Ink, ink set, inkjet printing device, and inkjet printing method

Abstract

To provide an ink having excellent image density on a plain paper medium and also having excellent curling resistance.SOLUTION: An ink is for use in an inkjet printer having an inkjet head that has a nozzle for discharging ink and further having a nozzle plate with an ink-repelling layer containing silicon resin or fluororesin at least on an ink discharge side surface. An ink contains a colorant, a water-soluble organic solvent, naphthalenesulfonic acid-formaldehyde condensate or the like, or polyoxyethylene-β-naphthyl ether or the like, and water. The product of a viscosity η [mPa s] at 25°C with a rotational viscometer and a surface tension σ [mN / m] with a bubble life time of 150 ms at 25°C by the maximum bubble pressure method is 100 or more and 130 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an ink, an ink set, an inkjet printing apparatus, and an inkjet printing method. [Background technology]

[0002] Patent Document 1 describes a double-sided printing method in which the sheet is conveyed from the start of printing on the front side to the start of printing on the back side within three seconds. Patent Document 2 describes an ink containing two or more polysiloxane surfactants with different HLBs. Patent Document 3 describes an ink containing carbon black having a hydrophilic group and carbon black dispersed with a sodium naphthalenesulfonate formalin condensate. Summary of the Invention [Problem to be solved by the invention]

[0003] An object of the present invention is to provide an ink that exhibits good image density and curl resistance, and also has good storage stability, particularly when applied to plain paper media. [Means for solving the problem]

[0004] The present invention, which solves the above problems, relates to an ink as described in (1) below. (1) An ink for use in an inkjet printing device having an inkjet head equipped with a nozzle plate having a nozzle for ejecting ink and further having an ink-repellent layer containing a silicone resin or a fluororesin on at least the ink ejection surface side, the ink contains a colorant, a water-soluble organic solvent, a compound represented by the following general formula (1) or the following general formula (2), and water, An ink characterized in that the product of the viscosity η [mPa s] at 25°C measured with a rotational viscometer and the surface tension σ [mN / m] at 25°C measured with a maximum bubble pressure method when the bubble life time is 150 ms is 100 or more and 130 or less. [ka] (In general formula (1), m represents an integer of 1 to 4.) [ka] (In general formula (2), R 1 represents an alkyl group having 1 to 20 carbon atoms, an aralkyl group having 7 to 8 carbon atoms, or an allyl group, l represents an integer of 0 to 7, and n represents an integer of 20 to 200. [Effects of the Invention]

[0005] The ink of the present invention exhibits good image density and curl resistance when applied to plain paper media, and also has good storage stability. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a perspective view showing an example of an inkjet printing apparatus of the present invention. [Figure 2] FIG. 2 is a cross-sectional view showing an example of the overall configuration of the inkjet printing apparatus of the present invention. [Figure 3] FIG. 3 is an explanatory plan view showing an example of a nozzle plate in the inkjet printing apparatus of the present invention. [Figure 4] FIG. 4 is an enlarged cross-sectional view illustrating a nozzle portion of a nozzle plate in the inkjet printing apparatus of the present invention. [Figure 5] FIG. 5 is a diagram showing a state in which an ink-repellent layer is formed by applying silicone resin using a dispenser. DETAILED DESCRIPTION OF THE INVENTION

[0007] Generally, the degree of ink penetration into plain paper media is determined by the viscosity and surface tension of the ink. If both values ​​are high, the ink will not penetrate easily, and conversely, if both values ​​are low, the ink will penetrate easily. If the ink does not penetrate easily, the coloring material remains on the surface of the media, which can be expected to produce a high density, but on the other hand, the fixability deteriorates and the media surface curls significantly due to the slow penetration. On the other hand, if the ink penetrates easily, improvement in fixation can be expected, but the image density decreases and the back surface of the media curls significantly due to the rapid penetration.

[0008] The degree of ink penetration into media is affected by both viscosity and surface tension, and if either value is extremely small, the ink will penetrate easily, and conversely, if either value is extremely large, the ink will penetrate less. It is believed that specifying the ink viscosity and surface tension separately will make it impossible to achieve both good image density and curl resistance. The ink of the present invention controls the permeability by specifying the product (η × σ) of the viscosity η [mPa s] and the surface tension σ [mN / m], and when applied to plain paper, it exhibits good image density and curl resistance as well as good storage stability.

[0009] The ink of the present invention comprises a colorant, a water-soluble organic solvent, a compound represented by general formula (1) or (2), and water, and the product of the viscosity η [mPa s] at 25°C as measured with a rotational viscometer and the surface tension σ [mN / m] at 25°C when the bubble life time is 150 ms as measured with the maximum bubble pressure method is 100 or more and 130 or less. The ink of the present invention is used in an inkjet printing device having an inkjet head equipped with a nozzle plate having a nozzle for ejecting ink and further having an ink-repellent layer containing a silicone resin or a fluororesin on at least the surface on the ink ejection surface side. By using the ink of the present invention in the inkjet printing device, excellent ejection stability can be obtained, and in particular, both image density and curl resistance can be achieved on plain paper media. The components of the ink of the present invention will be described below.

[0010] <Ink> The organic solvent, water, coloring material, resin, additives, etc. used in the ink will be described below.

[0011] <Organic solvents> The organic solvent used in the present invention is not particularly limited, and any water-soluble organic solvent can be used, including, for example, polyhydric alcohols, ethers such as polyhydric alcohol alkyl ethers and polyhydric alcohol aryl ethers, nitrogen-containing heterocyclic compounds, amides, amines, and sulfur-containing compounds. Specific examples of the water-soluble organic solvent include ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 3-methyl-1,3-butanediol, triethylene glycol, polyethylene glycol, polypropylene glycol, 1,2-pentanediol, 1,3-pentanediol, 1,4-pentanediol, 2,4-pentanediol, 1,5-pentanediol, and the like. Polyhydric alcohols such as hexanediol, 1,2-hexanediol, 1,6-hexanediol, 1,3-hexanediol, 2,5-hexanediol, 1,5-hexanediol, glycerin, 1,2,6-hexanetriol, 2-ethyl-1,3-hexanediol, ethyl-1,2,4-butanetriol, 1,2,3-butanetriol, 2,2,4-trimethyl-1,3-pentanediol, and petriol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, Examples of the alkyl ether include polyhydric alcohol alkyl ethers such as ethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, and propylene glycol monoethyl ether; polyhydric alcohol aryl ethers such as ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether; nitrogen-containing heterocyclic compounds such as 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, ε-caprolactam, and γ-butyrolactone; amides such as formamide, N-methylformamide, N,N-dimethylformamide, 3-methoxy-N,N-dimethylpropionamide, and 3-butoxy-N,N-dimethylpropionamide; amines such as monoethanolamine, diethanolamine, triethylamine, and trimethylglycine; sulfur-containing compounds such as dimethyl sulfoxide, sulfolane, and thiodiethanol; propylene carbonate; and ethylene carbonate.

[0012] Among the organic solvents, it is preferable to select one or more solvents that have a boiling point of 200°C or higher and a saturated moisture content of 50% or higher at a temperature of 25°C and a humidity of 50% RH, from the viewpoint of penetrating into the media, drying characteristics, etc. Specific examples of organic solvents include trimethylglycine, and it is preferable that the amount of such organic solvents be 5% by mass or more of the total amount of organic solvents contained in the ink.

[0013] In addition, from the viewpoint of ink storage stability, the SP value (Solubility Parameter) of the mixed solvent of organic solvents in the ink is 14.3 (cal / cm 3 ) 0.5 It is preferable that the above is set. In addition, when the organic solvent in the ink is a mixed solvent consisting of a mixture of multiple organic solvents, the SP value of the mixed solvent is 14.3 (cal / cm 3 ) 0.5 It is preferable that this is equal to or greater than this. When a mixed solvent is composed of n kinds of organic solvents, the SP value of the mixed solvent can be calculated specifically by the following formula. SP value of the mixed organic solvent in the ink (cal / cm 3 ) 0.5 = [SP value of organic solvent S1 × volume fraction of organic solvent S1] + +[Organic Solvent S n SP value × organic solvent S n volume fraction of

[0014] Polyol compounds having 8 or more carbon atoms and glycol ether compounds are also preferably used. Specific examples of polyol compounds having 8 or more carbon atoms include 2-ethyl-1,3-hexanediol and 2,2,4-trimethyl-1,3-pentanediol. Specific examples of glycol ether compounds include polyhydric alcohol alkyl ethers such as 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; and polyhydric alcohol aryl ethers such as ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether.

[0015] Polyol compounds having 8 or more carbon atoms and glycol ether compounds can improve the permeability of ink when paper is used as the recording medium.

[0016] The content of the organic solvent in the ink is not particularly limited and can be selected appropriately depending on the purpose. From the viewpoint of the drying property and ejection reliability of the ink, however, the content is preferably 10% by mass or more and 60% by mass or less, and more preferably 20% by mass or more and 60% by mass or less.

[0017] <Water> The water content in the ink is not particularly limited and can be selected appropriately depending on the purpose, but from the viewpoint of the drying property and ejection reliability of the ink, it is preferably 10% by mass or more and 90% by mass or less, and more preferably 20% by mass to 60% by mass.

[0018] <Colorant> The coloring material is not particularly limited, and pigments and dyes can be used. The pigment may be an inorganic pigment or an organic pigment. These may be used alone or in combination of two or more. Mixed crystals may also be used. Examples of pigments that can be used include black pigments, yellow pigments, magenta pigments, cyan pigments, white pigments, green pigments, orange pigments, glossy pigments such as gold and silver pigments, and metallic pigments. As inorganic pigments, titanium oxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, chrome yellow, as well as carbon black produced by known methods such as the contact method, furnace method, and thermal method can be used. In addition, examples of organic pigments that can be used 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, and quinophthalone pigments), dye chelates (e.g., basic dye chelates and acid dye chelates), nitro pigments, nitroso pigments, and aniline black. Of these pigments, those with good affinity for the solvent are preferably used. In addition, resin hollow particles and inorganic hollow particles can also be used. Specific examples of pigments for black 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 oxide, and organic pigments such as aniline black (CI Pigment Black 1). In addition, for color, 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, CI Pigment Yellow Ranges 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 (Red Iron), 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 Pigment 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; CI Pigment Green 1, 4, 7, 8, 10, 17, 18, 36, etc. The dye is not particularly limited, and acid dyes, direct dyes, reactive dyes, and basic dyes can be used, and one type may be used alone, or two or more types may be used in combination. Examples of the 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. 14, 32, 55, 79, 249, and CI Reactive Black 3, 4, and 35.

[0019] It is preferable that the colorant for the black ink is carbon black, the colorant for the cyan ink is Pigment Blue 15:3, the colorant for the magenta ink is Pigment Red 122 or 269, and the colorant for the yellow ink is Pigment Yellow 74, as this provides storage stability and an expanded color gamut.

[0020] Methods for dispersing a pigment to obtain an ink include a method of introducing a hydrophilic functional group into the pigment to make it a self-dispersing pigment, a method of dispersing the pigment by coating the surface of the pigment with a resin, and a method of dispersing the pigment using a dispersant. As a method for introducing a hydrophilic functional group into a pigment to make it a self-dispersible pigment, for example, a method of adding a functional group such as a sulfone group or a carboxyl group to a pigment (e.g., carbon) to make it dispersible in water can be mentioned. One method for dispersing a pigment by coating its surface with a resin is to encapsulate the pigment in microcapsules to make it dispersible in water. This can be rephrased as a resin-coated pigment. In this case, it is not necessary for all of the pigments blended into the ink to be coated with resin; uncoated or partially coated pigments may be dispersed in the ink, provided that the effects of the present invention are not impaired. Examples of the method for dispersing using a dispersant include a method for dispersing using a known low molecular weight dispersant or a high molecular weight dispersant, such as a surfactant.

[0021] The dispersant used is a compound represented by the following general formula (1) or (2). By using this dispersant, it is possible to obtain an aqueous pigment dispersion and an aqueous ink having a small average particle size and excellent storage stability. The content of the dispersant represented by general formula (1) or (2) is preferably 0.01 to 0.5, and more preferably 0.1 to 0.4, by mass ratio relative to the pigment in the ink 1. A content within this range is preferable because it allows the ink to have a small volume average particle size, improves the dispersibility of the pigment, and allows the ink viscosity to be adjusted appropriately.

[0022] [ka] (In general formula (1), m represents an integer of 1 to 4.) [ka] (In general formula (2), R 1 represents an alkyl group having 1 to 20 carbon atoms, an aralkyl group having 7 to 8 carbon atoms, or an allyl group, l represents an integer of 0 to 7, and n represents an integer of 20 to 200.

[0023] It is preferable to use a naphthalenesulfonic acid formalin condensate as the compound represented by general formula (1) and polyoxyethylene-β-naphthyl ether as the compound represented by general formula (2), since good dispersibility can be obtained.

[0024] <Fluorescent whitening agents> Fluorescent brightening agents absorb invisible short-wavelength ultraviolet light and convert it into visible purple to blue light, and are also called fluorescent dyes. These fluorescent brightening agents may be used to achieve a higher visual density. The fluorescent whitening agent used may be, for example, one having a structural unit represented by the following structural formula (1) or (2).

[0025] [ka] [ka]

[0026] Those having the structural unit represented by the structural formula (1) are benzoxazole or derivatives thereof, and those having the structural unit represented by the structural formula (2) are coumarin or derivatives thereof, and may be either hydrophilic or hydrophobic.

[0027] The content of the fluorescent brightening agent in the ink is preferably 0.001% by mass or more and 1% by mass or less, and more preferably 0.005% by mass or more and 0.2% by mass or less. By setting the content of the fluorescent brightening agent to 0.001% by mass or more, a high concentration can be visually observed. On the other hand, by setting the content of the fluorescent brightening agent to 1% by mass or less, concentration quenching, in which incident light is quickly absorbed or fluorescence intensity is reduced due to collisions between molecules, can be suppressed. Examples of commercially available fluorescent whitening agents include TINOPAL OB (manufactured by BASF), Nikkafluor OB, Nikkabright PAW-L, and Nikkafluor MCT (manufactured by Nippon Chemical Industry Co., Ltd.).

[0028] <Fluorescent whitening enhancer> In the present invention, a fluorescent brightening enhancer may be used to improve the effect of the fluorescent brightening agent. The fluorescent brightening enhancer improves the dispersibility of the fluorescent brightening agent and migrates it to the surface, thereby improving the effect of the fluorescent brightening agent. Specifically, the fluorescent brightening enhancer is a polyether polyol. The content of the fluorescent brightening enhancer in the ink is preferably 0.2% by mass or more and 2% by mass or less, and more preferably 0.5% by mass or more and 2% by mass or less, relative to the content of the colorant. By setting the content of the fluorescent brightening enhancer to 0.2% by mass or more relative to the content of the colorant, a high visual density can be achieved. On the other hand, by setting the content of the fluorescent brightening enhancer to 2% by mass or less relative to the content of the colorant, it is possible to improve ejection stability. As a fluorescent whitening enhancer, for example, a commercially available product such as Optiact I-10 manufactured by San Nopco Ltd. may be mentioned.

[0029] <Pigment dispersion> Ink can be obtained by mixing a pigment with water, an organic solvent, or other materials. Alternatively, ink can be produced by mixing a pigment with other materials such as water and a dispersant to form a pigment dispersion, and then mixing the resulting mixture with water, an organic solvent, or other materials. The pigment dispersion is obtained by mixing and dispersing water, a pigment, a pigment dispersant, and optionally other components, and adjusting the particle size. Dispersion is preferably performed using a disperser. Although there are no particular restrictions on the particle size of the pigment in the pigment dispersion, the maximum frequency, calculated as the maximum number, is preferably 20 nm or more and 500 nm or less, and more preferably 20 nm or more and 150 nm or less, in order to improve the dispersion stability of the pigment and the image quality such as ejection stability and image density. The particle size of the pigment can be measured using a particle size analyzer (Nanotrac Wave-UT151, manufactured by Microtrac Bell Co., Ltd.). The content of the pigment in the pigment dispersion is not particularly limited and can be appropriately selected depending on the purpose. However, from the viewpoint of obtaining good ejection stability and increasing image density, the content is preferably 0.1% by mass or more and 50% by mass or less, and more preferably 0.1% by mass or more and 30% by mass or less. It is preferable that the pigment dispersion is degassed, if necessary, by filtering coarse particles using a filter, a centrifugal separator, or the like.

[0030] <Resin> In the present invention, the ink contains a polyether-based urethane resin represented by the following general formula (7). The inclusion of the polyether-based urethane resin represented by general formula (7) stabilizes the dispersion of the pigment, resulting in particularly excellent storage stability. The resin represented by general formula (7) can be identified, for example, using GC-MS and NMR.

[0031] [ka]

[0032] The acid value of the polyether-based urethane resin is preferably 48 (KOH mg / g) or more and 80 (KOH mg / g) or less. If the acid value is 48 (KOH mg / g) or less or 80 (KOH mg / g) or more, the pigment dispersion becomes unstable and storage stability deteriorates. The acid value can be measured by dissolving a measurement sample in an ethanol / ether mixed solution, adding a phenolphthalein indicator solution thereto, and then titrating with 0.1 mol / L potassium hydroxide solution. The acid value can be calculated from the amount of 0.1 mol / L potassium hydroxide solution required for titration.

[0033] The polyether-based urethane resin may be in the form of polyether-based urethane resin particles. The resin particles may be appropriately synthesized or may be commercially available products, such as Takelac W5661 and W932 manufactured by Mitsui Chemicals, Inc. These may be used alone or in combination of two or more types of resin particles.

[0034] The ink may contain other resins. The type of resin contained in the ink is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include urethane resin, polyester resin, acrylic resin, vinyl acetate resin, styrene resin, butadiene resin, styrene-butadiene resin, vinyl chloride resin, acrylic styrene resin, and acrylic silicone resin. Resin particles made of these resins may also be used. The resin particles are dispersed in water as a dispersion medium to form a resin emulsion, which can be mixed with materials such as coloring materials and organic solvents to obtain an ink.

[0035] The volume average particle size of the resin particles is not particularly limited and can be appropriately selected depending on the purpose. However, from the viewpoint of obtaining good fixing properties and high image hardness, the volume average particle size is preferably 10 nm or more and 1,000 nm or less, more preferably 10 nm or more and 200 nm or less, and particularly preferably 10 nm or more and 100 nm or less. The volume average particle size can be measured using, for example, a particle size analyzer (Nanotrac Wave-UT151, manufactured by Microtrac Bell Co., Ltd.).

[0036] The resin content is not particularly limited and can be selected appropriately depending on the purpose. From the viewpoint of fixability and ink storage stability, however, it is preferably from 1% by mass to 30% by mass, and more preferably from 5% by mass to 20% by mass, of the total amount of ink.

[0037] There are no particular restrictions on the particle size of the solids in the ink and they can be selected appropriately depending on the purpose. However, to improve image quality such as ejection stability and image density, the maximum frequency, calculated as the maximum number, is preferably 20 nm or more and 1000 nm or less, and more preferably 20 nm or more and 150 nm or less. The solids include resin particles and pigment particles. Particle size can be measured using a particle size analyzer (Nanotrac Wave-UT151, manufactured by Microtrac Bell Co., Ltd.).

[0038] To improve image density and fixability, the ratio (R / P) of the colorant amount (P) to the total resin amount (R) is preferably 0.05 or more and 0.35 or less. The total resin amount refers to all resins contained in the ink, including resins used to coat the colorant and resins contained in the ink as binder resins. Resin refers to organic substances with a weight-average molecular weight of 5,000 or more.

[0039] <Additives> If necessary, surfactants, antifoaming agents, antiseptic and antifungal agents, antirust agents, pH adjusters, etc. may be added to the ink.

[0040] <Surfactant> In the ink of the present invention, silicon compounds, acetylene compounds, and polyoxyethylene alkyl ether compounds can be suitably used as surfactants. Surfactants are added to improve penetration or wettability into the substrate, and surfactants with a low HLB (Hydrophilic Lipophilic Balance) are generally used. However, surfactants with a low HLB generally have low solubility in vehicles containing water, which can cause problems such as poor storage stability and separation. In order to solve the above-mentioned problems, the present invention includes one of a silicon-based compound represented by the following general formula (3) or (4), an acetylene-based compound represented by the following general formula (5), and a polyoxyethylene alkyl ether-based compound represented by the following general formula (6). The compounds of the following general formulas (3) to (6) can be identified by using, for example, GC-MS and NMR.

[0041] [ka] (In the general formula (3), a represents an integer of 0 to 23, b represents an integer of 1 to 10, c represents an integer of 1 to 23, d represents an integer of 0 to 23, and R represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.)

[0042] [ka] (In the general formula (4), a represents an integer of 1 to 8, and R represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.)

[0043] [ka] (In the general formula (5), R1 to R4 represent an alkyl group, m+n represents an integer of 1 to 20, and Y represents an acetylene group.)

[0044] [ka]

[0045] In the present invention, it is preferable to use a polysiloxane compound having a low HLB represented by the general formula (3) and a polysiloxane compound having a high HLB represented by the general formula (4), and they may be used alone or in combination. In particular, when they are used in combination, the polysiloxane compound having a low HLB can be made compatible with the polysiloxane compound having a high HLB, so that separation over time can be suppressed while maintaining wettability to the substrate.

[0046] The content of the silicon compound is preferably 0.001% by mass or more and 3% by mass or less, and more preferably 0.01% by mass or more and 1% by mass or less, based on the total amount of the ink. The silicon-based compound may be a synthesized compound or a commercially available product, such as KF-6028, KF-6038 (manufactured by Shin-Etsu Chemical Co., Ltd.), SAG002, or SAG503A (manufactured by Nissin Chemical Industry Co., Ltd.), and among these, KF6028 and SAG503A are particularly preferred from the viewpoint of storage stability.

[0047] In the present invention, it is preferable to use an acetylene-based compound represented by the general formula (5) having an HLB value of 8 or more and 13 or less. When the HLB is 8 or more, the composition is not difficult to dissolve in a vehicle containing water, and the storage stability is improved. When the HLB is 13 or less, the composition does not have poor defoaming properties. The content of the acetylene-based compound is preferably 0.1% by mass or more and 3.0% by mass or less, and more preferably 0.5% by mass or more and 2.0% by mass or less, based on the total amount of the ink. The acetylene-based compound may be synthesized appropriately or may be a commercially available product. Examples of commercially available products include Surfynol 104 series, Surfynol 420, 440, 465, 485, Olfine PD-002W, EXP.4001, EXP.4200, EXP.4123 (manufactured by Nissin Chemical Industry Co., Ltd.), and Acetinol E60, E100, E200 (manufactured by Kawaken Fine Chemicals Co., Ltd.). Among these, Surfynol 440, 465, Olfine PD-002W, EXP.4001, EXP.4200, EXP.4123 (manufactured by Nissin Chemical Industry Co., Ltd.) are particularly preferred from the viewpoint of defoaming properties and storage stability. These compounds may be used alone or in combination of two or more.

[0048] In the present invention, it is preferable to use a polyoxyethylene alkyl ether compound represented by the above general formula (6). The content of the polyoxyethylene alkyl ether compound is preferably 0.1% by mass or more and 2.0% by mass or less, and more preferably 0.5% by mass or more and 1.0% by mass or less, based on the total amount of ink. When the content of the compound represented by general formula (6) is 0.1% by mass or more based on the total amount of ink, dots do not spread after the ink lands on a recording medium, and the desired image density can be obtained. On the other hand, when the content is 2.0% by mass or less, the surface tension does not decrease, and after ejection from an ink ejection means such as an inkjet head, the time it takes for ink to overflow from the nozzle to return to the nozzle does not increase, and there is no risk of frequent deflection of the ink.

[0049] The polyoxyethylene alkyl ether compound may be a synthesized compound or a commercially available product. Examples of commercially available products include TRITON (registered trademark) HW-1000, TMN-3, TMN-6, TMN-100X, and TMN-10 (manufactured by The Dow Chemical Company). Among these, TRITON (registered trademark) HW-1000 and TMN-6 are particularly preferred. These compounds may be used alone or in combination of two or more.

[0050] The above surfactants may be used in combination with other surfactants, and for example, any of fluorine-based surfactants, amphoteric surfactants, nonionic surfactants, and anionic surfactants may be used. Silicone surfactants are not particularly limited and can be appropriately selected depending on the purpose.Among them, those that do not decompose even at high pH are preferred, such as side-chain modified polydimethylsiloxane, both-end modified polydimethylsiloxane, one-end modified polydimethylsiloxane, and both-end modified polydimethylsiloxane of side chain, and those having a polyoxyethylene group or a polyoxyethylene polyoxypropylene group as a modifying group are particularly preferred because they exhibit good properties as aqueous surfactants.In addition, polyether-modified silicone surfactants can also be used as the silicone surfactant, and examples thereof include compounds in which a polyalkylene oxide structure is introduced into the Si part side chain of dimethylsiloxane. As fluorosurfactants, 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 the side chain are particularly preferred due to their low foaming properties. Examples of the perfluoroalkyl sulfonic acid compounds include perfluoroalkyl sulfonic acids and perfluoroalkyl sulfonate salts. Examples of the perfluoroalkyl carboxylic acid compounds include perfluoroalkyl carboxylic acids and perfluoroalkyl carboxylate salts. Examples of the polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups in the side chain include sulfate ester salts of polyoxyalkylene ether polymers having perfluoroalkyl ether groups in the side chain, and salts of polyoxyalkylene ether polymers having perfluoroalkyl ether groups in the side chain. Counterions of the salts in these fluorosurfactants include Li, Na, K, NH, NHCHCHOH, NH(CHCHOH), NH(CHCHOH), and the like. Examples of amphoteric surfactants include lauryl aminopropionate, lauryl dimethyl betaine, stearyl dimethyl betaine, and lauryl dihydroxyethyl betaine. Examples of nonionic surfactants include polyoxyethylene alkylphenyl ethers, polyoxyethylene alkyl esters, polyoxyethylene alkylamines, polyoxyethylene alkylamides, polyoxyethylene propylene block polymers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, and ethylene oxide adducts of acetylene alcohol. Examples of anionic surfactants include polyoxyethylene alkyl ether acetates, dodecylbenzenesulfonates, laurates, and salts of polyoxyethylene alkyl ether sulfates. These may be used alone or in combination of two or more.

[0051] <Antifoaming agent> The antifoaming agent is not particularly limited, and examples thereof include silicone-based antifoaming agents, polyether-based antifoaming agents, fatty acid ester-based antifoaming agents, and acetylene-based compounds.

[0052] The acetylene-based compound may be either a synthesized compound or a commercially available product, such as Surfynol DF1100, Olfine D-10A, D-10PG (manufactured by Nissin Chemical Industry Co., Ltd.), and Acetinol E13T, E40 (manufactured by Kawaken Fine Chemicals Co., Ltd.). In addition to the acetylene-based compound, Surfynol AD01 (2,4,7,9-tetramethyldecane-4,7-diol, manufactured by Nissin Chemical Industry Co., Ltd.) may also be used as the defoaming agent in the present invention. Among the defoamers, from the viewpoints of defoaming property and storage stability, as the acetylene-based compound, Orfin D-10PG manufactured by Nissin Chemical Industry Co., Ltd. and Acetynol E40 manufactured by Kawaken Fine Chemicals Co., Ltd. are particularly preferred. As others, Surfynol AD01 manufactured by Nissin Chemical Industry Co., Ltd. is particularly preferred. These may be used alone or in combination of two or more.

[0053] <Antiseptic and mildew-proof agent> There is no particular limitation on the antiseptic and mildew-proof agent, and examples thereof include 1,2-benzisothiazolin-3-one.

[0054] <Rust preventive> There is no particular limitation on the rust preventive, and examples thereof include acid sulfite and sodium thiosulfate.

[0055] <pH adjuster> There is no particular limitation on the pH adjuster as long as it can adjust the pH to 7 or higher, and examples thereof include amines such as diethanolamine and triethanolamine.

[0056] There is no particular limitation on the physical properties of the ink, and it can be appropriately selected according to the purpose. For example, it is preferable that the viscosity, surface tension, pH, etc. are in the following ranges. The viscosity of the ink at 25°C is preferably 5 mPa·s or more and 30 mPa·s or less, more preferably 5 mPa·s or more and 25 mPa·s or less, from the viewpoints of improving the printing density and character quality and obtaining good discharge property. Here, for example, a rotary viscometer (RE-80L manufactured by Toki Sangyo Co., Ltd.) can be used to measure the viscosity. The measurement conditions are as follows: at 25°C, using a standard cone rotor (1°34’×R24), a sample liquid volume of 1.2 mL, a rotation speed of 50 rpm, and it can be measured in 3 minutes. The surface tension of the ink is preferably 35 mN / m or less, and more preferably 32 mN / m or less, at 25° C., from the viewpoints of ensuring good ink leveling on the recording medium and shortening the drying time of the ink. Furthermore, in order to prevent color mixing (bleeding) between ink colors, the surface tension of the cyan ink, magenta ink, and yellow ink is lower than that of the black ink, and the difference therebetween is preferably 3.0 mN / m or more, and more preferably 3.0 mN / m or more but 7.0 mN / m or less. The pH of the ink is preferably 7 to 12, and more preferably 8 to 11, from the viewpoint of preventing corrosion of metal members that come into contact with the ink.

[0057] <Pretreatment liquid> The pretreatment liquid contains a flocculant, an organic solvent, and water, and may also contain surfactants, antifoaming agents, pH adjusters, antiseptics, antifungals, rust inhibitors, and the like, as required. The organic solvent, surfactant, antifoaming agent, pH adjuster, antiseptic / fungal agent, and antirust agent may be the same as those used in ink, and other materials used in known treatment liquids may also be used. The type of flocculant is not particularly limited, and examples thereof include water-soluble cationic polymers, acids, and polyvalent metal salts.

[0058] <Post-processing liquid> The post-treatment liquid is not particularly limited as long as it can form a transparent layer. The post-treatment liquid can be obtained by selecting and mixing organic solvents, water, resins, surfactants, antifoaming agents, pH adjusters, antiseptic and antifungal agents, anti-rust agents, etc. as needed. The post-treatment liquid may be applied to the entire recording area formed on the recording medium, or may be applied only to the area where the ink image is formed.

[0059] <Recording Media> The recording medium used for recording is not particularly limited, but examples thereof include plain paper, glossy paper, special paper, cloth, film, OHP sheets, and general-purpose printing paper.

[0060] <Recordings> The ink recorded matter of the present invention comprises an image formed on a recording medium using the ink of the present invention. Recording can be performed using an inkjet recording apparatus and an inkjet recording method to produce a recorded product.

[0061] <Recording device> 1, the inkjet recording device used in the present invention comprises a device main body 101, a paper feed tray 102 for loading paper sheets that are attached to the device main body 101, and a paper discharge tray 103 for stocking paper sheets that have images recorded on them that are attached to the device main body 101. The top surface of an upper cover 111 of the device main body 101 is flat, and a front surface 112 of a front cover of the device main body 101 is inclined diagonally downward and rearward relative to the top surface, and below the inclined front surface 112 of the front cover are provided the paper discharge tray 103 and paper feed tray 102 that protrude forward (toward the viewer). Furthermore, at one end of the front surface 112, there is an ink cartridge loading section 104 that protrudes forward from the front surface 112 and is lower than the upper cover 111, and this ink cartridge loading section 104 has an openable front cover 115 for installing and removing ink cartridges.

[0062] As shown in FIG. 2, inside the device body 101, a carriage 133 is slidably supported in the main scanning direction by a guide rod 131 and a stay 132, which are guide members that are hung between the left and right side plates, and is moved and scanned by a main scanning motor. This carriage 133 is fitted with a recording head 134 consisting of four inkjet heads that eject ink droplets of each color: yellow (Y), cyan (C), magenta (M), and black (K). The recording head 134 has multiple ink ejection ports arranged in a direction that intersects with the main scanning direction, and the ink droplet ejection direction faces downward.

[0063] The inkjet head constituting the recording head 134 may be equipped with an energy generating means for ejecting ink, such as a piezoelectric actuator such as a piezoelectric element, a thermal actuator that uses an electrothermal conversion element such as a heating resistor to utilize a phase change caused by film boiling of a liquid, a shape memory alloy actuator that uses a metal phase change caused by a temperature change, or an electrostatic actuator that uses static electricity.

[0064] The carriage 133 also carries sub-tanks 135 of each color for supplying ink of each color to the recording head 134. Ink is replenished and supplied to these sub-tanks 135 via ink supply tubes from the ink cartridges according to the present invention that are loaded in the ink cartridge loading section 104.

[0065] On the other hand, as a paper feed section for feeding the paper 142 loaded on the paper stacking section 141 of the paper feed tray 103, there is provided a crescent roller (paper feed roller) 143 that separates and feeds the paper 142 one sheet at a time from the paper stacking section 141, and a separation pad 144 that faces the paper feed roller 143 and is made of a material with a large friction coefficient, and this separation pad 144 is urged toward the paper feed roller 143.

[0066] On the other hand, the conveying section for conveying the paper 142 fed from this paper feed section below the recording head 134 includes a conveying belt 151 for electrostatically attracting and conveying the paper 142, a counter roller 152 for sandwiching and conveying the paper 142 fed from the paper feed section via a guide 145 between the conveying belt 151, a conveying guide 153 for turning the paper 142 fed vertically upward by 90 degrees so that it follows the conveying belt 151, and a tip pressure roller 155 urged toward the conveying belt 151 by a pressing member 154. Also, a charging roller 156 is provided as charging means for charging the surface of the conveying belt 151.

[0067] Here, the conveyor belt 151 is an endless belt that is stretched between a conveyor roller 157 and a tension roller 158 and configured to rotate in the belt conveyance direction. The conveyor belt 151 has a surface layer that serves as a paper adsorption surface and is formed, for example, from a pure resin material with a thickness of about 40 μm that is not subjected to resistance control, such as pure ETFE material, and a back layer (earth layer) that is made of the same material as the surface layer and has resistance control using carbon. Further, a guide member 161 is disposed on the rear side of the conveyor belt 151 in correspondence with the printing area of ​​the recording head 134 . Furthermore, as a paper discharge section for discharging the paper 142 recorded by the recording head 134, a separation claw 171 for separating the paper 142 from the conveyor belt 151, a paper discharge roller 172 and a paper discharge roller 173 are provided, and a paper discharge tray 103 is provided below the paper discharge roller 172.

[0068] The recording paper is adsorbed to the conveyor belt and ejected by the ejection rollers, which press down from above. The conveyor belt and rollers are the primary means of transporting the recording paper, and the ejection rollers in this printer only play a secondary role, such as preventing the paper from floating. This makes it possible to significantly reduce the number of rollers compared to conventional inkjet printers, thereby reducing smudges and scratches on the recorded image. A duplex paper feed unit 181 is detachably mounted on the rear surface of the apparatus main body 101. This duplex paper feed unit 181 takes in paper 142 returned by the reverse rotation of the conveyor belt 151, turns it over, and feeds paper 142 again between the counter roller 152 and the conveyor belt 151. A manual paper feed unit 182 is also provided on the top surface of this duplex paper feed unit 181.

[0069] When double-sided printing is performed, the paper is transported to the double-sided paper feed unit and reversed immediately after printing on the front side, without waiting time. The ink of the present invention has high permeability into paper and, because it has little moisture, evaporates quickly, making it possible to reverse the paper without smearing the printed image, without the need for drying time or drying means such as a heater. In the inkjet recording device configured in this manner, the paper 142 is separated and fed one sheet at a time from the paper feed section, and the paper 142 fed vertically upward is guided by a guide 145, sandwiched between a conveyor belt 151 and a counter roller 152 and conveyed, and further, the leading edge is guided by a conveyor guide 153 and pressed against the conveyor belt 151 by a leading edge pressure roller 155, and the conveying direction is changed by 90°. At this time, the transport belt 157 is charged by the charging roller 156, and the paper 142 is electrostatically attracted to the transport belt 151 and transported. There, by driving the recording head 134 in accordance with an image signal while moving the carriage 133, ink droplets are ejected onto the stopped paper 142 to record one line, and after transporting the paper 142 a predetermined distance, the next line is recorded. Upon receiving a recording end signal or a signal indicating that the rear end of the paper 142 has reached the recording area, the recording operation is terminated and the paper 142 is discharged to the paper discharge tray 103.

[0070] An AC bias is applied to the charging belt, alternating positive and negative charges on the conveyor belt at a constant pitch. The electrostatic force generated by the intermittent micro-electric fields attracts the recording paper to the conveyor belt. The preferred range of the applied AC bias is ±1.2 kV to ±2.6 kV, more preferably ±1.6 kV to ±2.4 kV. If the AC bias value is below the lower limit, sufficient attraction force cannot be obtained. If it is above the upper limit, the tiny droplets generated when ink is ejected from the nozzles are affected by the charge and return to the head instead of landing on the paper, contaminating the area around the head. The electrical properties of the ink play a role in the influence of the charge on the tiny droplets. That is, the higher the electrical conductivity of the ink, the more susceptible the ejected droplets are to the charge, so it is necessary to suppress the electrical conductivity of the ink. When it is detected that the remaining amount of ink in the sub-tank 135 is low, a predetermined amount of ink is replenished from the ink cartridge to the sub-tank 135.

[0071] FIG. 3 is an explanatory plan view showing an example of a nozzle plate in the inkjet printing apparatus of the present invention. Here, the nozzle plate used in the inkjet printing apparatus of the present invention will be described with reference to FIGS. FIG. 3 is an explanatory plan view of the nozzle plate, and FIG. 4 is an enlarged cross-sectional view of one nozzle portion.

[0072] The nozzle plate 10 has a nozzle substrate 20 in which holes (hereinafter sometimes referred to as "nozzles") 21 that become nozzles 11 for ejecting liquid are formed, an intermediate layer 30 formed on the surface of the nozzle substrate 20, and an ink-repellent layer 40 formed on the liquid ejection surface side. The nozzle substrate 20 is, for example, a metal flat plate member. Although a stainless steel metal flat plate member is used as the nozzle substrate 20, the nozzle substrate 20 is not limited to this. The nozzle 11 has a cylindrical portion 21a on the liquid ejection surface side, and a truncated cone portion 21b on the surface opposite to the liquid ejection surface.

[0073] The intermediate layer 30 is composed of one or more layers that serve as a base layer, such as an SiO2 layer, a silane coupling agent layer, etc. The intermediate layer 30 does not necessarily have to be provided.

[0074] The ink-repellent layer 40 is a layer containing a silicone resin. The ink-repellent layer 40 has a sloped region 41 formed on the outer periphery of the nozzle 11, where the sloped surface 41a is inclined in a direction in which the film thickness becomes thinner toward the edge 11a of the nozzle 11. A region 42 of the ink-repellent layer 40 other than the sloped region 41 is flat and has a substantially constant film thickness. The sloped surface 41a of the sloped region 41 may be inclined linearly or curvedly inclined in cross section. The average film thickness of the ink-repellent layer 40 on the ink ejection surface side is preferably 1 μm or more and 3 μm or less. Furthermore, the intermediate layer 30 is preferably a silane coupling agent layer having an amino group as a layer underlying the ink-repellent layer 40. This allows the amino group to interact with the liquid-repellent film material, resulting in high adhesion.

[0075] (Method for manufacturing nozzle members of inkjet heads) FIG. 5 is a diagram showing a configuration in which an ink-repellent layer 31 is formed on the surface of a nozzle plate 32 by applying silicone resin using a dispenser 34 according to this embodiment. A dispenser 34 is arranged to apply a silicone solution to the ink ejection surface side of the Ni electroformed nozzle plate 32, and the dispenser 34 is scanned while ejecting silicone resin from the tip of the needle 35 so that a predetermined constant distance is maintained between the nozzle plate 32 and the tip of the needle 35, thereby selectively forming a silicone resin coating on the ink ejection surface of the nozzle plate 32.

[0076] In this embodiment, room-temperature curing silicone resin SR2411 (manufactured by Dow Corning Toray Co., Ltd.) was used as the silicone resin. However, some silicone was observed to have infiltrated into the nozzle holes and the back surface of the nozzle plate. The thickness of the silicone resin coating selectively formed in this way was 1.2 μm, and the surface roughness (Ra) was 0.18 μm.

[0077] Any material that repels ink can be used as the material for the ink-repellent layer, and specifically, a silicone-based water-repellent material can be used. The silicone-based water-repellent material may be a room temperature curing liquid silicone resin or elastomer, which is preferably applied to the surface of a substrate and left in the air at room temperature to polymerize and harden to form an ink-repellent coating.

[0078] The above-mentioned silicone-based water-repellent material may be a heat-curing liquid silicone resin or elastomer, which is applied to the surface of the substrate and cured by heat treatment to form an ink-repellent coating. The silicone-based water-repellent material may be an ultraviolet-curable liquid silicone resin or elastomer, which is applied to the surface of the substrate and cured by irradiating it with ultraviolet light to form an ink-repellent coating. The viscosity of the silicone-based water-repellent material is preferably 1000 cp or less.

[0079] The critical surface tension of the ink-repellent layer is preferably 5 mN / m to 40 mN / m, more preferably 5 mN / m to 30 mN / m. If the critical surface tension exceeds 30 mN / m, the nozzle plate may become too wet with ink over long-term use, which may result in deflected ink ejection or abnormal particle formation during repeated printing. Furthermore, if the pressure exceeds 40 mN / m, the ink may become too wet on the nozzle plate from the beginning, which may cause the ink to be ejected in a curved direction or to become abnormally particulate from the beginning.

[0080] In addition, in the present invention, the terms image formation, recording, printing, printing, etc. are all synonymous.

[0081] Recording medium, media, and printed material are all synonymous terms. [Example]

[0082] The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. In the examples, "parts" and "%" mean "parts by mass" and "% by mass" unless otherwise specified. Unless otherwise specified, preparation, evaluation, etc. were carried out under conditions of 23°C and 50% humidity.

[0083] (Preparation of pigment dispersion) <Preparation of black pigment dispersion> A mixed slurry was prepared by premixing 250 parts of carbon black (Degussa), 50 parts of a compound represented by formula (1) (Takesurf A-45-K, manufactured by Takemoto Oil & Fat Co., Ltd.), and 700 parts of distilled water. The mixture was then circulated and dispersed using a disk-type media mill (UMA type, manufactured by Kotobuki Industries Co., Ltd.) with 0.015 mm zirconia beads (filling rate: 70%) at a peripheral speed of 6 m / s and a liquid temperature of 10°C until a volume average particle diameter of approximately 100 nm was achieved. Coarse particles were then separated using a centrifuge (Model-7700, manufactured by Kubota Shoji Co., Ltd.). The mixture was then filtered through a 1.2 μm pore filter, and the water content was adjusted to a solids concentration of 15%, yielding a black pigment dispersion with a pigment concentration of 15%.

[0084] <Preparation of blue pigment dispersion> A mixed slurry was obtained by premixing 250 parts of Pigment Blue 15:3 (manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.), 50 parts of a compound represented by formula (2) (Paionin D-7240, manufactured by Takemoto Yushi Co., Ltd.), and 700 parts of distilled water. The mixture was then circulated and dispersed using a disk-type media mill (UMA type, manufactured by Kotobuki Industries Co., Ltd.) with 0.015 mm zirconia beads (filling rate 70%) at a peripheral speed of 6 m / s and a liquid temperature of 10°C until a volume average particle diameter of approximately 100 nm was achieved. Coarse particles were then separated using a centrifuge (Model-7700, manufactured by Kubota Shoji Co., Ltd.). The mixture was then filtered through a 1.2 μm pore filter, and the water content was adjusted to a solids concentration of 15%, yielding a blue pigment dispersion with a pigment concentration of 15%.

[0085] <Preparation of red pigment dispersion> A red pigment dispersion with a pigment concentration of 15% was obtained in the same manner as in the preparation of the blue pigment dispersion, except that Pigment Blue 15:3 was changed to Pigment Red 122 (manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.).

[0086] <Preparation of yellow pigment dispersion> A yellow pigment dispersion with a pigment concentration of 15% was obtained in the same manner as in the preparation of the blue pigment dispersion, except that Pigment Blue 15:3 was changed to Pigment Yellow 74 (manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.).

[0087] (Preparation of styrene-acrylic resin coated pigment dispersion) <Preparation of Resin-Coated Black Pigment Dispersion> 11.2 g of styrene, 2.8 g of acrylic acid, 12 g of lauryl methacrylate, 4 g of polyethylene glycol methacrylate, 4 g of styrene macromer, and 0.4 g of mercaptoethanol were mixed and heated to 65°C. Next, a mixed solution of 100.8 g of styrene, 25.2 g of acrylic acid, 108 g of lauryl methacrylate, 36.2 g of polyethylene glycol methacrylate, 60 g of hydroxyethyl methacrylate, 36 g of styrene macromer, 3.6 g of mercaptoethanol, 2.4 g of azobismethylvaleronitrile, and 18 g of methyl ethyl ketone was added dropwise to the flask over 2.5 hours. After the dropwise addition, a mixed solution of 0.8 g of azobismethylvaleronitrile and 18 g of methyl ethyl ketone was added dropwise to the flask over 0.5 hours. After aging at 65°C for 1 hour, 0.8 g of azobismethylvaleronitrile was added, and the mixture was further aged for 1 hour. After the reaction was completed, 364 g of methyl ethyl ketone was added to the flask, and 800 g of a polymer solution with a solid content of 50% was obtained.

[0088] Next, 25 g of the polymer solution, 50 g of carbon black (Cabot Corporation), 13.6 g of a 1 mol / L aqueous potassium hydroxide solution, 20 g of methyl ethyl ketone, and 13.6 g of water were thoroughly stirred and then kneaded using a roll mill. The resulting paste was added to 200 g of pure water and thoroughly stirred, after which the methyl ethyl ketone was removed using an evaporator. The mixture was then pressure-filtered through a polyvinylidene fluoride membrane filter with an average pore size of 5 μm. The water content was then adjusted to a solids concentration of 20%, yielding a styrene-acrylic resin-coated black pigment dispersion with a solids concentration of 20% (pigment concentration 15%, coating resin concentration 5%).

[0089] <Preparation of Resin-Coated Blue Pigment Dispersion> In the preparation of the above resin-coated black pigment dispersion, a styrene-acrylic resin-coated blue pigment dispersion with a solids concentration of 20% (pigment concentration 15%, coating resin concentration 5%) was obtained in the same manner as in the preparation of the resin-coated black pigment dispersion, except that the carbon black was changed to Pigment Blue 15:3 (manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.).

[0090] <Preparation of Resin-Coated Red Pigment Dispersion> In the preparation of the above resin-coated black pigment dispersion, a styrene-acrylic resin-coated red pigment dispersion with a solids concentration of 20% (pigment concentration 15%, coating resin concentration 5%) was obtained in the same manner as in the preparation of the resin-coated black pigment dispersion, except that carbon black was changed to Pigment Red 122 (manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.).

[0091] <Preparation of Resin-Coated Yellow Pigment Dispersion> In the preparation of the above resin-coated black pigment dispersion, a styrene-acrylic resin-coated yellow pigment dispersion with a solids concentration of 20% (pigment concentration 15%, coating resin concentration 5%) was obtained in the same manner as in the preparation of the resin-coated black pigment dispersion, except that the carbon black was changed to Pigment Yellow 74 (manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.).

[0092] <Synthesis of aqueous dispersion of water-based polyurethane resin> A four-neck flask equipped with a stirrer, a Dimroth condenser, a nitrogen inlet tube, a silica gel drying tube, and a thermometer was charged with 119.70 g of 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate as a polyisocyanate component, 60.90 g of dimethylolpropionic acid, 60.40 g of bisphenoxyethanolfluorene (manufactured by Osaka Gas Chemicals Co., Ltd.), and 13.37 g of polytetramethylene glycol having a number average molecular weight of 2,000 as active hydrogen components, and 300.00 g of methyl ethyl ketone as a solvent, and the mixture was heated to 80°C under a nitrogen atmosphere and stirred for 12 hours.

[0093] After confirming the disappearance of the isocyanate absorption band by infrared absorption spectroscopy, the temperature was lowered to 40°C and 45.99 g of triethylamine was added to neutralize, followed by the addition of 700.00 g of water and dispersion using a Homodisper. The methyl ethyl ketone was then removed by distillation at 50°C under a reduced pressure of 6.66 kPa, yielding a substantially solvent-free aqueous polyurethane resin dispersion with a fluorene skeleton content of 20% by mass, an acid value of 85 KOHmg / g, a solids concentration of 30% by mass, and a viscosity of 200 mPa s.

[0094] The other ink components used were as follows:

[0095] <Organic solvents> Organic solvent A (trimethylglycine, manufactured by Asahi Kasei Finechem Co., Ltd.: saturated water content = 52%) Organic solvent B (Glycerin, manufactured by Sakamoto Pharmaceutical Co., Ltd.: saturated water content = 26%) Organic solvent C (Tokyo Chemical Industry Co., Ltd., 1,3-butylene glycol: saturated water content = 15%)

[0096] <Resin particles> Polyether-based urethane resin particles A (Mitsui Chemicals, Inc., Takelac W5661: acid value = 48 KOH mg / g) *Compound of general formula (7) Polyether-based urethane resin particles B (Mitsui Chemicals, Inc., Takelac W932: acid value = 80 KOH mg / g) *Compound of general formula (7) Urethane resin particles (synthetic product: acid value = 85KOHmg / g)

[0097] <Surfactant> Silicone surfactant A (KF-6028, manufactured by Shin-Etsu Chemical Co., Ltd.) *Compound of general formula (3) Silicone surfactant B (Nissin Chemical Industry Co., Ltd., SAG503A) *Compound of general formula (4) Acetylene-based surfactant (Nissin Chemical Industry Co., Ltd., Surfynol 440) ※Compound of general formula (5) ·Polyoxyethylene alkyl ether surfactant (TRITON HW-1000 manufactured by Dow Chemical Company) ※Compound of general formula (6) ·Fluorine-based surfactant (PF656 manufactured by OMNOVA)

[0098] <Defoaming agent> ·2,4,7,9-Tetramethyldecane-4,7-diol (Surfinol AD01 manufactured by Nissin Chemical Industry Co., Ltd.)

[0099] <pH adjuster> ·2-Amino-2-ethyl-1,3-propanediol (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0100] <Antiseptic and mildew-proof agent> ·LV(S) (manufactured by Abisia)

[0101] (Preparation of ink) <Examples 1 to 21, Comparative Examples 1 to 5> Table 1 to 3 show the compounding compositions of the inks of each example and comparative example. First, for each example and comparative example, a water-soluble organic solvent, surfactant, other additives (defoaming agent, pH adjuster, antibacterial agent, etc.), and ion-exchanged water shown in Tables 1 to 3 were mixed and then stirred for 1 hour. Next, resin particles were added and stirred for another 1 hour to mix uniformly. Then, various pigment dispersions were added and stirred for another 1 hour to mix uniformly. This mixture was pressure-filtered through a polyvinylidene fluoride membrane filter with an average pore diameter of 0.8 μm to remove coarse particles and dust, and inks of Examples 1 to 21 and Comparative Examples 1 to 5 were obtained.

[0102] <Method for evaluating curl resistance> The black, cyan, magenta, and yellow inks listed in Tables 1-3 were printed at a print resolution of 600 x 600 dpi onto a recording medium (NBS Ricoh MyPaper) using an image forming device (Ricoh IPSiO GXe5500) equipped with a nozzle plate with an ink-repellent layer made of silicone resin (Toray Dow Corning Co., Ltd., room-temperature curing silicone resin SR2411) or fluororesin (Toray DuPont Co., Ltd., fluororesin coating agent L-8030). The print sample was placed on a level surface and the curl amount at four points on the edge of the paper was measured, and the average value was used. Measurements were taken 10 seconds after printing and 12 hours after printing. If the difference in curl amount between 10 seconds and 12 hours was 50 mm or less, the product was deemed usable.

[0103] <Printing method> The black, cyan, magenta, and yellow inks listed in Table 1 were printed at a print resolution of 600 x 600 dpi onto a recording medium (NBS Ricoh My Paper) using an image forming device (Ricoh IPSiO GXe5500) equipped with a nozzle plate with an ink-repellent layer made of silicone resin (Toray Dow Corning Co., Ltd., room temperature curing silicone resin SR2411) or fluororesin (Toray DuPont Co., Ltd., fluororesin coating agent L-8030) and dried overnight at room temperature to prepare print samples. The print charts used were a 2cm square solid image and an image with a black solid image and a color solid image next to each other.

[0104] <Image density evaluation> The image density in the solid image of the print sample was measured using an image measuring device (X-Rite Exact). The image densities for the color image that can be actually used are as follows: Black: 1.15 or higher Cyan: 0.95 or higher Magenta: 0.90 or higher Yellow: 0.75 or above

[0105] <Adhesion evaluation> A solid image in the print sample was rubbed five times with a rubbing device (Crockmeter, manufactured by Daiei Scientific Instruments Co., Ltd.) equipped with a cotton cloth, and the density of the ink transferred to the cotton cloth was measured with an image measuring device (Exact, manufactured by X-Rite), and a rating was made according to the following rating standards. Note that a rating value of less than 0.10 is at a level suitable for practical use. (Evaluation criteria) ○: Less than 0.05 △: 0.05 or more and less than 0.10 ×: 0.10 or more

[0106] <Bleeding evaluation> The bleeding at the boundary between the black solid image and the color solid image was visually evaluated. The black ink used was the ink of Example 10, which has the lowest surface tension among the examples. (Evaluation criteria) 〇: No bleeding △: Some bleeding is observed, but it is not a problem in actual use. ×: Blurring

[0107] <Storage stability evaluation> The ink was placed in an airtight container (I-Boy, manufactured by AS ONE Corporation) and stored in a thermostatic chamber (PR-3J, manufactured by ESPEC) at 70°C for 14 days. The viscosity was measured before and after storage using a viscometer (RE-85L, manufactured by Toki Sangyo Co., Ltd.) and evaluated according to the following criteria. Note that if the rate of change in viscosity is less than ±10% of the initial viscosity, the ink is at a level suitable for practical use. (Evaluation criteria) ○: Viscosity change rate: 0 to less than ±5% △: Viscosity change rate: ±5% or more to less than ±10% ×: Viscosity change rate: ±10% or more

[0108] <Viscosity evaluation when water evaporates> 5g of ink was weighed into a 33mm diameter glass petri dish (manufactured by AS ONE Corporation) and left in a thermostatic chamber (manufactured by ESPEC Corporation, PR-3J) at 23°C and 10%RH for 5 hours. After leaving it, the viscosity was measured using a viscometer (manufactured by Toki Sangyo Co., Ltd., RE-85L) and evaluated according to the following criteria. If the viscosity after leaving it is less than 1,000mPa·s, it is at a level suitable for practical use. (Evaluation criteria) ○: Less than 500 mPa·s △: 500 mPa·s or more and less than 1,000 mPa·s ×: 1,000mPa·s or more

[0109] <Ink viscosity measurement> The viscosity of the ink was measured using a viscometer (RE-85L manufactured by Toki Sangyo Co., Ltd.).

[0110] <Ink surface tension measurement (150ms)> The surface tension of the ink was measured using a dynamic surface tensiometer (Dynotester manufactured by SITA) when the bubble life time was 150 ms using the maximum bubble pressure method.

[0111] The evaluation results are shown in Tables 1 to 3.

[0112] [Table 1]

[0113] [Table 2]

[0114] [Table 3]

[0115] The present invention relates to the ink of (1) below, but also includes the following (2) to (12) as embodiments. (1) An ink for use in an inkjet printing device having an inkjet head equipped with a nozzle plate having a nozzle for ejecting ink and an ink-repellent layer containing a silicone resin or a fluororesin on at least the ink ejection surface side, the ink contains a colorant, a water-soluble organic solvent, a compound represented by the following general formula (1) or the following general formula (2), and water, An ink characterized in that the product of the viscosity η [mPa s] at 25°C measured with a rotational viscometer and the surface tension σ [mN / m] at 25°C measured with a maximum bubble pressure method when the bubble life time is 150 ms is 100 or more and 130 or less. [ka] (In general formula (1), m represents an integer of 1 to 4.) [ka] (In general formula (2), R 1 represents an alkyl group having 1 to 20 carbon atoms, an aralkyl group having 7 to 8 carbon atoms, or an allyl group, l represents an integer of 0 to 7, and n represents an integer of 20 to 200. (2) The ink according to (1) above, wherein the water-soluble organic solvent includes one or more solvents having a saturated water content of 50% or more at 25°C and 50% RH. (3) The ink according to (1) or (2) above, further comprising any one of a silicon-based compound represented by the following general formula (3) or (4), an acetylene-based compound represented by the following general formula (5), and a polyoxyethylene alkyl ether-based compound represented by the following general formula (6). [ka] (In the general formula (3), a represents an integer of 0 to 23, b represents an integer of 1 to 10, c represents an integer of 1 to 23, d represents an integer of 0 to 23, and R represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.) [ka] (In the general formula (4), a represents an integer of 1 to 8, and R represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.) [ka] (In the general formula (5), R1 to R4 represent an alkyl group, m+n represents an integer of 1 to 20, and Y represents an acetylene group.) [ka] (4) The ink according to any one of (1) to (3) above, further comprising 2,4,7,9-tetramethyldecane-4,7-diol. (5) The ink according to any one of (1) to (4) above, further comprising a polyether-based urethane resin represented by the following general formula (7): [ka] (6) The ink according to (5) above, wherein the acid value of the polyether-based urethane resin is 48 (KOHmg / g) or more and 80 (KOHmg / g) or less. (7) The ink according to any one of (1) to (6) above, which contains as a coloring material a pigment whose surface is partially or entirely covered with a styrene-acrylic resin. (8) The ink according to any one of (1) to (7) above, wherein the mass ratio (R / P) of the amount of coloring material (P) to the amount of total resin (R) in the ink is 0.05 or more and 0.35 or less. (9) An ink set including black ink, cyan ink, magenta ink, and yellow ink for use in an inkjet printing device having an inkjet head equipped with a nozzle plate having a nozzle for ejecting ink and further having an ink-repellent layer containing a silicone resin or a fluororesin on at least the surface on the ink ejection surface side, Each of the inks contains a colorant, a water-soluble organic solvent, a compound represented by the following general formula (1) or the following general formula (2), and water, a colorant of the black ink is carbon black, a colorant of the cyan ink is Pigment Blue 15:3, a colorant of the magenta ink is Pigment Red 122 or 269, and a colorant of the yellow ink is Pigment Yellow 74; An ink set, characterized in that the product of the viscosity η [mPa s] at 25°C as measured with a rotational viscometer and the surface tension σ [mN / m] at 25°C when the bubble life time is 150 ms as measured with a maximum bubble pressure method is 100 or more and 130 or less. [ka] (In general formula (1), m represents an integer of 1 to 4.) [ka] (In general formula (2), R 1 represents an alkyl group having 1 to 20 carbon atoms, an aralkyl group having 7 to 8 carbon atoms, or an allyl group, l represents an integer of 0 to 7, and n represents an integer of 20 to 200. (10) The ink set according to (9) above, wherein the surface tension of each of the cyan ink, the magenta ink, and the yellow ink is at least 3 mN / m lower than the surface tension of the black ink. (11) An inkjet printing device having an inkjet head having nozzles for ejecting ink, and ink, the inkjet head is an inkjet head including a nozzle plate having an ink-repellent layer on at least the ink ejection surface side, the ink-repellent layer containing a silicone resin or a fluorine resin; An inkjet printing device, wherein the ink is the ink described in any one of (1) to (8) above. (12) An inkjet printing method comprising a step of applying ink to a substrate using an inkjet head having nozzles for ejecting ink, As the inkjet head, an inkjet head having a nozzle plate with an ink-repellent layer on at least the ink ejection surface side is used, An inkjet printing method, characterized in that the ink described in any one of (1) to (8) above is used as the ink. [Explanation of symbols]

[0116] 10, 32 nozzle plate 11 nozzles 11a Edge 20 Nozzle base material 21 holes, nozzle 21a Cylindrical part 21b frustum-shaped part 30 Middle Class 31, 40 ink-repellent layer 34 Dispenser 35 Needle 41 Slope area 41a Slope 101 Device body 102 Paper tray 103 Paper output tray 104 Ink cartridge loading section 105 Operation section 111 Upper cover 112 Front of front cover 115 Front cover 131 Guide rod 132 Stay 133 Carriage 134 Recording head 135 Subtank 141 Paper stacking section 142 Paper 143 Paper feed roller 144 Separation Pad 145 Guide 151 Conveyor belt 152 Counter Roller 153 Transport guide 154 Holding member 155 Tip pressure roller 156 Charging roller 157 Transport roller 158 Tension Roller 161 Guide member 171 Separation claw 172 Paper ejection roller 173 Paper ejection roller 181 Duplex paper feed unit 182 Manual paper feed unit [Prior art documents] [Patent documents]

[0117] [Patent Document 1] Patent No. 6582615 [License 2] Patent No. 4138593 [License 3] Patent No. 5958788

Claims

1. An ink for use in an inkjet printing device having an inkjet head equipped with a nozzle plate having a nozzle for ejecting ink and an ink-repellent layer containing a silicone resin or a fluororesin on at least the ink ejection surface side, the ink contains a colorant, a water-soluble organic solvent, a compound represented by the following general formula (1), and water, An ink characterized in that the product of the viscosity η [mPa s] at 25°C as measured by a rotational viscometer and the surface tension σ [mN / m] at 25°C as measured by a maximum bubble pressure method when the bubble life time is 150 ms is 100 or more and 130 or less. 【Chemistry 1】 (In general formula (1), m represents an integer of 1 to 4.)

2. 2. The ink according to claim 1, wherein the water-soluble organic solvent comprises at least one solvent having a saturated water content of 50% or more at 25°C and 50% RH.

3. The ink according to claim 1 or 2, further comprising any one of a silicon-based compound represented by the following general formula (3) or (4), an acetylene-based compound represented by the following general formula (5), and a polyoxyethylene alkyl ether-based compound represented by the following general formula (6): 【Transformation 3】 (In general formula (3), a is an integer of 0 to 23, b is an integer of 1 to 10, c is an integer of 1 to 23, d is an integer of 0 to 23, and R is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.) 【Chemistry 4】 (In general formula (4), a represents an integer of 1 to 8, and R represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.) 【Transformation 5】 (In general formula (5), R １ ~R ４ represents an alkyl group, m+n represents an integer of 1 to 20, and Y represents an acetylene group. 【Transformation 6】

4. The ink according to any one of claims 1 to 3, further comprising 2,4,7,9-tetramethyldecane-4,7-diol.

5. The ink according to claim 1 , further comprising a polyether-based urethane resin represented by the following general formula (7): 【Transformation 7】

6. 6. The ink according to claim 5, wherein the acid value of the polyether-based urethane resin is 48 (KOH mg / g) or more and 80 (KOH mg / g) or less.

7. 7. The ink according to claim 1, wherein the coloring material comprises a pigment whose surface is partially or entirely covered with a styrene-acrylic resin.

8. The ink according to claim 1 , wherein the mass ratio (R / P) of the amount of coloring material (P) to the total amount of resin (R) in the ink is 0.05 or more and 0.35 or less.

9. An ink set including a black ink, a cyan ink, a magenta ink, and a yellow ink, for use in an inkjet printing device having an inkjet head equipped with a nozzle plate having nozzles for ejecting ink and further having an ink-repellent layer containing a silicone resin or a fluororesin on at least the surface on the ink ejection surface side, Each of the inks contains a colorant, a water-soluble organic solvent, a compound represented by the following general formula (1), and water, a colorant for the black ink is carbon black, a colorant for the cyan ink is Pigment Blue 15:3, a colorant for the magenta ink is Pigment Red 122 or 269, and a colorant for the yellow ink is Pigment Yellow 74; an ink set, wherein the product of the viscosity η [mPa s] at 25°C as measured with a rotational viscometer and the surface tension σ [mN / m] at 25°C as measured with a maximum bubble pressure method when the bubble life time is 150 ms is 100 or more and 130 or less. 【Chemistry 1】 (In general formula (1), m represents an integer of 1 to 4.)

10. 10. The ink set according to claim 9, wherein the surface tension of each of the cyan ink, the magenta ink, and the yellow ink is at least 3 mN / m lower than the surface tension of the black ink.

11. An inkjet printing device having an inkjet head having nozzles for ejecting ink, and ink, the inkjet head is an inkjet head including a nozzle plate having an ink-repellent layer on at least the ink ejection surface side, the ink-repellent layer containing a silicone resin or a fluorine resin; An inkjet printing apparatus, wherein the ink is the ink according to any one of claims 1 to 8.

12. An inkjet printing method comprising a step of applying ink to a substrate using an inkjet head having nozzles for ejecting ink, As the inkjet head, an inkjet head having a nozzle plate with an ink-repellent layer on at least the ink ejection surface side is used, An ink-jet printing method, comprising using the ink according to any one of claims 1 to 8 as the ink.

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