Inkjet ink composition

Abstract

Provided is an inkjet ink composition having excellent discharge stability and excellent antibacterial properties against bacteria and mildew resistance against bacteria. This inkjet ink composition contains water and a compound A represented by formula (1), and has a pH of 7.5 or more at 25 DEG C. It is preferable that the inkjet ink composition contains a humectant having an HSP value of 15.0 or less. Furthermore, it is preferable that the inkjet ink composition contains a polyol compound having three or more OH groups in the molecule, and the content of the polyol compound in the inkjet ink composition is 1.0 mass% or more. [Chemical Formula 1] (wherein R represents a hydrocarbon group having 6-12 carbon atoms)

Description

Technical Field

[0001] This invention relates to an inkjet ink composition. Background Technology

[0002] Water-based inks, which contain water, are widely used as inks. Because water is a cause of spoilage, water-based inks require antibacterial and antifungal properties. Furthermore, in recent years, the applications of inkjet printing have expanded beyond office and home printing to include commercial printing, textile printing, and more. Inkjet inks are typically used in an alkaline environment for spray stability.

[0003] Therefore, for example, Patent Document 1 discloses an alkaline inkjet ink containing isothiazolinone compounds as antibacterial agents.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2024-54979

[0007] However, while the inkjet ink in Patent Document 1 has antibacterial properties, it suffers from insufficient resistance to mold and mildew. Therefore, there is a need for an inkjet ink composition that exhibits excellent ejection stability and excellent antibacterial and antimildew properties. Summary of the Invention

[0008] This invention was made to solve the above-mentioned technical problems and can be implemented as the following application examples.

[0009] The inkjet ink composition involved in the application example of the present invention comprises compound A represented by the following formula (1) and water, with a pH of 7.5 or higher at 25°C.

[0010] [Chemical Formula 1]

[0011]

[0012] (In the formula, R is a hydrocarbon group with 6 or more but less than 12 carbon atoms.) Attached Figure Description

[0013] Figure 1 Table 1 shows the composition of the inkjet ink compositions of Examples 1 to 12.

[0014] Figure 2 Table 2 shows the composition of the inkjet ink compositions of Examples 13-17 and Comparative Examples 1-6.

[0015] Figure 3Table 3 shows the evaluation results of the inkjet ink compositions of Examples 1-17 and Comparative Examples 1-6. Detailed Implementation

[0016] The inkjet ink composition of the present invention will now be described based on preferred embodiments.

[0017] [1] Inkjet ink composition

[0018] First, the inkjet ink composition involved in the embodiments will be described.

[0019] The inkjet ink composition of the present invention comprises compound A represented by the following formula (1) and water, with a pH of 7.5 or higher at 25°C.

[0020] [Chemical Formula 2]

[0021]

[0022] (In the formula, R is a hydrocarbon group with 6 or more but less than 12 carbon atoms.)

[0023] Based on this configuration, it is possible to provide an inkjet ink composition that exhibits excellent ejection stability, antibacterial properties, and antifungal properties.

[0024] More specifically, compound A exhibits excellent antibacterial and antifungal properties even in alkaline solutions. Therefore, inkjet ink compositions containing compound A also possess antibacterial and antifungal properties in alkaline solutions. Furthermore, since the inkjet ink composition is alkaline, it provides inkjet ink compositions with excellent ejection stability.

[0025] Such excellent results are obtained by satisfying all of the conditions; even if one of the conditions is not satisfied, such excellent results cannot be obtained.

[0026] For example, without compound A, the antibacterial and antifungal properties of the inkjet ink composition are reduced. Furthermore, if other compounds are used instead of compound A, neither antibacterial nor antifungal properties are achieved. For instance, when isothiazolinone is used instead of compound A as the antibacterial agent, while antibacterial properties are achieved, antifungal properties are not sufficiently obtained.

[0027] Furthermore, if the number of carbon atoms in the hydrocarbon group represented by R is less than the lower limit, the hydrophobicity of the R portion becomes insufficient, reducing the antibacterial and antifungal properties of the inkjet ink composition. On the other hand, if the number of carbon atoms in the hydrocarbon group represented by R exceeds the upper limit, compound A has difficulty entering cells and thus cannot exert its antibacterial and antifungal effects.

[0028] Furthermore, if the pH of the inkjet ink composition is lower than the aforementioned lower limit, the solubility and dispersibility of the pigments and resins contained in the inkjet ink composition decrease. Consequently, the ejection stability of the inkjet ink composition decreases.

[0029] Furthermore, in this invention, pH (hydrogen ion index) refers to a value determined according to the method of JIS Z 8802. The pH value in this specification is the measurement value at 25°C.

[0030] The composition of the inkjet ink composition of the present invention will be described in detail below.

[0031] [1-1] Antibacterial agents

[0032] The inkjet ink composition of the present invention comprises compound A of formula (1) above as an antibacterial agent. R in formula (1) above is a hydrocarbon group having 6 or more and 12 or fewer carbon atoms. Compound A enters the cell through the hydrophobic R portion having a hydrocarbon group, thereby exerting antibacterial and antifungal effects.

[0033] The hydrocarbon group represented by R has 6 or more and 12 or less carbon atoms, preferably 7 or more and 10 or less, and more preferably 8. This increases the hydrophobicity of the R portion and facilitates the entry of compound A into cells. Therefore, the antibacterial and antifungal properties of the inkjet ink composition are improved. Furthermore, the increased solubility of compound A in water makes it suitable for use as an inkjet ink.

[0034] The hydrocarbon group represented by R can be either cyclic or chain-like. In the case of chain-like hydrocarbons, branched chains are possible, but straight chains are preferred. This allows compound A to easily enter cells.

[0035] The hydrocarbon group represented by R preferably does not have multiple bonds. By not having multiple bonds, the stability of the inkjet ink composition can be improved.

[0036] As for compound A that satisfies the above conditions, N-octyldiethanolamine is particularly preferred.

[0037] The content of compound A in the inkjet ink composition is not particularly limited, but is preferably 100 ppm or more and 1000 ppm or less, more preferably 250 ppm or more and 950 ppm or less, and even more preferably 400 ppm or more and 900 ppm or less. This allows for a higher balance between the antibacterial and antifungal properties of the inkjet ink composition and the water solubility of compound A.

[0038] [1-2] Water

[0039] The inkjet ink composition of the present invention contains water. Water functions as a solvent for dissolving compound A. Furthermore, water also functions as a solvent and dispersion medium for the components described later.

[0040] The water content in the inkjet ink composition is not particularly limited, but is preferably 50% by mass or more and 90% by mass or less, more preferably 60% by mass or more and 85% by mass or less. This results in particularly excellent storage stability and ejection stability of the inkjet ink composition. Furthermore, when the ink pigment described later is included, the image density formed using the inkjet ink composition can be particularly high.

[0041] [1-3] Moisturizers

[0042] The inkjet ink composition of the present invention preferably contains a humectant with an HSP value of 15.0 or less. Compound A contains a hydrocarbon group in the R portion and has low solubility in water. Therefore, by including a humectant with an HSP value of 15.0 or less in the inkjet ink composition, the solubility of compound A in the ink can be improved.

[0043] Here, "HSP value" refers to the three-dimensional solubility parameter value of Hansen as shown in the following mathematical formula (1). In this invention, the unit is omitted; the unit is (cal / cm³). 3 ) 0.5 The HSP value can be obtained, for example, by referring to the values ​​of δD, δP, and δH in the International Chemical Identifier database and calculating using mathematical formula (1).

[0044] HSP value = (δD² + δP² + δH²) 0.5 / 4.1868 0.5 …(1)

[0045] Dispersion term δD: Energy based on intermolecular dispersion forces

[0046] Polar term δP: Energy based on intermolecular dipole interactions

[0047] Hydrogen bond term δH: based on the energy of intermolecular hydrogen bonds

[0048] The HSP value of such a humectant included in the inkjet ink composition is preferably 5.0 or higher and 15.0 or lower, more preferably 8.0 or higher and 14.5 or lower. This further improves the solubility of compound A in the ink.

[0049] There are no particular limitations on the type of humectant with an HSP value of 15.0 or lower; examples include alkyl glycols, glycol monoethers, and amides. More specifically, examples of alkyl glycols include propylene glycol, diethylene glycol, triethylene glycol, 1,2-hexanediol, and 1,3-butanediol; examples of glycol monoethers include triethylene glycol monobutyl ether and triethylene glycol monomethyl ether; and examples of amides include 1-(2-hydroxyethyl)-2-pyrrolidone, ε-caprolactam, and 2-pyrrolidone. Among these, propylene glycol is preferred as a humectant with an HSP value of 15.0 or lower.

[0050] The content of humectants with an HSP value of 15.0 or less in the inkjet ink composition is preferably 0.1% by mass or more and 35.0% by mass or less, more preferably 1.0% by mass or more and 30.0% by mass or less, and even more preferably 3.0% by mass or more and 25.0% by mass or less. This further improves the solubility of compound A in water. Furthermore, when the inkjet ink composition contains multiple humectants with an HSP value of 15.0 or less, it is preferable that the sum of their contents is within the aforementioned range.

[0051] [1-4] Polyol compounds

[0052] The inkjet ink composition of the present invention preferably contains a polyol compound having three or more OH groups in its molecule.

[0053] Polyol compounds prevent the nozzles from drying out, thus improving inkjet ink composition ejection stability. However, on the other hand, polyol compounds can become a nutrient source for bacteria and fungi, leading to spoilage of the inkjet ink composition. The inkjet ink composition of the present invention possesses antibacterial and antifungal properties, thus preventing spoilage even when containing polyol compounds. Therefore, by including polyol compounds in the inkjet ink composition, ejection stability can be improved while maintaining sufficient antibacterial and antifungal properties.

[0054] There are no particular limitations on the polyol compound, and examples include glycerol, sorbitol, diglycerol, polyglycerol, mannitol, xylitol, erythritol, lactitol, maltitol, galactitol, and trehalose. Among these, glycerol and sorbitol are preferred as polyol compounds.

[0055] The content of polyol compounds in the inkjet ink composition is preferably 1.0% by mass or more, more preferably 5.0% by mass or more and 30.0% by mass or less, and even more preferably 10.0% by mass or more and 25.0% by mass or less. This maintains sufficient antibacterial and antifungal properties while further improving ejection stability. Furthermore, when the inkjet ink composition contains multiple polyol compounds, it is preferable that the sum of their contents is within the aforementioned range.

[0056] [1-5] pH adjusters

[0057] [1-5-1] Acidic pH adjuster

[0058] Compound A contained in the inkjet ink composition of the present invention is strongly alkaline. Therefore, the inkjet ink composition of the present invention preferably contains an acidic pH adjuster, and more preferably contains an organic acid. This allows for more appropriate adjustment of the pH of the inkjet ink composition, resulting in superior antibacterial and antifungal properties.

[0059] Examples of organic acids include adipic acid, citric acid, succinic acid, fumaric acid, lactic acid, tartaric acid, gluconic acid, and other carboxylic acids.

[0060] The content of organic acids in the inkjet ink composition is preferably 0.05% by mass or more and 3.0% by mass or less, more preferably 0.1% by mass or more and 2.0% by mass or less. This allows for more appropriate adjustment of the pH of the inkjet ink composition. Furthermore, when the inkjet ink composition contains multiple organic acids, it is preferable that the sum of their contents is within the aforementioned range.

[0061] [1-5-2] Alkaline pH adjuster

[0062] Inkjet ink compositions may also contain alkaline pH adjusters. It is particularly preferred that they be used in conjunction with acidic pH adjusters. This allows for more appropriate adjustment of the pH of the inkjet ink composition. Furthermore, compound A is not included in the alkaline pH adjuster.

[0063] Examples of alkaline pH adjusters include, for example, alkanolamines other than compound A, alkali metal hydroxides, alkali metal carbonates, and aminosulfonic acids. More specifically, the following compounds can be cited: For example, alkanolamines other than compound A include diethanolamine, dimethylethanolamine, diethylethanolamine, triethanolamine, and triisopropanolamine. Alkali metal hydroxides include lithium hydroxide, sodium hydroxide, potassium hydroxide, and ammonium hydroxide. Alkali metal carbonates include lithium carbonate, sodium carbonate, and potassium carbonate. Aminosulfonic acids include taurine.

[0064] The content of the alkaline pH adjuster in the inkjet ink composition is preferably 0.05% by mass or more and 3.0% by mass or less, more preferably 0.1% by mass or more and 2.0% by mass or less. This allows for more appropriate adjustment of the pH of the inkjet ink composition. Furthermore, when the inkjet ink composition contains multiple alkaline pH adjusters, it is preferable that the sum of their contents is within the aforementioned range.

[0065] When the content of the alkaline pH adjuster is set as XA (mass%) and the content of compound A is set as XB (mass%), the XB / XA ratio is preferably 0.05 or more and 0.50 or less, more preferably 0.08 or more and 0.45 or less, and even more preferably 0.10 or more and 0.40 or less. This allows for more appropriate adjustment of the pH of the inkjet ink composition, resulting in superior antibacterial and antifungal properties.

[0066] [1-6] Pigments

[0067] The inkjet ink composition of the present invention preferably contains a pigment. Therefore, the inkjet ink composition can be suitably used for the formation of images, as described later.

[0068] As a colorant, various dyes and pigments can be used. Examples of dyes include disperse dyes, reactive dyes, and acid dyes. Examples of disperse dyes include Disperse Red 60. Examples of reactive dyes include Reactive Orange 13. Examples of acid dyes include Acid Yellow 79 and Acid Yellow 95. Examples of pigments include Pigment Red 122 and Pigment Blue 15:3. Furthermore, while not specifically limited, various dyes and pigments listed in color indexes can be used.

[0069] The inkjet ink composition of the present invention preferably contains one or more selected from reactive dyes and pigments containing chlorine atoms within the molecule. Reactive dyes and pigments containing chlorine atoms within the molecule have a corrosive effect on metal parts. Therefore, rust prevention measures are required during use. The inkjet ink composition of the present invention has a rust-preventive effect by containing compound A. Therefore, by including at least one of reactive dyes and pigments containing chlorine atoms within the molecule in the inkjet ink composition, the effect of the present invention can be improved.

[0070] Examples of colorants that contain chlorine atoms within their molecules include Reactive Orange 13 and Reactive Blue 49.

[0071] Furthermore, the inkjet ink composition may also contain non-metallic pigments (non-gold pigments). Gold pigments containing metals inherently possess antibacterial and antifungal properties. On the other hand, non-gold pigments lack antibacterial and antifungal properties, and are therefore more prone to spoilage compared to gold pigments. Because the inkjet ink composition of the present invention exhibits excellent antibacterial and antifungal properties, spoilage can be suppressed even when non-gold pigments, which tend to have poor antibacterial and antifungal properties when added to the inkjet ink composition, are included. Therefore, the effects of the present invention can be maintained even when the inkjet ink composition contains non-gold pigments. Furthermore, it is preferable not to contain gold pigments. "Not containing gold pigments" means that the inkjet ink composition substantially does not contain gold pigments, and the content of gold pigments is preferably 0.5% by mass or less, more preferably 0.3% by mass or less, and even more preferably 0.1% by mass or less.

[0072] Examples of non-gold-containing pigments include Disperse Red 60, Reactive Orange 13, Acid Yellow 79, and Pigment Red 122. Examples of gold-containing pigments include Pigment Blue 15:3.

[0073] The pigment content in the inkjet ink composition of the present invention is preferably 0.1% by mass or more and 20.0% by mass or less, more preferably 0.2% by mass or more and 15.0% by mass or less. If the pigment content is within this range, a higher level of balance can be achieved between inkjet-based ejection stability and the density of the image formed by the inkjet ink composition. Furthermore, when the inkjet ink composition contains multiple pigments, it is preferable that the sum of their contents is within the range.

[0074] [1-7] Other ingredients

[0075] Inkjet ink compositions may also contain ingredients other than those described above. Hereinafter, such ingredients will also be referred to as "other ingredients" within the scope of this project.

[0076] Other components include, for example, chelating agents, preservatives other than those mentioned above, flame retardants, various dispersants, resins, rust inhibitors other than those mentioned above, antioxidants, ultraviolet absorbers, oxygen absorbers, solvent aids, penetrants, defoamers, surfactants, and colorants other than those mentioned above.

[0077] Examples of chelating agents include ethylenediaminetetraacetic acid (EDTA). Examples of preservatives include sodium benzoate, sodium pentachlorophenolate, sodium 2-mercaptopyridine-1-oxide, sodium sorbate, sodium dehydroacetate, 1,2-dibenzisothiazolin-3-one, and 4-chloro-3-methylphenol.

[0078] Examples of resins include styrene-acrylic resins, polyethylene waxes, and vinyl chloride-vinyl acetate copolymer resins. By including a resin in the inkjet ink composition, the fixing properties of the inkjet ink composition in the recording medium described later can be improved.

[0079] Examples of ultraviolet absorbers include benzophenone compounds, cinnamic acid compounds, triazine compounds, stilbene compounds, and so-called fluorescent whitening agents (compounds that absorb ultraviolet light and emit fluorescence, represented by benzoxazole compounds).

[0080] Examples of defoamers include highly oxidized oil compounds, glycerol fatty acid ester compounds, fluorinated compounds, organosilicon compounds, and acetylene compounds.

[0081] As surfactants, various surfactants can be used, such as anionic surfactants, cationic surfactants, and nonionic surfactants. Examples of nonionic surfactants include silicone surfactants and acetylenic diol surfactants.

[0082] The content of other components in the inkjet ink composition of the present invention is preferably 10.0% by mass or less, more preferably 5.0% by mass or less.

[0083] [1-8] Other conditions

[0084] As described above, the pH of the inkjet ink composition of the present invention is 7.5 or higher, preferably 7.7 or higher and 11.0 or lower, more preferably 8.0 or higher and 10.0 or lower. This significantly enhances the effects of the present invention described above.

[0085] The surface tension (surface tension at 20°C) of the inkjet ink composition of the present invention is preferably 20 mN / m or more and 50 mN / m or less, more preferably 25 mN / m or more and 40 mN / m or less. Furthermore, the surface tension of the inkjet ink composition can be determined, for example, by measuring it according to JIS K3362 using a surface tension meter CBVP-A3 (manufactured by Kyowa Interface Science Co., Ltd.).

[0086] The viscosity (viscosity at 20°C) of the inkjet ink composition of the present invention is preferably 2 mPa·s or more and 20 mPa·s or less. This results in particularly excellent ejection stability (stability of ejection volume, droplet flight characteristics, etc.) and ejection responsiveness (response speed, high-frequency response (frequency characteristics), etc.) of the inkjet ink composition. Furthermore, the viscosity of the inkjet ink composition can be determined by measuring it using a vibratory viscometer according to JIS Z8809.

[0087] [2] Recording method

[0088] Next, an example of the recording method according to the present invention will be described. This recording method includes a step of ejecting the inkjet ink composition of the present invention by inkjet printing and adhering it to a recording medium. The inkjet ink composition of the present invention exhibits excellent ejection stability, as well as excellent antibacterial and antifungal properties. Therefore, by using the inkjet ink composition of the present invention, a recording method capable of stably manufacturing recordings with excellent antibacterial and antifungal properties can be provided.

[0089] In the recording method of this invention, the inkjet ink composition of this invention is ejected as droplets by an inkjet method, and the droplets adhere to the recording medium. Thus, a desired image is formed. Various inkjet ink compositions, such as various inkjet ink compositions of this invention, can be used in image formation.

[0090] The inkjet method for ejecting inkjet ink compositions can be any type, such as charged deflection, continuous, piezoelectric, bubble jet (registered trademark), and other on-demand methods.

[0091] There are no particular limitations on the recording medium. Examples include various types of cloth, ordinary paper, special paper for inkjet printing, coated paper, and other recording media with an ink receiving layer, as well as plastic films made of various plastics such as polyethylene terephthalate and polypropylene.

[0092] In the recording method of the present invention, not only the inkjet ink composition of the present invention can be used, but other ink compositions can also be used in combination.

[0093] In addition to the steps described above, the recording method of the present invention may include other steps. For example, steps such as applying a coating layer to the recording medium, heating the recording medium, and cleaning the recording medium can be included.

[0094] [3] Records

[0095] The recording medium of this invention is a recording medium manufactured using the inkjet ink composition of this invention described above, and can be manufactured using the recording method described above. Therefore, a recording medium with excellent antibacterial and antifungal properties can be provided.

[0096] The preferred embodiments of the present invention have been described above, but the present invention is not limited thereto.

[0097] Example

[0098] Next, specific embodiments of the present invention will be described, but the present invention is not limited thereto. In the processing and measurement in the following embodiments, where no temperature conditions are specified, the measurements were performed at room temperature (25°C).

[0099] [4] Preparation of inkjet ink composition

[0100] (Example 1)

[0101] By mixing the components in a predetermined ratio, the following is obtained: Figure 1 The inkjet ink composition shown is an inkjet ink composition.

[0102] (Examples 2-17)

[0103] Besides changing the types of components used in the preparation of inkjet ink compositions and the proportions of each component, it also becomes... Figure 1 as well as Figure 2 Except for the components shown, the inkjet ink composition was prepared in the same manner as in Example 1 above.

[0104] (Comparative Examples 1-6)

[0105] Besides changing the types of components used in the preparation of inkjet ink compositions and the proportions of each component, it also becomes... Figure 2 Except for the components shown, the inkjet ink composition was prepared in the same manner as in Example 1 above.

[0106] The composition of the inkjet ink compositions of each embodiment and comparative example is summarized in the table below. Figure 1 as well as Figure 2 .exist Figure 1 as well as Figure 2In the composition column, the unit of the numerical value is mass%, and the column without a value or marked with "-" means it does not contain any. Additionally, in the table, antibacterial agents other than compound A are represented as "other antibacterial agents," and polyol compounds with three or more OH groups in the molecule are represented as "polyol compounds." Furthermore, the solid content of Silface SAG503A (trade name, manufactured by Nissin Chemical Industry Co., Ltd.), an organosilicon surfactant, is represented as "Silface SAG503A," and the solid content of BYK-315N (trade name, manufactured by BYK Chemical Co., Ltd.), an organosilicon surfactant, is represented as "BYK-315N." The solid content of Olfine E1010 (trade name, manufactured by Nissin Chemical Industry Co., Ltd.), an alkynyl glycol surfactant, is represented as "Olfine E1010," and the solid content of Olfine PD002W (trade name, manufactured by Nissin Chemical Industry Co., Ltd.), an alkynyl glycol surfactant, is represented as "Olfine PD002W." The solid composition of resin particles made of styrene-acrylic resin, namely Joncryl 67 (trade name, manufactured by BASF), is designated as "Joncryl 67". The solid composition of resin particles made of polyethylene wax, namely CA-383 (trade name, manufactured by BASF), is designated as "CA-383". The solid composition of resin particles made of vinyl chloride-vinyl acetate copolymer resin, namely Solbin CLL (trade name, manufactured by Nissin Chemical Industry Co., Ltd.), is designated as "Solbin CLL".

[0107] [5] Evaluation of inkjet ink compositions

[0108] [5-1] Solubility

[0109] For each embodiment and comparative example, inkjet ink compositions in which pigments and resins were removed from their respective components were prepared and stirred for 20 minutes using a magnetic stirrer (200 rpm). Afterward, the dissolution state of each component was visually confirmed, and the solubility was evaluated.

[0110] A: Colorless and transparent

[0111] C: Turbidity or separation

[0112] [5-2] Antibacterial properties (bacteria)

[0113] In each example and comparative example, 0.1 mL of inkjet ink composition was inoculated into 10 mL to prepare 10 × 10⁻⁶ inks. 8The test bacterial suspension of *Escherichia coli* (CFU / mL) was incubated at 25°C for 24 hours. Using SCDLP liquid medium, a 10-fold dilution series of the inkjet ink composition was prepared, and these dilutions were spread onto standard agar plates and incubated at 30°C for 48 hours. After incubation, the viable count was calculated based on the number of colonies formed. The initial bacterial count was calculated using the viable count of the test bacterial suspension and the inoculum size. In each example and comparative example, the count was performed three times, and the average value was used as the result. Antimicrobial activity was evaluated according to the following evaluation criteria.

[0114] A: Viable bacteria count is below the detection limit.

[0115] B: The viable count is above the detection limit and less than 50% of the initial count.

[0116] C: The viable count is more than 50% of the initial count.

[0117] [5-3] Antifungal properties (fungi)

[0118] In each example and comparative example, 0.1 mL of inkjet ink composition was inoculated into 10 mL to prepare 10 × 10⁻⁶ inks. 8 A test culture of *Penicillium funiculosum* at CFU / mL was incubated at 25°C for 24 hours. Using SCDLP liquid medium, a 10-fold dilution series of the inkjet ink composition was prepared and inoculated onto standard agar medium, then incubated at 20°C for 3 days. After incubation, the viable count was calculated based on the number of colonies formed. The initial count was calculated using the viable count of the test culture and the inoculum size. In each example and comparative example, the count was performed three times, and the average value was used as the result. Antifungal activity was evaluated according to the following evaluation criteria.

[0119] A: Viable bacteria count is below the detection limit.

[0120] B: The viable count is above the detection limit and less than 50% of the initial count.

[0121] C: The viable count is more than 50% of the initial count.

[0122] [5-4] Spray stability

[0123] The inkjet ink compositions of each embodiment and each comparative example were filled into the ink cartridges of the PX-G930 inkjet recording device (manufactured by Seiko Epson Corporation), and it was confirmed that ink could be ejected from all nozzles. Thereafter, the inkjet head was offset from the position of the cap provided by the inkjet recording device, and placed in an environment with a temperature of 40°C and a humidity of 20% for 5 days without the head cap being put on.

[0124] After placement, as a cleaning of the inkjet head, ink suction was performed three times at room temperature with suction amounts of 4g, 2g, and 2g. After each suction action, ejection stability was evaluated based on the number of nozzles that recovered without ejection, according to the following evaluation criteria.

[0125] A: No nozzles were not restored.

[0126] B: One or more but fewer than ten nozzles have not been restored.

[0127] C: More than 11 nozzles have not been restored.

[0128] [5-5] Rust prevention

[0129] The test and grade determination were conducted according to the "Rust Inhibition Determination Method" described in JIS K2246:2018 "Rust Inhibitor (Rust Oil)". Additionally, the environmental conditions were set at 80°C and 95% humidity for 10 days.

[0130] A: Class A~D

[0131] C: Class E

[0132] These evaluation results are summarized and presented in Figure 3 .

[0133] from Figure 3 It is evident that the inkjet ink compositions of the various embodiments exhibit excellent solubility, antibacterial properties, antifungal properties, ejection stability, and rust prevention. In contrast, satisfactory results were not obtained in the inkjet ink compositions of the comparative examples.

Claims

1. An inkjet ink composition, It contains compound A represented by the following formula (1) and water. The pH is above 7.5 at 25°C. In the formula, R is a hydrocarbon group with 6 or more carbon atoms and less than 12 carbon atoms.

2. The inkjet ink composition according to claim 1, wherein, The inkjet ink composition contains a humectant with an HSP value of 15.0 or less.

3. The inkjet ink composition according to claim 1 or 2, wherein, The inkjet ink composition comprises a polyol compound having three or more OH groups within its molecule. The polyol compound in the inkjet ink composition contains 1.0% by mass or more.

4. The inkjet ink composition according to claim 1 or 2, wherein, R is a hydrocarbon group with 8 carbon atoms.

5. The inkjet ink composition according to claim 1 or 2, wherein, The content of compound A in the inkjet ink composition is more than 100 ppm and less than 1000 ppm.

6. The inkjet ink composition according to claim 1 or 2, wherein, The inkjet ink composition contains organic acids.

7. The inkjet ink composition according to claim 1, wherein, The inkjet ink composition contains colorants.

8. The inkjet ink composition according to claim 7, wherein, The colorant includes non-metallic colorants.

9. The inkjet ink composition according to claim 7 or 8, wherein, The colorant comprises one or more selected from reactive dyes and colorants containing chlorine atoms within the molecule.

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