Water-based ink composition for writing instruments, writing instruments, and cartridge ink for writing instruments

Abstract

[Problem] The present invention addresses the problem of providing an ink composition for a writing implement having various characteristics such as dry-up resistance and writing density in addition to dispersion stability and writing fastness such as writing water resistance, and a writing implement that uses the same. [Solution] The ink composition for a writing implement according to the present invention includes a self-dispersing pigment, an α-glucan or an α-glucan derivative, and water. The present invention relates to the ink composition for a writing implement and to a writing implement and a cartridge for a writing implement that house the same.

Description

[Technical Field]

[0001] The present invention relates to a water-based ink composition for a writing instrument, a writing instrument, and a cartridge ink for a writing instrument. [Background technology]

[0002] Writing instruments that form handwriting using an ink composition form handwriting by ejecting an ink composition containing a colorant from a pen tip onto a writing object. There are a wide variety of ink compositions depending on the purpose, such as paint compositions that form a coating layer that covers the surface of a substrate, and ink compositions for printers such as inkjet printers that eject tiny droplets to form an image on a target. However, unlike these, ink compositions for writing instruments must have physical properties that allow an appropriate amount of ink composition to be ejected onto a writing object using capillary action or the like.

[0003] Colorants contained in ink compositions can be broadly classified into dyes and pigments, and are selected according to the purpose. Dyes tend to produce ink compositions with high uniformity and are widely used in various ink compositions. However, dyes generally tend to lack handwriting fastness, such as water resistance and light fastness, and improvements are desired. On the other hand, pigments have high handwriting fastness, but improvements are needed in terms of the dispersion stability of the ink composition. In particular, ink compositions used in fountain pens and the like are required to have low viscosity because the ink is guided to the pen tip by capillary action through a pen core having a comb groove for temporarily storing ink, an ink flow channel, and an air passage. In such low-viscosity ink compositions, improvement of the dispersion stability of the ink composition is particularly desired. Increasing the viscosity of the ink composition using a thickener or the like is often effective in improving dispersion stability, but it is difficult to combine additives with thickening properties with ink compositions requiring low viscosity.

[0004] In addition to the handwriting fastness such as water resistance and light resistance of the handwriting and dispersion stability described above, the ink composition is also required to have handwriting density, resistance to drying up (writing start performance), handwriting fixation, writing quality (handwriting with little smearing, bleeding, or show-through), ink reversal within the ink reservoir, and resistance to dripping.

[0005] When a pigment is used as a colorant, the dispersion stability may be insufficient as described above, and various studies have been conducted to improve this. However, in conventional ink compositions for writing instruments using pigments, there is still room for improvement in properties other than handwriting fastness. Furthermore, there has been a demand for the development of an ink composition that simultaneously satisfies various performance requirements at high levels.

[0006] To solve the above problems, ink compositions have been proposed that improve resistance to dry-up by adding polyhydric alcohol solvents such as ethylene glycol and glycerin, and various humectants such as urea or urea derivatives to the ink (see, for example, Patent Documents 1 and 2).

[0007] However, although good resistance to dry-up can be obtained depending on the type and amount of humectant added, when water droplets adhere to the resulting handwriting, the handwriting may smudge, making it difficult to see the handwriting. In addition, the fixation of the handwriting to the surface on which it is written may decrease, and when the handwriting is rubbed, the handwriting may become smudged. For example, there is room for improvement in the water resistance and fixation of the handwriting.

[0008] Therefore, there is a demand for a water-based ink composition for a writing instrument and a writing instrument that can provide excellent handwriting fastness such as water resistance without deteriorating various properties. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Publication No. 08-127446 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-217730 [Patent Document 3] Japanese Patent Publication No. 61-247774 [Patent Document 4] Japanese Patent Application Laid-Open No. 2016-069490 Summary of the Invention [Problem to be solved by the invention]

[0010] The object of the present invention is to solve the above-mentioned problems and to provide an aqueous ink composition for a writing instrument, which has excellent handwriting fastness such as water resistance of the handwriting and excellent handwriting color development, and at the same time has excellent dispersion stability, and further has other properties that are preferable for a writing instrument, and a writing instrument using the same. [Means for solving the problem]

[0011] The aqueous ink composition for a writing instrument according to the present invention is characterized by comprising a self-dispersing pigment, an α-glucan or an α-glucan derivative, and water.

[0012] The writing instrument according to the present invention is characterized by containing the above-mentioned water-based ink composition for a writing instrument.

[0013] The cartridge ink for a writing instrument according to the present invention is characterized by containing the above-mentioned water-based ink composition for a writing instrument. [Effects of the Invention]

[0014] According to the present invention, there are provided a water-based ink composition for a writing instrument which is excellent in various properties such as handwriting density in addition to handwriting fastness such as water resistance of handwriting and dispersion stability, and a writing instrument using the same. DETAILED DESCRIPTION OF THE INVENTION

[0015]

[0023] In the present specification, unless otherwise specified, the terms "parts," "%," "ratio," and the like that indicate the composition are based on mass, and the content is the mass % of the constituent component based on the mass of the ink composition.

[0016] <<Water-based ink composition for writing instruments>> The aqueous ink composition for a writing instrument according to the present invention (hereinafter simply referred to as the "ink composition") comprises a self-dispersing pigment, α-glucan or an α-glucan derivative, and water. The components of the ink composition of the present invention will be described in detail below.

[0017] <Self-dispersing pigment> The ink composition according to the present invention contains a self-dispersing pigment as a colorant. Self-dispersing pigments have excellent dispersion stability and can leave handwriting that is excellent in color development and water resistance.

[0018] Self-dispersing pigments can be dispersed in an aqueous medium without using a pigment dispersant to disperse pigment particles. Specifically, examples of self-dispersing pigments include those in which the pigment particle surface is subjected to a physical or chemical treatment to provide hydrophilic functional groups (hydrophilic groups) on the pigment surface.

[0019] In the present invention, the use of a self-dispersing pigment eliminates the need for a pigment dispersant. Because pigment dispersants generally tend to inhibit the color development of handwriting, the ink composition of the present invention, which does not contain such a dispersant, is more likely to produce handwriting with good color development. Among commonly used pigment dispersants, resin-based pigment dispersants in particular can also function to fix the pigment to the writing surface. However, in the present invention, other components such as α-glucans function to fix the pigment, resulting in excellent water resistance and fixability of handwriting.

[0020] In particular, in the present invention, it is preferable to use self-dispersing carbon black as the self-dispersing pigment. Examples of self-dispersing carbon black include carbon black that has been subjected to physical or chemical treatment to bond hydrophilic functional groups (hydrophilic groups) to the surface of the carbon black. Examples of hydrophilic groups include sulfo groups, carboxyl groups, and phosphate groups.

[0021] In addition, in the present invention, it is preferable to use anionic self-dispersing carbon black because it is easy to fully obtain the effects of α-glucan and its derivatives described below, and it is easy to obtain handwriting with excellent water resistance while maintaining dispersion stability. Furthermore, self-dispersing carbon black in which carboxyl groups or sulfo groups, especially carboxyl groups, are bonded to the surface of the carbon black is more preferable.

[0022] Furthermore, as will be described later, the ink composition of the present invention can be easily prepared into a low-viscosity ink for use in a writing instrument having a fiber tip, felt tip, or plastic tip, or even into an ultra-low-viscosity ink for use in a writing instrument having a pen core with a comb groove for temporarily storing ink, an ink flow path, and an air passage, and in this case, it is more effective to use a self-dispersing pigment. This is because the self-dispersing pigment can improve dispersibility without using a pigment dispersant, thereby making it possible to keep the ink viscosity lower, achieving good ink dischargeability from the start of writing, and making it easier to leave uniform, good-quality handwriting.

[0023] The self-dispersion pigment that can be used in the present invention is not particularly limited, and examples of commercially available products include the BONJET BLACK series manufactured by Orient Chemical Industries Co., Ltd., the CAB-O-JET series manufactured by Cabot Corporation, the Aqua-Black series manufactured by Tokai Carbon Co., Ltd., and the Fuji-JET Black series manufactured by Fuji Pigment Co., Ltd.

[0024] When self-dispersing carbon black is used in the self-dispersing pigment, there are no restrictions on the size of the pigment particles contained in the self-dispersing carbon black. Carbon black generally consists of primary particles agglomerated to form secondary particles, and in order to maintain high levels of dispersion stability, handwriting fastness, ink jettability, etc., the average particle size of these secondary particles is preferably 20 to 1,000 nm, more preferably 50 to 500 nm, and even more preferably 100 to 200 nm.

[0025] As a physical property of the self-dispersing carbon black dispersion, the viscosity is preferably 1.0 to 10.0 mPa s, more preferably 2.0 to 10.0 mPa s, and even more preferably 5.0 to 10.0 mPa s. When the viscosity of the self-dispersing carbon black dispersion is within the above range, it is easy to adjust the ink viscosity of the ink composition to a desired value, and it is easy to obtain handwriting with excellent ink dischargeability and color development.

[0026] The pH of the self-dispersible carbon black dispersion is preferably 5.0 to 9.0, more preferably 6.0 to 8.0, and even more preferably 6.0 to 7.0. The surface tension of the self-dispersible carbon black dispersion is preferably 40 to 72 mN / m, more preferably 50 to 72 mN / m, and even more preferably 60 to 72 mN / m. When the surface tension of the self-dispersible carbon black dispersion is within the above range, it is easy to adjust the surface tension of the ink composition to a desired value, making it easy to obtain good handwriting with reduced bleeding. Furthermore, the pen core can fully function, providing excellent ink dischargeability and reducing drooling from the pen tip while producing good handwriting with little smearing.

[0027] The content of the self-dispersing pigment in the ink composition of the present invention is preferably 0.1 to 30% by mass, and more preferably 0.1 to 10% by mass, based on the total mass of the ink composition.

[0028] <α-glucan or α-glucan derivative> The ink composition according to the present invention contains α-glucan or an α-glucan derivative (hereinafter sometimes simply referred to as α-glucans).

[0029] Alpha-glucans have excellent water retention and film-forming properties. Therefore, the ink composition forms a film on the pen tip, suppressing water evaporation and maintaining good resistance to dry-up. The film formed is easily destroyed by the physical stress applied during writing, so the film is not easily destroyed at the start of writing and does not hinder the formation of handwriting. Furthermore, after the handwriting is formed, water resistance is imparted to the handwriting, improving its fastness. This is thought to be because a film is formed on the surface of the resulting handwriting, which prevents the self-dispersing pigment from leaking out even if water droplets later adhere to the handwriting.

[0030] Alpha-glucans are polymers with a weight-average molecular weight of 5,000 or more, preferably 10,000 or more, in which multiple glucose units are linked by alpha bonds. They are classified into alpha-1,3 glucans, alpha-1,4 glucans, alpha-1,6 glucans, alpha-1,4-1,6 glucans, etc., depending on the type of bond. Specifically, examples of alpha-1,3 glucans include mutan, examples of alpha-1,4 glucans include amylose, examples of alpha-1,6 glucans include dextran, and examples of alpha-1,4-1,6 glucans include glycogen, amylopectin, and pullulan. Alpha-glucan derivatives are obtained by chemically modifying the above-mentioned alpha-glucans. Alpha-glucans also include dextrins with relatively small molecular weights, which are obtained by enzymatically hydrolyzing starch.

[0031] The α-glucans used in the present invention are not particularly limited, but are preferably α-1,4-1,6 glucans or α-1,4-1,6 glucan derivatives. Furthermore, α-glucans preferably have a weight-average molecular weight of 5,000 to 500,000, and more preferably 50,000 to 400,000. In the present invention, synthetic α-glucans are preferred from the perspective of quality stability of the ink composition. While low-molecular-weight dextrins obtained by starch degradation are also included in α-glucans, synthetic α-glucans are preferred. Pullulan and pullulan derivatives are particularly preferred due to their significant improvement effects in the above-mentioned properties.

[0032] Pullulan is a water-soluble polymeric polysaccharide whose structural unit is maltotriose, consisting of three glucose molecules linked together via α-1,4 bonds, as shown in formula (I) below, with the maltotriose units linked via α-1,6 bonds. It is readily soluble in water and is non-toxic, non-irritating, tasteless, and odorless to the human body. While there are no limitations on the origin or production method of pullulan, a commonly used method involves culturing microorganisms capable of producing pullulan and then harvesting pullulan-containing material from the culture. An example of such a microorganism is Aureobasidium pullulans.

[0033] [ka] In the formula, n1 represents an integer.

[0034] The pullulan derivative is not limited as long as it is a substance derived from pullulan, obtained by chemically modifying the pullulan, etc. Examples include dialdehyde pullulan, aminoalkylated pullulan, carboxylated pullulan, crosslinked pullulan, sulfate ester derivatives of pullulan, and pullulan-sterol derivatives such as cholesterol pullulan.

[0035] Furthermore, the pullulan derivative is preferably a pullulan-sterol derivative, and it is particularly preferable to use a pullulan-cholesterol derivative, which is a compound obtained by introducing cholesterol into pullulan via a chemical bond. This is thought to be because pullulan-cholesterol derivatives are easily adsorbed to metals, synthetic resins, etc., and are likely to form a good coating on the pen tip. Furthermore, considering ease of availability and the stability of the compound over time, the pullulan-cholesterol derivative is preferably hexyldicarbamate cholesteryl pullulan (cholesterol pullulan), which is a compound obtained by adding cholesterol to pullulan with hexamethylene diisocyanate. Examples of the hexyldicarbamate cholesteryl pullulan include the compound represented by the following formula (II):

[0036] [ka] In the formula, n2 represents an integer.

[0037] Therefore, in the present invention, pullulan or hexyldicarbamate cholesteryl pullulan (cholesterol pullulan), which are likely to provide excellent dry-up resistance and water resistance of handwriting, are particularly preferably used. Among them, hexyldicarbamate cholesteryl pullulan tends to provide excellent dry-up resistance and water resistance of handwriting as well as excellent handwriting fixability (abrasion resistance), so in consideration of improving handwriting fixability, it is preferable to use hexyldicarbamate cholesteryl pullulan.

[0038] Commercially available pullulan products that can be suitably used include pharmaceutical-grade pullulan (trade name "Japanese Pharmacopoeia Pullulan"), cosmetic-grade pullulan (trade name "Cosmetic Pullulan"), and food-additive-grade pullulan (trade name "Food Additive Pullulan"), all manufactured by Hayashibara Co., Ltd.

[0039] Examples of commercially available products containing cholesterol pullulan include the Meduseeds series (manufactured by NOF Corporation), specifically Meduseeds-C1 and Meduseeds-CP, etc. Meduseeds-CP contains cholesteryl hexyldicarbamate pullulan, water, butylene glycol, methylparaben, and phenoxyethanol.

[0040] The content of α-glucans in the ink composition of the present invention is preferably 0.001 to 1% by mass, based on the total mass of the ink composition. If it is 0.001% by mass or more, the water retention and film-forming ability of the α-glucan or α-glucan derivative is sufficiently obtained, making it easy to obtain excellent dry-up resistance, water resistance of handwriting, and handwriting fixation. If it is 1% by mass or less, the solubility in the ink composition is stable, and good ink discharge from the pen tip is maintained, making it easy to leave good handwriting. Furthermore, 0.005 to 0.5% by mass is more preferable, and 0.01 to 0.1% by mass is particularly preferable.

[0041] In addition, α-glucans can also be used as a mixture of two or more types.

[0042] The ink composition according to the present invention comprises a self-dispersing pigment and α-glucans, and the content ratio of α-glucans to the self-dispersing pigment (α-glucans / self-dispersing pigment) is preferably 0.0001 to 0.1 by mass, and more preferably 0.001 to 0.1. If the content ratio is within the above range, a good balance of dispersion stability, handwriting water resistance, and dry-up resistance can be obtained.

[0043] <Water> The ink composition according to the present invention contains water. The water to be used is not particularly limited, and examples thereof include tap water, ion-exchanged water, ultrafiltered water, and distilled water.

[0044] <Other additives> The ink composition of the present invention may contain any additives as needed. The additives that can be used are described below.

[0045] <Surfactant> The ink composition according to the present invention can further contain a surfactant. Examples of such surfactants include nonionic surfactants, anionic surfactants, cationic surfactants, surfactants having an acetylene bond in their structure, silicone surfactants, phosphate ester surfactants, and fluorine-based surfactants. These surfactants adjust the surface tension of the ink composition within an appropriate range and also maintain appropriate wettability for the inner surface of the ink reservoir and the pen core. This improves ink reversal and drip resistance within the ink reservoir, facilitates smooth ink ejection, and produces good handwriting with reduced blurring.

[0046] It is preferable to use a nonionic surfactant as such a surfactant. This is because the nonionic surfactant does not inhibit the effects of the self-dispersing pigment or α-glucan, and the effects of the surfactant can be fully obtained. Furthermore, among nonionic surfactants, those having a polyoxyalkylene structure, such as polyetheramines and polyoxyalkylene glycols, are particularly effective in the present invention because they are more likely to provide the above effects. Furthermore, among those having a polyoxyalkylene structure, surfactants having a polyoxyethylene structure are preferred. This is because they have excellent solubility stability in water and are more likely to provide the effects.

[0047] Polyetheramines and polyoxyalkylene glycols can maintain the dispersion stability of the self-dispersible pigment while also maintaining adequate wettability to the inner surface of the ink reservoir. Therefore, when a writing instrument with the nib facing sideways or upwards is turned to face downwards for writing, the aqueous ink composition does not remain in its original position within the ink reservoir but can smoothly flow downward toward the nib. In other words, these have the effect of improving the ink reversibility within the ink reservoir.

[0048] Furthermore, polyetheramine and polyoxyalkylene glycol can maintain appropriate wettability of the ink composition not only to the inner surface of the ink reservoir, but also to the ink flow regulator such as the pen tip. As a result, the ink flow regulator can be more easily functioned properly, and excess ink can flow smoothly into the ink flow regulator, thereby suppressing ink dripping from the pen tip due to changes in temperature or pressure inside the writing instrument caused by attaching or detaching the cap.

[0049] The HLB value of the polyetheramine that can be used in the present invention is preferably 10 to 20. This is because when the HLB value of the polyetheramine is 10 or more, it dissolves completely in water and is less likely to form aggregates with self-dispersible pigments, particularly self-dispersible carbon black, and therefore does not adversely affect the dispersion stability in the ink composition.

[0050] The average number of moles of ethylene oxide added (EO number) of the polyetheramine is preferably 10 to 35, and more preferably 13 to 30. When the EO number of the polyetheramine is within the above range, the polyetheramine has high solubility in water, and therefore the effect of the polyetheramine can be stably obtained.

[0051] The polyetheramines include polyoxyethylene stearylamine, polyoxyethylene (20) alkyl (C 14 -C 18 ) amine, polyoxyethylene tallow alkylamine, polyoxyethylene alkylamine ether, polyoxyethylene laurylamine, polyoxyethylene alkyl (coconut)amine, etc.

[0052] As the polyoxyalkylene glycol, it is preferable to use polyoxyethylene polyoxypropylene glycol.

[0053] The average molecular weight of polyoxyethylene polyoxypropylene glycol is preferably 100 to 20,000, and more preferably 1,000 to 15,000. Furthermore, in consideration of excellent dissolution stability and fully obtaining the effects of polyoxyethylene polyoxypropylene glycol, it is even more preferably 3,000 to 15,000, and particularly preferably 10,000 to 15,000.

[0054] The EO number of the polyoxyethylene polyoxypropylene glycol is preferably 5-500, more preferably 100-400, and more preferably 200-300.

[0055] The average number of moles of propylene oxide added (PO number) of polyoxyethylene polyoxypropylene glycol is preferably 5-300, more preferably 10-200, further preferably 20-100, and particularly preferably 40-100.

[0056] The ethylene oxide content of the polyoxyethylene polyoxypropylene glycol is preferably 20 to 90% by mass, more preferably 30 to 80% by mass, and even more preferably 60 to 80% by mass.

[0057] The content of the surfactant in the aqueous ink composition is preferably 0.001 to 1.0 mass%, more preferably 0.01 to 0.5 mass%, and even more preferably 0.01 to 0.1 mass%, based on the total mass of the aqueous ink composition.

[0058] <Water-soluble organic solvent> In the present invention, it is preferable that the ink composition further contains a water-soluble organic solvent. As the water-soluble organic solvent, those used in conventional aqueous ink compositions for writing instruments can be used.

[0059] Examples include (i) glycols such as ethylene glycol, butylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, and glycerin, (ii) alcohols such as methanol, ethanol, 1-propanol, 2-propanol, isopropanol, isobutanol, t-butanol, propargyl alcohol, allyl alcohol, 3-methyl-1-butyn-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, and 3-methoxy-3-methylbutanol. Mixtures of two or more of these can also be used.

[0060] When a water-soluble organic solvent is used in the ink composition of the present invention, it is preferable to use a polyhydric alcohol solvent. This is because the moisture-absorbing effect of the polyhydric alcohol solvent can be imparted to the ink composition, tending to improve dry-up resistance. This is thought to be because the evaporation suppression due to the film formation of α-glucans and the evaporation suppression due to the moisture-absorbing effect of the polyhydric alcohol solvent effectively suppress the evaporation of water in the ink from the pen tip. Therefore, even if the pen tip is exposed to the atmosphere for a long period of time, even in a particularly dry environment, the ink is ejected smoothly from the start of writing, leaving a uniform, smooth handwriting without smudges. Furthermore, the ink composition can be suitably used in writing instruments, such as the retractable writing instruments described below, which are particularly suitable for use in environments where the pen tip is prone to drying out.

[0061] Among the polyhydric alcohol solvents, ethylene glycol, diethylene glycol, butylene glycol, and glycerin are preferred, ethylene glycol, diethylene glycol, and glycerin are more preferred, and ethylene glycol and diethylene glycol are particularly preferred. These polyhydric alcohols have a significant effect of improving the dry-up resistance.

[0062] When using the water-soluble organic solvent, its content is preferably 0.1 to 40% by mass based on the total mass of the ink composition. Further, considering improving the dry-up resistance performance, handwriting water resistance, and handwriting fixing property in a balanced manner, it is preferably 0.5 to 40% by mass, more preferably 0.5 to 10% by mass, and even more preferably 1 to 5% by mass.

[0063] <Other colorants> The ink composition according to the present invention contains a self-dispersing pigment as a colorant, but may also contain other colorants as necessary for color adjustment and the like. As the colorant, those that do not impair the effects of the present invention can be selected and used from conventionally known dyes and pigments. However, since dyes generally tend to reduce the handwriting fastness, it is preferable not to contain dyes. Also, as the pigment, a pigment containing a pigment dispersant can be used, but in order to more strongly express the effects of the present invention, it is preferable that the addition amount is small.

[0064] <pH adjuster> The ink composition according to the present invention can contain a pH adjuster. Examples of the pH adjuster include basic inorganic compounds such as ammonia, sodium carbonate, sodium phosphate, and sodium hydroxide, basic organic compounds such as sodium acetate, triethanolamine, and diethanolamine, lactic acid, and citric acid. Considering the stability of the ink composition over time, it is preferable to use a basic organic compound, and more preferably, to use triethanolamine, which is weakly basic. These pH adjusters can also be used as a mixture of two or more kinds.

[0065] The pH value of the ink composition is preferably 11 or less. This is because a pH value of 11 or less makes it difficult for α-glucans to decompose, and high stability over time is easily achieved. Furthermore, from the viewpoint of the stability over time of the ink composition and prevention of corrosion of metal members with which the ink composition comes into contact, the pH value is preferably 6 or more. Therefore, the pH value of the ink composition is more preferably 6 to 11, and even more preferably 7 to 10. In the present invention, the pH value indicates the value measured at 20°C using an HM-30R pH meter.

[0066] <Antibacterial substances> The ink composition according to the present invention may contain an antibacterial substance, such as phenol, phenoxyethanol, sodium benzoate, sodium dehydroacetate, potassium sorbate, propyl parahydroxybenzoate, 2,3,5,6-tetrachloro-4-(methylsulfonyl)pyridine, sodium 2-pyridinethiol-1-oxide, 1,2-benzisothiazolin-3-one, 2-methyl-4-isothiazolin-3-one, 2-n-octyl-4-isothiazolin-3-one, orthophenylphenol or a salt thereof, and more preferably phenoxyethanol, 1,2-benzisothiazolin-3-one (hereinafter sometimes referred to as BIT), 2-methyl-4-isothiazolin-3-one (hereinafter sometimes referred to as MIT), 2-n-octyl-4-isothiazolin-3-one (hereinafter sometimes referred to as OIT), or a mixture thereof.

[0067] Of these, phenoxyethanol is preferred because it is highly safe and tends to have a significant effect on improving dispersion stability when combined with a self-dispersing pigment.

[0068] Furthermore, the use of phenoxyethanol makes it easy to adjust the ink viscosity to a low level while maintaining dispersion stability, improving ink dischargeability, which in turn makes it easier to leave uniform, well-colored handwriting.

[0069] The content of phenoxyethanol is preferably 1,000 to 100,000 ppm, more preferably 3,000 to 30,000 ppm, and even more preferably 3,000 to 10,000 ppm, based on the total mass of the ink composition.

[0070] Furthermore, phenoxyethanol can be combined with an antibacterial substance having an isothiazolinone structure, such as BIT, MIT, or OIT, to achieve a more excellent antibacterial effect while maintaining good dispersion stability. When using these combinations, the blending ratio of phenoxyethanol to the antibacterial substance having an isothiazolinone structure is preferably 1:10 to 1:0.001 by mass, more preferably 1:1 to 1:0.001, even more preferably 1:0.5 to 1:0.005, particularly preferably 1:0.3 to 1:0.005, and most preferably 1:0.2 to 1:0.005.

[0071] Furthermore, when phenoxyethanol is used, the amount of phenoxyethanol added is preferably 1:1 to 1:0.01, more preferably 1:1 to 1:0.05, and most preferably 1:0.5 to 1:0.1, by mass ratio relative to the self-dispersion pigment. Within this range, the ink composition has improved antibacterial properties and dispersion stability of the self-dispersion pigment, particularly self-dispersion carbon black. As a result, writing performance, such as bleeding and strike-through, is improved.

[0072] In addition, conventional antibacterial substances have the risk of reducing ink reversibility when added to an ink composition in an amount sufficient to provide sufficient antibacterial properties. In contrast, phenoxyethanol does not reduce the ink reversibility of the ink composition in the ink reservoir. Therefore, phenoxyethanol is preferred because it can achieve both antibacterial properties and ink reversal properties.

[0073] Furthermore, when phenoxyethanol is used, the content ratio of phenoxyethanol to α-glucans (phenoxyethanol / α-glucan) is preferably 5 to 80 by mass, and more preferably 5 to 60. If the content ratio is within the above range, the solubility of α-glucan is well maintained while obtaining the effects of phenoxyethanol, and the effects of α-glucan can be fully obtained, resulting in excellent water resistance.

[0074] <Rust inhibitor> The ink composition according to the present invention may contain a rust inhibitor, such as benzotriazole and its derivatives, tolyltriazole, dicyclohexylammonium nitrite, diisopropylammonium nitrite, sodium thiosulfate, saponin, or dialkylthiourea.

[0075] <Chelating agent> The ink composition according to the present invention may contain a chelating agent, such as ethylenediaminetetraacetic acid (EDTA), hydroxyethylenediaminetriacetic acid (HEDTA), glycol ether diaminetetraacetic acid (GEDTA), nitrilotriacetic acid (NTA), hydroxyethyliminodiacetic acid (HIDA), dihydroxyethylglycine (DHEG), diethylenetriaminepentaacetic acid (DTPA), triethylenetetraminehexaacetic acid (TTHA), and alkali metal salts, ammonium salts, or amine salts thereof.

[0076] <Moisturizer> The ink composition according to the present invention may contain a humectant. While the α-glucans and polyhydric alcohol solvents used in the present invention also exhibit a moisturizing effect, the humectant referred to here refers to other substances. Suitable humectants include, for example, urea, sorbitol, N,N,N-trialkylamino acids, and hyaluronic acids.

[0077] N,N,N-trialkylamino acids have high moisture absorption properties, and when used in combination with α-glucans, even better dry-up resistance can be achieved. Furthermore, the excellent water resistance of handwriting provided by α-glucans can be maintained, without impairing handwriting fastness. Furthermore, while maintaining excellent dry-up resistance, they can be easily prepared as low-viscosity ink compositions and ultra-low-viscosity ink compositions, as described below, and also easily improve handwriting fixability. For this reason, it is preferable that the ink composition according to the present invention further contains an N,N,N-trialkylamino acid. The N,N,N-trialkylamino acid is, for example, represented by the following formula (III): R a 3N + (CH2) na COO - (III) R in formula (3) a are independently straight or branched chain alkyl groups, such as those selected from the group consisting of methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, and tert-butyl groups.

[0078] More specifically, examples of N,N,N-trialkylamino acids include trimethylglycine, triethylglycine, tripropylglycine, or triisopropylglycine where na = 1, trimethyl-β-alanine where na = 2, and trimethyl-γ-aminobutyric acid where na = 3. Of these, trimethylglycine is particularly preferred from the viewpoints of dry-up resistance and storage stability.

[0079] The content of the humectant, for example, N,N,N-trialkylamino acid, is more preferably 0.01 to 10%, more preferably 0.1 to 10%, and even more preferably 1 to 5%, based on the total mass of the ink composition.

[0080] <Water-soluble resin and water-insoluble resin> The ink composition according to the present invention may contain a water-soluble or water-insoluble resin. The water-soluble resin is dissolved in the ink composition, and the water-insoluble resin is contained in the ink composition in the form of solid particles or droplets. Examples of such water-soluble or water-insoluble resins include acrylic resins, urethane resins, styrene-butadiene resins, polyester resins, and vinyl acetate resins.

[0081] <Antifoaming agent> The ink composition according to the present invention may further comprise an antifoaming agent such as dimethylpolysiloxane.

[0082] <Lubricant> The ink composition according to the present invention may further contain a lubricant such as a fatty acid. Phosphate ester surfactants and the like may also function as lubricants, and may also be used.

[0083] <Shear thinning agent> The ink composition according to the present invention may contain a shear thinning agent. The shear thinning agent may impart an appropriate viscosity to the ink composition, thereby improving its practicality. In the present invention, the shear thinning agent may be appropriately selected from conventionally known agents. Specific examples include polysaccharides such as xanthan gum, succinoglycan, or carrageenan, and polymers such as polyacrylic acid or crosslinked polyacrylic acid. Synthetic polymeric nonionic surfactants such as associative urethanes, anionic surfactants, and the like may also be used as shear thinning agents. These shear thinning agents may be used as a mixture of two or more types.

[0084] <Physical properties of ink composition for writing instruments> The ink composition according to the present invention preferably has a relatively low viscosity. The ink composition according to the present invention contains various additives, including α-glucans and water-soluble organic solvents, which are generally considered to have a thickening effect. By appropriately adjusting the content of these additives, the ink composition can be made to have a viscosity of 380 s-1 Low viscosity of 50 mPa·s or less at a shear rate of 380 sec -1 The ink composition of the present invention can be an ink composition with an ultra-low viscosity of 2 mPa·s or less at 1000 kJ / min. When such an ink composition with a low viscosity is used in a writing instrument equipped with a pen core having a comb groove for temporarily storing ink, an ink flow path, and an air passage, as described below, the function of the pen core can be fully utilized, and excellent ink discharge properties can be obtained. For this reason, the ink composition of the present invention can be suitably used in writing instruments equipped with such a pen core. Furthermore, since the ink composition of the present invention can be adjusted to an ultra-low viscosity ink while maintaining the dispersion stability of the ink, it can be particularly suitably used in fountain pens equipped with such a pen core.

[0085] The surface tension of the ink composition according to the present invention is preferably 35 to 60 mN / m, and more preferably 40 to 55 mN / m, in an environment of 20°C. By having such a surface tension, the ink composition has an appropriate resistance to external forces such as gravity, atmospheric pressure, and kinetic energy due to impact, and also has appropriate wettability with respect to ink flow rate adjusting components such as pen cores, making it possible to effectively suppress ink dripping from the pen tip. The surface tension of the ink composition can be appropriately adjusted by adjusting the surfactant content, etc.

[0086] <<Method for producing ink composition>> The ink composition according to the present invention can be produced by any conventionally known method, specifically by blending the required amounts of the above-mentioned components and mixing them using various types of stirrers such as a magnetic stirrer, a propeller stirrer, a homogenizer stirrer, a homodisper, a homomixer, or a planetary stirrer, or various types of dispersers such as a bead mill.

[0087] <<Writing implements>> The structure and shape of the writing instrument itself to be filled with the aqueous ink composition for writing instruments of the present invention are not particularly limited, and conventional general-purpose ones can be applied, and the composition can be used for various writing instruments such as marking pens (sign pens) with fiber tips, felt tips, or plastic tips as nibs, ballpoint pens with ballpoint pen tips, and fountain pens with metal nibs.

[0088] Examples of materials for the nibs of writing instruments include metals such as cemented carbide, stainless steel, gold, and iridium, and ceramics such as silicon carbide for ballpoint pens and fountain pens, and synthetic resins such as polyester, nylon, polyurethane, polyethylene, polypropylene, and acrylic for marking pens (felt pens).

[0089] The ink composition according to the present invention tends to be easily adsorbed to metals such as stainless steel, gold-plated stainless steel, 14K gold, 18K gold, and 22K gold. Therefore, when the ink ejection portion of a writing instrument is made of metal, a coating is easily formed on the surface, and the coating is easily maintained over time. Therefore, the ink composition according to the present invention can be suitably used for writing instruments whose pen nibs are made of metal, and excellent resistance to dry-up can be obtained.

[0090] Compared to other writing instruments, the nib of a fountain pen is more often exposed to the outside air, and the ink composition at the nib is more likely to dry out, so high resistance to dry-up is particularly desirable. The ink composition of the present invention has sufficient resistance to dry-up, making it particularly suitable for use in fountain pens.

[0091] Furthermore, writing instruments that can use the ink composition of the present invention may be those configured to be filled directly with the ink composition, or those that have an ink reservoir that can be filled with the ink composition. The ink reservoir may also be a cartridge-type writing instrument or a converter-type writing instrument, which has a structure that allows it to be detachably replaced on the body or nib of the writing instrument. Examples of converter-type writing instruments include writing instruments that can be equipped with an ink reservoir (ink inhaler) that has the function of directly drawing ink into the ink reservoir from an ink container such as an ink bottle.

[0092] In addition, a writing instrument ink cartridge containing the ink composition of the present invention has excellent storage stability over time because the ink composition is stored in a sealed state, so there is little change in concentration due to evaporation of water, and the ink is less susceptible to the influence of outside air. In addition, since writing instrument ink cartridges generally have a shape optimized for each writing instrument, contact with outside air is minimized and leakage from connecting parts is also reduced. For this reason, it is preferable that the ink composition of the present invention be supplied or distributed in a sealed writing instrument ink cartridge.

[0093] Furthermore, examples of writing instruments that can use the ink composition of the present invention include cap-type writing instruments equipped with a cap that covers the nib, and retractable writing instruments equipped with a knock mechanism, a rotation mechanism, or a slide mechanism and capable of housing the nib within a barrel. The ink composition of the present invention has sufficient resistance to drying up, and therefore can be suitably used for retractable writing instruments that are often placed in environments where the nib is prone to drying out.

[0094] Furthermore, the ink supply mechanism of a writing instrument in which the ink composition of the present invention can be used is not particularly limited, and examples thereof include (mechanism 1) a mechanism that has an ink guide core made of a fiber bundle or the like as an ink flow rate adjusting member and guides the aqueous ink composition to the pen tip, (mechanism 2) a mechanism that guides the ink composition to the pen tip via a pen core that has a comb groove for temporarily storing ink, an ink flow passage, and an air passage, (mechanism 3) a mechanism that has an ink flow rate adjusting member with a valve mechanism and supplies the aqueous ink composition to the pen tip, and (mechanism 4) a mechanism that supplies the aqueous ink composition directly to the pen tip from an ink reservoir or barrel equipped with a pen tip.

[0095] As described above, the ink composition according to the present invention can be adjusted to a low viscosity ink composition or an ultra-low viscosity ink composition while sufficiently maintaining the dispersion stability of the ink composition, and therefore can be suitably used in a writing instrument equipped with a supply mechanism of (Mechanism 1), (Mechanism 2), or (Mechanism 3).

[0096] Furthermore, as mentioned above, the ink composition of the present invention can maintain appropriate wettability to the pen tip (mechanism 2), which improves ink discharge from the pen tip and makes it easier to form clear handwriting with little smearing, and even if the internal pressure of the ink reservoir changes due to changes in the outside temperature or the removal and attachment of the cap, the ink is retained between the comb grooves, preventing ink leakage from the pen tip and achieving excellent resistance to dripping. For this reason, the ink composition of the present invention is particularly suitable for use in writing instruments having (mechanism 2), i.e., writing instruments equipped with a pen tip having comb grooves that temporarily store ink, ink flow passages, and air passages.

[0097] Furthermore, in the case of a writing instrument using an ink composition (pigment ink) that uses a pigment as a colorant, as in the present invention, when the ink dries, it may adhere to writing instrument components such as the nib or ink reservoir (cartridge, converter) of the writing instrument due to resin components in the ink. In such cases, it is preferable to use a writing instrument cleaning liquid to clean the nib to which the ink has adhered. This is because by thoroughly removing the adhered ink using a writing instrument cleaning liquid, the effects on writing performance can be reduced, and if a different ink color is used on the writing instrument after cleaning, it is possible to prevent color mixing.

[0098] As the writing instrument cleaning liquid, it is preferable to use a writing instrument cleaning liquid containing a nonionic surfactant, taking into consideration the ink cleaning property and solubility in water. Specifically, the HLB value of the surfactant is preferably 4 to 15, more preferably 6 to 15. Furthermore, in consideration of cleaning property, it is preferable to use a writing instrument cleaning liquid containing a nonionic surfactant having a polyoxyalkylene group.

[0099] In particular, even in writing instruments that have a pen core with a complex shape that has a comb groove for temporarily storing ink, an ink flow passage, and an air passage, it is possible to effectively remove solidified ink by using a writing instrument cleaning liquid.

[0100] The writing instrument cleaning liquid is preferably contained in a film, sheet, or other packaging to form a writing instrument cleaning liquid package. From the standpoint of portability and convenience, it is preferable to individually package a single-use amount in a film or sheet package. Furthermore, considering improvements in long-term storage stability, such as moisture evaporation, it is preferable to package in a metal film. The writing instrument cleaning liquid package is preferably sold as a writing instrument set, combining the ink composition of the present invention, a writing instrument containing the ink composition, or a writing instrument ink cartridge containing the ink composition. Specifically, the writing instrument cleaning liquid package is preferably sold as a writing instrument set together with the ink composition contained in an ink bottle or the like, and a writing instrument such as a fountain pen, ballpoint pen, or marking pen (felt pen). It is more preferable to sell the writing instrument set together with an inhaler, such as a dropper, for collecting the writing instrument cleaning liquid, the writing instrument cleaning liquid package, and the writing instrument. [Example]

[0101] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0102] Example 1 The following raw materials were mixed by propeller stirring to obtain an ink composition of Example 1. Ethylene glycol: 2.00% by mass Triethanolamine: 2.00% by mass Betaine (N,N,N-trimethylglycine): 2.00 mass Pullulan: 0.03% by mass Aqua-Black 162 (product name, manufactured by Tokai Carbon Co., Ltd., anionic self-dispersing carbon black dispersion, surface functional group of carbon black: carboxyl group, secondary particle diameter (average) calculated from particle size distribution of carbon black: 110 nm, viscosity: 6.5 mPa·s, pH 6.5, surface tension: 72 mN / m, concentration 20% by mass): 15.00% by mass Phenoxyethanol: 0.50% by mass 1,2-benzisothiazolin-3-one (BIT): 0.05% Water: remainder

[0103] <Examples 2 to 4, Comparative Examples 1 to 4> The types and blending amounts of raw materials were changed to obtain ink compositions of Examples 2 to 4 and Comparative Examples 1 to 4. The raw materials used are as follows. Meduseeds-CP (trade name, manufactured by NOF Corporation, contains hexyldicarbamate cholesteryl pullulan, water, butylene glycol, methylparaben, and phenoxyethanol. Hexyldicarbamate cholesteryl pullulan concentration: 1% by mass) Sandec #70FN (product name, manufactured by Sanwa Starch Co., Ltd., dextrin) BONJET BLACK CW-1 (product name, manufactured by Orient Chemical Industries Co., Ltd., self-dispersing carbon black dispersion, concentration 20% by mass) FUJI SP Black 8112 (product name, manufactured by Fuji Pigment Co., Ltd., acrylic resin-dispersed carbon black dispersion, concentration 15%)

[0104] The compositions of the ink compositions prepared are shown in Table 1.

[0105] <Testing and Evaluation> The ink compositions thus obtained were evaluated by the following methods, and the results are shown in Table 1.

[0106] <Viscosity> The viscosity of the resulting ink composition was measured using a B-type rotational viscometer (model: BLII, rotor: BL adapter, manufactured by Toki Sangyo Co., Ltd., sample volume 20 ml, 20° C., rotation speed 60 rpm).

[0107] <Surface tension> The surface tension of the resulting ink composition was measured using a surface tension meter (model: DY-200, manufactured by Kyowa Interface Science Co., Ltd., 20°C, platinum plate, vertical plate method).

[0108] <ph> Measurement was performed using a pH meter (model: HM-30R, manufactured by DKK-TOA Corporation, 20°C).

[0109] <Dry-up resistance> A fountain pen was prepared by attaching an ink cartridge filled with an ink composition to a knock-type capless fountain pen (FCN-1MR, manufactured by Pilot Corporation) with a gold-plated stainless steel nib with a writing width of M and a pen core with a comb groove for temporarily storing ink, an ink flow passage, and an air passage. With the nib protruding, the fountain pen was left in an environment of 20°C and 65% RH for 30 minutes, after which the letter "V" was repeatedly written on a test piece of paper to check the number of characters that could not be written. A: 0 characters (immediately writable) B: 2~4 characters C: 5 characters or more ~ ​​impossible to write

[0110] <Handwriting water resistance> A fountain pen was prepared by attaching an ink cartridge filled with the ink composition to a Custom 74 fountain pen (FKKN-12SR, manufactured by Pilot Corporation) with a 14K gold nib with a writing width of M and a pen core with a comb groove for temporarily storing ink, an ink flow passage, and an air passage. Using this fountain pen, characters were written on test paper, and after leaving it in an environment of 25°C for 30 minutes, water was dropped on the characters and bleeding of the characters was observed. A: Almost no bleeding is observed B: Slight bleeding is observed, but this does not pose a problem in practical use. C: Bleeding is observed

[0111] <Handwriting density> A fountain pen was prepared by attaching an ink cartridge filled with the ink composition to a Custom 74 fountain pen (FKKN-12SR, manufactured by Pilot Corporation) with a 14-karat gold nib having a writing width of M and a pen core with a comb groove for temporarily storing ink, an ink flow passage, and an air passage. Using this fountain pen, characters were written on test paper, and the density was evaluated. A: The color density is sufficient. B: The color density is slightly low, but there is no problem in practical use. C: The color density is low, and there are concerns about its practical use.

[0112] [Table 1] *1: Aqua-Black 162 *2: BONJET BLACK CW-1 *3: FUJI SP Black 8112 *4: Hexyldicarbamate cholesteryl pullulan *5: Sandeck #70FN *6: Water-soluble organic solvents derived from water and additives

[0113] <Comparative Example 5> An ink composition using carbon black that was not surface-treated and did not contain a dispersant was also prepared as Comparative Example 5, but the pigment had low wettability and the dispersion stability was insufficient, making it impossible to evaluate. In contrast, the ink compositions of Examples 1 to 4 and Comparative Examples 1 to 4 had sufficient dispersion stability.

[0114] <Example 5> An ink composition not containing phenoxyethanol was prepared in contrast to the ink composition of Example 1, and designated the ink composition of Example 5. The ink compositions of Examples 1 and 5 were sealed in glass bottles and stored in an environment of 50°C for 12 weeks, after which samples of the ink composition were collected near the liquid surface and at the bottom of the bottle and the state of pigment dispersion was evaluated under a microscope. It was found that the pigment was more uniformly dispersed in Example 1 than in Example 5, and that the dispersion stability was superior. Furthermore, both Examples 1 and 5 had sufficient antibacterial properties.

[0115] <Examples 1a, 6 and 7> An ink composition having the same composition as in Example 1 was prepared (Example 1a). Furthermore, ink compositions were prepared by varying the content of phenoxyethanol in the ink composition of Example 1, and these were designated as the ink compositions of Examples 6 and 7. These compositions were evaluated in the same manner as in Example 1. The results obtained are shown in Table 2.

[0116] [Table 2]

[0117] Furthermore, the dispersion state and antibacterial performance of Examples 1a, 6, and 7 were evaluated in the same manner as in Examples 1 and 5. Compared to Example 5, Examples 1a, 6, and 7 had more uniformly dispersed pigments and were superior in dispersion stability, and furthermore, Examples 1a and 7 had more superior dispersion stability than Example 6. Furthermore, Examples 1a, 5, 6, and 7 all had sufficient antibacterial performance.

[0118] <Examples 8 and 9> An ink composition was prepared by further adding 0.1% by mass of polyetheramine to the ink composition of Example 1, and this was designated the ink composition of Example 8. Also, an ink composition was prepared by further adding 0.05% by mass of polyoxyethylene polyoxypropylene glycol to the ink composition of Example 1, and this was designated the ink composition of Example 9.

[0119] The physical properties of the polyetheramine used in Example 8 are as follows: Polyetheramine: Polyoxyethylene-alkylamine, HLB value 15.4, EO number 20

[0120] The physical properties of the polyoxyethylene polyoxypropylene glycol used in Example 9 are as follows: Polyoxyethylene polyoxypropylene glycol: average molecular weight 13,000, number of moles of ethylene oxide added 240, number of moles of propylene oxide added 60, EO content 75% by mass

[0121] A resin ink inhaler (containing a resin movable body movable back and forth within the ink inhaler) was placed with its opening facing upward, and the ink compositions of Examples 1, 8, and 9 were poured into it until the movable body was completely immersed in the ink composition. This ink inhaler was then attached to a writing instrument (Pilot Corporation, fountain pen, FKA-1SR-NCM) with a fountain pen-shaped nib and a pen core having a comb groove for temporarily storing ink, an ink flow passage, and an air passage, with the nib facing upward. Ten such writing instruments were prepared as test instruments, and when the test writing instruments with the nib facing upward were gently turned to face downward, the ink compositions of Examples 8 and 9 flowed down the nib in the ink reservoir in greater numbers within 10 seconds than those of Example 1, demonstrating superior ink reversal within the ink reservoir.

[0122] Furthermore, a fountain pen was prepared by attaching cartridges filled with the ink compositions of Examples 1, 8, and 9 to a knock-type capless fountain pen (manufactured by Pilot Corporation) having a gold-plated stainless steel nib with a writing width of M and equipped with a pen core having a comb groove for temporarily storing ink, an ink flow passage, and an air passage. This fountain pen was used as a test writing instrument and placed in a vacuum desiccator, and the pressure inside the desiccator was reduced to -70 mmHg relative to atmospheric pressure over 5 minutes. After that, the fountain pen was left in the desiccator for another 5 minutes while maintaining the reduced pressure of -70 mmHg relative to atmospheric pressure. When the ink compositions of Examples 8 and 9 were used, there was less dripping from the nib and better drip resistance than in Example 1.

[0123] Furthermore, when the ink compositions of Examples 8 and 9 were evaluated for dry-up resistance, water resistance of handwriting, and handwriting density by the above-mentioned methods, the evaluation results were the same as those of the ink composition of Example 1.

[0124] From the above results, it is clear that the ink composition of the present invention is excellent in all properties such as handwriting fastness, dispersion stability, resistance to drying up, handwriting density, and low viscosity.< / ph>

Claims

1. A water-based ink composition for a fountain pen, comprising a self-dispersing pigment, pullulan or a pullulan derivative, and water, wherein the content ratio of the pullulan or the pullulan derivative to the self-dispersing pigment is 0.0001 to 0.1 by mass, The aqueous ink composition for fountain pens further comprises a nonionic surfactant having a polyoxyalkylene structure and 3,000 to 30,000 ppm of phenoxyethanol based on the total mass of the ink composition.

2. The ink composition described in claim 1, wherein the weight average molecular weight of the pullulan or pullulan derivative is 10,000 or more.

3. 3. The ink composition according to claim 1, wherein the content of the pullulan or pullulan derivative is 0.001 to 1% by mass based on the total mass of the ink composition.

4. 4. The ink composition according to claim 1, wherein the self-dispersing pigment is anionic self-dispersing carbon black.

5. Shearing rate 380sec －１ The ink composition according to any one of claims 1 to 4, wherein the viscosity at 1000 kJ / min is 50 mPa·s or less.

6. A fountain pen containing the ink composition according to any one of claims 1 to 5.

7. 7. The fountain pen according to claim 6, further comprising a pen core having a comb groove for temporarily storing ink, an ink flow passage, and an air passage.

8. A cartridge ink for a fountain pen, characterized by containing the ink composition according to any one of claims 1 to 5.

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