Ink set, inkjet printing apparatus, and inkjet printing method

Abstract

To provide an ink set which can suppress granular feeling of a highlight part, and has good fixability even when ink of high pigment concentration having good color development property is used.SOLUTION: An ink set has standard ink and light ink, in which the standard ink contains cyan ink, magenta ink, and yellow ink, the light ink contains at least any one of light cyan ink and light magenta ink, pigment concentration of the cyan ink is 1.9 mass% or more and 3.6 mass% or less, pigment concentration of the light cyan ink is 0.4 mass% or more and 1.4 mass% or less, pigment concentration of the magenta ink is 1.9 mass% or more and 3.6 mass% or less, pigment concentration of the light magenta ink is 0.4 mass% or more and 1.4 mass% or less with respect to the magenta ink, the light ink contains water, an organic solvent and a resin, and the organic solvent contains an amide compound represented by a specific structural formula.SELECTED DRAWING: None

Description

Technical Field

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

Background Art

[0002] Compared with other recording methods, the inkjet recording method has a simple process, is easy to achieve full color, and even with a device having a simple configuration, a high-resolution image can be obtained. Therefore, it is spreading from personal and office use to the field of industrial printing.

[0003] In industrial printing, especially in the field of sign graphics, high color development of printed matter is required. On the other hand, when using an ink with a high pigment concentration that has good color development, there is a problem that the graininess deteriorates in the highlight part of low tones. Therefore, for the purpose of reducing graininess, for example, an inkjet recording method using six types of pigment inks of black, light cyan, cyan, light magenta, magenta, and yellow has been proposed (see, for example, Patent Document 1).

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present invention is to provide an ink set that can suppress the graininess of the highlight part even when using an ink with a high pigment concentration that has good color development and has good fixing properties.

Means for Solving the Problems

[0005] The ink set of the present invention as a means for solving the above problems is an ink set having a standard ink and a light ink. The standard ink includes at least cyan ink, magenta ink, and yellow ink. The light ink includes at least one of light cyan ink and light magenta ink. The content of the cyan pigment in the cyan ink is 1.9% by mass or more and 3.6% by mass or less. The content of the cyan pigment in the light cyan ink is 0.6 % by mass or more and 1.4% by mass or less. The content of the magenta pigment in the magenta ink is 1.9% by mass or more and 3.6% by mass or less. The content of the magenta pigment in the light magenta ink is 0.6 % by mass or more and 1.4% by mass or less. The light ink contains water, an organic solvent, and a resin. The organic solvent contains an amide compound represented by the following general formula (1). [Chemical formula] However, in the general formula (1), R1, R2, and R3 each independently represent a hydrocarbon group having 1 to 8 carbon atoms. [Advantages of the Invention]

[0006] According to the present invention, even when using an ink with a high pigment concentration and good color development, it is possible to suppress the granular feeling of the highlight part and provide an ink set with good fixing properties. [Brief Description of the Drawings]

[0007]

Figure 1

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DETAILED DESCRIPTION OF THE INVENTION

[0008] (Ink set) The ink set of the present invention is an ink set having a standard ink and a light ink, wherein the standard ink contains at least cyan ink, magenta ink, and yellow ink, the light ink contains at least one of light cyan ink and light magenta ink, the content of cyan pigment in the cyan ink is 1.9% by mass or more and 3.6% by mass or less, the content of cyan pigment in the light cyan ink is 0.4% by mass or more and 1.4% by mass or less, the content of magenta pigment in the magenta ink is 1.9% by mass or more and 3.6% by mass or less, the content of magenta pigment in the light magenta ink is 0.4% by mass or more and 1.4% by mass or less, the light ink contains water, an organic solvent, and a resin, and the organic solvent contains an amide compound represented by the following general formula (1).

[0009]

Chemical formula

[0010] When expressing the same highlighting part using standard ink and light ink, since the amount of ink adhesion is larger for the light ink than for the standard ink, in the prior art, when expressing the highlighting part using light ink, a problem is a decrease in fixing property due to poor drying. The highlighting part is a part with relatively low chroma and lightness. The light ink has a lower pigment concentration than the standard ink. When printing with the same chroma and the same lightness, comparing the standard ink and the light ink, the required amount of ink adhesion is larger when using the light ink. In the present invention, since the light ink contains water, an organic solvent, and a resin, and the organic solvent contains an amide compound represented by the above general formula (1), film formation of the resin can be promoted and the fixing property can be improved. Therefore, even when the standard ink and the light ink are used in combination, the granular feeling of the highlighting part can be suppressed.

[0011] Further, in the prior art, the receding contact angle of the ink with respect to the nozzle plate of the ejection head is not optimized, the ink easily wets the ink-repellent film of the nozzle plate of the ejection head, and the ejection stability deteriorates due to the ink adhering to the nozzle. In the present invention, since the receding contact angle of each ink in the ink set with respect to the nozzle plate of the ejection head is 35° or more, the ink hardly wets the ink-repellent film of the nozzle plate of the ejection head, and even if the ink adheres to the inner wall surface of the ink chamber of the ejection head, it easily repels again. Thus, the ejection stability of the ink becomes good and the landing accuracy of the ink droplets increases, so that the granular feeling of the highlighting part can be further suppressed.

[0012] The ink set of the present invention has a standard ink and a light ink. The standard ink contains at least cyan ink, magenta ink, and yellow ink, and preferably contains black ink, and is an ink containing pigments in standard contents. The light ink contains at least one of a light cyan ink and a light magenta ink, and is an ink containing a pigment in a content less than that of the standard ink.

[0013] The content of the cyan pigment in the cyan ink is 1.9% by mass or more and 3.6% by mass or less, preferably 2.1% by mass or more and 3.5% by mass or less, and more preferably 2.4% by mass or more and 3.0% by mass or less. By the content of the cyan pigment in the cyan ink being 1.9% by mass or more and 3.6% by mass or less, high color developability can be obtained. The content of the cyan pigment in the light cyan ink is 0.4% by mass or more and 1.4% by mass or less, preferably 0.6% by mass or more and 1.1% by mass or less, and more preferably 0.6% by mass or more and 0.9% by mass or less.

[0014] The content of the magenta pigment in the magenta ink is 1.9% by mass or more and 3.6% by mass or less, preferably 2.1% by mass or more and 3.5% by mass or less, and more preferably 2.4% by mass or more and 3.0% by mass or less. By the content of the magenta pigment in the magenta ink being 1.9% by mass or more and 3.6% by mass or less, high color developability can be obtained. The content of the magenta pigment in the light magenta ink is 0.4% by mass or more and 1.4% by mass or less, preferably 0.6% by mass or more and 1.1% by mass or less, and more preferably 0.7% by mass or more and 1.1% by mass or less.

[0015] <Light ink> The light ink contains water, an organic solvent, and a resin, preferably contains a surfactant, and further contains other components as required.

[0016] The light ink includes at least one of a light cyan ink containing a cyan pigment and a light magenta ink containing a magenta pigment.

[0017] The cyan pigment is not particularly limited and can be appropriately selected according to the purpose. For example, C.I. Pigment Blue 1, 2, 15 (phthalocyanine blue), 15:1, 15:2, 15:3, 15:4 (phthalocyanine blue), 16, 17:1, 56, 60, 63, etc. can be mentioned. These may be used alone or in combination of two or more.

[0018] The magenta pigment is not particularly limited and can be appropriately selected according to the purpose. For example, C.I. Pigment Red 1, 2, 3, 5, 17, 22, 23, 31, 38, 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 (vermilion), 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, etc. can be mentioned. These may be used alone or in combination of two or more.

[0019] In order to obtain ink by dispersing the pigment, methods such as introducing a hydrophilic functional group into the pigment to make a self-dispersing pigment, coating the surface of the pigment with a resin for dispersion, and using a dispersant for dispersion can be mentioned. As a method of introducing a hydrophilic functional group into the pigment to make a self-dispersing pigment, for example, a method of adding a functional group such as a sulfone group or a carboxyl group to the pigment (for example, carbon) to make it dispersible in water can be mentioned. As a method of coating the surface of the pigment with a resin for dispersion, for example, a method of including the pigment in microcapsules to make it dispersible in water can be mentioned. This can be paraphrased as a resin-coated pigment. In this case, it is not necessary for all the pigments incorporated in the ink to be coated with the resin. As long as the effects of the present invention are not impaired, uncoated pigments or partially coated pigments may be dispersed in the ink. Examples of the method of dispersion using a dispersant include methods of dispersion using known low molecular weight dispersants and high molecular weight dispersants typified by surfactants. As the dispersant, depending on the pigment, for example, anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, etc. can be used. RT-100 (nonionic surfactant) manufactured by Takemoto Yushi Co., Ltd. and sodium naphthalene sulfonate formalin condensate can also be suitably used as the dispersant. The above-mentioned dispersant may be used alone or in combination of two or more.

[0020] <<Pigment Dispersion>> It is possible to obtain ink by mixing materials such as water and organic solvents with the pigment. It is also possible to produce ink by mixing a pigment dispersion obtained by mixing a pigment with other materials such as water and a dispersant with materials such as water and organic solvents. The pigment dispersion is obtained by mixing, dispersing water, a pigment, a pigment dispersant, and other components as necessary, and adjusting the particle size. It is advisable to use a disperser for dispersion. Regarding the particle size of the pigment in the pigment dispersion, there is no particular limitation. However, from the viewpoints of good dispersion stability of the pigment and high image quality such as ejection stability and image density, the maximum frequency in terms of 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. The particle size of the pigment can be measured using, for example, a particle size analyzer (NanoTrack 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 according to the purpose. However, from the viewpoints of obtaining good ejection stability and increasing the image density, it 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. The pigment dispersion is preferably filtered to remove coarse particles and degassed using a filter, a centrifuge, etc. as necessary.

[0021] <<Organic Solvent>> The organic solvent is not particularly limited, and a water-soluble organic solvent can be used. Examples thereof include ethers such as polyhydric alcohols, polyhydric alcohol alkyl ethers, and polyhydric alcohol aryl ethers, nitrogen-containing heterocyclic compounds, amide compounds, amines, and sulfur-containing compounds. Examples of the water-soluble organic solvent include polyhydric alcohols such as 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, 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; 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; 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; amide compounds represented by the following general formula (1); amines such as monoethanolamine, diethanolamine, and triethylamine; sulfur-containing compounds such as dimethyl sulfoxide, sulfolane, and thiodiethanol; propylene carbonate; and ethylene carbonate.

[0022]

Chem.

[0023] Among these, from the viewpoint of promoting film formation of the resin and improving the fixing property, the amide compound represented by the general formula (1) is preferable. The hydrocarbon group is not particularly limited as long as it has 1 to 8 carbon atoms, and examples thereof include linear or branched or cyclic alkyl groups. Examples of the alkyl group include methyl group, ethyl group, propyl group, butyl group, isopropyl group, isobutyl group, pentyl group, hexyl group, heptyl group, ethylhexyl group, octyl group, cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, and the like. Examples of the amide compound represented by the general formula (1) include 3-methoxy-N,N-dimethylpropanamide, 3-butoxy-N,N-dimethylpropanamide, and the like. The content of the amide compound represented by the general formula (1) is preferably 5% by mass or more and 20% by mass or less based on the total amount of the light ink.

[0024] Polyol compounds having 8 or more carbon atoms and glycol ether compounds are also preferably used. Examples of the polyol compound having 8 or more carbon atoms include 2-ethyl-1,3-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, and the like. 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.

[0025] A polyol compound having 8 or more carbon atoms and a glycol ether compound can improve the ink permeability when paper is used as a recording medium.

[0026] The content of the organic solvent in the light ink is not particularly limited and can be appropriately selected according to the purpose. However, from the viewpoints of ink drying property and ejection reliability, 10% by mass or more and 60% by mass or less are preferable, and 20% by mass or more and 60% by mass or less are more preferable.

[0027] <<Water>> The water is not particularly limited and can be appropriately selected according to the purpose. Examples include pure water such as ion-exchanged water, ultrafiltration water, reverse osmosis water, and distilled water, and ultrapure water. These may be used alone or in combination of two or more. The content of water in the light ink is not particularly limited and can be appropriately selected according to the purpose. However, from the viewpoints of ink drying property and ejection reliability, 10% by mass or more and 90% by mass or less are preferable, and 20% by mass to 60% by mass are more preferable.

[0028] <<Resin>> There are no particular restrictions on the type of the resin, and it can be appropriately selected according to the purpose. For example, urethane resins, polyester resins, acrylic resins, vinyl acetate resins, styrene resins, butadiene resins, styrene-butadiene resins, vinyl chloride resins, acrylic-styrene resins, acrylic silicone resins, etc. can be mentioned. Resin particles composed of these resins may also be used. It is possible to obtain an ink by mixing resin particles in a state of a resin emulsion dispersed with water as a dispersion medium with materials such as coloring materials and organic solvents. As the resin particles, those synthesized as appropriate may be used, or commercially available products may be used. Further, these may be used alone or in combination of two or more kinds of resin particles.

[0029] There are no particular restrictions on the volume average particle diameter of the resin particles, and it can be appropriately selected according to the purpose. However, from the viewpoints of obtaining good fixing property and high image hardness, it 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 diameter can be measured, for example, using a particle size analyzer (NanoTrac Wave-UT151, manufactured by Microtrac Bell Corporation).

[0030] There are no particular restrictions on the content of the resin, and it can be appropriately selected according to the purpose. However, from the viewpoints of fixing property and storage stability of the ink, it is preferably 1% by mass or more and 30% by mass or less, more preferably 5% by mass or more and 20% by mass or less, based on the total amount of the ink.

[0031] There are no particular restrictions on the particle diameter of the solid content in the light ink, and it can be appropriately selected according to the purpose. However, from the viewpoint of improving image quality such as ejection stability and image density, the maximum frequency in terms of the maximum number conversion is preferably 20 nm or more and 1,000 nm or less, more preferably 20 nm or more and 150 nm or less. The solid content includes resin particles, pigment particles, etc. The particle diameter can be measured using a particle size analyzer (NanoTrac Wave-UT151, manufactured by Microtrac Bell Corporation).

[0032] <<Surfactant>> As the surfactant, any of silicone surfactants, fluorine surfactants, amphoteric surfactants, nonionic surfactants, and anionic surfactants can be used. There are no particular restrictions on the silicone surfactant, and it can be appropriately selected according to the purpose. Among them, those that do not decompose even at high pH are preferable. For example, side-chain modified polydimethylsiloxane, both-terminal modified polydimethylsiloxane, one-terminal modified polydimethylsiloxane, side-chain and both-terminal modified polydimethylsiloxane, etc. can be mentioned. Those having a polyoxyethylene group or a polyoxyethylene polyoxypropylene group as the modifying group are particularly preferable because they exhibit good properties as aqueous surfactants. In addition, as the silicone surfactant, a polyether-modified silicone surfactant can also be used, for example, a compound in which a polyalkylene oxide structure is introduced into the Si part side chain of dimethylsiloxane.

[0033] As the fluorine surfactant, for example, perfluoroalkyl sulfonic acid compounds, perfluoroalkyl carboxylic acid compounds, perfluoroalkyl phosphate ester compounds, perfluoroalkyl ethylene oxide adducts, and polyoxyalkylene ether polymer compounds having a perfluoroalkyl ether group in the side chain are particularly preferable because of their low foaming properties. Examples of the perfluoroalkyl sulfonic acid compound include perfluoroalkyl sulfonic acid and perfluoroalkyl sulfonate. Examples of the perfluoroalkyl carboxylic acid compound include perfluoroalkyl carboxylic acid and perfluoroalkyl carboxylate. Examples of the polyoxyalkylene ether polymer compound having a perfluoroalkyl ether group in the side chain include sulfate salts of polyoxyalkylene ether polymers having a perfluoroalkyl ether group in the side chain and salts of polyoxyalkylene ether polymers having a perfluoroalkyl ether group in the side chain. Examples of the counter ions of the salts in these fluorine surfactants include Li, Na, K, NH4, NH3CH2CH2OH, NH2(CH2CH2OH)2, NH(CH2CH2OH)3, etc. Examples of the amphoteric surfactant include lauryl aminopropionate, lauryldimethyl betaine, stearyldimethyl betaine, lauryldihydroxyethyl betaine, and the like. Examples of the nonionic surfactant include polyoxyethylene alkyl phenyl ether, polyoxyethylene alkyl ester, polyoxyethylene alkyl amine, polyoxyethylene alkyl amide, polyoxyethylene propylene block polymer, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, ethylene oxide adduct of acetylene alcohol, and the like. Examples of the anionic surfactant include polyoxyethylene alkyl ether acetate, dodecylbenzene sulfonate, laurate, salts of polyoxyethylene alkyl ether sulfate, and the like. The surfactant may be used alone or in combination of two or more.

[0034] The silicone-based surfactant is not particularly limited and can be appropriately selected according to the purpose. For example, side chain-modified polydimethylsiloxane, both-end modified polydimethylsiloxane, one-end modified polydimethylsiloxane, side chain and both-end modified polydimethylsiloxane, and the like can be mentioned. Among them, a polyether-modified silicone-based surfactant having a polyoxyethylene group or a polyoxyethylene polyoxypropylene group as a modifying group exhibits good properties as an aqueous surfactant, so it is particularly preferred. As such a surfactant, those synthesized as appropriate may be used, or commercially available products may be used. Examples of the commercially available products include those available from BYK Chemie Japan Co., Ltd., Shin-Etsu Chemical Co., Ltd., Toray Dow Corning Silicone Co., Ltd., Nippon Emulsion Co., Ltd., Kyoeisha Chemical Co., Ltd., and the like. The polyether-modified silicone-based surfactant is not particularly limited and can be appropriately selected according to the purpose. For example, those in which a polyalkylene oxide structure is introduced into the Si part side chain of dimethylpolysiloxane represented by the following general formula (S-1) can be mentioned.

[0035] [Chemical formula] (However, 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.)

[0036] As the above polyether-modified silicone surfactant, commercially available products can be used. For example, KF-618, KF-642, KF-643 (manufactured by Shin-Etsu Chemical Co., Ltd.), EMALEX-SS-5602, SS-1906EX (manufactured by Nippon Emulsion Co., Ltd.), FZ-2105, FZ-2118, FZ-2154, FZ-2161, FZ-2162, FZ-2163, FZ-2164 (manufactured by Toray Dow Corning Silicone Co., Ltd.), BYK-33, BYK-387 (manufactured by BYK-Chemie GmbH), TSF4440, TSF4452, TSF4453 (manufactured by Toshiba Silicone Co., Ltd.), etc. can be mentioned.

[0037] As the fluorosurfactant, a compound having 2 to 16 carbon atoms substituted with fluorine is preferable, and a compound having 4 to 16 carbon atoms substituted with fluorine is more preferable. As the fluorosurfactant, perfluoroalkyl phosphate ester compounds, perfluoroalkyl ethylene oxide adducts, polyoxyalkylene ether polymer compounds having a perfluoroalkyl ether group in the side chain, etc. can be mentioned. Among these, polyoxyalkylene ether polymer compounds having a perfluoroalkyl ether group in the side chain are preferable because they have less foaming property, and in particular, fluorosurfactants represented by any of the following general formulas (F-1) and (F-2) are preferable.

[0038] [Chemical formula] In the compound represented by the above general formula (F-1), in order to impart water solubility, m is preferably an integer of 0 to 10, and n is preferably an integer of 0 to 40.

[0039] [General formula (F-2)] C n F 2n+ -CH2CH(OH)CH2-O-(CH2CH2O) a -Y In the compound represented by the above general formula (F-2), Y is H, or C m F 2m+1 where m is an integer from 1 to 6, or CH2CH(OH)CH2-C m F 2m+1 where m is an integer from 4 to 6, or C p H 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.

[0040] As the fluorosurfactant, commercially available products may be used. Examples of the commercially available products include Surfron S-111, S-112, S-113, S-121, S-131, S-132, S-141, S-145 (all manufactured by Asahi Glass Co., Ltd.); Fluorad FC-93, FC-95, FC-98, FC-129, FC-135, FC-170C, FC-430, FC-431 (all manufactured by Sumitomo 3M Limited); Megafac F-470, F-1405, F-474 (all manufactured by DIC Corporation); 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), Uni-Dyn DSN-403N (manufactured by Daikin Industries, Ltd.), and the like. Among these, from the viewpoints of excellent printing quality, particularly color development, penetration into paper, wettability, and leveling property, FS-3100, FS-34, FS-300 manufactured by Chemours, FT-110, FT-250, FT-251, FT-400S, FT-150, FT-400SW manufactured by Neos Co., Ltd., Polyfox PF-151N manufactured by Omnova, and Uni-Dyn DSN-403N manufactured by Daikin Industries, Ltd. are particularly preferred.

[0041] The content of the surfactant is not particularly limited and can be appropriately selected according to the purpose. However, from the viewpoints of improving wettability and image quality, 0.01% by mass or more and 5% by mass or less, more preferably 0.05% by mass or more and 5% by mass or less, based on the total amount of the light ink, is preferred.

[0042] The light ink may contain, as other components, an antifoaming agent, an antiseptic and antifungal agent, a rust preventive, a pH adjuster, etc. as required.

[0043] - Antifoaming agent - There are no particular restrictions on the defoaming agent. For example, silicone-based defoaming agents, polyether-based defoaming agents, fatty acid ester-based defoaming agents, etc. may be mentioned. These may be used alone or in combination of two or more. Among these, silicone-based defoaming agents are preferred because of their excellent defoaming effect.

[0044] -Antiseptic and mildew-proof agent- There are no particular restrictions on the antiseptic and mildew-proof agent. For example, 1,2-benzisothiazolin-3-one, etc. may be mentioned.

[0045] -Rust inhibitor- There are no particular restrictions on the rust inhibitor. For example, acid sulfite, sodium thiosulfate, 1,2,3-benzotriazole, etc. may be mentioned.

[0046] -pH adjuster- There are no particular restrictions on the pH adjuster as long as it can adjust the pH to 7 or higher. Amines such as diethanolamine and triethanolamine, 2-amino-2-ethyl-1,3-propanediol, etc. may be mentioned.

[0047] There are no particular restrictions on the physical properties of the light 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 light 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 the quality of characters and obtaining good ejection properties. Here, for example, a rotational viscometer (manufactured by Toki Sangyo Co., Ltd., RE-80L) can be used to measure the viscosity. As the measurement conditions, it can be measured at 25°C with a standard cone rotor (1°34’×R24), a sample liquid volume of 1.2 mL, a rotation speed of 50 rpm, and for 3 minutes. The surface tension of the light ink is preferably 35 mN / m or less, more preferably 32 mN / m or less at 25°C, from the viewpoints of the ink being preferably leveled on the recording medium and the drying time of the ink being shortened. The pH of the light ink is preferably 7 to 12, more preferably 8 to 11, from the viewpoint of preventing corrosion of the wetted metal members.

[0048] <Standard ink> The standard ink contains a coloring material, water, an organic solvent, and a resin, preferably contains a surfactant, and further contains other components as necessary.

[0049] <<Coloring material>> The coloring material is not particularly limited, and a pigment or a dye can be used. As the pigment, an inorganic pigment or an organic pigment can be used. These may be used alone or in combination of two or more. Also, mixed crystals may be used. As the pigment, for example, a black pigment, a yellow pigment, a magenta pigment, a cyan pigment, a white pigment, a green pigment, an orange pigment, a metallic pigment such as a metallic color pigment like gold or silver can be used. As the inorganic pigment, for example, titanium oxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, chrome yellow, and in addition, carbon black produced by known methods such as the contact method, the furnace method, and the thermal method can be used. Examples of the organic pigment include azo pigments, polycyclic pigments (for example, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, etc.), dye chelates (for example, basic dye type chelates, acidic dye type chelates, etc.), nitro pigments, nitroso pigments, aniline black, etc. Among these pigments, those having good affinity with the solvent are preferably used. In addition, the use of resin hollow particles and inorganic hollow particles is also possible. Specific examples of the pigment include, for black, carbon blacks (C.I. Pigment Black 7) such as furnace black, lamp black, acetylene black, and channel black, or metals such as copper, iron (C.I. Pigment Black 11), and titanium oxide, and organic pigments such as aniline black (C.I. Pigment Black 1). Furthermore, for colors, C.I. 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, C.I. Pigment Orange 5, 13, 16, 17, 36, 43, 51, C.I. Pigment Red 1, 2, 3, 5, 17, 22, 23, 31, 38, 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 (vermilion), 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, C.I. Pigment Violet 1 (rhodamine lake), 3, 5:1, 16, 19, 23, 38, C.I. Pigment Blue 1, 2, 15 (phthalocyanine blue), 15:1, 15:2, 15:3, 15:4 (phthalocyanine blue), 16, 17:1, 56, 60, 63, C.I. Pigment Green 1, 4, 7, 8, 10, 17, 18, 36, etc. can be mentioned.

[0050] As the dye, without particular limitation, acid dyes, direct dyes, reactive dyes, and basic dyes can be used, and they may be used alone or in combination of two or more. As the dye, for example, C.I. Acid Yellow 17, 23, 42, 44, 79, 142, C.I. Acid Red 52, 80, 82, 249, 254, 289, C.I. Acid Blue 9, 45, 249, C.I. Acid Black 1, 2, 24, 94, C.I. Food Black 1, 2, C.I. Direct Yellow 1, 12, 24, 33, 50, 55, 58, 86, 132, 142, 144, 173, C.I. Direct Red 1, 4, 9, 80, 81, 225, 227, C.I. Direct Blue 1, 2, 15, 71, 86, 87, 98, 165, 199, 202, C.I. Direct Black 19, 38, 51, 71, 154, 168, 171, 195, C.I. Reactive Red 14, 32, 55, 79, 249, C.I. Reactive Black 3, 4, 35 can be mentioned.

[0051] The standard ink contains at least cyan ink, magenta ink, and yellow ink, and preferably contains black ink. The content of the cyan pigment in the cyan ink is 1.9% by mass or more and 3.6% by mass or less, and preferably 2.4% by mass or more and 3.0% by mass or less. The content of the magenta pigment in the magenta ink is 1.9% by mass or more and 3.6% by mass or less, and preferably 2.4% by mass or more and 3.0% by mass or less. The content of the yellow pigment in the yellow ink is preferably 1.9% by mass or more and 3.6% by mass or less. Also, the content of the black pigment in the black ink is preferably 1.9% by mass or more and 3.6% by mass or less.

[0052] Regarding water, organic solvents, resins, surfactants, and other components in the standard ink, since they are the same as those in the light ink, the description thereof is omitted.

[0053] <Recording medium> The recording medium is not particularly limited, and plain paper, glossy paper, special paper, cloth, etc. can be used, but good image formation is also possible using a non-permeable substrate. The non-permeable base material is a base material having a surface with low water permeability and absorbency, and includes materials that have a large number of cavities inside but do not open to the outside. More quantitatively, in the Bristow method, from the start of contact to 30 msec 1 / 2 The base material refers to a base material with a water absorption amount of 10 mL / m2 or less. As the non-permeable base material, for example, plastic films such as vinyl chloride resin film, polyethylene terephthalate (PET) film, polypropylene, polyethylene, polycarbonate film, and board base materials such as polystyrene, acrylic, polypropylene, aluminum composite board, and polycarbonate can be preferably used.

[0054] <Recording Device and Recording Method> In the following description of the recording device and recording method, the case of using black (K) ink, cyan (C) ink, magenta (M) ink, and yellow (Y) ink will be described. In addition to these, light inks such as light cyan ink or light magenta ink can be used. Each ink in the ink set used in the present invention can be preferably used in various recording devices using the inkjet recording method, such as printers, facsimile machines, copying machines, printers, faxes, copier multifunction machines, and three-dimensional modeling devices. The inkjet printing device includes, unless otherwise particularly limited, both a serial type device that moves the ejection head and a line type device that does not move the ejection head. Furthermore, the inkjet printing device includes not only desktop types but also wide-width recording devices, such as continuous printers that can use continuously wound paper in roll form as a recording medium. In the present invention, the recording device and recording method are a device capable of ejecting ink and various processing liquids onto a recording medium, and a method of performing recording using the device. The recording medium means something to which ink and various processing liquids can adhere even temporarily. This recording apparatus can include not only a head portion that discharges ink, but also means related to the feeding, conveyance, and paper discharge of a recording medium, and other apparatuses such as those referred to as a preprocessing apparatus and a postprocessing apparatus. Also, the recording apparatus and the recording method are not limited to those in which a significant image such as characters or graphics is visualized by ink. For example, those that form patterns such as geometric patterns and those that create three-dimensional images are also included. Also, the recording apparatus includes, unless otherwise particularly limited, both a serial type apparatus that moves the discharge head and a line type apparatus that does not move the discharge head. Furthermore, this recording apparatus includes not only desktop types, but also wide-format recording apparatuses that enable printing on A0-sized recording media. For example, it also includes a continuous accounting printer that can use continuous paper wound in a roll as a recording medium.

[0055] An example of an inkjet printing apparatus will be described with reference to FIGS. 1 and 2. FIG. 1 is a perspective explanatory view of the recording apparatus. FIG. 2 is a perspective explanatory view of the main tank. The image forming apparatus 400 as an example of the recording apparatus is a serial type image forming apparatus. A mechanism unit 420 is provided inside the exterior 401 of the image forming apparatus 400. Each ink storage unit 411 of the main tanks 410 (410k, 410c, 410m, 410y) for each color of black (K), cyan (C), magenta (M), and yellow (Y) is formed by a packaging member such as an aluminum laminate film, for example. The ink storage unit 411 is housed in a storage container case 414 made of plastics, for example. Thereby, the main tank 410 is used as an ink cartridge for each color. On the other hand, a cartridge holder 404 is provided on the back side of the opening when the cover 401c of the apparatus main body is opened. The main tank 410 is detachably attached to the cartridge holder 404. Thereby, in the image forming apparatus 400, each ink discharge port 413 of the main tank 410 communicates with each color discharge head 434 via a supply tube 436 for each color, and ink can be discharged from the discharge head 434 onto the recording medium.

[0056] The recording device can include not only the part that discharges ink, but also devices such as those referred to as a pretreatment device and a post-treatment device. As one aspect of the pretreatment device and the post-treatment device, in the case of inks such as black (K), cyan (C), magenta (M), and yellow (Y), a liquid storage part having a pretreatment liquid and a post-treatment liquid and a liquid discharge head are added, and there is an aspect of discharging the pretreatment liquid and the post-treatment liquid by an inkjet recording method. As another aspect of the pretreatment device and the post-treatment device, there is an aspect of providing a pretreatment device and a post-treatment device by methods other than the inkjet recording method, such as the blade coating method, the roll coating method, and the spray coating method.

[0057] Note that the method of using the ink is not limited to the inkjet recording method and can be widely used. In addition to the inkjet recording method, for example, the blade coating method, the gravure coating method, the bar coating method, the roll coating method, the dip coating method, the curtain coating method, the slide coating method, the die coating method, the spray coating method, etc. can be mentioned.

[0058] The use of the ink is not particularly limited and can be appropriately selected according to the purpose. For example, it can be applied to printed matter, paints, coating materials, substrates, etc. Furthermore, it can be used not only to form two-dimensional characters and images as ink, but also as a material for three-dimensional stereoscopic image (stereoscopic modeling object) formation to form a three-dimensional stereoscopic image. As a three-dimensional modeling apparatus for modeling a three-dimensional object, a known one can be used and it is not particularly limited. For example, one equipped with an ink storage means, a supply means, a discharge means, a drying means, etc. can be used. The three-dimensional object includes a three-dimensional object obtained by, for example, overcoating ink. Further included is a formed processed product obtained by processing a structure having ink applied on a base material such as a recording medium. The formed processed product is, for example, a recording material and a structure formed in a sheet shape or a film shape, which have been subjected to forming processes such as heat stretching and punching. The formed processed product is suitably used, for example, for applications such as meters of automobiles, OA equipment, electrical equipment, electronic equipment, cameras, etc., and panels of operation parts, where the surface is decorated and then formed.

[0059] The inkjet printing apparatus of the present invention includes an ink storage unit that stores each ink in the ink set of the present invention, and a discharge head that discharges each ink in the ink set, and further includes other members as required.

[0060] The receding contact angle of each ink in the ink set with respect to the nozzle plate of the discharge head is 35° or more, preferably 35° or more and 80° or less, and more preferably 40° or more and 70° or less. If the receding contact angle is 35° or more, it becomes easy for each ink in the ink set to repel again even if it adheres to the inner wall surface of the ink chamber of the discharge head. Note that the upper limit of the receding contact angle is not particularly limited with respect to wettability because the larger the receding contact angle, the more difficult it is to get wet. However, considering the penetrability to the recording medium, etc., it is preferable not to exceed 80° (80° or less). The receding contact angle can be measured, for example, using an automatic contact angle measuring device - expansion or contraction method. Examples of the automatic contact angle measuring device include the automatic contact angle measuring device - DMo-501 (manufactured by Kyowa Interface Science Co., Ltd.). The receding contact angle can be measured by the contraction method using the nozzle plate used in the present invention, extruding 3 μL of each ink from a syringe onto its outer surface, and using the said apparatus. The receding contact angle in the present invention means the value at a measurement temperature of 25°C.

[0061] <Ink storage section> The ink storage section stores each ink in the ink set of the present invention. The ink storage section is not particularly limited as long as it is a member capable of storing ink, and examples thereof include an ink storage container and an ink tank. The ink storage container stores the ink in a container and further has other members appropriately selected as necessary. The container is not particularly limited, and its shape, structure, size, material, etc. can be appropriately selected according to the purpose. Examples thereof include those having at least an ink bag formed of an aluminum laminate film, a resin film, etc. Examples of the ink tank include a main tank and a sub-tank.

[0062] Next, the ejection head used in the inkjet printing apparatus of the present invention will be described. <Ejection head> The ejection head has a nozzle plate and further has other members as necessary.

[0063] -Nozzle plate- The nozzle plate has a nozzle substrate and a non-wetting ink film on the nozzle substrate.

[0064] -Nozzle substrate- The nozzle substrate has nozzle holes, and there are no particular restrictions on the number, shape, size, material, structure, etc. thereof, and they can be appropriately selected according to the purpose. The nozzle substrate has a surface on the ink ejection side from which ink is ejected from the nozzle holes and a liquid chamber joint surface located on the side opposite to the ink ejection side surface. The ink-repellent film is formed on the surface of the nozzle substrate on the ink ejection side, which faces the object to be printed. The receding contact angle of each ink with respect to the surface facing the object to be printed is 35° or more.

[0065] There is no particular limitation on the planar shape of the nozzle substrate, and it can be appropriately selected according to the purpose. For example, a rectangle, a square, a rhombus, a circle, an ellipse, etc. can be mentioned. Moreover, as the cross-sectional shape of the nozzle substrate, for example, a flat plate shape, a plate shape, etc. can be mentioned. There is no particular limitation on the size of the nozzle substrate, and it can be appropriately selected according to the size of the nozzle plate.

[0066] There is no particular limitation on the material of the nozzle substrate, and it can be appropriately selected according to the purpose. For example, stainless steel, Al, Bi, Cr, InSn, ITO, Nb, Nb2O5, NiCr, Si, SiO2, Sn, Ta2O5, Ti, W, ZAO (ZnO + Al2O3), Zn, etc. can be mentioned. These may be used alone or in combination of two or more. Among these, from the viewpoint of rust prevention, the material of the nozzle substrate is preferably stainless steel.

[0067] There is no particular limitation on the stainless steel, and it can be appropriately selected according to the purpose. For example, austenitic stainless steel, ferritic stainless steel, martensitic stainless steel, precipitation hardening type stainless steel, etc. can be mentioned. These may be used alone or in combination of two or more.

[0068] At least the surface of the nozzle substrate on the ink ejection side may be subjected to oxygen plasma treatment to introduce hydroxyl groups from the viewpoint of improving the adhesion between the ink-repellent film and the nozzle substrate.

[0069] -Nozzle hole- There is no particular limitation on the number, arrangement, interval, opening shape, opening size, cross-sectional shape of the opening, etc. of the nozzle hole, and it can be appropriately selected according to the purpose. The arrangement of the nozzle holes is not particularly limited and can be appropriately selected according to the purpose. For example, there is a mode in which a plurality of the nozzle holes are arranged at equal intervals along the length direction of the nozzle substrate. The arrangement of the nozzle holes can be appropriately selected according to the type of ink to be ejected. One to a plurality of rows are preferable, and one to four rows are more preferable. The number of the nozzle holes per row is not particularly limited and is appropriately selected according to the purpose, but is preferably 10 or more and 10,000 or less, and more preferably 50 or more and 500 or less. The interval (pitch) P, which is the shortest distance between the centers of adjacent nozzle holes, is not particularly limited and can be appropriately selected according to the purpose. For example, it is preferably 21 μm or more and 169 μm or less. The opening shape of the nozzle holes is not particularly limited and can be appropriately selected according to the purpose. For example, a circular shape, an elliptical shape, a rectangular shape, etc. can be mentioned. Among these, the opening shape of the nozzle holes is preferably circular from the viewpoint of ejecting ink droplets.

[0070] Here, FIG. 9 is a plan view showing the nozzle configuration of the recording head 20. FIG. 9 shows the nozzle rows of the recording head 20 transparently from above. As shown in FIG. 9, the recording head 20 includes a first nozzle group 20a, a second nozzle group 20b, and a third nozzle group 20c.

[0071] As shown in FIG. 9, each of the nozzle groups 20a, 20b, 20c is arranged in two rows in the main scanning direction and alternately in a staggered manner in the sub-scanning direction. That is, each of the nozzle groups 20a, 20b, 20c is arranged in the order of the third nozzle group 20c, the second nozzle group 20b, and the first nozzle group 20a so that the nozzle rows do not overlap from the upstream side to the downstream side in the conveyance direction A of the recording medium 40. Further, as shown in FIG. 9, the second nozzle group 20b is arranged with its position shifted in the main scanning direction from the first nozzle group 20a and the third nozzle group 20c.

[0072] The first nozzle group 20a and the third nozzle group 20c each include a single row of nozzle holes for discharging ink droplets of auxiliary ink (background ink, undercoat ink) and three rows of nozzle holes for discharging ink droplets of CMY (process color) ink for image formation. Each nozzle row has 192 nozzle holes from the nozzle hole with nozzle number No. 1 to the nozzle hole with nozzle number No. 192. In the example shown in FIG. 9, each nozzle hole is numbered from No. 1 to No. 192 in the order from the nozzle hole on the downstream side in the conveyance direction A of the recording medium 40 to the nozzle hole on the upstream side. The pitch P between these nozzle holes is 150 dpi (dots per inch).

[0073] As shown in FIG. 9, the first nozzle group 20a and the third nozzle group 20c each have a cyan ink nozzle row NC for discharging cyan (C) ink droplets, a magenta ink nozzle row NM for discharging magenta (M) ink droplets, a yellow ink nozzle row NY for discharging yellow (Y) ink droplets, and a black ink nozzle row NK for discharging black (K) ink droplets. The second nozzle group 20b has a gray ink nozzle row G for discharging gray (G) ink droplets, a light cyan ink nozzle row LC for discharging light cyan (LC) ink droplets, a light magenta ink nozzle row LM for discharging light magenta (LM) ink droplets, and a light yellow ink nozzle row LY for discharging light yellow (LY) ink droplets.

[0074] Similar to the first nozzle group 20a, the second nozzle group 20b also has four rows of nozzle holes, each row having 192 nozzle holes numbered from No. 1 to No. 192. Similar to the first nozzle group 20a, the pitch P between the nozzle holes in the second nozzle group 20b is 150 dpi.

[0075] As described above, since the number of nozzle rows and the number of nozzles in each nozzle group 20a, 20b, 20c are the same, each nozzle group 20a, 20b, 20c can be configured with the same components, reducing the number of component types and thus enabling cost reduction of the device. As shown in FIG. 9, standard ink and light ink may be ejected using each nozzle group 20a, 20b, 20c.

[0076] - Ink repellent film - The ink repellent film preferably contains a fluorine-containing acrylate polymer or a polymer having a fluorine-containing heterocyclic structure in the main chain. When the ink repellent film contains the fluorine-containing acrylate polymer or the polymer having a fluorine-containing heterocyclic structure in the main chain, the surface free energy becomes very small, and even the ink with low surface tension used in the present invention can maintain a state of being difficult to wet. However, when other materials other than the fluorine-containing acrylate polymer or the polymer having a fluorine-containing heterocyclic structure in the main chain are used for the ink repellent film, the surface free energy becomes very large, and the ink with low surface tension used in the present invention may get wet.

[0077] -- Fluorine-containing acrylate polymer -- The fluorine-containing acrylate polymer preferably contains at least one of a compound represented by the following general formula (I) and a compound represented by the following general formula (II) as a monomer unit.

[0078]

Chemical formula

[0079]

Chemical formula

[0080] In addition, a polymer obtained by polymerizing at least one of the compounds represented by the general formulas (I) and (II) is a polymer having at least one of a structural unit represented by the following general formula (III) and a structural unit represented by the following general formula (IV).

[0081]

Chemical formula

Chemical formula

[0082] R1 preferably has 1 to 18 carbon atoms, more preferably 1 to 4 carbon atoms, and examples thereof include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, and the like. R2 is an alkylene group having 2 to 6 carbon atoms, and examples thereof include an ethylene group, a propylene group, a butylene group, and the like. Among these, R2 is preferably an ethylene group. R3 is an alkylene group having 2 to 6 carbon atoms, and examples thereof include an ethylene group, a propylene group, a butylene group, and the like. Among these, R3 is preferably an ethylene group. Y is an acid group, and examples thereof include a sulfonic acid group, a succinic acid group, an acetic acid group, a phthalic acid group, a hydrogenated phthalic acid group, a maleic acid group, and the like.

[0083] Rf is a linear or branched fluoroalkyl group having 1 to 21 carbon atoms, preferably a perfluoroalkyl group, and more preferably 1 to 10 carbon atoms for Rf. Examples of Rf include -CF3, -CF2CF3, -CF2CF2CF3, -CF(CF3)2, -CF2CF2CF2CF3, -CF2CF(CF3)2, -C(CF3)3, -(CF2)4CF3, -(CF2)2CF(CF3)2, -CF2C(CF3)3, -CF(CF3)CF2CF2CF3, -(CF2)5CF3, -(CF2)3CF(CF3)2, -(CF2)4CF(CF3)2, -(CF2)7CF3, -(CF2)5CF(CF3)2, -(CF2)6CF(CF3)2, -(CF2)9CF3, and the like.

[0084] m is preferably 1 to 10, more preferably 1 to 3. n is preferably 2 to 90, more preferably 3 to 50, and still more preferably 4 to 30. p is preferably 1 to 90, more preferably 1 to 30. q is preferably 1 to 10, more preferably 1 to 3.

[0085] As the fluorine-containing acrylate polymer, one synthesized as appropriate may be used, or a commercially available product may be used. The fluorine-containing acrylate polymer represented by the general formula (II) (where Rf is C6F 13 can be synthesized, for example, according to the following reaction formula.

[0086]

Chemical formula

[0087] The fluorine-containing acrylate polymer represented by the general formula (II) (where Rf is C6F 13 can be synthesized, for example, according to the following reaction formula.

[0088]

Chemical formula

[0089] From the viewpoint of ink repellency (contact angle), the fluorine content in the fluorine-containing acrylate polymer is preferably 10% by mass or more, more preferably 25% by mass or more, and still more preferably 50% by mass or more. Examples of the commercially available products include krytoxFSL (manufactured by DuPont), krytoxFSH (manufactured by DuPont), FomblinZ (manufactured by Solvay Solexis), FLUOROLINKS10 (manufactured by Solvay Solexis), Optool DSX (manufactured by Daikin Industries, Ltd.), FLUOROLINKC10 (manufactured by Solvay Solexis), Moresco Phosphallol A20H (manufactured by Matsumura Petrochemical Research Institute, Inc.), Moresco Phosphallol ADOH (manufactured by Matsumura Petrochemical Research Institute, Inc.), Moresco Phosphallol DDOH (manufactured by Matsumura Petrochemical Research Institute, Inc.), Fluorosurf FG5010 (manufactured by Fluorotechnology Co., Ltd.), Fluorosurf FG5020 (manufactured by Fluorotechnology Co., Ltd.), Fluorosurf FG5060 (manufactured by Fluorotechnology Co., Ltd.), Fluorosurf FG5070 (manufactured by Fluorotechnology Co., Ltd.), and the like.

[0090] The ink-repellent film is composed of a compound film containing a fluorine-containing acrylate polymer skeleton in the molecule. An inorganic oxide layer can also be provided between the nozzle substrate and the ink-repellent film to improve the adhesion by increasing the presence of hydroxyl groups that serve as bonding points with the compound containing a fluorine-containing acrylate polymer skeleton in the molecule. Examples of the material of the inorganic oxide layer include SiO2, TiO2, and the like. The average thickness of the inorganic oxide layer is preferably 0.001 μm or more and 0.2 μm or less, more preferably 0.01 μm or more and 0.1 μm or less.

[0091] Examples of the compound containing a fluorine-containing acrylate polymer skeleton in the molecule include low molecular substances, resins, and the like. Examples of the compound containing a fluorine-containing acrylate polymer skeleton in the molecule include those disclosed in Japanese Patent Publication No. 3-43065, Japanese Unexamined Patent Application Publication No. 6-210857, Japanese Unexamined Patent Application Publication No. 10-32984, Japanese Unexamined Patent Application Publication No. 2000-94567, Japanese Unexamined Patent Application Publication No. 2002-145645, Japanese Unexamined Patent Application Publication No. 2003-341070, Japanese Unexamined Patent Application Publication No. 2007-106024, Japanese Unexamined Patent Application Publication No. 2007-125849, and the like. Among these, as the compound containing the fluorine-containing acrylate ester polymer skeleton in the molecule, modified perfluoropolyoxetane (manufactured by Daikin Industries, Ltd., Optool DSX) is preferable. The average thickness of the ink repellent film is preferably 0.001 μm or more and 0.2 μm or less, more preferably 0.01 μm or more and 0.1 μm or less.

[0092] Examples of the method for forming the ink repellent film using the compound containing the fluorine-containing acrylate ester polymer skeleton in the molecule include methods such as spin coating, roll coating, dipping, etc. using a fluorine-based solvent, printing, and vacuum deposition. Examples of the fluorine-based solvent include Novec (manufactured by 3M), Bartrel (manufactured by DuPont), Galden (manufactured by Solvay Solexis), etc.

[0093] -- Polymer having a fluorine-containing heterocyclic structure in the main chain -- As the polymer having a fluorine-containing heterocyclic structure in the main chain, it is particularly preferable to use an amorphous polymer among the fluorine-containing polymers having a heterocyclic structure. Since the amorphous polymer is excellent in film strength, adhesion to the substrate, film uniformity, etc., the effects of the present invention can be further exerted. Examples of the polymer having a fluorine-containing heterocyclic structure in the main chain include polymers described in, for example, U.S. Patent No. 3,418,302, U.S. Patent No. 3,978,030, JP-A-63-238111, JP-A-63-238115, JP-A-1-131214, JP-A-1-131215, etc. Among these, as the polymer having a fluorine-containing heterocyclic structure in the main chain, polymers having the following heterocyclic structures are representative. However, the polymer having a fluorine-containing heterocyclic structure in the main chain is not limited to these.

[0094]

Chemical formula

[0095]

Chem.

[0096]

Chem.

[0097]

Chem.

[0098]

Chem.

[0099]

Chem.

[0100]

Chem.

[0101]

Chem.

[0102] Furthermore, in order to improve the adhesion to the substrate, control the glass transition temperature (Tg), and solubility in solvents, a structure represented by the following general formula (iii) may be introduced into the main chain. The structure represented by the general formula (iii) is obtained by copolymerizing with a comonomer represented by the following structural formulas (vii) to (ix).

[0103]

Chem.

[0104]

Chemical formula

[0105]

Chemical formula

[0106]

Chemical formula

[0107] Examples of those having a specific chemical structure as described above and being suitable as an ink repellent treatment agent include product name: Cytop CTX-105 (manufactured by Asahi Glass Co., Ltd.), product name: Cytop CTX-805 (manufactured by Asahi Glass Co., Ltd.), product name: Teflon (registered trademark) AF1600, product name: AF2400 (manufactured by DuPont), etc.

[0108] Examples of the method for forming an ink repellent film using the polymer having a fluorine-containing heterocyclic structure in the main chain include methods such as spin coating, roll coating, dipping, etc. using a fluorine-based solvent, printing, or vacuum evaporation. The fluorinated solvent is not particularly limited as long as it can dissolve the polymer having a fluorine-containing heterocyclic structure in the main chain, and can be appropriately selected according to the purpose. For example, perfluorobenzene, "trade name: Aflurode" (a fluorinated solvent manufactured by Asahi Glass Co., Ltd.), "Fluorinate FC-75" (a liquid containing perfluoro(2-butyltetrahydrofuran) manufactured by 3M) and other fluorinated solvents are preferred. These may be used alone or in combination of two or more. Among these, in the case of a mixed solvent, a hydrocarbon-based, chlorinated hydrocarbon, fluorochlorinated hydrocarbon, alcohol, or other organic solvent can also be used in combination. The solution concentration is preferably 0.01% by mass or more and 50% by mass or less, more preferably 0.01% by mass or more and 20% by mass or less. If the average thickness of the ink repellent film is 0.01 μm or more, the above object can be sufficiently achieved, but it is preferably 0.01 μm or more and 2 μm or less.

[0109] The heat treatment conditions (temperature) of the polymer having a fluorine-containing heterocyclic structure in the main chain are determined by the boiling point of the solvent, the glass transition temperature of the polymer, and the heat resistance temperature of the substrate. That is, a temperature higher than the boiling point of the solvent and the glass transition temperature of the polymer and lower than the heat resistance temperature of the substrate may be selected. The glass transition temperature of the polymer having a fluorine-containing heterocyclic structure in the main chain varies depending on its structure. For example, those having the structures of the structural formula (iv) to the structural formula (vi) often have a temperature of 50 ° C or more and 110 ° C or less. Therefore, the heat treatment conditions are preferably a temperature of 120 ° C or more and 170 ° C or less, and a time of 30 minutes to 2 hours.

[0110] In addition, a copolymer having the structure of the general formula (ii) and the structure of the following structural formula (x) in the main chain is sold by DuPont under the trade name "Teflon (registered trademark) AF".

[0111]

Chemical formula

[0112] The above-mentioned Teflon (registered trademark) AF can have various glass transition temperatures by changing its copolymerization ratio. That is, as the ratio of the PDD [perfluoro(2,2-dimethyl-1,3-dioxole)] component increases, the glass transition temperature rises. There are those with a glass transition temperature in the range of 80°C or higher and 330°C or lower depending on the ratio of the PDD component. Commercially available products have a glass transition temperature of 160°C (AF1600) and a glass transition temperature of 240°C (AF2400). For example, considering the heat resistance temperature of the substrate, the heat treatment temperature of the one with a glass transition temperature of 160°C is preferably 165°C or higher and 180°C or lower.

[0113] -Other members- There are no particular restrictions on the above-mentioned other members, and they can be appropriately selected according to the purpose. For example, a pressurizing chamber, a stimulation generating means, etc. can be mentioned.

[0114] --Pressurizing chamber-- The above-mentioned pressurizing chamber is arranged corresponding to each of the plurality of nozzle holes provided in the nozzle plate. The pressurizing chamber is a plurality of individual flow paths communicating with the nozzle holes, and may also be referred to as an ink flow path, a pressurized liquid chamber, a pressure chamber, a discharge chamber, a liquid chamber, etc.

[0115] --Means for discharging ink-- The discharge head has a means for generating a stimulation to be applied to the ink. There are no particular restrictions on the stimulation in the above-mentioned stimulation generating means, and it can be appropriately selected according to the purpose. For example, heat (temperature), pressure, vibration, light, etc. can be mentioned. These may be used alone or in combination of two or more. Among these, the stimulation in the above-mentioned stimulation generating means preferably includes heat and pressure. Examples of the above-mentioned stimulation generating means include a heating device, a pressurizing device, a piezoelectric element, a vibration generating device, an ultrasonic oscillator, a light, etc. As the stimulation generating means, specifically, piezoelectric actuators such as piezoelectric elements, thermal actuators that utilize the phase change due to film boiling of ink using electrothermal conversion elements such as heating resistors, shape memory alloy actuators that utilize metal phase change due to temperature change, electrostatic actuators that utilize electrostatic force, and the like can be mentioned.

[0116] When the stimulation is "heat", thermal energy corresponding to the recording signal is applied to the ink in the ink ejection head, for example, using a thermal head or the like. Examples of methods include generating bubbles in the ink by the thermal energy, and ejecting the ink as droplets from the nozzle holes of the nozzle plate by the pressure of the bubbles. When the stimulation is "pressure", for example, a voltage is applied to the piezoelectric element adhered to a position called the pressure chamber in the ink flow path in the ink ejection head, causing the piezoelectric element to flex. Examples of methods include the volume of the pressure chamber contracting due to the piezoelectric element flexing, and ejecting the ink as droplets from the nozzle holes of the ink ejection head. Among these, when the stimulation is "pressure", the piezo method of applying a voltage to the piezo element to fly the ink is preferable.

[0117] Here, an example of the ejection head used in the present invention will be described with reference to FIGS. 3 to 8. Note that FIG. 3 is an exploded perspective explanatory view of the ejection head, FIG. 4 is a cross-sectional explanatory view along the direction orthogonal to the nozzle arrangement direction of the ejection head (longitudinal direction of the liquid chamber), and FIG. 5 is a cross-sectional explanatory view along the nozzle arrangement direction of the ejection head (lateral direction of the liquid chamber).

[0118] The ejection head includes a flow path plate (liquid chamber substrate, flow path member) 1, a diaphragm 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. An inkjet printing apparatus having an ejection head in which the receding contact angle of each ink in the ink set with respect to the surface of the nozzle plate 3 facing the object to be printed is 35° or more can be used. The ejection head has a plurality of liquid chambers 6 as individual flow paths in which a plurality of nozzle holes 4 for ejecting droplets (ink droplets) communicate with each other via nozzle communication passages 5, a fluid resistance portion 7 that also serves as a supply path for supplying ink to the liquid chambers 6, and a communication portion 8 that communicates with the liquid chambers 6 via the fluid resistance portion 7. Ink is supplied from a common liquid chamber 10 formed in a frame member 17 through a supply port 19 formed with a diaphragm member 2 in the communication portion 8. Note that the plurality of liquid chambers may also be referred to as pressurized liquid chambers, pressure chambers, flow paths, etc.

[0119] The flow path plate 1 is formed by etching a silicone substrate to form openings such as the communication passages 5, the liquid chambers 6, and the fluid resistance portion 7. Note that the flow path plate 1 can also be formed, for example, by etching a SUS substrate using an acidic etching solution or by machining such as punching (pressing).

[0120] The diaphragm member 2 has respective vibration regions (diaphragm portions) 2a that form the wall surfaces corresponding to the respective liquid chambers 6. The diaphragm member 2 has island-shaped convex portions 2b on the outer side in the out-of-plane direction (the side opposite to the liquid chambers 6) of the vibration regions 2a. Laminated piezoelectric elements 12, which are drive elements (actuator means, pressure generating means) for deforming the vibration regions 2a in the island-shaped convex portions 2b to generate energy for ejecting droplets, are joined to the upper end surfaces (bonding surfaces) of the respective piezoelectric element columns 12A, 12B of the piezoelectric elements 12, 12. Also, the lower end surface of the laminated piezoelectric element 12 is joined to a base member 13.

[0121] Here, the piezoelectric element 12 is formed by alternately laminating piezoelectric material layers 21 such as PZT and internal electrodes 22a, 22b. The piezoelectric element 12 draws out the internal electrodes 22a, 22b to the end surfaces, that is, the side surfaces substantially perpendicular to the diaphragm member 2 of the piezoelectric element 12. The piezoelectric element 12 is connected to end surface electrodes (external electrodes) 23a, 23b formed on the side surface substantially perpendicular to the diaphragm member 2 of the piezoelectric element 12, and a displacement in the lamination direction is generated by applying a voltage to the end surface electrodes (external electrodes) 23a, 23b. This piezoelectric element 12 is formed by performing groove processing by half-cut dicing to form a required number of piezoelectric element columns 12A and 12B on one piezoelectric element member.

[0122] Note that the piezoelectric element columns 12A and 12B of the piezoelectric element 12 are the same, but the piezoelectric element column to which a driving waveform is applied and driven is defined as the driving piezoelectric element column 12A, and the piezoelectric element column that is used as a mere support without applying a driving waveform is defined as the support piezoelectric element column 12B. In this case, either a bi-pitch configuration in which the driving piezoelectric element column 12A and the support piezoelectric element column 12B are used alternately or a normal pitch configuration in which all the piezoelectric element columns are used as the driving piezoelectric element column 12A can be adopted.

[0123] As a result, the piezoelectric element columns 12A and 12B of the piezoelectric element 12 have a configuration in which two rows of drive element columns (rows of drive piezoelectric element columns 12A) in which a plurality of drive piezoelectric element columns 12A as drive elements are arranged side by side are provided on the base member 13.

[0124] Also, the piezoelectric direction of the laminated piezoelectric element 12 is configured to pressurize the ink in the liquid chamber 6 using the displacement in the lamination direction of the piezoelectric material layer. The piezoelectric direction of the laminated piezoelectric element 12 can also be configured to pressurize the ink in the pressurizing liquid chamber 6 using the displacement in the plane direction of the piezoelectric material layer: that is, the direction orthogonal to the electric field.

[0125] Also, there is no particular limitation on the piezoelectric element material, and electro-mechanical conversion elements 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 piezoelectric element is used for the piezoelectric element, a single-plate piezoelectric element may be used. The single-plate piezoelectric element may be a cut one, a thick film formed by screen printing and sintering, a thin film formed by sputtering, vapor deposition, or the sol-gel method. Also, the laminated piezoelectric element 12 provided on one base member 13 may be in one row or may have a structure in which a plurality of rows are provided.

[0126] Then, the external electrode 23a of each piezoelectric element column 12A of the piezoelectric element 12 directly connects the FPC 15 as a wiring means with a solder member to apply a drive signal. The FPC 15 has a drive circuit (driver IC) 16 mounted thereon for selectively applying a drive waveform to each piezoelectric element column 12A of the piezoelectric element 12. Note that the external electrodes 23b of all the piezoelectric element columns 12A for driving are electrically commonly connected and are also connected to the common wiring of the FPC 15 with a solder member. Also, here, the output terminal portion of the FPC 15 joined to the piezoelectric element 12 is solder plated to enable soldering, but the piezoelectric element 12 side rather than the FPC 15 may be solder plated. Also, regarding the joining method, in addition to soldering, joining with an anisotropic conductive film or wire bonding can also be used.

[0127] The nozzle plate 3 is configured by forming a repellent ink film 32 on the droplet ejection side surface (the surface in the ejection direction: ejection surface, or the surface opposite to the liquid chamber 6 side, nozzle formation surface) of a nozzle substrate 31 in which hole portions forming nozzle holes 4 having a diameter of 10 μm or more and 35 μm or less are formed corresponding to the respective liquid chambers 6.

[0128] Also, on the outer peripheral side of the piezoelectric actuator unit 100 composed of the piezoelectric element 12 with the FPC 15 mounted (connected) and the base member 13, a frame member 17 formed by injection molding with an epoxy resin or polyphenylene sulfite is joined. Then, this frame member 17 forms the common liquid chamber 10 described above, and further forms a supply port 19 for supplying ink from the outside to the common liquid chamber 10. This supply port 19 is further connected to an ink supply source such as a sub-tank or an ink storage container (not shown).

[0129] In an ejection head configured in this manner, for example, the voltage applied to the driving piezoelectric element columns 12A is lowered from the reference potential, causing the driving piezoelectric element columns 12A to contract. The vibration region 2a of the vibration plate member 2 descends and the volume of the liquid chamber 6 expands, causing ink to flow into the liquid chamber 6. Thereafter, the voltage applied to the piezoelectric element columns 12A is increased to cause the piezoelectric element columns 12A to expand in the stacking direction. The vibration plate member 2 is deformed toward the nozzle hole 4 to contract the volume or capacity of the liquid chamber 6, whereby the ink in the liquid chamber 6 is pressurized and droplets of ink are ejected (jetted) from the nozzle hole 4.

[0130] Then, by returning the voltage applied to the piezoelectric columns 12A to the reference potential, the diaphragm member 2 is restored to its initial position, and the liquid chamber 6 expands, generating negative pressure. At this time, ink is filled into the liquid chamber 6 from the common liquid chamber 10. Therefore, after the vibration of the meniscus surface of the nozzle hole 4 has attenuated and stabilized, the operation shifts to the next droplet ejection.

[0131] The method of driving the ejection head is not limited to the above example (pull-push shot), and pull shot or push shot can be performed depending on the driving waveform applied.

[0132] Next, details of the nozzle plate 3 in the inkjet printing apparatus of the present invention will be described with reference to Figures 6 to 8. Figure 6 is an explanatory plan view of the nozzle plate 3, Figure 7 is an explanatory cross-sectional view of the nozzle plate 3, and Figure 8 is an enlarged cross-sectional view of one nozzle portion in the nozzle plate. The nozzle plate 3 is formed, for example, on the ejection surface 31a of a nozzle substrate 31 made of a Ni metal plate, by depositing a Ti layer 33 as an underlayer, a SiO2 film 34, and a perfluoropolyether film having alkoxysilane in its molecules (this film is called a "water-repellent film") 32 in this order on the surface of the nozzle substrate 31. The receding contact angle of each ink of the ink set with respect to the surface of the nozzle plate 3 other than the nozzle holes and facing the substrate is 35° or more. Then, in the vicinity of the outlet of the inner wall surface 4a of the nozzle hole 4, an underlayer (Ti layer) 33 is continuously formed on the SiO2 film 35 formed on the liquid chamber surface 31b of the nozzle substrate 31, and the underlayer (Ti layer) 33 is exposed on the outermost surface.

[0133] As the nozzle substrate 31, a Ni metal plate or the like can be used, but it is not limited thereto.

[0134] Here, the water-repellent film 32 of the nozzle plate 3 is formed by vapor deposition, and no vapor deposition film for forming the water-repellent film 32 is formed in the vicinity of the outlet of the inner wall surface of the nozzle hole 4. Thereby, the nozzle plate 3 can perform stable droplet ejection without impairing ejection failure and liquid filling properties.

Example

[0135] Hereinafter, examples of the present invention will be described, but the present invention is not limited to these examples. Unless otherwise specified, the preparation, production, evaluation, etc. in the examples were carried out under the conditions of room temperature 25°C and humidity 60%RH.

[0136] (Preparation Example 1 of Pigment Dispersion Liquid) <Preparation of Black Pigment Dispersion Liquid 1> -Synthesis of Polymer A- 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 g of polyethylene glycol methacrylate, 60 g of hydroxyethyl methacrylate, 36 g of styrene macromer, 3.6 g of mercaptoethanol, 2.4 g of azobis(methylvaleronitrile), and 18 g of methyl ethyl ketone was dropped into the flask over 2.5 hours. After dropping, a mixed solution of 0.8 g of azobis(methylvaleronitrile) and 18 g of methyl ethyl ketone was dropped into the flask over 0.5 hours. After aging at 65°C for 1 hour, 0.8 g of azobis(methylvaleronitrile) was added and aging was continued for another 1 hour. After completion of the reaction, 364 g of methyl ethyl ketone was added to the flask to obtain 800 g of polymer solution A with a solid content concentration of 50% by mass.

[0137] - Preparation of Black Pigment Dispersion 1 - Next, 28 g of the polymer solution A, 42 g of carbon black (manufactured by Cabot Corporation, Black Pearls 1000), 13.6 g of 1 mol / L potassium hydroxide aqueous solution, 20 g of methyl ethyl ketone, and 13.6 g of water were sufficiently stirred and then kneaded with a roll mill. The obtained paste was put into 200 g of pure water and sufficiently stirred, then methyl ethyl ketone was removed with an evaporator, and after pressure filtration with a polyvinylidene fluoride membrane filter having an average pore size of 5 μm, the water content was adjusted so that the solid content concentration became 20% by mass, and styrene - acrylic resin - coated black pigment dispersion 1 with a solid content concentration of 20% by mass and a pigment concentration of 15% by mass was obtained.

[0138] (Preparation Example 2 of Pigment Dispersion) (Preparation of Cyan Pigment Dispersion 1) In Preparation Example 1 of the pigment dispersion, except that pigment blue 15:4 (manufactured by SENSIENT, SMART Cyan 3154BA) was used instead of carbon black, in the same manner as Preparation Example 1 of the pigment dispersion, styrene - acrylic resin - coated cyan pigment dispersion 1 with a solid content concentration of 20% by mass and a pigment concentration of 15% by mass was obtained.

[0139] (Preparation Example 3 of Pigment Dispersion) (Preparation of Magenta Pigment Dispersion 1) In Preparation Example 1 of the pigment dispersion, except that Pigment Red 122 (manufactured by Sun Chemical, Pigment Red 122) was used instead of carbon black, in the same manner as in Preparation Example 1 of the pigment dispersion, a styrene-acrylic resin-coated magenta pigment dispersion 1 with a solid content concentration of 20% by mass and a pigment concentration of 15% by mass was obtained.

[0140] (Preparation Example 4 of the pigment dispersion) (Preparation of Yellow Pigment Dispersion 1) In Preparation Example 1 of the pigment dispersion, except that Pigment Yellow 74 (manufactured by SENSIENT, SMART Yellow 3074BA) was used instead of carbon black, in the same manner as in Preparation Example 1 of the pigment dispersion, a styrene-acrylic resin-coated yellow pigment dispersion 1 with a solid content concentration of 20% by mass and a pigment concentration of 15% by mass was obtained.

[0141] (Preparation Example 1 of the polyurethane resin emulsion) (Preparation of Polyester-based Urethane Resin Emulsion 1) In a nitrogen-substituted container equipped with a thermometer, a nitrogen gas inlet tube, and a stirrer, 200.4 g of polyester polyol (trade name: Polyolite OD-X-2251, manufactured by DIC Corporation, average molecular weight 2,000), 15.7 g of 2,2-dimethylolpropionic acid, 48.0 g of isophorone diisocyanate, and 77.1 g of methyl ethyl ketone as an organic solvent were reacted using 0.06 g of DMTDL (dibutyltin dilaurate) as a catalyst. After continuing the reaction for 4 hours, 30.7 g of methyl ethyl ketone was supplied as a diluting solvent, and the reaction was further continued. When the average molecular weight of the reaction product reached the range of 20,000 to 60,000, 1.4 g of methanol was added to terminate the reaction, thereby obtaining an organic solvent solution of the urethane resin. Next, 13.4 g of a 48% by mass aqueous potassium hydroxide solution was added to the organic solvent solution of the urethane resin to neutralize the carboxyl groups possessed by the urethane resin. Then, 715.3 g of water was added and stirred well, and after aging and desolventizing, a polyester-based urethane resin emulsion 1 with a solid content concentration of 30% by mass was obtained. Regarding the obtained polyester-based urethane resin emulsion 1, the minimum film-forming temperature (MFT) measured with a "film-forming temperature test device" (manufactured by Imoto Seisakusho Co., Ltd.) was 74°C.

[0142] (Production Example 1 of Ink) ><Production of Black Ink A> The following ink formulation was adjusted by adding ion-exchanged water to a total of 100 parts by mass. After mixing and stirring, it was filtered through a filter with an average pore size of 5 μm (Mini Sartorius, manufactured by Sartorius) to prepare Black Ink A. [Ink Formulation] ·The above black pigment dispersion 1: 18.0 parts by mass ·Polyester-based urethane resin emulsion 1 (solid content concentration 30% by mass): 20.0 parts by mass ·3-Methoxy-N,N-dimethylpropanamide represented by the above general formula (1): 10.0 parts by mass ·Propylene glycol: 20.0 parts by mass ·2-Ethyl-1,3-hexanediol: 1.0 part by mass ·2,2,4-Trimethyl-1,3-pentanediol: 2.0 parts by mass ·Silface SAG503A (manufactured by Nissin Chemical Industry Co., Ltd.): 1.0 part by mass ·Ion-exchanged water: the balance (total: 100 parts by mass)

[0143] (Production Examples 2 to 33 of Ink) ><Production of Black Ink B to C, Cyan Ink A to H, Magenta Ink A to H, Yellow Ink A to C, Light Cyan Ink A to E, and Light Magenta Ink A to F> In Production Example 1 of Ink, except that the ink formulations described in Tables 1 to 6 were changed, Black Ink B to C, Cyan Ink A to H, Magenta Ink A to H, Yellow Ink A to C, Light Cyan Ink A to E, and Light Magenta Ink A to F were prepared in the same manner as in Production Example 1 of Ink. Note that in Tables 1 to 6, Uni-Dyn DSN403N is a fluorine-based surfactant (manufactured by Daikin Industries, Ltd.).

[0144]

Table 1

[0145]

Table 2

[0146]

Table 3

[0147]

Table 4

[0148]

Table 5

[0149]

Table 6

[0150] (Manufacturing Example 1 of Nozzle Plate) <Fabrication of Nozzle Plate A> <<Synthesis of Fluorine-Containing Acrylate Polymer A>> -Synthesis of Fluorine Monomer Containing Ethylene Oxide Chain (MPOERfA)- The reaction formula of the synthesis reaction of the fluorine monomer containing an ethylene oxide chain is shown below.

[0151]

Chem.

[0152] A four-necked flask was charged with 52.13 g of monomethoxypolyethylene glycol (average EO number: 8 - 9, Uniox M - 400, manufactured by NOF Corporation) and 0.94 g of boron trifluoride diethyl ether complex. Under a nitrogen stream, 50 g of 3-perfluorohexyl-1,2-epoxypropane was added dropwise at room temperature over 30 to 40 minutes while paying attention to heat generation. After completion of the dropwise addition, the reaction was continued at room temperature for about 2 hours, and then it was confirmed by gas chromatography (GC) that the peak of 3-perfluorohexyl-1,2-epoxypropane had disappeared. 0.03 g of tertiary butyl catechol was added thereto and stirred. Furthermore, 14.81 g of triethylamine was added, and 12.04 g of acryloyl chloride was added dropwise over about 20 minutes while paying attention to heat generation. After completion of the dropwise addition, the reaction was continued at room temperature for about 2 hours, and then it was confirmed by GC that the peak of acryloyl chloride had almost disappeared. The identification of the product was carried out by IR spectrum, 1 1H-NMR spectrum, 19 and 19F-NMR spectrum.

[0153] - Synthesis of fluorine-containing acrylate ester polymer A - Into a 200 mL four-necked flask, 60 g of isopropyl alcohol was charged according to the monomer composition of 10% by mass of the synthesized MPOERfA monomer, 60% by mass of 2-(perfluorohexyl)ethyl acrylate, 20% by mass of polyethylene glycol monoacrylate (EO: 10 moles, manufactured by NOF Corporation, AE - 400), 5% by mass of 2-hydroxyethyl acrylate, 2.5% by mass of acetoxyethyl methacrylate, and 2.5% by mass of dimethylaminoethyl acrylate, and nitrogen was blown for 60 minutes to replace the air in the system with nitrogen. While continuing the nitrogen flow, after raising the internal temperature to 75°C - 80°C, 0.25 g of azobisisobutyronitrile was added, and a polymerization reaction was carried out for 8 hours. When the polymerization solution was analyzed by gas chromatography (GC) and gel permeation chromatography, it was confirmed that the peaks derived from the monomers had almost disappeared and the peaks derived from the polymer had occurred. The weight average molecular weight of the obtained polymer was 17,000 (in terms of polystyrene). Finally, 0.42 g of acetic acid was added for neutralization, and the mixture was diluted with water to obtain a 20% by mass solution of the fluorine-containing acrylate polymer A.

[0154] -Fabrication of nozzle plate- Next, a nozzle substrate made of stainless steel (SUS304) with a size of 34 mm in length × 16 mm in width and an average thickness of 20 μm was prepared. Note that on the nozzle substrate, nozzle holes with an average pore diameter of 25 μm are arranged in 4 rows with a pitch of 85 μm (300 dpi), which is the shortest distance between the centers of the nozzle holes, and there are 320 nozzle holes per row. A 20% by mass solution of the prepared fluorine-containing acrylate polymer A was applied to the ink ejection side surface of the nozzle substrate by the dipping method and dried to form an ink repellent film with an average thickness of 50 nm. Thus, nozzle plate A was fabricated. At this time, the nozzle holes were masked with a water-soluble resin, and the back surface of the nozzle substrate was masked with tape. After forming the ink repellent film, they were peeled off and removed. Also, the ink repellent film was formed by heating at 120 °C for 1 hour.

[0155] (Production Example 2 of nozzle plate) (Fabrication of nozzle plate B) (Synthesis of fluorine-containing acrylate polymer B) (Synthesis of Rf epoxy adduct (FAGMA) of 2-hydroxyethyl acrylate (HEA)) The reaction formula for the synthesis reaction of the Rf epoxy adduct of 2-hydroxyethyl acrylate is shown below. [Chemical formula] However, in the above reaction formula, n is 1 to 3.

[0156] 20 g of 2-hydroxyethyl acrylate (HEA), 0.61 g of boron trifluoride diethyl ether complex, and 0.026 g of tertiary butyl catechol were charged into a four-necked flask. 64.83 g of 3-perfluorohexyl-1,2-epoxypropane was added dropwise at room temperature over 30 to 40 minutes while paying attention to exotherm. After completion of the dropwise addition, the reaction was continued at room temperature for about 2 hours, and then it was confirmed by gas chromatography (GC) that the peak of 3-perfluorohexyl-1,2-epoxypropane had disappeared. After completion of the reaction, the reaction product was dissolved in 100 g of 1,1-dichloro-1,2,2,3,3-pentafluoropropane (HCFC225), and 100 g of water was further added. After washing with a separatory funnel and liquid separation, the organic layer was taken out. This washing and liquid separation operation was repeated once again. After taking out the organic layer, 5 g of anhydrous magnesium sulfate was added and dried overnight. HCFC225 was evaporated to obtain the Rf epoxy adduct (FAGMA) of HEA. The identification of the product was carried out by IR spectrum, 1 1H-NMR, 19 19F-NMR spectra. From the analysis results of the product, a mixed monomer of about 64 mass% of the 1-molar adduct (n = 1) of 3-perfluorohexyl-1,2-epoxypropane, about 27 mass% of the 2-molar adduct (n = 2), and about 9 mass% of the 3-molar adduct was obtained.

[0157] -Synthesis of sulfonic acid-containing fluoromonomer- The reaction formula for the synthesis reaction of the sulfonic acid-containing fluoromonomer is shown below.

Chemical formula

[0158] 30 g of the synthesized Rf epoxy adduct (FAGMA) of HEA, 30 g of dichloromethane, 7.8 g of triethylamine, and 0.024 g of hydroquinone monomethyl ether were charged into a four-necked flask. The mixed solution was cooled in an ice bath to 0 °C to 10 °C. A dichloromethane solution of chlorosulfonic acid (7.48 g of chlorosulfonic acid + 15 g of dichloromethane) was gradually added dropwise thereto over about 30 minutes while paying attention to exotherm. After completion of the dropwise addition, the reaction was carried out at room temperature for 3 hours. 100 g of water was added to the reaction product, and the washing and liquid separation operations were repeated twice. The organic layer was taken out, 5 g of anhydrous magnesium sulfate was added, and it was dried overnight. The identification of the product (sulfonic acid-containing fluoromonomer) was carried out by IR spectrum, 1 1H-NMR, 19 and 19F-NMR spectra.

[0159] - Synthesis of fluorine-containing acrylate ester polymer B - In Production Example 1 of the nozzle plate, except that the monomer composition was changed to 60% by mass of 2-(perfluorohexyl)ethyl acrylate, 20% by mass of the sulfonic acid-containing fluoromonomer, 17.5% by mass of polyethylene glycol monoacrylate (EO: 10 moles, manufactured by NOF Corporation, AE-400), and 2.5% by mass of acetoacetoxyethyl methacrylate, a fluorine-containing acrylate ester polymer B was synthesized in the same manner as in Production Example 1 of the nozzle plate. The weight average molecular weight of the obtained polymer was 17,000 (polystyrene conversion). Finally, 0.42 g of acetic acid was added for neutralization, and it was diluted with water to obtain a 20% by mass solution of the fluorine-containing acrylate ester polymer B.

[0160] - Production of nozzle plate - A 20% by mass solution of the prepared fluorine-containing acrylate ester polymer B was applied by a dipping method onto the ink ejection side surface of the same nozzle substrate as in Production Example 1 of the nozzle plate and dried to form an ink repellent film with an average thickness of 30 nm. Thus, a nozzle plate B was produced. At this time, the nozzle holes were masked with a water-soluble resin, and the back surface of the nozzle substrate was masked with tape. After the ink-repellent film was formed, it was peeled off and removed. Also, it was heated at 120 °C for 1 hour to form an ink-repellent film.

[0161] (Production Example 3 of Nozzle Plate) <Fabrication of Nozzle Plate C> A fluorine-containing acrylate polymer solution (Optool DSX, manufactured by Daikin Industries, Ltd.) was prepared. The fluorine-containing acrylate polymer solution (Optool DSX, manufactured by Daikin Industries, Ltd.) was applied by dipping on the ink ejection side surface of the same nozzle substrate as in Production Example 1 of the nozzle plate, and dried to form an ink-repellent film with an average thickness of 20 nm. Thus, nozzle plate C was fabricated. At this time, the nozzle holes were masked with a water-soluble resin, and the back surface of the nozzle substrate was masked with tape. After the ink-repellent film was formed, it was peeled off and removed. Also, it was heated at 120 °C for 1 hour to form an ink-repellent film.

[0162] (Production Example 4 of Nozzle Plate) <Fabrication of Nozzle Plate D> A silicone resin solution (SR 2441 RESIN, manufactured by Toray Dow Corning Co., Ltd.) was prepared. The silicone resin solution was applied by dipping on the ink ejection side surface of the same nozzle substrate as in Production Example 1 of the nozzle plate, and dried to form an ink-repellent film with an average thickness of 100 nm. Thus, nozzle plate D was fabricated. At this time, the nozzle holes were masked with a water-soluble resin, and the back surface of the nozzle substrate was masked with tape. After the ink-repellent film was formed, it was peeled off and removed. This was heated and cured at 150 °C for 2 hours in the atmosphere to form an ink-repellent film.

[0163] (Examples 1 to 8 and Comparative Examples 1 to 2) <Image Formation> To the head of an inkjet printer (GXe5500, manufactured by Ricoh Company, Ltd.), the fabricated nozzle plates A to D were attached as shown in Tables 7 and 8. The ink cartridges were filled with the respective inks of the ink sets of Examples 1 to 8 and Comparative Examples 1 and 2 shown in Tables 7 and 8. The ink cartridges filled with the respective inks were attached to the modified inkjet printer GXe5500, and inkjet printing was performed. After printing a solid image with a 100% tone and a halftone image with a 30% tone at a resolution of 600 × 600 dpi with a volume of 21 pL per drop of ink, the printed matter was dried in a hot air drying oven at 70°C for 3 minutes to perform fixing. As the recording medium, PVC (product name: GIY-11Z5, manufactured by Lintec Corporation) was used.

[0164] Next, various characteristics were evaluated as follows. The results are shown in Tables 7 and 8.

[0165] <Image density> The solid image of the standard inks (black, cyan, yellow, magenta) was colorimetrically measured with an X-Rite eXact (manufactured by X-Rite Inc.) and evaluated according to the following criteria. It is desirable in actual use that the evaluation be B or higher. 〔Evaluation criteria〕 - Black - A: 2.0 or more B: 1.8 or more and less than 2.0 C: 1.6 or more and less than 1.8 D: Less than 1.6 - Cyan - A: 1.6 or more B: 1.5 or more and less than 1.6 C: 1.4 or more and less than 1.5 D: Less than 1.4 - Magenta - A: 1.2 or more B: 1.1 or more and less than 1.2 C: 1.0 or more and less than 1.1 D: Less than 1.0 - Yellow - A: 1.0 or more B: 0.9 or more and less than 1.0 C: 0.8 or more and less than 0.9 D: Less than 0.8

[0166] <Dot density> The dot density of the halftone image of the light ink (light cyan, light magenta) was measured by Pias-II (manufactured by Trek Japan Co., Ltd.) and evaluated according to the following criteria. It is desirable in actual use that the evaluation is B or higher. The dot density evaluation results of the standard inks (cyan, magenta) are shown in Tables 7 and 8 as reference values. [Evaluation criteria] A: Less than 2.0 B: 2.0 or more and less than 4.0 C: 4.0 or more and less than 6.0 D: 6.0 or more

[0167] <Fixing property> For the solid image, the number of remaining squares out of 100 test squares was counted by a checkerboard peeling test using a cloth adhesion tape (manufactured by Nichiban Co., Ltd., 123LW-50), and the fixing property to the recording medium was evaluated based on the following evaluation criteria. It is desirable in actual use that the evaluation is B or higher. [Evaluation criteria] A: The number of remaining squares is 90 or more B: The number of remaining squares is 70 or more and less than 90 C: The number of remaining squares is less than 70

[0168] <Contact angle of receding> For the ink-repellent film on the surface of the nozzle plate prepared above, that is, the surface facing the object to be printed, at 25°C, 2.0 μL of each ink was extruded from a syringe equipped with a syringe needle having an inner diameter of 0.37 μm and a length of 0.18 mm, and the contact angle of receding (°) at 25°C was measured by an automatic contact angle measuring device _DMo-501 (manufactured by Kyowa Interface Science Co., Ltd.) by the shrinkage method.

[0169] <Continuous discharge evaluation> Immediately after passing 1 L each of individually adjusted inks from the ink cartridges of an inkjet printing apparatus (IPSiO GXe-5500, manufactured by Ricoh Company, Ltd.) to the ejection heads of each color, 200 consecutive sheets of a chart obtained by filling 80% of the area of A4-sized paper created by Microsoft Word 2000 with a solid image were printed on MyPaper (manufactured by Ricoh Company, Ltd.). Further, after printing, a nozzle check chart was printed, and the ejection irregularities of each nozzle were evaluated according to the following criteria. The printing mode used was the mode in which the "plain paper - standard fast" mode in the user settings of plain paper was modified to "without color correction" using the driver attached to the printer. 〔Evaluation Criteria〕 A: No ejection irregularity B: Slight ejection irregularity C: Ejection irregularity or non-ejecting part D: Severe ejection irregularity or many non-ejecting nozzles

[0170]

Table 7

[0171]

Table 8

[0172] As aspects of the present invention, for example, they are as follows. <1> In an ink set having standard ink and light ink, the standard ink contains at least cyan ink, magenta ink, and yellow ink, the light ink contains at least one of light cyan ink and light magenta ink, the content of cyan pigment in the cyan ink is 1.9% by mass or more and 3.6% by mass or less, the content of cyan pigment in the light cyan ink is 0.4% by mass or more and 1.4% by mass or less, The content of the magenta pigment in the magenta ink is 1.9% by mass or more and 3.6% by mass or less, and the content of the magenta pigment in the light magenta ink is 0.4% by mass or more and 1.4% by mass or less. The light ink contains water, an organic solvent, and a resin, and the organic solvent contains an amide compound represented by the following general formula (1). The ink set is characterized by this.

Chemical formula

Chemical formula

Chemical formula

Chemical formula

Chemical formula

[0173] According to the ink set according to any one of <1> to <2>, the inkjet printing apparatus according to any one of <3> to <7>, and the inkjet printing method according to <8>, various problems in the prior art can be solved, and the object of the present invention can be achieved.

Explanation of reference numerals

[0174] 1 Flow path plate, liquid chamber substrate, flow path member 2 Diaphragm member 2a Vibration region (diaphragm part) 2b Island-shaped convex part 3 Nozzle plate 4 Nozzle hole 5 Nozzle communication path 6 Liquid chamber, pressurized liquid chamber, pressure chamber, pressurized chamber, flow path 7 Fluid resistance part 8 Communication part 10 Common liquid chamber 12 Piezoelectric element, laminated piezoelectric element 12A Piezoelectric element column, driving piezoelectric element column 12B Piezoelectric element column, supporting piezoelectric element column 13 Base member 15 FPC 16 Driving circuit (driver IC) 17 Frame member 19 Supply port 21 Piezoelectric material layer 22a, 22b Internal electrodes 23a, 23b End face electrodes (external electrodes) 31 Nozzle substrate 31a Ejection surface 32 Water-repellent film 33 Ti layer (underlayer) 34 SiO2 film on the ejection surface side SiO2 film on the liquid chamber side 100 Piezoelectric actuator unit 400 Image forming apparatus 401 Exterior 401c Cover 404 Cartridge holder 410, 410k, 410c, 410m, 410y Main tank 411 Ink storage section 413 Ink discharge port 414 Storage container case 420 Mechanism section 434 Discharge head 436 Supply tube L Ink storage container

Prior art documents

Patent documents

[0175]

Patent Document 1

Claims

1. In an ink set having a standard ink and a light ink, the standard ink contains at least cyan ink, magenta ink, and yellow ink, the light ink contains at least one of light cyan ink and light magenta ink, the content of cyan pigment in the cyan ink is 1.9% by mass or more and 3.6% by mass or less, the content of cyan pigment in the light cyan ink is 0.6% by mass or more and 1.4% by mass or less, the content of magenta pigment in the magenta ink is 1.9% by mass or more and 3.6% by mass or less, the content of magenta pigment in the light magenta ink is 0.6% by mass or more and 1.4% by mass or less, the light ink contains water, an organic solvent, and a resin, and the organic solvent contains an amide compound represented by the following general formula (1), and the ink set is characterized in that. 【Chemical 1】 However, in the general formula (1), R １ , R ２ , and R ３ each independently represents a hydrocarbon group having 1 to 8 carbon atoms.

2. The ink set according to claim 1, wherein the light ink contains a surfactant.

3. An ink storage unit for storing each ink in the ink set according to any one of claims 1 to 2, and a discharge head for discharging each ink in the ink set, and an inkjet printing apparatus characterized in that a receding contact angle of each ink with respect to a nozzle plate of the discharge head is 35° or more.

4. The inkjet printing apparatus according to claim 3, wherein the nozzle plate has a non-ink-attracting film, and the non-ink-attracting film contains a fluorine-containing acrylate polymer.

5. The inkjet printing apparatus according to claim 4, wherein the fluorine-containing acrylate polymer contains a polymer obtained by polymerizing at least one of a compound represented by the following general formula (I) and a compound represented by the following general formula (II). [Chemical 2] [Chemical Formula 3] However, in the general formulas (I) and (II), X is a hydrogen atom, a linear or branched alkyl group having 1 to 21 carbon atoms, a halogen atom, CFX １ X ２ group (wherein X １ and X ２ are each independently either a hydrogen atom or a halogen atom), a cyano group, a linear or branched fluoroalkyl group having 1 to 21 carbon atoms, a substituted or unsubstituted benzyl group, and a substituted or unsubstituted phenyl group, R １ is an alkyl group having 1 to 18 carbon atoms, R ２ is an alkylene group having 2 to 6 carbon atoms, R ３ is an alkylene group having 2 to 6 carbon atoms, Y is an acid group, and Rf is a linear or branched fluoroalkyl group having 1 to 21 carbon atoms. m is 1 to 10, n is 2 to 90, p is 1 to 90, and q is 1 to 10.

6. The inkjet printing apparatus according to claim 4, wherein the fluorine-containing acrylate polymer contains a polymer having at least one of a structural unit represented by the following general formula (III) and a structural unit represented by the following general formula (IV). 【Chemical Formula 4】 【Chemical Formula 5】 However, in the general formulas (III) and (IV), X is a hydrogen atom, a linear or branched alkyl group having 1 to 21 carbon atoms, a halogen atom, CFX １ X ２ group (provided that X １ and X ２ are each independently either a hydrogen atom or a halogen atom), a cyano group, a linear or branched fluoroalkyl group having 1 to 21 carbon atoms, a substituted or unsubstituted benzyl group, and a substituted or unsubstituted phenyl group, R １ is an alkyl group having 1 to 18 carbon atoms, R ２ is an alkylene group having 2 to 6 carbon atoms, R ３ is an alkylene group having 2 to 6 carbon atoms, Y is an acid group, and Rf is a linear or branched fluoroalkyl group having 1 to 21 carbon atoms. m is from 1 to 10, n is from 2 to 90, p is from 1 to 90, and q is from 1 to 10.

7. The inkjet printing apparatus according to any one of claims 4 to 6, wherein the non-ink-attracting film contains a polymer having a fluorine-containing heterocyclic structure in the main chain.

8. including an ink discharge step of discharging each ink in the ink set according to any one of claims 1 to 2 from a discharge head, An inkjet printing method characterized in that a receding contact angle of each of the inks with respect to a nozzle plate of a discharge head is 35° or more.

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