Ink, ink manufacturing method, printing method, and printing device

Abstract

To provide an ink which has both fixability and liquid permeability, and an ink which has high image density, excellent liquid permeability, and excellent discharge stability.SOLUTION: An ink contains water, an organic solvent, a polyurethane resin, and a cyclic ester including a structure represented by general formula (I) in the figure, where the content of the cyclic ester having a crystal with a particle diameter of 1 μm or more is less than 4 ppm of the total of the ink after the ink is stored to stand in a normal temperature environment (25±5°C) for one month.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an ink, a method for producing the ink, a printing method, and a printing apparatus. [Background technology]

[0002] Inkjet recording methods have been rapidly gaining popularity in recent years because they enable color image recording with ease, have low running costs, etc. However, this method has the problem that, depending on the combination of ink and recording medium, image defects such as character bleeding are likely to occur, resulting in a significant decrease in image quality. For example, non-permeable media for signage do not absorb ink, so there are issues with images bleeding severely and not fixing properly. Furthermore, when recording is performed on coated paper using fillers such as calcium carbonate or kaolin as the coating layer material, such as coated paper for commercial printing or publication printing, the image may bleed severely or the density may not be expressed.

[0003] Therefore, in order to improve drying and fixation properties, ink compositions are changing to use hydrophobic organic solvents, such as organic solvents with an SP value of 8.9 to 12.0 or organic solvents with high vapor pressure, and also to use more water-dispersible resin particles.

[0004] Furthermore, because non-permeable media for signage have poor ink fixation properties, it is necessary to select water-dispersible resin particle materials, and the amount of these particles added is increasing. In particular, to improve the ink fixation properties of non-permeable media films, there are increasing cases of using polyurethane resin particles synthesized from polyol raw materials containing aromatic rings as ink components. Although the image quality has improved due to the above-mentioned changes in circumstances, problems have arisen in the storage stability, permeability and ejection stability of the ink.

[0005] Patent Document 1 discloses an invention relating to an aqueous inkjet ink that not only has excellent drying properties and print fixation when printed on the surface of a hydrophobic resin medium, but also has excellent dispersion stability of the resin binder. Claim 1 specifies that the ink contains an amide solvent having a specific structure, an aqueous emulsion polymer, and a crosslinker for the polymer. Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide an ink that has both fixability and liquid permeability. [Means for solving the problem]

[0007] The above issues are as follows: <1> This problem is solved by the invention. <1> An ink containing water, an organic solvent, and polyurethane resin particles, the ink also containing a cyclic ester having a structure represented by the following general formula (I), and after the ink is left to stand for one month in a room temperature environment (25±5°C), the content of crystals of the cyclic ester having a particle size of 1 μm or more is less than 4 ppm in the entire ink. [ka] [Effects of the Invention]

[0008] An object of the present invention is to provide an ink that has both fixability and liquid permeability. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing an example of a printing apparatus according to the present invention. [Figure 2] FIG. 2 is a diagram showing an example of a recording apparatus using the ink of the present invention. [Figure 3] FIG. 3 is a perspective view of the main tank that contains the ink of the present invention. [Figure 4]FIG. 4 is an exploded perspective view showing an example of an ink ejection head used in the present invention. [Figure 5] FIG. 5 is a cross-sectional explanatory view taken along the longitudinal direction of the liquid chamber of the ink ejection head. [Figure 6] FIG. 6 is a cross-sectional explanatory view taken along the lateral direction of the liquid chamber of the ink ejection head. [Figure 7] FIG. 7 is a plan view illustrating the nozzle plate of the ink ejection head. [Figure 8] FIG. 8 is a cross-sectional view illustrating the nozzle plate shown in FIG. [Figure 9] FIG. 9 is an enlarged cross-sectional explanatory view of one nozzle portion. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, the present invention <1> The present invention will be described in detail below. <1> The present invention relates to the following embodiments: <2> ~ <21> These will also be explained below. <1> An ink containing water, an organic solvent, and polyurethane resin particles, the ink also containing a cyclic ester having a structure represented by the following general formula (I), and after the ink is left to stand for one month in a room temperature environment (25±5°C), the content of crystals of the cyclic ester having a particle size of 1 μm or more is less than 4 ppm in the entire ink. [ka] <2> The polyurethane resin contains a polyurethane resin having a structure represented by the general formula (I). <1> The ink described in <3> The ink contains a colorant. <1> or <2> The ink described in <4> The ink contains polyurethane resin particles in a solid content of 3% by mass or more, and the solid content ratio of the colorant to the polyurethane resin particles is 1.0:(2.0 to 11.0). <3> The ink described in <5> The above, wherein the colorant is a pigment. <3> or <4> The ink described in <6> The organic solvent contains a diol compound and an organic solvent having a solubility parameter (SP value) of 8.9 to 12.0. <1> ~ <5> 1. The ink according to any one of the preceding claims. <7> The ink has a pH of 8.5 or higher. <1> ~ <6> 1. The ink according to any one of the preceding claims. <8> The ink containing a strongly basic compound <7> The ink described in <9> The method according to any one of the preceding claims, wherein the strongly basic compound is sodium hydroxide or potassium hydroxide. <8> The ink described in <10> The ink further contains a polyether-modified siloxane compound as a surfactant. <1> ~ <9> 1. The ink according to any one of the preceding claims. <11> A method for producing an ink containing water, an organic solvent, and polyurethane resin particles, comprising the steps of: mixing water, an organic solvent, and polyurethane resin particles; and heating the mixture obtained by the above step at a temperature of 40°C or higher but lower than 70°C for 6 hours or longer. <1> ~ <10> 1. A method for producing the ink according to any one of the preceding claims. <12> The ink further contains a colorant, and the method comprises the steps of mixing water, an organic solvent, polyurethane resin particles, and the colorant, and heating the mixture obtained by the steps at 40°C or higher but lower than 70°C for 6 hours or longer. <11> A method for producing the ink described in <13> the above <1> ~ <10> 10. A printing method comprising the step of depositing the ink according to any one of the above onto a substrate and printing. <14> the step of depositing the ink on a substrate and printing is a step of ejecting the ink from an ink ejection head having a nozzle plate that ejects the ink and depositing the ink on the substrate; The ink contains water, an organic solvent, polyurethane resin particles, and a cyclic ester having a structure represented by the following general formula (I), and after being left to stand for one month in a room temperature environment (25±5°C), the content of crystals of the cyclic ester having a particle size of 1 μm or more is less than 4 ppm of the entire ink, and the receding contact angle with respect to the nozzle plate is 35° or more. <13> The printing method described in [ka] <15> the above <1> ~ <10> 10. A printing device comprising an ink cartridge containing the ink according to any one of claims 1 to 9, and a discharge means for discharging the ink. <16> The ink cartridge according to any one of the preceding claims, wherein a filter is provided between the ink flow path and the ink ejection means. <15> The printing device described in <17> The ink ejection means is an ink ejection head having a nozzle plate for ejecting the ink, and the receding contact angle of the ink with respect to the nozzle plate is 35° or more. <15> or <16> The printing device described in <18> The nozzle plate has an ink-repellent film, and the ink-repellent film of the nozzle plate contains a fluorine-containing acrylate ester polymer. <17> The printing device described in <19> The fluorine-containing acrylate ester polymer comprises a polymer obtained by polymerizing at least one of a compound represented by the following general formula (II) and a compound represented by the following general formula (III): <18> The printing device described in [ka] [ka] In the general formulas (II) and (III), X represents a hydrogen atom, a linear or branched alkyl group having 1 to 21 carbon atoms, a halogen atom, a CFX1X2 group (wherein X1 and X2 are each independently 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, or a substituted or unsubstituted phenyl group; R1 represents an alkyl group having 1 to 18 carbon atoms; R2 represents an alkylene group having 2 to 6 carbon atoms; R3 represents an alkylene group having 2 to 6 carbon atoms; Y represents an acid group; and Rf represents a linear or branched fluoroalkyl group having 1 to 21 carbon atoms. m represents 1 to 10, n represents 2 to 90, p represents 1 to 90, and q represents 1 to 10. <20> The fluorine-containing acrylate ester polymer comprises a polymer having at least one of a structural unit represented by the following general formula (IV) and a structural unit represented by the following general formula (V): <19> The printing device described in [ka] [ka] In the general formulas (IV) and (V), X represents a hydrogen atom, a linear or branched alkyl group having 1 to 21 carbon atoms, a halogen atom, a CFX1X2 group (wherein X1 and X2 are each independently 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, or a substituted or unsubstituted phenyl group; R1 represents an alkyl group having 1 to 18 carbon atoms; R2 represents an alkylene group having 2 to 6 carbon atoms; R3 represents an alkylene group having 2 to 6 carbon atoms; Y represents an acid group; and Rf represents a linear or branched fluoroalkyl group having 1 to 21 carbon atoms. m represents 1 to 10, n represents 2 to 90, p represents 1 to 90, and q represents 1 to 10. <21> The ink-repellent film comprises a polymer having a fluorine-containing heterocyclic structure in its main chain. <18> ~ <20> 10. The printing device according to claim 9, wherein

[0011] (ink) The ink of the present invention comprises water, an organic solvent, and polyurethane resin particles, and further comprises a cyclic ester having a structure represented by the following general formula (I), and after the ink is left to stand for one month in a room temperature environment (25±5°C), the content of crystals of the cyclic ester having a particle size of 1 μm or more is less than 4 ppm in the entire ink. [ka]

[0012] In particular, non-permeable media for signage have poor ink fixation properties, so it is necessary to select a water-dispersible resin particle material or increase the amount added. Furthermore, to improve the ink fixation properties of non-permeable media films, there are increasing cases of using polyurethane resin particles synthesized from polyol raw materials containing aromatic rings with the structure shown in the following general formula (I) as an ink component. [ka]

[0013] However, the polyol raw material containing an aromatic ring having the structure represented by general formula (I), which is used as a raw material for polyurethane resin particles, contains, as a by-product, a cyclic ester having the structure represented by general formula (I), which is difficult to dissolve in water and water-soluble solvents.Since this cyclic ester is contained in the high-viscosity polyol, it becomes polyurethane resin particles in a state where it cannot be removed. When ink is produced using the polyurethane resin particles and stored in an ink pack at room temperature (25±5°C) for one month or more, the cyclic ester compound having the structure represented by general formula (I) elutes from the polyurethane resin particles, and cyclic ester crystals having the structure represented by general formula (I) precipitate in the ink. The precipitation of the cyclic ester crystals in the ink has been found to deteriorate the ink permeability and further make the ink ejection unstable.

[0014] The cyclic ester having the structure represented by general formula (I) contained in the ink is thought to include raw materials used in the production of polyurethane resin and by-products of the raw materials, and examples thereof include the cyclic ester represented by the following structural formula A. [ka] In the structural formula (A), R represents alkylene, and is usually alkylene having 3 to 10 carbon atoms. It has been found that raw materials and by-products that are not removed during the refining or ink manufacturing process end up being contained in the ink, and over time, the cyclic ester having the structure represented by general formula (I) crystallizes in the ink. The inventors have found that the object of the present invention can be achieved by making the content of crystals of the cyclic ester having the structure represented by general formula (I) with a particle size of 1 μm or more in the ink less than 4 ppm of the entire ink. Furthermore, according to the present invention, it is possible to provide an ink that has high fixability and drying properties even on non-penetrable media for signage and commercial printing paper, and that also has high image density, good liquid permeability and ejection stability, and excellent storage stability.

[0015] Cyclic esters having the structure represented by general formula (I) are generally insoluble in water. Even if no cyclic esters having the structure represented by general formula (I) are found in the water content of an aqueous dispersion of urethane resin particles, when the aqueous dispersion of urethane resin particles is mixed with other components such as an organic solvent to produce an ink, crystals of the cyclic ester having the structure represented by general formula (I) may precipitate in the ink. It is presumed that the cyclic ester having the structure represented by general formula (I) contained in the urethane resin particles dissolves and crystallizes upon mixing with the organic solvent.

[0016] It was found that when the ink was stored at room temperature (25±5°C) for one month or more, if the ink contained 4 ppm or more of cyclic ester crystals with a particle size of 1 μm or more, practical problems with liquid permeability occurred, ultimately resulting in ejection defects. It was also confirmed that if the ink contained less than 4 ppm of cyclic ester crystals with a particle size of 1 μm or more, there were no practical problems. Here, "less than 4 ppm" means that the content of crystals relative to the total mass of the ink was less than 0.0004% by mass. Furthermore, static storage means storage without intentional vibration. Furthermore, the inventors discovered that the amount of precipitated cyclic ester crystals decreases when ink containing a cyclic ester compound having a structure represented by general formula (I) is heated at a temperature of 40°C or higher but lower than 70°C for 6 hours or longer, and that the cyclic ester crystals precipitated in the ink disappear.

[0017] However, the mechanisms by which the amount of cyclic ester crystals precipitated decreases and the cyclic ester crystals disappear are unclear. In the case of heating at 40°C, the precipitation of the cyclic ester crystals decreases after heating at 40°C for two weeks or more. In the case of heating at 68°C, the precipitation of the cyclic ester crystals disappears after heating at 68°C for six hours, and the cyclic ester crystals precipitated in the ink also disappear. The heating time is preferably 2 weeks to 1 month when heated at 40°C, and preferably 6 to 12 hours when heated at 68°C. Heating below 40°C has no effect in reducing the precipitation of cyclic ester crystals, and heating above 70°C can change the ink properties and cause ink separation. Particularly preferably, storage at a temperature of 55°C to 65°C for 12 to 24 hours is highly effective and causes little damage to the ink.

[0018] In the present invention, the precipitated crystals are filtered using a filter paper with a particle retention capacity of 1 μm (for example, Kiriyama Funnel Filter Paper No. 5C), and the mass of the filter paper before filtration and the mass of the crystals retained after filtration are weighed and the difference is calculated to quantify the crystals of the cyclic ester having the structure represented by general formula (I). Therefore, the crystals retained after filtration have a particle size of 1 μm or more, and the amount of crystals of the cyclic ester having the structure represented by general formula (I) with a particle size of 1 μm or more is less than 4 ppm of the entire ink.

[0019] Although it is only a guess as to the mechanism by which the cyclic ester crystals decrease and disappear, it is thought that when the ink is heated in the presence of a pH adjuster (basic compound) contained in the ink, the cyclic ester compound is hydrolyzed, and a basic compound is added to the ring-opened carboxyl group, resulting in a water-soluble compound, which ultimately decreases and disappears from the ink. Under the above circumstances, the image quality was improved, and the ink storage stability, liquid permeability and ejection stability were also improved.

[0020] The ink containing the cyclic ester having the structure represented by the general formula (I) can be confirmed by separating the crystals precipitated in the ink from the ink and analyzing them by GC-MS and LC-MS. 13 -NMR+H 1 - Qualitative analysis can be performed using NMR and FT-IR.

[0021] Furthermore, in order to ensure sufficient wetting of the ink on non-penetrable media for signage and commercial printing paper, it is preferable to reduce the dynamic surface tension of the ink at 25°C with a surface life of 15 msec as measured by the maximum bubble pressure method to 34.0 mN / m or less, and to maintain the static surface tension of the ink at 25°C to 20.0 mN / m or more. Under the above circumstances, the image quality was improved, and the ink storage stability, liquid permeability and ejection stability were also improved.

[0022] The dynamic surface tension of the ink at a surface life of 15 msec according to the maximum bubble pressure method can be measured at 25° C. using, for example, a SITA DynoTester (manufactured by SITA). The static surface tension of the ink can be measured at 25° C. using, for example, an automatic surface tensiometer (DY-300, manufactured by Kyowa Interface Science Co., Ltd.). By optimizing the balance between the dynamic surface tension and the static surface tension in the ink and making the receding contact angle of the ink with respect to the nozzle plate 35° or more, the ink becomes less likely to wet the ink-repellent film on the nozzle plate of the ink ejection head, ensuring ejection stability and resulting in an extremely stable and ideal printing device in which no nozzles are missing during continuous ejection.

[0023] The receding contact angle of the ink with respect to the nozzle plate 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, even if ink adheres to the wall surface of the ink chamber of the ink ejection head, the ink will be easily repelled again. Note that the upper limit of the receding contact angle is not particularly limited in terms of wettability, since the larger the receding contact angle, the more difficult it is to wet. However, taking into consideration the wettability and permeability to the recording medium, it is preferable that the upper limit of the receding contact angle does not exceed 80° (80° or less). The receding contact angle can be measured, for example, using an automatic contact angle measuring device - expansion / contraction method. The automatic contact angle measuring device may be, for example, a contact angle meter DMo-501 (manufactured by Kyowa Interface Science Co., Ltd.). The receding contact angle can be measured by, for example, using the nozzle plate used in the present invention, extruding 2 μL of ink from a syringe onto the outer surface of the nozzle plate, and using the above-mentioned device, by the contraction method. The receding contact angle in the present invention means the value at a measurement temperature of 25° C.

[0024] The static surface tension B of the ink at 25° C. is preferably 20.0 mN / m or more and 30.0 mN / m or less. When the static surface tension is 20.0 mN / m or more and 30.0 mN / m or less, the ink can be sufficiently wetted onto non-penetrable media for signage and commercial printing paper, the effect of reducing cockling and curling is enhanced, and penetration and drying are good even when printing on plain paper.

[0025] Next, the ink and the method for producing the ink will be described in detail. <Ink> -Organic solvents- The ink of the present invention preferably contains at least one organic solvent (hereinafter referred to as "organic solvent X") having a solubility parameter (SP value) of 8.9 to 12.0 as the organic solvent. This improves wettability to recording media, allowing the ink components to penetrate even commercial printing paper with a coating layer and poor ink absorption, such as coated paper, and suppressing beading. It also facilitates wetting of non-permeable media. As described below, the ink of the present invention preferably contains a diol as an organic solvent, but the diol compound may also serve as an organic solvent with a solubility parameter (SP value) of 8.9 to 12.0. This improves wettability to recording media, allowing the ink components to penetrate even commercial printing paper with poor ink absorption, such as coated paper with a coating layer, and suppressing beading. It also facilitates wetting of non-permeable media.

[0026] Organic solvents with an SP value of 8.9 or more are generally highly soluble in water and less likely to separate, making them suitable for aqueous inks such as those of the present invention. Organic solvents with an SP value of 12.0 or less also exhibit improved drying properties and beading resistance. The SP value is a value defined by the regular solution theory introduced by Hildebrand, and serves as a measure of the solubility of a binary solution. The SP value in the present invention is a value calculated by the Fedors method. It is expressed as the square root of the cohesive energy density in the regular solution theory, and its unit is (J / cm 3 ) 0.5 This can be calculated using commonly available simple software.

[0027] The organic solvent X is preferably a water-soluble one, and is particularly preferably an amide compound of the following general formula (VI) or an oxetane compound of the following general formula (VII).

[0028] [ka] (In the formula, R represents an alkyl group having 1 to 6 carbon atoms.)

[0029] [ka] (In the formula, R1 represents an alkyl group having 1 to 2 carbon atoms.)

[0030] Examples of the amide compound represented by the general formula (VI) include the compounds of the following formulae (1) to (4). [ka]

[0031] Examples of the oxetane compound represented by the general formula (VII) include the compounds of the following formulae (5) and (6). [ka]

[0032] The content of organic solvent X is preferably 3% by mass or more of the total ink, and more preferably 5 to 20% by mass. If the content is 5% by mass or more, the ink components can penetrate commercial printing paper, making it possible to suppress beading and achieving the effect of easily wetting non-penetrating media. Furthermore, if the content is 20% by mass or less, the ink viscosity does not increase, which does not deteriorate the ejection stability.

[0033] Furthermore, in the present invention, by incorporating a glycol ether compound (compound Z) as an organic solvent, which exhibits a vapor pressure of 50 mmHg or more in an environment of 100°C, the drying property is improved, making it possible to increase the drying property even on commercial printing paper. In addition, even if the image area comes into contact with the transport roller immediately after hot air drying at 100°C, the image does not transfer, ensuring high-speed productivity. Compound Z is preferably one that is soluble in highly purified water, such as propylene glycol monopropyl ether (bp 150°C, vapor pressure 107 mmHg), propylene glycol monoethyl ether (bp 133°C, vapor pressure 252 mmHg), propylene glycol monomethyl ether (bp 120°C, vapor pressure 360 mmHg), propylene glycol monobutyl ether (bp 170°C, vapor pressure 59 mmHg), 3-methoxy-1-butanol (bp 161°C, vapor pressure 76 mmHg), and 3-methoxy-3-methyl-1-butanol (bp 174°C, vapor pressure 50 mmHg).

[0034] The content ratio (mass ratio) of organic solvent X to compound Z in the ink is preferably 1:1 to 8:1, and more preferably 3:1 to 5:1. When this ratio is 1:1 or more, i.e., when the organic solvent X is greater than the compound Z, the ink does not dry too quickly, and the inkjet head does not dry out, causing problems with ejection stability. When the ratio is 8:1 or less, the organic solvent X is not too high, improving the ink's drying properties on commercial printing paper and increasing productivity. The total content of organic solvents in the ink, including organic solvent X and compound Z, is preferably 5 to 30% by mass of the entire ink. If it is 5% by mass or more, the effect of suppressing beading on commercial printing paper will not be reduced. Also, if it is 30% by mass or less, the ink viscosity will not increase significantly, causing problems with ejection stability.

[0035] For the sake of ejection stability and ink storage stability, it is preferable to use polyhydric alcohols as the organic solvent. Specifically, diethylene glycol (bp 245°C), triethylene glycol (bp 285°C), tetraethylene glycol (bp 324 to 330°C), 1,3-butanediol (bp 203 to 204°C), glycerin (bp 290°C), diglycerin (bp 270°C / 20 hPa), 1,2,3-butanetriol (bp 175°C / 33 hPa), 1,2,4-butanetriol (bp 190 to 191°C / 24 hPa), dipropylene glycol (bp 232°C), 1,5-pentanediol (bp 242°C), Examples include propylene glycol (bp 187°C), 2-methyl-2,4-pentanediol (bp 197°C), ethylene glycol (bp 196 to 198°C), tripropylene glycol (bp 267°C), hexylene glycol (bp 197°C), polyethylene glycol (viscous liquid to solid), 1,6-hexanediol (bp 253 to 260°C), 1,2,6-hexanetriol (bp 178°C), trimethylolethane (solid, mp 199 to 201°C), and trimethylolpropane (solid, mp 61°C).

[0036] The organic solvent preferably contains at least one non-wetting polyol compound or glycol ether compound having 8 to 11 carbon atoms. The polyol compound preferably contains a diol compound. Here, "non-wetting" means having a solubility of 0.2 to 5.0% by mass in water at 25°C. Among these compounds, 1,3-diol compounds represented by the following general formula (VIII) are preferred, with 2-ethyl-1,3-hexanediol [solubility: 4.2% (25°C)] and 2,2,4-trimethyl-1,3-pentanediol [solubility: 2.0% (25°C)] being particularly preferred. [ka] (In the above formula, R' is a methyl group or an ethyl group, R'' is hydrogen or a methyl group, and R''' is an ethyl group or a propyl group.)

[0037] Other non-wetting polyol compounds include, for example, aliphatic diols such as 2-ethyl-2-methyl-1,3-propanediol, 3,3-dimethyl-1,2-butanediol, 2,2-diethyl-1,3-propanediol, 2-methyl-2-propyl-1,3-propanediol, 2,4-dimethyl-2,4-pentanediol, 2,5-dimethyl-2,5-hexanediol, and 5-hexene-1,2-diol. The content of the non-humectant polyol compound and glycol ether compound having 8 to 11 carbon atoms in the ink is preferably 0.5 to 4% by mass, more preferably 1 to 3% by mass. If the content is 0.5% by mass or more, the ink will have a good penetration effect, improving image quality. If the content is 4% by mass or less, the compound dissolves sufficiently in the ink, preventing problems such as separation or high initial ink viscosity.

[0038] -Water dispersible resin particles- Water-dispersible resin particles that have excellent film-forming properties (image-forming properties) and solvent resistance, high water resistance, and high weather resistance are useful for recording images with high water resistance and high image density (high color development), and examples of such resins include condensation-based synthetic resins, addition-based synthetic resins, and natural polymer compounds. The present invention contains polyurethane resin particles. Furthermore, because non-penetrable media for signage have poor ink fixation properties, it is necessary to select a water-dispersible resin particle material or increase the amount added.Furthermore, to improve fixation properties on non-penetrable media films, polyurethane resin particles synthesized from polyol raw materials containing aromatic rings with the structure shown in general formula (I) are often used. [ka]

[0039] Examples of polyol raw materials containing an aromatic ring having the structure represented by the general formula (I) include terephthalic acid and isophthalic acid. When terephthalic acid or isophthalic acid is used as a raw material, a cyclic ester compound is produced. When the above two types of raw materials are used, it has been confirmed by GC-MS that a cyclic ester containing a mixture of two types of phthalic acid is produced. In the present invention, it is preferable that the polyurethane resin particles contain polyurethane resin particles having a structure represented by general formula (I) using a polyol raw material containing an aromatic ring having a structure represented by general formula (I) as a raw material for the polyurethane resin particles. The proportion of the polyol raw material containing an aromatic ring having the structure represented by general formula (I) in the polyurethane resin particles having the structure represented by general formula (I) is about half of the polyol, and preferably about 10 to 30% of the polyurethane resin. When the proportion of the polyol raw material is within the above range, excellent alcohol resistance is achieved. The content of polyurethane resin particles having the structure represented by general formula (I) is preferably in the range of 2.0 to 20.0 mass % in terms of resin solid content, and more preferably 2.8 to 15.0 mass %.

[0040] Other condensation-based synthetic resins include, for example, polyester resins, polyurethane resins, polyepoxy resins, polyamide resins, polyether resins, poly(meth)acrylic resins, acrylic-silicone resins, and fluorine-based resins. Examples of the addition-based synthetic resins include, for example, polyolefin resins, polystyrene-based resins, polyvinyl alcohol-based resins, polyvinyl ester-based resins, polyacrylic acid-based resins, and unsaturated carboxylic acid-based resins. Examples of the natural polymer compounds include, for example, celluloses, rosins, and natural rubber. Among these, polyurethane resin particles are preferred in consideration of the fixability of the ink. Two or more of the above water-dispersible resins may be used in combination.

[0041] Water-dispersible resins that can be used include those that have hydrophilic groups and are self-dispersible, and those that do not have dispersibility but are made dispersible by surfactants or resins with hydrophilic groups. Among these, emulsions of resin particles obtained by emulsifying and suspension polymerizing ionomers of polyester resins or polyurethane resins or unsaturated monomers are optimal. In the case of emulsion polymerization of unsaturated monomers, a resin emulsion is obtained by reacting the unsaturated monomer, a polymerization initiator, a surfactant, a chain transfer agent, a chelating agent, a pH adjuster, and the like in water to which the unsaturated monomer, a polymerization initiator, a surfactant, a chain transfer agent, a chelating agent, a pH adjuster, and the like have been added. This makes it easy to obtain a water-dispersible resin, and it is easy to change the resin composition and to create desired properties.

[0042] Since the water-dispersible resin undergoes dispersion destruction or hydrolysis or other cleavage of molecular chains under strong alkaline or strong acidic conditions, the pH is preferably 4 to 12, and from the viewpoint of miscibility with the water-dispersible colorant in particular, a pH of 7 to 11 is more preferable, and a pH of 8 to 10.5 is even more preferable.

[0043] The water-dispersible resin also functions to fix the water-dispersible colorant to the media, forming a film at room temperature or higher to improve the fixation of the colorant. Therefore, the minimum film-forming temperature (MFT) of the water-dispersible resin is preferably 100°C or lower. Furthermore, if the glass transition temperature of the water-dispersible resin is -40°C or lower, the resin film becomes too viscous and tacky, so the glass transition temperature is preferably -30°C or higher. The content of the water-dispersible resin in the ink is preferably 0.5 to 20% by mass, more preferably 1 to 15% by mass, in terms of solid content. However, in consideration of the substrate fixability of the colorant to non-permeable media for signage and commercial printing paper, the ink preferably contains polyurethane resin particles at a solid content of 3 mass% or more, and the solid content ratio of the colorant to the polyurethane resin particles is preferably 1.0:(2.0 to 12.0), and particularly preferably 1.0:(2.0 to 11.0). The content of the polyurethane resin particles is the total amount of polyurethane resin particles, which are the solid content contained in the ink.

[0044] -Coloring agent- The ink of the present invention may be a clear ink that does not contain a colorant, but may also be an ink that contains a colorant. The colorant is preferably a pigment. The colorant may be a surfactant-dispersed pigment in which a pigment is dispersed in a surfactant, a resin-dispersed pigment in which a pigment is dispersed in a resin, a resin-coated pigment in which the surface of a pigment is coated with a resin, or a self-dispersed pigment in which a hydrophilic group is provided on the pigment surface, but water-dispersible pigments are preferred. Of these, the resin-coated pigment or self-dispersed pigment having at least one hydrophilic group on the pigment surface is preferred. Examples of such hydrophilic groups include -COOM, -SO3M, -PO3HM, -PO3M2, -CONM2, -SO3NM2, -NH-C6H4-COOM, -NH-C6H4-SO3M, -NH-C6H4-PO3HM, -NH-C6H4-PO3M2, -NH-C6H4-CONM2, and -NH-C6H4-SO3NM2. These hydrophilic groups can be introduced by known methods.

[0045] The counter ion M in the hydrophilic group is preferably a quaternary ammonium ion, specific examples of which include a tetramethylammonium ion, a tetraethylammonium ion, a tetrapropylammonium ion, a tetrabutylammonium ion, a tetrapentylammonium ion, a benzyltrimethylammonium ion, a benzyltriethylammonium ion, and a tetrahexylammonium ion, with the tetraethylammonium ion, tetrabutylammonium ion, and benzyltrimethylammonium ion being preferred, and the tetrabutylammonium ion being particularly preferred. Inks using the above pigments have particularly high storage stability and suppress an increase in viscosity when water evaporates. This is presumably because the hydrophilic group containing the quaternary ammonium ion allows the pigment dispersion to be kept stable even when the water evaporates from the water-rich ink and the ink becomes organic solvent-rich.

[0046] As a colorant other than the pigment having a hydrophilic group, a polymer emulsion containing a pigment in polymer fine particles is preferred. The pigment may be encapsulated in the polymer fine particles or adsorbed on the surface of the polymer fine particles. In this case, it is not necessary for all the pigment to be encapsulated or adsorbed, and a portion may be dispersed in the emulsion. Examples of polymers for the polymer fine particles include vinyl polymers, polyester polymers, and polyurethane polymers, with vinyl polymers and polyester polymers being particularly preferred. Specific examples thereof include those disclosed in Japanese Patent Laid-Open Nos. 2000-53897 and 2001-139849.

[0047] Alternatively, a composite pigment in which particles of a general organic pigment or inorganic pigment are coated with an organic pigment or carbon black can be used. The composite pigment can be prepared by a method in which an organic pigment is precipitated in the presence of inorganic pigment particles, or by a mechanochemical method in which an inorganic pigment and an organic pigment are mechanically mixed and ground. Furthermore, if necessary, a layer of an organosilane compound generated from a polysiloxane or an alkylsilane can be provided between the inorganic pigment and the organic pigment to improve adhesion between them. The mass ratio of the inorganic pigment particles to the organic pigment or carbon black colorant is preferably 3:1 to 1:3, and more preferably 3:2 to 1:2. When the amount of colorant is within the above range, the color development and coloring power are not reduced, and the transparency and color tone are not impaired. As the composite pigment, silica / carbon black composite material, silica / phthalocyanine PB15:3 composite material, silica / disazo yellow composite material, silica / quinacridone PR122 composite material, etc. manufactured by Toda Kogyo Co., Ltd. are suitable because they have small average primary particle diameters.

[0048] If inorganic pigment particles with a primary particle diameter of 20 nm are coated with an equal amount of organic pigment, the resulting primary particle diameter will be approximately 25 nm. If an appropriate dispersant can be used to disperse these particles down to the primary particle size, it will be possible to produce an extremely fine pigment dispersion ink with a dispersed particle diameter of 25 nm. In this composite pigment, not only does the organic pigment on the surface contribute to dispersion, but the properties of the inorganic pigment at the center also emerge through a thin layer of organic pigment approximately 2.5 nm thick. Therefore, it is important to select a pigment dispersant that can simultaneously stabilize the dispersion of both.

[0049] Examples of the inorganic pigment include titanium oxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, chrome yellow, carbon black, etc. Among these, carbon black is particularly preferred, and examples thereof include channel black, furnace black, gas black, and lamp black produced by known methods such as the contact method, furnace method, and thermal method.

[0050] Examples of the organic pigments include azo pigments, polycyclic pigments, dye chelates, nitro pigments, nitroso pigments, and aniline black. Among these, azo pigments and polycyclic pigments are preferred. Examples of the azo pigments include azo lakes, insoluble azo pigments, condensed azo pigments, and chelate azo pigments. Examples of the polycyclic pigments include phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, isoindolinone pigments, and quinophthalone pigments. Examples of the dye chelates include basic dye chelates and acid dye chelates.

[0051] Examples of the organic pigment include 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, 408, 109, 110, 117, 120, 128, 139, 150, 151, 155, 153, 180, and 183. , 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, 48:2 (Permanent Red 2B (Ca)), 48:3, 48:4, 49:1, 52:2, 53:1, 57:1 (Brilliant Carmine 6B), 60:1, 6 3:1, 63:2, 64:1, 81, 83, 88, 101 (Red Iron), 104, 105, 106, 108 (Cadmium Red), 112, 114, 122 (Quinacridone Magenta), 123, 146, 149, 166, 168, 170, 172, 177, 178, 179, 185, 190, 193, 209, 219, CI Pigment Rhodamine Lake 1 (Rhodamine Lake), 3, 5:1, 16, 19, 23, 38; CI Pigment Blue 1, 2, 15 (Phthalocyanine Blue), 15:1, 15:2, 15:3 (Phthalocyanine Blue), 16, 17:1, 56, 60, 63; CI Pigment Green 1, 4, 7, 8, 10, 17, 18, 36, etc.

[0052] The BET specific surface area of the pigment used is preferably about 10 to about 1500 m 2 / g, more preferably about 20 to about 600 m 2 / g, more preferably about 50 to about 300m 2 / g. If the desired specific surface area is not readily available, the pigment can be subjected to conventional size reduction or milling processes (e.g., ball milling, jet milling, ultrasonication) to reduce the particle size to a relatively small size. The median diameter (D50) of the water-dispersible colorant in the ink is preferably 10 to 200 nm. The content of the water-dispersible colorant in the ink is preferably 1 to 15% by mass, more preferably 1.5 to 10% by mass, in terms of solid content. A content of 1% by mass or more improves the color development and image density of the ink, while a content of 15% by mass or less prevents the ink from thickening and impairing the ejection properties, and is also economically preferable. In the present invention, dyes may be used in combination for the purpose of adjusting the color tone, but they must be used within a range that does not deteriorate the weather resistance.

[0053] -Surfactants- In the present invention, it is preferable to use a polyether-modified siloxane compound as the surfactant. This makes the ink less likely to wet the ink-repellent layer of the head nozzle plate, preventing ejection failures due to ink adhesion to the nozzles and improving ejection stability. Furthermore, the ink is less likely to adhere to the nozzle ink-repellent layer surface, which is particularly problematic, making the ink less likely to cause ejection failures. Among these, those represented by the following general formulas (IX) to (XII) are preferred, and in particular, those that do not impair dispersion stability depending on the type of water-dispersible colorant or the combination with an organic solvent, have low dynamic surface tension, and have high penetration and leveling properties are preferred. These surfactants may be used alone or in combination of two or more.

[0054] [ka] (In the above formula, R represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, m represents an integer of 0 to 23, n represents an integer of 1 to 10, a represents an integer of 1 to 23, and b represents an integer of 0 to 23.)

[0055] Examples of the compound represented by the general formula (IX) include the compounds of the following formulae (7) to (14). [ka]

[0056] [ka]

[0057] [ka] (In the above formula, R2 and R3 represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, m represents an integer of 1 to 8, and c and d represent integers of 1 to 10.)

[0058] Examples of the compound represented by the above general formula (X) include the compound represented by the following formula (15). [ka]

[0059] [ka] (In the above formula, R4 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and e represents an integer of 1 to 8.)

[0060] Examples of the compound represented by the above general formula (XI) include the compound represented by the following formula (16). [ka]

[0061] [ka] [In the above formula, R5 represents a polyether group of the following general formula (A), and f represents an integer of 1 to 8.]

[0062] [ka] (In the above formula, R6 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, g represents an integer of 0 to 23, and h represents an integer of 0 to 23, except when g and h are both 0.)

[0063] Examples of the compound represented by the above general formula (XII) include the compounds of the following formulae (17) to (19). [ka]

[0064] Furthermore, commercially available polyether-modified siloxane compound surfactants that exhibit the same effect as the above compounds include 71ADDITIVE, 74ADDITIVE, 57ADDITIVE, 8029ADDITIVE, 8054ADDITIVE, 8211ADDITIVE, 8019ADDITIVE, 8526ADDITIVE, FZ-2123, and FZ-2191 manufactured by TORAY Dow Corning; TSF4440, TSF4441, TSF4445, TSF4446, TSF4450, TSF4452, and TSF4460 manufactured by Momentive Performance Materials; and Silface manufactured by Nissin Chemical Industry Co., Ltd. Examples of such surfactants include SAG002, Silface SAG003, Silface SAG005, Silface SAG503A, Silface SAG008, and Silface SJM003, as well as TEGO_Wet_KL245, TEGO_Wet_250, TEGO_Wet_260, TEGO_Wet_265, TEGO_Wet_270, and TEGO_Wet_280 manufactured by Evonik, and BYK-345, BYK-347, BYK-348, BYK-375, and BYK-377 manufactured by BYK Japan.

[0065] If necessary, the polyether-modified siloxane compound surfactant may be used in combination with a fluorine-based surfactant, a silicone-based surfactant, or an acetylene glycol or acetylene alcohol-based surfactant. The content of the surfactant in the ink is preferably 0.001 to 5% by mass, more preferably 0.5 to 3% by mass. If the content is 0.001% by mass or more, the effect of adding the surfactant can be obtained. However, if the amount exceeds 5 masses, the effect of addition becomes saturated, so there is no point in increasing the amount.

[0066] -Other ingredients- In addition to the above components, the ink of the present invention may contain various known additives as needed, such as penetrants, antifoaming agents (defoamers), pH adjusters, antiseptics and antifungals, chelating agents, rust inhibitors, antioxidants, ultraviolet absorbers, oxygen absorbers, and light stabilizers.

[0067] -Foam suppressor- A foam inhibitor is added in small amounts to the ink to suppress foaming. Here, foaming refers to a liquid forming a thin film that encases air. The formation of this foam is related to the surface tension, viscosity, and other properties of the ink. That is, liquids with high surface tension, such as water, are less likely to foam because of the forces that act to minimize the surface area of the liquid. In contrast, inks with high viscosity and high permeability tend to foam easily because of their low surface tension, and the viscosity of the solution makes it easier for the foam to be maintained and difficult to eliminate.

[0068] Typically, foam suppressors destroy bubbles by locally lowering the surface tension of the foam film, or by dotting the surface of the foaming liquid with foam suppressors that are insoluble in the foaming liquid. When a polyether-modified siloxane compound surfactant, which has a very strong surface tension-reducing effect, is used in the ink, the use of a foam suppressor that works by the former mechanism does not result in a localized reduction in the surface tension of the foam film. Therefore, foam suppressors that are insoluble in the foaming liquid are used, but in this case, the stability of the ink is reduced by the foam suppressor being insoluble in the solution. In contrast, the foam suppressor of the following general formula (XIII) does not have as strong a surface tension reducing effect as the polyether-modified siloxane compound surfactant, but it is highly compatible with the surfactant. For this reason, the foam suppressor is efficiently incorporated into the foam film, and the difference in surface tension between the surfactant and the foam suppressor causes the surface of the foam film to become locally unbalanced, resulting in foam collapse.

[0069] [ka] (In the above formula, R7 and R8 each independently represent an alkyl group having 3 to 6 carbon atoms; R9 and R 10each independently represents an alkyl group having 1 to 2 carbon atoms, and n represents an integer of 1 to 6.

[0070] Preferred examples of the compound represented by general formula (XIII) include 2,4,7,9-tetramethyldecane-4,7-diol and 2,5,8,11-tetramethyldodecane-5,8-diol, with 2,5,8,11-tetramethyldodecane-5,8-diol being particularly preferred due to its anti-foaming effect and high compatibility with ink. The content of the anti-foaming agent in the ink is preferably 0.01 to 10% by mass, more preferably 0.1 to 5% by mass. If the content is 0.01% by mass, the anti-foaming effect is obtained, and if the content is 10% by mass or less, the anti-foaming effect does not plateau and there is no adverse effect on the ink properties such as viscosity and particle size.

[0071] - pH adjuster - There are no particular restrictions on the pH adjuster, as long as it can adjust the pH to 7 to 11 without adversely affecting the ink being prepared, and it can be selected appropriately depending on the purpose. Examples thereof include alcohol amines, hydroxides of alkali metal elements, hydroxides of ammonium, phosphonium hydroxides, and carbonates of alkali metals. If the pH is outside the range of 7 to 11, the inkjet head and ink supply unit will be dissolved to a large extent, which may cause problems such as ink deterioration, leakage, and ejection failure. Examples of the alcohol amines include diethanolamine, triethanolamine, and 2-amino-2-ethyl-1,3 propanediol. Examples of the hydroxides of alkali metal elements include lithium hydroxide, sodium hydroxide, and potassium hydroxide. Examples of the hydroxide of ammonium include ammonium hydroxide and quaternary ammonium hydroxide. Examples of the phosphonium hydroxide include quaternary phosphonium hydroxide. Examples of the alkali metal carbonate include lithium carbonate, sodium carbonate, and potassium carbonate. As the pH adjuster, it is preferable to use a strongly basic compound.

[0072] By including a strongly basic compound in the ink, it is possible to suppress the precipitation of crystals of the cyclic ester having the structure represented by general formula (I). This improves the fixability of the ink and also increases the liquid permeability. When ejecting the ink using an inkjet method, ejection failures can be avoided, enabling stable printing. It is presumed that the strong basic compound acts on the cyclic ester compound having the structure represented by general formula (I), causing hydrolysis, which results in the effect of suppressing crystal precipitation. There are no particular limitations on the strong basic compound, but it is preferable to use sodium hydroxide or potassium hydroxide in order to effectively suppress crystallization. The content of the strong basic compound contained in the ink is preferably 0.05% by mass or more and 0.24% by mass or less in order to effectively suppress crystallization. It is also preferable to use 2-amino-2-ethyl-1,3 propanediol as a pH adjuster.

[0073] -Preservative and fungicidal agent- Examples of antiseptic and antifungal agents include sodium dehydroacetate, sodium sorbate, sodium 2-pyridinethiol-1-oxide, sodium benzoate, and sodium pentachlorophenol.

[0074] -Chelating reagents- Examples of chelating agents include sodium ethylenediaminetetraacetate, sodium nitrilotriacetate, sodium hydroxyethylethylenediaminetriacetate, sodium diethylenetriaminepentaacetate, and sodium uramildiacetate.

[0075] -Rust inhibitor- Examples of the rust inhibitor include acid sulfite, sodium thiosulfate, ammonium thiodiglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, and dicyclohexylammonium nitrite.

[0076] -Antioxidants- Examples of antioxidants include phenol-based antioxidants (including hindered phenol-based antioxidants), amine-based antioxidants, sulfur-based antioxidants, and phosphorus-based antioxidants.

[0077] -Ultraviolet absorber- Examples of the ultraviolet absorber include benzophenone-based ultraviolet absorbers, benzotriazole-based ultraviolet absorbers, salicylate-based ultraviolet absorbers, cyanoacrylate-based ultraviolet absorbers, and nickel complex salt-based ultraviolet absorbers.

[0078] -Ink manufacturing- The ink of the present invention can be produced by the following steps: dispersing or dissolving water, an organic solvent, polyurethane resin particles, a colorant (if added as needed), and other components in an aqueous medium, and further stirring and mixing as needed; and heating the mixture obtained in the previous step at a temperature of 40° C. or higher but lower than 70° C. for 6 hours or longer. This stirring and mixing can be carried out using, for example, a sand mill, a homogenizer, a ball mill, a paint shaker, an ultrasonic disperser, or the like; the stirring and mixing can be carried out using a conventional mixer with stirring blades, a magnetic stirrer, a high-speed disperser, or the like.

[0079] -Ink properties- There are no particular restrictions on the physical properties of the ink of the present invention, and they can be appropriately selected depending on the purpose. However, if the static surface tension of the ink is 20 mN / m or more and the dynamic surface tension at a bubble lifetime of 15 msec as measured by the maximum bubble pressure method is 34 mN / m or less, the ink will have sufficient wettability to the recording medium, but will not easily wet the water-repellent film of the nozzle plate Optool of the inkjet head, and ejection stability will be ensured, resulting in an extremely stable ink, which is preferable. The viscosity of the ink at 25° C. is preferably 5 to 25 mPa·s, and more preferably 6 to 20 mPa·s. If the viscosity is 5 mPa·s or higher, the print density and character quality can be improved. Furthermore, if the viscosity is 25 mPa·s or less, ink ejection properties can be ensured. The viscosity can be measured at 25°C using, for example, a viscometer (RE-85L, manufactured by Toki Sangyo Co., Ltd.). To ensure ink storage stability, the pH is preferably 8 to 11, and more preferably 8.5 to 11.

[0080] The ink of the present invention can be used well in printers equipped with any type of inkjet head, such as a so-called piezoelectric type inkjet head that uses a piezoelectric element as pressure generating means to pressurize the ink in the ink flow path, thereby deforming a vibration plate that forms the wall of the ink flow path, changing the internal volume of the ink flow path and ejecting ink droplets (see JP 2-51734 A); a so-called thermal type that uses a heating resistor to heat the ink in the ink flow path and generate bubbles (see JP 61-59911 A); or an electrostatic type that arranges a vibration plate that forms the wall of the ink flow path opposite an electrode, and deforms the vibration plate by electrostatic force generated between the vibration plate and the electrode, changing the internal volume of the ink flow path and ejecting ink droplets (see JP 6-71882 A). The ink of the present invention may be used by being contained in a container such as an ink cartridge.

[0081] <Recording Media> There are no particular limitations on the recording media on which recording can be performed using the ink of the present invention, and they can be appropriately selected depending on the purpose, and examples include plain paper, glossy paper, special paper, cloth, film, OHP sheets, general-purpose printing paper, etc. However, the ink of the present invention is extremely advantageous in that it can print as well on non-permeable media for signage and commercial printing paper as on other papers. Printed matter bearing an image formed using the ink of the present invention has high image quality, is free from bleeding, and has excellent stability over time, and can be suitably used for a variety of purposes, such as documents on which various types of printing or images are recorded.

[0082] Next, the ink ejection head will be described. <Ink ejection head> The ink ejection head includes a nozzle plate, and may further include other members as required.

[0083] -Nozzle plate- The nozzle plate has a nozzle substrate and an ink-repellent film on the nozzle substrate.

[0084] -Nozzle board- The nozzle substrate is provided with 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 ink is ejected from the nozzle holes, and a liquid chamber joining surface located on the opposite side to the ink ejection side surface. The ink-repellent film is formed on the surface of the nozzle substrate on the ink ejection side.

[0085] The planar shape of the nozzle substrate is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include a rectangle, a square, a rhombus, a circle, an ellipse, etc. Furthermore, examples of the cross-sectional shape of the nozzle substrate include a flat plate shape, a plate shape, etc. The size of the nozzle substrate is not particularly limited and can be appropriately selected depending on the size of the nozzle plate.

[0086] The material of the nozzle substrate is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include stainless steel, Al, Bi, Cr, InSn, ITO, Nb, Nb2O5, NiCr, Si, SiO2, Sn, Ta2O5, Ti, W, ZAO (ZnO + Al2O3), and Zn. These may be used alone or in combination of two or more. Among these, stainless steel is preferred from the viewpoint of rust prevention.

[0087] 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.

[0088] 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.

[0089] -Nozzle hole- The nozzle holes are not particularly limited in number, arrangement, spacing, opening shape, opening size, cross-sectional shape of the openings, etc., and can be appropriately selected depending on the purpose. The arrangement of the nozzle holes is not particularly limited and can be appropriately selected depending on the purpose. For example, 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, a circle is preferred from the viewpoint of ejecting ink droplets.

[0090] -Ink-repellent film- The ink-repellent film preferably contains a fluorine-containing acrylate ester polymer or a polymer having a fluorine-containing heterocyclic structure in the main chain. The ink-repellent film preferably contains the fluorine-containing acrylate ester polymer or the polymer having a fluorine-containing heterocyclic structure in the main chain, since the surface free energy is extremely small and the film can maintain a state in which the ink has low surface tension and is resistant to wetting, even with the ink having low surface tension used in the present invention. However, if other materials are used as the ink-repellent film, the surface free energy becomes extremely small and the film may become wet with the ink having low surface tension and be wetted.

[0091] --Fluorine-containing acrylate ester polymer-- The fluorine-containing acrylate ester polymer preferably contains at least one of a compound represented by the following general formula (II) and a compound represented by the following general formula (III) as a monomer unit. [ka] [ka] In the general formulas (II) and (III), X represents a hydrogen atom, a linear or branched alkyl group having 1 to 21 carbon atoms, a halogen atom, a CFX1X2 group (wherein X1 and X2 are each independently 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, or a substituted or unsubstituted phenyl group; R1 represents an alkyl group having 1 to 18 carbon atoms; R2 represents an alkylene group having 2 to 6 carbon atoms; R3 represents an alkylene group having 2 to 6 carbon atoms; Y represents an acid group; and Rf represents a linear or branched fluoroalkyl group having 1 to 21 carbon atoms. m represents 1 to 10, n represents 2 to 90, p represents 1 to 90, and q represents 1 to 10. Furthermore, a polymer obtained by polymerizing at least one of the compounds represented by the general formula (II) and the general formula (III) is a polymer having at least one of a structural unit represented by the general formula (IV) and a structural unit represented by the general formula (V).

[0092] 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, and an undecyl group. The R2 is an alkylene group having 2 to 6 carbon atoms, such as an ethylene group, a propylene group, a butylene group, etc. Among these, an ethylene group is preferred. The R3 is an alkylene group having 2 to 6 carbon atoms, such as an ethylene group, a propylene group, a butylene group, etc. Among these, an ethylene group is preferred. The 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, and a maleic acid group.

[0093] The Rf is a linear or branched fluoroalkyl group having 1 to 21 carbon atoms, preferably a perfluoroalkyl group, and more preferably has 1 to 10 carbon atoms. 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.

[0094] The m is preferably 1 to 10, and more preferably 1 to 3. The above n is preferably 2 to 90, more preferably 3 to 50, and further preferably 4 to 30. The above p is preferably 1 to 90, and more preferably 1 to 30. The q is preferably 1 to 10, and more preferably 1 to 3.

[0095] The fluorine-containing acrylate ester polymer may be suitably synthesized or may be a commercially available product. The fluorine-containing acrylate ester polymer represented by the general formula (III) (Rf is C6F 13 can be synthesized, for example, by the following reaction scheme:

[0096] [ka]

[0097] The fluorine-containing acrylate ester polymer represented by the general formula (III) (Rf is C6F 13 can be synthesized, for example, by the following reaction scheme:

[0098] [ka]

[0099] The fluorine content in the fluorine-containing acrylate ester polymer is preferably 10% by mass or more, more preferably 25% by mass or more, and even more preferably 50% by mass or more, from the viewpoint of ink repellency (contact angle). Examples of commercially available products include krytox FSL (manufactured by DuPont), krytox FSH (manufactured by DuPont), Fomblin Z (manufactured by Solvay Solexis), FLUOROLINKS 10 (manufactured by Solvay Solexis), Optool DSX (manufactured by Daikin Industries, Ltd.), FLUOROLINK C10 (manufactured by Solvay Solexis), Moresco Phospharol A20H (manufactured by Matsumura Oil Research Institute Co., Ltd.), Moresco Phospharol ADOH (manufactured by Matsumura Oil Research Institute Co., Ltd.), Moresco Phospharol DDOH (manufactured by Matsumura Oil Research Institute Co., Ltd.), Fluorosurf FG5010 (manufactured by Fluorotechnology Co., Ltd.), Fluorosurf FG5020 (manufactured by Fluorotechnology Co., Ltd.), Fluorosurf FG5060 (manufactured by Fluorotechnology Co., Ltd.), and Fluorosurf FG5070 (manufactured by Fluorotechnology Co., Ltd.).

[0100] 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 substrate 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 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.

[0101] Examples of the compound containing a fluorine-containing acrylate ester polymer skeleton in the molecule include low molecular weight substances and resins. Examples of the compound containing a fluorine-containing acrylate ester polymer skeleton in the molecule include those disclosed in JP-B-3-43065, JP-A-6-210857, JP-A-10-32984, JP-A-2000-94567, JP-A-2002-145645, JP-A-2003-341070, JP-A-2007-106024, and JP-A-2007-125849. A particularly preferred example is modified perfluoropolyoxetane (Optool DSX, manufactured by Daikin Industries, Ltd.). The average thickness of the ink-repellent film 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.

[0102] Examples of methods for forming an ink-repellent film from a compound containing a fluorine-containing acrylate ester polymer skeleton in its molecule include coating methods such as spin coating, roll coating, and dipping using a fluorine-based solvent, printing, and vacuum deposition. Examples of the fluorine-based solvent include Novec (manufactured by 3M Corporation), Vertrel (manufactured by DuPont), and Galden (manufactured by Solvay Solexis).

[0103] --Polymer having a fluorine-containing heterocyclic structure in the main chain-- The polymer having a fluorine-containing heterocyclic structure in the main chain is preferably an amorphous fluorine-containing polymer having a heterocyclic structure, since the amorphous polymer is excellent in film strength, adhesion to the substrate, film uniformity, etc., and can further exhibit the effects of the present invention. Suitable examples of the polymer having a fluorine-containing heterocyclic structure in the main chain include the polymers described in U.S. Pat. No. 3,418,302, U.S. Pat. No. 3,978,030, JP-A-63-238111, JP-A-63-238115, JP-A-1-131214, and JP-A-1-131215. Among these, the following polymers having a heterocyclic structure are representative, however, the scope of the present invention is not limited to these only.

[0104] [ka]

[0105] [ka] In the general formulae (i) and (ii), Rf1, Rf2, and Rf3 each represent a fluorine-containing alkyl group.

[0106] [ka]

[0107] [ka]

[0108] [ka]

[0109] [ka]

[0110] [ka]

[0111] [ka]

[0112] Furthermore, in order to improve adhesion to a substrate and control the glass transition temperature (Tg) and solubility in a solvent, a structure represented by the following general formula (iii) may be introduced into the main chain, and these structures can be obtained by copolymerizing with comonomers represented by the following structural formulas (vii) to (ix).

[0113] [ka] In the general formula (iii), R4, R5, and R6 each represent a hydrogen atom, a fluorine atom, a chlorine atom, or Rf4, where Rf4 is a fluorine-containing alkyl group. X represents a hydrogen atom, a fluorine atom, a chlorine atom, Rf5, or Rf6, where Rf5 is a fluorine-containing organic substituent having a functional group such as an acid, ester, alcohol, amine, or amide at its terminal, and Rf6 is a fluorine-containing alkyl group or a fluorine-containing ether group.

[0114] [ka]

[0115] [ka]

[0116] [ka]

[0117] Examples of agents having the specific chemical structure as described above and suitable as ink repellent agents include Cytop CTX-105 (manufactured by Asahi Glass Co., Ltd.), Cytop CTX-805 (manufactured by Asahi Glass Co., Ltd.), Teflon (registered trademark) AF1600, and AF2400 (manufactured by DuPont).

[0118] Examples of methods for forming an ink-repellent film using a polymer having a fluorine-containing heterocyclic structure in the main chain include coating methods such as spin coating, roll coating, and dipping using a fluorine-based solvent, printing, and vacuum deposition. The fluorine-containing 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 depending on the purpose. For example, fluorine-containing solvents such as perfluorobenzene, "Afluid" (trade name: fluorine-containing solvent manufactured by Asahi Glass Co., Ltd.), and "Fluorinert FC-75" (trade name: liquid containing perfluoro(2-butyltetrahydrofuran) manufactured by 3M Corporation) are suitable. These may be used alone or in combination of two or more. Among these, in the case of mixed solvents, hydrocarbons, chlorinated hydrocarbons, fluorochlorohydrocarbons, alcohols, or other organic solvents may also be used in combination. The solution concentration is preferably from 0.01% by mass to 50% by mass, more preferably from 0.01% by mass to 20% by mass. The above-mentioned object can be sufficiently achieved if the average thickness of the ink-repellent film is 0.01 μm or more, but it is preferably 0.01 μm or more and 2 μm or less.

[0119] The heat treatment conditions (temperature) for the polymer having a fluorinated heterocyclic structure in its 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 should be selected. The glass transition temperature of the polymer having a fluorine-containing heterocyclic structure in the main chain varies depending on the structure. For example, since most of the polymers having the structures of the structural formulas (iv) to (vi) have a temperature of 50°C or higher and 110°C or lower, the heat treatment conditions are preferably a temperature of 120°C or higher and 170°C or lower for 30 minutes to 2 hours.

[0120] Furthermore, a copolymer having the structure of the general formula (ii) above 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."

[0121] [ka]

[0122] Teflon® AF can have a variety of glass transition temperatures by varying its copolymerization ratio. In other words, the glass transition temperature increases as the proportion of PDD [perfluoro(2,2-dimethyl-1,3-dioxole)] increases. Depending on the component ratio, the glass transition temperature can range from 80°C to 330°C. Commercially available glass transition temperatures are 160°C (AF1600) and 240°C (AF2400). For example, the heat treatment temperature for the 160°C glass transition temperature is preferably 165°C to 180°C, taking into account the heat resistance of the substrate.

[0123] -Other parts- The other members are not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include a pressure chamber and a stimulus generating means.

[0124] --Pressure chamber-- The pressure chambers are arranged to correspond individually to the plurality of nozzle holes provided in the nozzle plate, and 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.

[0125] --Means for ejecting ink-- The ink ejection head has means for generating a stimulus that is applied to the ink. The stimulus in the stimulus generating means 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, heat and pressure are preferred. Examples of the stimulus generating means include a heating device, a pressure applying device, a piezoelectric element, a vibration generating device, an ultrasonic oscillator, a light, etc. Specific examples of the stimulus generating means include a piezoelectric actuator such as a piezoelectric element, a thermal actuator that uses a phase change caused by film boiling of ink 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.

[0126] When the stimulus is "heat," thermal energy corresponding to a recording signal is applied to the ink in the ink ejection head using, for example, a thermal head, etc. The thermal energy generates bubbles in the ink, and the pressure of the bubbles causes the ink to be ejected as droplets from the nozzle holes in the nozzle plate. When the stimulus is "pressure," for example, a method is exemplified in which a voltage is applied to the piezoelectric element attached to a position called the pressure chamber in the ink flow path of the ink ejection head, causing the piezoelectric element to bend, thereby contracting the volume of the pressure chamber and ejecting the ink as droplets from the nozzle hole of the ink ejection head. Among these, the piezo method, in which a voltage is applied to a piezo element to cause ink to fly, is preferred.

[0127] An example of an ink ejection head used in the present invention will now be described with reference to Figures 4 to 6. Figure 4 is an exploded perspective view of the head, Figure 5 is a cross-sectional view of the head taken along a direction perpendicular to the nozzle arrangement direction (longitudinal direction of the liquid chambers), and Figure 6 is a cross-sectional view of the head taken along the nozzle arrangement direction (lateral direction of the liquid chambers).

[0128] The ink ejection head has a flow path plate (liquid chamber substrate, flow path member) 1, a vibration plate member 2 joined to the underside 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, and these form a plurality of liquid chambers (also called pressurized liquid chambers, pressure chambers, pressure chambers, flow paths, etc.) 6 as individual flow paths to which a plurality of nozzle holes 4 which eject liquid droplets (ink droplets) are each connected via nozzle connection paths 5, a fluid resistance section 7 which also serves as a supply path for supplying ink to the liquid chambers 6, and a communication section 8 which communicates with the liquid chambers 6 via this fluid resistance section 7, and ink is supplied to the communication section 8 from a common liquid chamber 10 formed in a frame member 17 via a supply port 19 formed in the vibration plate member 2.

[0129] The flow path plate 1 is formed by etching a silicone substrate to form openings such as the communication channels 5, the liquid chambers 6, and the fluid resistance portions 7. The flow path plate 1 can also be formed, for example, by etching a SUS substrate using an acid etching solution or by machining such as punching (pressing).

[0130] The vibration plate member 2 has vibration regions (diaphragm portions) 2a that form the wall surfaces of the respective liquid chambers 6, and an island-shaped convex portion 2b is provided on the outer surface of the vibration region 2a (the surface opposite the liquid chamber 6). The upper end surfaces (bonding surfaces) of the piezoelectric element pillars 12A, 12B of the laminated 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 portion 2b. The lower end surface of the laminated piezoelectric element 12 is bonded to a base member 13.

[0131] Here, the piezoelectric element 12 is formed by alternately laminating piezoelectric material layers 21 such as PZT and internal electrodes 22a, 22b, and the internal electrodes 22a, 22b are drawn out to the end faces, i.e., the side faces of the piezoelectric element 12 that are approximately perpendicular to the vibration plate member 2, and connected to end face electrodes (external electrodes) 23a, 23b formed on these side faces, and displacement in the lamination direction occurs when a voltage is applied to the end face electrodes (external electrodes) 23a, 23b. This piezoelectric element 12 is formed by forming grooves by half-cut dicing to form the required number of piezoelectric element columns 12A, 12B for one piezoelectric element member.

[0132] It should be noted that the piezoelectric element columns 12A and 12B of the piezoelectric element 12 are the same, but are distinguished by the fact that the piezoelectric element columns that are driven by applying a drive waveform are called piezoelectric element columns 12A, and the piezoelectric element columns that are used simply as support columns without applying a drive waveform are called piezoelectric element columns 12B. In this case, either a bi-pitch configuration in which driving piezoelectric element columns 12A and support piezoelectric element columns 12B are used alternately, or a normal pitch configuration in which all piezoelectric element columns are used as driving piezoelectric element columns 12A, can be employed.

[0133] As a result, two rows of drive elements (rows of drive piezoelectric element columns 12A) are provided on the base member 13, each row having a plurality of drive piezoelectric element columns 12A arranged side by side as drive elements.

[0134] In addition, the ink in the liquid chamber 6 is pressurized by using displacement in the d33 direction (the stacking direction of the piezoelectric material layers) as the piezoelectric direction of the stacked piezoelectric element 12, but it is also possible to use displacement in the d31 direction (the surface direction of the piezoelectric material layers: the direction perpendicular to the electric field) as the piezoelectric direction of the stacked piezoelectric element 12 to pressurize the ink in the pressurized liquid chamber 6.

[0135] Furthermore, the piezoelectric element material is not particularly limited, and electromechanical transducers such as ferroelectrics commonly used as piezoelectric element materials, such as BaTiO3, PbTiO3, and (NaK)NbO3, can also be used. Furthermore, although a laminated piezoelectric element is used, a single-plate piezoelectric element can also be used. The single-plate piezoelectric element can be one that is machined, a thick film that is screen-printed and sintered, or a thin film formed by sputtering, vapor deposition, or a sol-gel method. Furthermore, the laminated piezoelectric elements 12 provided on one base member 13 can be arranged in a single row or in multiple rows.

[0136] An FPC 15 serving as wiring means is directly connected to the external electrodes 23a of each driving piezoelectric element column 12A of the piezoelectric element 12 by solder to apply a drive signal, and a drive circuit (driver IC) 16 is mounted on this FPC 15 to selectively apply drive waveforms to each driving piezoelectric element column 12A of the piezoelectric element 12. The external electrodes 23b of all the piezoelectric element columns 12A are electrically connected in common and are also connected to the common wiring of the FPC 15 by solder. Here, the output terminal portion of the FPC 15 that is joined to the piezoelectric element 12 is solder-plated to enable solder bonding, but solder plating may also be applied to the piezoelectric element 12 side rather than the FPC 15. Regarding the bonding method, bonding using an anisotropic conductive film or wire bonding can also be used in addition to solder bonding.

[0137] The nozzle plate 3 is constructed 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.

[0138] A frame member 17 formed by injection molding of epoxy resin or polyphenylene sulfite is bonded to the outer periphery of the piezoelectric actuator unit 100, which is composed of the piezoelectric element 12 mounted (connected) with the FPC 15 and the base member 13. The frame member 17 has the common liquid chamber 10 described above formed therein, and further has a supply port 19 formed therein for supplying ink from the outside to the common liquid chamber 10, and this supply port 19 is further connected to an ink supply source such as a sub-tank or ink storage container (not shown).

[0139] In an ink ejection head configured in this manner, for example, by lowering the voltage applied to the driving piezoelectric element column 12A from the reference potential, the piezoelectric element column 12A contracts, the vibration area 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, by increasing the voltage applied to the piezoelectric element column 12A, the piezoelectric element column 12A expands in the stacking direction, and the vibration plate member 2 deforms toward the nozzle hole 4, causing the volume of the liquid chamber 6 to contract. This pressurizes the ink in the liquid chamber 6, and ink droplets are ejected (sprayed) from the nozzle hole 4.

[0140] 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, the liquid chamber 6 expands, and negative pressure is generated, at which point ink fills the liquid chamber 6 from the common liquid chamber 10. After the vibration of the meniscus surface of the nozzle hole 4 has attenuated and stabilized, the operation proceeds to eject the next droplet.

[0141] The method of driving the ink ejection head is not limited to the above example (pull-push shot), and pull shots or push shots can also be performed depending on the driving waveform applied.

[0142] Next, details of the nozzle plate 3 according to the present invention will be described with reference to Figures 7 to 9. Figure 7 is an explanatory plan view of the nozzle plate 3, Figure 8 is an explanatory cross-sectional view of the same, and Figure 9 is an enlarged cross-sectional view of one nozzle portion. The nozzle plate 3 has a nozzle substrate 31 made of, for example, a Ni metal plate, on whose ejection surface 31a thereof is formed a Ti layer 33 as an underlayer, an SiO2 film 34, and a perfluoropolyether film having alkoxysilane in its molecules (this film is called a "water-repellent film") 32, which are formed in this order from the surface of the nozzle substrate 31. Then, near the outlet of the inner wall surface 4a of the nozzle hole 4, a underlayer (Ti layer) 33 is formed continuously from the ejection surface on an 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.

[0143] The nozzle substrate 31 may be made of a Ni metal plate or the like, but is not limited to this.

[0144] Here, the water-repellent layer 32 of the nozzle plate 3 is formed by vapor deposition, and no vapor-deposited film for forming the water-repellent layer 32 is formed near the outlet of the inner wall surface of the nozzle hole 4. This prevents ejection defects and impairs liquid filling properties, allowing for stable droplet ejection.

[0145] <Printing method and printing device> The printing method of the present invention is a printing method in which printing is performed by ejecting the ink of the present invention, and includes at least an ink ejection step, and further includes other steps appropriately selected as necessary, such as a stimulus generation step and a control step. The printing device of the present invention has at least an ink cartridge that contains the ink of the present invention and ink ejection means that ejects the ink, and further has other means that are appropriately selected as necessary, such as a stimulus generation means and a control means. The printing method of the present invention can be suitably carried out by the printing apparatus of the present invention, the ink ejection step can be suitably carried out by the ink ejection means, and the other steps can be suitably carried out by the other means.

[0146] -Ink ejection process (an example of the printing process)- The ink ejection process is a process in which a stimulus (energy) is applied to the ink to eject the ink onto a recording medium and perform printing. In this process, a known inkjet recording method can be applied as a method for ejecting the ink and printing onto a recording medium. Examples of such a method include an inkjet recording method that uses a scanning head and an inkjet recording method that uses a line-arranged head to record an image on a sheet of recording medium. There are no particular limitations on the driving method of the recording head, which is the ink ejection means, and it is possible to use an on-demand type head that uses a piezoelectric element actuator using PZT or the like, a method that uses thermal energy, an actuator that uses electrostatic force, etc., or it is also possible to record using a continuous ejection type charge control type head.

[0147] In the printing method of the present invention, a heating and drying step can be provided after the ink ejection step, if necessary. For example, the recording medium can be dried using an infrared drying device, a microwave drying device, a roll heater, a drum heater, hot air, or the like.

[0148] An example of the above printing device is shown in FIG. This diagram shows a case in which an image forming process and a drying process are performed, with 1 representing the recording medium, 2 representing the ink ejection section, 3 representing the conveyor belt, 4 representing the hot air drying device, 5 representing the image forming section, 6 representing the drying processing section, and 7 representing the transfer roll.

[0149] <Recording device and recording method> The ink of the present invention can be suitably used in various recording devices using the ink jet recording method, such as printers, facsimile machines, copying machines, printer / fax / copier combination machines, and three-dimensional modeling devices. In the present invention, the term "recording apparatus" and "recording method" refer to an apparatus capable of ejecting ink or various treatment liquids onto a recording medium, and a method of recording using the apparatus. The term "recording medium" refers to an object onto which ink or various treatment liquids can be attached, even if only temporarily. This recording device can include not only the head portion that ejects ink, but also means related to feeding, transporting, and discharging the recording medium, as well as other devices called pre-processing devices and post-processing devices. The recording apparatus and recording method may have a heating means used in the heating step and a drying means used in the drying step. The heating means and drying means include, for example, means for heating and drying the printed surface and back surface of the recording medium. The heating means and drying means are not particularly limited, but for example, a hot air heater or an infrared heater can be used. Heating and drying can be carried out before, during, or after printing. Furthermore, the recording device and recording method are not limited to those that visualize meaningful images such as letters and figures using ink. For example, they also include those that form patterns such as geometric designs and those that create three-dimensional images. Furthermore, unless otherwise specified, the recording 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, this recording device includes not only desktop types, but also wide-width recording devices that can print on A0-sized recording media, and continuous feed printers that can use continuous paper wound into a roll as a recording medium, for example. An example of a recording apparatus will be described with reference to FIGS. 2 and 3. FIG. 2 is a perspective view of the apparatus. FIG. 3 is a perspective view of a main tank. An image forming apparatus 400, as an example of a recording apparatus, is a serial-type 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 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 device body is opened. A main tank 410 is detachably attached to the cartridge holder 404. This allows each ink outlet 413 of the main tank 410 to communicate with the ejection head 434 for each color via the supply tube 436 for each color, making it possible to eject ink from the ejection head 434 onto a recording medium.

[0150] It is preferable to have a filter in the ink flow path from ink storage unit (ink cartridge) 411 to ejection head (ejection means for ejecting ink) 434 in Fig. 3. A filter may also be provided at ink outlet 413. The filter is preferably one that can retain particles of 10 µm or larger, and by providing a filter, particles of 10 µm or larger can be removed, making it possible to provide a printing device with excellent ejection stability. Since the filter is constantly in contact with ink, it is preferably made of stainless steel from the viewpoint of corrosion resistance, and among these, austenitic stainless steel, more particularly SUS304, SUS316 or SUS316L, is desirable because of its excellent corrosion resistance. It is preferable that the composition contains any one of the above, and more preferably, it consists of any one of these.

[0151] Filters with different filtration accuracy are commercially available, and for example, the Acro Last Chance filter manufactured by Nippon Pall Corporation can be used. Using a filter with a filtration accuracy of 10 μm or less is preferred because it can remove solids present in the ink and improve ejection stability. Using a filter with a filtration accuracy of 6 μm or more and 10 μm or less is preferred because it allows ink to be efficiently supplied to the ejection means. A specific example of a product is a 10 μm disposable filter, PALL ACRO25 LCF-12100, filtration accuracy: 10 μm, material: polypropylene.

[0152] The ink contains water, an organic solvent, polyurethane resin particles, and a cyclic ester having a structure represented by general formula (I), and after being stored at room temperature (25±5°C) for one month, the content of crystals of the cyclic ester having a structure represented by general formula (I) with a particle size of 1 μm or more is less than 4 ppm of the entire ink. By using this ink, it has become possible to provide an ink, a printing method, and a printing device that have high fixation and drying properties even on non-penetrable media for signage and commercial printing paper, high image density, good liquid permeability and ejection stability, and excellent storage stability. [ka]

[0153] By using a printing device in which a filter is provided in the ink flow path from the ink cartridge to the ejection means that ejects the ink, it is possible to remove crystals present in the ink, for example, those with a particle size exceeding 10 μm, thereby achieving favorable ejection stability.

[0154] In the manufacturing process of an ink containing at least water, an organic solvent, and polyurethane resin particles, by adding a step of heating the resulting mixture at 40°C or higher but lower than 70°C for at least 6 hours after the step of mixing water, organic solvent, and polyurethane resin particles, the content of crystals of cyclic esters having a structure represented by general formula (I) with a particle size of 1 μm or larger in the ink can be reduced to less than 4 ppm of the total ink. By reducing the content of cyclic esters having a structure represented by general formula (I) in the ink, an ink can be obtained that has high fixability and drying properties, high image density, good liquid permeability, good ejection stability, and excellent storage stability. Regarding the crystals, even if large crystals with a particle size exceeding 10 μm remain, removing the large crystals with a filter is believed to further improve ejection stability.

[0155] The shape of the filter used in the present invention is not particularly limited, and any known filter can be used. Among them, a sintered filter made by laminating stainless steel fibers in a felt-like form and sintering them, or a twill woven filter made by weaving stainless steel fibers in a twill weave is preferably used, as this will result in an inkjet recording device (ink supply unit) with longer-term ejection reliability.

[0156] In the present invention, the terms image formation, recording, printing, printing, etc. are all synonymous.

[0157] Recording medium, media, and printed material are all synonymous terms. [Example]

[0158] The present invention will be explained in more detail below by showing Preparation Examples, Production Examples, Examples, and Comparative Examples, but the present invention is not limited to these Examples. In the Examples, "parts" and "%" mean "parts by mass" and "% by mass" unless otherwise specified. Unless otherwise specified, ink preparation and evaluation were carried out at room temperature of 25°C and humidity of 60%.

[0159] <Preparation of pigment dispersion> (Preparation Example 1) -Preparation of surface-modified black pigment dispersion- 100 g of Cabot Corporation's Black Pearls® 1000 (carbon black with a BET specific surface area of 343 m / g and a dibutyl phthalate absorption (DBPA) of 105 mL / 100 g), 100 mmol of sulfanilic acid, and 1 L of highly purified ion-exchanged water were mixed at room temperature using a Silverson mixer (6000 rpm). Next, 100 mmol of nitric acid was added to the resulting slurry, and after 30 minutes, 100 mmol of sodium nitrite (100 mmol) dissolved in 10 mL of highly purified ion-exchanged water was slowly added. The mixture was heated to 60°C with stirring and reacted for 1 hour to obtain a modified pigment in which sulfanilic acid was attached to the carbon black. The pH was then adjusted to 9 with a 10% tetrabutylammonium hydroxide solution (methanol solution), and after 30 minutes, a modified pigment dispersion was obtained. This dispersion and highly purified ion-exchanged water were then subjected to ultrafiltration using a dialysis membrane, followed by ultrasonic dispersion to obtain a modified pigment dispersion containing 20% pigment solids. The surface treatment level of the pigment was 0.75 mmol / g, and the median diameter (D50) measured with a particle size distribution analyzer (Nanotrac UPA-EX150 manufactured by Nikkiso Co., Ltd.) was 120 nm.

[0160] (Preparation Example 2) -Preparation of surface-modified magenta pigment dispersion- 1 kg of SENSIENT pigment dispersion SMART Magenta 3122BA (Pigment Red 122 surface-treated dispersion, 14.5% pigment solids) was acidified with 0.1 N HCl aqueous solution. The pH was then adjusted to 9 with 10% tetraethylammonium hydroxide aqueous solution, and after 30 minutes, a modified pigment dispersion was obtained. The modified pigment dispersion, containing a pigment bonded to at least one aminobenzoic acid group or aminobenzoic acid tetraethylammonium salt, was subjected to ultrafiltration using a dialysis membrane with ion-exchange high-purity water, followed by ultrasonic dispersion to obtain a modified pigment dispersion containing 20% pigment solids. The median diameter (D50) measured using a particle size distribution analyzer (Nikkiso Nanotrac UPA-EX150) was 104 nm.

[0161] (Preparation Example 3) -Preparation of surface-modified cyan pigment dispersion- 1 kg of SENSIENT pigment dispersion SMART Cyan 3154BA (Pigment Blue 15:4 surface-treated dispersion, pigment solids content 14.5%) was subjected to acid precipitation with 0.1 N aqueous HCl. The pH was then adjusted to 9 with 40% benzyltrimethylammonium hydroxide solution (methanol solution), and after 30 minutes, a modified pigment dispersion was obtained. The modified pigment dispersion, containing a pigment bonded to at least one aminobenzoic acid group or aminobenzoic acid benzyltrimethylammonium salt, was subjected to ultrafiltration using a dialysis membrane with ion-exchange high-purity water, followed by ultrasonic dispersion to obtain a modified pigment dispersion containing 20% pigment solids. The median diameter (D50) measured using a particle size distribution analyzer (Nikkiso Nanotrac UPA-EX150) was 116 nm.

[0162] (Preparation Example 4) -Preparation of surface-modified yellow pigment dispersion- 1 kg of SENSIENT SMART Yellow 3074BA pigment dispersion (surface-treated Pigment Yellow 74 dispersion, 14.5% pigment solids) was adjusted to pH 9 with 10% tetrabutylammonium hydroxide solution (methanol), and after 30 minutes, a modified pigment dispersion was obtained. The modified pigment dispersion, containing a pigment bonded to at least one aminobenzoic acid group or tetrabutylammonium aminobenzoate salt, was subjected to ultrafiltration using a dialysis membrane with ion-exchanged high-purity water, followed by ultrasonic dispersion to obtain a modified pigment dispersion containing 20% pigment solids. The median diameter (D50) measured using a particle size distribution analyzer (Nikkiso Nanotrac UPA-EX150) was 145 nm.

[0163] (Preparation Example 5) -Preparation of magenta pigment-containing polymer particle dispersion- <Preparation of Polymer Solution A> A 1-L flask equipped with a mechanical stirrer, a thermometer, a nitrogen gas inlet tube, a reflux condenser, and a dropping funnel was thoroughly purged with nitrogen gas, and then 11.2 g of styrene, 2.8 g of acrylic acid, 12.0 g of lauryl methacrylate, 4.0 g of polyethylene glycol methacrylate, 4.0 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, 108.0 g of lauryl methacrylate, 36.0 g of polyethylene glycol methacrylate, 60.0 g of hydroxyethyl methacrylate, 36.0 g of styrene macromer, 3.6 g of mercaptoethanol, 2.4 g of azobismethylvaleronitrile, and 18 g of methyl ethyl ketone was added dropwise to the flask over 2.5 hours. After the dropwise addition, a mixed solution of 0.8 g of azobismethylvaleronitrile and 18 g of methyl ethyl ketone was added dropwise to the flask over 0.5 hours. After aging at 65 °C for 1 hour, 0.8 g of azobismethylvaleronitrile was added, and the mixture was further aged for 1 hour. After completion of the reaction, 364 g of methyl ethyl ketone was added to the flask, yielding 800 g of polymer solution A with a concentration of 50% by mass.

[0164] <Preparation of Pigment-Containing Polymer Microparticle Dispersion> 28 g of polymer solution A, 42 g of CI Pigment Red 122, 13.6 g of 1 mol / L potassium hydroxide aqueous solution, 20 g of methyl ethyl ketone, and 13.6 g of ion-exchanged water were thoroughly stirred and then kneaded using a roll mill. The resulting paste was added to 200 g of pure water and thoroughly stirred. The methyl ethyl ketone and water were then distilled off using an evaporator. The resulting dispersion was then pressure-filtered through a polyvinylidene fluoride membrane filter with an average pore size of 5.0 μm to remove coarse particles, resulting in a magenta pigment-containing polymer microparticle dispersion with a pigment content of 15% by weight and a solids content of 20% by weight. The median diameter (D50) of the polymer microparticles in the resulting magenta pigment-containing polymer microparticle dispersion was measured and found to be 127 nm. The median diameter (D50) was measured using a particle size distribution analyzer (Nanorak UPA-EX150, manufactured by Nikkiso Co., Ltd.).

[0165] (Preparation Example 6) -Preparation of cyan pigment-containing polymer particle dispersion- A cyan pigment-containing polymer fine particle dispersion was prepared in the same manner as in Preparation Example 5, except that CI Pigment Red 122 used in Preparation Example 5 was changed to a phthalocyanine pigment (CI Pigment Blue 15:3). The median diameter (D50) of the polymer fine particles in the obtained cyan pigment-containing polymer fine particle dispersion was measured using a particle size distribution measuring device (Nanotrac UPA-EX150, manufactured by Nikkiso Co., Ltd.) and was found to be 93 nm.

[0166] (Preparation Example 7) -Preparation of yellow pigment-containing polymer particle dispersion- A yellow pigment-containing polymer fine particle dispersion was prepared in the same manner as in Preparation Example 5, except that CI Pigment Red 122 used in Preparation Example 5 was changed to a bisazo yellow pigment (CI Pigment Yellow 155). The median diameter (D50) of the polymer fine particles in the obtained yellow pigment-containing polymer fine particle dispersion was measured using a particle size distribution measuring device (Nanotrac UPA-EX150, manufactured by Nikkiso Co., Ltd.) and was found to be 76 nm.

[0167] (Preparation Example 8) -Preparation of carbon black pigment-containing polymer particle dispersion- A carbon black pigment-containing polymer fine particle dispersion was prepared in the same manner as in Preparation Example 5, except that CI Pigment Red 122 used in Preparation Example 5 was replaced with carbon black (FW100, manufactured by Degussa). The median diameter (D50) of the polymer fine particles in the obtained carbon black pigment-containing polymer fine particle dispersion was measured using a particle size distribution measuring device (Nanotrac UPA-EX150, manufactured by Nikkiso Co., Ltd.) and was found to be 104 nm.

[0168] <Example of resin particle preparation> <Preparation of Water-Dispersible Polyurethane Resin (A)> (Preparation of Polyester Polyol P-1) In a reaction vessel equipped with a thermometer, a nitrogen gas inlet tube, and a stirrer, 830 parts of terephthalic acid, 830 parts of isophthalic acid, 374 parts of ethylene glycol, 598 parts of neopentyl glycol, and 0.5 parts of dibutyltin oxide were charged while introducing nitrogen gas, and a polycondensation reaction was carried out at 230°C for 15 hours at 180 to 230°C until the acid value became 1 or less, thereby obtaining polyester polyol P-1 having a hydroxyl value of 74.5, an acid value of 0.2, and an average molecular weight of 1,500.

[0169] (Preparation of Hydrophobic Polyester Polyol Q-1) In a reaction vessel equipped with a thermometer, a nitrogen gas inlet tube, and a stirrer, 1,660 parts of orthophthalic acid, 1,637 parts of diethylene glycol, and 0.5 parts of dibutyltin oxide were charged while introducing nitrogen gas, and a polycondensation reaction was carried out at 230°C for 15 hours at 180 to 230°C until the acid value reached 1 or less, thereby obtaining polyester polyol Q-1 having an aromatic cyclic structure with a hydroxyl value of 190 and an acid value of 0.3.

[0170] (Preparation of Water-Dispersible Polyurethane Resin (A)) 1,000 parts of polyester polyol P-1 were dehydrated at 100°C under reduced pressure, and then cooled to 80°C. 907 parts of methyl ethyl ketone was added and the mixture was thoroughly stirred to dissolve, and 80 parts of 2,2'-dimethylolpropionic acid was added, followed by 281 parts of isophorone diisocyanate, and the mixture was reacted at 75°C for 8 hours to carry out a urethane-forming step. After confirming that the isocyanate value was 0.1% or less, the mixture was cooled to 50°C, and 340 parts of the polyester polyol Q-1 was added to form a homogeneous solution. After that, 60 parts of triethylamine was added to neutralize the solution, and then 7,000 parts of water was added to dissolve the solution in water. Methyl ethyl ketone was removed from the resulting transparent reaction product at 40-60°C under reduced pressure, and then water was added to adjust the concentration to obtain a stable translucent colloidal aqueous dispersion with a nonvolatile content of 25%.

[0171] <Preparation of Water-Dispersible Polyurethane Resin (B)> 1,000 parts of the polyester polyol P-1 described above was dehydrated at 100°C under reduced pressure, and then cooled to 80°C. 907 parts of methyl ethyl ketone was added and the mixture was thoroughly stirred to dissolve, and 80 parts of 2,2'-dimethylolpropionic acid was added, followed by 281 parts of isophorone diisocyanate, and the mixture was reacted at 75°C for 8 hours to carry out the urethane-forming step. After it was confirmed that the isocyanate value had fallen to 0.1% or less, the mixture was cooled to 50°C, neutralized by adding 60 parts of triethylamine, and then dissolved in water by adding 7000 parts of water. Methyl ethyl ketone was removed from the resulting transparent reaction product at 40-60°C under reduced pressure, and then water was added to adjust the concentration to obtain a stable translucent colloidal aqueous dispersion with a nonvolatile content of 25%.

[0172] <Preparation of Water-Dispersible Polyurethane Resin (C)> (Preparation of Polyester Polyol P-2) While introducing nitrogen gas into a reaction vessel equipped with a thermometer, a nitrogen gas inlet tube, and a stirrer, 664 parts of terephthalic acid, 631 parts of isophthalic acid, 472 parts of 1,4-butanediol, 447 parts of neopentyl glycol, and 0.5 parts of dibutyltin oxide were charged and esterified at 180 to 230 ° C. for 5 hours, and then polycondensation reaction was carried out at 230 ° C. for 6 hours until the acid value was 1 or less. Next, the mixture was cooled to 120 ° C., and 321 parts of adipic acid and 268 parts of 2,2'-dimethylolpropionic acid were added. The mixture was heated again to 170 ° C. and reacted at this temperature for 20 hours to obtain a polyester polyol P-2 containing carboxyl groups with an acid value of 46.5 and a hydroxyl value of 59.8.

[0173] (Preparation of Water-Dispersible Polyurethane Resin (C)) 1,000 parts of polyester polyol P-2 were dehydrated at 100°C under reduced pressure, then cooled to 80°C, and 812 parts of methyl ethyl ketone were added and thoroughly stirred to dissolve. 20 parts of 1,4-butanediol were then added, followed by 198 parts of dicyclohexylmethane-4,4'-diisocyanate (hydrogenated MDI), and the mixture was reacted at 75°C for 8 hours. After it was confirmed that the isocyanate value had fallen to 0.1% or less, the mixture was cooled to 50°C, neutralized by adding 84 parts of triethylamine, and then dissolved in water by adding 7000 parts of water. Methyl ethyl ketone was removed from the resulting transparent reaction product at 40-60°C under reduced pressure, and then water was added to adjust the concentration to obtain a stable translucent colloidal aqueous dispersion with a nonvolatile content of 25%.

[0174] <Preparation of Water-Dispersible Polyurethane Resin (D)> 1,000 parts of polyester polyol P-1 were dehydrated at 100°C under reduced pressure, and then cooled to 80°C. 907 parts of methyl ethyl ketone was added and the mixture was thoroughly stirred to dissolve, and 80 parts of 2,2'-dimethylolpropionic acid was added, followed by 281 parts of isophorone diisocyanate, and the mixture was reacted at 75°C for 8 hours to carry out a urethane-forming step. After it was confirmed that the isocyanate value had fallen to 0.1% or less, the mixture was cooled to 50°C, neutralized by adding 60 parts of triethylamine, and then dissolved in water by adding 7000 parts of water. Methyl ethyl ketone was removed from the resulting transparent reaction product at 40-60°C under reduced pressure, and then water was added to adjust the concentration to obtain a stable translucent colloidal aqueous dispersion with a nonvolatile content of 25%.

[0175] <Preparation of Acrylic-Silicone Polymer Microparticles A> After thoroughly replacing the air in a 1-L flask equipped with a mechanical stirrer, thermometer, nitrogen gas inlet tube, reflux condenser, and dropping funnel with nitrogen, 350 g of ion-exchanged water was mixed with 8.0 g of Latemul S-180 (Kao Corporation, reactive anionic surfactant) and heated to 65 °C. Next, 3.0 g of reaction initiator t-butyl peroxobenzoate and 1.0 g of sodium isoascorbate were added, and after 5 minutes, a mixture of 45 g of methyl methacrylate, 160 g of 2-ethylhexyl methacrylate, 5 g of acrylic acid, 45 g of butyl methacrylate, 30 g of cyclohexyl methacrylate, 15 g of vinyltriethoxysilane, 8.0 g of Latemul S-180, and 340 g of ion-exchanged water was added dropwise over 3 hours. Next, the mixture was heated and aged at 80 °C for 2 hours, cooled to room temperature, and the pH was adjusted to 7-8 with sodium hydroxide. The ethanol was then removed using an evaporator, and the moisture content was adjusted to obtain 730 g of acrylic-silicone polymer microparticles with a solids content of 40%. The median diameter (D50) of the polymer microparticles in the dispersion was measured using a particle size distribution analyzer (Nikkiso Co., Ltd., Nanotrac UPA-EX150) and found to be 125 nm.

[0176] (Examples 1 to 26 and Comparative Examples 1 to 19 ) <Pre-ink manufacturing example> (Pre-ink manufacturing example 1) A vessel equipped with a stirrer was charged with 7.50 parts of 3-methoxy-N,N-dimethylpropanamide represented by the above formula (1), 5.00 parts of propylene glycol monopropyl ether, 18.00 parts of propylene glycol, 2.00 parts of 2,2,4-trimethyl-1,3-pentanediol, and 0.50 parts of 2,4,7,9-tetramethyldecane-4,7-diol, and 1.00 parts of the polyether-modified siloxane compound represented by the above formula (8), and the mixture was stirred for 30 minutes. Next, 0.05 parts of a preservative and antifungal agent (Proxel GXL manufactured by Avecia), 0.30 parts of 2-amino-2-ethyl-1,3-propanediol, 56.00 parts of the prepared water-dispersible polyurethane resin (A), 1.62 parts of polyurethane dispersion "Takelac W-6110 manufactured by Mitsui Chemicals, Inc.", and a total of 100 parts of highly purified water were added, and the mixture was stirred for 60 minutes. The resulting mixture was then pressure filtered through a polyvinylidene fluoride membrane filter with an average pore size of 1.2 μm to remove coarse particles and dust, thereby obtaining pre-ink 1.

[0177] (Pre-ink manufacturing example 2) In a container equipped with a stirrer, 7.50 parts of 3-methoxy-N,N-dimethylpropanamide represented by the above formula (1), 5.00 parts of propylene glycol monopropyl ether, 22.00 parts of propylene glycol, 2.00 parts of 2-ethyl-1,3-hexanediol, and 0.50 parts of 2,4,7,9-tetramethyldecane-4,7-diol, and 1.50 parts of the polyether-modified siloxane compound represented by the above formula (8) were placed and mixed with stirring for 30 minutes. Next, 0.05 parts of an antiseptic and antifungal agent (Proxel GXL manufactured by Avecia), 0.30 parts of 2-amino-2-ethyl-1,3-propanediol, 24.00 parts of the prepared water-dispersible polyurethane resin (A), 1.62 parts of a polyurethane dispersion "Takelac W-6110 manufactured by Mitsui Chemicals, Inc.", 15.00 parts of the surface-modified black pigment dispersion of Preparation Example 1, and a quantity of highly purified water sufficient to make the total mixture 100 parts were added and mixed and stirred for 60 minutes. The resulting mixture was then pressure-filtered through a polyvinylidene fluoride membrane filter with an average pore size of 1.2 μm to remove coarse particles and debris, yielding Pre-ink 2.

[0178] (Pre-ink manufacturing example 3) 16、19~ twenty four) Pre-ink Production Examples 3 to 4 in Tables 1 to 3 below were prepared in the same manner as in Pre-ink Production Examples 1 and 2. 16、19~ The organic solvent, surfactant, and antifoaming agent shown in each column of 24 were mixed and stirred, then the antiseptic and antifungal agent, pH adjuster, and colorant (pigment dispersion) were mixed and stirred, and then the water-dispersible polyurethane resin and resin particles were mixed and stirred. The resulting mixture was pressure-filtered through a polyvinylidene fluoride membrane filter with an average pore size of 1.2 μm to remove coarse particles and dust, and the resulting mixture was collected as pre-ink 3 to 5. 16、19~ I got 24.

[0179] [Table 1]

[0180] [Table 2]

[0181] [Table 3]

[0182] Details of the abbreviations in Tables 1 to 3 are as follows: Direct Blue 199 (water-soluble cyan dye): EKTA INTERNATIONAL Superflex 300: Polyurethane dispersion, solids 30.0%, Tg = -42°C, manufactured by Daiichi Kogyo Seiyaku Co., Ltd. Takelac W-6110: Polyurethane dispersion, solids 30.9%, Tg = -20°C, manufactured by Mitsui Chemicals Compound of formula (1): 3-methoxy-N,N-dimethylpropanamide Compound of formula (2): 3-n-butoxy-N,N-dimethylpropanamide Compound of formula (5): 3-ethyl-3-hydroxymethyloxetane Compound of formula (6): 3-methyl-3-hydroxymethyloxetane TEGO Wet270: Polyether-modified siloxane compound (Evonik, 100% active ingredient) Silface SAG503A: Polyether-modified siloxane compound (Made by Nissin Chemical Industry Co., Ltd., 100% active ingredient) Unidyne DSN403N: Polyoxyethylene perfluoroalkyl ether (Made by Daikin Industries, 100% active ingredient) ·Proxel GXL:1,2-benzisothiazolin-3-one Main ingredient: antiseptic and antifungal agent (Avecia, 20% ingredients, contains dipropylene glycol)

[0183] The physical properties of each of the inks in Pre-ink Production Examples 1 to 24 were measured as follows. The results are shown in Table 4. <Viscosity> Measurement was carried out at 25°C using a viscometer (RE-85L, manufactured by Toki Sangyo Co., Ltd.). <ph> The measurement was carried out at 25°C using a pH meter (HM-30R model, manufactured by TOA-DKK). <Static surface tension> Measurement was carried out at 25°C using an automatic surface tensiometer (DY-300, manufactured by Kyowa Interface Science Co., Ltd.). <Dynamic surface tension> The dynamic surface tension of the ink of the present invention was measured at 25° C. using a SITA DynoTester (manufactured by SITA) at a surface life of 15 msec according to the maximum bubble pressure method.

[0184] [Table 4]

[0185] <Ink manufacturing example> The pre-ink 1 16、19~ 24 was heated under the conditions shown in Table 5. 18、21~27 The physical properties of each ink were measured in the same manner as for the pre-ink. The results are shown in Table 5. [Table 5]

[0186] The pre-ink and the ink heated under each condition were filled into an ink pack and left to stand at room temperature (25±5°C) for one month. The ink was then evaluated as described below, and images were formed, and the properties were evaluated. The results are shown in Table 6.

[0187] -Qualitative and quantitative analysis of cyclic ester crystals having the structure represented by general formula (I) contained in ink- <Qualitative method, quantitative method> The amount of cyclic ester crystals having the structure represented by general formula (I) contained in the ink can be quantified simply by filtering each ink in the manufacturing examples using a 60mm Kiriyama funnel fitted with 60mm No. 5C Kiriyama funnel filter paper (particle retention capacity 1μm), thoroughly rinsing the crystals and filter paper retained after filtration with high-purity water, and then drying the filter paper to its original moisture content before filtration. The difference between the mass of the filter paper before filtration and the mass of the crystals and filter paper retained after filtration can be measured to quantify the amount of cyclic ester crystals having the structure represented by general formula (I). In order to improve the accuracy of quantification, 3000 g of ink was filtered to determine the amount of ink to be quantified. The crystals on the filter paper were all dissolved in tetrahydrofuran, and the remaining filter paper was dried and then weighed. The difference between the weighed filter paper mass and the filter paper mass before filtration was checked, but there was no difference. The solution dissolved in tetrahydrofuran was analyzed by LC-MS to check whether it contained any other components. The structure of the crystals precipitated in the ink and obtained by filtration was confirmed by GC-MS analysis and LC-MS analysis + C 13 -NMR+H 1 Qualitative analysis by NMR+FT-IR confirmed that all of the compounds were cyclic esters having the structure represented by the following structural formula (B). [ka]

[0188] -Ink ejection process (image formation process)- Under environmental conditions adjusted to 23±0.5°C and 50±5% RH, an inkjet recording device (IPSiO GXe-5500, manufactured by Ricoh Co., Ltd.) was used, and the driving voltage of the piezo element was varied so as to uniformly eject the ink. 2 ) were set so that the same amount of ink was adhered to the ink cartridge. In addition, in Examples 18 and 19 and Comparative Examples 18 and 19, a filter was installed between the ink storage section (ink cartridge) and the ink flow path leading to the ejection head (ejection means for ejecting ink). The following filter was used: Acro Last Chance filter manufactured by Nippon Pall Corporation. 10μm disposable filter: PALL ACRO25 LCF-12100, filtration accuracy: 10μm, Material: Polypropylene

[0189] Next, the preparation of the nozzle plate to be attached to the inkjet head will be described. (Manufacturing Example 101) <Fabrication of Nozzle Plate A> <<Synthesis of Fluorine-Containing Acrylate Ester Polymer A>> -Synthesis of ethylene oxide chain-containing fluoromonomer (MPOERfA)- The reaction formula for the synthesis of an ethylene oxide chain-containing fluorine monomer is shown below. [ka] In the reaction formula, the average value of n is 8 to 9.

[0190] Next, 52.13 g of single-terminated methoxy polyethylene glycol (average EO number: 8-9, Uniox M-400, NOF Corporation) and 0.94 g of boron trifluoride diethyl ether complex were charged into a four-neck flask. Under a nitrogen stream, 50 g of 3-perfluorohexyl-1,2-epoxypropane was added dropwise over 30-40 minutes at room temperature, while taking care not to generate heat. After the addition was completed, the reaction was continued at room temperature for approximately 2 hours, after which gas chromatography (GC) confirmed that the 3-perfluorohexyl-1,2-epoxypropane peak had disappeared. 0.03 g of tert-butylcatechol was added to the mixture and stirred thoroughly. 14.81 g of triethylamine was then added, and 12.04 g of acrylic acid chloride was added dropwise over approximately 20 minutes, while taking care not to generate heat. After the addition was completed, the reaction was continued at room temperature for approximately 2 hours, after which GC confirmed that the acrylic acid chloride peak had almost disappeared. The product was identified by IR spectrum, 1H-NMR, and 19F-NMR spectrum.

[0191] -Synthesis of fluorine-containing acrylate ester polymer A- A 200 mL four-neck flask was charged with 60 g of isopropyl alcohol and a 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 mol, NOF Corporation, AE-400), 5% by mass of 2-hydroxyethyl acrylate, 2.5% by mass of acetoacetoxyethyl methacrylate, and 2.5% by mass of dimethylaminoethyl acrylate. Nitrogen was blown into the flask for 60 minutes to replace the air in the system. While continuing the nitrogen flow, the internal temperature was raised to 75-80°C, and then 0.25 g of azobisisobutyronitrile was added. The polymerization reaction was carried out for 8 hours. Analysis of the polymerization solution by gas chromatography (GC) and gel permeation chromatography confirmed that the peaks derived from the monomer had almost disappeared and that peaks derived from the copolymer had appeared. The weight-average molecular weight of the copolymer was 17,000 (polystyrene equivalent). Finally, 0.42 g of acetic acid was added to neutralize the solution, and the solution was diluted with water to a 20% by mass solution of fluorine-containing acrylate ester copolymer A.

[0192] -Making the nozzle plate- Next, a nozzle substrate made of stainless steel (SUS304) measuring 34 mm long x 16 mm wide and 20 μm thick was prepared. The nozzle substrate had four rows of nozzle holes, each with an average diameter of 25 μm, arranged at a pitch of 85 μm (300 dpi), which is the shortest distance between the centers of the nozzle holes, with 320 holes per row. A 20% by mass solution of the prepared fluorine-containing acrylate ester polymer A was applied by dipping onto the ink ejection side surface of the nozzle substrate, and dried to form an ink-repellent film with an average thickness of 50 nm. In this way, nozzle plate A of Production Example 101 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 forming an ink-repellent film, the masking tape was peeled off and removed. In addition, the plate was heated at 120°C for 1 hour to form an ink-repellent film.

[0193] (Manufacturing Example 102) <Preparation of nozzle plate B> <<Synthesis of Fluorine-Containing Acrylate Ester Polymer B>> -Synthesis of Rf epoxy adduct (FAGMA) of 2-hydroxyethyl acrylate (HEA)- The reaction formula for the synthesis of the Rf epoxy adduct of 2-hydroxyethyl acrylate is shown below. [ka]

[0194] A four-neck flask was charged with 20 g of 2-hydroxyethyl acrylate (HEA), 0.61 g of boron trifluoride diethyl ether complex, and 0.026 g of tertiary butyl catechol. 64.83 g of 3-perfluorohexyl-1,2-epoxypropane was added dropwise over 30 to 40 minutes at room temperature, while taking care to avoid heat generation. After the addition was complete, the reaction was continued at room temperature for approximately 2 hours, after which gas chromatography (GC) confirmed that the 3-perfluorohexyl-1,2-epoxypropane peak had disappeared. After the reaction was complete, the reactant was dissolved in 100 g of 1,1-dichloro-1,2,2,3,3-pentafluoropropane (HCFC225), and 100 g of water was added. The mixture was washed with a separatory funnel and separated. The organic layer was then removed. This washing and separation procedure was repeated once more, and the organic layer was removed. 5 g of anhydrous magnesium sulfate was added and dried overnight. HCFC225 was evaporated to obtain the Rf epoxy adduct of HEA (FAGMA). The product was identified using IR, H-NMR, and F-NMR spectra. Analysis of the product revealed that a mixed monomer was obtained consisting of approximately 64% by mass of the 1-mol adduct (n=1) of 3-perfluorohexyl-1,2-epoxypropane, approximately 27% by mass of the 2-mol adduct (n=2), and approximately 9% by mass of the 3-mol adduct.

[0195] -Synthesis of sulfonic acid-containing fluoromonomers- The reaction formula for the synthesis of the sulfonic acid-containing fluorine monomer is shown below. [ka]

[0196] 30 g of the synthesized HEA Rf epoxy adduct (FAGMA), 30 g of dichloromethane, 7.8 g of triethylamine, and 0.024 g of hydroquinone monomethyl ether were placed in a four-neck flask. This mixture was cooled in an ice bath to 0-10°C. A dichloromethane solution of chlorosulfonic acid (7.48 g of chlorosulfonic acid + 15 g of dichloromethane) was slowly added dropwise over approximately 30 minutes, while taking care to avoid heat generation. After the addition was complete, the mixture was allowed to react at room temperature for 3 hours. 100 g of water was added to the reaction mixture, and the washing and separation procedures were repeated twice. The organic layer was removed, 5 g of anhydrous magnesium sulfate was added, and the mixture was dried overnight. The product (sulfonic acid-containing fluoromonomer) was identified by IR, H-NMR, and F-NMR spectroscopy.

[0197] -Synthesis of fluorine-containing acrylate ester polymer B- A fluorine-containing acrylate ester polymer B was synthesized in the same manner as in Production Example 101, except that the monomer composition was changed to 60 mass% of 2-(perfluorohexyl)ethyl acrylate, 20 mass% of the sulfonic acid group-containing fluorine monomer, 17.5 mass% of polyethylene glycol monoacrylate (EO: 10 mol, manufactured by NOF Corporation, AE-400), and 2.5 mass% of acetoacetoxyethyl methacrylate. The weight-average molecular weight of the obtained copolymer was 17,000 (polystyrene equivalent). Finally, the mixture was neutralized with 0.42 g of acetic acid and diluted with water to give a 20 mass% solution of the fluorine-containing acrylate ester polymer B.

[0198] -Making the nozzle plate- A 20% by mass solution of the prepared fluorine-containing acrylate ester polymer B was applied by dipping to the ink ejection side surface of the same nozzle substrate as in Production Example 101, and dried to form an ink-repellent film with an average thickness of 30 nm. In this way, nozzle plate B of Production Example 102 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, these were peeled off and removed. In addition, the ink-repellent film was formed by heating at 120°C for 1 hour.

[0199] (Manufacturing Example 103) <Fabrication of Nozzle Plate C> A fluorine-containing acrylate ester polymer solution (Optool DSX, manufactured by Daikin Industries, Ltd.) was prepared. The fluorine-containing acrylate ester polymer solution (Optool DSX, manufactured by Daikin Industries, Ltd.) was applied by dipping to the ink ejection side surface of the same nozzle substrate as in Manufacturing Example 101, and then dried to form an ink-repellent film with an average thickness of 20 nm. In this way, nozzle plate C of Production Example 103 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, these were peeled off and removed. In addition, the ink-repellent film was formed by heating at 120°C for 1 hour.

[0200] (Manufacturing Example 104) <Fabrication of Nozzle Plate D> A silicone resin solution (SR 2441 RESIN, manufactured by Dow Corning Toray Co., Ltd.) was prepared. The silicone resin solution was applied by dipping to the ink ejection side of the same nozzle substrate as in Production Example 101, and then dried to form an ink-repellent film with an average thickness of 100 nm. In this way, nozzle plate D of Production Example 104 was produced. The nozzle holes were masked with a water-soluble resin, and the back surface of the nozzle substrate was masked with tape, which was then peeled off and removed after the ink-repellent film was formed. This was then heated and cured in air at 150°C for 2 hours to form an ink-repellent film.

[0201] (Example 105) <Fabrication of Nozzle Plate E> The ink repellent agent used was a solution prepared by diluting Cytop CTX-105 (trade name, manufactured by Asahi Glass Co., Ltd.) to 0.2% by mass with a solution prepared by mixing CT-solv.100 (manufactured by Asahi Glass Co., Ltd.) and CT-solv.180 (manufactured by Asahi Glass Co., Ltd.) in a volume ratio of 1:1. Silicone rubber was placed on a spinner, and 2 mL of this liquid was dropped onto the silicone rubber. After dropping, the silicone rubber was rotated on the spinner to produce a uniform film. The rotation speed was set as follows: 1st: 1,000 rpm, 5 seconds; 2nd: 3,000 rpm, 20 seconds. The same nozzle substrate surface as in Production Example 101 was pressed onto the silicone rubber to transfer the pattern. This was done three times with a pressing pressure of 2 kg / head. After the transfer, the entire head was placed in an oven at 150° C. for two and a half hours for heat treatment, thereby producing a nozzle plate E of Production Example 105.

[0202] (Example 106) <Fabrication of nozzle plate F> The ink repellent agent used was a solution obtained by diluting AF1600 (Teflon (registered trademark) AF, manufactured by DuPont) with Fluorinert FC-75 (manufactured by 3M) to 0.5% by mass. As in Production Example 105, silicone rubber was placed on a spinner, and 2 mL of this liquid was dropped onto the silicone rubber. After dropping, the silicone rubber was rotated on the spinner to produce a uniform film. The rotation speed was set as follows: 1st: 1,000 rpm, 5 seconds; 2nd: 3,000 rpm, 20 seconds. The same nozzle substrate surface as in Example 1 was pressed onto the silicone rubber to transfer the image, three times, with a pressing pressure of 2 kg / head. After the transfer, the entire head was placed in an oven at 165° C. for 2 hours and 30 minutes for heat treatment, thereby producing a nozzle plate F of Production Example 106.

[0203] -Ink ejection process (printing process)- Under environmental conditions adjusted to 23±0.5°C and 50±5% RH, an inkjet printing device (IPSiO GXe-5500, manufactured by Ricoh Co., Ltd.) was used, and the driving voltage of the piezo element was varied to ensure a uniform amount of ink was ejected, and settings were made to ensure that the same amount of ink was deposited on the recording medium (manufactured by Oji Paper Co., Ltd.: OK top coat + U.S. basis weight 104.7 g / m2).

[0204] <Image density> Using each ink, a chart containing the 64-point JIS X 0208 (1997), 2223 general symbols was created using Microsoft Word 2000 and printed onto MyPaper (manufactured by Ricoh Co., Ltd.). The symbols were measured using a spectrodensitometer (X-Rite 939, manufactured by X-Rite Co., Ltd.), and the image density of each color was evaluated according to the following criteria. The print mode used was the "plain paper - standard fast" mode in the printer driver, modified to "no color correction." JIS X 0208 (1997), 2223 symbols have a square outline and are completely filled in with ink. [Evaluation criteria] A: Black: 1.25 or higher Yellow: 0.80 or higher Magenta: 1.00 or higher Cyan: 1.05 or higher B: Black: 1.20 or more, less than 1.25 Yellow: 0.75 or more, less than 0.80 Magenta: 0.95 or more, less than 1.00 Cyan: 1.00 or more, less than 1.05 C: Black: 1.15 or more, less than 1.20 Yellow: 0.70 or more, less than 0.75 Magenta: 0.90 or more, less than 0.95 Cyan: 0.95 or more, less than 1.00 D: Black: Less than 1.15 Yellow: Less than 0.70 Magenta: Less than 0.90 Cyan: Less than 0.95

[0205] <Ink storage stability> Using the viscometer, the storage stability was calculated from the viscosity measured before storage and after storage in a sealed container at 60°C for 7 days according to the following formula, and evaluated based on the following evaluation criteria.

number

[0206] <Liquid permeability> Using a cellulose acetate membrane filter (28CP manufactured by Advantec Toyo Co., Ltd.) with a pore size of 0.8 μm, pressure filtration was performed at an air pressure of 1 kgf / cm2, and the ink permeability was evaluated from the slope (attenuation rate) of the linear approximation of the decrease in filtration speed relative to the amount of liquid passed through the filter and the maximum filtration speed. [Evaluation criteria] Liquid permeability Good_A <---------> D_Bad A: Decay rate is 1.5×10 -3 / sec and the maximum filtration rate is 1.0g / sec or more B: Decay rate is 1.5×10 -3 / sec and maximum filtration rate is less than 1.0 g / sec C: Decay rate is 1.5×10 -3 / sec or more 2.5 x 10 -3 / sec D: Decay rate is 2.5×10 -3 / seconds or more

[0207] <Discharge stability-1> -Continuous discharge evaluation- Immediately after 1 L of each individually adjusted ink was passed from the ink cartridge of an inkjet printing device (IPSiO GXe-5500, manufactured by Ricoh Co., Ltd.) through the ejection head of each color, a chart created using Microsoft Word 2000, in which 80% of the area of an A4-sized sheet of paper was filled with a solid image, was printed out consecutively on 200 sheets of MyPaper (manufactured by Ricoh Co., Ltd.), and after printing, a nozzle check chart was printed out and the ejection disturbance of each nozzle was evaluated according to the following criteria. The print mode used was the driver that came with the printer, with the "Plain Paper - Standard Fast" mode modified from the plain paper user settings to "No color correction." [Evaluation criteria] A: No disturbance in discharge B: Some irregular discharge C: Discharge is disturbed or there are areas where no discharge occurs D: Severely disturbed ejection or many nozzles that do not eject

[0208] <Ejection stability-2> -Evaluation of ink repellency time of nozzle plate- In an environment adjusted to a temperature of 23°C ± 0.5°C and a relative humidity of 50% ± 5%, 50 g of each ink shown in Table 7 was placed in a 50 mL beaker, the nozzle plate was removed from the image forming apparatus (IPSiO GXe-5500, manufactured by Ricoh Company, Ltd.), the nozzle plate prepared above was held with tweezers, and immersed in the ink at a speed of 315 mm / min. The nozzle plate was then removed at the same speed. The ink repellency time (ink retraction time) from the ink-repellent film of the nozzle plate was measured and evaluated according to the following criteria. [Evaluation criteria] A: Ink repellency time is less than 10 seconds B: Ink repellency time is 10 seconds or more but less than 30 seconds C: Ink repellency time is 30 seconds or more but less than 60 seconds D: Ink repellency time is 60 seconds or more If the ink repellency time is long, the nozzle plate becomes easily wetted with ink, and therefore nozzles are likely to be missing in a continuous ejection evaluation.

[0209] <Retreating contact angle> 2.0 μL of each ink shown in Tables 4 and 5 was extruded onto the nozzle plate surface prepared above from a syringe equipped with a syringe needle having an inner diameter of 0.37 μm and 0.18 mm in an environment of 25°C, and the receding contact angle (°) at 25°C was measured using the contraction method with an automatic contact angle measuring device DMo-501 (manufactured by Kyowa Interface Science Co., Ltd.).

[0210] <Drying> Using the image forming apparatus shown in Figure 1, a chart with the same general symbols as for image density was printed on Oji Paper OK Topcoat + with a basis weight of 104.7 g / m². After drying by exposing the print to hot air at 100°C for 10 seconds, the dried image area was visually inspected to see if the ink in the image area adhered to the transfer roll, and the evaluation was based on the following criteria. [Evaluation criteria] A: No transfer at all B: Slight transfer to the extent that it does not cause any problems in practical use C: With transcription D: Severe transfer

[0211] <Alcohol resistance (adhesion)> Using each ink, a chart containing 64-point JIS X 0208 (1997), 2223 general symbols, created using Microsoft Word 2000, was printed onto NIJ-PVCM PVC media (manufactured by Panasia Co., Ltd.) The print mode used was the "plain paper - standard fine" mode in the driver attached to the printer, modified to "no color correction." A cotton swab was soaked in 0.5 mL of ethanol and rubbed back and forth 10 times on the solid image area printed above, and the image was visually observed and evaluated according to the following criteria. [Evaluation criteria] A: No change in the image area B: The image is legible but slightly damaged. C: The image is legible but damaged. D: The image area is peeled off and the recording media area is visible.

[0212] [Table 6] [Explanation of symbols]

[0213] (About Figures 1 to 3) 1. Recording media 2 Ink ejection section 3 conveyor belt 4. Hot air drying device 5 Image forming unit 6 Drying processing section 7 Transfer roll 400 Image forming device 401 Exterior of image forming device 401c Device body cover 404 Cartridge Holder 410 Main Tank 410k, 410c, 410m, 410y Main tanks for black (K), cyan (C), magenta (M), and yellow (Y) 411 Ink storage unit 413 Ink outlet 414 Storage container case 420 Mechanism Department 434 Discharge Head 436 Supply Tube (About Figures 4 to 9) 1 Flow path plate, liquid chamber substrate, flow path member 2. Diaphragm member 2a Vibration area (diaphragm part) 2b Island-shaped convex part 3 Nozzle Plate 4 nozzle holes 5 Nozzle connection passage 6 Liquid chamber, pressurized liquid chamber, pressure chamber, pressurized chamber, flow path 7 Fluid resistance section 8 Communication section 10 Common liquid chamber 12 Piezoelectric elements, stacked piezoelectric elements 12A Piezoelectric element column, driving piezoelectric element column 12B Piezoelectric element column, piezoelectric element column for support 13 Base material 15 FPC 16 Drive circuit (driver IC) 17 Frame members 19 Supply port 21 Piezoelectric material layer 22a, 22b internal electrodes 23a, 23b End electrode (external electrode) 31 Nozzle base material 31a Discharge surface 32 Water-repellent film 33 Ti layer (base layer) 34 SiO2 film on the ejection surface 35 SiO2 film on the liquid chamber side 100 Piezoelectric actuator unit [Prior art documents] [Patent documents]

[0214] [Patent Document 1] Patent Publication No. 2012-241135 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-207202 [Patent Document 3] Japanese Patent Application Laid-Open No. 2014-94998< / ph>

Claims

1. In an ink containing water, an organic solvent, and polyurethane resin particles, The polyurethane resin particles contain a polyurethane resin having a structure represented by the following general formula (I): The ink contains a cyclic ester having a structure represented by the following general formula (I), and after the ink is left to stand for one month in a room temperature environment (25±5°C), the content of crystals of the cyclic ester having a particle size of 1 μm or more is less than 4 ppm of the entire ink. 【Chemical 1】

2. The ink of claim 1 , wherein the ink includes a colorant.

3. 3. The ink according to claim 2, wherein the solid content of the polyurethane resin particles in the ink is 3% by mass or more, and the solid content ratio of the colorant to the polyurethane resin particles is 1.0:(2.0 to 11.0).

4. 4. The ink according to claim 2, wherein the colorant is a pigment.

5. 5. The ink according to claim 1, wherein the organic solvent comprises a diol compound and an organic solvent having a solubility parameter (SP value) of 8.9 to 12.

0.

6. The ink according to any one of claims 1 to 5, wherein the ink has a pH of 8.5 or higher.

7. 7. The ink according to claim 6, wherein the ink contains a strongly basic compound.

8. 8. The ink of claim 7, wherein the strongly basic compound is sodium hydroxide or potassium hydroxide.

9. 9. The ink according to claim 1, further comprising a polyether-modified siloxane compound as a surfactant.

10. 10. A method for producing an ink containing water, an organic solvent, and polyurethane resin particles, comprising: a step of mixing water, an organic solvent, and polyurethane resin particles; and a step of heating the mixture obtained in the step at 40° C. or higher but lower than 70° C. for 6 hours or longer.

11. 11. The method for producing an ink according to claim 10, wherein the ink further contains a colorant, the method comprising the steps of: mixing water, an organic solvent, polyurethane resin particles, and the colorant; and heating the mixture obtained by the above steps at a temperature of 40°C or higher but lower than 70°C for 6 hours or longer.

12. A printing method comprising the step of depositing the ink according to any one of claims 1 to 9 onto a substrate and printing.

13. the step of depositing the ink on a substrate and printing is a step of ejecting the ink from an ink ejection head having a nozzle plate that ejects the ink and depositing the ink on the substrate; 13. The printing method according to claim 12, wherein the ink contains water, an organic solvent, polyurethane resin particles containing a polyurethane resin having a structure represented by the following general formula (I), and a cyclic ester having a structure represented by the following general formula (I), and after being left to stand for one month in a room temperature environment (25±5°C), the content of crystals of the cyclic ester having a particle size of 1 μm or more is less than 4 ppm of the entire ink, and the receding contact angle with the nozzle plate is 35° or more. 【Chemical 1】

14. A printing device having an ink ejection head that ejects ink and an ink cartridge that contains the ink in a container, A printing device, wherein the ink is the ink according to any one of claims 1 to 9.

15. 15. The printing apparatus according to claim 14, further comprising a filter in an ink flow path from the ink cartridge to the ink ejection means.

16. 16. The printing device according to claim 14, wherein the ejection means for ejecting the ink is an ink ejection head having a nozzle plate for ejecting the ink, and the receding contact angle of the ink with respect to the nozzle plate is 35 degrees or more.

17. 17. The printing apparatus according to claim 16, wherein the nozzle plate has an ink-repellent film, and the ink-repellent film of the nozzle plate contains a fluorine-containing acrylate ester polymer.

18. 18. The printing device according to claim 17, wherein the fluorine-containing acrylate ester polymer comprises a polymer obtained by polymerizing at least one of a compound represented by the following general formula (II) and a compound represented by the following general formula (III): 【Chemistry 2】 【Chemistry 3】 In the general formulas (II) and (III), X represents any one of a hydrogen atom, a linear or branched alkyl group having 1 to 21 carbon atoms, a halogen atom, a CFX1X2 group (wherein X1 and X2 each independently represent 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; and R １ is an alkyl group having 1 to 18 carbon atoms, and R ２ is an alkylene group having 2 to 6 carbon atoms, and 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.

19. 19. The printing device according to claim 18, wherein the fluorine-containing acrylate ester polymer comprises a polymer having at least one of a structural unit represented by the following general formula (IV) and a structural unit represented by the following general formula (V): 【Chemistry 4】 【Chemistry 5】 In the general formulas (IV) and (V), X represents any one of a hydrogen atom, a linear or branched alkyl group having 1 to 21 carbon atoms, a halogen atom, a CFX1X2 group (wherein X1 and X2 each independently represent 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; and R １ is an alkyl group having 1 to 18 carbon atoms, and R ２ is an alkylene group having 2 to 6 carbon atoms, and 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.

20. 20. The printing device according to claim 17, wherein the ink-repellent film contains a polymer having a fluorine-containing heterocyclic structure in the main chain.

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