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

Abstract

To provide a dispersion liquid or the like that enable a solidified coloring material to be easily re-dispersed and allows improved stability during re-ejection after drying.SOLUTION: A dispersion liquid includes water, a coloring material, and a dispersion resin that disperses the coloring material. The dispersion resin has a constituent unit A containing a hydrophobic monomer, a constituent unit B containing a hydrophilic acrylic acid monomer, and a constituent unit C containing a hydrophilic vinyl monomer having a sulfonate group, and a weight-average molecular weight of the dispersion resin is 10,000 to 100,000. A content of the constituent unit A is 60 mol% or more relative to a total amount of the dispersion resin.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 relates to a dispersion liquid that includes water, a colorant, and a dispersion resin that disperses the colorant, the dispersion resin having a structural unit A including a hydrophobic monomer, a structural unit B including a hydrophilic acrylic acid monomer, and a structural unit C including a hydrophilic vinyl monomer having a sulfonic acid group, the weight-average molecular weight of the dispersion resin being 10,000 to 100,000, and the content of the structural unit A being 60 mol % or more relative to the total amount of the dispersion resin.

[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.

[0007] Furthermore, the present invention relates to a dispersion resin having a structural unit A containing a hydrophobic monomer, a structural unit B containing a hydrophilic acrylic acid monomer, and a structural unit C containing a hydrophilic vinyl monomer having a sulfonic acid group, the weight average molecular weight of the dispersion resin being 10,000 to 100,000, and the content of the structural unit A being 60 mol% or more relative to the total amount of the dispersion resin. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] 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.

[0009] 1.Dispersion liquid The dispersion liquid of the present embodiment contains water, a colorant, and a dispersion resin that disperses the colorant. The dispersion resin has a structural unit A containing a hydrophobic monomer, a structural unit B containing a hydrophilic acrylic acid monomer, and a structural unit C containing a hydrophilic vinyl monomer having a sulfonic acid group, and the weight average molecular weight of the dispersion resin is 10,000 to 100,000, and the content of the structural unit A is 60 mol% or more relative to the total amount of the dispersion resin.

[0010] A dispersion liquid or ink composition using a conventional 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, it is possible to easily redisperse the solidified coloring material, and further improve the re-ejection property (hereinafter also referred to as "ejection characteristic when dry") of the ink in the nozzle even when it dries. Each component will be described in detail below.

[0011] 1.1.Dispersion resin The dispersion resin of this embodiment is a copolymer having a structural unit A containing a hydrophobic monomer, a structural unit B containing a hydrophilic acrylic acid monomer, and a structural unit C containing a hydrophilic vinyl 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.

[0012] The dispersion resin may be a random copolymer or a block copolymer. Examples of the block copolymer include a triblock copolymer having a block A composed of a structural unit A, a block B composed of a structural unit B, and a block C composed of a structural unit C, 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 a structural unit C. By using such a dispersion resin, the redispersibility after solidification is improved, and the ejection characteristics when dried tend to be improved.

[0013] The content of the dispersion resin is preferably 2.5 to 12.5% ​​by mass, more preferably 3.5 to 10% by mass, and even more preferably 4.5 to 9.0% 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 the ejection characteristics when dried tend to be improved.

[0014] 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 the ejection characteristics when dried tend to be improved.

[0015] 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.

[0016] 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.

[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 benzyl acrylate. By using such a hydrophobic monomer, the adsorption of the dispersion resin to the coloring material is improved, the redispersibility after solidification is improved, and the ejection characteristics when dried tend to be improved.

[0018] The content of the structural unit A is 60 mol% or more, preferably 62 to 90 mol%, and more preferably 62 to 82 mol% based on the total amount of the dispersion resin. When the content of the structural unit A is 60 mol% or more, the adsorption of the dispersion resin to the coloring material is further improved. In addition, when the content of the hydrophobic structural unit A is 60 mol% or more, the hydrophilicity of the dispersion resin itself is usually reduced, but the dispersion resin of this embodiment can ensure the water solubility of the dispersion resin due to the contribution of other structural units, particularly the structural unit C. This tends to further improve the adsorption of the dispersion resin to the coloring material, further improve the redispersibility after solidification, and further improve the ejection characteristics when dried.

[0019] 1.1.2. Building block B The structural unit B is a structural unit containing a hydrophilic acrylic acid monomer, 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. Furthermore, the structural unit B softens the structural unit A and the structural unit C, which have significantly different polarities, and by having the structural unit B, the affinity with the colorant is further improved, and the redispersibility, the ejection property during drying, and the ejection stability are further improved.

[0020] The hydrophilic acrylic acid monomer constituting the structural unit B 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.

[0021] Among these, it is preferable to contain at least one 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, the redispersibility after solidification is improved, and the ejection characteristics when dried tend to be improved.

[0022] The molecular weight of the hydrophilic acrylic acid monomer constituting the structural unit B is preferably less than 300, and more preferably 70-290.

[0023] The content of the structural unit B is preferably 3 to 25 mol%, more preferably 5 to 20 mol%, and even more preferably 8 to 18 mol%, based on the total amount of the dispersion resin. 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 ejection characteristics when dried tend to be improved.

[0024] 1.1.3. Building Block C The structural unit C is a structural unit containing a hydrophilic vinyl monomer having a sulfonic acid group, and partially imparts hydrophilicity to the dispersion resin. Although not particularly limited, the structural unit C is oriented on the side opposite to the surface of the colorant, and can contribute to improving dispersibility.

[0025] The hydrophilic vinyl monomer having a sulfonic acid group constituting the structural unit C is not particularly limited, and may be, for example, a compound represented by the following formula (1). Among these, vinyl sulfonic acid is more preferable. By using such a hydrophilic vinyl monomer, the hydrophilicity of the dispersion resin is improved even if the hydrophilic portion is reduced, the redispersibility after solidification is improved, and the ejection characteristics when dried tend to be improved. The hydrophilic vinyl monomer may be used alone or in combination of two or more kinds. CH 2 =CH-R-SO 3 H (1) (In the formula, R represents a linear, branched, or cyclic alkyl group having 1 to 6 carbon atoms.)

[0026] The sulfonic acid group in the hydrophilic vinyl monomer 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.

[0027] The content of the structural unit C is preferably 5.0 to 30 mol%, more preferably 7.5 to 25 mol%, and even more preferably 10 to 20 mol% 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, the redispersibility after solidification is improved, and the ejection characteristics when dried tend to be improved. In particular, by having the structural unit C, the redispersibility after solidification is improved.

[0028] 1.1.4. Weight average molecular weight and molecular weight distribution The weight average molecular weight of the dispersion resin is 10,000 to 100,000, preferably 10,000 to 80,000, and more preferably 10,000 to 60,000. When the weight average molecular weight of the dispersion resin is within the above range, redispersibility after solidification is improved, and the ejection characteristics when dried tend to be improved.

[0029] The molecular weight distribution (Mw / Mn) of the dispersion resin is preferably 1.05 to 2.00, more preferably 1.10 to 1.90, even more preferably 1.20 to 1.85, and particularly preferably 1.30 to 1.80. 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 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.

[0030] 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.

[0031] 1.1.5. Manufacturing method The dispersion resin of the present embodiment can be obtained by copolymerizing a hydrophobic monomer, a hydrophilic acrylic acid monomer, and a hydrophilic vinyl monomer having a sulfonic acid group. The polymerization reaction is not particularly limited, but for example, radical polymerization, particularly living radical polymerization, can be used.

[0032] 1.2.Water The water content is preferably 60 to 95% by mass, more preferably 65 to 95% by mass, and further preferably 75 to 90% by mass, based on the total amount of the dispersion.

[0033] 1.3.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 characteristics during drying tend to be improved. The coloring material may be used alone or in combination of two or more kinds.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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 the ejection characteristics when dried tend to be improved.

[0041] 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 the ejection characteristics when dried tend to be improved.

[0042] 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 the ejection characteristics when dried tend to be improved.

[0043] 2.2.Surfactants The surfactant is not particularly limited, but examples thereof include acetylene glycol surfactants, fluorine-based surfactants, and silicone-based surfactants.

[0044] 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.

[0045] 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.

[0046] Examples of silicone surfactants include polysiloxane compounds and polyether-modified organosiloxanes.

[0047] 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.

[0048] 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 the water-soluble organic solvent include glycol monoethers such as ethyl 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, 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 monomethyl ether, and glycerin are more preferred. The water-soluble organic solvent may be used alone or in combination of two or more.

[0049] 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 the ejection characteristics when dried tend to be improved.

[0050] 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 the ejection characteristics when dried tend to be improved.

[0051] 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.

[0052] The content of the pH adjuster 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.

[0053] 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.

[0054] 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.

[0055] 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:

[0056] 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.

[0057] 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

[0058] 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.

[0059] 1. Synthesis of copolymer 1.1. Manufacturing Example 1 In a three-neck flask equipped with a stirrer and a Dimroth condenser, 82 parts by mass of styrene (manufactured by Tokyo Chemical Industry Co., Ltd.), 10 parts by mass of vinyl sulfonic acid (manufactured by Asahi Kasei Corporation), and 8 parts by mass of acrylic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) were placed and dissolved in 30 parts by mass of N,N-dimethylformamide (manufactured by Tokyo Chemical Industry Co., Ltd.) In a separate glass bottle, 1 part by mass of azobisisobutyronitrile (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and 10 parts by mass of N,N-dimethylformamide (manufactured by Tokyo Chemical Industry Co., Ltd.) were placed to prepare an initiator solution.

[0060] 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 1. The weight average molecular weight of the obtained Dispersion Resin was 15414.

[0061] 1.2. Manufacturing Examples 2 to 8 Dispersion resins 2 to 8 were synthesized in the same manner as in Production Example 1, except that the type and amount of the monomer used was changed so as to obtain the dispersion resins shown in Table 1 below.

[0062] 1.3. 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: Super AW-L Column: Super AW3000 Column temperature: 25℃ Eluent Dimethylacetamide: Flow rate: 0.6 mL / min Detector RI:

[0063] [Table 1] St: styrene BzA: benzyl acrylate BA: Butyl acrylate AA: Acrylic acid MAA: Methacrylic acid HEA: 2-hydroxyethyl acrylate VS A : Vinyl sulfonic acid

[0064] 2. Preparation of Varnish Solution In a 1 L eggplant flask equipped with a stirrer and a Dimroth condenser, 15 parts by mass of the copolymer and 70 parts by mass of pure water were added, heated to 80°C, and stirred. Triethanolamine was added to the mixture until the pH reached 8.0, and pure water was further added to make the total amount 100 parts by mass. The mixture was then cooled to 25°C to obtain a varnish solution containing 15% by mass of the copolymer.

[0065] 3. Preparation of Dispersions 50 parts by weight of the varnish liquid, 15 parts by weight of DISPERSE YELLOW 82, and 35 parts by weight of pure water were added, and the mixture was thoroughly mixed by dispersion processing using a bead mill to which zirconia beads having a diameter of 0.3 mm were added, to obtain a dispersion containing 7.5% by weight of the copolymer and 15% by weight of the colorant.

[0066] 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 2. Table 2 also shows the composition of the ink water used in the redispersibility test described later.

[0067] 5. Evaluation 5.1. 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.

[0068] 5.2.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%. 5.3.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

[0069] [Table 2] BYK-348: Silicone surfactant, manufactured by BYK-Chemie Olfine E1010: Acetylene glycol surfactant, manufactured by Nissin Chemical Industry Co., Ltd.

[0070] 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 for dispersing the colorant (excluding a resin for encapsulating a pigment and core / shell type resin particles), The dispersion resin has a structural unit A including a vinyl monomer having an aromatic group as a hydrophobic monomer, a structural unit B including at least one of acrylic acid, methacrylic acid, and 2-hydroxyethyl acrylate as a hydrophilic acrylic acid monomer, and a structural unit C including vinyl sulfonic acid or a hydrophilic vinyl monomer having a sulfonic acid group represented by formula (1), CH2=CH-R-SO3H... (1) (In the formula, R represents a linear, branched, or cyclic alkyl group having 1 to 6 carbon atoms.) The weight average molecular weight of the dispersion resin is 10,000 to 100,000; The content of the structural unit A is 60 mol% or more based on the total amount of the dispersion resin. dispersion liquid.

2. The molecular weight distribution (Mw / Mn) of the dispersion resin is 1.05 to 2.

00. The dispersion of claim 1.

3. The content of the structural unit A is 62 to 82 mol% based on the total amount of the dispersion resin.

3. The dispersion according to claim 1 or 2.

4. The content of the structural unit B is 8 to 18 mol% based on the total amount of the dispersion resin. The dispersion according to any one of claims 1 to 3.

5. The content of the structural unit C is 10 to 20 mol% based on the total amount of the dispersion resin. The dispersion according to any one of claims 1 to 4.

6. The hydrophobic monomer further comprises an acrylic ester monomer having a hydrocarbon group. The dispersion according to any one of claims 1 to 5.

7. The colorant is a disperse dye. The dispersion according to any one of claims 1 to 6.

8. The content of the coloring material is 7.5 to 30% by mass based on the total amount of the dispersion liquid. The dispersion according to any one of claims 1 to 7.

9. The content of the dispersion resin is 2.5 to 12.5% ​​by mass based on the total amount of the dispersion liquid. The dispersion according to any one of claims 1 to 8.

10. The dispersion liquid according to any one of claims 1 to 9, a surfactant, and a water-soluble organic solvent; Including, An ink composition for ink-jet recording.

11. A dispersion resin (excluding resins that encapsulate pigments and core / shell type resin particles), comprising: The composition has a structural unit A containing a vinyl monomer having an aromatic group as a hydrophobic monomer, a structural unit B containing at least one of acrylic acid, methacrylic acid, and 2-hydroxyethyl acrylate as a hydrophilic acrylic acid monomer, and a structural unit C containing vinyl sulfonic acid or a hydrophilic vinyl monomer having a sulfonic acid group represented by formula (1), CH2=CH-R-SO3H... (1) (In the formula, R represents a linear, branched, or cyclic alkyl group having 1 to 6 carbon atoms.) The weight average molecular weight of the dispersion resin is 10,000 to 100,000; The content of the structural unit A is 60 mol% or more based on the total amount of the dispersion resin. Dispersion resin.

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