JP7362027B2 - Ink, ink container, printing method, and printing device - Google Patents

Description

The present invention relates to ink, an ink container, a printing method, and a printing device.

Inkjet printers have advantages such as low noise, low running costs, and easy color printing, so they are widely used in general households as digital signal output devices. Furthermore, in recent years, they have been used not only for household use but also for industrial purposes such as displays, posters, bulletin boards, etc.

However, in the case of industrial use, the recording medium is not limited to paper, and a wide variety of recording media are used, from transparent recording media to colored recording media. When expressing white or coloring these recording media with color ink, it is necessary to cover up the transparency of the recording medium with the ink, or to sufficiently hide the color of the recording medium with the ink. For this reason, white ink is used to make transparent recording media or colored recording media white. Furthermore, when color ink is used, white ink is printed on the recording medium as a base for the color ink to improve color development in order to make it common with color ink used for general images.

As the pigment for the white ink, titanium dioxide, which is a white pigment with excellent hiding power, coloring power, etc., is widely used. In order to obtain a high hiding power using titanium dioxide, it is necessary to disperse the particle size in a range of 200 nm to 400 nm in order to scatter visible light. However, since the titanium dioxide has a higher specific gravity than the ink medium, it easily settles, and furthermore, the settling rate increases in low viscosity inks such as water-based inks and solvent inks. Furthermore, when the titanium dioxide settles, it forms a close-packed structure, making it difficult to redisperse it.

To address these issues, inks using hollow particles have been reported. Since the ink medium exists in the pores of the hollow particles in the ink, the apparent specific gravity becomes small and it becomes difficult to settle. Further, the hiding property of the hollow particles is obtained by utilizing the difference in refractive index between the hollow shell after the coating film dries and the pores through which the ink medium has passed.
For example, an ink containing organic particles having a hollow structure and inorganic particles having a hollow structure has been proposed (see, for example, Patent Document 1).
Furthermore, in addition to hollow resin particles, an ink containing a polyurethane resin has been proposed for the purpose of improving the fastness of printed matter (see, for example, Patent Document 2).

SUMMARY OF THE INVENTION An object of the present invention is to provide an ink that is resistant to sedimentation, can suppress a decrease in whiteness even during heat drying, and can provide images with excellent abrasion resistance and adhesion.

The ink of the present invention as a means for solving the above problems is an ink containing water, a water-soluble organic solvent, a pigment, and resin particles A, wherein the pigment is a hollow resin particle, and the water-soluble organic solvent All the solvents are water-soluble organic solvents with boiling points of 250°C or lower, and the resin particles A are characterized in that they have a glass transition temperature of 40°C or higher.

According to the present invention, it is possible to provide an ink that is resistant to sedimentation, can suppress reduction in whiteness even during heat drying, and can provide images with excellent abrasion resistance and adhesion.

FIG. 1 is a diagram showing an example of a printing device using the ink of the present invention. FIG. 2 is a perspective view of a main tank containing ink of the present invention.

Examples of aspects of the present invention are as follows.
(1) An ink containing water, a water-soluble organic solvent, a pigment, and resin particles A,
The pigment is a hollow resin particle,
The water-soluble organic solvents are all water-soluble organic solvents with a boiling point of 250°C or less,
The resin particles A are inks having a glass transition temperature of 40° C. or higher.
(2) The ink according to (1), wherein the hollow resin particles contain silicon.
(3) The ink according to (1) or (2), wherein the resin particles A are polyurethane resin particles and have a cumulative 50% volume particle diameter D ₅₀ of 41 nm or less.
(4) The ink according to (1) or (2), wherein the resin particles A are polyester resin particles and have a cumulative 50% volume particle diameter D ₅₀ of 90 to 150 nm.
(5) The ink according to any one of (1) to (4), further containing second resin particles B.
(6) The ink according to (5), wherein the resin particles B have a glass transition temperature of 0° C. or lower.
(7) The ink according to any one of (1) to (6), wherein the hollow resin particles have a number average primary particle diameter of 300 nm or more and 800 nm or less.
(8) The ink according to any one of (1) to (7), wherein the hollow resin particles have a hollowness ratio of 20% to 60%.
(9) The brightness of a 50 mm x 50 mm solid image formed on a polyethylene terephthalate film after being dried for 1 hour in a constant temperature bath at 50°C is L * The brightness when drying for 1 hour in a constant temperature bath at 50°C and 100°C is L. *The ink according to any one of (1) to (8), wherein the absolute value of the lightness difference ΔL* expressed by the following formula (1) is less than 10 when the temperature is 100°C.
ΔL*=(L*100℃)-(L*50℃)...Formula (1)
(10) An ink container containing the ink according to any one of (1) to (9).
(11) An image forming step of forming an image on a recording medium using the ink according to any one of (1) to (9) by an inkjet method, and a drying step of heating and drying the image, A printing method in which the heating temperature in the drying step is 50°C or more and 200°C or less.
(12) A printing device comprising the ink container according to (10) and an ejection head for ejecting ink.

<Ink>
In the present invention, the ink contains water, a water-soluble organic solvent, a pigment, and resin particles A, wherein the pigment is a hollow resin particle, and the water-soluble organic solvent is a water-soluble organic solvent with a boiling point of 250°C or less. The resin particles A have a glass transition temperature of 40° C. or higher. Preferably, the hollow resin particles contain silicon.
Since the pigment is a hollow resin particle, it becomes difficult to settle. In addition, since the boiling point of all water-soluble organic solvents is 250°C or lower, good drying properties are obtained, and the ink medium remains in the hollow resin particles after the coating film dries, which prevents the whiteness from decreasing. can. Furthermore, since the glass transition temperature of the resin particles A is 40° C. or higher, it is possible to provide an ink that provides images with excellent abrasion resistance and adhesion.
When hollow resin particles are heated in an ink solvent during drying, the particles may not be able to maintain their shape, resulting in a decrease in whiteness. In the present invention, since the hollow resin particles contain silicon, the heat resistance and solvent resistance are further improved, and the whiteness is less likely to decrease.

Therefore, the ink of the present invention is resistant to sedimentation, can suppress a decrease in whiteness even during heat drying, and can provide images with both abrasion resistance and adhesion.

<Hollow resin particles>
Hollow resin particles are used as pigments in the ink. The ink is white ink.
The method for synthesizing the hollow resin particles is not particularly limited and can be appropriately selected depending on the purpose. A so-called emulsion polymerization method in which a hollow resin particle emulsion is formed by stirring while stirring is preferred. As a specific method, its production method has been studied for a long time, and a well-known method is Rohm &Haas's"method using alkali swelling" (Japanese Patent Application Laid-open No. 56-32513), Japan. "Method using polymerization shrinkage" by Synthetic Rubber Co., Ltd. (JP-A No. 61-87734, JP-A No. 62-127336), Sekisui Chemical's "Method using phase separation" (JP-A No. 2005-146223) (No. Publication), etc.

Hollow resin particles containing silicon can be synthesized by a method using a silicone-based crosslinking agent as a crosslinking agent. Examples of the silicone crosslinking agent include vinyltrimethoxysilane, vinyltriethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, and 3-acryloxypropyltrimethoxysilane. These may be used alone or in combination of two or more.

Examples of the vinyl monomer include nonionic monofunctional ethylenically unsaturated monomers, difunctional vinyl monomers, and trifunctional or higher functional vinyl monomers. These may be used alone or in combination of two or more.

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

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

Examples of the difunctional vinyl monomer include divinylbenzene, allyl (meth)acrylate, ethylene glycol di(meth)acrylate, 1,5-butanediol di(meth)acrylate, diethylene glycol di(meth)acrylate, and the like. .

Examples of the trifunctional or higher-functionality vinyl monomer include trimethylolpropane tri(meth)acrylate.

By copolymerizing and highly crosslinking the nonionic monofunctional ethylenically unsaturated monomer with at least one of the difunctional vinyl monomer and the trifunctional or higher functional vinyl monomer, it is possible to improve not only light scattering properties but also heat resistance. It is possible to obtain hollow resin particles having properties such as hardness, solvent resistance, and solvent dispersibility.

The surfactant may be one that forms molecular aggregates such as micelles in water, such as anionic surfactants, nonionic surfactants, cationic surfactants, amphoteric surfactants, etc. can be mentioned. These may be used alone or in combination of two or more.

As the polymerization initiator, known water-soluble compounds can be used, such as hydrogen peroxide and potassium persulfate. These may be used alone or in combination of two or more.

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

The hollowness ratio of the hollow resin particles can be appropriately selected depending on the purpose, but is preferably 20% or more and 60% or less. When the hollowness ratio is 20% or more, the whiteness of the printed image can be improved, and when it is 60% or less, the abrasion resistance of the printed image can be ensured.
Examples of the method for measuring the hollowness ratio include a method using a scanning electron microscope (SEM). Note that the hollowness ratio is the ratio of the volume when approximated to a sphere from the outer diameter and inner diameter (diameter of the hollow part) of the hollow resin particle, and can be expressed by the following formula (2).
Hollowness rate (%)
= (Internal volume of hollow resin particles/Volume of hollow resin particles) x 100...Formula (2)
Internal volume of hollow resin particle = (4π/3) x (inner radius of hollow resin particle) ³
Volume of hollow resin particle = (4π/3) x (outer radius of hollow resin particle) ³

The number average primary particle diameter of the hollow resin particles can be appropriately selected depending on the purpose, but is preferably 300 nm or more and 800 nm or less. When the number average primary particle diameter is 300 nm or more, whiteness can be ensured. When the primary particle diameter is 800 nm or less, the degree of sedimentation is excellent.
The number average primary particle diameter is, for example, a constant value that includes 200 to 500 primary particles in a 30,000x field of view using a transmission electron microscope (manufactured by JEOL Ltd., device name: JEM-2100F). Measure the diameter in a certain direction between two parallel lines in the direction, remove the top 5% and bottom 5%, calculate the average value of the remaining 90%, and calculate that value as the number average of the hollow resin particles. It was taken as the primary particle size.

The hollowness ratio and number average primary particle diameter of the hollow resin particles can be adjusted by the sheet particle diameter and the shell thickness of the shell layer when producing the hollow resin particles. The shell thickness can be adjusted by adjusting the amount of monomer added when forming the shell layer.

Since the inner layer of the hollow resin particles is hollow, the specific gravity as an ink is around 1, and unlike titanium dioxide, it does not easily settle over time.

The content of the hollow resin particles is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 3.0% by mass or more and 14.0% by mass or less based on the total amount of the ink.5. More preferably 0% by mass or more and 12.5% by mass or less. When the content is 5.0% by mass or more, the whiteness of the printed image can be ensured. When the content is 12.5% by mass or less, the degree of sedimentation is excellent.

<Water>
Examples of the water used in the present invention include pure water such as ion-exchanged water, ultrafiltrated water, reverse osmosis water, distilled water, and ultrapure water.

The water content in the ink is not particularly limited and can be appropriately selected depending on the purpose, but from the viewpoint of ink drying properties and ejection reliability, it is preferably 10% by mass or more and 90% by mass or less, and 20% by mass or less. % or more and 60% by mass or less is more preferable.

<Water-soluble organic solvent>
The ink of the present invention can obtain hiding properties by utilizing scattering between the shell of the hollow resin particle and the internal pores. Therefore, if the ink medium remains within the hollow resin particles after the coating film dries, the hiding power of the coating film will be reduced. From the above point, it is necessary that the water-soluble organic solvent has a boiling point of 250° C. or lower.
As long as the hiding property of the coating film is maintained, an ink in which the ink medium is contained within hollow resin particles may be used.

Examples of the water-soluble organic solvent include polyhydric alcohols, ethers such as polyhydric alcohol alkyl ethers and polyhydric alcohol aryl ethers; nitrogen-containing heterocyclic compounds, amides, amines, sulfur-containing compounds, etc. can be mentioned.
The water-soluble nature of the water-soluble organic solvent means that the organic solvent can be dissolved in water in an amount of 30% by mass or more.

The water-soluble organic solvent is not particularly limited and can be appropriately selected depending on the purpose, for example, ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butane. Diol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 3-methyl-1,3-butanediol, triethylene glycol, polyethylene glycol, polypropylene glycol, 1,2-pentanediol , 1,3-pentanediol, 1,4-pentanediol, 2,4-pentanediol, 1,5-pentanediol, 1,2-hexanediol, 1,6-hexanediol, 1,3-hexanediol, 2,5-hexanediol, 1,5-hexanediol, glycerin, 1,2,6-hexanetriol, 2-ethyl-1,3-hexanediol, ethyl-1,2,4-butanetriol, 1,2 , 3-butanetriol, 2,2,4-trimethyl-1,3-pentanediol, polyhydric alcohols such as petriol; ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, Polyhydric alcohol alkyl ethers such as diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, propylene glycol monoethyl ether; polyhydric alcohol aryl ethers such as ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether; 2-pyrrolidone, N- Nitrogen-containing heterocyclic compounds such as methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, and ε-caprolactam; formamide, N-methylformamide, N,N-dimethyl Amides such as formamide, 3-methoxy-N,N-dimethylpropionamide, 3-butoxy-N,N-dimethylpropionamide; Amines such as monoethanolamine, diethanolamine, triethylamine; dimethylsulfoxide, sulfolane, thiodiethanol, etc. Sulfur-containing compounds; propylene carbonate, ethylene carbonate, 3-methoxy-3-methyl-1-butanol, N,N-dimethyl-β-butoxypropionamide (manufactured by Idemitsu Kosan Co., Ltd., Ekuamide B100), N,N-dimethyl -β-methoxypropionamide (manufactured by Idemitsu Kosan Co., Ltd., Ekuamide M100) and the like. These may be used alone or in combination of two or more.
Note that it is necessary to use a water-soluble organic solvent with a boiling point of 250° C. or lower because it not only functions as a wetting agent but also provides good drying properties.
In the present invention, two or more types of water-soluble organic solvents may be used in combination, but it is necessary that all water-soluble organic solvents have a boiling point of 250°C or less.

Among these, polyol compounds having 8 or more carbon atoms and glycol ether compounds are preferably used.
Examples of the polyol compound having 8 or more carbon atoms include 2-ethyl-1,3-hexanediol and 2,2,4-trimethyl-1,3-pentanediol.
Examples of the glycol ether compound include polyhydric alcohol alkyls 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. Ethers: Examples include 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.

The content of the water-soluble organic solvent in the water-based ink is not particularly limited and can be appropriately selected depending on the purpose, but from the viewpoint of ink drying properties and ejection reliability, it is 10% by mass or more and 60% by mass. The following is preferable, and 20% by mass or more and 60% by mass or less is more preferable.

<Resin particles A>
The resin particles A need to have a glass transition temperature of 40°C or higher, preferably 40°C or higher and 80°C or lower. Since the resin particles having a glass transition temperature of 40° C. or higher form an image so as to spread appropriately on the recording medium, the hollow resin particles can be firmly fixed on the recording medium. Thereby, an image having excellent abrasion resistance and adhesion can be obtained.

The glass transition temperature of resin particles can be measured using DSC system Q-2000 (manufactured by TA Instruments). Specifically, first, about 5.0 mg of resin in an aluminum sample container was set in the apparatus, and measurements were performed under the following measurement conditions under a nitrogen stream. The DSC curve obtained during the second temperature rise was selected, and the glass transition temperature was determined by the midpoint method.
・Hold for 5 minutes after cooling to -70℃ ・Raise the temperature to 120℃ at 10℃/min ・Hold for 5 minutes after cooling to −70℃ ・Raise the temperature to 120℃ at 10℃/min In addition, analyze the ink and check the resin When measuring the glass transition temperature of particles, it is performed as follows. The difference in particle size between hollow resin particles and resin particles is used to separate them using a filter. For example, the target ink is separated using a syringe filter with a pore size of 0.22 μm (Membrane-Solutions LLC). Since resin particles with a small particle size pass through, the liquid that has passed through the filter is dried under reduced pressure to form a dry powder of resin particles, and the glass transition temperature can be measured by the method described above.

The resin of the resin particles A is not particularly limited and can be appropriately selected depending on the purpose, for example, 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 and adhesion, either polyurethane resin or polyester resin is preferred.

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 A are dispersed.
Here, the above-mentioned "resin particles that can be dispersed 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 refers to Generally, they include what are called emulsions, dispersions, latexes, or suspensions.
As the resin particles A, appropriately synthesized ones may be used, or commercially available products may be used.

Although the detailed reason is unknown, when the resin particles A are polyurethane resin particles, the cumulative 50% volume particle diameter (D ₅₀ ) is preferably 41 nm or less, and 10 nm or more, from the viewpoint of the abrasion resistance of the printed image. More preferably, the thickness is 41 nm or less. When the resin particles are polyester resin particles, the cumulative 50% volume particle diameter (D ₅₀ ) is preferably 90 nm or more and 150 nm or less, more preferably 90 nm or more and 135 nm or less, from the viewpoint of the abrasion resistance of the printed image.
The content of the resin particles A 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 abrasion resistance of the printed image improves. Further, when the content is 7.5% by mass or less, the resin particles can be stably maintained in the ink.

<Resin particles B>
It is preferable that the ink of the present invention further contains second resin particles B. The glass transition temperature of the second resin particles B is preferably 0°C or lower, more preferably -20°C or higher and 0°C or lower. By using the second resin particles B having a glass transition temperature of 0° C. or less, the adhesion of the printed image is improved.
The resin of the second resin particles B is not particularly limited and can be appropriately selected depending on the purpose, for example, polyurethane resin, polyester resin, acrylic resin, vinyl acetate resin, styrene resin, butadiene resin, styrene resin. - Examples include 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, polyurethane resins are preferred from the viewpoint of obtaining excellent adhesion.
The content of the resin particles B is preferably 0.1% by mass or more and 5.0% by mass or less based on the total amount of the ink.

<Additives>
A surfactant, an antifoaming agent, a preservative and fungicide, a rust preventive, a pH adjuster, and the like may be added to the ink as necessary.

<Surfactant>
As the surfactant, any of silicone surfactants, fluorine surfactants, amphoteric surfactants, nonionic surfactants, and anionic surfactants can be used.
The silicone surfactant is not particularly limited and can be appropriately selected depending on the purpose. Among these, those that do not decompose even at high pH are preferred. Examples of the silicone surfactant include side chain-modified polydimethylsiloxane, both end-modified polydimethylsiloxane, one-end modified polydimethylsiloxane, and side-chain both end-modified polydimethylsiloxane. Particularly preferred are those having a polyoxyethylene group or a polyoxyethylene polyoxypropylene group as a modified group, since they exhibit good properties as a water-based surfactant. Further, as the silicone surfactant, a polyether-modified silicone surfactant can also be used, such as a compound in which a polyalkylene oxide structure is introduced into the side chain of the Si part of dimethylsiloxane.
Examples of fluorine-based surfactants include perfluoroalkyl sulfonic acid compounds, perfluoroalkyl carboxylic acid compounds, perfluoroalkyl phosphate ester compounds, perfluoroalkyl ethylene oxide adducts, and perfluoroalkyl ether groups in their side chains. Polyoxyalkylene ether polymer compounds are particularly preferred because they have low foaming properties. Examples of the perfluoroalkylsulfonic acid compound include perfluoroalkylsulfonic acid, perfluoroalkylsulfonic acid salts, and the like. Examples of the perfluoroalkylcarboxylic acid compound include perfluoroalkylcarboxylic acids, perfluoroalkylcarboxylic acid salts, and the like. Examples of polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups in their side chains include sulfate ester salts of polyoxyalkylene ether polymers having perfluoroalkyl ether groups in their side chains, and polyoxyalkylene ether polymers having perfluoroalkyl ether groups in their side chains. Examples include salts of oxyalkylene ether polymers. Counter ions of the salts in these fluorosurfactants include Li, Na, K, NH ₄ , NH ₃ CH ₂ CH ₂ OH, NH ₂ (CH ₂ CH ₂ OH) ₂ , NH(CH ₂ CH ₂ OH) _3rd grade is mentioned.
Examples of the amphoteric surfactant include lauryl aminopropionate, lauryl dimethyl betaine, stearyl dimethyl betaine, lauryl dihydroxyethyl betaine, and the like.
Examples of nonionic surfactants include polyoxyethylene alkylphenyl ether, polyoxyethylene alkyl ester, polyoxyethylene alkylamine, polyoxyethylene alkylamide, polyoxyethylene propylene block polymer, sorbitan fatty acid ester, polyoxyethylene sorbitan Examples include fatty acid esters and ethylene oxide adducts of acetylene alcohol.
Examples of the anionic surfactant include polyoxyethylene alkyl ether acetate, dodecylbenzene sulfonate, laurate, polyoxyethylene alkyl ether sulfate salt, and the like.
These may be used alone or in combination of two or more.

（但し、一般式（Ｓ－１）式中、ｍ、ｎ、ａ、及びｂは、それぞれ独立に、整数を表わし、Ｒは、アルキレン基を表し、Ｒ’は、アルキル基を表す。）
上記のポリエーテル変性シリコーン系界面活性剤としては、市販品を用いることができ、例えば、ＫＦ－６１８、ＫＦ－６４２、ＫＦ－６４３（信越化学工業株式会社）、ＥＭＡＬＥＸ－ＳＳ－５６０２、ＳＳ－１９０６ＥＸ（日本エマルション株式会社）、ＦＺ－２１０５、ＦＺ－２１１８、ＦＺ－２１５４、ＦＺ－２１６１、ＦＺ－２１６２、ＦＺ－２１６３、ＦＺ－２１６４（東レ・ダウコーニング・シリコーン株式会社）、ＢＹＫ－３３、ＢＹＫ－３８７（ビックケミー株式会社）、ＴＳＦ４４４０、ＴＳＦ４４５２、ＴＳＦ４４５３（東芝シリコン株式会社）などが挙げられる。 The silicone surfactant is not particularly limited and can be selected as appropriate depending on the purpose, but examples include side chain-modified polydimethylsiloxane, double-end modified polydimethylsiloxane, single-end modified polydimethylsiloxane, and side-chain modified polydimethylsiloxane. Examples include polydimethylsiloxane modified at both ends, and polyether-modified silicone surfactants having a polyoxyethylene group or polyoxyethylene polyoxypropylene group as a modifying group are particularly preferred since they exhibit good properties as a water-based surfactant. .
Such surfactants may be appropriately synthesized or commercially available. Commercially available products are available from, for example, BIC Chemie Co., Ltd., Shin-Etsu Chemical Co., Ltd., Toray Dow Corning Silicone Co., Ltd., Nippon Emulsion Co., Ltd., Kyoeisha Chemical Co., Ltd., etc.
The above-mentioned polyether-modified silicone surfactant is not particularly limited and can be appropriately selected depending on the purpose. Examples include those introduced into the side chain of the Si part of siloxane.

(However, in the general formula (S-1), m, n, a, and b each independently represent an integer, R represents an alkylene group, and R' represents an alkyl group.)
Commercial products can be used as the polyether-modified silicone surfactant, such as KF-618, KF-642, KF-643 (Shin-Etsu Chemical Co., Ltd.), EMALEX-SS-5602, SS- 1906EX (Japan Emulsion Co., Ltd.), FZ-2105, FZ-2118, FZ-2154, FZ-2161, FZ-2162, FZ-2163, FZ-2164 (Toray Dow Corning Silicone Co., Ltd.), BYK-33, Examples include BYK-387 (BYK-Chemie Corporation), TSF4440, TSF4452, and TSF4453 (Toshiba Silicon Corporation).

上記一般式（Ｆ－１）で表される化合物において、水溶性を付与するためにｍは０～１０の整数が好ましく、ｎは０～４０の整数が好ましい。

上記一般式（Ｆ－２）で表される化合物において、ＹはＨ、又はＣ_mＦ_2m+1でｍは１～６の整数、又はＣＨ₂ＣＨ(ＯＨ)ＣＨ₂－Ｃ_mＦ_2m+1でｍは４～６の整数、又はＣ_ｐＨ_2p+1でｐは１～１９の整数である。ｎは１～６の整数である。ａは４～１４の整数である。
上記のフッ素系界面活性剤としては市販品を使用してもよい。この市販品としては、例えば、サーフロンＳ－１１１、Ｓ－１１２、Ｓ－１１３、Ｓ－１２１、Ｓ－１３１、Ｓ－１３２、Ｓ－１４１、Ｓ－１４５（いずれも、旭硝子株式会社製）；フルラードＦＣ－９３、ＦＣ－９５、ＦＣ－９８、ＦＣ－１２９、ＦＣ－１３５、ＦＣ－１７０Ｃ、ＦＣ－４３０、ＦＣ－４３１（いずれも、住友スリーエム株式会社製）；メガファックＦ－４７０、Ｆ－１４０５、Ｆ－４７４（いずれも、大日本インキ化学工業株式会社製）；ゾニール（Ｚｏｎｙｌ）ＴＢＳ、ＦＳＰ、ＦＳＡ、ＦＳＮ－１００、ＦＳＮ、ＦＳＯ－１００、ＦＳＯ、ＦＳ－３００、ＵＲ、キャプストーンＦＳ－３０、ＦＳ－３１、ＦＳ－３１００、ＦＳ－３４、ＦＳ－３５（いずれも、Ｃｈｅｍｏｕｒｓ社製）；ＦＴ－１１０、ＦＴ－２５０、ＦＴ－２５１、ＦＴ－４００Ｓ、ＦＴ－１５０、ＦＴ－４００ＳＷ（いずれも、株式会社ネオス社製）、ポリフォックスＰＦ－１３６Ａ，ＰＦ－１５６Ａ、ＰＦ－１５１Ｎ、ＰＦ－１５４、ＰＦ－１５９（オムノバ社製）、ユニダインＤＳＮ－４０３Ｎ（ダイキン工業株式会社製）などが挙げられ、これらの中でも、良好な印字品質、特に発色性、紙に対する浸透性、濡れ性、均染性が著しく向上する点から、Ｃｈｅｍｏｕｒｓ社製のＦＳ－３１００、ＦＳ－３４、ＦＳ－３００、株式会社ネオス製のＦＴ－１１０、ＦＴ－２５０、ＦＴ－２５１、ＦＴ－４００Ｓ、ＦＴ－１５０、ＦＴ－４００ＳＷ、オムノバ社製のポリフォックスＰＦ－１５１Ｎ及びダイキン工業株式会社製のユニダインＤＳＮ－４０３Ｎが特に好ましい。 As the fluorine-based surfactant, a fluorine-substituted compound having 2 to 16 carbon atoms is preferable, and a fluorine-substituted compound having 4 to 16 carbon atoms is more preferable.
Examples of the fluorosurfactant include perfluoroalkyl phosphate compounds, perfluoroalkyl ethylene oxide adducts, and polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups in their side chains.
Among these, polyoxyalkylene ether polymer compounds having a perfluoroalkyl ether group in the side chain are preferred because of their low foaming properties, and in particular, fluorine-based polymer compounds represented by general formulas (F-1) and (F-2) are preferred. Surfactants are preferred.

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.

In the compound represented by the above general formula (F-2), Y is H, or C _m F _2m+1 and m is an integer of 1 to 6, or CH ₂ CH(OH)CH ₂ -C _m F _{2m+ 1} and m is an integer of 4 to 6, or C _p H _2p+1 and p is an integer of 1 to 19. n is an integer from 1 to 6. a is an integer from 4 to 14.
Commercially available products may be used as the above-mentioned fluorosurfactant. Examples of 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, FC-431 (all manufactured by Sumitomo 3M Ltd.); Megafac F-470, F -1405, F-474 (all manufactured by Dainippon Ink and Chemicals Co., Ltd.); 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 Corporation), Polyfox PF-136A, PF-156A, PF-151N, PF-154, PF-159 (manufactured by Omnova), Unidyne DSN-403N (manufactured by Daikin Industries, Ltd.) Among these, Chemours' FS-3100, FS-34, FS- 300, FT-110, FT-250, FT-251, FT-400S, FT-150, FT-400SW manufactured by Neos Corporation, Polyfox PF-151N manufactured by Omnova, and Unidyne DSN- manufactured by Daikin Industries, Ltd. 403N is particularly preferred.

The content of the surfactant in the ink is not particularly limited and can be selected as appropriate depending on the purpose, but from the viewpoint of excellent wettability, ejection stability, and improved image quality, 0.001 mass % or more and 5% by mass or less, more preferably 0.05% or more and 5% by mass or less.

<Defoaming agent>
The antifoaming agent is not particularly limited and includes, for example, silicone antifoaming agents, polyether antifoaming agents, fatty acid ester antifoaming agents, and the like. These may be used alone or in combination of two or more. Among these, silicone antifoaming agents are preferred because they have excellent foam-breaking effects.

<Preservative and fungicide>
The preservative and fungicide is not particularly limited and includes, for example, 1,2-benzisothiazolin-3-one.

<Rust inhibitor>
There are no particular limitations on the rust preventive, and examples thereof include acidic sulfites, sodium thiosulfate, and the like.

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

The physical properties of the ink are not particularly limited and can be appropriately selected depending on the purpose. For example, the viscosity, surface tension, pH, etc. are preferably within the following ranges.
The viscosity of the ink at 25°C is preferably 5 mPa·s or more and 30 mPa·s or less, and 5 mPa·s or more and 25 mPa·s or less, from the viewpoint of improving print density and character quality and obtaining good ejection properties. More preferred. 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′×R24), sample liquid volume of 1.2 mL, rotation speed of 50 rpm, and 3 minutes.
The surface tension of the ink is preferably 35 mN/m or less, more preferably 32 mN/m or less at 25° C., from the viewpoint of suitably leveling the ink on the recording medium and shortening the drying time of the ink.
The pH of the ink is preferably 7 to 12, more preferably 8 to 11, from the viewpoint of preventing corrosion of metal members in contact with the ink.

The amount of ink deposited by the inkjet recording method is preferably 1.5 g/m ² to 25 g/m ² . When the ink adhesion amount is 1.5 g/m ² or more, sufficient image density can be obtained, and when it is 25 g/m ² or less, sufficient fixability can be obtained.

<Recording medium>
The recording medium is not particularly limited, and plain paper, glossy paper, special paper, cloth, etc. can be used, but good image formation is also possible using a non-permeable base material.
Impermeable substrates are substrates that have surfaces with low water permeability and low absorbency, and also include materials that have many cavities inside but are not open to the outside. Refers to a base material whose water absorption amount is 10 mL/m ² or less from the start of contact to 30 msec ^1/2 in the Bristow method.
As the impermeable base material, for example, plastic films such as vinyl chloride resin film, polyethylene terephthalate (PET) film, polypropylene, polyethylene, and polycarbonate film can be suitably used.

The recording medium is not limited to those used as general recording media, and may be appropriately used such as wallpaper, flooring materials, building materials such as tiles, cloth for clothing such as T-shirts, textiles, leather, etc. Further, by adjusting the configuration of the path for conveying the recording medium, ceramics, glass, metal, etc. can also be used.

<Ink storage container>
The ink storage container of the present invention stores the ink of the present invention in the container, and further includes 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, an ink bag made of an aluminum laminate film, a resin film, etc. Preferred examples include those having the following.

<Printing device, printing method>
The ink of the present invention can be suitably used in various recording devices using an inkjet recording method, such as printers, facsimile machines, copying machines, printer/fax/copier multifunction devices, and three-dimensional modeling devices.
In the present invention, a printing device and a printing method refer to a device capable of ejecting ink, various processing liquids, etc. onto a recording medium, and a method of performing recording using the device. A recording medium means something to which ink or various processing liquids can be attached even temporarily.
The printing device of the present invention includes the ink storage container of the present invention and an ejection head for ejecting ink.
This printing device can include not only a head portion that discharges ink, but also means for feeding, transporting, and discharging the recording medium, and other devices called pre-processing devices and post-processing devices. .
The printing device and the printing method may include 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 performed before, during, or after printing.
Further, the printing device and the printing method are not limited to those in which significant images such as characters and figures are visualized using ink. For example, it includes those that form patterns such as geometric patterns, and those that form three-dimensional images.
Furthermore, unless specifically limited, the printing device includes both a serial type device in which the ejection head is moved and a line type device in which the ejection head is not moved.
Furthermore, this printing device is not only a desktop type but also a wide printing device that can print on A0 size recording media, and it is also possible to use, for example, continuous paper wound into a roll as a recording medium. This also includes continuous book printers.

An example of a printing device will be described with reference to FIGS. 1 and 2. The following describes the case where black (K), cyan (C), magenta (M), and yellow (Y) color inks are used. However, the ink of the present invention is a white ink, and the black (K) , cyan (C), magenta (M), and yellow (Y), printing is performed using white ink in the same manner as the color ink described above to form an ink layer.
FIG. 1 is a perspective explanatory view of the device. FIG. 2 is a perspective explanatory view of the main tank. Image forming apparatus 400, which is an example of a printing apparatus, is a serial type image forming apparatus. A mechanism section 420 is provided within the exterior 401 of the image forming apparatus 400. Each ink storage section 411 of the main tank 410 (410k, 410c, 410m, 410y) for each color of black (K), cyan (C), magenta (M), and yellow (Y) is made of packaging such as aluminum laminated film. It is formed from members. The ink storage section 411 is housed in a container case 414 made of plastic, for example. Thereby, the main tank 410 is used as an ink cartridge for each color.
On the other hand, a cartridge holder 404 is provided on the back side of the opening when the cover 401c of the apparatus main body is opened. A main tank 410 is detachably attached to the cartridge holder 404. As a result, each ink discharge port 413 of the main tank 410 and the ejection head 434 for each color communicate with each other via the supply tube 436 for each color, and ink can be ejected from the ejection head 434 onto the recording medium.

This printing device can include not only a portion that discharges ink but also devices called a pre-processing device, a post-processing device, and the like.
One aspect of the pre-processing device and the post-processing device includes a pre-processing liquid and a post-processing liquid, as in the case of inks such as black (K), cyan (C), magenta (M), yellow (Y), etc. There is a mode in which a liquid storage section and a liquid ejection head are added, and a pre-processing liquid and a post-processing liquid are ejected using an inkjet recording method.
As another aspect of the pre-processing device and post-processing device, there is a mode in which a pre-processing device and a post-processing device using a blade coating method, a roll coating method, or a spray coating method other than the inkjet recording method are provided.

The printing method of the present invention includes an image forming step of forming an image on a recording medium using the ink of the present invention using an inkjet method;
a drying step of heating and drying the image,
The heating temperature in the drying step is 50°C or more and 200°C or less. According to this temperature range, the influence of heat on the recording medium is less likely to occur.

The ink of the present invention has a brightness of L* when a solid image of 50 mm x 50 mm formed on a polyethylene terephthalate (PET) film is dried for 1 hour in a 50°C constant temperature bath. When the brightness at that time is L*100°C, the absolute value of the brightness difference ΔL* expressed by the following formula (1) is preferably less than 10, more preferably 5 or less. When the absolute value of the brightness difference ΔL* is less than 10, the stability of the image (for example, whiteness) is excellent.
ΔL*=(L*50℃)-(L*100℃)...Formula (1)
The brightness can be measured using, for example, a spectrophotometric densitometer (X-Rite 939, manufactured by X-Rite).

Note that the method of using the ink is not limited to the inkjet recording method, and can be used in a wide variety of ways. In addition to inkjet recording methods, examples include blade coating, gravure coating, bar coating, roll coating, dip coating, curtain coating, slide coating, die coating, and spray coating.

<Recorded material>
The ink recorded matter of the present invention has an image formed using the ink of the present invention on a recording medium.
A recorded matter can be recorded by an inkjet recording device and an inkjet recording method.

The ink of the present invention can provide images with particularly good color development when applied to transparent films or colored recording media.
Examples of the transparent film include those made of plastic materials such as polyvinyl chloride film, polyethylene terephthalate (PET) film, polycarbonate film, acrylic film, polypropylene film, polyimide film, and polystyrene film.
For example, a polyethylene terephthalate (PET) film may have a total light transmittance of 80% or more at a thickness of 100 μm.
Examples of the colored recording medium include colored paper, the colored transparent film, cloth, clothing, ceramic, and the like. Note that by printing with the white ink before ink during color printing, the color of the recording medium can be made uniform to white, and the color development of the ink can be improved.

Further, in the terms of the present invention, image formation, recording, printing, printing, etc. are all synonymous.

Examples of the present invention will be described below, but the present invention is not limited to these Examples in any way.
Further, unless otherwise specified, ink preparation and evaluation were performed at a room temperature of 25° C. and a humidity of 60%. Note that "parts" in the examples are "parts by mass."

<Number average primary particle diameter and hollowness ratio of hollow resin particles>
Using a transmission electron microscope (manufactured by JEOL Ltd., "JEM-2100F"), two parallel lines in a certain direction sandwiching 200 to 500 hollow resin particles and 500 to 500 primary particles at a 30,000x field of view. The number-average primary particle diameter and shell thickness of each of the 200 hollow resin particles were determined by measuring the diameter in a certain direction at intervals of . Among the number average primary particle diameter and shell thickness of 200 hollow resin particles, remove the top 5% and bottom 5% values, calculate the average value of the remaining 90%, and use that value as the number average primary particle diameter of the hollow resin particles. The particle size and shell thickness were determined. The hollow ratio was calculated from the above-mentioned formula (2).

<Production example of hollow resin particles 1>
(Synthesis of seed particle emulsion 1)
Deionized water (385.42 parts) was charged into a four-neck separable flask equipped with a stirrer, a thermometer, a condenser, and a dropping funnel under a nitrogen atmosphere and heated to 80° C. with stirring. Next, sodium dodecylbenzenesulfonate (0.22 parts) and 10% ammonium persulfate aqueous solution (5.00 parts) were added, and a mixed monomer of methyl methacrylate (66.19 parts) and methacrylic acid (43.06 parts) was added. It was evenly dropped over 2 hours. After completion of the dropwise addition, the mixture was aged at 80° C. for 3 hours, and after cooling, a seed particle emulsion was obtained using a 120 mesh filter cloth. The solid content of the obtained seed particle emulsion was 20% by mass, the pH was 2.8, and the number average primary particle diameter of the seed particles was 120 nm.

(Synthesis of hollow resin particle emulsion 1)
-1st stage polymerization-
Deionized water (388.35 parts) was charged into a four-necked separable flask equipped with a stirrer, a thermometer, a condenser, and a dropping funnel under a nitrogen atmosphere, and the seed particle emulsion 1 (46.36 parts) obtained above was charged. part) was added and heated to 80° C. with stirring. Meanwhile, butyl methacrylate (3.90 parts), methyl methacrylate (41.07 parts), methacrylic acid (1.35 parts), sodium dodecylbenzenesulfonate (0.18 parts), deionized water (14.61 parts) was emulsified with homodisper to obtain pre-emulsion 1. Next, 10% ammonium persulfate aqueous solution (4.13 parts) was added to the solution heated to 80° C., and the pre-emulsion 1 obtained above was uniformly dropped over 60 minutes. After the addition was completed, the mixture was aged at 80° C. for 2 hours.

-Second stage polymerization-
Styrene (55.34 parts), sodium dodecylbenzenesulfonate (0.15 parts), and deionized water (23.30 parts) were emulsified using a homodisper to prepare Preemulsion 2. Next, a 10% aqueous sodium persulfate solution (4.61 parts) was added to the solution obtained in the first stage polymerization, and the pre-emulsion 2 obtained above was uniformly dropped over 120 minutes. After the addition was completed, the mixture was aged at 80° C. for 2 hours.
After aging at 80°C for 2 hours, 28% ammonia water (4.44 parts) was added to swell and dissolve the seed particles, and the mixture was aged at 80°C for 1 hour. After cooling, it was filtered using a 120 mesh filter cloth to obtain Hollow Resin Particle Emulsion 1. The solid content of the obtained emulsion was adjusted to 16% by mass. The pH of the hollow resin particle emulsion 1 was 8.9, the number average primary particle diameter of the hollow resin particles was 350 nm, the shell thickness was 75 nm, and the hollow ratio was 19%.

<Production example of hollow resin particles 2 to 13>
(Synthesis of seed particle emulsions 2 to 5)
Seed particle emulsions 2 to 5 were synthesized by changing the amount of sodium dodecylbenzenesulfonate (0.22 parts) to 0.18 parts, 0.14 parts, 0.10 parts, and 0.1 parts, respectively, in the synthesis of seed particle emulsion 1. The same method was used except that the number was changed to 08 parts. The number average primary particle diameters of the seed particles in Seed Particle Emulsions 2 to 5 were 180 nm, 220 nm, 260 nm, and 280 nm, respectively.

(Synthesis of hollow resin particle emulsion 2)
Synthesis of Hollow Resin Particle Emulsion 1 was carried out in the same manner except that styrene (55.34 parts) in the second stage polymerization was changed to styrene (49.94 parts) and vinyltriethoxysilane (2.63 parts). Ta. The number average primary particle diameter of the hollow resin particles of Hollow Resin Particle Emulsion 2 was 350 nm, the shell thickness was 60 nm, and the hollow ratio was 28%.

(Synthesis of hollow resin particle emulsion 3)
Synthesis of Hollow Resin Particle Emulsion 1 was carried out in the same manner except that styrene (55.34 parts) in the second stage polymerization was changed to styrene (47.32 parts) and vinyltriethoxysilane (2.49 parts). Ta. The number average primary particle diameter of the hollow resin particles of Hollow Resin Particle Emulsion 3 was 350 nm, the shell thickness was 40 nm, and the hollow ratio was 46%.

(Synthesis of hollow resin particle emulsion 4)
Synthesis of Hollow Resin Particle Emulsion 1 was carried out in the same manner except that styrene (55.34 parts) in the second stage polymerization was changed to styrene (42.06 parts) and vinyltriethoxysilane (2.21 parts). Ta. The number average primary particle diameter of the hollow resin particles in Hollow Resin Particle Emulsion 4 was 350 nm, the shell thickness was 25 nm, and the hollow ratio was 63%.

(Synthesis of hollow resin particle emulsion 5)
In the synthesis of Hollow Resin Particle Emulsion 1, the same method was used except that Seed Particle Emulsion 1 in the first stage polymerization was changed to Seed Particle Emulsion 2. The number average primary particle diameter of the hollow resin particles of Hollow Resin Particle Emulsion 5 was 500 nm, the shell thickness was 70 nm, and the hollow ratio was 37%.

(Synthesis of hollow resin particle emulsion 6)
In the synthesis of Hollow Resin Particle Emulsion 1, Seed Particle Emulsion 1 in the first stage polymerization was changed to Seed Particle Emulsion 2, and styrene (55.34 parts) in the second stage polymerization was replaced with styrene (55.20 parts) and vinyl trifluoride. The same method was followed except that ethoxysilane (2.91 parts) was used. The number average primary particle diameter of the hollow resin particles of Hollow Resin Particle Emulsion 6 was 500 nm, the shell thickness was 80 nm, and the hollow ratio was 31%.

(Synthesis of hollow resin particle emulsion 7)
In the synthesis of Hollow Resin Particle Emulsion 1, Seed Particle Emulsion 1 in the first stage polymerization was changed to Seed Particle Emulsion 2, and styrene (55.34 parts) in the second stage polymerization was replaced with styrene (52.57 parts) and vinyl trifluoride. The same method was followed except that ethoxysilane (2.77 parts) was used. The number average primary particle diameter of the hollow resin particles of Hollow Resin Particle Emulsion 7 was 500 nm, the shell thickness was 70 nm, and the hollow ratio was 37%.

(Synthesis of hollow resin particle emulsion 8)
In the synthesis of Hollow Resin Particle Emulsion 1, Seed Particle Emulsion 1 in the first stage polymerization was changed to Seed Particle Emulsion 3, and styrene (55.34 parts) in the second stage polymerization was replaced with styrene (49.94 parts) and vinyl trifluoride. The same procedure was followed except that ethoxysilane (2.63 parts) was used. The number average primary particle diameter of the hollow resin particles of Hollow Resin Particle Emulsion 8 was 650 nm, the shell thickness was 60 nm, and the hollow ratio was 54%.

(Synthesis of hollow resin particle emulsion 9)
In the synthesis of Hollow Resin Particle Emulsion 1, Seed Particle Emulsion 1 in the first stage polymerization was changed to Seed Particle Emulsion 3, and styrene (55.34 parts) in the second stage polymerization was replaced with styrene (55.20 parts) and vinyl trifluoride. The same method was followed except that ethoxysilane (2.91 parts) was used. The number average primary particle diameter of the hollow resin particles in Hollow Resin Particle Emulsion 9 was 650 nm, the shell thickness was 90 nm, and the hollow ratio was 38%.

(Synthesis of hollow resin particle emulsion 10)
In the synthesis of Hollow Resin Particle Emulsion 1, Seed Particle Emulsion 1 in the first stage polymerization was changed to Seed Particle Emulsion 3, and styrene (55.34 parts) in the second stage polymerization was replaced with styrene (57.83 parts) and vinyl trifluoride. The same method was followed except that ethoxysilane (3.04 parts) was used. The number average primary particle diameter of the hollow resin particles of Hollow Resin Particle Emulsion 10 was 650 nm, the shell thickness was 130 nm, and the hollow ratio was 22%.

(Synthesis of hollow resin particle emulsion 11)
In the synthesis of Hollow Resin Particle Emulsion 1, Seed Particle Emulsion 1 in the first stage polymerization was changed to Seed Particle Emulsion 4, and styrene (55.34 parts) in the second stage polymerization was replaced with styrene (55.20 parts) and vinyl trifluoride. The same method was followed except that ethoxysilane (2.91 parts) was used. The number average primary particle diameter of the hollow resin particles of Hollow Resin Particle Emulsion 11 was 800 nm, the shell thickness was 100 nm, and the hollow ratio was 42%.

(Synthesis of hollow resin particle emulsion 12)
In the synthesis of Hollow Resin Particle Emulsion 1, Seed Particle Emulsion 1 in the first stage polymerization was changed to Seed Particle Emulsion 5, and styrene (55.34 parts) in the second stage polymerization was replaced with styrene (57.83 parts) and vinyl trifluoride. The same method was followed except that ethoxysilane (3.04 parts) was used. The number average primary particle diameter of the hollow resin particles of Hollow Resin Particle Emulsion 12 was 900 nm, the shell thickness was 120 nm, and the hollow ratio was 39%.

(Synthesis of hollow resin particle emulsion 13)
In the synthesis of Hollow Resin Particle Emulsion 1, Seed Particle Emulsion 1 in the first stage polymerization was changed to Seed Particle Emulsion 2, and styrene (55.34 parts) in the second stage polymerization was changed to styrene (58.11 parts). Other than that, the same method was used. The number average primary particle diameter of the hollow resin particles of Hollow Resin Particle Emulsion 13 was 500 nm, the shell thickness was 75 nm, and the hollow ratio was 34%.

<Preparation of titanium oxide dispersion>
In a beaker, 18.0 parts by mass of acrylic copolymer (dispersant, manufactured by BYK Chemie Japan Co., Ltd., product name: "DISPERBYK-2008", active ingredient 100% by mass, amine value: 66mgKOH/g) was added to 62.0 parts by mass of pure water. 20.0 parts by mass of titanium dioxide (manufactured by Teika, product name "JR-600A", number average primary particle diameter 250 nm, surface treatment: Al) was added, and while cooling with water, a homogenizer (Hitachi Koki Dispersion was performed using a HG30, C20 cutter (manufactured by Co., Ltd., 8,000 rpm, 60 minutes). The obtained titanium dioxide pigment dispersion was filtered through a membrane filter (cellulose acetate membrane) with an average pore size of 5 μm to obtain a [titanium oxide dispersion] (titanium dioxide particle concentration: 20% by mass).

<Examples 1 to 17, Comparative Examples 1 to 4>
(Ink 1-21)
-Preparation of ink-
Inks having the composition shown in Table 1 below were prepared by a conventional method and filtered through a membrane filter (cellulose acetate membrane) having an average pore size of 5 μm to produce Inks 1 to 21.

ただし、Ｒ＝ＣＨ₃である。
・グリセリン（沸点２９０℃） Details of the materials used in the inks in Table 1 are as follows.
(Organic solvent)
・1,2-propanediol (boiling point 188℃)
・1,2-butanediol (boiling point 195°C)
・1,5-pentanediol (boiling point 242°C)
・1,6-hexanediol (boiling point 223℃)
・3-methoxy-3-methyl-1-butanol (boiling point 174°C)
・3-Methyl-1,3-butanediol (boiling point 204°C)
・Diethylene glycol monoethyl ether (boiling point 196°C)
・Diethylene glycol monobutyl ether (boiling point 230℃)
・Amide compound: An amide compound represented by the following structural formula (manufactured by Idemitsu Kosan Co., Ltd., Equamide M100, boiling point 216°C)

However, R= _CH3 .
・Glycerin (boiling point 290℃)

(Resin particles A)
・Resin particle a1: Polyurethane resin (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Superflex 210,
Glass transition temperature 41℃, _D50 : 45nm)
・Resin particle a2: Acrylic silicone resin (manufactured by Toyochem Co., Ltd., W5343,
Glass transition temperature 45℃, _D50 : 71nm)
・Resin particle a3: Polyurethane resin (manufactured by Mitsui Chemicals, W5661,
Glass transition temperature 70℃, _D50 : 21nm)
・Resin particle a4: Polyester resin (manufactured by Unitika, KT-8701,
Glass transition temperature 60℃, _D50 : 50nm)
・Resin particle a5: Polyester resin (manufactured by Unitika, KZT-1449,
Glass transition temperature 45℃, _D50 : 145nm)
・Resin particle a6: Polyester resin (manufactured by Unitika, KA-5071S,
Glass transition temperature 67℃, _D50 : 131nm)
・Resin particle a7: Polyurethane resin (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Superflex 150,
Glass transition temperature 40℃, _D50 : 41nm)
・Resin particle a8: Polyester resin obtained by the following method for synthesizing polyester resin particles
fat particles, glass transition temperature 62°C, _D50 : 92nm)

(Method for synthesizing polyester resin particles)
<Synthesis of polyester>
In a reaction tank equipped with a cooling tube, a stirrer, and a nitrogen inlet tube, 220 parts of a 2-mole adduct of bisphenol A ethylene oxide, 560 parts of a 3-mole adduct of bisphenol A propion oxide, 220 parts of terephthalic acid, 50 parts of adipic acid, and dibutyl were added. 3 parts of tin oxide was added, and the mixture was reacted at 230° C. for 7 hours under normal pressure.
Next, the reaction solution was reacted for 5 hours under a reduced pressure of 10 to 15 mmHg, and then 40 parts of trimellitic anhydride was added to the reaction vessel and reacted for 5 hours at 180°C under normal pressure to form a polyester. Synthesized.
The obtained polyester had a THF-soluble weight average molecular weight (Mw) of 6200 and a glass transition temperature (Tg) of 62°C.

<Synthesis of polyester resin particles>
After mixing 25 parts of the synthesized polyester, 50 parts of acetone, 200 parts of ion-exchanged water, and 2.2 parts of 5N sodium hydroxide, the acetone and some of the ion-exchanged water were distilled off using an evaporator to form polyester resin particles. An aqueous dispersion (solid content 30%) was obtained. The cumulative 50% volume particle diameter of the obtained polyester resin particles was measured and found to be 92 nm.

(Resin particles B)
・Resin particle b1: Polyurethane resin (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Superflex 420,
Glass transition temperature -10℃, _D50 : 15nm)
・Resin particle b2: Polyurethane resin (manufactured by Mitsui Chemicals, W6061,
Glass transition temperature 25℃, _D50 : 100nm)
・Resin particle b3: Polyester resin (manufactured by Eastman Chemical Japan Co., Ltd.,
Eastek1300, glass transition temperature 36℃, _D50 : 26nm)
・Resin particle b4: Styrene resin (manufactured by Nippon Zeon Co., Ltd., LX407S1,
Glass transition temperature -1℃, _D50 : 121nm)

(Additive)
・Surfactant A: Fluorine surfactant
(Capstone FS-34 manufactured by Chemours)
・Surfactant B: Fluorine surfactant
(Capstone FS-3100 manufactured by Chemours)
・Surfactant C: Fluorine surfactant
(Capstone FS-30 manufactured by Chemours)
・Defoaming agent: Envirogem AD01 (manufactured by Air Products)
・Preservative and fungicidal agent: Proxel LV (manufactured by Avecia)
・pH adjuster: 1N-NaOH

The physical properties of the inks of Examples 1 to 17 and Comparative Examples 1 to 4 are shown in Table 2 below.

<Evaluation of ink sedimentation>
The settling properties of particles of each ink used in Examples 1 to 17 and Comparative Examples 1 to 4 were evaluated using Turviscan MA2000 (manufactured by Eiko Seiki Co., Ltd.).
As a method, the evaluation ink was subjected to ultrasonic dispersion treatment (100 W, 20 minutes) while being cooled with water, and after uniformly dispersing the evaluation ink, 5.0 mL of the evaluation ink was put into a special glass cell using a pipette. Measurement was performed 30 minutes after the liquid level of the evaluation ink in the cell became stable, and this time was taken as the start of sedimentation evaluation. Thereafter, the sample was allowed to stand at 23° C., and measurement was performed until 100 hours later, and the sedimentation property was evaluated by displaying the deviation based on the start of the sedimentation property evaluation. Sedimentability was evaluated by integrating the backscattered light due to the formation of supernatant by peak integration (relative value mode), and rank-evaluated based on the following criteria.
[Evaluation criteria]
A: The absolute value of the relative change 100 hours after the start of evaluation is less than 5.0% B: The absolute value of the relative change 100 hours after the start of evaluation is 5.0% or more and less than 10.0% C: 100 hours after the start of evaluation The absolute value of the relative change is 10.0% or more and less than 15.0% D: The absolute value of the relative change 100 hours after the start of the evaluation is 15.0% or more

<Recording conditions>
Remove the exterior of the inkjet printer (IPSiO GXe5500 manufactured by Ricoh Co., Ltd.), attach the rear multi-manual feeder, and clean it by passing pure water through the ink supply path including the recording head until the cleaning liquid stops discoloring. The cleaning liquid was completely drained from the device to prepare a printing device for evaluation.
Further, the prepared ink was stirred for 30 minutes under a reduced pressure condition of 5 Pa to 10 Pa to degas the gas in the evaluation ink, and the ink was filled into an ink cartridge to obtain an evaluation ink cartridge. Perform the filling operation, confirm that all nozzles are filled with the evaluation ink and no abnormal images appear, select glossy paper clean mode with the driver attached to the printer, and then set color matching off to the print mode in the user settings. In this print mode, the ejection amount was adjusted by changing the drive voltage of the head so that the amount of ink adhering to the recording medium for a solid image was 15 g/m ² .

<Concealability evaluation>
- Image brightness evaluation -
Each ink used in Examples 1 to 17 and Comparative Examples 1 to 4 was filled into the inkjet printer (IPSiO GXe5500, manufactured by Ricoh Co., Ltd.), and placed on My Paper (manufactured by Ricoh Co., Ltd., PPC plain paper) with double-sided tape. After printing a 50 cm x 50 cm solid image created using Microsoft Word 2003 (manufactured by Microsoft) on a fixed transparent PET film (manufactured by Toyobo Co., Ltd., Ester Film E5100), it was dried for 60 minutes in a constant temperature bath at 50 °C. I let it happen.
With commercially available black paper placed under the printed PET film, the brightness (L*a) of the printed area was measured using a spectrophotometric densitometer (X-Rite 939, manufactured by X-Rite). It was measured and evaluated based on the following criteria.
[Evaluation criteria]
A: L*a value is 70 or more B: L*a value is 60 or more and less than 70 C: L*a value is less than 60 For reference, unprinted PET film was placed on black paper. The measured L*A value was 23.

- Image whiteness stability -
Each ink prepared in Examples 1 to 17 and Comparative Examples 1 to 4 was filled into the inkjet printer (IPSiO GXe5500, manufactured by Ricoh Co., Ltd.), and placed on My Paper (PPC plain paper, manufactured by Ricoh Co., Ltd.) with double-sided tape. After printing a solid image of 50 cm x 50 cm created using Microsoft Word 2003 (manufactured by Microsoft) on a fixed transparent PET film (manufactured by Toyobo Co., Ltd., Ester Film E5100), it was dried for 60 minutes in a constant temperature bath at 90 °C. I let it happen.
After printing, the brightness of the recording medium was placed in a constant temperature bath at 50°C and dried for 60 minutes, and the medium was placed in a constant temperature bath at 90°C and dried for 60 minutes, and the brightness was measured, and the absolute value of the difference in brightness |ΔL*| Evaluation was performed by calculating =|(L*50°C)−(L*90°C)|.
To measure the brightness, place commercially available black paper under the printed PET film, and measure the printed area using a spectrophotometric densitometer (X-Rite 939, manufactured by X-Rite). It was evaluated based on the criteria.
[Evaluation criteria]
A: |ΔL*| value is less than 5 B: |ΔL*| value is 5 or more and less than 10 C: |ΔL*| value is 10 or more

<Abrasion resistance evaluation>
For the brightness evaluation of the image above, the printed solid image was rubbed with dry cotton (Kanakin No. 3) under a load of 100 g, and the condition of the image was visually observed. ``Sex'' was evaluated. In practical use, it is desirable that the evaluation is B- or higher.
[Evaluation criteria]
A: The image did not change even after being rubbed 50 times or more.B+: Some scratches remained after 50 times, but it did not affect the image density.B-: The image remained after being rubbed 31 times or more and less than 50 times. Density decreased C: Image density decreased after rubbing 30 times or less

<Adhesion evaluation>
For the brightness evaluation of the image above, the printed solid image was subjected to a checkerboard peel test (based on JIS K5600-5-6-1999) using cloth adhesive tape (product name: 123LW-50, manufactured by Nichiban Co., Ltd.). The number of remaining squares of 100 test squares was counted, and the "adhesion" to the base material was evaluated based on the following evaluation criteria. In practical use, it is desirable that the evaluation is B or higher.
[Evaluation criteria]
A: The number of remaining squares was 90 or more. B: The number of remaining squares was 70 or more and less than 90. C: The number of remaining squares was less than 70.

From the above results, Examples 1 to 17 using water, a water-soluble organic solvent with a boiling point of 250°C or lower, hollow resin particles, and resin particles with a glass transition temperature of 40°C or higher compared to Comparative Examples 1 to 4, Even during heat drying, it suppresses a decrease in whiteness and does not easily settle, and has excellent abrasion resistance and adhesion.
In Comparative Example 1, a water-soluble organic solvent with a high boiling point was used, and high whiteness could not be obtained because the solvent remained within the hollow resin particles. Comparative Examples 2 and 3 had poor abrasion resistance and adhesion because the glass transition temperature of the resin particles was less than 40°C, and because the hollow resin particles did not contain silicon, they had low heat resistance and solvent resistance, making it difficult to print. There is a large change in brightness of the image. Comparative Example 4 using titanium oxide resulted in easy sedimentation due to the large particle specific gravity.

400 Image forming apparatus 401 Exterior of image forming apparatus 401c Cover of apparatus body 404 Cartridge holder 410 Main tank 410k, 410c, 410m, 410y For each color of black (K), cyan (C), magenta (M), yellow (Y) Main tank 411 Ink storage section 413 Ink discharge port 414 Storage container case 420 Mechanism section 434 Discharge head 436 Supply tube

Japanese Patent Application Publication No. 2012-7089 Japanese Patent Application Publication No. 2014-196590

Claims (8)

An ink containing water, a water-soluble organic solvent, a pigment, and resin particles A,
The pigment is a hollow resin particle,
The hollow resin particles are hollow resin particles whose resin is crosslinked with a silicone crosslinking agent,
The water-soluble organic solvents are all water-soluble organic solvents with a boiling point of 250°C or less,
The resin particles A are polyester resin particles having a glass transition temperature of 40° C. or higher, and an ink having a cumulative 50% volume particle diameter D ₅₀ of 90 nm or more and 150 nm or less. The ink according to claim 1 , further comprising second resin particles B having a glass transition temperature of 0° C. or lower. The ink according to claim 1 or 2, wherein the hollow resin particles have a number average primary particle diameter of 300 nm or more and 800 nm or less. The ink according to any one of claims 1 to 3 , wherein the hollow resin particles have a hollowness ratio of 20% or more and 60% or less. The brightness when a 50 mm x 50 mm solid image formed on a polyethylene terephthalate film is dried for 1 hour in a 50°C constant temperature bath is L*50℃, and the brightness when dried for 1 hour in a 90℃ constant temperature bath is L*90. 5. The ink according to claim 1, wherein the absolute value of the lightness difference ΔL* expressed by the following formula (1) is less than 10 when the temperature is expressed as Celsius.
|ΔL*|=|(L*50℃)-(L*90℃)|...Formula (1) An ink container containing the ink according to claim 1 . An image forming step of forming an image on a recording medium using the ink according to any one of claims 1 to 5 by an inkjet method, and a drying step of heating and drying the image, the heating temperature in the drying step A printing method in which the temperature is 50°C or more and 200°C or less. A printing device comprising the ink storage container according to claim 6 and an ejection head for ejecting ink.

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