Inkjet recording ink, inkjet printing method, and inkjet printing device

Abstract

To provide an ink for inkjet recording capable of printing without generating dripping, and excellent in discharge stability.SOLUTION: An ink for inkjet recording includes: a coloring agent, a resin, a water-soluble organic solvent, and water, where the storage modulus (a) of the ink for inkjet recording is 0.1 Pa or more, the evaporation rate (b) of the ink for inkjet recording calculated by the following formula (1) is 14.5%≤(b)≤85.0%, and 1.45≤(a)×(b)≤8.5 is satisfied. Evaporation rate (b)(%)=(X-Y) / X×100: formula (1). In the formula (1), X is an initial mass (g) of the ink for inkjet recording, and Y is a mass (g) of the ink for inkjet recording after leaving for 1 hour under an environment of 25°C, and 20% of a relative humidity.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Inkjet printing is a method of printing text and images by ejecting small ink droplets from a fine nozzle onto a recording medium such as paper. Its low noise, simple process, and ease of color printing make it popular as a home printer. In recent years, inkjet printing has expanded into commercial printing due to its advantages, such as variable printing and compatibility with a wide range of media. Commercial printing involves printing on a wide variety of papers, which can be broadly categorized as plain paper and coated paper. Direct printing on films and metals is also becoming increasingly common, and the required performance differs from that of paper. For metals in particular, it is extremely difficult to satisfy all required characteristics, such as adhesion, ink dripping (image drying), abrasion resistance, lightfastness, bleeding, beading, and ejection stability. Therefore, inks are selected based on the characteristics prioritized for each application.

[0003] To date, in order to achieve both ejection stability and suppression of bleeding and beading, inkjet recording inks have been proposed that contain a poorly water-soluble alkanediol, a resin, and a colorant, and that have a surface tension and a thixotropy index at evaporation within specific ranges (see Patent Document 1). Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide an ink for ink jet recording that can be printed without dripping and has excellent ejection stability. [Means for solving the problem]

[0005] The inkjet recording ink of the present invention, which is a means for solving the above-mentioned problems, is an inkjet recording ink containing a colorant, a resin, a water-soluble organic solvent, and water, characterized in that the storage modulus (a) of the inkjet recording ink is 0.1 Pa or more, the evaporation rate (b) of the inkjet recording ink calculated by the following formula (1) is 14.5%≦(b)≦85.0%, and 1.45≦(a)×(b)≦8.5 is satisfied: Evaporation rate (b)(%)=(XY) / X×100 ··· Equation (1) In the formula (1), "X" represents the initial mass (g) of the inkjet recording ink, and "Y" represents the mass (g) of the inkjet recording ink after it has been left to stand for 1 hour in an environment of 25°C and a relative humidity of 20%. [Effects of the Invention]

[0006] According to the present invention, it is possible to provide an ink for ink jet recording that can be printed without dripping and has excellent ejection stability. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram showing an example of an inkjet printing apparatus for carrying out the inkjet printing method of the present invention. [Figure 2] FIG. 2 is a perspective view illustrating an example of a main tank of the inkjet printing apparatus of FIG. [Figure 3] FIG. 3 is an exploded perspective view showing an example of a discharge head used in the inkjet printing apparatus of the present invention. [Figure 4] FIG. 4 is an explanatory cross-sectional view taken along the longitudinal direction of the liquid chamber of the ejection head used in the inkjet printing apparatus of the present invention. [Figure 5] FIG. 5 is an explanatory cross-sectional view taken along the shorter side of the liquid chamber of the ejection head used in the inkjet printing apparatus of the present invention. [Figure 6] FIG. 6 is an explanatory plan view of a nozzle plate of a discharge head used in the inkjet printing apparatus of the present invention. [Figure 7] FIG. 7 is a cross-sectional view illustrating the nozzle plate shown in FIG. [Figure 8] FIG. 8 is an enlarged cross-sectional explanatory view of one nozzle portion in the nozzle plate. [Figure 9] FIG. 9 is a diagram showing an example of the case of evaluation standard "A" in the evaluation of the writing start distortion of the examples and the comparative examples. [Figure 10] FIG. 10 is a diagram showing an example of the case of evaluation standard "D" in the evaluation of the writing start distortion of the examples and the comparative examples. DETAILED DESCRIPTION OF THE INVENTION

[0008] (Inkjet recording ink) The inkjet recording ink of the present invention contains a coloring material, a resin, a water-soluble organic solvent, and water, and further contains other components such as additives, if necessary.

[0009] The inkjet recording ink has a storage modulus (a) of 0.1 Pa or more, and an evaporation rate (b) of the inkjet recording ink calculated by the following formula (1) is 14.5%≦(b)≦85.0%, and satisfies the relationship 1.45≦(a)×(b)≦8.5. Evaporation rate (b)(%)=(XY) / X×100 ··· Equation (1) In the formula (1), "X" represents the initial mass (g) of the inkjet recording ink, and "Y" represents the mass (g) of the inkjet recording ink after it has been left to stand for 1 hour in an environment of 25°C and a relative humidity of 20%.

[0010] Conventionally, it has been extremely difficult to satisfy all of the required characteristics for non-permeable substrates such as metal, including adhesion, ink dripping (image drying), abrasion resistance, lightfastness, bleeding, beading, and ejection stability, and inks have been selected based on the characteristics prioritized depending on the application. To solve this problem, methods have been proposed, such as applying a material to fix the ink when an ink image is formed on the surface of a substrate or heating the surface. However, these proposals have not been widely adopted due to the cost, labor hours, and operating equipment required.

[0011] Furthermore, in the industrial field, higher productivity is required compared to consumer printing. However, unlike paper, ink does not penetrate non-permeable substrates such as metal, so only evaporation of the ink contributes to the drying of the ink. If the ink dries slowly, the ink may move, affecting the image. Therefore, it is necessary to improve the ink drying speed, but there is a trade-off between improving the ink drying speed and ejection stability.

[0012] The inkjet recording ink described in Patent Document 1 (JP 2015-11079 A) is capable of achieving both ejection stability and suppression of bleeding and beading. While this method is certainly considered effective for general printers, when printing on an object whose printing surface is approximately horizontal to the direction of gravity, such as an assembled automobile body or an already assembled and standing substrate, dripping occurs on the printing surface, making it difficult to say that a clear image can be printed.

[0013] Therefore, the present inventors conducted extensive research and found that by setting the storage modulus and evaporation rate of the inkjet recording ink within specific ranges, it is possible to print without dripping, even when the printing surface is approximately horizontal to the direction of gravity, due to the inkjet recording ink's appropriate viscosity and volume reduction due to evaporation, and by keeping the initial viscosity of the inkjet recording ink low, the resistance as a fluid is reduced and the inkjet recording ink is less likely to thicken even when evaporated, so the inkjet recording ink is less likely to clog the nozzles of the ejection head and has excellent ejection stability.

[0014] The storage modulus (a) of the inkjet recording ink is not particularly limited as long as it is 0.1 Pa or more and can be appropriately selected depending on the purpose, but is preferably 0.15 Pa or more. The upper limit of the storage modulus (a) of the inkjet recording ink is also not particularly limited, but is preferably 0.5 Pa or less, more preferably 0.35 Pa or less, and even more preferably 0.27 Pa or less, in order to facilitate breaking through the meniscus at the ejection pressure during ejection. The lower and upper limits of the storage modulus (a) of the inkjet recording ink can be appropriately combined, but is preferably 0.1 Pa or more and 0.5 Pa or less, more preferably 0.15 Pa or more and 0.35 Pa or less, and even more preferably 0.15 Pa or more and 0.27 Pa or less. If the storage modulus (a) of the inkjet recording ink is less than 0.1 Pa, the viscosity of the inkjet recording ink itself will be low when it lands, and therefore, when the printing surface is approximately horizontal to the direction of gravity, the ink will quickly drip under its own weight regardless of the viscosity.

[0015] In the present invention, the storage modulus (a) [Pa] of the inkjet recording ink is a value measured under the following measurement conditions. [Measurement conditions] Equipment: Rheometer (MCR-301, manufactured by Anton Paar) · Measurement frequency: 2Hz · Measurement temperature: 25℃ Displacement: 0.01% to 100%

[0016] The evaporation rate (b) of the inkjet recording ink is not particularly limited as long as it is 14.5%≦(b)≦85.0%, and can be appropriately selected depending on the purpose, but from the viewpoint of both suppressing dripping and achieving ejection stability, 14.5%≦(b)≦30.0%, and more preferably 14.5%≦(b)≦20.0%. If the evaporation rate (b) of the inkjet recording ink is less than 14.5%, dripping occurs, and if it exceeds 85.0%, the inkjet recording ink will solidify in the nozzles of the ejection head, causing nozzle clogging.

[0017] In the present invention, the evaporation rate (b) of the inkjet recording ink is a value calculated by the above formula (1), and specifically, it can be calculated by the method described in the examples.

[0018] The inkjet recording ink cannot be ejected if its viscosity increases due to evaporation or if its viscosity becomes too high. On the other hand, if its viscosity is too low, it will drip. Therefore, the balance between the storage modulus (a) and the evaporation rate (b) of the inkjet recording ink must satisfy the relationship 1.45≦(a)×(b)≦8.5, preferably 1.5≦(a)×(b)≦8.0, and more preferably 1.5≦(a)×(b)≦7.0. If (a)×(b) is less than 1.45, dripping will occur, and if it exceeds 8.5, the inkjet recording ink will not be ejected. In (a) × (b), (b) represents the evaporation rate (%), so it is actually calculated as an integer, (a) × [(b) / 100 × 100].

[0019] By satisfying all of the storage modulus (a), evaporation rate (b), and (a) × (b) values, the inkjet recording ink can be prevented from dripping even when the printing surface is approximately horizontal with respect to the direction of gravity. Furthermore, in addition to suppressing the fluidity of the inkjet recording ink by the viscosity of the inkjet recording ink, the weight loss of the inkjet recording ink due to evaporation of water can also suppress dripping due to its own weight.

[0020] The coloring material, resin, water-soluble organic solvent, water, additives, and other components used in the inkjet recording ink will be described below.

[0021] <Colorant> The coloring material is not particularly limited, and pigments and dyes can be used. The pigment may be an inorganic pigment or an organic pigment. These may be used alone or in combination of two or more. Mixed crystals may also be used.

[0022] Examples of the pigment that can be used include black pigments, yellow pigments, magenta pigments, cyan pigments, white pigments, green pigments, orange pigments, glossy pigments such as gold and silver pigments, and metallic pigments.

[0023] Examples of the inorganic pigment that can be used include titanium oxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, and chrome yellow, as well as carbon black produced by known methods such as a contact method, a furnace method, and a thermal method.

[0024] Examples of the organic pigment that can be used include azo pigments, polycyclic pigments (e.g., phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, etc.), dye chelates (e.g., basic dye chelates, acid dye chelates, etc.), nitro pigments, nitroso pigments, and aniline black. Of these pigments, those with good affinity with the solvent are preferably used. In addition, resin hollow particles and inorganic hollow particles can also be used.

[0025] Specific examples of the pigments for black include carbon blacks (CI Pigment Black 7) such as furnace black, lamp black, acetylene black, and channel black; metals such as copper, iron (CI Pigment Black 11), and titanium oxide; and organic pigments such as aniline black (CI Pigment Black 1).

[0026] Additionally, for color, CI Pigment Yellow 1, 3, 12, 13, 14, 17, 24, 34, 35, 37, 42 (yellow iron oxide), 53, 55, 74, 81, 83, 95, 97, 98, 100, 101, 104, 108, 109, 110, 117, 120, 128, 138, 150, 153, 155, 180, 185, 213; CI Pigment Orange 5, 13, 16, 17, 36, 43, 51; CI 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, 10 1 (Red Iron), 104, 105, 106, 108 (Cadmium Red), 112, 114, 122 (Quinacridone Magenta), 123, 146, 149, 166, 168, 170, 172, 177, 178, 179, 184, 185, 190, 193, 202, 207, 208, 209, 213, 219, 224, 254, 264; CI Pygme CI Pigment Violet 1 (Rhodamine Lake), 3, 5:1, 16, 19, 23, 38; CI Pigment Blue 1, 2, 15 (Phthalocyanine Blue), 15:1, 15:2, 15:3, 15:4 (Phthalocyanine Blue), 16, 17:1, 56, 60, 63; CI Pigment Green 1, 4, 7, 8, 10, 17, 18, 36, etc.

[0027] The dye is not particularly limited, and acid dyes, direct dyes, reactive dyes, and basic dyes can be used, and one type may be used alone, or two or more types may be used in combination.

[0028] The dye is not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include CI Acid Yellow 17, 23, 42, 44, 79, 142; CI Acid Red 52, 80, 82, 249, 254, 289; CI Acid Blue 9, 45, 249; CI Acid Black 1, 2, 24, 94; CI Food Black 1, 2; CI Direct Yellow 1, 12, 24, 33, 50, 55, 58, 8 6, 132, 142, 144, 173; CI Direct Red 1, 4, 9, 80, 81, 225, 227; CI Direct Blue 1, 2, 15, 71, 86, 87, 98, 165, 199, 202; CI Directed Black 19, 38, 51, 71, 154, 168, 171, 195; CI Reactive Red 14, 32, 55, 79, 249; CI Reactive Black 3, 4, 35, etc.

[0029] The content of the coloring material in the inkjet recording ink is not particularly limited and can be appropriately selected depending on the purpose. From the viewpoints of improving image density, good fixability, and ejection stability, the content is preferably from 0.1% by mass to 15% by mass, and more preferably from 1% by mass to 10% by mass.

[0030] Examples of methods for dispersing the pigment to obtain the inkjet recording ink include a method of introducing a hydrophilic functional group into the pigment to make it a self-dispersible pigment, a method of dispersing the pigment by coating the surface of the pigment with a resin, and a method of dispersing the pigment using a dispersant.

[0031] Examples of a method for introducing a hydrophilic functional group into the pigment to make it a self-dispersible pigment include a method in which a functional group such as a sulfone group or a carboxyl group is added to the pigment (e.g., carbon) to make it dispersible in water.

[0032] Examples of methods for coating the surface of the pigment with a resin and dispersing it include a method in which the pigment is encapsulated in microcapsules to make it dispersible in water. This can be rephrased as a resin-coated pigment. In this case, the pigment blended in the inkjet recording ink does not need to be entirely coated with a resin, and uncoated or partially coated pigments may be dispersed in the inkjet recording ink as long as the effects of the present invention are not impaired.

[0033] Examples of the method for dispersing using the dispersant include a method for dispersing using a known low molecular weight dispersant or a high molecular weight dispersant, such as a surfactant.

[0034] The dispersant is not particularly limited and can be appropriately selected depending on the type of pigment, etc. For example, anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, etc. can be used. Olfin PD-201 (a nonionic surfactant, manufactured by Nissin Chemical Industry Co., Ltd.) and sodium naphthalenesulfonate formalin condensate can also be suitably used as the dispersant. The dispersants may be used alone or in combination of two or more.

[0035] <<Pigment dispersions>> The inkjet recording ink can be obtained by mixing the pigment with materials such as water and the water-soluble organic solvent. Alternatively, the inkjet recording ink can be produced by mixing the pigment with other components such as water and a dispersant to form a pigment dispersion, and then mixing the pigment with materials such as water and the water-soluble organic solvent.

[0036] The pigment dispersion is obtained by mixing and dispersing the water, the pigment, the dispersant, and optionally other components, and adjusting the particle size.

[0037] There are no particular restrictions on the particle size of the pigment in the pigment dispersion. However, in terms of the maximum number, the maximum frequency is preferably 20 nm or more and 500 nm or less, and more preferably 20 nm or more and 150 nm or less, in order to improve the dispersion stability of the pigment and to enhance the image quality such as ejection stability and image density. The particle size of the pigment can be measured using a particle size analyzer (Nanotrac Wave-UT151, manufactured by Microtrac Bell Co., Ltd.).

[0038] The content of the pigment in the pigment dispersion is not particularly limited and can be appropriately selected depending on the purpose. However, from the viewpoint of obtaining good ejection stability and increasing image density, the content is preferably 0.1% by mass or more and 50% by mass or less, and more preferably 0.1% by mass or more and 30% by mass or less.

[0039] It is preferable that the pigment dispersion is degassed as needed by filtering coarse particles using a filter, a centrifugal separator, or the like.

[0040] The content of the coloring material in the inkjet recording ink is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 1% by mass or more and 10% by mass or less, and more preferably 2% by mass or more and 5% by mass or less.

[0041] <Resin> The type of resin contained in the inkjet recording ink is not particularly limited and can be appropriately selected depending on the purpose. Examples of the resin include urethane resin, polyester resin, acrylic resin, vinyl acetate resin, styrene resin, butadiene resin, styrene-butadiene resin, vinyl chloride resin, acrylic-styrene resin, and acrylic-silicone resin.

[0042] Resin particles made of these resins may also be used. The inkjet recording ink can be obtained by mixing the resin particles in the form of a resin emulsion dispersed in water as a dispersion medium with materials such as the colorant and the water-soluble organic solvent. The resin particles may be appropriately synthesized or commercially available. These may be used alone or in combination of two or more types of resin particles.

[0043] The volume average particle size of the resin particles is not particularly limited and can be appropriately selected depending on the purpose. However, in order to obtain good fixability and high image hardness, the volume average particle size is preferably 10 nm or more and 500 nm or less, more preferably 10 nm or more and 200 nm or less, and particularly preferably 10 nm or more and 100 nm or less. The volume average particle size can be measured using a particle size analyzer (for example, Nanotrac Wave-UT151, manufactured by Microtrac Bell Co., Ltd.).

[0044] Among these, the resin preferably contains a resin having a minimum film forming temperature (MFT) of 0°C or more and 50°C or less, since the resin is easily swollen by the water-soluble organic solvent, and more preferably contains a resin having an MFT of 0°C or more and 30°C or less. The MFT of the resin can be measured using a minimum film-forming thermometer (for example, MFFTB90, manufactured by Sanyo Trading Co., Ltd.).

[0045] In addition, from the viewpoint of abrasion resistance, the resin preferably contains, in addition to the resin having an MFT of 0°C or more and 50°C or less, a silicone-acrylic resin, a styrene-acrylic resin, a urethane resin, or the like having an MFT of more than 50°C.

[0046] The content of the resin is not particularly limited and can be appropriately selected depending on the purpose. However, from the viewpoint of fixability and storage stability of the inkjet recording ink, the content of the resin is preferably from 1% by mass to 30% by mass, and more preferably from 5% by mass to 20% by mass, relative to the total amount of the inkjet recording ink.

[0047] <Water-soluble organic solvent> The water-soluble organic solvent is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include monohydric alcohols, polyhydric alcohols, ethers such as polyhydric alcohol alkyl ethers and polyhydric alcohol aryl ethers, nitrogen-containing heterocyclic compounds, amides, amines, sulfur-containing compounds, etc. These may be used alone or in combination of two or more.

[0048] Specific examples of the water-soluble organic solvent include monohydric alcohols such as methanol and ethanol; 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- Polyhydric alcohols such as 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; ethylene glycol monoethyl ether, ethylene glycol Examples of suitable alkyl ethers include polyhydric alcohols such as 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 alcohols such as ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether; nitrogen-containing heterocyclic compounds such as 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, ε-caprolactam, and γ-butyrolactone; amides such as formamide, N-methylformamide, N,N-dimethylformamide, 3-methoxy-N,N-dimethylpropionamide, and 3-butoxy-N,N-dimethylpropionamide; amines such as monoethanolamine, diethanolamine, and triethylamine; sulfur-containing compounds such as dimethyl sulfoxide, sulfolane, and thiodiethanol; propylene carbonate; and ethylene carbonate.Among these, it is more preferable to contain ethanol, since this can make the evaporation rate of the inkjet recording ink 14.5%≦(b)≦85.0% and can make the resin compatible with the water-soluble organic solvent, thereby preventing dripping of the inkjet recording ink and ensuring good ejection stability.

[0049] The water-soluble organic solvent preferably has a boiling point of 250° C. or less, since it not only functions as a wetting agent but also provides good drying properties.

[0050] The content of the water-soluble organic solvent in the ink for inkjet recording is not particularly limited and can be appropriately selected depending on the purpose. From the viewpoint of the drying property and ejection stability of the ink for inkjet recording, the content is preferably 3% by mass or more and 60% by mass or less, and more preferably 7% by mass or more and 20% by mass or less.

[0051] <Water> The water is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include pure water such as ion-exchanged water, ultrafiltered water, reverse osmosis water, distilled water, and ultrapure water, etc. These may be used alone or in combination of two or more.

[0052] The content of water in the inkjet recording ink is not particularly limited and can be appropriately selected depending on the purpose. However, from the viewpoint of the drying property and ejection stability of the inkjet recording ink, the content of water is preferably 10% by mass or more and 90% by mass or less, and more preferably 20% by mass to 75% by mass.

[0053] <Other ingredients> The inkjet recording ink may contain, as necessary, additives such as a surfactant, an antifoaming agent, an antiseptic / fungal agent, an antirust agent, a pH adjuster, etc. Furthermore, the inkjet recording ink may contain a hydrophobic organic solvent in addition to the water-soluble organic solvent.

[0054] <<Surfactants>> The surfactant is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include silicone surfactants, fluorine surfactants, amphoteric surfactants, nonionic surfactants, anionic surfactants, etc. These may be used alone or in combination of two or more.

[0055] -Silicone surfactants- The silicone surfactant is not particularly limited and can be appropriately selected according to purpose.Among these, those that do not decompose even at high pH are preferred, for example, side chain modified polydimethylsiloxane, both end modified polydimethylsiloxane, one end modified polydimethylsiloxane, side chain both end modified polydimethylsiloxane, etc., and silicone surfactants having polyoxyethylene group or polyoxyethylene polyoxypropylene group as modified group are particularly preferred because they exhibit good properties as aqueous surfactants.In addition, polyether modified silicone surfactants can also be used as the silicone surfactant, for example, compounds in which polyalkylene oxide structure is introduced into the Si part side chain of dimethylsiloxane, etc.

[0056] Such silicone surfactants may be synthesized appropriately or commercially available products, such as those available from BYK Corporation, Shin-Etsu Chemical Co., Ltd., Dow Corning Toray Silicone Co., Ltd., Nippon Emulsion Co., Ltd., and Kyoeisha Chemical Co., Ltd.

[0057] The polyether-modified silicone surfactant is not particularly limited and can be appropriately selected depending on the purpose. Examples include surfactants represented by the following general formula (S-1), in which a polyalkylene oxide structure is introduced into the Si moiety side chain of dimethylpolysiloxane. [ka] (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.)

[0058] The polyether-modified silicone surfactant may be a commercially available product, and examples thereof include KF-618, KF-642, and KF-643 (all manufactured by Shin-Etsu Chemical Co., Ltd.), EMALEX SS-5602 and EMALEX SS-1906EX (all manufactured by Nippon Emulsion Co., Ltd.), DOWSIL FZ-2105, DOWSIL FZ-2118, DOWSIL FZ-2154, DOWSIL FZ-2161, DOWSIL FZ-2162, DOWSIL FZ-2163, and DOWSIL FZ-2164 (all manufactured by Dow Corning Toray Silicone Co., Ltd.), BYK-33 and BYK-387 (all manufactured by BYK-Chemie Corporation), and TSF4440, TSF4452, and TSF4453 (all manufactured by Momentive Performance Materials Japan, LLC).

[0059] -Fluorosurfactants- The fluorine-based surfactant is not particularly limited and can be appropriately selected depending on the purpose, but is preferably a compound having 2 to 16 fluorine-substituted carbon atoms, and more preferably a compound having 4 to 16 fluorine-substituted carbon atoms.

[0060] Examples of the fluorine-based surfactant include perfluoroalkyl sulfonic acid compounds, perfluoroalkyl carboxylic acid compounds, perfluoroalkyl phosphate ester compounds, perfluoroalkyl ethylene oxide adducts, polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups on the side chains, etc. These may be used alone or in combination of two or more.

[0061] Examples of the perfluoroalkylsulfonic acid compound include perfluoroalkylsulfonic acid and perfluoroalkylsulfonic acid salts.

[0062] Examples of the perfluoroalkyl carboxylic acid compound include perfluoroalkyl carboxylic acids and perfluoroalkyl carboxylates.

[0063] Examples of the polyoxyalkylene ether polymer compound having a perfluoroalkyl ether group on the side chain include sulfate ester salts of polyoxyalkylene ether polymers having a perfluoroalkyl ether group on the side chain, and salts of polyoxyalkylene ether polymers having a perfluoroalkyl ether group on the side chain.

[0064] Counter ions of the salts in these fluorine-based surfactants include, for example, Li, Na, K, NH4, NH3CH2CH2OH, NH2(CH2CH2OH)2, and NH(CH2CH2OH)3.

[0065] Among these, as the fluorosurfactant, polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups in the side chains are preferred because of their low foaming properties, and fluorosurfactants represented by the following general formula (F-1) and the following general formula (F-2) are particularly preferred. [ka] (However, in the general formula (F-1), m and n each independently represent an integer.)

[0066] In the compound represented by the general formula (F-1), m is preferably an integer of 0 to 10, and n is preferably an integer of 0 to 40, in order to impart water solubility. [ka] (However, in the general formula (F-2), Y is H, C m F 2m+1 (where m is an integer from 1 to 6), CH2CH(OH)CH2-C m F 2m+1 (where m is an integer of 4 to 6), or C p H 2p+1(wherein p represents an integer of 1 to 19, n represents an integer of 1 to 6, and a represents an integer of 4 to 14.)

[0067] As the fluorine-based surfactant, commercially available products can be used, for example, Surflon (registered trademark) S-111, S-112, S-113, S-121, S-131, S-132, S-141, S-145 (all manufactured by AGC Seimi Chemical Co., Ltd.); Fullard 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 (registered trademark) TBS, FSP, Examples include FSA, FSN-100, FSN, FSO-100, FSO, FS-300, UR, Capstone FS-30, FS-31, FS-3100, FS-34, and FS-35 (all manufactured by Chemours Corporation); Ftergent (FT)-110, FT-250, FT-251, FT-400S, FT-150, and FT-400SW (all manufactured by Neos Corporation), Polyfox (PF)-136A, PF-156A, PF-151N, PF-154, and PF-159 (all manufactured by Omnova), and Unidyne DSN-403N (manufactured by Daikin Industries, Ltd.). Among these, FS-3100, FS-34, and FS-300 manufactured by Chemours Corporation, FT-110, FT-250, FT-251, FT-400S, FT-150, and FT-400SW manufactured by Neos Corporation, PF-151N manufactured by Omnova, and Unidyne DSN-403N manufactured by Daikin Industries, Ltd. are particularly preferred, as they provide good print quality, particularly significant improvements in color development, paper penetration, wettability, and dye uniformity.

[0068] -Amphoteric surfactant- Examples of the amphoteric surfactant include lauryl aminopropionate, lauryl dimethyl betaine, stearyl dimethyl betaine, and lauryl dihydroxyethyl betaine.

[0069] -Nonionic surfactants- Examples of the nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene alkyl esters, polyoxyethylene alkylamines, polyoxyethylene alkylamides, polyoxyethylene propylene block polymers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, and ethylene oxide adducts of acetylene alcohol.

[0070] -Anionic surfactants- Examples of the anionic surfactant include polyoxyethylene alkyl ether acetates, dodecylbenzenesulfonates, laurates, and salts of polyoxyethylene alkyl ether sulfates.

[0071] The content of the surfactant in the inkjet recording ink is not particularly limited and can be appropriately selected depending on the purpose. However, from the viewpoint of achieving excellent wettability and ejection stability and improving image quality, the content is preferably from 0.001% by mass to 5% by mass, and more preferably from 0.05% by mass to 5% by mass.

[0072] <<Antifoaming agent>> The antifoaming agent is not particularly limited, and examples thereof include silicone-based antifoaming agents, polyether-based antifoaming agents, fatty acid ester-based antifoaming agents, nonionic surfactants, etc. These may be used alone or in combination of two or more. Among these, silicone-based antifoaming agents are preferred because of their excellent foam-breaking effect.

[0073] The content of the defoaming agent in the inkjet recording ink is not particularly limited and can be appropriately selected depending on the purpose.

[0074] <<Preservative and fungicide>> The antiseptic and antifungal agent is not particularly limited, and examples thereof include 1,2-benzisothiazolin-3-one.

[0075] The content of the antiseptic and antifungal agent in the ink for inkjet recording is not particularly limited and can be appropriately selected according to the purpose.

[0076] <<Rust inhibitor>> The rust inhibitor is not particularly limited, and examples thereof include acid sulfite, sodium thiosulfate, and the like.

[0077] The content of the rust inhibitor in the ink for inkjet recording is not particularly limited and can be appropriately selected according to the purpose.

[0078] <<pH adjuster>> The pH adjuster is not particularly limited, but a pH adjuster capable of adjusting the pH to 7 or more is preferable, and examples thereof include amines such as diethanolamine and triethanolamine.

[0079] The content of the pH adjuster in the ink for inkjet recording is not particularly limited as long as it can be adjusted to the desired pH, and can be appropriately selected according to the purpose.

[0080] The particle size of the solid content in the ink for inkjet recording is not particularly limited and 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, and more preferably 20 nm or more and 150 nm or less. The solid content includes resin particles, pigment particles, and the like. The particle size can be measured using a particle size analyzer (NanoTrack Wave-UT151, manufactured by Microtrac·BEL Corporation).

[0081] The physical properties of the ink for inkjet recording are not particularly limited and can be appropriately selected according to the purpose. For example, it is preferable that the viscosity, surface tension, pH, etc. are in the following ranges.

[0082] The viscosity (c) of the inkjet recording ink at 25°C is not particularly limited and can be selected appropriately depending on the purpose, but from the viewpoints of improving print density and character quality and obtaining good ejection stability, 0.5 mPa·s≦(c)≦10 mPa·s is preferred, and 3 mPa·s≦(c)≦7 mPa·s is more preferred. When the viscosity (c) of the inkjet recording ink at 25°C is 0.5 mPa·s≦(c)≦10 mPa·s, the ink flows easily as a fluid and is less likely to thicken during evaporation, making it possible to maintain the ink in a state where the nozzle is less likely to clog. Here, the viscosity can be measured using, for example, an E-type viscometer (TV-35, manufactured by Toki Sangyo Co., Ltd.) The measurement conditions are 25°C, a standard cone rotor (1°34' x R24), a sample liquid volume of 1.2 mL, a rotation speed of 50 rpm, and 3 minutes.

[0083] The surface tension of the inkjet recording ink is not particularly limited and can be appropriately selected depending on the purpose. However, from the viewpoints of suitably leveling the inkjet recording ink on the substrate and shortening the drying time of the inkjet recording ink, the surface tension is preferably 35 mN / m or less, and more preferably 32 mN / m or less at 25°C. Here, the surface tension can be measured using a static surface tensiometer (for example, manufactured by Kyowa Interface Science Co., Ltd.).

[0084] The pH of the inkjet recording ink is not particularly limited and can be appropriately selected depending on the purpose. However, from the viewpoint of preventing corrosion of substrates (e.g., metal members) that come into contact with the ink, the pH is preferably 7 to 12, and more preferably 8 to 11.

[0085] -Base material- The substrate used for recording with the inkjet recording ink is not limited to those generally used as recording media, and may also be wallpaper, flooring, building materials such as tiles, vehicles, etc. Furthermore, the substrate is not limited to those having a flat surface (printing surface), and may also be a substrate whose printing surface is a three-dimensional curved surface or a substrate whose printing surface has an uneven shape. In the present invention, the substrate means a material to which the ink jet recording ink can be attached even temporarily.

[0086] The material of the substrate is not particularly limited, and paper such as plain paper, glossy paper, special paper, or cloth may be used, but good image formation is also possible using an impermeable substrate. Alternatively, the substrate may be paper or cloth that has been subjected to a water-repellent treatment, or a substrate made of a so-called ceramic material obtained by firing an inorganic material at a high temperature.

[0087] The non-permeable substrate is a substrate having a surface with low water permeability and absorbency, and includes materials that have many cavities inside but are not open to the outside. More quantitatively, in the Bristow method, 1 / 2 Water absorption up to 10mL / m 2 The term "substrate" refers to a substrate that is:

[0088] Specific examples of the impermeable substrate include plastic films such as vinyl chloride resin film, polyethylene terephthalate (PET) film, polypropylene, polyethylene, and polycarbonate film; metals such as brass, iron, aluminum, SUS, and copper; and non-metallic substrates that have been subjected to a metal coating treatment by a method such as vapor deposition.

[0089] The surface (printing surface) of the metal may be surface-treated. The surface treatment may be, for example, primer coating.

[0090] The inkjet recording ink can be suitably used in various recording devices using the inkjet recording method, such as printers, facsimile machines, copying machines, fax machines, copier-combined machines, and three-dimensional modeling devices.

[0091] The uses of the inkjet recording ink are not particularly limited and can be appropriately selected depending on the purpose. For example, the inkjet recording ink can be used for printed materials, paints, coating materials, and base coats. It can be used not only to form two-dimensional characters and images, but also as a three-dimensional modeling material for forming three-dimensional objects (three-dimensional models). Furthermore, the inkjet recording ink can prevent dripping and has ejection stability. Therefore, it can be used not only for printing when the printing surface of the substrate is placed perpendicular to the direction of gravity, as in the conventional method, but also for printing when the printing surface of the substrate is placed approximately horizontally to the direction of gravity and the ejection direction of the inkjet recording ink is perpendicular to the printing surface of the substrate. Therefore, the inkjet recording ink is particularly suitable for printing on the sides of automobiles and trucks, for example.

[0092] In the present invention, the terms "recording" and "printing" are used synonymously.

[0093] (Inkjet printing method and inkjet printing device) <Inkjet printing method> The inkjet printing method of the present invention includes a discharge step, and may further include other steps, such as a heating step, a pretreatment step, a posttreatment step, a substrate feeding step, a substrate transport step, and a substrate discharge step, as necessary.

[0094] In the present invention, the inkjet printing method is a method of printing using an apparatus capable of ejecting the inkjet recording ink and, if necessary, various treatment liquids and the like onto a substrate.

[0095] <Inkjet printing device> The inkjet printing apparatus of the present invention comprises an ink reservoir that contains the ink for inkjet recording of the present invention, and an ejection head that ejects the ink for inkjet recording, and may further comprise other means, as necessary, such as a heating means, a pressure chamber, a pre-treatment means, a post-treatment means, and means related to feeding, transporting, or discharging the substrate.

[0096] In the present invention, the inkjet printing device is a device capable of ejecting the inkjet recording ink and, if necessary, various treatment liquids and the like onto a substrate.

[0097] Unless otherwise specified, the inkjet printing apparatus includes both a serial type apparatus in which the ejection head moves and a line type apparatus in which the ejection head does not move. Furthermore, the inkjet printing device includes not only desktop types but also wide-width recording devices that can print on A0-sized recording media, such as continuous feed printers that can use continuous paper wound into a roll as the substrate.

[0098] Furthermore, the inkjet printing apparatus and the inkjet printing method are not limited to those that visualize meaningful images such as characters and figures using the inkjet recording ink, but also include those that form patterns such as geometric designs and those that create three-dimensional images.

[0099] The inkjet printing method of the present invention will be described below together with the inkjet printing apparatus of the present invention.

[0100] <<Ink storage section>> The ink reservoir contains the ink for ink-jet recording of the present invention. The ink storage section is not particularly limited as long as it is a member capable of storing the ink for inkjet recording, and examples thereof include an ink storage container and an ink tank.

[0101] The ink container contains the ink and may further include other members appropriately selected as required. The container is not particularly limited, and its shape, structure, size, material, etc. can be appropriately selected depending on the purpose. For example, it may include a container having at least an ink bag formed from an aluminum laminate film, a resin film, etc.

[0102] The ink tanks include, for example, a main tank and a sub-tank.

[0103] <<Discharge process and discharge head>> The ejection step is a step of ejecting the ink for ink-jet recording of the present invention. The ejection head is a means for ejecting the ink for ink-jet recording of the present invention from nozzles formed on a nozzle surface, and has a nozzle plate and, if necessary, other members such as a stimulus generating member.

[0104] The inkjet printing method can suppress dripping of the inkjet recording ink due to its own weight, even when the printing surface of the substrate is at an angle of 0° to 180° with respect to the direction of gravity, and can form a good image. In particular, the ejection step is advantageous in that it can suppress dripping of the inkjet recording ink due to its own weight, even when the printing surface of the substrate is set so as to be approximately horizontal with respect to the direction of gravity, and the ejection direction of the inkjet recording ink is perpendicular to the printing surface of the substrate, and can form a good image.

[0105] In the present invention, "the printing surface of the substrate is approximately horizontal with respect to the direction of gravity" means not only when the printing surface of the substrate is at 0° or 180° with respect to the direction of gravity, but also in the range of 0°±20° or 180°±20°. For example, if the printing surface of the substrate is flat, printing can be performed without causing dripping even when the printing surface is in the range of 0°±20° or 180°±20° with respect to the direction of gravity. Furthermore, even if the printing surface of the substrate is a three-dimensional curved surface or has an uneven shape, printing can be performed without causing dripping.

[0106] -Nozzle plate- The nozzle plate has a nozzle substrate and an ink-repellent film on the nozzle substrate.

[0107] The nozzle substrate has nozzle holes, and there are no particular limitations on the number, shape, size, material, structure, etc. of the nozzle holes, and they can be appropriately selected depending on the purpose. The nozzle substrate has an ink ejection side surface from which the ink for ink jet recording is ejected from the nozzle holes, and a liquid chamber joining surface located on the opposite side to the ink ejection side surface. The ink-repellent film is formed on the ink ejection side surface of the nozzle substrate, which surface faces the base material.

[0108] The planar shape of the nozzle substrate is not particularly limited and can be appropriately selected depending on the purpose. Examples include rectangular, square, rhombic, circular, and elliptical shapes. The cross-sectional shape of the nozzle substrate may be, for example, a flat plate or a plate. The size of the nozzle substrate is not particularly limited and can be appropriately selected depending on the size of the nozzle plate.

[0109] The material of the nozzle substrate is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include stainless steel, Al, Bi, Cr, InSn, ITO, Nb, Nb2O5, NiCr, Si, SiO2, Sn, Ta2O5, Ti, W, ZAO (ZnO + Al2O3), and Zn. These may be used alone or in combination of two or more. Among these, stainless steel is preferred as the material of the nozzle substrate from the viewpoint of rust prevention.

[0110] The stainless steel is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include austenitic stainless steel, ferritic stainless steel, martensitic stainless steel, precipitation hardening stainless steel, etc. These may be used alone or in combination of two or more.

[0111] At least the surface of the nozzle substrate on the ink ejection side may be subjected to oxygen plasma treatment to introduce hydroxyl groups, in order to improve adhesion between the ink-repellent film and the nozzle substrate.

[0112] The number, arrangement, spacing, opening shape, opening size, cross-sectional shape of the nozzle holes, etc. are not particularly limited and can be appropriately selected depending on the purpose. The arrangement of the nozzle holes is not particularly limited and can be selected appropriately depending on the purpose. For example, a plurality of the nozzle holes may be arranged at equal intervals along the longitudinal direction of the nozzle substrate. The arrangement of the nozzle holes can be appropriately selected depending on the type of ink to be ejected, but one to multiple rows is preferred, and one to four rows is more preferred. The number of nozzle holes per row is not particularly limited and may be appropriately selected depending on 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 depending on the purpose, but is preferably, for example, 21 μm or more and 169 μm or less. The opening shape of the nozzle hole is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include a circle, an ellipse, a rectangle, etc. Among these, the opening shape of the nozzle hole is preferably a circle from the viewpoint of ejecting droplets of the ink for inkjet recording.

[0113] -Ink-repellent film- The ink-repellent film preferably contains a silicone resin or a fluorine resin from the viewpoint of ink repellency. The ink-repellent film may also be called an ink-repellent material-containing film, a polymer-containing film, a silicone resin-containing film, a fluororesin-containing film, or the like.

[0114] --Silicone resin-- Silicone resins are resins with a basic skeleton of siloxane bonds made of Si and O, and are commercially available in various forms such as oil, resin, elastomer, etc. In addition to ink repellency, they also have various properties such as heat resistance, release properties, defoaming properties, and adhesiveness. Silicone resins are available in room temperature curing, heat curing, and ultraviolet curing types, and can be selected depending on the production method and intended use.

[0115] The method for forming the ink-repellent film containing the silicone resin on the nozzle surface (the ink ejection side) is not particularly limited and can be selected appropriately depending on the purpose. Examples include a method of vacuum-depositing a liquid silicone resin material, a method of forming the film by plasma polymerization of silicone oil, a method of forming the film by application such as spin coating, dipping, or spray coating, and an electrodeposition method. When forming the ink-repellent layer, in addition to the electrodeposition method, the nozzle holes and the surface of the nozzle plate opposite the ink ejection side can be masked with a photoresist, a water-soluble resin, or the like, and after the ink-repellent layer is formed, the resist can be peeled off and removed, thereby forming an ink-repellent layer containing the silicone resin only on the ejection side of the nozzle plate. In this case, care must be taken when using a highly alkaline stripping solution, as this can damage the ink-repellent layer.

[0116] The thickness of the ink-repellent film containing the silicone resin is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 0.1 μm or more and 5.0 μm or less, and more preferably 0.1 μm or more and 1.0 μm or less.

[0117] --Fluorine resin-- The fluororesin is not particularly limited, but is preferably a fluorine-containing acrylate ester polymer or a polymer having a fluorine-containing heterocyclic structure in the main chain. When the ink-repellent film contains the fluorine-containing acrylate ester polymer or the polymer having a fluorine-containing heterocyclic structure in the main chain, the surface free energy becomes extremely small, and the ink used in the present invention can maintain a state where it is difficult to wet even with the ink having a low surface tension, which is preferable.

[0118] The fluorine content in the fluorine-containing acrylate ester polymer is not particularly limited and can be appropriately selected depending on the purpose. From the viewpoint of ink repellency (contact angle), the fluorine content is preferably 10% by mass or more, more preferably 25% by mass or more, and even more preferably 50% by mass or more.

[0119] The fluorine-containing acrylate ester polymer may be suitably synthesized or may be a commercially available product. Examples of commercially available products include krytox (registered trademark) FSL and krytox (registered trademark) FSH (manufactured by DuPont), Fomblin Z and FLUOROLINKS 10 (manufactured by Solvay Solexis), Optool DSX (manufactured by Daikin Industries, Ltd.), Moresco Phospharol A20H, Moresco Phospharol ADOH, and Moresco Phospharol DDOH (manufactured by MORESCO Corporation), Fluorosurf FG5010, Fluorosurf FG5020, Fluorosurf FG5060, and Fluorosurf FG5070 (manufactured by Fluorotechnology Co., Ltd.), Cytop CTX-105 and Cytop CTX-805 (manufactured by AGC Inc.), Teflon (registered trademark) AF1600, and Teflon (registered trademark) AF2400 (manufactured by DuPont).

[0120] The ink-repellent film is composed of a compound film containing the fluorine-containing acrylate ester polymer skeleton in its molecule. An inorganic oxide layer can be provided between the nozzle plate and the ink-repellent film to improve adhesion by providing many hydroxyl groups that serve as bonding points with the compound containing the fluorine-containing acrylate ester polymer skeleton in its molecule. Examples of materials for the inorganic oxide layer include SiO2 and TiO2. The average thickness of the inorganic oxide layer is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 0.001 μm or more and 0.2 μm or less, and more preferably 0.01 μm or more and 0.1 μm or less.

[0121] The method for forming an ink-repellent film from a compound containing a fluorine-containing acrylate ester polymer skeleton in its molecule is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include coating methods such as spin coating, roll coating, and dipping using a fluorine-containing solvent, printing, and vacuum deposition.

[0122] Examples of the fluorine-based solvent include Novec (manufactured by 3M Japan Limited), Vertrel (manufactured by DuPont), Galden (manufactured by Solvay Solexis), Afluid (registered trademark) (a fluorine-based solvent manufactured by AGC Asahi Glass Co., Ltd.), and Fluorinert FC-75 (a liquid containing perfluoro(2-butyltetrahydrofuran) manufactured by 3M Japan Limited).

[0123] -Stimulus generating component- The method for ejecting the ink for inkjet recording from the ejection head is not particularly limited, and examples thereof include a method in which a stimulus to be applied to the ink for inkjet recording is generated from the stimulus generating member, thereby ejecting the ink for inkjet recording.

[0124] The stimulus is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include heat (temperature), pressure, vibration, light, etc. These may be used alone or in combination of two or more. Among these, preferred examples of the stimulus include heat and pressure.

[0125] Examples of the stimulus generating member include a heating member, a pressure applying member, a piezoelectric element, a vibration generating member, an ultrasonic oscillator, a light, etc. Specific examples of the stimulus generating member include a piezoelectric actuator such as a piezoelectric element, a thermal actuator that utilizes a phase change caused by film boiling of the ink for inkjet recording using an electrothermal conversion element such as a heating resistor, a shape memory alloy actuator that uses a metal phase change caused by a temperature change, and an electrostatic actuator that uses electrostatic force. These may be used alone or in combination of two or more.

[0126] When the stimulus is "heat," thermal energy corresponding to a recording signal is applied to the inkjet recording ink in the ejection head using, for example, a thermal head. The thermal energy is used to generate bubbles in the ink for inkjet recording, and the pressure of the bubbles causes the ink for inkjet recording to be ejected as droplets from the nozzle holes of the nozzle plate.

[0127] When the stimulus is "pressure," for example, the piezoelectric element is bent by applying a voltage to the piezoelectric element bonded to a position called the pressure chamber in the ink flow path inside the ink ejection head. The piezoelectric element is bent, thereby contracting the volume of the pressure chamber, and the ink for ink jet recording is ejected as droplets from the nozzle hole of the ejection head. Among these, when the stimulus is "pressure," the piezo method in which a voltage is applied to a piezo element to eject the ink for ink-jet recording is preferred.

[0128] <<Other processes and other means>> -Pressure chamber- The pressure chambers are arranged to correspond individually to the plurality of nozzle holes provided in the nozzle plate. The pressure chambers are a plurality of individual flow paths that communicate with the nozzle holes, and may also be referred to as ink flow paths, pressurized liquid chambers, pressure chambers, ejection chambers, liquid chambers, etc.

[0129] -Heating process and heating means- The heating step is a step of heating the printed surface and the back surface of the substrate, and can be performed before, during, or after printing. The heating means is a means for heating the printed surface and the back surface of the substrate. The heating step is preferably performed by the heating unit, and the inkjet recording ink printed on the substrate is dried by the heating step and the heating unit. The heating means is not particularly limited, but for example, a hot air heater or an infrared heater can be used.

[0130] -Pretreatment process and pretreatment means- The pretreatment step is a step of discharging a pretreatment liquid onto the substrate. The pretreatment means is a means for discharging a pretreatment liquid onto the substrate. The pretreatment step can be suitably carried out by the pretreatment means. The pretreatment unit preferably includes a pretreatment liquid container that contains the pretreatment liquid, and a pretreatment liquid ejection head. The method for discharging the pretreatment liquid is preferably an inkjet recording method, but methods other than the inkjet recording method, such as a blade coating method, a roll coating method, or a spray coating method, may also be used.

[0131] -Pretreatment liquid- The pretreatment liquid is not particularly limited and can be appropriately selected depending on the purpose. For example, the pretreatment liquid contains a flocculant, an organic solvent, and water, and may further contain, as necessary, a surfactant, an antifoaming agent, a pH adjuster, an antiseptic / fungal agent, a rust inhibitor, etc. The organic solvent, surfactant, defoaming agent, pH adjuster, antiseptic and antifungal agent, and rust inhibitor in the pretreatment liquid may be the same as the materials used in the inkjet recording ink described above, and other materials used in known pretreatment liquids may also be used. The type of the flocculant is not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include water-soluble cationic polymers, acids, and polyvalent metal salts.

[0132] <<Post-processing step and post-processing means>> The post-treatment step is a step of ejecting a post-treatment liquid onto a recording medium. The post-treatment unit is a unit that ejects a post-treatment liquid onto a recording medium. The post-treatment step can be suitably carried out by the post-treatment means. The post-treatment unit preferably includes a post-treatment liquid container that contains the post-treatment liquid, and a post-treatment liquid ejection head. The method for ejecting the post-treatment liquid is preferably an inkjet recording method, but methods other than the inkjet recording method, such as a blade coating method, a roll coating method, or a spray coating method, may also be used.

[0133] -Post-processing liquid- The post-treatment liquid is not particularly limited as long as it can form a transparent layer, and is obtained by appropriately selecting and mixing, as needed, from, for example, organic solvents, water, resins, surfactants, antifoaming agents, pH adjusters, antiseptics and fungicides, and anti-rust agents. The organic solvent, the water, the resin, the surfactant, the defoaming agent, the pH adjuster, the antiseptic and antifungal agent, and the rust inhibitor in the post-treatment liquid can be the same materials as those used in the inkjet recording ink described above, and other materials used in known post-treatment liquids can also be used. The post-treatment liquid may be applied to the entire print area formed on the substrate, or may be applied only to the area where the ink image is formed using the ink for inkjet recording.

[0134] The inkjet printing method and inkjet printing apparatus of the present invention will be described below with reference to the drawings, but the present invention is not limited thereto.

[0135] An example of the inkjet printing apparatus will be described with reference to FIGS. 1 and 2. FIG. 1 is a perspective view of the inkjet printing apparatus. FIG. 2 is a perspective view of a main tank. An image forming apparatus 400, which is an example of an inkjet printing apparatus, is a serial image forming apparatus. A mechanism unit 420 is provided within an 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 from a packaging material such as an aluminum laminate film. The ink storage unit 411 is housed in a storage container case 414 made of, for example, plastic. As a result, the main tanks 410 are used as ink cartridges for each color. On the other hand, a cartridge holder 404 is provided at the back of the opening when the cover 401c of the apparatus main body is opened. A main tank 410 is detachably attached to the cartridge holder 404. As a result, in the image forming apparatus 400, each ink outlet 413 of the main tank 410 communicates with the ejection head 434 for each color via the supply tube 436 for each color, and ink can be ejected from the ejection head 434 onto a recording medium.

[0136] The inkjet printing apparatus may include not only a portion that ejects the inkjet recording ink, but also a device called a pre-treatment device and a post-treatment device. As an example of a pre-treatment device and a post-treatment device, a liquid storage unit containing a pre-treatment liquid and a post-treatment liquid and a liquid ejection head are added, and the pre-treatment liquid and the post-treatment liquid are ejected by an inkjet recording method, as in the case of inks such as black (K), cyan (C), magenta (M), and yellow (Y).

[0137] A known three-dimensional modeling device can be used to form a three-dimensional object, and is not particularly limited. For example, a device equipped with a storage means, supply means, discharge means, drying means, etc. for the inkjet recording ink can be used. Three-dimensional models include three-dimensional models obtained by, for example, applying multiple coats of the inkjet recording ink. Also included are molded products obtained by processing a structure on a substrate to which the inkjet recording ink has been applied. The molded products are, for example, records and structures formed in a sheet or film form that have been subjected to molding processes such as heat stretching and punching. The molded products are suitable for use in applications where the surface is decorated and then molded, such as meters and operation panel panels for automobiles, office automation equipment, electrical equipment, electronic devices, cameras, etc.

[0138] Next, an example of the ejection head of the inkjet recording apparatus of the present invention will be described with reference to FIGS. Note that Figure 3 is an exploded perspective view of the ejection head, Figure 4 is a cross-sectional view taken along a direction perpendicular to the nozzle arrangement direction of the ejection head (longitudinal direction of the liquid chamber), and Figure 5 is a cross-sectional view taken along the nozzle arrangement direction of the ejection head (lateral direction of the liquid chamber).

[0139] The ejection head has a flow path plate (liquid chamber substrate, flow path member) 1, a vibration plate member 2 joined to the lower surface of this 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. The ejection head has a plurality of liquid chambers 6 as individual flow paths that communicate with a plurality of nozzle holes 4, which eject droplets (droplets of ink for inkjet recording), via nozzle communication paths 5, a fluid resistance section 7 that also serves as a supply path for supplying ink for inkjet recording to the liquid chambers 6, and a communication section 8 that communicates with the liquid chambers 6 via the fluid resistance section 7. Ink is supplied to the communication section 8 from a common liquid chamber 10 formed in a frame member 17 via a supply port 19 formed in a vibration plate member 2. The plurality of liquid chambers may also be referred to as pressurized liquid chambers, pressure chambers, flow paths, etc.

[0140] The flow path plate 1 is formed by etching a silicone substrate to form openings for the nozzle communication passages 5, the liquid chambers 6, the fluid resistance portions 7, and the like. The flow path plate 1 can also be formed by etching a SUS substrate using an acid etching solution or by machining such as punching (pressing).

[0141] The vibration plate member 2 has vibration regions (diaphragm portions) 2a that form the wall surfaces of the respective liquid chambers 6. The vibration plate member 2 has island-shaped convex portions 2b on the outer side of the vibration region 2a (the side opposite the liquid chambers 6). The upper end surfaces (bonding surfaces) of the piezoelectric element pillars 12A, 12B of the stacked piezoelectric elements 12, 12 that act as drive elements (actuator means, pressure generating means) that deform the vibration region 2a and generate energy to eject droplets are bonded to the island-shaped convex portions 2b. The lower end surfaces of the stacked piezoelectric elements 12 are bonded to a base member 13.

[0142] Here, the piezoelectric element 12 is formed by alternately laminating piezoelectric material layers 21 such as PZT and internal electrodes 22a, 22b. The internal electrodes 22a, 22b of the piezoelectric element 12 are drawn out to the end faces, i.e., the side faces of the piezoelectric element 12 that are approximately perpendicular to the diaphragm member 2. The piezoelectric element 12 is connected to end face electrodes (external electrodes) 23a, 23b formed on the side faces of the piezoelectric element 12 that are approximately perpendicular to the diaphragm member 2, and applying a voltage to the end face electrodes (external electrodes) 23a, 23b generates displacement in the lamination direction. This piezoelectric element 12 is formed by forming a required number of piezoelectric element columns 12A, 12B in one piezoelectric element member by groove processing using half-cut dicing.

[0143] Although the piezoelectric element columns 12A and 12B of the piezoelectric element 12 are the same, the piezoelectric element column that is driven by applying a drive waveform is called the driving piezoelectric element column 12A, and the piezoelectric element column that is used simply as a support column without applying a drive waveform is called the support piezoelectric element column 12B. In this case, either a double pitch configuration in which the driving piezoelectric element columns 12A and the support piezoelectric element columns 12B are used alternately, or a normal pitch configuration in which all the piezoelectric element columns are used as driving piezoelectric element columns 12A can be employed.

[0144] As a result, the piezoelectric element columns 12A and 12B of the piezoelectric element 12 are configured to have two rows of driving elements (rows of driving piezoelectric element columns 12A) in which a plurality of driving piezoelectric element columns 12A as driving elements are arranged side by side on the base member 13.

[0145] The piezoelectric direction of the multi-layer piezoelectric element 12 is configured to use displacement in the stacking direction of the piezoelectric material layers to pressurize the ink in the liquid chamber 6. The piezoelectric direction of the multi-layer piezoelectric element 12 can also be configured to use displacement in the surface direction of the piezoelectric material layers, i.e., in the direction perpendicular to the electric field, to pressurize the ink in the pressurized liquid chamber 6.

[0146] Furthermore, the piezoelectric element material is not particularly limited, and electromechanical 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 type piezoelectric element is used, a single-plate piezoelectric element may also be used. The single-plate piezoelectric element may be one that has been machined, a thick film that has been screen printed and sintered, or a thin film that has been formed by sputtering, vapor deposition, or a sol-gel method. Furthermore, the multi-layer piezoelectric elements 12 provided on one base member 13 may be arranged in one row or in multiple rows.

[0147] The external electrodes 23a of the driving piezoelectric element columns 12A of the piezoelectric element 12 are directly connected to an FPC 15 as wiring means by soldering in order to apply a driving signal. A driving circuit (driver IC) 16 is mounted on the FPC 15 to selectively apply a driving waveform to each of the driving piezoelectric element columns 12A of the piezoelectric element 12. The external electrodes 23b of all the driving piezoelectric element columns 12A are electrically connected in common and are also connected to the common wiring of the FPC 15 by the same solder member. Also, here, the output terminal portion of the FPC 15 that is joined to the piezoelectric element 12 is solder-plated to enable solder joining, but solder plating may be applied to the piezoelectric element 12 side instead of the FPC 15. As for the joining method, in addition to solder joining, joining using an anisotropic conductive film or wire bonding can also be used.

[0148] The nozzle plate 3 is configured by forming an ink-repellent film 32 on the droplet ejection side (surface in the ejection direction: ejection surface, or surface opposite the liquid chamber 6 side, nozzle formation surface) of a nozzle substrate 31 in which hole portions that form nozzle holes 4 with a diameter of 10 μm or more and 35 μm or less are formed corresponding to each liquid chamber 6.

[0149] In addition, a frame member 17 formed by injection molding of epoxy resin or polyphenylene sulfite is joined to the outer periphery of the piezoelectric actuator unit 100, which is composed of a piezoelectric element 12 mounted (connected) to an FPC 15 and a base member 13. This frame member 17 forms the common liquid chamber 10 described above, and also 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 ink storage container (not shown).

[0150] 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, causing the volume of the liquid chamber 6 to expand, and ink flows into the liquid chamber 6. Thereafter, the voltage applied to the piezoelectric element columns 12A is increased, causing the piezoelectric element columns 12A to expand in the stacking direction. By deforming the vibration plate member 2 toward the nozzle hole 4 and contracting the volume of the liquid chamber 6, the ink in the liquid chamber 6 is pressurized, and ink droplets are ejected (jetted) from the nozzle hole 4.

[0151] Then, by returning the voltage applied to the piezoelectric element 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 for discharging the next droplet begins.

[0152] The method of driving the ejection head is not limited to the above example (pull-push shot), and it is also possible to perform pull shot or push shot depending on the driving waveform applied.

[0153] 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 of the nozzle plate. The nozzle plate 3 is formed by depositing, on the ejection surface 31a of a nozzle substrate 31 made of, for example, a Ni metal plate, a Ti layer 33 as a base layer, an SiO2 film 34, and a perfluoropolyether film having alkoxysilane in its molecules (this film is called an "ink-repellent film") 32 in this order from the surface of the nozzle substrate 31. Near the outlet of the inner wall surface 4a of the nozzle hole 4, a base layer (Ti layer) 33 is formed continuously from the ejection surface on the SiO2 film 34 formed on the liquid chamber surface 31b of the nozzle substrate 31, and the base layer (Ti layer) 33 is exposed on the outermost surface.

[0154] The nozzle substrate 31 may be made of a Ni metal plate or the like, but is not limited to this.

[0155] Here, the ink-repellent film 32 of the nozzle plate 3 is formed by vapor deposition, and no vapor-deposited film for forming the ink-repellent film 32 is formed on the inner wall surface of the nozzle hole 4 near the outlet. As a result, the nozzle plate 3 can stably eject droplets without causing ejection defects or impairing the liquid filling property. [Example]

[0156] The present invention will be specifically described below with reference to Preparation Examples, Examples, and Comparative Examples, but the present invention is not limited to these Preparation Examples and Examples. In the Preparation Examples, Examples, and Comparative Examples, "%" indicates "% by mass" unless otherwise specified.

[0157] (Preparation Example 1) <Preparation of cyan pigment dispersion> A cyan pigment, CI Pigment Blue 15:3, was subjected to low-temperature plasma treatment to prepare a cyan pigment having a carboxylic acid group introduced therein. This cyan pigment was dispersed in ion-exchanged water and then desalted and concentrated using an ultrafiltration membrane to obtain a "cyan pigment dispersion" of Preparation Example 1 having a pigment concentration (solid content concentration) of 15% by mass.

[0158] (Examples 1 to 7 and Comparative Examples 1 to 5) Each inkjet recording ink was prepared according to the following procedure. The colorant (cyan pigment dispersion liquid prepared in Preparation Example 1), resin, organic solvent, antiseptic and rust inhibitor, surfactant, antifoaming agent, and pH adjuster were mixed and stirred according to the compositions and contents shown in Tables 1 and 2 below, and then the mixture was filtered under pressure using a polyvinylidene fluoride membrane filter with an average pore size of 1.5 μm to remove coarse particles and dust, thereby preparing inkjet recording inks for Examples 1 to 7 and Comparative Examples 1 to 4. In Tables 1 and 2, the content of each material is shown as a solid content. The storage modulus (a) (Pa), evaporation rate (b) (%), and "(a) x (b)" are all rounded to two decimal places.

[0159] <Physical properties of inkjet recording ink> The physical properties of the inkjet recording inks obtained in Examples 1 to 7 and Comparative Examples 1 to 4, including storage modulus (a), evaporation rate (b), and viscosity (c), were measured as follows. The results are shown in Tables 1 and 2 below.

[0160] -Storage modulus (a)- The storage modulus (Pa) of each of the inkjet recording inks obtained in Examples 1 to 7 and Comparative Examples 1 to 4 was measured under the following measurement conditions. [Measurement conditions] Equipment: Rheometer (MCR-301, manufactured by Anton Paar) · Measurement frequency: 2Hz · Measurement temperature: 25℃ Displacement: 0.01% to 100%

[0161] -Evaporation rate (b)- 1 g of each of the inkjet recording inks obtained in Examples 1 to 7 and Comparative Examples 1 to 4 was weighed into a Petri dish with a diameter of 30 mm. After leaving it in a room temperature, low humidity environment (25°C, RT 20%) for 1 hour, the mass (hereinafter referred to as "Yg") was measured again, and the evaporation rate (%) of the inkjet recording ink was calculated using the following formula (1). Evaporation rate (%) = (1 - Y) / 1 x 100 Equation (1)

[0162] -Viscosity(c)- The viscosity (mPa s) at 25°C of each of the inkjet recording inks obtained in Examples 1 to 7 and Comparative Examples 1 to 4 was measured using an E-type viscometer (TV-35, manufactured by Toki Sangyo Co., Ltd.) at 25°C under the following measurement conditions: a standard cone rotor (1°34' x R24), a sample liquid volume of 1.2 mL, a rotation speed of 50 rpm, and a time period of 3 minutes.

[0163] <Evaluation of inkjet recording ink> The inkjet recording inks obtained in Examples 1 to 7 and Comparative Examples 1 to 4 were evaluated for deviation in writing direction and dripping as follows. The results are shown in Tables 1 and 2 below.

[0164] -Bent writing- Using an auto body printer (manufactured by Ricoh Digital Painting Co., Ltd.), lines were printed on an A2 size aluminum composite board, the linearity at the start of printing was visually confirmed, and the "start of printing curve" was evaluated based on the following evaluation criteria. The printing surface of the aluminum composite plate was flat and was placed so that the printing surface was at an angle of 0° or 180° with respect to the direction of gravity, and the ejection direction of the inkjet recording ink was perpendicular to the printing surface. An example of evaluation standard "A" is shown in Figure 9, and an example of evaluation standard "D" is shown in Figure 10. Evaluation standards "AA", "A", and "B" are levels that pose no problems in practical use. [Evaluation criteria] AA: No distortion at the beginning of writing. A: A slight bend can be seen at the beginning of writing. B: The line starts to curve, but returns to a straight line quickly (within 1 cm). C: The writing starts to bend and is difficult to return to its original shape (returns to a straight line within 3 cm). D: The writing starts to bend and is difficult to return to a straight line (it takes more than 3 cm to return to a straight line).

[0165] -Dripping- Using an auto body printer (manufactured by Ricoh Digital Painting Co., Ltd.), lines were printed on an A2 size aluminum composite board, a 5 cm square solid patch was printed, and the occurrence of dripping was visually confirmed and evaluated based on the following evaluation criteria. The printing surface of the aluminum composite plate was flat and was placed so that the printing surface was at an angle of 0° or 180° with respect to the direction of gravity, and the ejection direction of the inkjet recording ink was perpendicular to the printing surface. The evaluation criteria "AA", "A", and "B" are levels that pose no problems in practical use. [Evaluation criteria] AA: No dripping at all. A: From a distance of 1m, unevenness due to dripping can be seen within the solid patch. B: At a distance of 3m, unevenness due to dripping can be seen within the solid patch. C: At a distance of 5m, unevenness due to dripping can be seen within the solid patch. D: Dripping occurs outside the solid patch.

[0166] [Table 1]

[0167] [Table 2]

[0168] The details of the various materials used in Examples 1 to 7 and Comparative Examples 1 to 4 are as follows. -resin- The "urethane resin" used was Takelac (registered trademark) W-5661 (MFT 70°C) (manufactured by Mitsui Chemicals, Inc.). The silicone-acrylic resin used was Movinyl (registered trademark) 7523 (MFT 25°C), manufactured by Japan Coating Resin Co., Ltd. -Anti-corrosion and anti-rust agent- The antiseptic and rust inhibitor used was Proxel (registered trademark) LV (main ingredient: 1,2-benzisothiazolin-3-one) (manufactured by Avecia). -Surfactants- The nonionic surfactant used was TRITON HW-1000 (polyoxyethylene alkyl ether, manufactured by Dow Chemical). -Antifoaming agent- The 2,4,7,9-tetramethyl-4,7-decanediol used was Surfynol AD01 (manufactured by Nissin Chemical Industry Co., Ltd.).

[0169] The present invention includes, for example, the following aspects. <1> An inkjet recording ink containing a colorant, a resin, a water-soluble organic solvent, and water, the storage elastic modulus (a) of the inkjet recording ink is 0.1 Pa or more; The evaporation rate (b) of the inkjet recording ink calculated by the following formula (1) is 14.5%≦(b)≦85.0%, and The inkjet recording ink is characterized in that 1.45≦(a)×(b)≦8.5 is satisfied. Evaporation rate (b)(%)=(XY) / X×100 ··· Equation (1) In the formula (1), "X" represents the initial mass (g) of the inkjet recording ink, and "Y" represents the mass (g) of the inkjet recording ink after it has been left to stand for 1 hour in an environment of 25°C and a relative humidity of 20%. <2> the viscosity (c) of the ink for ink-jet recording at 25°C is 0.5 mPa·s≦(c)≦10 mPa·s; <1> 1. The ink for ink-jet recording according to claim 1. <3> The resin contains a resin having a minimum film-forming temperature of 0°C or higher and 50°C or lower. <1> from <2> 1. The ink for ink-jet recording according to claim 1, wherein the ink is a fluororesin. <4> The resin further contains a resin having a minimum film-forming temperature of more than 50°C. <3> 1. The ink for ink-jet recording according to claim 1. <5> The above-mentioned is used for printing on metal or a surface of a metal that has been surface-treated. <1> from <4> 1. The ink for ink-jet recording according to claim 1, wherein the ink is a fluororesin. <6> For the substrate, <1> from <5> 1. An inkjet printing method comprising an ink ejection step of ejecting the ink for inkjet recording according to any one of the above items. <7> In the ejection step, the substrate is placed so that the printing surface thereof is substantially horizontal with respect to the direction of gravity, and the ejection direction of the inkjet recording ink is perpendicular to the printing surface of the substrate. <6> 2. The inkjet printing method according to claim 1, wherein the ink is a fluororesin. <8> The aforementioned <1> from <5> an ink reservoir that accommodates the ink for ink-jet recording according to any one of the above items; an ejection head that ejects the ink for inkjet recording; The inkjet printing apparatus is characterized by having:

[0170] The aforementioned <1> from <4> The ink for ink-jet recording according to any one of the preceding claims. <5> from <6> The inkjet printing method according to any one of the preceding claims, <7> The inkjet printing apparatus described in the above can solve the above-mentioned problems in the prior art and achieve the object of the present invention. [Explanation of symbols]

[0171] 400 Image forming device 401 Exterior 401c cover 404 Cartridge Holder 410 Main Tank 411 Ink storage unit 413 Ink outlet 414 Storage container case 420 Mechanism Department 434 Discharge Head 436 Supply Tube 1 Flow path plate 2. Diaphragm member 2a Vibration area 2b Island-shaped convex part 3 Nozzle Plate 4 nozzle holes 4a Inner wall surface 5 Nozzle connection passage 6 Liquid chamber 7 Fluid resistance section 8 Communication section 10 Common liquid chamber 12 Piezoelectric element 12A, B Piezoelectric element column 13 Base material 15 FPC 16 Drive circuit 17 Frame members 19 Supply port 21 Piezoelectric material layer 22a,b Internal electrode 23a,b End electrode 31 Nozzle board 31a Discharge surface 31b Liquid chamber surface 32 Ink-repellent film 33 Ti layer 34 SiO2 film 100 Piezoelectric actuator unit [Prior art documents] [Patent documents]

[0172] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-11079

Claims

1. An inkjet recording ink containing a self-dispersing pigment having a hydrophilic functional group introduced therein, a resin, a water-soluble organic solvent having a boiling point of 250°C or less, a surfactant, and water, the content of the self-dispersing pigment having a hydrophilic functional group introduced therein in the inkjet recording ink is 0.1% by mass or more and 15% by mass or less, the resin contains at least one of a urethane resin and an acrylic-silicone resin, and the content of the resin in the inkjet recording ink is 5% by mass or more and 8% by mass or less; the water-soluble organic solvent contains at least 1,2-butanediol and at least one of ethanol and propylene glycol monoethyl ether, and the content of the water-soluble organic solvent in the inkjet recording ink is 3% by mass or more and 60% by mass or less; the surfactant contains polyoxyethylene alkyl ether, and the content of the surfactant in the inkjet recording ink is 0.05% by mass or more and 5% by mass or less; the content of the water in the inkjet recording ink is 20% by mass or more and 75% by mass or less, the storage elastic modulus (a) of the inkjet recording ink is 0.1 Pa or more; the evaporation rate (b) of the inkjet recording ink calculated by the following formula (1) is 14.5%≦(b)≦85.0%, and An ink for ink jet recording, wherein 1.45≦(a)×(b)≦8.5 is satisfied. Evaporation rate (b) (%) = (X - Y) / X × 100 Formula (1) In the formula (1), "X" represents the initial mass (g) of the inkjet recording ink, and "Y" represents the mass (g) of the inkjet recording ink after being left to stand for 1 hour in an environment of 25°C and a relative humidity of 20%.

2. 2. The ink jet recording ink according to claim 1, wherein the viscosity (c) of the ink jet recording ink at 25° C. is 0.5 mPa·s≦(c)≦10 mPa·s.

3. 3. The ink jet recording ink according to claim 1, wherein the resin contains a resin having a minimum film-forming temperature of 0°C or higher and 50°C or lower.

4. The ink jet recording ink according to claim 3 , wherein the resin further contains a resin having a minimum film-forming temperature of more than 50° C.

5. The ink for ink-jet recording according to claim 1 , which is used for printing on a metal or a surface of a metal that has been surface-treated.

6. An inkjet printing method comprising an ink ejection step of ejecting the ink for inkjet recording according to claim 1 onto a substrate.

7. 7. The inkjet printing method according to claim 6, wherein the ejection step comprises placing the substrate so that the printing surface of the substrate is substantially horizontal with respect to the direction of gravity, and ejecting the ink for inkjet recording in a direction perpendicular to the printing surface of the substrate.

8. an ink reservoir that contains the ink for ink-jet recording according to any one of claims 1 to 5; an ejection head that ejects the ink for inkjet recording; 1. An inkjet printing apparatus comprising:

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