Dispersion liquid, ink composition for inkjet recording, and dispersion resin

Abstract

To provide a dispersion liquid and the like which can easily re-disperse a solidified coloring material, and can improve stability in drying and re-discharge.SOLUTION: A dispersion liquid contains water, a coloring material, and a dispersion resin dispersing the coloring material, in which the dispersion resin has a constitutional unit A including a hydrophobic monomer, and a predetermined constitutional unit B.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a dispersion, an ink composition for inkjet recording, and a dispersion resin. [Background technology]

[0002] Inkjet recording methods are capable of recording high-resolution images using relatively simple equipment, and have been rapidly developing in various fields. In the process, various studies have been conducted on the color development properties of coloring materials in inks. For example, Patent Document 1 discloses the use of a specific dye in order to provide an ink set with excellent color development properties for composite black. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-190937 Summary of the Invention [Problem to be solved by the invention]

[0004] One method for improving the dispersibility of colorants is to use a dispersant. For example, Patent Document 1 discloses the use of an (α-methyl)styrene-maleic acid (anhydride) copolymer or an acrylic acid ester-maleic acid (anhydride) copolymer as a dispersant.

[0005] However, ink compositions containing conventional dispersants such as the (α-methyl)styrene-(maleic anhydride) copolymer described in Patent Document 1 have the problem that once the ink dries and the colorant solidifies, it is difficult to redisperse the ink, which can easily cause problems when the ink is re-ejected after drying. [Means for solving the problem]

[0006] The present invention provides a dispersion liquid containing water, a colorant, and a dispersion resin that disperses the colorant, wherein the dispersion resin has a structural unit A containing a hydrophobic monomer and a structural unit B represented by any one of the following formulas (1-1) to (1-2): [ka] (In the formula, R 1 each independently represents a divalent organic group having 1 to 20 carbon atoms, and R 2 each independently represents a sulfonic acid group or a salt thereof.

[0007] The present invention also provides an ink composition for ink jet recording, which comprises the above dispersion, a surfactant, and a water-soluble organic solvent.

[0008] Furthermore, the present invention is a dispersion resin having a structural unit A containing a hydrophobic monomer and a structural unit B represented by any one of the above formulas (1-1) to (1-2). DETAILED DESCRIPTION OF THE INVENTION

[0009] Below, we will explain in detail the embodiment of the present invention (hereinafter referred to as the ``present embodiment''), but the present invention is not limited to this and various modifications are possible within the scope of the gist of the present invention.

[0010] 1.Dispersion liquid The dispersion of the present embodiment contains water, a colorant, and a dispersion resin that disperses the colorant, and the dispersion resin has a structural unit A containing a hydrophobic monomer and a structural unit B represented by any one of the following formulas (1-1) to (1-2). [ka] (In the formula, R 1 each independently represents a divalent organic group having 1 to 20 carbon atoms, and R 2 each independently represents a sulfonic acid group or a salt thereof.

[0011] Dispersions or ink compositions using conventional dispersion resins have the problem that once the colorant solidifies, it is difficult to redisperse it. In contrast, in this embodiment, by using a dispersion resin having the above-mentioned configuration, it is possible to easily redisperse the solidified colorant and further improve the re-ejection properties (hereinafter also referred to as "dry-state ejection properties") of the ink in the nozzle even when it dries. Each component will be described in detail below.

[0012] 1.1.Dispersion resin The dispersion resin has a structural unit A containing a hydrophobic monomer, and a structural unit B represented by any one of the above formulas (1-1) to (1-2), and may optionally have a structural unit C described below. In this embodiment, the term "structural unit" refers to a repeating unit that constitutes a part of the dispersion resin after polymerization, and the term "monomer" refers to a monomer having a polymerizable unsaturated bond before polymerization.

[0013] The dispersion resin may be a random copolymer, a block copolymer, or a graft copolymer. Examples of the block copolymer include a diblock copolymer having a block A composed of structural unit A and a block B composed of structural unit B, as well as a diblock copolymer having a block A composed of structural unit A and a random block B / C composed of structural unit B and structural unit C. The use of such a dispersion resin tends to further improve redispersibility after solidification, and also further improve ejection stability and ejection characteristics when dried.

[0014] The content of the dispersion resin is preferably 0.3 to 10% by mass, more preferably 0.5 to 5.0% by mass, and even more preferably 1.0 to 3.0% by mass, relative to the total amount of the dispersion liquid. When the content of the dispersion resin is within the above range, redispersibility after solidification is further improved, and ejection stability and ejection characteristics when dried also tend to be further improved.

[0015] The content of the dispersing resin is preferably 10 to 100 parts by mass, more preferably 20 to 80 parts by mass, and even more preferably 30 to 60 parts by mass, relative to 100 parts by mass of the colorant. When the content of the dispersing resin is within the above range, redispersibility after solidification is further improved, and the ejection stability and ejection characteristics when dried also tend to be further improved.

[0016] 1.1.1. Building Block A The structural unit A is a structural unit containing a hydrophobic monomer and partially imparts hydrophobicity to the dispersed resin. Although not particularly limited, the structural unit A may be oriented on the surface of the colorant due to hydrophobic interactions or the like, and contribute to the adsorption of the dispersed resin to the colorant.

[0017] The hydrophobic monomer constituting the structural unit a is not particularly limited, but examples thereof include vinyl monomers having an aromatic group, such as styrene, α-methylstyrene, allylbenzene, vinyltoluene, 1-vinylnaphthalene, and 2-vinylnaphthalene; and acrylic acid ester monomers having a hydrocarbon group, such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, isopropyl (meth)acrylate, isobutyl (meth)acrylate, pentyl (meth)acrylate, isoamyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and benzyl (meth)acrylate. In this embodiment, "(meth)acrylate" includes acrylate and methacrylate. The monomers constituting the structural unit A may be used alone or in combination of two or more.

[0018] Among these, vinyl monomers having an aromatic group are preferred, and one or more selected from the group consisting of styrene, α-methylstyrene, allylbenzene, vinyltoluene, 1-vinylnaphthalene, and 2-vinylnaphthalene are more preferred. The use of such hydrophobic monomers tends to improve the adsorption of the dispersing resin to the colorant, improve redispersibility after solidification, and also improve ejection stability and ejection characteristics when dried.

[0019] The content of the structural unit A is preferably 40 to 85 mol %, more preferably 45 to 80 mol %, and even more preferably 50 to 75 mol %, relative to the total amount of the dispersion resin. When the content of the structural unit A is within the above range, redispersibility after solidification is further improved, and the ejection stability and ejection characteristics when dried also tend to be further improved.

[0020] 1.1.2. Building Block B The structural unit B is a structural unit represented by any one of the following formulas (1-1) to (1-2), and partially imparts hydrophilicity to the dispersing resin. Although not particularly limited, the structural unit B is oriented on the side opposite to the surface of the colorant, which can contribute to improving dispersibility. The monomer that constitutes the structural unit B may be used alone, or two or more types may be used in combination. [ka] (In the formula, R 1 each independently represents a divalent organic group having 1 to 20 carbon atoms, and R 2 each independently represents a sulfonic acid group or a salt thereof.

[0021] In the formula, R 1 The divalent organic group having 1 to 20 carbon atoms represented by the formula (I) is not particularly limited, and examples thereof include divalent aliphatic hydrocarbon groups (alkylene groups, cycloalkylene groups, alkylene-cycloalkylene groups, etc.), divalent aromatic hydrocarbon groups (arylene groups, alkylene-arylene groups, etc.), etc.

[0022] Among these, R 1 The divalent organic group represented by the formula (I) preferably contains one or more selected from the group consisting of divalent aliphatic hydrocarbon groups and divalent aromatic hydrocarbon groups, and more preferably an alkylene group or an arylene group. This tends to further improve redispersibility after solidification, as well as further improve ejection stability and ejection characteristics when dried.

[0023] The alkylene group is not particularly limited, but examples thereof include a methylene group, an ethylene group, a propylene group, an isopropylene group, a butylene group, a 1,2-dimethylethylene group, a pentylene group, a 1-methylbutylene group, a 2-methylbutylene group, a heptylene group, an octylene group, a nonylene group, and a decylene group.

[0024] The cycloalkylene group is not particularly limited, but examples thereof include a cyclopropylene group, a cyclobutylene group, a cyclopentylene group, a cyclohexylene group, a cyclooctylene group, a cyclodecylene group, a cyclododecylene group, a cyclohexadecylene group, and a cyclooctadecylene group.

[0025] Examples of the alkylene-cycloalkylene group include a group in which the above alkylene group and cycloalkylene group are combined.

[0026] The arylene group is not particularly limited, but examples thereof include a phenylene group, a naphthylene group, a methylphenylene group, an ethylphenylene group, a methylnaphthylene group, and a dimethylnaphthylene group.

[0027] The alkylene-arylene group is not particularly limited, but examples thereof include groups in which the above alkylene group and arylene group are combined.

[0028] Also, R 1 The divalent organic group represented by the formula (I) has 1 to 20 carbon atoms, preferably 1 to 12 carbon atoms, and more preferably 1 to 8 carbon atoms.

[0029] R 2 The salt of the sulfonic acid group represented by the formula (I) is not particularly limited, but examples thereof include sodium salt, lithium salt, potassium salt, and ammonium salt.

[0030] Such structural unit B may be a structural unit obtained by introducing a compound having a sulfonic acid group and a hydroxyl group into a structural unit containing maleic anhydride. Use of such structural unit B tends to further improve redispersibility after solidification, and also to further improve ejection stability and ejection characteristics when dried. Note that, when esterification occurs with one carboxylic acid of maleic anhydride, esterification of the other carboxylic acid tends to be less likely to occur even if the above compound is present in a slight excess.

[0031] Here, the compound having a sulfonic acid group and a hydroxyl group is not particularly limited, but examples thereof include compounds represented by the following formula (1-3): 1 and R 2 is the same group as that explained in the above formulas (1-1) to (1-2). Among these, the compound having a sulfonic acid group and a hydroxyl group is not particularly limited, but is, for example, isethionic acid or p-toluenesulfonic acid is preferred. R 2 -R 1 -OH (1-3) (In the formula, R 1 each independently represents a divalent organic group having 1 to 20 carbon atoms, and R 2 each independently represents a sulfonic acid group or a salt thereof.

[0032] The content of the structural unit B is preferably 15 to 60 mol % or more, more preferably 20 to 55 mol %, and even more preferably 22 to 50 mol %, relative to the total amount of the dispersion resin. When the content of the structural unit B is within the above range, redispersibility after solidification is further improved, and the ejection stability and ejection characteristics when dried also tend to be further improved.

[0033] 1.1.3. Building Block C The dispersing resin is represented by the following formula ( 2 The polymerizable composition may further include a structural unit C represented by the formula (I) wherein R is a hydrogen atom or a hydrogen atom. The presence of such a structural unit C tends to further improve redispersibility after solidification, and also to further improve ejection stability and ejection characteristics when dried. [ka]

[0034] Such structural unit C may be a structural unit obtained by hydrolysis of the acid anhydride group in a structural unit containing maleic anhydride.

[0035] The content of the structural unit C is preferably 0.5 to 15 mol %, more preferably 0.5 to 10 mol %, and even more preferably 1.0 to 5.0 mol %, relative to the total amount of the dispersion resin. When the content of the structural unit C is within the above range, redispersibility after solidification is further improved, and the ejection stability and ejection characteristics when dried also tend to be further improved.

[0036] 1.1.4.Weight average molecular weight The weight-average molecular weight of the dispersion resin is 5000 to 30000, preferably 5000 to 20000, and more preferably 5000 to 15000. When the weight-average molecular weight of the dispersion resin is within the above range, redispersibility after solidification is further improved, and the ejection stability and ejection characteristics when dried also tend to be further improved.

[0037] The weight average molecular weight can be measured by a known method, such as a chromatography method, more specifically, by the method described in the Examples.

[0038] 1.1.5. Manufacturing method The dispersion resin of this embodiment can be obtained by copolymerizing the monomers constituting each of the above structural units. The polymerization reaction is not particularly limited, but for example, radical polymerization, particularly living radical polymerization, can be used. Furthermore, the structural unit containing maleic anhydride in the styrene-maleic anhydride copolymer may be modified to structural unit B or structural unit C.

[0039] 1.2.Water The content of water is preferably 60 to 95% by mass, more preferably 65 to 95% by mass, and even more preferably 75 to 90% by mass, based on the total amount of the dispersion.

[0040] 1.3.Colorants The coloring material is not particularly limited, but examples thereof include disperse dyes and pigments. Among these, disperse dyes are preferred. The use of disperse dyes tends to further improve redispersibility after solidification, and also to further improve ejection stability and ejection characteristics when dried. The coloring material may be used alone or in combination of two or more types.

[0041] The disperse dye is not particularly limited, and known disperse dyes such as CI Disperse Yellow, CI Disperse Orange, CI Disperse Blue, CI Disperse Violet, and CI Disperse Black can be used.

[0042] The inorganic pigment is not particularly limited, but examples thereof include carbon blacks (CI Pigment Black 7) such as furnace black, lamp black, acetylene black, and channel black, iron oxide, and titanium oxide.

[0043] The organic pigment is not particularly limited, but examples thereof include quinacridone pigments, quinacridonequinone pigments, dioxazine pigments, phthalocyanine pigments, anthrapyrimidine pigments, anthanthrone pigments, indanthrone pigments, flavanthrone pigments, perylene pigments, diketopyrrolopyrrole pigments, perinone pigments, quinophthalone pigments, anthraquinone pigments, thioindigo pigments, benzimidazolone pigments, isoindolinone pigments, azomethine pigments, and azo pigments.

[0044] The content of the coloring material is preferably 7.5 to 30% by mass, more preferably 7.5 to 25% by mass, and even more preferably 8.5 to 20% by mass, based on the total amount of the dispersion.

[0045] 1.4. pH adjuster The dispersion liquid may further contain a pH adjuster. Examples of pH adjusters include, but are not limited to, inorganic acids (e.g., sulfuric acid, hydrochloric acid, nitric acid, etc.), inorganic bases (e.g., lithium hydroxide, sodium hydroxide, potassium hydroxide, ammonia, etc.), organic bases (e.g., triethanolamine, diethanolamine, monoethanolamine, tripropanolamine), and organic acids (e.g., adipic acid, citric acid, succinic acid, etc.). The pH adjusters may be used alone or in combination of two or more.

[0046] 2. Ink composition for inkjet recording The ink composition for inkjet recording of this embodiment (also simply referred to as "ink composition") contains the above-mentioned dispersion liquid, a surfactant, and a water-soluble organic solvent, and may contain other components as necessary. Note that "for inkjet recording" means that the composition is used by an inkjet method in which ink droplets are ejected from the nozzles of an inkjet head.

[0047] 2.1.Dispersion liquid The dispersion liquid is as described above. The content of the dispersion resin added to the ink composition together with the dispersion liquid is preferably 0.1 to 3.5 mass %, more preferably 0.3 to 3.0 mass %, and even more preferably 0.5 to 2.5 mass %, relative to the total amount of the ink composition. When the content of the dispersion resin is within the above range, redispersibility after solidification is further improved, and ejection stability and ejection characteristics when dried also tend to be further improved.

[0048] The content of the colorant added to the ink composition together with the dispersion liquid is preferably 0.5 to 7.0% by mass, more preferably 1.0 to 6.0% by mass, and even more preferably 1.5 to 4.5% by mass, relative to the total amount of the ink composition. When the content of the colorant is within the above range, redispersibility after solidification is improved, and ejection stability and ejection characteristics when dried also tend to be improved.

[0049] In the ink composition, the content of the dispersion resin is preferably 10 to 100 parts by mass, more preferably 20 to 80 parts by mass, and even more preferably 30 to 60 parts by mass, relative to 100 parts by mass of the colorant. When the content of the dispersion resin is within the above range, redispersibility after solidification is further improved, and ejection stability and ejection characteristics when dried also tend to be further improved.

[0050] 2.2.Surfactants The surfactant is not particularly limited, but examples thereof include acetylene glycol surfactants, fluorine-based surfactants, and silicone-based surfactants.

[0051] The acetylene glycol surfactant is not particularly limited, but is preferably at least one selected from the group consisting of 2,4,7,9-tetramethyl-5-decyne-4,7-diol, alkylene oxide adducts of 2,4,7,9-tetramethyl-5-decyne-4,7-diol, and alkylene oxide adducts of 2,4-dimethyl-5-decyne-4-ol and alkylene oxide adducts of 2,4-dimethyl-5-decyne-4-ol.

[0052] The fluorine-based surfactant is not particularly limited, but examples thereof include perfluoroalkyl sulfonates, perfluoroalkyl carboxylates, perfluoroalkyl phosphates, perfluoroalkyl ethylene oxide adducts, perfluoroalkyl betaines, and perfluoroalkyl amine oxide compounds.

[0053] Examples of silicone surfactants include polysiloxane compounds and polyether-modified organosiloxanes.

[0054] The content of the surfactant is preferably 0.1 to 3.0% by mass, and more preferably 0.1 to 1.0% by mass, relative to the total amount of the ink composition.

[0055] 2.3. Water-soluble organic solvents The water-soluble organic solvent is not particularly limited, and examples thereof include glycerin; glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, 1,3-propanediol, 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, and propylene glycol monomethyl ether. Examples of suitable water-soluble organic solvents include glycol monoethers such as ethylene glycol ether, propylene glycol monoethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, and triethylene glycol monomethyl ether; nitrogen-containing solvents such as 2-pyrrolidone, N-methyl-2-pyrrolidone, and N-ethyl-2-pyrrolidone; and alcohols such as methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, 2-butanol, tert-butanol, isobutanol, n-pentanol, 2-pentanol, 3-pentanol, and tert-pentanol. Among these, glycerin, glycols, and glycol monoethers are preferred, and diethylene glycol, propylene glycol, triethylene glycol monomethyl ether, and glycerin are more preferred. The water-soluble organic solvents may be used alone or in combination of two or more.

[0056] The content of the water-soluble organic solvent is preferably 5.0 to 30% by mass, and more preferably 10 to 20% by mass, relative to the total amount of the ink composition. When the content of the water-soluble organic solvent is within the above range, redispersibility after solidification is further improved, and ejection stability and ejection characteristics when dried also tend to be further improved.

[0057] 2.4.Water The water content is preferably 60 to 90% by mass, and more preferably 70 to 85% by mass, relative to the total amount of the ink composition. When the water content is within this range, redispersibility after solidification is further improved, and ejection stability and ejection characteristics when dried also tend to be further improved.

[0058] 2.5. pH adjuster The ink composition may further contain a pH adjuster. The pH adjuster is not particularly limited, but examples thereof include those exemplified for the dispersion. The pH adjuster in the ink composition may be one that is originally mixed into the dispersion, or may be one that is added separately when preparing the ink composition.

[0059] The content of the pH adjuster is preferably 0.1 to 2.0% by mass, and more preferably 0.5 to 1.5% by mass, relative to the total amount of the ink composition.

[0060] 2.6.Other resins The ink composition may further contain a resin other than the dispersion resin. Examples of the other resin include, but are not limited to, an anionic resin, a cationic resin, and a nonionic resin. By including such a resin, the colorant can be fixed to the recording medium.

[0061] The cationic resin is not particularly limited, but examples thereof include starch derivatives such as cationic starch, cationic urethane resins, cationic olefin resins, and cationic allylamine resins.

[0062] Examples of anionic resins include carboxymethyl cellulose salts, cellulose derivatives such as viscose, alginates, gum arabic, gum tragacanth, and lignin sulfonates. Examples of natural resins include:

[0063] The nonionic resin is not particularly limited, but examples thereof include acrylic resins, styrene-acrylic resins, urethane resins, ester resins, olefin resins, and vinyl acetate resins.

[0064] The content of the other resins is preferably 0.1 to 2.0% by mass, and more preferably 0.5 to 1.5% by mass, relative to the total amount of the ink composition. [Example]

[0065] The present invention will be described in more detail below using examples and comparative examples, but the present invention is not limited to the following examples.

[0066] 1. Example of dispersion resin synthesis 1.1. Synthesis Example 1 A three-neck separable flask equipped with a stirrer and a Dimroth condenser was charged with 50 parts by mass of a styrene-maleic anhydride copolymer containing structural unit A (Kawahara Oil Chemical Co., Ltd., SMA3000P, 75 mol% styrene units, 25 mol% maleic anhydride units, weight-average molecular weight 9500), 60 parts by mass of sodium isethionate (Tokyo Chemical Industry Co., Ltd.), and 30 parts by mass of dimethylformamide (Tokyo Chemical Industry Co., Ltd.). The system was heated to 100°C and reacted for 8 hours. After completion of the reaction, the reaction product was dropped into water to precipitate a white solid. The white solid was collected by suction filtration, repeatedly washed with water, and vacuum-dried at 50°C for 10 hours to obtain a copolymer. The resulting copolymer was used as dispersion resin A.

[0067] 1.2.Synthesis Example 2 A copolymer was obtained in the same manner as in Synthesis Example 1, except that a styrene-maleic anhydride copolymer (Kawahara Oil Chemical Co., Ltd., SMA2000P, styrene unit 66.6 mol %, maleic anhydride unit 33.3 mol %, weight average molecular weight 7500) was used instead of the styrene-maleic anhydride copolymer (SMA3000P), and this copolymer was used as Dispersion Resin B.

[0068] 1.3.Synthesis Example 3 A copolymer was obtained in the same manner as in Synthesis Example 1, except that a styrene-maleic anhydride copolymer (Kawahara Oil Chemical Co., Ltd., SMA1000P, styrene unit 50 mol %, maleic anhydride unit 50 mol %, weight average molecular weight 5500) was used instead of the styrene-maleic anhydride copolymer (SMA3000P), and this copolymer was used as Dispersion Resin C.

[0069] 1.4. Synthesis Example 4 A copolymer was obtained in the same manner as in Synthesis Example 3, except that 80 parts by mass of p-phenolsulfonic acid (Tokyo Chemical Industry Co., Ltd.) was used instead of 60 parts by mass of sodium isethionate, and this copolymer was used as Dispersion Resin B.

[0070] Table 2 shows the weight average molecular weight Mw of each copolymer obtained in the above synthesis examples and the composition ratio of each structural unit.

[0071] [Table 1]

[0072] 1.5.NMR analysis The composition ratio of each structural unit was confirmed by 1H-NMR analysis and 13C-NMR analysis. For the NMR analysis, a nuclear magnetic resonance spectrometer (JNM-ECX400 manufactured by JEOL Ltd.) was used.

[0073] 1.6.Weight average molecular weight The weight average molecular weight Mw of each dispersion resin was measured by chromatography under the following conditions. (Measurement conditions) Device name: HLC8320GPC (Tosoh) Guard column: Super AW-L Column: Super AW3000 Column temperature: 25℃ Eluent: dimethylacetamide Flow rate: 0.6 mL / mIn Detector: RI

[0074] 2. Preparation of Dispersion Liquid (Examples 1 to 4 and Comparative Example 1) A 1 L eggplant-shaped flask (stirring bar, Dimroth condenser) was set up, and 15 parts by mass of the copolymer shown in Table 1 and 70 parts by mass of pure water were added, followed by heating and stirring at 80°C. Triethanolamine was added to this until the pH reached 8.0, and then the total volume was adjusted to 100 parts by mass with pure water. After cooling to 25°C, the resulting aqueous solution was used as a varnish solution.

[0075] Next, zirconia beads, 10 parts by mass of the varnish liquid, 4 parts by mass of DISPERSE YELLOW 232 (hereinafter also referred to as "DY232") as a water-insoluble colorant, and 17 parts by mass of pure water were added and ground in a bead mill for 1 hour. After that, the zirconia beads were removed, and pure water was added to make up 100 parts by weight, to prepare a dispersion containing 1.5% by mass of the copolymer and 4% by mass of the colorant.

[0076] 3. Preparation of Ink Composition The dispersion liquid and other components were mixed to obtain the compositions shown in Table 2 below, thereby obtaining each ink composition.

[0077] 4. Evaluation 4.1. Redispersibility 5 μL of the ink composition prepared as described above was dropped onto a glass slide and dried in a dryer at 40°C for 16 hours to solidify. The slide was then immersed in a sample bottle containing ink water, and the redispersion behavior of the solid matter was visually confirmed. Note that care was taken to avoid stirring the ink water during this operation. Note that ink water in Table 2 refers to ink water that does not contain colorant or dispersing resin. The evaluation criteria for redispersibility are shown below. (Evaluation criteria) A: The solids disappeared and redispersed. B: Some solid matter remained, but re-dispersion was observed. C: Solid matter remained and no redispersion was observed.

[0078] 4.2.Discharge stability An inkjet recording ink composition was filled into an inkjet printer EM-930C (product name, manufactured by Seiko Epson Corporation), and printing was performed continuously for 2 hours. Before and after printing, a nozzle check pattern was printed for the nozzles used in printing to identify nozzles with worsened landing position deviation. The number of nozzles was 180. The evaluation criteria were as follows: An evaluation result of A or B was considered to be good. (Evaluation criteria) A: The number of nozzles with worsening landing position deviation is 1% or less B: The number of nozzles with worsening landing position deviation is over 1% and 5% or less C: The number of nozzles with worsening landing position deviation exceeds 5%

[0079] 4.3.Dry discharge characteristics An inkjet recording ink composition was filled into an inkjet printer EM-930C (product name, manufactured by Seiko Epson Corporation), the ejection head was removed from the suction cap, and the printer was left standing for one day. After leaving the printer standing, cleaning was performed once, and 20 pages were continuously printed while ejecting from all nozzles. The number of nozzles with missing prints and bent prints was evaluated based on the following criteria. An evaluation result of A or B was considered to be good. (Evaluation criteria) A: No missing or bent nozzles B: Missing or bending nozzles 1 to 5 C: Missing or bending nozzles: 6 or more

[0080] [Table 2] BYK-348: Silicone surfactant, manufactured by BYK-Chemie Olfine E1010: Acetylene glycol surfactant, manufactured by Nissin Chemical Industry Co., Ltd.

[0081] As described above, it can be seen that the ink compositions of the examples using the dispersion liquid of the present invention have excellent redispersibility, improved ejection characteristics when dried, and excellent ejection stability compared to the comparative examples.

Claims

1. The ink contains water, a colorant, and a dispersion resin that disperses the colorant, The dispersion resin has a structural unit A containing a hydrophobic monomer and a structural unit B represented by any one of the following formulas (1-1) to (1-2): Dispersion for ink. 【Chemical 1】 (In the formula, R 1 each independently represents a divalent organic group having 1 to 20 carbon atoms; R 2 each independently represents a sulfonic acid group or a salt thereof.

2. the structural unit A contains, as the hydrophobic monomer, one or more selected from the group consisting of styrene, α-methylstyrene, allylbenzene, vinyltoluene, 1-vinylnaphthalene, and 2-vinylnaphthalene; The dispersion of claim 1.

3. The structural unit B is a structural unit obtained by introducing a compound having a sulfonic acid group and a hydroxyl group into a structural unit containing maleic anhydride.

3. The dispersion according to claim 1 or 2.

4. The R 1 The divalent organic group represented by the formula (I) contains at least one selected from the group consisting of a divalent aliphatic hydrocarbon group and a divalent aromatic hydrocarbon group. The dispersion according to any one of claims 1 to 3.

5. The content of the structural unit A is 40 to 85 mol% relative to the total amount of the dispersion resin. The dispersion according to any one of claims 1 to 4.

6. The content of the structural unit B is 15 to 60 mol% relative to the total amount of the dispersion resin. The dispersion according to any one of claims 1 to 5.

7. The dispersion resin further has a structural unit C represented by the following formula (2): The dispersion according to any one of claims 1 to 6. 【Chemistry 2】

8. the content of the structural unit C is 0.5 to 15 mol% relative to the total amount of the dispersion resin; The dispersion of claim 7.

9. The weight average molecular weight of the dispersion resin is 5,000 to 30,000. The dispersion according to any one of claims 1 to 8.

10. The colorant is a disperse dye. The dispersion according to any one of claims 1 to 9.

11. A dispersion liquid comprising the dispersion liquid according to any one of claims 1 to 10, a surfactant, and a water-soluble organic solvent. An ink composition for inkjet recording.

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