Aqueous ink composition for writing utensils and writing utensil equipped with said aqueous ink composition

Abstract

Provided is an aqueous ink composition for writing utensils which is capable of more effectively preventing pen tips from drying up without lowering the drying properties of the drawn lines. Also provided is a writing utensil equipped with this aqueous ink composition.　This aqueous ink composition for writing utensils is characterized by comprising at least a colorant, a water-soluble solvent, a film-forming non-drying agent having a solubility in water of less than 40 g / 100 mL, and water and characterized in that the molar fraction of the film-forming non-drying agent to the water-soluble components in the ink is 0.25 or greater. This writing utensil is characterized by being equipped with the aqueous ink composition for writing utensils, which comprises the above-mentioned components.

Description

Aqueous ink composition for writing instruments, and writing instruments equipped with the aqueous ink composition

[0001] The present specification relates to an aqueous ink composition for a writing instrument that can enhance the resistance to dry-up of the pen tip without reducing the drying properties of the drawn lines, and to a writing instrument equipped with this aqueous ink composition.

[0002] Conventionally, water-soluble solvents (soluble in water and liquid at room temperature) or water-soluble powders (soluble in water and solid at room temperature) have been blended as volatilization inhibitors for aqueous ink compositions for writing instruments, etc. Among these, increasing the content of water-soluble solvents in an aqueous ink composition significantly reduces the drying speed of drawn lines, and although volatilization at the pen tip can be suppressed, there is a problem of reduced drying speed of drawn lines. On the other hand, water-soluble powders are sometimes used instead of water-soluble solvents, but they have the same problems as water-soluble solvents. Furthermore, water-soluble powders with low solubility in water (hereinafter simply referred to as "film-forming non-drying agents") are sometimes used, but the use of water-soluble solvents or solvents with high solubility in water in combination reduces the film-forming effect of the film-forming non-drying agent at the pen tip, and as a result, film-forming properties are not exhibited, and the volatilization inhibitory effect is not exhibited.

[0003] On the other hand, Patent Document 1 discloses an aqueous ink composition comprising a colorant, water, and a mixture of one or more selected from pentaerythritol, trimethylolethane, and trimethylolpropane, which, when a certain substance is incorporated into the aqueous ink, is an excellent aqueous ink that has good resistance to drying, does not rapidly increase in viscosity, does not emit a strong odor, does not erase recorded images or handwriting on thermal paper or non-carbon paper, and does not discolor handwriting even on thermal paper.

[0004] Furthermore, Patent Document 2 filed by the same applicant discloses a writing instrument that includes at least a barrel containing water-based ink, a nib that is provided on the tip side of the barrel and is capable of ejecting water-based ink, and a cap that is removably attached to the nib side of the barrel in order to prevent condensation inside the cap, wherein the water-based ink has a vapor pressure of 10.3 to 12.3 kPa at 50°C.

[0005] However, conventional aqueous ink compositions including those described in Patent Documents 1 and 2 above have not yet been able to enhance the dry-up resistance of the pen tip, and there is currently a strong demand for an aqueous ink composition for a writing instrument that can enhance the dry-up resistance of the pen tip without reducing the drying properties of the drawn lines, and for a writing instrument using such an aqueous ink composition.

[0006] JP-A-5-271601 (claims, etc.) JP-A-2023-90636 (claims, etc.)

[0007] The present disclosure is made in view of the above-mentioned problems and current state of the prior art, and aims to solve these problems, and to provide an aqueous ink composition for a writing instrument that can increase the dry-up resistance of the pen tip without reducing the drying properties of the drawn lines, and a writing instrument equipped with this aqueous ink composition.

[0008] In view of the above-mentioned conventional problems, the present inventors have conducted extensive research and have found that the above-mentioned aqueous ink composition for a writing instrument, and a writing instrument, can be obtained by containing at least a colorant and water and setting the ink physical properties within specific ranges, etc., and have thus completed the present disclosure.

[0009] That is, the aqueous ink composition for a writing instrument of the present disclosure is characterized by containing at least a colorant, a water-soluble solvent, a film-forming non-drying agent having a solubility in water of less than 40 g / 100 mL, and water, and the molar fraction of the film-forming non-drying agent relative to the water-soluble components in the ink is 0.25 or more. The melting point of the film-forming non-drying agent is preferably 25°C or higher. The solubility of the film-forming non-drying agent in water is preferably 10 g / 100 mL or less. The writing instrument of the present disclosure is characterized by being equipped with the aqueous ink composition for a writing instrument having the above-mentioned configuration.

[0010] According to the present disclosure, there is provided an aqueous ink composition for a writing instrument that can improve the dry-up resistance of the pen tip without reducing the dryness of the drawn line, and a writing instrument equipped with this aqueous ink composition. The objects and advantages of the present disclosure will be realized and attained by use of the elements and combinations particularly pointed out in the claims. Both the foregoing general description and the following detailed description are exemplary and explanatory and are not intended to limit the present disclosure, which is set forth in the claims.

[0011] 1 is a diagram showing an example of an embodiment (first embodiment) of a writing instrument equipped with a cap formed from a transparent material of the present disclosure, where (a) is a plan view, (b) is a front view, and (c) is a front longitudinal cross-sectional view. It is an enlarged perspective view of the nib of the writing instrument of FIG. 1, where (a) is an enlarged perspective view of the nib seen from one direction, and (b) is an enlarged perspective view of the nib seen from a 180° expanded direction of (a). It is a diagram showing another example (second embodiment) of an embodiment of a writing instrument equipped with a cap formed from a transparent material of the present disclosure, where (a) is a plan view, (b) is a front view, and (c) is a front longitudinal cross-sectional view. It is an enlarged perspective view of the nib of the writing instrument of FIG. 3, where (a) is an enlarged perspective view of the nib seen from one direction, and (b) is an enlarged perspective view of the nib seen from a 180° expanded direction of (a). It is a diagram showing another example (third embodiment) of an embodiment of a writing instrument equipped with a cap formed from a transparent material of the present disclosure, where (a) is a central longitudinal cross-sectional view, and (b) is a central transverse cross-sectional view. 6A and 6B are diagrams showing an example of the writing instrument of Fig. 5 in a state where the cap is removed, (a) being a perspective view from the front side, (b) being a perspective view from the rear side, and (d) being a diagram showing an example of the writing instrument of Fig. 5 in a state where the cap body is attached, (a) being a front view, (b) being a plan view, (c) being a left side view, and (d) being a right side view.

[0012] The following describes in detail the embodiments of the present disclosure. However, please note that the technical scope of the present disclosure is not limited to the embodiments described in detail below, but extends to the inventions set forth in the claims and their equivalents. Furthermore, the present disclosure can be implemented based on the contents disclosed in this specification and common general technical knowledge in the relevant field (including design matters and obvious matters).

[0013] <Aqueous Ink Composition for Writing Instruments> The aqueous ink composition for writing instruments of the present disclosure contains at least a colorant, a water-soluble solvent, a film-forming non-drying agent having a solubility in water of less than 40 g / 100 mL, and water, and is characterized in that the molar fraction of the film-forming non-drying agent relative to the water-soluble components in the ink is 0.25 or more.

[0014] <Colorant> Examples of colorants used in the present disclosure include those used in writing instruments, such as dyes that dissolve or disperse in water, conventionally known inorganic and organic pigments such as titanium oxide, colored resin microparticles or dispersions thereof (including pigment-containing resin particle pigments, pseudopigments in which resin emulsions are colored with dyes, white plastic pigments, hollow resin pigments (particles), etc.), pigments with a silica or mica base and a multilayer surface coating of iron oxide or titanium oxide, thermochromic pigments, photochromic pigments, etc., and composite pigments thereof can be used. Examples of dyes that can be used include fluorescent dyes, water-soluble dyes, and oil-soluble dyes.

[0015] The fluorescent dye that can be used is not particularly limited as long as it has good color development properties, and examples thereof include Basic Yellow 1, Basic Yellow 40, Basic Red 1, Basic Red 1:1, Basic Violet 13, Basic Violet 7, Basic Violet 10, Basic Violet 11:1, Basic Orange 22, Basic Blue 7, Basic Green 1, Acid Yellow 3, Acid Yellow 7, Acid Red 52, Acid Red 77, Acid Red 87, Acid Red 92, Acid Blue 9, Disperse Yellow 121, Disperse Yellow 82, Disperse Yellow 83, Disperse Orange 11, Disperse Red 58, Disperse Blue 7, Direct Yellow 85, Direct Orange 8, Direct Red 9, Direct Blue 22, Direct Green 6, Solvent Yellow 44, Solvent Red 49, Solvent Blue 5, and Solvent Green 7. Among the fluorescent dyes, azomethine-based, xanthene-based, and triphenylmethane-based fluorescent dyes are particularly preferred from the standpoints of color development properties and ink stability. Specifically, particularly preferred fluorescent dyes include azomethine fluorescent dyes such as Basic Yellow 1 and Basic Yellow 40, xanthene fluorescent dyes such as Basic Red 1:1 and Basic Violet 11:1, and triphenylmethane fluorescent dyes such as Basic Violet 1. These dyes may be used alone or in combination of two or more.

[0016] Examples of colored resin microparticles or dispersions thereof include a dispersion of colored resin microparticles in which colored resin microparticles composed of at least a carboxyl group-containing vinyl monomer (A) having a solubility in water of 10% by mass or less as an acidic functional group, an ester monomer (B) of acrylic acid or methacrylic acid with a linear or cyclic alcohol having 2 to 18 carbon atoms, and a basic dye or oil-soluble dye are dispersed in water; and a dispersion of colored resin microparticles in which colored resin microparticles composed of a cyclohexyl (meth)acrylate monomer and a basic dye or oil-soluble dye are dispersed in water, wherein the content of the cyclohexyl (meth)acrylate monomer is 30% by mass or more relative to the total polymer components constituting the colored resin microparticles, and the content of the basic dye or oil-soluble dye is 15% by mass or more relative to the total polymer components.

[0017] Examples of thermochromic pigments include those produced by microencapsulating a thermochromic composition containing at least a leuco dye that functions as a color former, a developer that is a component capable of causing the leuco dye to develop color, and a color change temperature regulator that controls the color change temperature during color development of the leuco dye and the developer, to a predetermined average particle size (e.g., 0.1 to 10 μm). Examples of photochromic pigments include photochromic particles composed of at least one selected from photochromic dyes (compounds), fluorescent dyes, and the like, and a resin such as a terpene phenol resin, and those produced by microencapsulating a photochromic composition containing at least one selected from photochromic dyes (compounds), fluorescent dyes, and the like, an organic solvent, and additives such as antioxidants, light stabilizers, and sensitizers, to a predetermined average particle size (e.g., 0.1 to 10 μm). In the present disclosure (including examples), the "average particle size" is the D50 value calculated on a volume basis with a refractive index of 1.81 using a particle size distribution analyzer HR9320-X100 (manufactured by Nikkiso Co., Ltd.).

[0018] These coloring materials can be used alone or in combination of two or more (hereinafter simply referred to as "at least one type"). The (total) (solid content) content of these coloring materials is preferably 0.1 to 40% by mass, and more preferably 1 to 30% by mass, based on the total amount of the aqueous ink. By setting the content of this coloring material to 0.1% by mass or more, sufficient line density can be obtained, while by setting it to 40% by mass or less, an increase in viscosity is suppressed, resulting in good ink flowability, which is preferable.

[0019] The water-soluble solvent used in the present disclosure is used for the purpose of improving various qualities of the ink, such as preventing the ink from freezing at low temperatures, stabilizing the dissolution of water, preventing the ink from drying due to evaporation of water, etc. In the present disclosure, a water-soluble solvent (including water) is a component that dissolves in water, and among these, a "water-soluble solvent (component)" refers to one that is liquid (having a melting point below 25°C) at room temperature (25°C; the same applies hereinafter). Examples of water-soluble solvents that can be used include polyhydric alcohol solvents such as ethylene glycol (melting point -12.9°C), diethylene glycol (melting point -10.45°C), triethylene glycol (melting point -7.2°C), propylene glycol (melting point -59°C), polyethylene glycol, and glycerin (melting point 17.8°C); alcohol-based solvents 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; glycol ether-based solvents such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, 3-methoxybutanol, and 3-methoxy-3-methylbutanol; and triethanolamine (melting point 20.5°C), which can be used alone or in combination of two or more. The total content of these water-soluble solvents is preferably 1 to 40% by mass based on the total amount of the ink composition.

[0020] The film-forming non-drying agent used in the present disclosure is a water-soluble powder with low solubility in water, i.e., a water-soluble powder with a solubility of less than 40 g / 100 mL. In the present disclosure, a "non-drying agent" refers to a substance that is solid at room temperature (a melting point of 25°C or higher), and among non-drying agents, a film-forming non-drying agent refers to a non-film-forming non-drying agent with a solubility of less than 40 g / 100 mL in water. Other non-drying agents are referred to as non-film-forming non-drying agents or film-formation inhibitors. Specific film-forming non-drying agents that can be used include pentaerythritol (solubility in water: 5.6 g / 100 mL), dipentaerythritol (solubility in water: 0.2 g / 100 mL), erythritol (solubility in water: 36 g / 100 mL), sucralose (solubility in water: 0.2 g / 100 mL), and acesulfame potassium (solubility in water: 27 g / 100 mL), which can be used alone or in combination of two or more.

[0021] From the viewpoints of film-forming ability and film-forming speed, the film-forming non-drying agent preferably has a melting point of 25° C. or higher, more preferably 100° C. or higher, and is desirably a film-forming non-drying agent with a solubility in water of 10 g / 100 mL or lower. The (total) content of these film-forming non-drying agents with a solubility in water of less than 40 g / 100 mL may be such that the molar fraction of the film-forming non-drying agent relative to the water-soluble components in the aqueous ink is 0.25 or higher, as will be described later.

[0022] Note that film-forming non-drying agents with a water solubility of 40 g / 100 mL or more, as well as non-film-forming non-drying agents and film-formation inhibitors, will not be able to exhibit the effects of the present disclosure. Film-forming non-drying agents with a water solubility of 40 g / 100 mL or more are not preferred because they have high solubility in water and do not form a film when water evaporates in the non-drying test. Furthermore, non-film-forming non-drying agents are liquid at room temperature, so their use is also undesirable. The film-formation inhibitor has a water solubility of 20 g / 100 mL or more, inhibits film formation, and contains a miscible solvent such as glycerin or ethylene glycol. When this film-formation inhibitor is contained, it is preferable that the film-forming non-drying agent / film-formation inhibitor (molar ratio) be within a predetermined range, as described below. Examples of non-film-forming non-drying agents and film-forming inhibitors include trimethylglycine (solubility in water: 160 g / 100 mL), trimethylolpropane (solubility in water: 100 g / 100 mL), and trimethylolethane (solubility in water: 60 g / 100 mL).

[0023] <Other Components> The aqueous ink composition for a writing instrument of this embodiment contains the above-mentioned colorant, water-soluble solvent, and film-forming non-drying agent having a solubility in water of less than 40 g / 100 mL, and the remainder is water (tap water, purified water, distilled water, ion-exchanged water, pure water, etc.) as the solvent. In addition, as described below, the composition may contain various components typically used in aqueous inks, such as dispersants, surfactants, viscosity adjusters, fixing resins, rust inhibitors, preservatives or antibacterial agents, and pH adjusters, as necessary, within the range in which the effects of the present disclosure are achieved, as long as the composition has a molar fraction of the film-forming non-drying agent relative to the water-soluble components in the ink of 0.25 or more, as described below.

[0024] The dispersant and adhesive resin may contain a water-soluble resin, for example, at least one selected from water-soluble resins such as acrylic resins, polyvinyl alcohol, polyvinylpyrrolidone, polyethylene oxide, and urethane resins, and resin emulsions such as acrylic emulsions, vinyl acetate emulsions, urethane emulsions, and polyolefin emulsions.

[0025] The surfactant that can be used is not particularly limited, but at least one surfactant selected from the group consisting of fluorine-based surfactants, acetylene glycol-based surfactants, and silicone-based surfactants can be used.

[0026] Viscosity adjusters that can be used include natural polymers such as polysaccharides and synthetic polymers. Examples of polysaccharides that can be used include gum arabic, tragacanth gum, guar gum, locust bean gum, alginic acid, carrageenan, gelatin, xanthan gum, welan gum, succinoglycan, diutan gum, and dextran, as well as cellulose derivatives such as methylcellulose, ethylcellulose, hydroxyethylcellulose, and carboxymethylcellulose, and starch glycolic acid and its salts. Examples of synthetic polymers that can be used include polyvinylpyrrolidone, polyvinyl methyl ether, polyacrylic acid and its salts, polyethylene oxide, vinyl acetate-polyvinylpyrrolidone copolymer, styrene-acrylic acid copolymer and its salts, and isobutylene-maleic anhydride copolymer and its salts.

[0027] Usable antiseptics or antibacterial agents include phenol, sodium omadine, sodium benzoate, benzisothiazoline, and benzimidazole compounds. Usable rust inhibitors include benzotriazole, tolyltriazole, dicyclohexylammonium nitrite, and saponins. Usable pH adjusters include amine compounds such as triethanolamine, diethanolamine, monoethanolamine, dimethylethanolamine, morpholine, and triethylamine; ammonia; and alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, and lithium hydroxide.

[0028] <Mole Fraction of Film-Forming Non-Drying Agent to Water-Soluble Component> In order to achieve the effects of the present disclosure, an aqueous ink composition for a writing instrument is used in which the molar fraction of the film-forming non-drying agent to the water-soluble component is 0.25 (25%) or more. This molar fraction can be calculated by calculating the number of moles and molar fraction of all water-soluble components and the number of moles and molar fraction of the film-forming non-drying agent from the water-soluble components (molecular weight and number of moles of each component), respectively, and then calculating the molar fraction of the film-forming non-drying agent / (molar fraction of water-soluble component + molar fraction of the film-forming non-drying agent). As described above, in the present disclosure, by using an aqueous ink composition for a writing instrument in which the molar fraction is 0.25 (25%) or more, an excellent film-forming effect at the pen tip can be achieved, allowing the effects of the present disclosure to be achieved. More preferably, the molar fraction of the film-forming non-drying agent to the water-soluble component is 0.5 (50%) or more, and particularly preferably 0.55 (55%) or more. If the molar fraction of the film-forming non-drying agent relative to the water-soluble component is less than 0.25 (25%), the non-drying effect after film formation will be insufficient, which is undesirable. When a film-forming inhibitor is contained, it is preferable that the film-forming non-drying agent / film-forming inhibitor (molar ratio) be in the range of 0.3 to 1.5, from the viewpoints of preventing the loss of the film-forming effect and suppressing precipitation of the film-forming non-drying agent.

[0029] The aqueous ink composition for a writing instrument of the present disclosure is prepared by appropriately combining at least the above-mentioned colorant, water-soluble solvent, film-forming non-drying agent having a solubility in water of less than 40 g / 100 mL, water, and other components according to the intended use of the writing instrument ink (e.g., for a marking pen), and combining them in suitable amounts, followed by stirring and mixing with a stirrer such as a homomixer, homogenizer, or disper, and, if necessary, removing coarse particles from the ink composition by filtration or centrifugation, thereby obtaining an aqueous ink composition for a writing instrument having a molar fraction of the film-forming non-drying agent relative to the water-soluble components of 0.25 (25%) or more. Furthermore, from the viewpoints of usability, safety, the stability of the ink itself, and compatibility with the ink container, the pH (25°C) of the aqueous ink composition for a writing instrument is preferably adjusted to 5 to 10 with a pH adjuster or the like, and more preferably 6 to 9.5.

[0030] The aqueous ink composition for a writing instrument of the present disclosure configured in this manner contains at least a colorant, a water-soluble solvent, a film-forming non-drying agent having a solubility in water of less than 40 g / 100 mL, and water. By setting the molar fraction of the film-forming non-drying agent to the water-soluble components in the ink to be 0.25 or more, the film-forming non-drying agent can efficiently form a film (a volatilization-suppressing film) on the pen tip, and the moisture of the ink can be retained within the film. This increases the dry-up resistance of the pen tip without reducing the drying properties of the drawn lines. Furthermore, the volatilization-suppressing film easily disintegrates when writing with the pen tip, and an aqueous ink composition for a writing instrument can be obtained that does not impair writing performance (this point will be described in more detail in the examples, etc., described later).

[0031] The writing instrument of the present disclosure is equipped with the aqueous ink composition for a writing instrument having the above-described characteristics, and can provide a writing instrument that can enhance the dry-up resistance of the pen tip without reducing the drying property of the drawn line. The writing instrument can be equipped with, for example, a ballpoint pen or marking pen equipped with a pen tip portion such as a ballpoint pen tip, fiber tip, felt tip, plastic tip, fiber core, or porous core.

[0032] In this disclosure, the term "marking pen" refers to a pen having a mechanism for supplying ink stored in an ink reservoir to a resin writing element by capillary action, and also includes pens referred to as "sign pens." Furthermore, the term "ballpoint pen" refers to a pen having a mechanism for causing ink stored in an ink reservoir to seep out by the rotation of a ball provided in the writing element. The ballpoint pen contains an aqueous ink composition for a writing instrument having the above-described composition in a ballpoint pen ink reservoir (refill) equipped with a ball having a diameter of 0.18 to 2.0 mm, and an ink follower is also added. The ink follower is a liquid that is incompatible with the aqueous ink composition for a writing instrument having the above-described characteristics contained in the ink reservoir and has a low specific gravity relative to the aqueous ink composition, such as polybutene, silicone oil, or mineral oil. The structure of the ballpoint pen, marking pen, etc. is not particularly limited, and may be, for example, a direct ink type ballpoint pen or marking pen having a collector structure (ink retention mechanism) in which the barrel itself serves as an ink container and is filled with the aqueous ink composition for a writing instrument having the above-described structure.

[0033] 1(a) to 1(c), a writing instrument A of this embodiment includes at least a barrel 10 in which an aqueous ink composition for a writing instrument having the above-described characteristics is housed via an ink occlusion body 15; a pen tip 20 provided on the tip side of the barrel 10 and capable of ejecting the aqueous ink composition for a writing instrument; and a cap 60 formed of a visible or invisible material and detachably attached to the pen tip 20 side of the barrel 10, wherein the aqueous ink composition for a writing instrument contains at least the above-described colorant, water-soluble solvent, film-forming non-drying agent having a solubility in water of less than 40 g / 100 mL, and water, and the molar fraction of the film-forming non-drying agent relative to the water-soluble components in the ink is 0.25 or more. The aqueous ink composition for a writing instrument used is an aqueous ink composition for a writing instrument in which the molar fraction of the film-forming non-drying agent relative to the water-soluble components in the ink is 0.25 (25%) or more, and therefore a detailed description thereof will be omitted.

[0034] 1(a) is a plan view of a writing instrument equipped with a cap formed of a transparent (visible) material according to this embodiment, (b) is a front view thereof, and (c) is a longitudinal cross-sectional view thereof. Fig. 2 is an enlarged perspective view of the nib of the writing instrument shown in Fig. 1, with (a) being an enlarged perspective view of the nib as seen from one direction and (b) being an enlarged perspective view of the nib as seen from a 180° expanded direction of (a). The writing instrument A according to this embodiment is equipped with aqueous ink having the above-described characteristics, and as shown in Figs. 1(a) to 1(c), it is a twin-type writing instrument equipped with a nib 20 having a window (visible portion) that guides aqueous ink supplied from an ink occlusion body 15 of a barrel (writing instrument body) 10 and allows the writing direction to be visually confirmed, and a rod-shaped nib 50 made of polyacetal on the opposite side of the nib 20. In addition, a cap 60 made of a transparent material that protects the detachable pen tip 20, and a cap 70 made of a transparent material that protects the pen tip 50 are attached to both sides of the writing instrument body 10.

[0035] The barrel 10 is formed, for example, from a thermoplastic resin, a thermosetting resin, or the like, and is a cylindrical body containing an ink occlusion body 15 impregnated with the water-based ink having the above-described characteristics. One end, which is the right side of the drawing, is a holder 11 having a fitting for fastening a holder 55 for holding a fine-point, rod-shaped nib 50. The other end, which is the left side, is equipped with a tip barrel 16 for fastening a nib 20 having a viewing window that allows the writing direction to be visually confirmed. The barrel 10 is molded into a cylindrical shape using a resin such as polypropylene, and functions as the main body (shaft) of the writing instrument. The barrel 10 is molded opaque or transparent (and translucent), but either may be used from the standpoint of appearance and practicality.

[0036] The ink occlusion body 15 is impregnated with the aqueous ink composition for a writing instrument having the above-mentioned characteristics, and includes, for example, fiber bundles made of one or a combination of two or more types of natural fibers, animal hair fibers, polyacetal resins, acrylic resins, polyester resins, polyamide resins, polyurethane resins, polyolefin resins, polyvinyl resins, polycarbonate resins, polyether resins, polyphenylene resins, etc., processed fiber bundles such as felt, and porous bodies such as sponges, resin particles, and sintered bodies. This ink occlusion body 15 is contained and held within the barrel 10, which is the main body of the writing instrument.

[0037] 2(a) and 2(b), the pen tip 20 is composed of at least a writing lead 30 having a writing portion 25 and a holder 40 having a visible portion. The writing lead 30 having the writing portion 25 is attached to the holder 40 (described later) by gluing, welding, fitting, or the like. The writing lead 30 has the writing portion 25 that is inclined (knife-cut) to facilitate writing, and apart from the writing portion 25, has thin plate members (sheet members) 31, 31 extending from both ends of the writing portion 25, which are integrally connected and have a substantially U-shaped (including U-shaped) external shape, with the cross section of the thin plate members 31, 31 being rectangular.

[0038] The writing core 30 is not particularly limited as long as it efficiently guides (supplies) the water-based ink with the above-described properties stored in the barrel 10 to the writing portion 25 via the thin plates 31, 31, and examples thereof include those made from fabrics such as nonwoven fabrics, woven fabrics, or knitted fabrics, or liquid-permeable materials such as liquid-permeable foams and sintered bodies. The writing core 30 including the writing portion 25 can be made from a single type of material, but it can also be made by combining, for example, stacking multiple materials, or by connecting or joining the writing portion 25 and the parts other than the writing portion 25 together using separate members.

[0039] The shape, thickness, etc. of the writing lead 30 having the writing portion 25 are set based on factors such as the manner of attachment to the holder 40, the shape of the writing portion 25, maximizing the area of ​​the visible portion 43, and efficiently allowing ink to flow (supply) to the writing portion, and preferably the widthwise length and longitudinal length correspond to the widthwise length and circumferential length of the attachment surface of the holder 40 (described below) to which the thin plate members 31, 31 of the writing lead 30 are fixed, respectively, and are set to lengths suitable for efficiently allowing ink to flow to the writing portion 25. Furthermore, the thickness of the thin plate members 31, 31 of the writing lead 30 other than the writing portion 25 is preferably 0.3 to 3.0 mm, and most preferably 0.5 to 1.0 mm, based on factors such as maximizing the area of ​​the visible portion 43.

[0040] In this embodiment, the writing portion 25 is integrally formed with the thin plate members 31, 31 of the writing lead 30 and is inclined (knife-cut) to facilitate writing, with the inclination being appropriately set according to ease of use. Furthermore, the writing portion 25 is designed to draw thick lines, preferably 1 mm or more, and more preferably 2 mm or more. The writing lead 30, including the writing portion 25 of this embodiment, is integrally formed from a sintered core made of sintered plastic powder.

[0041] In the above embodiment, the writing part 25 of the writing lead 30 and the thin plates 31, 31 are integrally formed from the same material, but the writing part 25 and the thin plates 31, 31 may be formed from separate members and then connected, joined, abutted, etc. The writing part 25 may be formed, for example, from a porous material having pores, such as a sponge, sintered body, fiber bundle, foam, spongy body, felt, or porous body. Examples of materials that can be used to form the porous body include natural fibers, animal hair fibers, polyacetal resins, polyethylene resins, acrylic resins, polyester resins, polyamide resins, polyurethane resins, polyolefin resins, polyvinyl resins, polycarbonate resins, polyether resins, and polyphenylene resins. Specifically, the writing portion 25 may be made of a sintered body obtained by sintering various types of plastic powder, and the thin plate bodies 31, 31 may be made of a fabric such as a nonwoven fabric, woven fabric, or knitted fabric, or a liquid-permeable material such as a liquid-permeable foam.

[0042] The holder 40 secures the writing portion 25 and thin plate members 31, 31 of the writing lead 30 and is fixed to the tip opening of the front barrel 16 of the barrel tube 10, and has a viewing portion (visible portion) 43 that allows the writing direction to be visually confirmed. Furthermore, the portions of the holder 40 (thin plate members 31, 31) that abut against the side of the holder 40 of the writing lead 30 have a rectangular cross section, and the outer peripheral edge of the viewing portion 43, which forms the front end of the holder 40, is formed with inclined refracted surfaces 43a, 43a. By forming the portions of the writing lead 30 that abut against the side of the holder 40 with a rectangular cross section, the width of the viewing portion 43 relative to the cross-sectional area can be increased, and by forming the outer peripheral edges of the viewing portion 43 of the holder 40 with inclined refracted surfaces 43a, 43a, the rectangular cross section can be made to appear thinner, making the area of ​​the viewing portion 43 appear even larger than before.

[0043] The entire holder 40 configured in this manner is made of a hard material, such as a hard material with visibility, such as glass or a resin without rubber elasticity. Examples of resins without rubber elasticity that allow visibility include PP, PE, PET, PEN, nylon (including amorphous nylon in addition to common nylons such as nylon 6 and nylon 12), acrylic, polymethylpentene, polystyrene, and ABS, which are molded from a material with a visible light transmittance of 50% or more, thereby enabling characters written in the writing direction to be effectively seen through the viewing portion 43. Alternatively, only the viewing portion 43 (including the inclined refractive surfaces 43a, 43a) may be made of a material with visibility. Visible light transmittance (transmittance) can be determined by measuring reflectance using a multi-light source spectrophotometer (MSC-5N, manufactured by Suga Test Instruments Co., Ltd.).

[0044] Furthermore, the holder 40 may be made of one of the above materials, or two or more of them to further improve durability and visibility, and can be molded by various molding methods such as injection molding and blow molding.

[0045] The thin plate members 31, 31 of the writing lead 30 are fixed to the mounting surface of the U-shaped holding groove of the holder 40 by adhesive bonding, welding, or the like, and are thus fixed to the writing portion 25. In this embodiment, in order to maximize the visibility area of ​​the visibility portion 43, the thickness of the thin plate members 31, 31 is thinner than the thickness of the writing portion 25, and it is desirable that the width of the ink guide portion is less than 90% of the width of the visibility portion 43 of the holder 40, and more preferably 50 to 80%.

[0046] 1(a) to 1(c), the pen tip 50 is a rod-shaped pen tip for fine writing with a circular cross section, the rear end (ink occlusion body side) of the pen tip 50 is inserted into the ink occlusion body 15, and aqueous ink having the vapor pressure characteristics described above of the ink occlusion body is supplied to the pen tip 50 by capillary force. The pen tip 50 is made of a porous material, such as a parallel fiber bundle made of one or a combination of two or more types of natural fibers, animal hair fibers, polyacetal resin, polyethylene resin, acrylic resin, polyester resin, polyamide resin, polyurethane resin, polyolefin resin, polyvinyl resin, polycarbonate resin, polyether resin, polyphenylene resin, etc.; a fiber core made by processing fiber bundles such as felt or resin-processing such fiber bundles; or a porous body (sintered core) made by sintering plastic powder such as thermoplastic resin such as polyolefin resin, acrylic resin, polyester resin, polyamide resin, polyurethane resin, etc.

[0047] Preferred pen tips 50 include fiber bundle tips, fiber tips, sintered tips, felt tips, sponge tips, and inorganic porous tips, with fiber tips being particularly preferred in terms of deformation moldability and productivity. The porosity, size, hardness, and other properties of the pen tip 50 used vary depending on the type of ink and writing implement, and a porosity of 30 to 60%, for example, is preferred. In the present disclosure, "porosity" is calculated as follows: First, a writing tip with a known mass and apparent volume is immersed in water, and after allowing the tip to fully soak in water, the mass is measured after it is removed from the water. The volume of water soaked into the writing tip is calculated from the measured mass. The volume of this water is considered to be the same as the pore volume of the writing tip, and the porosity is calculated from the following formula: Porosity (unit: %) = (volume of water) / (apparent volume of pen tip 50) × 100

[0048] 1( a) to 1(c), caps 60 and 70 made of a transparent material are attached to the outer periphery of one barrel 10, the nib 20 side, and the nib 50 side, respectively, in a detachable manner by fitting. The caps 60 and 70 are made of a transparent (visible) material, such as glass or a resin without rubber elasticity. Examples of transparent (visible) resins without rubber elasticity include PP, PE, PET, PEN, nylon (including amorphous nylon in addition to common nylons such as nylon 6 and nylon 12), acrylic, polymethylpentene, polystyrene, and ABS. These caps are molded from a material with a visible light transmittance of 50% or more, allowing the nibs 20 and 50 to be viewed (visually recognized) from the outside through the caps 60 and 70, respectively.

[0049] The entire cap 60, 70 may be made of a transparent (visible) material, or only part of the cap 60, 70 may be made of a transparent material as long as the pen tip 20, 50 and the color of the ink can be seen (visually recognized). Furthermore, when the aqueous ink having the above characteristics in this embodiment is a thermochromic ink, a thermoplastic elastomer having an erasability (erasability) of pencil lines of less than 70% as specified in JIS S 6050-2002 is formed on the top of the cap 60, making it a friction body that easily generates frictional heat and has low wear when rubbed, thereby reducing the generation of eraser dust during friction and preventing stains on the surrounding area.

[0050] In the writing instrument A configured in this manner, an ink absorbing body 15 absorbing the water-based ink of the above characteristics is inserted and held within the barrel 10, and the pen tip 20 of the above configuration is fixed to the tip side via the tip barrel 16 by sequentially fitting or the like, and a holder 55 to which the pen tip 50 is fixed is fixed to the other end side by fitting, thereby easily producing a twin-type writing instrument A, and the water-based ink of the above-mentioned molar fraction characteristics absorbed in the ink absorbing body 15 is efficiently supplied to the writing part 25 and the pen tip 50 in the pen tip 20 via the thin plate bodies 31, 31 of the writing core 30 due to capillary force, and is used for writing.

[0051] In the marking pen-type writing instrument A of this embodiment, a cap 60 (including cap 70, the same applies below) made of a transparent (visible) material and having a large internal volume is used to show the pen tip 20, and the aqueous ink composition used has a molar fraction of the film-forming non-drying agent relative to the above-mentioned water-soluble component of 0.25 (25%) or more, which makes it possible to increase the dry-up resistance of the pen tip 20 without reducing the drying properties of the drawn lines.In addition, the shape of the pen tip 20, 50 and the color of the aqueous ink (for example, the ink color is yellow, pink, etc.) can be seen through the caps 60, 70, resulting in a writing instrument with high quality and commercial value.

[0052] Furthermore, in this writing instrument A, the nib 50 is the same as a conventional general-purpose nib, so to explain the function of the nib 20, as shown in Figures 1 and 2, the nib 20 has a viewing portion (window portion) 43 that allows the writing direction to be viewed, and the water-based ink with the above-mentioned vapor pressure characteristics in the ink occlusion body 15 reaches the writing portion 25 by the capillary force of the thin plates 31, 31 of the writing core 30 and is used for writing. When writing, by looking at the viewing side through the viewing portion (window portion) 43, it is easy to align the start position of the stroke and also to stop exactly where you want to stop the stroke, preventing over-stroking or overdrawing.

[0053] Furthermore, the pen tip 20 guides ink from the ink occlusion body 15 to the writing part 25 via the thin plates 31, 31 of the writing lead 30, which are thinner than the thickness of the writing part 25 and have a tendency to flow out. Furthermore, since these thin plates 31, 31 are made of a sheet-like porous body, the ink flows well and do not need to be designed to be thick, and the visible part 43 is not obstructed. Furthermore, by making the part of the writing lead 30 that abuts against the side of the holder 40 rectangular in cross section, the width of the visible part 43 relative to the cross-sectional area can be increased, and the periphery of the visible part 43 of the holder 40 can be made wider. By making the edges into inclined refractive surfaces 43a, 43a, the rectangular cross section can be made to look thinner, so that when a right-handed person writes from left to right, they can draw lines with the writing part 25 while viewing the writing direction with the viewing part 43.In addition, in addition to maximizing the effective area of ​​the viewing part relative to the entire pen tip, ink is efficiently supplied to the integrally constructed writing part 25 by the thin plate bodies 31, 31 with the above-mentioned characteristics, so that the ink outflow is also good, and a writing instrument can be obtained that can achieve maximization of the effective area of ​​the viewing part 43 without impairing the outflow of ink.

[0054] <Writing Instrument of Second Embodiment: Overall Configuration: Figs. 3 to 4> As shown in Fig. 3, the writing instrument of the second embodiment is characterized by being a writing instrument comprising: a barrel 10 having an aqueous ink composition for a writing instrument, the aqueous ink composition having the above-described characteristics, the aqueous ink composition containing the aqueous ink composition via an ink occlusion body 15, the aqueous ink composition having a molar fraction of at least 0.25 (25%) of a film-forming non-drying agent relative to the water-soluble components in the ink, a nib 20 provided on the tip side of the barrel 10 and capable of ejecting aqueous ink; and a cap 60 made of a transparent material and removably attached to the barrel 10 on the nib 20 side.

[0055] <Writing instrument of second embodiment: specific configuration> Figure 3(a) is a plan view of a writing instrument having a cap formed from a transparent material of this second embodiment, (b) is a front view thereof, and (c) is a front longitudinal cross-sectional view thereof. Figure 4 is an enlarged oblique view of the nib of the writing instrument of Figure 1, where (a) is an enlarged oblique view of the nib seen from one direction, and (b) is an enlarged oblique view of the nib seen from a direction expanded 180 degrees from (a). 3, the writing instrument of this embodiment is a writing instrument B comprising a barrel 10 in which an aqueous ink composition for a writing instrument is housed in an ink occlusion body 15, the aqueous ink composition having a molar fraction of at least 0.25 (25%) of film-forming non-drying agent relative to the water-soluble components in the ink, a pen tip 20 provided at the tip of the barrel 10 and capable of ejecting the aqueous ink, and a cap 60 made of a transparent material and detachably attached to the pen tip 20 side of the barrel 10, wherein the aqueous ink contains at least a colorant and water, and the molar fraction of the film-forming non-drying agent relative to the water-soluble components in the ink is at least 0.25 (25%). Note that in the second embodiment below, writing instruments having the same configuration and function as the writing instrument A of the first embodiment will be designated by the same reference numerals in the drawings and the like, and their description will be omitted.

[0056] The writing instrument B of the second embodiment uses a writing lead 30 with a U-shaped outer shape in the above-described embodiment, but in the second embodiment, as shown in Figures 3 and 4, an L-shaped writing lead 35 is attached to a holder 40. The writing portion 36 of the writing lead 35 of the second embodiment has the same shape as the writing portion of the above-described embodiment, and is inclined (knife-cut) to facilitate writing. In the writing lead 35, a thin plate 37 is integrally connected to the end side of the writing portion 36, and the outer shape is formed in an L-shape, with the cross section of the thin plate 37 being rectangular. As shown in Figure 4, the holder 40 secures the writing portion 36 and thin plate body 37 of the writing lead 35 and is fixed to the tip opening of the front barrel 16 of the barrel tube 10. In the embodiment of Figure 1, mounting surfaces for attaching the thin plate bodies 31, 31 were formed on the top and bottom, but in this embodiment, since the outer shape is L-shaped, the holder 40 is attached only to the bottom side.

[0057] In the writing instrument B of the second embodiment, a cap 60 made of a visible material and having a large internal volume is used to show the nib 20. For example, even when the writing instrument B is placed in a place exposed to direct sunlight or near a heat source such as a PC, the aqueous ink composition used is an aqueous ink composition for a writing instrument in which the molar fraction of the film-forming non-drying agent relative to the water-soluble components in the ink is 0.25 (25%) or more. This makes it possible to obtain an aqueous ink composition for a writing instrument that can increase the dry-up resistance of the nib without reducing the drying properties of the drawn lines. Furthermore, the shape of the nib 20, 50 and the color of the aqueous ink (for example, the ink color is yellow, pink, etc.) can be seen through the caps 60, 70, resulting in a writing instrument with high quality and commercial value (this point will be described in more detail in the examples, etc., described further below).

[0058] Furthermore, in the writing instrument B of this second embodiment, the writing core 35 has an L-shaped outer shape, and therefore, unlike the U-shaped outer shape of Figure 1, the thin plate body 31 is not attached to the upper surface of the visible portion 43, so there is nothing obstructing it and the area of ​​the visible portion can be increased accordingly.Furthermore, by making the portion of the writing core 35 that abuts the side of the holder 40 rectangular in cross section, the width of the visible portion 43 relative to the cross-sectional area on the bottom side can be increased, and further, by making the outer peripheral edge of the visible portion 43 of the holder 40 into inclined refractive surfaces 43a, 43a, the rectangular cross section can be made to appear thinner, and the area of ​​the visible portion 43 can be made to appear even larger than in Figure 1.

[0059] The pen tip 20 of this second embodiment is attached in the same manner as the writing implement in Figure 1 and has a viewing portion (window portion) 43 that allows the writing direction to be viewed, and the water-based ink in the ink occlusion body 15 reaches the writing portion 36 by the capillary force of the writing core 35 and is used for writing. When writing, looking at the viewing side through the viewing portion (window portion) 43 makes it easier to align the start position of the stroke and also allows the stroke to be stopped exactly where you want it to end, preventing over-stroking or overdrawing. In the second embodiment, the pen tip 20 guides the water-based ink from the ink occlusion body 15 to the writing part 36 via a thin plate 37 of the writing lead 35 that is thinner than the thickness of the writing part 36 and has a tendency to flow out. Furthermore, this thin plate 37 is made of a material that has a better ink supplying ability than the embodiment of FIG. 1, so the ink flow is good, there is no need to design it thick, and the visible part 43 is not obstructed. Furthermore, by making the part of the writing lead 35 that abuts against the side of the holder 40 rectangular in cross section, the width of the visible part 43 relative to the cross-sectional area can be increased, and the width of the holder 40 can be reduced. By making the outer edge of the visible portion 43 into inclined refractive surfaces 43a, 43a, the rectangular cross section can be made to appear thinner, so that when a right-handed person writes from left to right, they can draw lines with the writing portion 36 while viewing the writing direction with the visible portion 43.Furthermore, in addition to maximizing the effective area of ​​the visible portion relative to the entire pen tip, the thin plate body 37 with the above-mentioned characteristics allows ink to be efficiently supplied to the integrally constructed writing portion 36, so that the ink outflow properties are also good, and a writing instrument can be obtained that can maximize the effective area of ​​the visible portion 43 more than the embodiment of Figure 1 without impairing the outflow properties of ink.

[0060] <Writing Instrument of Third Embodiment: Overall Configuration: Figs. 5 to 7> Writing instrument C of the third embodiment is a marking pen type writing instrument, and includes at least a barrel 80 containing aqueous ink, a nib 90 provided on the tip side of said barrel 80 and capable of ejecting aqueous ink, and a cap 65 formed of a transparent material and detachably attached to the nib 90 side of said barrel 80, wherein said aqueous ink uses an aqueous ink composition for a writing instrument in which the molar fraction of a film-forming non-drying agent relative to the water-soluble components in the ink is 0.25 (25%) or more.

[0061] As shown in FIGS. 5 to 7 , the writing instrument C of the third embodiment includes a barrel 80, an ink occlusion body 85, a relay core 95, a nib 90, and a cap body 65, which constitute the main body of the writing instrument. The barrel 80 is made of the same material as the barrel 10 of the first embodiment, and includes a bottomed, tubular rear barrel 81 that houses an ink occlusion body 85 impregnated with the water-based ink having the above-described characteristics, and a front barrel 86 to which the nib 40 is fixed. The rear barrel 81 is molded into a long, bottomed, elliptical cylindrical shape using a synthetic resin such as PP, and functions as the main body (barrel) of the writing instrument. As shown in FIGS. 5( a) and 5(b) , the rear barrel 81 is provided with a retaining member 82 formed of a retaining piece that holds the rear end of the ink occlusion body 85 inside the rear end. The entire rear barrel and the front barrel, described below, are molded opaque or transparent (and translucent), although either may be adopted from the standpoint of appearance and practicality. Further, the front barrel 86 is fixed to the opening on the pen tip side of the rear barrel 81 by fitting or the like.

[0062] The ink occlusion body 85 is made of the same material as the ink occlusion body 15 of the first embodiment. The relay core 95 serves as a relay core for supplying the aqueous ink in the ink occlusion body 85 to an ink guide section 97 provided in the holder 96 (described later). Like the ink occlusion bodies 15 and 85, the relay core 95 is a fiber bundle core made of processed fiber bundles such as fiber bundles or felt, or a hard sponge, a porous resin particle body made of sintered resin particles, or a sliver core having continuous pores (flow paths). The shape and structure of the relay core 95 are not particularly limited as long as it can supply the aqueous ink having the vapor pressure characteristics or blending characteristics described above impregnated in the ink occlusion body 85 to the ink guide section 97 of the holder 96 via the relay core 95. Examples of the cross-sectional shape of the relay core 95 include a circle, an ellipse, a square, a rectangle, a trapezoid, a parallelogram, a diamond, a semi-cylindrical shape, and a crescent shape. In this embodiment, the cross-sectional shape is a circle.

[0063] The pen tip 90 includes a pen core 98 that serves as the writing portion, and a holder 96 that holds the pen core 98 and has an ink guide portion 97 for supplying ink to the writing portion.

[0064] The entire pen tip 90 configured in this manner or the holder 96 described below is made of a visible material, such as PP, PE, PET, PEN, nylon (including amorphous nylon in addition to common nylons such as nylon 6 and nylon 12), acrylic, polymethylpentene, polystyrene, ABS, etc., and is preferably made of a material with a visible light transmittance of 50% or more. The entire pen tip 90 or the holder 96 described below can be made of one of the above materials, or, to further improve durability and visibility, two or more materials. If made of two or more materials, it is preferable that at least one of them is made of a material with a visible light transmittance of 50% or more, and the material can be molded by various molding methods such as injection molding and blow molding.

[0065] 6(a) and (b) are drawings showing an example of a writing instrument C of this embodiment with the cap removed, and FIGS. 7(a) to (d) are drawings showing an example of a writing instrument C with the cap attached. In the writing instrument C of this embodiment, an ink occlusion body 85 occluding ink and a relay core 95 are held within a rear barrel 81 constituting the barrel of the writing instrument, and the writing instrument C can be easily produced by sequentially attaching a pen tip 90 with a pen core 98 attached and a front barrel 86 by fitting or the like. The cap 65 is detachably attached to the front barrel 86 by fitting or the like, and is composed of an inner cap portion 66 that protects the pen core 98 and a cylindrical outer cap portion 67, and the outer cap portion 67 has a surface formed with a concave portion 68 that enhances design. Like the cap of the first embodiment described above, this cap 65 is made of a transparent (visible) material and is molded from a material with a visible light transmittance of 50% or more, so that the pen tip 90 can be seen (visually recognized) through the cap 65 from the outside.

[0066] The writing instrument C of this embodiment, configured as described above, can improve the dry-up resistance of the pen tip without reducing the drying properties of the drawn lines, as in the first and second embodiments, and can provide a writing instrument with high writing quality and commercial value because the shape of the pen tip 90 and the color of the aqueous ink (e.g., yellow, pink, etc.) can be seen through the cap 65. Furthermore, the aqueous ink with the above characteristics can be continuously and efficiently supplied from the ink occlusion body 85 to the relay core 95, ink guide portion 97, and pen core 98 by capillary action, ensuring an appropriate ink flow rate to prevent smearing during writing, and providing a writing instrument that stabilizes the writing flow rate and allows the aqueous ink in the ink occlusion body 85 to be fully used up. Furthermore, as described above, the pen tip 90 comprises a pen core 98 that serves as the writing portion, and a holder 96 that holds the pen core 98 and has at least one ink guide portion 97 for supplying ink to the writing portion. The pen tip 90 also has a relay core 95 for supplying the water-based ink contained in the ink occluder 85 to the ink guide portion 97 provided in the holder 96. Furthermore, the holder 96 is made of a visible material, so that the entire surface (entire surface) of the holder 96, except for the ink guide portion 97, serves as a visible portion that allows the writing direction to be visually confirmed. This allows the area ratio of the visible portion to be 40% or more of the nib protruding from the tip of the front barrel 86, and preferably the visible portion on the side of the nib holder 96 is also 40% or more.Furthermore, by forming the ink guide portion 97 in the longitudinal center of the holder 96 and suitably setting the widthwise length, diameter, cross-sectional area, etc. of the ink guide portion 97 within a preferred predetermined range, it is possible to provide sufficient visibility that allows characters written in the writing direction to be read reliably compared to conventional methods, and a writing instrument is provided that can be used until the end of the stroke.

[0067] In the writing instruments of the above-mentioned embodiments A to C, the ink occlusion body 15, 85 is described as occluding an aqueous ink composition for a writing instrument characterized by a molar fraction of the film-forming non-drying agent relative to the water-soluble component of 0.25 (25%) or more. However, since the writing instrument of the present disclosure is characterized by incorporating an aqueous ink composition for a writing instrument having the above-mentioned characteristics, it may also be a direct-flow writing instrument, for example, a collector-type writing instrument in which the aqueous ink is stored directly in the barrel and supplied to the writing portion of the nib via a relay core. Furthermore, in the writing instruments of the above-mentioned embodiments A to C, a cap made of a transparent (visible) material is attached, and the writing instrument nib 20, 90 has a window through which the writing direction can be seen, but an opaque cap that cannot be seen from the window may also be used, and the shape and structure of the nib are not particularly limited.

[0068] Next, the aqueous ink composition for a writing instrument and the writing instrument of the present disclosure will be described in more detail with reference to examples and comparative examples, but the present disclosure is not limited to the following examples, etc.

[0069] Examples 1 to 8 and Comparative Examples 1 to 4 Each aqueous ink composition for a writing instrument was prepared by a conventional method according to the formulation shown in Table 1 below. Table 1 lists the number of moles, molar fraction, solubility in water, melting point, and film-forming non-drying agent / total water-soluble components (molar fraction ratio) of the film-forming non-drying agent, film-forming inhibitor, etc. used. Each aqueous ink composition for a writing instrument obtained was also loaded into a writing instrument having the following configuration. Using each of the resulting writing instruments, the non-drying properties of the thick and thin twin-type pen tips were evaluated using the following evaluation method. The results are shown in Table 1 below.

[0070] (Configuration of Writing Instrument) A pen tip and a writing instrument having the following configuration and conforming to Figures 1 and 2 were used. The dimensions and physical properties of the pen tip, holder, etc. are as follows.

[0071] (Configuration of pen tip 20) Made of acrylic resin, visible light transmittance 85% (reflectance was measured using a multi-light source spectrophotometer (MSC-5N) manufactured by Suga Test Instruments Co., Ltd., and used as the visible light transmittance.) Size of viewing portion (window portion) 43 (square): 9 mm x 8 mm x 5 mm x 4 mm Width of viewing portion: 3.0 mm Writing lead (thick lead) 30: Configuration of thin plate bodies 31, 31: polyethylene sintered lead, width direction length: 2 mm, longitudinal direction length: 20 mm, thickness: 0.5 mm Writing portion 25: polyethylene sintered lead, porosity: 50%, 4 x 3 x 6 mm, thickness = 3 mm, longitudinal direction length = 5.5 mm

[0072] Ink occlusion body 15: PET fiber bundle, porosity 85%, φ6×77 mm Barrel (writing instrument body) 10, caps 60, 70: made of polypropylene (PP) Pen tip (fine core) 50: polyester fiber bundle core, porosity 60%, φ2.0×40.0 mm Cap 60: made of polypropylene (PP), transmittance: 70% Cap 70: made of polypropylene (PP), transmittance: 60%

[0073] (Method for evaluating non-drying properties) Each of the resulting writing instruments was left in an atmosphere of 25°C and 30% RH for 1 to 4 hours (1h to 4h) with each writing instrument placed sideways and with the cap removed, and the non-drying properties of each pen tip (thick tip, thin tip) were evaluated for each time period using the following evaluation criteria. The non-drying properties were evaluated visually by comparing with the initial state of the drawn line. Evaluation criteria: A: No change B: Slight fading observed C: Overall fading observed D: Faded and unable to write

[0074]

[0075] As is clear from the results in Table 1 above, it was confirmed that the aqueous ink compositions for writing instruments in Examples 1 to 8, which fall within the scope of the present disclosure, and the writing instruments equipped with these aqueous ink compositions, can enhance the dry-up resistance of the pen tip without reducing the drying properties of the drawn line, compared to Comparative Examples 1 to 4, which fall outside the scope of the present disclosure. Furthermore, it was confirmed that with writing instruments within the scope of the present disclosure, even those equipped with caps made of transparent materials, writing performance is not impaired, and further, the shape of the pen tip and the color of the aqueous ink can be seen through the cap, resulting in writing instruments with high writing instrument quality and commercial value.

[0076] 1 and 2, and the ink is guided from the ink occlusion body 15 to the writing part 25 by thin plate members 31, 31 that are thinner than the thickness of the writing part 25 and have a good outflow property. Furthermore, the writing core 30, which has a U-shaped outline and includes the writing part 25 and the thin plate members 31, 31, is made of a polyethylene sintered core having the above-mentioned configuration. Therefore, the capillary force relative to the porosity is strong, and the thickness can be made extremely thin, resulting in good ink outflow. There is no need to design the ink guide part to be thick, and the visible part 43 is not obstructed. Furthermore, by making the cross-sectional shape of the part of the writing core 30 that abuts against the side of the holder 40 rectangular, the cross-sectional shape of the writing core 30 is good. The width of the visible portion 43 relative to the area can be increased, and by forming the outer peripheral edge of the visible portion 43 of the holder 40 into inclined refractive surfaces 43a, 43a, the rectangular cross section can be made to appear thinner. Therefore, when a right-handed person writes from left to right, they can draw lines with the writing portion 25 while visually checking the writing direction with the visible portion 43. Furthermore, since the effective area of ​​the visible portion relative to the entire pen tip is maximized and ink is efficiently supplied to the integrally constructed writing portion 25 by the thin plate bodies 31, 31 having the above-described characteristics, ink flow is also good, and it was confirmed that a writing instrument can be obtained that can maximize the effective area of ​​the visible portion 43 without impairing ink flow. It was also confirmed that writing can be done without smearing even after being dropped from a height of 1 meter.

[0077] The resulting aqueous ink composition for writing instruments can be suitably used in writing instruments of the type known as felt-tip pens, marking pens, and the like.

[0078] 10 barrel 20 nib 25 writing part 30 writing lead 40 holder 43 visual part 60 cap

Claims

1. An aqueous ink composition for a writing instrument, comprising at least a colorant, a water-soluble solvent, a film-forming non-drying agent having a solubility in water of less than 40 g / 100 mL, and water, wherein the molar fraction of the film-forming non-drying agent relative to the water-soluble components in the ink is 0.25 or more.

2. The aqueous ink composition for writing implements according to claim 1, wherein the melting point of the film-forming non-drying agent is 25°C or higher.

3. The aqueous ink composition for a writing instrument according to claim 1 or 2, characterized in that the solubility of the film-forming non-drying agent in water is 10 g / 100 mL or less.

4. A writing instrument equipped with the aqueous ink composition for writing instruments according to claim 1 or 2.

Images