the above-mentioned reactive emulsifier together with the above-mentioned monomer mixture. By using the reactive emulsifier, an emulsion of resin B can be obtained. When preparing the ink composition according to this embodiment, it is preferable to use such an emulsion of resin B.

[0070] The amount of reactive emulsifier used when synthesizing resin B is not particularly limited. As a guideline for the amount used, it is usually 0.1 to 10% by mass, preferably 0.3 to 5% by mass, more preferably 0.5 to 3% by mass, and even more preferably 1 to 3% by mass, relative to the total mass of the above monomer mixture. By using the reactive emulsifier within the above range, resin B can be synthesized stably, the average particle size of resin B can be controlled within a suitable range, and the viscosity of the resin B emulsion can be adjusted within a suitable range.

[0071] The average particle size of resin B is typically 10 to 500 nm, preferably 20 to 300 nm, more preferably 40 to 200 nm, and even more preferably 50 to 150 nm. By setting the average particle size within this range, clogging of the inkjet head and re-aggregation of resin B tend to be suppressed.

[0072] The glass transition temperature (Tg) of resin B is typically 70 to 280°C, preferably 100 to 270°C, more preferably 150 to 260°C, and even more preferably 200 to 250°C. The acid value of resin B is typically 3 to 80 mg KOH / g, preferably 5 to 70 mg KOH / g, more preferably 10 to 60 mg KOH / g, and even more preferably 15 to 50 mg KOH / g.

[0073] The insolubility of resin B in tetrahydrofuran is typically 60-100%, preferably 70-80%. This degree of insolubility allows for control of the average molecular weight of resin B and tends to result in a resin free from unreacted monomers and other impurities.

[0074] In the total mass of the ink composition according to this embodiment, the lower limit of the content of resin B (in terms of solid content) is usually 0.1% by mass, preferably 0.2% by mass, more preferably 0.3% by mass, and the upper limit is usually 10% by mass, preferably 7% by mass, more preferably 6% by mass, and even more preferably 5% by mass.

[0075] Resins A and B can be used in any combination ratio. By changing the combination ratio, it is possible to improve washability, scratch resistance of printed materials, color development, and gloss, and further reduce VOCs during ink design. In the ink composition according to this embodiment, let A be the content of resin A (in terms of solid content) and B be the content of resin B (in terms of solid content). If the combination ratio is expressed as "A / B", then A / B is preferably 0.1 to 10, more preferably 0.2 to 5, even more preferably 0.2 to 4, particularly preferably 0.25 to 2.34, and most preferably 0.25 to 1.0.

[0076] [water] As for the water, it is preferable to use water with a low content of impurities (such as metal ions), such as deionized water or distilled water.

[0077] The water content in the total mass of the ink composition according to this embodiment is typically 30 to 80% by mass, preferably 35 to 75% by mass, and more preferably 40 to 70% by mass.

[0078] [Water-soluble organic solvents] The ink composition according to this embodiment preferably further contains a water-soluble organic solvent. Examples of water-soluble organic solvents include C1-C6 alkanols such as methanol, ethanol, propanol, isopropanol, butanol, isobutanol, derbutanol, and terbutanol; carboxylic acid amides such as N,N-dimethylformamide and N,N-dimethylacetamide; lactams such as 2-pyrrolidone, N-methyl-2-pyrrolidone, and N-methylpyrrolidine-2-one; cyclic ureas such as 1,3-dimethylimidazolidine-2-one and 1,3-dimethylhexahydropyrimido-2-one; ketones or keto alcohols such as acetone, 2-methyl-2-hydroxypentan-4-one, and ethylene carbonate; cyclic ethers such as tetrahydrofuran and dioxane; and ethyleneglycerides. Mono-, oligo-, or polyalkylene glycols and thioglycols having C2-C6 alkylene units, such as glycerin, diethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butylene glycol, 1,4-butylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, polyethylene glycol (preferably with molecular weights of 400, 800, 1540 or higher), polypropylene glycol, thiodiglycol, and dithiodiglycol; C3-C9 polyols (triols) such as glycerin, diglycerin, hexane-1,2,6-triol, and trimethylolpropane;Examples of glycol ethers include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoallyl ether, ethylene glycol monoisopropyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, propylene glycol monopropyl ether, prolene glycol monobutyl ether, and dipropylene glycol monomethyl ether (preferably glycol ethers selected from the group consisting of C3-C10 mono, di, or triethylene glycol ethers and C4-C13 mono, di, or tripropylene glycol ethers); C5-C9 alkanediols such as 1,2-pentanediol, 1,5-pentanediol, 1,2-hexanediol, 1,6-hexanediol, 2-methyl-2,4-pentanediol, 2-ethyl-1,3-hexanediol, and 2,4-diethyl-1,5-pentanediol; γ-butyrolactone; dimethyl sulfoxide; and the like. Among these, it is preferable to use at least one water-soluble organic solvent selected from the group consisting of glycol ethers and C5-C9 alkanediols.

[0079] The content of the water-soluble organic solvent in the total mass of the ink composition according to this embodiment is typically 0 to 60% by mass, preferably 1 to 60% by mass, more preferably 2 to 50% by mass, even more preferably 3 to 45% by mass, and particularly preferably 5 to 40% by mass.

[0080] [Other ingredients] The ink composition according to this embodiment may further contain an ink preparation agent in addition to the components described above. Examples of ink preparation agents include surfactants (excluding those equivalent to reactive emulsifiers), preservatives and antifungal agents, pH adjusters, and defoamers.

[0081] The total content of the ink preparation agent in the total mass of the ink composition according to this embodiment is usually 0 to 30% by mass, preferably 0.1 to 20% by mass, and more preferably 0.5 to 10% by mass.

[0082] Examples of surfactants include anionic, cationic, nonionic, amphoteric, silicone-based, and fluorine-based surfactants. Among these, surfactants selected from silicone-based and fluorine-based surfactants are preferred, and from the viewpoint of safety for living organisms and the environment, silicone-based surfactants are more preferred.

[0083] Examples of anionic surfactants include alkyl sulfocarboxylates, α-olefin sulfonates, polyoxyethylene alkyl ether acetates, polyoxyethylene alkyl ether sulfates, N-acyl amino acids or their salts, N-acyl methyl taurates, alkyl sulfates, polyoxyalkyl ether sulfates, alkyl sulfates, polyoxyethylene alkyl ether phosphates, rosinic acid soaps, castor oil sulfates, lauryl alcohol sulfates, alkylphenol type phosphates, alkyl type phosphates, alkylaryl sulfonates, diethyl sulfosaturates, diethylhexyl sulfosaturates, and dioctyl sulfosaturates.

[0084] Examples of cationic surfactants include 2-vinylpyridine derivatives and poly-4-vinylpyridine derivatives.

[0085] Examples of nonionic surfactants include ether-based surfactants such as polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene dodecylphenyl ether, polyoxyethylene oleyl ether, polyoxyethylene lauryl ether, polyoxyethylene alkyl ether, and polyoxyethylene distyrenated phenyl ether (e.g., Emulgen A-60, A-90, A-500 manufactured by Kao Corporation); ester-based surfactants such as polyoxyethylene oleate, polyoxyethylene distearate, sorbitan laurate, sorbitan monostearate, sorbitan monooleate, sorbitan sesquioleate, polyoxyethylene monooleate, and polyoxyethylene stearate; acetylene glycol (alcohol)-based surfactants such as 2,4,7,9-tetramethyl-5-decine-4,7-diol, 3,6-dimethyl-4-octin-3,6-diol, and 3,5-dimethyl-1-hexyn-3-ol; and polyglycol ether-based surfactants. Examples of these commercially available products include Surfinol 104, 104PG50, 82, 420, 440, 465, 485, and Olfin STG from Nisshin Chemical Industry Co., Ltd.; and Emulgen A-60, A-90, and A-500 from Kao Corporation.

[0086] Examples of amphoteric surfactants include lauryldimethylaminoacetic acid betaine, 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine, coconut oil fatty acid amidopropyl dimethylaminoacetic acid betaine, polyoctyl polyaminoethylglycine, and imidazoline derivatives.

[0087] Examples of silicone-based surfactants include polyether-modified siloxanes and polyether-modified polydimethylsiloxanes. Some examples include Dynol 960 and 980 from Air Products Corporation; Silface SAG001, SAG002, SAG003, SAG005, SAG503A, SAG008, SAG009, and SAG010 from Nisshin Chemical Industry Co., Ltd.; BYK-345, 347, 348, 349, 3455, LP-X23288, LP-X23289, and LP-X23347 from BYK Additives & Instruments; and TEGO Twin 4000, TEGO Wet KL 245, 250, 260, 265, 270, and 280 from Evonic Tego Chemie.

[0088] Examples of fluorine-based surfactants include perfluoroalkyl sulfonic acid compounds, perfluoroalkyl carboxylic acid compounds, perfluoroalkyl phosphate ester compounds, perfluoroalkyl ethylene oxide adducts, and polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups in their side chains.

[0089] Examples of preservatives and fungicides include compounds such as organic sulfur, organic nitrogen sulfur, organic halogen, haloaryl sulfone, iodopropagyl, haloalkylthio, nitrile, pyridine, 8-oxyquinoline, benzothiazole, isothiazoline, dithiol, pyridine oxide, nitropropane, organotin, phenol, quaternary ammonium salt, triazine, thiazine, anilide, adamantane, dithiocarbamate, brominated indanone, benzyl bromacetate, and inorganic salts; sodium dehydroacetate, sodium benzoate, sodium pyridinethion-1 oxide, p-hydroxybenzoate ethyl ester, 1,2-benzisothiazolin-3-one and their salts; and commercially available preservatives and fungicides include Proxel GXL(S) and XL-2(S) manufactured by Lonza.

[0090] Any substance can be used as a pH adjuster, as long as it is a compound that can adjust the pH of the prepared ink composition to 5-11 without adversely affecting it. Specific examples include alkanolamines such as diethanolamine, triethanolamine, and N-methyldiethanolamine; alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide; ammonium hydroxide (ammonia water); alkali metal carbonates such as lithium carbonate, sodium carbonate, sodium bicarbonate, and potassium carbonate; alkali metal salts of organic acids such as sodium silicate and potassium acetate; and inorganic bases such as disodium phosphate.

[0091] Examples of defoaming agents include silicone-based, silica mineral oil-based, olefin-based, and acetylene-based compounds. Examples of commercially available defoaming agents include Surfinol DF37, DF58, DF110D, DF220, MD-20, and Olfin SK-14, all manufactured by Shin-Etsu Chemical Co., Ltd.

[0092] When using an antifoaming agent, the antifoaming agent content is usually 0.01 to 5% by mass, preferably 0.03 to 3% by mass, and more preferably 0.05 to 1% by mass. A content of 0.01% by mass or more of the antifoaming agent tends to provide an effective antifoaming effect, while a content of 5% by mass or less tends to improve dispersion stability.

[0093] [Physical properties of the ink composition, etc.] When using the ink composition according to this embodiment as an ink for inkjet recording, it is preferable to use one that has a low content of inorganic impurities such as metal cation chlorides (e.g., sodium chloride) and sulfates (e.g., sodium sulfate) in the ink composition. The guideline for the content of inorganic impurities is approximately 1% by mass or less relative to the total mass of the colorant. The lower limit may be below the detection limit of the analytical instrument, i.e., 0% by mass.

[0094] Inorganic impurities are often present in colorants. Therefore, it is possible to purify colorants by removing inorganic impurities as needed. Examples of purification methods include suspending the solid colorant in a mixed solvent such as methanol (a C1-C4 alcohol) and water; or, after preparing the ink, exchanging and adsorbing inorganic impurities with an ion exchange resin.

[0095] The pH of the ink composition according to this embodiment at 25°C is typically 7 to 11, preferably 8 to 10. The surface tension of the ink composition according to this embodiment at 25°C is typically 10 to 50 mN / m, preferably 20 to 40 mN / m. The viscosity of the ink composition according to this embodiment at 25°C is typically 2 to 30 mPa·s, preferably 3 to 20 mPa·s. The pH, surface tension, and viscosity of the ink composition according to this embodiment can be appropriately adjusted by selecting the type and amount of pH adjusters, surfactants, water-soluble organic solvents, etc.

[0096] The ink composition according to this embodiment exhibits excellent storage stability, ejection stability, resolubility, and redispersibility, and can also reduce VOCs. Furthermore, by printing using the ink composition according to this embodiment, it is possible to obtain printed materials with a good balance of lightfastness, ozone resistance, moisture resistance, saturation, color development, gloss, abrasion resistance, bronzing, silvering resistance, and bleeding resistance.

[0097] The ink composition according to this embodiment can be used in various types of recording. For example, the ink composition according to this embodiment is suitable for writing instruments, various types of printing, information recording, textile printing, etc., and is particularly preferred for use in inkjet recording.

[0098] <Inkjet recording method, inkjet printer, and recording media> The inkjet recording method according to this embodiment records by ejecting droplets of the above-described ink composition using an inkjet printer in accordance with a recording signal and adhering them to a recording medium. When performing inkjet recording, the above-described method can be used by loading a container filled with the above-described ink composition into a predetermined position in the inkjet printer.

[0099] In the inkjet recording method according to this embodiment, the ink composition described above may be used alone or in combination with other ink compositions. For example, in order to obtain a full-color recorded image, the ink composition described above may be used in combination with another ink composition having a different hue.

[0100] Industrial inkjet printers, in order to achieve high printing speeds, are configured as line-head type inkjet printers, and single-pass printing is also preferred. With the ink composition described above, even under such printing conditions, it is possible to obtain recorded images with good color development and excellent scratch resistance.

[0101] Any known inkjet method can be used. Specific examples of inkjet methods include, for example, charge control methods, drop-on-demand (pressure pulse) methods, acoustic inkjet methods, and thermal inkjet methods. Other methods include: methods that improve image quality by ejecting many small volumes of ink compositions with a low colorant content; methods that improve image quality by using multiple ink compositions with substantially the same hue but different concentrations of colorants; and methods that improve the fixation of colorants by using a colorless and transparent ink composition.

[0102] A recording medium refers to a substance to which an ink composition can adhere. Examples of recording media include paper, film, fibers or cloth (cellulose, nylon, wool, etc.), leather, and substrates for color filters.

[0103] Recording media can be broadly classified into those with an ink-receiving layer and those without.

[0104] Recording media with an ink-receiving layer are commonly referred to as inkjet paper, inkjet film, glossy paper, etc. Representative examples of commercially available products include Canon Inc.'s Professional Photo Paper, Super Photo Paper, Glossy Gold, and Matte Photo Paper; Seiko Epson Corporation's Photo Paper Crispia (High Gloss), Photo Paper (Glossy), and Photo Matte Paper; Hewlett-Packard Japan Ltd.'s Advanced Photo Paper (Glossy); and Fujifilm Corporation's Gakusai Photo Finish Pro.

[0105] Examples of recording media without an ink-receiving layer include various types of paper such as coated paper and art paper used for gravure printing and offset printing; and cast-coated paper used for label printing. The ink composition described above can be suitably used with recording media without an ink-receiving layer.

[0106] When using recording media that does not have an ink-receiving layer, it is also preferable to perform surface modification treatment on the recording media in order to improve the fixation of colorants, etc. Examples of surface modification treatments include corona discharge treatment, plasma treatment, and flame treatment.

[0107] For all the matters mentioned above, a combination of desirable items is more desirable, and a combination of more desirable items is even more desirable. The same applies to combinations of desirable items and more desirable items, and combinations of more desirable items and even more desirable items, and so on. [Examples]

[0108] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0109] In the examples, unless otherwise specified, "parts" refers to parts by mass, and "%" refers to mass percent. Unless otherwise specified, all synthesis, preparation, and other operations in the examples were carried out under stirring. Furthermore, when measuring the solid content in the liquid, it was determined by the dry weight method using an MS-70 manufactured by A&D Co., Ltd.

[0110] The "water" used in the examples is deionized water. Furthermore, the reactive emulsifier used in the examples is an ammonium salt of the sulfated ester of the oxirane polyadduct of the reaction product of {C10-C14 branched chain alkanol and 1-(allyloxy)-2,3-epoxypropane}, with {α-[2-(allyloxy)-1-({C10-C14 alkyloxy}methyl)ethyl]-ω-hydroxypoly(n=1~100)(oxyethylene)} as the main component.

[0111] [Preparation Example 1: Preparation of Resin A] A glass reaction vessel (capacity 3L) equipped with a stirrer was fitted with a reflux condenser, thermometer, and dropping funnel, and 152 parts deionized water, 1.4 parts sodium polyoxyethylene alkyl ether sulfate, and 0.3 parts potassium persulfate were charged into it. After replacing the internal air with nitrogen, the internal temperature was adjusted to 80°C while stirring, and the raw material solution (emulsifier) ​​was continuously added dropwise over 3 hours. The raw material solution was prepared by emulsifying 62 parts deionized water, 0.99 parts sodium polyoxyethylene alkyl ether sulfate, and 1 part reactive emulsifier, along with 41 parts butyl acrylate, 47 parts methyl methacrylate, 10 parts methacrylic acid, 0.5 parts sodium styrene sulfonate, and 1.5 parts allyl methacrylate, by mixing and stirring them in a separate container beforehand. During the dropwise addition, the reaction was carried out at 80°C while introducing nitrogen. After the dropwise addition was complete, the mixture was stirred at 85°C for 2 hours and then cooled to 40°C. After cooling, triethanolamine (1.1 parts) was added to obtain an emulsion of resin A (modified acrylic resin). The acid value of the obtained resin A was 65 mg KOH / g, and the Tg was 47°C.

[0112] [Preparation Example 2: Preparation of Resin B] A glass reaction vessel (3 L capacity) equipped with a stirrer was fitted with a reflux condenser, thermometer, and dropping funnel, and 289 parts deionized water, 0.7 parts sodium lauryl sulfate, and 0.1 parts sodium persulfate were charged into it. After replacing the internal air with nitrogen, the internal temperature was adjusted to 80°C while stirring, and the raw material solution (emulsifier) ​​was continuously added dropwise over 3 hours. The raw material solution was prepared by emulsifying 84 parts deionized water, 6.6 parts sodium lauryl sulfate, and 1 part reactive emulsifier with 37.06 parts styrene, 1.8 parts methacrylic acid, 1.15 parts acrylic acid, 59.04 parts divinylbenzene, 0.57 parts n-dodecyl mercaptan, and 0.38 parts sodium styrenesulfonate in a separate container by mixing and stirring beforehand. During the dropwise addition, the reaction was carried out at 80°C while introducing nitrogen. After the dropwise addition was complete, the mixture was stirred at 85°C for 2 hours and then cooled to 40°C. After cooling, polyoxyethylene lauryl ether (4 parts) and triethanolamine (1.5 parts) were added to obtain an emulsion of resin B (styrene resin crosslinked with divinylbenzene). The acid value of the obtained resin B was 21 mg KOH / g, and the Tg was 225°C.

[0113] [Preparation Example 3: Preparation of a dispersion of coloring agents] A block copolymer (block copolymer A) was obtained by replicating Synthesis Example 3 of International Publication No. 2013 / 115071. 2-butanone (8.2 parts) and block copolymer A (10.62 parts) were added to a solution prepared by dissolving sodium hydroxide (0.36 parts) in deionized water (64.4 parts) and stirring for 1 hour to obtain a homogeneous solution. CIPigment Blue 15:4 (BASF, Heliogen Blue D 7115 F) (16 parts) was added to this solution, and the mixture was dispersed in a sand grinder at 1500 rpm for 15 hours to obtain the solution. Water (100 parts) was added dropwise to the obtained solution, and the solution was filtered to obtain the filtrate. From the obtained filtrate, 2-butanone and a portion of the water were removed by vacuum distillation using an evaporator to obtain a dispersion of a colorant with a colorant content of 12.4%. The average particle size (D50) of this colorant was 138 nm, the average particle size (D90) was 230 nm, and the average particle size (D10) was 81 nm.

[0114] [Examples 1-5: Preparation of Ink Compositions] Each component listed in Table 3 below was mixed to obtain 100 parts of each liquid. The obtained liquids were then filtered through a membrane filter with a pore size of 3 μm to obtain the ink compositions of Examples 1 to 5 for evaluation testing.

[0115] [Comparative Examples 1-2: Preparation of Ink Compositions] Each component listed in Table 3 below was mixed to obtain 100 parts of each solution. The resulting solutions were then filtered through a membrane filter with a pore size of 3 μm to obtain the ink compositions of Comparative Examples 1 and 2 for evaluation testing.

[0116] [Preparation Example 4: Preparation of Washing Solution] A cleaning solution for evaluation testing was obtained in the same manner as in Examples 1 to 5, except that the components listed in Table 3 below were used.

[0117] The abbreviations in Table 3 below have the following meanings. The numerical values ​​in the column for each component in Table 3 represent the amount (parts) of that component used, and "-" means that the component was not used. In addition, the parts in the columns for Resin A and Resin B in Table 3 are the solid content equivalent values ​​for each resin. PG: Propylene glycol (manufactured by Junsei Chemical Co., Ltd.) 2Py:2-Pyrrolidone (manufactured by Junsei Chemical Co., Ltd.) 12HD: 1,2-Hexanediol (manufactured by Kanto Chemical Co., Ltd.) TEA: Triethanolamine (manufactured by Kanto Chemical Co., Ltd.) TEX: Texanol (manufactured by Eastman Chemical Company) BYK-349: Silicone-based surfactant (manufactured by BYK, BYK-349) GXL(S): Proxel GXL(S) (manufactured by Lonza) Resin A: Emulsion of Resin A obtained in Preparation Example 1 Resin B: Emulsion of Resin B obtained in Preparation Example 2

[0118] [Table 3]

[0119] [Inkjet recording] The ink compositions obtained in each example and comparative example were inkjet recorded on OK Topcoat+ coated paper manufactured by Oji Paper Co., Ltd. using a printer equipped with a Kyocera Corporation inkjet head KJ4B-YH (600dpi x 600dpi) under conditions of droplet size 12pl and speed 25m / min. Inkjet recording was performed to obtain a solid image with 100% duty cycle, and recorded images were obtained using the ink composition of each example or comparative example. These were used as test pieces for color development tests and scratch tests. A colorimeter manufactured by X-rite, product name eXact, was used to measure the color of each test piece. The color measurement conditions were density standard ISO status T, viewing angle 2°, and light source D50.

[0120] [Color development test] The Dc value (OD value) was measured for each test specimen obtained as described above. The results are shown in Table 4 below. A higher Dc value indicates superior color development.

[0121] [Scratch test] The scratch resistance of each test specimen was evaluated using a pencil and spring load type scratch hardness tester (compliant with JIS K5600-5-4, manufactured by Cortec Co., Ltd.). Specifically, the test involved pressing the inkjet-printed area of ​​the test specimen with a 45° angle and a 750g load applied to the test specimen, and evaluating it according to the following three evaluation criteria. The results are shown in Table 4 below. -Evaluation Criteria- A: There are almost no scratches visible in the recorded images. B: A small scratch was found in the recorded image. C: The recorded image is severely damaged.

[0122] [Cleaning performance test] 20 μL of the ink composition from each example and comparative example was dropped onto a glass petri dish (Flat Petri Dish 70, manufactured by Tokyo Glass Instruments Co., Ltd.), and left to dry in a 60°C constant temperature bath for 1 hour to obtain solid material from the solidified ink composition. 10 mL of the washing solution obtained in Preparation Example 4 was dropped onto the obtained solid material, and the ability to dissolve and remove the solid was visually evaluated. The evaluation criteria were as follows (four levels). The results are shown in Table 4 below. -Evaluation Criteria- A: No solid matter was found to remain, and the liquid was uniform. B: A small amount of solid matter remains, but the liquid is almost uniform. C: Clearly, solid matter remained, and it could not be considered a uniform liquid.

[0123] [Glossiness (20°, 60°)] The gloss (20° and 60°) of each test specimen was measured using a handheld gloss meter (manufactured by Nippon Denshoku Industries Co., Ltd.). The results are shown in Table 4 below. Generally, higher color development leads to higher gloss values.

[0124] [VOC content] The VOC content in the ink compositions of each example and comparative example was evaluated. The evaluation criteria were set to the following four levels. The results are shown in Table 4 below. -Evaluation Criteria- A: The VOC component content in the ink composition is 23% by mass or less. B: The VOC component content in the ink composition is greater than 23% by mass and less than or equal to 25% by mass. C: The content of VOC components in the ink composition exceeds 25% by mass.

[0125] [Table 4]

[0126] As is clear from the results in Table 4, the ink compositions of each example exhibited excellent color development and scratch resistance. Furthermore, it was confirmed that even when the ink compositions of each example dried and formed solid matter, the solid matter could be thoroughly washed away. On the other hand, the ink compositions of each comparative example had inferior color development and were unable to achieve both scratch resistance and washability.

Claims

1. It contains a water-insoluble coloring agent, a dispersant, resin A, resin B, and water. The resin A is a resin obtained by polymerizing at least C1-C4 alkyl methacrylate and C2-C6 alkyl acrylate. The resin B is a resin obtained by polymerizing at least a styrene monomer and divinylbenzene. An ink composition in which, when the content of resin A is A and the content of resin B is B, the value obtained by A / B is 0.1 to 10.

2. The ink composition according to claim 1, wherein resin A and resin B are resins obtained by polymerizing a reactive emulsifier having a radically polymerizable double bond in its molecule.

3. The ink composition according to claim 2, wherein the reactive emulsifier is a reactive emulsifier having an anionic group in its molecule.

4. The ink composition according to claim 3, wherein the anionic group is a salt of a sulfate ester group.

5. Furthermore, the ink composition according to any one of claims 1 to 4, further containing a water-soluble organic solvent.

6. An inkjet recording method that performs recording by ejecting droplets of the ink composition described in any one of claims 1 to 4 using an inkjet printer in accordance with a recording signal and adhering them to a recording medium.

7. The inkjet recording method according to claim 6, wherein the recording medium is a recording medium having an ink receiving layer.

8. The inkjet recording method according to claim 6, wherein the recording medium is a recording medium that does not have an ink receiving layer.

9. The inkjet recording method according to claim 6, wherein the inkjet printer is a line-head type inkjet printer.

10. A recording medium to which the ink composition according to any one of claims 1 to 4 is attached.

11. The recording medium according to claim 10, wherein the recording medium is selected from a recording medium having an ink receiving layer and a recording medium not having an ink receiving layer.

12. An inkjet printer comprising a container filled with the ink composition according to any one of claims 1 to 4.

13. The inkjet printer according to claim 12, wherein the inkjet printer is a line-head type inkjet printer.

Images