JP7523941B2 - Oil-based ballpoint pen - Google Patents

Description

The present invention relates to an oil-based ballpoint pen.

Conventionally, in order to prevent ink leakage from the gap between the ball and the tip end (writing end) in ink compositions for oil-based ballpoint pens, technologies have been proposed that use a solvent with a vapor pressure of 0.001 mmHg or more at 25°C, use a terpene phenol resin as an ink leakage inhibitor, or set the ink viscosity high using a gelling agent.

As such ink compositions for oil-based ballpoint pens, techniques using alcohol, polyhydric alcohol, and glycol ether solvents with a vapor pressure of 0.001 mmHg or more at 25°C are disclosed in JP 2004-107591 A, "Oil-based ink composition for writing implements"; techniques using ink leakage inhibitors are disclosed in JP 10-195365 A, "Oil-based ink for ballpoint pens" using silica with a primary average particle size of 7 to 40 nm; techniques using terpene phenol resins with an OH value of 150 or more are disclosed in JP 2007-126528 A, "Oil-based ink for ballpoint pens"; and techniques using hydrogenated castor oil and fatty acid amide wax as shear thinning agents are disclosed in JP 7-196972 A, "Oil-based ink composition for ballpoint pens".

"JP 2004-107591 A" "JP 2007-126528 A" "Unexamined Japanese Patent Publication No. 7-196972"

However, although Patent Document 1 has an effect of suppressing ink leakage to a certain degree, when the ink viscosity is reduced, the solvent used in Patent Document 1 alone cannot sufficiently suppress ink leakage. In Patent Document 2, the terpene phenol resin with an OH value of 150 or more has a high OH value, so that the solubility in oil-based ink is poor, and each of them cannot exhibit a sufficient effect. In Patent Document 3, hydrogenated castor oil and fatty acid amide wax can suppress ink leakage to a certain degree, but the ink viscosity at rest is high, ink tracking is easily deteriorated, and smearing may occur in handwriting, leaving room for improvement.
Furthermore, when a new ink leakage inhibitor is used, the agent may be incompatible with other ink components, which can easily affect stability over time in the ink.

When more ink is consumed to produce thicker strokes, or when the viscosity of oil-based ink is reduced to produce a smooth writing feel, more ink is consumed, which can easily lead to ink leakage from the gap between the ball and the tip end (writing tip), which can be problematic.

The object of the present invention is to provide an oil-based ballpoint pen that suppresses ink leakage while maintaining a thick handwriting.

In order to solve the above problems, the present invention
"1. An oil-based ballpoint pen having a ballpoint pen tip at the tip of an ink reservoir and containing an ink composition for an oil-based ballpoint pen in the ink reservoir, characterized in that the ink consumption per 100 m of the oil-based ballpoint pen is 20 to 70 mg, and the ink composition for an oil-based ballpoint pen contains a colorant, an organic solvent, and amino resin particles.
2. The oil-based ballpoint pen according to item 1, wherein the content of the amino resin particles is 0.1 to 5% by mass based on the total amount of the ink composition.
3. The oil-based ballpoint pen according to claim 1 or 2, wherein the amino resin particles have an average particle size of 5 μm or less.
4. The oil-based ballpoint pen according to any one of items 1 to 3, wherein the amino resin particles are methacrylic acid ester resin particles.
5. The oil-based ballpoint pen according to any one of items 1 to 4, wherein the amount of movement of the ball in the ballpoint pen tip in the longitudinal direction is 3 to 20 μm.
6. The oil-based ballpoint pen according to any one of items 1 to 5, wherein the organic solvent is an alcohol solvent, and the content of the alcohol solvent is 50% or more of the total organic solvent content in the oil-based ballpoint pen composition.
7. The oil-based ballpoint pen according to any one of items 1 to 6, characterized in that the ink composition for the oil-based ballpoint pen contains a polyvinyl butyral resin or a ketone resin.

It is possible to create an oil-based ballpoint pen that consumes more ink and maintains thick writing while suppressing ink leakage from the gap between the ball and the tip.

The present invention is characterized in that even when the ink consumption of an oil-based ballpoint pen is increased to 20 to 70 mg per 100 m in order to produce a thicker handwriting, ink leakage can be suppressed by including amino resin particles in the ink composition for the oil-based ballpoint pen.

(Amino resin particles)
In the present invention, it has been found that ink leakage can be suppressed by including amino resin particles in the ink composition for oil-based ballpoint pens. This is because the amino resin particles cause physical obstacles in the gap between the ball and the inner wall of the tip end, making it possible to suppress ink leakage, and further, the amino resin particles are partially deformed and adhere to each other to form a structure formed by weak aggregation, which forms a structure in the ink that has high resistance to ink leakage when left stationary, making it possible to highly suppress ink leakage. On the other hand, since the structure is formed by weak aggregation, the aggregated structure is broken down by physical actions such as the rotation of the ball during writing, so that it is possible to write well and obtain thick handwriting without impeding the ink fluidity during writing. In addition, since the amino resin particles are stable against solvents, they can be used preferably because they can maintain the ink stability over time and also impart high solvent resistance and water resistance to handwriting.

The average particle diameter of the amino resin particles is preferably 5 μm or less, more preferably 3 μm or less, because the smaller the average particle diameter, the easier it is for the particles to adhere to each other and form a weak aggregate structure, which makes it easier to suppress ink leakage. Furthermore, considering the dispersion stability of the amino resin particles in the ink (ink stability over time), 2 μm or less is preferable, and more preferably less than 1 μm. On the other hand, if the average particle diameter is too small, the ink leakage suppression effect is likely to be inferior, so the average particle diameter is preferably 0.1 μm or more, more preferably 0.3 μm or more. In addition, the average particle diameter can be determined by measuring the particle diameter (D50) at 50% cumulative volume of the particle size distribution measured based on values calibrated using standard samples and other measurement methods using a Coulter Multisizer™3 (a measuring device manufactured by Beckman Coulter, Inc.) by the Coulter counter method.

The amino resin particles used in the present invention are a general term for resins obtained by the condensation reaction of a compound containing an amino group with an aldehyde, and include melamine resin particles, benzoguanamine resin particles, urea resin, and aniline aldehyde resin. Among these, in consideration of the ease of improving ink leakage suppression, it is preferable to use melamine resin particles and benzoguanamine resin particles. Furthermore, in consideration of the stability to the solvent in the ink and the suppression of ink leakage, it is preferable to use melamine-formaldehyde resin particles, benzoguanamine-formaldehyde resin particles, and benzoguanamine-melamine-formaldehyde resin particles, and from further consideration, it is most preferable to use melamine-formaldehyde resin particles.

Considering that it is easier to improve ink leakage suppression, it is preferable to use amino resin particles having a heterocyclic structure as the amino resin particles. This is presumably because the heterocyclic structure forms a stable particle structure, which is easier to stabilize in the ink and makes it easier to improve ink leakage suppression.

The amino resin particles may be spherical or irregularly shaped, but spherical resin particles are preferred in view of the ink leakage suppression effect due to the adhesion between the amino resin particles. The spherical resin particles mentioned here are not limited to true spheres, but may be approximately spherical resin particles or approximately elliptical resin particles.

The content of the amino resin particles is more preferably 0.01 to 10% by mass relative to the total amount of the ink composition. This is because if the content of the amino resin particles is less than 0.01% by mass, it is difficult to prevent ink leakage, and if it exceeds 10% by mass, the aggregate structure tends to become stronger, which tends to affect the ink stability over time, writing feel, and writing performance. From further consideration, 0.1 to 5% by mass is more preferable, 0.3 to 3% by mass is more preferable, and 0.5 to 3% by mass is most preferable.

Specific examples of amino resin particles include Eposter SS (melamine-formaldehyde condensate, average particle size 0.1 μm), Eposter S (melamine-formaldehyde condensate, average particle size 0.2 μm), Eposter FS (melamine-formaldehyde condensate, average particle size 0.2 μm), Eposter S6 (melamine-formaldehyde condensate, average particle size 0.4 μm), Eposter S12 (melamine-formaldehyde condensate, average particle size 1.2 μm), Eposter MS (benzoguanamine-formaldehyde condensate, average particle size 2 μm), Eposter L15 (benzoguanamine-formaldehyde condensate, average particle size 9 μm) (all manufactured by Nippon Shokubai Co., Ltd.), and Percopack M3 (urea-formaldehyde copolymer, average particle size 5 μm, manufactured by Lonza Japan Co., Ltd.).

(Ballpoint pen)
In addition, the ink consumption of the ballpoint pen per 100 m is preferably 20 to 70 mg. This is because if the ink consumption per 100 m is less than 20 mg, it is difficult to obtain thick handwriting or a good writing feel, and if the ink consumption per 100 m exceeds 70 mg, the gap between the ball and the tip end is likely to affect the suppression of ink leakage, and further, writing performance and blobbing are likely to occur.
Regarding the ink consumption, a spiral writing test was performed using five test samples at a writing speed of 4 m/min on JIS P3201 writing paper at 20°C, with a writing angle of 70° and a writing load of 200 g. The average ink consumption per 100 m was defined as the ink consumption per 100 m.

In order to obtain thicker handwriting and to improve ink leakage suppression, it is effective not only to set the ink consumption but also to consider the relationship with the ball diameter. Specifically, the ratio of the ball diameter (mm) to the ink consumption (mg) per 100 m of an oil-based ballpoint pen (ball diameter: ink consumption) is preferably 1:20 to 1:100, which is a different relationship from the conventional one, and is therefore more likely to obtain thicker handwriting and to suppress ink leakage. Taking this into further consideration, it is preferable that the ratio is 1:30 to 1:90, and more preferably 1:40 to 1:80.
The ball diameter is not particularly limited, but balls having a diameter of about 0.1 to 2.0 (mm) are used.

In addition, the amount of movement of the ball in the ballpoint pen tip used in the present invention in the vertical direction is preferably 3 to 20 μm. This is because if it is less than 3 μm, it becomes difficult to obtain thick handwriting or a good writing feel, and if it exceeds 20 μm, it is likely to affect the suppression of ink leakage. From further consideration, it is preferable to make it 5 to 18 μm, and more preferably 7 to 16 μm.
In the present invention, the amount of movement of the ball of the ball-point pen tip in the vertical axis direction is the shape of the ball-point pen tip in the initial state before writing begins.

To improve ink leakage suppression, it is effective not only to set the amount of movement (μm) of the ball in the ballpoint pen tip in the vertical axis direction, but also to consider the relationship with the average particle diameter (μm) of the amino resin particles. Specifically, the ratio of the amount of movement (μm) of the ball in the ballpoint pen tip in the vertical axis direction to the average particle diameter (μm) of the amino resin particles (average particle diameter of amino resin particles: amount of movement of ball in the vertical axis direction) is preferably 1:1 to 1:200, since this makes it easier to suppress ink leakage, and a relationship of 1:1 to 1:100 is preferable, and taking further consideration, a ratio of 1:1 to 1:50 is preferable, and a ratio of 1:2 to 1:30 is preferable.

(Coloring Agent)
The colorant used in the present invention is not particularly limited and may be a dye, a pigment, or the like, and may be appropriately selected and used. The combined use of a dye and a pigment is preferred because it is easy to obtain the following effects.
The dyes include oil-soluble dyes, acid dyes, basic dyes, metal-containing dyes, and various salt-forming dyes thereof, such as salt-forming dyes of acid dyes and basic dyes, salt-forming dyes of organic acids and basic dyes, and salt-forming dyes of acid dyes and organic amines. These dyes may be used alone or in combination of two or more. As the dye, it is preferable to use at least a salt-forming dye in consideration of the stability over time due to the compatibility with the amino resin particles, and further, it is preferable to use a salt-forming dye of a basic dye and an organic acid, a salt-forming dye of an acid dye and a basic dye, or a salt-forming dye of an acid dye and an organic amine in consideration of the stability over time due to the stable salt-forming bond. Specific examples of dyes include Balifast Black 1802, Balifast Black 1805, Balifast Black 1807, Balifast Violet 1701, Balifast Violet 1704, Balifast Violet 1705, Balifast Blue 1601, Balifast Blue 1605, Balifast Blue 1613, Balifast Blue 1621, Balifast Blue 1631, Balifast Red 1320, Balifast Red 1355, Balifast Red 1360, Balifast Yellow 1101, Balifast Yellow 1151, Nigrosine Base EXBP, Nigrosine Base EX, BASE OF BASIC DYES ROB-B, BASE OF BASIC DYES RO6G-B, BASE OF BASIC DYES VPB-B, and BASE OF BASIC DYES. VB-B, BASE OF BASIC DYES MVB-3 (all manufactured by Orient Chemical Industry Co., Ltd.), Aizen Spiron Black GMH-Special, Aizen Spiron Violet C-RH, Aizen Spiron Blue GNH, Aizen Spiron Blue 2BNH, Aizen Spiron Blue C-RH, Aizen Spiron Red C-GH, Aizen Spiron Red C-BH, Aizen Spiron Yellow C-GNH, Aizen Spiron Yellow C-2GH, S.P.T. Blue 111, S.P.T. Blue GLSH-Special, S.P.T. Red 533, S.P.T. Orange 6, S.B.N. Violet 510, S.B.N. Yellow 530, S.R. C-BH (the above are manufactured by Hodogaya Chemical Co., Ltd.).

Pigments include inorganic, organic and processed pigments, but specific examples include carbon black, aniline black, ultramarine, yellow lead, titanium oxide, iron oxide, phthalocyanine, azo, quinacridone, diketopyrrolopyrrole, quinophthalone, threne, triphenylmethane, perinone, perylene, dioxazine, metallic pigments, pearl pigments, fluorescent pigments and phosphorescent pigments.

It is preferable to use a pigment as the colorant, because in the case of a ballpoint pen, the use of pigment particles creates a physical barrier in the gap between the ball and the inner wall of the tip, making it easier to suppress ink leakage. Furthermore, in the present invention, the use of the amino resin particles is preferable because a synergistic effect is achieved by the formation of a coating on the writing tip and the physical barrier of the pigment, resulting in a higher ink leakage suppression effect and at the same time a pigment dispersion effect. Pigments are also preferable because they provide excellent handwriting fastness, especially excellent light resistance.

The colorant content is preferably 5.0 to 30.0% by mass of the total ink composition. If it is less than 5.0% by mass, it tends to be difficult to obtain thick handwriting, and if it exceeds 30.0% by mass, it tends to affect the solubility in the ink. Taking this tendency into consideration, 7.0 to 25.0% by mass is preferable, and if further consideration is given, 10.0 to 25.0% by mass is preferable.

(Organic solvent)
Examples of the organic solvent used in the present invention include organic solvents that are generally used as inks for oil-based ballpoint pens, such as glycol ether solvents such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol dimethyl ether, ethylene glycol monophenyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, diethylene glycol dimethyl ether, 3-methoxybutanol, and 3-methoxy-3-methylbutanol; glycol solvents such as diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, butylene glycol, and ethylene glycol; and alcohol solvents such as benzyl alcohol, methanol, ethanol, 1-propanol, 2-propanol, isopropanol, isobutanol, t-butanol, propargyl alcohol, allyl alcohol, 3-methyl-1-butyn-3-ol, ethylene glycol monomethyl ether acetate, and other higher alcohols.

Among these organic solvents, in consideration of the dispersion stability with the amino resin particles, it is preferable to use a water-insoluble organic solvent, which is preferable because it is easy to suppress ink leakage.
Among them, it is preferable to use an alcohol solvent, because the alcohol solvent evaporates and dries easily at the tip of the ballpoint pen tip, and ink leakage from the outside of the tip tip is easily suppressed. In particular, in the present invention, as described above, the inclusion of the amino resin particles provides an ink leakage suppression effect from the inside of the tip due to physical obstacles and the formation of a weak coagulation structure, and therefore a higher ink leakage suppression effect can be expected due to the ink leakage suppression effect from both the inside and outside of the tip of the ballpoint pen tip. Furthermore, aromatic alcohols such as benzyl alcohol are preferable because they stabilize the dispersion of amino resin particles. In particular, the content of the alcohol solvent is preferably 50% or more of the total organic solvent content in the oil-based ballpoint pen composition, and from a more detailed perspective, it is preferably 70% or more, and more preferably 80% or more.

The content of the organic solvent is preferably 10.0 to 90.0% by mass of the total ink composition in consideration of improving solubility, writing drying properties, bleeding, etc., and is preferably 20.0 to 90.0% by mass, and more preferably 40.0 to 70.0% by mass in consideration of drying properties at the tip end.

(resin)
In order to further improve the ink leakage suppression, it is preferable to use a resin as an ink viscosity adjuster, and examples of the resin include polyvinyl butyral resin, ketone resin, polyacetal resin, polyvinyl alcohol resin, cellulose resin, terpene resin, alkyd resin, phenoxy resin, polyvinyl acetate resin, etc., and among these, it is preferable to use a polyvinyl butyral resin or a ketone resin, because this makes it easier to improve the ink leakage suppression effect.

In addition, in consideration of the ink leakage suppression effect and the improvement of the writing feel, it is preferable to use polyvinyl butyral resin. This is because the coating formed on the outside of the tip end by the polyvinyl butyral resin makes it easier to improve ink leakage. In particular, as described above, the ink leakage suppression effect works from the inside of the tip end due to the inclusion of the amino resin particles, and the ink leakage suppression effect works from the inside of the tip end due to the physical obstacle and the formation of a weak coagulation structure, so that a higher ink leakage suppression effect can be expected due to the ink leakage suppression effect from both the inside and outside of the ballpoint pen tip end.
In addition, polyvinyl butyral resin forms a constantly elastic ink layer between the ball and the ball seat, making it difficult for them to come into direct contact, thereby improving the writing feel. In addition, when a pigment is used as the colorant, it is preferable to use polyvinyl butyral resin because it also has a pigment dispersion effect.
Here, the polyvinyl butyral resin is obtained by reacting polyvinyl alcohol (PVA) with butyraldehyde (BA), and has a structure having butyral groups, acetyl groups, and hydroxyl groups.
In particular, when the ink consumption of an oil-based ballpoint pen is increased to 20 to 70 mg per 100 m, ink leakage from the gap between the ballpoint pen tip body and the ball is likely to occur, so it is effective to use polyvinyl butyral resin, and it is even more effective to use the amino resin particles used in the present invention in combination with polyvinyl butyral resin.

In addition, the polyvinyl butyral resin preferably has a hydroxyl group amount of 20 mol% or more. This is because polyvinyl butyral resins with a hydroxyl group amount of less than 20 mol are insufficient in organic solvents, making it difficult to obtain sufficient lubrication effects and ink leakage suppression effects, and furthermore, considering the writing performance due to moisture absorption, it is preferable to use polyvinyl butyral resins with a hydroxyl group amount of 20 mol% or more. Furthermore, considering the ink leakage suppression, the hydroxyl group amount is preferably 28 mol% or more, and the hydroxyl group amount is preferably 32 mol% or more. In addition, when a polyvinyl butyral resin with a hydroxyl group amount of more than 45 mol% is used, the moisture absorption amount is likely to increase, and the stability over time with the ink components is likely to be affected, so polyvinyl butyral resins with a hydroxyl group amount of 45 mol% or less are preferred, and polyvinyl butyral resins with a hydroxyl group amount of 40 mol% or less are preferred.
The amount (mol %) of hydroxyl groups in the polyvinyl butyral resin refers to the content of hydroxyl groups (mol %) relative to the total molar amount of butyral groups (mol %), acetyl groups (mol %), and hydroxyl groups (mol %).

With regard to the average degree of polymerization of polyvinyl butyral resin, if the average degree of polymerization is 200 or more, the ink leakage suppression performance is likely to be improved, and if the average degree of polymerization exceeds 2500, the ink viscosity tends to become too high and affect the writing feel, so the average degree of polymerization is preferably 200 to 2500. Furthermore, in order to further consider the suppression of ink leakage, the average degree of polymerization is preferably 1500 or less. Here, the average degree of polymerization refers to the number of basic units that make up one molecule of polyvinyl butyral resin, and a value measured based on the method specified in JIS K6728 (2001 edition) can be used.

Specific examples of polyvinyl butyral resins include those manufactured by Sekisui Chemical Co., Ltd. under the trade names of S-LEC BH-3 (hydroxyl group amount: 34 mol%, average degree of polymerization: 1700), S-LEC BH-6 (hydroxyl group amount: 30 mol%, average degree of polymerization: 1300), S-LEC BX-1 (hydroxyl group amount: 33±3 mol%, average degree of polymerization: 1700), S-LEC BX-5 (hydroxyl group amount: 33±3 mol%, average degree of polymerization: 2400), and S-LEC BM-1 ( BM-2 (hydroxyl group amount: 34 mol%, average degree of polymerization: 650), BM-2 (hydroxyl group amount: 31 mol%, average degree of polymerization: 800), BM-5 (hydroxyl group amount: 34 mol%, average degree of polymerization: 850), BL-1 (hydroxyl group amount: 36 mol%, average degree of polymerization: 300), BL-1H (hydroxyl group amount: 30 mol%), BL-2 (hydroxyl group amount: 36 mol%, average degree of polymerization: 450), BL-2H (hydroxyl group amount: 29 mol%), Mobital BL-10 (hydroxyl group amount: 28 mol%), and the like, and trade names of Mobital B20H (hydroxyl group amount: 26-31 mol%, average polymerization degree: 250-500), Mobital B30T (hydroxyl group amount: 33-38 mol%, average polymerization degree: 400-650), Mobital B30H (hydroxyl group amount: 26-31 mol%, average polymerization degree: 400-650), Mobital B30HH (hydroxyl group amount: 30-34 mol%), and the like, manufactured by Kuraray Co., Ltd. %, average degree of polymerization: 400-650), B45H (hydroxyl group amount: 26-31 mol%, average degree of polymerization: 600-850), B60T (hydroxyl group amount: 34-38 mol%, average degree of polymerization: 750-1000), B60H (hydroxyl group amount: 26-31 mol%, average degree of polymerization: 750-1000), B75H (hydroxyl group amount: 26-31 mol%, average degree of polymerization: 1500-1750), etc. These may be used alone or in combination of two or more.

In addition, the ketone resin is used in combination with the amino resin particles to synergistically suppress ink leakage, and also to suppress bleeding. In particular, when the ink consumption per 100 m of an oil-based ballpoint pen is increased to 20 to 70 mg, bleeding and bleeding due to excess ink easily occur at the tip end, and the use of a ketone resin is more effective because it suppresses the ink from creeping up and thus makes it easier to suppress bleeding and bleeding. Furthermore, in consideration of suppressing bleeding and bleeding, it is preferable to use a ketone resin having a ring structure such as an aromatic ring skeleton (having a benzene ring such as a phenyl group, an acetophenone group, or a naphthalene group) or a cyclohexane skeleton (having a cyclohexane ring such as a cyclohexane group or a cyclohexanone group) among the ketone resins.
Furthermore, oil-based ballpoint pens are often used for writing on copy paper, and when writing on copy paper, a higher writing pressure is applied than usual (high writing pressure writing), so there is a demand for improved high-pressure writing properties. The use of a ketone resin is effective and preferable, as it improves lubricity under high writing pressure (writing load of 300 to 500 gf) and makes it easier to further improve wear suppression of the ball seat.

If the total content of the resins is less than 1.0% by mass relative to the total amount of the ink composition, the amount of resin film formed may be insufficient, and ink leakage prevention performance may be poor, while if it exceeds 40.0% by mass, solubility in the ink may be poor, so a content of 1.0 to 40.0% by mass relative to the total amount of the ink composition is preferable. Furthermore, in consideration of ink leakage prevention performance, a content of 5.0% by mass or more is preferable, and if it exceeds 30.0% by mass, the ink viscosity may become too high, which may affect the writing feel and writing performance, so a content of 5.0 to 30.0% by mass is preferable.

Resins other than polyvinyl butyral resin and ketone resin may be appropriately used with a spinnability imparting agent. In particular, polyvinylpyrrolidone resin is preferably contained since blending with polyvinylpyrrolidone resin enhances the ink binding property and makes it easier to suppress the generation of excess ink at the tip end. If the content of the polyvinylpyrrolidone resin is less than 0.01% by mass relative to the total amount of the ink composition, it tends to be difficult to suppress the generation of excess ink, and if it exceeds 3.0% by mass, it tends to be less soluble in the ink, so it is preferably 0.01 to 3.0% by mass relative to the total amount of the ink composition. Considering the above reasons, it is preferably 0.1 to 2.0% by mass. Specific examples include PVP K-15, PVP K-30, PVP K-90, and PVP K-120, which are trade names manufactured by ISP Japan Co., Ltd. These may be used alone or in combination of two or more.

(Surfactant)
In the present invention, it is preferable to use a surfactant in consideration of improving lubricity and writing performance when the tip of the tip is left in the air and the tip is dried. This is because the use of a surfactant tends to soften the coating formed, improving writing performance and further improving lubricity. Examples of surfactants include fatty acids, fatty acid esters, silicone surfactants, fluorine surfactants, and phosphate surfactants. Among them, it is preferable to use one or more of fatty acids, silicone surfactants, and phosphate surfactants in consideration of the above effects.

Regarding the surfactant, in order to improve both lubricity and writing performance, the HLB value is preferably 6 to 14. This is because when the HLB value exceeds 14, the surfactant is likely to be highly hydrophilic, and therefore the solubility in oil-based ink is likely to be poor, making it difficult to obtain the effects of the surfactant and the lubricating effect. Also, when the HLB value is less than 6, the surfactant is too lipophilic, which is likely to affect the compatibility with organic solvents, making it difficult for the ink to stabilize over time, and making it difficult to improve writing performance. Furthermore, in order to improve lubricity, the HLB value is preferably 12 or less, and the HLB value is preferably 6 to 12, and in order to improve writing performance, the HLB value is preferably 7 to 12.
The HLB can be determined by the Griffin method, the Kawakami method, etc. In particular, in retractable writing instruments such as knock-type writing instruments and rotary-type writing instruments, unlike cap-type writing instruments, the pen tip is always exposed to the outside, which is likely to affect the writing performance when the writing tip dries, so it is more preferable to use a surfactant with the above HLB value.

Specific examples of the surfactant include fatty acids such as oleic acid, stearic acid, and linoleic acid; silicone surfactants include dimethyl silicone, methylphenyl silicone, polyether-modified silicone, and higher fatty acid ester-modified silicone; fluorine-based surfactants include perfluoro-butyl sulfonate, perfluoro-containing carboxylate, perfluoro-containing phosphate, perfluoro-containing phosphate-type compound, perfluoroalkyl betaine, and perfluoroalkylamine oxide compound; and phosphate surfactants include phosphate having an alkoxyethyl group (C _n H _2n+1 OCH ₂ CH ₂ O) or an alkoxy group (C _m H _2m+1 O), polyoxyethylene alkyl ether or polyoxyethylene alkylaryl ether phosphate monoester, polyoxyethylene alkyl ether or polyoxyethylene alkylaryl ether phosphate diester, polyoxyethylene alkyl ether or polyoxyethylene alkylaryl ether phosphate triester, alkyl phosphate, alkyl ether phosphate, or derivatives thereof.

Furthermore, oil-based ballpoint pens are often used for writing on copy paper, and when writing on copy paper, writing pressure is higher than usual (high writing pressure writing), so there is a demand for improving the high writing pressure writing properties; among surfactants, it is preferable to use a phosphate ester surfactant because it is easy to improve lubrication under high writing pressure (300 to 500 gf). This is because the phosphate group of the phosphate ester surfactant makes it easier for the lubricating action to work, exerts a greater extreme pressure effect, improves the lubrication between the ball and the tip body even under high writing pressure (300 to 500 gf), suppresses wear of the ball seat, and makes it easy to produce good handwriting without smearing, etc., and therefore can be used more preferably in the present invention.
Furthermore, among phosphate ester surfactants, in order to improve the lubricity between the ball and the tip body even under high writing pressure (300 to 500 gf) and suppress wear of the ball seat, it is preferable to use a phosphate ester surfactant having an alkoxyethyl group (C _n H _2n+1 OCH ₂ CH ₂ O) or an alkoxyl group (C _m H _2m+1 O), and from this perspective, it is more preferable to use a phosphate ester surfactant having an alkoxyethyl group (C _n H _2n+1 OCH ₂ CH ₂ O).

For the phosphate ester surfactant, the carbon chain (n, m) of the terminal alkyl group of the alkoxyethyl group ( _{CnH2n +1OCH2CH2O )} or alkoxyl group ( _{CmH2m +1O )} is preferably 1 to 10. This is because the carbon chain of the terminal alkyl group of the alkoxyethyl group ( _{CnH2n + 1OCH2CH2O} ) or alkoxyl group ( _{CmH2m +1O )} becomes too long, and although the writing feel and writing performance are good, it may be difficult to suppress the wear of the ball seat under high writing pressure (writing load of 300 to 500 gf). This is because, when the carbon chain (n, m) of the terminal alkyl group exceeds 10, especially when the carbon chain (n, m) exceeds 5, steric hindrance is likely to occur between the carbon chains, and even if the phosphate groups adsorbed on the metal of the ballpoint pen tip material become dense, the arrangement of the carbon chains is unlikely to become dense, a lubricating layer with sufficient lubricity is not obtained, and it is difficult to suppress the wear of the ball seat under high writing pressure. Furthermore, since the polarity of the terminal alkyl group is closer to the oily side, the affinity for organic solvents is inferior, which is likely to affect the dissolution stability, and problems are likely to occur in the dissolution stability in the ink. For this reason, metal salt precipitates are likely to occur due to the influence of metal ions in the metal tip during long-term storage, and the ink stability over time is likely to be inferior, making it difficult to obtain the lubricating effect of the present invention. Therefore, it is preferable that the carbon chain (n, m) of the terminal alkyl group is 1 to 10, and from a more consideration, it is preferable that the carbon chain (n, m) of the terminal alkyl group is 1 to 5.
On the other hand, when the carbon chain (n, m) of the terminal alkyl group is 3 or less, the wear of the ball seat under high writing pressure is suppressed well, but the alkyl group does not extend sufficiently in the ink, and the lubricating layer between the ball and the ball seat has insufficient cushioning, so that the writing feel and writing performance are likely to be affected. Therefore, it is preferable to use butoxyethyl acid phosphate (n=4) or butyl acid phosphate (m=4) in which the terminal alkyl group has a butyl group (carbon chain of the terminal alkyl group: 4), because it is easy to obtain the effect of suppressing the wear of the ball seat under high writing pressure and improving the writing feel and writing performance.

The surfactant content is preferably 0.1 to 5.0% by mass based on the total amount of the ink composition. This is because if it is less than 0.1% by mass, it tends to be difficult to obtain the desired lubricity, and if it exceeds 5.0% by mass, the ink tends to become unstable over time. Taking this tendency into consideration, it is preferable to have a surfactant content of 0.3 to 3.0% by mass based on the total amount of the ink composition, and more particularly, 0.5 to 3.0% by mass is most preferable.

(Organic amine)
In the present invention, in consideration of the stability of the ink components in the ink, it is preferable to use an organic amine. Examples of the organic amine include amines having ethylene oxide such as oxyethylene alkylamines and polyoxyethylene alkylamines, alkyl amines such as laurylamine and stearylamine, and aliphatic amines such as dimethyl alkyl amines such as distearylamine, dimethyl laurylamine, dimethyl stearylamine, and dimethyl octylamine, and among them, in consideration of the stability in the ink, amines having ethylene oxide and dimethyl alkyl amines are preferable. In particular, when a phosphate surfactant is used, it is preferable because it is stabilized in the ink by neutralization, and the effect of the phosphate surfactant is easily obtained.

In addition, the reactivity of the organic amines with other components in the ink is strongest with primary amines, followed by secondary amines and then tertiary amines, and therefore, taking into consideration the stability of the ink over time, it is preferable to use secondary or tertiary amines. These may be used alone or in combination of two or more.

The content of the organic amine is preferably 0.1 to 10.0% by mass based on the total amount of the ink composition, taking into consideration the stability with the ink components, and more preferably 0.2 to 5.0% by mass, taking into consideration the neutralization of the phosphate ester surfactant described below.

(Fatty acid ester)
Other than the above-mentioned surfactants, fatty acid esters are preferably used in consideration of improving lubricity and writing performance when the tip of the tip is left in the air and the tip is dried. In particular, fatty acid esters are preferred because they tend to maintain lubricity even under high writing pressure (writing load of 300 to 500 gf), suppressing wear of the ball seat (high writing pressure writing performance), and improving both the writing feel and writing performance.

Fatty acid esters are produced by esterification of fatty acids with alcohols such as monohydric alcohols and polyhydric alcohols, but among the above fatty acid esters, it is preferable to use fatty acid esters with branched alkyl groups in order to improve writing performance. This is because fatty acid esters with branched alkyl groups have a bulkier structure than straight chain structures, and the bulkiness of the branched alkyl groups makes them more likely to be adsorbed to the metal ball surface and the ball seat of the tip body, forming a thicker lubricating film and improving lubricity. At the same time, the bulkiness of the branched alkyl groups softens the strength of the coating formed when the ink dries at the tip end, improving writing performance.

Furthermore, the fatty acid ester preferably has an acid value of 0.01 to 5 (mgKOH/g), because it has good compatibility with the acidic phosphate ester and other components in the oil-based ink and is stable in the ink for a long period of time, which makes it possible to improve the writing performance for a long period of time, improve the lubricity for a long period of time, and facilitate the improvement of the writing feel. From further consideration, the acid value is preferably 0.01 to 2.5 (mgKOH/g), and more preferably 0.05 to 1.0 (mgKOH/g).
The acid value is expressed as the number of milligrams of potassium hydroxide required to neutralize the acidic components (free fatty acids) contained in 1 g of a sample.

The alcohol used in the esterification reaction of the fatty acid ester is preferably a polyhydric alcohol. Although the reason for this is unclear, it is presumed that the more hydroxyl groups in the alcohol used in the esterification reaction of the fatty acid ester, the easier it is for the alcohol to have a moisturizing effect, and the strength of the coating formed when the tip end dries is softened, resulting in smoother ball rotation, and thus improved writing performance without blurring of the writing. Considering the need to further improve writing performance, it is preferable for the hydroxyl group to be a polyhydric alcohol with a hydroxyl group of 4 or more, and more preferably a hydroxyl group of 5 or more. In addition, since too many hydroxyl groups can easily affect stability in oil-based ink, it is preferable for the hydroxyl group to be 8 or less.

Specific examples of alcohols used in the esterification reaction of the fatty acid ester include monohydric alcohols such as pentanol, cyclohexanol, hexanol, heptanol, octanol, 2-ethylhexanol, nonanol, isononanol, decanol, lauryl alcohol, myristyryl alcohol, stearyl alcohol, and docosanol. Examples of polyhydric alcohols include ethylene glycol, propylene glycol, polyalkylene glycol, 1,3-propanediol, diethylene glycol, glycerin, 2-methylpropanetriol, neopentyl glycol, trimethylolethane, triethylolethane, trimethylolpropane, pentaerythritol, dipentaerythritol, and tripentaerythritol. Among these, in order to further improve the writing performance and take into consideration the ink stability over time, it is preferable to include a fatty acid ester esterified with pentaerythritol such as pentaerythritol, dipentaerythritol, or tripentaerythritol, and from further consideration, it is preferable to include a fatty acid ester esterified with dipentaerythritol.

The content of the fatty acid ester is more preferably 0.1 to 10.0% by mass relative to the total amount of the ink composition. This is because if it is less than 0.1% by mass, it is difficult to obtain the desired lubricity and writing performance, and if it exceeds 10.0% by mass, the ink tends to become unstable over time. Taking this tendency into consideration, 0.1 to 5.0% by mass is preferable, and more preferably 0.1 to 3.0% by mass, with 0.3 to 2.0% by mass being the most preferable.

In addition, as viscosity adjusters, pseudoplasticity imparting agents such as fatty acid amides and hydrogenated castor oil, colorant stabilizers, plasticizers, chelating agents, water, etc. may be used as appropriate. These may be used alone or in combination of two or more.

The ink viscosity of the ink composition for oil-based ballpoint pens of the present invention is not particularly limited, but if the ink viscosity exceeds 30,000 mPa·s at 20° C. and a shear rate of 5 sec ⁻¹ (at rest), the writing performance and writing feel tend to deteriorate, so the ink viscosity at 20° C. and a shear rate of 5 sec ⁻¹ (at rest) is preferably 30,000 mPa·s or less. Also, if the ink viscosity at 20° C. and a shear rate of 5 sec ⁻¹ (at rest) is less than 1,000 mPa·s, it is difficult to suppress ink leakage, so in consideration of ink leakage, it is preferably 1,000 mPa·s or more. Considering further improvement in ink leakage suppression, writing feel, ink tracking performance, and writing start performance, the ink viscosity is more preferably 1500 to 25000 mPa·s, and even more preferably 2000 to 20000 mPa·s, and more preferably 2000 to 15000 mPa·s.
In addition, in retractable oil-based ballpoint pens such as knock-type oil-based ballpoint pens and rotary-type oil-based ballpoint pens, it is necessary to give special consideration to suppressing ink leakage, and therefore this is effective and preferable.

The arithmetic mean roughness (Ra) of the ball surface of the ballpoint pen tip used in the present invention is preferably 0.1 to 12 nm. If the arithmetic mean roughness (Ra) is less than 0.1 nm, it is difficult for ink to be applied sufficiently to the ball surface, making it difficult to obtain thick handwriting during writing, and line skips and smears are likely to occur in the handwriting. If the arithmetic mean roughness (Ra) exceeds 12 nm, the ball surface is too rough and the rotation resistance of the ball and the ball seat is large, so the writing feel is likely to be poor, and further, writing performance is likely to be affected by smears, line skips, and line unevenness in the handwriting. In addition, it is more preferable for the arithmetic mean roughness (Ra) to be 0.1 to 10 nm, since ink is easily applied to the ball surface, and more preferably 2 to 8 nm. The surface roughness can be measured using a Seiko Epson Corporation model (SPI3800N).

The material used for the balls is not particularly limited, but examples include cemented carbide balls whose main component is tungsten carbide, metal balls such as stainless steel, ceramic balls such as silicon carbide, silicon nitride, alumina, silica, and zirconia, and ruby balls.

Materials for ballpoint pen tips include metals such as stainless steel, nickel silver, brass, aluminum bronze, and aluminum, and resins such as polycarbonate, polyacetal, and ABS. Taking into consideration the writing feel and workability such as cutting, a tip body made of nickel silver is preferable, and taking into consideration wear of the ball seat and stability over time, a tip body made of stainless steel is preferable.

Example 1
The ink composition for an oil-based ballpoint pen in Example 1 employed a dye as a colorant, benzyl alcohol as an organic solvent, amino resin particles, a phosphate ester surfactant having an alkoxyethyl group as a surfactant, an oxyethylene alkylamine as an organic amine, a fatty acid ester having a branched alkyl group, a polyvinyl butyral resin, and polyvinylpyrrolidone as a stringiness imparting agent, and these were weighed out in predetermined amounts, heated to 60° C., and then completely dissolved using a Disper stirrer to obtain an ink composition for an oil-based ballpoint pen.
The specific blending amounts are as follows:

Example 1 (Ink Formulation)
Colorant (dye, salt-forming dye of acid dye and basic dye) 8.0% by mass
Coloring agent (dye, salt-forming dye of organic acid and basic dye) 5.0% by mass
Organic solvent (benzyl alcohol) 72.5% by mass
Amino resin particles (melamine-formaldehyde condensate, average particle size: 0.4 μm)
1.0 mass%
Surfactant (phosphate ester surfactant having an alkoxyethyl group (C _n H _2n+1 OCH ₂ CH ₂ O: n=4)) 1.0% by mass
Organic amine (oxyethylene alkylamine) 1.0 mass%
Fatty acid ester having a branched alkyl group (fatty acid ester esterified with a fatty acid and dipentaerythritol) 1.0% by mass
Polyvinyl butyral resin 10.0% by mass
Threadability imparting agent (polyvinylpyrrolidone resin) 0.5% by mass

Examples 2 to 24
As shown in Table 1, except that the ink components and tip specifications were changed, the ink compositions for oil-based ballpoint pens of Examples 2 to 24 were obtained in the same manner as in Example 1. The measurement and evaluation results are shown in the table.
The ink viscosities of Examples 1, 9, and 10 were measured using a viscometer, Viscometer RVDVII+Pro CP-52 spindle, manufactured by Brookfield Corporation, at an environment of 20° C. and a shear rate of 10 sec ⁻¹ . The results were as follows: Example 1: ink viscosity = 2000 mPa·s, Example 9: ink viscosity = 5000 mPa·s, Example 10: ink viscosity = 12000 mPa·s.

Comparative Examples 1 to 4
As shown in the table, except that the ink components and tip specifications were changed, the ink compositions for oil-based ballpoint pens of Comparative Examples 1 to 4 were obtained in the same manner as in Example 1. The measurement and evaluation results are shown in the table.

Tests and Evaluations The ink compositions (0.27 g) for oil-based ballpoint pens prepared in Example 1 and Comparative Example 1 were filled into oil-based ballpoint pen refills equipped with a ballpoint pen tip (movement amount in the vertical axis direction of the ball: 10 μm, arithmetic mean roughness (Ra) of the ball surface: 6 nm) that rotatably holds a ball with a ball diameter of φ0.5 mm in an ink storage tube (polypropylene), to prepare oil-based ballpoint pens. Similarly, in Examples 2 to 24 and Comparative Examples 2 to 4, the ink compositions (0.27 g) for oil-based ballpoint pens prepared were filled into oil-based ballpoint pen refills equipped with a ballpoint pen tip with a ballpoint pen tip with tip specifications changed as shown in the table in an ink storage tube (polypropylene), to prepare oil-based ballpoint pens. The following tests and evaluations were performed using writing paper JIS P3201 as the writing test paper.
The ink consumption per 100 m of Example 1 was 36 mg/100 m when a spiral writing test was carried out using an oil-based ballpoint pen.
The ratio of the ball diameter (mm) to the ink consumption (mg) per 100 m of the oil-based ballpoint pen (ball diameter:ink consumption) was 1:72.
The ratio of the movement amount (μm) in the longitudinal direction of the ball of the ballpoint pen tip to the average particle size (μm) of the amino resin particles (average particle size of amino resin particles: movement amount in the longitudinal direction of the ball) was 1:12.5.

Ink leakage prevention test: The pen was left for 7 days in an environment of 30° C. and 85% RH with the pen tip facing downward, and ink leakage from the tip end was confirmed.
No ink droplets at the tip...◎
The ink droplet at the tip end is within 1/4 of the tapered part...
The ink droplet at the tip end is between 1/4 and 1/2 of the tapered section... △
The ink drop at the tip is more than half the size of the tapered part... ×

Thickness of handwriting: The handwritten characters were observed.
Thick and clear handwriting...◎
Thick handwriting...○
The handwriting is thick enough that it does not cause any problems for practical use.
Faint handwriting... ×

Abrasion resistance test under high writing pressure (wear test of ball seat): Wear of the ball seat after the writing test was measured using a running test machine with a load of 400 gf, a writing angle of 70°, and a speed of 4 m/min.
Wear of the ball seat is less than 8μm...
Wear of the ball seat is 8 μm or more and less than 15 μm...
Wear of the ball seat is between 15 μm and 25 μm, but writing is possible: △
The ball seat is worn out so much that writing becomes difficult... ×

In Examples 1 to 24, good performance was obtained in the ink leakage suppression test, the thickness of the writing, and the abrasion resistance test under high writing pressure (ball seat abrasion test). In addition, among Examples 1 to 24, the inks that used pigments as colorants had good pigment dispersibility when viewed under a microscope.

In Comparative Example 1, since no amino resin particles were used, the ink leakage suppression was poor.
In Comparative Example 2, a polystyrene resin was used, but it was deformed in the ink, and the ink leakage suppression properties were poor.
In Comparative Example 3, the ink consumption was small, so dark handwriting was not obtained.
In Comparative Example 4, the ink consumption was too large, and therefore the effect of suppressing ink leakage was not obtained.

In addition, when using a retractable oil-based ballpoint pen (retractable ballpoint pen) such as a knock-type oil-based ballpoint pen or a twist-type oil-based ballpoint pen, ink leakage prevention performance is one of the most important performances, so it is effective to use an ink composition for an oil-based ballpoint pen containing amino resin particles such as that of the present invention, which can prevent ink leakage from the gap at the writing tip (ink leakage from the gap between the ball and the tip tip) and achieve good ink leakage prevention performance.

In general, the ballpoint pen tip of an oil-based ballpoint pen is equipped with a valve mechanism that presses the ball, which is rotatably held at the tip of the ballpoint pen tip, against the inner wall of the tip edge directly or through a pressing body, with a resilient member such as a coil spring, against the inner wall of the tip edge edge of the tip to prevent ink leakage, and the small gap at the tip edge is closed when not in use. However, when an ink composition for an oil-based ballpoint pen, which has a particularly high ink leakage prevention effect as in the present invention, is used, ink leakage can be prevented even without a resilient member such as a coil spring. Therefore, the resistance between the ball and the resilient member is eliminated, the writing feel is improved, and the fluidity of the ink is improved, which improves the ink tracking ability and makes it easier to obtain thick handwriting, and further leads to a reduction in the number of parts, making it possible to reduce costs, which is more effective. In particular, in retractable ballpoint pens, etc., more importance is attached to preventing ink leakage, so it can be used preferably.

In addition, for convenience, this embodiment shows an example of an oil-based ballpoint pen that contains an oil-based ballpoint pen refill in which an ink composition for an oil-based ballpoint pen is directly contained in the barrel, but the oil-based ballpoint pen of the present invention may be a direct-fill type ballpoint pen or an oil-based ballpoint pen in which the barrel serves as an ink storage barrel and the ink composition for an oil-based ballpoint pen is directly contained in the barrel. In addition, this embodiment shows an example of a ballpoint pen tip formed by cutting a wire material for convenience, but it may also be a ballpoint pen tip formed by pressing a pipe material.

In the present embodiment, an oil-based ballpoint pen is exemplified in which a ballpoint pen refill containing an oil-based ballpoint pen ink composition in an ink storage tube is disposed in the barrel, but the oil-based ballpoint pen of the present invention may be a direct-loading type oil-based ballpoint pen in which the barrel itself is the ink storage tube and the ink composition for an oil-based ballpoint pen is directly stored in the barrel, or may have a structure in which the ink storage tube contains an ink composition for an oil-based ballpoint pen (ballpoint pen refill) and is used as a ballpoint pen as is.

The present invention can be used as an oil-based ballpoint pen, and more specifically, can be widely used as an oil-based ballpoint pen, such as a cap type or a retractable type.

Claims (3)

An oil-based ballpoint pen having a ballpoint pen tip at the tip of an ink reservoir, and an ink composition for an oil-based ballpoint pen contained in the ink reservoir, wherein the ink consumption of the oil-based ballpoint pen per 100 m is 20 to 70 mg;
The amount of movement of the ball of the ballpoint pen tip in the vertical axis direction in the initial state before writing begins is 7 to 16 μm,
The ink composition for an oil-based ballpoint pen comprises a colorant, an organic solvent, amino resin particles, and a phosphoric acid ester surfactant having an alkoxyethyl group ( _{CnH2n +1OCH2CH2O )} or an alkoxyl group ( _{CmH2m +1O )} ;
the organic solvent is an alcohol solvent, and the content of the alcohol solvent is 70% or more based on the total content of organic solvents in the oil-based ballpoint pen composition;
The oil-based ballpoint pen is characterized in that the ratio of the average particle diameter (μm) of the amino resin particles to the amount of movement (μm) of the ball in the vertical axis direction of the ball of the ballpoint pen tip (average particle diameter of amino resin particles: amount of movement of the ball in the vertical axis direction) is 1:2 to 1:30 . The oil-based ballpoint pen according to claim 1, characterized in that the carbon chain (n, m) of the terminal alkyl group of the phosphate ester surfactant having an alkoxyethyl group ( _{CnH2n +1OCH2CH2O )} or an alkoxyl group ( _{CmH2m +1O )} is 1 to 10. The oil-based ballpoint pen according to claim 1 or 2, characterized in that the average particle diameter of the amino resin particles is 5 μm or less.