JP6855312B2 - Ink composition for writing instruments and writing instruments using it - Google Patents

Description

The present invention relates to an ink composition for a writing instrument and a writing instrument using the same.

Conventionally, in the ink composition for writing tools, in the case of a ballpoint pen, ink leaks from the gap at the tip of the writing (ink leaks from the gap between the ball and the tip of the tip), and in the case of a marking pen, felt-tip pen, etc., from the tip of the writing. In order to suppress ink leakage, a solvent having a steam pressure of 0.001 mmHg or more at 25 ° C. is used, silica or felt-tip penphenol resin is used as an ink leakage inhibitor, or an ink gelling agent is used to obtain ink viscosity. A technique for ink compositions for felt-tip pens with a high setting has been proposed.

As a technique using an alcohol, a polyhydric alcohol, or a glycol ether solvent having a steam pressure of 0.001 mmHg or more at 25 ° C. as such an ink composition for writing tools, Japanese Patent Application Laid-Open No. 2004-107591 "Oil property for writing tools". As a technique using an "ink composition" or an ink leakage inhibitor, JP-A-10-195365 "Oil-based ink for ballpoint pens" using silica having a primary average particle diameter of 7 to 40 nm, and an OH value of 150 or more. As a technique using a terpenphenol resin, Japanese Patent Application Laid-Open No. 2007-126528 "Oil-based ink for ballpoint pens", and as a technique using hydrogenated castor oil or fatty acid amide wax as a shear reducing viscosity imparting agent, JP-A-7- It is disclosed in Japanese Patent Application Laid-Open No. 196972 "Oil-based ink composition for ballpoint pens".

"Japanese Patent Laid-Open No. 2004-107591" "Japanese Patent Laid-Open No. 10-195365" "Japanese Patent Laid-Open No. 2007-126528" "Japanese Patent Laid-Open No. 7-196972"

However, although Patent Document 1 has an effect of suppressing ink leakage to some extent, when the ink viscosity is lowered, ink leakage cannot be sufficiently suppressed only by the solvent used in Patent Document 1. Further, in Patent Document 2, silica having a primary average particle diameter of 7 to 40 nm has a small particle size and a large specific gravity of silica, so that the dispersion stability in oil-based ink is inferior. In the terpenphenol resin having a value of 150 or more, since the OH value is high, the solubility in the oil-based ink is poor, and sufficient effects cannot be exhibited. Further, in Patent Document 4, hydrogenated castor oil and fatty acid amide wax can suppress ink leakage to some extent, but the ink viscosity at rest becomes high, the ink followability tends to be inferior, and the brush strokes are blurred. It sometimes occurred, and had a problem that affected the writing quality.
In particular, when the ball diameter is 1.0 to 2.0 mm, the ballpoint pen tip is set so that the amount of ink ejected is large, so the effect of ink leakage is likely to occur, and writing when the writing tip is dry. Performance tends to be inferior.

More recently, in order to obtain a smooth writing feel, the viscosity of oil-based ink has been reduced, and the amount of ink ejected has increased accordingly, and ink leakage is likely to occur from the tip of the writing, which tends to cause a problem.

An object of the present invention is to obtain an ink composition for a writing instrument that suppresses ink leakage and has good writing performance, and a writing instrument using the same.

２．前記環状リン化合物の重量平均分子量が、２０００以下であることを特徴とする第１項に記載の筆記具用インキ組成物。
３．前記環状リン化合物の含有量が、インキ組成物全量に対して、０．１〜１０．０質量％であることを特徴とする第１項または第２項に記載の筆記具用インキ組成物。
４．前記筆記具用インキ組成物に、ポリビニルブチラール樹脂 またはケトン樹脂を含んでなることを特徴とする第１項ないし第３項のいずれか１項に記載の筆記具用インキ組成物。
５．２０℃、剪断速度５ｓｅｃ^−１におけるインキ粘度が、１５０００ｍＰａ・ｓ以下であることを特徴とする第１項ないし第４項のいずれか１項に記載の筆記具用インキ組成物。
６．第１項〜第５項のいずれか１項に記載の筆記具用インキ組成物を収容してなることを特徴とする筆記具。
７．ンキ収容筒の先端部に、ボールを回転自在に抱持したボールペンチップを有し、前記インキ収容筒内に第１項ないし第５項のいずれか１項に記載の筆記具用インキ組成物を収容してなることを特徴とする油性ボールペン。」とする。 The present invention is to solve the above problems.
"1. An ink composition for a writing instrument containing a colorant, an organic solvent, and a cyclic phosphorus compound, wherein the cyclic phosphorus compound has the following general formula (Chemical formula 1).

2. The ink composition for writing instruments according to item 1, wherein the cyclic phosphorus compound has a weight average molecular weight of 2000 or less.
3. 3. The ink composition for writing instruments according to item 1 or 2, wherein the content of the cyclic phosphorus compound is 0.1 to 10.0% by mass with respect to the total amount of the ink composition.
4. The writing instrument ink composition according to any one of items 1 to 3, wherein the writing instrument ink composition contains a polyvinyl butyral resin or a ketone resin.
5. The ink composition for a writing instrument according to any one of Items 1 to 4, wherein the ink viscosity at 20 ° C. and a shear rate of 5 sec ^{-1 is 15000 mPa · s or less.}
6. A writing instrument comprising the ink composition for a writing instrument according to any one of paragraphs 1 to 5.
7. A ballpoint pen tip that rotatably holds a ball is provided at the tip of the ink storage cylinder, and the ink composition for a writing instrument according to any one of items 1 to 5 is stored in the ink storage cylinder. An oil-based ballpoint pen that is characterized by being made of. ".

The present invention contains the cyclic phosphorus compound of the following general formula (Chemical Formula 1), so that when the writing tip is dried, the ink is locally thickened at the writing tip to form a film. Ink composition for writing instruments that suppresses ink leakage from the tip (in the case of a ballpoint pen, ink leakage from the gap between the ball and the tip of the tip) and further improves writing performance by the coating on the tip of the writing, and uses it. I was able to get the writing utensils I had.

A feature of the present invention is that the ink composition for writing instruments contains a cyclic phosphorus compound of the general formula (Chemical Formula 1).

(Cyclic phosphorus compound)
In the present invention, it has been found that ink leakage can be suppressed by containing the cyclic phosphorus compound of the following general formula (Chemical Formula 1) in the ink composition for writing instruments. This is because when the writing tip dries, the ink locally thickens at the writing tip to form a film, which synergistically leaks ink from the writing tip (in the case of a ballpoint pen, the ball and tip). This is to suppress ink leakage from the gap at the tip). Further, by forming a film on the writing tip, the writing performance can be improved. In particular, the cyclic phosphorus compound of the following general formula (Chemical Formula 1) is suitable when used as an oil-based ink composition because it has the effect of suppressing ink leakage and improving writing performance.

The cyclic phosphorus compound used in the present invention is a compound having a cyclic structure containing a phosphorus element, but when the writing tip is dried, it is locally localized at the writing tip by a polymer of the styrene compound of the cyclic phosphorus compound. By thickening the ink and forming a film, it is possible to suppress ink leakage from the writing tip. Further, the cyclic phosphorus compound of the general formula (Chemical Formula 1) can improve the writing performance by the film formed when the writing tip is dried. In particular, in the case of a ballpoint pen, the ball and the tip body are made of metals. Since the O atom adjacent to the P atom of the cyclic phosphorus compound is easily adsorbed on the writing tip, a more stable film can be easily formed, which is effective. Further, when a pigment is used as a colorant, a pigment dispersion effect can be obtained, the compatibility between the pigment and the cyclic phosphorus compound of the general formula (Chemical Formula 1) is good, and the stability over time is also good, so that it is preferably used. it can

The weight average molecular weight of the cyclic phosphorus compound is preferably 2000 or less. This is because when the weight average molecular weight exceeds 2000, it is difficult to dissolve and stabilize in the ink, so that the effect of the present invention is difficult to obtain. Further, when the writing tip is dried, the ink is locally thickened at the writing tip. Because it is too much, the writing performance is likely to be affected. Considering the above effects, the weight average molecular weight is preferably 1000 or less.

Regarding the general formula (Chemical formula 1) of the cyclic phosphorus compound, it is preferable to set m = 1 to 5, which means that when m exceeds 5, the molecular weight increases and the dissolution is stable in the ink as described above. Since it is difficult to obtain the effect of the present invention, it is preferable to set m = 1 to 2 in consideration of the above.
X of the general formula (Chemical formula 1) _{may have only one of H or C m} H _{2 m + 1} (alkyl group), or may have both H and C _m H _{2 m + 1} (alkyl group). Specifically, in the molecule of the general formula (Chemical formula 1), X is only H, X is only C _m H _{2 m + 1} (alkyl group), and X is H and C _m H _{2 m + 1} (alkyl group). ) May be included. Among them, considering that ink leakage is suppressed and the writing performance is improved, X may have both H and _Cm H _{2m + 1} (alkyl group) in the molecule of the general formula (Chemical formula 1). Preferably, the intramolecular ratio of H and C _m H _{2 m + 1} (alkyl group) is preferably 0.1 ≦ H / C _m H _{2 m + 1} (alkyl group) ≦ 5, and more preferably 0.5. ≤H / C _m H _{2m + 1} (alkyl group) ≤2 is preferable.

The content of the cyclic phosphorus compound is preferably 0.1 to 10.0% by mass with respect to the total amount of the ink composition. This is because if it is less than 0.1% by mass, it is difficult to suppress ink leakage, and if it exceeds 10.0% by mass, the dissolution stability is likely to be affected and the writing performance is likely to be inferior. Further, in consideration of the above effect, 0.3 to 5.0% by mass is preferable, and if it exceeds 3.0% by mass, the writing performance is likely to be affected, so 0.3 to 3.0% by mass. % Is preferable.

The ink viscosity of the ink composition for writing utensils of the present invention is not particularly limited, but when the cyclic phosphorus compound of the general formula (Chemical Formula 1) is used, ^{the ink at 20 ° C. and a shear rate of 5 sec -1} (at rest). If the viscosity exceeds 15,000 mPa · s, the writing performance, writing taste, and ink following performance tend to be inferior ^{. Therefore, the ink viscosity at 20 ° C. and a shear rate of 5 sec -1} (at rest) is preferably 15,000 mPa · s or less. Furthermore, since it is easy to obtain a remarkable effect of suppressing ink leakage by using the cyclic phosphorus compound of the general formula (Chemical Formula 1), ^{the ink viscosity at 20 ° C. and a shear rate of 5 sec -1} (at rest) should be 3000 mPa · s or more. The ink viscosity is preferably 3000 to 15000 mPa · s because it is easy to suppress ink leakage at the writing tip (ink leakage from the gap between the ball and the tip) due to the coating film made of the cyclic phosphorus compound. Further, considering that the writing performance and the ink tracking performance are further improved, the ink viscosity is more preferably 3000 to 10000 mPa · s, and further, more preferably 5000 to 10000 mPa · s. Further, in a haunting type writing instrument such as a knock type writing instrument and a rotary feeding type writing instrument, since it is necessary to further consider the suppression of ink leakage, 5000 to 15000 mPa · s is preferable. Therefore, in order to improve writing performance, writing taste, ink following performance, and ink leakage suppression in a well-balanced manner, it is preferably set to 5000 to 10000 mPa · s.

(Colorant)
The colorant used in the present invention is not particularly limited to dyes, pigments and the like, and can be appropriately selected and used. The combined use of dyes and pigments is preferable because the following effects can be easily obtained.
Examples of dyes include oil-soluble dyes, acidic dyes, basic dyes, gold-containing dyes, and various salt-forming type dyes such as salt-forming dyes of acidic dyes and basic dyes, organic acids and basic dyes. Types such as salt-forming dyes with and salt-forming dyes with acidic dyes and organic amines can be mentioned. 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 time-dependent stability due to the compatibility with the cyclic phosphorus compound of the general formula (Chemical Formula 1), and further, the stable salt-forming bond makes it stable over time. Considering that the above can be maintained, it is preferable to use a salt-forming dye of a basic dye and an organic acid, a salt-forming dye of a basic dye with an acidic dye, and a salt-forming dye of an acidic dye and an organic amine. Considering this, salt-forming dyes of basic dyes and organic acids are preferable. Further, regarding the organic acid constituting the salt-forming dye, if it is an organic acid having a phenylsulfon group, it is easy to form a lubricating film that is easily adsorbed on the metal, the lubricity is improved, and the writing taste and the wear of the ball seat are suppressed. Specific examples thereof include alkylbenzene sulfonic acid, naphthalene sulfonic acid, naphthalene sulfonic acid-formaldehyde condensate, alkyldiphenyl ether disulfonic acid, and polyoxyethylene alkylphenyl ether phosphoric acid, which are stable in ink for a long period of time. In consideration of the above, it is preferable to use alkylbenzene sulfonic acid as the organic acid. Specifically, regarding the dyes, Bali First Black 1802, Bali First Black 1805, Bali First Black 1807, Bali First Violet 1701, Bali First Violet 1704, Bali First Violet 1705, Bali First Blue 1601, Bali First Blue 1605, Bali First Blue 1613, Bali First Blue 1621, Bali First Blue 1631, Bali First Red 1320, Bali First Red 1355, Bali First Red 1360, Bali First Yellow 1101, Bali First Yellow 1151, Nigrosin Base EXBP, Nigrosin Base EX, BASE OF BASIC DYES ROB-B, BASE OF BASIC DYES RO6GB, BASE OF BASIC DYES VPB-B, BASE OF BASIC DYES VB-B, BASE OF BASIC DYES MVB-3 (manufactured by Orient Chemical Industry Co., Ltd.), Eisenspiron Black GMH-Special, Eisenspiron Violet C-RH, Eisenspiron Blue GNH, Eisenspiron Blue 2BNH, Eisenspiron Blue C-RH, Eisenspiron Red C-GH, Eisenspiron Red C-BH, Eisenspiron Yellow C-GNH, Eisenspiron Yellow C-2GH, S.A. P. T. Blue 111, S.A. P. T. Blue GLSH-Special, S.M. P. T. Red 533, S.M. P. T. Orange 6, S.M. B. N. Violet 510, S.A. B. N. Yellow 530, S.A. R. C-BH (above, manufactured by Hodogaya Chemical Co., Ltd.) and the like can be mentioned.

Examples of pigments include inorganic, organic, and processed pigments. Specifically, carbon black, aniline black, ultramarine, yellow lead, titanium oxide, iron oxide, phthalocyanine, azo, quinacridone, and diketo Examples thereof include pyrrolopyrrole-based, quinophthalone-based, threne-based, triphenylmethane-based, perinone-based, perylene-based, dioxazine-based, metallic pigments, pearl pigments, fluorescent pigments, phosphorescent pigments and the like.

It is preferable to use a pigment as the colorant. In the case of a ballpoint pen, a pigment particle is used, which causes a physical obstacle in the gap between the ball and the inner wall of the tip tip to suppress ink leakage. This is because it is easy to do. Further, in the present invention, by using the polyglycerin fatty acid ester, a higher ink leakage suppressing effect can be obtained by forming a film on the tip of the writing and acting synergistically due to physical damage of the pigment. At the same time, a pigment dispersion effect can be obtained, which is preferable. Further, the pigment is preferable because it has excellent handwriting fastness and particularly excellent light resistance.
Furthermore, by using a pigment, in the case of a ballpoint pen, the pigment particles enter the gap between the ball and the tip body, which makes it easier for the action like a bearing to work, and by suppressing metal contact, the lubricity is improved. It is preferable to use a pigment because it is easy to obtain the effect of improving the writing quality and suppressing the wear of the ball seat. Further, the average secondary particle size is preferably 1 to 500 nm in consideration of the gap relationship inside the ballpoint pen tip. It is more preferably 10 to 350 nm, and even more preferably 50 to 300 nm. As in the present invention, it is preferable to use a pigment because the writing quality can be improved by lowering the viscosity of the ink by using a polyglycerin fatty acid ester.
Here, the average particle size is the particle size when the volume accumulation of 50% of the particle size distribution measured by the laser diffraction method using a laser diffraction type particle size distribution measuring machine (trade name "Microtrac HRA9320-X100", Nikkiso Co., Ltd.) ( It can be measured by D50).

As the type of pigment, considering lubricity, it is preferable to use from carbon black, quinacridone-based, slene-based, and diketopyrrolopyrrole-based pigments, and further, due to compatibility with time, ink stability with time is considered. Therefore, it is preferable to use a quinacridone-based pigment.

The content of the colorant is preferably 5.0 to 30.0% by mass with respect to the total amount of the ink composition. This is because if it is less than 5.0% by mass, it tends to be difficult to obtain a dark handwriting, and if it exceeds 30.0% by mass, it tends to affect the solubility in the ink. In consideration, it is preferably 7.0 to 25.0% by mass, and further considered, it is 10.0 to 25.0% by mass.

(Organic solvent)
Examples of the organic solvent used in the present invention include 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, and diethylene glycol dimethyl ether, 3. Glycol ether solvents such as −methoxybutanol, 3-methoxy-3-methylbutanol, glycol solvents such as diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, butylene glycol, ethylene glycol, benzyl alcohol, methanol, ethanol , 1-propanol, 2-propanol, isopropanol, isobutanol, t-butanol, propagyl alcohol, allyl alcohol, 3-methyl-1-butin-3-ol, ethylene glycol monomethyl ether acetate and other higher alcohols. Examples thereof include organic solvents generally used as inks for writing tools, such as alcohol solvents.

Among these organic solvents, considering the solubility with the cyclic phosphorus compound of the general formula (Chemical Formula 1), it is preferable to use a water-insoluble organic solvent to prepare an ink composition for writing instruments, and in particular, for writing instruments. It is preferable because it is easy to obtain the effect of suppressing ink leakage and improving the writing performance by stabilizing the dissolution of the oil-based ink composition.
Among them, it is preferable to use a glycol ether solvent. This is because when a glycol ether solvent is used, it easily absorbs moisture, so that the strength of the film formed when the tip of the chip dries is softened and the writing performance is easily improved. Considering the effectiveness and stability in the ink, it is preferable to use an aromatic glycol ether solvent. Further, as an organic solvent other than the glycol ether solvent, it is preferable to use an alcohol solvent, but this is because the alcohol solvent volatilizes and is easily dried at the tip of the chip, and the cyclic of the general formula (Chemical Formula 1). By containing a phosphorus compound, the inside of the writing tip (inside the tip) is thickened more quickly, thereby suppressing ink leakage from the gap between the writing tips (ink leakage from the gap between the ball and the tip). This is preferable because it improves the ink leakage suppression performance. Further, aromatic alcohols such as benzyl alcohol also have an effect of improving lubricity, and therefore it is preferable to use at least.

Regarding the organic solvent, when the content of the alcohol solvent with respect to the total amount of the ink composition is X and the content of the glycol ether solvent with respect to the total amount of the ink composition is Y, the relationship is 0.01 ≦ X / Y ≦ 3. Is preferable. This is preferably X / Y ≦ 3 because too much alcohol solvent tends to affect the writing performance, while too much glycol ether solvent absorbs too much water and the resin film becomes soft and the ink This is because 0.01 ≦ X / Y is preferable because it easily affects the hanging performance and the stability of the ink over time. Further, considering that the writing performance is improved by the synergistic effect of the polyglycerin fatty acid ester and the phosphoric acid ester-based surfactant used in the present invention, 0.1 ≦ X / Y ≦ 2 is preferable, and the writing performance is further improved. In consideration, 0.1 ≦ X / Y ≦ 1 is preferable.

The content of the organic solvent is preferably 10.0 to 90.0% by mass, and is dried at the tip of the chip, in consideration of improving solubility, handwriting drying property, bleeding, and the like. Considering the property, it is preferably 20.0 to 90.0% by mass, more preferably 40.0 to 70.0% by mass.

(resin)
Further, in order to further improve the suppression of ink leakage, it is preferable to use a resin as an ink viscosity modifier. As the resin, polyvinyl butyral resin, ketone resin, polyacetal resin, polyvinyl alcohol resin, cellulose resin, terpene resin, etc. Examples thereof include alkyd resin, phenoxy resin, and polyvinyl acetate resin, and among them, polyvinyl butyral resin or ketone resin is preferably contained. This is because the ink leakage suppressing effect is more likely to be improved. In particular, the ketone resin synergistically achieves a higher ink leakage suppressing effect by using the cyclic phosphorus compound of the general formula (Chemical Formula 1) in combination with the ketone resin. This is because it can be expected to have an effect of suppressing crying.
In particular, when the ball diameter is made larger than usual to 1.0 mm to 2.0 mm, the amount of ink ejected becomes large, and crying and sticking due to excess ink are likely to occur at the tip of the chip, and a ketone resin is used. As a result, it is easy to suppress crying and sticking by suppressing the ink from rising, so that it is preferable, and when it is set to 1.2 mm to 2.0 mm, it is more effective. Furthermore, considering the suppression of crying and botting, among the ketone resins, among the ketone resins, an aromatic ring skeleton (having a benzene ring such as a phenyl group, an acetophenone group, and a naphthalene group) and a cyclohexane skeleton (having a cyclohexane ring such as a cyclohexane group and a cyclohexanone group), etc. It is preferable to use a ketone resin having the cyclic structure of.

Further, considering the effect of suppressing ink leakage and improving the writing quality, it is most preferable to use polyvinyl butyral resin. This is because when the cyclic phosphorus compound and the polyvinyl butyral resin are used in combination, the film formed makes it easier to improve ink leakage, and the polyvinyl butyral resin always has elasticity between the balls and the ball seat. This is because a certain ink layer is formed to make it difficult to make direct contact with the ink layer, so that the writing quality can be improved. When a pigment is used as the colorant, a polyvinyl butyral resin is preferably used because a pigment dispersion effect can be obtained. In particular, when the cyclic phosphorus compound used in the present invention is used in combination with a polyvinyl butyral resin, a higher ink leakage suppressing effect can be obtained, which is more preferable.
Here, the polyvinyl butyral resin is obtained by reacting polyvinyl alcohol (PVA) with butyraldehyde (BA), and has a structure having a butyral group, an acetyl group, and a hydroxyl group.
In particular, when the ball diameter is made larger than usual to 1.0 mm to 2.0 mm, the influence of ink leakage is likely to occur from the gap between the ballpoint pen tip body and the ball, so it is effective to use polyvinyl butyral resin. Therefore, it is more effective when the cyclic phosphorus compound used in the present invention and the polyvinyl butyral resin are used in combination, and particularly when the thickness is 1.2 mm to 2.0 mm.

The polyvinyl butyral resin preferably has a hydroxyl group content of 25 mol% or more. This is because polyvinyl butyral resin with a hydroxyl group content of less than 25 mol does not have sufficient solubility in an organic solvent, and it is difficult to obtain a sufficient lubricating effect and an effect of suppressing ink leakage. Further, considering the writing performance due to hygroscopicity, This is because it is preferable to use a polyvinyl butyral resin having a hydroxyl group content of 25 mol% or more. Further, the polyvinyl butyral resin having a hydroxyl group content of 30 mol% or more is preferable because the writing quality is easily improved. This is because frictional heat is generated by the rotation of the ball during writing, which warms the ink at the tip of the chip and raises the temperature of the ink, but the polyvinyl butyral resin is different from other resins. Even if the ink temperature rises, it has the property of making it difficult for the ink viscosity to decrease, and an elastic ink layer is always formed between the ball and the ball seat to make it difficult to make direct contact, improving the writing quality. It tends to be easy. In particular, ballpoint pens are effective with writing instruments because they often write with high writing pressure. Further, when a polyvinyl butyral resin having a hydroxyl group content of more than 40 mol% is used, the amount of moisture absorbed tends to increase and the stability with time with the ink component tends to be affected. Therefore, a polyvinyl butyral resin having a hydroxyl group content of 40 mol% or less is preferable. Therefore, a polyvinyl butyral resin having a hydroxyl group content of 30 to 40 mol% is preferable, and a hydroxyl group content of 30 to 36 mol% is more preferable.
The amount of hydroxyl groups (mol%) of the polyvinyl butyral resin is the content of hydroxyl groups (mol%) with respect to the total amount of mol of butyral groups (mol%), acetyl groups (mol%), and hydroxyl groups (mol%). It shows the rate.

Regarding the average degree of polymerization of the polyvinyl butyral resin, when the average degree of polymerization is 200 or more, the ink leakage suppression performance is likely to be improved, and when the average degree of polymerization exceeds 2500, the ink viscosity becomes too high. The average degree of polymerization is preferably 200 to 2500 because it tends to affect the writing taste. Further, considering 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 constituting one molecule of polyvinyl butyral resin, and a value measured based on the method specified in JIS K6728 (2001 version) can be adopted. ..

Specifically, the polyvinyl butyral resin is a trade name manufactured by Sekisui Chemical Industry Co., Ltd .; Eslek BH-3 (hydroxyl amount: 34 mol%, average degree of polymerization: 1700), BH-6 (hydroxyl amount: 30 mol%). , Average degree of polymerization: 1300), BX-1 (hydroxyl amount: 33 ± 3 mol%, average degree of polymerization: 1700), BX-5 (hydroxyl amount: 33 ± 3 mol%, average degree of polymerization: 2400), BM -1 (Amount of hydroxyl groups: 34 mol%, average degree of polymerization: 650), BM-2 (Amount of hydroxyl groups: 31 mol%, average degree of polymerization: 800), BM-5 (Amount of hydroxyl groups: 34 mol%, average degree of polymerization: 850) ), BL-1 (Amount of hydroxyl groups: 36 mol%, average degree of polymerization: 300), BL-1H (Amount of hydroxyl groups: 30 mol%), BL-2 (Amount of hydroxyl groups: 36 mol%, average degree of polymerization: 450), BL-2H (hydroxyl amount: 29 mol%), BL-10 (hydroxyl amount: 28 mol%), etc., and trade name manufactured by Kuraray Co., Ltd .; Mobital B20H (hydroxyl amount: 26 to 31 mol%, average degree of polymerization: 250-500), B30T (amount of hydroxyl groups: 33-38 mol%, average degree of polymerization: 400-650), B30H (amount of hydroxyl groups: 26-31 mol%, average degree of polymerization: 400-650), B30HH (amount of hydroxyl groups) : 30-34 mol%, average degree of polymerization: 400-650), B45H (hydroxyl amount: 26-31 mol%, average degree of polymerization: 600-850), B60T (hydroxyl amount: 34-38 mol%, average degree of polymerization: 750 to 1000), B60H (amount of hydroxyl groups: 26 to 31 mol%, average degree of polymerization: 750 to 1000), B75H (amount of hydroxyl groups: 26 to 31 mol%, average degree of polymerization: 1500 to 1750) and the like. These may be used alone or in mixture of 2 or more types.

If the total content of the resin is less than 1.0% by mass with respect to the total amount of the ink composition, the amount of resin film formed may be insufficient, and the ink leakage suppression performance tends to be inferior, exceeding 40.0% by mass. Since the solubility in the ink tends to be inferior, 1.0 to 40.0% by mass is preferable with respect to the total amount of the ink composition. Further, considering the ink leakage suppression performance, 5.0% by mass or more is preferable, and if it exceeds 30.0% by mass, the ink viscosity tends to be too high and the writing taste and writing performance tend to be affected. 0 to 30.0% by mass is preferable.

As the resin other than the polyvinyl butyral resin and the ketone resin, a spinnability imparting agent may be appropriately used. In particular, it is preferable to contain the polyvinylpyrrolidone resin because the binding property of the ink is enhanced and the generation of excess ink at the tip of the chip is easily suppressed by blending the polyvinylpyrrolidone resin. If the content of the polyvinylpyrrolidone resin is less than 0.01% by mass with respect to the total amount of the ink composition, it tends to be difficult to suppress the generation of excess ink. Therefore, if it exceeds 3.0% by mass, it is contained in the ink. Since the solubility tends to be inferior, 0.01 to 3.0% by mass is preferable with respect to the total amount of the ink composition. Considering the above reasons, 0.1 to 2.0% by mass is preferable. Specific examples thereof include trade names manufactured by ASP Japan Co., Ltd .; PVP K-15, PVP K-30, PVP K-90, PVP K-120 and the like. These may be used alone or in mixture of 2 or more types.

(Surfactant)
In the present invention, it is preferable to use a phosphoric acid ester-based surfactant or a fatty acid in consideration of improving the writing performance. This is because the use of phosphate ester surfactants or fatty acids tends to soften the film formed and may improve writing performance. Among them, the number of carbon atoms contained in the alkyl group of the phosphoric acid ester-based surfactant or fatty acid is preferably 10 to 20, and more preferably, the number of carbon atoms is 12 to 18. Further, considering the lubricity (high load performance) under a high writing pressure (300 to 500 gf), it is preferable to use a phosphate ester-based surfactant, which is a high writing pressure (300) in the case of a ballpoint pen. Even at ~ 500 gf), the lubricity between the ball and the chip body is improved, the wear of the ball seat is suppressed, and it is easy to obtain a good handwriting without blurring, so that it can be used more preferably in the present invention. is there.

Examples of the phosphoric acid ester-based surfactant include a phosphoric acid monoester of a polyoxyethylene alkyl ether or a polyoxyethylene alkylaryl ether, a phosphoric acid diester of a polyoxyethylene alkyl ether or a polyoxyethylene alkyl aryl ether, and a polyoxyethylene alkyl ether. Alternatively, a phosphoric acid triester of a polyoxyethylene alkylaryl ether, an alkyl phosphoric acid ester, an alkyl ether phosphoric acid ester or a derivative thereof and the like can be mentioned, and the alkyl group of the phosphoric acid ester-based surfactant is a styrene phenol-based or nonylphenol. Examples include systems, lauryl alcohol-based, tridecyl alcohol-based, and octylphenol-based. Examples of the fatty acid include oleic acid, stearic acid, linoleic acid and the like, and these phosphoric acid ester-based surfactants or fatty acids may be used alone or in combination of two or more. Among them, in consideration of lubricity (high load performance) under high writing pressure (300 to 500 gf), it is preferable to use a phosphoric acid ester-based surfactant, and in particular, the number of carbon atoms contained in the alkyl group is 5 to 5. It is preferably 18, and if further considered, the number of carbon atoms is more preferably 10 to 18, and more preferably, the number of carbon atoms is 12 to 18. It should be noted that if the number of carbon atoms of the alkyl group is excessively small, the lubricity tends to be insufficient, and if the number of carbon atoms is excessively large, the stability of the ink with time tends to be affected.
Further, the acid value of the phosphoric acid ester-based surfactant is preferably 200 or less, which is the lubricity (high load performance) of the phosphoric acid ester-based surfactant under high writing pressure (300 to 500 gf). The acid value is preferably 30 to 200, and more preferably 70 to 200, in consideration of stability in ink and lubricity.
The acid value is expressed in mg of potassium hydroxide required to neutralize the acidic component contained in 1 g of the sample.

The content of the phosphoric acid ester-based surfactant is more preferably 0.1 to 5.0% by mass with respect to 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. In consideration of the above, 0.3 to 3.0% by mass is preferable with respect to the total amount of the ink composition, and more consideration is given, 0.5 to 3.0% by mass is most preferable.

Specific examples of the phosphoric acid ester-based surfactant include Plysurf A217E (alkyl group: 14 carbon atoms, acid value: 45 to 58) and A219B from the Plysurf series (Daiichi Kogyo Seiyaku Co., Ltd.). (Alkyl group: 12 carbon atoms, acid value: 44 to 58), A215C (alkyl group: 12 carbon atoms, acid value: 80 to 95), A208B (alkyl group: 12 carbon atoms, acid value: 135 to 155) ), A208N (alkyl group: mixture of 12 and 13 carbon atoms, acid value: 160 to 185), phospanol series (manufactured by Toho Kagaku Kogyo Co., Ltd.), phospanol RB-410 (alkyl group) : 18 carbon atoms, acid value: 80-90), RS-610 (alkyl group: 13 carbon atoms, acid value: 75-90), RS-710 (alkyl group: 13 carbon atoms, acid value: 55- 75) and the like. These surfactants may be used alone or in combination of two or more.

(Organic amine)
In the present invention, it is preferable to use an organic amine in consideration of the stability of the ink component in the ink. Amines having ethylene oxide such as oxyethylenealkylamine and polyoxyethylenealkylamine, alkylamines such as laurylamine and stearylamine, dimethylalkylamines such as distearylamine, dimethyllaurylamine, dimethylstearylamine and dimethyloctylamine, etc. Among them, amines having ethylene oxide and dimethylalkylamines are preferable in consideration of stability in ink. In particular, when a phosphoric acid ester-based surfactant is used, it is preferable because it is neutralized and stabilized in the ink, so that the effect of improving the writing performance and the writing taste can be easily obtained.

Regarding the reactivity of the organic amine with other components in the ink, the primary amine is the strongest, followed by the secondary amine and the tertiary amine, and the reactivity is smaller. It is preferable to use a secondary amine or a tertiary amine. These may be used alone or in mixture of 2 or more types.

Specific examples of organic amines include oxyethylene alkylamines, and specific examples of polyoxyethylene alkylamines include nymine L-201 (total amine value: 232-246, secondary amines) and L-202. (Total amine value: 192 to 212, tertiary amine), L-207 (total amine value: 107 to 119, tertiary amine), S-202 (total amine value: 152 to 166, tertiary amine), S-204 (total amine value: 120 to 134, tertiary amine), S-210 (total amine value: 75 to 85, tertiary amine), DT-203 (total amine value: 227 to 247, 3, Grade amines), DT-208 (total amine value: 146 to 180, tertiary amines) (manufactured by Nippon Oil & Fats Co., Ltd.) and the like. Specific examples of the alkylamine include fermin 80 (total amine value: 204 to 210, primary amine), fermin D86 (total amine value: 110-119, secondary amine), and fermin DM2098 (total amine value: 254). ~ 265, tertiary amine), Farmin DM8680 (total amine value: 186 to 197, tertiary amine) (Kao Co., Ltd.), Nissan tertiary amine BB (total amine value: 243-263, tertiary amine), same FB (total amine value: 230 to 250, tertiary amine) (manufactured by Nippon Oil & Fats Co., Ltd.) and the like can be mentioned. These may be used alone or in mixture of 2 or more types.

The content of the organic amine is preferably 0.1 to 10.0% by mass with respect to the total amount of the ink composition in consideration of the stability with the salt-forming dye and other components, and the phosphoric acid described later. Considering neutralization with respect to the ester-based surfactant, 0.2 to 5.0% by mass is preferable.

Further, in the present invention, it is preferable that the polyglycerin fatty acid ester is contained, which means that the polyglycerin fatty acid ester forms a three-dimensional structure in the ink, so that the ink viscosity at rest can be set high. By suppressing the flow of ink, ink is prevented from seeping out from the gap between the ball and the tip of the tip, and by forming a film when the tip of the writing is dried, ink leaks from the gap between the tip of the writing (ball and tip). This is because it is easy to suppress ink leakage from the gap at the tip. In particular, the combined use of the cyclic phosphorus compound of the general formula (Chemical Formula 1) and the polyglycerin fatty acid ester is effective because it is easy to synergistically suppress ink leakage. In particular, in a haunting type writing instrument such as a knock type writing instrument and a rotary feeding type writing instrument, it is necessary to consider ink leakage suppression more, which is preferable.
Furthermore, the polyglycerin fatty acid ester can improve the writing performance by softening the film formed when the writing tip is dried, and can be written out by using it in combination with a cyclic phosphorus compound such as the general formula (Chemical formula 1). It is preferable because the performance is easily improved. Further, when a pigment is used as the colorant, it can be preferably used because a pigment dispersion effect can be obtained.

（式１）分子量＝７４ｍ＋１８
（式２）水酸基価＝５６１１０（ｍ＋２）／分子量

上記（式２）中の水酸基価とは、ポリグリセリンに含まれる水酸基数の大小の指標となる数値であり、１ｇのポリグリセリンに含まれる遊離ヒドロキシル基をアセチル化するために必要な酢酸を中和するのに要する水酸化カリウムのミリグラム数をいう。水酸化カリウムのミリグラム数は、社団法人日本油化学会編纂、「日本油化学会制定、基準油脂分析試験法（１）、１９９６年度版」に準じて算出される。 The polyglycerin fatty acid ester used in the present invention is represented by the following general formula (Chemical Formula 2). Regarding the average degree of polymerization (m) of polyglycerin constituting the polyglycerin fatty acid ester, considering that ink leakage is suppressed and the writing performance is improved, the average degree of polymerization is 10 or less and the molecular weight does not increase. The average degree of polymerization (m) is preferably in the range of 1 to 10, and the average degree of polymerization (m) is 4 to 10 in consideration of softening the film formed when the writing tip is dried. The range of 10 is preferable, and more consideration is given, the average degree of polymerization (m) is preferably in the range of 4 to 6. Examples of such polyglycerin fatty acid esters having an average degree of polymerization in the range of 1 to 10 include diglycerin fatty acid ester (average degree of polymerization (m): 2) and tetraglycerin fatty acid ester (average degree of polymerization (m): 4). ), Hexaglycerin fatty acid ester (average degree of polymerization (m): 6), decaglycerin fatty acid ester (average degree of polymerization (m): 10).
Here, the average degree of polymerization (m) is the average degree of polymerization (m) of polyglycerin calculated from the hydroxyl value by the end group analysis method. Specifically, the average degree of polymerization is calculated from the following equations (Equation 1) and (Equation 2).

(Formula 1) Molecular weight = 74m + 18
(Equation 2) Hydroxyl value = 56110 (m + 2) / molecular weight

The hydroxyl value in the above (formula 2) is a numerical value that is an index of the number of hydroxyl groups contained in polyglycerin, and contains acetic acid required for acetylating the free hydroxyl group contained in 1 g of polyglycerin. The number of milligrams of potassium hydroxide required for summing. The number of milligrams of potassium hydroxide is calculated according to the compilation of the Japan Oil Chemists'Association, "Established by the Japan Oil Chemists' Society, Standard Oil and Fat Analysis Test Method (1), 1996 Edition".

The fatty acid (fatty acid residue) constituting the polyglycerin fatty acid ester is selected from fatty acids having 8 to 22 carbon atoms. By forming a three-dimensional structure in the ink and increasing the viscosity of the ink at rest, the fatty acid is increased. The number of carbon atoms is preferably 14 to 20 in consideration of ink leakage suppression and writing performance, and more preferably 18 carbon atoms. Examples of such fatty acids having 8 to 22 carbon atoms include stearic acid, oleic acid, lauric acid, mistylic acid, caprylic acid, behenic acid, erucic acid, linoleic acid, condensed linoleic acid, and the like. It may be used in combination of two or more types depending on the purpose.

Among the fatty acids (fatty acid residues) constituting the polyglycerin fatty acid ester, by using stearic acid as the constituent fatty acid, a structure having a crystal structure is obtained, and the crystal structure is arranged to have a thickening effect due to a stable crystal structure. Because of the above, a more stable effect of suppressing ink leakage can be obtained, and due to the more stable crystal structure, the formed film when the writing tip is dried is easily softened, and the writing performance is easily improved. It is preferably ester.

The HLB value of the polyglycerin fatty acid ester is preferably in the range of 4 to 14 in consideration of facilitating improvement of writing performance by forming a film when the writing tip is dried. This is because if the HLB value is less than 4, it is difficult to dissolve and stabilize in an organic solvent, and if the HLB value exceeds 14, the hydrophilicity is strong and moisture absorption into the ink is likely to occur. Therefore, the HLB value is 4. If it is out of the range of ~ 14, the stability over time of the ink is likely to be affected, and the effect of the present invention is difficult to obtain. Considering the above effects, the HLB value is preferably in the range of 4 to 12, and further considering, the HLB value is preferably in the range of 7 to 12.

Further, in the ink composition for writing utensils according to the present invention, as other additives, in order to improve the lubricity and the stability of the ink with time, (i) a surfactant, for example, a fluorine-based surfactant or a silicone-based surfactant. Agents, fatty acid alkanolamides, anionic surfactants, cationic surfactants, amphoteric surfactants, and salt-forming compounds of anionic surfactants and / or cationic surfactants, (ii). Pseudoplasticizing agents such as viscosity modifiers such as fatty acid amide, hydrogenated castor oil, and water as (iii) colorant stabilizers, (iv) plasticizers, (v) chelating agents, or (vi) auxiliary solvents. Etc. may be used as appropriate. These may be used alone or in combination of two or more.

Further, in the case of using a ballpoint pen in the present invention, the amount of movement of the ball of the ballpoint pen tip in the vertical axis direction is not particularly limited, but if the amount of movement of the ball in the vertical axis direction is large, the movement amount of the ballpoint pen tip body and the ball Ink leakage is likely to occur, and the writing performance is likely to be inferior when the writing tip is dried. Therefore, when the amount of movement of the ball in the vertical axis direction is made larger than usual to 10 μm or more, the amount of ink ejected is large. Therefore, the effect is likely to occur, and it is effective to use the cyclic phosphorus compound used in the present invention, and it is particularly remarkable and more effective when the thickness is 12 μm or more. On the other hand, if the amount of movement of the ball in the vertical axis direction exceeds 30 μm and is too large, ink leakage suppression tends to be inferior. Therefore, 30 μm or less is preferable, and more consideration is given, 25 μm or less is preferable.

The arithmetic average roughness (Ra) of the ball surface of the ballpoint pen tip used in the present invention is preferably 0.1 to 12 nm. This is because if the arithmetic mean roughness (Ra) is less than 0.1 nm, it is difficult for ink to be sufficiently applied to the ball surface, it is difficult to obtain a dark handwriting when writing, and lines are likely to be skipped and blurring is likely to occur in the handwriting. When the roughness (Ra) exceeds 12 nm, the surface of the ball is too rough and the rotation resistance between the ball and the ball seat is large, so that the writing quality tends to be inferior. This is because it is easy to affect. Further, when the arithmetic mean roughness (Ra) is 0.1 to 10 nm, the ink is likely to be placed on the ball surface, which is more preferable, and more preferably 2 to 8 nm. The surface roughness can be measured by (model name SPI3800N manufactured by Seiko Epson Corporation).

The material used for the balls is not particularly limited, but is limited to cemented carbide balls containing tungsten carbide as a main component, metal balls such as stainless steel, and ceramics such as silicon carbide, silicon nitride, alumina, silica, and zirconia. Examples include balls and ruby balls.
The diameter of the ball is not particularly limited, but if the diameter of the ball is large, ink tends to leak from the gap between the ballpoint pen tip body and the ball, and the writing performance tends to be inferior when the writing tip is dried. When the diameter is 1.0 mm to 2.0 mm, which is larger than usual, the effect is likely to occur, and it is effective to use the cyclic phosphorus compound used in the present invention, especially when the diameter is 1.2 mm to 2.0 mm. Is noticeable and more effective.

The ink consumption per 100 m is preferably 10 to 120 mg. This is because if the ink consumption per 100 m is less than 10 mg, it is difficult to obtain dark handwriting and good writing quality, and if the ink consumption per 100 m exceeds 120 mg, ink leaks from the gap between the ball and the tip of the chip. This is because writing performance and crying are likely to occur.
When the ball diameter is made larger than usual to 1.0 to 2.0 mm, as described above, 100 m in consideration of dark handwriting, ink leakage suppression, writing taste, writing performance, crying bottom, etc. The amount of ink consumed per ink is preferably 20 to 110 mg, and more preferably 30 to 100 mg when the ball diameter is 1.2 to 1.6 mm.
Regarding the amount of ink consumed, a spiral was used at a writing speed of 4 m / min under the conditions of 20 ° C., writing paper JIS P3201 writing paper, writing angle 70 °, and writing load 200 g. A written test is performed, and the average value of the ink consumption per 100 m is defined as the ink consumption per 100 m.

The material of the ball pen tip includes metal materials such as stainless steel, nickel silver, brass (brass), aluminum bronze and aluminum, and resin materials such as polycarbonate, polyacetal and ABS. A nickel silver chip body is preferable in consideration of properties, and a stainless steel chip body is preferable in consideration of wear of the ball seat and stability over time.

Example 1
The ink composition for writing utensils of Example 1 has dyes and pigments as colorants, benzyl alcohol as organic solvents, ethylene glycol monophenyl ethers, cyclic phosphorus compounds, ketone resins, fatty acids as surfactants, and oxyethylene alkyl amines as organic amines. Polyvinylpyrrolidone was adopted as a spinnability-imparting agent, weighed a predetermined amount, heated to 60 ° C., and then completely dissolved using a disper stirrer to obtain an ink composition for writing utensils. The specific blending amount is as follows. When the ink viscosity of Example 1 was measured using a viscometer Viscometer RVDVII + Pro CP-52 spindle manufactured by Brookfield Co., Ltd., the shear rate was 5 sec ^-1 and the ink viscosity was 3500 mPa · s in an environment of 20 ° C. Met.

Example 1 (ink blending)
Colorant (dye, salt-forming dye with organic acid basic dye) 5.0% by mass
Colorant (dye, acid dye and amine salt-forming dye) 5.0% by mass
Colorant (pigment dispersion, pigment red) 20.0% by mass
Organic solvent (benzyl alcohol) 5.3% by mass
Organic solvent (ethylene glycol monophenyl ether) 40.0% by mass
Cyclic phosphorus compound (with X = H, CH ₃ ) 2.5% by mass
Surfactant (fatty acid oleic acid) 1.5% by mass
Organic amine (oxyethylene alkylamine) 0.5% by mass
Ketone resin 20.0% by mass
Spinning property imparting agent (polyvinylpyrrolidone resin) 0.2% by mass

Examples 2-13
As shown in Table 1, ink compositions for writing instruments of Ink Dispensing Examples 2 to 13 were obtained in the same procedure as in Example 1 except that the ink components and chip specifications were changed. The measurement and evaluation results are shown in the table.

Comparative Examples 1 to 3
As shown in the table, the ink compositions for writing instruments of Comparative Examples 1 to 3 were obtained in the same procedure as in Example 1 except that the ink components and the chip specifications were changed. The measurement and evaluation results are shown in the table.

Test and Evaluation The writing instrument ink composition (0.27 g) prepared in Examples 1 to 13 and Comparative Examples 1 to 3 is rotatably held in an ink containing cylinder (polypropylene) with a ball diameter of φ1.2 mm. A writing instrument was prepared by filling a refill for a writing instrument equipped with a ballpoint pen tip (movement amount of the ball in the vertical axis direction of 12 μm). The following tests and evaluations were carried out using the writing paper JIS P3201 as the writing test paper.
The ink consumption per 100 m of Example 1 was 45 mg / 100 m when a spiral writing test was performed with an oil-based ballpoint pen.

Ink leakage suppression test: The pen tip was left facing downward for 7 days in an environment of 30 ° C. and 85% RH, and ink leakage from the tip tip was confirmed.
No ink droplets on the tip tip ・ ・ ・ ◎
Ink droplets on the tip of the chip are within 1/4 of the taper part ... ○
Ink droplets on the tip of the chip are 1/4 or more and 1/2 or less of the tapered part ... △
Ink droplets on the tip of the chip are more than 1/2 of the taper part ... ×

Writing performance test: After writing by hand, leave the tip in an environment of 20 ° C and 65% RH for 24 hours, then write in the running test under the following writing conditions, and the length of the handwriting blur in writing. Was measured.
<Writing conditions> Under the conditions of a writing load of 200 gf, a writing angle of 70 °, and a writing speed of 4 m / min, straight-line writing was performed with a running tester and evaluated.
The length of the handwriting blur is less than 8 mm ... ◎◎
Handwriting cassoulet length is less than 15 mm ... ◎
The length of the handwriting blur is 15 mm or more and less than 20 mm ... ○
The length of the handwriting blur is 20 mm or more and less than 40 mm ... △
Handwriting cassoulet length of 40 mm or more ... ×

Crying / body test: Handwritten and evaluated.
Things with no or little crying / bottom ... ◎
There is crying and sickness, but there is no problem in practical use ... ○
Those with severe crying and sickness that pose a problem in practice ... ×

In Examples 1 to 13, good performances were obtained in all of the ink leakage suppression test, writing performance, writing taste, and crying / bottoming test. Further, when the inks using the pigment as the colorant in Examples 1 to 13 were observed under a microscope, the pigment dispersibility was good and there were no precipitates.

In Comparative Examples 1 and 2, since the cyclic phosphorus compound was not used, the ink leakage suppressing performance and the writing performance were inferior.

In Comparative Example 3, the fatty acid amide wax was added as a shear thinning agent to increase the ink viscosity, but since the cyclic phosphorus compound was not used, the ink leakage suppressing performance and the writing performance were inferior.

In addition, when using a spill-type writing instrument (striking-type ballpoint pen) such as a knock-type writing instrument or a rotary feeding-type writing instrument, ink leakage suppression performance is one of the most important performances. Ink composition for writing instruments containing a cyclic phosphorus compound as in the present invention, which can suppress ink leakage (ink leakage from the gap between the ball and the tip of the tip) from the gap of the ink leakage suppression performance. It is effective to use things.

As in the present invention, in order to suppress ink leakage and improve writing performance, a ball rotatably held at the tip of a ballpoint pen tip is pressed against the inner wall of the tip edge of the tip directly by a coil spring or via a pressing body. Therefore, it is preferable to provide a valve mechanism that gives a gap between the inner wall of the tip edge of the chip and the ball by the pressing force at the time of writing to allow ink to flow out, and closes even a minute gap at the tip of the tip when not in use.

Further, in the present embodiment, for convenience, a writing tool in which a writing tool refill in which the writing tool ink composition is directly stored is illustrated is illustrated, but in the writing tool of the present invention, the shaft cylinder is contained in the ink housing cylinder. It may be a direct-packed ballpoint pen or a writing tool in which the ink composition for a writing tool is directly stored in the barrel. Further, in this embodiment, for convenience, a ballpoint pen tip formed by cutting a wire rod is illustrated, but a ballpoint pen tip formed by pressing a pipe material may be used.

Further, in the present embodiment, a writing tool in which a ballpoint pen refill containing an ink composition for a writing tool is arranged in a shaft cylinder is illustrated, but in the writing tool of the present invention, the shaft cylinder itself is used as an ink storage cylinder. , A direct-packed writing tool in which the ink composition for writing tools is directly stored in the shaft cylinder may be used, and a ballpoint pen containing the ink composition for writing tools in the ink storage cylinder (ballpoint pen refill) is used as it is. The structure may be the same.

The present invention can be used as a writing instrument, and more specifically, it can be widely used as a writing instrument such as a cap type or a haunting type or a ballpoint pen.

Claims (6)

Colorants, organic solvents, comprises a cyclic phosphorus compound, wherein the cyclic phosphorus compound represented by the following general formula (Formula 1) der is, weight average molecular weight, the ink composition for a writing instrument, characterized in that it is 2000 or less.

The ink composition for writing instruments according to claim 1, wherein the content of the cyclic phosphorus compound is 0.1 to 10.0% by mass with respect to the total amount of the ink composition. The ink composition for writing instruments according to claim 1 or 2, wherein the ink composition for writing instruments contains a polyvinyl butyral resin or a ketone resin. The ink composition for a writing instrument according to any one of claims 1 to 3 , wherein the ink viscosity at 20 ° C. and a shear rate of 5 sec ^-1 is 15,000 mPa · s or less. A writing instrument comprising the ink composition for a writing instrument according to any one of claims 1 to 4. A ballpoint pen tip that rotatably holds a ball is provided at the tip of the ink accommodating cylinder, and the ink composition for writing instruments according to any one of claims 1 to 4 is accommodated in the ink accommodating cylinder. An oil-based ballpoint pen characterized by becoming.