Unit quantities, ink sets, and ink products

Abstract

To provide easily color-matchable inks and unit quantities. [Solution] An ink comprising an ink composition and a soluble film containing at least some of the components contained in the ink composition.

Description

Technical Field

[0001] The present invention relates to unit amounts of substances, ink sets, and ink products.

Background Art

[0002] By mixing a plurality of color ink compositions used in writing instruments such as fountain pens and markers, ink of a desired color tone is adjusted for the user (see, for example, Patent Document 1). Further, color adjustment is performed by mixing a powdery drawing material or a solid watercolor paint composition and water using a brush or the like (see, for example, Patent Documents 2 to 5, etc.).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the prior art, in order to use the color-adjusted ink obtained by mixing a desired amount of an ink composition with a solvent such as water or an ink composition of another color for color adjustment, the user needs to adjust the visual amount and the degree of contact of the pen for color adjustment, and it has been difficult to perform color adjustment easily.

[0005] The present invention has been made in view of the above, and provides a unit amount of substance, an ink set, and an ink product that can be easily color-adjusted. The purpose is to provide. [Means for solving the problem]

[0006] The above problems are solved by the present invention as described below.

[0007] In other words, the present invention aims to solve the above problems. "1. A unit quantity product consisting of a soluble film in which a water-soluble ink composition containing a colorant and an aqueous medium is individually encapsulated in unit quantities." 2. The unit quantity of the product described in paragraph 1, wherein the aqueous medium is water, and its content relative to the total mass of the water-soluble ink composition is 30% by mass or less. 3. The unit quantity according to paragraph 1 or 2, wherein the aqueous medium is a water-soluble organic solvent, and its content relative to the total mass of the ink composition is 0.1% by mass or more and 60% by mass or less. 4. The soluble film has a thickness of 10 μm or more and 200 μm or less, and is a unit quantity as described in any one of paragraphs 1 to 3. 5. The unit quantity of the unit quantity of the unit quantity is 1.0 g or more and 100.0 g or less, as specified in any one of paragraphs 1 to 4. 6. The unit quantity of any one of items 1 to 5, wherein the soluble film is a water-soluble film. 7. An ink set containing the unit quantity specified in any one of paragraphs 1 through 6. 8. Ink products containing the unit quantity specified in any one of paragraphs 1 to 6. [Effects of the Invention]

[0008] According to the present invention, a unit quantity, ink set, and ink product that can be easily color-matched are available. We can provide this. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 shows the measurement results of the absorption wavelengths of the ink compositions in the examples. [Modes for carrying out the invention]

[0010] Hereinafter, embodiments of the present invention will be described in detail. In this specification, "parts", "%", "ratio", etc. indicating formulation are based on mass unless otherwise specified.

[0011] The ink of this embodiment includes an ink composition and a soluble film containing at least some of the components contained in the ink composition.

[0012] The soluble film contains at least some of the components contained in the ink composition. The soluble film contains, for example, at least some of the components contained in the ink composition as individual unit amounts per unit amount.

[0013] The ink of this embodiment includes an ink composition and a soluble film containing at least some of the components contained in the ink composition. Therefore, the user can easily perform color adjustment to a desired color by using the unit amount objects formed by the soluble film containing at least some of the components contained in the ink composition for the desired number of color adjustments.

[0014] In this embodiment, color adjustment means making the ink composition into a color-adjusted ink in a usable state. The usable state means a state that can be applied to dyeing an object such as cloth or writing with a writing instrument. Specifically, in this embodiment, color adjustment means adjusting the color-adjusted ink by at least one of adjusting the amount used for color adjustment of each of the one or more color ink compositions and adjusting the amount used for color adjustment of each of the plurality of components contained in the ink composition. <00,00085> Also, in this embodiment, the color-adjusted ink will be described as a color-adjusted ink.

[0016] <Ink composition> The ink composition contained in the ink of this embodiment will be described in detail.

[0017] The ink composition contained in the ink of this embodiment may be either a single-color ink composition or a plurality of ink compositions of different colors.

[0018] When the ink compositions contained in the ink are a plurality of ink compositions of different colors, the ink compositions are preferably a first ink composition, a second ink composition, and a third ink composition, each having a maximum absorption wavelength in the visible light region and different colors from each other. The difference in the maximum absorption wavelengths of these first ink composition, second ink composition, and third ink composition preferably satisfies the following relationship.

[0019] The difference between the maximum absorption wavelength of the first ink composition and the maximum absorption wavelength of the second ink composition is preferably 100 nm or more, and the difference between the maximum absorption wavelength of the second ink composition and the maximum absorption wavelength of the third ink composition is preferably 100 nm or more.

[0020] The visible light region is a region of the wavelength range of light visible to the human eye. According to the definition of JIS Z8120, the lower limit of the visible light region is in the range of 360 nm or more and 400 nm or less, and the upper limit is in the range of 760 nm or more and 830 nm or less.

[0021] When the difference in the maximum absorption wavelengths of the plurality of ink compositions contained in the ink satisfies the above relationship, the range of adjustable color tones in the visible light region can be widened compared to the case where the difference in the maximum absorption wavelengths of at least one of the first ink composition and the second ink composition and the second ink composition and the third ink composition is less than 100 nm.

[0022] Therefore, when the difference in the maximum absorption wavelengths of the plurality of ink compositions contained in the ink satisfies the above relationship, inks with a wide range of color tones can be adjusted by mixing the first ink composition, the second ink composition, and the third ink composition at an arbitrary mixing ratio.

[0023] There are no upper limits on the difference between the maximum absorption wavelength of the first ink composition and the maximum absorption wavelength of the second ink composition, nor on the difference between the maximum absorption wavelength of the second ink composition and the maximum absorption wavelength of the third ink composition. These upper limits only need to be less than or equal to the difference between the lower and upper limits of wavelengths in the visible light region.

[0024] In the visible light region, considering the need to adjust a wide range of colors well, the difference between the maximum absorption wavelength of the first ink composition and the maximum absorption wavelength of the second ink composition, and the difference between the maximum absorption wavelength of the second ink composition and the maximum absorption wavelength of the third ink composition, is preferably 180 nm or less, more preferably 160 nm or less, and even more preferably 155 nm or less.

[0025] As described above, it is preferable that the first ink composition, the second ink composition, and the third ink composition each have a maximum absorption wavelength in the visible light region, the difference in maximum absorption wavelengths satisfies the above relationship, and that they are ink compositions of different colors. In this embodiment, a configuration in which the first ink composition is a cyan ink composition, the second ink composition is a magenta ink composition, and the third ink composition is a yellow ink composition will be described as an example.

[0026] Furthermore, if the ink composition contained in the ink is a multi-color ink composition of different colors, it is preferable that the ink composition further comprises a transparent fourth ink composition. By further comprising a transparent fourth ink composition, it becomes possible to easily adjust the density and brightness of the toned ink.

[0027] Furthermore, if the ink composition contained in the ink is a multi-color ink composition with different colors from each other, it is preferable that the ink composition further comprises a fifth ink composition. The fifth ink composition is an ink composition having a maximum absorption wavelength between any two of the maximum absorption wavelengths of the first ink composition, the second ink composition, and the third ink composition.

[0028] In this embodiment, we will describe, as an example, the case in which the fifth ink composition is an ink composition having a maximum absorption wavelength between the maximum absorption wavelength of the first cyan ink composition and the maximum absorption wavelength of the second magenta ink composition. Specifically, in this embodiment, we will describe, as an example, a form in which the fifth ink composition is a black ink composition.

[0029] By further incorporating a fifth black ink composition, it becomes possible to easily adjust the saturation of the color-matched ink.

[0030] In the following, the first ink composition may be referred to as the cyan ink composition, the second ink composition as the magenta ink composition, and the third ink composition as the yellow ink composition. The fourth ink composition may be referred to as the transparent ink composition, and the fifth ink composition as the black ink composition. Furthermore, when referring to the first, second, third, fourth, and fifth ink compositions collectively, they may simply be referred to as the ink composition.

[0031] Furthermore, considering the need to improve color adjustment and obtain a toned ink with excellent color clarity when mixed, the maximum absorption wavelength of the cyan ink composition is preferably 610 nm to 750 nm, the maximum absorption wavelength of the magenta ink composition is preferably 500 nm to 560 nm, and the maximum absorption wavelength of the yellow ink composition is preferably 400 nm to 500 nm.

[0032] Furthermore, considering the improvement of a wide range of color adjustments, the maximum absorption wavelength of the cyan ink composition is particularly preferably 650 nm to 700 nm, the maximum absorption wavelength of the magenta ink composition is particularly preferably 500 nm to 530 nm, and the maximum absorption wavelength of the yellow ink composition is particularly preferably 420 nm to 450 nm.

[0033] (Ink composition) This section provides a detailed explanation of each component included in the ink composition.

[0034] The ink composition comprises a colorant and a medium. However, transparent ink compositions may be in a form that does not contain a colorant.

[0035] (Coloring agent) The colorants included in the ink composition of this embodiment will now be described. The colorants used in the ink composition are not particularly limited and can be selected and used as appropriate, such as dyes and pigments.

[0036] The dye is not particularly limited as long as it can be dissolved or dispersed in an aqueous medium. Examples of dyes include acid dyes, basic dyes, reactive dyes, direct dyes, disperse dyes, and food colorings. These dyes can be used individually or in combination of two or more. The dye content is preferably 0.1% to 80% by mass, more preferably 0.1% to 60% by mass, and particularly preferably 0.1% to 40% by mass, based on the total mass of the ink composition.

[0037] Examples of acid dyes include CI Acid Red 18, CI Acid Orange 10, CI Acid Yellow 3, CI Acid Yellow 7, CI Acid Yellow 23 (Tartrazine), 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, CI Acid Violet 49, CI Acid Black 1, CI Acid Black 2, CI Acid Red 52, CI Acid Red 289, CI Acid Red 388, CI Acid Red 87 (Eosin), CI Acid Red 92 ( Examples include Phloxine, CI Acid Red 97, CI Acid Red 51 (Erythrosine), CI Acid Red 94 (Rose Bengal), Acridine Red (CI 45000), Rhodamine 110, Rhodamine 123, Rhodamine 6G (CI Basic Red 1), Rhodamine 6G Extra, Rhodamine 116, Rhodamine B (CI 45170), Tetramethylrhodamine perchlorate, Rhodamine 3B, Rhodamine 19, Sulforhodamine, Pyronin G (CI 45005), Rhodamine S (CI 45050), Rhodamine G (CI 45150), Ethylrhodamine B (CI 45175), Rhodamine 4G (CI 45166), Rhodamine 3GO (CI 45215), Sulforhodamine G, etc.

[0038] Examples of 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, Chrysoidine (CI 11270), Methyl Violet FN (CI 42535), Crystal Violet (CI 42555), Malachite Green (CI 42000), Victoria Blue FB (CI 44045), Acridine Orange NS (CI 46005), and Methylene Blue B (CI 52015).

[0039] Examples of direct dyes include CI Direct Red 28, CI Direct Yellow 44, CI Direct Blue 86, CI Direct Blue 87, CI Direct Violet 51, and CI Direct Black 19.

[0040] Examples of food colorings include CI Food Yellow 3, CI Food Black 2, Congo Red (CI22120), Direct Sky Blue 5B (CI24400), Violet BB (CI27905), Direct Deep Black EX (CI30235), Kayaras Black G Concentrate (CI35225), Direct Fast Black G (CI35255), and Phthalocyanine Blue (CI74180).

[0041] Examples of pigments include inorganic, organic, and processed pigments. Specifically, examples of pigments include carbon black, aniline black, ultramarine, lead yellow, titanium dioxide, iron oxide, phthalocyanine-based, azo-based, quinacridone-based, quinophthalone-based, triphenylmethane-based, perinone-based, perylene-based, dioxazine-based, aluminum pigments, pearl pigments, fluorescent pigments, phosphorescent pigments, and complementary pigments. In addition, microcapsule pigments may be used as pigments. Microcapsule pigments are obtained by dispersing a pigment in a medium and then encapsulating or solid-solubilizing a colored body made of a resin wall-forming material within a known microencapsulation method. Furthermore, as pigments, colored resin particles in which the pigment is covered with a transparent or translucent resin, or colorless resin particles colored with a pigment or dye can also be used.

[0042] These colorants may be used individually or in combination of two or more. The colorant content is preferably 0.1% to 80% by mass, more preferably 0.1% to 60% by mass, and particularly preferably 0.1% to 40% by mass, based on the total mass of the ink composition. Dyes and pigments may also be used in combination.

[0043] (medium) Next, the medium contained in the ink composition will be described. The ink composition contained in the ink of this embodiment may be either a water-soluble ink composition or an oil-soluble ink composition.

[0044] (aqueous medium) Water-soluble ink compositions may contain an aqueous medium as a medium.

[0045] The aqueous medium comprises at least water or a water-soluble organic solvent.

[0046] The type of water is not particularly limited; for example, tap water, deionized water, ultrafiltered water, distilled water, etc., can be used.

[0047] The water content relative to the total mass of the ink composition is preferably as low as possible. For example, the water content relative to the total mass of the ink composition is preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 10% by mass or less, and particularly preferably 5% by mass or less.

[0048] By setting the water content relative to the total mass of the ink composition within the above range, film stability can be improved when a water-soluble film is used as the soluble film. Furthermore, by suppressing the water content of the ink composition, the amount of preservatives contained in the ink composition can be suppressed, thereby improving safety, such as suppressing skin sensitization.

[0049] Examples of water-soluble organic solvents include (i) polyhydric alcohols such as dihydric alcohols like ethylene glycol, diethylene glycol, triethylene glycol, and polyethylene glycol, or trihydric alcohols like glycerin; (ii) alcohols such as methanol, ethanol, 1-propanol, 2-propanol, isopropanol, isobutanol, t-butanol, propagyl alcohol, allyl alcohol, 3-methyl-1-butyne-3-ol, ethylene glycol monomethyl ether acetate, and other higher alcohols; and (iii) glycol ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, 3-methoxybutanol, or 3-methoxy-3-methylbutanol.

[0050] The content of the water-soluble organic solvent is preferably 0.1% by mass or more and 80% by mass or less, more preferably 0.1% by mass or more and 60% by mass or less, and particularly preferably 0.1% by mass or more and 40% by mass or less, based on the total mass of the ink composition.

[0051] (oily medium) Oil-soluble ink compositions may contain an oily medium as a medium.

[0052] Examples of oily media include glycol ether solvents such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol dimethyl ether, ethylene glycol monophenyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, diethylene glycol dimethyl ether, 3-methoxybutanol, and 3-methoxy-3-methylbutanol; glycol solvents such as diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, butylene glycol, and ethylene glycol; alcohol solvents (aliphatic alcohols, aromatic alcohols, etc.) such as benzyl alcohol, methanol, ethanol, 1-propanol, 2-propanol, isopropanol, isobutanol, t-butanol, propagyl alcohol, allyl alcohol, 3-methyl-1-butyne-3-ol, ethylene glycol monomethyl ether acetate, and other higher alcohols; and organic solvents such as hydrocarbon solvents such as hexane, toluene, and xylene. These may be used individually or in combination of two or more.

[0053] (Other additives) The medium contained in the ink composition of this embodiment may include various additives such as pH adjusters, humectants, surfactants, resins, preservatives, rust inhibitors, chelating agents, and fragrances for the purpose of improving the ink's physical properties and functions.

[0054] Examples of pH adjusting agents include basic inorganic compounds such as ammonia, sodium carbonate, sodium phosphate, and sodium hydroxide; water-soluble basic organic compounds such as sodium acetate, alkanolamines such as triethanolamine and diethanolamine; amines containing ethylene oxide such as lactic acid and citric acid, oxyethylene alkylamines, and polyoxyethylene alkylamines; alkylamines such as laurylamine and stearylamine; and aliphatic amines such as dimethylalkylamines such as distearylamine, dimethyllaurylamine, dimethylstearylamine, and dimethyloctylamine.

[0055] The pH adjusting agent content is preferably 0.1% to 80% by mass, more preferably 0.1% to 60% by mass, and particularly preferably 0.1% to 40% by mass, based on the total mass of the ink composition.

[0056] Examples of humectants include urea and sorbitol. The content of the humectant is preferably 0.1% to 80% by mass, more preferably 0.1% to 60% by mass, even more preferably 0.1% to 40% by mass, and particularly preferably 0.1% to 20% by mass, based on the total mass of the ink composition.

[0057] As surfactants, known surfactants used in inks can be used. Examples include polyoxyalkylene surfactants, acetylene surfactants, fluorine surfactants, silicone surfactants, phosphate ester surfactants, fatty acids, and fatty acid esters.

[0058] In this embodiment, it is preferable to use at least one of a polyoxyalkylene-based surfactant and an acetylene-based surfactant as the surfactant.

[0059] Examples of polyoxyalkylene surfactants include polyoxyethylene polyoxypropylene glycol and polyoxyethylene polyoxypropylene alkyl ether. Polyoxyethylene polyoxypropylene alkyl ether is a compound represented by the following general formula (1), and is a copolymer having a structure in which ethylene oxide and propylene oxide are polymerized in any order. Polyoxyethylene polyoxypropylene glycol is a compound in which R in general formula (1) is H.

[0060] [ka]

[0061] In general formula (1), R represents an alkyl group or H, and m and n each independently represent an integer between 1 and 40.

[0062] Examples of acetylene-based surfactants include acetylene alcohol-based surfactants and acetylene glycol-based surfactants. Specifically, examples include 2,4,7,9-tetramethyl-5-decine-4,7-diol and alkylene oxide adducts of 2,4,7,9-tetramethyl-5-decine-4,7-diol, as well as 2,4-dimethyl-5-decine-4-ol and alkylene oxide adducts of 2,4-dimethyl-5-decine-4-ol.

[0063] As for the surfactant, from the viewpoint of suppressing blotting, bleeding, and show-through of the colored ink, it is preferable to use a polyoxyalkylene-based surfactant among the above surfactants, and it is even more preferable to use polyoxyethylene polyoxypropylene glycol.

[0064] Furthermore, it is particularly preferable to use polyoxyethylene polyoxypropylene glycol, which has the following general formula (2).

[0065] [ka]

[0066] In general formula (2), a, b, and c are all positive numbers.

[0067] Furthermore, the average molecular weight of polyoxyethylene polyoxypropylene glycol is preferably 100 to 100,000, more preferably 1,000 to 50,000, even more preferably 5,000 to 30,000, and particularly preferably 10,000 to 15,000.

[0068] Ink dripping refers to the phenomenon where, even when not writing, when the pen tip of a pen using colored ink is held vertically downwards, the colored ink may overflow due to changes in atmospheric pressure or leak due to shock or vibration. In the following, vertically downwards may be simply referred to as downwards. Transparent ink compositions, which do not contain colorants, are particularly prone to dripping. For this reason, transparent ink compositions preferably contain polyoxyethylene polyoxypropylene glycol as a surfactant.

[0069] The surfactant content is preferably 0.001% by mass or more and 20% by mass or less, relative to the total mass of the ink composition, and more preferably 0.005% by mass or more and 10% by mass or less.

[0070] Examples of preservatives include 2-methyl-4-isothiazolin-3-one, 1,2-benzisothiazolin-3-one, 2-n-octyl-4-isothiazolin-3-one, 2-methyl-4,5-trimethylene-4-isothiazolin-3-one, N-(n-butyl)-1,2-benzisothiazolin-3-one, 2-pyridinethiol-1-oxide sodium, 3-iodo-2-propynylbutylcarbamate, sodium benzoate, benzotriazole, and phenol. Hereafter, 1,2-benzisothiazolin-3-one may be abbreviated as BIT.

[0071] Examples of rust inhibitors include benzotriazole and its derivatives, tolyltriazole, dicyclohexylammonium nitride, diisopropylammonium nitride, sodium thiosulfate, saponin, or dialkylthiourea. Water-soluble resins such as acrylic resins, alkyd resins, cellulose derivatives, polyvinylpyrrolidone, and polyvinyl alcohol can also be used. Furthermore, resin emulsions containing acrylic resins, urethane resins, styrene-butadiene resins, polyester resins, vinyl acetate resins, etc., can be added.

[0072] Furthermore, fluorine-based surfactants, nonionic, anionic, or cationic surfactants, and defoaming agents such as dimethylpolysiloxane can be added to improve the penetration of the ink composition.

[0073] Examples of chelating agents include ethylenediaminetetraacetic acid (EDTA), hydroxyethylenediaminetriacetic acid (HEDTA), glycol etherdiaminetetraacetic acid (GEDTA), nitrilotriacetic acid (NTA), hydroxyethyliminodiacetic acid (HIDA), dihydroxyethylglycine (DHEG), diethylenetriaminepentaacetic acid (DTPA), triethylenetetraminehexaacetic acid (TTHA), and their alkali metal salts, ammonium salts, or amine salts.

[0074] Considering the need for sufficient alkaline components and the need to minimize changes in the physical properties and performance of the ink composition before and after the addition of the chelating agent, it is preferable to use aminocarboxylic acids and their salts as chelating agents, and more preferably ethylenediaminetetraacetic acid (EDTA) and its salts.

[0075] Ink compositions containing yellow colorants may present challenges in terms of ink color clarity during mixing, such as dullness of the ink when mixed, and may also be prone to the "flowering" phenomenon. The flowering phenomenon is a phenomenon in which solid components such as colorants in the ink composition precipitate on the pen tip of a writing instrument due to the evaporation of water.

[0076] Therefore, among the colorants mentioned above, it is preferable to use CI Acid Yellow 23 (tartrazine) as the colorant included in the yellow ink composition, from the viewpoint of improving the vividness of the ink color development when mixed.

[0077] Furthermore, the medium contained in the ink composition preferably contains polyhydric alcohols and alkanolamines from the viewpoint of suppressing the flowering phenomenon. In addition, considering the effect of further suppressing the flowering phenomenon, the medium contained in the ink composition preferably further contains urea.

[0078] Furthermore, from the viewpoint of suppressing the flowering phenomenon, it is preferable to use glycerin as the polyhydric alcohol. Moreover, in order to improve the long-term stability of all ink compositions, including the cyan, magenta, and yellow ink compositions, and to consider the ink stability of the mixed inks, it is particularly preferable that the polyhydric alcohol comprises glycerin and diethylene glycol.

[0079] Furthermore, alkanolamines are compounds having a hydroxyl group and an amino group on an alkane skeleton. In this embodiment, it is preferable to use an alkanolamine represented by the following formula (3).

[0080] [ka]

[0081] In formula (3), R1 represents an ethylene group, a trimethylene group, or a propylene group, and R2 and R3 independently represent hydrogen, a methyl group, an ethyl group, or a -R1-OH group.

[0082] Specific examples of such alkanolamines include, for instance, methylethanolamine, monoisopropanolamine, diethylethanolamine, monoethanolamine, propanolamine, methyldiethanolamine, diethanolamine, and triethanolamine.

[0083] In this embodiment, considering the long-term stability of the color-matched ink and the suppression of the flowering phenomenon, it is preferable to use triethanolamine, which is weakly basic, among the alkanolamines mentioned above.

[0084] Therefore, considering the suppression of the flowering phenomenon and the long-term stability of the ink composition and the toned ink, the medium contained in the ink composition is particularly preferably composed of glycerin, triethanolamine, and urea, and more preferably composed of glycerin, diethylene glycol, triethanolamine, and urea.

[0085] Furthermore, if the ink composition contained in the ink consists of multiple ink compositions of different colors, it is preferable that the difference in the content of each colorant in the multiple ink compositions be 0% by mass or more and less than 1.0% by mass. Moreover, it is even more preferable that this difference in content be 0% by mass or more and 0.5% by mass or less, particularly preferable that be 0% by mass or more and 0.1% by mass or less, and most preferable that be 0% by mass.

[0086] If the difference in the content of each colorant in multiple ink compositions is within the above range, the dissolution or dispersion state of the colorants in the multiple ink compositions will be substantially the same. Therefore, when mixing multiple ink compositions to create a color, changes in the concentration of the colorants are less likely to occur, which suppresses aggregation and precipitation of the colorants and improves the ink stability of the mixed ink.

[0087] Furthermore, it is preferable that the constituent components of the media included in a multi-color ink composition are of the same type. Constituent components refer to the type of colorant, the type of solvent, the type of pH adjuster, the type of surfactant, etc. By making the constituent components of the media included in a multi-color ink composition the same, when the multi-color ink compositions are mixed to create a color, changes in the concentration of the constituent components of the media are less likely to occur. This suppresses aggregation and precipitation of colorants, and improves the ink stability of the mixed ink.

[0088] (Method for manufacturing ink composition) The ink composition contained in the ink of this embodiment can be manufactured by any conventionally known method. For example, it can be manufactured by blending the required amounts of each component and mixing them using various stirrers such as magnetic stirrers, propeller stirrers, homogenizer stirrers, homodispersers, homomixers, or rotational and revolutionary stirrers, or various dispersers such as bead mills.

[0089] In this embodiment, when the ink composition contained in the ink is a multi-color ink composition of different colors, by adjusting the type of colorant added, each of the cyan, magenta, and yellow ink compositions is produced such that each has a maximum absorption wavelength in the visible light region, the difference in maximum absorption wavelengths satisfies the aforementioned relationship, and each is of a different color.

[0090] Furthermore, by adjusting the type of colorant added, it is possible to produce a black ink composition whose maximum absorption wavelength satisfies the aforementioned relationship. That is, it is possible to produce a black ink composition whose maximum absorption wavelength falls between the maximum absorption wavelengths of any two of the cyan, magenta, and yellow ink compositions.

[0091] The transparent ink composition may be manufactured as an ink composition that does not contain colorants.

[0092] The maximum absorption wavelength of the ink composition is measured by the following method. Specifically, the maximum absorption wavelength is measured using a UV-2550 ultraviolet-visible spectrophotometer manufactured by Shimadzu Corporation. The ink composition is diluted 100,000 times with deionized water, and the solution is loaded into a quartz cell with a path length of 10 mm. The absorption wavelength is measured under the conditions of a wavelength range of 400 nm to 900 nm, a medium scan speed, and a sampling pitch of 2.0 nm. The maximum absorption wavelength is then identified from the measurement results.

[0093] (Soluble film) This section will explain soluble films.

[0094] The soluble film can be any film that is soluble in a solvent. More specifically, the soluble film is either a water-soluble film or an oil-soluble film. When the ink composition to be incorporated is a water-soluble ink composition, it is preferable to use a water-soluble film for the soluble film. When the ink composition to be incorporated is an oil-soluble ink composition, it is preferable to use an oil-soluble film for the soluble film.

[0095] The thickness of the soluble film should be such that the components contained within the soluble film do not leak out of the film at room temperature, and should be adjusted according to the type and amount of components contained, the composition of the soluble film, etc. For example, the thickness of the soluble film is preferably in the range of 10 μm to 200 μm, 20 μm to 150 μm, or 35 μm to 125 μm.

[0096] (Water-soluble film) A water-soluble film can be any material that dissolves in water. Examples of water-soluble films include at least one selected from polyvinyl alcohol, polyvinylpyrrolidone, polyalkylene oxide, acrylamide, acrylic acid, cellulose, cellulose ether, cellulose ester, celluloseamide, polyvinyl acetate, polycarboxylic acid and salts, polyamino acids or peptides, polyamides, polyacrylamide, maleic acid / acrylic acid copolymers, pullulan, polysaccharides including starch and gelatin, xanthan gum, and natural rubbers such as kara rubber.

[0097] The water-soluble film is preferably at least one selected from polyacrylate and water-soluble acrylate copolymer, methylcellulose, sodium carboxymethylcellulose, dextrin, ethylcellulose, hydroxyethylcellulose, hydroxypropyl methylcellulose, maltodextrin, and polymethacrylate. More preferably, the water-soluble film is selected from polyvinyl alcohol, pullulan, polyvinyl alcohol copolymer and hydroxypropyl methylcellulose (HPMC), and even more preferably, polyvinyl alcohol, pullulan, and combinations thereof.

[0098] Particularly preferably, the water-soluble film is mainly composed of polyvinyl alcohol. Being the main component means, as described above, that the polyvinyl alcohol content relative to the total weight of the water-soluble film is 50% by weight or more.

[0099] Polyvinyl alcohol is biodegradable and has gas barrier properties. Therefore, by using a water-soluble film with polyvinyl alcohol as the main component, it is possible to protect the environment and suppress the oxidation of the ink composition or at least some of its components contained within the soluble film.

[0100] In addition to general polyvinyl alcohol, various modified polyvinyl alcohols such as anionic modified polyvinyl alcohol, silanol modified polyvinyl alcohol, and acetoacetyl modified polyvinyl alcohol can also be used as polyvinyl alcohol for water-soluble films. One type of polyvinyl alcohol may be used alone, or two or more types may be used in combination.

[0101] The molecular weight of the resin contained in the water-soluble film is not limited. For example, if the water-soluble film is mainly composed of polyvinyl alcohol, the weight-average molecular weight of the polyvinyl alcohol may fall within the ranges of 1,000 to 1,000,000, 10,000 to 300,000, or 20,000 to 150,000.

[0102] Water-soluble films are preferably soluble in room temperature water within 5 minutes. Solubility can be measured by placing the water-soluble film in a container of room temperature water and measuring the time it takes for its shape to change while stirring. Room temperature water is an example of a solvent used in the color matching of colored inks.

[0103] The solubility of water-soluble films, when polyvinyl alcohol is the main component, is adjusted by the degree of hydrolysis of the polyvinyl alcohol obtained by hydrolysis of polyvinyl acetate, the use of a crosslinking agent, or partial saponification (saponification degree 87% to 89%).

[0104] The water used as the solvent for the water-soluble film is not particularly limited and can include, for example, tap water, deionized water, ultrafiltered water, distilled water, etc.

[0105] (Oil-soluble film) An oil-soluble film can be any material that dissolves in oil components. Examples of oil-soluble films include at least one of the following: polyvinyl butyral resin / ketone resin / phenol resin / polyvinylpyrrolidone / vinyl acetate, acrylate, acrylate / silicone copolymer, polybutene, polyethylene, polyurethane-14, AMP-acrylate copolymer, octylacrylamide / acrylate copolymer, polyquaternium-11, vinylcaprolactam / vinylpyrrolidone, and methylacrylamide terpolymer.

[0106] It is preferable that the oil-soluble film dissolves within 5 minutes in the solvent used in the color matching of the colored ink. Solubility can be determined by placing the oil-soluble film into a container containing a solvent at room temperature and measuring the time it takes for the shape to change while stirring.

[0107] The oil component that serves as the solvent for the oil-soluble film is not particularly limited, and examples include glycol ether solvents such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol dimethyl ether, ethylene glycol monophenyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, diethylene glycol dimethyl ether, 3-methoxybutanol, and 3-methoxy-3-methylbutanol; glycol solvents such as diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, butylene glycol, and ethylene glycol; alcohol solvents such as benzyl alcohol, methanol, ethanol, 1-propanol, 2-propanol, isopropanol, isobutanol, t-butanol, propagyl alcohol, allyl alcohol, 3-methyl-1-butyne-3-ol, ethylene glycol monomethyl ether acetate, and other higher alcohols (aliphatic alcohols, aromatic alcohols, etc.); and organic solvents such as hydrocarbon solvents such as hexane, toluene, and xylene. Among these, aliphatic alcohols are preferred from the viewpoint of safety and stability with oil-soluble films, and more preferably lower aliphatic alcohols (with 1 to 4 carbon atoms) are preferred.

[0108] (Additives) The soluble film may contain one or more additive components. Examples of plasticizers include glycerol, ethylene glycol, diethylene glycol, propylene glycol, sorbitol, and mixtures thereof.

[0109] Furthermore, the soluble film may further contain an aversive agent. The aversive agent may be contained in any one of the following locations: on the surface of the soluble film, within the soluble film, or within the ink composition incorporated in the soluble film or within the components contained in the ink composition.

[0110] An aversive agent is any compound that produces an unpleasant taste when ingested or put in the mouth. Unpleasant tastes include bitterness, spiciness, pungent taste, unpleasant odor, sourness, coldness, or a combination thereof. The aversive agent may be a bittering agent. Preferably, the aversive agent is any compound that is safe for the human body and produces the unpleasant tastes described above.

[0111] The aversive agent may be selected from the group consisting of, for example, naringin, octaacetylsucrose, quinine hydrochloride, denatonium benzoate, capsicinoids (such as capsaicin), vanillyl ethyl ether, vanillyl propyl ether, vanillyl butyl ether, vanillin propylene, glycol acetal, ethyl vanillin propylene glycol acetal, capsaicin, gingerol, 4-(1-menthoxymethyl)-2-(3'-methoxy-4'-hydroxyphenyl)-1,3-dioxolane, pepper oil, pepper oleoresin, ginger oleoresin, nonylic acid vanillylamide, jambu oleoresin, sansho bark extract, sanshool, sanshoamide, black pepper extract, chavicin, piperine, spiranthol, and mixtures thereof.

[0112] The soluble film may be transparent, opaque, or translucent. The soluble film may also be colored. Furthermore, the soluble film may include a printable area. For example, the soluble film may include a printable area on which the incorporated ink composition or identification information of the components contained in the incorporated ink composition is printed.

[0113] The soluble film can be formed into a film shape by any thermoforming or plasticizing technique.

[0114] (Ink) (Unit quantity) The ink of this embodiment comprises an ink composition and a soluble film containing at least some of the components included in the ink composition.

[0115] The ink of this embodiment is provided as one unit quantity or a group of multiple unit quantities, each consisting of a soluble film containing at least some of the components included in the ink composition in unit quantities.

[0116] A unit quantity is an object in which at least some of the components contained in the ink composition are individually contained in predetermined unit quantities by a soluble film.

[0117] In detail, for example, a unit quantity comprises each of several ink compositions of different colors individually, in predetermined unit quantities.

[0118] For example, consider a case where the ink composition consists of a cyan ink composition, a magenta ink composition, and a yellow ink composition. In this case, the unit quantity can be an object that individually contains each of the cyan ink composition, magenta ink composition, and yellow ink composition in predetermined unit quantities. Alternatively, consider a case where the ink composition consists of a cyan ink composition, a magenta ink composition, a yellow ink composition, a black ink composition, and a transparent ink composition. In this case, the unit quantity can be an object that individually contains each of the cyan ink composition, magenta ink composition, yellow ink composition, black ink composition, and transparent ink composition in predetermined unit quantities.

[0119] Furthermore, the unit quantity may consist of a predetermined unit quantity of components individually included in each of several groups, which are formed by classifying the components contained in the ink composition according to predetermined classification conditions. The classification conditions can be predetermined.

[0120] For example, the classification criteria may be components belonging to colorants and components belonging to non-colorants. In this case, the unit quantity may be composed of colorants contained in the ink composition and components other than colorants contained in the ink composition, with each group individually containing predetermined unit quantities of components.

[0121] Alternatively, for example, a classification criterion may be that components that become unstable when coexisting are classified into different unit quantities. In this case, the unit quantity may be a unit quantity that encompasses multiple components contained in the ink composition, grouped by the components that exist stably even when coexisting. In other words, in this case, the unit quantity may be a structure in which multiple components contained in the ink composition are separately encompassed by a soluble film, with the components that become unstable when coexisting being classified into different unit quantities.

[0122] Alternatively, for example, components having the same function may be used as classification criteria. In this case, the unit quantity can be configured by classifying the multiple components contained in the ink composition into multiple groups based on the group of components having the same function, and individually including a predetermined unit quantity of the component for each group. Specifically, for example, a vehicle that has a function to promote drying in order to impart quick-drying properties to the color-matched ink and a vehicle that has a function to suppress bleeding and show-through of the color-matched ink can be individually included as separate unit quantities by a soluble film.

[0123] By defining the unit quantity as an object in which an ink composition, or at least some of the components contained in the ink composition, are individually enclosed in predetermined unit quantities by a soluble film, the following effects can be obtained.

[0124] In this embodiment, the ink composition contained in the ink, or at least some of the components contained in the ink composition, exist as separate unit quantities enclosed by a soluble film.

[0125] These unit quantities are then mixed during the color matching process to create a color-matched ink. In other words, the ink composition contained within the soluble film, or at least some of the components contained in the ink composition, exist as separate unit quantities before color matching and are mixed for the first time during color matching. This allows for improved stability, such as the time-dependent stability and suppression of precipitation, of the ink composition contained within the soluble film and at least some of the components of the ink composition that exist as unit quantities.

[0126] Furthermore, since the ink composition contained in the ink, or at least some of the components contained in the ink composition, exist as separate unit quantities enclosed by a soluble film, it is possible to reduce the number of containers that house the ink composition, reduce transportation costs, and reduce energy consumption such as CO2 emissions.

[0127] Furthermore, even when the unit quantity is stored in an ink container such as a glass bottle, the following effects can be obtained. Glass bottles are inexpensive, easy to mold, and easily achieve the desired strength. On the other hand, if a particularly inexpensive and versatile glass such as soda-lime glass is used as the glass bottle, there is a high possibility that the alkaline components in the glass will leach into the ink composition when the ink composition is stored in it for a long period of time. These leached alkaline components may react with the components of the water-soluble ink composition, potentially forming precipitates. As a result, these precipitates may cause blurring of the ink's lines or make writing impossible.

[0128] On the other hand, in this embodiment, the ink composition or at least some of the components contained in the ink composition are contained in the ink container in the form of unit quantities enclosed by a soluble film. Therefore, the ink composition contained in the ink of this embodiment is prevented from directly contacting the ink container at the stage before color mixing. Thus, the ink of this embodiment can suppress the generation of precipitates in the color-mixed ink.

[0129] The unit amounts of the ink composition or components contained in the ink composition that are contained in the soluble film may be predetermined according to the type of ink composition and the target application of the adjusted ink. The unit amounts are, for example, in the range of 0.1g to 10.0g, 0.5g to 50.0g, 1.0g to 100.0g, etc., but are not limited to these ranges.

[0130] Furthermore, at least a portion of the ink composition encompassed by the soluble film, or the components contained in the ink composition, may be either liquid or solid. Solids include, for example, powders.

[0131] (Method for producing unit quantities) The method for producing the unit quantity is not limited. For example, the ink composition or components contained in the ink composition can be produced by encapsulating the ink composition or components contained in the ink composition in unit quantities using a soluble film in a known manner.

[0132] For incorporating an ink composition or components contained in an ink composition using a soluble film, for example, a vertical pillow packaging machine, a rotary drum packaging machine, a pleated packaging machine, etc., can be used.

[0133] (Ink set) An ink set consists of a group of multiple unit quantities, each containing multiple color ink compositions and at least some of the components contained in each of the multiple color ink compositions, enclosed in a soluble film in unit quantities.

[0134] (Ink products) A unit quantity consisting of a soluble film containing at least some of the components of an ink composition is provided, for example, as an ink product by housing it in an ink container made of glass or the like. Alternatively, a group of unit quantities may be provided as an ink product.

[0135] Furthermore, an ink product may consist of a group of unit quantities or an ink container containing unit quantities, an empty container, a dropper, a graduated cylinder, and at least one of a color matching sample. An empty container is an empty container used for mixing one or more unit quantities. A dropper is an example of a component used to draw up the solvent that dissolves the soluble film contained in the unit quantities and transfer it to another container such as an empty container. A graduated cylinder is an example of a component used for quantifying the solvent of the soluble film. A color matching sample is a paper or electronic medium containing information indicating the correspondence between the mixing ratio of the ink composition, the type and number of unit quantities required to achieve the mixing ratio, and the color achieved by the mixing ratio.

[0136] The user can create a toned ink of any desired color by taking out a desired number of units of the unit quantity material and placing them into an empty container, and then adding water or an oily component, which is the solvent for the soluble film contained in the unit quantity material, to the empty container and mixing them.

[0137] Furthermore, users can easily mix colored inks to their desired shade by adjusting at least one of the types and quantities of unit materials used for color matching.

[0138] Furthermore, the color-matching ink of this embodiment can be used as a color-matching ink for various writing instruments such as fountain pens, ballpoint pens, brush pens, calligraphy pens, dip pens, and various markers. In other words, the ink composition of this embodiment can be used as an ink composition for writing instruments. Moreover, the color-matching ink of this embodiment is not limited to writing instruments, but can also be used as a coloring liquid for various dyeing media such as cloth and paper.

[0139] The structure and shape of the writing instrument to which the color-matched ink of this embodiment can be applied are not particularly limited.

[0140] For example, writing instruments include marking pens with fiber tips, felt tips, or plastic tips, ballpoint pens with ballpoint pen tips, and fountain pens with metal tips.

[0141] Furthermore, the writing instrument may have an ink reservoir inside the writing instrument body into which the color-matched ink is directly filled. Alternatively, the writing instrument may have an ink reservoir for filling the color-matched ink located inside the writing instrument body.

[0142] Ink storage containers include cartridge-type containers that can be detachably replaced on the writing instrument body or pen nib and are pre-filled with color-matched ink, and ink-filling types equipped with an ink-filling mechanism that allows color-matched ink to be filled from an ink container such as an ink bottle.

[0143] The ink filling mechanism may be directly installed within the writing instrument body, or it may be detachably attached to the writing instrument body or nib, like a converter.

[0144] Furthermore, writing instruments include capped writing instruments with a cap that covers the pen tip, and retractable writing instruments such as click-type, twist-type, and slide-type writing instruments in which the pen tip can be stored inside the barrel.

[0145] Furthermore, the ink supply mechanism in the writing instrument is not particularly limited, and the ink supply mechanism may be, for example, one of the following mechanisms 1 to 4.

[0146] (Mechanism 1) A mechanism that supplies color-matched ink to the pen tip, equipped with an ink guide core made of fiber bundles or the like as an ink flow rate adjustment member. (Mechanism 2) A mechanism that supplies color-matched ink to the pen tip via a pen nib having a comb groove for temporarily storing color-matched ink, an ink flow passage, and an air passage. (Mechanism 3) A mechanism that supplies color-matched ink to the pen tip, equipped with an ink flow rate adjustment member using a valve mechanism. (Mechanism 4) A mechanism for supplying color-matched ink directly to the pen tip from an ink reservoir or barrel equipped with a pen tip.

[0147] In particular, the writing instrument using the color-matched ink of this embodiment can be used particularly suitably in writing instruments having the above-mentioned (mechanism 2), that is, in writing instruments equipped with a pen tip having a comb groove for temporarily storing the color-matched ink, an ink flow passage, and an air passage.

[0148] This is because, using the color-matched ink of this embodiment, the pen nib functions effectively, supplying the color-matched ink from the ink reservoir to the writing tip, and easily temporarily holding the color-matched ink that spills out due to an increase in internal pressure in the ink reservoir. Furthermore, the ink discharge performance from the pen tip is improved, making it possible to form clear lines with less smudging. In addition, even if the internal pressure of the ink reservoir changes due to changes in ambient temperature or the attachment and removal of the cap, the color-matched ink is retained between the comb grooves, suppressing ink leakage from the pen tip and providing excellent resistance to ink blotting.Specific examples of the writing instruments mentioned above include fountain pens, ballpoint pens, and calligraphy pens, but among them, the ink composition of this embodiment is particularly suitable for use as an ink composition for fountain pens. [Examples]

[0149] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[0150] (Cyan ink composition (1)) • Diethylene glycol 1.00 part Glycerin 1.00 part Triethanolamine 2.00 parts ·Urea 1.00 parts • Unilube 75DE-2620 (manufactured by NOF Corporation) (Polyoxyethylene polyoxypropylene glycol) 0.05 parts Department WaterBlue105 (CI Acid Blue 90) 2.00 liters The above composition was stirred and mixed using a rotating agitator to obtain a cyan-colored ink composition (1).

[0151] (Ink composition (2) to ink composition (42)) An ink composition was obtained in the same manner as ink composition (1), except that the composition of each component contained in the ink composition was changed to those shown in Tables 1 to 4.

[0152] The absorption wavelengths of each of the prepared ink compositions (1) to (36) were measured using a UV-2550 ultraviolet-visible spectrophotometer manufactured by Shimadzu Corporation. The ink compositions were diluted 100,000 times with deionized water, and the solutions were loaded into a quartz cell with a path length of 10 mm. The measurements were taken under the conditions of a wavelength range of 400 nm to 900 nm, a medium scan speed, and a sampling pitch of 2.0 nm. The maximum absorption wavelength was then identified from the measurement results. The results are shown in Tables 1 to 4.

[0153] [Table 1]

[0154] [Table 2]

[0155] [Table 3]

[0156] [Table 4]

[0157] (Preparation of unit quantities) For each of the ink compositions (1) to (42), the mass obtained by converting the proportion of each ink composition listed in Tables 1 to 4 into grams was used as the unit quantity, and was encased by heat welding using Kuraray's POVA, a water-soluble film mainly composed of polyvinyl alcohol. Through this encasing process, inks were prepared consisting of a group of unit quantities in which each ink composition was individually encased by a water-soluble film, with each quantity equal to the mass obtained by converting the proportion of each ink composition listed in Tables 1 to 4 into grams.

[0158] (Evaluation of film stability) The stability of the water-soluble films was evaluated by observing the state of the films when five unit quantities of each ink composition (1) to (42) were left for 24 hours in an environment of 20°C and 65% humidity, based on their resistance to solubility and swelling. The evaluation criteria are shown below. The evaluation results are shown in Tables 1 to 4.

[0159] A: No change in the shape of the water-soluble film. No leakage of the encapsulated ink composition to the outside. B: The water-soluble film shows deformation in its shape. There is no leakage of the encapsulated ink composition to the outside. C: The water-soluble film has deformed in shape. The encapsulated ink composition has leaked out.

[0160] (Example 1) The ink set used in Example 1 consisted of a unit quantity containing a cyan ink composition (5) encapsulated in the water-soluble film, a unit quantity containing a magenta ink composition (17) encapsulated in the water-soluble film, a unit quantity containing a yellow ink composition (27) encapsulated in the water-soluble film, a unit quantity containing a black ink composition (34) encapsulated in the water-soluble film, and a unit quantity containing a transparent ink composition (38) encapsulated in the water-soluble film.

[0161] (Examples 2 to 32) An ink set was prepared in the same manner as in Example 1, except that the combination of ink compositions used as the ink set, i.e., the unit quantity of the ink composition encapsulated in a water-soluble film, was changed to the combinations shown in Tables 5 and 6.

[0162] [Table 5]

[0163] [Table 6]

[0164] Figure 1 shows the measurement results of the absorption wavelengths of ink compositions (1) to (36) used in the examples. In Figure 1, the horizontal axis represents wavelength, and the vertical axis represents absorbance. The correspondence between the absorption wavelength diagrams shown in Figure 1 and the ink compositions is as follows.

[0165] Diagram A1: Ink composition (1) Diagram A2: Ink composition (2)(3) Diagram A3: Ink composition (4)(5)(6)(7)(8)(9)(10) Diagram A4: Ink composition (11)(12) Diagram A5: Ink composition (13)(14)(15)(16)(17)(20)(21) Diagram A6: Ink composition (18) Diagram A7: Ink composition (19) Diagram A8: Ink composition (22)(23) Diagram A9: Ink composition (24)(25) Diagram A10: Ink composition (26)(27)(28)(29)(30)(31)(32)(33) Diagram A11: Ink composition (34)(35)(36)

[0166] For the ink sets of Examples 1 to 32, the difference in maximum absorption wavelengths between the cyan ink composition and the magenta ink composition, and the difference in maximum absorption wavelengths between the magenta ink composition and the yellow ink composition were calculated. The calculation results are shown in Tables 5 and 6.

[0167] (evaluation) -Color adjustment evaluation- Color adjustment evaluations were performed for each of the ink sets from Examples 1 to 32.

[0168] For color adjustment evaluation, the mixing ratio of the ink compositions contained in each ink set was adjusted, and the adjustable wavelength range in the visible light region was confirmed. The evaluation criteria are shown below. The evaluation results are shown in Tables 5 and 6.

[0169] A: It can be mixed to a wide range of shades. B: Slightly adjustable to a wide range of tones. C: Cannot be adjusted to a wide range of tones.

[0170] —Ink Stability Evaluation— The ink stability during mixing was evaluated for each of the ink sets from Examples 1 to 32. Specifically, for each ink set, the ink compositions of each color used in each example shown in the table were mixed in the same number ratio (the same number of unit quantities between the colors of the ink compositions), and 500 ml of deionized water was added to prepare the mixed ink. 100 ml of the mixed ink was placed in a glass container (AS ONE Corporation, product name Labran screw-cap bottle No. 8, 110 ml), and the container was left in a 50°C environment for 12 weeks with the lid on. The mixed ink was then sampled from the bottom of the container and observed under a microscope. The evaluation criteria for ink stability are shown below. The evaluation results are shown in Tables 5 and 6.

[0171] Evaluation Criteria for Ink Stability Assessment A: No precipitates are observed at all. B: Precipitates are observed.

[0172] —Ink color clarity evaluation— For each of the ink sets from Examples 1 to 32 (only those examples containing yellow and cyan ink compositions), the vividness of the handwriting produced by the toned ink was evaluated. Specifically, for each ink set, the yellow ink composition and the cyan ink composition were mixed in a ratio of 49:1 by number, and then 5,000 ml of deionized water was added to prepare the toned ink.

[0173] 0.4 ml of the adjusted color-matched ink was injected into a resin converter (Pilot Corporation, CON-40, ink capacity 0.4 ml) through its opening. This converter was attached to a writing instrument with a fountain pen-type nib (Pilot Corporation, fountain pen, product name: Kakuno (nib width M)). This writing instrument was used as the test pen. The test pen was held with the nib facing downwards for a while to allow the filled ink to flow to the nib and make it ready for writing. Then, arbitrary characters were written with the test pen, and the resulting handwriting was visually observed to evaluate the ink color clarity. The evaluation criteria for ink color clarity are shown below. The evaluation results are shown in Tables 5 and 6.

[0174] Evaluation Criteria for Ink Color Vividness A: The vivid color tones can be adjusted. B: The colors are dull, and it's impossible to adjust the vibrant tones.

[0175] The ink compositions (1) to (42) used in Examples 1 to 32 are unit quantities contained within a water-soluble film. Therefore, color matching was easier compared to mixing ink compositions that are not contained within a water-soluble film by directly placing them in a container.

[0176] Furthermore, the ink sets of Examples 1 to 32 were adjustable to a wide range of colors.

[0177] Furthermore, as shown in Examples 1 to 3, the ink set of Example 1, which includes a black ink composition, was able to be adjusted to a wider range of colors compared to the ink sets of Examples 2 and 3, which do not include a black ink composition.

[0178] Furthermore, Examples 1 to 4, Examples 11 to 17, and Examples 21 to 32, which used yellow ink compositions with tartrazine as a coloring agent, showed better ink color clarity evaluation results compared to Examples 5 to 10, which used yellow ink compositions with coloring agents other than tartrazine.

[0179] Furthermore, Examples 1 to 4, 9, 10, 13, 26, 27, and 30 to 32, which satisfy both requirements of having the same type of constituent components in the aqueous medium of the multiple ink compositions and having a difference of 0% by mass or more and less than 1.0% by mass in the content of cyan, magenta, and yellow colorants, showed better evaluation results for ink stability compared to Examples 5 to 8, 11, 12, 14 to 17, 21 to 25, 28, and 29, which do not satisfy at least one of these requirements for main components and content. [Industrial applicability]

[0180] The ink according to the present invention can be used as an ink for various writing instruments such as fountain pens, ballpoint pens, brush pens, calligraphy pens, dip pens, and various markers. Furthermore, the ink according to the present invention is not limited to writing instruments, but can be used as a coloring liquid for various dyeing media such as cloth and paper.

Claims

1. A unit quantity product comprising a soluble film in which a water-soluble ink composition containing a colorant and an aqueous medium is individually encapsulated in unit quantities.

2. The unit quantity according to claim 1, wherein the aqueous medium is water, and its content relative to the total mass of the water-soluble ink composition is 30% by mass or less.

3. The unit quantity according to claim 1 or claim 2, wherein the aqueous medium is a water-soluble organic solvent, and its content relative to the total mass of the ink composition is 0.1% by mass or more and 60% by mass or less.

4. The unit quantity according to any one of claims 1 to 3, wherein the thickness of the soluble film is 10 μm or more and 200 μm or less.

5. The unit quantity of the unit quantity is 1.0 g or more and 100.0 g or less, as described in any one of claims 1 to 4.

6. The unit quantity according to any one of claims 1 to 5, wherein the soluble film is a water-soluble film.

7. An ink set comprising the unit quantity of any one of claims 1 to 6.

8. An ink product comprising the unit quantity of any one of claims 1 to 6.

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