Water-based ink composition for felt-tip pens

Abstract

To provide an aqueous ink composition for a signature pen capable of suppressing a blur when an aqueous pen is used after long-term storage.SOLUTION: An aqueous ink composition for a signature pen contains at least a pigment, resin, humectant, and water. The aqueous ink composition for a signature pen of 10 g is put in a cylindrical vessel of 21 mm inner diameter and 14 ml capacity and reserved for 4 weeks at 50°C. After that, the cumulative 10% volume particle diameter D10Lo measured by a Dynamic Light Scattering Method (DLS) of the aqueous ink composition for a signature pen taken from within 5 mm from the vessel bottom and the cumulative 10% volume particle diameter D10Up measured by a Dynamic Light Scattering Method (DLS) of the aqueous ink composition for a signature pen taken from within 5 mm from the liquid level of the ink satisfy the relation D10Lo / D10Up<1.6.SELECTED DRAWING: None

Description

[Technical Field] 【0001】 This invention relates to an aqueous ink composition for felt-tip pens. In particular, it relates to an aqueous ink composition for felt-tip pens that, when used in aqueous marking pens and aqueous felt-tip pens, exhibits less smudging during writing after storage. [Background technology] 【0002】 Various types of water-based ink compositions for felt-tip pens are known. However, when water-based marking pens and felt-tip pens using these water-based ink compositions were used for writing after long-term storage, smudging or skipping sometimes occurred. Such streaking is thought to be caused by the sedimentation of ink components, and measures are taken to prevent it, such as adjusting (increasing) the viscosity of the water-based ink composition for felt-tip pens, or adjusting the average dispersion particle size (D50) of specific ink components. 【0003】 Patent Document 1 describes that a felt-tip pen using an aqueous ink composition for felt-tip pens containing water, a colorant, and silicone-acrylic copolymer particles with an average particle size of 100 nm to 900 nm does not produce any smudging in the lines drawn when first used, even after being stored for 24 hours in a 25°C, 65% RH environment with the cap removed. Patent Document 2 describes a felt-tip pen using an aqueous pigment ink composition in which two or more pigments are blended as colorants, wherein the settling index and the difference in settling indices of the pigments are within a specific range, and the pen does not smudge even when left for a long period of time. [Prior art documents] [Patent Documents] 【0004】 [Patent Document 1] Japanese Patent Publication No. 2021-11547 [Patent Document 2] Japanese Patent Publication No. 2001-158868 【Summary of the Invention】 【Problems to be Solved by the Invention】 【0005】 The aqueous ink composition for a sign pen described in Patent Document 1 contains silicone-acrylic copolymer particles having an average particle diameter of 100 nm to 900 nm as an essential component, and it is difficult to apply this finding to an aqueous ink composition for a sign pen that does not require silicone-acrylic copolymer particles. The aqueous pigment ink composition described in Patent Document 2 contains two or more pigments as essential components, and it is difficult to apply it to the general aqueous ink composition for a sign pen. The problem to be solved by the present invention is to provide an aqueous ink composition for a sign pen that can suppress bleeding when writing after long-term storage of the aqueous pen. 【Means for Solving the Problems】 【0006】 As a result of intensive studies to solve the above problems, the present inventor has found that the above problems can be solved by a specific aqueous ink composition for a sign pen, and has completed the present invention. Specifically, it is as follows. [Item 1] An aqueous ink composition for a sign pen containing at least a pigment, a resin, a wetting agent, and water, After putting 10 g of the aqueous ink composition for a sign pen into a cylindrical container with an inner diameter of 21 mm and a volume of 14 ml and storing it at 50°C for 4 weeks, Collect the aqueous ink composition for a sign pen within 5 mm from the bottom surface of the container, and the cumulative 10% volume particle diameter D10 determined by the dynamic light scattering method (DLS: Dynamic Light Scattering) Lo and Collect the aqueous ink composition for a sign pen within 5 mm from the ink liquid surface, and the cumulative 10% volume particle diameter D10 determined by the dynamic light scattering method (DLS: Dynamic Light Scattering) Up are D10 LO / D10 Up<1.6 satisfies the relationship of An aqueous ink composition for a sign pen. [Item 2] An aqueous pen comprising a refill containing the aqueous ink composition for a sign pen according to Item 1. [Advantages of the Invention] 【0007】 According to the present invention, there is provided an aqueous ink composition for a sign pen that can suppress bleeding when writing after long-term storage of the aqueous pen. This aqueous ink composition for a sign pen can be suitably used as an aqueous ink composition for a marking pen, a sign pen, particularly a refill type sign pen. [Embodiments for Carrying Out the Invention] 【0008】 [Aqueous Ink Composition for Sign Pen] The aqueous ink composition for a sign pen of the present invention is an aqueous ink composition for a sign pen containing at least a pigment, a resin, a wetting agent, and water. Furthermore, the aqueous ink composition for a sign pen of the present invention is obtained by putting 10 g of the aqueous ink composition for a sign pen into a cylindrical container with an inner diameter of 21 mm and a capacity of 14 ml and storing it at 50°C for 4 weeks, collecting the aqueous ink composition for a sign pen within 5 mm from the bottom surface of the container, and the cumulative 10% volume particle diameter D10 determined by the dynamic light scattering method (DLS: Dynamic Light Scattering) Lo and collecting the aqueous ink composition for a sign pen within 5 mm from the ink liquid surface, and the cumulative 10% volume particle diameter D10 determined by the dynamic light scattering method (DLS: Dynamic Light Scattering) Up are D10 LO / D10 Up <1.6 satisfies the relationship of. The aqueous ink composition for a sign pen of the present invention may further contain a surfactant, a hydrophilic organic solvent, an antiseptic and antifungal agent, etc. Hereinafter, it will be described in detail. 【0009】 <Pigments> As the pigment, one or more of the various pigments conventionally used in aqueous ink compositions for felt-tip pens, such as inorganic pigments, organic pigments, and extender pigments, can be used to achieve the desired color tone. In the present invention, it is preferable to use a pigment that can be used as a coloring agent. 【0010】 Examples of inorganic pigments include one or more selected from the group consisting of carbon black, graphite, titanium dioxide, zinc oxide, red iron oxide, yellow iron oxide, ultramarine, Prussian blue, metal powders such as aluminum powder and bronze powder, extender pigments such as talc, silica, alumina, mica, and alumina silicate, fluorescent pigments, glass flakes, and luminous pigments. Examples of organic pigments include one or more selected from the group consisting of coloring pigments and fluorescent pigments such as phthalocyanine, azo, quinacdrine, anthraquinone, quinacridone, isoindolinone, diketopyrrolopyrrole, dioxane, indigo, thioindigo, perinone, perylene, indolenone, and azomethine. 【0011】 Colored resin spheres (colored resin particles) are resin spheres (resin particles) that are spherical, irregularly shaped, hollow, or flattened, and are colored with one or more inorganic pigments, organic pigments, or dyes that exhibit any desired color tone. Examples of resin materials that form colored resin spheres (colored resin particles) include polyethylene, polypropylene, vinyl chloride, polymethacrylate, benzoguanamine, melamine resin, and nylon. As inorganic pigments and organic pigments used to impart color to the colored resin spheres (colored resin particles), one or more selected from the group consisting of the aforementioned inorganic pigments and organic pigments are used. Furthermore, as dyes used to impart color to the colored resin spheres (colored resin particles), water-soluble dyes are preferred, and one or more selected from the group consisting of direct dyes, acid dyes, food dyes, basic dyes, and, for example, anthraquinone-based, methine-based, carbonium-based, metal complex salt-based coloring dyes and fluorescent dyes are used. 【0012】 In the present invention, one or more pigments selected from inorganic pigments and organic pigments are preferably used as the pigment. Furthermore, in the present invention, it is preferable not to use colored resin spheres (colored resin particles) as the pigment. Colored resin spheres (colored resin particles) are undesirable because their dispersibility may decrease over time in the aqueous ink composition for felt-tip pens, leading to the formation of aggregated particles, which may cause streaking. 【0013】 In the present invention, the number-average primary particle diameter of the pigment is not particularly limited and can be within the range commonly used as the volume-average primary particle diameter of pigments used in aqueous ink compositions for felt-tip pens. In the present invention, for example, it can be 500 nm or less, preferably 300 nm or less, more preferably 250 nm or less, and for example, 5 nm or more, preferably 10 nm or more, more preferably 20 nm or more. 【0014】 The pigment content is 0.05% by mass or more, preferably 0.15% by mass or more, 10.0% by mass or less, preferably 5.0% by mass or less, and more preferably 3.0% by mass or less, based on 100% by mass of the total amount of the aqueous ink composition for felt-tip pens. If the pigment content is less than 0.05% by mass, the color tone of the aqueous ink composition for felt-tip pens may become too light, failing to achieve the desired color tone and potentially resulting in poor color development. If the pigment content exceeds 10.0% by mass, the color tone of the ink composition may become too dark, failing to achieve the desired color tone. 【0015】 <Resin> The aqueous ink composition for felt-tip pens of the present invention contains a resin to disperse the pigment, increase viscosity, and fix the ink mark on a suitable writing surface after the solvent has evaporated. A water-soluble and / or water-dispersible resin can be used as the resin. When using a water-dispersible resin, it may be used in the form of a resin emulsion that is pre-dispersed in a solvent or has film-forming properties at room temperature. Examples of resins include one or more resins selected from the group consisting of acrylic resins, styrene-(meth)acrylic resins, styrene-maleic acid resins, vinyl acetate resins, urethane resins, and the like. 【0016】 In the present invention, one or more resins selected from the group consisting of acrylic resins, styrene-(meth)acrylic resins, and styrene-maleic acid resins are preferred. As acrylic resins, commercially available products such as the Hi-Loss series (X-310, BS-1144, VS-1029, etc.; manufactured by Seikoh PMC Co., Ltd.) and the Dianaal series (BR-52, BR-102, BR-107, etc.; manufactured by Mitsubishi Chemical Corporation) may be used. As the styrene-acrylic resin, commercially available products such as the Hyros series (X-1, VS1063, RS-1191, etc.; manufactured by Seikoh PMC) and the Joncryl series (67, 611, 678, 682, 683, 690, etc.; manufactured by BASF) may be used. As the styrene-maleic acid resin, commercially available products such as the Hyros series (X-205, etc.; manufactured by Seikoh PMC Co., Ltd.) and the Alastor series (700, etc.; manufactured by Arakawa Chemical Industries, Ltd.) may be used. 【0017】 Furthermore, in the present invention, an emulsion of one or more resins selected from the group consisting of acrylic resins, styrene-(meth)acrylic resins, and styrene-maleic acid resins can be used. Examples of acrylic resin emulsions include one or more selected from the group consisting of, for example, the PRIMAL series manufactured by Dow Chemical Japan and the Rheovis series manufactured by BASF. Examples of styrene-(meth)acrylic resin emulsions include one or more selected from the group consisting of, for example, the Johncryl series manufactured by Johnson Polymers and the Movinyl series manufactured by Japan Coating Resin Co., Ltd. Examples of styrene-maleic acid resin emulsions include one or more selected from the group consisting of, for example, the X series manufactured by Seikoh PMC Co., Ltd. Examples of vinyl acetate resin emulsions include one or more selected from the group consisting of the Nikazol series, etc. 【0018】 The resin content in the water-based ink composition for felt-tip pens is not particularly limited. Taking the total amount of the water-based ink composition for felt-tip pens as 100% by mass, the resin (solids) content is, for example, 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 1.0% by mass or more, and for example, 10.0% by mass or less, preferably 7.0% by mass or less, more preferably 5.0% by mass or less. If the resin (solids) content is less than 0.1% by mass, the viscosity of the water-based ink composition for felt-tip pens may be low, the amount of ink flowing during writing may be inappropriate, causing bleeding, ink leakage, or no markings. If the resin (solids) content exceeds 10.0% by mass, the viscosity of the water-based ink composition for felt-tip pens may be high, the amount of ink flowing during writing may be inappropriate, causing streaking, or the cap-off properties may be reduced. 【0019】 <Humectant> The aqueous ink composition for felt-tip pens of the present invention contains a wetting agent to adjust properties such as drying time. The wetting agent is not limited to those used in water-based ink compositions for felt-tip pens, particularly water-based marking pens and water-based felt-tip pens. For example, one or more selected from the group consisting of glycerin, diglycerin, triglycerin, polyhydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polyethylene glycol, and polypropylene glycol, sugars such as sorbitol, ureas such as urea, and derivatives thereof can be used. In the present invention, it is preferable to use one or more selected from the group consisting of ethylene glycol, glycerin, propylene glycol, and diethylene glycol, with ethylene glycol and / or glycerin being particularly preferred. 【0020】 The content of the wetting agent in the aqueous ink composition for felt-tip pens is not particularly limited. Taking the total amount of the aqueous ink composition for felt-tip pens as 100% by mass, the wetting agent content is, for example, 5.0% by mass or more, preferably 7.0% by mass or more, more preferably 10.0% by mass or more, and for example, 40.0% by mass or less, preferably 35% by mass or less, more preferably 30% by mass or less. If the wetting agent content is less than 5.0% by mass, the dispersion of each component in the aqueous ink composition for felt-tip pens may become unstable, the ink viscosity may decrease, the amount of ink flowing during writing may become inappropriate and cause bleeding, and the cap-off properties may decrease. If the wetting agent content exceeds 40.0% by mass, the dispersion of each component in the aqueous ink composition for felt-tip pens may become unstable, the drying speed of the writing may decrease, the ink viscosity may increase, and the amount of ink flowing during writing may become inappropriate and cause streaking, etc. 【0021】 <Water> Water-based ink compositions for felt-tip pens contain water, which functions as a solvent to dissolve or disperse the constituent components. Examples of water used include tap water, purified water, distilled water, deionized water, or pure water. Preferably, pure water, deionized water, or distilled water is used. 【0022】 The water content can be appropriately adjusted according to the content and viscosity of each component in the water-based ink composition for felt-tip pens. Taking the total amount of the water-based ink composition for felt-tip pens as 100% by mass, the water content is, for example, 25.0% by mass or more, preferably 30.0% by mass or more, and 75.0% by mass or less, preferably 65.0% by mass or less. If the water content is less than 25.0% by mass, the viscosity of the water-based ink composition for felt-tip pens may increase, the amount of ink flowing during writing may become inappropriate, causing streaking, and storage stability may decrease. If the water content exceeds 75.0% by mass, the viscosity of the water-based ink composition for felt-tip pens may decrease, the amount of ink flowing during writing may become inappropriate, causing bleeding, and ink leakage may occur. 【0023】 <Surfactants> The aqueous ink composition for felt-tip pens of the present invention may contain surfactants to improve storage stability, adjust viscosity, and improve pigment dispersibility. Any of the following surfactants may be used: anionic, cationic, nonionic, or amphoteric surfactants. For example, one or more surfactants selected from the group consisting of anionic surfactants such as sulfonic acid-based surfactants (e.g., alkylaryl sulfonic acid (salt), sulfosuccinate ester, sulfosuccinate diester, etc.) and phosphorus-based surfactants (e.g., alkyl phosphate ester, alkyl ether phosphate ester, alkylaryl phosphate ester, etc.); cationic surfactants such as quaternary ammonium-based surfactants; nonionic surfactants such as ether-based surfactants (e.g., polyoxyalkylene alkyl ether), ester-based surfactants (e.g., polyoxyalkylene fatty acid ester, polyoxyalkylene alkylaryl ether, sorbitan fatty acid ester, glycerin fatty acid ester, etc.); and fluorine-based surfactants. In the present invention, among these surfactants, anionic surfactants, particularly phosphorus-based surfactants (for example, phosphanol (manufactured by Toho Chemical Industry Co., Ltd.)), are preferred in terms of wetting and penetrating functions, emulsifying functions, and dispersion functions. 【0024】 The surfactant content is not particularly limited. It is 1.5% by mass or less, preferably 1.0% by mass or less, and more preferably 0.7% by mass or less, based on the total amount of the aqueous ink composition for felt-tip pens as 100% by mass. If the surfactant content exceeds 1.5% by mass, there is a risk of ink bleeding through the paper when writing, inappropriate ink flow during writing resulting in bleeding, and ink leakage. 【0025】 <Water-soluble organic solvents> The aqueous ink composition for felt-tip pens of the present invention may contain a water-soluble organic solvent to improve storage stability, adjust viscosity, and improve pigment dispersibility. The water-soluble organic solvent is an organic solvent that has a solubility in water at 20°C of 1 g / L or more, preferably 10 g / L or more, more preferably 100 g / L or more, and is uniformly miscible in any proportion, and is other than the compounds listed as wetting agents. For example, one or more selected from the group consisting of monoalcohols, lower alkyl ethers of polyhydric alcohols having 1 to 6 carbon atoms, ketones, ethers, esters, nitrogen-containing compounds, etc. In the present invention, it is preferable to use monoalcohols and / or lower alkyl ethers of polyhydric alcohols having 1 to 6 carbon atoms. 【0026】 Examples of monoalcohols include one or more selected from the group consisting of methanol, ethanol, n-propanol, n-butanol, n-pentanol, n-hexanol, n-heptanol, n-octanol, cyclopentanol, cyclohexanol, and the like. 【0027】 Examples of lower alkyl ethers of polyhydric alcohols having 1 to 6 carbon atoms include one or more selected from the group consisting of ethylene glycol monomethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether (butyl cellosolve), ethylene glycol monoisobutyl ether, diethylene glycol monomethyl ether, propylene glycol monomethyl ether, propylene glycol monopropyl ether, dipropylene glycol monomethyl ether, diethylene glycol dimethyl ether, diethylene glycol methyl ethyl ether, and diethylene glycol diethyl ether. 【0028】 The content of the water-soluble organic solvent is not particularly limited. It is 10.0% by mass or less, preferably 5.0% by mass or less, and more preferably 3.0% by mass or less, based on the total amount of the aqueous ink composition for felt-tip pens as 100% by mass. If the surfactant content exceeds 10.0% by mass, the amount of ink flow during writing may be inappropriate, leading to bleeding, ink leakage, or failure to form a writing line. 【0029】 <Other additives> The aqueous ink composition for a sign pen of the present invention may contain other additives as necessary. The other additives are not particularly limited as long as they are used in the aqueous ink composition for a sign pen. For example, one or more selected from the group consisting of preservatives, fungicides, pH adjusters, rust inhibitors, viscosity adjusters (thickeners / thickening inhibitors), chelating agents, dyes, lubricants, defoamers, leveling agents, ultraviolet absorbers, infrared absorbers, antioxidants, dyes, fluorescent brighteners, etc. can be used in an appropriate amount as necessary. 【0030】 【0031】 【0032】 Lo / D10<D10 Up > > After putting 10 g of the aqueous ink composition for a sign pen of the present invention into a cylindrical container with an inner diameter of 21 mm and a volume of 14 ml and storing it at 50 °C for 4 weeks, collect the aqueous ink composition for a sign pen within 5 mm from the bottom surface of the container, and the cumulative 10% volume particle diameter D10 determined by the dynamic light scattering method (DLS: Dynamic Light Scattering) Lo and A sample of the water-based ink composition for felt-tip pens was taken from within 5 mm of the ink surface, and the cumulative 10% volume particle size D10 was determined by dynamic light scattering (DLS). Up but, D10 LO / D10 Up <1.6 It satisfies the relationship. 【0033】 Cumulative 10% volume particle size D10 Lo It can be measured and obtained by the following method. (a1) Place 10 g of water-based ink composition for felt-tip pens into a cylindrical container with an inner diameter of 21 mm and a capacity of 14 ml, and store at 50°C for 4 weeks. (a2) After the storage period has ended, take a sample of the water-based ink composition for the felt-tip pen from a range of 5 mm from the bottom of the container. (a3) Dilute the collected aqueous ink composition for felt-tip pens 5,000 times with deionized water to prepare a pigment dispersion. (a4) Using the prepared pigment dispersion, the cumulative 10% volume particle size D10 of the lower layer was determined by dynamic light scattering (DLS). Lo We seek. 【0034】 After the storage period has ended, the water-based ink composition for felt-tip pens that is present in a 5mm area from the bottom of the container is highly likely to contain aggregated particles that formed during storage. The inventors believe that if the pigment is over-dispersed during the preparation of the water-based ink composition for felt-tip pens, the dispersion stability of the pigment is not high, making it easy for aggregated pigment particles to form. As a result, aggregated pigment particles accumulate in the lower layer of the water-based ink composition for felt-tip pens after storage (a 5mm area from the bottom of the container), and therefore, the cumulative 10% volume particle size D10 Lo It is hypothesized that a large value of this factor, along with the resulting aggregated pigment particles, causes blockage of the tip slit in the water-based pen, resulting in streaking during writing. However, the present invention is not limited to this hypothesis. 【0035】 Cumulative 10% volume particle size D10 UpIt can be measured and obtained by the following method. (b1) Place 10 g of water-based ink composition for felt-tip pens into a cylindrical container with an inner diameter of 21 mm and a capacity of 14 ml, and store at 50°C for 4 weeks. (b2) After the storage period has ended, take a sample of the water-based ink composition for felt-tip pens from a range of 5 mm from the liquid surface. (b3) Dilute the collected aqueous ink composition for felt-tip pens 5,000 times with deionized water to prepare a pigment dispersion. (b4) Using the prepared pigment dispersion, the cumulative 10% volume particle size D10 of the upper layer was measured by dynamic light scattering (DLS). Up We seek. 【0036】 After the storage period ends, the particle size of the pigment in the water-based ink composition for felt-tip pens, which is within 5 mm of the liquid surface, is unlikely to change drastically before and after storage. It is highly probable that the particle size will remain close to the value of the dispersed particle size before storage. Therefore, the cumulative 10% volume particle size D10 of the pigment in the upper layer (within 5 mm of the liquid surface) of the water-based ink composition for felt-tip pens after storage will be... Up Therefore, the cumulative 10% volume particle size D10 of the pigment in the lower layer of the water-based ink composition for felt-tip pens after storage (a range of 5 mm from the bottom of the container) Lo By dividing by (or divisor), we can find out the rate of change of D10 before and after storage. 【0037】 In the present invention, D10 Lo / D10 Up Setting the value to less than 1.60, preferably less than 1.55, and more preferably less than 1.51, is extremely effective in preventing smudging after long-term storage. In the present invention, D10 Lo / D10 Up The method for achieving a value of less than 1.60 is not particularly limited. Examples include adjusting the amount of dispersant used, adjusting the primary particle size of the pigment used, adjusting the dispersion time and dispersion force, and preventing overdispersion. 【0038】 In the present invention, D10 LoThe range of the value is not particularly limited. For example, it is 40 nm or more, preferably 50 nm or more, more preferably 60 nm or more, and for example, 200 nm or less, preferably 150 nm or less, more preferably 130 nm or less. In the present invention, D10 Up The range of the value is not particularly limited. For example, it is 20 nm or more, preferably 30 nm or more, more preferably 40 nm or more, and for example, 150 nm or less, preferably 100 nm or less, more preferably 80 nm or less. 【0039】 Furthermore, according to the present invention, D10 Lo D10 Up and D10 Lo / D10 Up By specifying each of these as described above, it is possible to construct a method for imparting long-term storage stability to an aqueous ink composition for felt-tip pens and a method for preventing smudging after long-term storage. 【0040】 <Viscosity> The viscosity of the aqueous ink composition for felt-tip pens of the present invention is not particularly limited and can be set as appropriate. In particular, it is preferable that the viscosity of the aqueous ink composition for felt-tip pens is 100 mPa·s or less. For example, it can be 1.0 mPa·s or more, preferably 2.0 mPa·s or more, more preferably 3.0 mPa·s or more, and can be in the range of, for example, 35.0 mPa·s or less, preferably 15.0 mPa·s or less, and more preferably 6.0 mPa·s or less (using an E-type rotational viscometer (for example, a TVE-type viscometer manufactured by Toki Sangyo Co., Ltd., 1°34' cone, 50 rpm)). If the viscosity of the aqueous ink composition for felt-tip pens is less than 1.0 mPa·s, there is a risk that the ink will flow out excessively from the tip of the writing instrument, making it impossible to accurately form a writing line. If the viscosity exceeds 35.0 mPa·s, the viscosity becomes too high, which may prevent ink from flowing out of the tip of the writing instrument. This may also cause problems in terms of ink handling, sedimentation stability, ink streaking, and manufacturing costs. 【0041】 <Method for manufacturing a water-based ink composition for felt-tip pens> The method for producing the aqueous ink composition for felt-tip pens of the present invention is not particularly limited. Known methods for producing aqueous ink compositions can be used. For example, a water-based ink composition for felt-tip pens can be produced by placing all the components that make up the composition into a container and mixing and stirring them using a mixing and stirring device such as a ball mill, bead mill, roll mill, Henschel mixer, homomixer, propeller stirrer, homogenizer, high-pressure homogenizer, kneader, or dissolver to disperse them. 【0042】 For example, some components of a water-based ink composition for felt-tip pens, such as pigment, water-soluble organic solvent, water, and dispersant, can be placed in a container and mixed and stirred using the aforementioned mixing and stirring device to produce a color base (pigment paste, pigment dispersion). After that, the remaining components can be added and mixed and stirred to produce a water-based ink composition for felt-tip pens. In the present invention, a preferred method involves manufacturing a color base containing at least a pigment, resin, wetting agent, and water, and then mixing and stirring the color base with the remaining components. This makes it possible to easily adjust the degree of pigment dispersion (dispersed particle size) during the color base preparation stage. When preparing the water-based ink composition for felt-tip pens, operations such as filtration, centrifugation, and degassing may be performed to remove coarse particles, gases, and bubbles. Heating, cooling, pressurizing, depressurizing, and inert gas replacement may also be employed during the preparation of the water-based ink composition for felt-tip pens. Furthermore, an aging process may be performed after the preparation of the water-based ink composition for felt-tip pens. 【0043】 [Water-based pen] The water-based pen comprising the water-based ink composition for sign pens of the present invention comprises a pen tip made of a fiber core or a plastic core and an ink storage section, wherein the water-based ink composition for sign pens is stored in the ink storage section. The aqueous ink composition for felt-tip pens of the present invention can be suitably used, in particular, as an aqueous ink composition for felt-tip pens with a core. The water-based ink composition for felt-tip pens of the present invention can be suitably used, for example, as a water-based marking pen or a water-based felt-tip pen. Examples of water-based marking pens and water-based sign pens include writing instruments also known as felt pens, which have a pen tip made of a fiber bundle, a sintered body, or plastic, and an ink storage means within the body in which ink is impregnated into a so-called core made of felt or a fiber bundle. Ink is supplied from this ink storage means to the pen tip using capillary action, enabling writing. These are so-called core-type pens. Other examples include non-core type or so-called free-ink type pens, which store ink directly in a cylindrical body and supply this ink to the pen tip. The water-based ink composition for felt-tip pens according to the present invention is suitably used in both water-based marking pens and water-based felt-tip pens. [Examples] 【0044】 The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, "%" means "mass%" and "parts" means "parts by mass". 【0045】 The following components were used as the constituents of the color base and aqueous ink composition for felt-tip pens described in the examples. Pigment A: Pigment Yellow 3 (PY3); Primary particle size 180 nm ·Pigment B: Pigment Blue 15:3(PB15:3); Primary particle size 210nm • Resin A: Styrene-(meth)acrylic resin (manufactured by Seikoh PMC, Hyros X-1) • Surfactant: Phosphanol PE-510, manufactured by Toho Chemical Industry Co., Ltd. • Preservative: Proxel XL-2, manufactured by Lonza Japan Co., Ltd. • Antifungal agent: Courtside PH2, manufactured by Osaka Gas Chemical Co., Ltd. 【0046】 [Color base preparation] <Preparation of yellow color base A> 25.0 parts of pigment A, 25.0 parts of resin A aqueous dispersion (5.0% by mass of resin), 20.0 parts of ethylene glycol, and 30.0 parts of deionized water were placed in a container and dispersed and mixed using a bead mill to obtain dispersion A. The dispersion and mixing conditions using the bead mill were as follows. Vessel: Batch-type 150mL glass container Beads: 0.6~0.8mm glass beads Circumferential speed: 10m / s Bead filling amount: 85% Dispersion time: 300min Next, 68.0 parts of dispersion A, 31.8 parts of water, 0.1 parts of preservative, and 0.1 parts of fungicide were mixed to prepare a yellow color base A with a pigment concentration of 17.0% by mass and an initial dispersion particle size of 181.8 nm. 【0047】 <Preparation of yellow color bases B-D> Yellow color bases B to D were prepared in the same manner as yellow color base A, except for a change in the dispersion conditions of the bead mill, with the initial dispersion particle sizes of the pigments shown in Table 1. 【0048】 <Preparation of blue color base A> Blue color base A was prepared in the same manner as yellow color base A, except that pigment B was used instead of pigment A and the dispersion time in the bead mill was changed. 【0049】 [Preparation of water-based ink composition for felt-tip pens] <Example 1> 39.9 parts yellow color base A, 4.6 parts blue color base A, 10.0 parts ethylene glycol, 10.0 parts glycerin, 1.0 part surfactant, 0.1 parts preservative, 0.1 parts antifungal agent, 10.0 parts urea, and 24.3 parts deionized water were mixed in a stirrer, and coarse particles in the ink were removed using a high-speed centrifuge to prepare the aqueous ink composition for felt-tip pens according to Example 1. 【0050】 <Examples 2-4, Comparative Example 1> Except for the components and amounts (parts) of the aqueous ink compositions for felt-tip pens shown in Table 1, the aqueous ink compositions for felt-tip pens according to Examples 2 to 4 and Comparative Example 1 were prepared in the same manner as in Example 1. 【0051】 [Making a water-based pen] The tip was attached to the pen body (a refillable felt-tip pen made by Sakura Color Products), and the cap was also attached. The cores were filled with the water-based ink compositions for felt-tip pens from Examples 1-4 and Comparative Example 1, respectively. These were then placed in pen bodies, and end caps were attached to create three water-based pens for each water-based ink composition. 【0052】 [evaluation] The aqueous ink compositions for felt-tip pens of Examples 1-4 and Comparative Example 1 were evaluated as follows. The results are also shown in Table 1. 【0053】 <Initial dispersed particle size> The initial dispersed particle size was obtained for each water-based ink composition for felt-tip pens by measuring under the following conditions. Measuring instrument: ELSZ-2000ZS (manufactured by Otsuka Electronics Co., Ltd.) Measurement principle: Dynamic light scattering method Diluent: Deionized water Dilution ratio: 5000 times Measurement temperature: 20℃ Measurement waiting time: 180 seconds Total number of times: 70 Analysis method: Marquardt 【0054】 <D10 Lo > The aqueous ink composition for felt-tip pens according to Example 1 was stirred again for 10 minutes, and 10 g was taken and placed in a cylindrical container with an inner diameter of 21 mm and a capacity of 14 ml, and stored at 50°C for 4 weeks. After the storage period, the aqueous ink composition for felt-tip pens was stirred at 50°C for 10 minutes, and a sample of the composition was taken from a range of 5 mm from the bottom of the container. The composition was measured by dynamic light scattering (DLS) and the cumulative 10% volume particle size D10 of the lower layer was determined. LoThe (nm) value was calculated. The results are shown in Table 1. The aqueous ink compositions for felt-tip pens in Examples 2-4 and Comparative Example 1 were also prepared in the same manner as the aqueous ink composition for felt-tip pens in Example 1, with a cumulative 10% volume particle size D10 in the lower layer. Lo The (nm) value was calculated. The results are shown in Table 1. 【0055】 <D10 Up > The aqueous ink composition for felt-tip pens according to Example 1 was stirred again for 10 minutes, then 10 g was taken and placed in a cylindrical container with an inner diameter of 21 mm and a capacity of 14 ml, and stored at 50°C for 4 weeks. After the storage period, the aqueous ink composition for felt-tip pens was stirred at 50°C for 10 minutes, and a sample of the composition within a 5 mm range from the liquid surface was taken and measured by dynamic light scattering (DLS). The average value was taken as the particle size, and the cumulative 10% volume particle size D10 of the lower layer was determined. Up The (nm) value was calculated. The results are shown in Table 1. The aqueous ink compositions for felt-tip pens in Examples 2-4 and Comparative Example 1 were also prepared in the same manner as the aqueous ink composition for felt-tip pens in Example 1, with a cumulative 10% volume particle size D10 in the lower layer. Up The (nm) value was calculated. The results are shown in Table 1. 【0056】 <D10 Lo / D10 Up > The cumulative 10% volume particle size D10 of the lower layer obtained above Lo And, the cumulative 10% volume particle size D10 of the upper layer Up Using D10 Lo / D10 Up The value of was calculated. The results are shown in Table 1. 【0057】 <Fusure Rating> Using the aqueous ink composition for felt-tip pens described in Example 1, three aqueous pens were prepared, and a 10-circle test was performed by manually writing 10 consecutive circles with a diameter of approximately 8 mm in a spiral pattern on high-quality paper with each pen. After the 10-circle test, the three aqueous pens were placed in a 50°C constant temperature bath in three different positions: upright, inverted, and horizontal, and left to stand for 4 weeks. After that, the three aqueous pens were removed from the constant temperature bath, and the 10-circle test was repeated by manually writing 10 consecutive circles with a diameter of approximately 8 mm in a spiral pattern on high-quality paper with each pen. In the 10-circle test conducted again after standing, a score of 5 points was assigned if 9 or more circles were written without smudging, 4 points for 7 to 8 circles, 3 points for 5 to 6 circles, 2 points for 3 to 4 circles, and 1 point for 2 circles or less. The average value of three water-based pens using each water-based ink composition for felt-tip pens was used as the smudging evaluation. In this invention, a smudging evaluation of less than 3.0 is considered a failure. The results are also shown in Table 1. Except for using water-based pens prepared with the water-based ink compositions for felt-tip pens described in Examples 2-4 and Comparative Example 1, the streaking evaluation was performed in the same manner as in Example 1. The results are shown in Table 1. 【0058】 [Table 1] 【0059】 Table 1 shows an aqueous ink composition for a felt-tip pen containing at least a pigment, resin, wetting agent, and water. A sample of the water-based ink composition for felt-tip pens was taken from within 5 mm of the container bottom, and the cumulative 10% volume particle size D10 was determined by dynamic light scattering (DLS). Lo and, A sample of the water-based ink composition for felt-tip pens was taken from within 5 mm of the ink surface, and the cumulative 10% volume particle size D10 was determined by dynamic light scattering (DLS). Up but, D10 LO / D10 Up <1.6 It has been found that water-based pens using a water-based ink composition for felt-tip pens that satisfies the given relationship are less prone to smudging even after long-term storage.

Claims

[Claim 1] A water-based ink composition for felt-tip pens comprising at least a pigment, a resin, a wetting agent, a phosphorus-based surfactant, and water, The resin is one or more resins selected from the group consisting of styrene-(meth)acrylic resins, styrene-maleic acid resins, vinyl acetate resins, and urethane resins. The phosphorus-based surfactant content is greater than 0% by mass and less than or equal to 1.5% by mass, based on 100% by mass of the total amount of the aqueous ink composition for felt-tip pens. After placing 10 g of the aforementioned water-based ink composition for felt-tip pens into a cylindrical container with an inner diameter of 21 mm and a capacity of 14 ml and storing it at 50°C for 4 weeks, A sample of the water-based ink composition for felt-tip pens was taken from within 5 mm of the container bottom, and the cumulative 10% volume particle size D10 was determined by dynamic light scattering (DLS). Ｌｏ and, A sample of the water-based ink composition for felt-tip pens was taken from within 5 mm of the ink surface, and the cumulative 10% volume particle size D10 was determined by dynamic light scattering (DLS). Ｕｐ but, D10 Ｌｏ / D10 Ｕｐ <1.6 Satisfying the relationship, Water-based ink composition for felt-tip pens. [Claim 2] A water-based pen comprising a core containing the water-based ink composition for a felt-tip pen described in claim 1.

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