Water-based ink composition for writing instrument and writing instrument incorporating the water-based ink composition

Abstract

To provide a water-based ink composition for a writing instrument capable of enhancing drying resistance of a pen tip without reducing drying properties of written lines and to provide a writing instrument incorporating the water-based ink composition.SOLUTION: There is provided a water-based ink composition for a writing instrument which comprises 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 mole fraction of the film-forming non-drying agent to the water-soluble components in the ink is 0.25 or more. Further, there is provided a writing instrument incorporating the water-based ink composition.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention 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. [Background technology]

[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 evaporation inhibitors in aqueous ink compositions for writing instruments and the like. Among these, when the content of water-soluble solvent in the aqueous ink composition is increased, the drying speed of the drawn lines is significantly reduced, and although evaporation at the pen tip can be suppressed, there is a problem that the drying speed of the drawn lines is reduced. 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. In addition, water-soluble powders with low solubility in water (hereinafter simply referred to as "film-forming non-drying agents") are sometimes used, but the reality is that when they are used in combination with water-soluble solvents or solvents with high solubility in water, which reduce the film-forming effect of the film-forming non-drying agent on the pen tip, the film-forming properties are not expressed and the evaporation-inhibiting effect is not exerted.

[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, has good resistance to drying, does not rapidly increase 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 to prevent condensation inside the cap, a nib on the tip side of the barrel that can eject water-based ink, and a cap that is removably attached to the nib side of the barrel, 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 line, and for a writing instrument using such an aqueous ink composition. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 5-271601 A (Claims, etc.) [Patent Document 2] JP 2023-90636 A (Claims, etc.) Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been 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 resistance to dry-up of the pen tip without reducing the drying properties of the drawn lines, and a writing instrument equipped with this aqueous ink composition. [Means for solving the problem]

[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 invention.

[0009] That is, the aqueous ink composition for a writing instrument of the present invention 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 having a molar fraction of the film-forming non-drying agent relative to the water-soluble components in the ink of 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 invention is characterized by being equipped with the aqueous ink composition for a writing instrument having the above-described configuration. [Effects of the Invention]

[0010] According to the present invention, there are provided an aqueous ink composition for a writing instrument that can increase the resistance to dry-up of the pen tip without reducing the drying properties of the drawn lines, and a writing instrument equipped with this aqueous ink composition. The objects and advantages of the invention will be realized and attained by means 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 restrictive of the invention as claimed. [Brief explanation of the drawings]

[0011] [Figure 1] 1A and 1B are drawings showing an example (first embodiment) of an embodiment of a writing instrument having a cap formed of a transparent material of the present invention, in which (a) is a plan view, (b) is a front view, and (c) is a vertical cross-sectional view from the front. [Figure 2] 2A and 2B are enlarged perspective views of the pen tip of the writing instrument of FIG. 1, where FIG. 2A is an enlarged perspective view of the pen tip as seen from one direction, and FIG. 2B is an enlarged perspective view of the pen tip as seen from a direction 180° expanded from FIG. [Figure 3] 1A and 1B are drawings showing another example (second embodiment) of an embodiment of a writing instrument having a cap formed of a transparent material of the present invention, in which (a) is a plan view, (b) is a front view, and (c) is a vertical cross-sectional view from the front. [Figure 4] 4A and 4B are enlarged perspective views of the pen tip of the writing implement of FIG. 3, where FIG. 4A is an enlarged perspective view of the pen tip as seen from one direction, and FIG. 4B is an enlarged perspective view of the pen tip as seen from a direction 180° expanded from FIG. 3A. [Figure 5] 1A and 1B are drawings showing another example (third embodiment) of an embodiment of a writing instrument having a cap formed of a transparent material of the present invention, where (a) is a central longitudinal cross-sectional view and (b) is a central transverse cross-sectional view. [Figure 6] 6A and 6B are diagrams showing an example of the writing implement of FIG. 5 with the cap removed, where (a) is a perspective view seen from the front side, and (b) is a perspective view seen from the rear side. [Figure 7] 6A to 6D are diagrams showing an example of the writing implement of FIG. 5 with the cap attached, where (a) is a front view, (b) is a plan view, (c) is a left side view, and (d) is a right side view. DETAILED DESCRIPTION OF THE INVENTION

[0012] The following describes in detail the embodiments of the present invention. However, please note that the technical scope of the present invention 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 invention 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] <Water-based ink composition for writing instruments> The aqueous ink composition for a writing instrument of the present invention 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 by having a molar fraction of the film-forming non-drying agent relative to the water-soluble components in the ink of 0.25 or more.

[0014] <Colorant> Examples of coloring materials that can be used in the present invention include those used for 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 resin particle pigments containing pigments, pseudo-pigments 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, titanium oxide, etc., thermochromic pigments, photochromic pigments, and composite pigments of these can be used. Examples of the dye include fluorescent dyes, water-soluble dyes, and oil-soluble dyes.

[0015] The fluorescent dyes that can be used are not particularly limited as long as they have good color development, 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 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 color developer that is a component capable of causing the leuco dye to develop color, and a color change temperature regulator that can control the color change temperature during color development of the leuco dye and the color developer, so that the resulting microencapsulated particles have 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, etc., and a resin such as a terpene phenol resin; and photochromic pigments produced by microencapsulating a photochromic composition containing at least one selected from photochromic dyes (compounds), fluorescent dyes, etc., an organic solvent, and additives such as an antioxidant, a light stabilizer, and a sensitizer, so as to have a predetermined average particle diameter (for example, 0.1 to 10 μm). In the present invention (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 either alone or in combination of two or more (hereinafter simply referred to as "at least one"). The (total) (solid 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 water-based 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 can be suppressed and the ink fluidity can be improved, which is preferable.

[0019] The water-soluble solvent used in the present invention is used for various purposes as an ink, such as preventing the ink from freezing at low temperatures, stabilizing the dissolution of water, preventing the ink from drying by preventing water evaporation, etc. In the present invention, a water-soluble solvent (including water) is a component that dissolves in water, and among these, a "water-soluble solvent (component)" is defined as one that is liquid (having a melting point of less than 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 invention is composed of a water-soluble powder with low solubility in water, i.e., a water-soluble powder with a solubility in water of less than 40 g / 100 mL. In the present invention, a "non-drying agent" refers to an agent that is solid at room temperature (having a melting point of 25°C or higher), and among non-drying agents, one with a solubility in water of less than 40 g / 100 mL is referred to as a film-forming non-drying agent, while others are referred to as non-film-forming non-drying agents or film-formation inhibitors. Specific examples of 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 further preferably has 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 agents relative to the water-soluble components in the aqueous ink is 0.25 or more, as described below.

[0022] It should be noted that film-forming non-drying agents and non-film-forming non-drying agents or film-formation inhibitors having a solubility in water of 40 g / 100 mL or more cannot exhibit the effects of the present invention. Film-forming non-drying agents with a water solubility of 40 g / 100 mL or more are not preferred because they do not form a film when water evaporates in the non-drying test due to their high water solubility. Non-film-forming non-drying agents are also not preferred because they are liquid at room temperature. Film-forming inhibitors have a water solubility of 20 g / 100 mL or more, inhibit film formation, and contain miscible solvents such as glycerin and ethylene glycol. When this film-forming inhibitor is included, it is preferable that the film-forming non-drying agent / film-forming inhibitor (molar ratio) be within a specified 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 ingredients> 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, with the remainder being water as the solvent (tap water, purified water, distilled water, ion-exchanged water, pure water, etc.). As described below, the composition may also 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 invention are achieved, so long as the composition is such that the molar fraction of the film-forming non-drying agent relative to the water-soluble components in the ink is 0.3 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] Usable viscosity adjusters include natural polymers such as polysaccharides and synthetic polymers. Examples of polysaccharides include gum arabic, tragacanth gum, guar gum, locust bean gum, alginic acid, carrageenan, gelatin, xanthan gum, and cellulose gum. Examples of suitable synthetic polymers include ellagum, succinoglycan, diutan gum, dextran, cellulose derivatives such as methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, and carboxymethyl cellulose, and starch glycolic acid and its salts. Examples of suitable synthetic polymers 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, benzimidazole compounds, etc. Usable rust inhibitors include benzotriazole, tolyltriazole, dicyclohexylammonium nitrite, saponins, etc. Examples of pH adjusters that can be used 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 relative to water-soluble component> In the present invention, in order to achieve the effects of the present invention, an aqueous ink composition for a writing instrument is used in which the molar fraction of the film-forming non-drying agent relative 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 the total 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), and then calculating the molar fraction of the film-forming non-drying agent / (molar fraction of water-soluble components+molar fraction of the film-forming non-drying agent). In the present invention, as described above, 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, and the effects of the present invention can be exerted. More preferably, the molar fraction of the film-forming non-drying agent relative 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, the film-forming non-drying agent / film-forming inhibitor (molar ratio) is preferably in the range of 0.3 to 1.5 in order to prevent the film-forming effect from disappearing and to prevent the film-forming non-drying agent from precipitating.

[0029] The aqueous ink composition for a writing instrument of the present invention is prepared by 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 in an appropriate amount according to the intended use of the writing instrument ink (for use in a marking pen, etc.), and mixing the components in suitable amounts using a stirrer such as a homomixer, homogenizer, or disper, and then, 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 0.3 (30%) or more. Furthermore, the pH (25°C) of the aqueous ink composition for writing instruments is preferably adjusted to 5 to 10 using a pH adjuster or the like, from the viewpoints of usability, safety, the stability of the ink itself, and compatibility with the ink container, and more preferably 6 to 9.5.

[0030] The aqueous ink composition for a writing instrument of the present invention thus constructed 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 ensuring 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, the film-forming non-drying agent can efficiently form a film (a volatilization-suppressing film) on the pen tip, and the moisture in 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 thus 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] <Writing instruments> The writing instrument of the present invention is equipped with an aqueous ink composition for a writing instrument having the above-described characteristics, and can provide a writing instrument that can increase the dry-up resistance of the pen tip without reducing the drying properties of the drawn lines. As a writing instrument, for example, it is mounted on a ballpoint pen, marking pen, or the like having a pen tip portion such as a ballpoint tip, fiber tip, felt tip, plastic tip, fiber core, or porous core.

[0032] In this invention, a "marking pen" refers to a pen that has a mechanism for supplying ink stored in an ink reservoir to a resin writing part by capillary action, and includes pens referred to as "sign pens." Also, a "ballpoint pen" refers to a pen that has a mechanism for causing ink stored in an ink reservoir to seep out by the rotation of a ball provided in the writing part. For a ballpoint pen, the aqueous ink composition for a writing instrument having the above-described composition is contained in a ballpoint pen ink container (refill) equipped with a ball having a diameter of 0.18 to 2.0 mm, and an ink follower is 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 container and has a lower specific gravity than 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 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 configuration.

[0033] <Writing instrument of preferred embodiment: Figures 1 and 2> As shown in Figures 1(a) to 1(c), the writing instrument of this embodiment is a writing instrument A comprising at least a barrel 10 in which an aqueous ink composition for a writing instrument having the above-mentioned characteristics is housed via an ink occlusion body 15, a nib 20 provided at the tip 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 nib 20 side of the barrel 10, wherein the aqueous ink composition for a writing instrument contains 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, 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 writing instruments used is an aqueous ink composition for writing instruments in which the molar fraction of the film-forming non-drying agent relative to the water-soluble components in the ink is 0.3 (30%) or more, and therefore a detailed description thereof will be omitted.

[0034] Figure 1(a) is a plan view of a writing instrument equipped with a cap formed from a transparent (visible) material of this embodiment, (b) is a front view thereof, and (c) is a front longitudinal cross-sectional view thereof. Figure 2 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 180° expanded direction of (a). 1(a) to 1(c), the writing instrument A of this embodiment is loaded with water-based ink having the above-described characteristics, and is a twin-type writing instrument that includes a pen tip 20 that guides the water-based ink supplied from the ink occlusion body 15 of the barrel (writing instrument body) 10 and has a window (visible portion) through which the writing direction can be visually confirmed, and also includes a rod-shaped polyacetal pen tip 50 on the opposite side of the pen tip 20. Also attached to both sides of the writing instrument body 10 are a cap 60 having a clip portion 60a 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.

[0035] The barrel 10 is made of, for example, a thermoplastic resin, a thermosetting resin, or the like, and is a cylindrical body that contains an ink absorbing body 15 impregnated with the water-based ink having the above-mentioned characteristics. One end, which is on the right side in the drawing, is a holding portion 11 having a fitting portion for fastening, by fitting, a holder 55 that holds a fine-point, rod-shaped nib 50, and the other end, which is on the left side, is fitted with a tip barrel 16 to which is fastened a nib 20 having a viewing portion that serves as a window through which the writing direction can be seen. 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 to be opaque or transparent (and translucent), but either may be adopted from the viewpoint 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 (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 adhesion, welding, fitting, or the like. The writing core 30 has a writing portion 25 that is inclined (knife-cut) to make writing easier, and other than the writing portion 25, thin plate bodies (sheet bodies) 31, 31 extending from both ends of the writing portion 25, which are connected together as a single unit, with the outer shape being formed into an approximately U-shape (including a C-shape), and the cross section of the thin plate bodies 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 part 25 via the thin plates 31, 31, and examples thereof include those made of 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 part 25 can be made of a single material, but it can also be made by combining, for example, stacking multiple materials, or by connecting or joining the writing part 25 and the parts other than the writing part 25 with each other using separate members.

[0039] The shape and thickness of the writing core 30 having the writing portion 25 are determined 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 flowing (supplying) ink to the writing portion. Preferably, the width and length correspond to the width and circumferential lengths of the attachment surface of the holder 40 (described below) to which the thin plate members 31 of the writing core 30 are fixed, respectively, and are set to lengths suitable for efficiently flowing ink to the writing portion 25. Furthermore, the thickness of the thin plate members 31 other than the writing portion 25 of the writing core 30 is preferably 0.3 to 3.0 mm, and most preferably 0.5 to 1.0 mm, in order to maximize the area of ​​the visible portion 43.

[0040] In this embodiment, the writing part 25 is formed integrally 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 for writing, etc. Furthermore, the writing part 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 lead made by sintering plastic powder.

[0041] In the above embodiment, the writing part 25 of the writing lead 30 and the thin plate members 31, 31 are integrally formed from the same material, but the writing part 25 and the thin plate members 31, 31 may be formed from separate members and then connected, joined, or abutted together. 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. Porous materials that can be used include, for example, 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 fixes the writing portion 25 and thin plate bodies 31, 31 of the writing lead 30 and is fixed to the tip opening of the tip shaft 16 of the writing instrument body 10, and has a visible portion (visible portion) 43 that allows the writing direction to be visually confirmed. In addition, the portion of the holder 40 (thin plate-like body 31, 31) that abuts against the side of the holder 40 of the writing core 30 has a rectangular cross-section, and the outer edge of the visible portion 43, which is the front end of the holder 40, is formed into an inclined refractive surface 43a, 43a. By making the portion of the writing core 30 that abuts against the side of the holder 40 rectangular in cross section, the width of the visible portion 43 relative to the cross-sectional area can be increased, and by making the outer 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, making the area of ​​the visible portion 43 appear even wider than before.

[0043] The entire holder 40 thus configured is made of a hard material, such as a hard material with visibility, such as glass or a resin with no rubber elasticity. Examples of resins with no 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 have a visible light transmittance of 50% or more. This allows characters written in the writing direction to be effectively seen through the visible portion 43. Alternatively, only the visible portion 43 (including the inclined refractive surfaces 43a, 43a) may be made of a visible material. 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 bodies 31, 31 of the writing lead 30 are fixed to the mounting surface of the U-shaped holding groove of this holding body 40 by adhesive bonding, welding, etc., and are fixed to the writing part 25. In this embodiment, in order to maximize the visibility area of ​​the visibility portion 43, the thickness of the thin plate bodies 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] As shown in Figures 1(a) to (c), the pen tip 50 is a fine-point rod-shaped pen tip 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 with the above-mentioned vapor pressure characteristics 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 natural fiber, animal hair fiber, polyacetal resin, polyethylene resin, acrylic resin, or polyester resin. The core is made of parallel fiber bundles made of one or a combination of two or more types of resins such as 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 these fiber bundles; or a porous body (sintered core) made by sintering plastic powders of thermoplastic resins 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 from the standpoints of deformation moldability and productivity. The porosity, size, hardness, and other properties of the pen tip 50 vary depending on the type of ink and writing implement, and a porosity of 30 to 60% is preferred, for example. In the present invention, "porosity" is calculated as follows: First, a writing tip with a known mass and apparent volume is immersed in water, allowed to soak sufficiently, and then removed from the water and its mass is measured. The volume of water soaked into the writing tip is calculated from the measured mass. The volume of water is considered to be the same as the pore volume of the writing tip, and the porosity is calculated using the following formula: Porosity (unit: %) = (volume of water) / (apparent volume of nib 50) x 100

[0048] In this embodiment, as shown in Figures 1(a) to (c), a cap 60 having a clip 60a made of a transparent material that is removably attached by fitting to the outer periphery of one of the barrel tubes 10 on the pen tip 20 side and the outer periphery of the other barrel tube 10 on the pen tip 50 side, and a cap 70 having an inner cap 70a are attached. The caps 60 and 70 are made of, for example, a transparent (visible) material, such as glass, a resin without rubber elasticity, etc. Examples of transparent (visible) resin 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, ABS, and other materials with a visible light transmittance of 50% or more, which allows the pen nibs 20 and 50 to be seen (visually recognized) through the caps 60 and 70 from the outside.

[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 defined in JIS S 6050-2002 may be 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 writing instrument body 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 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 by 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 0.3 (30%) 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 tips 20, 50 and the color tone 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 pen tip 50 is the same as a conventional general-purpose pen tip, so to explain the function of the pen tip 20, as shown in Figures 1 and 2, the pen tip 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 of 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 becomes easier 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, there is no need to design them 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 writing part 25 while viewing the writing direction with viewing part 43. Furthermore, 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, and the ink outflow is also good, resulting in a writing instrument that can achieve maximization of the effective area of ​​viewing part 43 without impairing ink outflow.

[0054] <Writing instrument of second embodiment: Overall configuration: Figs. 3 and 4> As shown in Figure 3, the writing instrument of this second embodiment is characterized by being a writing instrument comprising: a barrel 10 in which 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 having the above characteristics is 0.3 (30%) or more, is incorporated via an ink occlusion body 15; a pen tip 20 capable of ejecting aqueous ink, which is provided on the tip side of the barrel 10; and a cap 60 made of a transparent material and removably attached to the pen tip 20 side of the barrel 10.

[0055] <Specific configuration of the writing implement of the second embodiment> Figure 3(a) is a plan view of a writing instrument having a cap made of a transparent material according to the second embodiment, (b) is a front view thereof, and (c) is a longitudinal cross-sectional view thereof viewed from the front. 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 as seen from one direction, and (b) is an enlarged oblique view of the nib as seen from a 180° expanded direction of (a). As shown in Figure 3, the writing instrument of this embodiment is a writing instrument B that includes a barrel 10 in which an aqueous ink composition for a writing instrument is incorporated into 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 that is provided at the tip side of the barrel 10 and can eject the aqueous ink; and a cap 60 made of a transparent material that is detachably attached to the pen tip 20 side of the barrel 10. 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%). In the second embodiment below, when the writing instrument A has the same configuration and function as the writing instrument A of the first embodiment, the same reference numerals are used in the drawings and the description thereof will be omitted.

[0056] The writing instrument B of the second embodiment uses a writing lead 30 with a U-shaped outer shape as in the above embodiment, but the second embodiment differs in that a writing lead 35 with an L-shaped outer shape is attached to a holder 40, as shown in Figures 3 and 4. The writing portion 36 of the writing lead 35 of the second embodiment has the same shape as the writing portion of the above embodiment, and is inclined (knife-cut) to make writing easier. In the writing lead 35, a thin plate body 37 is integrally connected to the end side of the writing portion 36, and the outer shape is formed in an L-shape, and the cross section of the thin plate body 37 is 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 opening at the tip of the front barrel 16 of the writing instrument body 10. In the embodiment of Figure 1 above, 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 location 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, thereby making 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, because 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, a writing instrument with high quality and commercial value can be obtained (this point will be described in more detail in the examples, etc., described 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 a rectangular 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 of 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 35 by the capillary force of the writing core 36 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 starting 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 35 and has a good outflow property. 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 outflow 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.In addition, 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> The writing instrument C of this third embodiment is a marking pen type writing instrument, and is equipped with at least a barrel 80 containing aqueous ink, a nib 90 provided at the tip side of the barrel 80 and capable of ejecting aqueous ink, and a cap 65 formed of a transparent material and removably attached to the nib 90 side of the barrel 80, wherein the aqueous ink is characterized by using an aqueous ink composition for writing instruments 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.

[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 pen tip 90, and a cap body 65, which constitute the writing instrument body. The barrel 80 is made of the same material as the barrel 10 of the first embodiment, and has a bottomed, cylindrical rear barrel 81 that houses an ink absorbing body 85 impregnated with the water-based ink having the above-mentioned characteristics, and a front barrel 86 to which the nib 40 is fixed. Rear barrel 81 is molded into a long, bottomed elliptical cylinder using a synthetic resin such as PP, and functions as the main body (barrel tube) of the writing instrument. As shown in Figures 5(a) and (b), rear barrel 81 is provided with retaining member 82, consisting of a retaining piece that holds the rear end of ink occlusion body 85, inside the rear end. The entire rear barrel and the front barrel (described below) are molded to be opaque or transparent (and translucent), although either may be adopted from the standpoint of appearance and practicality. Furthermore, front barrel 86 is secured to the opening of rear barrel 81 on the nib side 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, which will be described later, and which, like the ink occlusion bodies 15 and 85, is a fiber bundle core made by processing a fiber bundle such as a fiber bundle or felt, or a hard sponge, a resin particle porous body made of a resin particle sintered body, or a sliver core having continuous pores (flow paths), is not particularly limited in shape or structure, as long as it can supply the aqueous ink having the vapor pressure characteristics or blending characteristics described above, which is 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 this 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. Furthermore, the entire pen tip 90 or the holder 96 described below can be made of one of the above materials, or two or more materials to further improve durability and visibility. 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 it can be molded by various molding methods such as injection molding and blow molding.

[0065] Figures 6(a) and (b) are drawings showing an example of the writing instrument C of this embodiment with the cap removed, and Figures 7(a) to (d) are drawings showing an example of the writing instrument C with the cap attached. In the writing instrument C of this embodiment, an ink absorbing body 85 containing ink and a relay core 95 are held within the rear barrel 81 that constitutes the barrel of the writing instrument, and the writing instrument C can be easily produced by sequentially attaching the pen tip 90 with the pen core 98 attached and the front barrel 86 by fitting or the like. The cap 65 can be attached to and detached from 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, with a concave portion 68 formed on the surface of the outer cap portion 67 to improve 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] In the writing instrument C of this embodiment, which is configured in this manner, as in the first and second embodiments described above, the dry-up resistance of the pen tip can be increased without reducing the drying properties of the drawn lines, and the shape of the pen tip 90 and the color of the water-based ink (for example, the ink color is yellow, pink, etc.) can be seen through the cap 65, resulting in a writing instrument with high quality and commercial value. Furthermore, the aqueous ink with the above-described characteristics can be continuously and efficiently supplied from the ink absorbing body 85 to the relay core 95, the ink guide section 97, and the pen core 98 by capillary action, thereby ensuring an appropriate ink flow rate, preventing smearing during writing, and providing a writing instrument that stabilizes the writing flow rate and allows the aqueous ink in the ink absorbing 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, and the holder 96 is made of a visible material, so that the entire surface (entire surface) of the holder 96 other than 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 each of 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 having the characteristic that the molar fraction of the film-forming non-drying agent relative to the water-soluble component is 0.25 (25%) or more. However, since the writing instrument of the present invention is characterized by being equipped with an aqueous ink composition for a writing instrument having the above-mentioned characteristics, it may also be a direct ink type writing instrument, for example, a collector type writing instrument in which the aqueous ink is stored directly in the barrel and the aqueous ink is supplied to the writing part of the pen tip via an intermediate core. Furthermore, in each of the writing instruments of the above embodiments A to C, a cap made of a transparent (visible) material is attached, and the writing instrument nib 20, 90 has a window portion through which the writing direction can be seen, but an opaque cap that cannot be seen from the outside may also be used, and the shape and structure of the nib are not particularly limited. [Example]

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

[0069] [Examples 1 to 8 and Comparative Examples 1 to 4] According to the formulations shown in Table 1 below, aqueous ink compositions for writing instruments were prepared by conventional methods. Table 1 lists the number of moles, molar fraction, water solubility, melting point, and molar fraction ratio of film-forming non-drying agent to total water-soluble components of the film-forming non-drying agent and film-forming inhibitor used. Each of the resulting aqueous ink compositions for writing instruments was loaded onto 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] (Writing instrument configuration) The pen tip and writing implement used were configured as follows and conforming to Figures 1 and 2. The dimensions and physical properties of the pen tip, holder, etc. used were as follows:

[0071] (20 nib configuration) 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 the visible light transmittance was calculated.) Size of the viewing area (window) 43 (square): 9mm x 8mm x 5mm x 4mm Visible width: 3.0 mm Writing lead (thick lead) 30: Thin plate body 31, 31 composition: polyethylene sintered lead, width direction length: 2 mm, length direction length: 20 mm, thickness: 0.5 mm, writing part 25: polyethylene sintered lead, porosity: 50%, 4 x 3 x 6 mm, thickness = 3 mm, length direction = 5.5 mm

[0072] Ink occlusion body 15: PET fiber bundle, porosity 85%, φ6 x 77 mm Writing instrument body 10, caps 60, 70: Made of polypropylene (PP) Pen tip (fine core) 50: Polyester fiber bundle core, porosity 60%, φ2.0 x 40.0 mm Cap 60: Made of polypropylene (PP), transparency: 70% Cap 70: Made of polypropylene (PP), transparency: 60%

[0073] (Method for evaluating non-drying properties) Each of the resulting writing instruments was left in a 25°C, 30% RH atmosphere with the writing instrument placed sideways and the cap removed for 1 to 4 hours, and the non-drying properties of each pen tip (thick tip, thin tip) were evaluated after each hour using the following evaluation criteria. The non-drying properties were evaluated visually by comparing with the initial state of the drawn line. Evaluation criteria: ◎: No change 〇: Some fading is observed △: Overall fading is observed ×: Blurred and unable to write

[0074] [Table 1]

[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 invention, and the writing instruments equipped with these aqueous ink compositions, can improve 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 invention. Furthermore, it was confirmed that writing instruments within the scope of the present invention, even those equipped with caps made of transparent materials, do not impair writing performance, and furthermore, 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 lead 30, which has a U-shaped outline and includes the writing part 25 and thin plate members 31, 31, is made of a polyethylene sintered lead 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 section of the part of the writing lead 30 that abuts against the side of the holder 40 rectangular, the cross section 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, so that 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, in addition to maximizing the effective area of ​​the visible portion relative to the entire pen tip, the thin plate bodies 31, 31 with the above characteristics efficiently supply ink to the integrally constructed writing portion 25, resulting in good ink outflow. It was confirmed that a writing instrument can be obtained that maximizes the effective area of ​​the visible portion 43 without impairing ink outflow. It was also confirmed that writing can be done without smearing even after being dropped from a height of 1 meter. [Industrial Applicability]

[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. [Explanation of symbols]

[0078] 10 shaft cylinder 20 nibs 25 Writing section 30 writing lead 40 Holder 43 Visibility section 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. 2. The aqueous ink composition for a writing instrument according to claim 1, wherein the melting point of the film-forming non-drying agent is 25[deg.] C. or higher.

3. 3. The aqueous ink composition for a writing instrument according to claim 1, wherein 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.

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