Printing device

Abstract

To provide a printer which can perform drying well while suppressing curling of thin paper and cardboard, and can be down-sized.SOLUTION: A printer comprises: a first ink application part 51 which applies a first ink to a first face of a recording medium; a second ink application part 52 which applies a second ink to a second face of the recording medium; a first drying part 61 which dries the first face of the recording medium onto which the first ink has been discharged; a second drying part 62 which dries the second face of the recording medium onto which the second ink has been discharged; a first cooling part 71 which cools the recording medium dried by the first drying part; and a second cooling part 72 which cools the recording medium dried by the second drying part. The ink has a water content of 62 mass% or more, and contains an organic solvent having a boiling point of 240°C or more and 280°C or less, and the total amount of the organic solvent having the boiling point of 240°C or more and 280°C or less is 3.0 mass% or more and 15.0 mass% or less to the total amount of ink. In a direction from one end side to the other end side of the printer, the first drying part, the second drying part, and the first cooling part are arranged in this order.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a printing apparatus.

Background Art

[0002] Printing apparatuses such as inkjet printers have advantages such as low noise, low running cost, and easy color printing, and are widely popular as output devices for digital signals. As recording media used in inkjet printers, absorbent media such as plain paper, low-absorbent recording media such as coated paper, and non-absorbent recording media such as plastic films are used. In recent years, particularly in the field of commercial printing, it has been required to be able to print with a smaller housing, and development has been carried out on smaller devices that can be used more space-savingly and the inks that can be used at that time.

[0003] In the prior art, a technique has been proposed in which an aqueous ink is ejected onto a non-absorbent recording medium or the like by an apparatus provided with a heating and drying means to perform printing. Patent Document 1 discloses a recording apparatus including an ejection head that ejects an aqueous ink onto the surface of a recording medium and a drying device that dries the aqueous ink. The aqueous ink used in Patent Document 1 contains a colorant, polymer particles having a glass transition temperature of 35°C or higher and 65°C or lower, water, and an aqueous organic solvent, and is adjusted to have a predetermined viscosity ratio. Further, the relationship between the head temperature Th of the ejection head, the glass transition temperature Tg of the polymer particles, and the drying temperature Td of the drying device is set to satisfy Th < Tg < Td. According to Patent Document 1, in a recording apparatus that heats and dries an aqueous ink ejected from a temperature-controlled ejection head onto a recording medium, even when a predetermined aqueous ink having good fixability to a slow-permeable or non-permeable recording medium is applied, it is said that the occurrence of latency can be prevented.

[0004] Also, in the prior art, it has been proposed to perform heating and drying and cooling. Patent document 2 discloses an inkjet printing system that includes a first processing device having a printing unit that ejects ink droplets, a drying unit, a first cooling unit and a second cooling unit that cool the printing medium, and a second processing device that is positioned downstream of the second cooling unit and performs a predetermined processing on the printing medium. According to Patent Document 2, even if the heat treatment in the drying unit is strengthened, it is possible to prevent adverse effects on downstream processing. Summary of the Invention [Problem to be solved by the invention]

[0005] However, in devices that perform heat drying, there is a problem that the recording medium curls, and the device disclosed in Patent Document 1 cannot suppress the occurrence of curling. If the heat drying is weakened to suppress the occurrence of curling, for example, thick paper cannot be dried well, while if an attempt is made to dry well, for example, thin paper will curl. Also, the device configuration disclosed in Patent Document 2 has a low degree of freedom in device layout, and the device cannot be made compact.

[0006] SUMMARY OF THE PRESENT DISCLOSURE An object of the present invention is to provide a printing device that can be made compact and that can perform good drying while suppressing curling of thin and thick paper. [Means for solving the problem]

[0007] In order to achieve the above object, a printing device of the present invention includes a first ink application unit having a first ink containing a pigment, an organic solvent, and water, and a first liquid ejection head that ejects the first ink onto a first surface of a recording medium; a second ink application unit having a second ink containing a pigment, an organic solvent, and water, and a second liquid ejection head that ejects the second ink onto a second surface of the recording medium opposite to the first surface; a first drying unit that dries a first surface of the recording medium onto which the first ink is ejected; a second drying unit that dries a second surface of the recording medium onto which the second ink has been ejected; a first cooling unit that cools the recording medium dried by the first drying unit; a second cooling unit that cools the recording medium dried by the second drying unit; A printing device comprising: the first ink and the second ink each contain water in an amount of 62 mass % or more relative to the total amount of the ink, and contain, as the organic solvent, an organic solvent having a boiling point of 240° C. or more and 280° C. or less; the total amount of the organic solvents having a boiling point of 240° C. or more and 280° C. or less is 3.0% by mass or more and 15.0% by mass or less with respect to the total amount of each ink, The printing device is characterized in that the first drying unit, the second drying unit, and the first cooling unit are arranged in this order in a direction from one end side to the other end side of the printing device. Effect of the Invention

[0008] According to the present invention, it is possible to provide a printing device that can perform good drying while suppressing curling of thin paper and thick paper and that can be made compact. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram illustrating an example of a printing device according to the present invention. [Diagram 2] FIG. 2 is an exploded perspective view illustrating an example of an ink ejection head. [Diagram 3] 1 is an explanatory cross-sectional view taken along a direction (longitudinal direction of a liquid chamber) perpendicular to the nozzle arrangement direction in an example of an ink ejection head. [Figure 4] 1 is an explanatory cross-sectional view taken along a direction (short side direction of a liquid chamber) perpendicular to the nozzle arrangement direction in an example of an ink ejection head. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The printing device according to the present invention will be described below with reference to the drawings. Note that the present invention is not limited to the embodiment shown below, and can be modified within the scope of what a person skilled in the art can imagine, such as other embodiments, additions, modifications, deletions, etc., and any aspect is within the scope of the present invention as long as it provides the functions and effects of the present invention.

[0011] The printing device of the present invention includes a first ink application unit having a first ink containing a pigment, an organic solvent, and water, and a first liquid ejection head that ejects the first ink onto a first surface of a recording medium; a second ink application unit having a second ink containing a pigment, an organic solvent, and water, and a second liquid ejection head that ejects the second ink onto a second surface of the recording medium opposite to the first surface; a first drying unit that dries a first surface of the recording medium onto which the first ink is ejected; a second drying unit that dries a second surface of the recording medium onto which the second ink has been ejected; a first cooling unit that cools the recording medium dried by the first drying unit; a second cooling unit that cools the recording medium dried by the second drying unit; A printing device comprising: the first ink and the second ink each contain water in an amount of 62 mass % or more relative to the total amount of the ink, and contain, as the organic solvent, an organic solvent having a boiling point of 240° C. or more and 280° C. or less; the total amount of the organic solvents having a boiling point of 240° C. or more and 280° C. or less is 3.0% by mass or more and 15.0% by mass or less with respect to the total amount of each ink, The printing device is characterized in that the first drying unit, the second drying unit, and the first cooling unit are arranged in this order in a direction from one end side to the other end side of the printing device.

[0012] An embodiment of the present invention will be described below, firstly, the ink used in the present invention will be described, and then the apparatus will be described.

[0013] (ink) The organic solvent, water, coloring material, resin, additives, etc. used in the ink will be described below. The first ink and the second ink used in the present invention may have the same formulation or may have different formulations. When the first ink and the second ink are described without distinction, they are simply referred to as inks.

[0014] <Organic solvent> The organic solvent used in the present invention is not particularly limited, and any water-soluble organic solvent can be used. Examples of the organic solvent include polyhydric alcohols, ethers such as polyhydric alcohol alkyl ethers and polyhydric alcohol aryl ethers, nitrogen-containing heterocyclic compounds, amides, amines, and sulfur-containing compounds.

[0015] Specific examples of polyhydric alcohols 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, and 1,4-pentanediol. Examples of such hexanediol include 2,4-pentanediol, 1,5-pentanediol, 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.

[0016] Examples of polyhydric alcohol alkyl ethers include ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, and propylene glycol monoethyl ether.

[0017] Examples of polyhydric alcohol aryl ethers include ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether.

[0018] Examples of the nitrogen-containing heterocyclic compounds include 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, ε-caprolactam, and γ-butyrolactone. Examples of the amides include formamide, N-methylformamide, N,N-dimethylformamide, 3-methoxy-N,N-dimethylpropionamide, and 3-butoxy-N,N-dimethylpropionamide.

[0019] Examples of the amines include monoethanolamine, diethanolamine, and triethylamine.

[0020] Examples of sulfur-containing compounds include dimethyl sulfoxide, sulfolane, and thiodiethanol.

[0021] Other organic solvents include propylene carbonate, ethylene carbonate, and the like.

[0022] It is preferable to use an organic solvent having a boiling point of 250° C. or less, since this not only functions as a wetting agent but also provides good drying properties.

[0023] The first ink and the second ink contain an organic solvent having a boiling point of 240°C or more and 280°C or less as an organic solvent, and the total amount of the organic solvent having a boiling point of 240°C or more and 280°C or less is 3.0% by mass or more and 15.0% by mass or less relative to the total amount of the first ink or the second ink.

[0024] It is believed that organic solvents with boiling points of 240°C to 280°C can reduce the affinity between solvent molecules and increase the permeability into the recording medium. Therefore, it is believed that by using such organic solvents, the organic solvent can penetrate into the recording medium to compensate for the loss of moisture in the recording medium due to drying, thereby suppressing the occurrence of curling. In addition, when two or more organic solvents with boiling points of 240°C to 280°C are included, better curl resistance can be obtained. With regard to "two or more organic solvents with boiling points of 240°C or higher and 280°C or lower," if the organic solvents have the same boiling point but different structures or chemical formulas, they are considered to be different types of organic solvents.

[0025] From the viewpoint of improving curl resistance on thin paper, the total amount of organic solvents having a boiling point of 240° C. or more and 280° C. or less is preferably 3.0% by mass or more based on the total amount of ink. From the viewpoint of improving drying performance on thick paper, the total amount of organic solvents having a boiling point of 240° C. or more and 280° C. or less is preferably 15.0% by mass or less.

[0026] In the organic solvents contained in the ink, the total amount of organic solvents having a boiling point of 290° C. or less is preferably 23.0% by mass or more and 48.0% by mass or less with respect to the total amount of the ink. When it is in this range, curl resistance can be further improved. More preferably, the total amount of organic solvents having a boiling point of 197° C. or more and 290° C. or less is 23.0% by mass or more and 48.0% by mass or less with respect to the total amount of the ink.

[0027] <Water> The water content in the ink can be appropriately selected depending on the purpose, but is preferably from 10% by mass to 90% by mass from the viewpoints of the drying property and ejection reliability of the ink. In the present invention, the ink contains 62% by mass or more of water based on the total amount of the ink. In order to ensure good drying properties, the ink preferably contains 62% by mass or more of water. Note that both the first ink and the second ink preferably contain 62% by mass or more of water based on the total amount of the ink.

[0028] The water content is more preferably 74% by mass or less based on the total amount of the ink, which can improve curl resistance on thin paper. Furthermore, the water content is preferably 64% by mass or more, and more preferably 71% by mass or more, based on the total amount of the ink. If the water content is 64% by mass or more, the drying properties of cardboard can be improved.

[0029] <Coloring material> The coloring material is not particularly limited, and pigments and dyes can be used. As the pigment, an inorganic pigment or an organic pigment can be used. These pigments can be used alone or in combination of two or more. Also, mixed crystals can be used as the pigment.

[0030] 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.

[0031] As organic pigments, azo pigments, polycyclic pigments (e.g., phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, etc.), dye chelates (e.g., basic dye chelates, acid dye chelates, etc.), nitro pigments, nitroso pigments, aniline black, etc. can be used. Among these pigments, those having good affinity with the solvent are preferably used. In addition, resin hollow particles and inorganic hollow particles can also be used.

[0032] Specific examples of pigments for black colors 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 Range 5, 13, 16, 17, 36, 43, 51, CI Pigment Red 1, 2, 3, 5, 17, 22, 23, 31, 38, 48:2, 48:2 (Permanent Red 2B (Ca)), 48:3, 48:4, 49:1, 52:2, 53:1, 57:1 (Brilliant Carmine 6B), 60:1, 63:1, 63:2, 64:1, 81, 83, 88 , 101 (red oxide), 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.

[0033] The dye is not particularly limited, and acid dyes, direct dyes, reactive dyes, and basic dyes can be used. One type of dye may be used alone, or two or more types may be used in combination. Dyes such as 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 Directed Black 19, 38, 51, 71, 154, 168, 171, 195, CI Reactive Red 14, 32, 55, 79, 249, and CI Reactive Black 3, 4, and 35.

[0034] The content of the coloring material in the ink is preferably from 0.1% to 15% by mass, and more preferably from 1% to 10% by mass, from the viewpoints of improving image density, good fixing property and ejection stability.

[0035] Methods for dispersing a pigment to obtain an ink include a method in which a hydrophilic functional group is introduced into the pigment to make it a self-dispersing pigment, a method in which the surface of the pigment is coated with a resin and then dispersed, and a method in which a dispersant is used to disperse the pigment.

[0036] As a method for introducing a hydrophilic functional group into a pigment to make it a self-dispersing pigment, for example, a method in which a functional group such as a sulfone group or a carboxyl group is added to a pigment (e.g., carbon) to make it dispersible in water can be mentioned.

[0037] As a method for dispersing a pigment by coating its surface with a resin, there is a method in which the pigment is encapsulated in a microcapsule to make it dispersible in water. This can be called a resin-coated pigment. In this case, it is not necessary for all of the pigments blended in the ink to be coated with a resin, and uncoated or partially coated pigments may be dispersed in the ink as long as the effect of the present invention is not impaired.

[0038] Examples of the method for dispersing using a dispersant include a method for dispersing using a known low molecular weight dispersant or a polymeric dispersant, typified by a surfactant.

[0039] As the dispersant, for example, anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, etc. can be used depending on the pigment. As the dispersant, RT-100 (nonionic surfactant) manufactured by Takemoto Oil Co., Ltd. and sodium naphthalenesulfonate formalin condensate can also be suitably used. The dispersants may be used alone or in combination of two or more.

[0040] <Pigment dispersion> It is possible to obtain ink by mixing a pigment with materials such as water or an organic solvent, or it is also possible to manufacture ink by mixing a pigment with other materials such as water and a dispersant to prepare a pigment dispersion, and then mixing the resulting mixture with materials such as water or an organic solvent.

[0041] The pigment dispersion is obtained by mixing and dispersing water, a pigment, a pigment dispersant, and other components as necessary, and adjusting the particle size. Dispersion is preferably performed using a dispersing machine. The particle size of the pigment in the pigment dispersion is not particularly limited, but the maximum frequency in terms of the maximum number is preferably 20 nm or more and 500 nm or less, 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.).

[0042] The pigment content in the pigment dispersion is not particularly limited and can be appropriately selected depending on the purpose. From the viewpoints of obtaining good ejection stability and increasing image density, the pigment content is preferably from 0.1% by mass to 50% by mass, and more preferably from 0.1% by mass to 30% by mass. It is preferable to filter out coarse particles from the pigment dispersion using a filter or a centrifugal separator, and degas the pigment dispersion, if necessary.

[0043] <Resin> The type of resin contained in the ink is not particularly limited and can be appropriately selected depending on the purpose. Examples of the resin 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.

[0044] Resin particles made of these resins may be used. The resin particles may be dispersed in water as a dispersion medium to form a resin emulsion, and the resin particles may be mixed with materials such as coloring materials and organic solvents to obtain an ink. The resin particles may be appropriately synthesized or may be commercially available. These may be used alone or in combination of two or more types of resin particles.

[0045] The volume average particle size of the resin particles is not particularly limited and can be appropriately selected depending on the purpose. From the viewpoint of obtaining good fixing property and high image hardness, however, it is preferably from 10 nm to 1,000 nm, more preferably from 10 nm to 200 nm, and particularly preferably from 10 nm to 100 nm.

[0046] The volume average particle size can be measured, for example, using a particle size analyzer (Nanotrac Wave-UT151, manufactured by Microtrac-Bell Co., Ltd.).

[0047] The resin content is not particularly limited and can be appropriately selected depending on the purpose. From the viewpoints of fixation property and storage stability of the ink, however, the resin content 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 the ink.

[0048] The particle size of the solid content in the ink is not particularly limited and can be appropriately selected according to the purpose. In order to improve the image quality such as ejection stability and image density, the maximum frequency of the particle size of the solid content in the ink is preferably 20 nm or more and 1000 nm or less, more preferably 20 nm or more and 150 nm or less, in terms of the maximum number. The solid content includes resin particles, pigment particles, etc. The particle size can be measured using a particle size analyzer (Nanotrac Wave-UT151, manufactured by Microtrac Bell Co., Ltd.).

[0049] <Additives> If necessary, surfactants, antifoaming agents, antiseptic and antifungal agents, rust inhibitors, pH adjusters, etc. may be added to the ink.

[0050] <Surfactant> As the surfactant, any of silicone-based surfactants, fluorine-based surfactants, amphoteric surfactants, nonionic surfactants, and anionic surfactants can be used.

[0051] The silicone surfactant is not particularly limited and can be appropriately selected according to the purpose. Among them, those that do not decompose even at high pH are preferable. Examples of silicone surfactants include side chain modified polydimethylsiloxane, both end modified polydimethylsiloxane, one end modified polydimethylsiloxane, and both end modified polydimethylsiloxane of side chain. Those having a polyoxyethylene group or a polyoxyethylene polyoxypropylene group as a modified group are particularly preferable because they show good properties as an aqueous surfactant. In addition, polyether modified silicone surfactants can also be used as silicone surfactants, and examples thereof include compounds in which a polyalkylene oxide structure is introduced into the Si part side chain of dimethylsiloxane.

[0052] As the fluorosurfactant, for example, perfluoroalkylsulfonic acid compounds, perfluoroalkyl carboxylic acid compounds, perfluoroalkyl phosphate compounds, perfluoroalkyl ethylene oxide adducts, and polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups in the side chain are particularly preferred because they have low foaming properties. As the perfluoroalkylsulfonic acid compounds, for example, perfluoroalkylsulfonic acid, perfluoroalkyl sulfonate, etc. are included. As the perfluoroalkyl carboxylic acid compounds, for example, perfluoroalkyl carboxylic acid, perfluoroalkyl carboxylate, etc. are included. As the polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups in the side chain, sulfate ester salts of polyoxyalkylene ether polymers having perfluoroalkyl ether groups in the side chains, salts of polyoxyalkylene ether polymers having perfluoroalkyl ether groups in the side chains, etc. are included. As the counter ions of the salts in these fluorosurfactants, Li, Na, K, NH4, NH3CH2CH2OH, NH2(CH2CH2OH)2, NH(CH2CH2OH)3, etc. are included.

[0053] Examples of amphoteric surfactants include lauryl aminopropionate, lauryl dimethyl betaine, stearyl dimethyl betaine, and lauryl dihydroxyethyl betaine.

[0054] 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.

[0055] Examples of the anionic surfactant include polyoxyethylene alkyl ether acetates, dodecylbenzene sulfonates, laurates, and polyoxyethylene alkyl ether sulfates.

[0056] These may be used alone or in combination of two or more.

[0057] The silicone surfactant is not particularly limited and can be appropriately selected depending on the purpose. Examples of the silicone surfactant include side-chain modified polydimethylsiloxane, both-end modified polydimethylsiloxane, one-end modified polydimethylsiloxane, and both-end side-chain modified polydimethylsiloxane. Polyether-modified silicone surfactants having a polyoxyethylene group or a polyoxyethylene polyoxypropylene group as the modifying group are particularly preferred because they exhibit good properties as aqueous surfactants.

[0058] Such surfactants may be appropriately synthesized or commercially available products, such as those available from BYK-Chemie Co., Ltd., Shin-Etsu Chemical Co., Ltd., Dow Corning Toray Silicone Co., Ltd., Nippon Emulsion Co., Ltd., and Kyoeisha Chemical Co., Ltd.

[0059] The polyether-modified silicone surfactant is not particularly limited and can be appropriately selected depending on the purpose. For example, it can be a surfactant represented by the general formula (S-1) in which a polyalkylene oxide structure is introduced into the Si part side chain of dimethylpolysiloxane.

[0060] [ka]

[0061] (In the general formula (S-1), m, n, a, and b each independently represent an integer, R represents an alkylene group, and R' represents an alkyl group.)

[0062] As the polyether-modified silicone surfactant, commercially available products can be used, such as KF-618, KF-642, KF-643 (Shin-Etsu Chemical Co., Ltd.), EMALEX-SS-5602, SS-1906EX (Nihon Emulsion Co., Ltd.), FZ-2105, FZ-2118, FZ-2154, FZ-2161, FZ-2162, FZ-2163, FZ-2164 (Dow Corning Toray Silicone Co., Ltd.), BYK-33, BYK-387 (BYK-Chemie Co., Ltd.), TSF4440, TSF4452, TSF4453 (Toshiba Silicon Co., Ltd.), and the like.

[0063] As the fluorine-based surfactant, a compound having 2 to 16 fluorine-substituted carbon atoms is preferable, and a compound having 4 to 16 fluorine-substituted carbon atoms is more preferable.

[0064] Examples of fluorine-based surfactants include perfluoroalkyl phosphate compounds, perfluoroalkyl ethylene oxide adducts, and polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups in side chains, etc. Among these, polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups in side chains are preferred because they have low foaming properties, and fluorine-based surfactants represented by general formula (F-1) and general formula (F-2) are particularly preferred.

[0065] [ka]

[0066] In the compound represented by the above general formula (F-1), m is preferably an integer of 0 to 10, and n is preferably an integer of 0 to 40 in order to impart water solubility.

[0067] [ka]

[0068] In the compound represented by the above general formula (F-2), Y is H or C mF 2m+1 m is an integer from 1 to 6, or CH2CH(OH)CH2-C m F 2m+1 where m is an integer between 4 and 6, or CpH 2p+1 where p is an integer from 1 to 19. n is an integer from 1 to 6. a is an integer from 4 to 14.

[0069] As the fluorine-based surfactant, commercially available products may be used. Examples of such commercially available products include Surflon S-111, S-112, S-113, S-121, S-131, S-132, S-141, and S-145 (all manufactured by Asahi Glass Co., Ltd.); Fullard FC-93, FC-95, FC-98, FC-129, FC-135, FC-170C, FC-430, and FC-431 (all manufactured by Sumitomo 3M Limited); Megafa F-470, F-1405, F-474 (all manufactured by Dainippon Ink & Chemicals, Inc.); Zonyl TBS, FSP, FSA, FSN-100, FSN, FSO-100, FSO, FS-300, UR, Capstone FS-30, FS-31, FS-3100, FS-34, FS-35 (all manufactured by Chemours); FT-110, FT- 250, FT-251, FT-400S, FT-150, FT-400SW (all manufactured by NEOS Co., Ltd.), Polyfox PF-136A, PF-156A, PF-151N, PF-154, PF-159 (manufactured by OMNOVA Co., Ltd.), Unidyne DSN-403N (manufactured by Daikin Industries, Ltd.), and the like. Among these, FS-3100, FS-34, FS-300 manufactured by Chemours Co., Ltd., FT-110, FT-250, FT-251, FT-400S, FT-150, FT-400SW manufactured by NEOS Co., Ltd., Polyfox PF-151N manufactured by OMNOVA Co., Ltd., and Unidyne DSN-403N manufactured by Daikin Industries, Ltd. are particularly preferred from the viewpoint of excellent print quality, particularly color development, penetration into paper, wettability, and uniform dyeing.

[0070] The content of the surfactant in the ink is not particularly limited and can be appropriately selected according to the purpose. However, from the viewpoints of excellent wettability and ejection stability and improved image quality, it is preferably 0.001% by mass or more and 5% by mass or less, and more preferably 0.05% by mass or more and 5% by mass or less.

[0071] <Antifoaming agent> The antifoaming agent is not particularly limited, and examples thereof include silicone-based antifoaming agents, polyether-based antifoaming agents, and fatty acid ester-based antifoaming agents. These may be used alone or in combination of two or more. Among these, silicone-based antifoaming agents are preferred from the viewpoint of excellent defoaming effect.

[0072] <Preservative and mildew-proof agent> The preservative and mildew-proof agent is not particularly limited, and examples thereof include 1,2-benzisothiazolin-3-one.

[0073] <Rust inhibitor> The rust inhibitor is not particularly limited, and examples thereof include acid sulfite and sodium thiosulfate.

[0074] <pH adjuster> The pH adjuster is not particularly limited as long as it can adjust the pH to 7 or more, and examples thereof include amines such as diethanolamine and triethanolamine.

[0075] <Physical properties of ink> The physical properties of the ink are not particularly limited and 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 3 mPa·s or more and 30 mPa·s or less, and more preferably 5 mPa·s or more and 25 mPa·s or less, from the viewpoints of improved printing density and character quality and good ejectability. Here, for example, a rotational 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 measurement can be performed 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., in order to ensure that the ink is appropriately leveled on the recording medium and the drying time of the ink is shortened. The pH of the ink is preferably from 7 to 12, and more preferably from 8 to 11, from the viewpoint of preventing corrosion of metal members that come into contact with the ink.

[0076] The application of the ink used in the present invention is not particularly limited and can be appropriately selected depending on the purpose, and can be applied to, for example, printed matter, paint, coating material, undercoat, etc. Furthermore, the ink can be used not only to form two-dimensional characters and images using the ink, but also as a material for three-dimensional modeling to form three-dimensional solid images (three-dimensional objects).

[0077] In the present invention, the terms image formation, recording, printing, printing, etc. are all synonymous. Recording medium, media, and printed material are all synonymous.

[0078] (Recording medium) There are no particular limitations on the recording medium, and although plain paper, glossy paper, special paper, cloth, etc. can be used, good image formation is also possible using a non-permeable substrate. A non-permeable substrate is a substrate with a surface that has low water permeability and absorbency. It also includes materials that have many cavities inside but are not open to the outside. More quantitatively, in the Bristow method, 1 / 2 Water absorption up to 10mL / m 2 The term "substrate" refers to a substrate that is: As the impermeable substrate, for example, a plastic film such as a polyvinyl chloride resin film, a polyethylene terephthalate (PET) film, a polypropylene film, a polyethylene film, or a polycarbonate film can be suitably used. The recording medium is not limited to those generally used as recording media, and may be wallpaper, flooring, building materials such as tiles, cloth for clothing such as T-shirts, textiles, leather, etc. By adjusting the configuration of the path for conveying the recording medium, ceramics, glass, metal, etc. may also be used.

[0079] (Recorded material) The ink recorded matter obtained by the present invention has an image formed on a recording medium using the printing apparatus and ink of the present invention. The recorded matter can be obtained by recording using an inkjet recording apparatus and an inkjet recording method.

[0080] (Printing device) Next, a detailed example of the printing apparatus according to the present embodiment will be described. The printing apparatus of the present embodiment includes a first ink applying unit, a second ink applying unit, a first drying unit, a second drying unit, a first cooling unit, and a second cooling unit, and may include other means as necessary. The printing apparatus of the present embodiment may also be called a recording apparatus, an inkjet recording apparatus, an image forming apparatus, or the like.

[0081] The first ink application unit has the first ink and a first liquid ejection head that ejects the first ink onto a first surface of a recording medium. The second ink application section has a second liquid ejection head that ejects the second ink onto a second surface, which is the surface opposite to the first surface of the recording medium onto which the second ink and the first ink are ejected. In this manner, the printing apparatus of this embodiment prints on both sides of the recording medium. The first side may be called the front side, and the second side may be called the back side.

[0082] As the liquid ejection head, for example, an inkjet head can be used. The first ink applying unit and the second ink applying unit may have a plurality of different types of ink, for example, may apply a plurality of inks having different color materials to the recording medium. For example, when the first ink applying unit has KCMY inks, all of these four inks satisfy the requirements for the first ink. A detailed example of the liquid ejection head will be described later.

[0083] The ink can be used in a wide variety of ways, including, but not limited to, inkjet recording, blade coating, gravure coating, bar coating, roll coating, dip coating, curtain coating, slide coating, die coating, and spray coating.

[0084] The first drying section dries the first surface of the recording medium onto which the first ink has been ejected. The second drying section dries the second surface of the recording medium onto which the second ink has been ejected. The drying method in these drying sections can be appropriately selected, and for example, an IR heater, a hot air heater, an infrared heater, etc. can be used. The drying temperature can be appropriately selected, and for example, it is preferable to set it to 60° C. or higher and 130° C. or lower. The drying section may also be called a drying unit, etc.

[0085] The first cooling section cools the recording medium dried by the first drying section. The second cooling section cools the recording medium dried by the second drying section. The cooling method in these cooling sections can be appropriately selected, and for example, a cooling roller, a method of blowing cold air onto the recording medium, etc. can be used. The cooling temperature can be appropriately selected. The cooling section may also be called a cooling unit, etc. By using the first and second cooling sections, the temperature of the recording medium increased by the drying section can be lowered, making it easier to prevent curling. This is because paper tends to curl if the recording medium has a high paper temperature and low moisture content after drying.

[0086] In the first cooling section, it is preferable to sufficiently lower the temperature of the recording medium. If the temperature of the recording medium cannot be sufficiently lowered, the ink is applied in the second ink application section while the temperature of the recording medium remains high, which may cause image distortion in the second ink application section. From this viewpoint, it is preferable to increase the distance between the first drying section and the first cooling section, and by increasing the distance between the first drying section and the first cooling section, it becomes easier to cool in the first cooling section. In addition, if the distance between the first drying section and the first cooling section can be increased, the freedom of the device layout is created, such as by providing other components in the space that is freed up.

[0087] In this embodiment, the first drying unit, the second drying unit, and the first cooling unit are arranged in this order from one end side to the other end side of the printing device. By arranging the second drying unit between the first drying unit and the first cooling unit, the distance from the first drying unit to the first cooling unit can be increased, the degree of freedom in device layout can be increased, and the device can be made more compact.

[0088] In this embodiment, the direction from one end side to the other end side of the printing device may be the transport direction of the recording medium, which will be described later. The one end side may be the upstream side in the transport direction of the recording medium, and the other end side may be the downstream side in the transport direction of the recording medium.

[0089] However, when the distance between the first drying section and the first cooling section is increased, the time from drying to cooling is increased, and the recording medium becomes more likely to curl. When the recording medium is dried, the temperature of the recording medium increases and the moisture content of the recording medium becomes low, but in this state, curling is likely to occur, and the longer the time until cooling, the more likely the curling will occur.

[0090] Therefore, in this embodiment, by using the above-mentioned first ink and second ink, for example inks with the above-mentioned type and content of organic solvent, curling of the recording medium can be suppressed. In this way, by using ink containing an organic solvent that has a curl suppressing effect, it is possible to perform good drying while suppressing curling of thin paper and thick paper even with a compact device.

[0091] The second cooling section only needs to be able to cool the recording medium dried by the second drying section, and the arrangement within the device can be appropriately selected. For example, it is preferable that the first drying section, the second drying section, and the second cooling section are arranged in this order in the transport direction (the direction from one end side to the other end side of the printing device). In this case, the degree of freedom in the device layout can be increased, and the device can be made more compact.

[0092] 1 is a schematic diagram showing an example of a printing device according to the present embodiment. In the device of the present invention, the layout within the device and the transport path of the recording medium are devised to reduce the size of the device. As will be described later, the transport direction of the recording medium and the transport path of the recording medium are different.

[0093] In the printing device of this example, the continuous paper P is transported between the paper feeder 42 and the winding device 47. The continuous paper P passes through a transport section 43 that turns around and transports it. The transported continuous paper P is wiped by a wiping device 44 before printing.

[0094] Next, the first ink is applied by the first ink application unit 51. In this example, KCMY inkjet heads are used as an example, but the present embodiment is not limited to this. Note that only the inkjet head K is given the reference symbol 51K. The arrangement of the inkjet head 51K in the first ink application unit 51 can also be changed.

[0095] Next, the first side of the recording medium is dried in the first drying section 61. As described above, the first side of the recording medium is the surface of the recording medium onto which the first ink is ejected. In this example, an IR heater is used as the first drying section 61. The arrows in the figure show the drying direction of the IR heater in a schematic manner, but are not limited thereto, and may be, for example, to the left of the paper or downward of the paper. From the viewpoint of lengthening the distance from drying in the first drying section 61 to cooling in the first cooling section, it is preferable to set the drying direction, for example, to the upward direction of the paper, as shown in the figure.

[0096] Next, the continuous paper P passes under the second drying section 62. At this time, the second drying section 62 does not dry the continuous paper P.

[0097] Next, the web P is cooled in the first cooling section 71. In this example, the first cooling section 71 uses a cooling roller.

[0098] Here, the transport direction of the recording medium will be described. In the figure, the transport direction of the recording medium is shown by an arrow. In this embodiment, the direction from one end side of the printing device to the other end side is the transport direction of the recording medium. For example, the direction from the paper feed device 42 side to the winding device 47 side can be the transport direction of the recording medium. In this embodiment, a distinction is made between the transport direction of the recording medium and the transport path of the recording medium. Note that the transport path of the recording medium is the location through which the continuous paper P (recording medium) passes, as shown by the solid line in the figure.

[0099] 1, in this example, the first drying section 61, the second drying section 62, and the first cooling section 71 are arranged in this order in the transport direction of the recording medium. By arranging them in this manner, it is possible to increase the distance from the location where the first drying section 61 dries the continuous paper P to the location where the first cooling section 71 cools the continuous paper P. This allows for a high degree of freedom in the layout of the device, and allows the device to be made more compact.

[0100] Next, the continuous paper P is inverted by the inverting device 45 .

[0101] Next, the second ink is applied to the second surface of the recording medium by the second ink application unit 52. In this example, KCMY inkjet heads are used as an example, but the present embodiment is not limited to this. Note that only the inkjet head K is given the reference symbol 52K. The arrangement of the inkjet head 52K in the second ink application unit 52 can also be changed.

[0102] Next, the second side of the recording medium is dried in the second drying section 62. As described above, the second side of the recording medium is the surface of the recording medium onto which the second ink is ejected. In this example, an IR heater is used as the second drying section 62. The arrows in the figure show a schematic representation of the drying direction of the IR heater.

[0103] Next, the web P is cooled in the second cooling section 72. In this example, the first cooling section 72 uses a cooling roller.

[0104] Next, the printed continuous paper P passes through a conveying section 46 which conveys the paper by folding it back, and is wound up by a winding device 47. In addition, the passage of the continuous paper P through the transport sections 43 and 46 has the effect of smoothing out wrinkles in the paper.

[0105] As described above, in this example, the recording medium is transported through the recording medium transport path in the order of the first ink application unit 51, the first drying unit 61, the first cooling unit 71, the second ink application unit 52, the second drying unit 62, and the second cooling unit 72. In detail, the recording medium in this example is provided with ink by the first ink application unit 51, dried by the first drying unit 61, cooled by the first cooling unit 71, provided with ink by the second ink application unit 52, dried by the second drying unit 62, and cooled by the second cooling unit 72, in that order.

[0106] <3D modeling device> The printing device of the present invention can also be used as a three-dimensional modeling device for forming a three-dimensional object. The three-dimensional modeling device for forming a three-dimensional object can be, for example, one equipped with an ink storage means, a supply means, a discharge means, a drying means, etc. The three-dimensional object includes a three-dimensional object obtained by applying ink in layers. Also included is a molded product obtained by processing a structure to which ink is applied on a substrate such as a recording medium. The molded product is, for example, a recorded material or structure formed in a sheet or film shape, which is molded by heat stretching, punching, etc., and is preferably used for applications in which the surface is molded after decoration, such as meters and operation panel of automobiles, office automation equipment, electric and electronic equipment, cameras, etc.

[0107] <Liquid ejection head> As the liquid ejection head, for example, an inkjet head (hereinafter also referred to as an "ink ejection head") can be used, and a printing device using an inkjet head is also called an inkjet recording device.

[0108] An ink ejection head is a component provided in an inkjet recording device that ejects ink. The ink ejection head has nozzles (hereinafter also referred to as "nozzle holes") that eject ink. The ink ejection head also has a nozzle plate, which has a nozzle substrate with nozzle holes and an ink-repellent film provided on the nozzle substrate.

[0109] The nozzle substrate has an ink ejection side surface from which ink is ejected from the nozzle holes, and a liquid chamber joining surface located on the opposite side to the ink ejection side surface. The ink-repellent film is formed on the ink ejection side surface of the nozzle substrate.

[0110] The material of the nozzle substrate is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include stainless steel, Al, Bi, Cr, InSn, ITO, Nb, Nb2O5, NiCr, Si, SiO2, Sn, Ta2O5, Ti, W, ZAO (ZnO+Al2O3), and Zn. These may be used alone or in combination of two or more. Among these, stainless steel is preferred from the viewpoint of rust resistance.

[0111] The stainless steel is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include austenitic stainless steel, ferritic stainless steel, martensitic stainless steel, precipitation hardening stainless steel, etc. These may be used alone or in combination of two or more.

[0112] The ink-repellent film preferably contains a fluorine-containing acrylate ester polymer or a polymer having a fluorine-containing heterocyclic structure in the main chain. By containing a fluorine-containing acrylate ester polymer or a polymer having a fluorine-containing heterocyclic structure in the main chain, the ink-repellent film preferably has a very small surface free energy and can maintain a state in which it is difficult to wet even with ink having a low surface tension.

[0113] Here, an example of an ink ejection head will be described with reference to Figures 2 to 4. Figure 2 is an exploded perspective explanatory view showing an example of the head, Figure 3 is a cross-sectional explanatory view taken along a direction perpendicular to the nozzle arrangement direction of the head (longitudinal direction of the liquid chamber), and Figure 4 is a cross-sectional explanatory view taken along the nozzle arrangement direction of the head (lateral direction of the liquid chamber).

[0114] The ink ejection head has a flow path plate (liquid chamber substrate, flow path member) 1, a vibration plate member 2 joined to the lower surface of the flow path plate 1, and a nozzle plate 3 which is a nozzle forming member joined to the upper surface of the flow path plate 1. These form a plurality of liquid chambers (also called pressurized liquid chambers, pressure chambers, pressure chambers, flow paths, etc.) 6 as individual flow paths to which a plurality of nozzle holes 4 which eject liquid droplets (ink droplets) are each connected via a nozzle communication passage 5, a fluid resistance section 7 which also serves as a supply path for supplying ink to the liquid chambers 6, and a communication section 8 which communicates with the liquid chambers 6 via this fluid resistance section 7, and ink is supplied to the communication section 8 from a common liquid chamber 10 formed in a frame member 17 via a supply port 19 formed in the vibration plate member 2.

[0115] Flow path plate 1 is formed by etching a silicone substrate to form openings such as communication passage 5, pressurized liquid chamber 6, and fluid resistance portion 7. Note that flow path plate 1 can also be formed by etching a SUS substrate using an acid etching solution or by machining such as punching (pressing).

[0116] The vibration plate member 2 has vibration regions (diaphragm portions) 2a that form the wall surfaces corresponding to the liquid chambers 6, and an island-shaped protrusion 2b is provided on the outer surface of the vibration region 2a (the surface opposite to the liquid chambers 6). The upper end surfaces (joining surfaces) of the piezoelectric element columns 12A of the multi-layer piezoelectric elements 12, 12, which act as driving elements (actuator means, pressure generating means) that generate energy to deform the vibration region 2a and eject droplets, are joined to the island-shaped protrusion 2b. The lower end surface of the multi-layer piezoelectric element 12 is joined to a base member 13.

[0117] Here, the piezoelectric element 12 is formed by alternately laminating piezoelectric material layers 21 such as PZT and internal electrodes 22a, 22b, and the internal electrodes 22a, 22b are each drawn out to the end face, i.e., the side face of the piezoelectric element 12 that is approximately perpendicular to the vibration plate 2, and connected to end face electrodes (external electrodes) 23a, 23b formed on this side face, and displacement in the lamination direction occurs when a voltage is applied to the end face electrodes (external electrodes) 23a, 23b. This piezoelectric element 12 is formed by forming a required number of piezoelectric element columns 12A, 12B for one piezoelectric element member by groove processing using half-cut dicing.

[0118] Although the piezoelectric element columns 12A and 12B of the piezoelectric element 12 are the same, the piezoelectric element column that is driven by applying a driving waveform is called the piezoelectric element column 12A, and the piezoelectric element column that is used simply as a support without applying a driving waveform is called the piezoelectric element column 12B. In this case, either a bi-pitch configuration in which the driving piezoelectric element columns 12A and the support piezoelectric element columns 12B are used alternately, or a normal pitch configuration in which all the piezoelectric element columns are used as the driving piezoelectric element columns 12A, can be adopted.

[0119] As a result, two rows of drive elements (rows of drive piezoelectric element columns 12A) are provided on the base member 13, in which a plurality of drive piezoelectric element columns 12A as drive elements are arranged side by side.

[0120] Furthermore, the piezoelectric element material is not particularly limited, and electromechanical transducers such as ferroelectrics, such as BaTiO3, PbTiO3, (NaK)NbO3, etc., which are generally used as piezoelectric element materials, can also be used. Furthermore, although a laminated type piezoelectric element is used, a single-plate piezoelectric element can also be used. The single-plate piezoelectric element can be one that is machined, a thick film that is screen printed and sintered, or a thin film that is formed by sputtering, vapor deposition, or a sol-gel method. Furthermore, the laminated type piezoelectric elements 12 provided on one base member 13 can be in one row or a structure in which multiple rows are provided.

[0121] The external electrodes 23a of the driving piezoelectric element columns 12A of the piezoelectric elements 12 are directly connected to the FPC 15 as wiring means by a solder member in order to provide a driving signal, and a driving circuit (driver IC) 16 for selectively applying a driving waveform to each driving piezoelectric element column 12A of the piezoelectric elements 12 is mounted on the FPC 15. The external electrodes 23b of all the piezoelectric element columns 12A are electrically connected in common and are connected to the common wiring of the FPC 15 by the same solder member. Here, the output terminal portion of the FPC 15 that is joined to the piezoelectric elements 12 is solder-plated to enable solder bonding, but solder plating may be applied to the piezoelectric elements 12 side instead of the FPC 15. As for the bonding method, bonding using an anisotropic conductive film or wire bonding may be used in addition to solder bonding.

[0122] The nozzle plate 3 is configured by forming an ink-repellent film 32 on the droplet ejection side surface (surface in the ejection direction: ejection surface, or surface opposite to the liquid chamber 6 side, nozzle formation surface) of a nozzle substrate 31 in which holes constituting nozzle holes 4 with nozzle diameters of 5 μm or more and 50 μm or less corresponding to each liquid chamber 6 are formed. Note that the nozzle diameter refers to the diameter of the nozzle when the nozzle shape is circular, and refers to the longest length of the straight line connecting two points on the outer periphery of the nozzle when the nozzle shape is other than circular.

[0123] A frame member 17 formed by injection molding of epoxy resin or polyphenylene sulfite is joined to the outer periphery of the piezoelectric actuator unit 100, which is composed of the piezoelectric element 12 on which the FPC 15 is mounted (connected) and the base member 13. The frame member 17 has the above-mentioned common liquid chamber 10 formed therein, and further has a supply port 19 for supplying ink from the outside to the common liquid chamber 10, which is connected to an ink supply source such as a sub-tank or an ink storage container.

[0124] In the ink ejection head configured in this manner, ink droplets are ejected (sprayed) from the nozzle holes 4, for example, in the following manner. First, the voltage applied to the driving piezoelectric element columns 12A is lowered from the reference potential, causing the piezoelectric element columns 12A to contract. Next, the vibration region 2a of the vibration plate member 2 descends, causing the volume of the liquid chamber 6 to expand, and ink flows into the liquid chamber 6. Next, the voltage applied to the piezoelectric element columns 12A is increased, causing the piezoelectric element columns 12A to expand in the stacking direction. Next, the vibration plate member 2 is deformed toward the nozzle hole 4, causing the volume of the liquid chamber 6 to contract. As a result, the ink in the liquid chamber 6 is pressurized, and droplets of ink are ejected (jetted) from the nozzle hole 4.

[0125] Then, by returning the voltage applied to the piezoelectric element columns 12A to the reference potential, the vibration plate member 2 is restored to its initial position, and the liquid chamber 6 expands, generating negative pressure. At this time, ink fills the liquid chamber 6 from the common liquid chamber 10. Then, after the vibration of the meniscus surface of the nozzle hole 4 is attenuated and stabilized, the operation proceeds to eject the next droplet.

[0126] The method of driving the ink ejection head is not limited to the above example (pull-push shot), and pull shots, push shots, etc. can also be performed depending on the driving waveform applied. EXAMPLES

[0127] The present invention will be described in more detail below by way of examples, but the present invention is not limited to these examples.

[0128] (Ink Preparation) <Preparation of pigment dispersion> 100 g of copper phthalocyanine pigment (CI Pigment Blue 15:4, product name: LX4033) manufactured by Toyo Ink Co., Ltd. was added to 3000 mL of 2.5N (normal) sodium hypochlorite solution, and the mixture was stirred at a temperature of 60°C and a speed of 300 rpm for 10 hours to carry out an oxidation treatment, thereby obtaining a pigment having carboxylic acid groups added to the surface of the copper phthalocyanine pigment. This reaction liquid was filtered, and the copper phthalocyanine pigment separated by filtration was neutralized with a sodium hydroxide solution and subjected to ultrafiltration. Next, the pigment dispersion and ion-exchanged water were subjected to ultrafiltration using a dialysis membrane, and further subjected to ultrasonic dispersion to obtain a cyan pigment dispersion having a volume average particle size of 75 nm and having a pigment solid content concentrated to 20%.

[0129] <Preparation of organic solvent> As the organic solvent, the following commercially available products were used. Triethylene glycol monobutyl ether (Tokyo Chemical Industry Co., Ltd., boiling point 278°C) Tetraethylene glycol dimethyl ether (Tokyo Chemical Industry Co., Ltd., boiling point 275°C) Triethylene glycol butyl methyl ether (Tokyo Chemical Industry Co., Ltd., boiling point 261°C) 2-Pyrrolidone (Tokyo Chemical Industry Co., Ltd., boiling point 245°C) Diethylene glycol (Tokyo Chemical Industry Co., Ltd., boiling point 245°C) Glycerin (Tokyo Chemical Industry Co., Ltd., boiling point 290℃) Diethylene glycol monobutyl ether (Tokyo Chemical Industry Co., Ltd., boiling point 230°C) Ethylene glycol (Tokyo Chemical Industry Co., Ltd., boiling point 197°C)

[0130] <Preparation of surfactant> As the surfactant, the following commercially available products were used. Olefin E1004 (manufactured by Nissin Chemical Industry Co., Ltd.)

[0131] <Ink preparation example> Each material was prepared based on the ink formulations shown in Tables 1 to 4 below, then mixed and stirred, filtered through a filter with an average pore size of 5 μm (Minisart, manufactured by Sartorius), and then filtered through a 0.5 μm polypropylene filter to prepare each ink. The units of the values ​​for various materials in the table are "mass %." The values ​​showing the content of the pigment dispersion in the table all represent the solid content.

[0132] (Preparation of recording media) The following commercially available products were used: Snowbrite (Town Rivers, 40gsm) ·NPi Form NEXT-IJ 70 (Made by Nippon Paper Industries, basis weight 81.4gsm) ·NPi Form NEXT-IJ 135 (Nippon Paper, basis weight 157gsm) Crown Letsgo Silk (Crown van Gelder, 250gsm) Although there is no particular limitation, herein, for example, a paper having a basis weight of 100 gsm or less is considered to be thin paper, and a paper having a basis weight of more than 100 gsm is considered to be thick paper.

[0133] (evaluation) Next, the drying property and curl resistance of the obtained ink were evaluated based on the following methods. The evaluation results are shown in Tables 1 to 4 below. The first ink and the second ink were the same ink, the temperature of the first drying section was 100°C, the temperature of the second drying section was 100°C, and the IR heater used a heat source with a wavelength of 2 to 3 μm. The temperature of the first cooling section was 20°C, and the temperature of the second cooling section was 20°C.

[0134] <Drying> The ink thus prepared was used to form a solid image at a resolution of 600 dpi x 600 dpi using the device shown in Figure 1. Within 2 minutes of printing, the solid image was rubbed 20 times with a blank portion of a recording medium cut into a square of 1.2 cm, and the ink transfer stain onto the blank portion of the coated paper was measured using a reflective color spectrophotometric densitometer (manufactured by X-Rite). The transfer density was calculated by subtracting the background color of the rubbed white paper, and the drying property was evaluated based on the following criteria. AA or A is within the acceptable range.

[0135] [Evaluation Criteria] AA: Transfer density is less than 0.01 A: Transfer density is 0.01 or more and less than 0.03 B: Transfer density is 0.03 or more and less than 0.10 C: Transfer density is 0.10 or more

[0136] <Curl resistance> The ink was used to form a solid image at a resolution of 600 dpi x 600 dpi using the device shown in Figure 1. Within 2 minutes of printing, an A4 size sheet was cut out and placed on a flat surface. The height of the four corners of the recording media from the flat surface was measured and rated according to the following evaluation criteria. AA or A is within the acceptable range.

[0137] [Evaluation Criteria] AA: Less than 5mm A: 5mm to less than 10mm B: 10mm or more and less than 20mm C:20mm or more

[0138] [Table 1]

[0139] [Table 2]

[0140] [Table 3]

[0141] [Table 4]

[0142] Comparing Examples 1 to 23 with Comparative Examples 1 to 4, 7, and 8, it can be seen that when the amount of organic solvent with a boiling point of 240°C or more and 280°C or less is 3.0% by mass or more and 15.0% by mass or less relative to the total amount of ink, both curl resistance of thin paper and drying performance of thick paper can be achieved. Comparing Examples 1 to 16 with Examples 17 to 19, it can be seen that the curl resistance of thin paper is improved when the amount of water added is 62 mass % or more and 74 mass % or less with respect to the total amount of ink. Comparing Examples 1 to 10 with Examples 11 to 15, it can be seen that the drying properties of cardboard become better when the amount of water added is 64 mass % or more with respect to the total amount of ink. Comparing Examples 1 to 15 with Examples 20 to 23, it can be seen that the curl resistance of thin paper is improved when the ink contains two or more organic solvents with boiling points of 240°C or more and 280°C or less in a total amount of 3.0% by mass or more and 15.0% by mass or less of the total amount of ink. Comparing Examples 1 to 23 with Comparative Examples 5 and 6, it is clear that when the amount of water added is 62 mass % or more with respect to the total amount of ink, the drying properties of cardboard become good. [Explanation of symbols]

[0143] 42 Paper feeder 43, 46 Conveyor section 44 Wiping section 45 Reversal section 47 Winding device 51 First ink application unit 52 Second ink application unit 61 First Drying Section 62 Second Drying Section 71 First cooling section 72 Second cooling section P Continuous paper [Prior art documents] [Patent documents]

[0144] [Patent Document 1] JP 2017-170851 A [Patent Document 2] JP 2020-001282 A

Claims

1. a first ink applying unit having a first ink containing a pigment, an organic solvent, and water, and a first liquid ejection head that ejects the first ink onto a first surface of a recording medium; a second ink application unit including a second ink containing a pigment, an organic solvent, and water, and a second liquid ejection head that ejects the second ink onto a second surface of the recording medium, the second surface being the surface opposite to the first surface onto which the first ink has been ejected; a first drying unit that dries a first surface of the recording medium onto which the first ink is ejected; a second drying unit that dries a second surface of the recording medium onto which the second ink has been ejected; a first cooling unit that cools the recording medium dried by the first drying unit; a second cooling unit that cools the recording medium dried by the second drying unit; A printing device comprising: the first ink and the second ink each contain water in an amount of 62 mass % or more relative to a total amount of the ink, and contain, as the organic solvent, an organic solvent having a boiling point of 240° C. or more and 280° C. or less; the total amount of the organic solvents having a boiling point of 240° C. or more and 280° C. or less is 3.0% by mass or more and 15.0% by mass or less with respect to the total amount of each ink, A printing device, characterized in that the first drying unit, the second drying unit, and the first cooling unit are arranged in this order in a direction from one end side to the other end side of the printing device.

2. 2. The printing apparatus according to claim 1, wherein the ink contains two or more kinds of organic solvents having a boiling point of 240[deg.] C. or more and 280[deg.] C. or less.

3. 3. The printing device according to claim 1, wherein the first drying unit, the second drying unit, and the second cooling unit are arranged in this order in a direction from one end side to the other end side of the printing device.

4. 4. The printing device according to claim 1, wherein the total amount of the organic solvents contained in the first ink and the second ink, the organic solvents having a boiling point of 290° C. or less, is 23.0% by mass or more and 48.0% by mass or less with respect to the total amount of the first ink or the second ink.

5. 5. The printing device according to claim 1, wherein the amount of water contained in the first ink and the second ink is 74 mass % or less with respect to the total amount of the first ink or the second ink.

6. A printing device according to any one of claims 1 to 5, characterized in that the recording medium is transported in the order of the first ink application unit, the first drying unit, the first cooling unit, the second ink application unit, the second drying unit, and the second cooling unit.

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