Ink composition precursor, method for producing ink composition precursor, method for producing ink composition using ink composition precursor, and kit for production of ink composition

Abstract

To provide an ink composition precursor that enables easy production of a uniform ink composition by blending with a vehicle, and a method for producing the same.SOLUTION: An ink composition precursor contains (A) a colorant, (B) an amphoteric organic compound, and (C) urea, exhibiting a water activity of 0.50 or less.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an ink composition precursor, a method for producing an ink composition precursor, a method for producing an ink composition using the ink composition precursor, and a kit for producing an ink composition. [Background technology]

[0002] Various writing instruments that form handwriting using an ink composition are known, including fountain pens, dip pens, ballpoint pens, and marker pens. The ink compositions used in these writing instruments generally contain a solvent or dispersion medium and a colorant as main components. The handwriting is formed mainly by the colorant, and the solvent or dispersion medium has the function of adjusting the density of the handwriting and stabilizing the supply of the ink composition to the paper surface by the writing instrument.

[0003] However, since the ink composition contains a solvent or a dispersion medium, microorganisms such as bacteria, fungi, and yeasts may grow in the composition, causing deterioration of the ink composition, and therefore it may become necessary to use an antibacterial substance or the like to prevent deterioration of the ink composition.

[0004] In addition, when an ink composition produced at a manufacturing factory for an ink composition is transported to another factory for dividing into small containers or for filling into writing instruments, the transportation cost tends to be high because the ink composition contains a high proportion of a solvent or dispersion medium and therefore has a large overall weight or volume.

[0005] From this perspective, concentrating or drying the ink composition has also been considered. A powdered composition obtained by drying an ink composition has the advantages of eliminating the need for antibacterial substances because it does not contain a solvent or the like, and of enabling users to mix and match powdered compositions of different hues. However, when an ink composition is simply dried, it is often the case that a homogeneous composition cannot be obtained even if a solvent or the like is added. On the other hand, when a raw material mixture is prepared by blending the raw materials of the ink composition in a dry state, it is often the case that a homogeneous composition cannot be obtained even if a solvent or the like is added.

[0006] Also, a method of drying the ink composition by freeze-drying has been proposed, but according to the studies of the present inventors, it has been found that even when the ink composition is dried by freeze-drying and a solvent or the like is added, a uniform composition is not obtained, and the dried product is often charged and difficult to handle. For this reason, there is a demand for an ink composition precursor that can easily obtain a uniform ink composition when a solvent or the like is added. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2023-031243 A Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide an ink composition precursor which has high storage stability and which can easily form a uniform ink composition by blending a solvent or dispersion medium therewith. [Means for solving the problem]

[0009] According to the present invention, the following inventions are provided. [1] (A) a colorant, (B) amphoteric organic compounds, and (C)Urea and having a water activity of 0.50 or less. [2] The ink composition precursor according to [1], having a porous structure. [3] The ink composition precursor according to [1] or [2], wherein the colorant is a dye. [4] The ink composition precursor according to any one of [1] to [3], further comprising a surfactant. [5] The ink composition precursor according to [4], wherein the surfactant has a polyoxyalkylene structure. [6] The ink composition precursor according to any one of [1] to [5], further comprising a chelating agent. [7] The ink composition precursor according to [6], wherein the chelating agent is selected from the group consisting of ethylenediaminetetraacetic acid (EDTA), hydroxyethylenediaminetriacetic acid (HEDTA), glycol ether diaminetetraacetic acid (GEDTA), nitrilotriacetic acid (NTA), hydroxyethyliminodiacetic acid (HIDA), dihydroxyethylglycine (DHEG), diethylenetriaminepentaacetic acid (DTPA), and triethylenetetraminehexaacetic acid (TTHA), as well as alkali metal salts, ammonium salts, and amine salts thereof. [8] The ink composition precursor according to any one of [1] to [7], wherein the amphoteric organic compound is a compound selected from amino acids, alkyl betaines, alkyl amide betaines, imidazoline betaines, glycine betaines, and amine oxides. [9] The ink composition precursor according to any one of [1] to [8], further comprising biomass nanofibers.

[10] The ink composition precursor according to [9], wherein the biomass nanofibers have a fiber diameter of 1 to 100 nm and an aspect ratio of 100 or more.

[11] (A) a colorant, (B) amphoteric organic compounds, (C) urea, and (D)Water A preparation step of preparing an ink composition comprising: A preliminary freezing step of freezing the ink composition; and a drying step in which the frozen material obtained by the preliminary freezing is dried in a reduced pressure atmosphere to a water activity of 0.50 or less; A method for producing an ink composition precursor comprising the steps of:

[12] The temperature of the preliminary freezing step is −70 to −10° C. The method according to

[11] , wherein the reduced pressure atmosphere in the drying step is 1 to 100 Pa.

[13] A method for producing an ink composition, comprising blending a vehicle with the ink composition precursor according to any one of [1] to

[10] to produce an ink composition.

[14] The method according to

[13] , wherein the vehicle comprises 90% by mass or more of water, based on the total mass of the vehicle.

[15]

[10] . A kit for producing an ink composition comprising the ink composition precursor according to any one of [1] to

[10] and a vehicle capable of uniformly dissolving the ink composition precursor.

[16] (A) a colorant, (B) amphoteric organic compounds, (C) urea, and (D)Water An ink composition precursor produced by freeze-drying an ink composition comprising the above formula (1) by a freeze-drying method to adjust the water activity to 0.50 or less. Effect of the Invention

[0010] According to the present invention, there is provided an ink composition precursor that has high storage stability and can easily form a uniform ink composition by blending a solvent or a dispersion medium. This ink composition precursor is difficult to be charged, has excellent handleability, and has excellent solubility or dispersibility in a vehicle. By using this ink composition precursor, an ink composition can be prepared using a simple device. Furthermore, a kit that combines this ink composition precursor with a vehicle allows manufacturers and consumers to easily prepare ink compositions with arbitrary tones by combining multiple ink composition precursors. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, the embodiments of the present invention will be described in detail. In this specification, unless otherwise specified, the terms "parts", "%", "ratio" and the like indicating the composition are based on mass, and the content is the mass% of the constituent components based on the mass of the ink composition or the ink composition precursor.

[0012] <<Ink composition precursor>> The ink composition precursor according to the present invention (hereinafter sometimes simply referred to as "precursor") and its constituent components will be described in detail.

[0013] In the present invention, the ink composition precursor is a material that can form an ink composition by blending with a solvent or dispersion medium (hereinafter, sometimes simply referred to as "vehicle"). The components of the ink composition precursor may be the same as the so-called solid components of the ink composition (hereinafter, sometimes simply referred to as "composition") excluding the vehicle, but the ink composition precursor does not simply mean a blend of solid components that constitute the ink composition. Specifically, the ink composition precursor has a porous structure or a fine particle shape, and the contact area is made large when it comes into contact with the vehicle. In addition, the porous structure referred to here is preferably one that has a micron-sized structural pattern formed by ice crystals by a freeze-drying method.

[0014] <(A) Colorant> The precursor according to the present invention contains a colorant. The colorant is not particularly limited, and can be arbitrarily selected from dyes and pigments generally used in ink compositions. The precursor according to the present invention can be a precursor for either an aqueous ink composition or an oil-based ink composition depending on the vehicle to be blended, but it is preferable to select the colorant according to the properties of the ink composition. In the present invention, it is preferable to use an aqueous solvent, particularly water, as the vehicle, and it is preferable to use a colorant that can be dissolved or dispersed in an aqueous solvent.

[0015] As the colorant, either dyes or pigments can be used, but dyes are preferred because it is easy to obtain a uniform composition when the precursor is mixed with a vehicle. Examples of dyes include various dyes such as acid dyes, basic dyes, reactive dyes, direct dyes, disperse dyes, and food dyes, and these can be used alone or in combination of two or more kinds.

[0016] Specifically, examples of acid dyes include CI Acid Red 18, CI Acid Red 51, CI Acid Red 52, CI Acid Red 87, CI Acid Red 92, CI Acid Red 289, CI Acid Orange 10, CI Acid Yellow 3, CI Acid Yellow 7, CI Acid Yellow 23, CI Acid Yellow 42, CI Acid Green 3, CI Acid Green 16, CI Acid Blue 1, CI Acid Blue 9, CI Acid Blue 22, CI Acid Blue 90, CI Acid Blue 239, CI Acid Blue 248, CI Acid Violet 15, and CI Acid Violet 49. , CI Acid Black 1, CI Acid Black 2; basic dyes include CI Basic Orange 2, CI Basic Orange 14, CI Basic Green 4, CI Basic Blue 9, CI Basic Blue 26, CI Basic Violet 1, CI Basic Violet 3, CI Basic Violet 10; direct dyes include CI Direct Red 28, CI Direct Yellow 44, CI Direct Blue 86, CI Direct Blue 87, CI Direct Violet 51, CI Direct Black 19; and food dyes include CI Food Yellow 3 and CI Food Black 2.

[0017] Since dyes can serve as nutrients for microorganisms, aqueous ink compositions can have problems such as the generation of foreign matter such as microorganisms in the composition, but the precursor of the present invention has a low water content and a water activity of 0.50 or less even though it contains a dye, so such problems do not occur. Therefore, the precursor of the present invention does not need to contain antibacterial substances, which were generally added to conventional aqueous ink compositions.

[0018] Examples of pigments that can be used in the present invention include inorganic pigments, organic pigments, and processed pigments, and more specifically, carbon black, aniline black, ultramarine, yellow lead, titanium oxide, iron oxide, phthalocyanine, azo, quinacridone, quinophthalone, threne, triphenylmethane, perinone, perylene, dioxazine, aluminum pigments, pearl pigments, fluorescent pigments, and phosphorescent pigments. In addition, microencapsulated pigments may be used in which a colored body obtained by dispersing a pigment in a medium is encapsulated or solid-dissolved in a shell made of a resin wall-forming substance by a known microencapsulation method or the like as a colored resin particle body. In addition, the pigment may be a water-dispersed pigment product that is finely and stably dispersed in an aqueous medium using a surfactant or resin.

[0019] Among the pigments, self-dispersing pigments are preferably used. Self-dispersing pigments, particularly self-dispersing carbon black, are excellent in dispersion stability and can leave handwriting with excellent color development and water resistance.

[0020] Self-dispersing pigments can be dispersed in an aqueous medium without using a pigment dispersant to disperse pigment particles. Specifically, examples of self-dispersing pigments include pigments that have hydrophilic functional groups (hydrophilic groups) on the surface of the pigment particles by subjecting the surface of the pigment particles to physical or chemical treatment.

[0021] In the present invention, the content of the colorant contained in the precursor is not particularly limited, but the content of the colorant based on the total mass of the precursor is preferably 30 to 95 mass%, and more preferably 30 to 90 mass%.

[0022] <(B) Amphoteric organic compounds> The precursor according to the present invention contains an amphoteric organic compound. By containing the amphoteric organic compound, the precursor according to the present invention is prevented from being charged, and the handleability can be improved, particularly when the precursor is made into a powder composition.

[0023] The amphoteric organic compound is an organic compound having both an acidic group and a basic group in its structure, and specifically, a compound selected from amino acids, alkyl betaines, alkyl amide betaines, imidazoline betaines, glycine betaines, and amine oxides is preferable. Among amino acids, N,N,N-trialkyl amino acid represented by the following formula (1) is particularly preferable. R3N + -(CH2) n -COO - (1) During the ceremony, R is, independently, a linear or branched alkyl group, preferably a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, or a tert-butyl group; n is 1 to 5.

[0024] Specific examples include trimethylglycine, triethylglycine, tripropylglycine, triisopropylglycine, trimethyl-β-alanine, trimethyl-γ-aminobutyric acid, and 2-oxo-2-oxylato-N,N,N-trimethylethanaminium.

[0025] In the present invention, the content of the amphoteric organic compound contained in the precursor is not particularly limited, but the content of the amphoteric organic compound based on the total mass of the precursor is preferably 5 to 70 mass%, and more preferably 10 to 50 mass%.

[0026] <(C)Urea> The precursor according to the present invention further comprises urea. In the present invention, urea has a moisturizing function for the precursor, and is considered to have an effect of maintaining a suitable moisture content in the precursor and suppressing charging. The precursor in the present invention has a low water activity, and if the moisture content is too low, it may become charged and become difficult to handle, but adding urea can suppress charging of the precursor.

[0027] In the present invention, the content of urea contained in the precursor is not particularly limited, but when it is blended, the content of urea based on the total mass of the precursor is preferably 5 to 70 mass%, and more preferably 10 to 50 mass%.

[0028] <Surfactant> The precursor according to the present invention may contain a surfactant in addition to the above components.

[0029] The surfactant has the effect of dispersing or dissolving the colorant and other components uniformly in the composition and adjusting the wettability of the ink composition when the precursor is mixed with a vehicle to form a composition. To obtain such effects, any surfactant may be selected from among conventionally known surfactants, but nonionic surfactants are preferred, and those having a polyoxyalkylene structure are more preferred.

[0030] As the nonionic surfactant having a polyoxyalkylene structure, polyoxyalkylene alkyl ether, polyoxyalkylene glycol, polyoxyalkylene phenyl ether, polyoxyalkylene fatty acid ester, etc. can be mentioned, and various ones are commercially available.Among these, polyoxyalkylene glycol is preferably used in the present invention.The polyoxyalkylene structure contained in polyoxyalkylene glycol includes ethylene oxide and propylene oxide, and may contain either of them, or may contain a combination thereof.In addition, it may be one that contains two or more kinds of polyoxyalkylene structures as blocks, for example, polyoxyethylene polyoxypropylene block polymer.

[0031] Polyoxyalkylene glycols are commercially available, such as the Pronon (trade name) series (manufactured by NOF Corporation), the Unilube (trade name) series (manufactured by NOF Corporation), and the Newpol (trade name) series (manufactured by Sanyo Chemical Industries, Ltd.), and any of these can be selected according to the purpose.

[0032] In the present invention, the content of the surfactant contained in the precursor is not particularly limited, but when it is blended, the content of the surfactant based on the total mass of the precursor is preferably 0.1 to 10 mass%, and more preferably 0.5 to 5 mass%.

[0033] <Chelating agent> The precursor according to the present invention may contain a chelating agent in addition to the above components.

[0034] When a precursor is mixed with a vehicle to form a composition, the chelating agent captures alkaline components and the like eluted from a container containing the composition or from the ink reservoir of a writing instrument, and prevents the components from reacting with other components in the composition to generate water-insoluble precipitates, etc. In addition, the chelating agent, which can capture trivalent iron ions essential for the growth of microorganisms, is also effective in suppressing microorganisms in the composition.

[0035] Specific examples of the chelating agent used in the present invention include ethylenediaminetetraacetic acid (EDTA), hydroxyethylenediaminetriacetic acid (HEDTA), glycol ether diaminetetraacetic acid (GEDTA), nitrilotriacetic acid (NTA), hydroxyethyliminodiacetic acid (HIDA), dihydroxyethylglycine (DHEG), diethylenetriaminepentaacetic acid (DTPA), and triethylenetetraminehexaacetic acid (TTHA), as well as alkali metal salts, ammonium salts, and amine salts thereof.

[0036] Among the above-mentioned chelating agents, the use of ethylenediaminetetraacetate, which is an alkali metal salt, ammonium salt, or amine salt of ethylenediaminetetraacetic acid, is preferred because it can adequately capture the alkaline components eluted from the container and can also supplement trivalent iron ions essential for the growth of microorganisms.

[0037] In the present invention, the content of the chelating agent contained in the precursor is not particularly limited, but when it is blended, the content of the chelating agent based on the total mass of the precursor is preferably 1 to 30 mass%, and more preferably 1 to 25 mass%.

[0038] <Biomass nanofiber> The precursor according to the present invention may further contain biomass nanofibers in addition to the above-mentioned components. In the present invention, the biomass nanofibers are cellulose, chitin, or chitosan that have been uniformly pulverized at the nano level. The biomass nanofibers may have a chemically treated surface.

[0039] In the present invention, it is believed that the biomass nanofibers are useful for maintaining the physical structure of the precursor, i.e., the biomass nanofibers are effective in allowing the precursor to maintain a physical structure that can be easily homogenized during vehicle blending, such as a porous structure as described below.

[0040] Biomass nanofibers that can be used for the precursor according to the present invention can be arbitrarily selected from known ones. Specifically, commercially available biomass nanofibers and biomass nanofibers described in JP 2011-56456 A and WO 2010 / 073758 A can be used. In addition, "oxidatively modified cellulose" described in JP 2013-181167 A, "anion-modified cellulose" described in JP 2016-69617 A, and "phosphorylated cellulose" described in JP 2017-106012 A can also be used. Commercially available biomass nanofibers that can be used include the "BiNFi-s" series, BiNFi-sIMa-10002, BiNFi-sBMa-10002, BiNFi-sWMa-10002, BiNFi-sAMa-10002, BiNFi-sFMa-10002 (all of the above are product names of cellulose nanofiber), BiNFi-sSFo-20002 (product name, chitin nanofiber), BiNFi-sEFo-08002 (product name, chitosan nanofiber) manufactured by Sugino Machine Co., Ltd., the "Cerish" series, KY100S, KY100G, KY110N manufactured by Daicel FineChem Co., Ltd., the "nanoforest" series manufactured by Chuetsu Pulp Industry Co., Ltd., the "Cellenpia" series, TC-01A, TC-02X manufactured by Nippon Paper Industries Co., Ltd. (all of the above are product names of cellulose nanofiber), and the like.

[0041] The biomass nanofibers that can be used in the present invention are preferably fibers with a large aspect ratio, that is, a fiber diameter of 1 to 100 nm and an aspect ratio of 100 or more. The aspect ratio of the biomass nanofibers used in the present invention is preferably 1000 or less, and more preferably 300 or less. The aspect ratio is determined by the ratio of the fiber diameter to the fiber length. If the fiber length is large, the ink viscosity tends to increase, and there is a possibility that the targeted low-viscosity ink composition cannot be obtained, so the aspect ratio is preferably within the above range. The fiber diameter can be measured using an electron microscope photograph.

[0042] In the present invention, the content of biomass nanofibers contained in the precursor is not particularly limited, but when incorporated, the content of biomass nanofibers based on the total mass of the precursor is preferably 0.05 to 10 mass%, and more preferably 0.1 to 5 mass%.

[0043] <Solubilizing agent> The precursor according to the present invention can be produced by the production method described later, and in that case, a vehicle or a dissolving aid may be used to dissolve each component uniformly. The vehicle, for example, water, is mostly removed in the production process, but a part or all of the dissolving aid may be contained in the precursor. The vehicle is typically water, but may contain other low-boiling organic solvents, specifically organic solvents with a boiling point of 150°C or less. On the other hand, organic solvents with a boiling point exceeding 150°C, for example, polyhydric alcohols such as propylene glycol, diethylene glycol, ethylene glycol, and glycerin, may be used as dissolving aids. The precursor according to the present invention may contain such a dissolving aid. However, it is difficult to make such a precursor containing a polyhydric alcohol into a structure that can be easily dissolved when a vehicle is blended. This is thought to be because the presence of a polyhydric alcohol makes it difficult for the structure of the precursor to become a porous structure. For this reason, it is preferable that the content of an organic solvent with a boiling point exceeding 150°C is low.

[0044] Specifically, the content of the dissolution aid contained in the precursor is preferably 30% by mass or less, more preferably 20% by mass or less, based on the total mass of the precursor. Also, the precursor may contain no dissolution aid at all.

[0045] <Other additives> The precursor according to the present invention contains the above-mentioned components, but may also contain other components as necessary. Such components include: (i) a moisturizer (e.g., α-glucan, an α-glucan derivative, or a sugar alcohol, etc.); (ii) pH adjusters (e.g., triethanolamine, sodium carbonate, etc.); (iii) antifoaming agents (e.g. dimethylpolysiloxane); (iv) shear thinning agents (e.g., xanthan gum, succinoglycan, or carrageenan, polyacrylic acid, or crosslinked polyacrylic acid, etc.); (v) Rust inhibitors (e.g., benzotriazole and its derivatives, tolyltriazole, dicyclohexylammonium nitrite, diisopropylammonium nitrite, sodium thiosulfate, saponin, or dialkylthiourea, etc.) etc.

[0046] The precursor according to the present invention may also contain (vi) an antibacterial substance. Examples of the antibacterial substance include phenol, phenoxyethanol, sodium benzoate, sodium dehydroacetate, potassium sorbate, propyl paraoxybenzoate, 2,3,5,6-tetrachloro-4-(methylsulfonyl)pyridine, sodium 2-pyridinethiol-1-oxide, 1,2-benzisothiazolin-3-one, 2-methyl-4-isothiazolin-3-one, 2-n-octyl-4-isothiazolin-3-one, orthophenylphenol or a salt thereof, and more preferably, phenoxyethanol, 1,2-benzisothiazolin-3-one (hereinafter sometimes referred to as BIT), 2-methyl-4-isothiazolin-3-one (hereinafter sometimes referred to as MIT), 2-n-octyl-4-isothiazolin-3-one (hereinafter sometimes referred to as OIT), and a mixture thereof. However, since the precursor according to the present invention has a low moisture content, the generation of microorganisms such as bacteria hardly occurs. Therefore, when a user prepares an ink composition by mixing a vehicle with the precursor according to the present invention immediately before use, it is not necessary to mix an antibacterial substance. Therefore, when the precursor according to the present invention or a kit including the precursor and a vehicle is made into a consumer product, it is preferable not to mix an antibacterial substance with the precursor.

[0047] <Ink composition precursor> The ink composition precursor according to the present invention is characterized in that it contains the above-mentioned components and has a water activity of 0.50 or less. Furthermore, the ink composition precursor according to the present invention preferably has a water activity of 0.40 or less, more preferably 0.30 or less. Substances with low water activity are less susceptible to the growth of microorganisms such as bacteria, fungi, and yeasts and have high storage stability, but the precursor according to the present invention has a water activity of 0.50 or less, which makes it possible to inhibit the growth of microorganisms and has a very small volume relative to the ink composition, which is effective in reducing transportation costs and the like and also makes it possible to inhibit the growth of microorganisms.

[0048] In the present invention, the water activity is a value that indicates the proportion of free water contained in the ink composition precursor. Specifically, the water activity Aw is the ratio of the water vapor pressure P in a closed container containing the ink composition to the vapor pressure PO of pure water: Aw = P / PO In the present invention, the water activity Aw is measured at 25°C.

[0049] The precursor according to the present invention is used for producing an ink composition, and since the precursor has a porous structure, a uniform ink composition can be easily obtained when mixed with a vehicle. The size and number of pores forming the porous structure are not particularly limited, but it is preferable that the precursor has a micron-sized structural pattern formed by ice crystals, for example. Such a porous structure can be formed by sublimation of ice crystals by applying a freeze-drying method, as described below.

[0050] <<Method for producing ink composition precursor>> The ink composition precursor according to the present invention can be produced by any method, for example, the following steps: preparing an ink composition comprising: (A) a colorant; (B) an amphoteric organic compound; (C) urea; and (D) water; and A preliminary freezing step of freezing the ink composition; and a drying step in which the frozen material obtained by the preliminary freezing is dried by sublimation under a reduced pressure atmosphere to a water activity of 0.50 or less; The method of freezing the ink composition and drying it by sublimation is well known as the freeze-drying method.

[0051] First, in the preparation step, an ink composition is prepared. This composition is prepared by dissolving or dispersing the above-mentioned (A) to (C) components in (D) water. The (D) water used here is not particularly limited, and examples thereof include tap water, ion-exchanged water, ultrafiltered water, and distilled water. In addition, other components may be blended into this composition as necessary. Here, the composition prepared in the preparation step does not need to be the same as the composition prepared at the time of use via the precursor. That is, water is removed from the composition prepared in the preparation step by a subsequent treatment to form a precursor. Then, a vehicle is mixed with the precursor to prepare the composition, but the vehicle used at that time may contain components other than water, and it is not necessary to blend the same amount of vehicle as the water removed. Therefore, a composition with a relatively high concentration can be prepared in the preparation step to facilitate drying in the drying step. In addition, even if an organic solvent can be blended into the ink composition used, there are some that are difficult to remove in the freeze-drying method because the degree of vacuum required for removal is very high. It is preferable that such organic solvents, such as methanol, ethanol, acetonitrile, etc., are not blended into the composition prepared in the preparation step.

[0052] Next, in the pre-freezing step, the prepared composition is frozen. Since most of the liquid components blended into the composition are water, pre-freezing is performed at a temperature at which water freezes, i.e., 0°C or lower. In order to form sufficient ice crystals, the temperature in the pre-freezing step is preferably set to -70 to -10°C. In addition, since the freezing speed affects the size of the ice crystals, it is preferable to adjust the freezing speed to make the ice crystals have a desired size so that the voids in the porous structure of the precursor have a desired size.

[0053] The pre-frozen composition is then dried in a drying step. The drying is carried out under a reduced pressure atmosphere. The pressure at this time is preferably 1 to 100 Pa.

[0054] <<Method of manufacturing ink composition>> The precursor according to the present invention can easily form an ink composition by mixing with a vehicle. Therefore, an ink composition can be produced by blending a vehicle with the precursor according to the present invention.

[0055] At this time, it is preferable that the vehicle is mainly water. Specifically, the proportion of water is, for example, 50% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more, based on the total mass of the vehicle to be blended. In addition, the vehicle can be blended with the components listed as precursor components. In addition, organic solvents and the like that are difficult to remove when freeze-drying by the freeze-drying method can be blended in the vehicle without being blended in the precursor. The water used is not particularly limited, and examples thereof include tap water, ion-exchanged water, ultrafiltered water, and distilled water.

[0056] It is also possible to mix two or more types of precursors according to the present invention and add a vehicle to the mixture. According to such a method, it is possible to prepare ink compositions of various hues by preparing a plurality of precursors with different hues and changing the mixing ratio thereof.

[0057] The concentration of each component contained in the ink composition produced by the method for producing an ink composition according to the present invention varies depending on the blending ratio of the components contained in the precursor, the dilution rate with the vehicle, etc., but for example, based on the total mass of the ink composition, 0.1 to 10% by weight of a colorant, 0.01 to 10 mass % of an amphoteric organic compound, It contains 0.01 to 10 mass % of urea. Furthermore, if each is included, 0.01 to 1% by mass of a surfactant, 0.01 to 1% by mass of a chelating agent, 0.01 to 10% by mass of biomass nanofibers, and It may contain 0.1 to 10% by mass of a dissolution aid or the like.

[0058] <<Ink composition manufacturing kit>> The precursor according to the present invention can be combined with a vehicle capable of dissolving the precursor uniformly to prepare a kit for producing an ink composition. With such a kit, manufacturers and consumers can prepare an ink composition immediately before use, and therefore there is no need to worry about the occurrence or proliferation of microorganisms such as bacteria and fungi in the composition. In addition, by combining a plurality of precursors with different hues, manufacturers and consumers can mix and use the precursors as necessary to prepare an ink composition of any hue. EXAMPLES

[0059] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0060] <Example 1, Comparative Examples 1 to 3> The components shown in Table 1 were mixed together to prepare an ink composition. The ink composition thus obtained was pre-frozen at -40°C, and then placed in a dry chamber (DRC-3L (Tokyo Rikakikai Co., Ltd.)) attached to a freeze dryer (FDU-1200 (Tokyo Rikakikai Co., Ltd.)), and dried at a trap temperature of -45°C and a pressure of 10 to 20 Pa until moisture was sufficiently removed to obtain an ink composition precursor. The water activity of the obtained precursor was measured using a water activity measuring device (LabSwift-aw (Novacina Co., Ltd.)). In addition, each characteristic was evaluated according to the following criteria.

[0061] Static electricity suppression The obtained precursor was crumbled with a medicine spoon, and the state was visually observed to evaluate the effect of suppressing static electricity of the precursor. A: The crumbled precursor was not charged with static electricity and did not adhere to the inner wall of the resin container. B: The crumbled precursor was slightly electrostatically charged but did not adhere to the inner wall of the resin container. C: The crumbled precursor was charged with static electricity and adhered to the inner wall of the resin container.

[0062] structure maintenance The obtained precursor was dispensed with a spoon and its condition was visually observed to evaluate the structural maintenance of the precursor. A: The shape was maintained while the particles were separated. B: A portion of the sample was separated while still maintaining its shape. C: The shape could not be maintained and the powder was collected.

[0063] [Table 1] In the table, the cellulose nanofiber dispersion used was a TEMPO-oxidized cellulose nanofiber dispersion ("Cellenpia TC-01A" manufactured by Nippon Paper Industries Co., Ltd., active ingredient 1% by mass).

Claims

1. (A) a colorant, (B) an amphoteric organic compound, and (C) Urea and having a water activity of 0.50 or less.

2. The ink composition precursor according to claim 1 , which has a porous structure.

3. The ink composition precursor of claim 1 or 2, wherein the colorant is a dye.

4. The ink composition precursor according to claim 1 or 2, further comprising a surfactant.

5. The ink composition precursor according to claim 4 , wherein the surfactant has a polyoxyalkylene structure.

6. The ink composition precursor according to claim 1 or 2, further comprising a chelating agent.

7. 7. The ink composition precursor of claim 6, wherein the chelating agent is selected from the group consisting of ethylenediaminetetraacetic acid (EDTA), hydroxyethylenediaminetriacetic acid (HEDTA), glycoletherdiaminetetraacetic acid (GEDTA), nitrilotriacetic acid (NTA), hydroxyethyliminodiacetic acid (HIDA), dihydroxyethylglycine (DHEG), diethylenetriaminepentaacetic acid (DTPA), and triethylenetetraminehexaacetic acid (TTHA), and alkali metal, ammonium, and amine salts thereof.

8. 3. The ink composition precursor according to claim 1, wherein the amphoteric organic compound is a compound selected from the group consisting of amino acids, alkyl betaines, alkyl amide betaines, imidazoline betaines, glycine betaines, and amine oxides.

9. The ink composition precursor according to claim 1 or 2, further comprising biomass nanofibers.

10. The ink composition precursor according to claim 9, wherein the biomass nanofibers have a fiber diameter of 1 to 100 nm and an aspect ratio of 100 or more.

11. (A) a colorant, (B) an amphoteric organic compound; (C) urea, and (D) Water A preparation step of preparing an ink composition comprising: A preliminary freezing step of freezing the ink composition; and a drying step in which the frozen product obtained by the preliminary freezing is dried in a reduced pressure atmosphere to have a water activity of 0.50 or less; A method for producing an ink composition precursor comprising the steps of:

12. The temperature of the preliminary freezing step is −70 to −10° C. The method according to claim 11, wherein the reduced pressure atmosphere in the drying step is 1 to 100 Pa.

13. A method for producing an ink composition, comprising blending the ink composition precursor according to claim 1 or 2 with a vehicle to produce an ink composition.

14. The method of claim 13 , wherein the vehicle comprises 90% or more by weight of water, based on the total weight of the vehicle.

15. 3. A kit for producing an ink composition, comprising: the ink composition precursor according to claim 1 or 2; and a vehicle capable of uniformly dissolving the ink composition precursor.

16. (A) a colorant, (B) an amphoteric organic compound; (C) urea, and (D) Water and freeze-drying the ink composition comprising the above compound by a freeze-drying method to adjust the water activity to 0.50 or less, thereby producing an ink composition precursor.

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