Oil-based ballpoint pen ink composition and oil-based ballpoint pen using the same

Abstract

[Problem] The present invention addresses the problem of providing: an ink composition for an oil-based ballpoint pen, said ink composition improving writability and suppression of wear of a ball seat under a high writing pressure (writing load of 300-500 gf) and having good writing performance, temporal stability, and ink followability; and an oil-based ballpoint pen using said ink composition. [Solution] This ink composition for an oil-based ballpoint pen is characterized by containing a colorant, an organic solvent, and polyoxyalkylene glyceryl ether.

Description

Technical Field

[0001] The present invention relates to an ink composition for an oil-based ballpoint pen and an oil-based ballpoint pen using the same.

Background Art

[0002] A ballpoint pen is likely to affect the writing feel of the ballpoint pen due to writing resistance between the writing tip and the writing surface during writing. It has a configuration in which a ballpoint pen tip composed of a metal tip made of stainless steel or the like and a transfer ball made of a metal such as super steel held in the ball socket of the metal tip is attached to an ink storage cylinder. However, due to the rotation of the ball during writing, wear occurs in the ball socket, resulting in drawbacks such as skipping lines and streaks in the handwriting and inferior writing feel. Furthermore, when a new lubricant is used, there is also compatibility with other ink components, and it is likely to affect the stability of the ink composition over time. Also, when the tip of the tip is left exposed to the atmosphere, when the solvent in the ink evaporates and the colorant, resin, etc. dry and solidify, streaks are likely to occur during writing.

[0003] In order to solve such problems, in order to suppress the writing resistance between the writing tip and the writing surface during writing, many ink compositions for oil-based ballpoint pens using various lubricants have been proposed for the purpose of improving lubricity and the like.

[0004] Oil-based ballpoint pen ink compositions using such additives are disclosed in Patent Document 1, "Oil-based ballpoint pen ink," which uses alkyl β-D-glucoside; in Patent Document 2, "Oil-based ballpoint pen ink composition," which uses polyethylene glycol with an average molecular weight of 200 to 4,000,000; in Patent Document 3, "Oil-based ballpoint pen ink," which uses N-acyl amino acids, N-acylmethyl tauric acid, and N-acylmethylalanine; and in Patent Document 4, "Oil-based ballpoint pen ink composition," which contains at least deca-macadamia nut oil fatty acid decaglyceryl and polyoxyethylene alkyl ether with 16 or more carbon atoms in the alkyl group and solid at room temperature. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 5-331403 [Patent Document 2] Japanese Patent Application Publication No. 7-196971 [Patent Document 3] Japanese Patent Publication No. 2007-176995 [Patent Document 4] Japanese Patent Publication No. 2008-88264 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, while using various additives such as those described in Patent Documents 1-4 can reduce writing resistance between the writing tip and the writing surface to some extent, it is not satisfactory, and there is room for improvement.

[0007] Furthermore, in recent years, in order to improve the writing feel of oil-based ballpoint pen inks, the viscosity of the ink has been reduced. However, when writing with high pressure (high pressure resistance writing, writing load 300-500 gf), this can easily affect lubrication, leading to increased wear on the ball bearing and thus impacting writing performance. Therefore, there is a need to further improve lubrication and resistance to high pressure writing in order to reduce writing resistance between the pen tip and the writing surface.

[0008] Furthermore, in the case of retractable ballpoint pens such as click-type or twist-type ballpoint pens, the tip of the pen tip is important because leaving it exposed to the air can easily affect its writing performance.

[0009] Therefore, it is necessary to satisfy both lubricity under high writing pressure (writing load of 300-500 gf) and writing performance at the start of writing.

[0010] The object of the present invention is to provide an oil-based ballpoint pen ink composition and an oil-based ballpoint pen using the same, which suppresses wear of the ball seat under high writing pressure (writing load of 300 to 500 gf), improves writing feel, and has good initial writing performance, long-term stability of the ink composition, and ink followability. [Means for solving the problem]

[0011] The present invention employs the following configuration to solve the above problems. 1. An oil-based ballpoint pen ink composition characterized by comprising a colorant, an organic solvent, and a polyoxyalkylene glyceryl ether. 2. The ink composition according to item 1, wherein the coloring agent is a pigment. 3. The ink composition according to item 1 or 2, wherein the content of the polyoxyalkylene glyceryl ether is 0.1 to 40% by mass with respect to the total amount of the ink composition. 4. The ink composition according to any one of items 1 to 3, wherein the organic solvent is an aromatic alcohol. 5. An ink composition according to any one of items 1 to 4, further comprising a surfactant. 6. The ink composition according to item 5, wherein the surfactant is a nonionic surfactant. 7. The ink composition according to item 6, wherein the nonionic surfactant is selected from the group consisting of fatty acid esters, polyalkylene alkyl ethers, polyoxyethylene alkylamines, alkylimidazolines, alkylalkanolamides, and mixtures thereof. 8. The ink composition according to item 5, wherein the surfactant is an anionic surfactant. 9. The ink composition according to item 5, wherein the surfactant is a combination of a nonionic surfactant and an anionic surfactant. 10. 20℃, shear rate 5sec -1 An ink composition according to any one of items 1 to 9, wherein the viscosity in is 30,000 mPa·s or less. 11. An oil-based ballpoint pen characterized by having a ballpoint pen tip at the tip of an ink reservoir cylinder that rotatably holds a ball, and containing an ink composition comprising a colorant, an organic solvent, and a polyoxyalkylene glyceryl ether in the ink reservoir cylinder. 12. The oil-based ballpoint pen according to item 11, wherein the arithmetic mean roughness (Ra) of the surface of the ball is 0.1 to 12 nm. 13. The oil-based ballpoint pen according to item 11 or 12, wherein the ink consumption per 100m is 20 to 120 mg. 14. An oil-based ballpoint pen according to any one of items 11 to 13, wherein the amount of movement of the ball in the ballpoint pen tip in the longitudinal axis direction is 3 to 30 μm. [Effects of the Invention]

[0012] The present invention improves lubricity to maintain the lubricity between the writing tip and the writing surface (including the lubricity between the ball and the tip body), suppresses the writing resistance of the writing tip, suppresses wear of the ball seat under high writing pressure (writing load: 300 - 500 gf), improves writing feel, and provides an ink composition for an oil-based ballpoint pen with good writing performance, temporal stability of the ink composition, and ink followability, and an oil-based ballpoint pen using the same.

Brief Description of Drawings

[0013] [Figure 1] Conceptual cross-sectional view of a ballpoint pen refill used in an embodiment of the present invention. [Figure 2] Conceptual cross-sectional view of a ballpoint pen tip used in an oil-based ballpoint pen according to an embodiment of the present invention.

Modes for Carrying Out the Invention

[0014] Hereinafter, embodiments of the present invention will be described in detail. In this specification, "parts", "%", "ratio", etc. indicating formulation are based on mass unless otherwise specified, and the content is the mass % of the constituent components based on the mass of the ink composition.

[0015] The feature of the present invention is to provide an ink composition for an oil-based ballpoint pen containing polyoxyalkylene glyceryl ether. This forms a lubricating layer by containing polyoxyalkylene glyceryl ether, which maintains the lubricity between the writing tip and the writing surface (including the lubricity between the ball and the tip body), suppresses the writing resistance of the writing tip, suppresses wear of the ball seat under high writing pressure (writing load: 300 - 500 gf), improves writing feel, and even when the writing tip is left in the air, suppresses evaporation of the solvent in the ink, improves writing performance, does not generate precipitates, etc. in the ink, and improves the temporal stability (hereinafter simply referred to as temporal stability) of the ink composition. Therefore, it is possible to suppress wear of the ball seat under high writing pressure (writing load: 300 - 500 gf), and improve all of the writing feel, writing performance, and temporal stability.

[0016] (Polyoxyalkylene glyceryl ether) The polyoxyalkylene glyceryl ethers used in this invention are obtained by addition polymerization of alkylene oxide to glycerin or polyglycerin, and include polyoxyalkylene glyceryl ether, polyoxyalkylene diglyceryl ether, and polyoxyalkylene triglyceryl ether.

[0017] Polyoxyalkylene glyceryl ether is a compound that contains alkylene oxide in its structure and is hydrophilic and lipophilic. Because it has highly polar hydrophilic groups in its structure, it readily adheres to the metal material of the ballpoint pen tip, further improving lubrication. Therefore, even under high writing pressure (writing load of 300-500 gf), it can suppress wear on the ball seat and improve writing feel.

[0018] Furthermore, because polyoxyalkylene glyceryl ethers generally have low volatility, even if the writing tip is left in the air, it improves the initial writing performance and enhances ink followability by minimizing ink viscosity increase in the oil-based ballpoint pen ink composition. In addition, when pigments are used as colorants, ink viscosity generally increases over time due to pigment aggregation, reducing ink followability. However, the polar groups within the structure of polyoxyalkylene glyceryl ether adsorb to the pigment surface, stably dispersing the pigment in the oil-based ink. This suppresses the increase in ink viscosity due to pigment aggregation, thereby improving ink followability.

[0019] Furthermore, polyoxyalkylene glyceryl ethers include polyoxyethylene glyceryl ether and polyoxypropylene glyceryl ether. Of these, polyoxypropylene glyceryl ether has a propylene group, which gives it excellent lipophilicity and tends to improve the long-term stability of the ink composition by suppressing moisture absorption. For this reason, it is preferable to use polyoxypropylene glyceryl ether.

[0020] When considering the suppression of ball bearing wear under high writing pressure (writing load of 300-500 gf), the average number of added alkylene oxide moles (average number of added alkylene oxide moles) is preferably 1 to 50, and when considering further stability over time due to ink moisture absorption, the average number of added alkylene oxide moles is preferably 1 to 30. Furthermore, when considering the suppression of ball bearing wear under high writing pressure, the improvement of writing feel, the improvement of starting performance, and stability over time, oxide The average number of moles added is preferably 1 to 20, and more preferably 5 to 20.

[0021] In particular, considering the suppression of ball seat wear under high writing pressure, the average number of moles of propylene oxide added is preferably 1 to 30, more preferably 1 to 20, even more preferably 5 to 20, even more preferably 1 to 12, and particularly preferably 5 to 12. Furthermore, considering the ease with which the effects of the present invention are exhibited, the structure of the polyoxyalkylene glyceryl ether is preferably represented by the following formula (1) or (2). [ka] In the formula, m, n, o, p, w, x, y, and z are numbers that independently represent the number of alkylene oxide additions. Here, m+n+o+p is the average number of moles of propylene oxide added, and w+x+y+z is the average number of moles of ethylene oxide added.

[0022] Of these, polyoxyalkylene glyceryl ether represented by formula (1) is preferred because it has a significant effect in improving stability over time.

[0023] Furthermore, the weight-average molecular weight of the polyoxyalkylene glyceryl ether is preferably 5,000 or less. This is because if the weight-average molecular weight is too high, it tends to affect the stability over time, and the viscosity of the ink composition tends to increase, which tends to affect the ink's ability to follow the ink. If stability over time and ink ability to follow the ink are taken into consideration, the weight-average molecular weight is preferably 3,000 or less, more preferably 1,500 or less, and more preferably 1,200 or less. Also, if wear suppression of the ball seat under high writing pressure is taken into consideration, it is preferably 900 or less. On the other hand, if the weight-average molecular weight is too low, wear suppression of the ball seat under high writing pressure tends to affect the ability to start writing and pigment dispersibility, so the weight-average molecular weight is preferably 300 or more, and if wear suppression of the ball seat under even higher writing pressure is taken into consideration, the weight-average molecular weight is preferably 500 or more. The weight-average molecular weight is a value obtained using GPC (gel permeation chromatography) in terms of polystyrene equivalent.

[0024] Furthermore, regarding the solubility parameter (SP value) of polyoxyalkylene glyceryl ether, considering the suppression of ball seat wear under high writing pressure, stability over time, and writing performance, a solubility parameter (SP value) of 16 to 30 is preferable, and a value of 16 to 27 is more preferable.

[0025] Furthermore, if the polyoxyalkylene glyceryl ether content is less than 0.1% by mass relative to the total amount of ink composition, the effects of suppressing ball seat wear under high writing pressure, as well as writing feel, initial writing performance, and ink followability may not be obtained. If it exceeds 40% by mass, it may affect stability over time. Therefore, a content of 0.1 to 40% by mass, and more preferably 3 to 30% by mass, relative to the total amount of ink composition is preferred. Moreover, considering the balance between suppressing ball seat wear and stability over time, a content of 5 to 25% by mass is preferred, and most preferably 8 to 25% by mass.

[0026] (Organic solvents) Examples of organic solvents used in the present invention include 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, propagyl alcohol, allyl alcohol, 3-methyl-1-butyne-3-ol, ethylene glycol monomethyl ether acetate, and other higher alcohols. These are organic solvents commonly used in oil-based ballpoint pen inks.

[0027] Among these organic solvents, aromatic alcohols are preferred because they improve lubricity due to the presence of aromatic rings, and they also have high compatibility with polyoxyalkylene glyceryl ethers, thus improving the stability of the solution.

[0028] Furthermore, using a glycol ether solvent allows for proper moisture retention in the film formed when the tip of the pen dries, due to its appropriate hygroscopic properties, thereby softening the film and improving writing performance. Combining it with polyoxyalkylene glyceryl ether yields even better results. Considering stability in the ink composition, it is preferable to use an aromatic glycol ether solvent.

[0029] Furthermore, considering improvements in solubility, lubricity, and ink drying properties, the content of the organic solvent is preferably 10 to 90% by mass, more preferably 20 to 90% by mass, and particularly preferably 40 to 70% by mass, based on the total amount of the ink composition.

[0030] (Coloring agent) The colorants used in this invention are not particularly limited and can be selected and used as appropriate, such as dyes and pigments, and dyes and pigments may be used in combination. Examples of dyes include oil-soluble dyes, acid dyes, basic dyes, metal-containing dyes, and various salt-forming types thereof, such as salt-forming dyes of acid dyes and basic dyes, salt-forming dyes of basic dyes and organic acids, and salt-forming dyes of acid dyes and organic amines. These dyes may be used individually or in combination of two or more types.

[0031] Furthermore, when considering lubrication, it is preferable to use pigments as colorants. This is because pigment particles can easily fill the gap between the ball and the tip body, creating a bearing-like effect that suppresses direct contact between metal parts, thereby improving lubrication, enhancing writing feel, and reducing wear on the ball seat. In addition, pigments are preferable because they have excellent water resistance and lightfastness, and produce good color development. Specifically, it is preferable to use pigments from among carbon black, quinacridone-based, surene-based, and diketopyrrolopyrrole-based pigments, and from the viewpoint of long-term stability, it is even preferable to use carbon black or diketopyrrolopyrrole-based pigments.

[0032] Pigments include inorganic, organic, and processed pigments, but specifically include carbon black, aniline black, ultramarine, lead yellow, titanium dioxide, iron oxide, phthalocyanine, azo, quinacridone, diketopyrrolopyrrole, quinophthalone, surene, triphenylmethane, perinone, perylene, dioxazine, metallic pigments, pearl pigments, fluorescent pigments, and phosphorescent pigments.

[0033] These pigments, particularly polyoxyalkylene glyceryl ether, and the synergistic effect of a lubricating layer consisting of a nonionic or anionic surfactant (especially a phosphate ester surfactant), along with the bearing action of the pigment particles, make it easier to maintain lubrication, suppress wear on the ball seat, and improve writing feel. Furthermore, considering the ink composition flow paths and component spacing inside the ballpoint pen tip, the average particle size of the pigment is preferably 1 to 500 nm. More preferably, it is 30 to 350 nm, and even more preferably, 50 to 300 nm. Here, the average particle size can be determined by the laser diffraction method, specifically by the particle size (D50) at 50% volume accumulation of the particle size distribution measured using a laser diffraction particle size distribution analyzer (product name "MicrotracHRA9320-X100", Nikkiso Co., Ltd.), based on values ​​calibrated using standard samples or other measurement methods.

[0034] Furthermore, since the aforementioned effects are achieved by the dispersion state of the pigment in the oil-based ballpoint pen ink composition, it is preferable to determine the particle size in the dispersed state.

[0035] Furthermore, pigments are preferable because they have excellent water resistance and lightfastness, resulting in good color development and good ink fastness. From the viewpoint of the excellent water resistance, lightfastness, and lubricity of the pigment, it is preferable that the pigment content relative to the colorant content in the oil-based ballpoint pen ink composition be high. Specifically, by setting the pigment content relative to the colorant content to 10% by mass or more, water resistance, lightfastness, and lubricity can be improved to the required level, but in order to further reduce the likelihood of ink line changes in terms of water resistance and lightfastness, it is preferable to set it to 50% by mass or more, preferably 70% by mass or more, more preferably 90% by mass, and particularly preferably 100% by mass.

[0036] Generally, ink compositions containing pigments tend to have insufficient initial writing performance and ink-following ability when the writing tip dries. However, the ink composition according to the present invention contains polyoxyalkylene glyceryl ether, which helps maintain good initial writing performance and ink-following ability even when the pigment content is high.

[0037] Furthermore, when using dyes, it is preferable to use salt-forming dyes because their long-term stability is enhanced when combined with polyoxyalkylene glyceryl ether. Moreover, because the salt-forming bond is stable, even greater long-term stability can be obtained, so it is preferable to use salt-forming dyes selected from salt-forming dyes of basic dyes and organic acids, salt-forming dyes of acidic dyes and basic dyes, and salt-forming dyes of acidic dyes and organic amines. Considering the stability when combined with the components of the ink composition, salt-forming dyes of basic dyes and organic acids are preferred.

[0038] The colorant content is preferably 3.0 to 40.0% by mass, and more preferably 5.0 to 30.0% by mass, based on the total amount of the ink composition. This is because if the colorant content is too low, it tends to be difficult to obtain a dark writing line, and if it is too high, it tends to result in insufficient solubility in the ink composition. The colorant content is preferably 7.0 to 25.0% by mass, and more preferably 10.0 to 20.0% by mass, based on the total amount of the ink composition.

[0039] (Surfactants) The ink composition according to the present invention preferably contains a surfactant. This is because the surfactant softens the film formed on the tip of the pen by the resin and other components contained in the ink composition, making it easier to improve the initial writing performance and further improve the lubricity, thereby improving the writing feel. Examples of surfactants include nonionic surfactants, anionic surfactants, and cationic surfactants, but it is preferable to use a nonionic surfactant. This is because, being nonionic, it is less likely to cause precipitates from other components contained in the ink composition, thus improving stability over time.

[0040] For nonionic surfactants, considering long-term stability, an HLB value of 16 or less is preferable, more preferably 3 to 14, and particularly preferable 3 to 11. The HLB value can be determined by methods such as the Griffin method.

[0041] Unlike capped writing instruments, retractable writing instruments such as click-type and twist-type writing instruments have the pen tip constantly exposed to the outside. In such cases, the tip of the writing instrument is prone to drying out. Since surfactants with the above HLB value can improve this problem, it is preferable to use them.

[0042] Nonionic surfactants include fatty acid esters, polyalkylene alkyl ethers, polyoxyethylene alkylamines, alkylimidazolines, alkyl alkanolamides, oxyethylene oxypropylene block copolymers, and surfactants having acetylene bonds. Among these, considering the write-out performance and stability over time as described above, it is preferable to select one or more from fatty acid esters, polyalkylene alkyl ethers, polyoxyethylene alkylamines, alkylimidazolines, and alkyl alkanolamides. In particular, if the write-out performance is to be improved, it is preferable to use fatty acid esters. These may be used individually or in combination of two or more.

[0043] Furthermore, examples of fatty acid esters include sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, fatty acid esters, glycerin fatty acid esters, polyglycerin fatty acid esters, and polyoxyethylene fatty acid esters. Of these, it is preferable to select one or more from sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, glycerin fatty acid esters, and alkylimidazolines, as their interaction with polyoxyalkylene glyceryl ether improves the writing performance. It is also preferable to use sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, and alkylimidazolines, which have a cyclic skeleton structure. In addition, fatty acid esters having multiple hydroxyl groups can appropriately retain moisture in the film formed at the tip of the pen, so it is preferable to select one or more from sorbitan fatty acid esters, such as sorbitan fatty acid esters or polyoxyethylene sorbitan fatty acid esters.

[0044] Furthermore, considering the initial writing performance, it is preferable that the alkyl group of the sorbitan fatty acid ester has 1 to 20 carbon atoms. In addition, by setting the length to be suitable for forming a lubricating layer, the suppression of wear of the ball seat under high writing pressure is easily improved, so it is preferable that the alkyl group of the sorbitan fatty acid ester has 10 to 20 carbon atoms, and preferably 12 to 18.

[0045] Examples of sorbitan fatty acid esters include sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan monooleate, sorbitan monococoate, sorbitan dilaurate, sorbitan distearate, sorbitan dioleate, sorbitan trioleate, sorbitan trystearate and their compound products, as well as polyoxyethylene sorbitan fatty acid esters such as polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan trioleate, polyoxyethylene sorbitan trystearate and their compound products.

[0046] The content of nonionic surfactant is more preferably 0.1 to 15% by mass relative to the total amount of ink composition. This is because if it is less than 0.1% by mass, it is difficult to suppress wear of the ball seat under the desired high writing pressure (writing load of 300 to 500 gf), improve the writing feel, and obtain the desired initial writing performance and ink followability. If it exceeds 15% by mass, the ink tends to become unstable over time. Considering this tendency, 0.5 to 10% by mass is preferred, and 1 to 5% by mass is most preferred, relative to the total amount of ink composition.

[0047] In the present invention, it is preferable to include an anionic surfactant to improve the lubricity of the writing tip (the ball and ball seat of a ballpoint pen), improve the writing feel, and further improve the writing performance when the writing tip is left in the air and dries. Examples of such anionic surfactants include phosphate ester surfactants. Furthermore, it is preferable to use a combination of a nonionic surfactant and anionic surfactant to maintain good lubricity while maintaining good stability over time.

[0048] Because phosphate ester surfactants contain phosphate groups, they readily adsorb to metal surfaces and, in particular, can form a lubricating film between the ball and the ball seat. As a result, lubrication is improved, and the writing experience can be enhanced. Therefore, by combining phosphate ester surfactants with polyoxyalkylene glyceryl ether, the lubricating effects of both substances work synergistically to further improve the lubrication between the ball and the ball seat, resulting in a smooth writing experience. Furthermore, phosphate ester surfactants also have the effect of improving initial writing performance, and by using them in combination with polyoxyalkylene glyceryl ether, initial writing performance can be further enhanced.

[0049] Furthermore, since phosphate ester surfactants have a rust-preventive effect, they are preferable when the ball is made of metal, as they suppress corrosion of the ball, maintain good writing performance, and reduce wear of the ball seat. This is especially preferable when the ball is made of an alloy containing cobalt, nickel, chromium, etc., as these metals are less susceptible to corrosion over time due to the rust-preventive effect of the phosphate ester surfactant. This tendency is particularly pronounced and preferable when the ball material is a cemented carbide ball, especially when the ball material is a cemented carbide ball mainly composed of tungsten carbide with cobalt, nickel, chromium, etc. as a binder.

[0050] Therefore, in the present invention, it is effective to use an anionic surfactant, particularly a phosphate ester surfactant, in combination with polyoxyalkylene glyceryl ether.

[0051] Furthermore, the ink composition according to the present invention may also contain polyvinyl butyral. Polyvinyl butyral also has the effect of improving lubricity, but when combined with a phosphate ester surfactant, the synergistic effect of the improving effect of polyvinyl butyral and the improving effect of the anionic surfactant, especially the phosphate ester surfactant, makes it easier to further improve lubricity, which is preferable.

[0052] The interaction between the phosphate ester surfactant and the polyoxyalkylene glyceryl ether can further improve both lubricity and writing performance, so the HLB value of the phosphate ester surfactant is preferably 6 to 18, and more preferably 6 to 14. This is because if the HLB value exceeds 18, the hydrophilicity tends to increase, and the solubility in oil-based ink compositions tends to decrease, making it difficult to obtain the effect of the phosphate ester surfactant, especially the lubrication effect. Also, if the HLB value is less than 6, the lipophilicity becomes too strong, which tends to affect compatibility with organic solvents, making it difficult to obtain stability over time and further hindering the improvement of writing performance. Furthermore, considering lubricity, the HLB value is preferably 17 or less, and more preferably 12 or less. That is, the HLB value is preferably 6 to 17, and more preferably 6 to 12. Furthermore, considering writing performance, the HLB value is preferably 7 to 17, and more preferably 7 to 12. In particular, with retractable ballpoint pens such as retractable ballpoint pens and twist-action ballpoint pens, the pen tip is constantly exposed to the outside, making the writing tip prone to drying out. For this reason, it is preferable to use a phosphate ester surfactant having the above-mentioned HLB value in order to improve the writing performance. The HLB value can be determined by methods such as the Griffin method or the Kawakami method.

[0053] Phosphate ester surfactants include those with an alkoxy group (C a H 2a+1 Examples include phosphate esters containing O), monophosphate esters of polyoxyethylene alkyl ethers or polyoxyethylene alkylaryl ethers, diphosphate esters of polyoxyethylene alkyl ethers or polyoxyethylene alkylaryl ethers, triesters of polyoxyethylene alkyl ethers or polyoxyethylene alkylaryl ethers, alkyl phosphate esters, alkyl ether phosphate esters, or derivatives thereof.

[0054] Among these, considering the suppression of ball seat wear under high writing pressure (writing load of 300-500 gf), it is preferable to use a phosphate ester surfactant having an alkyl group. In particular, it is preferable that the alkyl group contains 8 to 18 carbon atoms, more preferably 10 to 18, and even more preferably 12 to 18. This is because if the alkyl group has too few carbon atoms, lubricity tends to be insufficient, and if the number of carbon atoms is too many, it tends to affect stability over time.

[0055] Furthermore, when using a phosphate ester surfactant, the acid value is preferably 200 mgKOH / g or less, more preferably 170 mgKOH / g or less, and even more preferably 150 mgKOH / g or less, in order to facilitate the improvement in lubricity provided by the phosphate ester surfactant. Moreover, considering stability and lubricity in the ink composition, the acid value is preferably 30 to 170 mgKOH / g, more preferably 40 to 160 mgKOH / g, and more preferably 70 to 120 mgKOH / g.

[0056] The acid value shall be expressed as the number of milligrams of potassium hydroxide required to neutralize the acidic components contained in 1 gram of the sample.

[0057] When the ink composition according to the present invention contains a surfactant, the blending ratio of the polyoxyalkylene glyceryl ether represented by formula (1) or (2) to the surfactant, particularly the nonionic surfactant and phosphate ester surfactant as described above (polyoxyalkylene glyceryl ether / surfactant), is preferably 1 to 40 times by mass, more preferably 2 to 30 times, more preferably 1 to 25 times, more preferably 1 to 20 times, more preferably 1 to 15 times, more preferably 2 to 15 times, and most preferably 5 to 10 times. Within this range, it is possible to balance the suppression of ball bearing wear with the improvement of writing feel, initial writing performance, and ink followability.

[0058] (Organic amines) The ink composition according to the present invention preferably contains an organic amine in order to improve the stability of the components contained in the ink composition. Examples include amines having ethylene oxide, such as oxyethylene alkylamines and polyoxyethylene alkylamines; alkylamines, such as laurylamines and stearylamines; and aliphatic amines, such as distearylamines, dimethyl laurylamines, dimethyl stearylamines, and dimethyl octylamines. Among these, amines having ethylene oxide and dimethyl alkylamines are preferred. In particular, amines having ethylene oxide are preferred when considering the suppression of ball seat wear under high writing pressure (writing load of 300 to 500 gf).

[0059] Furthermore, the total amine value of the organic amine is preferably between 100 and 300 mgKOH / g, considering its stability with the surfactant, colorant, and other components. This is because if it exceeds 300 mgKOH / g, the reactivity is too strong, making it prone to reacting with the above components, which tends to result in poor stability over time. Also, if the total amine value is less than 100 mgKOH / g, the stability of the surfactant in the ink composition tends to decrease, and the lubrication performance tends to decrease when used in an oil-based ballpoint pen. From the viewpoint of stability with the above components and lubricity, a range of 150 to 300 mgKOH / g is more preferable. Furthermore, from the viewpoint of stability, a range of 180 to 300 mgKOH / g is preferable, and a range of 230 to 270 mgKOH / g is more preferable.

[0060] In this invention, the total amine value represents the total amount of primary, secondary, and tertiary amines, and is expressed in milligrams of potassium hydroxide equivalent to the amount of hydrochloric acid required to neutralize 1 g of the sample.

[0061] Furthermore, regarding the reactivity of organic amines with other components in the ink composition, primary amines exhibit the strongest reactivity, followed by secondary amines and then tertiary amines, which have decreasing reactivity. Therefore, considering stability over time, it is preferable to use secondary or tertiary amines. These may be used individually or in combination of two or more.

[0062] (resin) Furthermore, in order to further improve ink leakage suppression, it is preferable to use a resin as an ink viscosity modifier. Examples of resins include polyvinyl butyral resin, ketone resin, polyacetal resin, polyvinyl alcohol resin, cellulose resin, terpene resin, alkyd resin, phenoxy resin, and polyvinyl acetate resin, but among these, it is preferable to include polyvinyl butyral resin or ketone resin.

[0063] Polyvinyl butyral resin readily forms a lubricating layer that provides a higher lubrication effect. This is because using polyvinyl butyral resin creates a consistently elastic ink layer between the ball and the ball seat, making direct contact difficult. As a result, the writing feel tends to improve. Furthermore, the synergistic effect of using polyvinyl butyral resin in combination with polyoxyalkylene glyceryl ether makes it easier to obtain an even higher lubrication effect. In addition, using polyvinyl butyral resin is preferable because the film formed at the tip of the pen makes it easier to prevent ink leakage. Moreover, when using pigments as colorants, polyvinyl butyral resin is preferable because it also provides a pigment dispersion effect.

[0064] Here, polyvinyl butyral resin is produced by reacting polyvinyl alcohol (PVA) with butyraldehyde (BA), and has a structure containing butyral groups, acetyl groups, and hydroxyl groups.

[0065] Furthermore, it is preferable that the polyvinyl butyral resin has a hydroxyl group content of 25 mol% or more. This is because polyvinyl butyral resin with a hydroxyl group content of 25 mol% or more has sufficient solubility in organic solvents and has a great effect on lubrication, ink leakage suppression, and improvement of writing performance. Polyvinyl butyral resin with a hydroxyl group content of 30 mol% or more is particularly preferable because it tends to improve writing feel. In general, when writing, frictional heat is generated by the rotation of the ball, so the temperature of the ink composition at the tip of the tip rises, the viscosity of the ink composition decreases, and the writing feel may deteriorate. However, unlike other resins, polyvinyl butyral resin has the property of not easily decreasing the viscosity of the ink composition even when the ink temperature rises, and it always forms an elastic ink layer between the ball and the ball seat, making direct contact difficult, so it tends to improve writing feel. This is especially effective in oil-based ballpoint pens, where high pressure is often used when writing. Furthermore, polyvinyl butyral resins with a hydroxyl group content of 40 mol% or less are preferred because they have low hygroscopicity and their stability over time is less likely to be impaired. For this reason, polyvinyl butyral resins with a hydroxyl group content of 30 to 40 mol% are preferred, and those with a hydroxyl group content of 30 to 36 mol% are even more preferred.

[0066] The hydroxyl group content (mol%) of polyvinyl butyral resin refers to the percentage of hydroxyl groups (mol%) relative to the total mole amounts of butyral groups (mol%), acetyl groups (mol%), and hydroxyl groups (mol%).

[0067] Furthermore, regarding the average degree of polymerization of polyvinyl butyral resin, an average degree of polymerization of 200 or higher tends to improve ink leakage suppression performance, while an average degree of polymerization exceeding 2,500 tends to increase ink viscosity too much, affecting writing feel. Therefore, an average degree of polymerization of 200 to 2,500 is preferable, and 1,500 or less is more preferable. In addition, considering the synergistic lubricity improvement effect with polyoxyalkylene glyceryl ether, an average degree of polymerization of 200 to 1,000 is preferable. Here, the average degree of polymerization refers to the number of basic units constituting one molecule of polyvinyl butyral resin, and values ​​measured based on the method specified in JIS K6728 (2001 edition) can be used.

[0068] The polyvinyl butyral resin content in the oil-based ballpoint pen ink composition should be 50% or more of the total resin content, and it is preferable to use it as the main resin. This is because if the polyvinyl butyral resin content is less than 50% of the total resin content, the other resins tend to inhibit the formation of an elastic ink layer, making it difficult to obtain the effect of improving writing feel. Furthermore, it tends to inhibit the formation of a resin coating at the tip of the pen tip, making it difficult to suppress ink dripping. Considering the tendency to further improve writing feel and ink drip performance, the polyvinyl butyral resin content is preferably 70% or more, and preferably 90% or more, of the total resin content.

[0069] If the resin content is less than 1% by mass relative to the total amount of ink composition, the desired lubricity and ink leakage suppression performance tend to be poor, and if it exceeds 40% by mass, the solubility in the ink tends to be poor. For this reason, the resin content is preferably 1 to 40% by mass relative to the total amount of ink composition. Furthermore, a resin content of 5% by mass or more is preferable. Also, if the resin content exceeds 30% by mass, the ink viscosity tends to become too high, affecting the writing feel. From these points of view, the resin content is preferably 5 to 30% by mass, more preferably 6 to 25% by mass, and most preferably 6 to 18% by mass.

[0070] In addition, other materials such as viscosity modifiers, including plasticizers like fatty acid amides and hydrogenated castor oil, as well as colorant stabilizers, plasticizers, chelating agents, and water, may be used as appropriate. These may be used individually or in combination of two or more.

[0071] The viscosity of the oil-based ballpoint pen ink composition of the present invention is not particularly limited, but if the viscosity is excessively high, the initial writing performance, writing feel, and ink followability tend to be poor. -1 The ink viscosity (at rest) is preferably 30,000 mPa·s or less. Furthermore, if the viscosity is excessively low, it is difficult to suppress ink leakage, so it is preferably 500 mPa·s or higher, and more preferably 1,000 mPa·s or higher. Considering the need to further improve ink leakage suppression, writing feel, ink followability, and initial writing performance, the viscosity of the ink composition is preferably 500 to 25,000 mPa·s, more preferably 1,000 to 25,000 mPa·s, and more preferably 800 to 25,000 mPa·s. Moreover, from the viewpoint of writing feel and initial writing performance, it is more preferably 1,000 to 20,000 mPa·s, and more preferably 2,000 to 20,000 mPa·s. Furthermore, in order to improve the writing feel and increase ink consumption to produce darker lines, a viscosity of 500 to 10,000 mPa·s is preferred, and 1,000 to 5,000 mPa·s is more preferred.

[0072] (Oil-based ballpoint pen) The oil-based ballpoint pen ink composition according to the present invention can be applied to various types of oil-based ballpoint pens, but it is particularly preferable to use it in retractable ballpoint pens such as retractable or twist-action pens. Such a ballpoint pen comprises a container holding the oil-based ink composition according to the present invention, and a ballpoint pen tip located at the tip of the container, which rotatably holds a ball in a ball-holding chamber. The ballpoint pen tip can be extended and retracted from the tip opening of the barrel, and has a structure generally known as a retractable ballpoint pen. Generally, when an ink composition is used in a retractable ballpoint pen where the pen tip is not sealed, the tip is constantly exposed to the air, causing the tip to dry out and making it prone to skipping or smudging when writing begins. However, using the composition according to the present invention improves such problems, making it preferable.

[0073] The preferred configuration of the oil-based ballpoint pen according to this embodiment will be described below with reference to the figures.

[0074] The oil-based ballpoint pen according to the present invention contains an ink composition housed in a refill cylinder. The housing may be in the form of a refill with a tip attached to the end, or it may be the barrel itself with a tip attached to the end. The ink composition according to the present invention is suitable for retractable ballpoint pens, and it is preferable that the refill is housed in the barrel. Figure 1 is a conceptual cross-sectional view of a ballpoint pen refill that can be used in the oil-based ballpoint pen according to this embodiment.

[0075] The ballpoint pen refill 1 that can be used in the present invention has a ballpoint pen tip 4 at one end of an ink reservoir 2, and the ink composition according to the present invention is contained in the ink reservoir 2. A ball 3 is contained at the tip of the tip.

[0076] The ink container is a molded body made of a thermoplastic resin such as polyethylene, polypropylene, polyethylene terephthalate, or nylon.

[0077] In addition to directly connecting the tip to the ink reservoir, the ink reservoir and tip may also be connected via a connecting member.

[0078] It is preferable that the rear end of the ink contained in the ink container is filled with an ink backflow prevention material. The ink backflow prevention material composition consists of a non-volatile liquid or a low-volatility liquid.

[0079] The ballpoint pen tip, which is positioned at one end of the refill, can be arbitrarily selected from commonly used types. Figure 2 is a conceptual cross-sectional view of a ballpoint pen tip 4 that can be used in the oil-based ballpoint pen according to this embodiment.

[0080] The ballpoint pen tip 4 comprises at least a ballpoint pen tip body and a ball 3. The ballpoint pen tip body is generally made from a metal material. For example, it can be manufactured by cutting stainless steel wire to a desired length, creating a ball-holding chamber 6, an ink flow hole 7, and an ink flow groove 8 extending radially from the ink flow hole 7, and then forming a roughly arc-shaped ball seat 9 on the bottom wall of the ball-holding chamber 6. The ball 3 is placed on the ball seat 9 of this ballpoint pen tip body, and the tip end 5 is crimped inward to form the ballpoint pen tip 4.

[0081] The shape of the ballpoint pen tip affects writing performance and is therefore adjusted as needed. For example, the ball protrusion H from the tip of the pen when the ball 3 is resting on the ball seat 9 is generally set to 10-30% of the ball diameter, for example, 30%. Having the ball protrusion within this range allows for appropriate adjustment of ink consumption per 100m.

[0082] Furthermore, if the crimping angle α is too large, the angle of contact with the paper becomes small, which can easily affect writing performance. Therefore, it is preferable to set it to 110 degrees or less, preferably 95 degrees or less. If the crimping angle is less than 50 degrees, the space for accumulating ink between the ball 3 and the tip edge tends to become small, which can cause poor writing performance. For this reason, it is preferable to set the crimping angle α to 50 degrees to 110 degrees, more preferably to 60 degrees to 95 degrees, for example, to 80 degrees.

[0083] Furthermore, the inner diameter of the ball-holding chamber can generally be 101-120% of the ball diameter, for example, 104%, and the diameter of the ball seat 9 can generally be 70-95% of the ball diameter, for example, 86%. Being within this range allows for appropriate adjustment of ink consumption per 100m.

[0084] In such a ballpoint pen tip, the material used for the ball 3 is not particularly limited, but examples include cemented carbide balls mainly composed of tungsten carbide, metal balls such as stainless steel, ceramic balls such as silicon carbide, silicon nitride, alumina, silica, zirconia, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, and ruby ​​balls. Among these, cemented carbide balls are preferred because they are less prone to cracking and have good processability and productivity, cemented carbide balls mainly composed of tungsten carbide are preferred, and furthermore, considering bonding stability, it is also preferable to use cemented carbide containing cobalt as a binder.

[0085] In addition, individual metals such as steel, copper, aluminum, or nickel may be used, or alloys such as nickel silver or stainless steel may be used. Furthermore, carbides, oxides, nitrides, borides, or silicates of metals may also be used. As carbides, titanium, vanadium, chromium, tantalum, niobium, molybdenum, boron, zirconium, tungsten, or silicon carbides can be used. As oxides, aluminum, chromium, magnesium, silicon, beryllium, thorium, titanium, calcium, or zirconium oxides can be used. As nitrides, titanium, boron, silicon, silicon, or aluminum nitrides can be used. As borides, zirconium, chromium, or titanium borides can be used.

[0086] Furthermore, the ballpoint 3 is generally used with a diameter in the range of 0.25 mm to 1.6 mm, preferably 0.5 mm to 1.6 mm, and even more preferably 0.5 mm to 1.0 mm. Specifically, ballpoint 3 is available in multiple sizes depending on the desired stroke width, for example, with diameters of 0.3 mm, 0.4 mm, 0.5 mm, 0.7 mm, 1.0 mm, 1.2 mm, and 1.6 mm.

[0087] Furthermore, the arithmetic mean roughness (Ra) of the surface of the ball 3 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 sufficient ink to adhere to the ball surface, making it difficult to obtain a dark line when writing, and causing skipped lines and streaks in the writing. If the arithmetic mean roughness (Ra) exceeds 12 nm, the ball surface is too rough, resulting in high rotational resistance between the ball and the ball base, which can lead to wear of the ball base and poor writing quality, as well as affecting writing performance such as streaks, skipped lines, and uneven lines. Moreover, an arithmetic mean roughness (Ra) of 0.1 to 10 nm is more preferable when using an ink composition like the one in the present invention, as it improves writing quality and allows ink to adhere more easily to the ball surface. For even better writing quality, 2 to 8 nm is preferable. Regarding the arithmetic mean roughness of a ball surface, the arithmetic mean roughness (Ra) can be determined from the roughness curve measured by a surface roughness measuring instrument (SPI3800N, manufactured by Seiko Epson Corporation). Specifically, a reference length is extracted in the direction of the mean line of the roughness curve, and the absolute values ​​of the deviations from the mean line of this extracted portion to the measured roughness curve are summed and averaged.

[0088] Furthermore, the material of the ballpoint pen tip body is not particularly limited, but may be, for example, a single metal or alloy of various metals, ceramics, resin, etc. Specifically, a single metal such as steel, copper, aluminum, or nickel may be used, or an alloy such as nickel silver or stainless steel may be used. A nickel silver tip body is preferable because it can improve writing feel and has high machinability such as cutting. Alternatively, a stainless steel tip body is preferable because it has high wear resistance and stability over time for the ball seat, and among these, ferritic stainless steel is preferred.

[0089] Furthermore, regarding the ballpoint pen tip, it is preferable that the amount of movement (clearance) of the ball in the vertical axis direction of the ballpoint pen tip is 3 to 30 μm. This is because if it is too small, it tends to affect writing quality and feel, such as skipping, blotting, and uneven dots in the writing, and if it is too large, it tends to affect blotting, ink-following performance, and ink leakage suppression. It is more preferable that the amount of movement be 3 to 25 μm, even more preferable that it be 5 to 25 μm, and especially preferable that it be 7 to 20 μm, considering the drying time of the writing, ink-following performance, and skipping of the writing.

[0090] In this invention, the amount of movement of the ball of the ballpoint pen tip in the vertical axis direction is determined by the shape of the ballpoint pen tip in its initial state before writing begins.

[0091] The ink consumption of a ballpoint pen per 100m is preferably 20 to 150mg. This is because if the ink consumption per 100m is less than 20mg, ink smudging and unevenness are likely to occur, making it difficult to obtain dark lines and a good writing feel. If the ink consumption per 100m exceeds 150mg, it affects ink flow, makes ink leakage more likely through the gap between the ball and the tip, and can lead to dry lines and blobs. The ink consumption of a ballpoint pen per 100m is more preferably 25 to 140mg, more preferably 30 to 130mg, and even more preferably 40 to 110mg.

[0092] Regarding ink consumption, a spiral writing test was conducted using five test samples at a writing speed of 4 m / min, under the conditions of 20°C, a writing angle of 70°, a writing load of 200 g, and on JIS P3201 writing paper. The average value of the ink consumption per 100 m was defined as the ink consumption per 100 m.

[0093] Furthermore, to improve darker lines, writing feel, ink responsiveness, and ink leakage prevention, it is effective to consider not only the ink consumption but also its relationship with the ball diameter. Specifically, for oil-based ballpoint pens, a ratio of ball diameter to ink consumption (mg) per 100m of ball diameter (mm) of 1:40 to 1:140 tends to result in darker lines, better writing feel, ink responsiveness, ink leakage prevention, and faster drying of the ink. A ball diameter to ink consumption ratio of 1:50 to 1:130 is more preferable, and 1:60 to 1:120 is even more preferable.

[0094] As described in the present invention, by using an oil-based ballpoint pen ink composition containing polyoxyalkylene glyceryl ether, wear of the ball seat can be suppressed, and ink consumption remains stable from the beginning to the end of writing. This is preferable because it makes it easier to consistently obtain good writing performance, such as smooth writing, less skipping in the handwriting, and dark lines. Specifically, when the ink consumption Emg at the initial 0-100m is the ink consumption Fmg at the 100m before the ink runs out, the ratio of the ink consumption Fmg at the 100m before the ink runs out to the ink consumption Emg at the initial 0-100m is preferable (E:F) when it is between 1:0.7 and 1:1.3. This is preferable because it makes it easier to consistently obtain good writing performance, such as smooth writing, less skipping in the handwriting, and dark lines. The ratio of E:F is more preferably 1:0.8 to 1:1.2, and even more preferably 1:0.9 to 1:1.1.

[0095] (Examples) The present invention will now be explained with reference to examples. In Example 1, an oil-based ballpoint pen ink composition was prepared by first adding an organic solvent, pigment, and pigment dispersant, and then dispersing them in a three-roll disperser to create a pigment dispersion. Subsequently, the pigment dispersion, dye, organic solvent, polyoxyalkylene glyceryl ether, nonionic surfactant, polyvinylpyrrolidone, and polyvinyl butyral resin were used, weighed in predetermined amounts, heated to 60°C, and then completely dissolved using a disperser stirrer to obtain an oil-based ballpoint pen ink composition. The specific proportions are as follows.

[0096] Furthermore, using a viscometer (Viscometer RVDVII+Pro and CP-52 spindle, both product names, manufactured by Brookfield Corporation), the shear rate was 5 sec in an environment of 20°C. -1 When the ink viscosity of Example 1 was measured at a rotation speed of 2.5 rpm, the ink viscosity was found to be 3,000 mPa·s.

[0097] Example 1 Pigment dispersion (carbon black, average particle size 150 nm, 20% pigment, 20% polyvinyl butyral) 50.0% by mass Alcohol solvent (benzyl alcohol) 26.5% by mass Polyoxyalkylene glyceryl ether (Formula (1), polyoxypropylene diglyceryl ether) 20.0% by mass Nonionic surfactant (sorbitan fatty acid ester) 2.0% by mass Polyvinylpyrrolidone 0.5% by mass Polyvinyl butyral resin 1.0% by mass

[0098] Examples 2-34 As shown in the table, the ink formulations for oil-based ballpoint pens of Examples 2 to 34 were obtained by following the same procedure as in Example 1, except that each component was changed. In Examples 18, 22, and 28 to 34, the arithmetic mean roughness of the ball surface or the amount of ball displacement in the longitudinal direction of the ball in the ballpoint pen tip was also changed. The evaluation results are shown in the table.

[0099] Comparative Examples 1-3 As shown in the table, oil-based ballpoint pen ink compositions for Comparative Examples 1 to 3 were obtained using the same procedure as in Example 1, except that each component was changed. The evaluation results are shown in the table.

[0100] Furthermore, using the same method as in Example 1, Examples 3, 21, 25, and 31 were subjected to a shear rate of 5 sec in an environment of 20°C. -1When the ink viscosity was measured at a rotation speed of 2.5 rpm, the results were as follows: Example 3: 2000 mPa·s, Example 21: 2800 mPa·s, Example 25: 4800 mPa·s, and Example 31: 3000 mPa·s. [Table 1]

[0101] [Table 2]

[0102] [Table 3]

[0103] 1. Carbon black manufactured by Fuji Pigment Co., Ltd., average particle size 150 nm, contains 20% pigment and 20% polyvinyl butyral resin. 2. Manufactured by Fuji Pigment Co., Ltd., diketopyrrolopyrrole pigment (average particle size 250 nm), contains 20% pigment and 20% polyvinyl butyral resin. 3. Manufactured by Orient Chemical Co., Ltd. 4. SC-P750 (product name), manufactured by Sakamoto Pharmaceutical Co., Ltd.: Average number of moles of propylene oxide added (m+n+o+p) = 9, solubility parameter (SP value): 22.7 5. SC-P400 (product name), manufactured by Sakamoto Pharmaceutical Co., Ltd. Average number of moles of propylene oxide added (m+n+o+p) = 4, Solubility parameter (SP value): 26.1 6. SC-P1000 (product name), manufactured by Sakamoto Pharmaceutical Co., Ltd., average number of moles of propylene oxide added (m+n+o+p) = 14. 7. SC-P1600 (product name), manufactured by Sakamoto Pharmaceutical Co., Ltd., average number of moles of propylene oxide added (m+n+o+p) = 24. 8. SC-E2000 (product name), manufactured by Sakamoto Pharmaceutical Co., Ltd. Average number of moles of ethylene oxide added (w+x+y+z) = 4, Solubility parameter (SP value): 21.0 9. Solgen 40 (product name), manufactured by Daiichi Kogyo Seiyaku Co., Ltd., alkyl group carbon number = 18 10. Kao Corporation, Leodor TW-S320V (product name), number of carbon atoms in alkyl group = 18 11. Kao Corporation, Leodor SP-P10 (product name), number of carbon atoms in the alkyl group = 16 12. PS-5S (product name), manufactured by Sakamoto Pharmaceutical Co., Ltd. 13. Manufactured by Kao Corporation. 14. Noigen TDS-120 (product name), manufactured by Daiichi Kogyo Seiyaku Co., Ltd. 15. Phosphanol (product name) series, manufactured by Toho Chemical Industry Co., Ltd. 16. Daiichi Kogyo Seiyaku Co., Ltd. - Prysurf (product name) series 17. Kao Corporation's Farmin DM2098 (product name) - Tertiary amine 18. Nimmine (product name), a secondary amine manufactured by Nippon Oil & Fats Co., Ltd. 19. PVP K-90 (product name) manufactured by IBS Japan Co., Ltd. 20. Manufactured by Sekisui Chemical Co., Ltd. 21. Manufactured by Hitachi Chemical Co., Ltd.

[0104] Testing and evaluation The oil-based ballpoint pen ink compositions prepared in Examples 1-34 and Comparative Examples 1-3 were used to create a ballpoint pen. A ballpoint pen tip (with a coil spring inside the tip that directly presses the ball against the inner wall of the tip edge, ball axial movement: 12 μm, material: ferritic stainless steel) was fitted to the tip of an ink reservoir (made of polypropylene), which rotatably holds a ball (φ0.7 mm, arithmetic mean roughness (Ra) of the ball surface: 7 nm, material: cemented carbide ball mainly composed of tungsten carbide (containing cobalt as a binder)). The ballpoint pen tip had a coil spring inside which the ball was directly pressed against the inner wall of the tip edge, and the axial movement of the ball: 12 μm. The oil-based ballpoint pen ink (0.2 g) of Example 1 was directly placed in the ink reservoir, and the ballpoint pen refill was placed in an oil-based ballpoint pen manufactured by Pilot Corporation (product name: Super Grip (registered trademark)) to create an oil-based ballpoint pen. The following tests and evaluations were performed on the writing test paper in accordance with JIS P3201.

[0105] When the ink compositions of Examples 1, 3, 21, 25, and 31 were placed in oil-based ballpoint pens and a spiral writing test was conducted, the ink consumption per 100m of writing was 70mg / 100m, 75mg / 100m, 60mg / 100m, 50mg / 100m, and 98mg / 100m, respectively.

[0106] Furthermore, the ratio of ink consumption (mg) to ball diameter (mm) per 100m of writing for these oil-based ballpoint pens (ball diameter:ink consumption) was 1:100, 1:107, 1:86, 1:71, and 1:140, respectively.

[0107] Furthermore, when oil-based ballpoint pens equipped with the ink compositions of Examples 1, 3, 21, 25, and 31 were used, and the ink consumption Emg from 0 to 100m at the start of writing and Fmg from 100m before the end of writing to the end of writing were used, the ink consumption ratios E:F were 70:73 (1:1.04), 75:72 (1:0.96), 60:65 (1:1.08), 50:46 (1:0.9), and 98:101 (1:1.03), respectively.

[0108] Abrasion resistance test (ball seat abrasion test): The abrasion of the ball seat after the writing test was measured using a running test machine with a load of 400gf, a writing angle of 70°, and a speed of 4m / min. A: Ball bearing wear of less than 5 μm B: Ball seat wear of 5 μm or more and less than 10 μm C: The ball bearing wear is between 10 μm and 20 μm, but the pen is still writable. D: The ball bearing is severely worn, resulting in poor writing performance.

[0109] Writing feel: Evaluated through a sensory test using handwriting. A: Something very smooth B: Something that is smooth C: Smoothness that is acceptable for practical use. D: Heavy things

[0110] Initial writing performance test: After writing by hand, the pen tip was left exposed in an environment of 20°C and 65% RH for 24 hours. Then, a running test was conducted under the following writing conditions, and the length of the initial ink smudging was measured. <Writing Conditions> The test was performed by writing in a straight line on a running test machine under the following conditions: writing load of 200gf, writing angle of 70°, and writing speed of 4m / min. A: Those with a stroke length of less than 5mm. B: The length of the ink smudge is 5mm or more but less than 10mm. C: The length of the ink smudge is 10mm or more but less than 20mm. D: The length of the ink stroke is 20mm or longer.

[0111] Ink aging test: The ink inside the chip body was observed under a microscope after one month in a 50°C environment. A: No precipitates, in good condition. B: Cases with only minute precipitate formation C: Precipitates have formed, but do not pose a practical problem. D: Precipitates can form, causing problems such as smudging or poor writing quality.

[0112] Ink tracking performance test: After one month in a 50°C environment, continuous rapid handwriting was performed for 10 seconds. A: No smudging or skipped lines in the handwriting. B: There was some slight smudging and skipping of lines, but it was at a level that did not cause any problems in practical use. C: Items with smudged or skipped lines. D: Severely smudged handwriting and skipped lines.

[0113] Water resistance test: After writing spirally on writing paper and letting it dry, the paper was immersed in water for 10 seconds, and the condition of the writing was observed. A: Those with good handwriting. B: The handwriting is faint but still legible. C: Items where the handwriting is not visible.

[0114] Lightfastness Test: A spiral writing test was performed on writing paper at a writing angle of 70°, a writing load of 150g, and a writing speed of 4.5m / min. After leaving it for 1 hour, the paper was irradiated using a xenon fade meter X15F (manufactured by Suga Test Instruments Co., Ltd.) until the blue scale faded to grade 3, and the handwriting was observed. A: Does not fade B: Fading is visible, but the items are still identifiable. C: Items with noticeable fading.

[0115] In Examples 1 to 34, good performance was obtained in all tests, including abrasion resistance (ball bearing abrasion test), writing feel, initial writing performance test, ink aging test, ink followability test, water resistance test, and lightfastness test. In Examples 1-17 and 19-34, pigments were used as colorants, and they exhibited good pigment dispersibility and stability.

[0116] Furthermore, in Comparative Examples 1-3, because polyoxyalkylene glyceryl ether was not used, the abrasion resistance test (abrasion test of the ball seat) was poor, and the ink followability test was also inferior.

[0117] Furthermore, when using retractable oil-based ballpoint pens such as retractable or twist-action oil-based ballpoint pens, the initial writing performance is one of the important performance characteristics, so using the ink composition according to the present invention is effective.

[0118] The ink composition according to the present invention is preferably used in a ballpoint pen tip that has a valve mechanism that, in order to suppress ink leakage and improve writing performance, presses a ball rotatably held at the tip of the ballpoint pen tip against the inner wall of the tip edge directly or via a pressing body using an elastic member (such as a coil spring), thereby creating a gap between the inner wall of the tip edge and the ball due to the pressure applied during writing, allowing ink to flow out. With a ballpoint pen tip having such a structure, it is preferable that even the minute gap at the tip of the tip is closed when not in use.

[0119] Furthermore, in this embodiment, an oil-based ballpoint pen was illustrated in which a ballpoint pen refill containing an oil-based ballpoint pen ink composition is disposed inside the barrel. However, the oil-based ballpoint pen according to the present invention may also be an oil-based ballpoint pen in which the barrel itself serves as the ink storage cylinder and the oil-based ballpoint pen ink composition is directly stored inside the barrel, or it may be a structure in which the oil-based ballpoint pen ink composition stored inside the ink storage cylinder (ballpoint pen refill) is used as a ballpoint pen as is. [Industrial applicability]

[0120] The present invention can be used as an ink composition for oil-based ballpoint pens, and more specifically, it can be widely used as an oil-based ballpoint pen, such as a capped or retractable pen, filled with the oil-based ballpoint pen ink composition. [Explanation of Symbols]

[0121] 1 Ballpoint pen refill 2 ink cartridges 3 balls 4 ballpoint pen tips 5 Tip of the chip 6 Ball Holding Room 7 Ink flow holes 8 Ink flow grooves 9 Ball Seat 10. Ink for oil-based ballpoint pens H Ball α crimping angle

Claims

1. It comprises a colorant, an organic solvent, polyvinyl butyral resin, polyoxyalkylene glyceryl ether, and a surfactant. The surfactant is an anionic surfactant selected from nonionic surfactants selected from the group consisting of fatty acid esters, polyalkylene alkyl ethers, polyoxyethylene alkylamines, alkylimidazolines, alkyl alkanolamides and mixtures thereof, and / or phosphate ester surfactants. The ratio of the polyoxyalkylene glyceryl ether to the surfactant is 5 to 20 times by mass. The aforementioned organic solvent is an aromatic alcohol. The content of the polyvinyl butyral resin is 70% or more of the total resin content. An oil-based ballpoint pen ink composition characterized in that the average number of alkylene oxide addition moles of the polyoxyalkylene glyceryl ether is 5 to 20.

2. The ink composition according to claim 1, wherein the coloring agent is a pigment.

3. The ink composition according to claim 1 or 2, wherein the content of the polyoxyalkylene glyceryl ether is 0.1 to 40% by mass with respect to the total amount of the ink composition.

4. The ink composition according to any one of claims 1 to 3, wherein the surfactant is a nonionic surfactant.

5. The ink composition according to any one of claims 1 to 3, wherein the surfactant is an anionic surfactant.

6. The ink composition according to any one of claims 1 to 3, wherein the surfactant is a combination of a nonionic surfactant and an anionic surfactant.

7. 20℃, shear rate 5sec －１ The ink composition according to any one of claims 1 to 6, wherein the viscosity in is 30,000 mPa·s or less.

8. The ink reservoir has a ballpoint pen tip that rotatably holds a ball at its tip, and the ink reservoir contains a colorant, an organic solvent, polyvinyl butyral resin, polyoxyalkylene glyceryl ether, and a surfactant. The surfactant is an anionic surfactant selected from nonionic surfactants selected from the group consisting of fatty acid esters, polyalkylene alkyl ethers, polyoxyethylene alkylamines, alkylimidazolines, alkyl alkanolamides and mixtures thereof, and / or phosphate ester surfactants. The ratio of the polyoxyalkylene glyceryl ether to the surfactant is 5 to 20 times by mass. The aforementioned organic solvent is an aromatic alcohol. The content of the polyvinyl butyral resin is 70% or more of the total resin content. An oil-based ballpoint pen characterized by containing an ink composition in which the average number of alkylene oxide addition moles of the polyoxyalkylene glyceryl ether is 5 to 20.

9. The oil-based ballpoint pen according to claim 8, wherein the arithmetic mean roughness (Ra) of the surface of the ball is 0.1 to 12 nm.

10. The oil-based ballpoint pen according to claim 8 or 9, wherein the ink consumption per 100 m of the oil-based ballpoint pen is 20 to 150 mg.

11. An oil-based ballpoint pen according to any one of claims 8 to 10, wherein the amount of movement of the ball in the vertical axis direction in the ballpoint pen tip is 3 to 30 μm.

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