JP2018039872A - Ink composition and recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink composition that reduces unevenness of density of an image, compared with an ink composed of a colorant, resin particles of just one kind, water, and a water-soluble organic solvent.SOLUTION: An ink composition contains a colorant, resin particles of at least two kinds having different glass transition temperatures, water, and a water-soluble organic solvent. The difference in glass transition temperature between the resin particles of at least two kinds is 20°C or more.SELECTED DRAWING: None

Description

  The present invention relates to an ink composition and a recording apparatus.

  In recent years, there has been an increasing demand for recording an image with a water-based ink on a recording medium such as a coated paper for printing, which has a slow liquid penetration (hereinafter referred to as a non-permeable recording medium).

  As conventional water-based inks, for example, those described in Patent Document 1 are known. Patent Document 1 discloses a water-based inkjet ink composition containing a pigment (colorant), an alkali-soluble resin, a wax emulsion, a basic compound, an aqueous medium, and a surfactant. The average particle size is 150 to 200 nm, the solid content of the wax emulsion is 0.5 to 4% by mass in the aqueous inkjet ink composition, and the surfactant is an acetylenic diol surfactant. Certain aqueous inkjet ink compositions are described.

  For example, Patent Document 2 discloses pigments (colorants), water, acrylic resins, vinyl acetate resins, ethylene / vinyl acetate resins, vinyl acetate / acrylic copolymer resins, and styrene. A water-based ink containing at least a resin emulsion composed of one or more selected from acrylic copolymer resins and having a minimum film-forming temperature of 25 ° C. or less and a silicone emulsion is described.

  By the way, the resin particles contained in the ink composition are mainly used as a component for improving the fixing property of the ink to the non-permeable recording medium. After the ink composition is ejected onto the non-permeable recording medium, as the water in the ink composition evaporates, the resin particles in the ink composition are fused to form an ink film. It is fixed as an ink image on a non-permeable recording medium. Normally, when an ink film is formed, a difference in surface tension at each location occurs due to a difference in the amount of evaporation of water or the like at each location on the surface of the ink membrane, and irregularities are formed on the ink film. There is a case. In particular, when one kind of resin particle is contained in the ink, liquid cross-linking tends to remain partially, and the unevenness of the ink film is promoted, which may cause uneven density of the image.

JP-A-2015-137318 JP 2004-175827 A

  An object of the present invention is to provide an ink composition in which uneven density of an image is suppressed as compared with an ink composed of a colorant, a single resin particle, water, and a water-soluble organic solvent, and the ink composition. Is provided.

  The invention according to claim 1 includes a colorant, at least two kinds of resin particles having different glass transition temperatures, water, and a water-soluble organic solvent, and a difference in glass transition temperature between the two kinds of resin particles is 20 ° C. or more. Is an ink composition.

  The invention according to claim 2 is the ink composition in which the glass transition temperature of the resin particles is 40 ° C. or higher.

  According to a third aspect of the invention, there is provided a recording apparatus comprising an ejection head for ejecting ink onto a recording medium, wherein the ink is the ink composition according to the first or second aspect.

  According to the invention of claim 1, an ink composition in which uneven density of an image is suppressed as compared with an ink composition comprising a colorant, a single resin particle, water, and a water-soluble organic solvent. Is provided.

  According to the second aspect of the present invention, an ink composition having excellent offset resistance is provided as compared with an ink composition in which the glass transition temperature of the resin particles is less than 40 ° C.

  According to the invention of claim 3, compared with a recording apparatus comprising an ejection head that ejects an ink composition composed of a colorant, a single type of resin particle, water, and a water-soluble organic solvent onto a recording medium. Thus, a recording apparatus is provided in which uneven density of images is suppressed.

FIG. 3 is a schematic cross-sectional view for explaining the state of resin particles in an ink composition discharged onto a recording medium. It is a schematic structure figure showing an example of a recording device concerning this embodiment.

  Embodiments of the present invention will be described below. This embodiment is an example for carrying out the present invention, and the present invention is not limited to this embodiment.

<Ink composition>
The ink composition according to the present embodiment includes a colorant, resin particles, water, and a water-soluble organic solvent. The resin particles include at least two types of resin particles having different glass transition temperatures, and the difference in glass transition temperature between the two types of resin particles is 20 ° C. or more. As in the ink composition according to the present embodiment, the difference in glass transition temperature between at least two kinds of resin particles contained in the ink composition is set to 20 ° C. or more so that the ink using one kind of resin particles is used. Compared with the composition, the density unevenness of the image is suppressed. Although this mechanism is not sufficiently clear, the following can be inferred.

  FIG. 1 is a schematic cross-sectional view for explaining the state of resin particles in an ink composition discharged onto a recording medium. In FIG. 1, for ease of explanation, only resin particles are shown as components in the ink composition, and colorants and the like are omitted. Generally, when the ink composition 2 is ejected onto the non-permeable recording medium 1, the ink composition 2 that has landed on the recording medium 1 does not penetrate or hardly penetrates the recording medium 1. The object 2 remains with a height (see FIG. 1A). Then, as water or the like in the ink composition 2 evaporates at the time of connection, the resin particles 3 in the ink composition 2 are fused together (see FIGS. 1B and 1C), and finally. An ink film 4 is formed (see FIG. 1D).

  As described above, normally, when forming an ink film, a difference in the surface tension at each location occurs due to a difference in evaporation amount of water or the like at each location on the surface of the ink film. Asperities may be formed on the surface. In particular, when one kind of resin particle is contained in the ink composition, liquid cross-linking tends to remain partially, and unevenness of the ink film is promoted, which may cause uneven density of the image. However, as in this embodiment, at least two types of resin particles having different glass transition temperatures are used, and the difference between the glass transition temperatures of the two types of resin particles is set to 20 ° C. or more, so that one type of resin is used. Compared to the case where particles are used, the leveling property of the ink film during the drying process is improved, and the unevenness of the ink film is considered to be suppressed. As a result, the density unevenness of the image is suppressed as compared with the case where one kind of resin particle is used.

  The ink composition according to this embodiment may be, for example, any of black ink, cyan ink, magenta ink, yellow ink, and intermediate color inks other than these colors. In addition, when using multiple colors of ink, at least one ink may be the ink composition according to the present embodiment, but all the inks are preferably the ink composition according to the present embodiment.

  Hereinafter, each component of the ink composition according to the present embodiment will be described.

[Resin particles]
The ink composition used in the present embodiment contains at least two resin particles having different glass transition temperatures. The difference (absolute value) in glass transition temperature between at least two kinds of resin particles contained in the ink composition of the present embodiment is not particularly limited as long as it is 20 ° C. or higher, but is 20 ° C. or higher and 50 ° C. or lower. It is preferably 20 ° C. or higher and 40 ° C. or lower. In the ink composition in which the difference in glass transition temperature between the two kinds of resin particles is less than 20 ° C., the leveling property is improved as compared with the ink composition in which the difference in glass transition temperature between the two kinds of resin particles is 20 ° C. or more. The effect cannot be sufficiently obtained, the effect of suppressing the formation of the unevenness of the ink film is small, and the density unevenness of the image may occur. In addition, when the difference of the glass transition temperature of 2 types of resin particles exceeds 50 degreeC, the effect of a leveling improvement may not fully be acquired.

  Here, the difference in glass transition temperature in the case of containing two or more kinds of resin particles means the difference in glass transition temperature between the two kinds of resin particles having the greatest difference. That is, when the resin particles of A, B, and C3 types are included, for example, if the difference in glass transition temperature between the resin particles A and B is 20 ° C. or more, the difference in glass transition temperature between the resin particles A, C, B, and C. May be less than 20 ° C.

  The glass transition temperature (Tg) of the resin particles is determined by a differential scanning calorimeter (Shimadzu) according to the measurement method of extrapolated glass transition start temperature of JIS K7121-1987 “Plastic transition temperature measurement method” 9.3 (2). It is determined by measuring from room temperature to 150 ° C. under a temperature increase rate of 20 ° C./min. The gas transition temperature was the temperature at the intersection of the extension line of the base line and the rising line in the endothermic part.

  In addition, the content ratio of the two types of resin particles having a glass transition temperature difference of 20 ° C. or more (resin particles having a higher glass transition temperature / resin having a lower glass transition temperature) is not particularly limited. However, in terms of further suppressing density unevenness of the image, for example, the mass ratio is preferably in the range of 80/20 to 20/80, and more preferably in the range of 60/40 to 40/60.

  Further, in the two types of resin particles having a glass transition temperature difference of 20 ° C. or more, each glass transition temperature is preferably 40 ° C. or more, more preferably 40 ° C. or more and 100 ° C. or less, and 40 ° C. or more. More preferably, it is 80 ° C. or lower.

  The glass transition temperature of the resin particles is adjusted by, for example, the type of resin used and, if the resin particles are a copolymer, the ratio of monomers forming the copolymer, the particle diameter of the resin particles, and the like. For the two types of resin particles having different glass transition temperatures, it is preferable to use the same type of resin particles in terms of the compatibility of the resin particles. In this case, what is necessary is just to control the ratio of the monomer which forms a copolymer, the particle diameter of a resin particle, etc. so that the difference of the glass transition temperature of said 2 types of resin particle may be 20 degreeC or more.

  Examples of the resin particles include styrene-acrylic acid copolymer, styrene-acrylic acid-sodium acrylate copolymer, styrene-butadiene copolymer, polystyrene, acrylonitrile-butadiene copolymer, acrylic ester copolymer, Examples thereof include particles (latex particles) such as polyurethane, silicone-acrylic acid copolymer, and acrylic-modified fluororesin. Examples of the resin particles include core / shell type resin particles having different compositions at the center and outer edge of the particles.

  The resin particles may be dispersed in the ink composition using an emulsifier, or may be dispersed in the ink composition without using an emulsifier. Examples of the emulsifier include a polymer having a hydrophilic group such as a surfactant, a sulfonic acid group, and a carboxyl group (for example, a polymer having a hydrophilic group grafted thereto, a hydrophilic monomer, and a hydrophobic part. And a polymer obtained from a monomer having

  The volume average particle size of the resin particles is preferably, for example, from 10 nm to 300 nm, and more preferably from 10 nm to 200 nm, from the viewpoint of glossiness and scratch resistance of the image. The volume average particle diameter of the resin particles in the present embodiment is measured with a Microtrac UPA particle size analyzer UPA-UT151 (manufactured by Microtrac). The measurement is performed by placing 1,000-fold diluted ink in a measurement cell. As input values at the time of measurement, the viscosity is the viscosity of the ink diluent, and the particle refractive index is the refractive index of the polymer.

  The content of the resin particles is, for example, preferably from 0.1% by weight to 10% by weight and more preferably from 0.5% by weight to 5% by weight with respect to the total weight of the ink composition. .

[Colorant]
The ink composition used in the present embodiment contains a colorant. Examples of the colorant include pigments. Examples of the pigment include organic pigments and inorganic pigments.

  Specific examples of black pigments (black pigments) include, for example, Raven7000, Raven5750, Raven5250, Raven5000 ULTRAII, Raven3500, Raven2000, Raven1500, Raven1250, Raven10R, Raven1170, Raven1170R (Manufactured by Carbon Co., Ltd.), Regal 400R, Regal 330R, Regal 660R, Mogul L, Black Pearls L, Monarch 700, Monarch 800, Monarch 880, Monarch 900, Monarch 1000, Monarch 1100, Monarch 13 0, Monarch 1400 (above, manufactured by Cabot Corporation), Color Black FW1, Color Black FW2, Color Black FW2V, Color Black 18, Color Black FW200, Color Black S150, Color Black S150, Color Black Sr, 160 V, Printex 140U, Printex 140V, Special Black 6, Special Black 5, Special Black 4A, Special Black 4 (manufactured by Degussa), No. 25, no. 33, no. 40, no. 47, no. 52, no. 900, no. 2300, MCF-88, MA600, MA7, MA8, MA100 (above, manufactured by Mitsubishi Chemical Corporation), and the like, but are not limited thereto.

  Specific examples of the cyan pigment include C.I. I. Pigment Blue 1, 2, 3, 15, 15: 1, 15: 2, 15: 3, 15: 4, 16, 22, 60, and the like, but are not limited thereto.

  Specific examples of the magenta pigment include C.I. I. Pigment Red 5, 7, 12, 48, 48: 1, 57, 112, 122, 123, 146, 168, 177, 184, 202, C.I. I. Pigment Violet 19 and the like, but are not limited thereto.

  Specific examples of yellow pigments include C.I. I. Pigment Yellow 1, 2, 3, 12, 13, 14, 16, 17, 73, 74, 75, 83, 93, 95, 97, 98, 114, 128, 129, 138, 151, 154, 180, etc. However, it is not limited to these.

  Here, when a pigment is used as the colorant, the ink composition preferably contains a pigment dispersant. Examples of the pigment dispersant used include a polymer dispersant, an anionic surfactant, a cationic surfactant, an amphoteric surfactant, and a nonionic surfactant.

  As the polymer dispersant, for example, a polymer having a hydrophilic structure part and a hydrophobic structure part is preferable. As the polymer having a hydrophilic structure portion and a hydrophobic structure portion, for example, a condensation polymer and an addition polymer are used. Examples of the condensation polymer include known polyester dispersants. Examples of the addition polymer include addition polymers of monomers having an α, β-ethylenically unsaturated group. For example, by copolymerizing a monomer having an α, β-ethylenically unsaturated group having a hydrophilic group and a monomer having an α, β-ethylenically unsaturated group having a hydrophobic group The polymer dispersant is obtained. A homopolymer of a monomer having an α, β-ethylenically unsaturated group having a hydrophilic group is also used.

  Examples of the monomer having an α, β-ethylenically unsaturated group having a hydrophilic group include a monomer having a carboxyl group, a sulfonic acid group, a hydroxyl group, a phosphoric acid group, such as acrylic acid, methacrylic acid, and the like. , Crotonic acid, itaconic acid, itaconic acid monoester, maleic acid, maleic acid monoester, fumaric acid, fumaric acid monoester, vinyl sulfonic acid, styrene sulfonic acid, sulfonated vinyl naphthalene, vinyl alcohol, acrylamide, methacryloxyethyl phosphate Bismethacryloxyethyl phosphate, methacryloxyethyl phenyl acid phosphate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate and the like.

  Examples of the monomer having an α, β-ethylenically unsaturated group having a hydrophobic group include styrene derivatives such as styrene, α-methylstyrene, vinyltoluene, vinylcyclohexane, vinylnaphthalene, vinylnaphthalene derivatives, and acrylic acid. Examples include alkyl esters, methacrylic acid alkyl esters, methacrylic acid phenyl esters, methacrylic acid cycloalkyl esters, crotonic acid alkyl esters, itaconic acid dialkyl esters, maleic acid dialkyl esters, and the like.

  Examples of preferred copolymers as the polymer dispersant include styrene-styrene sulfonic acid copolymer, styrene-maleic acid copolymer, styrene-methacrylic acid copolymer, styrene-acrylic acid copolymer, vinyl naphthalene- Maleic acid copolymer, vinyl naphthalene-methacrylic acid copolymer, vinyl naphthalene-acrylic acid copolymer, alkyl acrylate ester-acrylic acid copolymer, alkyl methacrylate ester-methacrylic acid copolymer, styrene-methacrylic acid Alkyl ester-methacrylic acid copolymer, styrene-acrylic acid alkyl ester-acrylic acid copolymer, styrene-methacrylic acid phenyl ester-methacrylic acid copolymer, styrene-methacrylic acid cyclohexyl ester-methacrylic acid copolymer, and These salts It is. Moreover, you may copolymerize the monomer which has a polyoxyethylene group and a hydroxyl group with these polymers.

  The weight average molecular weight (Mw) of the polymer dispersant is preferably 2,000 or more and 50,000 or less, for example.

  A pigment dispersant may be used individually by 1 type, or may use 2 or more types together. Although the content of the pigment dispersant varies greatly depending on the pigment, it cannot be generally stated, but it is preferably 0.1 parts by weight or more and 100 parts by weight or less with respect to 100 parts by weight of the pigment.

  Examples of the pigment include a pigment that self-disperses in water (hereinafter also referred to as “self-dispersing pigment”). The self-dispersing pigment refers to a pigment that has a water-solubilizing group on the pigment surface and disperses in water without the presence of a polymer dispersant. The self-dispersing pigment can be obtained, for example, by subjecting the pigment to surface modification treatment such as acid / base treatment, coupling agent treatment, polymer graft treatment, plasma treatment, oxidation / reduction treatment, and the like.

  As the self-dispersing pigment, in addition to the above-described pigment subjected to surface modification treatment, Cab-o-jet-200, Cab-o-jet-300, Cab-o-jet-400 manufactured by Cabot Corporation. , IJX-157, IJX-253, IJX-266, IJX-273, IJX-444, IJX-55, Cab-o-jet-250C, Cab-o-jet-260M, Cab-o-jet-270Y, Cab -O-jet-450C, Cab-o-jet-465M, Cab-o-jet-470Y, Cab-o-jet-480M, Microjet Black CW-1, CW-2 manufactured by Orient Chemical Industries, Ltd. Commercially available self-dispersing pigments can also be mentioned.

  The self-dispersing pigment is preferably a pigment having at least a sulfonic acid, a sulfonate, a carboxylic acid, or a carboxylate as a functional group on the surface, and at least a carboxylic acid or a carboxylic acid as a functional group on the surface. A pigment having a salt is more preferable.

  Here, examples of the pigment include a pigment coated with a resin. This is called a microcapsule pigment, and examples thereof include commercially available microcapsule pigments manufactured by DIC Corporation and Toyo Ink Corporation. In addition, it is not restricted to a commercially available microcapsule pigment, You may use the microcapsule pigment produced according to the objective.

  Examples of the pigment also include a resin dispersion type pigment in which a polymer compound is physically adsorbed or chemically bonded to the pigment.

  In addition to black pigments, cyan, magenta, and yellow primary pigments, specific pigments such as red, green, blue, brown, and white, metallic luster pigments such as gold and silver, and colorless or light colored pigments. Examples include extender pigments and plastic pigments.

  Examples of the pigment include particles having silica, alumina, polymer beads or the like as a core, and a dye or pigment fixed on the surface thereof, an insoluble lake of the dye, a colored emulsion, a colored latex, and the like.

  As colorants, in addition to pigments, other hydrophilic anionic dyes, direct dyes, cationic dyes, reactive dyes, polymer dyes and oil-soluble dyes, wax powders and resin powders colored with dyes And emulsions, fluorescent dyes and fluorescent pigments.

  The volume average particle diameter of the colorant is preferably 10 nm or more and 1,000 nm or less. The volume average particle diameter of the colorant refers to the particle diameter of the colorant itself, or the particle diameter to which the additive has adhered when an additive such as a dispersant is attached to the colorant. The volume average particle size is measured with a Microtrac UPA particle size analyzer UPA-UT151 (manufactured by Microtrac). The measurement is performed by placing 1,000-fold diluted ink in a measurement cell. As input values at the time of measurement, the viscosity is the viscosity of the ink diluent, and the particle refractive index is the refractive index of the colorant.

  The content (concentration) of the colorant is, for example, preferably from 1% by weight to 25% by weight and more preferably from 2% by weight to 20% by weight with respect to the total weight of the ink composition.

〔water〕
The ink composition used in the present embodiment contains water. As water, ion-exchanged water, ultrapure water, distilled water, and ultrafiltered water are particularly preferable from the viewpoint of preventing contamination of impurities or generation of microorganisms.

  The water content is preferably, for example, from 10% to 95% by weight, and more preferably from 30% to 90% by weight, based on the total weight of the ink composition.

(Water-soluble organic solvent)
The ink composition according to this embodiment contains a water-soluble organic solvent. Examples of the water-soluble organic solvent include polyhydric alcohols, polyhydric alcohol derivatives, nitrogen-containing solvents, alcohols, sulfur-containing solvents, and the like. In addition, examples of the water-soluble organic solvent include propylene carbonate and ethylene carbonate.

  Examples of polyhydric alcohols include ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,5-pentanediol, 1,2-hexanediol, 1,2,6-hexanetriol, glycerin, Examples thereof include sugar alcohols such as trimethylolpropane and xylitol; sugars such as xylose, glucose and galactose.

  Examples of the polyhydric alcohol derivatives include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monobutyl ether, dipropylene glycol monobutyl ether, Examples thereof include ethylene oxide adducts of diglycerin.

  Examples of the nitrogen-containing solvent include pyrrolidone, N-methyl-2-pyrrolidone, cyclohexyl pyrrolidone, triethanolamine and the like.

  Examples of alcohols include ethanol, isopropyl alcohol, butyl alcohol, and benzyl alcohol.

  Examples of the sulfur-containing solvent include thiodiethanol, thiodiglycerol, sulfolane, dimethyl sulfoxide, and the like.

  The water-soluble organic solvent may be contained singly or in combination of two or more. The content of the water-soluble organic solvent is preferably from 0.1% by weight to 60% by weight, more preferably from 1% by weight to 50% by weight, based on the total weight of the ink composition. It is more preferably 5% by weight or more and 40% by weight or less, and particularly preferably 10% by weight or more and 30% by weight or less.

[Surfactant]
The ink composition used in the present embodiment preferably contains a surfactant. By containing the surfactant, the ink ejection stability, the ink wettability with respect to the non-permeable recording medium, and the like may be improved as compared with the case where the surfactant is not contained.

  Examples of the surfactant include an ethylene oxide adduct of acetylene glycol, an ethylene oxide adduct of acetylene alcohol, and a polyether-modified silicone. Among these, ethylene oxide adduct of acetylene glycol and polyether-modified silicone are preferable.

The ethylene oxide adduct of acetylene glycol is, for example, an —O— (CH ₂ CH ₂ O) _n —H structure in which ethylene oxide is added to at least one hydroxyl group of acetylene glycol (for example, n is an integer of 1 to 30) And the like. Examples of commercially available acetylene glycol ethylene oxide adducts (numbers in parentheses indicate HLB catalog values) include, for example, Olphine E1004 (from 7 to 9), Olphine E1010 (from 13 to 14), Olfin EXP. 4001 (8 to 11), Olphin EXP. 4123 (11 to 14), Olphin EXP. 4300 (from 10 to 13), Surfinol 104H (4), Surfinol 420 (4), Surfinol 440 (4), Dinol 604 (8) (all manufactured by Nissin Chemical Industry Co., Ltd.) and the like. .

  The polyether-modified silicone is, for example, a compound in which a polyether group is bonded to a silicone chain (polysiloxane main chain) in a graft shape, or a compound in which a polyether group is bonded in a block shape. Examples of the polyether group include a polyoxyethylene group and a polyoxypropylene group. The polyether group may be, for example, a polyoxyalkylene group in which an oxyethylene group and an oxypropylene group are added in a block form or randomly. Examples of commercially available polyether-modified silicones (the values in parentheses indicate HLB catalog values) are Silface SAG002 (12), Silface SAG503A (11), Silface SAG005 (7) Shin Chemical Industry Co., Ltd.).

  Examples of other surfactants other than those described above include anionic surfactants, nonionic surfactants, cationic surfactants, amphoteric surfactants, and the like. Among these, anionic surfactants, Nonionic surfactants and the like are preferable.

  Examples of the anionic surfactant include alkylbenzene sulfonate, alkylphenyl sulfonate, alkylnaphthalene sulfonate, higher fatty acid salt, sulfate of higher fatty acid ester, sulfonate of higher fatty acid ester, higher alcohol ether. And sulfates and sulfonates thereof, higher alkyl sulfosuccinates, polyoxyethylene alkyl ether carboxylates, polyoxyethylene alkyl ether sulfates, alkyl phosphates, polyoxyethylene alkyl ether phosphates, and the like. Among these, for example, dodecylbenzenesulfonate, isopropylnaphthalenesulfonate, monobutylphenylphenol monosulfonate, monobutylbiphenylsulfonate, monobutylbiphenylsulfonate, dibutylphenylphenol disulfonate, etc. preferable.

  Nonionic surfactants include, for example, polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, glycerin fatty acid ester , Polyoxyethylene glycerin fatty acid ester, polyglycerin fatty acid ester, sucrose fatty acid ester, polyoxyethylene alkylamine, polyoxyethylene fatty acid amide, alkyl alkanolamide, polyethylene glycol polypropylene glycol block copolymer, acetylene glycol and the like. Among these, for example, polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene alkyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester , Fatty acid alkylolamide, polyethylene glycol polypropylene glycol block copolymer, acetylene glycol and the like are preferable.

  Other nonionic surfactants include silicone surfactants such as polysiloxane oxyethylene adducts, fluorine surfactants such as perfluoroalkyl carboxylates, perfluoroalkyl sulfonates, and oxyethylene perfluoroalkyl ethers, Examples thereof include biosurfactants such as spicrispolic acid, rhamnolipid, and lysolecithin.

  The content of the surfactant in the ink is, for example, preferably from 0.01% by weight to 20% by weight, and preferably from 0.1% by weight to 10% by weight, based on the total weight of the ink composition. Is more preferably 0.5% by weight or more and 8% by weight or less, and particularly preferably 2% by weight or more and 5% by weight or less.

[Other additives]
The ink composition used in the present embodiment may contain additives other than those described above. There is no restriction | limiting in particular as another additive, A well-known additive is used. Specifically, for example, an ink dischargeability improving agent (polyethyleneimine, polyamines, polyvinylpyrrolidone, polyethylene glycol, ethylcellulose, carboxymethylcellulose, etc.), conductivity / pH adjuster (potassium hydroxide, sodium hydroxide, lithium hydroxide) Etc.), reactive diluents, penetrants, pH buffers, antioxidants, fungicides, viscosity modifiers, conducting agents, chelating agents, ultraviolet absorbers, infrared absorbers, etc. Is mentioned.

  The pH of the ink composition used in the present embodiment is, for example, preferably 4 or more and 10 or less, and more preferably 5 or more and 9 or less. As the pH of the ink, a value measured with a pH / conductivity meter (MPC227 manufactured by METTLER TOLEDO) under a temperature of 23 ± 0.5 ° C. and a humidity of 55 ± 5% RH is adopted.

  The conductivity of the ink composition used in the present embodiment is, for example, preferably 0.01 S / m or more and 0.5 S / m or less, and preferably 0.01 S / m or more and 0.25 S / m or less. More preferably, it is 0.01 S / m or more and 0.20 S / m or less. The conductivity is measured by MPC227 (pH / Conductivity Meter, manufactured by METTLER TOLEDO).

The viscosity of the ink composition used in the present embodiment is, for example, preferably from 1.5 mPa · s to 30 mPa · s, and more preferably from 1.5 mPa · s to 20 mPa · s. Viscosity is measured using TV-20 (manufactured by Toki Sangyo Co., Ltd.) as a measuring device, at a measurement temperature of 23 ° C. and a shear rate of 1,400 s ⁻¹ .

(Recording device)
The recording apparatus of the present embodiment is a recording apparatus that includes an ejection head that ejects the ink composition according to the present embodiment onto a non-permeable recording medium. In addition, the recording method according to the present embodiment is a recording method including, for example, a discharge step of discharging the ink composition according to the present embodiment onto a non-permeable recording medium.

  The recording apparatus of the present embodiment may include an ink cartridge that accommodates the ink composition according to the present embodiment and is made into a cartridge so as to be attached to and detached from the recording apparatus.

(recoding media)
Examples of the impermeable recording medium used in the recording apparatus of the present embodiment include coated paper and resin film. In the present embodiment, a non-permeable recording medium having a transfer amount of pure water to a recording medium of 3 ml / m ² or more and 15 ml / m ² or less at a contact time of 100 ms measured with a dynamic scanning absorption meter is used. It is preferable.

  Hereinafter, an example of the image recording apparatus of the present embodiment will be described with reference to the drawings.

  FIG. 2 is a schematic configuration diagram illustrating an example of a recording apparatus according to the present embodiment. A recording apparatus 10 shown in FIG. 2 has an ejection head 122 (an ejection apparatus having the ejection head 122) that ejects the ink composition (hereinafter also referred to as “ink”) according to the above-described embodiment onto a non-permeable recording medium P. 121). In the recording apparatus 10, a recording method including an ejection process for ejecting ink onto the impermeable recording medium P is realized. As a result, an ink image is recorded on the impermeable recording medium P.

  Specifically, the recording apparatus 10 includes, for example, an image recording unit 12 that records an image on continuous paper (hereinafter, also referred to as “continuous paper P”) as an impermeable recording medium P. .

  The recording apparatus 10 adjusts the pre-processing unit 14 in which the continuous paper P supplied to the image recording unit 12 is accommodated, the conveyance amount of the continuous paper P supplied from the pre-processing unit 14 to the image recording unit 12, and the like. And a buffer unit 16. The buffer unit 16 is disposed between the image recording unit 12 and the preprocessing unit 14.

  The recording apparatus 10 includes, for example, a post-processing unit 18 that stores the continuous paper P discharged from the image recording unit 12, and a conveyance amount of the continuous paper P discharged from the image recording unit 12 to the post-processing unit 18. A buffer unit 20 to be adjusted. The buffer unit 20 is disposed between the image recording unit 12 and the post-processing unit 18.

  The recording apparatus 10 includes a cooling unit 22 that is disposed between the image recording unit 12 and the buffer unit 20 and cools the continuous paper P that is carried out of the image recording unit 12.

  The image recording unit 12 includes, for example, a roll member (not shown) that guides the continuous paper P along the conveyance path 124 of the continuous paper P, and a continuous paper that is conveyed along the conveyance path 124 of the continuous paper P. And an ejection device 121 that ejects ink (ink droplets) onto the paper P to record an image.

  The ejection device 121 includes an ejection head 122 that ejects ink onto the continuous paper P. The ejection head 122 has, for example, an effective recording area (arrangement area of nozzles for ejecting ink) equal to or greater than the width of the continuous paper P (the length in a direction intersecting (for example, orthogonal to) the continuous paper P conveyance direction). This is a long recording head. The ejection head 122 is not limited to this, and is an ejection head that is shorter than the width of the continuous paper P, and is a system that discharges ink by moving in the width direction of the continuous paper P (so-called carriage system). ).

  The ejection head 122 may be a so-called thermal system that ejects ink droplets by heat, or may be a so-called piezo system that ejects ink droplets by pressure. Applied.

  The ejection head 122 includes, for example, an ejection head 122K that ejects ink onto the continuous paper P and records a K (black) color image, an ejection head 122Y that records a Y (yellow) color image, and an M (magenta). ) A discharge head 122M that records a color image, and a discharge head 122C that records a C (cyan) color image. The ejection head 122K, the ejection head 122Y, the ejection head 122M, and the ejection head 122C are in this order in the transport direction of the continuous paper P (hereinafter, simply referred to as “paper transport direction”). Are arranged so as to face the continuous paper P from the upstream side to the downstream side. In the description of the ejection head, when K, Y, M, and C are not distinguished, the symbols K, Y, M, and C are omitted.

  The ejection heads 122K, 122Y, 122M, and 122C are connected to ink cartridges 123K, 123Y, 123M, and 123C of each color that are attached to and detached from the recording apparatus 10 through supply pipes (not shown). Are supplied to the ejection head 122, respectively.

  The ejection head 122 is not limited to the form in which the four ejection heads 122 corresponding to each of the above four colors are arranged, and according to the purpose, four or more ejections corresponding to each of four or more colors including other intermediate colors. The form which has arrange | positioned the head 122 may be sufficient.

  As the ejection head 122, for example, a low-resolution ejection head 122 (for example, a 600 dpi ejection head) that ejects ink in an ink droplet amount range of 1 pl to 15 pl, and ejects ink in an ink droplet amount range of less than 10 pl. Any of the high-resolution ejection heads 122 (for example, a 1,200 dpi ejection head) may be provided. Further, the ejection device 121 may include both a low resolution ejection head 122 and a high resolution ejection head 122. The ink droplet amount of the ejection head 122 is in the range of the maximum ink droplet amount. In addition, dpi means “dot per inch”.

  For example, the back side of the continuous paper P is wound on the downstream side of the discharge head 122 in the paper conveyance direction, and the image on the continuous paper P is in contact with the conveyed continuous paper P and rotated in a driven manner. A drying drum 126 (an example of a drying device) for drying (ink) is disposed.

  For example, a heating source (for example, a halogen heater or the like: not shown) is built in the drying drum 126. The drying drum 126 dries the image (ink) on the continuous paper P by heating with a heating source.

  Around the drying drum 126, for example, a hot air blowing device 128 (an example of a drying device) that dries images (ink) on the continuous paper P is disposed. The image (ink) on the continuous paper P wound around the drying drum 126 is dried by the warm air from the warm air blower 128.

  Other drying devices such as a near-infrared heater (not shown) for drying the image (ink) on the continuous paper P and a laser irradiation device are disposed on the downstream side in the paper conveyance direction with respect to the ejection head 122. Also good. Other drying devices such as a near-infrared heater and a laser irradiation device are arranged instead of at least one of the drying drum 126 and the hot air blowing device 128 or in addition to the drying drum 126 and the hot air blowing device 128.

  On the other hand, the preprocessing unit 14 includes a supply roll 14A around which the continuous paper P supplied to the image recording unit 12 is wound. The supply roll 14A is rotatably supported by a frame member (not shown). ing.

  In the buffer unit 16, for example, a first pass roller 16A, a dancer roller 16B, and a second pass roller 16C are arranged along the paper transport direction. The dancer roller 16 </ b> B moves up and down in FIG. 2 to adjust the tension of the continuous paper P conveyed to the image recording unit 12 and the conveyance amount of the continuous paper P.

  The post-processing unit 18 includes, for example, a winding roll 18A as an example of a transport unit that winds the continuous paper P on which images are recorded. The take-up roll 18 </ b> A receives a rotational force from a motor (not shown) and rotates so that the continuous paper P is transported along the transport path 124.

  In the buffer unit 20, for example, a first pass roller 20A, a dancer roller 20B, and a second pass roller 20C are arranged along the paper transport direction. The dancer roller 16 </ b> B moves up and down in FIG. 1 to adjust the tension of the continuous paper P discharged to the post-processing unit 18 and the conveyance amount of the continuous paper P.

  For example, a plurality of cooling rollers 22 </ b> A are arranged in the cooling unit 22. The continuous paper P is cooled by conveying the continuous paper P between the plurality of cooling rollers 22A.

  Next, an operation (recording method) by the recording apparatus 10 according to the present embodiment will be described.

  In the recording apparatus 10 according to the present embodiment, first, the continuous paper P is conveyed from the supply roll 14 </ b> A of the preprocessing unit 14 to the image recording unit 12 through the buffer unit 16.

  Next, in the image recording unit 12, ink is ejected from the ejection heads 122 of the ejection device 121 onto the continuous paper P. As a result, an ink image is formed on the continuous paper P.

  Thereafter, the image (ink) on the continuous paper P is dried from the back side of the continuous paper P (the surface opposite to the recording surface) by the drying drum 126. Then, the ink (image) discharged onto the continuous paper P is dried from the surface side (recording surface) of the continuous paper P by the hot air blower 128. That is, the ink discharged onto the continuous paper P is dried by the drying drum 126 and the hot air blowing device 128.

  Next, in the cooling unit 22, the continuous paper P on which the images are recorded is cooled by the cooling roller 22A.

  Next, through the buffer unit 16, the post-processing unit 18 winds the continuous paper P on which the images are recorded by the winding roll 18A.

  Through the steps described above, an ink image is recorded on the continuous paper P as the recording medium P. In the recording apparatus 10, the ink droplets are directly ejected onto the surface of the recording medium P by the ejection device 121 (ejection head 122). However, the present invention is not limited to this. Alternatively, the ink droplets on the intermediate transfer member may be transferred to the recording medium P after the ink is discharged.

  In the recording apparatus 10, the method of recording an image by ejecting ink onto the continuous paper P as the recording medium P has been described. However, as the recording medium P, an image is recorded by ejecting ink onto a sheet of paper. There may be.

  Hereinafter, although an example and a comparative example are given and the present invention is explained more concretely in detail, the present invention is not limited to the following examples.

<Example 1>
The following components were mixed to prepare an ink.
-CAB-O-JET 400 (manufactured by Cabot): 6% by mass- M6969D (resin particle dispersion: manufactured by Nippon Synthetic Chemical Industry): 2 parts by mass (resin solid content)
(Acrylic resin particles, glass transition temperature = 80 ° C.)
M7980 (resin particle dispersion: manufactured by Nippon Synthetic Chemical Industry Co., Ltd.): 2 parts by mass (resin solid content) (acrylic resin, glass transition temperature = 55 ° C.)
Propylene glycol: 15 parts by mass 3-Methyl-1,3-butanediol: 10 parts by mass Surfynol 440 (surfactant; manufactured by Air Products): 1.5 parts by mass Ion-exchanged water: 100 in total Remaining amount

  After mixing the above components, the mixture was filtered with a 5 μm filter to obtain an ink. The difference in glass transition temperature between M6969D resin particles and M7980 resin particles in the ink is 25 ° C.

<Examples 2-3>
In Example 2, an ink was prepared in the same manner as in Example 1 except that the resin particle dispersion M7980 was changed to M7180 (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.). The resin particle dispersion M7180 used in Example 2 is a dispersion containing acrylic resin particles having a glass transition temperature of 53 ° C. Therefore, the difference in glass transition temperature between the M6969D resin particles and the M7180 resin particles in the ink of Example 2 is 27 ° C.

  In Example 3, ink was prepared in the same manner as in Example 1 except that the resin particle dispersion M7980 was changed to M6520 (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.). The resin particle dispersion M6520 used in Example 3 is a dispersion containing acrylic resin particles having a glass transition temperature of 41 ° C. Therefore, the difference in glass transition temperature between the M6520 resin particles and the M6969D resin particles in the ink of Example 3 is 39 ° C.

<Example 4>
In Example 4, an ink was prepared in the same manner as in Example 1 except that the resin particle dispersion M7980 was changed to MLDM7582 (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.). The resin particle dispersion MLDM7582 used in Example 4 is a dispersion containing acrylic resin particles having a glass transition temperature of 26 ° C. Moreover, MLDM7582 resin particle / M6969D resin particle in the ink of Example 4 is 50/50 by mass ratio. The difference in glass transition temperature between MLDM7582 resin particles and M6969D resin particles in the ink of Example 4 is 54 ° C.

<Examples 5-6>
In Example 5, an ink was prepared in the same manner as in Example 1 except that the mass ratio of M7980 resin particles / M6969 resin particles in the ink was changed to 40/60. In Example 6, an ink was prepared in the same manner as in Example 1 except that the mass ratio of M7980 resin particles / M6969 resin particles in the ink was changed to 10/90.

<Comparative Example 1>
In Comparative Example 1, an ink was prepared in the same manner as in Example 1 except that the resin particle dispersion M6969D was not added.

<Comparative example 2>
In Comparative Example 2, an ink was prepared in the same manner as in Example 1 except that the resin particle dispersion M7980 was not added.

<Comparative Examples 3-4>
In Comparative Example 3, an ink was prepared in the same manner as in Example 1 except that the resin particle dispersion M6969 was changed to M7180, and in Comparative Example 4, the resin particle dispersion M6969 was changed to M6520. The difference in glass transition temperature between the M7980 resin particles and the M7180 resin particles in the ink of Comparative Example 3 is 2 ° C. The difference in glass transition temperature between M7980 resin particles and M7180 resin particles in the ink of Comparative Example 4 is 11 ° C.

<Motor (σ) evaluation>
Using an automatic bar coater K101 (manufactured by Matsuo Sangyo Co., Ltd.), the above ink was applied onto “OK Topcoat +” made by Oji Paper as a non-permeable recording medium and dried. The dried ink-coated sample is scanned by a scanner (ES-10000G: manufactured by Seiko Epson), and density data (1 pxl width / image J) in the direction perpendicular to the coating direction (width direction of the ink-coated sample) is acquired. did. The standard deviation of the density data was calculated from the obtained density data, and the value was defined as σ (motor). The value of σ (Motor) is an alternative index for density unevenness, and the smaller the value, the less the density unevenness of the coated sample.

  In Table 1, the glass transition temperature of the resin particle in Examples 1-6 and Comparative Examples 1-4, the difference of glass transition temperature, mass ratio, and (sigma) (motor) value are shown.

(Evaluation of density unevenness with actual machine)
A recording apparatus having the same configuration as that shown in FIG. 2 and having a 600 dpi piezo head (maximum ink droplet amount 12 pl) was prepared as an ink ejection head. Then, the ink tanks of the recording apparatuses were filled with the inks of the examples and comparative examples. The following image recording was performed using this recording apparatus.

  Using the above recording apparatus, ink is ejected from a 600 dpi piezo head (maximum ink droplet amount 11 pl) onto Oji Paper's “OK Topcoat +” at a recording speed (recording medium transport speed) of 100 m / min, and printing is performed. And a solid image (1.5 cm × 1.5 cm) was formed. The formed solid image was visually observed, and the density unevenness of the image was evaluated according to the following criteria. The results are shown in Table 1.

-Evaluation criteria for uneven density-
A: No density unevenness is observed.
○: Slight density unevenness is observed.
Δ: Density unevenness is observed.
X: Remarkable density unevenness is observed.

  The inks of Examples 1 to 6 using two kinds of resin particles having a glass transition temperature difference of 20 ° C. or more both have a σ (motor) value of 2, and one kind of resin particles was used. Compared to the inks of Comparative Examples 1 and 2 and the inks of Comparative Examples 3 to 4 using two kinds of resin particles having a glass transition temperature difference of less than 20 ° C., the density unevenness was small. Also, in the evaluation with actual machines, the density unevenness of the inks of Examples 1 to 6 was suppressed as compared with the inks of Comparative Examples 1 to 4.

  Further, Example 5 in which the mass ratio of M7980 resin particles / M6969D resin particles in the ink is 80/20 or more and 20/80 or less is more uneven in image density than Example 6 which is outside the above range. Suppressed.

DESCRIPTION OF SYMBOLS 1 Impermeable recording medium, 2 Ink composition, 3 Resin particle, 4 Ink film, 10 Recording apparatus, 12 Image recording unit, 14 Pre-processing unit, 14A Supply roll, 16 Buffer unit, 16A Pass roller, 16B Dancer roller, 16C pass roller, 18 post-processing unit, 18A take-up roll, 20 buffer unit, 20A pass roller, 20B dancer roller, 20C pass roller, 22 cooling unit, 22A cooling roller, 121 discharge device, 122, 122K, 122Y, 122M, 122C discharge head , 123, 123K, 123Y, 123M, 123C Ink cartridge, 124 transport path, 126 drying drum, 128 hot air blower.

Claims (3)

A colorant, at least two resin particles having different glass transition temperatures, water, and a water-soluble organic solvent;
The difference in glass transition temperature between the two types of resin particles is 20 ° C. or more.   The ink composition according to claim 1, wherein the resin particles have a glass transition temperature of 40 ° C. or higher. An ejection head for ejecting ink onto a recording medium;
The recording apparatus according to claim 1, wherein the ink is the ink composition according to claim 1.

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