JP7451383B2 - ballpoint pen - Google Patents

Description

The present invention relates to a ballpoint pen tip.

Ballpoint pens have traditionally been used as writing instruments.
A ballpoint pen has a ballpoint tip disposed at its tip and a writing ball rotatably held at the tip. When the writing ball at the tip of the ballpoint pen tip rotates on the writing surface, ink on the back side of the writing ball is sent to the front side to draw a line.
In addition to the above-mentioned writing ball, the ballpoint pen tip provided in such a ballpoint pen is provided with a cylindrical holder portion in which an ink guiding hole communicating from the rear end to the tip is formed.
A caulking portion is provided at the tip of the holder portion, which is formed by caulking the periphery of the tip inward. This caulking portion holds the writing ball, which is rotatably provided inside the tip of the holder portion, so that it does not slip out of the holder portion.

Here, the ballpoint pen tip generally has a conical tapered part from the maximum outer diameter part of the holder part to the part near the caulking part at the tip (Patent Document 1).
In a ballpoint pen equipped with such a ballpoint pen tip, the pen tip is in the shadow of the conical taper part, so it may be difficult to see the line drawn by the pen tip.
Therefore, instead of the conical tapered part, we provided a cylindrical pipe (needle) tip that protrudes from the maximum outer diameter part of the holder part toward the tip and has an outer diameter smaller than the maximum outer diameter part. It is known that a writing ball is rotatably held at the tip of this pipe (needle) type tip, thereby making it easier to see the line drawn by the pen tip (Patent Document 2).
In addition, there is also disclosed a holder having a concave curved surface from the maximum outer diameter part of the holder part to the vicinity of the caulking part at the tip (Patent Document 3).

Japanese Patent Application Publication No. 2002-326487 Re-table 2005/080094 publication JP2015-13426A

The present invention makes the tip of the ballpoint pen tip as thin as possible to prevent the drawn line from being in the shadow of the ballpoint pen tip as much as possible. The challenge is to avoid bending.

In view of the above problems, the present invention includes a cylindrical holder portion 11 having a back hole 12 formed therein that communicates from the rear end to the tip;
a writing ball 16 rotatably held inside the tip of the holder portion 11;
a caulking portion 11E in which the periphery of the tip of the holder portion 11 is caulked inward to hold the writing ball 16 inside the tip of the holder portion 11;
A ballpoint pen tip 10 comprising:
The tip end portion of the holder portion 11 is provided with a tip curved surface 11C formed of a multidimensional curved surface whose outer diameter gradually increases toward the rear from the vicinity of the caulking portion 11E and which is convex inward.
When the outer diameter at an arbitrary point of the tip curved surface 11C is a (mm), and the inner diameter of the back hole 12 at the arbitrary point is b (mm),
P=π(a ⁴ - b ⁴ )/(32a)
It is characterized in that the value P defined by is greater than 0.03 (mm ³ ).

Here, the "multidimensional curved surface" that forms the "tip curved surface 11C" is defined as a surface whose outline locus is a multidimensional curve (for example, a quadratic curve, a cubic curve, etc.) (or such a multidimensional curve). A curved surface that can be approximated by Here, the term "multidimensional curved surface" has the meaning that the rate of decrease in the outer diameter of the holder portion 11 decreases toward the tip.

In addition to the above characteristics, in the present invention, when a load of 10 N is applied to the rear end of the caulked portion 11E in a direction perpendicular to the axis, the distance from the caulked portion 11E to the arbitrary point is When the distance along the axis is d (mm),
Q=10d/P
It is desirable that the value Q defined by is less than 900 (N/mm ² ).
In other words, the values of a (mm) and b (mm) at the position of the distance d are set so that the P is 0.03 (mm ³ ), and the Q derived from the P and d is It is desirable to form the tip curved surface 11C so that the pressure is less than 900 (N/mm ² ).
With this configuration, it is possible to prevent bending or buckling from occurring at the arbitrary point due to stress concentration due to pen pressure during writing, within the range of normally assumed pen pressure.

It is preferable that a truncated conical surface 11B whose diameter decreases toward the tip is provided between the rear end edge of the tip curved surface 11C and the tip edge of the maximum outer diameter section 11A of the holder portion 11. With this configuration, when manufacturing the refill 30, the ballpoint pen tip 10 can be held by a nib assembly machine in a conventional production line in the step of attaching the ballpoint pen tip 10 to the refill 30.
Further, from the viewpoint of ensuring the strength and workability of the ballpoint pen tip 10, the holder portion 11 is desirably made of ferritic stainless steel containing lead or bismuth and having a Vickers hardness of 200 to 450.

Furthermore, it is desirable that the ballpoint pen 20 be provided with the ballpoint pen tip 10 described above.

As configured as above, according to the present invention, the tip of the ballpoint pen tip is made as thin as possible to prevent the drawn line portion from being in the shadow of the ballpoint pen tip as much as possible, and even if it is made so thin, It is possible to prevent the refill from bending or buckling before the ink is consumed.

In a ballpoint pen equipped with a ballpoint pen tip according to an embodiment of the present invention, a state (A) with the cap removed is shown in a partially sectional side view, and a state (B) with the cap attached is shown in a partially sectional side view. 1 shows a partially cross-sectional side view of a refill equipped with a ballpoint pen tip according to an embodiment of the present invention. FIG. 1 shows a front view of a ballpoint pen tip according to an embodiment of the present invention. FIG. FIG. 4 is a cross-sectional view of FIG. 3;

Embodiments of the present invention will be described below with reference to the drawings. In the following description, the writing tip side of the ballpoint pen will be referred to as the "tip" or "tip side," and the opposite side will be referred to as the "rear end" or "rear end side."

(1) Ballpoint pen 20
As shown in FIGS. 1 and 2, the ballpoint pen 20 according to this embodiment includes a cap 24 (FIG. 1 (B)) that removably covers the tip for protection, and a refill 30 (FIG. 2) that is housed inside. It is equipped with a shaft cylinder 21 that Furthermore, a ballpoint pen tip 10 is provided at the tip of the refill 30.
The cap 24 is made of polycarbonate resin and has a cylindrical shape. Inside the cap 24, a rubber ball 26 made of silicone rubber is inserted at the tip side. This is to protect the tip of the ballpoint pen tip 10 when the cap 24 is attached. Further, the cap 24 is provided with a clip 25.

The shaft tube 21 is made of polycarbonate resin and has a cylindrical shape. The above-mentioned cap 24 is removably attached to the distal end side of the shaft cylinder 21. On the other hand, a tail plug 27 is fitted into the rear end of the shaft cylinder 21.
A substantially truncated conical base 23 made of stainless steel is screwed onto the tip of the shaft tube 21. The tip of the ballpoint pen tip 10 protrudes from the base 23. The front end surface of the cap 23 is preferably coaxial with a truncated conical surface 11B, which is a tapered surface of the ballpoint pen tip 10, which will be described later. Furthermore, a grip portion 22 made of thermoplastic rubber is provided on the side surface near the tip of the shaft tube 21.

As shown in FIG. 2, the refill 30 housed inside the barrel 21 has a ballpoint pen tip 10 made of polypropylene (PP) or polybutylene terephthalate (PBT) at the tip of a cylindrical ink storage tube 31 made of polypropylene resin. It has a structure in which it is connected via a resin joint 32 such as . Note that a check ball 33 is inserted inside the joint 32 to prevent the ink 34 from flowing backward from the rear end when the front end is turned upward.
Ink 34 is stored inside the ink storage tube 31. Furthermore, a grease-like follower 35 is injected into the rear end of the ink 34 to prevent backflow and evaporation of the ink 34.

(2) Ink 34
The ink 34 will be explained in detail. When the ink 34 is a so-called aqueous ink composition, it contains at least water, a colorant, and a water-soluble solvent, and the fine particles of alumina, titanium oxide, silica, silicon carbide, and tungsten carbide contained in the ink composition are Ultrafine particles with an average particle diameter of less than 0.1 μm are required to suppress wear on the catch and improve dispersion stability in the ink composition, improving writing feel. Therefore, the shape is preferably spherical. The ultrafine particles herein refer to fine particles having a particle diameter of 0.001 to less than 0.1 μm.

Preferred ultrafine particle aluminas include aluminum oxide C (primary particle size: 0.013 μm) manufactured by Nippon Aerosil Co., Ltd., Nanotech Al ₂ O ₃ (primary particle size: 0.033 μm) manufactured by CI Kasei, and Daimei Chemical Industry Co., Ltd. Taimicron TM-100J (primary particle size: 0.014 μm) is mentioned. Examples of ultrafine titanium oxide include titanium oxide P25 (primary particle size: 0.03 μm) manufactured by Nippon Aerosil Co., Ltd. and TTO-55A (primary particle size: 0.05 μm) manufactured by Ishihara Sangyo Co., Ltd.

In Ink 34, the content of ultrafine particles selected from alumina, titanium oxide, silica, silicon carbide, and tungsten carbide having an average particle diameter of less than 0.1 μm based on the ink composition is 0.002 to 2% by weight, or more. Preferably, it is 0.05 to 1% by weight. The ultrafine particles may be used alone within these ranges, or two or more types may be used in combination.

Fine particles with a particle diameter of 0.1 μm or more are difficult to obtain a sufficient effect in suppressing wear of the seat in ballpoint pens with a ball diameter of 0.5 mm or less. In addition, ballpoint pens with a ball diameter of 0.4 mm or less tend to suffer from poor writing due to abrasion of the seat, deterioration of writing feel, deterioration of line quality, and clogging due to sedimentation, making it impossible to write. Particularly in the case of a fine-point ballpoint pen with a ball diameter of 0.28 mm or less, the deterioration of writing performance over time becomes significant due to a further decrease in the ink guide hole diameter, a decrease in the ball protrusion, and an increase in abrasion resistance. Therefore, in a fine-point ballpoint pen, it is essential that the particles be ultrafine particles with an average particle diameter of less than 0.1 μm. Furthermore, if the content exceeds 2% by weight, the writing feel may be poor, the flowability may be reduced, and the abrasion resistance may be poor.

The viscosity of the ink 34 is 50 to 2,000 mPa·s (at 25°C), preferably 100 to 1,000 mPa·s at 1 rpm using a cone-plate rotational viscometer (1° 34′ R24 cone). is desirable. If the viscosity is less than 50 mPa·s (at 25° C.), the ultrafine particles described above will settle over time, and there may be concerns that the particles will fall off, making it impossible to write. Furthermore, if the viscosity exceeds 2,000 mPa·s (25° C.), the flowability may decrease and the writing feel may become poor, which is not preferable.

The water-soluble solvent of the ink 34 is used to improve various qualities of the ink, such as to prevent the ink from freezing at low temperatures and to prevent the ink from drying at the pen tip. Specifically, glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, polyethylene glycol, 1,3-butylene glycol, thiodiethylene glycol, glycerin, ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, etc. They can be used alone or in combination. The amount used is 5 to 50% by weight, preferably 10 to 30% by weight in the ink composition.

For ultrafine particles, in order to improve stability over time, coagulation and sedimentation can be suppressed by adding a dispersant, and nonionic, anionic surfactants, water-soluble resins, etc. are used as the dispersant. Examples of water-soluble resins include synthetic water-soluble polymers such as polyvinyl alcohol, polyacrylic acid, acrylic acid copolymers, maleic acid resins, polyvinylpyrrolidone, polyethylene oxide, water-soluble acrylic resins, water-soluble styrene-acrylic resins, and acrylic Examples include water-dispersible emulsions of resins, alkyd resins, vinyl resins, polyester resins, styrene resins, maleic acid resins, urethane resins, etc., and can be blended after being made into an aqueous dispersion (slurry) using a dispersion machine in advance. preferable.

Colorants for the ink 34 include pigments and/or water-soluble dyes. There are no particular restrictions on the type of pigment, and any inorganic and organic pigments commonly used in conventional aqueous ink compositions can be used.

Examples of inorganic pigments include carbon black and metal powder.
Examples of organic pigments include azo lakes, insoluble azo pigments, chelate azo pigments, phthalocyanine pigments, perylene and perinone pigments, anthraquinone pigments, quinacridone pigments, dye lakes, nitro pigments, and nitroso pigments. Specifically, Phthalocyanine Blue (C.I.74160), Phthalocyanine Green (C.I.74260), Hansa Yellow 3G (C.I.11670), Disazo Yellow GR (C.I.21100), Permanent Red 4R. (C.I. 12335), Brilliant Carmine 6B (C.I. 15850), Quinacridone Red (C.I. 46500), etc. can be used. Furthermore, plastic pigments composed of particles of styrene or acrylic resin can also be used. Further, hollow resin particles with voids inside the particles can be used as a white pigment or as a pseudo pigment dyed with a dye for multicolor applications.

Any of direct dyes, acid dyes, food dyes, and basic dyes can be used as the water-soluble dye.
An example of a direct dye is described below. C. I. Direct black 17, 19, 22, 32, 38, 51, 71, C. I. Direct Hero 4, 26, 44, 50, C. I. Direct Red 1, 4, 23, 31, 37, 39, 75, 80, 81, 83, 225, 226, 227, C. I. Examples include Direct Blue 1, Direct Blue 15, Direct Blue 71, Direct Blue 86, Direct Blue 106, and Direct Blue 119.

An example of an acidic dye is described below. C. I. Acid Black 1, 2, 24, 26, 31, 52, 107, 109, 110, 119, 154, C. I. Acid Yellow 7, 17, 19, 23, 25, 29, 38, 42, 49, 61, 72, 78, 110, 127, 135, 141, 142, C. I. Acid Red 8, 9, 14, 18, 26, 27, 35, 37, 51, 52, 57, 82, 87, 92, 94, 115, 129, 131, 186, 249, 254, 265, 276, C. I. Acid Violet 18, Acid Violet 17, C. I. Acid Blue 1, 7, 9, 22, 23, 25, 40, 41, 43, 62, 78, 83, 90, 93, 103, 112, 113, 158, C. I. Examples include Acid Green 3, Acid Green 9, Acid Green 16, Acid Green 25, and Acid Green 27.

Most food dyes are included in direct dyes or acid dyes, but examples of food dyes that are not included include C.I. I. Food Yellow 3 is an example.
An example of the basic dye is described below. C. I. Basic Yellow 1, 2, 21, C. I. Basic Orange 2, 14, 32, C. I. Basic Red 1, 2, 9, 14, C. I. Examples include Basic Brown 12, Basic Black 2, and Basic Black 8.

These colorants may be used alone or in combination of two or more, and the content in the total ink composition is usually 0.5 to 30% by weight, preferably 1 to 15% by weight. is within the range of If the amount exceeds 30% by weight and is stored for a long period of time, the pigments may aggregate or the dye may precipitate, clogging the pen tip and causing poor writing. If it is less than 0.5% by weight, the coloring becomes weak and the hue of handwriting becomes unclear, which is not preferable.

When a pigment is used as a coloring agent, it is necessary to use a dispersant. This dispersant has the effect of adsorbing onto the surface of the pigment, improving its affinity with water, and stably dispersing the pigment in water, and nonionic, anionic surfactants and water-soluble resins are used. Preferably, water-soluble polymers are used.

It is effective and preferable to add a small amount of a thickener to the aqueous ink composition of the ink 34, especially for the purpose of increasing the viscosity of the ink to suppress sedimentation of ultrafine particles. As the thickener that can be added, it is preferable to use a shear thinning agent that imparts pseudoplasticity in improving ink flowability and suppressing sedimentation of fine particles, and known ones can be used. For example, one or more selected from the group consisting of synthetic polymers, natural rubber, cellulose, and polysaccharides are desirable.

Specifically, for example, gum arabic, succinoglycan, welan gum, gum tragacanth, guar gum, locust bean gum, alginic acid, carrageenan, gelatin, casein santhan gum, dextran, methylcellulose, ethylcellulose, hydroxyethylcellulose, carboxymethylcellulose, sodium starch glycolate. , alginate propylene glycol ester, polyvinyl alcohol, polyvinylpyrrolidone, polyvinyl methyl ether, sodium polyacrylate, carboxyvinyl polymer, polyethylene oxide, copolymer of vinyl acetate and polyvinylpyrrolidone, crosslinked acrylic acid polymer, styrene acrylic acid copolymer Examples include coalescent salts. The content thereof is preferably 0.1 to 0.6% by weight, more preferably 0.1 to 0.4% by weight as a solid content, based on the total amount of the ink composition.

In the ink 34, a pH adjuster, a rust preventive agent, an antiseptic/antibacterial agent, a lubricant, etc. may be added as necessary. Nonionic lubricants such as fatty acid esters of polyhydric alcohols, higher fatty acid esters of sugars, polyoxyalkylene higher fatty acid esters, and alkyl phosphate esters, which are also used as surface treatment agents for pigments, and alkyl sulfonates of higher fatty acid amides are used as lubricants. , anionic surfactants such as alkylaryl sulfonates, polyalkylene glycol derivatives, fluorine-based surfactants, and polyether-modified silicones. Rust inhibitors include benzotriazole, tolyltriazole, dicyclohexyl ammonium nitrite, saponins, etc.; pH adjusters include ammonia, urea, triethanolamine, aminomethylpropanol, sodium hydroxide, and preservatives or antibacterial agents. Examples include phenol, sodium omazine, sodium benzoate, and benzimidazole compounds.

The ink 34 can be produced by a conventionally known method, for example, by blending a predetermined amount of each of the above components and stirring and mixing with a stirrer such as a homomixer or a disper. Further, if necessary, coarse particles in the ink composition may be removed by filtration or centrifugation.

The mechanism by which ultrafine particles selected from alumina, titanium oxide, silica, silicon carbide, and tungsten carbide suppress ball seat wear is not clear, but ultrafine particles less than 0.1 μm cause the ball to rotate during writing. At the same time as the ink flows out, in fine point ballpoint pens, the large pressure during writing causes the ball to become embedded in the seat, resulting in an increase in the surface hardness of the seat, which reduces the wear of the seat as the ball rotates. It is thought that it is being suppressed. This effect is due to the uniform presence of ultrafine particles in the ink interposed between the ball receiving seats during writing, so that the rotation of the ball is not inhibited. Therefore, it is considered that the aqueous ink composition of the present invention stably suppresses wear of the ball seat, does not impair the quality of drawn lines, and provides a good writing feel.

On the other hand, when the ink 34 is a so-called oil-based ink composition, the main solvent (50% by weight or more of the total solvent) is an alcohol, polyhydric alcohol, or glycol ether with a vapor pressure of 0.001 mmHg or more at 25°C. Use a solvent selected from: By using a specific solvent with such a high vapor pressure, it is possible to provide an oil-based ballpoint pen with excellent smooth handwriting feel. Oil-based ink compositions have been developed with the aim of solving problems specific to the use of specific solvents with high vapor pressures. The main solvent is used in an amount of 50% by weight or more of the total solvent, but if necessary, it can be used in an amount of 70% by weight or more, further 80% by weight or more, especially 90% by weight or more.

Specifically, alcohols include aliphatic alcohols having 2 or more carbon atoms, such as ethanol, n-propanol, isopropanol, n-butanol, isobutanol, tert-butyl alcohol, 1-pentanol, isoamyl alcohol, and sec- Amyl alcohol, 3-pentanol, tert-amyl alcohol, n-hexanol, methyl amyl alcohol, 2-ethylbutanol, n-heptanol, 2-heptanol, 3-heptanol, n-octanol, 2-octanol, 2-ethylhexanol , 3,5,5-trimethylhexanol, nonanol, n-decanol, undecanol, n-decanol, trimethylnonyl alcohol, tetradecanol, heptadecanol, cyclohexanol, 2-methylcyclohexanol, benzyl alcohol and many other high grade alcohols. Examples include alcohol.

In addition, polyhydric alcohols include ethylene glycol, diethylene glycol, 3-methyl-1,3-butanediol, triethylene glycol, dipropylene glycol, 1,3-propanediol, 1,3-butanediol, and 1,5-pentanediol. Examples include polyhydric alcohols having two or more carbon atoms and two or more hydroxyl groups in the molecule, such as diol, hexylene glycol, and octylene glycol.

Examples of glycol ethers include methyl isopropyl ether, ethyl ether, ethylpropyl ether, ethyl butyl ether, isopropyl ether, butyl ether, hexyl ether, 2-ethylhexyl ether, ethylene glycol monohexyl ether, ethylene glycol monophenyl ether, and ethylene glycol mono-2- Ethyl butyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monobutyl ether, 3-methyl-3- Methoxy-1-butanol, 3-methoxy-1-butanol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, propylene glycol phenyl ether, propylene glycol tertiary butyl ether dipropylene glycol monomethyl Examples include ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monobutyl ether, and tetrapropylene glycol monobutyl ether.

Among the above-mentioned solvents, glycol ethers having 2 to 7 carbon atoms are particularly preferred because their effects are easy to understand. Furthermore, from the viewpoint of safety and oral toxicity, it is preferable to use organic solvents other than ethylene glycol derivatives.
In addition to the solvents listed above, it is also possible to add the following solvents to the extent that they do not interfere with the solubility or performance of the mixture of phosphoric acid ester and amine compound.
Examples of these include polyhydric alcohol derivatives, and also derivatives such as sorbitan fatty acid, polyglycerin higher fatty acid, sucrose fatty acid, and propylene glycol fatty acid.

Examples of solvents for esters include propylene glycol methyl ether acetate, propylene glycol diacetate, 3-methyl-3-methoxybutyl acetate, propylene glycol ethyl ether acetate, ethylene glycol ethyl ether acetate, butyl formate, isobutyl formate, isoamyl formate, Propyl acetate, butyl acetate, isopropyl acetate, isobutyl acetate, isoamyl acetate, methyl propionate, ethyl propionate, propyl propionate, isobutyl propionate, isoamyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, methyl isobutyrate, isobutyric acid Ethyl, propyl isobutyrate, methyl valerate, ethyl valerate, propyl valerate, methyl isovalerate, ethyl isovalerate, propyl isovalerate, methyl trimethyl acetate, ethyl trimethyl acetate, propyl trimethyl acetate, methyl caproate, capron Ethyl acid, propyl caproate, methyl caprylate, ethyl caprylate, propyl caprylate, methyl laurate, ethyl laurate, methyl oleate, ethyl oleate, triglyceride caprylate, tributyl acetate citrate, octyl oxystearate, propylene Various esters include glycol monoricinolate, methyl 2-hydroxyisobutyrate, and 3-methoxybutyl acetate.

Further, specific examples of solvent diethers and diesters that do not have a hydroxyl group in the molecule include ethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, diethylene glycol dimethyl ether, and dipropylene glycol dimethyl ether.

The coloring agent (coloring material) is not limited, but it is preferably used in the form of a pigment or a combination of a pigment and a dye. The use of pigments has the effect of improving fastness. Pigments include carbon black, phthalocyanine type, insoluble azo type such as monoazo, disazo, condensed azo, chelate azo, azo type including soluble azo such as hardly soluble azo, soluble azo, quinacridone type, diketopyrrolopyrrole type, srene type, etc. Organic pigments such as dioxazine and isoindolinone can be used.

In particular, carbon black should have a specific surface area as small as possible, preferably 100 m ² /g or less as measured by the BET method. Specifically, Mitsubishi Kasei carbon blacks include #33, #32, #30, #25, CF9, etc., and Cabot carbon blacks include REGAL (400R, 500R, 330R, 300R) and ELFTEX (8, 12). ), STERLING R, etc.; Printex (45, 40, 300, 30, 3, 35, 25, 200, A, G), SB (250, 200), etc. manufactured by Degussa; RAVEN (1040, 1035, 1020, 1000, 890, 890H, 850, 500, 450, 420, 410, H20, 22, 16, 14), etc.

Furthermore, the pigment is preferably one that is difficult to dissolve in the organic solvent used and has an average particle diameter of 30 nm to 700 nm after being dispersed. The pigment may be added in an amount of 0.5 to 25% by weight, preferably 0.5 to 20% by weight, based on the total amount of the ink composition, as required.

The pigments that can be used can be used alone or in combination of two or more. Further, if necessary, a dispersion using an inorganic pigment, a dye, etc. can be added to an extent that does not adversely affect dispersion stability. The use of dyes has the effect of providing excellent color development. Furthermore, resin emulsions obtained by polymerizing styrene, acrylic acid, acrylic esters, methacrylic acid, methacrylic esters, acrylonitrile, and olefin monomers, hollow resin emulsions that swell and become amorphous in ink, Alternatively, examples include organic multicolor pigments made of dyed resin particles obtained by dyeing these emulsions themselves with colorants.

When the coloring material used in the present invention is a pigment, various conventionally known methods can be employed to produce a pigment-dispersed ink composition. For example, by blending each of the above components and stirring with a stirrer such as a dissolver, or after mixing and pulverizing with a ball mill, roll mill, bead mill, sand mill, pin mill, etc., coarse pigment particles and It can be easily obtained by removing undissolved matter and mixed solid matter.

The dye used in combination with these pigments can be used without any particular restriction as long as it does not destroy the dispersion system. These dyes include direct dyes, acid dyes, basic dyes, mordants/acid mordant dyes, alcohol soluble dyes, azoic dyes, sulfurized/sulfurized vat dyes, vat dyes, and dispersed dyes used in ordinary dye ink compositions. Any dye, oil-soluble dye, food dye, metal complex dye, etc., and inorganic and organic pigments used in ordinary pigment ink compositions can be used. The blending amount is selected within the range of 1 to 50% by weight based on the total amount of the composition.

A resin is used in the case of an oil-based ink composition. The resin used in the oil-based ink composition is added for the purpose of adjusting viscosity and improving wear on the pen tip, but if it contains a pigment, it is also used as a dispersant. Such resins include ketone resins, styrene resins, styrene-acrylic resins, terpene phenolic resins, rosin-modified maleic acid resins, rosin phenolic resins, alkylphenolic resins, phenolic resins, styrene maleic resins, rosin-based resins, and acrylic resins. There are resins represented by resin, urea aldehyde resin, maleic acid resin, cyclohexanone resin, polyvinyl butyral, polyvinylpyrrolidone, and the like.

The blending amount of these resins is preferably 1 to 30% by weight, more preferably 1 to 20% by weight. If the blending amount is less than 1% by weight, it becomes difficult to adjust the viscosity or wear the pen tip, and if it exceeds 30% by weight, it may become impossible to blend raw materials other than the resin, and the writing quality may be adversely affected.

In a preferred embodiment, when a pigment is used as a coloring material in an ink composition, the dispersant used can be selected from among the resins listed above that can disperse the pigment, and activators and Any type of oligomer can be used as long as it meets the purpose. Specific dispersants include polyvinyl alcohol, polyvinylpyrrolidone, polyvinyl butyral, polyvinyl ether, styrene-maleic acid copolymer, ketone resin, hydroxyethyl cellulose and its derivatives, synthetic resins such as styrene-acrylic acid copolymer, and PO. - Examples include EO adducts and amine-based oligomers of polyester.

When the ink 34 is an oil-based ink composition, it contains a neutralized phosphate ester. The neutralized phosphate ester has the effect of making it easier to remove ink adhered substances on the ball surface, thereby suppressing writing blurring at the beginning of writing, and in the present invention, it works in cooperation with polypropylene glycol to make it easier to remove ink adhered substances on the ball surface. This has the effect of suppressing writing blurring at the beginning of time writing and also lubricates ink transfer properties when writing at low speed.

The phosphoric acid esters used usually consist of phosphoric acid monoesters, diesters, and trace amounts of triesters, and are mainly surfactants having two types of ester structures: aromatic and aliphatic. Regarding the alkyl group capable of forming a phosphate ester structure, alkyl groups obtained from natural and synthetic higher alcohols are introduced. A phosphoric ester having an alkyl group having 10 to 20 carbon atoms and a polyoxyethylene chain of 0 to 50 is used. Particularly suitable are phosphoric acid esters having an alkyl group having 15 to 20 carbon atoms and 0 to 4 polyoxyethylene chains. Further, as the amine-based substance for neutralization, it is desirable to use an amine-based compound such as an alkanolamine, a polyoxyethylene alkylamine, an amphoteric surfactant, or a fatty amine-based substance.

Regarding the amount of these additives, it is preferable to add them in an amount of 0.01% to 15% by weight, more preferably 0.1% to 10% by weight, based on the total amount of the ink composition in the mixture obtained by neutralization. . Further, the content is particularly preferably 0.1 to 8% by weight. If these are less than 0.01% by weight, they will be less effective in making it easier to remove ink adhered substances from the ball surface, and if they exceed 15% by weight, the drawn lines will be too repelled from the ball, causing cracks in the drawn lines, etc. This may make it easier to cause problems.

When the ink 34 is an oil-based ink composition, it is desirable to add polypropylene glycol. The addition has the effect of making it difficult to cause blurring at the beginning of writing. This phenomenon not only suppresses fading obtained by repelling ink on metal balls, but also makes it difficult to form an ink film, thereby making it possible to suppress fading in a short period of 1 to 20 minutes.

The molecular weight of polypropylene glycol is preferably as large as possible because the amount added can be reduced and line drawing drying properties can be improved. The molecular weight (calculated molecular weight) is preferably 1,000 or more, more preferably 2,000 or more, and even more preferably 4,000 or more.

The amount of polypropylene glycol added is preferably 0.01% to 10% by weight, particularly preferably 0.1 to 10% by weight. Within this range, ink that uses pigments and dries easily will be less likely to form an ink film on the metal ball, so it will have a great effect in preventing blurring at the beginning of writing.

If the addition amount is less than 0.1% by weight, the effect will be poor and the ball may stop rotating, and if it exceeds 10% by weight, depending on the raw materials used, the non-volatile components in the ink will be reduced. If the number increases, the drying properties of drawn lines may be reduced and strike-through may occur more easily.

Furthermore, in the present invention, a rust preventive agent, a fungicide, a surfactant, a lubricant, a wetting agent, etc., which are compatible with the ink and do not have an adverse effect on the ink, may be added as necessary. In particular, fatty acids and the like can be suitably used as lubricants. In addition, non-volatile solvents that are compatible with the main solvent may also be blended as additives for suppressing drying to the extent that they do not adversely affect the product properties.

(3) Ballpoint pen tip 10
As shown in FIGS. 3 and 4, the ballpoint pen tip 10 has a cylindrical holder portion 11 in which a back hole 12 communicating from the rear end to the vicinity of the tip is formed, and a rotatable portion inside the tip of the holder portion 11. The writing ball 16 is provided with a writing ball 16 made of super steel alloy, and a caulking part 11E that holds the writing ball 16 so that it does not fall off the holder part 11. The holder portion 11 is formed by cutting a cylindrical material made of ferritic stainless steel containing lead or bismuth, which has a Vickers hardness of 270 and has good workability.

A truncated conical surface 11B, which is a short tapered surface, is formed on the tip side of the cylindrical maximum outer diameter portion 11A, which has the largest outer diameter in the holder portion 11, and an inwardly convex tip on the tip side. A curved surface 11C is formed. In other words, a truncated conical surface 11B whose diameter decreases toward the tip is provided between the rear edge of the curved tip surface 11C and the tip edge of the maximum outer diameter portion 11A. This tip curved surface 11C is formed as a multidimensional curved surface whose contour line is approximated by a multidimensional curve (quadratic curve in this embodiment). Therefore, the outer diameter of the tip curved surface 11C gradually decreases toward the tip, but the rate of decrease becomes smaller toward the tip. Therefore, the tip curved surface 11C exhibits a steep slope near the maximum outer diameter portion 11A, but gradually becomes gentler as it approaches the tip.

A tapered tip portion 11D is formed on the tip side of the tip curved surface 11C, and furthermore, the tip is a caulked portion 11E that is caulked inward to hold the writing ball 16.
On the other hand, the rear end portion of the holder portion 11 is a substantially cylindrical fixing portion 11F cut so that the outer diameter is smaller than the maximum outer diameter portion 11A, and this portion is attached to the tip of the joint 32. It is press-fitted and fixed (see Figure 2).

As shown in FIG. 4, the internal space of the holder part 11 has a back hole 12 formed by cutting from the rear end to the vicinity of the front end. On the other hand, a ball house 13 for accommodating a writing ball 16 is formed by cutting in the internal space of the tapered tip portion 11D. Further, an ink guide hole 14 passing through the back hole 12 and the ball house 13 is also formed. Further, around the ink guide hole 14, a plurality of channel grooves 15 communicating between the ball house 13 and the back hole 12 are equally distributed. Furthermore, by forming an inner tapered portion 17 inclined at 15° to 45° with respect to the axis between the ink guide hole 14 and the back hole 12, bending around the ink guide hole 14 during writing can be suppressed. can. When the angle is less than 15°, it is difficult to form the channel groove 15, and when the angle is 45° or more, bending stress is strongly applied in the radial direction, so that no effect is produced.

In the tip curved surface 11C of the ballpoint pen tip 10 according to this embodiment, the outer diameter a (mm) and the inner diameter b (mm) of the back hole 12 at a position at an arbitrary distance d (mm) along the axis from the caulked part 11E The value P defined as below is
P=π(a ⁴ - b ⁴ )/(32a)>0.03(mm ³ )
The tip curved surface 11C and the back hole 12 are cut so that the relationship holds true.

Further, when a load of 10 N is applied to the caulking portion 11E in a direction perpendicular to the axis, the value Q defined as below from the d value and the P value is:
Q=10d/P<900 (N/mm ² )
A relationship is established. In other words, extremely large stress does not concentrate at any point on the tip curved surface 11C, so it is less likely to bend or bend during writing compared to a straight pipe (needle) tip with approximately the same tip outer diameter. Buckling is less likely to occur. On the other hand, since the width of the ballpoint pen tip 10 near the writing tip is similar to such a pipe (needle) type tip, the drawn line is not shaded by the ballpoint pen tip 10 and is easy to see.

(1) Example 1
The ballpoint pen tip in the ballpoint pen according to Example 1 had a shape based on the embodiment described above. The outside diameter of the writing ball was 0.38 mm.
The ink had the following composition.
Carbon black #25 (manufactured by Mitsubishi Kasei): 10% by weight
Polyvinyl butyral (BL-S, Sekisui Chemical): 5% by weight
Terpene phenol resin (YP90L, manufactured by Yasuhara Chemical): 8% by weight
Polypropylene glycol (average molecular weight: 4000): 5% by weight
Phosphoric acid ester (Plysurf A208B): 1.47% by weight
Amine compound (polyoxyethylene alkylamine: AMIET105): 1.03% by weight
3-methoxybutanol: 5% by weight
3-methoxy-3-methyl-1-butanol: 64.5% by weight

(2) Example 2
The ballpoint pen tip in the ballpoint pen according to Example 2 had a shape based on the embodiment described above. The outside diameter of the writing ball was 0.28 mm.
The ink had the following composition.
Colorant (pigment: carbon black): 5% by weight
Shear thinning agent (crosslinked polyacrylic acid): 0.2% by weight
Water-soluble organic solvent (glycerin): 20% by weight
Lubricant (phosphate ester alkyl ether): 0.8% by weight
Rust inhibitor (benzotriazole): 0.3% by weight
Preservative (1,2-benzisothiazolin-3-one): 0.1% by weight
pH adjuster (triethanolamine): 2% by weight
Alumina (primary particle size 0.033 μm): 0.05% by weight
Water-soluble resin (styrene acrylic acid copolymer salt): 0.5% by weight
Purified water: remainder

(3) Comparative example 1
As the ballpoint pen tip of the ballpoint pen according to Comparative Example 1, a pipe (needle) type tip of UM-201, a product of the applicant, having a writing ball diameter of 0.38 mm was used. This ballpoint pen tip had an outer diameter a of 0.60 mm and an inner diameter b of the back hole of 0.42 mm. The length of the portion where the outer diameter a was 0.60 mm was 2.75 mm.
The ink had the following composition.
Carbon black #25 (manufactured by Mitsubishi Kasei): 10% by weight
Polyvinyl butyral (BL-S, Sekisui Chemical): 5% by weight
Terpene phenol resin (YP90L, manufactured by Yasuhara Chemical): 8% by weight
Phosphoric acid ester (Plysurf A208B): 1.47% by weight
Amine compound (polyoxyethylene alkylamine: AMIET105): 1.03% by weight
3-methoxybutanol: 5% by weight
3-methoxy-3-methyl-1-butanol: 69.5% by weight

(4) Comparative Examples 2 and 3
The ballpoint pen tips of the ballpoint pens according to Comparative Examples 2 and 3 had a curved tip similar to that of the embodiment described above. The outer diameter of the writing ball was the same as in Example 1, 0.38 mm. However, in Comparative Example 2, the inner diameter b of the back hole was formed slightly larger than in Example 1 (see Table 1 below). Furthermore, in Comparative Example 3, the outer diameter a of the curved tip surface was slightly smaller than that in Example 1 (see Table 1 below). Note that the ink had the same composition as Comparative Example 1.

(5) Comparative example 4
As the ballpoint pen tip in the writing instrument according to Comparative Example 4, a pipe (needle) type tip of UM-201, a product of the applicant, with a writing ball diameter of 0.28 mm was used. This ballpoint pen tip had an outer diameter a of 0.60 mm and an inner diameter b of the back hole of 0.32 mm. The length of this portion where the outer diameter a was 0.60 mm was 2.81 mm.
The ink had the following composition.
Colorant (pigment: carbon black): 5% by weight
Shear thinning agent (crosslinked polyacrylic acid): 0.22% by weight
Water-soluble organic solvent (glycerin): 20% by weight
Lubricant (phosphate ester alkyl ether): 0.8% by weight
Rust inhibitor (benzotriazole): 0.3% by weight
Preservative (1,2-benzisothiazolin-3-one) 0.1% by weight
pH adjuster (triethanolamine): 2% by weight
Water-soluble resin (styrene acrylic acid copolymer salt) 0.3% by weight
Purified water: remainder

(6) Comparative Examples 5 and 6
The ballpoint pen tips of the ballpoint pens according to Comparative Examples 5 and 6 had a tip curved surface similar to that of the embodiment described above. The outer diameter of the writing ball was the same as in Example 2, 0.28 mm. However, in Comparative Example 5, the inner diameter b of the back hole was formed slightly larger than in Example 2 (see Table 1 below). Furthermore, in Comparative Example 6, the outer diameter a of the curved tip surface was slightly smaller than that in Example 2 (see Table 1 below). Note that the ink had the same composition as Comparative Example 4.

(7) P value and Q value In the above examples and comparative examples, the outer diameter a and the inner diameter b at the distance d from the rear end of the caulked part were measured. In Example 1 and Comparative Examples 2 and 3, which have a writing ball diameter of 0.38 mm and a curved tip, this distance d is 0.64 mm (position A), 1.49 mm (position B), .59 mm (position C) and 3.79 mm (position D). In addition, in Example 2 and Comparative Examples 5 and 6, which have a writing ball diameter of 0.28 mm and a curved tip, the diameter of the writing ball is 0.59 mm (position A), 1.53 mm (position B), and 2.63 mm (in order from the tip side). position C) and 3.83 mm (position D). Further, in Comparative Example 1 (writing ball diameter 0.38 mm), which is a pipe (needle) type tip, it was 2.75 mm, and in Comparative Example 4 (writing ball diameter 0.28 mm), it was 2.81 mm. The P value and Q value calculated from them are as shown in Table 1 below.

(7-1) Example From the above, in Example 1 where the writing ball diameter was 0.38 mm, the Q value at position B was the highest at 327.6 N/mm ² among the four calculated points. However, this value was less than 900 N/mm ² . The Q value further decreases at a position closer to the rear end than that. Therefore, there seems to be very little risk of bending or buckling when writing within the normal writing pressure range.
This is almost the same in Example 2, where the writing ball diameter is smaller at 0.28 mm, and the Q value at position B was the highest at 337.7 N/ ^mm2 , but this value was less than 900 N/ ^mm2. It was something. The Q value further decreases at a position closer to the rear end than that.

(7-2) Comparative example (pipe (needle) type tip)
On the other hand, in Comparative Example 1, which has the same writing ball diameter as Example 1 but has a pipe (needle) type tip, the Q value at the position where the distance d is 2.75 mm is 1,706.6 N/mm ² and 900 N. / ^mm2 . Incidentally, the Q value at almost the same position C (distance d was 2.59 mm) in Example 1 was 253.4 N/mm ² .
Similarly, the diameter of the writing ball is the same as in Example 2, but in Comparative Example 4 with a pipe (needle) type tip, the Q value at the position where the distance d is 2.81 mm is 1,441.8 N/mm ² and 900 N. / ^mm2 . Incidentally, the Q value at almost the same position C (distance d is 2.63 mm) in Example 2 was 221.8 N/mm ² .
From the above, the ballpoint pen tip with a curved tip as in the example has a significantly lower possibility of bending or buckling when writing, compared to a conventional pipe (needle) tip with a similar tip outer diameter. It is something.

(7-3) Comparative example (outer diameter a and inner diameter b of the curved tip surface)
In Comparative Example 2, which had a writing ball diameter of 0.38 mm and a curved tip as in Example 1, the P value at position A was 0.0284 mm ³ , which was less than 0.03 mm ³ . This is because the inner diameter b at this position A was 0.65 mm, which was larger than the inner diameter b (0.55 mm) at the same position A in Example 1. Along with this, the Q value also becomes larger than that at the same position A in Example 1, so it is thought that stress concentration occurs more easily than in Example 1.
In addition, in Comparative Example 3, which has a writing ball diameter of 0.38 mm and a curved tip as in Example 1, the Q value at position D was 1,008.6 N/mm ² , which greatly exceeds 900 N/mm ² . Ta. This is because the outer diameter a at this position D was 1.22 mm, which was smaller than the outer diameter a (1.86 mm) at the same position D in Example 1. This value greatly exceeds the value (70.2 N/mm ² ).
Therefore, in Example 1, as compared to Comparative Example 3, the possibility of bending or buckling during writing at a position away from the load, such as position D, is significantly reduced.

In Comparative Example 5, which had a writing ball diameter of 0.28 mm and a curved tip surface as in Example 2, the P value at position B was 0.0277 mm ³ , which was less than 0.03 mm ³ . This is because the inner diameter b at this position B was 0.70 mm, which was larger than the inner diameter b (0.55 mm) at the same position B in Example 2. Along with this, the Q value also becomes larger than that at the same position B in Example 2, so it is thought that stress concentration occurs more easily than in Example 2.
Furthermore, in Comparative Example 6, which had a writing ball diameter of 0.28 mm and a curved tip like Example 2, the Q value at position D was 938.6 N/mm ² , which exceeded 900 N/mm ² . This is because the outer diameter a at this position was 1.27 mm, which was smaller than the outer diameter a (1.93 mm) at the same position D in Example 2, and this resulted in the Q value at the same position D in Example 2. (62.1 N/mm ² ).
Therefore, in comparison with Comparative Example 6, in Example 2, the possibility of bending or buckling during writing at a position away from the load, such as position D, is significantly reduced.

INDUSTRIAL APPLICATION This invention can be utilized for a ballpoint pen. Further, the present invention is not limited to a ballpoint pen in which the writing tip is protected by a removable cap as shown in the above embodiment, but can also be used in a retractable ballpoint pen in which the writing tip comes out and goes in and out by a knocking operation or a rotating operation of the barrel.

10 Ballpoint pen tip 11 Holder section 11A Maximum outer diameter section
11B truncated conical surface 11C tip curved surface 11D tip tapered section
11E Caulking part 11F Fixed part 12 Back hole
13 Ball house 14 Ink guide hole 15 Channel groove
16 Writing ball 17 Inner tapered part
20 Ballpoint pen 21 Barrel 22 Grip
23 Base 24 Cap 25 Clip
26 Rubber ball 27 Tail plug
30 Refill 31 Ink storage tube 32 Fitting
33 Check ball 34 Ink 35 Follower

Claims (2)

A cylindrical holder part with a back hole that communicates from the rear end to the tip,
a writing ball rotatably held within the tip of the holder;
a caulking portion in which the periphery of the tip of the holder portion is caulked inward to hold the writing ball inside the tip of the holder portion;
A ballpoint pen tip comprising:
The tip portion of the holder portion is provided with a tip curved surface formed of a multidimensional curved surface whose outer diameter gradually increases from the vicinity of the caulking portion toward the rear and which is convex inward;
When the outer diameter at an arbitrary point of the tip curved surface is a (mm), and the inner diameter of the back hole at the arbitrary point is b (mm),
P=π(a ⁴ - b ⁴ )/(32a)
When the value P defined by is greater than 0.03 (mm ³ ) , and when a load of 10 N is applied to the rear end of the caulked portion in a direction perpendicular to the axis, the arbitrary When the distance along the axis to the point is d (mm),
Q=10d/P
The value ^Q defined by A ballpoint pen tip is provided with a truncated conical surface having a diameter and is made of bismuth-containing ferritic stainless steel with a Vickers hardness of 200 or more and 450 or less,
One or more ultrafine particles selected from the group consisting of alumina, titanium oxide, silica, silicon carbide, and tungsten carbide, containing at least water, a coloring agent, and a water-soluble solvent, and having an average particle size of 0.001 μm to less than 0.1 μm. An aqueous ink composition containing 0.002 to 2 wt% of A distinctive ballpoint pen. A cylindrical holder part with a back hole that communicates from the rear end to the tip,
a writing ball rotatably held within the tip of the holder;
a caulking portion in which the periphery of the tip of the holder portion is caulked inward to hold the writing ball inside the tip of the holder portion;
A ballpoint pen tip comprising:
The tip portion of the holder portion is provided with a tip curved surface formed of a multidimensional curved surface whose outer diameter gradually increases toward the rear from the vicinity of the caulking portion and which is convex inward;
When the outer diameter at an arbitrary point of the tip curved surface is a (mm), and the inner diameter of the back hole at the arbitrary point is b (mm),
P=π(a ⁴ - b ⁴ )/(32a)
When the value P defined by is greater than 0.03 (mm ³ ) , and when a load of 10 N is applied to the rear end of the caulked portion in a direction perpendicular to the axis, the arbitrary When the distance along the axis to the point is d (mm),
Q=10d/P
The value ^Q defined by A ballpoint pen tip is provided with a truncated conical surface and is made of bismuth-containing ferritic stainless steel with a Vickers hardness of 200 or more and 450 or less,
A ballpoint pen comprising an oil-based ink composition containing at least a colorant and a resin, and a solvent selected from alcohols, polyhydric alcohols, and glycol ethers having a vapor pressure of 0.001 mmHg or more at 25°C.