Water-based ink composition for writing instruments, and writing instruments and ink cartridges containing the same.

Abstract

To provide an aqueous ink composition for a writing instrument which enables formation of a handwriting that has a thick black color, is clear and suppresses bleeding, has good water resistance and dryness of the handwriting, and shows an excellent cap-off performance and thereby can suppress writing failures such as blurring even after left in the cap-off state and is excellent in a re-writing property, and a writing instrument and an ink cartridge for a writing instrument storing the same.SOLUTION: There are provided an aqueous ink composition for a writing instrument which is composed of at least self-dispersion type carbon black, a specific surface active agent having an acetylene bond, and an urethane resin emulsion, and water; and a writing instrument and an ink cartridge for a writing instrument storing the same.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an aqueous ink composition for writing instruments, a writing instrument containing the same, and an ink cartridge for writing instruments.

Background Art

[0002] Conventionally, dyes and pigments have been used as colorants in inks contained in writing instruments. In particular, inks using pigments as colorants are more widely used because they are superior in light resistance to dyes and have less fading over time. Regarding inks containing pigments, studies have been conducted to improve the density and water resistance of handwriting (see, for example, Patent Document 1). Patent Document 1 discloses an aqueous ink composition for writing instruments comprising self-dispersing carbon black having a specific average particle diameter and an acrylic resin emulsion having a glass transition temperature of 0°C or lower. Handwriting formed by a writing instrument containing the above ink composition (ink) has a high black density and is water-resistant.

[0003] However, since the above ink has insufficient permeability to paper, it is difficult to form handwriting with excellent drying properties when the ink is applied to a writing instrument. In particular, when applied to writing instruments such as fountain pens where a large amount of ink is applied to the paper, it is even more difficult to achieve good drying properties of the handwriting. In addition, when a writing instrument containing the above ink is left in a state where the pen tip is exposed, that is, in a so-called cap-off state, the resin solidifies and precipitates due to the evaporation of moisture from the pen tip, and writing defects such as streaks may occur during rewriting.

Prior Art Documents

Patent Documents

[0004] [[ID=3,0]]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present invention aims to provide a water-based ink composition for writing instruments that can form dark black ink lines, has good drying and water-resistant properties, and also exhibits excellent cap-off performance, as well as a writing instrument and an ink cartridge for writing instruments containing the same. [Means for solving the problem]

[0006] The present invention relates to an aqueous ink composition for writing instruments comprising at least self-dispersing carbon black, a surfactant having an acetylene bond represented by the following formula (1), a urethane resin emulsion, and water. A water-based ink composition for writing instruments, wherein the resin content in the urethane-based resin emulsion relative to the total mass of the ink composition is 0.03 to 2% by mass. This is a requirement. [ka] (In the formula, R1, R2, R3, and R4 are each independently alkyl groups. R5 is an ethylene group, l and m are each independent integers of 0 or greater. Furthermore, the requirement is a writing instrument containing the aforementioned ink composition. Furthermore, the writing instrument Marking pen or The requirements are that the brush pen comprises a pen tip, an ink filling mechanism, and an ink supply mechanism, the ink filling mechanism comprises an ink cartridge, the ink filling mechanism consists of a barrel with an ink storage chamber on the inside, the pen tip and the ink filling mechanism are joined via the ink supply mechanism, and the ink supply mechanism comprises a pen nib in which a number of disc bodies are arranged in parallel with comb-like spacing, a slit-shaped ink guide groove that penetrates the disc bodies in the axial direction and a ventilation groove wider than the groove, and an ink guide core for guiding ink to the pen tip is arranged in the center of the barrel. Furthermore, the requirement is an ink cartridge containing the aforementioned ink composition. [Effects of the Invention]

[0007] The present invention provides a water-based ink composition for writing instruments that can form dark, vivid, and smudge-free lines, has good water resistance and drying properties, and exhibits excellent cap-off performance, thereby suppressing writing defects such as smudging even after being left in a cap-off state, and has excellent re-writing properties, as well as a writing instrument and an ink cartridge for writing instruments containing the same. [Brief explanation of the drawing]

[0008] [Figure 1] This is an explanatory diagram showing one embodiment of the writing instrument (brush pen) according to the present invention. [Figure 2] This is an explanatory diagram showing one embodiment of an ink cartridge for a writing instrument (brush pen) according to the present invention. [Figure 3] This is an explanatory diagram showing another embodiment of the writing instrument (brush pen) according to the present invention. [Modes for carrying out the invention]

[0009] The aqueous ink composition for writing instruments according to the present invention (hereinafter sometimes referred to as "ink composition" or "ink") comprises at least self-dispersing carbon black, a surfactant having an acetylene bond represented by formula (1) above, a urethane resin emulsion, and water. The components constituting the ink composition according to the present invention are described below.

[0010] The ink composition according to the present invention comprises self-dispersing carbon black. Self-dispersing carbon black refers to carbon black that can be dispersed in an aqueous medium without the use of dispersants such as resins or surfactants. By subjecting carbon black to physical or chemical treatment to form hydrophilic functional groups (hereinafter sometimes referred to as "hydrophilic groups") on its surface, it becomes possible to disperse the carbon black in an aqueous medium without the use of dispersants. Examples of hydrophilic functional groups include -COOM, -SO3M, -SO2M, -CO-, -COO-, -OM, -SO2NH2, -RSO2M, -PO3HM, -PO3M2, -SO2NHCOR, -NH3, and -NR3. In the functional groups described above, M is independently a hydrogen atom, an alkali metal, an ammonium compound, a optionally substituted phenyl group, or an organic ammonium compound. Furthermore, R in the functional groups is independently a C1-C12 alkyl group or an optionally substituted naphthyl group. Examples of physical processing include vacuum plasma treatment. Examples of chemical treatments include a wet oxidation method in which oxidation is carried out with an oxidizing agent in water, and a method in which carboxyl groups are bonded via phenyl groups by bonding p-aminobenzoic acid to the carbon black surface.

[0011] Inks using pigments, which have excellent paper penetration properties, allow the pigment to easily penetrate into the paper along with the vehicle, but on the other hand, tend to impair the color development of the handwriting. However, the ink composition according to the present invention, by containing self-dispersing carbon black, can produce a dark black color and vivid handwriting while maintaining excellent paper penetration properties. Furthermore, by using self-dispersing carbon black, it is also possible to suppress the bleeding of the handwriting. This is presumed to be because the hydrophilic groups on the surface of the self-dispersing carbon black have a high affinity for the cellulose in the paper fibers. As a result, when the ink comes into contact with the paper surface, the self-dispersing carbon black is quickly adsorbed onto the cellulose on the paper surface via the hydrophilic groups on the surface, which prevents the self-dispersing carbon black from penetrating into the paper and prevents the ink from spreading to the area surrounding the contact point.

[0012] Specific examples of the self-dispersible carbon black include BONJET BLACK CW-1, CW-2, CW-3 [manufactured by Orient Chemical Industries, Ltd.], CAB-O-JET 200, 300 [manufactured by Cabot Corporation], Aqua-Black 001, 162 [manufactured by Tokai Carbon Co., Ltd.], FUJI JET BLACK A-20, B-15, B-22, D-12 [manufactured by Fuji Pigment Co., Ltd.] and the like.

[0013] The content rate of the self-dispersible carbon black with respect to the total mass of the ink composition is not particularly limited, but is preferably in the range of 5 to 15% by mass, more preferably 6 to 14% by mass. When the content rate of the self-dispersible carbon black is within the above range, the black color of the handwriting is dark and vivid, and it is possible to suppress the self-dispersible carbon black from adhering to the periphery of the handwriting and contaminating the paper surface when the handwriting is erased. In addition, when the moisture in the ink evaporates and dries from the pen tip of the writing instrument, it becomes easier to suppress the inability to rewrite.

[0014] The ink composition according to the present invention further comprises a surfactant having an acetylene bond represented by the following formula (1).

Chemical formula

[0015] By including the specific surfactant having an acetylene bond as described above, the ink composition according to the present invention can have good paper surface permeability. For example, writing instruments with a generous amount of ink at the tip, such as brush pens, tend to impair the drying properties of the writing because a large amount of ink is applied to the paper when writing. However, the ink composition according to the present invention, by containing the surfactant represented by formula (1) above, has excellent paper penetration properties, and can ensure good drying properties of the writing even when a large amount of ink is applied to the paper. Furthermore, the above-mentioned surfactant allows the ink composition to move smoothly through the ink flow path of a writing instrument equipped with a pen tip, ink filling mechanism, ink supply mechanism, etc., as described later. Therefore, the ink composition according to the present invention can also improve the ink ejection performance of a writing instrument.

[0016] The surfactant represented by formula (1) is preferable to have an HLB value of 4 to 18, more preferably 8 to 17, and even more preferably 12 to 16, as it easily improves the paper penetration of the ink composition. The HLB value is a numerical value based on the Griffin method and is calculated by the following formula (2). Note that the HLB value obtained by the Griffin method is in the range of 0 to 20, and a higher value indicates that the compound is hydrophilic. HLB value = 20 × (mass of hydrophilic groups %) = 20 × (sum of formula weights of hydrophilic groups / molecular weight of surfactant) (2) Furthermore, the sum of l and m in equation (1), (l+m), is preferably 0 ≤ (l+m) ≤ 30, and more preferably 0 ≤ (l+m) ≤ 20. The above-mentioned surfactants can be used individually or in combination of two or more types.

[0017] Specifically, surfactants having an acetylene bond as shown in formula (1) include Orphine D-10A, D-10PG, E1004, E1010, E1020, E1030W, PD-001, PD-002W, PD-003, PD-004, PD-201, PD-301, EXP.4001, EXP.4200, EXP.4123, and EXP.4300. Examples include Surfinol 82, 104E, 104H, 104A, 104PA, 104-PG50, 104S, 420, 440, 465, 485, 2502, Dynol 604, 607 [manufactured by Nisshin Chemical Industry Co., Ltd.], Acetylenel E13T, EX, EL, E40, E60, E81, E100, and 85 [manufactured by Kawaken Fine Chemical Co., Ltd.]. Among these, Olphine E1010, Olphine E1020, and Surfinol 485 are preferred because they easily provide good paper surface penetration and ink discharge properties for the ink composition.

[0018] The ink composition according to the present invention may also contain surfactants other than the surfactant having an acetylene bond described above. By adjusting the ink composition to a desired viscosity and surface tension, it is possible to improve ink ejection stability, suppress writing defects, and reduce bleeding and show-through of ink on the paper, thereby creating an ink composition that produces better writing. Other surfactants besides those containing an acetylene bond include nonionic surfactants, anionic surfactants, phosphate ester surfactants, and silicone surfactants.

[0019] The content of the surfactant having an acetylene bond represented by formula (1) relative to the total mass of the ink composition is not particularly limited, but is preferably in the range of 0.5 to 3% by mass, and more preferably in the range of 0.5 to 2.5% by mass. By having the surfactant content within the above range, the ink composition can be made to penetrate the paper surface more effectively, thereby improving the drying speed of the writing and further suppressing the bleeding of the writing.

[0020] The ink composition according to the present invention further comprises a urethane resin emulsion. A resin emulsion is a resin in which the resin does not dissolve in an aqueous medium but is dispersed in the aqueous medium as particulate matter. Urethane resin emulsions include forced emulsification types, in which a surfactant is used as an emulsifier to forcibly emulsify and disperse the resin in an aqueous medium, and self-emulsification types, in which hydrophilic groups or hydrophilic segments are imparted to the resin and dispersed in an aqueous medium. In the present invention, any type is acceptable as long as the resin is dispersed in the aqueous medium as particulate matter.

[0021] In the ink composition according to the present invention, the urethane resin emulsion has the effect of providing excellent water resistance to the writing formed by a writing instrument containing the ink composition. This is presumably because, when the ink comes into contact with the paper surface, the urethane-based resin contained in the ink adheres firmly to the paper surface.

[0022] Furthermore, the ink composition according to the present invention contains a urethane resin emulsion, which provides the effect of improving the cap-off performance of the writing instrument containing the ink composition. Generally, when a writing instrument containing an ink composition with resin is left with the cap off, the resin at the tip solidifies and precipitates due to the evaporation of moisture from the tip, making it prone to writing defects such as skipping when writing again. However, the urethane resin emulsion contained in the ink composition according to the present invention makes it difficult for the resin to solidify and precipitate at the tip of the writing instrument due to the evaporation of moisture. Therefore, even after leaving a writing instrument containing the ink composition with the cap off, the occurrence of writing defects such as skipping is suppressed, and a good writing line can be formed. In other words, in the ink composition according to the present invention, the urethane resin emulsion provides good water resistance to the writing and gives the writing instrument containing the ink composition excellent cap-off performance.

[0023] As the urethane resin constituting the urethane resin emulsion, urethane resins such as polyether polyol copolymer type, polyester polyol copolymer type, and polycarbonate polyol copolymer type can be used. Urethane resin emulsions can be used individually or in combination of two or more types.

[0024] Examples of urethane resin emulsions include U-Coat UWS-145 (manufactured by Sanyo Chemical Industries, Ltd.), Hydran WLS-210, WLS-221, HW-140SF (manufactured by DIC Corporation), Superflex 150HS, 210, 420NS, 470 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), NeoTan UE-1100 (manufactured by Toagosei Co., Ltd.), NeoRez R-9660, R-966, R-9603 (manufactured by Kusumoto Kasei Co., Ltd.), and others.

[0025] The resin content in the urethane resin emulsion relative to the total mass of the ink composition is not particularly limited, but is preferably in the range of 0.01 to 3% by mass, more preferably 0.03 to 2% by mass, and even more preferably 0.1 to 1.5% by mass. By having the resin (urethane resin) content within the above range, it is possible to suppress the occurrence of resin solidification and precipitation due to moisture evaporation at the pen tip of the writing instrument containing the ink composition, while achieving a higher level of balance between the water resistance of the ink composition and the cap-off performance of the writing instrument.

[0026] The ink composition according to the present invention, through the coexistence of self-dispersing carbon black, a specific surfactant having an acetylene bond, and a urethane resin emulsion, achieves a high degree of balance between the color development of black ink, the drying speed of the ink formed on the paper surface, water resistance, and the cap-off performance of the writing instrument containing the ink composition, thereby providing an excellent effect on writing instruments, particularly brush pens, that contain this ink composition.

[0027] The ink composition according to the present invention further comprises water. There are no particular restrictions on the type of water used; for example, tap water, deionized water, ultrafiltered water, and distilled water are examples. The water content relative to the total mass of the ink composition is not particularly limited, but is preferably in the range of 10 to 90% by mass, and more preferably in the range of 30 to 80% by mass.

[0028] The ink composition according to the present invention can be formulated with a water-soluble organic solvent that is compatible with water, and has the effect of suppressing the evaporation of moisture from the pen tip of a writing instrument. Examples of water-soluble organic solvents include glycerin, ethylene glycol, diethylene glycol, propylene glycol, polyethylene glycol, 3-methoxy-3-methyl-1-butanol, monoethanolamine, diethanolamine, triethanolamine, and 2-pyrrolidone. Among these, glycerin, ethylene glycol, diethylene glycol, propylene glycol, 3-methoxy-3-methyl-1-butanol, and 2-pyrrolidone are preferred because they can further enhance the drying properties of the ink. Water-soluble organic solvents can be used individually or in combination of two or more types. When the ink composition according to the present invention contains a water-soluble organic solvent, the content of the water-soluble organic solvent relative to the total mass of the ink composition is not particularly limited, but is preferably in the range of 1 to 40% by mass, more preferably 5 to 30% by mass, and even more preferably 10 to 25% by mass. If the content of the water-soluble organic solvent exceeds 40% by mass, the ink viscosity tends to increase, reducing the ink discharge performance of the writing instrument containing the ink composition and making writing problems more likely. On the other hand, if the content is less than 1% by mass, the effect of suppressing water evaporation becomes poor.

[0029] The ink composition according to the present invention may also contain various additives as needed. Examples of additives include dyes, pigments other than the self-dispersing carbon black mentioned above, preservatives, fungicides, wetting agents, defoaming agents, specific gravity adjusters, pH adjusters, and the like.

[0030] The method for producing the ink composition according to the present invention is not particularly limited, and any conventionally known method can be used. Specifically, the ink composition can be produced by stirring a mixture containing the above-mentioned components with various stirrs such as propeller stirrs, homodispersers, or homomixers, or by dispersing it with various dispersers such as bead mills.

[0031] The viscosity of the ink composition according to the present invention is not particularly limited, but is preferably 1 to 6 mPa·s and more preferably 2 to 5 mPa·s at a temperature of 20°C. Having a viscosity within this range makes it easy to improve ink discharge performance while increasing ink penetration into the paper surface and thus improving the drying time of the writing. The viscosity was measured using an EL-type rotational viscometer [manufactured by Toki Sangyo Co., Ltd., product name: RE-80L, cone-type rotor: standard type (1°34′×R24)] with the ink composition placed in an environment of 20°C.

[0032] The surface tension of the ink composition according to the present invention is not particularly limited, but is preferably 25 to 40 mN / m, and more preferably 25 to 35 mN / m, at a temperature of 20°C. Having the surface tension within this range makes it easier to suppress ink bleeding while ensuring good ink penetration into the paper surface. The surface tension was measured using a surface tension meter [Kyowa Interface Science Co., Ltd., product name: DY-300] with the ink composition placed in a 20°C environment, using the vertical plate method with a platinum plate.

[0033] The ink composition according to the present invention is used when contained in a writing instrument. Examples of writing instruments include ballpoint pens, marking pens, fountain pens, and brush pens. The ink composition according to the present invention is suitable for use in brush pens because it exhibits good drying properties of the ink even when applied to writing instruments where a large amount of ink is applied to the paper surface, and also provides excellent cap-off performance.

[0034] As for brush pens, their structure and shape are not particularly limited as long as they have a brush-shaped nib; for example, a brush pen equipped with a brush-shaped nib and an ink filling mechanism can be given as an example.

[0035] The pen tip is not particularly limited as long as it is in the shape of a brush. Examples include a fiber bundle such as a calligraphy brush in which fibers are tightly bundled together in the longitudinal direction, a plastic porous body having continuous pores, a heat-fused or resin-processed body of synthetic resin fibers, or a brush-shaped tip made of an extruded body of a soft resin or elastomer. The chips may be glued together with water-soluble substances such as polyvinyl alcohol, polyvinylpyrrolidone, starch, or gum arabic.

[0036] The ink filling mechanism is not particularly limited; for example, a barrel with an internal ink storage chamber that allows for direct ink filling can be provided as an example. The material of the barrel is not particularly limited, and examples include synthetic resins such as polyethylene, polypropylene, polymethylpentene, polycarbonate, polyethylene terephthalate, polyacetal, acrylonitrile-butadiene-styrene copolymer resin (ABS resin), polyurethane, and polystyrene, as well as metal, glass, and rubber. Among these, polyethylene or polypropylene is preferred.

[0037] The ink filling mechanism may be an ink container or an ink absorber capable of being filled with ink. For the ink container, for example, a molded body made of thermoplastic resin such as polyethylene, polypropylene, polyethylene terephthalate, or nylon, or a metal tubular body can be used. The ink-absorbing material is a fiber bundle formed by gathering crimped fibers in the longitudinal direction, and is used in a configuration where it is embedded in a plastic cylinder or a film covering, and the porosity is adjusted to be in the range of approximately 40-90%.

[0038] The ink filling mechanism may be an ink cartridge, and the ink filling mechanism of a writing instrument such as a brush pen can be made detachable. In this case, after the ink in the ink cartridge of the writing instrument is used up, the writing instrument can be used again by replacing it with a new ink cartridge. Ink cartridges can be those that connect to the writing instrument body and also serve as the barrel of the writing instrument, or those that cover and protect the barrel (rear barrel) after being connected to the writing instrument body. In the latter case, the writing instrument body and the ink cartridge may be connected, or the ink cartridge may be housed inside the barrel in a disconnected state, allowing the user to connect it when using the writing instrument to begin use.

[0039] The structure of the ink cartridge is not particularly limited; for example, a bottomed cylindrical body with a circular cross-section perpendicular to the longitudinal direction can be exemplified. A cylindrical body is a hollow, elongated rod-shaped body. Furthermore, the ink cartridge may have a structure that allows for deformation under pressure and recovery, or the outer and inner surfaces of the cylindrical body may be tapered. Alternatively, the ink cartridge may have a structure that incorporates an ink supply mechanism, as described later.

[0040] If the ink filling mechanism is configured to directly fill with ink, the barrel or ink container into which the ink is filled may contain an agitator, such as an agitator ball, to facilitate the redispersion of the self-dispersing carbon black. The shape of the agitator may be spherical, rod-shaped, or the like. The material of the agitator is not particularly limited and can be, for example, metal, ceramic, resin, or glass.

[0041] A writing instrument comprising a pen tip and an ink filling mechanism may further be equipped with an ink supply mechanism for supplying the ink to be filled in the ink filling mechanism to the pen tip. The ink supply mechanism is not particularly limited, and examples include: (1) a mechanism that provides an ink guide core made of a fiber bundle or the like as an ink flow rate regulator and supplies ink to the pen tip via this interposed element; (2) a mechanism that provides a comb-shaped ink flow rate regulator and supplies ink to the pen tip via this interposed element; (3) a mechanism that provides a porous body having continuous pores that can be impregnated with ink as an ink flow rate regulator and supplies ink to the pen tip via this interposed element; (4) a mechanism in which a number of discs are arranged in parallel with comb-shaped spacing, and a slit-shaped ink guide groove that penetrates the discs axially and a ventilation groove wider than the groove is provided, and an ink guide core for guiding ink from the ink filling mechanism to the pen tip is arranged in the center of the axis and ink is supplied to the pen tip via this pen core; and (5) a mechanism that provides an ink flow rate regulator by a valve mechanism and supplies ink to the pen tip by opening the valve.

[0042] The material of the pen tip is not particularly limited as long as it is a synthetic resin that can be injection molded into a comb-groove structure with numerous discs. Examples of synthetic resins include general-purpose polycarbonate, polypropylene, polyethylene, and acrylonitrile-butadiene-styrene copolymer resin (ABS resin). In particular, acrylonitrile-butadiene-styrene copolymer resin (ABS resin) is preferably used because it has high moldability and makes it easy to obtain the desired pen tip performance.

[0043] As for the valve mechanism, a conventional pumping type, which is opened by the pressure of a tip, can be used, and it is preferable to use one in which the spring pressure is set to allow it to be opened by the pressure of a pen.

[0044] The writing instrument according to the present invention is equipped with a cap that covers the pen tip, thereby preventing the pen tip from drying out and becoming unusable, as well as preventing contamination and damage to the writing tip. Furthermore, the form of the writing instrument according to the present invention is not limited to the configuration described above, but may also be a compound writing instrument (double-ended writing instrument) with different shaped tips attached.

[0045] A preferred writing instrument according to the present invention is a brush pen comprising a brush-shaped tip as the pen tip, an ink filling mechanism, and an ink supply mechanism. The ink composition according to the present invention moves smoothly through the ink channel of the brush pen with the above configuration, and the ink that is filled into the ink filling mechanism is stably supplied to the pen tip. As a result, the brush pen with the above configuration can clearly form black lines with excellent color development, and is a writing instrument that has excellent quick-drying and water-resistant properties, as well as good cap-off performance, and is therefore suitable for use. A more preferable configuration for a brush pen is one in which the ink supply mechanism is arranged in parallel with a number of discs spaced apart in a comb-like pattern, and a slit-shaped ink guide groove that runs vertically through the discs in the axial direction, and a ventilation groove wider than the groove, and an ink guide core is positioned at the center of the shaft to guide ink from the ink filling mechanism to the pen tip, thereby supplying ink to the pen tip. A brush pen with the above configuration is more preferable because the ink flow rate from the ink filling mechanism is appropriately regulated, the ink is supplied to the pen tip more stably, and the ink discharge stability is excellent.

[0046] Among the writing instruments according to the present invention, a brush pen comprising a brush-shaped tip as the pen tip, an ink filling mechanism, and an ink supply mechanism is specifically: (1) a brush pen in which the ink filling mechanism consists of a barrel with an ink storage chamber inside, and the ink supply mechanism is a mechanism that supplies ink to the pen tip via a pen core in which a number of disc bodies are arranged in parallel with comb-like spacing between them, a slit-shaped ink guide groove that penetrates the disc bodies in the axial direction and a ventilation groove wider than the groove, and an ink guide core that guides ink from the ink filling mechanism to the pen tip is arranged in the center of the barrel, and the pen tip and the ink filling mechanism are joined via the ink supply mechanism, (2) a brush pen comprising an ink cartridge as the ink filling mechanism, and the ink supply mechanism is Examples of a brush pen include: (3) a brush pen (double-ended brush pen) in which the ink supply mechanism is connected to one end of the barrel via the ink supply mechanism, and the ink supply mechanism is connected to the pen tip via the ink supply mechanism, and the ink supply mechanism is connected to the pen tip via the ink supply mechanism, and the ink supply mechanism is connected to the pen tip via the ink supply mechanism, and the ink supply mechanism is connected to the pen tip via the ink supply mechanism, and the ink supply mechanism is connected to the pen tip via the ink supply mechanism, and the ink supply mechanism is connected to one end of the barrel and the other end of the barrel via the ink supply mechanism, and the ink supply mechanism is connected to the pen tip via the ink supply mechanism, and the ink supply mechanism is connected to one end of the barrel and the other end of the barrel, respectively.

[0047] In (1) above, a more specific structure is one in which a pen tip and an ink supply mechanism are attached to the front of a barrel made of a bottomed cylindrical body, and an ink storage chamber is formed inside the barrel behind the ink supply mechanism. In (2) above, more specific structures include a structure in which a front barrel, to which a pen tip and an ink supply mechanism are attached, and a rear barrel, consisting of an ink cartridge, are connected in a manner that allows them to be separated, and a structure in which a front barrel, to which a pen tip and an ink supply mechanism are attached, and an ink cartridge are connected in a manner that allows them to be separated, and the ink cartridge is covered by the rear barrel. In (3) above, a more specific structure is one in which a pen tip and an ink supply mechanism are attached to one end and the other end of a barrel that is open at both ends, and the barrel has two ink storage chambers formed by a partition wall, and the ink storage chambers are separated from each other so that ink does not flow between them. The pen tips attached to the one end and the other end of the barrel may be tips of different shapes. [Examples]

[0048] Examples are shown below, but the present invention is not limited thereto. Unless otherwise specified, "parts" in the examples refers to "parts by mass".

[0049] Example 1 Preparation of ink composition An ink composition was prepared by mixing 40 parts of self-dispersing carbon black [manufactured by Tokai Carbon Co., Ltd., product name: Aqua-Black 162 (solids content: 20%)], 1 part of a surfactant containing an acetylene bond [manufactured by Nisshin Chemical Industry Co., Ltd., product name: Orphine E1010], 0.86 parts of a urethane resin emulsion [manufactured by Daiichi Kogyo Seiyaku Co., Ltd., product name: Superflex 210 (solids content: 35%)], 0.5 parts of triethanolamine, 10 parts of ethylene glycol, 5 parts of glycerin, 0.4 parts of a preservative [manufactured by Lonza Japan Co., Ltd., product name: Proxel XL-2], and 42.24 parts of water. The content of the urethane resin relative to the total mass of the ink composition was 0.3% by mass.

[0050] Making brush pen A A brush pen A was prepared by filling the ink cartridge of a brush pen, which has a brush-shaped tip as the pen tip, an ink cartridge as the ink filling mechanism, and an ink supply mechanism, with the ink filling mechanism and the pen tip being joined via the ink supply mechanism, with the ink composition of Example 1, and attaching a cap. The specific configuration of brush pen A and the ink cartridge installed in brush pen A is as described below.

[0051] Composition of brush pen A (see Figure 1) The brush pen A(1) consists of a rear barrel made of a polyethylene bottomed cylindrical ink cartridge (2) that is deformable under pressure and can be restored, and a front barrel (3) to which a pen tip (4) made of a bundle of thermoplastic polyester elastomer and an annular porous body (5) with continuous pores are attached, and these two barrels are detachably connected. An inner stopper (7) with a central hole (6) is fitted to one end of the ink cartridge (2), and the pen tip (4) has a fixing layer (8) with a projection (9) on its rear end surface, and the annular porous body (5) is loosely inserted into the rear side circumference of the pen tip (4), and the projection (9) and the front end of the inner stopper (7) are in contact with each other, forming a guide gap (10) between the fixing layer (8) and the front end of the inner stopper (7).

[0052] The configuration of the ink cartridge installed in brush pen A (see Figure 2) The ink cartridge (2) has a first mounting hole (20) larger in diameter than the central hole (6) and a second mounting hole (21) larger in diameter than the first mounting hole, arranged concentrically at the rear of the inner stopper (7), and an inner pipe (22) and an outer pipe (23) are fitted into the first mounting hole (20) and the second mounting hole (21).

[0053] Making brush pen B A brush pen B was manufactured by filling the ink filling mechanism of a brush pen, which has a brush-shaped tip as the pen tip, a barrel with an ink storage chamber inside as the ink filling mechanism, and an ink supply mechanism, with the pen tip and the ink filling mechanism joined via the ink supply mechanism, with the ink composition of Example 1, and attaching a cap. The components of brush pen B are as follows:

[0054] Composition of brush pen B The brush pen B (11) has an ink supply mechanism (13) attached to the front of a barrel (12) made of a bottomed polyethylene cylinder, with a pen tip (14) made of an extruded soft resin coated with polyurethane on its surface. An ink storage chamber (15) is formed inside the barrel behind the ink supply mechanism (13). The ink supply mechanism (13) has a number of disc bodies (16) arranged in parallel with comb-like spacing, with slit-shaped ink guide grooves (17) that penetrate the disc bodies (16) axially and ventilation holes (18) wider than the grooves, an ink guide core (19) positioned at the center of the barrel, and the ink guide core (19) connected to the pen tip (14).

[0055] Examples 2-8 and Comparative Examples 1-3 An ink composition was prepared in the same manner as in Example 1, except that the types and amounts of materials used were changed to those listed in Table 1 below. The content of urethane resin relative to the total mass of the ink composition is as shown in Table 1. Furthermore, brush pens A and B were prepared in the same manner as in Example 1.

[0056] [Table 1]

[0057] The contents of the materials in Table 1 are explained according to the note numbers. (1) Self-dispersing carbon black dispersion A (a dispersion in which carbon black with carboxyl groups bonded to its surface by surface treatment is dispersed, without containing a dispersant) [Manufactured by Tokai Carbon Co., Ltd., Product name: Aqua-Black 162 (Solid content: 20%)] (2) Self-dispersing carbon black B (a dispersion in which carbon black with carboxyl groups bonded to its surface by surface treatment is dispersed, without containing a dispersant) [Manufactured by Fuji Color Co., Ltd., product name: FUJI JET BLACK D-12 (solid content: 12.5%)] (3) Resin-dispersed carbon black [A dispersion in which carbon black is dispersed by acrylic resin, with a solid content of 15%] (4) Surfactant A having an acetylene bond [Manufactured by Nisshin Chemical Industry Co., Ltd., Product name: Orphine E1010 (HLB value: 13.3)] (5) Surfactants having an acetylene bond B [Manufactured by Nisshin Chemical Industry Co., Ltd., Product name: Orphine E1020 (HLB value: 15-16)] (6) Phosphate ester surfactants [Manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Product name: Prysurf AL] (7) Urethane resin emulsion A [Manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Product name: Superflex 210 (Solid content: 35%)] (8) Urethane resin emulsion B [Manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Product name: Superflex 150HS (Solid content: 38%)] (9) Urethane resin emulsion C [Manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Product name: Superflex 420NS (Solid content: 32%)] (10) Urethane resin emulsion D [Manufactured by Sanyo Chemical Industries, Ltd., Product name: U-Coat UWS-145 (Solid content: 35%)] (11) Urethane resin emulsion E [Manufactured by Toagosei Co., Ltd., product name: Neotan UE-1100 (solid content: 35%)] (12) Acrylic resin emulsion [Manufactured by Toagosei Co., Ltd., product name: Julimar AT-210 (solid content: 30%)] (13) Preservatives [Manufactured by Lonza Japan Co., Ltd., Product name: Proxel XL-2]

[0058] [Surface tension measurement] For each ink composition prepared in Examples 1-8 and Comparative Examples 1-3, the surface tension was measured using an automatic surface tension meter [Kyowa Interface Science Co., Ltd., product name: DY-300] at room temperature (20°C) using the vertical plate method with a platinum plate. The measurement results are shown in Table 1.

[0059] [Note Test] Using each pen A and pen B prepared in Examples 1 to 8 and Comparative Examples 1 to 3, at room temperature (20 °C), the characters "Kozuke naru" were handwritten on A4-sized test paper (vertically). For the test paper, note paper conforming to JWIMA M 003:2015 (Standard of the Japan Writing Instrument Manufacturers Association, "Pen") [manufactured by Nippon Paper Industries Co., Ltd., product name: NPi Form <55>] was used.

[0060] [Evaluation of Writing Density] Regarding the writing of the characters "Kozuke naru", the density of the writing was visually confirmed, and the writing density was evaluated according to the following criteria. The evaluation results are as shown in Table 2 below, and evaluation "A" was regarded as passing. A: The writing was thick and a vivid black color. B: The writing was a slightly thin black or a light gray color. Also, the drawn line part of the writing of "Kozuke naru" above was set on the measurement part of a fluorescence spectrophotometer [manufactured by Konica Minolta, Inc., product name: FD-7 type], and the density value of the writing was measured from the K value of the fluorescence spectrophotometer. The evaluation results are as shown in Table 2 below. The density value (K value) is the average value of three measurements, and the larger the numerical value, the higher the density of the writing.

[0061] [Evaluation of Writing Drying Property] Using each pen A and pen B prepared in Examples 1 to 8 and Comparative Examples 1 to 3, at room temperature (20 °C), the character "Eiji" was handwritten on A4-sized test paper (vertically). After a certain time from the writing, the character "Eiji" was rubbed, and it was visually confirmed whether the ink spread around the writing. Based on the time until the writing dried, the writing drying property was evaluated according to the following criteria. The evaluation results are as shown in Table 2 below, and evaluations "A" and "B" were regarded as passing. Kent paper (continuous quantity: 125 kg) was used for the test paper. A: When the writing was rubbed 1 second after writing, no trace of the ink spreading around the writing was confirmed. B: When the handwriting was erased 1 second after writing, the ink spread around the handwriting. However, when the handwriting was erased 3 seconds after writing, no trace of the ink spreading around the handwriting was observed. C: Even after 4 seconds had passed since writing, when the handwriting was erased, a trace of the ink spreading around the handwriting was observed.

[0062] [Handwriting water resistance evaluation] Using each pen B prepared in Examples 1 to 8 and Comparative Examples 1 to 3, the character "永" was handwritten on A4-sized test paper (vertically) at room temperature (20°C). After 24 hours had passed since writing, 1 drop of water was dripped onto the character "永", and then the water was allowed to dry naturally. It was visually confirmed whether bleeding occurred in the handwriting. Based on the following criteria, the handwriting water resistance was evaluated. The evaluation results are as shown in Table 2 below, and evaluations "A" and "B" were considered passing. Calligraphy semi-paper was used for the test paper. A: No bleeding was observed in the handwriting. B: Some bleeding was observed in the handwriting, but it was at a level that caused no practical problems. C: Marked bleeding was observed in the handwriting.

[0063] [Cap-off performance evaluation] The caps of each pen A and pen B prepared in Examples 1 to 8 and Comparative Examples 1 to 3 were removed and left horizontally in a thermostatic chamber set at a temperature of 20°C and a humidity of 65% for 2 hours. After 2 hours had passed, it was taken out from the thermostatic chamber, and at room temperature (20°C), the character "小諸なる古城のほとりくも白く遊子かなしむ(20 characters)" was handwritten on A4-sized test paper (vertically). The obtained handwriting was visually confirmed, and the cap-off performance was evaluated based on the following criteria from the presence or absence of streaks in the handwriting. The evaluation results are as shown in Table 2 below, and evaluations "A" and "B" were considered passing. Writing paper conforming to JWIMA M 003:2015 (the standard of the Japan Writing Instruments Industrial Association for "pens") [manufactured by Nippon Paper Industries Co., Ltd., product name: NPi Form <55>] was used for the test paper. A: No streaks occurred in the handwriting from the start of writing, and good handwriting was obtained. B: There was some slight smudging in the handwriting from the start of writing, but the smudging disappeared by the time 10 characters were written, and it was at a level that did not pose any practical problems. C: Skipping occurred in the handwriting from the start of writing, and the skipping did not disappear by the time 11 characters were written.

[0064] [Table 2] [Explanation of Symbols]

[0065] 1. Brush pen 2 ink cartridges 3 Front barrel 4. Pen nib 5. Annular porous body 6 center hole 7. Inner stopper 8. Attached layer 9 Protrusion 10 Induction gap 11 Brush pens 12 shaft cylinder 13. Ink supply mechanism 14 nibs 15 Ink storage room 16 discs 17 Ink guide holes 18 ventilation holes 19 Ink guide core 20 First mounting hole 21 Second mounting hole 22 Inner pipe 23 Outer pipe

Claims

1. A water-based ink composition for writing instruments comprising at least self-dispersing carbon black, a surfactant having an acetylene bond represented by the following formula (1), a urethane resin emulsion, and water, wherein the resin content in the urethane resin emulsion relative to the total mass of the ink composition is 0.03 to 2% by mass. 【Chemistry 1】 (In the formula, R １ , R ２ , R ３ , and R ４ Each of these is independently an alkyl group, R ５ It is an ethylene group, l and m are each independent integers of 0 or greater.

2. A writing instrument comprising the ink composition described in Claim 1.

3. The writing instrument according to claim 2, wherein the writing instrument is a marking pen or a brush pen.

4. The writing instrument according to claim 3, wherein the brush pen comprises a pen tip, an ink filling mechanism, and an ink supply mechanism.

5. The writing instrument according to claim 4, further comprising an ink cartridge as the ink filling mechanism.

6. The writing instrument according to claim 4, wherein the ink filling mechanism consists of a barrel with an ink storage chamber on the inside, and the pen tip and the ink filling mechanism are joined via the ink supply mechanism.

7. The writing instrument according to any one of claims 4 to 6, wherein the ink supply mechanism comprises a number of disc bodies arranged in parallel with comb-like spacing between them, a slit-shaped ink guide groove that penetrates the disc bodies in the axial direction and a ventilation groove wider than the groove, and a pen nib having an ink guide core positioned at the center of the shaft for guiding ink to the pen tip.

8. An ink cartridge for a writing instrument, comprising the ink composition described in Claim 1.

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