JP2015168772A - Ink, ink cartridge, and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink in which a hydrophobic surface titanium dioxide as a coloring agent is hardly precipitated, and even it is precipitated, it can be easily dispersed again.SOLUTION: The ink comprises at least a hydrophobic surface titanium dioxide as a coloring agent and water, and surface energy of the hydrophobic surface titanium dioxide at 25°C is 28 mN/m-35 mN/m. Preferably, surface tension of a vehicle excluding the hydrophobic surface titanium dioxide at 25°C is 25 mN/m-35 mN/m.

Description

  The present invention relates to an ink, an ink cartridge, and an image forming method.

Ordinary ink jet recording inks are mostly highly transparent inks intended for printing on white recording media. When printed on transparent or low-lightness substrates, no contrast is obtained. As a result, a clear color developability cannot be obtained or a display with visibility becomes difficult. Therefore, attempts have been made to use white ink with high concealability.
As such a white ink, an ink using a white inorganic pigment as a colorant is used. In most cases, the inorganic pigment has a specific gravity greater than that of the organic pigment. For example, if an ink cartridge containing a commercially available inorganic pigment as a colorant (uses hydrophilic surface-treated titanium dioxide) is not used for 10 days or more, the ink cartridge is used after shaking. A cautionary note was described (see Non-Patent Document 1).
In addition, when using an ink containing an inorganic pigment such as titanium dioxide as a colorant, it is necessary to use an ink jet recording apparatus having a stirring mechanism or a circulation mechanism (see Patent Document 1).
Moreover, in patent document 2, although the hydrophobized titanium dioxide is used as an aqueous dispersion, titanium dioxide is not used as a colorant, and the aggregation of titanium dioxide particles is suppressed by the effect of the electrolyte. To do.

Further, an aqueous pigment dispersion containing titanium oxide, surface-treated with a silane coupling agent, a resin having an anionic group, a water-soluble organic solvent, and a basic compound after surface treatment with alumina and silica has been proposed. (See Patent Document 3).
However, the ink for ink jet recording using the proposed aqueous pigment dispersion has a level that requires a stirring mechanism of the ink jet recording apparatus because the hydrophobization treatment is not optimized.

  Therefore, it is desired to provide an ink that is less likely to precipitate surface hydrophobic titanium dioxide, which is a colorant, and that can be easily redispersed even if it settles.

  An object of the present invention is to solve the above-described problems and achieve the following objects. That is, an object of the present invention is to provide an ink in which surface hydrophobic titanium dioxide, which is a colorant, does not easily settle, and can be easily redispersed even if it settles.

The ink of the present invention as a means for solving the above problems comprises at least surface hydrophobic titanium dioxide as a colorant and water,
The surface hydrophobic titanium dioxide has a surface energy at 25 ° C. of 28 mN / m to 35 mN / m.

  According to the present invention, the above-mentioned problems can be solved and the above-mentioned object can be achieved, and the surface hydrophobic titanium dioxide, which is a colorant, is difficult to settle, and even if it settles, it can be easily redispersed. An ink can be provided.

FIG. 1 is a schematic diagram illustrating an example of an ink cartridge. FIG. 2 is a schematic view including the case of the ink cartridge of FIG. FIG. 3 is a perspective view showing an example of an ink jet recording apparatus. FIG. 4 is a schematic diagram illustrating another example of the ink jet recording apparatus. FIG. 5 is a schematic plan view of an essential part showing an example of a mechanism part of the ink jet recording apparatus. FIG. 6 is a schematic plan view showing an example of a mechanism part of the ink jet recording apparatus.

(ink)
The ink of the present invention preferably contains at least surface hydrophobic titanium dioxide as a colorant and water, and preferably contains a dispersant, a water-soluble organic solvent, and resin particles, and further contains other components as necessary. It contains.

In the present invention, in the ink containing at least surface hydrophobic titanium dioxide and water, the surface energy of the surface hydrophobic titanium dioxide at 25 ° C. is adjusted to 28 mN / m to 35 mN / m. The surface-hydrophobic titanium dioxide is difficult to settle, and even if it settles, it can be easily redispersed.
The surface energy of the surface hydrophobic titanium dioxide is preferably controlled by surface coating with a hydrophobizing agent. Further, in order to control the sedimentation property of the surface hydrophobic titanium dioxide in the ink, it is more preferable to cover a part of the surface of the titanium dioxide. In order to coat a part of the surface of the titanium dioxide, the amount of the hydrophobizing agent may be reduced, or anisotropic vapor phase growth may be performed. It is also possible to remove part of the hydrophobizing agent on the surface of the surface hydrophobic titanium dioxide by corona discharge treatment or sputtering after the entire surface of the titanium dioxide is coated with the hydrophobizing agent (hydrophobic removal treatment). ).
Here, when the surface energy value γ (mN / m) of the surface hydrophobic titanium dioxide at 25 ° C. satisfies the following formula (1) 1, the hydrophobizing agent is not the entire surface of the titanium dioxide but a part thereof. It can be seen that it is coated.
γmin <γ <γmax (1)
(However, in said Formula (1), (gamma) max represents the surface energy (72 mN / m) of the titanium dioxide which has not provided the hydrophobizing agent at 25 degreeC. (Gamma) min changes the value of the surface energy of 25 degreeC. This represents the surface energy of surface hydrophobic titanium dioxide to which a hydrophobizing agent is added to such an extent that it does not.)
Among these, the range of γmin + 3 <γ <γmax is more preferable from the viewpoint of ensuring the wettability of the surface hydrophobic titanium dioxide in the vehicle.

Furthermore, the present inventors blended not only water but also a colorant dispersant and a water-soluble organic solvent to control the surface tension of the vehicle, so that the surface hydrophobic titanium dioxide in the surface energy range is uniformly dispersed. It has been found that the surface hydrophobic titanium dioxide is less likely to settle in the dispersion and can be easily redispersed even if it is settled.
Therefore, the surface tension at 25 ° C. of the vehicle excluding the surface hydrophobic titanium dioxide is preferably 25 mN / m to 40 mN / m, and more preferably 25 mN / m to 33 mN / m. When the surface tension is 25 mN / m or more, ink ejection stability can be achieved, and when the surface tension is 40 mN / m or less, the titanium oxide surface having a low surface energy can be appropriately wetted. Furthermore, by setting the surface tension to 33 mN / m or less, it is possible to produce an ink having excellent sedimentation and redispersibility.
The surface tension can be measured by using a surface tension meter CBVP-Z manufactured by Kyowa Interface Science Co., Ltd. and a static surface tension after 5 seconds from the Wilhelmy plate method at a liquid temperature of 25 ° C.

<Surface hydrophobic titanium dioxide>
“Surface hydrophobicity” in the surface hydrophobic titanium dioxide means that the surface energy of titanium dioxide at 25 ° C. is 5 mN / m or less than the surface tension of water at 25 ° C. (72 mN / m). If the surface energy of titanium dioxide at 25 ° C. is 72 mN / m or more, it is determined that “the surface is not hydrophobic”.
The surface energy of the surface hydrophobic titanium dioxide can be obtained by a method of measuring a floating ratio of titanium dioxide with respect to a solvent in which the volume ratio of water and methanol is changed. For example, a powder wettability tester (WET-101P , Manufactured by Resuka Co., Ltd.) and can be measured as follows.
First, titanium dioxide (0.1 g) is suspended in 100 mL of water, the rotation speed of the liquid is 200 rpm, the methanol inflow rate is 3 mL / min, and precipitation of titanium dioxide at 25 ° C. is detected using an optical detector. The surface tension of titanium dioxide can be obtained by calculating the surface tension from the volume concentration of methanol when titanium dioxide settles.

The surface hydrophobic titanium dioxide has a surface energy at 25 ° C. of 28 mN / m to 35 mN / m. By setting the surface energy to 35 mN / m or less, it is possible to prevent sedimentation of surface hydrophobic dioxide easily. Further, by setting the surface energy to 28 mN / m or more, the amount of water-soluble organic solvent other than water can be suppressed, which is advantageous for image drying.
As a means for setting the surface energy of the surface hydrophobic titanium dioxide to 28 mN / m to 35 mN / m, for example, the application amount of a hydrophobizing agent such as silicone oil used for hydrophobizing titanium dioxide can be changed to 100% titanium dioxide. It is preferable to set it as 1 mass part-100 mass parts with respect to a mass part, and it is more preferable to set it as 4 mass parts-40 mass parts. Further, it is preferable to subject the surface hydrophobic titanium dioxide subjected to the surface hydrophobization treatment to a corona discharge treatment with an applied voltage of 8 kV to 14 kV.

The titanium dioxide in the surface-hydrophobic titanium dioxide is not particularly limited, and the surface may be untreated, and the wettability with the treatment agent during the hydrophobization treatment is increased to improve the hydrophobization treatment efficiency. Therefore, it may be surface-treated. Examples of the surface treatment include oxides such as aluminum, silicon, zirconium, and zinc.
Examples of the treatment for imparting hydrophobicity to the surface of the titanium dioxide include alkyl treatment, alkylsilane treatment, fluoroalkyl treatment, perfluoroalkyl treatment, and silicone treatment with silicone oil. Among these, silicone treatment and alkyl treatment are preferable.
As the surface-hydrophobic titanium dioxide, an appropriately manufactured product or a commercially available product may be used.
As the production method, for example, a known silane coupling agent such as dialkyl dihalogenated silane, trialkyl halogenated silane, alkyl trihalogenated silane, or silicone oil such as dimethyl silicone oil and titanium dioxide are contacted at high temperature. It can be produced by reacting.
Examples of the commercially available products include hydrophobic silicone surface-treated TiO ₂ (CR-63, manufactured by Ishihara Sangyo Co., Ltd.), hydrophobic silicone surface-treated TiO ₂ (MTY-02, manufactured by Teika Co., Ltd.), and the like.

The cumulative 50% particle size (D50) in the volume-based particle size distribution of the surface hydrophobic titanium dioxide is preferably 200 nm to 600 nm, more preferably 210 nm to 500 nm, and still more preferably 210 nm to 320 nm. If the cumulative particle diameter is in the range of 50%, the concealability of the printed image can be ensured, the clogging of the ink flow path and the discharge nozzle in the ink jet recording apparatus can be suppressed, and the apparatus can be operated stably. It becomes possible.
The cumulative 50% particle diameter (D50) can be measured by, for example, a particle size distribution measuring device (Microtrac UPA-EX150, manufactured by Nikkiso Co., Ltd.).
The content of the surface hydrophobic titanium dioxide is preferably 1% by mass to 20% by mass and more preferably 3% by mass to 15% by mass with respect to the total amount of the ink.

<Dispersant>
The surface-hydrophobic titanium dioxide can be dispersed in water using a water-soluble organic solvent, a dispersant or the like to obtain a pigment dispersion.
As the water-soluble organic solvent, those described later are used.
Examples of the dispersant for dispersing the surface hydrophobic titanium dioxide in the dispersion include water-soluble resins and surfactants.
Examples of the dispersion method include a dispersion method using general-purpose equipment such as ultrasonic irradiation, a homogenizer, a ball mill, a bead mill, and a paint shaker.
An ink can be obtained by mixing the titanium dioxide dispersion with a vehicle, and the prepared ink is not particularly limited, but can be suitably used for inkjet recording applications.

<< Water-soluble resin >>
Examples of the water-soluble resin include styrene, styrene derivatives, vinyl naphthalene derivatives, aliphatic alcohol esters of α, β-ethylenically unsaturated carboxylic acids, acrylic acid, acrylic acid derivatives, maleic acid, maleic acid derivatives, itacon. Examples thereof include block copolymers composed of at least two monomers selected from acids, itaconic acid derivatives, fumaric acid, and fumaric acid derivatives, random copolymers, and salts thereof.
These water-soluble resins are alkali-soluble resins that are soluble in an aqueous solution in which a base is dissolved. Among these, those having a weight average molecular weight of 3,000 to 20,000 are dispersed when used in ink. This is particularly preferable from the viewpoint that the viscosity of the liquid can be reduced and the dispersion is easy.
The content of the water-soluble resin is preferably 0.1% by mass to 10% by mass with respect to the total amount of the ink.

<< Surfactant >>
Examples of the surfactant include an anionic surfactant, a nonionic surfactant, an amphoteric surfactant, an acetylene glycol surfactant, a fluorine surfactant, and a silicone surfactant. Among these, it is preferable to select a surfactant that does not impair dispersion stability depending on the combination of the surface hydrophobic titanium dioxide and the water-soluble organic solvent.
The surfactant is not limited to these, and may be used alone or in combination. Even if it does not dissolve easily in the ink alone, it can be solubilized by mixing and exist stably.

  Examples of the anionic surfactant include polyoxyethylene alkyl ether acetate, dodecylbenzene sulfonate, oxalate sulfonate, laurate, and polyoxyethylene alkyl ether sulfate salt.

  Examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene polyoxypropylene alkyl ether, polyoxyethylene alkyl ester, polyoxyethylene polyoxypropylene alkyl ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene Examples thereof include ethylene alkyl phenyl ether, polyoxyethylene alkyl amine, and polyoxyethylene alkyl amide.

  Examples of the amphoteric surfactant include lauryl aminopropionate, lauryl dimethyl betaine, stearyl dimethyl betaine, and lauryl dihydroxyethyl betaine. Specific examples include lauryl dimethylamine oxide, myristyl dimethylamine oxide, stearyl dimethylamine oxide, dihydroxyethyl lauryl amine oxide, polyoxyethylene coconut oil alkyl dimethylamine oxide, dimethylalkyl (coconut) betaine, and dimethyl lauryl betaine. .

  Examples of the acetylene glycol surfactant include 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol, And acetylene glycols such as 5-dimethyl-1-hexyn-3-ol (for example, Surfynol 104, 82, 465, 485, TG, etc., manufactured by Air Products (USA)).

Examples of the fluorosurfactant include perfluoroalkyl sulfonate, perfluoroalkyl carboxylate, perfluoroalkyl phosphate, perfluoroalkyl ethylene oxide adduct, perfluoroalkyl betaine, and perfluoroalkylamine oxide. Examples thereof include a compound, a polyoxyalkylene ether polymer having a perfluoroalkyl ether group in the side chain, or a sulfate ester salt thereof, a fluorine-based aliphatic polymer ester.
Examples of commercially available fluorosurfactants include Surflon S-111, S-112, S-113, S121, S131, S132, S-141, S-145 (manufactured by Asahi Glass Co., Ltd.), Fullrad FC- 93, FC-95, FC-98, FC-129, FC-135, FC-170C, FC-430, FC-431, FC-4430 (manufactured by Sumitomo 3M Limited), FT-110, 250, 251, 400S (Manufactured by Neos), Zonyl FS-62, FSA, FSE, FSJ, FSP, TBS, UR, FSO, FSO-100, FSN, FSN-100, FS-300, FSK (manufactured by DuPont), Polyfox PF- 136A, PF-156A, PF-151N (manufactured by OMNOVA) and the like. These may be used individually by 1 type and may use 2 or more types together.

The silicone-based surfactant is not particularly limited and may be appropriately selected depending on the intended purpose. However, those that do not decompose even at high pH are preferable. For example, side chain-modified polydimethylsiloxane, both-end-modified polydimethylsiloxane , One-end-modified polydimethylsiloxane, side-chain both-end-modified polydimethylsiloxane, and the like. Among these, a polyether-modified silicone surfactant having a polyoxyethylene group or a polyoxyethylene polyoxypropylene group as a modifying group is particularly preferable.
As the polyether-modified silicone surfactant, commercially available products can be used. Examples of the commercially available products include KF-618, KF-642, and KF-643 (all manufactured by Shin-Etsu Chemical Co., Ltd.). Etc.

  The content of the surfactant is preferably 0.01% by mass to 5% by mass and more preferably 0.5% by mass to 2% by mass with respect to the total amount of the ink. When the content is 0.01% by mass or more, the added effect is obtained, and by setting the content to 5% by mass or less, the permeability to the recording medium can be controlled, the image density is high, and the occurrence of show-through is generated. Can be prevented.

<Resin particles>
The resin particles have the property of thickening and aggregating when the ink lands on the recording medium, suppressing the penetration of the coloring component, and further promoting the fixing on the recording medium. Further, depending on the type of the resin particles, a film is formed on the recording medium, and the printed material has an effect of improving the abrasion resistance. Furthermore, the dispersion stability of the surface hydrophobic titanium dioxide is improved by adding resin particles.

Examples of the resin particles include styrene acrylic resin particles, acrylic silicone resin particles, polyurethane resin particles, and acrylic urethane resin particles. Among these, polyurethane resin particles are particularly preferable.
The resin particles are present as solid particles when used as an ink preparation raw material or after ink preparation.
Self-emulsifying type in which a relatively hydrophilic polyurethane resin is made into particles by using an emulsifier and a functional group that functions as an emulsifier is introduced into the resin itself by means of copolymerization, etc. There are resin particles. In the present invention, any resin particle can be used, but care must be taken because there is a slight difference in the dispersion stability of the surface hydrophobic titanium dioxide and the resin particles depending on the combination of the ink composition. In various combinations with surface hydrophobic titanium dioxide and a dispersant, it is resin particles of an anionic self-emulsifying polyurethane that are always excellent in dispersion stability. In this case, the polyurethane resin is preferably an ether type rather than a polyester type or polycarbonate type in terms of adhesion and dispersion stability of the surface hydrophobic titanium dioxide. The reason is not clear, but many non-ether types are weak in solvent resistance, and the viscosity tends to aggregate when the ink is stored at high temperature.

As the resin particles, commercially available products can be used. Examples of the commercially available products include J-450, J-734, J-7600, J-352, J-390, J-7100, and J-741. , J-74J, J-511, J-840, J-775, HRC-1645, HPD-71 (styrene-acrylic resin particles, all manufactured by Johnson Polymer); UVA383MA (acrylic-silicone resin particles, BASF) AP4710 (acrylic-silicone resin particles, manufactured by Showa Polymer Co., Ltd.); SF460, SF460S, SF420, SF110, SF300, SF361 (polyurethane resin particles, all manufactured by Nihon Unicar Co., Ltd.), Acryte WEM-321U (acrylic) Urethane resin particles, manufactured by Taisei Kako Co., Ltd.). These may be used individually by 1 type and may use 2 or more types together.
The content of the resin particles is preferably 0.1% by mass to 20% by mass and more preferably 0.2% by mass to 10% by mass with respect to the total amount of the ink. When the content is less than 0.1% by mass, the dispersibility and redispersibility of the surface hydrophobic titanium dioxide decreases, and the amount of the resin covering the surface hydrophobic titanium dioxide after landing on the recording medium is small. If the amount exceeds 20% by mass, the viscosity of the ink tends to be too high, and printing using an inkjet method tends to be difficult.

<Water-soluble organic solvent>
In the present invention, when not only water but also a water-soluble organic solvent is mixed as a dispersion medium to control the hydrophilicity of the dispersion medium, not only the surface hydrophobic titanium dioxide can be uniformly dispersed but also the dispersion liquid. Among them, the surface hydrophobic titanium dioxide is difficult to settle, and even if it is settled, it can be easily redispersed.
The water-soluble organic solvent is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include polyhydric alcohols, polyhydric alcohol alkyl ethers, polyhydric alcohol aryl ethers, and nitrogen-containing heterocyclic compounds. Amides, amines, sulfur-containing compounds, propylene carbonate, ethylene carbonate and the like. These may be used individually by 1 type and may use 2 or more types together.

  Examples of the polyhydric alcohols include ethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, 1,5-pentanediol, 2-methyl-2,4-pentanediol, and hexylene. Glycol, 1,6-hexanediol, 1,2,6-hexanetriol, trimethylolethane, trimethylolpropane, 3-methyl-1,3-hexanediol, propylpropylene diglycol, glycerin, 1,3-butanediol 1,2,3-butanetriol, 1,2,4-butanetriol, diglycerin, triethylene glycol, tetraethylene glycol, diethylene glycol, 3-methyl-1,3-butanediol, 3-meth Sheet 3, such as methyl-1-butanol. These may be used individually by 1 type and may use 2 or more types together.

  Examples of the polyhydric alcohol alkyl ethers include ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, ethylene glycol mono-2-ethylhexyl ether, propylene glycol monoethyl ether. And triethylene glycol dimethyl ether. These may be used individually by 1 type and may use 2 or more types together.

Examples of the polyhydric alcohol aryl ethers include ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether.
Examples of the cyclic ethers include epoxies, oxetanes, tetrahydrofurans, tetrahydropyrans, and crown ethers.
Examples of the amines include monoethanolamine, diethanolamine, triethanolamine, N, N-dimethylmonoethanolamine, N-methyldiethanolamine, N-methylethanolamine, N-phenylethanolamine, and 3-aminopropyldiethylamine. Is mentioned.
Examples of the amide compounds include 2-pyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, ε-caprolactam, γ-butyrolactone, β-methoxy-N, N-dimethyl. Examples include propionamide and β-butoxy-N, N-dimethylpropionamide.
Examples of the sulfur-containing compounds include dimethyl sulfoxide, sulfolane, thiodiglycol, and the like.

  The content of the water-soluble organic solvent is preferably 10% by mass to 50% by mass and more preferably 15% by mass to 40% by mass with respect to the total amount of the ink. By setting the content to 10% by mass or more, it is possible to ensure ejection stability, and it is possible to prevent problems caused by drying in the maintenance device of the ink jet recording apparatus. Moreover, by making the content 50% by mass or less, it is possible to maintain the drying property on the paper surface and to speed up the color stability on the glossy paper.

<Other ingredients>
The other components are not particularly limited and may be appropriately selected as necessary. For example, penetrants, pH adjusters, antiseptic / antifungal agents, chelating reagents, rust preventives, oxygen absorbers, light stabilizers And the like, and the like.

-Penetration agent-
Examples of the penetrant include 2-ethyl-2-methyl-1,3-propanediol, 3,3-dimethyl-1,2-butanediol, 2,2-diethyl-1,3-propanediol, -Methyl-2-propyl-1,3-propanediol, 2,4-dimethyl-2,4-pentanediol, 2,5-dimethyl-2,5-hexanediol, 5-hexene-1,2-diol, Examples include 2,2,4-trimethyl-1,3-pentanediol and 2-ethyl-1,3-hexanediol. These may be used individually by 1 type and may use 2 or more types together. Among these, 2-ethyl-1,3-hexanediol and 2,2,4-trimethyl-1,3-pentanediol are preferable.

Other penetrants include, for example, alkyl and aryl ethers of polyhydric alcohols such as ethylene glycol monophenyl ether, ethylene glycol monoallyl ether, diethylene glycol monophenyl ether, diethylene glycol monobutyl ether, propylene glycol monobutyl ether, and tetraethylene glycol chlorophenyl ether. And lower alcohols such as ethanol.
The content of the penetrant is preferably 0.1% by mass to 4% by mass with respect to the total amount of ink. When the content is 0.1% by mass or more, a function of penetrating into a recording medium can be expressed. By setting the content to 4% by mass or less, the surface hydrophobic titanium dioxide that is a colorant is used. Dispersion stability can be ensured and high ejection stability can be obtained.

-PH adjuster-
The pH adjuster is not particularly limited as long as it can adjust the pH to 7 to 11 without adversely affecting the ink to be prepared, and can be appropriately selected according to the purpose. And alkali metal element hydroxides, ammonium hydroxides, phosphonium hydroxides, alkali metal carbonates, and the like.
If the pH is less than 7 or more than 11, the amount of the ink jet head or ink supply unit that melts out is large, and problems such as ink deterioration, leakage, and ejection failure may occur.
Examples of the alcohol amines include diethanolamine, triethanolamine, 2-amino-2-ethyl-1,3-propanediol, and the like.
Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, and potassium hydroxide.
Examples of the ammonium hydroxide include ammonium hydroxide and quaternary ammonium hydroxide.
Examples of the phosphonium hydroxide include quaternary phosphonium hydroxide.
Examples of the alkali metal carbonate include lithium carbonate, sodium carbonate, and potassium carbonate.

-Antiseptic and fungicide-
Examples of the antiseptic / antifungal agent include sodium dehydroacetate, sodium sorbate, 2-pyridinethiol-1-oxide sodium, sodium benzoate, sodium pentachlorophenol and the like.
Examples of the chelating reagent include sodium ethylenediaminetetraacetate, sodium nitrilotriacetate, sodium hydroxyethylethylenediaminetriacetate, sodium diethylenetriaminepentaacetate, sodium uramil diacetate, and the like.
Examples of the rust inhibitor include acidic sulfite, sodium thiosulfate, ammonium thiodiglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, and dicyclohexylammonium nitrite.

-Antioxidant-
Examples of the antioxidant include phenolic antioxidants (including hindered phenolic antioxidants), amine-based antioxidants, sulfur-based antioxidants, phosphorus-based antioxidants, and the like.
Examples of the phenolic antioxidant (including hindered phenolic antioxidant) include butylated hydroxyanisole, 2,6-di-tert-butyl-4-ethylphenol, stearyl-β- (3,5 -Di-tert-butyl-4-hydroxyphenyl) propionate, 2,2'-methylenebis (4-methyl-6-tert-butylphenol), 2,2'-methylenebis (4-ethyl-6-tert-butylphenol), 4,4′-butylidenebis (3-methyl-6-tert-butylphenol), 3,9-bis {1,1-dimethyl-2- [β- (3-tert-butyl-4-hydroxy-5-methylphenyl) ) Propionyloxy] ethyl} -2,4,8,10-tetraoxaspiro [5,5] undecane, 1,1,3-to Lis (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) Examples include benzene, tetrakis [methylene-3- (3 ′, 5′-di-tert-butyl-4′-hydroxyphenyl) propionate] methane, and the like.

  Examples of the amine-based antioxidant include phenyl-β-naphthylamine, α-naphthylamine, N, N′-di-sec-butyl-p-phenylenediamine, phenothiazine, N, N′-diphenyl-p-phenylenediamine. 2,6-di-tert-butyl-p-cresol, 2,6-di-tert-butylphenol, 2,4-dimethyl-6-tert-butyl-phenol, butylhydroxyanisole, 2,2′-methylenebis ( 4-methyl-6-tert-butylphenol), 4,4′-butylidenebis (3-methyl-6-tert-butylphenol), 4,4′-thiobis (3-methyl-6-tert-butylphenol), tetrakis [methylene -3- (3,5-di-tert-butyl-4-dihydroxyphenyl) propi Onate] methane, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, and the like.

Examples of the sulfur-based antioxidant include dilauryl-3,3′-thiodipropionate, distearyl thiodipropionate, lauryl stearyl thiodipropionate, dimyristyl-3,3′-thiodipropionate, di Stearyl-β, β′-thiodipropionate, 2-mercaptobenzimidazole, dilauryl sulfide and the like can be mentioned.
Examples of the phosphorus antioxidant include triphenyl phosphite, octadecyl phosphite, triisodecyl phosphite, trilauryl trithiophosphite, and trinonylphenyl phosphite.

-UV absorber-
Examples of the ultraviolet absorber include a benzophenone ultraviolet absorber, a benzotriazole ultraviolet absorber, a salicylate ultraviolet absorber, a cyanoacrylate ultraviolet absorber, and a nickel complex ultraviolet absorber.
Examples of the benzophenone-based ultraviolet absorber include 2-hydroxy-4-n-octoxybenzophenone, 2-hydroxy-4-n-dodecyloxybenzophenone, 2,4-dihydroxybenzophenone, and 2-hydroxy-4-methoxybenzophenone. 2,2 ′, 4,4′-tetrahydroxybenzophenone and the like.
Examples of the benzotriazole ultraviolet absorber include 2- (2′-hydroxy-5′-tert-octylphenyl) benzotriazole, 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2- (2′-hydroxy-4′-octoxyphenyl) benzotriazole, 2- (2′-hydroxy-3′-tert-butyl-5′-methylphenyl) -5-chlorobenzotriazole and the like.

Examples of the salicylate-based ultraviolet absorber include phenyl salicylate, p-tert-butylphenyl salicylate, p-octylphenyl salicylate, and the like.
Examples of the cyanoacrylate ultraviolet absorber include ethyl-2-cyano-3,3′-diphenyl acrylate, methyl-2-cyano-3-methyl-3- (p-methoxyphenyl) acrylate, and butyl-2- And cyano-3-methyl-3- (p-methoxyphenyl) acrylate.
Examples of the nickel complex ultraviolet absorber include nickel bis (octylphenyl) sulfide, 2,2′-thiobis (4-tert-octylferrate) -n-butylamine nickel (II), 2,2′-thiobis. (4-tert-octylferrate) -2-ethylhexylamine nickel (II), 2,2′-thiobis (4-tert-octylferrate) triethanolamine nickel (II) and the like.

<Ink production method>
The ink is further required by dispersing or dissolving a pigment dispersion containing surface-hydrophobic titanium dioxide, water and, if necessary, other components such as resin particles, a dispersant, and a water-soluble organic solvent in an aqueous medium. According to the above, the mixture is mixed by stirring. This stirring and mixing can be performed by, for example, a sand mill, a homogenizer, a ball mill, a paint shaker, an ultrasonic disperser, and the like. The stirring and mixing is performed by a stirrer using a normal stirring blade, a magnetic stirrer, a high-speed disperser, or the like. be able to.

<< Ink physical properties >>
The physical properties of the ink are not particularly limited and may be appropriately selected depending on the intended purpose. For example, the viscosity and surface tension are preferably in the following ranges.
The viscosity of the ink at 25 ° C. is preferably 2 mPa · s to 25 mPa · s, more preferably 2 mPa · s to 20 mPa · s, and still more preferably 10 mPa · s to 12 mPa · s. By setting the viscosity of the ink to 2 mPa · s or more, there is an effect that residual vibration is less likely to occur at the time of ink discharge, vibration after the discharge by the drive waveform can be easily suppressed, and the next discharge can be performed in a short time. This makes it suitable for high-speed printing. On the other hand, by suppressing the viscosity of the ink to 20 mPa · s or less, it becomes easy to stabilize the ejection performance.
Here, the viscosity can be measured at 25 ° C. using, for example, an R-type rotational viscometer (RE550L, manufactured by Toki Sangyo Co., Ltd.).
The surface tension of the ink is preferably 30 mN / m or less at 25 ° C., and more preferably 28 mN / m or less. When the surface tension of the ink is 30 mN / m or less, the permeability is improved and the beading is reduced, so that the drying property for printing on plain paper is improved. Moreover, since it becomes easy to get wet with a pre-processing layer, color developability improves and a white spot is also improved. On the other hand, if the surface tension of the ink exceeds 30 mN / m, leveling of the ink on the recording medium is difficult to occur, and the drying time may be prolonged (drying property is deteriorated).

The ink uses a piezoelectric element as pressure generating means for pressurizing the ink in the ink flow path, and deforms a vibration plate that forms the wall surface of the ink flow path to change the volume in the ink flow path to eject ink droplets. A so-called piezo type (refer to Japanese Patent Laid-Open No. 2-51734), or a so-called thermal type that generates bubbles by heating ink in an ink flow path using a heating resistor (Japanese Patent Laid-Open No. 61-59911). The volume of the ink flow path is changed by deforming the vibration plate by an electrostatic force generated between the vibration plate and the electrode. Therefore, it can be satisfactorily used for a printer equipped with any inkjet head such as an electrostatic type that discharges ink droplets (see JP-A-6-71882).
The ink can be used, for example, in a printer or the like having a function of accelerating print fixing by heating the recording medium and the ink at 50 ° C. to 200 ° C. before or after printing.

Since the ink of the present invention can perform recording with sufficient whiteness and high visibility on various surfaces such as low brightness substrates such as black and transparent substrates, industrial products such as plastic products It is useful for marking on
In addition, the surface hydrophobic titanium dioxide, which is a colorant, is unlikely to settle, and the ink can be easily redispersed even if it settles, so it can be used for various applications such as ink for ink jet recording and paint. However, the inkjet recording ink described below is preferable.

(ink cartridge)
The ink cartridge of the present invention includes the ink of the present invention and a container, and further includes other members such as an ink bag as necessary. Accordingly, it is not necessary to directly touch the ink in operations such as ink replacement, there is no concern about dirt on fingers and clothes, and foreign matters such as dust can be prevented from being mixed into the ink.
There is no restriction | limiting in particular as said container, The shape, a structure, a magnitude | size, a material, etc. can be suitably selected according to the objective, For example, it has an ink bag etc. which were formed with the aluminum laminate film, the resin film, etc. A thing etc. are suitable.

The ink cartridge will be described with reference to FIGS. FIG. 1 is a schematic diagram illustrating an example of an ink bag 241 of an ink cartridge, and FIG. 2 is a schematic diagram illustrating an ink cartridge 200 in which the ink bag 241 of FIG. 1 is accommodated in a cartridge case 244.
As shown in FIG. 1, after filling ink into the ink bag 241 from the ink inlet 242 and exhausting the air remaining in the ink bag, the ink inlet 242 is closed by fusion. In use, the needle of the apparatus main body is pierced into the ink discharge port 243 made of a rubber member and supplied to the apparatus. The ink bag 241 is formed of a packaging member such as a non-permeable aluminum laminate film. As shown in FIG. 2, the ink cartridge 200 is usually housed in a plastic cartridge case 244 and detachably mounted on the ink jet recording apparatus as the ink cartridge 200.
The ink cartridge is preferably detachable from the ink jet recording apparatus. Thereby, replenishment and replacement of ink can be simplified and workability can be improved.

(Inkjet recording method and inkjet recording apparatus)
The ink jet recording apparatus of the present invention includes at least ink flying means, and further includes other means appropriately selected as necessary, for example, stimulus generation means and control means.
The ink jet recording method of the present invention includes at least an ink flying step, and further includes other steps appropriately selected as necessary, for example, a stimulus generation step, a control step, and the like.
The ink jet recording method of the present invention can be preferably carried out by the ink jet recording apparatus of the present invention, and the ink flying step can be suitably carried out by the ink flying means. Moreover, the said other process can be suitably performed by the said other means.

-Ink flying process and ink flying means-
The ink flying step is a step of forming an image by applying a stimulus to the ink of the present invention and flying the ink for inkjet recording.
The ink flying means is means for applying a stimulus to the ink of the present invention and flying the ink for ink jet recording to form an image. There is no restriction | limiting in particular as this ink flying means, For example, an inkjet head etc. are mentioned.

  As the ink jet head, a piezoelectric element is used as a pressure generating means for pressurizing ink in the ink flow path, and a diaphragm that forms the wall surface of the ink flow path is deformed to change the volume in the ink flow path to eject ink droplets. A so-called piezo type (see Japanese Patent Laid-Open No. 2-51734), or a so-called thermal type that generates bubbles by heating ink in an ink flow path using a heating resistor (Japanese Patent Laid-Open No. 61-61). No. 59911), the diaphragm and the electrode forming the wall surface of the ink flow path are arranged opposite to each other, and the diaphragm is deformed by an electrostatic force generated between the diaphragm and the electrode, whereby the ink flow path inner volume is obtained. Any of the electrostatic type (see Japanese Patent Laid-Open No. 6-71882) that discharges ink droplets by changing the above is included.

  The stimulus can be generated, for example, by the stimulus generating means, and the stimulus is not particularly limited and can be appropriately selected according to the purpose, such as heat (temperature), pressure, vibration, light, etc. Can be mentioned. These may be used individually by 1 type and may use 2 or more types together. Among these, heat and pressure are preferable.

  Examples of the stimulus generating means include a heating device, a pressurizing device, a piezoelectric element, a vibration generating device, an ultrasonic oscillator, a light, and the like. Specifically, a piezoelectric actuator such as a piezoelectric element, a heating resistor, etc. Examples include a thermal actuator that uses a phase change caused by film boiling of a liquid using an electrothermal transducer, a shape memory alloy actuator that uses a metal phase change caused by a temperature change, and an electrostatic actuator that uses an electrostatic force.

  There is no particular limitation on the mode of the ink flying, and it varies depending on the type of the stimulus. For example, when the stimulus is “heat”, the heat corresponding to the recording signal is applied to the ink in the recording head. Examples include a method in which energy is applied using, for example, a thermal head, bubbles are generated in the ink by the thermal energy, and the ink is ejected and ejected as droplets from the nozzle holes of the recording head by the pressure of the bubbles. It is done. Further, when the stimulus is “pressure”, for example, by applying a voltage to a piezoelectric element bonded to a position called a pressure chamber in an ink flow path in the recording head, the piezoelectric element bends and the volume of the pressure chamber is increased. And a method of ejecting and ejecting the ink as droplets from the nozzle holes of the recording head.

The size of the ink droplets to be ejected is preferably 3 pl to 40 pl, for example, and the ejection jet speed is preferably 5 m / s to 20 m / s. The frequency is preferably 1 kHz or more, and the resolution is preferably 300 dpi or more.
The control means is not particularly limited as long as the movement of each means can be controlled, and can be appropriately selected according to the purpose. Examples thereof include devices such as a sequencer and a computer.

Here, the ink jet recording apparatus shown in FIG. 3 has an apparatus main body 101, a paper feed tray 102 for loading paper mounted on the apparatus main body 101, and paper on which an image is recorded (formed) mounted on the apparatus main body 101. And a paper discharge tray 103 for stocking. The upper surface of the upper cover 111 of the apparatus main body 101 is a substantially flat surface, and the front surface 112 of the front cover of the apparatus main body 101 is inclined obliquely rearward with respect to the upper surface. A paper discharge tray 103 and a paper feed tray 102 protruding toward the front side are provided. Further, an ink cartridge loading section 104 is provided on the end portion of the front surface 112 so as to protrude forward from the front surface 112 and lower than the upper cover 111. An operation key or the like is provided on the upper surface of the ink cartridge loading section 104. An operation unit 105 such as a display is arranged. The ink cartridge loading unit 104 has an openable / closable front cover 115 for attaching and detaching the ink cartridge.
As shown in FIGS. 4 and 5, in the apparatus main body 101, a carriage 133 is slidably held in the main scanning direction by guide rods 131 and stays 132 that are horizontally mounted on left and right side plates (not shown). The main scanning motor (not shown) moves and scans in the carriage scanning direction of FIG.

On the carriage 133, a recording head 134 composed of four ink jet heads for ejecting ink droplets of yellow, cyan, magenta, and black is arranged with a plurality of ink ejection openings in a direction intersecting with the main scanning direction to eject ink droplets. Wearing the direction downward.
As a head constituting the recording head 134, a piezoelectric actuator such as a piezoelectric element, a thermal actuator that uses a phase change caused by film boiling of a liquid using an electrothermal transducer such as a heating resistor, and a metal phase change caused by a temperature change are used. A shape memory alloy actuator, an electrostatic actuator using an electrostatic force, or the like provided as energy generating means for discharging ink can be used.

  In order to improve ejection stability and wiping properties, a layer formed of Ni / PTFE eutectoid, silicone resin, and fluorine-based water repellency-imparting agent is provided on the nozzle surface that is the ink ejection portion of the inkjet head. In the present invention, the surface energy of the inner wall of the nozzle hole is defined by the discharged liquid, but the surface energy of the nozzle surface is more effective when combined with that of the inner wall of the nozzle hole. Therefore, the inner wall of the nozzle hole is subjected to the same treatment as the nozzle surface as necessary.

  The carriage 133 is equipped with a sub tank 135 for each color for supplying ink of each color to the recording head 134. Ink is replenished and supplied from the ink cartridge loaded in the ink cartridge loading unit 105 to the sub tank 135 via an ink supply tube (not shown). On the other hand, as a paper feeding unit for feeding the paper 142 stacked on the paper stacking unit (pressure plate) 141 of the paper feed tray 103, half a month to separate and feed the paper 142 one by one from the paper stacking unit (pressure plate) 141. A separation pad 144 made of a material having a large coefficient of friction is provided opposite to the roller (sheet feeding roller) 143 and the sheet feeding roller 143, and the separation pad 144 is urged toward the sheet feeding roller 143 side.

  As a transport unit for transporting the paper 142 fed from the paper feed unit on the lower side of the recording head 134, a transport belt 151 for electrostatically attracting and transporting the paper 142, and a paper feed unit A counter roller 152 for transporting the paper 142 fed through the guide 145 while sandwiching it between the transport belt 151 and the paper 142 fed substantially vertically upward are changed by approximately 90 ° and copied onto the transport belt 151. A conveyance guide 153 for adjusting the pressure and a tip pressure roller 155 urged toward the conveyance belt 151 by a pressing member 154. In addition, a charging roller 156 that is a charging unit for charging the surface of the conveyance belt 151 is provided.

  Here, the conveyance belt 151 is an endless belt, and is configured to be looped around the conveyance roller 157 and the tension roller 158 in the belt conveyance direction. The transport belt 151 is, for example, a pure resin material having a thickness of about 40 μm that is not subjected to resistance control, for example, a surface layer that is a sheet adsorbing surface formed of ETFE pure material, and resistance control by carbon with the same material as the surface layer. And a back layer (medium resistance layer, ground layer). In addition, a guide member 161 is disposed on the back side of the conveyance belt 151 so as to correspond to a printing area by the recording head 134. Further, as a paper discharge unit for discharging the paper 142 recorded by the recording head 134, a separation claw 171 for separating the paper 142 from the transport belt 151, a paper discharge roller 172, and a paper discharge roller 173 are provided. A paper discharge tray 103 is provided below the paper discharge roller 172. A double-sided paper feeding unit 181 is detachably mounted on the back surface of the apparatus main body 101. The double-sided paper feeding unit 181 takes in the paper 142 returned by the reverse rotation of the transport belt 151, reverses it, and feeds it again between the counter roller 152 and the transport belt 151. Further, a manual paper feed unit 182 is provided on the upper surface of the double-sided paper feed unit 181.

  In the ink jet recording apparatus configured as described above, the sheet 142 is separated and fed one by one from the sheet feeding unit, and the sheet 142 fed substantially vertically upward is guided by the guide 145, and includes the transport belt 151 and the counter roller 152. The leading end is guided by a conveying guide 153 and pressed against the conveying belt 151 by a leading end pressing roller 155, and the conveying direction is changed by approximately 90 °. At this time, the conveyance belt 151 is charged by the charging roller 156, and the sheet 142 is electrostatically attracted to the conveyance belt 151 and conveyed. Therefore, by driving the recording head 134 according to the image signal while moving the carriage 133, ink droplets are ejected onto the stopped paper 142 to record one line, and after the paper 142 is conveyed by a predetermined amount, Record the next line. Upon receiving a recording end signal or a signal that the trailing edge of the paper 142 has reached the recording area, the recording operation is finished and the paper 142 is discharged onto the paper discharge tray 103. When a near-end remaining amount of ink in the sub tank 135 is detected, a required amount of ink is supplied to the sub tank 135 from the ink cartridge.

Further, as shown in FIG. 6, a maintenance device 91 according to the present invention for maintaining and recovering the nozzle state of the recording head 34 is arranged in the non-printing area on one side of the carriage 33 in the scanning direction. Yes.
The maintenance device 91 includes caps 92 for capping each nozzle surface of the recording head 34, a wiper blade 93 for wiping the nozzle surface, and a liquid that does not contribute to recording in order to discharge thickened ink. An empty discharge receiver 94 that receives droplets when performing an empty discharge for discharging droplets, a wiper cleaner 94 that is integrally formed with the empty discharge receiver and is a cleaning member for removing ink attached to the wiper blade 93, and a wiper A cleaner roller 96 that constitutes a cleaner means for pressing the wiper blade 93 against the wiper cleaner when the blade 93 is cleaned is provided.
In the above configuration, when the recording head 34 passes through the position of the wiper blade 93 and protrudes into the movement path, the ejection port of the recording head 34 is wiped.

<Ink record>
The ink recorded matter of the present invention has an image formed on the substrate using the ink of the present invention.
The substrate is not particularly limited as long as it is other than white, and can be appropriately selected according to the purpose. Examples thereof include glossy paper, special paper, cloth, an OHP sheet, and a film. Among these, a non-porous substrate such as a film is preferable.
Here, the non-porous substrate is a plastic material such as a transparent or colored polyvinyl chloride film, a polyethylene terephthalate (PET) film, a polycarbonate film, a polyethylene film, an acrylic film, a polypropylene film, a polyimide film, or a polystyrene film. It is made of a resin film, laminated paper, coated paper, etc. having a surface made of glass, metal, etc., and does not contain paper components such as wood pulp paper, Japanese paper, synthetic pulp paper, synthetic fiber paper. These may be used individually by 1 type and may use 2 or more types together.

A pigment ink containing titanium dioxide as a colorant can obtain a white ink. In particular, the white ink can be used suitably for recording on recording media other than white, and when recording on a transparent medium such as a film or an OHP sheet, an image is formed using the white ink. Is possible. Also, white ink is applied on a transparent recording medium to form a white layer, and an image is formed thereon using ink of other colors, thereby obtaining a clearer and higher quality image. It becomes possible. In this case, it is possible to first form the white layer on the transparent medium by applying the ink of the present invention, and then form an image on the transparent medium using an ink such as black ink or color ink. It is also possible to obtain a clear image by applying the ink of the present invention after forming an image on a transparent medium using an ink such as black ink or color ink.
The black ink and the color ink are not particularly limited, and for example, the inks disclosed in Japanese Patent Application Laid-Open No. 2009-280749, Japanese Patent No. 5304023, and the like can be used.

  In the ink of the present invention, the surface hydrophobic titanium dioxide that is a colorant is less likely to settle and can be easily redispersed even if it settles. Therefore, an ink record obtained using the ink of the present invention Can be suitably used for various purposes as a material on which various prints or images are recorded, etc.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

(Preparation Example 1-1 of Surface Hydrophobic Titanium Dioxide)
-Preparation of silicone surface-treated titanium dioxide-
10 parts by mass of titanium dioxide (CR-50, manufactured by Ishihara Sangyo Co., Ltd.) dried at 110 ° C. for 2 days in a vacuum dryer was put into a 200 mL flask equipped with an isobaric dropping funnel, and the nitrogen gas was replaced. A solution obtained by diluting 0.4 parts by mass of reactive silicone oil (KF-99, manufactured by Shin-Etsu Chemical Co., Ltd.) with 40 parts by mass of dehydrated toluene was stirred while being gradually added from the dropping funnel. After completion of dropping, the mixture was heated in an oil bath to distill off toluene, and then reacted at 150 ° C. for 3 hours. After completion of the reaction, the solid content was collected, washed thoroughly with toluene and then methanol, and then dried under reduced pressure at 60 ° C. for 1 day to obtain a surface-hydrophobized titanium dioxide of Preparation Example 1-1 subjected to silicone surface treatment.

  About the surface hydrophobized titanium dioxide of the obtained Preparation Example 1-1, the surface energy was measured as follows. The results are shown in Table 1.

<Surface energy of titanium dioxide>
The surface energy of titanium dioxide was measured as follows using a powder wettability tester (WET-101P, manufactured by Reska Co., Ltd.).
First, titanium dioxide (0.1 g) was suspended in 100 mL of water, the rotation speed of the liquid was 200 rpm, the methanol inflow rate was 3 mL / min, and precipitation of titanium dioxide at 25 ° C. was detected with an optical detector. The surface tension was calculated from the volume concentration of methanol at the time of precipitation of titanium dioxide and used as the surface energy of titanium dioxide.
Here, when the surface energy of titanium dioxide at 25 ° C. is 5 mN / m or more smaller than the surface tension of water at 25 ° C. (72 mN / m), it is determined that “surface hydrophobicity”, and titanium dioxide at 25 ° C. When the surface energy was 72 mN / m or more, it was judged as “no surface hydrophobicity”.

(Preparation Examples 1-2-7 of Surface Hydrophobic Titanium Dioxide)
-Preparation of silicone surface-treated titanium dioxide-
In Preparation Example 1-1, the charged amount of reactive silicone oil (KF-99, manufactured by Shin-Etsu Chemical Co., Ltd.) (based on 10 parts by mass of titanium dioxide) was changed as shown in Table 1, and Preparation Example 1-2 was performed. A surface hydrophobic titanium dioxide of ˜1-7 was obtained.
About the surface hydrophobic titanium dioxide of the obtained Preparation Examples 1-2 to 1-7, the surface energy of the surface hydrophobic titanium dioxide was measured in the same manner as in Preparation Example 1-1. The results are shown in Table 1.

* Since the surface energy is measured by a titration method using water-methanol, the surface energy measurement value of Preparation Example 1-7 that wets and settles with water alone is displayed as 72 mN / m or more. did.

(Preparation Example 2-1 of Surface Hydrophobic Titanium Dioxide)
-Hydrophobic removal treatment by corona discharge treatment-
Using a corona discharge surface modifying apparatus shown below, commercially available surface-treated surface hydrophobic titanium dioxide (CR-63, manufactured by Ishihara Sangyo Co., Ltd.) is formed on a polyethylene terephthalate (PET) film to a thickness of 20 μm. Granted. Next, hydrophobization removal treatment was performed under conditions of a PET film feed speed of 5 mm / s and an applied voltage of 8 kV to which the surface hydrophobic titanium dioxide was applied to the fixed electrode, and the surface hydrophobic titanium dioxide of Preparation Example 2-1 was removed. Obtained.
About the surface hydrophobic titanium dioxide of the obtained Preparation Example 2-1, the surface energy of the surface hydrophobic titanium dioxide was measured in the same manner as in Preparation Example 1-1. The results are shown in Table 2.
[Corona discharge treatment conditions]
-Corona discharge surface modification device (Corona Scanner ASA-4, manufactured by Shinko Electric Instrumentation Co., Ltd.)
・ Feeding speed: 5mm / s
・ Applied voltage: 8kV ~ 14kV

(Preparation Examples 2-2 to 2-5 of surface hydrophobic titanium dioxide)
-Hydrophobic removal treatment by corona discharge treatment-
In Preparation Example 2-1, as shown in Table 2, the applied voltage of corona discharge treatment was changed to obtain surface hydrophobic titanium dioxide of Preparation Examples 2-2 to 2-5.
About the surface hydrophobic titanium dioxide of the obtained Preparation Examples 2-2 to 2-5, the surface energy of the surface hydrophobic titanium dioxide was measured in the same manner as in Preparation Example 1-1. The results are shown in Table 2.

Example 1
-Preparation of titanium dioxide dispersion-
In a 100 mL vial, 11.4 parts by mass of ion-exchanged water, 30 parts by mass of 3-methoxy-3-methyl-1-butanol, and 0.6 parts by mass of DISPERBYK-190 (manufactured by Big Chemie) as a dispersing agent are stirred gently. After homogenization, 6 parts by mass of the surface hydrophobic titanium dioxide of Preparation Example 1-1 was added, and ultrasonic waves were irradiated (600 W) at 50 ° C. for 3 hours to obtain a titanium dioxide dispersion.
The obtained titanium dioxide dispersion was gradually cooled to room temperature, and then diluted with water using a particle size distribution analyzer (Microtrac UPA-EX150, manufactured by Nikkiso Co., Ltd.), and the cumulative 50% particle size in the volume-based particle size distribution. When (D50) was measured, it was 316 nm.

-Preparation of vehicle-
The following raw materials were mixed to prepare a vehicle.
-ACRYT WEM-321U (acrylic urethane resin particles, manufactured by Taisei Kako Co., Ltd., solid concentration 38 mass%) ... 12.3 parts by mass-Glycerin ... 11.7 parts by mass-3-methyl-1,3 -Butanediol ... 37.5 parts by mass-2-ethyl-1,3-hexanediol ... 6.3 parts by mass-Polyfox PF-156A (anionic fluorine-based surfactant, manufactured by OMNOVA)- -2.8 parts by mass-Proxel LV (antiseptic / antifungal agent, 1,2-Benzisothiazolin-3-one, manufactured by Avecia)-0.3 parts by mass-Triethanolamine-0.2 parts by mass・ Ion exchange water: 28.9 parts by mass

The prepared titanium dioxide dispersion and the vehicle were mixed in equal amounts in a vial to prepare an ink.
The viscosity of the obtained ink was 11.4 mPa · s at 25 ° C. as measured by an R-type rotational viscometer (RE550L, manufactured by Toki Sangyo Co., Ltd.).
The surface tension of the vehicle, excluding the surface hydrophobic titanium dioxide, was measured using a surface tension meter (CBVP-Z, manufactured by Kyowa Interface Science Co., Ltd.), and the static surface after 5 seconds of the Wilhelmy plate method at a liquid temperature of 25 ° C. When the tension was measured, it was 32.4 mN / m.
It was confirmed that the cumulative 50% particle diameter (D50) particle diameter of titanium dioxide in the ink was almost the same as that of the dispersion.
Next, using the ink of Example 1, sedimentation property, redispersibility, and whiteness of the printed image were evaluated as follows. The results are shown in Table 5.

<Sedimentation of titanium dioxide>
The sedimentation property of titanium dioxide in the ink was measured using Turbiscan (MA2000, manufactured by Eihiro Seiki Co., Ltd.).
The ink is subjected to ultrasonic dispersion treatment (100 W, 40 minutes) using an ultrasonic cleaner (US-3, manufactured by ASONE Co., Ltd.) to be in a uniform state, and then the ink is applied to a glass cell dedicated to the apparatus using a pipette. 5.5 mL was added. Measurement was performed 30 minutes after the ink level in the cell was stabilized, and this time was set as the start of sedimentation evaluation. Then, it left still at 60 degreeC, it measured until 240 hours later, and the sedimentation property was confirmed by the deviation display on the basis of the sedimentation evaluation start. The sedimentation was confirmed mainly by measuring the change in backscattered light due to the production of the supernatant by peak integration (relative value mode), and evaluating it according to the following criteria.
[Evaluation criteria]
A: Relative change of backscattered light 240 hours after starting evaluation is less than 5% B: Relative change of backscattered light 240 hours after starting evaluation is 5% or more and less than 10% C: Backscattered light 240 hours after starting evaluation The relative change of 10% or more

<Redispersibility of precipitated titanium dioxide>
30 mL of the prepared ink was placed in a 50 mL vial and allowed to stand at room temperature (25 ° C.) for 1 month, and then the redispersibility of the precipitated titanium dioxide was evaluated according to the following criteria.
[Evaluation criteria]
A: When the vial is shaken by hand for 10 seconds, the titanium dioxide settles and returns to the particle size before standing. B: An ultrasonic cleaner (US-3, When the ultrasonic irradiation treatment (100 W) is performed for 2 minutes by ASONE Co., Ltd., the titanium dioxide settles and returns to the particle size before standing. C: The solid content in the ink agglomerates. Not distributed

<Whiteness of printed image>
Fill the ink cartridge with ink, and use an inkjet printer (Ricoh Co., Ltd., IPSiO GX3000) to check that all nozzles are filled with ink and that no abnormal image is produced. After adjusting the discharge amount so as to be 20 g / m ² , a solid image of 50 mm × 50 mm was printed on an OHP sheet as a recording medium. With the commercially available black paper laid under the printed OHP sheet, the printed portion was measured for lightness (L ^* ) using a spectrocolorimetric densitometer X-Rite 938 (manufactured by X-Rite). Evaluation based on the criteria. For reference, the L ^* value measured with an unprinted OHP sheet laid on black paper was 22.4.
[Evaluation criteria]
A: L ^* value is 75 or more B: L ^* value is 65 or more and less than 75 C: L ^* value is less than 65

(Examples 2-14 and Comparative Examples 1-5)
In Example 1, a titanium dioxide dispersion was prepared in the same manner as in Example 1 except that the titanium dioxide shown in Table 3 and the water-soluble organic solvent were used.
A vehicle was prepared in the same manner as in Example 1 except that the vehicle composition shown in Table 4 was used.
Using the obtained titanium dioxide dispersion and the vehicle, inks of Examples 2 to 14 and Comparative Examples 1 to 5 were prepared in the same manner as Example 1.
About each obtained ink, it carried out similarly to Example 1, and evaluated sedimentation property, redispersibility, and the whiteness of the printed image. The results are shown in Table 5.

* The blanks in the cumulative 50% particle diameter (D50) of ink and the viscosity of ink in Table 5 indicate that measurement has not been performed. However, the cumulative 50% particle size (D50) of the ink is in the range of 200 nm to 600 nm. The viscosity of the ink at 25 ° C. is in the range of 2 mPa · s to 25 mPa · s.
From the result of Table 5, it turned out that Examples 1-14 are all provided with the outstanding sedimentation property, redispersibility, and the whiteness of the printed image compared with Comparative Examples 1-5.

As an aspect of this invention, it is as follows, for example.
<1> It contains at least surface hydrophobic titanium dioxide as a colorant and water,
The surface hydrophobic titanium dioxide has an surface energy at 25 ° C. of 28 mN / m to 35 mN / m.
<2> The ink according to <1>, wherein a surface tension of the vehicle excluding the surface hydrophobic titanium dioxide at 25 ° C. is 25 mN / m to 35 mN / m.
<3> The ink according to any one of <1> to <2>, wherein the surface hydrophobic titanium dioxide is subjected to a hydrophobizing treatment by adding a hydrophobizing agent to titanium dioxide.
<4> The ink according to <3>, wherein the amount of the hydrophobizing agent applied is 1 part by mass to 100 parts by mass with respect to 100 parts by mass of titanium dioxide.
<5> The ink according to any one of <1> to <4>, wherein the surface hydrophobic titanium dioxide is subjected to a hydrophobic removal treatment.
<6> The ink according to <5>, wherein the hydrophobization removal treatment is a corona discharge treatment.
<7> The ink according to any one of <1> to <6>, wherein a cumulative 50% particle size (D50) in a volume-based particle size distribution of the surface hydrophobic titanium dioxide is 200 nm to 600 nm.
<8> The ink according to any one of <1> to <7>, which is for inkjet recording.
<9> An ink cartridge comprising the container according to any one of <1> to <8>.
<10> An ink jet recording apparatus comprising at least ink flying means for applying a stimulus to the ink according to <8> and causing the ink to fly to record an image on a recording medium.
<11> An inkjet recording method comprising at least an ink flying step of applying a stimulus to the ink according to <8> and causing the ink to fly to record an image on a recording medium.
<12> An image forming method comprising forming an image on a substrate using the ink according to any one of <1> to <8>.
<13> An ink recorded matter comprising an image formed using the ink according to any one of <1> to <8> on a base material.

134 Recording Head 200 Ink Cartridge 241 Ink Bag 242 Ink Inlet 243 Ink Outlet 244 Cartridge Case

JP 2010-222385 A JP 2013-208760 A JP 2011-225867 A

http://dl.epson.jp/support/manual/data/ink/pxw8000/4118542_00.PDF

Claims (9)

It contains at least surface hydrophobic titanium dioxide that is a colorant and water,
The ink according to claim 1, wherein the surface hydrophobic titanium dioxide has a surface energy at 25 ° C. of 28 mN / m to 35 mN / m.   The ink according to claim 1, wherein a surface tension of the vehicle excluding the surface hydrophobic titanium dioxide at 25 ° C. is 25 mN / m to 35 mN / m.   The ink according to any one of claims 1 to 2, wherein the surface hydrophobic titanium dioxide is subjected to a hydrophobizing treatment by adding a hydrophobizing agent to the titanium dioxide.   The ink according to claim 3, wherein the amount of the hydrophobizing agent applied is 1 part by mass to 100 parts by mass with respect to 100 parts by mass of titanium dioxide.   The ink according to any one of claims 1 to 4, wherein the surface hydrophobic titanium dioxide is subjected to a hydrophobic removal treatment.   The ink according to claim 5, wherein the hydrophobization removal treatment is a corona discharge treatment.   The ink according to any one of claims 1 to 6, which is for ink jet recording.   An ink cartridge comprising the ink according to claim 1 contained in a container.   An image forming method comprising forming an image on a substrate using the ink according to claim 1.