JP2023104218A - Water-based ink composition for writing instrument and writing instrument comprising the water-based ink composition - Google Patents

Abstract

To provide a water-based ink composition for a writing instrument which excels in suppressing evaporation of moisture in an ink or the like without impairing writing performance even in an environment having severe temperature changes and temperature gradients and to provide a writing instrument comprising the water-based ink composition for the writing instrument.SOLUTION: There is provided a water-based ink composition for a writing instrument which comprises at least a coloring material and water, wherein the water mole fraction in the ink is 0.96 (96%) or less. The writing instrument is a writing instrument A comprising at least a shaft cylinder 10 into which the water-based ink composition for a writing instrument is incorporated, a pen point 20 which is provided on the tip side of the shaft cylinder 10 and from which the water-based ink can be ejected and a cap 60 formed of a material having transparency which is detachably attached to the pen point 20 side of the shaft cylinder 10. In the water-based ink composition for the writing instrument, the water mole fraction of the above characteristics is 0.96 (96%) or less.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a water-based ink composition for writing instruments that is excellent in suppressing evaporation of water and the like in the ink without impairing writing performance even in an environment with severe temperature changes and temperature gradients, and to a writing instrument equipped with this water-based ink composition. .

Conventionally, water-based ink compositions for writing instruments such as marking pens contain polyhydric alcohols such as ethylene glycol and propylene glycol to suppress the evaporation of solvents in the ink and to prevent the nib from drying out. etc. is known.

For example, the ink composition contains ethylene glycol, further contains propylene glycol and/or diethylene glycol, contains 4.0 to 12.0% by weight of these glycols in the ink composition, and further contains a resin emulsion in which the resin solid content is the ink composition. An ink composition for non-penetrating surfaces containing 20 to 45% by weight in the product and further containing a pigment and an aqueous solvent is known (see, for example, Patent Document 1).
However, even when this ink composition is written on the surface of glass or pottery, the handwriting has properties that are sufficiently excellent in water resistance, hot water resistance, and abrasion resistance, and the glassware and pottery are used. To provide an ink which sufficiently leaves handwriting even after repeated washing, and which suppresses evaporation of moisture, etc. of the ink without impairing the writing performance even in an environment with severe temperature changes and temperature gradients of the present invention. A water-based ink composition for writing utensils which is excellent in the above is different in terms of the subject and technical idea (configuration and effects thereof) of the invention.

On the other hand, conventionally, as a device for preventing moisture evaporation and dew condensation in a writing instrument, for example, in a writing instrument having an ink tube containing water-based ink inside the barrel, a liquid absorbent having continuous pores is installed in the barrel, A device for preventing moisture evaporation and dew condensation is known for a writing instrument, characterized by absorbing a saturated aqueous solution of salt that gives a relative humidity of 75 to 95% in a sealed atmosphere at room temperature (for example, , see Patent Document 2).
However, the moisture evaporation and dew condensation prevention device for a writing utensil disclosed in Patent Document 2 prevents moisture evaporation and condensation by installing a liquid absorbent having a specific physical property and having continuous pores in the barrel. Although it discloses a related technology, the present invention intends to suppress or prevent evaporation, condensation, etc. from the point of view of ink composition and physical properties, etc., and the technical idea of the present invention and the above-mentioned Patent Document 2 are different. It is something to do.

On the other hand, in recent years, it has been known that a cap made of a transparent material and having a large internal volume is used in some cases in order to expose the nib. In this type of writing instrument, under an environment with temperature changes or temperature gradients, the condensed liquid accumulates in the cap, which sometimes causes a problem that the appearance is poor.
In the past, in order to suppress condensation inside the cap, it was common to reduce the internal volume of the cap and use an opaque material (not conspicuous), but the pen tip has a window that allows the writing direction to be visible. In the case of a writing utensil or the like that uses a cap made of a transparent material, it is difficult to make the cap made of an opaque material. In particular, in writing instruments loaded with inks using oil-soluble dyes, water-soluble dyes, and pigments as colorants, the coloring of the condensed liquid is conspicuous, and countermeasures have been required.

JP 2017-71665 A (Claims, Tables 1, 2, etc.) Japanese Utility Model Publication No. 61-40551 (scope of utility model registration, Figure 1, etc.)

In view of the above-mentioned problems and current situation of the prior art, the present invention intends to solve them. To provide a water-based ink composition for a writing instrument that is excellent in suppressing evaporation, a writing instrument equipped with this water-based ink composition, and a writing instrument equipped with a cap formed of a material having transparency. By mounting objects, condensation does not occur inside the cap, which does not impair the appearance, and the shape of the nib and the color tone of the water-based ink can be seen through the cap, which enhances the quality and product value of the writing instrument. The purpose is to provide an expensive writing instrument.

In view of the above-mentioned conventional problems, the present inventors have made intensive studies, and as a result, have found that by containing at least a coloring material and water and setting the physical properties of the ink to a specific range, etc., The inventors have found that an ink composition and a writing instrument can be obtained, and have completed the present invention.

That is, the water-based ink composition for writing instruments of the present invention is characterized by containing at least a coloring material and water, and having a water molar fraction of 0.96 (96%) or less in the ink. .
The water-based ink composition for writing instruments preferably contains a water-soluble low-molecular-weight compound selected from Group A below.
Group A: Ethylene glycol, propylene glycol, diethylene glycol, glycerin, amines, trimethylglycine, pentaerythritol, trimethylolpropane, trimethylolethane The writing instrument of the present invention is characterized by incorporating the water-based ink composition for writing instruments having the composition described above. and
The writing instrument includes at least a barrel containing an aqueous ink composition for writing instruments, a pen tip provided on the tip side of the barrel and capable of ejecting the aqueous ink composition for writing instruments, and a pen tip side of the barrel. and a cap made of transparent material removably attached to the housing.
It is preferable that the pen tip has a window through which the writing direction can be visually recognized.

According to the present invention, there is provided an aqueous ink composition for a writing instrument that is excellent in suppressing evaporation of water and the like in the ink without impairing writing performance even in an environment with severe temperature changes and temperature gradients. A writing instrument is provided.
Moreover, even in a writing instrument to which the cap formed of the transparent material of the present invention is attached, the writing performance is not impaired, dew condensation does not occur in the cap, and the appearance is not impaired. Furthermore, since the shape of the pen tip and the color tone of the water-based ink can be visually recognized through the cap, a writing instrument with high quality and commercial value can be provided.
The objects and advantages of the invention may be realized and obtained 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 limiting of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS It is drawing which shows an example (1st embodiment) of embodiment of the writing instrument provided with the cap formed with the material which has transparency of this invention, (a) is a top view, (b) is a front view, ( c) is a longitudinal cross-sectional view in front view. FIG. 2 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 viewed from one direction, and (b) is an enlarged perspective view of the nib viewed from the direction in which (a) is developed 180°. It is a perspective view. FIG. 4 is a drawing showing another example (second embodiment) of the writing instrument having a cap made of a transparent material of the present invention, (a) is a plan view, (b) is a front view, (c) is a vertical cross-sectional view as seen from the front. FIG. 4 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 viewed from one direction, and (b) is an enlarged perspective view of the nib viewed from the 180° developed direction of (a). It is a perspective view. FIG. 4 is a drawing showing another example (third embodiment) of the writing instrument having a cap formed of a transparent material of the present invention, (a) is a central longitudinal sectional view, and (b) is a central It is a cross-sectional view. It is drawing which shows an example of the state which removed the cap of the writing instrument of FIG. 5, (a) is the perspective view seen from the front side, (b) is the perspective view seen from the back side. It is drawing which shows an example of the state which attached the cap body of the writing instrument of FIG. 5, (a) is a front view, (b) is a top view, (c) is a left view, (d) is a right view. .

Embodiments of the present invention are described in detail below. However, it should be noted that the technical scope of the present invention is not limited to the embodiments detailed below, but extends to the invention described in the claims and equivalents thereof. In addition, the present invention can be implemented based on the contents disclosed in this specification and common general technical knowledge (including design matters and self-evident matters) in the relevant field.

<Aqueous ink composition for writing instruments>
The water-based ink composition for writing instruments of the present invention contains at least a coloring material and water, and the molar fraction of water in the ink is 0.96 (96%) or less. is.

<Water mole fraction>
In the present invention, an aqueous ink composition for writing instruments having a water molar fraction of 0.96 (96%) or less is used. Evaporation and mole fraction of water contained in the ink are described below.
When water-based ink is placed in an environment with a certain temperature and humidity, the water contained in the ink does not evaporate until the water in the ink disappears. are correlated.
If the saturated water vapor pressure at a certain temperature is P (Pa), then the partial pressure of water in the atmosphere is expressed as P×W/100 (Pa) by the mole fraction W (%) of water (that is, the relative humidity). be done. On the other hand, since the frequency of evaporation of water molecules is approximately proportional to the molar fraction C (%) of water in the ink, the amount of evaporation of water is proportional to the molar fraction of water.

In the present invention, the "molar fraction of water" refers to the molar fraction of water in the water-soluble compound (including water) having a molecular weight of 300 or less contained in the ink.
When the ink contains n types (n≧0) of water-soluble compounds having a molecular weight of 300 or less other than water together with water, the mole fractions of the water are . In the following formula (1), MW ₁ , MW ₂ , MW ₃ , . show. Cw represents the water content (% by mass) in the ink, and C ₁ , _{C 2} , C ₃ , . , 3, . . . , n content (% by mass). When the ink does not contain water-soluble compounds having a molecular weight of 300 or less, the molar fraction of water in the ink is 100%.

The "molar fraction of water" in the present invention is a value calculated for a water-soluble compound (including water) having a "molecular weight of 300 or less".
The reason why the compound having a “molecular weight of 300 or less” is the target compound for calculating the molar fraction of water is that a compound having a sufficiently large molecular weight compared to water is usually contained in an aqueous ink composition for writing instruments. This is because the amount does not substantially affect the molar fraction of water. Pigments, resins, surfactants, etc., which are usually blended in formulations of water-based ink compositions for writing instruments, have much higher molecular weights than water, and the usual content in water-based ink compositions for writing instruments has a molar number of There is no need to consider it because it is extremely small. Furthermore, considering a compound having a content of 1.0% by mass or more among the water-soluble compounds in the water-based ink composition for writing instruments, the conditions for realizing the effect of the present invention are substantially is sufficient. Compounds meeting the above definition substantially include water-soluble solvents (including water-soluble low-molecular-weight compounds and solid substances) as described later.

In the present invention, as will be described later, the effect of the present invention can be exhibited by using an aqueous ink composition for writing instruments having a water molar fraction of 0.96 (96%) or less, which is more preferable. has a molar fraction of water of 0.75 (75%) or more and 0.96 (96%) or less, particularly preferably 0.85 (85%) or more and 0.91 (91%) or less desirable.
If the water mole fraction exceeds 0.96 (96%), condensation will occur inside the cap when the product is heated.

<Color material>
Examples of coloring materials that can be used 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 fine particles, and dispersions thereof. [including pigment-containing resin particles pigments, pseudo-pigments obtained by coloring resin emulsions with dyes, white plastic pigments, hollow resin pigments (particles), etc.], silica or mica as a base material, and iron oxide, titanium oxide, etc. on the surface layer multi-layer coated pigments, thermochromic pigments, photochromic pigments, etc., and composite pigments thereof can be used.
Examples of dyes include fluorescent dyes, water-soluble dyes, and oil-soluble dyes.

Fluorescent dyes that can be used are not particularly limited as long as they have good color development properties. , 10, 11:1, Basic Orange 22, Basic Blue 7, Basic Green 1, Acid Yellow 3, 7, Acid Red 52, 77, 87, 92, Acid Blue 9, Disperse Yellow 121, Disperse 82, Disperse 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, solvent green 7, and the like. Among the fluorescent dyes, azomethine-based, xanthene-based, triphenylmethane-based fluorescent dyes, and the like are preferably used from the viewpoint of color developability and ink stability. Specifically, as azomethine-based fluorescent dyes, Basic Yellow 1 and 40; as xanthene-based fluorescent dyes, Basic Red 1:1 and Basic Violet 11:1; and as triphenylmethane-based fluorescent dyes, Basic Violet 1 and the like are particularly preferred fluorescent dyes. These dyes may be used alone or in combination of two or more.

As the colored resin fine particles or a dispersion thereof, for example, 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, acrylic acid or methacrylic acid, and a carbon number of 2 to 18. Dispersions of colored resin fine particles in which colored resin fine particles composed of an ester monomer (B) with a linear or cyclic alcohol and a basic dye or an oil-soluble dye are dispersed in water, or cyclohexyl (meth)acrylate Colored resin fine particles composed of a monomer and a basic dye or an oil-soluble dye, wherein the content of the cyclohexyl (meth)acrylate monomer is 30% by mass with respect to the total polymer components constituting the colored resin fine particles. Dispersions of colored resin fine particles in which colored resin fine particles are dispersed in water, and in which the content of the basic dye or oil-soluble dye is 15% by mass or more with respect to the total polymer component. .

The thermochromic pigments include a leuco dye that functions as a color former, a color developer that is a component capable of developing the color of the leuco dye, and a color change temperature that can be controlled in the coloration of the leuco dye and the color developer. Thermochromic pigments produced by microencapsulating a thermochromic composition containing at least a discoloration temperature adjusting agent to have a predetermined average particle size (e.g., 0.1 to 10 μm). be able to.
As the photochromic pigment, for example, photochromic particles composed of at least one or more selected from photochromic dyes (compounds), fluorescent dyes, and resins such as terpene phenolic resins, and at least photochromic dyes (compounds ), a photochromic composition containing one or more selected from fluorescent dyes and the like, an organic solvent, and additives such as antioxidants, light stabilizers, and sensitizers, with a predetermined average particle size (e.g. , 0.1 to 10 μm), and photochromic pigments produced by microencapsulation.
In the present invention (including Examples, etc.), the "average particle size" is calculated using a particle size distribution analyzer HR9320-X100 (manufactured by Nikkiso Co., Ltd.) with a refractive index of 1.81 and a volume basis. D50 value.

These coloring materials can be used alone or in combination of two or more (hereinafter simply referred to as "at least one").
The (total) (solid content) content of these colorants is preferably 0.1 to 40% by mass, more preferably 1 to 30% by mass, relative to the total amount of the aqueous ink.
By setting the content of the coloring material to 0.1% by mass or more, a sufficient drawn line density can be obtained. It is preferable because it becomes good.

In the present invention, the molar fraction of the water is efficiently set to 0.96 (96%) or less without lowering the writing performance, and the effect of the present invention is further exhibited. The water-based ink composition preferably contains at least one water-soluble low-molecular-weight compound selected from Group A below.
Group A: ethylene glycol, propylene glycol, diethylene glycol, glycerin, amines, trimethylglycine, pentaerythritol, trimethylolpropane, trimethylolethane Examples of amines include triethanolamine and aminomethylpropane.
Particularly preferably, propylene glycol, ethylene glycol, glycerin, and trimethylglycine are used.
The (total) content of these water-soluble low-molecular-weight compounds of Group A is not particularly limited as long as the molar fraction of water in the ink composition is 0.96 (96%) or less. for,
It is about 15 to 50% by mass.

<Other ingredients>
The water-based ink of the present embodiment contains the above-mentioned colorant, the balance being water as a solvent (tap water, purified water, distilled water, ion-exchanged water, pure water, etc.), a water-soluble low-molecular-weight compound, and moles of water. As long as the water-based ink composition for writing instruments has a ratio of 0.96 (96%) or less, each component normally used in water-based inks, such as a dispersant, an interface Activators, viscosity modifiers, adhesive resins, rust inhibitors, preservatives or antibacterial agents, pH adjusters and the like can be contained.

A water-soluble resin can be included as a dispersing agent and a fixing resin that can be used. For example, 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, at least One can be selected.

The surfactant that can be used is not particularly limited, but at least one surfactant selected from fluorine-based surfactants, acetylene glycol-based surfactants, and silicone-based surfactants can be used.

Natural polymers such as polysaccharides and synthetic polymers can be used as viscosity modifiers that can be used. Examples of polysaccharides include gum arabic, tragacanth gum, guar gum, locust bean gum, alginic acid, carrageenan, gelatin, xanthan gum, welan gum, succinoglycan, diutan gum, dextran, and methylcellulose, ethylcellulose, hydroxyethylcellulose, carboxymethylcellulose, and the like. Cellulose derivatives, starch glycolic acid and salts thereof can be used. Synthetic polymers include, for example, polyvinylpyrrolidone, polyvinylmethyl ether, polyacrylic acid and its salts, polyethylene oxide, vinyl acetate-polyvinylpyrrolidone copolymers, styrene-acrylic acid copolymers and their salts, isobutylene-maleic anhydride copolymers, Polymers and salts thereof can be used.

As antiseptic agents or antibacterial agents that can be used, phenol, sodium omadine, sodium benzoate, benzisothiazoline, benzimidazole compounds, and the like can be used. Moreover, benzotriazole, tolyltriazole, dicyclohexylammonium nitrite, saponins and the like can be used as rust preventives.
Examples of usable pH adjusters include amine compounds such as triethanolamine, diethanolamine, monoethanolamine, dimethylethanolamine, morpholine and triethylamine, ammonia, and alkalis such as sodium hydroxide, potassium hydroxide and lithium hydroxide. A metal hydroxide or the like can be used.

The water-based ink composition for writing instruments of the present invention contains at least the coloring material, water, a water-soluble low-molecular-weight compound selected from the group A, and other components depending on the application of the ink for writing instruments (for marking pens, etc.). The components in the ink composition are mixed as appropriate by combining them appropriately, or by combining them so as to achieve a suitable blending amount, and stirring and mixing with a stirrer such as a homomixer, homogenizer, or disper, and if necessary, by filtering or centrifuging. By removing coarse particles and the like, an aqueous ink composition for writing instruments having a composition in which the molar fraction of water is 0.96 (96%) or less can be obtained.
The pH (25° C.) of the water-based ink composition for writing instruments is adjusted to 5 to 10 with a pH adjuster or the like from the viewpoints of usability, safety, stability of the ink itself, and compatibility with the ink container. is preferable, and more preferably 6 to 9.5.

The water-based ink composition for writing instruments of the present invention configured as described above contains at least a coloring material and water, and the water molar fraction in the ink is 0.96 (96%) or less. This makes it possible to suppress dew condensation in the cap, so even in environments with severe temperature changes and temperature gradients, the water-based ink composition for writing instruments is excellent in suppressing the evaporation of moisture etc. from the ink without impairing the writing performance. is obtained (this point will be described in detail in Examples and the like to be described later).

〈Writing implements〉
The writing instrument of the present invention is equipped with the water-based ink composition for writing instruments having the above characteristics, and even in environments with severe temperature changes and temperature gradients, it is possible to suppress the evaporation of moisture and the like in the ink without impairing the writing performance. An excellent writing instrument is obtained.
Examples of writing implements include ballpoint pens, marking pens, and the like having a pen tip such as a ballpoint tip, fiber tip, felt tip, plastic tip, fiber core, or porous core.

In the present invention, the "marking pen" means a pen having a mechanism for supplying the ink stored in the ink reservoir to the resin-made writing part by capillary action, and is referred to as a "sign-tip pen". also includes A "ballpoint pen" means a pen having a mechanism for exuding ink stored in an ink reservoir by rotation of a ball provided in a writing part.
As a ballpoint pen, the water-based ink composition for writing instruments having the above composition is contained in a ballpoint pen ink container (refill) having a ball with a diameter of 0.18 to 2.0 mm, and an ink follower is added. The ink follower contains a liquid that is not compatible with the water-based ink composition for writing instruments having the above-described characteristics contained in the ink container and has a low specific gravity relative to the water-based ink composition, such as polybutene and silicone oil. , mineral oil, etc. are used.
The structure of the ballpoint pen, the marking pen, etc. is not particularly limited, and for example, a collector structure (ink holding mechanism) in which the barrel itself is used as an ink reservoir and the aqueous ink composition for writing instruments having the above configuration is filled in the barrel. It may be a direct liquid ballpoint pen or a marking pen.

<Writing instrument of preferred embodiment: FIGS. 1 and 2>
As shown in FIGS. 1(a) to 1(c), the writing instrument of the present embodiment comprises at least a barrel 10 in which the water-based ink composition for writing instruments having the characteristics described above is incorporated via an ink absorbing body 15; A pen tip 20 which is provided on the tip side of the barrel 10 and is capable of ejecting a water-based ink composition for writing instruments, and a cap made of a transparent material detachably attached to the pen tip 20 side of the barrel 10. 60, wherein the aqueous ink composition for a writing instrument contains at least the colorant and water described above, and the molar fraction of water in the ink is 0.96 ( 96%) or less.
Since the water-based ink composition for writing instruments to be used is the water-based ink composition for writing instruments in which the molar fraction of water in the ink is 0.96 (96%) or less, a detailed description thereof will be omitted.

FIG. 1(a) is a plan view of a writing instrument provided with a cap made of a material having transparency according to the present embodiment, (b) is a front view thereof, and (c) is a front vertical cross-sectional view thereof. 2 is an enlarged perspective view of the pen tip of the writing instrument of FIG. 1, (a) is an enlarged perspective view of the pen tip seen from one direction, and (b) is an enlarged perspective view of the pen tip seen from a direction expanded 180° of (a). is an enlarged perspective view of the.
The writing instrument A of the present embodiment is equipped with the water-based ink having the above characteristics, and as shown in FIGS. A pen tip 20 having a window (viewing part) that guides water-based ink and allows the user to visually recognize the writing direction is provided, and a rod-like polyacetal pen tip 50 is provided on the opposite side of the pen tip 20. - 特許庁It is a twin-type writing instrument. Also, on both sides of the writing instrument main body 10, a cap 60 having a clip portion 60a made of transparent material for protecting the detachable pen tip 20 and a transparent material for protecting the pen tip 50 are provided. A cap 70 formed by is attached.

The shaft cylinder 10 is made of, for example, a thermoplastic resin, a thermosetting resin, or the like. One end side is a holding portion 11 having a fitting portion for fixing by fitting a holder 55 that holds a thin type rod-shaped pen tip 50, and the other end on the left side is a holding portion 11 in the writing direction A front barrel 16 is attached to which a pen tip 20 having a viewing portion serving as a window through which the pen tip 20 is fixed is attached.
The barrel 10 is formed in a cylindrical shape using a resin such as polypropylene, and functions as a writing instrument main body (barrel). The barrel 10 is molded opaque or transparent (and translucent), but either can be adopted from the viewpoint of appearance and practical use.

The ink occluding body 15 is impregnated with the water-based ink composition for writing instruments having the above properties, and is made of, for example, natural fibers, animal hair fibers, polyacetal resins, acrylic resins, polyester resins, polyamide resins, polyurethane resins. , fiber bundles made of one or a combination of two or more of polyolefin-based resins, polyvinyl-based resins, polycarbonate-based resins, polyether-based resins, polyphenylene-based resins, etc., processed fiber bundles such as felt, sponges, It includes porous bodies such as resin particles and sintered bodies. The ink occluding body 15 is accommodated and held in the barrel 10 which is the main body of the writing instrument.

As shown in FIGS. 2A and 2B, the pen tip 20 is composed of a writing core 30 having at least a writing portion 25 and a holder 40 having a viewing portion. The writing lead 30 having the writing portion 25 is attached to a 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) so that writing is easy, and a thin plate (sheet) 31 from both ends of the writing portion 25 except for the writing portion 25. , 31, which are integrally connected to form a substantially U-shaped (including U-shaped) outer shape, and the cross sections of the thin plates 31, 31 are rectangular.

Especially, if the writing lead 30 efficiently guides (supplies) the water-based ink having the above-described vapor pressure characteristics stored in the barrel 10 to the writing section 25 via the thin plates 31, 31, It is not limited, and examples thereof include fabrics such as non-woven fabrics, woven fabrics, and knitted fabrics, and those composed of liquid-permeable materials such as liquid-permeable foams and sintered bodies. Note that the writing lead 30 including the writing part 25 can be made of one kind of material, but it can be made by combining a plurality of materials such as by stacking them, or the writing part 25 and the writing part other than the writing part 25 can be made separately. The members may be connected or combined with each other.

The shape and thickness of the writing core 30 having the writing part 25 are determined by the manner of attachment to the holder 40, the shape of the writing part 25, the maximization of the visual recognition part area of the visual recognition part 43, and the efficient flow of ink to the writing part ( Preferably, the length in the width direction and the length in the length direction are the lengths in the width direction of the mounting surface of a holding body 40 to which the thin plates 31, 31 of the writing core 30 are fixed. and the length of the peripheral surface, and suitable lengths are set to allow the ink to flow out to the writing section 25 efficiently. In addition, the thickness of the thin plates 31, 31 other than the writing portion 25 of the writing lead 30 is preferably 0.3 to 3.0 mm from the viewpoint of maximizing the visible portion area of the visible portion 43. 0.5 to 1.0 mm is most preferred.

In this embodiment, the writing part 25 is integrally formed with the thin plates 31, 31 of the writing core 30, and is inclined (knife-cut) so as to facilitate writing. This inclination or the like is appropriately set according to usability such as writing. The writing portion 25 has a large line width, preferably 1 mm or more, more preferably 2 mm or more.
The writing lead 30 including the writing part 25 of the present embodiment is integrally constructed of a sintered lead obtained by sintering plastic powder.

In the above-described embodiment, the writing portion 25 of the writing core 30 and the thin plate members 31, 31 are integrally made of the same material. They may be brought into contact with each other. For example, the writing part 25 may be formed of a porous material having pores, and specific examples include a sponge body, a sintered body, a fiber bundle body, a foam body, a spongy body, a felt body, a porous body, and the like. can be mentioned. Examples of materials that 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, A polycarbonate-based resin, a polyether-based resin, a polyphenylene-based resin, or the like can be used. For example, it may be composed of fabric such as nonwoven fabric, woven fabric or knitted fabric, or a material having liquid permeability such as liquid permeable foam.

The holder 40 fixes the writing portion 25 of the writing core 30 and the thin plates 31, 31, and is fixed to the tip opening of the front barrel 16 of the writing instrument main body 10, so that the writing direction can be visually recognized. It has a visible portion (visible portion) 43 .
In addition, in this holder 40, the portions (thin plates 31, 31) of the writing core 30 that come into contact with the side surfaces of the holder 40 are formed in a rectangular cross section. are formed into inclined refracting surfaces 43a, 43a.
By making the portion of the writing lead 30 that contacts the side surface of the holding body 40 rectangular in cross section, the width of the visual recognition portion 43 with respect to the cross-sectional area can be widened, and the outer peripheral edge of the visual recognition portion 43 of the holding body 40 can be inclined. By forming the refracting surfaces 43a, 43a in the shape of the shape, the rectangular cross section can be made to appear thinner, and the area of the visual recognition portion 43 can be made to appear wider than before.

The entire holder 40 configured in this manner is made of a hard material, for example, a hard material having visibility, such as glass or a resin having no rubber elasticity. Resins that do not have visible rubber elasticity include, for example, PP, PE, PET, PEN, nylon (including amorphous nylon and the like in addition to general nylon such as 6 nylon and 12 nylon), acrylic, poly By molding from a material such as methylpentene, polystyrene, ABS, etc., which has a visible light transmittance of 50% or more, characters written in the writing direction can be effectively visually recognized in the visual recognition portion 43 . Note that only the visual recognition portion 43 (including the inclined refraction surfaces 43a, 43a) may be made of a material having visibility. The visible light transmittance (transmittance) can be obtained by measuring the reflectance with a multi-light source spectrophotometer (manufactured by Suga Test Instruments Co., Ltd., (MSC-5N)).

In addition, the holder 40 may be configured using one type of each of the materials described above, or two or more types of materials from the viewpoint of further improving durability and visibility, such as injection molding and blow molding. can be molded by various molding methods.

The thin plate members 31, 31 of the writing lead 30 are fixed to the mounting surface of the U-shaped (U-shaped) holding groove of the holding member 40 by adhesion, welding, or the like with an adhesive, and are fixed to the writing portion 25. there is
In this embodiment, the thickness of the thin plates 31, 31 is thinner than the thickness of the writing portion 25 in order to maximize the visible area of the visible portion 43, and the width of the ink guiding portion is It is desirable to be less than 90%, more preferably 50 to 80%, of the width of the visible portion 43 of the holder 40 .

As shown in FIGS. 1(a) to 1(c), the pen tip 50 is a thin-type, rod-shaped pen tip with a circular cross section. ) is inserted into the ink occluding body 15, and the water-based ink having the above-described vapor pressure characteristics of the ink occluding body is supplied to the pen tip 50 by capillary force.
The pen tip 50 is made of a porous member, and examples thereof include natural fibers, animal hair fibers, polyacetal resins, polyethylene resins, acrylic resins, polyester resins, polyamide resins, polyurethane resins, Parallel fiber bundles made of one or a combination of two or more of polyolefin-based resins, polyvinyl-based resins, polycarbonate-based resins, polyether-based resins, polyphenylene-based resins, etc., processing fiber bundles such as felt, etc. Made of processed fiber core or 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. It is.

Preferred pen tips 50 include fiber bundle cores, fiber cores, sintered cores, felt cores, sponge cores, and inorganic porous cores. Fiber cores are particularly preferred from the standpoints of deformability and productivity. desirable. The porosity, size, hardness, etc. of the nib 50 to be used vary depending on the type of ink, the type of writing instrument, etc. For example, the porosity is preferably 30 to 60%. Moreover, in the present invention, the "porosity" is calculated as follows. First, a writing lead having a known mass and apparent volume is immersed in water and soaked sufficiently with water, and then the mass is measured after being removed from the water. The volume of water impregnated into the writing lead is derived from the measured mass. Assuming that the volume of this water is the same as the pore volume of the writing lead, the porosity is calculated from the following formula.
Porosity (unit: %) = (volume of water) / (apparent volume of nib 50) x 100

In this embodiment, as shown in FIGS. 1(a) to 1(c), the pen tip 20 side and the other pen tip 50 side of the barrel 10 are fitted to each other so as to be detachable. A cap 60 having a clip 60a formed of a transparent material to be attached 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 or a resin having no rubber elasticity. Resins having transparency (visibility) and no rubber elasticity include, for example, PP, PE, PET, PEN, nylon (including amorphous nylon and the like in addition to general nylon such as 6 nylon and 12 nylon). , acrylic, polymethylpentene, polystyrene, ABS, and other materials with a visible light transmittance of 50% or more, so that the pen tips 20 and 50 can be seen from the outside through the respective caps 60 and 70 ( visible).

In addition to forming the entire caps 60 and 70 from a material having transparency (visibility), if the pen tips 20 and 50 can be seen (visible) and the color tone of the ink can be seen (confirmed), the caps 60, may be part or all of cap 70; In addition, when the water-based ink having the above characteristics in the present embodiment is a thermochromic ink, the cap 60 is made of a thermoplastic elastomer having a pencil-drawn line erasability (erasure rate) of less than 70% as defined in JIS S 6050-2002. By forming the friction body on the top of the , the frictional heat is easily generated by the rubbing action and the friction body is low in wear, so that the generation of eraser scum during rubbing can be reduced, thereby preventing contamination of the surroundings.

In the writing instrument A constructed as described above, the ink absorbing body 15 storing the water-based ink having the characteristics described above is inserted into the writing instrument main body 10 and held therein. A twin-type writing implement A can be easily manufactured by fixing by successive fitting or the like, and by fixing by fitting a holder 55 to which the pen tip 50 is fixed on the other end side. The occluded water-based ink having the above vapor pressure characteristics is efficiently supplied to the writing section 25 and the pen tip 50 via the thin plates 31, 31 of the writing core 30 at the pen tip 20 by capillary force, and is used for writing. will be made.

Even in the marking pen type writing instrument A of the present embodiment, the cap 60 (including the cap 70, the same shall apply hereinafter) made of a transparent material and having a large internal volume is used in order to show the pen tip 20, and the temperature Environments with changes or temperature gradients, such as places exposed to direct sunlight, places near heating vents, places near heat sources such as PCs, places placed on electric carpets, etc. However, by using an aqueous ink composition in which the molar fraction of water in the ink is 0.96 (96%) or less, dew condensation does not occur in the cap 60 and the appearance is spoiled. Also, the shape of the pen tips 20 and 50 and the color tone of the water-based ink (for example, the ink color is yellow, pink, etc.) can be visually recognized through the caps 60 and 70, so that the writing instrument has high writing instrument quality and commercial value. (This point will be described in detail later in Examples, etc.).

In this writing instrument A, the pen tip 50 is the same as a conventional general-purpose pen tip. The water-based ink of the above-described vapor pressure characteristic of the ink occluding body 15 is transferred to the writing part 25 by the capillary force of the thin plates 31, 31 of the writing core 30. It reaches and becomes available for writing. When writing, if you look at the visible side through the visible part (window part) 43, it becomes easy to adjust the starting position of the drawing, and you can stop it at the part you want to stop at the end of the drawing, preventing over-pulling and protrusion. It becomes possible.

Furthermore, the pen tip 20 guides the ink from the ink occluding body 15 to the writing section 25 through the thin plates 31, 31 of the writing core 30 which are thinner than the writing section 25 and have flowability. In addition, since the thin plates 31, 31 are composed of sheet-like porous bodies, they have good ink outflow properties, do not need to be thickly designed, do not interfere with the visual recognition portion 43, and can be used for writing. By making the cross-sectional rectangular shape of the portion of the core 30 that contacts the side surface of the holder 40, the width of the visual recognition portion 43 with respect to the cross-sectional area can be widened, and the outer peripheral edge of the visual recognition portion 43 of the holder 40 can be inclined. By forming the refracting 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, a line is drawn with the writing section 25 while visually checking the writing direction with the viewing section 43. In addition to maximizing the effective area of the visual recognition portion with respect to the entire pen tip, the ink is efficiently supplied to the integrally constructed writing portion 25 by the thin plate members 31, 31 having the above characteristics, so that the ink outflow property is improved. It is possible to obtain a writing instrument that can maximize the effective area of the visual recognition portion 43 without impairing the outflow property of the ink.

<Writing implement of the second embodiment: Overall configuration: FIGS. 3 and 4>
In the writing instrument of the second embodiment, as shown in FIG. 3, at least the water-based ink composition for writing instruments having the above-mentioned characteristics and the molar fraction of water in the ink is 0.96 (96%) or less. A barrel 10 built in via 15, a pen tip 20 provided on the tip side of the barrel 10 capable of ejecting water-based ink, and a transparent pen detachably attached to the pen tip 20 side of the barrel 10. and a cap 60 made of a material having properties.

<Writing implement of the second embodiment: specific configuration>
FIG. 3(a) is a plan view of a writing instrument provided with a cap formed of a material having transparency according to the second embodiment, (b) is a front view thereof, and (c) is a front vertical cross-sectional view thereof. 4 is an enlarged perspective view of the nib of the writing instrument of FIG. 1, (a) is an enlarged perspective view of the nib seen from one direction, and (b) is seen from the direction expanded 180° of (a). It is an enlarged perspective view of a pen tip.
In the writing instrument of the present embodiment, as shown in FIG. 3, at least an aqueous ink composition for writing instruments in which the molar fraction of water in the ink is 0.96 (96%) or less is incorporated in an ink occluding body 15. a pen tip 20 provided on the tip side of the barrel 10 and capable of ejecting water-based ink; and a transparent material removably attached to the pen tip 20 side of the barrel 10. and a cap 60 formed thereon, wherein the water-based ink includes at least a colorant and water, and the mole fraction of water in the ink is 0.96 (96%). It is characterized by using the following.
In the following second embodiment, when the writing instrument has the same configuration and function as those of the writing instrument A of the first embodiment, the same reference numerals are given to each drawing and the description thereof will be omitted.

In the writing instrument B of the second embodiment, the writing lead 30 of the above embodiment has a U-shaped outer shape, but in the second embodiment, as shown in FIGS. The difference is that a character-shaped writing core 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) so as to facilitate writing. . In the writing core 35, a thin plate member 37 is integrally connected from the end side of the writing portion 36. The thin plate member 37 has an L-shaped outer shape, and the cross section of the thin plate member 37 is rectangular.
As shown in FIG. 4, the holder 40 fixes the writing portion 36 of the writing core 35 and the thin plate member 37, and is fixed to the front end opening of the front barrel 16 of the writing instrument body 10. As shown in FIG. In the above embodiment, the mounting surfaces for mounting the thin plates 31, 31 are formed on the top and bottom. It has become.

Even in the writing instrument B of the second embodiment, a cap 60 made of a transparent material and having a large internal volume is used in order to show the pen tip 20, and in an environment with temperature changes and temperature gradients, for example, The water-based ink composition to be used should not be exposed to direct sunlight, placed near the nozzle of a heater, placed near a heat source such as a PC, or placed on an electric carpet by mistake. By using ink with a molar fraction of water in the ink of 0.96 (96%) or less, condensation does not occur in the cap 60 and appearance is not impaired. and the color tone of the water-based ink (for example, the ink color is yellow, pink, etc.) can be visually recognized through the caps 60 and 70, so a writing instrument with high quality and commercial value can be obtained (in this regard, This will be further described in detail in Examples and the like to be described later).

Further, in the writing instrument B of the second embodiment, the writing lead 35 has an L-shaped outer shape. , the area of the visual recognition part can be expanded accordingly, and the part of the writing lead 35 that contacts the side surface of the holding body 40 has a rectangular cross-sectional shape, so that the bottom side can widen the width of the visual recognition part 43 with respect to the cross-sectional area, and furthermore, by forming the outer peripheral edge of the visual recognition part 43 of the holding body 40 into inclined refracting surfaces 43a, 43a, the rectangular cross section can be made to look thin, The area of the visual recognition portion 43 can be made to appear wider than in FIG.

The pen tip 20 of the second embodiment is attached in the same manner as the writing instrument shown in FIG. The water-based ink reaches the writing portion 35 by the capillary force of the writing core 36 and is used for writing. When writing, if you look at the visible side through the visible part (window part) 43, it becomes easy to adjust the starting position of the drawing, and you can stop it at the part you want to stop at the end of the drawing, preventing over-pulling and protrusion. It becomes possible.
In the second embodiment, the pen tip 20 guides the water-based ink from the ink occluding body 15 to the writing section 36 through the thin plate 37 of the writing core 35 which is thinner than the writing section 35 and has flowability. Since the thin plate 37 is made of a material having a higher ink supply capability than the thin plate 37 of the embodiment shown in FIG. The visible portion 43 is not obstructed, and the portion of the writing lead 35 that contacts the side surface of the holder 40 has a rectangular cross-sectional shape. The oblique refracting surfaces 43a, 43a are provided at the outer peripheral edge of the viewing portion 43 of the holding body 40, so that the rectangular cross section can be made to look thin. It is possible to draw a line with the writing part 36 while visually recognizing the writing direction with 43. In addition, the effective area of the visual recognition part with respect to the entire pen tip is maximized, and the thin plate body 37 having the above characteristics allows the writing part 36 to be integrated. Since the ink is supplied efficiently, the ink outflow property is good, and the effective area of the visual recognition part 43 can be maximized more than the embodiment of FIG. 1 without impairing the ink outflow property. is obtained.

<Writing implement of the third embodiment: Overall configuration: FIGS. 5 to 7>
The writing instrument C of the third embodiment is a marking pen type writing instrument, and includes at least a barrel 80 containing water-based ink and a pen tip 90 provided on the tip side of the barrel 80 and capable of ejecting water-based ink. and a cap 65 made of a transparent material detachably attached to the nib 90 side of the barrel 80, wherein the water-based ink is is characterized by using an aqueous ink composition for writing instruments in which the molar fraction of water in is 0.96 (96%) or less.

As shown in FIGS. 5 to 7, the writing instrument C of the third embodiment includes a barrel 80, an ink absorbing body 85, a relay core 95, a pen tip 90, and a cap body 65, which constitute the body of the writing instrument.
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 accommodates an ink occluding body 85 impregnated with the water-based ink having the characteristics described above. and a front barrel 86 to which the pen tip 40 is fixed.
The rear barrel 81 is made of a synthetic resin such as PP, and is formed into a long elliptical cylindrical shape with a bottom, and functions as the main body (barrel) of the writing instrument. As shown in FIGS. 5(a) and 5(b), the rear shaft 81 is provided with a holding member 82 consisting of a holding piece for holding the rear end portion of the ink occluding body 85 inside the rear end side. The entire shaft and the front shaft, which will be described later, are molded opaque or transparent (and translucent). Further, the structure is such that the front barrel 86 is fixed by fitting or the like to the opening of the rear barrel 81 on the pen point side.

The ink occluding body 85 is made of the same material as the ink occluding body 15 of the first embodiment.
The relay core 95 serves as a relay core body for supplying the water-based ink of the ink occluding body 85 to the ink guide portion 97 provided in the holding body 96 described later. , a fiber bundle core obtained by processing a fiber bundle such as felt, a resin particle porous body made of a hard sponge, a resin particle sintered body, or the like, or a sliver core having continuous pores (flow paths). The shape, structure, etc. are particularly limited as long as the water-based ink having the above-described vapor pressure characteristics or blending characteristics impregnated in 85 can be supplied to the ink guide portion 97 of the holder 96 via the relay core 95. not. The cross-sectional shape of the relay core 95 includes, for example, a circle, an ellipse, a square, a rectangle, a trapezoid, a parallelogram, a rhombus, a semicylindrical shape, and a half-moon shape. It's becoming

The pen tip 90 includes a pen core 98 that serves as a 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.

The entire pen tip 90 configured in this manner or a holder 96 to be described later is made of a material having visibility, such as PP, PE, PET, PEN, or nylon (except general nylons such as 6 nylon and 12 nylon). (including crystalline nylon, etc.), acrylic, polymethylpentene, polystyrene, ABS, etc. It is preferably composed of a material having a visible light transmittance of 50% or more.
In addition, the entire pen tip 90 or a holder 96, which will be described later, can be made of one type of each of the materials described above, or two or more types of materials in order to further improve durability and visibility. , When composed of two or more materials, at least one is preferably composed of a material having a visible light transmittance of 50% or more, and can be molded by various molding methods such as injection molding and blow molding. .

6(a) and (b) are drawings showing an example of a state in which the cap is removed in the writing instrument C of the present embodiment, and FIGS. 7(a) to (d) show an example of a state in which the cap is attached. It is each drawing shown.
In the writing instrument C of the present embodiment, an ink absorbing body 85 that absorbs ink and a relay core 95 are held in a rear barrel 81 that constitutes the barrel of the writing instrument, and a pen tip 90 with a pen core 98 attached thereto and a front barrel 86 are held. The writing instrument C can be easily manufactured by sequentially attaching the parts 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 for protecting the pen core 98 and a cylindrical outer cap portion 67 . A concave surface portion 68 is formed on the surface portion to improve the design.
Like the cap of the first embodiment, the cap 65 is made of a transparent (visible) material having a visible light transmittance of 50% or more. The pen tip 90 can be seen (visually recognized) through the lens.

In the writing instrument C of this embodiment configured in this manner, as in the first and second embodiments, condensation does not occur in the cap 65, and the appearance is not impaired. Since the shape of 90 and the color tone of water-based ink (eg, yellow, pink, etc.) can be visually recognized through the cap 65, a writing instrument with high quality and commercial value can be obtained.
Further, since the water-based ink having the above characteristics from the ink occluding body 85 can be continuously and efficiently supplied to the relay core 95, the ink guiding portion 97, and the pen core 98 by capillary action, an appropriate ink flow rate can be secured. Thus, a writing utensil can be obtained which prevents blurring during writing, stabilizes the writing flow rate, and allows the water-based ink in the ink occluding body 85 to be used up sufficiently.
Furthermore, as described above, the pen tip 90 has a pen core 98 that serves as a 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. It has a relay core 95 for supplying the water-based ink contained in the ink occluding body 85 to the ink guide portion 97 provided in the holding body 96, and the holding body 96 is made of a material having visibility. , the entire surface (entire) of the holder 96 other than the ink guide portion 97 serves as a visible portion for visually recognizing the writing direction. It can be 40% or more of the protruding pen tip, preferably, the visible portion of the pen tip on the side of the holder 96 is also 40% or more, and the ink guide portion 97 is located in the center of the holder 96 in the longitudinal direction. By appropriately setting the width direction length, diameter, cross-sectional area, etc. of the ink guide portion 97 within preferable predetermined ranges, characters written in the writing direction can be read more reliably than before. It is possible to provide a writing instrument that can provide good visibility and that can be used until the end of the stroke.

In each of the writing instruments of the above embodiments A to C, a type is described in which the ink occluding bodies 15 and 85 store the water-based ink composition for writing instruments having the above-described water molar fraction of 0.96 (96%) or less. However, since the writing instrument of the present invention is characterized by being equipped with the water-based ink composition for writing instruments having the above characteristics, the writing instrument of the direct liquid type, for example, the water-based ink is directly contained in the barrel, and the water-based ink is stored directly in the barrel. A writing instrument such as a collector type that supplies water-based ink to the writing portion of the nib through a core may be used.
Further, each of the writing instruments of Embodiments A to C described above is equipped with a cap made of a transparent material, and the nib 20, 90 of the writing instrument has a window through which the writing direction can be visually recognized. However, as long as the cap is made of transparent material, the shape and structure of the nib are not particularly limited.

EXAMPLES Next, the water-based ink composition for writing instruments 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.

[Examples 1 to 8 and Comparative Examples 1 to 2]
Each water-based ink composition for writing instruments was prepared according to the formulation shown in Table 1 below.
The molar fraction (%) of water in the water-based ink composition for writing instruments in Table 1 is based on the above formula (I), and the molecular weights of water, glycerin, ethylene glycol, and trimethylglycine are 18.0 and 92, respectively. .1, 62.1 and 117.1.
In addition, each obtained water-based ink composition for writing instruments was evaluated for suppression of evaporation by the following evaluation method.
Further, each obtained water-based ink composition for writing instruments was mounted on a writing instrument having the following constitution. Using each of the obtained writing instruments, the presence or absence of dew condensation and writing performance were evaluated by the following evaluation methods. These results are shown in Table 1 below.

(Structure of writing instrument)
A pen tip and a writing implement conforming to the following configuration and FIGS. 1 and 2 were used. The dimensions, physical properties, etc. of the nib, holder, etc. used are shown below.

(Configuration of pen tip 20)
Made of acrylic resin, visible light transmittance 85% [Reflectance was measured with a multi-light source spectrophotometer (MSC-5N) manufactured by Suga Test Instruments Co., Ltd., and was taken as visible light transmittance. ]
Size of visible part (window part) 43 (square): 9 mm x 8 mm x 5 mm x 4 mm
Width of visible part: 3.0mm
Writing lead 30: Structure of thin plates 31, 31: Polyethylene sintered lead Width direction length: 2 mm Longitudinal length: 20 mm Thickness: 0.5 mm Writing part 25: Polyethylene sintered lead Pores Ratio: 50%, 4 x 3 x 6 mm, thickness = 3 mm, longitudinal length = 5.5 mm

Ink absorbing body 15: PET fiber bundle, porosity 85%, φ6×77 mm
Writing instrument main body 10, caps 60, 70: Made of polypropylene (PP) Pen tip 50: Polyester fiber bundle core, porosity 60%, φ2.0 × 40.0 mm
Cap 60: made of polypropylene (PP), transparency: 70%
Cap 70: made of polypropylene (PP), transparency: 60%

(Evaluation method for the presence or absence of dew condensation)
Using each obtained writing instrument, it was left on a hot carpet (about 32° C.) for 9 hours, and the presence or absence of dew condensation was evaluated according to the following evaluation criteria.
Evaluation criteria:
A: No dew condensation.
◯: Slightly cloudy.
Δ: Mostly cloudy.
△△: Droplets are generated.
x: The liquid is accumulated.

(Method for evaluating writing performance)
Using each of the obtained writing implements, 25 cm of writing was performed on PPC paper at a normal speed, and the writing performance was evaluated according to the following evaluation criteria.
Evaluation criteria:
◯: No abnormality in the written lines.
Δ: Partially blurred.
x: Almost blurred.

As is clear from the results in Table 1 above, the water-based ink compositions for writing instruments of Examples 1 to 8, which fall within the scope of the present invention, and the writing instruments equipped with these water-based ink compositions are outside the scope of the present invention. As compared with Comparative Examples 1 and 2, it was confirmed that even in environments with severe temperature changes and temperature gradients, the ink does not impair the writing performance and is excellent in suppressing the evaporation of water and the like from the ink. In addition, in the writing instrument within the scope of the present invention, even if it is a writing instrument to which a cap made of a material having transparency is attached, the writing performance is not impaired, condensation does not occur in the cap, and the appearance is improved. Furthermore, since the shape of the pen tip and the color tone of the water-based ink can be visually recognized through the cap, it was confirmed that a writing instrument with high quality and commercial value can be obtained.

Further, each of the writing implements of Examples 1 to 8 conforms to FIGS. , 31 lead to the writing part 25. The writing core 30, which has a U-shaped outer shape and includes the writing part 25 and the thin plates 31, 31, is composed of the sintered polyethylene core having the above structure. Therefore, the strength of capillary force with respect to the porosity is large, the thickness can be made extremely thin, and the ink outflow property is good. Further, by making the portion of the writing lead 30 that contacts the side surface of the holder 40 rectangular in cross section, the width of the visual recognition portion 43 with respect to the cross-sectional area can be widened, and the outer peripheral edge of the visual recognition portion 43 of the holder 40 can be increased. are inclined refracting surfaces 43a, 43a, the rectangular cross section can be made to look thinner. In addition, the effective area of the visual recognition portion with respect to the entire pen tip is maximized, and ink is efficiently supplied to the integrally constructed writing portion 25 by the thin plates 31, 31 having the above characteristics. It was confirmed that the ink outflow property is also good, and a writing instrument capable of maximizing the effective area of the visual recognition portion 43 can be obtained without impairing the ink outflow property. In addition, it was confirmed that even after being dropped from a height of 1 m, it was possible to write without being scratched.

The resulting water-based ink composition for writing instruments can be suitably used in writing instruments of the type called felt-tip pens, marking pens, and the like.

REFERENCE SIGNS LIST 10 barrel 20 pen tip 25 writing part 30 writing lead 40 holder 43 viewing part 60 cap

Claims (5)

An aqueous ink composition for a writing instrument, containing at least a coloring material and water, and having a water molar fraction of 0.96 (96%) or less. 2. The water-based ink composition for writing instruments according to claim 1, wherein said water-based ink composition for writing instruments contains a water-soluble low-molecular-weight compound selected from Group A below.
Group A: ethylene glycol, propylene glycol, diethylene glycol, glycerin, amines, trimethylglycine, pentaerythritol, trimethylolpropane, trimethylolethane A writing instrument comprising the water-based ink composition for writing instrument according to claim 1 or 2. The writing instrument includes at least a barrel containing an aqueous ink composition for writing instruments, a pen tip provided on the tip side of the barrel and capable of ejecting the aqueous ink composition for writing instruments, and a pen tip side of the barrel. 4. The writing instrument according to claim 3, further comprising a cap made of transparent material detachably attached to the writing instrument. 5. The writing instrument according to claim 4, wherein said pen tip has a window through which a writing direction can be visually recognized.

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