Dispersion liquid, ink composition for ink-jet recording, and dispersion resin

Abstract

To provide a dispersion liquid that makes it possible to readily re-dispersing a solidified colorant, and can improve discharge stability, stability during dry re-discharge, and furthermore can improve the wettability and viscosity.SOLUTION: A dispersion liquid contains water, a colorant, a dispersion resin that disperses the colorant, a compound having a sulfonic acid group and a polymerizable group, in which the dispersion resin comprises a constituent unit A containing a hydrophobic monomer, and a constituent unit B comprising a monomer having a sulfonic acid group, in which a weight average molecular weight of the dispersion resin is 5000 to 100000, a molecular weight of the compound is 300 or smaller.SELECTED DRAWING: None

Description

[Technical field]

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

[0002] Inkjet recording methods are capable of recording high-definition images with a relatively simple device, and have been rapidly developed in various fields. In the process, various studies have been conducted on obtaining high-quality images while suppressing mist contamination of the recording head. For example, Patent Document 1 discloses a pigment inkjet recording ink in which pigment particles are dispersed in a styrene-acrylic resin. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-002096 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, ink compositions containing conventional dispersants such as the styrene-acrylic resin described in Patent Document 1 have the problem that once the ink dries and the colorant solidifies, it is difficult to redisperse the ink, and problems tend to occur when the ink is re-ejected after drying. [Means for solving the problem]

[0005] The present invention provides a dispersion liquid comprising water, a colorant, a dispersion resin for dispersing the colorant, and a compound having a sulfonic acid group and a polymerizable group, the dispersion resin comprising a structural unit A containing a hydrophobic monomer and a structural unit B containing a monomer having a sulfonic acid group, the weight average molecular weight of the dispersion resin being 5,000 to 100,000, and the molecular weight of the compound being 300 or less.

[0006] The present invention also provides an ink composition for ink jet recording, comprising the above dispersion, a surfactant, and a water-soluble organic solvent. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] Below, we will explain in detail the embodiment of the present invention (hereinafter referred to as the "present embodiment"). However, the present invention is not limited to this embodiment, and various modifications are possible without departing from the gist of the present invention.

[0008] 1.Dispersion liquid The dispersion liquid of the present embodiment contains water, a colorant, a dispersion resin that disperses the colorant, and a compound having a sulfonic acid group and a polymerizable group, the dispersion resin having a structural unit A containing a hydrophobic monomer and a structural unit B containing a monomer having a sulfonic acid group, the weight average molecular weight of the dispersion resin is 5,000 to 100,000, and the molecular weight of the compound is 300 or less.

[0009] A conventional dispersion liquid or ink composition using a dispersion resin has a problem that once the coloring material solidifies, it is difficult to redisperse it. In contrast, in the present embodiment, by using a dispersion resin having the above-mentioned configuration and a specified compound, it becomes possible to easily redisperse the solidified coloring material. In addition, it is possible to further improve the ejection stability in a normal state and the re-ejection property even when the ink in the nozzle dries (hereinafter, also referred to as "ejection characteristics when dry"), and to improve the wettability and viscosity. Each component will be described in detail below.

[0010] 1.1.Dispersion resin The dispersion resin of this embodiment is a copolymer having a structural unit A containing a hydrophobic monomer and a structural unit B containing a monomer having a sulfonic acid group. In this embodiment, the term "monomer" refers to a monomer having a polymerizable unsaturated bond before polymerization, and the term "structural unit" refers to a repeating unit that constitutes a part of the dispersion resin after polymerization. In this embodiment, "hydrophobic" refers to a property of being incompatible with water at 25°C, and "hydrophilic" refers to a property of being compatible with water at 25°C.

[0011] The dispersion resin may be a random copolymer or a block copolymer. Examples of the block copolymer include a diblock copolymer having a block A composed of a structural unit A and a block B composed of a structural unit B, as well as a diblock copolymer having a block A composed of a structural unit A and a random block B / C composed of a structural unit B and another structural unit C. By using such a dispersion resin, the redispersibility after solidification is improved, and the ejection stability and the ejection characteristics when dried tend to be improved.

[0012] The content of the dispersion resin is preferably 2.0 to 14% by mass, more preferably 4.0 to 12% by mass, and even more preferably 6.0 to 10% by mass, based on the total amount of the dispersion liquid. By having the content of the dispersion resin within the above range, redispersibility after solidification is improved, and ejection stability and ejection characteristics when dried tend to be improved.

[0013] The content of the dispersion resin is preferably 20 to 100 parts by mass, more preferably 30 to 80 parts by mass, and even more preferably 40 to 70 parts by mass, relative to 100 parts by mass of the colorant. By having the content of the dispersion resin within the above range, redispersibility after solidification is improved, and ejection stability and ejection characteristics when dried tend to be improved.

[0014] 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 can be oriented on the surface of the colorant by hydrophobic interaction or the like, and contribute to the adsorption of the dispersed resin to the colorant.

[0015] The hydrophobic monomer constituting the structural unit A is not particularly limited, and examples thereof include vinyl monomers having an aromatic group such as styrene, methylstyrene, and other styrene derivatives; 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 hydrophobic monomer may be used alone or in combination of two or more.

[0016] In this embodiment, "(meth)acrylate" includes acrylate and methacrylate, and "(meth)acrylamide" includes acrylamide and methacrylamide.

[0017] Among these, it is more preferable to include at least one of a vinyl monomer having an aromatic group such as styrene, and an acrylic acid ester monomer having a hydrocarbon group such as butyl acrylate. By using such a hydrophobic monomer, the adsorption of the dispersion resin to the colorant is improved, redispersibility after solidification is improved, and ejection stability and ejection characteristics when dried tend to be improved.

[0018] The content of the structural unit A is preferably 10 to 90% by mass, more preferably 15 to 80% by mass, even more preferably 20 to 70% by mass, and even more preferably 25 to 60% by mass, based on the total amount of the dispersion resin. By having the content of the structural unit A within the above range, the adsorption of the dispersion resin to the colorant is improved, redispersibility after solidification is improved, and ejection stability and ejection characteristics when dried tend to be improved.

[0019] 1.1.2. Building block B The structural unit B is a monomer having a sulfonic acid group, and partially imparts hydrophilicity to the dispersion resin. Although not particularly limited, the structural unit B is oriented on the opposite side to the surface of the colorant, and can contribute to improving dispersibility. The monomer having a sulfonic acid group may be used alone or in combination of two or more kinds.

[0020] The monomer having a sulfonic acid group is not particularly limited, but may be, for example, a vinyl monomer having a sulfonic acid group, a (meth)acrylamide monomer having a sulfonic acid group, or a (meth)acrylic monomer having a sulfonic acid group, and more preferably at least one selected from the group consisting of a vinyl monomer having a sulfonic acid group, an acrylamide monomer having a sulfonic acid group, and an acrylic monomer having a sulfonic acid group.By using such a monomer having a sulfonic acid group, the redispersibility after solidification is improved, and the ejection stability and the ejection characteristics during drying tend to be improved.

[0021] The vinyl monomer having a sulfonic acid group is not particularly limited, but examples thereof include compounds represented by the following formula (1). CH2=CR 1 -R 2 -SO3H (1) (In the formula, R 1 represents a hydrogen atom or a methyl group, R 2 represents a linear, branched, or cyclic alkyl group having 1 to 6 carbon atoms.

[0022] The (meth)acrylamide monomer having a sulfonic acid group is not particularly limited, but examples thereof include compounds represented by the following formula (2). CH=CR 3 CONH-R 4 -SO3H (2) (In the formula, R 3 represents a hydrogen atom or a methyl group, R 4 represents a linear, branched, or cyclic alkyl group having 1 to 6 carbon atoms.

[0023] The (meth)acrylate monomer having a sulfonic acid group is not particularly limited, but examples thereof include compounds represented by the following formula (3). CH=CR 5 COO-R 6 -SO3H (3) (In the formula, R 5 represents a hydrogen atom or a methyl group, R 6 represents a linear, branched, or cyclic alkyl group having 1 to 6 carbon atoms.

[0024] The sulfonic acid group in the monomer having a sulfonic acid group may form a salt, and the salt is not particularly limited, but examples thereof include alkali metal salts such as potassium, alkaline earth metal salts such as calcium and magnesium, ammonium salts, and alkylamine salts.

[0025] Among these, at least one selected from the group consisting of vinyl sulfonic acid or its salt, allyl sulfonic acid or its salt, methallyl sulfonic acid or its salt, methacryl sulfonic acid or its salt, and 2-acrylamido-2-methylpropane sulfonic acid or its salt is preferred. By using such a monomer having a sulfonic acid group, redispersibility after solidification is improved, and ejection stability and ejection characteristics when dried tend to be improved.

[0026] The content of the structural unit B is preferably 3 to 70 mass % relative to the total amount of the dispersion resin, more preferably 5 to 60 mass %, even more preferably 10 to 55 mass %, and even more preferably 15 to 50 mass %. By having the content of the structural unit B within the above range, the hydrophilicity of the dispersion resin is improved, the redispersibility after solidification is improved, and the viscosity tends to be lower.

[0027] 1.1.3. Building Block C The dispersion resin may further include a hydrophilic monomer-containing structural unit C. By including the structural unit C, the affinity with the colorant is improved, and redispersibility, ejection property during drying, and ejection stability tend to be improved.

[0028] The hydrophilic monomer constituting the structural unit C is not particularly limited, and examples thereof include acrylic acid monomers having a carboxyl group, such as acrylic acid and methacrylic acid; and acrylic acid ester monomers, such as 2-hydroxyethyl (meth)acrylate. The hydrophilic acrylic acid monomers may be used alone or in combination of two or more. In this embodiment, "(meth)acrylic acid" includes acrylic acid and methacrylic acid.

[0029] Among these, it is preferable to contain at least one selected from the group consisting of acrylic acid, methacrylic acid, and 2-hydroxyethyl acrylate. By using such a hydrophilic acrylic acid monomer, the adsorption of the dispersion resin to the colorant is improved, redispersibility after solidification is improved, and ejection stability and ejection characteristics when dried tend to be improved.

[0030] The content of the structural unit C is preferably 3 to 70% by mass, more preferably 5 to 60% by mass, even more preferably 10 to 55% by mass, and even more preferably 15 to 50% by mass, based on the total amount of the dispersion resin. By having the content of the structural unit C within the above range, the hydrophilicity of the dispersion resin is improved, redispersibility after solidification is improved, and ejection stability and ejection characteristics when dried tend to be improved.

[0031] 1.1.4. Weight average molecular weight and molecular weight distribution The weight average molecular weight of the dispersion resin is 5000 to 100000, preferably 6000 to 80000, and more preferably 7000 to 60000. When the weight average molecular weight of the dispersion resin is within the above range, redispersibility after solidification is improved, and ejection stability and ejection characteristics when dried tend to be improved.

[0032] The molecular weight distribution (Mw / Mn) of the dispersion resin is preferably 1.05 to 3.00, more preferably 1.05 to 2.00, even more preferably 1.10 to 1.80, and particularly preferably 1.20 to 1.60. By having the molecular weight distribution of the dispersion resin within the above range, the molecular size becomes more uniform, and the redispersibility after solidification is improved, and the ejection stability and the ejection characteristics when dried tend to be improved. Such a relatively narrow molecular weight distribution can be achieved by living radical polymerization, which will be described later.

[0033] The weight average molecular weight and the molecular weight distribution can be measured by a known method, such as a chromatography method, and more specifically, by the method described in the Examples.

[0034] 1.1.5. Manufacturing method The dispersion resin of the present embodiment can be obtained by copolymerizing a hydrophobic monomer, a monomer having a sulfonic acid group, and, if necessary, a hydrophilic monomer. The polymerization reaction is not particularly limited, but for example, radical polymerization, particularly living radical polymerization, can be used.

[0035] 1.2. Compound having a sulfonic acid group and a polymerizable group By including a compound having a sulfonic acid group and a polymerizable group, the wettability and ejection stability of the resulting ink composition are further improved, and the viscosity is further reduced.

[0036] The compound having a sulfonic acid group and a polymerizable group is not particularly limited, but may be, for example, a vinyl compound having a sulfonic acid group, a (meth)acrylamide compound having a sulfonic acid group, or a (meth)acrylic compound having a sulfonic acid group.These compounds are not particularly limited, but may be, for example, those represented by the above formulas (1) to (3).The compound having a sulfonic acid group may be used alone or in combination of two or more.

[0037] The type of the monomer constituting the structural unit B of the dispersion resin and the type of the compound having a sulfonic acid group and a polymerizable group that is independently contained in the dispersion liquid may be the same or different.

[0038] The molecular weight of the compound having a sulfonic acid group and a polymerizable group is 300 or less, preferably 100 to 300, and more preferably 100 to 250. When the molecular weight of the compound having a sulfonic acid group and a polymerizable group is within the above range, the wettability and ejection stability of the resulting ink composition are further improved, and the viscosity is further reduced.

[0039] The content of the compound having a sulfonic acid group and a polymerizable group is preferably 100 to 50,000 ppm, more preferably 200 to 10,000 ppm, and even more preferably 300 to 5,000 ppm, relative to the total amount of the dispersion. When the content of the compound having a sulfonic acid group and a polymerizable group is within the above range, the wettability and ejection stability of the resulting ink composition tend to be further improved, and the viscosity to be further reduced.

[0040] 1.3.Water The water content is preferably 60 to 90% by mass, more preferably 65 to 90% by mass, and further preferably 70 to 85% by mass, based on the total amount of the dispersion.

[0041] 1.4.Colorants The coloring material is not particularly limited, but examples thereof include disperse dyes and pigments. Among these, disperse dyes are preferred. By using disperse dyes, redispersibility after solidification is improved, and ejection stability and ejection characteristics during drying tend to be improved. The coloring material may be used alone or in combination of two or more kinds.

[0042] 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.

[0043] 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.

[0044] Examples of organic pigments include, but are not limited to, 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.

[0045] The content of the coloring material is preferably 7.5 to 30% by mass, more preferably 7.5 to 25% by mass, and further preferably 8.5 to 20% by mass, based on the total amount of the dispersion.

[0046] 1.4.pH adjusters The dispersion liquid may further contain a pH adjuster. The pH adjuster is not particularly limited, but examples thereof include 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 (triethanolamine, diethanolamine, monoethanolamine, tripropanolamine), organic acids (e.g., adipic acid, citric acid, succinic acid, etc.), etc. The pH adjuster may be used alone or in combination of two or more.

[0047] 2. Ink composition for ink-jet 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.

[0048] 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 %, based on the total amount of the ink composition. By having the content of the dispersion resin within the above range, redispersibility after solidification is improved, and ejection stability and ejection characteristics when dried tend to be improved.

[0049] 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, based on the total amount of the ink composition. By having the content of the colorant within the above range, redispersibility after solidification is improved, and ejection stability and ejection characteristics when dried tend to be improved.

[0050] In the ink composition, the content of the dispersion resin is preferably 10 to 80 parts by mass, more preferably 15 to 70 parts by mass, and even more preferably 25 to 60 parts by mass, relative to 100 parts by mass of the colorant. By having the content of the dispersion resin within the above range, redispersibility after solidification is improved, and ejection stability and ejection characteristics when dried tend to be improved.

[0051] 2.2.Surfactants The surfactant is not particularly limited, but examples thereof include acetylene glycol surfactants, fluorine-based surfactants, and silicone-based surfactants.

[0052] The acetylene glycol surfactant is not particularly limited, but for example, one or more selected from 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 are preferred.

[0053] The fluorine-based surfactant is not particularly limited, but examples thereof include perfluoroalkyl sulfonate, perfluoroalkyl carboxylate, perfluoroalkyl phosphate, perfluoroalkyl ethylene oxide adduct, perfluoroalkyl betaine, and perfluoroalkyl amine oxide compound.

[0054] Examples of silicone surfactants include polysiloxane compounds and polyether-modified organosiloxanes.

[0055] 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.

[0056] 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, propylene glycol monomethyl ether, and propylene glycol monoethyl ether. Examples of the water-soluble organic solvent include glycol monoethers such as dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, triethylene glycol monomethyl ether, and triethylene glycol monobutyl 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, iso-butanol, 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 monobutyl ether, and glycerin are more preferred. The water-soluble organic solvent may be used alone or in combination of two or more kinds.

[0057] The content of the water-soluble organic solvent is preferably 5.0 to 30% by mass, more preferably 10 to 20% by mass, based on 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 improved, and ejection stability and ejection characteristics when dried tend to be improved.

[0058] 2.4.Water The water content is preferably 60 to 90% by mass, and more preferably 70 to 85% by mass, based on the total amount of the ink composition. When the water content is within the above range, redispersibility after solidification is improved, and ejection stability and ejection characteristics when dried tend to be improved.

[0059] 2.5. pH Adjusters The ink composition may further contain a pH adjuster. The pH adjuster is not particularly limited, but may be any of those exemplified in the dispersion liquid. The pH adjuster in the ink composition may be one that is mixed originating from the dispersion liquid, or may be one that is added separately when preparing the ink composition.

[0060] 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.

[0061] 2.6.Other resins The ink composition may further contain other resins other than the dispersion resin. The other resins are not particularly limited, but may include, for example, anionic resins, cationic resins, or nonionic resins. By including such resins, the colorant can be fixed to the recording medium.

[0062] 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.

[0063] 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:

[0064] 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.

[0065] The content of the other resin is preferably 0.1 to 2.0 mass %, and more preferably 0.5 to 1.5 mass %, relative to the total amount of the ink composition. EXAMPLES

[0066] 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.

[0067] 1. Synthesis of copolymer 1.1. Synthesis Example 1 In a three-neck flask equipped with a stirrer and a Dimroth condenser, 80 parts by mass of butyl acrylate, 10 parts by mass of acrylic acid, and 10 parts by mass of sodium methallylsulfonate were placed and dissolved in isopropyl alcohol. In a separate glass bottle, 1 part by mass of azobisisobutyronitrile and 10 parts by mass of isopropyl alcohol were placed to prepare an initiator solution.

[0068] After nitrogen bubbling was performed for 20 minutes on the solution in the three-neck flask, the initiator solution was dropped. Then, under a nitrogen atmosphere, the solution was heated to reflux temperature and polymerized for 8 hours. After the reaction was completed, the reactant was dropped into water to precipitate a white solid. The precipitated solid was collected by suction filtration and vacuum dried at 50°C for 10 hours to obtain Dispersion Resin A.

[0069] 1.2. Synthesis Example 2 In a three-neck flask equipped with a stirrer and a Dimroth condenser, 90 parts by mass of butyl acrylate, 5 parts by mass of acrylic acid, 5 parts by mass of sodium methallylsulfonate, and 1 part by mass of 2'-cyanobutan-2'-yl 4-chloro-3,5-dimethylpyrazole-1-carbodithioate were placed and dissolved in isopropyl alcohol. In a separate glass bottle, 1 part by mass of azobisisobutyronitrile and 10 parts by mass of isopropyl alcohol were placed to prepare an initiator solution.

[0070] After nitrogen bubbling was performed for 20 minutes on the solution in the three-neck flask, the initiator solution was dropped. Then, the solution was heated to reflux temperature under a nitrogen atmosphere and polymerized for 8 hours. After the reaction was completed, the reactant was dropped into water to precipitate a white solid. The precipitated solid was collected by suction filtration and vacuum dried at 50°C for 10 hours to obtain Dispersion Resin B.

[0071] 1.3. Synthesis Examples 3 to 10 Dispersion resins C to Z were synthesized in the same manner as in Synthesis Example 2, except that the types and amounts of the monomers used were changed so as to obtain the dispersion resins shown in Table 1 below.

[0072] 1.4. Weight average molecular weight and molecular weight distribution The weight average molecular weight and the molecular weight distribution (Mw / Mn) of each of the dispersed resins obtained as described above were measured by a chromatography method under the following conditions. (Measurement conditions) Device name: HLC8320GPC (Tosoh) Guard column: TSKgel guarcolumn SuperAWM-H Column: TSKgel SuperAWM-H Column temperature: 25℃ Eluent: 10mmol / L lithium bromide in dimethylacetamide Flow rate: 0.6 mL / mIn Detector: RI

[0073] [Table 1] BA: Butyl acrylate St: styrene AA: Acrylic acid MAA: Methacrylic acid HEA: 2-hydroxyethyl acrylate MSA: Sodium methallyl sulfonate ASA: Sodium allyl sulfonate VSH: Vinyl sulfonic acid ATBS: 2-acrylamido-2-methylpropanesulfonic acid

[0074] 2. Preparation of Varnish Solution In a 1 L eggplant flask equipped with a stirrer and a Dimroth condenser, 10 parts by mass of the copolymer and 70 parts by mass of pure water were added, and the mixture was heated to 80° C. and stirred. Triethanolamine was added to the mixture until the pH reached 8.0, and a compound having a sulfonic acid group and a polymerizable group shown in Table 2 below was added, and pure water was further added until the total amount became 100 parts by mass. The mixture was then cooled to 25° C. to obtain a varnish solution containing 10% by mass of the copolymer.

[0075] [Table 2]

[0076] 3. Preparation of Dispersions 100 parts by weight of the varnish liquid and 20 parts by weight of DISPERSE YELLOW 232 were added, and the mixture was thoroughly mixed by dispersion treatment using a bead mill to which zirconia beads having a diameter of 0.3 mm were added, to obtain a dispersion containing 8.3% by weight of the copolymer and 16.7% by weight of the colorant.

[0077] [Table 3]

[0078] 4. Preparation of Ink Composition Each ink composition was obtained by mixing the dispersion liquid and other components so as to obtain the composition shown in Table 4. Table 4 also shows the composition of the ink water used in the redispersibility test described later.

[0079] 5. Evaluation 5.1.Wettability The surface tension of the ink composition prepared as described above was measured by the Wilhelmy method using a surface tensiometer (such as CBVP-Z surface tensiometer manufactured by Kyowa Interface Science Co., Ltd.) at a liquid temperature of 25° C. The wettability was evaluated based on the obtained surface tension value. (Evaluation Criteria) A: Surface tension is 30mN / m or less B: Surface tension is between 30mN / m and 45mN / m or less C: Surface tension exceeds 45mN / m

[0080] 5.2.Viscosity The viscosity of the ink composition prepared as described above was measured using a rheometer PHYSICA MCR300 manufactured by Anton Paar, and evaluated in terms of η1 / η2, which is the ratio of the viscosity η1 at a shear rate of 10 s-1 to the viscosity η2 at a shear rate of 1000 s-1. (Evaluation Criteria) A: The above viscosity ratio is 1.3 or less B: The above viscosity ratio is more than 1.3 and 1.5 or less. C: The above viscosity ratio exceeds 1.5

[0081] 5.3. Redispersibility The ink composition prepared as above was dropped onto a glass slide and dried in a dryer at 40°C for 16 hours to solidify. The glass slide was then immersed in a sample bottle containing ink water, and the redispersion behavior of the solid matter was visually confirmed. Note that the operation was performed with care not to stir the ink water. Note that the ink water in Table 2 above does not contain coloring material and dispersing resin. The evaluation criteria for redispersibility are shown below. (Evaluation Criteria) A: The solid matter disappeared and redispersed. B: Some solid matter remained, but redispersion was observed. C: Solid matter remained and no redispersion was observed.

[0082] 5.4.Discharge stability An ink jet recording ink composition was filled into an ink jet 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 confirm nozzles with worsened landing position deviation. The number of nozzles was 180. The evaluation criteria were as follows. If the evaluation result was A or B, it was judged 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 more than 1% and less than 5%. C: The number of nozzles with worsening landing position deviation exceeds 5%.

[0083] 5.5.Dry discharge characteristics The ink composition for inkjet recording 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 ink composition was left for one day. After the ink composition was left for one day, cleaning was performed once, and 20 pages were continuously printed while ejecting from all nozzles, and the number of nozzles with missing prints and bent prints was evaluated based on the following criteria. If the evaluation result was A or B, the ink composition was judged to be good. (Evaluation Criteria) A: Nozzle with no missing or bent parts B: Missing or bending: 1 to 5 nozzles C: Missing or bending: 6 or more nozzles

[0084] [Table 4] BYK-348: Silicone surfactant, manufactured by BYK-Chemie Olfine E1010: Acetylene glycol surfactant, manufactured by Nissin Chemical Industry Co., Ltd.

[0085] As described above, it can be seen that the ink compositions of the examples using the dispersion liquid of the present invention have superior wettability and redispersibility, improved ejection characteristics when dried, and excellent ejection stability, compared to the comparative examples.

Claims

1. The ink contains water, a colorant, a dispersion resin for dispersing the colorant, and a compound having a sulfonic acid group and a polymerizable group, The dispersion resin has a structural unit A including a hydrophobic monomer and a structural unit B including a monomer having a sulfonic acid group, The weight average molecular weight of the dispersion resin is 5,000 to 100,000; The molecular weight of the compound is 300 or less, The content of the compound is 100 to 50,000 ppm based on the total amount of the dispersion. dispersion liquid.

2. The molecular weight distribution of the dispersion resin is 1.05 to 2.

00. The dispersion of claim 1.

3. The monomer having a sulfonic acid group includes at least one selected from the group consisting of a vinyl monomer having a sulfonic acid group, an acrylamide monomer having a sulfonic acid group, and an acrylic monomer having a sulfonic acid group.

3. The dispersion according to claim 1 or 2.

4. the monomer having a sulfonic acid group includes at least one selected from the group consisting of vinyl sulfonic acid or a salt thereof, allyl sulfonic acid or a salt thereof, methallylsulfonic acid or a salt thereof, methacrylsulfonic acid or a salt thereof, and 2-acrylamido-2-methylpropanesulfonic acid or a salt thereof; The dispersion according to any one of claims 1 to 3.

5. The hydrophobic monomer includes a vinyl monomer having an aromatic group and an acrylic ester monomer having a hydrocarbon group. The dispersion according to any one of claims 1 to 4.

6. The content of the structural unit A is 10 to 90 mass% based on the total amount of the dispersion resin. The dispersion according to any one of claims 1 to 5.

7. The content of the structural unit B is 3 to 70 mass% based on the total amount of the dispersion resin. The dispersion according to any one of claims 1 to 6.

8. The dispersion resin further has a structural unit C containing a hydrophilic monomer. The dispersion according to any one of claims 1 to 7.

9. The hydrophilic monomer includes at least one selected from the group consisting of acrylic acid, methacrylic acid, and 2-hydroxyethyl acrylate. 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. The dispersion liquid according to any one of claims 1 to 10, a surfactant, and a water-soluble organic solvent; Including, An ink composition for ink-jet recording.

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