Ink, ink container and printed matter

Abstract

To provide an ink that improves white color concealability of the printed image.SOLUTION: Provided is an ink which contains hollow particles and in which the distribution of hollow diameter of the hollow particles has two or more dispersion peaks in the range of 400 nm or more and 1000 nm or less, and the ratio of the contained amount of hollow particles at the peak position having the largest hollow diameter and the contained amount of hollow particles at the peak position having the smallest hollow diameter among the two or more dispersion peaks is 6:4 to 7:3.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an ink, an ink container, and a printed matter. [Background technology]

[0002] Inkjet printers have become widespread in general households as digital signal output devices due to their advantages of low noise, low running costs, and easy color printing. In recent years, inkjet printers have been used not only for home use but also for industrial purposes such as displays, posters, and bulletin boards.

[0003] However, for industrial applications, the recording medium is not limited to paper and can range from transparent to colored. When expressing white on these media or coloring them with color inks, it is necessary to conceal the transparency of the recording medium with ink or to sufficiently conceal the color of the recording medium with ink. Therefore, white ink is used to make such transparent media or colored media white. In addition, when using color inks, in order to make them common with color inks used for general images, white ink is printed on the recording medium as a base for the color inks to improve color development.

[0004] Titanium dioxide, a white pigment with excellent hiding power and coloring power, is widely used as a pigment for white ink. In order to obtain high hiding power using titanium dioxide, it is necessary to disperse the particles in a particle size range of approximately 200 nm to 300 nm in order to scatter visible light. However, titanium dioxide is prone to settling because its specific gravity is larger than that of the ink medium, and the settling speed is faster in low-viscosity inks such as water-based inks and solvent-based inks. In addition, once titanium dioxide has settled, it is difficult to disperse it again because it forms a close-packed structure.

[0005] In response to these issues, inks using hollow particles have been reported. In the ink, the ink medium exists in the pores of hollow particles, so the apparent specific gravity is low and they are less likely to settle. In addition, the hiding power of hollow particles is achieved by utilizing the difference in refractive index between the hollow shell after the coating is dried and the pores emptied of the ink components. For example, Patent Document 1 discloses a white inkjet ink having excellent ejection stability, the inkjet ink containing white hollow particles having a porosity of 40% or more and 80% or less, a number average particle diameter of 50 nm or more and 200 nm or less, and a ratio of particles having a particle diameter of 1 μm or more of 1000 ppm or less. Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide an ink having improved white hiding power in printed images. [Means for solving the problem]

[0007] The ink of the present invention as a means for solving the above problems has the following composition. The ink contains hollow particles, and the hollow particle diameter distribution has two or more dispersion peaks in the range of 300 nm to 900 nm, and the ratio of the particle content at the peak position with the largest hollow diameter among the two or more dispersion peaks to the particle content at the peak position with the smallest hollow diameter is 6:4 to 7:3. Effect of the Invention

[0008] According to the present invention, it is possible to provide an ink that can produce printed matter having high white hiding power. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing an example of an image forming apparatus using the ink of the present invention. [Diagram 2]FIG. 2 is a perspective view of a main tank that contains the ink of the present invention. [Diagram 3] FIG. 3 is a diagram showing how to determine the diameter of the hollow hole portion of a hollow particle. [Figure 4] FIG. 4 is a diagram showing how to determine the content of hollow particles having a hollow diameter R. [Diagram 5] FIG. 5 is a diagram showing an example of the distribution of hollow diameters of hollow particles. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The present invention relates to an ink-jet ink as shown in (1) below, but embodiments of the invention include the following (2) to (10).

[0011] The present invention relates to the ink of (1) below, and also includes the following (2) to (10) as embodiments: (1) An ink containing hollow particles, The hollow particle has a diameter distribution having two or more dispersion peaks in the range of 300 nm to 900 nm, Among the two or more dispersion peaks, the ratio of the hollow particle content at the peak position with the largest hollow particle diameter to the hollow particle content at the peak position with the smallest hollow particle diameter is 6:4 to 7:3. An ink characterized by: (2) The ink according to (1) above, wherein the content of hollow particles having a diameter of 300 nm or more and 900 nm or less contained in the ink is 80% or more of the total content of hollow particles in the ink. (3) The ink according to (2) above, wherein the content of hollow particles having a diameter of 300 nm or more and 900 nm or less contained in the ink is 95% or more of the total content of hollow particles in the ink. (4) The ink according to any one of (1) to (3) above, wherein the hollow particles contained in the ink consist of only hollow resin particles, or only hollow inorganic particles, or consist of a mixture of hollow resin particles and hollow inorganic particles. (5) The ink according to any one of (1) to (4) above, containing hollow particles in which the value obtained by dividing the shell thickness of the hollow particles by the primary particle diameter of the hollow particles is 0.01 or more and 0.1 or less. (6) The ink according to any one of (1) to (5) above, which is a white ink. (7) An ink container comprising the ink according to any one of (1) to (6) above contained therein. (8) A printed matter having a substrate and a printing layer, characterized in that the distribution of hollow particle diameters calculated from a cross-sectional observation image of the printing layer has two or more dispersion peaks in the range of 300 nm or more and 900 nm or less. (9) The printed matter described in (8) above, characterized in that the ratio of the hollow particle content at the peak position of the largest hollow particle diameter among the dispersion peaks of 300 nm or more and 900 nm or less in the distribution of hollow particle diameters of hollow particles calculated from a cross-sectional observation image of the printing layer to the hollow particle content at the peak position of the smallest hollow particle diameter is 6:4 to 7:3. (10) The printed matter according to (8) or (9) above, wherein the content of hollow particles having a diameter of 300 nm or more and 900 nm or less is 80% or more of the total content of hollow particles in the ink.

[0012] The ink of the present invention contains "hollow particles" such as hollow resin particles or hollow inorganic particles. A hollow particle consists of a shell layer and a void (hollow portion) surrounded by the shell layer. In the present invention, the hollow diameter of the hollow particles refers to the diameter of the hollow portion. In the present invention, the "distribution of hollow diameters" refers to a curve (distribution curve) obtained by plotting hollow diameters on the horizontal axis and the number of particles having the hollow diameters or the equivalent on the vertical axis. In the present invention, the "dispersion peak of a hollow system" refers to the peak position (position of the hollow diameter at the peak) in the "distribution of hollow diameters." Furthermore, "having two or more dispersion peaks in the range of 300 nm or more and 900 nm or less" means that there are two or more "peak positions (positions of the hollow diameter at which the peaks occur)" within the range of 300 nm or more and 900 nm or less.

[0013] <Definition of various parameters used in the present invention> <Hollow diameter R> In the present invention, the hollow diameter refers to the diameter of the hollow hole of a hollow particle, that is, the length obtained by subtracting the shell thickness from the primary particle diameter as shown in Figure 3 (1). In the present invention, the hollow diameter is measured using TEM images of particles in the ink observed with a transmission electron microscope (JEM-2100F, manufactured by JEOL Ltd.) and SEM images of the printed layer of the printed matter observed with a heated cathode field scanning microscope (Schottky, FE-SEM, ULTRA55, manufactured by Carl Zeiss). Since these observation images are two-dimensional images, the spherical hollow hole portion is observed as a circle. In this case, as shown in FIG. 3(1), the hollow diameter is the diameter of the observed circle. Also, as shown in FIG. 3(2) and FIG. 3(3), the observed hollow hole portion may not be a perfect circle but may be an ellipse or other shape that is not a circle. In such a case, the maximum diameter of the shape is defined as the hollow diameter R.

[0014] <Content of hollow particles with diameter R> In the present invention, the content of hollow particles having a hollow diameter R in the ink or printed matter is calculated from TEM images of the particles in the ink or SEM images of the printed layer, in the same manner as in the measurement of the hollow diameter. The content of hollow particles having a hollow diameter R is calculated from the TEM image of the ink as X(R), and from the SEM image of the printed layer as Y(R). X(R) and Y(R) are defined by the following formula (1).

number

[0015] <Methods of measuring and calculating various factors> The above-mentioned "hollow diameter R" and "total area S(R) occupied by the hollow parts of hollow particles having a hollow diameter R" can be calculated by processing TEM observation images or cross-sectional SEM images using image processing software (e.g., Image-Pro, manufactured by Hakuto Co., Ltd.). For example, if an observation image like that shown in Figure 4 is obtained, and particle A with a hollow diameter of 400 nm and particle B with a hollow diameter of 710 nm are observed in the image, the area of ​​the hollow hole of each particle size is first calculated using image processing software. Here, the sum of the areas of all particles with a hollow diameter of 400 nm is S(400 nm). S(710 nm) can be calculated in the same way. If there are no particles other than 400 nm and 710 nm in Figure 4, then S(total) = S(400 nm) + S(710 nm). Furthermore, by using these factors obtained by calculation, X(400 nm), X(710 nm), Y(400 nm), and Y(710 nm) can be obtained from the definition formula (1). In the present invention, the hollow diameter R [nm] is counted in 10 nm increments. The range in which a particle is counted as having a hollow diameter R [nm] is from R-5 nm to less than R+5 nm. For example, a particle with a hollow diameter of 395 nm is counted as having R=400 nm, and a particle with a hollow diameter of 405 nm is counted as having R=410 nm.

[0016] <Distribution of Hollow Particle Hollow Diameter> In the present invention, the "distribution of hollow diameters" refers to a distribution in which the horizontal axis is the "hollow diameter R" of hollow particles and the vertical axis is the "content X(R) or Y(R) of particles having the hollow diameter R." The peak position in the distribution is called the "dispersion peak of the distribution of hollow diameters." Furthermore, "having two or more dispersion peaks in the range of 400 nm to 1000 nm" means that the maximum point, which is the peak position of the dispersion peak, is in the range of 400 nm to 1000 nm. An example of the "distribution of hollow diameters" is shown in FIG. 5. Example 1 of FIG. 5 shows a case in which there are three dispersion peaks in the range of 300 nm to 900 nm, and Example 2 shows a case in which there are two dispersion peaks in the range of 300 nm to 900 nm.

[0017] <Ratio of particle content of hollow particles with different hollow diameters> For example, in the case of an observed image that contains hollow particle 1 with a hollow diameter R1 and hollow particle 2 with a hollow diameter R2, the ratio of the particle contents of these two particles is equal to the ratio of their respective contents X(R1) and X(R2) (or Y(R1) and Y(R2)), so this ratio can be calculated. When the distribution in FIG. 5 is obtained, the ratio of the particle content at the peak position of the largest hollow diameter to the particle content at the peak position of the smallest hollow diameter is 14:11 in Example 1 and 2:3 in Example 2.

[0018] <Calculation method for shell thickness / primary particle size> When the distribution peaks at hollow diameter R1, the shell thickness and primary particle diameter are measured for hollow particles counted as having a hollow diameter at peak position R1 (i.e., hollow particles with a hollow diameter of R1-5 nm or more and less than R1+5 nm), and the average shell thickness L1 and average primary particle diameter D1 are calculated. In the present invention, "the value obtained by dividing the shell thickness of the hollow particles by the primary particle diameter of the hollow particles" refers to "the value obtained by dividing the average shell thickness L1 by the average primary particle diameter D1". This value is preferably equal to or greater than 0.01 and equal to or less than 0.1. In addition, in the case of an ink or printing layer having multiple hollow diameter peaks, it is preferable to calculate the "average shell thickness divided by the average primary particle diameter" for each peak position, and for all of these multiple peak values ​​to be within the range of 0.01 or more and 0.1 or less.

[0019] <Resin> The resin contained in the ink of the present invention is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include polyurethane resin, polyester resin, acrylic resin, vinyl acetate resin, styrene resin, butadiene resin, styrene-butadiene resin, vinyl chloride resin, acrylic styrene resin, acrylic silicone resin, etc. These may be used alone or in combination of two or more. Among these, from the viewpoint of obtaining excellent abrasion resistance, polyurethane resin, polyester resin, acrylic resin, and vinyl chloride resin are preferable.

[0020] The resin is preferably resin particles that can be dispersed in water in the form of an aqueous emulsion, and is more preferably added to the ink in the form of a resin emulsion in which the resin particles are dispersed. Here, the "resin particles dispersible in water in the form of an aqueous emulsion" refers to a form in which a substantially water-insoluble resin is dispersed in water in the form of particles, and the resin emulsion in the present invention includes those generally called emulsions, dispersions, latexes, or suspensions. As the resin particles, appropriately synthesized ones or commercially available ones may be used.

[0021] The 50% cumulative volume particle size (D50) of the resin particles is preferably 10 nm or more and 350 nm or less, from the viewpoint of storage stability and ejection stability when made into ink. The content of the resin particles is preferably 2.0% by mass or more and 7.5% by mass or less, more preferably 3.0% by mass or more and 7.0% by mass or less, based on the total amount of the ink. When the content is 2.0% by mass or more, the hiding power is improved as described above. Also, when the content is 7.5% by mass or less, the resin particles can be stably maintained in the ink.

[0022] Other components in the ink of the present invention are not particularly limited and can be appropriately selected from known components. Examples thereof include the various components shown below.

[0023] <Volatile solvent> The volatile solvent used in the present invention is not particularly limited, and a water-soluble organic solvent can be used. When the volatile solvent is water, or water and a water-soluble organic solvent, the ink can be used as a water-based ink, and when the volatile solvent is an organic solvent, the ink can be used as a solvent ink. In recent years, the issue of VOCs (volatile organic compounds) has been much discussed, and water-based inks that can reduce the amount of VOCs emitted are widely desired. VOCs is a general term for organic compounds that easily volatilize into the atmosphere at room temperature and normal pressure, but in the present invention, the volatile solvent means one that is required to volatilize when heated on a recording medium and has a boiling point of 300°C or less.

[0024] -Volatile solvent for water-based ink- Examples of water used in the aqueous ink include pure water such as ion-exchanged water, ultrafiltered water, reverse osmosis water, and distilled water, and ultrapure water. Examples of the water-soluble organic solvent used in the aqueous ink include polyhydric alcohols, ethers such as polyhydric alcohol alkyl ethers and polyhydric alcohol aryl ethers, nitrogen-containing heterocyclic compounds, amides, amines, and sulfur-containing compounds. The water-solubility of the water-soluble organic solvent means that the organic solvent is soluble in water at a rate of 30 mass % or more.

[0025] The water-soluble organic solvent is not particularly limited and can be appropriately selected depending on the purpose. Examples of the water-soluble organic solvent include ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 3-methyl-1,3-butanediol, triethylene glycol, polyethylene glycol, polypropylene glycol, 1,2-pentanediol, 1,3-pentanediol, 1,4- Polyhydric alcohols such as pentanediol, 2,4-pentanediol, 1,5-pentanediol, 1,2-hexanediol, 1,6-hexanediol, 1,3-hexanediol, 2,5-hexanediol, 1,5-hexanediol, glycerin, 1,2,6-hexanetriol, 2-ethyl-1,3-hexanediol, ethyl-1,2,4-butanetriol, 1,2,3-butanetriol, 2,2,4-trimethyl-1,3-pentanediol, and petriol; ethylene glycol; polyhydric alcohol alkyl ethers such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, and propylene glycol monoethyl ether; polyhydric alcohol aryl ethers such as ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether; nitrogen-containing heterocyclic compounds such as 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, and ε-caprolactam; amides such as formamide, N-methylformamide, N,N-dimethylformamide, 3-methoxy-N,N-dimethylpropionamide, and 3-butoxy-N,N-dimethylpropionamide; amines such as monoethanolamine, diethanolamine, and triethylamine; sulfur-containing compounds such as dimethyl sulfoxide, sulfolane, and thiodiethanol;Examples of the ethylene carbonate include propylene carbonate, ethylene carbonate, 3-methoxy-3-methyl-1-butanol, N,N-dimethyl-β-butoxypropionamide (Idemitsu Kosan Co., Ltd., Equamide B100), and N,N-dimethyl-β-methoxypropionamide (Idemitsu Kosan Co., Ltd., Equamide M100). These may be used alone or in combination of two or more. It is preferable to use a water-soluble organic solvent having a boiling point of 260° C. or less, since this not only functions as a wetting agent but also provides good drying properties.

[0026] Among these, polyol compounds having 8 or more carbon atoms and glycol ether compounds are also preferably used. Specific examples of polyol compounds having 8 or more carbon atoms include 2-ethyl-1,3-hexanediol and 2,2,4-trimethyl-1,3-pentanediol. Specific examples of glycol ether compounds include polyhydric alcohol alkyl ethers such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, and propylene glycol monoethyl ether; and polyhydric alcohol aryl ethers such as ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether. These may be used alone or in combination of two or more.

[0027] The content of the water-soluble organic solvent in the aqueous ink is not particularly limited and can be appropriately selected depending on the purpose. From the viewpoints of the drying property and ejection reliability of the ink, however, the content is preferably from 10% by mass to 60% by mass, and more preferably from 20% by mass to 60% by mass.

[0028] <Water> The water content in the aqueous ink is not particularly limited and can be selected appropriately depending on the purpose. From the viewpoints of the drying properties and ejection reliability of the ink, however, it is preferably from 10% by mass to 90% by mass, and more preferably from 20% by mass to 60% by mass.

[0029] -Volatile solvent in solvent ink- The organic solvent used in the solvent ink is not particularly limited and can be appropriately selected depending on the purpose. For example, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether acetate, ethylene glycol monomethyl ether propionate, ethylene glycol monoethyl ether propionate, ethylene glycol monobutyl ether propionate, diethylene glycol glycol monoacetates such as ethylene glycol monomethyl ether propionate, diethylene glycol monoethyl ether propionate, diethylene glycol monobutyl ether propionate, propylene glycol monomethyl ether propionate, dipropylene glycol monomethyl ether propionate, ethylene glycol monomethyl ether butyrate, ethylene glycol monoethyl ether butyrate, ethylene glycol monobutyl ether butyrate, diethylene glycol monomethyl ether butyrate, diethylene glycol monoethyl ether butyrate, diethylene glycol monobutyl ether butyrate, propylene glycol monomethyl ether butyrate, and dipropylene glycol monomethyl ether butyrate;Ethylene glycol diacetate, diethylene glycol diacetate, propylene glycol diacetate, dipropylene glycol diacetate, ethylene glycol acetate propionate, ethylene glycol acetate butyrate, ethylene glycol propionate butyrate, ethylene glycol dipropionate, ethylene glycol acetate dibutyrate, diethylene glycol acetate propionate, diethylene glycol acetate butyrate, diethylene glycol propionate butyrate , diethylene glycol dipropionate, diethylene glycol acetate dibutyrate, propylene glycol acetate propionate, propylene glycol acetate butyrate, propylene glycol propionate butyrate, propylene glycol dipropionate, propylene glycol acetate dibutyrate, dipropylene glycol acetate propionate, dipropylene glycol acetate butyrate, dipropylene glycol propionate butyrate, dipropylene glycol dipropionate glycol diacetates such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol; glycols such as ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, propylene glycol monopropyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol diethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, tripropylene glycol monomethyl ether, triethylene glycol diethyl ether; lactic acid esters such as methyl lactate, ethyl lactate, propyl lactate, and butyl lactate, and γ-butyrolactone. These may be used alone or in combination of two or more. Solvent ink may also be prepared by using a water-soluble organic solvent used in water-based ink.

[0030] The content of the organic solvent in the solvent ink is preferably 30% by mass or more and 95% by mass or less, more preferably 30% by mass or more and 90% by mass or less, and even more preferably 39% by mass or more and 82% by mass or less, based on the total amount of the ink.

[0031] The solvent ink preferably does not contain water. By not containing water, it is possible to improve the stability of the pigment dispersion, suppress hydrolysis of the solvent, and suppress corrosion of the head. Therefore, it is more preferable that the water content in the solvent ink is 0.5% by mass or less, which is the normal moisture absorption amount.

[0032] <Additives> If necessary, surfactants, antifoaming agents, antiseptics, antifungals, rust inhibitors, pH adjusters, etc. may be added to the ink.

[0033] <Surfactant> As the surfactant, any of silicone-based surfactants, fluorine-based surfactants, amphoteric surfactants, nonionic surfactants, and anionic surfactants can be used. Silicone surfactants are not particularly limited and can be appropriately selected according to purpose.Among them, those that do not decompose even at high pH are preferred, such as side chain modified polydimethylsiloxane, both end modified polydimethylsiloxane, one end modified polydimethylsiloxane, side chain both end modified polydimethylsiloxane, etc., and those having polyoxyethylene group or polyoxyethylene polyoxypropylene group as modified group are particularly preferred because they show good properties as aqueous surfactants.In addition, polyether modified silicone surfactants can also be used as the silicone surfactant, such as a compound in which a polyalkylene oxide structure is introduced into the Si part side chain of dimethylsiloxane. As the fluorosurfactant, for example, perfluoroalkylsulfonic acid compounds, perfluoroalkyl carboxylic acid compounds, perfluoroalkyl phosphate compounds, perfluoroalkyl ethylene oxide adducts, and polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups on the side chain are particularly preferred because they have low foaming properties. As the perfluoroalkylsulfonic acid compounds, for example, perfluoroalkylsulfonic acid, perfluoroalkyl sulfonate, etc. are included. As the perfluoroalkyl carboxylic acid compounds, for example, perfluoroalkyl carboxylic acid, perfluoroalkyl carboxylate, etc. are included. As the polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups on the side chain, for example, sulfate ester salts of polyoxyalkylene ether polymers having perfluoroalkyl ether groups on the side chains, salts of polyoxyalkylene ether polymers having perfluoroalkyl ether groups on the side chains, etc. are included. As the counter ions of the salts in these fluorosurfactants, Li, Na, K, NH 4 , N.H. 3 CH 2 CH 2 OH, NH 2 (CH 2 CH 2 OH) 2 , NH(CH 2 CH 2 OH) 3 etc. Examples of amphoteric surfactants include lauryl aminopropionate, lauryl dimethyl betaine, stearyl dimethyl betaine, and lauryl dihydroxyethyl betaine. Examples of nonionic surfactants include polyoxyethylene alkylphenyl ethers, polyoxyethylene alkyl esters, polyoxyethylene alkylamines, polyoxyethylene alkylamides, polyoxyethylene propylene block polymers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, and ethylene oxide adducts of acetylene alcohol. Examples of the anionic surfactant include polyoxyethylene alkyl ether acetates, dodecylbenzene sulfonates, laurates, and salts of polyoxyethylene alkyl ether sulfates. These may be used alone or in combination of two or more.

[0034] The silicone surfactant is not particularly limited and can be appropriately selected depending on the purpose. Examples of the silicone surfactant include side-chain modified polydimethylsiloxane, both-end modified polydimethylsiloxane, one-end modified polydimethylsiloxane, and both-end side-chain modified polydimethylsiloxane. Polyether-modified silicone surfactants having a polyoxyethylene group or a polyoxyethylene polyoxypropylene group as a modifying group are particularly preferred because they exhibit good properties as an aqueous surfactant. Such surfactants may be appropriately synthesized or commercially available products, such as those available from BYK-Chemie Co., Ltd., Shin-Etsu Chemical Co., Ltd., Dow Corning Toray Silicone Co., Ltd., Nippon Emulsion Co., Ltd., and Kyoeisha Chemical Co., Ltd. The polyether-modified silicone surfactant is not particularly limited and can be appropriately selected depending on the purpose. For example, it can be a surfactant represented by the general formula (S-1) in which a polyalkylene oxide structure is introduced into the Si part side chain of dimethylpolysiloxane. [ka] (In the general formula (S-1), m, n, a, and b each independently represent an integer, R represents an alkylene group, and R' represents an alkyl group.) As the polyether-modified silicone surfactant, commercially available products can be used, such as KF-618, KF-642, KF-643 (Shin-Etsu Chemical Co., Ltd.), EMALEX-SS-5602, SS-1906EX (Nihon Emulsion Co., Ltd.), FZ-2105, FZ-2118, FZ-2154, FZ-2161, FZ-2162, FZ-2163, FZ-2164 (Dow Corning Toray Silicone Co., Ltd.), BYK-33, BYK-387 (BYK-Chemie Co., Ltd.), TSF4440, TSF4452, TSF4453 (Toshiba Silicon Co., Ltd.), and the like.

[0035] The fluorine-based surfactant is preferably a compound having 2 to 16 fluorine-substituted carbon atoms, and more preferably a compound having 4 to 16 fluorine-substituted carbon atoms. Examples of fluorine-based surfactants include perfluoroalkyl phosphate compounds, perfluoroalkyl ethylene oxide adducts, and polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups in side chains, etc. Among these, polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups in side chains are preferred because they have low foaming properties, and fluorine-based surfactants represented by general formula (F-1) and general formula (F-2) are particularly preferred. [ka] In the compound represented by the above general formula (F-1), m is preferably an integer of 0 to 10, and n is preferably an integer of 0 to 40 in order to impart water solubility. General formula (F-2) C n F 2n+1- CH 2 CH(OH)CH 2 -O-(CH 2 CH 2 O) a -Y In the compound represented by the above general formula (F-2), Y is H or CmF 2m+1 m is an integer from 1 to 6, or CH 2 CH(OH)CH 2 -CmF2m+1 where m is an integer between 4 and 6, or CpH 2p+1 where p is an integer from 1 to 19. n is an integer from 1 to 6. a is an integer from 4 to 14. As the fluorine-based surfactant, commercially available products may be used. Examples of such commercially available products include Surflon S-111, S-112, S-113, S-121, S-131, S-132, S-141, and S-145 (all manufactured by Asahi Glass Co., Ltd.); Fullard FC-93, FC-95, FC-98, FC-129, FC-135, FC-170C, FC-430, and FC-431 (all manufactured by Sumitomo 3M Limited); Megafa F-470, F-1405, F-474 (all manufactured by Dainippon Ink & Chemicals, Inc.); Zonyl TBS, FSP, FSA, FSN-100, FSN, FSO-100, FSO, FS-300, UR, Capstone FS-30, FS-31, FS-3100, FS-34, FS-35 (all manufactured by Chemours); FT-110, FT- 250, FT-251, FT-400S, FT-150, FT-400SW (all manufactured by NEOS Co., Ltd.), Polyfox PF-136A, PF-156A, PF-151N, PF-154, PF-159 (manufactured by OMNOVA Co., Ltd.), Unidyne DSN-403N (manufactured by Daikin Industries, Ltd.), and the like. Among these, FS-3100, FS-34, FS-300 manufactured by Chemours Co., Ltd., FT-110, FT-250, FT-251, FT-400S, FT-150, FT-400SW manufactured by NEOS Co., Ltd., Polyfox PF-151N manufactured by OMNOVA Co., Ltd., and Unidyne DSN-403N manufactured by Daikin Industries, Ltd. are particularly preferred from the viewpoint of excellent print quality, particularly color development, penetration into paper, wettability, and uniform dyeing.

[0036] The content of the surfactant in the ink is not particularly limited and can be appropriately selected depending on the purpose. From the viewpoints of excellent wettability and ejection stability and improved image quality, the content is preferably from 0.001% by mass to 5% by mass, and more preferably from 0.05% by mass to 5% by mass.

[0037] <Antifoaming agent> There are no particular restrictions on the antifoaming agent, and examples thereof include silicone-based antifoaming agents, polyether-based antifoaming agents, fatty acid ester-based antifoaming agents, and the like. These may be used alone or in combination of two or more. Among these, silicone-based antifoaming agents are preferred because of their excellent defoaming effect.

[0038] <Antiseptic and antifungal agent> There are no particular restrictions on the antiseptic and antifungal agent, and examples thereof include 1,2-benzisothiazolin-3-one and the like.

[0039] <Rust inhibitor> There are no particular restrictions on the rust inhibitor, and examples thereof include acid sulfite, sodium thiosulfate, and the like.

[0040] <pH adjuster> There are no particular restrictions on the pH adjuster as long as it can adjust the pH to 7 or higher, and examples thereof include amines such as diethanolamine and triethanolamine.

[0041] <Colorant> As the colorant, hollow resin particles or hollow inorganic particles, or both are used. <<Hollow resin particles>> As the hollow resin particles, those synthesized as appropriate may be used, or commercially available products may be used. There are no particular restrictions on the method for synthesizing the hollow resin particles, and it can be appropriately selected according to the purpose. For example, a so-called emulsion polymerization method in which a vinyl monomer, a surfactant, a polymerization initiator, and an aqueous dispersion medium are stirred while heating in a nitrogen atmosphere to form a hollow resin particle emulsion is preferred.

[0042] Examples of the vinyl monomer include nonionic monofunctional ethylenically unsaturated monomers, bifunctional vinyl monomers, and vinyl monomers having trifunctionality or higher. These may be used alone or in combination of two or more.

[0043] Examples of the nonionic monofunctional ethylenically unsaturated monomer include styrene, vinyl toluene, ethylene, vinyl acetate, vinyl chloride, vinylidene chloride, acrylonitrile, (meth)acrylamide, and (meth)acrylic acid esters. These may be used alone or in combination of two or more. Among these, (meth)acrylic acid esters are preferred.

[0044] Examples of the (meth)acrylic acid ester include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, benzyl (meth)acrylate, lauryl (meth)acrylate, oleyl (meth)acrylate, palmityl (meth)acrylate, and stearyl (meth)acrylate.

[0045] Examples of the bifunctional vinyl monomer include divinylbenzene, allyl(meth)acrylate, ethylene glycol di(meth)acrylate, 1,5-butanediol di(meth)acrylate, and diethylene glycol di(meth)acrylate.

[0046] Examples of the tri- or higher functional vinyl monomer include trimethylolpropane tri(meth)acrylate.

[0047] By copolymerizing the nonionic monofunctional ethylenically unsaturated monomer with at least one of the difunctional vinyl monomer and the trifunctional or higher vinyl monomer to cause a high degree of crosslinking, it is possible to obtain hollow resin particles that have not only light scattering properties but also properties such as heat resistance, solvent resistance, and solvent dispersibility.

[0048] The surfactant may be any surfactant that forms a molecular aggregate such as a micelle in water, and examples of such surfactants include anionic surfactants, nonionic surfactants, cationic surfactants, amphoteric surfactants, etc. These surfactants may be used alone or in combination of two or more.

[0049] As the polymerization initiator, a known compound soluble in water can be used, for example, hydrogen peroxide, potassium persulfate, etc. These may be used alone or in combination of two or more kinds.

[0050] Examples of the aqueous dispersion medium include water and water containing a hydrophilic organic solvent.

[0051] Examples of commercially available hollow resin particles include ROPAQUE HT1432, ROPAQUE ULTRA E, DUAL, and OP-62 manufactured by The Dow Chemical Company, the Cybinol series manufactured by Saiden Chemical Industry Co., Ltd., and the SX series manufactured by JSR Corporation. These may be used alone or in combination of two or more kinds.

[0052] The content of the hollow resin particles is not particularly limited and can be appropriately selected according to the purpose, but is preferably 3.0% by mass to 14.0% by mass, more preferably 5.0% by mass to 12.5% ​​by mass, based on the total amount of the ink. When the content is 5.0% by mass or more, whiteness can be ensured even on recording media such as fine paper. When the content is 12.5% ​​by mass or less, the degree of settling and ejection stability are excellent.

[0053] <<Hollow inorganic particles>> The hollow inorganic particles are not particularly limited and may be appropriately selected depending on the purpose, and examples thereof include oxides, nitrides, and oxynitrides of titanium, silicon, aluminum, zirconium, strontium, etc. Among these, titanium oxide is preferred from the viewpoint of hiding power. In addition, silicon oxide can be used as the hollow inorganic particles because it can obtain scattering from the shell corresponding to the outer shell of the hollow particles and the internal pores in addition to scattering from the particle surface. Also, from the viewpoint of sedimentation in the ink, it is preferable to use silicon oxide, which has a small specific gravity, as the hollow inorganic particles.

[0054] When the hollow inorganic particles are made of titanium dioxide (hereinafter, sometimes referred to as "titanium hollow particles"), there are no particular limitations on the manufacturing method thereof, and any known manufacturing method can be used, such as the method described in JP 2014-051401 A.

[0055] The content of the hollow inorganic particles is preferably 3% by mass or more and 10% by mass or less, more preferably 5% by mass or more and 9% by mass or less, based on the total amount of the ink. When the content is 3% by mass or more, sufficient hiding power can be obtained, and when the content is 10% by mass or less, sufficient coating density can be obtained, and good ejection stability can be obtained.

[0056] A dispersant may be added to enhance the dispersion stability of the hollow inorganic particles in the ink. The dispersant is not particularly limited and can be appropriately selected according to the purpose, but a dispersant polymer is suitable. Examples of the dispersant polymer include α-olefin-maleic anhydride copolymer, styrene-(meth)acrylic copolymer, acrylic block copolymer, water-soluble polyurethane resin, water-soluble polyester resin, etc. These may be used alone or in combination of two or more.

[0057] The content of the coloring material in the ink is preferably from 0.1% to 15% by mass, and more preferably from 1% to 10% by mass, from the viewpoints of improving image density, good fixing property and ejection stability.

[0058] <Hollow diameter dispersion peak> In the ink of the present invention, the hollow particle diameter distribution has two or more dispersion peaks in the range of 300 nm to 900 nm. This allows the hollow particles to scatter light in multiple visible light regions, resulting in high whiteness even with a small film thickness. In the present invention, the ratio of the hollow particle content at the peak position with the largest hollow diameter among the two or more dispersion peaks to the hollow particle content at the peak position with the smallest hollow diameter is 6:4 to 7:3. This ratio improves the balance of the scattering degree between the long wavelength region and the short wavelength region, making it possible to improve the whiteness. This balance also overcomes the problems of settling and ejection properties. Note that the "content" here refers to the "number of hollow particles."

[0059] In the ink of the present invention, the content of hollow particles having a hollow diameter of 300 nm or more and 900 nm or less is preferably 80% or more, and more preferably 95% or more, of the total content of hollow particles in the ink. By making the content of hollow particles having a hollow diameter of 300 nm or more and 900 nm or less 80% or more, the number of hollow particles (impurities) less than 300 nm or more than 900 nm is reduced, and the whiteness and low sedimentation properties are further improved.

[0060] The hollow particles contained in the ink may consist of only hollow resin particles or only hollow inorganic particles, or may consist of a mixture of hollow resin particles and hollow inorganic particles.

[0061] The hollow particles preferably have a shell thickness divided by the primary particle diameter of the hollow particles of 0.01 to 0.1, which allows the hollow particles to maintain low sedimentation while also maintaining high Hunter brightness.

[0062] Methods for dispersing a pigment to obtain an ink include a method of introducing a hydrophilic functional group into the pigment to make it a self-dispersing pigment, a method of dispersing the pigment by coating the surface of the pigment with a resin, and a method of dispersing the pigment using a dispersant. As a method for introducing a hydrophilic functional group into a pigment to make it a self-dispersing pigment, for example, a method in which a functional group such as a sulfone group or a carboxyl group is added to a pigment (e.g., carbon) to make it dispersible in water can be mentioned. As a method for dispersing a pigment by coating its surface with a resin, there is a method in which the pigment is encapsulated in a microcapsule to make it dispersible in water. This can be called a resin-coated pigment. In this case, it is not necessary for all of the pigments blended in the ink to be coated with a resin, and uncoated or partially coated pigments may be dispersed in the ink as long as the effect of the present invention is not impaired. Examples of the method for dispersing using a dispersant include a method for dispersing using a known low molecular weight dispersant or a polymeric dispersant, typified by a surfactant. As the dispersant, for example, anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, etc. can be used depending on the pigment. RT-100 (nonionic surfactant) manufactured by Takemoto Oil Co., Ltd. and sodium naphthalenesulfonate formalin condensate can also be suitably used as dispersants. The dispersants may be used alone or in combination of two or more.

[0063] The coloring material used in the present invention can be not only a white pigment such as the hollow resin particles or the hollow inorganic particles, but also other types of coloring materials. In this way, a white ink is produced when a white pigment is used alone, but by using other coloring materials (colored coloring materials) in combination, it is possible to produce an image that has the color of the coloring material used while having the desired hiding power. Coloring materials other than the white pigment are not particularly limited, and pigments and dyes can be used. The pigment may be an inorganic pigment or an organic pigment. These may be used alone or in combination of two or more. Mixed crystals may also be used.

[0064] Examples of pigments that can be used include black pigments, yellow pigments, magenta pigments, cyan pigments, white pigments, green pigments, orange pigments, glossy pigments such as gold and silver pigments, and metallic pigments. As inorganic pigments, titanium oxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, chrome yellow, as well as carbon black produced by known methods such as the contact method, furnace method, and thermal method can be used. As organic pigments, azo pigments, polycyclic pigments (e.g., phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, etc.), dye chelates (e.g., basic dye chelates, acid dye chelates, etc.), nitro pigments, nitroso pigments, aniline black, etc. can be used. Among these pigments, those having good affinity with the solvent are preferably used. In addition, hollow resin particles and hollow inorganic particles can also be used. Specific examples of pigments for black colors include carbon blacks (CI Pigment Black 7) such as furnace black, lamp black, acetylene black, and channel black; metals such as copper, iron (CI Pigment Black 11), and titanium oxide; and organic pigments such as aniline black (CI Pigment Black 1). In addition, for color, CI Pigment Yellow 1, 3, 12, 13, 14, 17, 24, 34, 35, 37, 42 (yellow iron oxide), 53, 55, 74, 81, 83, 95, 97, 98, 100, 101, 104, 108, 109, 110, 117, 120, 138, 150, 153, 155, 180, 185, 213, CI Pigment Yellow Range 5, 13, 16, 17, 36, 43, 51, CI Pigment Red 1, 2, 3, 5, 17, 22, 23, 31, 38, 48:2, 48:2 (Permanent Red 2B (Ca)), 48:3, 48:4, 49:1, 52:2, 53:1, 57:1 (Brilliant Carmine 6B), 60:1, 63:1, 63:2, 64:1, 81, 83, 88 , 101 (red oxide), 104, 105, 106, 108 (cadmium red), 112, 114, 122 (quinacridone magenta), 123, 146, 149, 166, 168, 170, 172, 177, 178, 179, 184, 185, 190, 193, 202, 207, 208, 209, 213, 219, 224, 254, 264, CI Pigment Violet 1 (Rhodamine Lake), 3, 5:1, 16, 19, 23, 38; CI Pigment Blue 1, 2, 15 (Phthalocyanine Blue), 15:1, 15:2, 15:3, 15:4 (Phthalocyanine Blue), 16, 17:1, 56, 60, 63; CI Pigment Green 1, 4, 7, 8, 10, 17, 18, 36, etc. The dye is not particularly limited, and acid dyes, direct dyes, reactive dyes, and basic dyes can be used. One type of dye may be used alone, or two or more types may be used in combination. Examples of the dyes include CI Acid Yellow 17, 23, 42, 44, 79, 142, CI Acid Red 52, 80, 82, 249, 254, 289, CI Acid Blue 9, 45, 249, CI Acid Black 1, 2, 24, 94, CI Food Black 1, 2, CI Direct Yellow 1, 12, 24, 33, 50, 55, 58, 86, 132, 142, 144, 173, CI Direct Red 1, 4, 9, 80, 81, 225, 227, CI Direct Blue 1, 2, 15, 71, 86, 87, 98, 165, 199, 202, CI Direct Black 19, 38, 51, 71, 154, 168, 171, 195, and CI Reactive Red. 14, 32, 55, 79, 249, and CI Reactive Black 3, 4, and 35.

[0065] <Pigment dispersion> It is possible to obtain ink by mixing a pigment with materials such as water or an organic solvent, or it is also possible to manufacture ink by mixing a pigment with other materials such as water and a dispersant to prepare a pigment dispersion, and then mixing the resulting mixture with materials such as water or an organic solvent. The pigment dispersion is obtained by mixing and dispersing water, a pigment, a pigment dispersant, and other components as required, and adjusting the particle size. Dispersion is preferably performed using a dispersing machine. The particle size of the pigment in the pigment dispersion is not particularly limited, but the maximum frequency in terms of the maximum number is preferably 20 nm or more and 500 nm or less, more preferably 20 nm or more and 150 nm or less, in order to improve the dispersion stability of the pigment and the image quality such as ejection stability and image density. The particle size of the pigment can be measured using a particle size analyzer (Nanotrac Wave-UT151, manufactured by Microtrac Bell Co., Ltd.). The content of the pigment in the pigment dispersion is not particularly limited and can be appropriately selected depending on the purpose. From the viewpoints of obtaining good ejection stability and increasing image density, the content is preferably 0.1% by mass or more and 50% by mass or less, and more preferably 0.1% by mass or more and 30% by mass or less. It is preferable that the pigment dispersion is degassed, if necessary, by filtering coarse particles using a filter, a centrifugal separator, or the like.

[0066] The physical properties of the ink are not particularly limited and can be appropriately selected depending on the purpose. For example, it is preferable that the viscosity, surface tension, pH, etc. are within the following ranges. The viscosity of the ink at 25°C is preferably from 5 mPa·s to 30 mPa·s, more preferably from 5 mPa·s to 25 mPa·s, in order to improve print density and character quality and to obtain good ejection properties. Here, the viscosity can be measured using, for example, a rotational viscometer (RE-80L manufactured by Toki Sangyo Co., Ltd.). The measurement conditions are 25°C, a standard cone rotor (1°34' x R24), a sample liquid volume of 1.2 mL, a rotation speed of 50 rpm, and 3 minutes. The surface tension of the ink is preferably 35 mN / m or less, and more preferably 32 mN / m or less at 25° C., in order to ensure that the ink is appropriately leveled on the recording medium and the drying time of the ink is shortened. The pH of the ink is preferably from 7 to 12, and more preferably from 8 to 11, from the viewpoint of preventing corrosion of metal members that come into contact with the ink.

[0067] The inks of the present invention can be used as ink-jet inks. The amount of ink applied by the inkjet recording method is 1.5 g / m 2 More than 25g / m 2 The ink deposition amount is preferably 1.5 g / m or less. 2 At or above this level, sufficient image density can be obtained, and the density is 25 g / m 2 If it is less than this, sufficient fixability can be obtained.

[0068] (ink container) The ink container of the present invention contains the ink of the present invention in a container, and further contains other members appropriately selected as necessary. The container is not particularly limited, and its shape, structure, size, material, etc. can be appropriately selected depending on the purpose. For example, a container having at least an ink bag formed of an aluminum laminate film, a resin film, etc. is preferably used.

[0069] <Ink cartridges> The ink cartridge contains the ink of the present invention in a container, and further contains other members appropriately selected as necessary. The container is not particularly limited, and its shape, structure, size, material, etc. can be appropriately selected depending on the purpose. For example, a container having at least an ink bag formed of an aluminum laminate film, a resin film, etc. is preferably used.

[0070] <Recording Media> There are no particular limitations on the recording medium, and although plain paper, glossy paper, special paper, cloth, etc. can be used, good image formation is also possible using a non-permeable substrate. The non-permeable substrate is a substrate having a surface with low water permeability and absorbency, and includes materials that have many cavities inside but are not open to the outside. More quantitatively, in the Bristow method, 1 / 2 Water absorption up to 10mL / m 2 The term "substrate" refers to a substrate that is: As the non-permeable substrate, for example, a plastic film such as a polyvinyl chloride resin film, a polyethylene terephthalate (PET) film, a polypropylene film, a polyethylene film, or a polycarbonate film can be suitably used. The recording medium is not limited to those generally used as recording media, and may be wallpaper, flooring, building materials such as tiles, cloth for clothing such as T-shirts, textiles, leather, etc. By adjusting the configuration of the path for conveying the recording medium, ceramics, glass, metal, etc. may also be used.

[0071] For example, a polyethylene terephthalate (PET) film having a thickness of 100 μm has a total light transmittance of 80% or more.

[0072] <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 recording apparatus and recording method refer to an apparatus capable of ejecting ink, various treatment liquids, etc. onto a recording medium, and a method of recording using the apparatus. The recording medium refers to an object onto which ink or various treatment liquids can be attached even temporarily. This recording device can include not only a 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 the 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 the drying means include, for example, a means for heating and drying the printed surface and the back surface of the recording medium. The heating means and the drying means are not particularly limited, but for example, a hot air heater and an infrared heater can be used. Heating and drying can be performed before, during, or after printing. In addition, the recording device and recording method are not limited to those that visualize meaningful images such as characters and figures with ink. For example, those that form patterns such as geometric designs and those that create three-dimensional images are also included. 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 capable of printing on A0-sized recording media, and continuous-feed printers that can use continuous paper wound into a roll as a recording medium. An example of a recording device will be described with reference to Figs. 1 and 2. Fig. 1 is a perspective view of the device. Fig. 2 is a perspective view of a main tank. An image forming device 400 as an example of a recording device is a serial type image forming device. A mechanism unit 420 is provided inside an exterior 401 of the image forming device 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 of a packaging material such as an aluminum laminate film. The ink storage unit 411 is stored in a storage container case 414 made of plastic, for example. As a result, the main tanks 410 are used as ink cartridges of each color. On the other hand, a cartridge holder 404 is provided at the back side of the opening when the cover 401c of the apparatus body is opened. A main tank 410 is detachably attached to the cartridge holder 404. As a result, each ink outlet 413 of the main tank 410 communicates with an ejection head 434 for each color via a supply tube 436 for each color, and ink can be ejected from the ejection head 434 to a recording medium.

[0073] This recording apparatus can include not only a portion that ejects ink, but also devices called pre-processing devices and post-processing devices. As an embodiment of the pre-treatment device and post-treatment device, a liquid storage section having a pre-treatment liquid and a liquid ejection head, similar to the case of inks such as black (K), cyan (C), magenta (M), and yellow (Y), and the like, are added, and the pre-treatment liquid and the post-treatment liquid are ejected by an inkjet recording method. As another embodiment of the pre-treatment device and the post-treatment device, there is an embodiment in which a pre-treatment device and a post-treatment device using a method other than the inkjet recording method, for example, a blade coating method, a roll coating method, or a spray coating method, are provided.

[0074] The temperature in the drying step after the ink of the present invention is recorded on a recording medium by the inkjet method is preferably from 50° C. to 200° C. Within this temperature range, the recording medium is less susceptible to heat effects. It is more preferable that the temperature is from 50° C. to 70° C. Within this temperature range, even when hollow resin particles are used, the hollow structure of the hollow resin particles will not be destroyed by heat.

[0075] Furthermore, the ink of the present invention has a Hunter whiteness of W when a 50 mm×50 mm solid image formed on a polyethylene terephthalate (PET) film is dried in a thermostatic chamber at 50° C. for 1 hour.

[0076] The application of the ink of the present invention is not particularly limited and can be appropriately selected depending on the purpose, and can be applied to, for example, printed matter, paint, coating material, undercoat, etc. Furthermore, the ink can be used not only to form two-dimensional characters and images when used as an ink, but also as a material for three-dimensional modeling to form three-dimensional solid images (three-dimensional objects). A known three-dimensional modeling device for forming a three-dimensional object can be used, and is not particularly limited. For example, a device equipped with an ink storage means, supply means, discharge means, drying means, etc. can be used. The three-dimensional object includes a three-dimensional object obtained by applying ink over and over. Also included is a molded product obtained by processing a structure to which ink is applied on a substrate such as a recording medium. The molded product is, for example, a recording material or structure formed in a sheet or film shape, which is molded by heat stretching, punching, etc., and is preferably used for applications in which the surface is molded after decoration, such as meters and operation panel of automobiles, office automation equipment, electric and electronic equipment, cameras, etc.

[0077] In the present invention, the terms image formation, recording, printing, printing, etc. are all synonymous.

[0078] Recording medium, media, and printed material are all synonymous. EXAMPLES

[0079] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0080] <Example of hollow particles> In the examples and comparative examples shown in Tables 3 and 4, the following hollow resin particles and hollow inorganic particles were used. Hollow resin particles A: Rohm and Haas SX-866(B) Hollow resin particles B: Rohm and Haas ROPAQUE ULTRA E Hollow resin particles C: Rohm and Haas Ropeake OP-62 Hollow resin particles D: A synthetic product obtained by the method described in JP 2019-155847 A Hollow resin particles E: Saibinol X-213-913E-43 manufactured by Saiden Chemical Co., Ltd. Hollow resin particles F: Rohm and Haas Ropeake HP-1055 Hollow inorganic particles G: Silica hollow particles as described in the Preparation Examples Hollow inorganic particles H: Silica hollow particles described in the Preparation Examples Table 1 shows the properties of the hollow resin particles A to F and the hollow inorganic particles G and H.

[0081] [Table 1]

[0082] <Preparation of hollow resin particles D> Hollow resin particles D were prepared by the same method as that described in JP 2019-155847 A. (1) Synthesis of seed particle emulsion In a four-necked separable flask equipped with a stirrer, a thermometer, a cooler, and a dropping funnel, deionized water (726.0 parts), methyl methacrylate (5.0 parts), and methacrylic acid (0.1 parts) were charged and heated with stirring. Then, when the internal temperature of the separable flask reached 70°C, 10% aqueous ammonium persulfate solution (1.0 parts) was added and heated at 80°C for 20 minutes. Meanwhile, methyl methacrylate (141.0 parts), methacrylic acid (94.9 parts), sodium alkylbenzenesulfonate (5.0 parts: Neogen SF-20 manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as an anionic emulsifier, and deionized water (120.0 parts) were emulsified with a homodisper to form a pre-emulsion, which was then poured into the dropping funnel. Next, while maintaining the internal temperature of the separable flask at 80°C, the pre-emulsion obtained above was added dropwise uniformly over 3 hours, and at the same time, a 10% aqueous ammonium persulfate solution (10.0 parts) was added dropwise uniformly over 3 hours. After completion of the addition, the mixture was aged at 80°C for 3 hours, cooled, and then filtered using a 120 mesh filter cloth to obtain a seed particle emulsion.

[0083] (2) Synthesis of hollow resin particles (1st stage polymerization) A four-necked separable flask equipped with a stirrer, a thermometer, a cooler, and a dropping funnel was charged with deionized water (188.2 parts), the seed particle emulsion (66.0 parts) obtained above was dropped, and the mixture was heated to 80°C while stirring. Meanwhile, butyl acrylate (2.4 parts), butyl methacrylate (1.1 parts), methyl methacrylate (19.5 parts), methacrylic acid (0.7 parts), sodium alkylbenzenesulfonate (5.0 parts: Neogen SF-20 manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), and deionized water (55.3 parts) were emulsified with a homodisper to obtain pre-emulsion 1, which was then poured into the dropping funnel. Then, while maintaining the internal temperature of the separable flask at 80°C, the pre-emulsion 1 obtained above was dropped uniformly over 30 minutes, and at the same time, a 10% aqueous sodium persulfate solution (1.2 parts) was dropped uniformly over 30 minutes.

[0084] (Second stage polymerization) Styrene (75.0 parts), sodium alkylbenzenesulfonate (5.0 parts: Neogen SF-20 manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), and deionized water (51.8 parts) were emulsified with a homodisper to obtain pre-emulsion 2, which was then poured into a dropping funnel. Then, while maintaining the internal temperature of the separable flask at 80°C, one hour after the completion of the dropping of pre-emulsion 1, the pre-emulsion 2 obtained above was dropped uniformly over 60 minutes, and at the same time, a 10% aqueous sodium persulfate solution (3.5 parts) was dropped uniformly over 60 minutes. After the completion of the dropping of pre-emulsion 2, 28% aqueous ammonia (7.5 parts) was dropped to swell and dissolve the seed particles, and the mixture was aged at 80°C for one hour. After cooling, the mixture was filtered using a 120-mesh filter cloth to obtain hollow resin particles D.

[0085] <Preparation of hollow inorganic particles G and H> Hollow inorganic particles G and H were prepared by the same method as that described in JP 2020-121528 A. The reaction components and reaction conditions for producing hollow inorganic particles G and H are shown in Table 2. (Production of hollow inorganic particles G) -Preparation of silica-coated particles- 1.3 parts by mass of non-crosslinked styrene acrylic resin particle water dispersion FS201E (manufactured by Nippon Paint Co., Ltd.) and 98.7 parts by mass of water were thoroughly dispersed using an ultrasonic homogenizer (manufactured by Nippon Seiki Co., Ltd., US-300T, tip diameter 7 mm, 100 μA, 10 minutes). After that, the mixture was transferred to a plastic container and stirred, and several drops of 1N sodium hydroxide aqueous solution (manufactured by Wako Pure Chemical Industries, Ltd.) were added to adjust the pH to 10.5. Then, 1.0 part by mass of 3-aminopropylethoxysilane: (APTES, manufactured by Tokyo Chemical Industry Co., Ltd.) and 1.2 parts by mass of tetraethoxysilane: (TEOS, manufactured by Tokyo Chemical Industry Co., Ltd.) were slowly added in this order, and the mixture was allowed to react at 25 ° C. for 20 hours, forming a silica shell on the surface of the resin particles using a sol-gel reaction, and silica-coated particles were obtained. -Preparation of 18% by mass aqueous phase of hollow inorganic particles G- Next, the obtained silica-coated particles were washed with water and centrifuged to obtain a wet cake of silica-coated particles. Further, tetrahydrofurone was added to dissolve the resin particles of the core material, and the mixture was stirred for 1 hour, washed with water, and dispersed in water again, followed by concentration to obtain [18% by mass aqueous phase of hollow inorganic particles G]. In any of the washing steps, the silica-coated particles or hollow inorganic particles were subjected to liquid-liquid replacement since there was a risk of aggregation if the particles were dried.

[0086] (Production of hollow inorganic particles H) [Hollow inorganic particles H 18% by mass aqueous phase] was obtained in the same manner as in the production of hollow inorganic particles G, except that the composition and reaction conditions were changed as shown in Table 2 in the production of hollow inorganic particles G.

[0087] [Table 2]

[0088] Details of the materials in Table 2 are as follows: -Core material (resin particles)- FS201E: (Non-crosslinked styrene acrylic resin particle water dispersion, solid content 27% by mass, negatively charged, manufactured by Nippon Paint Co., Ltd.) FS301E: (non-crosslinked styrene acrylic resin particle water dispersion, solid content 27% by mass, negatively charged, manufactured by Nippon Paint Co., Ltd.) -Core material (calcium carbonate)-

[0089] -Silicon alkoxide- 3-Aminopropylmethoxysilane: (APTMS, manufactured by Tokyo Chemical Industry Co., Ltd.) 3-Aminopropylethoxysilane: (APTES, manufactured by Tokyo Chemical Industry Co., Ltd.) Tetramethoxysilane: (TMOS, manufactured by Tokyo Chemical Industry Co., Ltd.) Tetraethoxysilane: (TEOS, manufactured by Tokyo Chemical Industry Co., Ltd.)

[0090] (Preparation Example 1) -Preparation of hollow inorganic particle dispersion G- To 100 parts by mass of the [18% by mass aqueous phase of hollow inorganic particles G], 6 parts by mass of an amino group-containing copolymer (dispersant, manufactured by BYK Japan, product name "Disperbyk-190" (active ingredient 100% by mass)) and 12 parts by mass of water were added and thoroughly stirred, and then dispersed using an ultrasonic homogenizer (manufactured by Nippon Seiki Seisakusho Co., Ltd., US-300T, tip diameter 7 mm, 100 μA, 30 minutes). Coarse particles in the resulting dispersion were removed using centrifugation (4000 rpm, 1 minute), and further filtration was performed using a membrane filter (cellulose acetate membrane) with an average pore size of 5 μm to prepare [hollow inorganic particle dispersion G] (hollow inorganic particle concentration: 15% by mass).

[0091] (Preparation Example 2) -Preparation of hollow inorganic particle dispersion H- [Hollow inorganic particle dispersion H] was prepared in the same manner as in Preparation Example 1 of hollow inorganic particle dispersion, except that in Preparation Example 1 of hollow inorganic particle dispersion, [18 mass % aqueous phase of hollow inorganic particle G] was changed to [18 mass % aqueous phase of hollow inorganic particle H].

[0092] Example 1 <Ink Preparation> 11.5 mass% of 1,2-propanediol (manufactured by Tokyo Chemical Industry Co., Ltd.), 1.5 mass% of 3-methoxy-3-methylbutanol (manufactured by Tokyo Chemical Industry Co., Ltd.), 1.3 mass% of 2-ethyl-1,3-hexanediol (manufactured by Tokyo Chemical Industry Co., Ltd.), 8.0 mass% of a urethane resin emulsion (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., product name: Superflex 210, 35 mass%) as a resin, 0.4 mass% of a silicone surfactant (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KF-640) as a surfactant, 0.1 mass% of 2-amino-2-ethyl-1,3-propanediol (manufactured by Tokyo Chemical Industry Co., Ltd.) as a pH adjuster, and 23.9 mass% of ion-exchanged water were stirred for 1 hour to uniformly mix. Next, 2.4% by mass of hollow resin particles A (manufactured by Rohm and Haas, product name: SX-866(A), hollow diameter: 201 nm) as pigment solids, 2.2% by mass of hollow resin particles C (manufactured by Rohm and Haas, Ropeake OP-62, hollow diameter: 311 nm) as pigment solids, and 3.4% by mass of hollow resin particles E (manufactured by Saiden Chemical Industry, Saibinol X-213-913E-43, hollow diameter: 500 nm) as pigment solids were added and further stirred for 1 hour to mix uniformly. This mixture was pressure filtered through a membrane filter (cellulose acetate membrane) with an average particle size of 5 μm to remove coarse particles and dust, and the ink of Example 1 was prepared. The pigment solid content in Tables 2 and 3 is the amount as pigment solid content, and the resin emulsion content in Tables 2 and 3 is the amount of the entire resin emulsion.

[0093] (Examples 2 to 9 and Comparative Examples 1 to 4) Inks of Examples 2 to 9 and Comparative Examples 1 to 4 were prepared in the same manner as in Example 1, except that the compositions in Example 1 were changed as shown in Tables 3 and 4 below.

[0094] Next, the "difference in sedimentation degree" and "Hunter brightness" were evaluated as follows. The results are shown in Tables 3 and 4 below.

[0095] <Difference in sedimentation rate before and after standing> Approximately 5 g of each of the obtained inks was placed in a 25 g glass tube (product name: screw-top test tube, manufactured by AS ONE Corporation) and allowed to stand for 168 hours in a 25° C. environment. The sedimentation degree of the ink before and after being left to stand for 168 hours was measured using a sedimentation degree measuring device (device name: Turbiscan Classic MA2000, manufactured by Eiko Seiki Co., Ltd.). The difference in sedimentation degree was calculated by subtracting the sedimentation degree of the ink before being left to stand from the sedimentation degree of the ink after being left to stand for 168 hours. Note that a difference in sedimentation degree of -2 or more is a feasible level. [Evaluation Criteria] S: The difference in sedimentation rate 168 hours after the start of evaluation is -0.5 or more A: The difference in sedimentation rate 168 hours after the start of the evaluation is between -1.0 and -0.5 B: The difference in sedimentation rate 168 hours after the start of evaluation is -4.0 or more and less than -1.0 C: The difference in sedimentation rate 168 hours after the start of evaluation is -5.0 or more and less than -4.0 D: The difference in sedimentation rate 168 hours after the start of evaluation is less than -5.0

[0096] <Printing conditions> The exterior of an inkjet printer (RICOH IPSiOGXe5500) was removed, a rear multi-manual feeder was attached, and pure water was passed through the ink supply path including the print head to clean it. The cleaning liquid was passed through sufficiently until it was no longer colored, and then the cleaning liquid was completely drained from the device to prepare an evaluation printing device. The prepared ink was stirred for 30 minutes under reduced pressure conditions of 5 to 10 Pa to remove the gas in the ink for evaluation, and then filled into an ink cartridge to prepare an ink cartridge for evaluation. A filling operation was performed to confirm that all nozzles were filled with the ink for evaluation and that no abnormal images were produced, and after selecting the glossy paper clean mode in the driver attached to the printer, the print mode was set to color matching off in the user settings. In this mode, the amount of ink adhering to the media for a solid image was 9.6 g / m 2 The discharge amount was adjusted by changing the head drive voltage so as to obtain the following.

[0097] <Hunter Whiteness> White hiding power was evaluated by measuring Hunter Whiteness. The inks prepared in Examples 1 to 9 and Comparative Examples 1 to 4 were filled into an inkjet printer (RICOH IPSiOGXe5500), and a 50 cm x 50 cm solid image created using Microsoft Word 2003 was printed on a transparent PET film (Toyobo Ester Film E5100) fixed with double-sided tape onto My Paper (RICOH PPC plain paper), and then the image was dried for 1 hour in a constant temperature bath at 50°C to obtain a fresh image. Place a sheet of commercially available black paper under the printed PET film and measure the L * , a * , and b * was measured using a spectrophotometric densitometer (device name: X-Rite939, manufactured by X-Rite Corporation), and the Hunter whiteness index was calculated according to the following formula (2). Hunter Whiteness = 100-[(100-L * )2+(a *2 +b *2 )] 0.5 ...Equation (2) The evaluation was based on the following criteria. [Evaluation Criteria] S: Hunter whiteness is 80 or more A: Hunter whiteness is 70 or more and less than 80 B: Hunter whiteness is 65 or more and less than 70 C: Hunter whiteness is 60 or more and less than 65 D: Hunter whiteness is less than 60 For reference, the Hunter brightness measured with an unprinted PET film placed on black paper was 26.

[0098] <Measurement of the diameter of hollow particles in pigment dispersions and inks> Observation was performed at a magnification of 30,000 using a transmission electron microscope (manufactured by JEOL Ltd., "JEM-2100F") to obtain a TEM image. The hollow diameter of the obtained TEM image was measured using the hollow diameter measurement method described above.

[0099] <Measurement of hollow diameter in cross section of printed matter> A cross section was prepared for a printed matter produced by an inkjet printer or the like using an ion milling device (IM4000, manufactured by Hitachi High-Technologies Corporation), and the obtained cross section was observed with a scanning electron microscope such as a heated cathode field scanning microscope (Schottky, FE-SEM, Carl Zeiss ULTRA55) to obtain an SEM image of the printed layer of the printed matter. The hollow diameter of the obtained SEM image was measured using the hollow diameter measurement method described above.

[0100] [Table 3]

[0101] [Table 4] [Explanation of symbols]

[0102] 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 [Prior art documents] [Patent documents]

[0103] [Patent Document 1] JP 2014-122310 A

Claims

1. An ink containing hollow particles, The hollow particle has a hollow diameter distribution having two or more dispersion peaks in the range of 300 nm or more and 900 nm or less, the ratio of the hollow particle content at the peak position with the largest hollow particle diameter among the two or more dispersion peaks to the hollow particle content at the peak position with the smallest hollow particle diameter is 6:4 to 7:3; An ink characterized by:

2. 2. The ink according to claim 1, wherein a content of hollow particles having a diameter of 300 nm or more and 900 nm or less contained in the ink is 80% or more with respect to a content of all hollow particles in the ink.

3. 3. The ink according to claim 2, wherein a content of hollow particles having a diameter of 300 nm or more and 900 nm or less contained in the ink is 95% or more with respect to a content of all hollow particles in the ink.

4. 4. The ink according to claim 1, wherein the hollow particles contained in the ink are composed of only hollow resin particles, only hollow inorganic particles, or a mixture of hollow resin particles and hollow inorganic particles.

5. 5. The ink according to claim 1, comprising hollow particles in which a value obtained by dividing the shell thickness of the hollow particles by the primary particle diameter of the hollow particles is 0.01 or more and 0.1 or less.

6. The ink according to claim 1 , which is a white ink.

7. 7. An ink container comprising the ink according to claim 1 contained therein.

8. A printed matter having a substrate and a printing layer, characterized in that the distribution of hollow diameters of hollow particles calculated from a cross-sectional observation image of the printing layer has two or more dispersion peaks in the range of 300 nm or more and 900 nm or less.

9. 9. The printed matter according to claim 8, wherein a ratio of the hollow particle content at a peak position with the largest hollow particle diameter among dispersion peaks with diameters of 300 nm or more and 900 nm or less in a distribution of hollow particle diameters calculated from a cross-sectional observation image of the printing layer to the hollow particle content at a peak position with the smallest hollow particle diameter is 6:4 to 7:

3.

10. 10. The printed matter according to claim 8, wherein the content of hollow particles having a hollow diameter of 300 nm or more and 900 nm or less is 80% or more of the total content of hollow particles in the ink.

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