Ink composition, ink cartridge, and liquid dispensing device

Abstract

To provide an ink composition with excellent image density and gloss. [Solution] An ink composition comprising a pigment, a dispersant, and a leveling agent, wherein the dispersant is a compound represented by the following general formula (1), and the leveling agent comprises an acrylic block copolymer. TIFF2026139128000011.tif50164 (In general formula (1), R 1 (where represents an alkyl group, allyl group, or aralkyl group with 1 to 20 carbon atoms, L represents an integer between 0 and 7, and n represents an integer between 20 and 200)

Description

[Technical Field]

[0001] The present invention relates to an ink composition, an ink cartridge, and a liquid ejection apparatus. [Background Art]

[0002] Conventionally, in inkjet recording, pigment inks have been applied to inkjet recording methods instead of dye inks, in order to solve the problems of light resistance, water resistance and ozone resistance (see, for example, Patent Document 1).

[0003] When recording on plain paper using a pigment ink, the pigment permeates into the recording medium instead of remaining on the paper surface, resulting in a low pigment density on the paper surface. Therefore, it is necessary to increase the pigment concentration of the ink to obtain a high image density on plain paper.

[0004] However, when recording on poorly permeable media such as coated paper and art paper, or non-permeable films, the pigment remains on the surface of the recording medium. Therefore, if the pigment concentration in the ink is high, the dot height increases, unevenness occurs on the surface, and there has been a problem that an image with low gloss is obtained. Further, although a higher image density can be obtained in plain paper printing as the amount of the pigment as a coloring material increases, there has been a problem that when the same ink is used, the image glossiness is lost on coated paper or art paper. [Summary of the Invention] [Problem to be Solved by the Invention]

[0005] An object of an ink composition according to one embodiment of the present invention is to provide an ink composition excellent in image density and glossiness. [Means for Solving the Problem]

[0006] An ink composition according to one embodiment of the present invention is an ink composition containing a pigment, a dispersant, and a leveling agent, wherein the dispersant is a compound represented by the following general formula (1), The leveling agent comprises an acrylic block copolymer, which is characterized by being an ink composition. [Chemical formula] (In General Formula (1), R 1 represents any one selected from an alkyl group having 1 to 20 carbon atoms, an allyl group, and an aralkyl group, L represents an integer of 0 to 7, and n represents an integer of 20 to 200) [Effects of the Invention]

[0007] According to the ink composition of one aspect of the present invention, an ink composition excellent in image density and glossiness can be provided. [Brief Description of the Drawings]

[0008] [Figure 1] FIG. 1 is a diagram illustrating an example of the ink cartridge according to the present embodiment. [Figure 2] FIG. 2 is an explanatory diagram including the case of the ink cartridge according to the present embodiment. [Figure 3] FIG. 3 is a schematic diagram illustrating an example of the liquid ejection apparatus according to the present embodiment. [Figure 4] FIG. 4 is a block diagram illustrating an example of a control configuration of the liquid ejection apparatus according to the present embodiment. [Figure 5] FIG. 5 is a plan view illustrating an example of a nozzle configuration of a recording head of the liquid ejection apparatus according to the present embodiment. [Figure 6] FIG. 6 is a schematic diagram simply illustrating an example of colors of respective nozzle arrays of the liquid ejection apparatus according to the present embodiment. [Mode for Carrying Out the Invention]

[0009] (Ink Composition) The ink composition according to the present embodiment includes a pigment, a dispersant, and a leveling agent, preferably further includes a resin, an organic solvent, and water, and may include other components as necessary. <Pigment> There are no particular restrictions on the pigments used; they can be appropriately selected according to the purpose. Examples include inorganic pigments and organic pigments. These may be used individually or in combination of two or more. Pigments and dyes may also be used in combination. Mixed crystals may also be used.

[0010] Examples of inorganic pigments include titanium dioxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, and chromium yellow. Furthermore, carbon black produced by known methods such as the contact method, furnace method, and thermal method can be used.

[0011] Examples of organic pigments include azo pigments, polycyclic pigments (e.g., phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, etc.), nitro pigments, nitroso pigments, and aniline black.

[0012] Pigments with good affinity to the solvent are preferred. Other options include the use of resin hollow particles and inorganic hollow particles.

[0013] There are no particular restrictions on the type of pigment used; it can be selected appropriately depending on the purpose. Examples include color pigments such as black, yellow, magenta, cyan, white, green, and orange pigments, as well as glossy and metallic pigments such as gold and silver.

[0014] Examples of black pigments include carbon blacks (CI Pigment Black 7) such as furnace black, lamp black, acetylene black, and channel black; metals such as copper, iron (CI Pigment Black 11), and titanium dioxide; and organic pigments such as aniline black (CI Pigment Black 1).

[0015] Examples of color pigments include CI Pigment Yellow 1, 3, 12, 13, 14, 17, 24, 34, 35, 37, 42 (yellow iron oxide), 53, 55, 74, 81, 83, 95, 97, 98, 100, 101, 104, 108, 109, 110, 117, 120, 138, 150, 153, 155, 180, 185, 213, and CI Pigment O Range 5, 13, 16, 17, 36, 43, 51, CI Pigment Red 1, 2, 3, 5, 17, 22, 23, 31, 38, 48:2, 48:2 (Permanent Red 2B(Ca)), 48:3, 48:4, 49:1, 52:2, 53:1, 57:1 (Brilliant Carmine 6B), 60:1, 63:1, 63:2, 64:1, 81, 83, 88, 101 (Bengara), 104, 105, 106, 108 (Cadmium Red), 112, 114, 122 (Quinacridone Magenta), 123, 146, 149, 166, 168, 170, 172, 177, 178, 179, 184, 185, 190, 193, 202, 207, 208, 209, 213, 219, 224, 254, 264, CI Pig Examples include Menthol Violet 1 (Rhodamine Lake), 3, 5:1, 16, 19, 23, 38; CI Pigment Blue 1, 2, 15 (Phthalocyanine Blue), 15:1, 15:2, 15:3, 15:4 (Phthalocyanine Blue), 16, 17:1, 56, 60, 63; and CI Pigment Green 1, 4, 7, 8, 10, 17, 18, 36.

[0016] There are no particular restrictions on the dyes used; they can be selected appropriately depending on the purpose. Examples include acid dyes, direct dyes, reactive dyes, basic dyes, and dye chelates (e.g., basic dye type chelates, acid dye type chelates, etc.). These may be used individually or in combination of two or more. Examples of the aforementioned dyes include CI Acid Yellow 17, 23, 42, 44, 79, 142; CI Acid Red 52, 80, 82, 249, 254, 289; CI Acid Blue 9, 45, 249; CI Acid Black 1, 2, 24, 94; CI Food Black 1, 2; CI Direct Yellow 1, 12, 24, 33, 50, 55, 58, 86, 132, 142, 144, 173; CI Direct Red 1, 4, 9, 80, 81, 225, 227; CI Direct Blue 1, 2, 15, 71, 86, 87, 98, 165, 199, 202; CI Direct Black 19, 38, 51, 71, 154, 168, 171, 195; and CI Reactive Red. Examples include 14, 32, 55, 79, 249, and CI Reactive Black 3, 4, 35.

[0017] The pigment content is preferably 0.1% to 15% by mass, and more preferably 1% to 10% by mass, relative to the total ink composition, from the viewpoint of improving image density, good fixation, and ejection stability.

[0018] In the ink composition according to this embodiment, the pigment is contained in the ink composition in a state dispersed by a dispersant.

[0019] <Dispersant> The dispersant is a compound represented by the following general formula (1). By using the compound represented by the following general formula (1) as a dispersant, high gloss can be obtained when printing on coated paper or art paper. In addition, aqueous pigment dispersions and aqueous inks with small volume-average particle size and excellent storage stability can be obtained. [ka] (In general formula (1), R 1 (where represents an alkyl group, allyl group, or aralkyl group with 1 to 20 carbon atoms, L represents an integer between 0 and 7, and n represents an integer between 20 and 200)

[0020] The dispersant content is preferably 0.01% to 0.5% by mass relative to the pigment, and more preferably 0.1% to 0.4% by mass. When the dispersant content is 0.01% to 0.5% by mass, an ink composition with a small volume-average particle size can be obtained, resulting in good pigment dispersibility and an appropriate viscosity for the ink composition.

[0021] <Leveling agent> Leveling agents are additives that reduce the surface tension of the coating film formed by the ink composition, thereby reducing the height of ink dots on the paper. The leveling agent includes an acrylic block copolymer.

[0022] Acrylic block copolymers are block copolymers having multiple (meth)acrylic polymers, which are formed by polymerizing (meth)acrylic monomers, as segments. Examples of acrylic block copolymers include block copolymers containing hydrophobic blocks and hydrophilic blocks.

[0023] There are no particular restrictions on the amine value of the acrylic block copolymer, and it can be appropriately selected depending on the purpose, but a value of 5 mg KOH / g or more is preferred, 10 mg KOH / g or more is more preferred from the viewpoint of superior glossiness, and 15 mg KOH / g or more is particularly preferred.

[0024] As the acrylic block copolymer, commercially available products may be used, or products synthesized as appropriate may be used. Examples of commercially available products include BYKJET-9151 (manufactured by BIC Chemie Japan, amine value: 18 mg KOH / g), DISPERBYK-2008 (manufactured by BIC Chemie Japan, amine value: 66 mg KOH / g), DISPERBYK-2012 (manufactured by BIC Chemie Japan, amine value: 7 mg KOH / g), DISPERBYK-2050 (manufactured by BIC Chemie Japan, amine value: 30.7 mg KOH / g), DISPERBYK-2055 (manufactured by BIC Chemie Japan, amine value: 45.1 mg KOH / g), DISPERBYK-2150 (manufactured by BIC Chemie Japan, amine value: 56.7 mg KOH / g), and DISPERBYK-2155 (manufactured by BIC Chemie Japan, amine value: 52.5 mg KOH / g).

[0025] There are no particular restrictions on the content of the acrylic block copolymer, and it can be appropriately selected depending on the purpose. However, it is preferable that it be 0.1% by mass or more and 5.0% by mass or less relative to the total amount of the ink composition, and 0.1% by mass or more and 1.0% by mass or less is preferable in terms of excellent image density on plain paper.

[0026] <Resin> The resin is included in the ink composition in the form of resin particles. The resin may also be included in the ink composition in a form other than resin particles.

[0027] The resin particles used are those with film-forming properties. Here, film-forming property refers to the property that when the resin particles are dispersed in water to form an emulsion, a resin film is formed when the water in this aqueous emulsion is evaporated.

[0028] When resin particles are included, they form a film when the volatile components in the water-based recording ink evaporate, firmly fixing the colorants in the water-based fluorescent ink to the recording medium. This makes it possible to achieve images with excellent scratch resistance and water resistance.

[0029] There are no particular restrictions on the type of resin particles, and they can be appropriately selected according to the purpose, but good adhesion can be obtained by using polyurethane resin and polyacrylic resin in combination.

[0030] Since the resin particles form a film at room temperature, those with a minimum film-forming temperature of 30°C or lower are preferred, and those with a minimum film-forming temperature of 10°C or lower are more preferred. Here, the minimum film-forming temperature refers to the lowest temperature at which a transparent, continuous film is formed when a resin emulsion obtained by dispersing resin particles in water is thinly cast onto a metal plate such as aluminum, and the temperature is increased. Examples of such resin particles include the Randy PL series manufactured by Miyoshi Oil & Fat Co., Ltd.

[0031] The volume-average particle diameter of the resin particles is preferably 5 to 200 nm, and more preferably 10 to 100 nm.

[0032] As resin particles, single-particle structures can be used. For example, if emulsion particles contain alkoxysilyl groups, they come into contact with remaining moisture as the emulsions fuse together due to water evaporation during the coating film formation process, and undergo hydrolysis to form silanol groups. Furthermore, if silanol groups remain, they can react with each other, either with alkoxysilyl groups or silanols, to form a strong crosslinked structure with siloxane bonds. In this way, by coexisting reactive functional groups within resin microparticles, a network structure can be formed during film formation by allowing these functional groups to react without the need to add a curing agent. Resin particles can be obtained by known methods such as emulsion polymerization of an unsaturated vinyl monomer (unsaturated vinyl resin) in water in the presence of a polymerization catalyst and an emulsifier. The resin particle content in the ink is preferably 0.5% to 20% by mass, and more preferably 1% to 5% by mass. If the content is less than 0.5% by mass, the functions of improving abrasion resistance and water resistance may not be sufficiently exhibited, and if it exceeds 20% by mass, problems such as poor dispensing may occur due to increased viscosity due to drying and adhesion of resin components.

[0033] The method for calculating the SP value of the resin particles differs from the method for calculating the SP value of the water-soluble organic solvent. Instead, it is calculated by turbidity titration using the following formulas by KWSUH and JMCORBETT.

[0034] [Mathematics 1] SP value of resin particles = {(Vml)¹ / ² × δH + (Vmh)¹ / ² × δD} / {(Vml)¹ / ² + (Vmh)¹ / ²} Here, Vml, Vmh, δH, and δD are values ​​calculated by applying the following formula to the titration volume H (mL) at the turbidity point when n-hexane is added to 0.5 g (solid content) of resin particles dissolved in 10 mL of acetone at a measurement temperature of 20°C, and the titration volume D (mL) at the turbidity point when deionized water is added to 0.5 g (solid content) of resin dissolved in 10 mL of acetone at a measurement temperature of 20°C. Vml=74.4×130.3 / {(1-VH)×130.3+VH×74.4} Vmh=74.4×18 / {(1-VD)×18+VD×74.4} VH = H / (10 + H) VD = D / (10 + D) δH=9.75×10 / (10+H)+7.24×H / (10+H) δD=9.75×10 / (10+D)+23.43×D / (10+D) The molecular volume (mL / mol) of each solvent is acetone: 74.4, n-hexane: 130.3, and deionized water: 18. The SP values ​​of each solvent are acetone: 9.75, n-hexane: 7.24, and deionized water: 23.43. The SP value of the obtained resin is expressed in units of (cal / cm³). 3 ) 0.5.

[0035] <Organic solvents> In the ink composition according to this embodiment, water is used as the solvent, but it is preferable to use a water-soluble organic solvent to prevent the ink from drying out and to improve the dispersion stability of the pigment. These water-soluble organic solvents may be used in combination.

[0036] There are no particular restrictions on the water-soluble organic solvents, and they can be appropriately selected depending on the purpose. Examples include polyhydric alcohols, polyhydric alcohol alkyl ethers, polyhydric alcohol aryl ethers, nitrogen-containing heterocyclic compounds, amides, amines, sulfur-containing compounds, propylene carbonate, ethylene carbonate, and the like.

[0037] Examples of polyhydric alcohols include glycerin, 1,3-butanediol, 3-methyl-1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, hexylene glycol, trimethylolethane, trimethylolpropane, glycerol, 1,2,3-butanetriol, 1,2,4-butanetriol, 1,2,6-hexanetriol, and petriol.

[0038] Examples of polyhydric alcohol alkyl ethers include ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, and propylene glycol monoethyl ether.

[0039] Examples of polyhydric alcohol aryl ethers include ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether.

[0040] Examples of nitrogen-containing heterocyclic compounds include 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 1,3-dimethylimidazolidinone, ε-caprolactam, and γ-ptylolactone.

[0041] Examples of amides include acetamide, dimethylformamide, and diethylacetamide.

[0042] Examples of amines include monoethanolamine, diethanolamine, triethanolamine, monoethylamine, diethylamine, and triethylamine. Examples of sulfur-containing compounds include dimethyl sulfoxide, sulfolane, and thiodiethanol.

[0043] Among these water-soluble organic solvents, glycerin, diethylene glycol, 1,3-butanediol, and 3-methyl-1,3-butanediol are preferred. These organic solvents offer excellent solubility and prevent poor spray characteristics due to water evaporation, and allow for the creation of ink compositions with excellent storage stability and discharge stability.

[0044] In addition to the water-soluble organic solvents described above, the ink composition according to this embodiment may also contain other water-soluble organic solvents, such as sugars or their derivatives, as needed.

[0045] Sugars are primarily used to improve drought resistance and include monosaccharides, disaccharides, oligosaccharides (including trisaccharides and tetrasaccharides), polysaccharides, and their derivatives. Specific examples of sugars include glucose, mannose, fructose, ribose, chloros, trehalose, and mantotriose. Here, polysaccharides refer to sugars in a broad sense and include substances widely found in nature, such as α-cyclodextrin and cellulose.

[0046] Examples of sugar derivatives include reducing sugars and oxidized sugars. Among these, sugar alcohols are preferred, specifically maltitol and sorbitol.

[0047] The sugar content is not particularly limited and can be appropriately selected depending on the purpose, but it is preferably 0.1% to 40% by mass relative to the ink composition, and more preferably 0.5% to 30% by mass.

[0048] The SP value of the organic solvent contained in the ink composition according to the present embodiment is 10 (cal / cm 3 ) 0.5 or more and 20 (cal / cm 3 ) 0.5 or less is preferable, and 11 (cal / cm 3 ) 0.5 or more and 13 (cal / cm 3 ) 0.5 or less is more preferable. When the SP value of the organic solvent is 11 (cal / cm 3 ) 0.5 or more and 13 (cal / cm 3 ) 0.5 or less, high glossiness can be obtained when printing on coated paper or art paper.

[0049] The SP value of an organic solvent (hereinafter sometimes referred to as "solubility parameter") is the SP value of a mixed solution of organic solvents in an ink composition (cal / cm 3 ) 0.5 (hereinafter sometimes referred to as "mixed SP value"), which is obtained by the following formula (A). [Formula 1] (SP A ×V A )+(SP B ×V B )+···+(SP N ×V N ) Formula (A) (In formula (A), SP A is the SP value of organic solvent A, SP B is the SP value of organic solvent B, SP N is the SP value of organic solvent N, V A is the volume fraction of organic solvent A in the mixed solution, V B is the volume fraction of organic solvent B in the mixed solution, and V N represents the volume fraction of organic solvent N in the mixed solution.)

[0050] The SP value is a numerical representation of the solubility of each organic solvent in a mixed solution. The SP value is expressed as the square root of the cohesive energy density (CED), which is the force of attraction between the molecules of the organic solvents. It can be calculated using the Fedors method with the following formula (B). The CED value is the amount of energy required to evaporate 1 mL of the solution. [Formula 2] SP value = (CED value) 1 / 2 =(E / V) 1 / 2 Formula (B) (In equation (B), E is the molecular cohesive energy (cal / mol), and V is the molecular volume (cm³). 3 (Represents / mol)

[0051] In equation (B), the molecular cohesive energy E (cal / mol) and the molecular volume V (cm³) 3 The volume ( / mol) is given by equations (C) and (D) below, where Δei is the evaporation energy of each atomic group in the molecule and Δvi is the molar volume. In equations (C) and (D) below, Σ represents the sum of Δei or Δvi of each atomic group in the molecule. [Formula 3] E = ΣΔei Equation (C) [Formula 4] V = ΣΔvi Equation (D)

[0052] Although there are various methods for calculating the SP value, in this embodiment, it refers to the value calculated by Fedors' method. For calculating the SP value, and for various data such as the evaporation energy Δei and molar volume Δvi of each atomic group used in the calculation, the data described in "Basic Theory of Adhesion" (by Minoru Imoto, published by Polymer Publishing Association, Chapter 5) can be used. Furthermore, for data not shown in the above literature, such as the -CF3 group, refer to RFFedors, Polym.Eng.Sci.14,147 (1974). For reference, the SP value shown in equation (B) is expressed in SI units (J / m). 3 ) 1 / 2To convert to this value, multiply by 2,046. In this embodiment, water-soluble organic solvents are considered in the calculation of the SP value above only if they are present in an amount of 3% by mass or more of the total ink composition.

[0053] <Other ingredients> Other ingredients are not particularly limited and can be selected as appropriate depending on the purpose. Examples include surfactants, antifoaming agents, penetrating agents, pH adjusters, preservatives and antifungal agents, and rust inhibitors.

[0054] - Surfactants - There are no particular restrictions on the surfactant, and it can be appropriately selected according to the purpose. The type and combination of pigments, water-soluble organic solvents, and penetrating agents can be used as long as they do not impair dispersion stability. Examples of surfactants include fluorinated surfactants, silicone surfactants, anionic surfactants, nonionic surfactants, and amphoteric surfactants. Among these, fluorinated surfactants and silicone surfactants are preferred from the viewpoint of low surface tension and excellent leveling properties.

[0055] As fluorine-based surfactants, for example, perfluoroalkyl sulfonic acid compounds, perfluoroalkyl carboxylic acid compounds, perfluoroalkyl phosphate ester compounds, perfluoroalkyl ethylene oxide adducts, and polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups in their side chains are preferred in terms of their low foaming properties.

[0056] Examples of perfluoroalkyl sulfonic acid compounds include perfluoroalkyl sulfonic acid and perfluoroalkyl sulfonate salts.

[0057] Examples of perfluoroalkylcarboxylic acid compounds include perfluoroalkylcarboxylic acids and perfluoroalkylcarboxylic acid salts.

[0058] Examples of perfluoroalkyl phosphate compounds include perfluoroalkyl phosphate esters and salts of perfluoroalkyl phosphate esters.

[0059] Examples of polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups in their side chains include sulfate ester salts of polyoxyalkylene ether polymers having perfluoroalkyl ether groups in their side chains, and salts of polyoxyalkylene ether polymers having perfluoroalkyl ether groups in their side chains.

[0060] Examples of counterions for salts in fluorinated surfactants include Li, Na, K, NH4, NH3CH2CH2OH, NH2(CH2CH2OH)2, and NH(CH2CH2OH)3.

[0061] As for the fluorine-based surfactant, a suitably synthesized one may be used, or a commercially available product may be used. Examples of commercially available products include the Surflon series from Asahi Glass Co., Ltd. (S-111, S-112, S-113, S-121, S-131, S-132, S-141, S-145), the Flurad series from Sumitomo 3M Co., Ltd. (FC-93, FC-95, FC-98, FC-129, FC-135, FC-170C, FC-430, FC-431), the Megafac series from Dainippon Ink & Chemicals Inc. (F-470, F-1405, F-474), and Zonyl from Dupont. Examples include TBS, FSP, FSA, FSN-100, FSN, FSO-100, FSO, FS-300, UR, FT-110, FT-250, FT-252, FT-400S, FT-150, FT-400SW from Neos Corporation, and PF-151N from Omnova Corporation. Among these, fluorinated surfactants represented by the following general formula (2) are preferred. [ka] General formula (2) (In general formula (2), n represents an integer from 2 to 6, a represents an integer from 15 to 50, and Y is -C) b H 2b+1(b represents an integer between 11 and 19) or -CH2CH(OH)CH2-C m F 2m+1 (This indicates that m represents an integer between 2 and 6.)

[0062] Examples of fluorine-based surfactants represented by general formula (2) include the compounds shown below. [ka] [ka]

[0063] Furthermore, the fluorine-based surfactant with the above structure does not contain PFOS (perfluorooctanesulfonic acid) or PFOA (perfluorooctanoic acid), making it superior from the standpoint of preventing global environmental pollution.

[0064] There are no particular restrictions on the silicone-based surfactant, and it can be appropriately selected depending on the purpose. Among these, those that do not decompose even at high pH are preferred, and examples include side-chain modified polydimethylsiloxane, both-end modified polydimethylsiloxane, one-end modified polydimethylsiloxane, and both-end modified polydimethylsiloxane. As for the modifying group, polyoxyethylene group and polyoxyethylene polyoxypropylene group are preferred from the viewpoint of exhibiting good properties as an aqueous surfactant.

[0065] As for the silicone-based surfactant, a synthetically produced one may be used as appropriate, or a commercially available product may be used. Examples of commercially available products include those from Bic Chemie, Shin-Etsu Silicone, and Toray Dow Corning Silicone.

[0066] As silicone-based surfactants, polyether-modified silicone compounds can also be used, such as compounds in which a polyalkylene oxide structure is introduced into the Si side chain of dimethylsiloxane.

[0067] As the polyether-modified silicone compound, a synthesized compound may be used as appropriate, or a commercially available product may be used. Examples of commercially available products include KF-618, KF-642, and KF-643 manufactured by Shin-Etsu Chemical Co., Ltd.

[0068] Examples of anionic surfactants include polyoxyethylene alkyl ether acetate, dodecylbenzene sulfonate, succinate ester sulfonate, lauryl salt, and polyoxyethylene alkyl ether sulfate salts.

[0069] Examples of nonionic surfactants include acetylene glycol-based surfactants, polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene alkyl esters, and polyoxyethylene sorbitan fatty acid esters.

[0070] Examples of acetylene glycol-based surfactants include 2,4,7,9-tetramethyl-5-decine-4,7-diol, 3,6-dimethyl-4-octin-3,6-diol, and 3,5-dimethyl-1-hexyn-3-ol. Examples of commercially available acetylene glycol-based surfactants include the Surfinol series (104, 82, 465, 485, TG) manufactured by Air Products.

[0071] Examples of amphoteric surfactants include laurylaminopyropionate, lauryldimethylbetaine, stearyldimethylbetaine, lauryldihydroxyethylbetaine, lauryldimethylamine oxide, myristyldimethylamine oxide, stearyldimethylamine oxide, dihydroethyllaurylamine oxide, polyoxyethylene coconut oil alkyldimethylamine oxide, dimethylalkyl (coconut) betaine, and dimethyllaurylbetaine. Examples of commercially available amphoteric surfactants include those from Nikko Chemicals, Nippon Emulsion Co., Ltd., Nippon Shokubai Co., Ltd., Toho Chemical Co., Ltd., Kao Corporation, Adeka Corporation, Lion Corporation, Aoki Oil & Fat Co., Ltd., Sanyo Chemical Corporation, and others.

[0072] Surfactants may be used individually or in combination of several. Even if a surfactant does not readily dissolve in an aqueous ink composition on its own, it may become solubilized and stable when mixed with others.

[0073] The surfactant content is preferably 0.01% to 4% by mass, and more preferably 0.1% to 1% by mass, relative to the total amount of the ink composition. When the surfactant content is 0.01% by mass or more, the effect of adding the surfactant can be obtained, and when it is 4% by mass or less, the penetration into the recording medium becomes appropriate, and a decrease in image density and show-through can be suppressed.

[0074] -Foam inhibitor- There are no particular restrictions on the foam inhibitor, and it can be appropriately selected depending on the purpose. Examples include N-octyl-2-pyrrolidone, 2,4,7,9-tetramethyldecane-4,7-diol, and 2,5,8,11-tetramethyldodecane-5,8-diol. These may be used individually or in combination of two or more. By using any one of these foam inhibitors in combination with a fluorine-based surfactant, the generation of bubbles can be suppressed, and problems caused by bubbles can be eliminated.

[0075] -Penetrating agent- There are no particular restrictions on the penetrating agent, and it can be appropriately selected depending on the purpose. Examples include polyol compounds with 8 to 11 carbon atoms and glycol ether compounds. These have the effect of accelerating the penetration rate into the recording medium and preventing bleeding, and are partially water-soluble compounds having a solubility of 0.1% to 4.5% by mass in water at 25°C.

[0076] Examples of polyol compounds having 8 to 11 carbon atoms include 2-ethyl-1,3-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, and 1,2-octanediol.

[0077] Examples of glycol ether compounds include polyhydric alcohol alkyl ether compounds and polyhydric alcohol aryl ether compounds.

[0078] Examples of polyhydric alcohol alkyl ether compounds include ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, and propylene glycol monoethyl ether.

[0079] Examples of polyhydric alcohol aryl ether compounds include ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether.

[0080] The penetrating agent is preferably a component with a higher boiling point than water and is liquid at 25°C.

[0081] There are no particular restrictions on the amount of penetrating agent, and it can be appropriately selected depending on the purpose, but it is preferably 0.1% to 10% by mass, and more preferably 0.5% to 5% by mass, relative to the total amount of the ink composition.

[0082] - pH adjuster - It is preferable to add pH adjusters to the mixed dispersion along with additives such as wetting agents and penetrating agents, rather than adding them when mixing and dispersing pigments with a dispersant in water. This is because some pH adjusters may disrupt the dispersion upon addition.

[0083] Examples of pH adjusting agents include alcohol amines, alkali metal hydroxides, ammonium hydroxides, phosphonium hydroxides, and alkali metal carbonates.

[0084] Examples of alcoholamines include diethanolamine, triethanolamine, and 2-amino-2-ethyl-1,3-propanediol.

[0085] Examples of alkali metal element hydroxides include lithium hydroxide, sodium hydroxide, and potassium hydroxide.

[0086] Examples of ammonium hydroxides include ammonium hydroxide, quaternary ammonium hydroxide, and quaternary phosphonium hydroxide.

[0087] Examples of alkali metal carbonates include lithium carbonate, sodium carbonate, and potassium carbonate.

[0088] -Preservative and fungicide- Examples of preservatives and fungicides include sodium dehydroacetate, sodium sorbate, sodium 2-pyridinethiol-1-oxide, sodium benzoate, and sodium pentachlorophenol.

[0089] -Rust Inhibitor- Examples of rust inhibitors include acidic sulfites, sodium thiosulfate, ammonium thiodiglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, and dicyclohexylammonium nitrite.

[0090] (Ink cartridge) The ink cartridge according to this embodiment contains an ink composition in a container and further includes other components as appropriate. There are no particular restrictions on the container, and its shape, structure, size, material, etc. can be appropriately selected according to the purpose. For example, it is preferable to have at least an ink bag made of aluminum laminate film, resin film, etc.

[0091] The ink cartridge will be explained with reference to Figures 1 and 2. Figure 1 shows an example of an ink cartridge, and Figure 2 shows the ink cartridge in Figure 1 including the case (outer casing). The ink cartridge 200 fills the ink bag 241 with ink from the ink inlet 242, evacuates the ink, and then closes the ink inlet 242 by fusion. During use, the needle on the device body is inserted into the ink outlet 243, which is made of rubber, to supply ink to the device. The ink bag 241 is made of a packaging material such as an airtight aluminum laminate film. As shown in Figure 2, this ink bag 241 is usually housed in a plastic cartridge case 244 and is designed to be detachably attached to various inkjet recording devices.

[0092] (Liquid discharge device) Figure 3 is a schematic diagram showing the configuration of the liquid dispensing device 1. The liquid dispensing device 1 is a serial-type liquid dispensing device. As shown in Figure 3, the liquid dispensing device 1 includes an image forming unit 2 for printing the required image, a drying device 3, a roll media storage unit 4, and a transport mechanism 5. The roll media storage unit 4 stores roll media (recording media) 40. The roll media storage unit 4 can store recording media 40 of different widths. The recording media 40 may be non-permeable media such as PVC (polyvinyl chloride) or PET (polyethylene terephthalate) film, or permeable media such as cloth or synthetic paper.

[0093] The transport mechanism 5 constitutes a roll-to-roll transport system. The transport mechanism 5 is equipped with a pair of nip rollers 51, a pair of driven rollers 52, and a take-up roller 53 on the transport path 54 of the recording media 40. The nip rollers 51 are located on the front side of the image forming unit 2 (upstream side in the transport direction A). The nip rollers 51 rotate in conjunction with the drive of the motor M (see Figure 4) to transport the gripped recording media 40 toward the image forming unit 2. The take-up rollers 53 rotate in conjunction with the drive of the motor M to wind up the printed recording media 40. The driven rollers 52 rotate in conjunction with the transport of the recording media 40.

[0094] The transport mechanism 5 is equipped with a wheel encoder 55 (see Figure 4) for detecting the transport speed. The transport speed of the transport mechanism 5 is controlled by controlling the motor M based on a target value and a speed detection value obtained by sampling detection pulses from the wheel encoder 55.

[0095] Specifically, the recording media 40 stored in the roll media storage section 4 is transported to the image forming section 2 via the driven roller 52 by the rotation of the nip roller 51. Upon reaching the image forming section 2, the recording media 40 has the required image printed on it by the image forming section 2. After printing, the recording media 40 is then wound up by the rotation of the take-up roller 53.

[0096] The image forming unit 2 includes a carriage 21. The carriage 21 is slidably held by a guide rod (guide rail) 22. The carriage 21 moves along the guide rod (guide rail) 22 in a direction perpendicular to the transport direction A of the recording medium 40 (main scanning direction) as the motor M is driven. More specifically, the carriage 21 reciprocates within the recording area, which is a movable area in the main scanning direction, and is printable by the image forming unit 2 on the recording medium 40 transported by the transport mechanism 5.

[0097] The carriage 21 is equipped with a recording head 20 having multiple nozzle holes arranged in a row, which are ejection ports for ejecting liquid droplets. The recording head 20 has an integrated tank for supplying ink to the recording head 20. However, the recording head 20 is not limited to having an integrated tank; it may also have a separate tank. The recording head 20 functions as a liquid ejection unit and ejects ink droplets of process color recording fluids: black (K), yellow (Y), magenta (M), and cyan (C). Black (K), yellow (Y), magenta (M), and cyan (C) are inks used for image formation. In addition, the recording head 20 ejects white (W) ink droplets, which are auxiliary inks (inks for backgrounds and undercoats).

[0098] The image forming unit 2 includes a platen 23 that supports the recording medium 40 below the recording head 20 when printing on the recording head 20.

[0099] Furthermore, the image forming unit 2 is equipped with an encoder sheet for detecting the main scanning position of the carriage 21 along the main scanning direction of the carriage 21. The carriage 21 is also equipped with an encoder 26 (see Figure 4). The image forming unit 2 detects the main scanning position of the carriage 21 by reading the encoder sheet using the encoder 26 of the carriage 21.

[0100] The carriage 21 is equipped with a sensor 24 that optically detects the edge of the recording medium 40 as the carriage 21 moves. The detection signal from this sensor 24 is used to calculate the position of the edge of the recording medium 40 in the main scanning direction and the width of the recording medium 40.

[0101] The drying apparatus 3 comprises a preheater 30, a platen heater 31, a drying heater 32, and a hot air fan 33. The preheater 30, platen heater 31, and drying heater 32 are electric heaters, for example, using ceramic or nichrome wire.

[0102] The preheater 30 is located upstream of the image forming unit 2 in the transport direction A of the recording medium 40. The preheater 30 preheats the recording medium 40 that is transported by the transport mechanism 5.

[0103] The platen heater 31 is located on the platen 23. The platen heater 31 heats the recording medium 40, which is onto which ink droplets ejected from the nozzle holes of the recording head 20 land.

[0104] The drying heater 32 is located downstream of the image forming unit 2 in the transport direction A of the recording medium 40. The drying heater 32 continues to heat the recording medium 40 printed by the image forming unit 2, promoting the drying of the deposited ink droplets.

[0105] The hot air fan 33 is located downstream of the drying heater 32 (image forming unit 2) in the transport direction A of the recording medium 40. The hot air fan 33 blows hot air onto the recording surface of the recording medium 40 where ink has landed. By directly applying hot air to the ink on the recording surface of the recording medium 40, the hot air fan 33 reduces the humidity of the atmosphere around the recording surface of the recording medium 40, allowing it to dry completely.

[0106] By equipping the liquid dispensing device 3 in this manner, the liquid dispensing device 1 can use non-permeable media such as polyvinyl chloride (PVC), polyethylene terephthalate (PET), or acrylic as the recording media 40.

[0107] In the liquid ejection device 1, in which the carriage 21 moves back and forth across the width of the recording medium 40 while ejecting ink from the recording head 20 to form an image, there are two types of printing: unidirectional printing, in which ink is ejected and an image is formed only when the carriage is moving forward, and bidirectional printing, in which ink is ejected and an image is formed when the carriage is moving both forward and backward. In the liquid ejection device 1, bidirectional printing, which is advantageous in terms of printing speed, is mainly used. Here, the operation in which the carriage 21 moves in the main scanning direction while ejecting ink from the recording head 20 is considered as one scan.

[0108] Next, the control configuration of the liquid dispensing device 1 will be described. Here, Figure 4 is a block diagram showing the control configuration of the liquid dispensing device 1.

[0109] As shown in Figure 4, the liquid dispensing device 1 is equipped with a control unit 10 that controls the entire device. The control unit 10 comprises a CPU (Central Processing Unit) 11, a ROM (Read Only Memory) 12, a RAM (Random Access Memory) 13, a memory 14, and an ASIC (Application Specific Integrated Circuit) 15. The ROM 12 stores computer programs and other fixed data executed by the CPU 11. The RAM 13 temporarily stores image data, etc. The memory 14 is a rewritable non-volatile memory that retains data even when the power to the liquid dispensing device 1 is cut off. The ASIC 15 performs image processing, such as various signal processing and rearrangement of image data, as well as input / output signal processing to control the entire device.

[0110] Furthermore, as shown in Figure 4, the control unit 10 includes a host interface (I / F) 16, a head drive control unit 17, a motor control unit 18, and an I / O 19.

[0111] The host interface 16 transmits and receives image data (print data) and control signals to and from the host via cable or network. Examples of hosts connected to the liquid dispensing device 1 include information processing devices such as personal computers, image reading devices such as image scanners, and imaging devices such as digital cameras.

[0112] I / O 19 receives detection pulses from encoder 26 and wheel encoder 55. In addition, I / O 19 connects to various sensors 25, including sensor 24, humidity sensor, temperature sensor, and other sensors. I / O 19 receives detection signals from sensor 24 and the various sensors 25.

[0113] The head drive control unit 17 controls the recording head 20 and includes data transfer means. More specifically, the head drive control unit 17 transfers image data as serial data. The head drive control unit 17 also generates a transfer clock and latch signal necessary for transferring and confirming the transfer of image data, as well as a drive waveform used when ejecting droplets from the recording head 20. The head drive control unit 17 then inputs the generated drive waveform and other signals to the drive circuit inside the recording head 20.

[0114] The motor control unit 18 drives the motor M. More specifically, the motor control unit 18 calculates a control value based on a target value provided by the CPU 11 and a speed detection value obtained by sampling detection pulses from the wheel encoder 55. Then, the motor control unit 18 drives the motor M via its internal motor drive circuit based on the calculated control value.

[0115] Furthermore, the control unit 10 includes a heater control unit 8 and a hot air fan control unit 9.

[0116] The heater control unit 8 controls the output of the preheater 30, platen heater 31, and drying heater 32 so that the temperature of each heater 30, 31, and 32 reaches a set temperature. More specifically, when controlling each heater 30, 31, and 32, the heater control unit 8 acquires temperature information from temperature sensors provided on each heater 30, 31, and 32. The heater control unit 8 then monitors the temperature of each heater 30, 31, and 32 and controls them so that the temperature of each heater 30, 31, and 32 reaches a set temperature. If heaters are provided on the tank or ink path of the recording head 20, the heater control unit 8 controls these heaters in the same manner.

[0117] The hot air fan control unit 9 controls the output of the hot air fan 33 so that air is supplied at a predetermined temperature and volume.

[0118] In addition, the control unit 10 is connected to an operation panel 60 for inputting and displaying information necessary for the liquid dispensing device 1.

[0119] The control unit 10 comprehensively controls each part by loading the computer program read by the CPU 11 from the ROM 12 (or memory 14) into the RAM 13 and executing it.

[0120] The computer program executed by the liquid dispensing device 1 of this embodiment is provided as an installable or executable file recorded on a computer-readable recording medium such as a CD-ROM, flexible disk (FD), CD-R, or DVD (Digital Versatile Disk).

[0121] Furthermore, the computer program executed by the liquid dispensing device 1 of this embodiment may be stored on a computer connected to a network such as the Internet and provided by being downloaded via the network. Alternatively, the computer program executed by the liquid dispensing device 1 of this embodiment may be provided or distributed via a network such as the Internet.

[0122] Furthermore, the computer program executed by the liquid dispensing device 1 of this embodiment may be provided pre-installed in ROM or the like.

[0123] Next, the image data transfer and printing process performed by the control unit 10 of the liquid dispensing device 1 will be briefly explained. The CPU 11 of the control unit 10 reads and analyzes the image data (print data) in the receive buffer included in the host I / F 16, and the ASIC 15 performs the necessary image processing, data rearrangement, etc. Subsequently, the CPU 11 of the control unit 10 transfers the image data (print data) processed by the ASIC 15 from the head drive control unit 17 to the recording head 20.

[0124] The generation of dot pattern data for image output can be performed, for example, by storing font data in ROM 12, or by having the host-side printer driver expand the image data into bitmap data and transfer it to the liquid dispensing device 1.

[0125] Next, the characteristic functions of the liquid ejection device 1 will be described. The liquid ejection device 1 of this embodiment has the following features when performing inkjet printing on a recording medium 40, which is a transparent, non-permeable medium.

[0126] In short, the liquid dispensing device 1 is designed to allow auxiliary layers, which are auxiliary layers made of auxiliary ink (e.g., white ink), to be placed as pre-printing, post-printing, and interprinting in relation to the image layer, which is the layer of the image formed with the image-forming ink, and to speed up the formation of the auxiliary layers.

[0127] Here, Figure 5 is a plan view showing the nozzle configuration of the recording head 20, and Figure 6 is a schematic diagram showing the colors of each nozzle row in a simplified manner. Figure 5 shows the nozzle rows of the recording head 20 transparently from above. As shown in Figure 5, the recording head 20 comprises a first nozzle group 20a, a second nozzle group 20b, and a third nozzle group 20c.

[0128] As shown in Figure 5, each nozzle group 20a, 20b, and 20c is arranged in two rows in the main scanning direction and alternately in a staggered pattern in the sub-scanning direction. That is, each nozzle group 20a, 20b, and 20c are arranged in the order of third nozzle group 20c, second nozzle group 20b, and first nozzle group 20a, so that the nozzle rows do not overlap from the upstream side to the downstream side in the transport direction A of the recording medium 40. Also, as shown in Figure 5, the second nozzle group 20b is positioned offset from the first nozzle group 20a and the third nozzle group 20c in the main scanning direction.

[0129] The first nozzle group 20a and the third nozzle group 20c are equipped with a single row of nozzles for ejecting ink droplets of auxiliary ink (background ink, undercoat ink) and three rows of nozzles for ejecting CMY (process color) ink droplets for image formation. Each nozzle row has 192 nozzle holes, from nozzle hole No. 1 to nozzle hole No. 192. In the example shown in Figure 5, the nozzle holes are numbered from nozzle hole No. 1 to nozzle hole No. 192, starting from the downstream nozzle hole in the transport direction A of the recording medium 40 to the upstream nozzle hole. The pitch P between these nozzle holes is 150 dpi (dots per inch).

[0130] As shown in Figure 5, the first nozzle group 20a and the third nozzle group 20c each have a cyan ink nozzle row NC that ejects cyan (C) ink droplets, a magenta ink nozzle row NM that ejects magenta (M) ink droplets, and a yellow ink nozzle row NY that ejects yellow (Y) ink droplets.

[0131] The second nozzle group 20b, like the first nozzle group 20a, has four rows of nozzles, each row containing 192 nozzle holes numbered from nozzle No. 1 to nozzle No. 192. Also like the first nozzle group 20a, the pitch P between nozzle holes in the second nozzle group 20b is 150 dpi.

[0132] The second nozzle group 20b includes a nozzle row for auxiliary recording. Specifically, the second nozzle group 20b includes one nozzle row for ejecting ink droplets of auxiliary ink (background ink, undercoat ink), two nozzle rows for ejecting ink droplets of special colors for image formation, and one nozzle row for ejecting K (process color) ink droplets for image formation.

[0133] As shown in Figure 6, the second nozzle group 20b has a nozzle row NW that ejects white (W) ink droplets as an example of auxiliary ink (background ink, undercoat ink). The second nozzle group 20b also has a nozzle row NO that ejects orange (O) ink droplets and a nozzle row NG that ejects green (G) ink droplets as examples of special inks for image formation. Furthermore, the second nozzle group 20b has a nozzle row NK that ejects black (K) ink droplets.

[0134] As described above, since each nozzle group 20a, 20b, and 20c has the same number of nozzle rows and nozzles, each nozzle group 20a, 20b, and 20c can be constructed with the same parts, thereby reducing the number of parts and thus lowering the cost of the device.

[0135] In this embodiment, as shown in Figure 5, white ink, orange ink, and green ink are listed as liquids other than process colors. However, these are not the only liquids other than process colors; for example, spot inks such as red and blue, as well as silver ink, gold ink, transparent ink, primers, and surface protectants can be applied as needed. These inks are used to enhance image quality or add texture.

[0136] For example, when printing on a transparent substrate, a white background image can be formed on the transparent substrate by printing white ink onto the substrate and then printing colored inks, such as process colors, on top of that. Alternatively, by printing with colored inks, such as process colors, and then printing white ink on top of that, an image with a white background can be formed when viewed from the substrate side. Furthermore, by printing colored inks such as process colors, then printing white ink on top of that, and then printing colored inks such as process colors again on top of that, it is possible to create different images depending on the viewer, with white as the background. [Examples]

[0137] The present invention will be described more specifically below based on examples, but the present invention is not limited to the following examples.

[0138] <Example 1 of Pigment Dispersion Preparation> A mixed slurry was obtained by premixing 250 parts of Pigment Blue 15:3 (manufactured by Dainichi Seika Kogyo Co., Ltd.) as a pigment, 50 parts of a compound represented by the following general formula (1) (Pionin D-7240, manufactured by Takemoto Oil Co., Ltd.) as a dispersant, and 700 parts of distilled water. Next, the mixed slurry was dispersed using a disc-type media mill (UMA type, manufactured by Kotobuki Kogyo Co., Ltd.) and 0.015 mm zirconia beads (70% packing rate) at a peripheral speed of 6 m / s and a liquid temperature of 10°C until the volume average particle size was approximately 100 nm. Next, coarse particles were separated from the dispersed mixed slurry using a centrifuge (Model-7700, manufactured by Kubota Shoji Co., Ltd.). Then, the mixed slurry from which the coarse particles had been separated was filtered through a filter with a pore size of 1.2 μm, and the water content was adjusted so that the solid content concentration was 15%, to obtain a blue pigment dispersion 1 with a pigment concentration of 15%.

[0139] [ka] (In general formula (1), R 1 (where represents an alkyl group, allyl group, or aralkyl group with 1 to 20 carbon atoms, L represents an integer between 0 and 7, and n represents an integer between 20 and 200)

[0140] <Example 2 of Pigment Dispersion Preparation> In Pigment Dispersion Preparation Example 1, a blue pigment dispersion 2 with a pigment concentration of 15% was obtained in the same manner as in Pigment Dispersion Preparation Example 1, except that the compound represented by general formula (1) (Pionin D-7240) used as a dispersant was changed to naphthalene sulfonic acid formalin condensate (Takesurf A-45-K, manufactured by Takemoto Oil Co., Ltd.).

[0141] <Example 3 of Pigment Dispersion Preparation> In Pigment Dispersion Preparation Example 1, a red pigment dispersion 1 with a pigment concentration of 15% was obtained in the same manner as in Pigment Dispersion Preparation Example 1, except that Pigment Blue 15:3 was replaced with Pigment Red 122 (manufactured by Dainichi Seika Kogyo Co., Ltd.) as the pigment.

[0142] (Examples 1-9 and Comparative Examples 1-3) In Examples 1-9 and Comparative Examples 1-3, the raw materials shown in Table 1 were uniformly mixed under stirring at room temperature, and then compressed and filtered using a polyvinylidene fluoride membrane filter with an average pore size of 0.8 μm to remove coarse particles and debris, thereby obtaining ink compositions 1-12.

[0143] [Table 1]

[0144] The following is a detailed explanation of the raw materials listed in Table 1.

[0145] <Resin> • Resin A: Polyether urethane resin (manufactured by Mitsui Chemicals, Inc., Takelac W932, SP value = 19.1 (cal / cm²) 3 ) 0.5 ) • Resin B: Polyether urethane resin (manufactured by Mitsui Chemicals, Inc., Takelac W5661, SP value = 11.1 (cal / cm²) 3 ) 0.5 ) • Resin C: Urethane resin (manufactured by Chuo Rika Kogyo Co., Ltd., SU100N, SP value = 9.6 (cal / cm²) 3 ) 0.5 ) <Organic solvents> • Organic solvent A (manufactured by Sakamoto Pharmaceutical Co., Ltd., glycerin, SP value = 17.4 (cal / cm³) 3 ) 0.5 ) • Organic solvent B (manufactured by Tokyo Chemical Industry Co., Ltd., 1,3-butanediol, SP value = 14.2 (cal / cm³) 3 ) 0.5 ) • Organic solvent C (manufactured by Tokyo Chemical Industry Co., Ltd., propylene glycol monomethyl ether, SP value = 10.9 (cal / cm³) 3 ) 0.5 ) • Organic solvent D (manufactured by Tokyo Chemical Industry Co., Ltd., 3-methoxy-3-methyl-1-butanol, SP value = 9.9 (cal / cm³) 3 ) 0.5 ) <Leveling agent> • Leveling agent A (BYKJET-9151, manufactured by BYK Chemie Japan, acrylic block copolymer, amine value = 18 mg KOH / g) • Leveling agent B (manufactured by BIC Chemie Japan, DISPERBYK-2012, acrylic block copolymer, amine value = 7 mg KOH / g)

[0146] Each ink composition 1 to 12 obtained in Examples 1 to 9 and Comparative Examples 1 to 3 was evaluated for "image density," "glossiness," and "discharge stability." The evaluation results are shown in Table 2.

[0147] <Image density> Each ink composition 1 to 12 obtained in Examples 1 to 9 and Comparative Examples 1 to 3 was loaded into an inkjet printer (Ricoh IPSiO GXe5500) and solid print was performed on plain paper (Xerox PPC paper 4024) at a resolution of 1,200 dpi × 1,200 dpi to form a solid image. The image density (OD value) of magenta and cyan in the formed solid image was measured using an X-Rite938 colorimeter, and the image density was evaluated based on the evaluation criteria below. For Examples 1 to 4, 7 to 9, and Comparative Examples 1 to 3, which use a blue pigment dispersion, the OD value of cyan was measured and evaluated based on the evaluation criteria below, while for Examples 5 to 6, which use a red pigment dispersion, the OD value of magenta was measured and evaluated based on the evaluation criteria below. [Evaluation Criteria] A: Magenta OD value of 0.95 or higher, or cyan OD value of 1.05 or higher B: Magenta OD value is 0.85 or higher and less than 0.95, or cyan OD value is 0.95 or higher and less than 1.05. C: Magenta OD value is 0.75 or higher but less than 0.85, or cyan OD value is 0.85 or higher but less than 0.95. D: Magenta OD value less than 0.75, or cyan OD value less than 0.85

[0148] <Glossiness> Each ink composition 1 to 12 obtained in Examples 1 to 9 and Comparative Examples 1 to 3 was loaded into an inkjet printer (Ricoh IPSiO GXe5500, manufactured by Ricoh Co., Ltd.) and solid prints were made on glossy paper (CPJET Star Glossy Photo 2, manufactured by Sakurai Co., Ltd.) at a resolution of 1,200 dpi × 1,200 dpi to form solid images. The glossiness of the formed solid images was measured using a glossiness meter (Microtrigloss, manufactured by BYK), and the glossiness was evaluated based on the evaluation criteria below. The 60° gloss value was defined as the glossiness. [Evaluation Criteria] ◎: Glossiness level of 80 or higher ○: Glossiness level is between 60 and 80 △: Glossiness level is between 40 and 60 ×: Glossiness less than 40

[0149] <Discharge stability> Each ink composition 1 to 12 obtained in Examples 1 to 9 and Comparative Examples 1 to 3 was placed in a polyethylene container and stored for 3 months under the respective temperature conditions of -20°C, 5°C, 20°C, and 70°C. The rate of change in surface tension and viscosity after storage was measured, and the presence or absence of precipitate precipitation was visually inspected. The discharge stability was evaluated based on the rate of change in surface tension and viscosity after storage and the presence or absence of precipitate precipitation, according to the evaluation criteria below. [Evaluation Criteria] ○: Under all temperature conditions, the rate of change in surface tension and viscosity after storage is less than 5%, and no precipitate is formed. ×: Under any temperature conditions, the rate of change in surface tension or viscosity after storage is 5% or more, or precipitate formation occurs.

[0150] [Table 2]

[0151] Examples of the present invention are as follows: <1> An ink composition comprising a pigment, a dispersant, and a leveling agent, The aforementioned dispersant is a compound represented by the following general formula (1), The leveling agent comprises an acrylic block copolymer. An ink composition characterized by the following features. [ka] (In general formula (1), R 1 (where represents an alkyl group, allyl group, or aralkyl group with 1 to 20 carbon atoms, L represents an integer between 0 and 7, and n represents an integer between 20 and 200) <2> The amine value of the acrylic block copolymer is 15 mg KOH / g or more. <1> The ink composition described above. <3> The content of the acrylic block copolymer is 0.1% by mass or more and 1.0% by mass or less relative to the total amount of the ink composition. <1> or <2> The ink composition described above. <4> It further contains a water-soluble organic solvent, The mixed SP value is 11 (cal / cm³). 3 ) 0.5 More than 13(cal / cm 3 ) 0.5 The following is: <1> from <3> An ink composition according to any one of the items. <5> It further contains resin, The SP value of the aforementioned resin is 11 (cal / cm³). 3 ) 0.5 That's all. <1> from <4> An ink composition according to any one of the items. <6> <1> from <5> An ink cartridge characterized by containing the ink composition described in any one of the above items in a container. <7> <6> The ink cartridges listed, A liquid dispensing means comprising a liquid dispensing unit for dispensing the ink composition, A liquid dispensing device characterized by comprising the following features. [Explanation of Symbols]

[0152] 1. Inkjet recording device 10 Control Unit 20 Recording heads 20a, 20b, 20c Nozzle Group 200 ink cartridges 241 Ink Bag 242 Ink refill port 243 Ink outlet 244 Cartridge Case [Prior art documents] [Patent Documents]

[0153] [Patent Document 1] Japanese Patent Publication No. 2005-194500

Claims

1. An ink composition comprising a pigment, a dispersant, and a leveling agent, The dispersant is a compound represented by the following general formula (1), The leveling agent comprises an acrylic block copolymer. An ink composition characterized by the following features. 【Chemistry 1】 (In general formula (1), R １ (where represents an alkyl group, allyl group, or aralkyl group having 1 to 20 carbon atoms, L represents an integer between 0 and 7, and n represents an integer between 20 and 200)

2. The ink composition according to claim 1, wherein the amine value of the acrylic block copolymer is 15 mg KOH / g or more.

3. The ink composition according to claim 1 or 2, wherein the content of the acrylic block copolymer is 0.1% by mass or more and 1.0% by mass or less based on the total amount of the ink composition.

4. It further contains a water-soluble organic solvent, The mixed SP value is 11 (cal / cm³). ３ ) ０．５ Above 13 (cal / cm ３ ) ０．５ The ink composition according to claim 1 or 2, which is as follows:

5. It further contains resin, The SP value of the aforementioned resin is 11 (cal / cm²). ３ ) ０．５ The ink composition according to claim 1 or 2, as described above.

6. An ink cartridge characterized by containing the ink composition described in claim 1 or 2 in a container.

7. The ink cartridge according to claim 6, A liquid dispensing means comprising a liquid dispensing unit for dispensing the ink composition, A liquid dispensing device characterized by comprising the following features.

Images