Water-based ink composition for ballpoint pens

Abstract

To provide a ballpoint pen refill that has excellent brilliance and color development on paper surfaces of various hues, and can stably form vivid handwriting in which blurring and breaks are suppressed over a long period of time.SOLUTION: A ballpoint pen refill includes a pen tip and an ink storage tube, in which a water-based ink composition is contained in the ink storage tube, and the end face of the water-based ink composition is filled with an ink backflow preventive body. The water-based ink composition contains water, water-soluble organic solvent, plate-like bright pigment, coloring pigment, one or more water-dispersible polymers selected from acrylic acid-based polymers, urethane-based polymers, and olefin-based polymers, which have water dispersibility, and thickener, and has a specific range of viscosity values and a shear thinning index n at 20°C. The ink storage tube is made of synthetic resin and has an outer diameter of 2.5 to 4.0 mm and a wall thickness of 0.3 to 1.0 mm. The backflow preventive body uses polybutene as a base oil.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an aqueous ink composition for a ballpoint pen, and more particularly to an aqueous ink composition for a ballpoint pen capable of forming handwriting having excellent brilliance and color development on paper for a long period of time, a ballpoint pen refill containing the same, and a ballpoint pen. [Background technology]

[0002] Water-based ballpoint pens capable of producing metallic luster-like handwriting have been known and are widely used for a variety of purposes, from lettering to drawing. In such ballpoint pens, plate-shaped luster pigments such as plate-shaped (scale-shaped) metal powders and pearl pigments are often used as reflective pigments in the ink components, because the resulting handwriting has high brightness. In addition, in order to adjust the hue of the ink, general-purpose pigments are added to the ink or the surface of the plate-like photoluminescent pigment is colored (see, for example, Patent Documents 1 and 2). As described in Patent Document 1, when a general-purpose color pigment is added to the ink, the paper surface has permeability, so that only the plate-shaped glitter pigment with a large particle size is layered on the surface of the paper during writing, and the color pigment penetrates the paper surface, making it difficult to obtain handwriting of the desired hue. In addition, when a plate-shaped glitter pigment with a colored surface is used, it is not necessary to consider the penetration of the color pigment described above, but in order to color the entire ink, it is necessary to increase the particle size of the plate-shaped glitter pigment used and to increase the amount added, so that settling of the plate-shaped glitter pigment occurs during storage, and the ink dischargeability is likely to decrease.

[0003] In recent years, since a single ballpoint pen can produce handwriting in different tones such as black, red, and blue, multi-color (multi-core) ballpoint pens that house ballpoint pen refills of multiple colors in the barrel are widely used. Ballpoint pens with thin barrels tend to be preferred for their ease of use, and such ballpoint pens often house thin refills because the internal volume of the barrel is small. However, thin refills often have ink reservoirs that are thin and thin-walled, and depending on the material of the ink reservoir, the permeation suppression of volatile solvents such as water is poor. Over time, the volatile solvent from the ink in the refill permeates the ink reservoir and volatilizes out of the refill, causing the ink to thicken excessively or the ink-insoluble components to aggregate, which tends to deteriorate the ink dischargeability. This tendency is particularly pronounced in ink reservoir tubes made of synthetic resins such as polyethylene terephthalate (PET).Furthermore, in cases where the ink uses a photoluminescent pigment as a colorant, a large amount of plate-shaped photoluminescent pigment is often added to the ink so that the ink can produce handwriting with excellent photoluminescence. However, since inks that contain a large amount of solid matter such as pigments have a relatively small amount of liquid in the ink, there is a significant increase in ink viscosity and aggregation of solid matter when the solvent evaporates, which makes it easy for the ink ejection properties to deteriorate further.

[0004] Ballpoint pens using such plate-like luster pigments in their inks are not always good in terms of writing performance and stability over time, and improvements are desired. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 11-29734 [Patent Document 2] JP 2003-12973 A Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention provides an aqueous ink composition for a ballpoint pen, which has excellent brilliance and color development on paper surfaces of various hues and can stably produce vivid handwriting with reduced smearing and interruption over a long period of time, even in a ballpoint pen refill equipped with a slender, thin-walled ink reservoir tube and containing highly luminous aqueous ink using a plate-shaped photoluminescent pigment, and also provides a ballpoint pen refill and a ballpoint pen containing the same. [Means for solving the problem]

[0007] The water-based ink composition for ballpoint pens of the present invention contains water, a water-soluble organic solvent, a plate-shaped glittering pigment, a coloring pigment, one or more water-dispersible polymers selected from the group consisting of acrylic acid-based polymers, urethane-based polymers, and olefin-based polymers, a water-soluble copolymer of acrylic acid and a sulfonic acid-based monomer, and a thickener, wherein, when the total mass of the water-dispersible polymers is X and the total mass of the copolymers of acrylic acid and a sulfonic acid-based monomer is Y, Y / X is 0.1 to 1.0, the content of the water-dispersible polymers is 0.5 to 3 mass% based on the total mass of the ink composition, A is the sum of the total mass of the plate-shaped glittering pigment and the total mass of the coloring pigment, and B is the total mass of the water-dispersible polymers, B / A is 0.1 to 0.4, and the viscosity of the ink composition at 20°C is 800 to 1000 at 3.84 sec-1. The ink composition is required to be a water-based ink composition for a ballpoint pen, having a viscosity coefficient of 1,600 mPa·s and a shear thinning index n of 0.15 to 0.5 at 20°C. Furthermore, the present invention provides a ballpoint pen refill containing the above-mentioned water-based ink composition. A further feature is a ballpoint pen containing the ballpoint pen refill. Effect of the Invention

[0008] The present invention provides an aqueous ink composition for a ballpoint pen, which has excellent brilliance and color development and can stably produce vivid handwriting with reduced smearing and interruption over a long period of time on paper surfaces of various hues, even in a ballpoint pen refill equipped with a slender, thin-walled ink reservoir tube and containing highly luminous aqueous ink using a plate-shaped photoluminescent pigment, and also provides a ballpoint pen refill and a ballpoint pen containing the same. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is a cross-sectional view showing an example of a ballpoint pen refill of the present invention. [Diagram 2] 2 is a cross-sectional view showing an example of a pen tip (ballpoint pen tip) provided in the ballpoint pen refill of the present invention. [Diagram 3] XX cross-sectional view of FIG. 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described in detail. In this specification, the units "parts", "%", "ratio" and the like indicating the composition are based on mass unless otherwise specified.

[0011] The ballpoint pen refill according to the present invention comprises a pen tip and an ink reservoir, and contains an aqueous ink composition (hereinafter, sometimes referred to as "ink composition" or "composition") containing a plate-shaped photoluminescent pigment in the ink reservoir, and an ink backflow preventive body is filled on the end surface of the aqueous ink composition. Each element constituting the aqueous ink composition and ballpoint pen refill according to the present invention will be described below. The average particle size of the plate-like pigment in the present invention is a value calculated by assuming that the minimum value on the particle size axis in a particle size distribution diagram is 0.5 μm when measured by a laser diffraction method (volume basis).

[0012] The aqueous ink composition contains water, a water-soluble organic solvent, a plate-shaped luster pigment, a coloring pigment, one or more water-dispersible polymers selected from acrylic acid-based polymers, urethane-based polymers, and olefin-based polymers, which are water-dispersible, a water-soluble copolymer of acrylic acid and a sulfonic acid-based monomer, and a thickener, and has an ink viscosity and shear thinning index within specific ranges.

[0013] The plate-like glittering pigment may be any plate-like or scaly pigment that exhibits glittering properties that reflect light when written, and in particular may include pearl pigments, aluminum pigments, metal or metal oxide coated glass flakes, etc. One or more of these may be selected and blended into the ink.

[0014] Specifically, the pearl pigments include natural products such as fish scale foil, and synthetic products in which the surface of natural mica, synthetic mica, silica, etc. is coated with a metal oxide, with the latter being generally more widely used. Pearl pigments exhibit various colors depending on the type of metal oxide coated on the mica surface and the coating thickness. Commercially available pearl pigments include, for example, Iriodin 100 (silver), Iriodin 111 (silver), Iriodin 151 (silver), Iriodin 153 (silver), Iriodin 201 (gold), Iriodin 217 (copper red), Iriodin 289 (blue), Iriodin 302 (gold), Iriodin 504 (wine red), Iriodin 530 (copper) (all manufactured by Merck Japan Co., Ltd.), and Ultimica SB-100 (silver) (all manufactured by Topy Industries Co., Ltd.). Further, there are HELICONE HCS and HCXS (both manufactured by Wacker Chemie) which are called cholesteric liquid crystal type photoluminescent pigments.

[0015] The aluminum pigment can be obtained as a paste of very thin, scaly aluminum particles by crushing and grinding aluminum flakes together with a petroleum-based solvent such as higher fatty acid or mineral spirits in a ball mill, etc. Commercially available products include Alpaste WXM-0630, EMERAL EMR-D5660, and WJC-U75C (all manufactured by Toyo Aluminum Co., Ltd.). Alternatively, thin film aluminum obtained by vacuum deposition may be finely pulverized, and commercially available products include METALURE W-52012 IL, Ultravario Aqua PG-24001 (both manufactured by ECKART), LG neo Silver#500 (silver), and LG neo Gold#500 (gold) (both manufactured by Oike Kogyo Co., Ltd.).

[0016] The metal-coated glass flakes are obtained by coating the glass surface with silver or nickel by electroless plating, and the metal oxide-coated glass flakes are obtained by coating the surface of the glass flake with titanium dioxide by a liquid phase method. By changing the thickness of the titanium oxide film, colors such as silver, yellow, red, blue, and green can be obtained. Commercially available metal or metal oxide-coated glass flakes include Metashine 2040PS, Metashine 2020PS, Metashine 5090NS, and Metashine 5090RC (all manufactured by Nippon Sheet Glass Co., Ltd.).

[0017] These plate-shaped bright pigments can be used alone or in combination of two or more depending on the desired hue and brightness. The amount of the plate-shaped bright pigment used is 1.0 to 20% by weight, preferably 1.5 to 10% by mass, based on the total amount of the ink composition.

[0018] In addition, the plate-shaped glittering pigment used in the ink composition is not particularly limited in particle size, but a particle size is selected that does not cause writing to be impossible with the ballpoint pen used, or that does not cause the pigment to clog the ejection groove (ink outlet hole) during writing, making writing impossible. If the particle size is too small, it is difficult to obtain a glittering feel in the handwritten state, and if it is too large, there is a strong tendency for the ink ejection property to be hindered and for seat wear to be promoted, so a particularly preferred average particle size is in the range of 3 to 25 μm.

[0019] The water-based ink composition contains one or more water-dispersible polymers selected from the group consisting of acrylic acid polymers, urethane polymers, and olefin polymers, which have water dispersibility. The water-dispersible polymers used are in the form of an emulsion. The water-dispersible polymer adsorbs to the plate-like glittering pigment and the coloring pigment, suppressing aggregation of the pigments and suppressing deterioration of ink dischargeability, and also adsorbs the coloring pigment to the plate-like glittering pigment or the paper surface via the water-dispersible polymer, suppressing penetration of the coloring pigment from the paper surface into the interior, forming handwriting that is suppressed in smearing and discontinuity and has excellent glittering and color development properties of the coloring pigment. The water-dispersible polymer may be neutralized with an alkaline substance such as sodium hydroxide, ammonia, or alkanolamine.

[0020] Examples of acrylic acid polymers that can be used include polyacrylic acid, polycarboxylic acid, acrylic acid / maleic acid copolymer, acrylic acid / sulfonic acid monomer copolymer, acrylic acid / unsaturated carboxylic acid copolymer, and styrene / acrylic acid copolymer.

[0021] Specific examples of the acrylic acid polymers include Joncryl PDX-7182, PDX-7630A, PDX-7692, and 7787 (all manufactured by BASF Japan), Boncoat 5400EF (all manufactured by DIC Corporation), Mowinyl 7525 (all manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), Neocryl A-639 and Neocryl A-6016 (all manufactured by Kusumoto Chemical Industry Co., Ltd.), and the like, and one or more of these may be used.

[0022] The urethane polymer is not particularly limited in type, and examples thereof include reaction products of polyisocyanate and polyol such as polyether, polyester, and polycarbonate. The urethane polymer has an amorphous portion and a crystalline urethane bond in the molecule that interact with the color pigment and the plate-like luster pigment, so that the color pigment is prevented from being absorbed by the paper surface during writing, and it is possible to form handwriting with a bright color tone and high color development. In particular, a self-emulsifying emulsion having an anionic functional group in the molecule is more useful because it exerts a high effect regardless of the pH of the ink. Specific examples include NeoRez R-972, R-2170, R-966, R-967, R-986, R-9603, and R-9404 (all manufactured by Kusumoto Chemical Industries, Ltd.), U-coat UX-485, UWS-145, and Euplen UXA-307 (all manufactured by Sanyo Chemical Industries, Ltd.), Hydran AP-40N and APX-101H (all manufactured by DIC Corporation), and Superflex 150, 460, 470, and 820 (all manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.), and one or more of these may be used.

[0023] The olefin polymer is not particularly limited in type, and examples thereof include polyethylene, polypropylene, ethylene-(meth)acrylic acid copolymer, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, etc., and emulsions formed by dispersing these in a medium are used. In particular, self-emulsifying emulsions having an anionic functional group in the molecule are more useful because they exhibit high effects regardless of the pH of the ink. Specific examples include ZAIKSON L, ZAIKSON A, and ZAIKSON A-GH (all manufactured by Sumitomo Seika Chemicals Co., Ltd.), HYTEC E-4A, E-5403, and E-9460 (all manufactured by Toho Chemical Industry Co., Ltd.), and one or more of these may be used.

[0024] The emulsion containing the water-dispersible polymer preferably has a film formation temperature (MFT) of 60° C. or higher, more preferably 70° C. or higher, and further preferably 80° C. or higher. When the film-forming temperature is within the above range, when the ballpoint pen refill is exposed to excessive temperature changes, the water-dispersible polymer in the ink forms a film, causing the pigment to aggregate, which in turn reduces the ink dischargeability and leads to smearing or interruption of handwriting.

[0025] Among the above-mentioned water-dispersible polymers, acrylic acid-based polymers are suitable for ink compositions because they are easily adsorbed not only to color pigments but also to plate-like glitter pigments and paper surfaces, and as a result, the color pigments are adsorbed to the plate-like glitter pigments and paper surfaces, and the penetration of the color pigments from the paper surfaces into the interior is easily inhibited, and the glitter and color development of handwriting can be made even more excellent.

[0026] The content of the water-dispersible polymer is preferably 0.1 to 5 mass %, more preferably 0.5 to 3 mass %, based on the total mass of the ink composition. When the content is within the above range, the ink composition is prevented from excessively thickening, while the dispersion stability of the plate-like glittering pigment and coloring pigment is improved, and handwriting with excellent glitter and color development and with reduced smearing and discontinuity is easily formed.

[0027] The ink composition further contains a water-soluble copolymer of acrylic acid and a sulfonic acid monomer, which further suppresses the penetration of the color pigment from the paper surface into the interior and the aggregation of the plate-shaped lustrous pigment, making it easier to form handwriting with excellent color development and lustrous properties while suppressing smearing and interruption of the handwriting. The copolymer is made water-soluble by neutralizing a copolymer of acrylic acid and a sulfonic acid monomer with an alkaline substance such as sodium hydroxide, ammonia, alkanolamine, etc., and is applied to an ink composition. Specific examples thereof include neutralized copolymers of acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid, and product names: Aron A-6012, A-6016, A-6017, and A-6020 (all of which are sodium salts of copolymers of acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid, manufactured by Toagosei Co., Ltd.) can be used. The copolymer of acrylic acid and a sulfonic acid monomer that can be used in the ink composition is not limited to the above. The copolymers may be used in combination of two or more kinds.

[0028] The content of the copolymer of acrylic acid and sulfonic acid monomer is preferably 0.05 to 2 mass %, more preferably 0.1 to 1 mass %, based on the total mass of the ink composition. When the content is within the above range, the ink composition is prevented from excessively thickening, which would cause a decrease in ink dischargeability from the pen tip, and handwriting with excellent brilliance and color development is easily formed.

[0029] In the aqueous ink composition, when the total mass of the water-dispersible polymer is X and the total mass of the copolymer of acrylic acid and sulfonic acid monomer is Y, Y / X is preferably 0.1 to 1.0, more preferably 0.2 to 0.8. Particularly preferably 0.3 to 0.6. When the total mass ratio is within the above range, the color pigment is prevented from penetrating into the paper from the surface and the plate-like glittering pigment is prevented from agglomerating, and excellent handwriting with excellent color development and glittering properties is easily formed.

[0030] Examples of the color pigment include inorganic pigments such as carbon black and ultramarine, organic pigments such as copper phthalocyanine blue and benzidine yellow, and water-dispersed pigment products that have been finely and stably dispersed in an aqueous medium using a surfactant or the like. Examples of such pigments include CI Pigment Blue 15:3B (product name: SS Blue GLL, pigment content 22%, manufactured by Sanyo Pigment Co., Ltd.), CI Pigment Red 146 (product name: SSPink FBL, pigment content 21.5%, manufactured by Sanyo Pigment Co., Ltd.), CI Pigment Yellow 81 (product name: TC Yellow FG, pigment content approximately 30%, manufactured by Dainichi Seika Color & Chemicals Mfg. Co., Ltd.), and CI Pigment Red 220 / 166 (product name: TC Red FG, pigment content approximately 35%, manufactured by Dainichi Seika Color & Chemicals Mfg. Co., Ltd.). As the fluorescent pigment, there can be used a fluorescent pigment in the form of fine particles of synthetic resin in which various fluorescent dyes are solid-dissolved in a resin matrix. Other examples include phosphorescent pigments, white pigments such as titanium dioxide, thermochromic compositions, photochromic compositions, and capsule pigments in which perfumes and the like are directly or microencapsulated.

[0031] The thermochromic composition is preferably a reversible thermochromic composition consisting of (i) an electron-donating color-forming organic compound, (ii) an electron-accepting compound, and (iii) a reaction medium that determines the temperature at which the color-forming reaction between the two occurs, and is applied as a reversible thermochromic microcapsule pigment by encapsulating it in microcapsules. As the reversible thermochromic composition, there can be used a heat-discoloring type microcapsule pigment in which a reversible thermochromic composition having a relatively small hysteresis width (ΔH=1 to 7° C.) is encapsulated in a microcapsule, the reversible thermochromic composition being described in JP-B-51-44706, JP-B-51-44707, JP-B-1-29398, etc., and discoloring around a predetermined temperature (discoloration point), exhibiting a discolored state in a temperature range above the high-temperature discoloration point and a colored state in a temperature range below the low-temperature discoloration point, and only one of the two states exists in the room temperature range, and the other state is maintained while the heat or cold required to express that state is applied, but returns to the state exhibited in the room temperature range when the application of the heat or cold is removed. Further, there are those exhibiting relatively large hysteresis characteristics (ΔH=8 to 50° C.) as described in JP-B-4-17154, JP-A-7-179777, JP-A-7-33997, JP-A-8-39936, etc., and those exhibiting large hysteresis characteristics as described in JP-A-2006-137886, JP-A-2006-188660, JP-A-2008-45062, JP-A-2008-280523, etc. In other words, the shape of the curve plotting the change in color density due to temperature change will change color along a path that is significantly different when the temperature is increased from a lower temperature side than the color change temperature range than when the temperature is decreased from a higher temperature side than the color change temperature range, and the colored state in a low temperature range below the complete color development temperature, or the decolored state in a high temperature range above the complete decolorization temperature, can also be applied to heat-discolorable microcapsule pigments that encapsulate a reversible thermochromic composition that has color memory properties in a specific temperature range. Specifically, the reversible thermochromic composition having color memory has a complete color-developing temperature that is a temperature that can only be obtained in a freezer or in a cold region, i.e., -50 to 0°C, preferably -40 to -5°C, more preferably -30 to -10°C, and a complete decolorization temperature that is a temperature obtained from frictional heat produced by a friction body or a familiar heating body such as a hair dryer, i.e., a range of 50 to 95°C, preferably 50 to 90°C, more preferably 60 to 80°C, and a ΔH value of 40 to 100°C, thereby allowing the composition to effectively function in maintaining the color that it exhibits under normal conditions (daily living temperature range).

[0032] Furthermore, if necessary, a dye soluble in an aqueous medium can be used in combination. As the dye, acid dyes, basic dyes, direct dyes, etc. can be used. As the acid dye, New Coccine (CI16255), Tartrazine (CI19140), Acid Blue Black 10B (CI20470), Guinea Green (CI42085), Brilliant Blue FCF (CI42090), Acid Violet 6B (CI42640), Soluble Blue (CI42755), Naphthalene Green (CI44025), Eosine (CI45380), Phloxine (CI45410), Erythrosine (CI45430), Nigrosine (CI50420), Acid Flavin (CI56205), etc. can be used. Examples of basic dyes that can be used include chrysoidine (CI11270), methyl violet FN (CI42535), crystal violet (CI42555), malachite green (CI42000), Victoria blue FB (CI44045), rhodamine B (CI45170), acridine orange NS (CI46005), and methylene blue B (CI52015). Direct dyes include Congo Red (CI 22120), Direct Sky Blue 5B (CI 24400), Violet BB (CI 27905), Direct Deep Black EX (CI 30235), Kayalas Black G Conc (CI 35225), Direct Fast Black G (CI 35255), Phthalocyanine Blue (CI 74180), etc.

[0033] The color pigments can be used alone or in a suitable mixture of two or more kinds, and are preferably used in an amount of 0.1 to 20% by mass, more preferably 0.5 to 15% by mass, in the ink composition.

[0034] Furthermore, in order to suppress smearing or interruption of handwriting while improving the color development and brilliance of handwriting, when the sum of the total mass of the color pigment and the total mass of the plate-like brilliant pigment in the aqueous ink composition is A and the total mass of the water-dispersible polymer is B, the ratio B / A is preferably 0.05 to 0.5, and more preferably 0.1 to 0.4.

[0035] Furthermore, a general-purpose pigment dispersant can be used in the ink composition. As the pigment dispersant, a water-soluble resin, a surfactant, etc. can be used. As the water-soluble resin, for example, a water-soluble maleic acid resin, a water-soluble styrene resin, a water-soluble styrene-maleic acid resin, a polyvinylpyrrolidone, a polyvinyl alcohol, a water-soluble urethane resin, etc. can be mentioned. In addition, as the surfactant, an optional one is selected from an anionic, a cationic, a nonionic, and an amphoteric surfactant.

[0036] A thickener is added to the ink composition, which can prevent the particulate components (plate-shaped photoluminescent pigment, color pigment) from settling and the writing from bleeding during storage. Any known thickener can be used as the thickener, but a substance capable of imparting shear thinning properties to the ink composition (shear thinning agent) is preferred. By using a shear thinning agent in the ink composition, it is possible to improve the anti-settling stability of the particles and the suppression of bleeding of handwriting without impairing the ink dischargeability during writing.

[0037] As the shear thinning agent, a substance that is soluble or dispersible in water is effective, and examples thereof include xanthan gum, welan gum, succinoglycan (average molecular weight: about 1 to 8 million), which is an organic acid-modified heteropolysaccharide whose constituent monosaccharides are glucose and galactose, guar gum, locust bean gum and derivatives thereof, hydroxyethyl cellulose, alginic acid alkyl esters, polymers having a molecular weight of 100,000 to 150,000 and mainly composed of alkyl esters of methacrylic acid, glucomannan, carbohydrates having gelling ability extracted from seaweed such as agar and carrageenin, benzylidene sorbitol and benzylidene xylitol or derivatives thereof, crosslinkable acrylic acid polymers, poly-N-vinyl carboxylic acid amide, inorganic fine particles, nonionic surfactants having an HLB value of 8 to 12, metal salts and amine salts of dialkyl sulfosuccinic acid, and the like. Furthermore, stable shear thinning can be imparted even when N-alkyl-2-pyrrolidone and anionic surfactants are added in combination to the ink composition.

[0038] The content of the thickener is preferably 0.01 to 3 mass % and more preferably 0.1 to 1 mass % based on the total mass of the ink composition. When the content of the thickener is within this range, it is easy to achieve both the ink dischargeability during writing, the anti-settling stability of the pigment, and the suppression of bleeding of handwriting.

[0039] In order to prevent the ink dischargeability from decreasing due to excessive evaporation of water from the ink contained in the refill, a conventional water-soluble organic solvent that is compatible with water is used in the aqueous ink composition. Specific examples of the organic solvent include ethanol, propanol, butanol, glycerin, sorbitol, triethanolamine, diethanolamine, monoethanolamine, ethylene glycol, diethylene glycol, thiodiethylene glycol, polyethylene glycol, propylene glycol, butylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, ethylene glycol monomethyl ether acetate, sulfolane, 2-pyrrolidone, and N-methyl-2-pyrrolidone. The water-soluble organic solvents can be used alone or in combination of two or more kinds, and are preferably used in the range of 1 to 20% by mass, more preferably 5 to 15% by mass. When the content of the organic solvent is within the above range, excessive evaporation of water can be easily suppressed without excessively increasing the ink viscosity, so that good ink ejection properties can be maintained and handwriting that is free of smudges and interruptions can be easily formed over a long period of time.

[0040] In addition, in order to increase the fluidity of the ink composition and improve the ink dischargeability from the pen tip, the water content is preferably 40 to 80 mass %, and more preferably 45 to 70 mass %, based on the total mass of the ink composition.

[0041] The ink composition preferably contains a phosphate ester surfactant. The phosphate ester surfactant also adsorbs to the surface of the ball and to the surface of the ball receiving seat of the ballpoint pen tip, forming a lubricating layer made of the phosphate ester surfactant on the surface of the ball and the surface of the ball receiving seat, making the ball rotate more smoothly when writing. Furthermore, the phosphate surfactant can also be adsorbed to the surface of the pigment, making it easier to inhibit the aggregation and sedimentation of the pigment.

[0042] The phosphate ester surfactant used in the ink composition is a compound represented by the following formula (1). [ka] In the formula, X1, X2, and X3 are a functional group shown in the following formula (2) or a hydroxyl group, and at least one of X1, X2, and X3 is a functional group shown in formula (2). [ka] In the formula, R1 is a hydrocarbon group, R2 is an alkylene group, and n is an integer of 1 or more.

[0043] The preferred phosphate ester surfactant for the ink composition is a phosphate ester surfactant in which the hydrocarbon group is an alkyl group, an alkenyl group, or an aryl group, and more preferably, the phosphate ester surfactant in which the hydrocarbon group is an alkyl group, an alkenyl group, or an aryl group, and the alkylene group is an ethylene group. A particularly preferred phosphate ester surfactant is a phosphate ester surfactant in which the hydrocarbon group is an alkyl group, and the alkylene group is an ethylene group, that is, polyoxyethylene alkyl ether phosphate. The use of the polyoxyethylene alkyl ether phosphate makes the ball rotate more smoothly during writing, improves the ink dischargeability during writing, and makes it easier to prevent the pigment from coagulating and settling. This is because the polyoxyethylene alkyl ether phosphate has a high affinity not only to the ball and the ball tip, but also to the pigment, and exerts the effects of excellent lubricating layer formation and pigment dispersibility on the ball surface and the ball tip surface. In particular, ballpoint pens that use the plate-like luster pigment as the ink colorant can struggle to provide a smooth writing feel or good ink discharge; however, polyoxyethylene alkyl ether phosphate is interposed between the plate-like luster pigment and the ball surface and the ball seat surface, and the pigment is adsorbed to the ball surface and the ball seat surface, so that the pigment acts as a roller when the ball rotates during writing, thereby making the ball rotate smoothly and providing a good writing feel and ink discharge. The phosphate ester surfactant may be an alkali metal salt or an amine salt.

[0044] The content of the phosphate ester surfactant is preferably 0.01 to 5 mass % and more preferably 0.1 to 3 mass % based on the total mass of the ink composition. By setting the content of the phosphate ester surfactant in the ink composition within the above range, it becomes easier to make the ball spin smooth while improving the dissolution stability of the phosphate ester surfactant, and it becomes easier to suppress pigment aggregation and sedimentation.

[0045] Furthermore, a water-soluble resin can be added to the ink composition to impart adhesion and viscosity to the paper surface. Examples of the water-soluble resin include alkyd resins, styrene-maleic acid copolymers, cellulose derivatives, polyvinylpyrrolidone, polyvinyl alcohol, dextrin, etc. The water-soluble resins can be used alone or in combination of two or more, and are used in the range of 1 to 30% by weight in the ink composition.

[0046] In addition, the ink composition may contain, as necessary, inorganic salts such as sodium carbonate, sodium phosphate, and sodium acetate; pH adjusters such as organic basic compounds such as water-soluble amine compounds; rust inhibitors such as benzotriazole, tolyltriazole, 2,5-dimercapto-1,3,4-thiadiazole, and saponin; preservatives or antifungal agents such as carbolic acid, the sodium salt of 1,2-benzthiazolin-3-one, sodium benzoate, sodium dehydroacetate, potassium sorbate, propyl paraoxybenzoate, and 2,3,5,6-tetrachloro-4-(methylsulfonyl)pyridine; wetting agents such as urea, nonionic surfactants, sorbitol, mannitol, sucrose, glucose, reduced starch hydrolysates, and sodium pyrophosphate; defoamers; and fluorine-based surfactants and nonionic surfactants that improve the penetration of the ink. Furthermore, air bubbles can be removed chemically by adding ascorbic acids, erythorbic acids, α-tocopherol, catechins, synthetic polyphenols, kojic acid, alkylhydroxylamines, oxime derivatives, α-glucosylrutin, α-lipoic acid, phosphonates, phosphinates, sulfites, sulfoxylates, dithionites, thiosulfates, thiourea dioxide, or the like. Furthermore, dextrin can be used to improve the resistance of the pen tip to drying up. In addition, by adding a thickening inhibitor such as an oligomer of N-vinyl-2-pyrrolidone, an oligomer of N-vinyl-2-piperidone, N-vinyl-2-pyrrolidone, N-cyclohexyl-2-pyrrolidone, ε-caprolactam, or an oligomer of N-vinyl-ε-caprolactam, the functionality in the retractable form can be improved. Furthermore, lubricants can be used, such as metal soaps, polyalkylene glycol fatty acid esters, ethylene oxide-added cationic surfactants, phosphate ester-based surfactants, β-alanine-type surfactants, N-acylamino acids, N-acylmethyltaurines, 2,5-dimercapto-1,3,4-thiadiazole and its salts and oligomers, 3-amino-5-mercapto-1,2,4-triazole, thiocarbamate, dimethyldithiocarbamate, α-lipoic acid, condensates of N-acyl-L-glutamic acid and L-lysine and its salts, and the like.

[0047] The viscosity of the water-based ink composition at 20°C is 3.84 sec -1 Under these conditions, it is important that the viscosity is 800 to 1600 mPa·s, and preferably 1000 to 1500 mPa·s. The viscosity can be measured, for example, using a rheometer "DHR-2" manufactured by TA Instruments.

[0048] It is important that the shear thinning index n of the aqueous ink composition at 20° C. is 0.15 to 0.5, preferably 0.2 to 0.4, and more preferably 0.25 to 0.35. Here, the shear thinning index n is expressed by the formula S=αD n where S is the shear stress (dyn / cm 2 =0.1 Pa), D is the shear rate (sec -1 ), and α is the viscosity coefficient. The shear thinning index n can be measured, for example, using a rheometer "DHR-2" manufactured by TA Instruments Co., Ltd., and is 3.84 sec -1 , 38.4sec -1 and 384sec -1 and the shear stresses obtained at those shear rates are applied to the above equation to find n. When the viscosity and shear thinning index of the aqueous ink composition are within the above-mentioned numerical ranges, settling and aggregation of the plate-like photoluminescent pigment and colored pigment when left to stand can be suppressed, while the ink can be discharged well from the pen tip when writing, and clear handwriting with excellent color development and photoluminescence can be produced with suppressed smearing and discontinuities.

[0049] The surface tension of the aqueous ink composition is preferably 25 to 55 mN / m in an environment of 20° C. If the surface tension is within the above range, it is possible to improve the writing properties by suppressing smearing, interruption, bleeding, etc. of handwriting. In consideration of the improvement of the writing properties, the surface tension of the aqueous ink composition is more preferably 30 to 50 mN / m. The surface tension is measured in an environment of 20° C. using a surface tension meter manufactured by Kyowa Interface Science Co., Ltd., and a platinum plate by the vertical plate method.

[0050] The pH of the aqueous ink composition is preferably 6 to 10, and more preferably 7 to 9. When the pH of the aqueous ink composition is within the above range, the dispersibility of the colorant is easily improved. In the present invention, the pH value can be measured at 20° C. using, for example, a pH meter "D-51" manufactured by Horiba, Ltd.

[0051] The aqueous ink composition can be produced by any conventional method. Specifically, the aqueous ink composition can be produced by mixing the required amounts of the above-mentioned components with various stirrers such as a propeller stirrer, a homodisper, or a homomixer, or various dispersers such as a bead mill.

[0052] The aqueous ink composition contains at least water, a water-soluble organic solvent, a plate-shaped photoluminescent pigment, a colored pigment, one or more water-dispersible polymers selected from acrylic acid-based polymers, urethane-based polymers and olefin-based polymers having water-dispersibility, and a thickener. By controlling the viscosity and shear thinning index to be within a specific range, the dispersion stability and ink dischargeability of the plate-shaped photoluminescent pigment and colored pigment are improved, and the colored pigment is prevented from sinking from the paper surface into the interior of the paper, thereby producing vivid handwriting with excellent color development and photoluminescence and with reduced smearing and discontinuities. The pigment dispersion stability is maintained even after long periods of aging or when the water content in the ink decreases over time and the concentrations of the plate-shaped photoluminescent pigment and color pigment increase. Furthermore, even when the water content in the ink decreases, the aqueous ink composition is prevented from excessively thickening and good ink discharge properties are maintained, so that the aqueous ink composition can form the above-mentioned vivid handwriting for a long period of time.

[0053] The ballpoint pen refill of the present invention contains the above-mentioned aqueous ink composition in an ink reservoir tube to which a ballpoint pen tip is attached directly or via a holder, and is filled with an ink backflow prevention body (liquid plug) that flows behind the ink as the ink is consumed.

[0054] The structure and shape of the pen tip (ballpoint pen tip) are not particularly limited. For example, there is a structure in which a tip body is provided with a ball holding chamber for holding a ball, which is cut by a drill or the like, an ink circulation hole formed in the center of the bottom wall of the ball holding chamber, and a plurality of ink circulation grooves extending radially from the ink circulation hole, and the tip tip of the tip body is crimped inward to make a part of the ball held in the ball holding chamber protrude from the tip tip edge and to hold the ball rotatably. There is also a so-called pipe-type ballpoint pen tip structure having a ball holding part in which the ball is rotatably held by a crimped part formed by pressing and deforming the tapered tip of a metal pipe inward in the radial direction and a plurality of inward protrusions formed by pressing and deforming the side wall near the tip of the pipe inward in the radial direction.

[0055] The pipe may have, for example, a cylindrical body with a straight tip (straight pipe-shaped cylindrical body) and an outer diameter and an inner diameter that increase rearward from the tip. The shape of the pipe may be a straight cylindrical body as a whole.

[0056] Considering the need to improve the ink ejection properties from the ballpoint pen tip, the ballpoint pen tip is preferably a pipe-type ballpoint pen tip in which the tip of the pipe is a straight cylinder and the outer and inner diameters expand rearward from the tip (hereinafter, sometimes referred to as a pipe-type ballpoint pen tip having a shape that expands rearward from the tip).

[0057] The pipe-type ballpoint pen tip, which has a shape that expands in diameter behind the tip, has a wide ink flow path formed behind the ball-holding chamber inside the ballpoint pen tip, and can supply abundant ink to the ball-holding chamber. A ballpoint pen refill equipped with such a ballpoint pen tip has good ink ejection properties from the pen tip, excellent glitter and color development, and is easy to form clear handwriting with reduced cutting and smudging.

[0058] The material of the ballpoint pen tip and the ball held by the ballpoint pen tip is preferably selected from stainless steel, cemented carbide based on tungsten carbide, silicon carbide, alumina, zirconia, silicon nitride, etc., taking into consideration good wear resistance of the ball and the ball seat.

[0059] The ball diameter is 0.2 to 0.7 mm, preferably 0.3 to 0.5 mm, and more preferably 0.3 to 0.45 mm.

[0060] A ballpoint pen refill with a ball diameter of 0.7 mm or less, particularly less than 0.5 mm, may have a small ink discharge amount and may not be able to produce clear handwriting. However, the above-mentioned pipe-type ballpoint pen tip having a shape with a diameter expanding behind the tip, even when equipped with a ball having such an outer diameter, has good ink discharge properties and can easily produce clear handwriting with reduced smearing and interruption, and can be preferably used in combination with a ball having a ball diameter in the above range.

[0061] The ballpoint pen tip may have a resilient member disposed therein that resilients the rear end of the ball forward, so that when writing, the ball can be moved backward by the pressure of writing, allowing the ink to flow out, and when not writing, the ball can be pressed against the inner edge of the tip tip to create a tight contact state, making it easy to prevent ink leakage when not in use.

[0062] The resilient member may be, for example, a thin metal wire spring, a spring with a spring at one end, or Examples of such products include those having straight portions (rod portions), linear plastic processed bodies, etc. It is configured so that it can be pressed with a resilient force of 10 g or more and 40 g or less.

[0063] Ink reservoir tubes to which a ballpoint pen tip is attached directly or via a holder are made of molded components of synthetic resins such as polyethylene, polypropylene, polyethylene terephthalate, or ethylene-vinyl acetate copolymer resins, because these have low water vapor permeability, good productivity, and transparency that allows excellent visibility of the filled ink. Examples of the polyethylene include low-density polyethylene, linear short-chain branched polyethylene, metallocene-catalyzed linear short-chain branched polyethylene, and high-density polyethylene, and examples of the polypropylene include homopolymer polypropylene, random copolymer polypropylene, and block copolymer polypropylene, all of which can be preferably used. Among these, polypropylene is preferably used because it has excellent strength and heat resistance, low moisture permeability, and is easily inhibited from thickening the ink due to evaporation of moisture over time. The ink reservoir tube is obtained by subjecting the synthetic resin to extrusion molding or injection molding. The surface of the resin may be coated with another material.

[0064] The ink reservoir tube made of the synthetic resin may be either single-layered or multi-layered, but it is preferable that the ink reservoir tube has a multi-layered structure and has a layer that prevents the permeation of gases such as oxygen, in order to prevent the ink from deteriorating over time. Furthermore, in order to prevent the ink from adhering to the inner wall of the ink reservoir tube, the inner surface of the ink reservoir tube may be coated with a silicone resin, a fluororesin, or the like to provide an ink-repellent treatment, as necessary.

[0065] The ink reservoir has an outer diameter of 2.5 to 4 mm and a wall thickness of 0.3 to 1 mm. An ink reservoir tube whose outer diameter and wall thickness are within the above-mentioned ranges is slender yet capable of balancing a sufficient ink capacity with high strength. Therefore, when a ballpoint pen refill equipped with the above-mentioned ink reservoir tube is contained in a composite retractable ballpoint pen which contains multiple ballpoint pen refills within a barrel and in which the writing tip of one of the ballpoint pen refills protrudes and retracts from the front end opening of the barrel by activation of the retraction mechanism, the ballpoint pen can be made to be a highly practical ballpoint pen which is capable of writing a sufficient distance while having a slim outer diameter of the barrel. In ballpoint pen refills having the ink reservoir tube, water from the ink contained therein tends to volatilize out of the refill over time through the ink reservoir tube, and as a result, the ink dischargeability tends to decrease due to the aggregation of solids and excessive thickening of the ink caused by the decrease in the amount of water. In particular, when the ink in the ballpoint pen refill contains a large amount of solids such as pigments, such as plate-shaped glittering pigment ink, this tendency is remarkable, and the ink dischargeability tends to deteriorate. However, although the ink composition is an ink using a plate-shaped glittering pigment, even after a long period of time or when the amount of water in the composition decreases over time, excessive thickening of the ink viscosity is suppressed, and good dispersibility of the plate-shaped glittering pigment and coloring pigment is maintained. Therefore, the ballpoint pen refill of the present invention containing the ink composition maintains good ink dischargeability even with the ink reservoir tube, and can stably form handwriting with excellent glitter and color development of the coloring pigment for a long period of time. In addition, in a ballpoint pen refill having the ink reservoir, the ink plug is less likely to deform when an impact is applied to the ink plug, so that ink leakage from the rear end of the refill when the ballpoint pen refill is dropped can be suppressed. This makes the ballpoint pen refill excellent in storage properties. The ink reservoir tube preferably has an outer diameter of 2.5 to 3.5 mm and a wall thickness of 0.5 to 0.8 mm.

[0066] Furthermore, an ink backflow prevention body (liquid plug) is disposed at the rear end of the ink composition filled in the ink reservoir tube. The ink backflow preventer is a viscous liquid that uses a non-volatile medium as a base oil and has a high viscosity due to the addition of solids such as silica, aluminum silicate, swellable mica, and fatty acid amide. Examples of non-volatile media used for the base oil include petrolatum, spindle oil, castor oil, olive oil, refined mineral oil, liquid paraffin, polybutene, α-olefin, α-olefin oligomer or cooligomer, dimethyl silicone oil, methylphenyl silicone oil, amino-modified silicone oil, polyether-modified silicone oil, fatty acid-modified silicone oil, etc., and polybutene is preferably used because it is easy to increase the viscosity when the solid is added, the solid is not easily separated over time, and further, it has low water vapor permeability and is easy to suppress thickening of the ink over time due to evaporation of water. Polybutene has a viscosity of 1000 to 10000 mm at 40°C. 2 s -1 It is preferable that the viscosity of the mixture is 1500 to 5000 mm. 2 s -1 More preferably, the thickness is 2000 to 4000 mm. 2 s -1 By using such a polybutene as the base oil of the liquid plug, the liquid plug can easily follow the ink when the ink is discharged during writing, making it easier to prevent the ink discharge from being hindered, and also making it easier to prevent the liquid plug from deforming and the ink from leaking from the rear end of the refill even if the ballpoint pen refill falls and the load of the ink composition is applied to the liquid plug. The ink backflow preventive material can be prepared by kneading the polybutene with the silica, aluminum silicate, swellable mica, fatty acid amide, etc., using a kneading machine such as a three-roll mill or a kneader. The kinematic viscosity can be measured in accordance with JIS K 2283:2000 "Crude oil and petroleum products -- Test method for kinematic viscosity and calculation method for viscosity index."

[0067] In addition, a ballpoint pen refill may be provided with a solid plug in addition to the ink backflow preventer to prevent ink from flowing back. The solid plugs are made of resin, such as polyethylene, polypropylene, and polymer. Examples of solid stoppers include those made of Tilpentene.

[0068] The ballpoint pen refill of the present invention is equipped with a cap-type, knock-type, rotating-type or sliding-type protrusion / retraction mechanism and is attached to a retractable ballpoint pen configured so that the pen tip can protrude and retract from the tip hole of the barrel.

[0069] When applying the retractable type to a ballpoint pen, the structure and shape of the retractable ballpoint pen are not particularly limited, and any structure can be used as long as the writing tip provided on the ballpoint pen refill is stored in the barrel while being exposed to the outside air, and the writing tip protrudes from the barrel opening by the operation of the retractable mechanism. Examples of the operation method of the retractable mechanism include a knock type, a rotation type, a slide type, and the like. The knock type can be exemplified by a configuration having a knock part at the rear end of the barrel or the side of the barrel, and the writing tip protrudes from the barrel front end opening by pressing the knock part, or a configuration in which the writing tip protrudes from the barrel front end opening by pressing a clip part provided on the barrel. The rotation type can be exemplified by a configuration having a rotating part at the rear of the barrel, and the writing tip protrudes from the barrel front end opening by rotating the rotating part. The sliding type may be exemplified by a configuration having a sliding part on the side of the barrel, and by operating the slide, the writing tip part is made to protrude and retract from the front end opening of the barrel, or a configuration in which a clip part provided on the barrel is slid, and the writing tip part is made to protrude and retract from the front end opening of the barrel. The retractable ballpoint pen may be a composite type retractable ballpoint pen (hereinafter sometimes referred to as a composite type retractable ballpoint pen) in which a plurality of ballpoint pen refills are accommodated in the barrel, and the writing tip part of any of the ballpoint pen refills protrudes and retracts from the front end opening of the barrel by the operation of the retractable mechanism. Furthermore, by using a transparent, colored transparent, or translucent molded body as the barrel, it is possible to check the ink color, the remaining amount of ink, etc.

[0070] The ballpoint pen refill of the present invention is slender yet has excellent brilliance and color development, and can produce vivid handwriting without smudges or interruptions over a long period of time, and therefore can be preferably used in composite type retractable ballpoint pens for which slender ballpoint pen refills are suitable.

[0071] An example of a ballpoint pen refill according to this embodiment will now be described with reference to the drawings.

[0072] Ballpoint pen refills An embodiment of the ballpoint pen refill is shown in Figs. The ballpoint pen refill 1 of this embodiment comprises a ballpoint pen tip 2 which rotatably holds a ball 4 at its front end, a spring 5 housed inside the ballpoint pen tip 2, a holder 6 to the front of which the ballpoint pen tip 2 is press-fitted, and an ink reservoir tube 7 to which the rear of the holder is press-fitted into the front end opening. In this embodiment, "front" refers to the pen tip ball side, and "rear" refers to the opposite side.

[0073] Ballpoint pen tip The ballpoint pen tip 2 comprises a tip body 3 and a ball 4. The tip body 3 is a metallic cylinder comprising a small-diameter cylindrical section 31 rotatably holding the ball 4 at its front end, a tapered cylindrical section 32 integrally connected to the rear of the small-diameter cylindrical section 31 and gradually increasing in diameter toward the rear, and a large-diameter cylindrical section 33 integrally connected to the rear of the tapered cylindrical section 32. The metallic cylinder can be made of austenitic stainless steel such as SUS304, SUS305, or SUS321.

[0074] A plurality of (for example, four) inward protrusions 31b are formed at equal intervals in the circumferential direction on the inner surface near the front end of the small diameter tube portion 31 of the tip body 3 by inward pressing deformation. The inward protrusions 31b form a ball receiving seat. The front end of the tip body 3 is also formed with an inward front edge portion 31a by being pressed inward in a circumferential manner. A ball holding portion that rotatably holds the ball 4 is formed between the front surface of the inward protrusions 31b (ball receiving seat) and the rear surface of the front edge portion 31a. An ink circulation hole 31c that extends radially outward from the center and penetrates in the axial direction is formed between the inward protrusions 31b. That is, the ink circulation hole 31c is formed in the ball receiving seat. The ball pen tip 2 may be a type in which a ball receiving seat is formed by cutting at the front end of the metal tip body 3.

[0075] · Straight cylindrical inner surface The inner surface of the small diameter cylindrical portion 31 rearward of the inward protruding portion 31b is formed to have a straight cylindrical inner surface. The inner surface of the large diameter cylindrical portion 33 is formed to have a straight cylindrical inner surface.

[0076] Tapered inner surface The tapered cylindrical portion 32 has an inner surface formed with a tapered shape (or a conical shape) that gradually increases in diameter toward the rear.

[0077] Spring The spring 5 has a front rod portion 51 and a rear coil portion 52 that are integrally connected to each other by a single metal wire (for example, a stainless steel wire having a wire diameter of 0.11 mm).

[0078] Rod section The rod portion 51 extends linearly in the axial direction and is inserted into the ink flow hole 31c of the ball receiving seat 31b. The front end of the rod portion 51 abuts against approximately the center of the rear surface of the ball 4, and the ball 4 is directly urged forward by the rod portion 51. This brings the ball 4 into close contact with the inner circumferential surface of the front end edge portion 31a, preventing ink from leaking from the front end of the tip body 3 and ink from evaporating.

[0079] Coil section The coil portion 52 is formed by winding a wire in a spiral shape. A tightly wound portion where the wire is tightly wound is formed at the front and rear ends of the coil portion 52. An effective winding portion with gaps between the wire is formed in the middle portion of the coil portion 52 excluding the front and rear ends. The elastic force of the spring 5 urging the ball 4 forward (specifically, the load when the ball 4 is pressed backward by 0.01 mm) is set in the range of 14 grams to 25 grams (preferably 15 grams to 22 grams).

[0080] ·holder The holder 6 is a cylindrical body obtained by injection molding of a synthetic resin (e.g., polypropylene). The holder 6 comprises a tapered front portion 61 to which the ballpoint pen tip 1 is attached, a flange portion 62 that abuts on the front end surface of the ink reservoir 7, and a rear portion 63 that is press-fitted into the front end opening of the ink reservoir 7. The rear portion of the tip body 3 is press-fitted and fixed into the mounting hole of the front portion 61 of the holder 6. A step portion 64 protrudes from the rear end of the inner surface of the mounting hole, and the rear end of the tip body 3 is engaged with the step portion 64, and the rear end of the spring 5 (the rear end of the coil portion 52) is engaged with the step portion 64.

[0081] Ink reservoir tube The ink reservoir 7 is a cylinder with both ends open, obtained by extrusion molding of a synthetic resin (e.g., polypropylene). The ink reservoir 7 has an outer diameter of 2.5 to 4 mm and a wall thickness of 0.3 to 1 mm, and is filled with ink 71 and an ink backflow preventer 72 made of a high-viscosity fluid that advances as the ink 71 is consumed. The ink 71 is a water-based ink composition according to the ballpoint pen refill of the present invention. The ink backflow preventer 72 has a flow rate of 1,000 to 10,000 mm at 40°C. 2 s -1 Examples of high viscosity fluids include those obtained by mixing solids with polybutene having a kinetic viscosity of 1000 g / L or more as a base oil.

[0082] ·ball The ball 4 has a diameter A in the range of 0.2 mm to 0.7 mm (preferably 0.3 mm to 0.5 mm, and more preferably 0.3 mm to 0.45 mm). Specifically, balls 4 are prepared in a variety of sizes according to the desired handwriting width, and balls with diameters of, for example, 0.2 mm, 0.25 mm, 0.3 mm, 0.4 mm, 0.5 mm, and 0.7 mm are used.

[0083] The amount of axial movement of the ball 4 by the ball holding part is preferably in the range of 0.02 mm to 0.05 mm in order to obtain smooth ink outflow. The amount of axial movement of the ball 4 by the ball holding part varies depending on the diameter A of the ball 4, and is set in the range of 5% to 15% (preferably 8% to 12%) of the diameter A of the ball 4, thereby obtaining smooth ink outflow and a sufficient amount of ball exposure.

[0084] The material of the ball 4 may be stainless steel, a cemented carbide based on tungsten carbide, silicon carbide, alumina, zirconia, silicon nitride, or the like. The amount E of exposure of the ball 4 forward in the axial direction is set in the range of 22% to 32% of the diameter A of the ball 4. The amount E of exposure of the ball 4 forward in the axial direction is measured when the ball 4 is pressed backward against the forward bias of the spring and the ball 4 is in contact with each inward protrusion 31b (ball receiving seat). When the diameter A is within the above range (particularly when the diameter A of the ball 4 is 0.3 mm to 0.45 mm), a common spring 6 is used to obtain a plurality of types of ballpoint pen tips 2 by using a plurality of types of balls 4 with different diameters.

[0085] ·Small diameter cylinder part When the diameter A of ball 4 is within the above range (particularly when the diameter A of ball 4 is 0.3 mm to 0.45 mm), the inner diameter B of the right cylindrical inner surface of the small diameter cylindrical portion 31 is set to be larger than the diameter A of ball 4. Specifically, the inner diameter B of the small diameter cylindrical portion 31 is set to be larger than the diameter A of ball 4 by 0.03 mm to 0.06 mm.

[0086] The axial length F of the right cylindrical inner surface behind the inward protrusion of the small diameter cylinder portion 31 is set to be smaller than the diameter A of the ball 4. This allows ink to be abundantly supplied to the rear surface of the ball 4, resulting in smooth ink outflow.

[0087] Tapered cylinder When the diameter A of the ball 4 is within the above range (particularly when the diameter A of the ball 5 is 0.3 mm to 0.45 mm), the angle α of the tapered inner surface of the tapered tube portion 32 (the angle α of the conical inner surface centered on the axis line) is set to 30 degrees to 40 degrees. The axial length G of the tapered inner surface is set to be larger than the diameter A of the ball 4. Specifically, the axial length G of the tapered inner surface is set to 1.1 times to 5.0 times (preferably 2 times to 4.5 times) the diameter A of the ball 4. The tapered tube portion 32 properly connects the small diameter tube portion 31 and the large diameter tube portion 33 to obtain smooth ink flowability.

[0088] Large diameter cylinder When the diameter A of the ball 4 is within the above range (particularly when the diameter A of the ball 4 is 0.3 mm to 0.45 mm), the inner diameter C of the straight cylindrical inner surface of the large diameter cylindrical portion 33 is set to 0.9 mm or more (preferably 1 mm or more), and the outer diameter D of the straight cylindrical inner surface of the large diameter cylindrical portion 33 is set to 1.2 mm or more (preferably 1.3 mm or more). The axial length H of the straight cylindrical inner surface of the large diameter cylindrical portion 333 is set in the range of 4.0 mm to 5.0 mm.

[0089] Furthermore, when the diameter A of the ball 4 is within the above-mentioned range (particularly when the diameter A of the ball 4 is 0.3 mm to 0.45 mm) and multiple types of balls 4 having different diameters are used to obtain multiple types of ballpoint pen tips 1, the inner diameter C of each large diameter cylindrical portion 33 is set to be the same, and the outer diameter D of each large diameter cylindrical portion 33 is set to be the same, thereby making it possible to standardize the shape of the attachment portion of the ballpoint pen tip 2 relative to the holder 6 and simplify the manufacturing process.

[0090] ·summary The ballpoint pen refill 1 of this embodiment has at least the following configuration requirements. The ballpoint pen refill 1 of this embodiment includes a ballpoint pen tip 2 that rotatably holds a ball 4 at its front end, a spring 5 that is accommodated and disposed inside the ballpoint pen tip 2, a holder 6 to which a rear portion 63 of the ballpoint pen tip 2 is fixed, and an ink reservoir 7 to whose front end opening the rear portion 63 of the holder 6 is fixed. The ink reservoir 7 is made of synthetic resin. The ink reservoir 7 has an outer diameter of 2.5 to 4 mm and a wall thickness of 0.3 to 1 mm. The inside of the ink reservoir 7 is filled with ink 71 and an ink backflow prevention body 72 made of a high-viscosity fluid that advances as the ink 71 is consumed. The ballpoint pen tip 2 is provided with a tip body 3 made of a metallic cylinder having a small diameter tube portion 31 in the shape of a straight cylinder, the ball 4 being rotatably supported at the front end thereof, a tapered tube portion 32 which is integrally connected to the rear of the small diameter tube portion 31 and which gradually expands in diameter as it moves rearward, and a large diameter tube portion 33 in the shape of a straight cylinder which is integrally connected to the rear of the tapered tube portion 32. The elastic force of the spring 5 that biases the ball 4 forward is set in the range of 14g to 25g. The diameter A of the ball 4 is set in the range of 0.2 mm to 0.7 mm. The amount of axial movement of the ball 4 of the ball holding portion is set in the range of 0.02 mm to 0.05 mm. The inner diameter B of the straight cylindrical inner surface of the small diameter cylindrical portion 31 rearward of the ball receiving seat 31b is set to be 0.03 mm to 0.06 mm larger than the diameter A of the ball 4, The axial length F of the straight cylindrical inner surface of the small-diameter cylindrical portion 31 rearward of the ball receiving seat 31b is set to be smaller than the diameter A of the ball 4, The inside diameter C of the straight cylindrical inner surface of the large diameter tube portion 33 is set to 0.9 mm or more. EXAMPLES

[0091] Examples will be described below, but the present invention is not limited to these examples. The compositions of the glittering inks for ballpoint pen refills of the Examples and Comparative Examples are shown in the following table. The numerical values ​​for the compositions in the table indicate parts by weight. The average particle size is measured using a laser particle size distribution analyzer LA-300 (volume basis) manufactured by Horiba, Ltd., and the median size is taken as the average particle size. In this case, the particle size of the plate-shaped luster pigment is calculated by setting the minimum value on the particle size axis in the particle size distribution diagram to 0.5 μm.

[0092] [Table 1]

[0093] The contents of the ingredients in the table are explained according to the note numbers. (1) Aluminum powder paste, manufactured by Toyo Aluminum Co., Ltd., product name: Alpaste WXM-0630 (aluminum powder content: 60% by mass, average particle size: 7 μm) (2) Aluminum powder paste, manufactured by Toyo Aluminum Co., Ltd., product name: Alpaste EMERAL EMR-D5660H (aluminum powder content: 60% by mass, average particle size: 9 μm) (3) Pearl pigment, Merck Japan, product name: Iriodin 221 (average particle size: 15 μm) (4) Water dispersion of blue pigment with an average particle size of 0.2 μm (solid content: 20% by mass) (5) Magenta pigment dispersion with an average particle size of 0.2 μm (solid content: 20% by mass) (6) Yellow pigment dispersion with an average particle size of 0.2 μm (solid content: 16% by mass) (7) Hodogaya Chemical Industry Co., Ltd., trade name: Phloxine (8) Olefin-based polymer emulsion [water dispersion, manufactured by Sumitomo Seika Chemicals Co., Ltd., product name: ZAIKXEN L, active ingredient: 25% by mass] (9) Urethane-based polymer emulsion [water dispersion, manufactured by Kusumoto Chemical Industries, Ltd., product name: NeoRez R-2170, active ingredient: 40% by mass] (10) Acrylic acid-based polymer emulsion [water dispersion, manufactured by Kusumoto Chemical Industries, Ltd., product name: NeoCryl A-639, active ingredient: 42% by mass] (11) Acrylic acid polymer emulsion [Kusumoto Chemical Industries, Ltd., product name: NeoCryl A-6016, active ingredient: 45% by mass] (12) Aqueous solution of sodium salt of copolymer of acrylic acid and sulfonic acid monomer [manufactured by Toagosei Co., Ltd., trade name: Aron A-6017 (solid content: 40% by mass)] (13) Polyoxyethylene alkyl ether phosphate [manufactured by Daiichi Kogyo Seiyaku Co., Ltd., trade name: Plysurf M208F] (14) Succinoglycan (15) Dextrin [manufactured by Sanwa Starch Co., Ltd., trade name: Sandec #100]

[0094] Ink Preparation Each component was added to water and stirred at 2000 rpm in a disperser at 20° C. for 1 hour, after which a shear thinning agent was added and stirred for a further 1 hour to prepare each ink.

[0095] Preparation of ink backflow preventer 1.5 parts of fatty acid amide as a thickener was added to 98.5 parts of polybutene as a base oil, and then the mixture was kneaded with a three-roll mill to obtain an ink backflow preventive material.

[0096] Making ballpoint pen refills The ink compositions of the examples and comparative examples were used to prepare ballpoint pen refills according to the embodiment. The ink reservoir was made of polypropylene resin, and the outer diameter of the ink reservoir was 3.07 mm and the wall thickness was 0.69 mm. The ball diameter was 0.4 mm, and the amount of ink contained in the ballpoint pen was 0.15 g. The ink backflow preventive body (liquid plug) was prepared by kneading 98.5 parts of polybutene and 1.5 parts of fatty acid amide with a three-roll mill.

[0097] Making a ballpoint pen The ballpoint pen refill was attached to an exterior (product number: LHKC15C-NC, manufactured by Pilot Corporation) for HI-TEC-C COLETO (product name: manufactured by Pilot Corporation) to prepare a ballpoint pen.

[0098] The following tests were carried out using the ballpoint pens prepared in the above-mentioned preparation of ballpoint pens. -Evaluation of blurred and broken handwriting The ballpoint pens that were confirmed to be writable were used to continuously write 20 spiral circles on JIS P3201 writing paper A using an automatic writing tester to confirm the condition of the writing (10 pens were tested each). The tester was used under the following conditions: writing load 100 g, writing angle 70°, and writing speed 4 m / min. ◯...Can produce good handwriting without smudges or breaks. △: Slight blurring and interruptions are observed. ×: There is noticeable blurring and interruption. Evaluation of the brightness and color of handwriting Ten spiral circles were handwritten in succession on a piece of black paper, and the marks were visually inspected and subjected to a sensory evaluation of brilliance and hue. ◎…Vivid metallic luster and color. ◯: The metallic luster is clear and the hue is visible. △: The metallic luster is clear, but the hue is slightly difficult to see. ×: The metallic luster is clear, but the hue is unclear. Storage evaluation After the ballpoint pens that were confirmed to be writable were left in a thermostatic chamber at 50°C for 30 days, a spiral circle was written by hand and the handwriting was visually confirmed. The writing paper used was the writing paper A, and the writing load, writing angle and writing speed were the same as those in the writing test. 〇…As with the early stages, there are no smudges or breaks in the handwriting. △: Compared to the initial state, the handwriting is more easily smudged and broken, but this does not cause any problems in practical use. ×: Writing is impossible, or the handwriting is noticeably smudged or broken compared to the initial state. The results of each of the above tests are shown in the following table.

[0099] [Table 2]

[0100] (Application example) Making a multi-color ballpoint pen Each ballpoint pen refill containing the ink composition of Examples 5, 6, and 10 was attached to an exterior (product number: LHKC15C-NC, manufactured by Pilot Corporation) for a product named HI-TEC-C COLETO (manufactured by Pilot Corporation) to prepare a composite type retractable ballpoint pen (slide type). The ballpoint pen allows easy attachment / detachment and sliding of each ballpoint pen refill, and allows writing with excellent brilliance and vivid red, blue and yellow hues to be formed over a long period of time without smearing or interruption. [Explanation of symbols]

[0101] The symbols for ballpoint pen refills shown in Figures 1 to 3 1 ballpoint pen refill 2 Ballpoint pen tip (pen tip) 3 Tip body 31 Small diameter cylindrical portion 31a Front end edge portion 31b Inward protruding portion 31c Ink flow hole 32 Tapered cylinder portion 33 Large diameter cylinder portion 4. Ball 5 Spring 51 Rod portion 52 Coil portion 6 Holder 61 Front part 62 Flange part 63 Rear part 64 Step part 7 Ink reservoir tube 71 Ink 72 Ink backflow prevention body (liquid stopper) A diameter of ball 4 B: Inside diameter of the straight cylindrical inner surface of the small diameter cylindrical portion 31 C: Inner diameter of the large diameter cylindrical portion 33 D Outer diameter of the large diameter cylindrical portion 33 E. Axial forward exposure of ball 4 F: Axial length of the straight cylindrical inner surface behind the inward protrusion of the small diameter cylindrical portion 31 G. Axial length of the tapered inner surface of the tapered tubular portion 32 H: the axial length of the inner surface of the straight cylindrical portion 33

Claims

1. An ink composition comprising water, a water-soluble organic solvent, a plate-like effective pigment, a color pigment, at least one water-dispersible polymer selected from the group consisting of an acrylic acid polymer, a urethane polymer, and an olefin polymer, a water-soluble copolymer of acrylic acid and a sulfonic acid monomer, and a thickener, wherein the total mass of the water-dispersible polymer is X and the total mass of the copolymer of acrylic acid and a sulfonic acid monomer is Y, Y / X is 0.1 to 1.0; The content of the water-dispersible polymer is 0.5 to 3 mass% based on the total mass of the ink composition, the sum of the total mass of the plate-like bright pigment and the total mass of the color pigment is A, and the total mass of the water-dispersible polymer is B, B / A is 0.1 to 0.4; The ink composition has a viscosity of 800 to 1600 mPa·s at 3.84 sec-1 at 20°C, and a shear thinning index n of 0.15 to 0.5 at 20°C.

2. A ballpoint pen refill containing the water-based ink composition according to claim 1.

3. A ballpoint pen containing the ballpoint pen refill according to claim 2.

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