JP2024054979A - Ink, printing method, and printed matter - Google Patents

Abstract

[Problem] The present invention aims to provide an ink that has good antibacterial properties, is excellent in stability and ejection, and can produce high-quality printed matter. [Solution] An ink containing an organic solvent and an antibacterial agent, characterized in that the antibacterial agent contains the following first antibacterial agent and the following second antibacterial agent. First antibacterial agent: an isothiazolinone compound with a water solubility of less than 1 g/L Second antibacterial agent: an isothiazolinone compound with a water solubility of 20 g/L or more [Selected Figure] None

Description

The present invention relates to an ink, a printing method, and a printed matter.

In recent years, inkjet printers have become increasingly popular due to their advantages such as low noise and low running costs.
In inkjet recording, in order to perform good print recording over a long period of time, the properties required of the ink used include excellent long-term storage stability and ejection stability, and also that the printed and recorded image is a clear image without bleeding and that the ink has excellent water resistance, light resistance, etc., i.e., storage stability.

Although many proposals have been made for inks used in inkjet recording to meet the above requirements, no ink has yet been developed that meets all of the above requirements. Preventing nozzle clogging is a particularly important issue, and possible causes of this include thickening of the ink due to evaporation of water at the nozzle tip, precipitation of dyes, formation of insoluble inorganic salts, or formation of insoluble solids due to the growth of microorganisms such as mold and putrefactive fungi.

Several proposals have been made so far regarding problems caused by mold and the like that develop in water-based inks.
For example, Patent Document 1 describes that the inclusion of 2,4,6-hexahydro-1,3,5-trihydroxyethyl-S-triazine in the ink provides antifungal and bactericidal effects.
In addition, Patent Document 2 claims that the inclusion of 1,2-benzisothiazolin-3-one in the ink is effective in preventing the growth of microorganisms such as mold, putrefactive fungi, and algae, and in preventing clogging of the nozzle tip due to the formation of insoluble solid matter. In addition, Patent Document 3 claims that the ink contains a basic substance and the pH of the ink is increased, thereby providing an ink that is resistant to the growth of bacteria, etc., without the addition of an antibacterial agent.

The above-mentioned conventional inks pose safety problems when users use printers. In addition, when a highly water-soluble antibacterial agent is used for a printed matter, the antibacterial properties of the image surface tend to be difficult to ensure due to its water solubility, when the surface is wiped with water, etc., and there are problems with obtaining antibacterial properties of both the ink liquid and the printed matter, especially with regard to water-based inks.
An object of the present invention is to provide an ink that has good antibacterial properties, is excellent in ink storage stability and ejection properties, and is capable of producing high-quality printed matter.

The ink of the present invention that can solve the above problems is as described in (1) below.
(1) An ink containing an organic solvent and an antibacterial agent,
The ink, characterized in that the antibacterial agent contains the following first antibacterial agent and the following second antibacterial agent.
First antibacterial agent: an isothiazolinone compound having a water solubility of less than 1 g/L. Second antibacterial agent: an isothiazolinone compound having a water solubility of 20 g/L or more.

The present invention provides an ink that has good antibacterial properties, excellent storage stability and ejection properties, and can produce high-quality printed matter.

FIG. 1 is a perspective view showing an example of a recording apparatus using the ink of the present invention. FIG. 2 is a perspective view showing an example of a main tank that contains the ink of the present invention.

（前記一般式（１）中、Ｒ_１、Ｒ_２、及びＲ_３は、それぞれ独立に、炭素数１以上８以下の炭化水素基を表す。）
（３）前記第１の抗菌剤及び前記第２の抗菌剤の合計量が、インク全質量に対し、０．０１質量％以上１．０質量％以下である、上記（１）又は（２）に記載のインク。
（４）前記第１の抗菌剤及び前記第２の抗菌剤の合計量が、インク全質量に対し、０．１質量％以上０．５質量％以下である、上記（１）又は（２）に記載のインク。
（５）基材上にインクを付与する印刷工程、及び、付与された前記インクを加熱する加熱工程を有する印刷方法であって、前記インクとして上記（１）乃至（４）のいずれか一項に記載のインクを用いることを特徴とする印刷方法。
（６）前記基材がプラスチックである、上記（５）に記載の印刷方法。
（７）基材上に印刷層を有する印刷物であって、前記印刷層は、第１の抗菌剤及び第２の抗菌剤を含有し、前記第１の抗菌剤が水溶解度１ｇ／Ｌ未満のイソチアゾリン系化合物であり、前記第２の抗菌剤が水溶解度２０ｇ／Ｌ以上のイソチアゾリン系化合物であることを特徴とする印刷物。 For example, aspects of the present invention are as follows.
(1) An ink containing an organic solvent and an antibacterial agent,
The ink, characterized in that the antibacterial agent contains the following first antibacterial agent and the following second antibacterial agent.
First antibacterial agent: an isothiazolinone compound having a water solubility of less than 1 g/L. Second antibacterial agent: an isothiazolinone compound having a water solubility of 20 g/L or more. (2) The ink according to (1) above, wherein the ink contains water and the organic solvent contains an amide solvent represented by the following general formula (1):

(In the general formula (1), R ₁ , R ₂ , and R ₃ each independently represent a hydrocarbon group having 1 to 8 carbon atoms.)
(3) The ink according to (1) or (2) above, wherein the total amount of the first antibacterial agent and the second antibacterial agent is 0.01% by mass or more and 1.0% by mass or less with respect to the total mass of the ink.
(4) The ink according to (1) or (2) above, wherein the combined amount of the first antibacterial agent and the second antibacterial agent is 0.1% by mass or more and 0.5% by mass or less with respect to the total mass of the ink.
(5) A printing method comprising a printing step of applying an ink onto a substrate, and a heating step of heating the applied ink, the printing method comprising using an ink according to any one of (1) to (4) above as the ink.
(6) The printing method according to (5) above, wherein the substrate is plastic.
(7) A printed matter having a printing layer on a substrate, the printed layer containing a first antibacterial agent and a second antibacterial agent, the first antibacterial agent being an isothiazolinone-based compound having a water solubility of less than 1 g/L, and the second antibacterial agent being an isothiazolinone-based compound having a water solubility of 20 g/L or more.

<<Ink>>
The ink of the present invention is an ink containing an organic solvent and an antibacterial agent, the antibacterial agent containing a first antibacterial agent and a second antibacterial agent, the first antibacterial agent being an isothiazolinone-based compound having a water solubility of less than 1 g/L, and the second antibacterial agent being an isothiazolinone-based compound having a water solubility of 20 g/L or more.
In the present invention, the water solubility is a value obtained by measuring the mass of a substance that dissolves in 1 L of water at 25°C.

The ink of the present invention contains an isothiazolinone compound with low water solubility as an antibacterial agent and an antibacterial agent with high water solubility as described above, and as such has excellent long-term storage stability (antiseptic and antifungal effects) and can provide printed matter with excellent antibacterial properties even after printing.

Generally, antibacterial agents that are highly water-soluble are added to water-based inks to ensure antibacterial properties in the ink liquid, but it is difficult to maintain antibacterial properties after the ink dries after printing and becomes a printed matter. Therefore, by further adding an antibacterial agent that is poorly water-soluble, it is possible to maintain the antibacterial properties of both the ink liquid and the printed matter.

The ink of the present invention contains an isothiazolinone compound having a water solubility of less than 1 g/L as a first antibacterial agent from the viewpoint of ensuring antibacterial properties in printed matter. Furthermore, from the viewpoint of ensuring antibacterial properties in the ink liquid, it contains an isothiazolinone compound having a water solubility of 20 g/L or more as a second antibacterial agent.

The combined amount of the first antibacterial agent and the second antibacterial agent added is preferably 0.01% to 1.0% by mass, and more preferably 0.1% to 0.5% by mass, based on the total mass of the ink. The desired effect is obtained when these preservatives and antifungal agents are added in an amount of 0.01% by mass or more, and when the amount is 1.0% by mass or less, they do not form coagulants with the humectant, or crystallize as the water in the ink evaporates, which can cause clogging.

（前記一般式（１）中、Ｒ_１、Ｒ_２、及びＲ_３は、それぞれ独立に、炭素数１以上８以下の炭化水素基を表す。） The ink of the present invention preferably contains a compound represented by the following general formula (1): When the ink contains the compound represented by the following general formula (1), the ink is accompanied by surface solubility when it lands on a substrate, thereby improving fixability and making it possible to achieve improved quality of printed matter.

(In the general formula (1), R ₁ , R ₂ , and R ₃ each independently represent a hydrocarbon group having 1 to 8 carbon atoms.)

The following describes the antibacterial agents, organic solvents, water, coloring materials, resins, additives, etc. used in the ink.

<Antibacterial Agent>
(Isothiazolinone compounds)
The isothiazolinone compound is a compound having a five-membered heterocyclic ring containing a nitrogen atom and a sulfur atom. A specific example thereof is 5-chloro-2-methyl-4-isothiazolin-3-one (exemplary compound 1), 5-chloro-2-ethyl-4-isothiazolin-3-one, 2-methyl-4-isothiazolin-3-one (exemplary compound 2), 2-ethyl-4-isothiazolin-3-one, 4,5-dichloro-2-methyl-4-isothiazolin-3-one, 2-n-octyl-4-isothiazolin-3-one (exemplary compound 3), 5-chloro-2-ethyl-4-isothiazolin-3-one, 5-chloro-2-t-octyl-4-isothiazolin-3-one, 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one (exemplary compound 4), 4,5-dichloro-2-cyclohexyl-4-isothiazolin-3-one, 1,2-benzisothiazolin-3-one (exemplary compound 5), 2-butyl-benzisothiazolin-3-one (exemplary compound 6), and the like are included, but the present invention is not limited thereto.
The structural formulae of the exemplary compounds are shown below.

<Organic Solvent>
The organic solvent used in the present invention is not particularly limited, and any water-soluble organic solvent can be used. Examples of the organic solvent include polyhydric alcohols, ethers such as polyhydric alcohol alkyl ethers and polyhydric alcohol aryl ethers, nitrogen-containing heterocyclic compounds, amides, amines, and sulfur-containing compounds.
Specific examples of the water-soluble organic solvent include ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 3-methyl-1,3-butanediol, triethylene glycol, polyethylene glycol, polypropylene glycol, 1,2-pentanediol, 1,3-pentanediol, 1,4-pentanediol, 2,4-pentanediol, 1,5-pentanediol, and the like. polyhydric alcohols such as pentanediol, 1,2-hexanediol, 1,6-hexanediol, 1,3-hexanediol, 2,5-hexanediol, 1,5-hexanediol, glycerin, 1,2,6-hexanetriol, 2-ethyl-1,3-hexanediol, ethyl-1,2,4-butanetriol, 1,2,3-butanetriol, 2,2,4-trimethyl-1,3-pentanediol, and petriol; ethylene glycol monoethyl ether; and ethylene glycol monobutyl ether. polyhydric alcohol alkyl ethers such as diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, and propylene glycol monoethyl ether; polyhydric alcohol aryl ethers such as ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether; nitrogen-containing heterocyclic compounds such as 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, ε-caprolactam, and γ-butyrolactone; amides such as formamide, N-methylformamide, N,N-dimethylformamide, 3-methoxy-N,N-dimethylpropionamide, and 3-butoxy-N,N-dimethylpropionamide; amines such as monoethanolamine, diethanolamine, and triethylamine; sulfur-containing compounds such as dimethyl sulfoxide, sulfolane, and thiodiethanol; propylene carbonate, and ethylene carbonate.
It is preferable to use an organic solvent having a boiling point of 250° C. or less, since this not only functions as a wetting agent but also provides good drying properties.

It is preferable that the diol compound having 5 or more carbon atoms is contained, since this can improve the permeability of the ink.
Specific examples of diol compounds having 5 or more carbon atoms include 2-ethyl-1,3-hexanediol and 2,2,4-trimethyl-1,3-pentanediol.
Furthermore, it is more preferable to have one of the group consisting of amide-based solvents and substituted butanol, since in the case of media such as PVC, the surface of the media can be slightly dissolved, thereby ensuring wettability and fixability.

<Surfactant>
As the surfactant, any of silicone-based surfactants, fluorine-based surfactants, amphoteric surfactants, nonionic surfactants, and anionic surfactants can be used.
Silicone surfactants are not particularly limited and can be appropriately selected according to purpose. Among them, those that do not decompose even at high pH are preferred, such as side chain modified polydimethylsiloxane, both end modified polydimethylsiloxane, one end modified polydimethylsiloxane, side chain both end modified polydimethylsiloxane, etc., and those having polyoxyethylene group or polyoxyethylene polyoxypropylene group as modified group are particularly preferred because they show good properties as aqueous surfactants. In addition, polyether modified silicone surfactants can also be used as the silicone surfactant, such as a compound in which a polyalkylene oxide structure is introduced into the Si part side chain of dimethylsiloxane.
As the fluorine-based surfactant, for example, perfluoroalkyl sulfonic acid compound, perfluoroalkyl carboxylic acid compound, perfluoroalkyl phosphate compound, perfluoroalkyl ethylene oxide adduct, and polyoxyalkylene ether polymer compound having perfluoroalkyl ether group in the side chain are particularly preferred because they have low foaming properties.As the perfluoroalkyl sulfonic acid compound, for example, perfluoroalkyl sulfonic acid, perfluoroalkyl sulfonate, etc. can be mentioned.As the perfluoroalkyl carboxylic acid compound, for example, perfluoroalkyl carboxylic acid, perfluoroalkyl carboxylate, etc. can be mentioned.As the polyoxyalkylene ether polymer compound having perfluoroalkyl ether group in the side chain, for example, sulfate ester salt of polyoxyalkylene ether polymer having perfluoroalkyl ether group in the side chain, salt of polyoxyalkylene ether polymer having perfluoroalkyl ether group in the side chain, etc. can be mentioned. Examples _of counter ions _of the salts in these fluorosurfactants include Li, Na, K _{, NH4} , _NH3CH2CH2OH , _{NH2 ( CH2CH2OH} ) ₂ , and NH( _CH2CH2OH ) ₃ .
Examples of amphoteric surfactants include lauryl aminopropionate, lauryl dimethyl betaine, stearyl dimethyl betaine, and lauryl dihydroxyethyl betaine.
Examples of nonionic surfactants include polyoxyethylene alkylphenyl ethers, polyoxyethylene alkyl esters, polyoxyethylene alkylamines, polyoxyethylene alkylamides, polyoxyethylene propylene block polymers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, and ethylene oxide adducts of acetylene alcohol.
Examples of the anionic surfactant include polyoxyethylene alkyl ether acetates, dodecylbenzene sulfonates, laurates, and salts of polyoxyethylene alkyl ether sulfates.
These may be used alone or in combination of two or more.

（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（日本エマルジョン株式会社）、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 appropriately selected depending on the purpose. Examples of the silicone surfactant include side-chain modified polydimethylsiloxane, both-end modified polydimethylsiloxane, one-end modified polydimethylsiloxane, and both-end modified polydimethylsiloxane of the side chain. Polyether-modified silicone surfactants having a polyoxyethylene group or a polyoxyethylene polyoxypropylene group as a modifying group are particularly preferred because they exhibit good properties as an aqueous surfactant.
Such surfactants may be synthesized appropriately or may be commercially available products, such as those available from BYK-Chemie Co., Ltd., Shin-Etsu Chemical Co., Ltd., Dow Corning Toray Silicone Co., Ltd., Nippon Emulsion Co., Ltd., and Kyoeisha Chemical Co., Ltd.
The polyether-modified silicone surfactant is not particularly limited and can be appropriately selected depending on the purpose. For example, it can be a surfactant represented by the general formula (S-1) in which a polyalkylene oxide structure is introduced into the Si part side chain of dimethylpolysiloxane.

(In the general formula (S-1), m, n, a, and b each independently represent an integer, R represents an alkylene group, and R′ represents an alkyl group.)
As the polyether-modified silicone surfactant, commercially available products can be used, for example, KF-618, KF-642, KF-643 (Shin-Etsu Chemical Co., Ltd.), EMALEX-SS-5602, SS-1906EX (Nihon Emulsion Co., Ltd.), FZ-2105, FZ-2118, FZ-2154, FZ-2161, FZ-2162, FZ-2163, FZ-2164 (Dow Corning Toray Silicone Co., Ltd.), BYK-33, BYK-387 (BYK-Chemie Co., Ltd.), TSF4440, TSF4452, TSF4453 (Toshiba Silicon Co., Ltd.), and the like.

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。
一般式（Ｆ－２）
Ｃ_ｎＦ_{２ｎ＋１－}ＣＨ_２ＣＨ（ＯＨ）ＣＨ_２－Ｏ－（ＣＨ_２ＣＨ_２Ｏ）_ａ－Ｙ
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ＣＨ_２ＣＨ（ＯＨ）ＣＨ_２－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）などが挙げられる。 The fluorine-based surfactant is preferably a compound having 2 to 16 fluorine-substituted carbon atoms, and more preferably a compound having 4 to 16 fluorine-substituted carbon atoms.
Examples of the fluorine-based surfactant include perfluoroalkyl phosphate compounds, perfluoroalkyl ethylene oxide adducts, and polyoxyalkylene ether polymer compounds having a perfluoroalkyl ether group on the side chain, etc. Among these, polyoxyalkylene ether polymer compounds having a perfluoroalkyl ether group on the side chain are preferred because they have low foaming properties, and the fluorine-based surfactants represented by the general formulas (F-1) and (F-2) are particularly 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.
General formula (F-2)
C _n F _2n+1- CH ₂ CH(OH)CH ₂ -O-(CH ₂ CH ₂ O) _a -Y
In the compound represented by the above general formula (F-2), Y is H, or C _m F _2m+1 where m is an integer from 1 to 6, or CH ₂ CH(OH)CH ₂ -C _m F _2m+1 where m is an integer from 4 to 6, or C _p H _2p+1 where p is an integer from 1 to 19. n is an integer from 1 to 6. a is an integer from 4 to 14.
As the fluorine-based surfactant, commercially available products may be used. Examples of the commercially available products include Surflon S-111, S-112, S-113, S-121, S-131, S-132, S-141, and S-145 (all manufactured by Asahi Glass Co., Ltd.); Fullard FC-93, FC-95, FC-98, FC-129, FC-135, FC-170C, FC-430, and FC-431 (all manufactured by Sumitomo 3M Limited); Megafac F-470, F-1405, and F-474 (all manufactured by Dainippon Ink and Chemicals, Inc.); Zonyl TBS, FSP, FSA, and FSN- 100, FSN, FSO-100, FSO, FS-300, UR, Capstone FS-30, FS-31, FS-3100, FS-34, FS-35 (all manufactured by Chemours Corporation); FT-110, FT-250, FT-251, FT-400S, FT-150, FT-400SW (all manufactured by Neos Co., Ltd.), Polyfox PF-136A, PF-156A, PF-151N, PF-154, PF-159 (manufactured by Omnova), Unidyne DSN-403N (manufactured by Daikin Industries, Ltd.), and the like.

<Coloring material>
The coloring material is not particularly limited, and pigments and dyes can be used.
As the pigment, inorganic pigments or organic pigments can be used. These pigments can be used alone or in combination of two or more. Mixed crystals can also be used.
Examples of pigments that can be used include black pigments, yellow pigments, magenta pigments, cyan pigments, white pigments, green pigments, orange pigments, glossy pigments such as gold and silver pigments, and metallic pigments.
As inorganic pigments, titanium oxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, chrome yellow, as well as carbon black produced by known methods such as the contact method, furnace method, and thermal method can be used.
As organic pigments, azo pigments, polycyclic pigments (e.g., phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, etc.), dye chelates (e.g., basic dye type chelates, acid dye type chelates, etc.), nitro pigments, nitroso pigments, aniline black, etc. can be used. Among these pigments, those having good affinity with the solvent are preferably used. In addition, resin hollow particles and inorganic hollow particles can also be used.
Specific examples of pigments for black colors include carbon blacks (C.I. Pigment Black 7) such as furnace black, lamp black, acetylene black, and channel black; metals such as copper, iron (C.I. Pigment Black 11), and titanium oxide; and organic pigments such as aniline black (C.I. Pigment Black 1).
Further, for color, C.I. Pigment Yellow 1, 3, 12, 13, 14, 17, 24, 34, 35, 37, 42 (yellow iron oxide), 53, 55, 74, 81, 83, 95, 97, 98, 100, 101, 104, 108, 109, 110, 117, 120, 138, 150, 153, 155, 180, 185, 213, C.I. Pigment Orange 5, 13, 16, 17, 36, 43, 51, C.I. Pigment Red 1, 2, 3, 5, 17, 22, 23, 31, 38, 48:2, 48:2 (Permanent Red 2B (Ca)), 48:3, 48:4, 49:1, 52:2, 53:1, 57:1 (Brilliant Carmine 6B), 60:1, 63:1, 63:2, 64:1, 81, 83, 88, 101 (Red ochre), 1 04, 105, 106, 108 (Cadmium Red), 112, 114, 122 (Quinacridone Magenta), 123, 146, 149, 166, 168, 170, 172, 177, 178, 179, 184, 185, 190, 193, 202, 207, 208, 209, 213, 219, 224, 254, 264, C.I. Pigment Violet 1 (Rhodamine Lake), 3, 5:1, 16, 19, 23, 38, C.I. Pigment Blue 1, 2, 15 (Phthalocyanine Blue), 15:1, 15:2, 15:3, 15:4 (Phthalocyanine Blue), 16, 17:1, 56, 60, 63, C.I. Pigment Green 1, 4, 7, 8, 10, 17, 18, 36, etc.
The dye is not particularly limited, and acid dyes, direct dyes, reactive dyes, and basic dyes can be used. One type of dye may be used alone, or two or more types may be used in combination.
Examples of the dyes include C.I. Acid Yellow 17,23,42,44,79,142, C.I. Acid Red 52,80,82,249,254,289, C.I. Acid Blue 9,45,249, C.I. Acid Black 1,2,24,94, C.I. Food Black 1,2, C.I. Direct Yellow 1,12,24,33,50,55,58,86,132,142,144,173, C.I. Direct Red 1,4,9,80,81,225,227, C.I. Direct Blue 1,2,15,71,86,87,98,165,199,202, C.I. Direct Black 19, 38, 51, 71, 154, 168, 171, 195, C.I. Reactive Red 14, 32, 55, 79, 249, C.I. Reactive Black 3, 4, 35.

Methods for dispersing a pigment to obtain an ink include a method of introducing a hydrophilic functional group into the pigment to make it a self-dispersing pigment, a method of dispersing the pigment by coating the surface of the pigment with a resin, and a method of dispersing the pigment using a dispersant.
As a method for making a pigment self-dispersible by introducing a hydrophilic functional group into the pigment, for example, a method for making the pigment dispersible in water by adding a functional group such as a sulfone group or a carboxyl group to the pigment (e.g., carbon) can be mentioned.
A method for dispersing a pigment by coating its surface with a resin includes a method for encapsulating the pigment in a microcapsule to make it dispersible in water. This can be called a resin-coated pigment. In this case, it is not necessary for all of the pigments blended in the ink to be coated with a resin, and uncoated or partially coated pigments may be dispersed in the ink as long as the effects of the present invention are not impaired.
The resin-coated pigment may be a microcapsule made of a vinyl polymer, a polyester polymer, a polyurethane polymer, or the like, with vinyl polymers and polyester polymers being particularly preferred.
Specific examples thereof include those disclosed in Japanese Patent Application Laid-Open Nos. 2000-53897 and 2001-139849.
Examples of the method for dispersing using a dispersant include a method for dispersing using a known low molecular weight dispersant or a high molecular weight dispersant, typified by a surfactant.
As the dispersant, for example, anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, etc. can be used depending on the pigment.
RT-100 (nonionic surfactant) manufactured by Takemoto Oil Co., Ltd. and sodium naphthalenesulfonate formalin condensate can also be suitably used as dispersants.
The dispersants may be used alone or in combination of two or more.

In the present invention, it is preferable to use a resin-coated pigment. The content of the coloring material in the ink is preferably 0.1% by mass or more and 15% by mass or less, and more preferably 1% by mass or more and 10% by mass or less, from the viewpoints of improving image density, good fixing property, and ejection stability.

<Pigment Dispersion>
The particle size of the pigment in the pigment dispersion is not particularly limited, but in terms of improving the dispersion stability of the pigment and improving the image quality such as ejection stability and image density, the maximum frequency in terms of the maximum number is preferably 20 nm or more and 500 nm or less, and more preferably 20 nm or more and 150 nm or less. The particle size of the pigment can be measured using a particle size analyzer (Nanotrac Wave-UT151, manufactured by Microtrac Bell Co., Ltd.).
The content of the pigment in the pigment dispersion is not particularly limited and can be appropriately selected depending on the purpose. From the viewpoints of obtaining good ejection stability and increasing image density, the content of the pigment is preferably from 0.1% by mass to 50% by mass, and more preferably from 0.1% by mass to 30% by mass.
It is preferable that the pigment dispersion is degassed, if necessary, by filtering coarse particles using a filter, a centrifugal separator, or the like.

<Resin>
The type of resin contained in the ink is not particularly limited and can be appropriately selected depending on the purpose. Examples of the resin include urethane resin, polyester resin, acrylic resin, vinyl acetate resin, styrene resin, butadiene resin, styrene-butadiene resin, vinyl chloride resin, acrylic styrene resin, and acrylic silicone resin.
Resin particles made of these resins may be used. The resin particles may be dispersed in water as a dispersion medium to form a resin emulsion, and the resin particles may be mixed with materials such as coloring materials and organic solvents to obtain an ink. The resin particles may be appropriately synthesized or may be commercially available. These may be used alone or in combination of two or more types of resin particles.

<pH Adjuster>
There are no particular limitations on the pH adjuster, so long as it can adjust the pH to 7 to 11 without adversely affecting the ink being prepared, and it can be appropriately selected depending on the purpose.
Examples of such an acid include alcohol amines, hydroxides of alkali metal elements, hydroxides of ammonium, phosphonium hydroxides, and carbonates of alkali metals.
From the viewpoint of ensuring the quality of the ink and the ejection stability, the pH is preferably 7 or more and 11 or less.

Examples of the alcohol amines include diethanolamine, triethanolamine, and 2-amino-2-ethyl-1,3-propanediol.
Examples of the hydroxides of the alkali metal elements include lithium hydroxide, sodium hydroxide, and potassium hydroxide.
Examples of the hydroxide of ammonium include ammonium hydroxide and quaternary ammonium hydroxide.
The phosphonium hydroxide may, for example, be a quaternary phosphonium hydroxide.
Examples of the alkali metal carbonate include lithium carbonate, sodium carbonate, and potassium carbonate.
As the pH adjuster, it is preferable to use a strongly basic compound.
The strong base compound is not particularly limited, but it is preferable to use sodium hydroxide or potassium hydroxide in order to effectively suppress crystallization.
In the present invention, the ink contains sodium hydroxide or potassium hydroxide, which can improve the wettability of the ink.

<Water>
The water content in the ink is not particularly limited and can be appropriately selected depending on the purpose. From the viewpoints of the drying property and ejection reliability of the ink, however, the water content is preferably from 10% by mass to 90% by mass, and more preferably from 20% by mass to 60% by mass.
If necessary, an antifoaming agent, an antiseptic, an antifungal agent, an antirust agent, etc. may be added to the ink.

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

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

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

<Liquid ejection device>
The ink of the present invention can be suitably used in various recording devices using the ink jet recording method, such as printers, facsimile machines, copying machines, printer/fax/copier combination machines, and three-dimensional modeling devices.
In the present invention, the recording apparatus and recording method refer to an apparatus capable of ejecting ink, various treatment liquids, etc. onto a recording medium, and a method of recording using the apparatus. The recording medium refers to an object onto which ink or various treatment liquids can be attached even temporarily.
This recording device can include not only the head portion that ejects ink, but also means related to feeding, transporting and discharging the recording medium, and other devices called pre-processing devices and post-processing devices.
The recording apparatus and the recording method may have a heating means used in the heating step and a drying means used in the drying step. The heating means and the drying means include, for example, a means for heating and drying the printed surface and the back surface of the recording medium. The heating means and the drying means are not particularly limited, but for example, a hot air heater and an infrared heater can be used. Heating and drying can be performed before, during, or after printing.
Furthermore, the recording device and recording method are not limited to those that visualize meaningful images such as characters and figures with ink. For example, those that form patterns such as geometric designs and those that form three-dimensional images are also included.
Furthermore, unless otherwise specified, the recording apparatus includes both a serial type apparatus in which the discharge head is moved and a line type apparatus in which the discharge head is not moved.
Furthermore, this recording device includes not only desktop types, but also wide-width recording devices capable of printing on A0-sized recording media, and continuous-feed printers that can use continuous paper wound into a roll as a recording medium.
An example of a recording apparatus will be described with reference to FIGS. 1 and 2. FIG. 1 is a perspective view of the apparatus. FIG. 2 is a perspective view of a main tank. An image forming apparatus 400 as an example of a recording apparatus is a serial type image forming apparatus. A mechanism unit 420 is provided in an exterior 401 of the image forming apparatus 400. For example, each ink storage unit 411 of the main tanks 410 (410k, 410c, 410m, 410y) for each color such as black (K), cyan (C), magenta (M), and yellow (Y) is formed of a packaging material such as an aluminum laminate film. The ink storage unit 411 is stored in a storage container case 414 made of plastic, for example. As a result, the main tanks 410 are used as ink cartridges of each color. The ink colors are not limited to those listed above, and any ink color can be used, and the same is true for the main tanks and ink storage units.
On the other hand, a cartridge holder 404 is provided at the rear of the opening when the cover 401c of the apparatus body is opened. A main tank 410 is detachably attached to the cartridge holder 404. This allows each ink outlet 413 of the main tank 410 to communicate with an ejection head 434 for each color via a supply tube 436 for each color, making it possible to eject ink from the ejection head 434 onto a recording medium.

This recording apparatus can include not only a portion that ejects ink, but also devices called pre-processing devices and post-processing devices.
As an embodiment of the pre-treatment device and the post-treatment device, a liquid storage section having a pre-treatment liquid and a liquid ejection head, similar to the case of inks such as black (K), cyan (C), magenta (M), and yellow (Y), and the like, are added, and the pre-treatment liquid and the post-treatment liquid are ejected by an inkjet recording method.

The recording device may further include a dispenser that applies cleaning liquid to the nozzle surface of the liquid ejection head that ejects ink, and a wiping member that wipes away the cleaning liquid and ink.

The antibacterial agent, organic solvent, resin, pigment, and other components contained in the ink of the present invention can be qualitatively and quantitatively analyzed, for example, by gas chromatography mass spectrometry (GC-MS). For example, a measuring device using gas chromatography mass spectrometry (GC-MS) can be GCMS-QP2020NX (manufactured by Shimadzu Corporation). The amount of water contained in the ink can be generally measured by quantifying the volatile components using gas chromatography mass spectrometry (GC-MS) or by measuring mass fluctuations using thermogravimetry-differential thermal analysis (TG-DTA).

<Recording media>
The recording medium used for recording is not particularly limited, but examples thereof include plain paper, glossy paper, special paper, cloth, film, OHP sheets, general-purpose printing paper, and the like.

The present invention will be described in more detail below with reference to Preparation Examples, Production Examples, Examples, and Comparative Examples, but the present invention is not limited to these Examples. In the Examples, "parts" and "%" are "parts by mass" and "% by mass" unless otherwise specified.
Unless otherwise specified, the preparation and evaluation of inks were carried out at room temperature of 25° C. and humidity of 60%.

[Preparation of pigment dispersion]
(Preparation Example 1)
<Preparation of Black Pigment-Containing Polymer Microparticle Dispersion>
<<Preparation of polymer solution>>
A 1 L flask equipped with a mechanical stirrer, a thermometer, a nitrogen gas inlet tube, a reflux condenser, and a dropping funnel was thoroughly purged with nitrogen gas, and then 11.2 g of styrene, 2.8 g of acrylic acid, 12.0 g of lauryl methacrylate, 4.0 g of polyethylene glycol methacrylate, 4.0 g of styrene macromer, and 0.4 g of mercaptoethanol were mixed and heated to 65° C.
Next, a mixed solution of 100.8 g of styrene, 25.2 g of acrylic acid, 108.0 g of lauryl methacrylate, 36.0 g of polyethylene glycol methacrylate, 60.0 g of hydroxyl ethyl methacrylate, 36.0 g of styrene macromer, 3.6 g of mercaptoethanol, 2.4 g of azobismethylvaleronitrile, and 18 g of methyl ethyl ketone was dropped into the flask over 2.5 hours. After the dropwise addition, a mixed solution of 0.8 g of azobismethylvaleronitrile and 18 g of methyl ethyl ketone was dropped into the flask over 0.5 hours. After aging at 65 ° C for 1 hour, 0.8 g of azobismethylvaleronitrile was added and further aged for 1 hour. After the reaction was completed, 364 g of methyl ethyl ketone was added to the flask, and 800 g of [polymer solution A] with a concentration of 50% by mass was obtained.

<<Preparation of Black Pigment-Containing Polymer Microparticle Dispersion>>
28 g of [polymer solution A], 42 g of carbon black (FW100, manufactured by Degussa), 13.6 g of 1 mol/L potassium hydroxide aqueous solution, 20 g of methyl ethyl ketone, and 13.6 g of ion-exchanged water were thoroughly stirred and then kneaded using a roll mill. The obtained paste was put into 200 g of pure water, thoroughly stirred, and then methyl ethyl ketone and water were distilled off using an evaporator. In order to further remove coarse particles, the dispersion was pressure-filtered with a polyvinylidene fluoride membrane filter having an average pore size of 5.0 μm to obtain a [black pigment-containing polymer microparticle dispersion] containing 15% by weight of pigment and 20% by weight of solids. The median diameter (D50) of the polymer microparticles in the obtained [black pigment-containing polymer microparticle dispersion] was measured and found to be 127 nm. The median diameter (D50) was measured using a particle size distribution measuring device (Nanorakku UPA-EX150, manufactured by Nikkiso Co., Ltd.).

(Preparation Example 2)
<Preparation of Cyan Pigment-Containing Polymer Microparticle Dispersion>
A cyan pigment-containing polymer fine particle dispersion was prepared in the same manner as in Preparation Example 1, except that the carbon black used in Preparation Example 1 was replaced with a phthalocyanine pigment (C.I. Pigment Blue 15:3).
The median diameter (D50) of the polymer fine particles in the obtained [cyan pigment-containing polymer fine particle dispersion] was 93 nm as measured with a particle size distribution measuring device (Nanotrac UPA-EX150, manufactured by Nikkiso Co., Ltd.).

(Preparation Example 3)
<Preparation of Magenta Pigment-Containing Polymer Microparticle Dispersion>
A magenta pigment-containing polymer fine particle dispersion was prepared in the same manner as in Preparation Example 1, except that the carbon black used in Preparation Example 1 was replaced with a magenta pigment (C.I. Pigment Red 122).
The median diameter (D50) of the polymer fine particles in the obtained [magenta pigment-containing polymer fine particle dispersion] was measured with a particle size distribution measuring device (Nanotrac UPA-EX150, manufactured by Nikkiso Co., Ltd.) and was found to be 76 nm.

(Preparation Example 4)
<Preparation of Yellow Pigment-Containing Polymer Particle Dispersion>
A yellow pigment-containing polymer fine particle dispersion was prepared in the same manner as in Preparation Example 1, except that the carbon black used in Preparation Example 1 was replaced with a bisazo yellow pigment (C.I. Pigment Yellow 155) as the pigment.
The median diameter (D50) of the polymer fine particles in the obtained [yellow pigment-containing polymer fine particle dispersion] was measured with a particle size distribution measuring device (Nanotrac UPA-EX150, manufactured by Nikkiso Co., Ltd.) and was found to be 76 nm.

(Preparation Example 5)
<Preparation of White Pigment Dispersion>
25 g of titanium oxide STR-100W (manufactured by Sakai Chemical Industry Co., Ltd.), 5 g of pigment dispersant TEGO Dispers 651 (manufactured by Evonik Corporation), and 70 g of water were mixed, and dispersed with 0.3 mmΦ zirconia beads at a filling rate of 60% and at 8 m/s for 5 minutes in a bead mill (Research Lab, manufactured by Shinmaru Enterprises Co., Ltd.) to obtain a [white pigment dispersion] having a volume average particle size of 285 nm.

<Ink manufacturing example>
Example 1
Into a vessel equipped with a stirrer were placed 10.0 parts of 1,2-propanediol, 1.0 part of glycerin, 5 parts of Equamide M-100 (an amide solvent represented by general formula (1), manufactured by Idemitsu Kosan Co., Ltd.), 10.0 parts of 3-methoxy-3-methyl-1-butanol, and 2.0 parts of a polyether-modified siloxane compound (Silface SAG503A, manufactured by Nissin Chemical Industry Co., Ltd.), and the mixture was mixed and stirred for 30 minutes. Next, 0.04 parts of antibacterial agent 1-1 (2-butyl-1,2-benzisothiazolin-3-one, Densil DN manufactured by Lonza Japan Co., Ltd.), 0.01 parts of antibacterial agent 2-1 (1,2-benzisothiazolin-3-one, Proxel GXL manufactured by Avecia Corporation), 0.50 parts of 2,4,7,9-tetramethyldecane-4,7-diol, 0.20 parts of 2-amino-2-ethyl-1,3-propanediol, 15.0 parts of urethane resin (Superflex 210 manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), 4.00 parts of [black pigment-containing polymer microparticle dispersion] of Preparation Example 1, and a total amount of highly pure water of 100 parts were added and mixed and stirred for 60 minutes. The resulting mixture was pressure-filtered through a polyvinylidene fluoride membrane filter having an average pore size of 1.2 μm to remove coarse particles and dust, thereby obtaining the ink of Example 1.

(Examples 2 to 6, Comparative Examples 1 to 4)
In the same manner as in Example 1, an organic solvent, a surfactant, and an antifoaming agent were mixed and stirred according to the ink formulation shown in Table 1, and then an antibacterial agent, a pH adjuster, a resin, and a colorant (pigment dispersion) were mixed and stirred. The resulting mixture was pressure filtered through a polyvinylidene fluoride membrane filter having an average pore size of 1.2 μm to remove coarse particles and dust, thereby obtaining the inks of Examples 2 to 6 and Comparative Examples 1 to 4.
The composition of each ink is shown in Table 1 below.
Table 2 shows the product names and manufacturer names of the ink components, and Table 3 shows the water solubility of the antibacterial agent types.

(evaluation)
For the inks of Examples 1 to 6 and Comparative Examples 1 to 4 obtained above, images were formed and evaluated as follows.
The evaluation results are shown in Table 4.

<Image Formation>
Each ink was filled into an inkjet printer (IPSiO GXe5500 manufactured by Ricoh Company, Ltd.), and using this printer, solid printing was performed on a PVC film (product name: GIY11Z5 manufactured by Lintec Corporation) at a resolution of 1200 x 1200 dpi. The resulting image was then left to dry on a hot plate at 80°C for 3 minutes to form an image sample.

<Antibacterial properties of ink>
Each ink was stored at room temperature (25°C) for one week, and then 1 mL of the ink was applied to a San-Ai Bio Checker TTC (for measuring total bacterial count, manufactured by San-Ai Oil Co., Ltd.) and held at 37°C for 24 hours. The presence or absence of colonies on the medium after that was checked, and if colonies were detected, the density of the colonies was used to evaluate the degree of bacterial contamination according to the following evaluation criteria, based on the attached judgment table.
The colonies are colonies of bacteria, including aerobic bacteria and fungi (mold and yeast). For example, Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, mold, etc., can form colonies. When colonies were formed, they were visually confirmed using the San-ai Biochecker TTC.
[Evaluation criteria]
A: No bacterial contamination B: Low level of bacterial contamination C: Medium level of bacterial contamination D: High level of bacterial contamination

<Antibacterial properties of the printing surface>
Image samples formed using each ink by the above image forming method were cut into 1 cm squares and attached to culture media, and then kept at 37°C for 24 hours. The degree of bacterial contamination was then evaluated in the same manner as in the evaluation of the "antibacterial properties of the ink liquid" described above.
[Evaluation criteria]
A: No bacterial contamination B: Low level of bacterial contamination C: Medium level of bacterial contamination D: High level of bacterial contamination

<Antibacterial properties of printed surface after wet rubbing>
The image sample formed by the above image forming method was cut into a size of 2.5 cm x 20 cm, and placed in a dyed fabric rubbing fastness tester (model: AR-2, manufactured by Intec Co., Ltd.). A white cloth (Kanakin No. 3) moistened with 100% pure water was rubbed 100 times at a reciprocating speed of 30 times/min with a load of 500 g to obtain an image sample. This image sample was assumed to be a sample after wiping with water in actual use, and a test for antibacterial properties was performed using this sample in the same manner as in the above-mentioned evaluation of antibacterial properties of the printed surface.
[Evaluation criteria]
A: No bacterial contamination B: Low level of bacterial contamination C: Medium level of bacterial contamination D: High level of bacterial contamination

<Image color unevenness>
For the image samples formed by the above image forming method, density unevenness (beading) was visually evaluated according to the following evaluation criteria.
[Evaluation criteria]
A: None at all.
B: Slight unevenness in density can be seen from a distance of 15 cm.
C: Slight unevenness in density can be seen from a distance of 30 cm.
D: Density unevenness can be confirmed even from a distance of 50 cm.

<Ink storage stability>
Each ink was placed in a sealed container and stored in an environment at 70° C. for 14 days.
The ink viscosity was measured before and after storage, and the rate of change in viscosity was calculated based on the following formula and evaluated according to the following criteria.
Viscosity change rate (%) = [(viscosity after storage - viscosity before storage) / viscosity before storage] x 100
The ink viscosity was measured at 25° C. using an R-type viscometer (manufactured by Toki Sangyo Co., Ltd.).
〔Evaluation criteria〕
A: The rate of change in viscosity before and after storage is less than 5%. B: The rate of change in viscosity before and after storage is 5% or more and less than 8%. C: The rate of change in viscosity before and after storage is 8% or more and less than 10%. D: The rate of change in viscosity before and after storage is 10% or more.

<Ink ejection properties>
Using an inkjet printer (IPSIO GXe3300 manufactured by Ricoh Co., Ltd.), ink was filled and an initial filling operation was performed. After that, a nozzle check pattern was printed, and ejection defects (nozzle non-ejection or ejection deflection) were confirmed using the nozzle check pattern. For those without ejection defects, printing was then performed on my paper, and the printing pattern was printed with each of the yellow, magenta, cyan, and black inks of the present invention at 100% duty in a chart in which the printing area of each color was 5% of the total area of the paper in the image region. The printing conditions were a recording density of 360 dpi and one-pass printing. After printing 20 sheets of the above chart in succession, the paper was placed in a paper feed state in which ejection was not performed for 20 minutes, and this was repeated 50 times, and after printing a total of 1,000 sheets, a nozzle check pattern was printed to confirm ejection defects (nozzle non-ejection or ejection deflection). The presence or absence of whiteout and ejection disturbance was visually evaluated in each nozzle check pattern.

[Evaluation criteria]
A: No disturbance in ejection B: Slight disturbance in ejection C: Disturbance in ejection, or some nozzles not ejecting D: Severe disturbance in ejection, or many nozzles not ejecting

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

Japanese Patent Application Laid-Open No. 55-16037 Japanese Patent Application Laid-Open No. 6-234943 Japanese Patent Application Laid-Open No. 1-213376

Claims (7)

An ink containing an organic solvent and an antibacterial agent,
The ink, characterized in that the antibacterial agent contains the following first antibacterial agent and the following second antibacterial agent.
First antibacterial agent: an isothiazolinone compound having a water solubility of less than 1 g/L. Second antibacterial agent: an isothiazolinone compound having a water solubility of 20 g/L or more. The ink according to claim 1 , wherein the ink contains water, and the organic solvent contains an amide solvent represented by the following general formula (1):

(In the general formula (1), R ₁ , R ₂ , and R ₃ each independently represent a hydrocarbon group having 1 to 8 carbon atoms.) The ink according to claim 1, wherein the total amount of the first antibacterial agent and the second antibacterial agent is 0.01% by mass or more and 1.0% by mass or less with respect to the total mass of the ink. The ink according to claim 1, wherein the total amount of the first antibacterial agent and the second antibacterial agent is 0.1% by mass or more and 0.5% by mass or less with respect to the total mass of the ink. A printing method having a printing step of applying ink onto a substrate and a heating step of heating the applied ink, characterized in that the ink used is an ink according to any one of claims 1 to 4. The printing method according to claim 5, wherein the substrate is plastic. A printed matter having a printed layer on a substrate, the printed layer containing a first antibacterial agent and a second antibacterial agent, the first antibacterial agent being an isothiazolinone-based compound having a water solubility of less than 1 g/L, and the second antibacterial agent being an isothiazolinone-based compound having a water solubility of 20 g/L or more.

Images