Oil-based ballpoint pen and ink composition for oil-based ballpoint pen for use therein

Abstract

To provide an oil-based ballpoint pen which suppresses wear of the ball seat under high writing pressure (writing load of 300 to 500 gf), improves the writing feel, and has good writing start performance, stability over time of the ink composition, and good ink following property, and an ink composition for an oil-based ballpoint pen used therein.SOLUTION: There is provided an oil-based ballpoint pen containing an ink composition for an oil-based ballpoint pen, the ink composition containing a colorant, an organic solvent, and a polyoxyalkylene glyceryl ether.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an oil-based ballpoint pen and an ink composition for an oil-based ballpoint pen used therein.

Background Art

[0002] When writing with a ballpoint pen, the writing resistance between the writing tip and the writing surface easily affects the writing feel of the ballpoint pen. The ballpoint pen tip consists 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 seat of the metal tip. The ballpoint pen tip is mounted on an ink cartridge. However, due to the rotation of the ball during writing, wear occurs on the ball seat, resulting in drawbacks such as skipping lines, 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 easy to affect the stability of the ink composition over time. Also, when the tip of the pen is left exposed to the air, when the solvent in the ink evaporates and the colorant, resin, etc. dry and solidify, streaks are likely to occur during writing.

[0003] To solve these 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] As an ink composition for an oil-based ballpoint pen using such an additive, for those using alkyl β-D-glucoside, there is Patent Document 1 "Oil-based ballpoint pen ink"; for those using polyethylene glycol with an average molecular weight of 200 to 4,000,000, there is Patent Document 2 "Ink composition for oil-based ballpoint pen"; for those using N-acyl amino acid, N-acyl methyl tauric acid, and N-acyl methyl alanine, there is Patent Document 3 "Oil-based ballpoint pen ink"; for those containing at least decaglyceryl decamacadamia nut oil fatty acid and polyoxyethylene alkyl ether with 16 or more carbon atoms in the alkyl group and being solid at room temperature, there is Patent Document 4 "Oil-based ink composition for ballpoint pen" and the like.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, when using various additives as in Patent Documents 1 to 4, although the writing resistance can be reduced to some extent between the tip of the writing instrument and the writing surface, it is not satisfactory and there is room for improvement.

[0007] Furthermore, in recent years, in order to improve the writing feel with oil-based ballpoint pen ink, the viscosity of the ink has been decreasing. When writing with a high pen pressure (high pen pressure writing, writing load: 300 - 500 gf), it is likely to affect lubricity, and as the wear of the ball seat progresses, it is likely to affect writing performance. Therefore, in order to further reduce the writing resistance between the writing tip and the writing surface, improving lubricity and improving high pen pressure writing are required.

[0008] Also, in the case of a retractable ballpoint pen such as a click-type ballpoint pen or a rotary feed ballpoint pen, it is important because it is likely to affect writing performance when the tip of the chip is left in the air.

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

[0010] An object of the present invention is to obtain an ink composition for an oil-based ballpoint pen that suppresses wear of the ball seat under high pen pressure (writing load: 300 - 500 gf), improves writing feel, and has good writing performance, temporal stability of the ink composition, and ink followability, and an oil-based ballpoint pen using the same.

Means for Solving the Problems

[0011] The present invention adopts the following configuration to solve the above problems. 1. An ink composition for an oil-based ballpoint pen, comprising a colorant, an organic solvent, and polyoxyalkylene glyceryl ether. 2. The ink composition according to item 1, wherein the colorant is a pigment. 3. The ink composition according to item 1 or 2, wherein the content of the polyoxyalkylene glyceryl ether is 0.1 - 40% by mass based on the total amount of the ink composition. 4. The ink composition according to any one of items 1 - 3, wherein the organic solvent is an aromatic alcohol. 5. The ink composition according to any one of items 1 - 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, alkyl imidazolines, alkyl alkanolamides, 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 °C, shear rate 5 sec -1 The ink composition according to any one of items 1 to 9, having a viscosity of 30,000 mPa·s or less. 11. An oil-based ballpoint pen, having a ballpoint pen tip that rotatably holds a ball at the tip of an ink containing cylinder, and containing an ink composition comprising a colorant, an organic solvent, and polyoxyalkylene glyceryl ether in the ink containing 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 100 m of the oil-based ballpoint pen is 20 to 120 mg. 14. The oil-based ballpoint pen according to any one of items 11 to 13, wherein the amount of movement of the ball in the longitudinal axis direction in the ballpoint pen tip is 3 to 30 μm.

Advantages 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 the wear of the ball seat under high writing pressure (writing load: 300 to 500 gf), improves the writing feel, and has good writing performance, temporal stability of the ink composition, and ink followability, thereby obtaining an ink composition for an oil-based ballpoint pen and an oil-based ballpoint pen using the same.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

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 percentage 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. By virtue of the lubricating layer formed by containing polyoxyalkylene glyceryl ether, the lubricity between the writing tip and the writing surface (including the lubricity between the ball and the tip body) is maintained, the writing resistance of the writing tip is suppressed, the wear of the ball seat under high writing pressure (writing load: 300 to 500 gf) is suppressed, the writing feel is improved, and even when the writing tip is left in the air, the evaporation of the solvent in the ink is suppressed, thereby improving the writing performance while preventing the generation of precipitates and the like in the ink and improving the temporal stability (hereinafter simply referred to as temporal stability) of the ink composition. Therefore, it is possible to suppress the wear of the ball seat under high writing pressure (writing load: 300 to 500 gf) and improve all of the writing feel, writing performance, and temporal stability.

[0016] (Polyoxyalkylene glyceryl ether) The polyoxyalkylene glyceryl ether used in the present invention is obtained by subjecting glycerin or polyglycerin to addition polymerization of alkylene oxide, and examples thereof include polyoxyalkylene glyceryl ether, polyoxyalkylene diglyceryl ether, and polyoxyalkylene triglyceryl ether.

[0017] The polyoxyalkylene glyceryl ether has an alkylene oxide in its structure and is a compound having hydrophilicity and lipophilicity. By having a highly polar hydrophilic group in the structure, it is likely to adsorb to the metal material of the ball pen tip, and the lubricity can be further improved. Therefore, even under a high writing pressure (writing load: 300 to 500 gf), wear of the ball seat can be suppressed and the writing feel can be improved.

[0018] Furthermore, since the polyoxyalkylene glyceryl ether generally has low volatility, even when the writing tip is left in the air, the writing performance can be improved, and by suppressing the ink thickening of the oily ball pen ink composition as much as possible, the ink followability can be improved. Also, when a pigment is used as the colorant, generally, the ink viscosity increases due to the aggregation of the pigment over time, and the ink followability decreases. However, the polar group in the structure of the polyoxyalkylene glyceryl ether adsorbs to the pigment surface and stably disperses the pigment in the oily ink. Therefore, by suppressing the increase in ink viscosity due to the aggregation of the pigment, the ink followability can be improved.

[0019] In addition, the polyoxyalkylene glyceryl ether includes polyoxyethylene glyceryl ether, polyoxypropylene glyceryl ether, and the like. Among these, the polyoxypropylene glyceryl ether has a propylene group, is excellent in lipophilicity, and tends to improve the stability over time by suppressing the moisture absorption of the ink composition. Therefore, it is preferable to use polyoxypropylene glyceryl ether.

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

[0021] In particular, considering the suppression of wear of the ball seat under high writing pressure, the average number of moles of added propylene oxide is preferably from 1 to 30, more preferably from 1 to 20, still more preferably from 5 to 20, yet more preferably from 1 to 12, and particularly preferably from 5 to 12. Also, considering that the effects of the present invention are easily exhibited, the structure of the polyoxyalkylene glyceryl ether is preferably a structure represented by the following formula (1) or (2).

Chemical formula

[0022] Among these, the polyoxyalkylene glyceryl ether represented by formula (1) is preferable because it has a great effect of improving stability over time.

[0023] Also, 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 large, it is likely to affect the stability over time, and furthermore, the viscosity of the ink composition is likely to increase, which is likely to affect the ink followability. Considering more the stability over time and the ink followability, the weight-average molecular weight is preferably 3,000 or less, more preferably 1,500 or less, and even more preferably 1,200 or less. Also, considering the suppression of wear of the ball seat under high writing pressure, it is preferably 900 or less. On the other hand, if the weight-average molecular weight is too small, it is likely to affect the suppression of wear of the ball seat under high writing pressure, the writing property, and the pigment dispersibility. Therefore, the weight-average molecular weight is preferably 300 or more, and considering more the suppression of wear of the ball seat under high writing pressure, the weight-average molecular weight is preferably 500 or more. The weight-average molecular weight is a value obtained in terms of polystyrene using GPC (gel permeation chromatography).

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

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

[0026] (Organic solvent) Examples of the 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, 3-methoxy-3-methylbutanol, etc., glycol solvents such as diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, butylene glycol, ethylene glycol, etc., alcohol solvents such as benzyl alcohol, methanol, ethanol, 1-propanol, 2-propanol, isopropanol, isobutanol, t-butanol, propargyl alcohol, allyl alcohol, 3-methyl-1-butyn-3-ol, ethylene glycol monomethyl ether acetate and other higher alcohols, and organic solvents generally used as inks for oil-based ballpoint pens can be exemplified.

[0027] Among these organic solvents, aromatic alcohols are preferred because they have an aromatic ring to improve lubricity, have high compatibility with polyoxyalkylene glyceryl ether, and also improve the stability of the solution.

[0028] In addition, when a glycol ether solvent is used, due to its appropriate hygroscopicity, it can appropriately retain the moisture of the film formed when the tip of the chip dries and soften the film, making it easy to improve the writing performance. Therefore, by combining it with polyoxyalkylene glyceryl ether, more excellent effects can be obtained. Considering the stability in the ink composition, it is preferable to use an aromatic glycol ether solvent.

[0029] Also, considering the improvement of solubility, lubricity, drying property of handwriting, etc., 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] (Colorant) The colorant used in the present invention is not particularly limited, such as dyes, pigments, etc., and can be appropriately selected and used. Dyes and pigments may be used in combination. Examples of dyes include oil-soluble dyes, acid dyes, basic dyes, metal-containing dyes, etc., and various salt-forming types of dyes 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 alone or in combination of two or more.

[0031] Also, considering lubricity, it is preferable to use pigments as the colorant. This is because pigment particles enter the gap between the ball and the chip body, making it easier for the action like that of a bearing to work. By suppressing the direct contact between metal members, the lubricity can be improved, the writing feel can be improved, and the effect of suppressing the wear of the ball seat can be easily obtained. Furthermore, pigments are excellent in water resistance and light resistance and can obtain good color development, so they are preferable. Specifically, it is preferable to use from among carbon black, quinacridone-based, perylene-based, and diketopyrrolopyrrole-based pigments. Further, from the viewpoint of stability over time, it is preferable to use carbon black and diketopyrrolopyrrole-based pigments.

[0032] Also, examples of pigments include inorganic, organic, and processed pigments, etc. Specifically, carbon black, aniline black, ultramarine, lead yellow, titanium oxide, iron oxide, phthalocyanine-based, azo-based, quinacridone-based, diketopyrrolopyrrole-based, quinophthalone-based, perylene-based, triphenylmethane-based, perinone-based, perylene-based, dioxazine-based, metallic pigments, pearl pigments, fluorescent pigments, phosphorescent pigments, etc.

[0033] These pigments can easily maintain lubricity due to the synergistic effect of, in particular, polyoxyalkylene glyceryl ethers, a lubricating layer formed by a nonionic surfactant or an anionic surfactant (especially a phosphate ester surfactant), and the bearing action between the pigment particles, which enables suppression of wear of the ball seat and improvement of writing quality. Also, considering the ink composition flow path and member spacing inside the ballpoint pen tip, the average particle diameter of the pigment is preferably 1 to 500 nm. More preferably, it is 30 to 350 nm, and even more preferably, it is 50 to 300 nm. Here, the average particle diameter is determined by the particle diameter (D50) at 50% volume cumulative of the particle size distribution measured using the laser diffraction method, specifically, a laser diffraction particle size distribution analyzer (trade name "Microtrac HRA9320-X100", Nikkiso Co., Ltd.) based on the calibrated numerical values using standard samples and other measurement methods.

[0034] In addition, since the above-mentioned pigments exhibit the above-described effects in the state of dispersion of the pigments in the ink composition for oil-based ballpoint pens, it is preferable to determine the particle diameter in the dispersed state.

[0035] Furthermore, the pigments are preferable because they are excellent in water resistance and light resistance and can provide good color development and good handwriting fastness. From the viewpoints of the excellent water resistance, light resistance, and lubricity of the pigments, it is preferable that the content of the pigments relative to the content of the colorants in the ink composition for oil-based ballpoint pens is high. Specifically, by setting the content of the pigments relative to the content of the colorants to 10% by mass or more, the water resistance, light resistance, and lubricity can be improved to the required levels. However, from the viewpoints of further water resistance and light resistance, to make it less likely for handwriting changes to occur, it is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass, and particularly preferably 100% by mass.

[0036] Generally, an ink composition containing a pigment tends to have insufficient writing performance and ink followability when the tip of the writing instrument dries. However, the ink composition according to the present invention contains polyoxyalkylene glyceryl ether, so that even when the pigment content ratio is high, the writing performance and ink followability are kept good.

[0037] When using a dye, the combination with polyoxyalkylene glyceryl ether results in high stability over time, so it is preferable to use a salt-forming dye. Furthermore, since the salt-forming bond is stable, higher stability over time can be obtained. Therefore, it is preferable to use a salt-forming dye selected from among salt-forming dyes of a basic dye and an organic acid, salt-forming dyes of an acidic dye and a basic dye, and salt-forming dyes of an acidic dye and an organic amine. Considering the stability when combined with the components of the ink composition, a salt-forming dye of a basic dye and an organic acid is preferable.

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

[0039] (Surfactant) The ink composition according to the present invention preferably contains a surfactant. This is because the surfactant softens the film formed at the tip of the writing instrument by a resin or the like contained in the ink composition, easily improves the writing performance, and further improves the lubricity and easily improves the writing feel. As the surfactant, there are nonionic surfactants, anionic surfactants, cationic surfactants, etc., but it is preferable to use a nonionic surfactant. This is because being nonionic makes it difficult for precipitates to be generated by other components contained in the ink composition, so the stability over time can be improved.

[0040] Regarding nonionic surfactants, considering the stability over time, it is preferable that the HLB value is 16 or less, more preferably 3 to 14, and particularly preferably 3 to 11. The HLB value can be determined by the Griffin method or the like.

[0041] In retractable writing instruments such as knock-type writing instruments and rotary retractable writing instruments, unlike cap-type writing instruments, the pen tip is constantly exposed to the outside. In such a case, the writing tip is likely to dry out. Since the surfactant having the above HLB value can also improve such problems, it is more preferable to use it.

[0042] Examples of nonionic surfactants include fatty acid esters, polyalkylene alkyl ethers, polyoxyethylene alkylamines, alkyl imidazolines, alkyl alkanolamides, oxyethylene oxypropylene block copolymers, and surfactants having an acetylene bond. Among them, considering the writing 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, alkyl imidazolines, and alkyl alkanolamides. Particularly considering improving the writing performance, it is preferable to use fatty acid esters. These may be used alone or in combination of two or more.

[0043] In addition, examples of the fatty acid esters include sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, fatty acid esters, glycerin fatty acid esters, polyglycerin fatty acid esters, polyoxyethylene fatty acid esters, and the like. Among these, since the writing performance is improved by the interaction with polyoxyalkylene glyceryl ether, it is preferable to select one or more from sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, glycerin fatty acid esters, and alkyl imidazolines. Furthermore, it is preferable to use sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, and alkyl imidazolines, which have a structure with a cyclic skeleton. In addition, since fatty acid esters having a plurality of hydroxyl groups can appropriately retain the moisture of the film formed at the tip of the writing instrument, it is preferable to select one or more from sorbitan fatty acid esters or sorbitan fatty acid esters that are polyoxyethylene sorbitan fatty acid esters.

[0044] Also, considering the writing performance, it is preferable that the number of carbon atoms contained in the alkyl group of the sorbitan fatty acid esters is 1 to 20. Furthermore, by making it a length suitable for forming the lubricating layer, it is easy to improve the wear suppression of the ball seat under high writing pressure. Therefore, it is preferable that the number of carbon atoms contained in the alkyl group of the sorbitan fatty acid esters is 10 to 20, and it is more preferable that it is 12 to 18.

[0045] Examples of sorbitan fatty acid esters specifically include sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan monooleate, sorbitan monococoate, sorbitan dilaurate, sorbitan distearate, sorbitan dioleate, sorbitan trioleate, sorbitan tristearate, and sorbitan fatty acid esters such as their composites; polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan trioleate, polyoxyethylene sorbitan tristearate, and polyoxyethylene sorbitan fatty acid esters such as their composites.

[0046] The content of the nonionic surfactant is more preferably 0.1 to 15% by mass based on the total amount of the ink composition. If it is less than 0.1% by mass, it is difficult to suppress the wear of the ball seat under a desired high writing pressure (writing load: 300 to 500 gf), improve the writing feel, and obtain 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 preferable based on the total amount of the ink composition, and 1 to 5% by mass is most preferable.

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

[0048] Since phosphate ester surfactants have phosphate groups, they are likely to adsorb on the metal surface, and in particular, can form a lubricating film between the ball and the ball seat. As a result, the lubricity can be improved and the writing feel can be enhanced. Therefore, by combining a phosphate ester surfactant and polyoxyalkylene glyceryl ether, the lubricating actions of both can work, synergistically further improving the lubricity between the ball and the ball seat and bringing about a smooth writing feel. Furthermore, phosphate ester surfactants also have the effect of improving the writing performance, and by using them in combination with polyoxyalkylene glyceryl ether, the writing performance can be further improved.

[0049] Furthermore, since phosphate ester surfactants have a rust-preventing effect, when the ball is made of metal, it is preferable because the corrosion of the ball is suppressed, the writing feel is maintained well, and the wear of the ball seat is suppressed. Especially when the ball is made of an alloy containing cobalt, nickel, chromium, etc., these metals are less likely to be corroded over time due to the rust-preventing effect of the phosphate ester surfactant, so it is preferable. This tendency is remarkable and preferable in the case of a cemented carbide ball as the ball material, especially a cemented carbide ball containing tungsten carbide as the main component and cobalt, nickel, chromium, etc. as the binder.

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

[0051] Furthermore, the ink composition according to the present invention may contain polyvinyl butyral. Polyvinyl butyral also has the effect of improving lubricity, but by combining it with a phosphate ester surfactant, due to the synergistic effect of the improvement effect by polyvinyl butyral and the improvement effect by an anionic surfactant, particularly a phosphate ester surfactant, the lubricity is more likely to be further improved, which is preferable.

[0052] Due to the interaction between the phosphate ester surfactant and polyoxyalkylene glyceryl ether, both lubricity and writing performance can be further improved. Therefore, the HLB value of the phosphate ester surfactant is preferably 6 to 18, more preferably 6 to 14. This is because when the HLB value exceeds 18, the hydrophilicity tends to be strong and the solubility in the oil-based ink composition tends to be poor. As a result, it is difficult to obtain the effect of the phosphate ester surfactant, especially the lubricating effect. Also, when the HLB value is less than 6, the lipophilicity becomes too strong, which easily affects the compatibility with the organic solvent, making it difficult to obtain stability over time and further difficult to improve the writing performance. Furthermore, considering lubricity, the HLB value is preferably 17 or less, more preferably 12 or less. That is, the HLB value is preferably 6 to 17, more preferably 6 to 12. Also, considering the writing performance further, the HLB value is preferably 7 to 17, more preferably 7 to 12. In particular, in retractable ball pens such as knock-type ball pens and rotary feed ball pens, since the pen tip is always exposed to the outside, the writing tip is likely to dry. Therefore, in order to improve the writing performance, it is more preferable to use the phosphate ester surfactant having the above HLB value. The HLB value can be determined by the Griffin method, Kawakami method, etc.

[0053] Examples of the phosphate ester surfactant include phosphate esters having an alkoxy group (C a H 2a+1 O), phosphate monoesters of polyoxyethylene alkyl ethers or polyoxyethylene alkyl aryl ethers, phosphate diesters of polyoxyethylene alkyl ethers or polyoxyethylene alkyl aryl ethers, phosphate triesters of polyoxyethylene alkyl ethers or polyoxyethylene alkyl aryl ethers, alkyl phosphate esters, alkyl ether phosphate esters, or their derivatives, etc.

[0054] Among these, in consideration of suppressing the wear of the ball seat under high writing pressure (writing load: 300 to 500 gf), it is preferable to use a phosphate ester surfactant having an alkyl group. In particular, the number of carbon atoms contained in the alkyl group is preferably 8 to 18, more preferably 10 to 18, and even more preferably 12 to 18. This is because if the number of carbon atoms in the alkyl group is excessively small, the lubricity tends to be insufficient, and if the number of carbon atoms is excessively large, the stability over time tends to be affected.

[0055] Further, 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 or less. This is to facilitate the improvement of lubricity by the phosphate ester surfactant. Furthermore, considering the stability and lubricity in the ink composition, the acid value is preferably 30 to 170 (mgKOH / g), preferably 40 to 160 (mgKOH / g), and more preferably 70 to 120 (mgKOH / g).

[0056] Note that the acid value is represented by the number of milligrams of potassium hydroxide required to neutralize the acidic components contained in 1 g 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 the above formula (1) or (2) to the surfactant, particularly the nonionic surfactant and the phosphate ester surfactant as described above (polyoxyalkylene glyceryl ether / surfactant) is preferably 1 to 40 times, 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 on a mass basis. This is because within the above range, it is possible to improve the wear suppression of the ball seat and the writing feel, writing performance, and ink followability in a well-balanced manner.

[0058] (organic amine) 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 of amines having ethylene oxide such as oxyethylene alkylamine and polyoxyethylene alkylamine, alkylamines such as laurylamine and stearylamine, and aliphatic amines such as dimethylalkylamines such as distearylamine, dimethyllaurylamine, dimethylstearylamine, and dimethyloctylamine can be mentioned. Among them, amines having ethylene oxide and dimethylalkylamines are preferred. And especially considering the wear suppression of the ball seat under high writing pressure (writing load: 300 to 500 gf), amines having ethylene oxide are preferred.

[0059] Furthermore, considering the stability with the surfactant, colorant and other components, the total amine value of the organic amine is preferably 100 to 300 (mgKOH / g). This is because if it exceeds 300 (mgKOH / g), the reactivity is too strong and it is likely to react with the above components, so the stability over time tends to be poor. 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 lubricating performance tends to decrease when used as an oil-based ballpoint pen. From the viewpoints of stability and lubricity with the above components, a range of 150 to 300 (mgKOH / g) is more preferable. Also, from the viewpoint of stability, it is preferably 180 to 300 (mgKOH / g), and more preferably 230 to 270 (mgKOH / g).

[0060] In the present invention, the total amine value indicates the total amount of primary, secondary, and tertiary amines, and is represented by the number of mg of potassium hydroxide equivalent to the hydrochloric acid required to neutralize 1 g of the sample.

[0061] Regarding the reactivity between the organic amine and other components in the ink composition, the primary amine has the strongest reactivity, followed by the secondary amine and the tertiary amine with decreasing reactivity. Therefore, considering the stability over time, it is preferable to use a secondary amine or a tertiary amine. These may be used alone or in combination of two or more.

[0062] (Resin) In addition, in order to further improve the suppression of ink leakage, it is preferable to use a resin as an ink viscosity regulator. Examples of the resin include polyvinyl butyral resin, ketone resin, polyacetal resin, polyvinyl alcohol resin, cellulose resin, terpene resin, alkyd resin, phenoxy resin, polyvinyl acetate resin, etc. Among them, it is preferably composed of polyvinyl butyral resin or ketone resin.

[0063] The polyvinyl butyral resin is likely to form a lubricating layer that provides a higher lubricating effect. This is because when using the polyvinyl butyral resin, an elastic ink layer is always formed between the ball and the ball seat, making direct contact difficult. As a result, the writing feel tends to be improved. And due to the synergistic effect of using the polyvinyl butyral resin and polyoxyalkylene glyceryl ether together, a higher lubricating effect is more likely to be obtained. Furthermore, when using the polyvinyl butyral resin, the film formed at the writing tip makes it easier to improve ink leakage, so it is preferable. Also, when using a pigment as a colorant, a pigment dispersion effect can also be obtained, so it is preferable to use the polyvinyl butyral resin.

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

[0065] Also, the polyvinyl butyral resin preferably has a hydroxyl group content of 25 mol% or more. This is because a polyvinyl butyral resin with a hydroxyl group content of 25 mol% or more has sufficient solubility in organic solvents and has great lubricating effects, effects of suppressing ink leakage, and effects of improving writing performance. A polyvinyl butyral resin with a hydroxyl group content of 30 mol% or more is particularly preferable because the writing feel is likely to be improved. Generally, during writing, frictional heat is generated due to the rotation of the ball, so the temperature of the ink composition at the tip of the chip increases, the viscosity of the ink composition decreases, and the writing feel may deteriorate. However, different from other resins, the polyvinyl butyral resin has the property of making it difficult for the viscosity of the ink composition to decrease even when the ink temperature increases, and always forms an elastic ink layer between the ball and the ball seat, making it difficult to come into direct contact, so there is a tendency to easily improve the writing feel. In particular, in the case of an oil-based ballpoint pen, since writing is often done with a high pen pressure, it is effective. Also, a polyvinyl butyral resin with a hydroxyl group content of 40 mol% or less is preferable because it has low hygroscopicity and is less likely to have its stability over time impaired. Therefore, a polyvinyl butyral resin with a hydroxyl group content of 30 to 40 mol% is preferable, and a hydroxyl group content of 30 to 36 mol% is even more preferable.

[0066] Note that the hydroxyl group content (mol%) of the polyvinyl butyral resin indicates the content rate of the hydroxyl group (mol%) with respect to the total mol amount of the butyral group (mol%), acetyl group (mol%), and hydroxyl group (mol%).

[0067] In addition, 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 improve. When the average degree of polymerization exceeds 2,500, the ink viscosity becomes too high and tends to affect the writing feel. Therefore, the average degree of polymerization is preferably 200 to 2,500, and more preferably 1,500 or less. Also, considering the synergistic lubricity improvement effect with polyoxyalkylene glyceryl ether, the average degree of polymerization is preferably 200 to 1,000. Here, the average degree of polymerization refers to the number of basic units constituting one molecule of the polyvinyl butyral resin, and a value measured based on the method specified in JIS K6728 (2001 edition) can be adopted.

[0068] The content of the polyvinyl butyral resin is preferably 50% or more based on the total resin content in the oil-based ballpoint pen ink composition and is preferably used as the main resin. This is because when the content of the polyvinyl butyral resin is less than 50% of the total resin content, it is likely to be inhibited from forming an elastic ink layer by other resins, making it difficult to obtain the effect of improving the writing feel. Furthermore, it is likely to inhibit the formation of the resin film at the tip of the nib and cannot suppress ink dripping. Considering the tendency to further improve the writing feel and ink dripping performance, the content of the polyvinyl butyral resin is preferably 70% or more, and more preferably 90% or more based on the total resin content.

[0069] When the resin content is less than 1% by mass based on the total amount of the ink composition, the desired lubricity and ink leakage suppression performance are likely to be inferior. When it exceeds 40% by mass, the solubility in the ink is likely to be inferior. Therefore, the resin content is preferably 1 to 40% by mass based on the total amount of the ink composition. Furthermore, a resin content of 5% by mass or more is preferable. Also, when the resin content exceeds 30% by mass, the ink viscosity becomes too high and tends to affect the writing feel. From these points, 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, as other additives, pseudoplasticity imparting agents such as fatty acid amides and hydrogenated castor oil may be used as viscosity modifiers, and colorant stabilizers, plasticizers, chelating agents, water, etc. may be appropriately used. These may be used alone or in combination of two or more.

[0071] The viscosity of the ink composition of the oil-based ballpoint pen ink composition of the present invention is not particularly limited. However, if the viscosity is excessively high, the writing performance, writing feel, and ink followability tend to be inferior. Therefore, at 20°C and a shear rate of 5 sec -1 (at rest), the ink viscosity is preferably 30,000 mPa·s or less. Also, if the viscosity is excessively low, it is difficult to suppress ink leakage. Therefore, it is preferably 500 mPa·s or more, and more preferably 1,000 mPa·s or more. Considering more improving ink leakage suppression, writing feel, ink followability, and 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 even more preferably 800 to 25,000 mPa·s. Further, from the viewpoints of writing feel and writing performance, it is more preferably 1,000 to 20,000 mPa·s, and even more preferably 2,000 to 20,000 mPa·s. Also, in order to further improve the writing feel, increase the ink consumption, and obtain a thick handwriting, the viscosity is preferably 500 to 10,000 mPa·s, and more preferably 1,000 to 5,000 mPa·s.

[0072] (Oil-based ballpoint pen) The ink composition for an oil-based ballpoint pen according to the present invention can be applied to various oil-based ballpoint pens, but is particularly preferably used for retractable ballpoint pens such as click-type and rotary feed-type ballpoint pens. Such a ballpoint pen includes a storage cylinder that stores the oil-based ink composition according to the present invention, and a ballpoint pen tip that is disposed at the tip of the storage cylinder and rotatably holds a ball in a ball holding chamber. The ballpoint pen tip can be projected in and out from the tip opening of the shaft cylinder, and has a structure generally called a retractable ballpoint pen. Generally, when an ink composition is used in a retractable ballpoint pen with an unsealed pen tip, the tip end of the tip is constantly exposed to the atmosphere, so the tip end of the tip dries, and streaks are likely to occur during writing. However, when the composition according to the present invention is used, such problems are improved, which is preferable.

[0073] Hereinafter, a preferred configuration of the oil-based ballpoint pen according to the present embodiment will be described with reference to the drawings.

[0074] The oil-based ballpoint pen in the present invention stores an ink composition in a storage cylinder. The storage etc. may be in the form of a refill with a tip attached to the tip portion, or may be the shaft cylinder itself with a tip attached to the tip portion. The ink composition according to the present invention is suitable for a retractable ballpoint pen, and it is preferable that the refill is stored in the shaft cylinder. FIG. 1 is a conceptual cross-sectional view of a ballpoint pen refill that can be used for the oil-based ballpoint pen according to the present embodiment.

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

[0076] As the ink storage cylinder for storing ink, for example, a molded body made of a thermoplastic resin such as polyethylene, polypropylene, polyethylene terephthalate, or nylon is used.

[0077] In addition to directly connecting the chip to the ink container, the ink container and the chip may be connected via a connecting member.

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

[0079] The ballpoint pen tip disposed at one end of the refill can be arbitrarily selected from commonly used ones. FIG. 2 is a conceptual cross-sectional view of the ballpoint pen tip 4 that can be used for the oil-based ballpoint pen according to this embodiment.

[0080] The ballpoint pen tip 4 includes at least a ballpoint pen tip body and a ball 3. The ballpoint pen tip body is generally formed of a metal material. For example, a stainless steel wire is cut to a desired length, and after forming a ball holding chamber 6, an ink flow hole 7, and an ink flow groove 8 extending radially from the ink flow hole 7, a substantially arc-shaped ball seat 9 is formed on the bottom wall of the ball holding chamber 6, thereby manufacturing it. By placing the ball 3 on the ball seat 9 of the ballpoint pen tip body and caulking the tip end portion 5 of the tip inward, the ballpoint pen tip 4 can be obtained.

[0081] Since the shape of the ballpoint pen tip affects writing performance and the like, it is adjusted as necessary. For example, the ball protrusion H of the ball 3 protruding from the tip of the tip in a state where the ball 3 is placed on the ball seat 9 is generally 10 to 30% of the ball diameter, for example, 30%. By having the ball protrusion within this range, the ink consumption per 100 m can be adjusted to an appropriate value.

[0082] Also, if the caulking angle α is too large, the paper contact angle becomes small and it is likely to affect writing performance. Therefore, it is preferably 110 degrees or less, more preferably 95 degrees or less. If the caulking angle is less than 50 degrees, the space for accumulating ink between the ball 3 and the tip edge of the chip tends to become small, which may cause inferior writing performance. For this reason, the caulking angle α is preferably 50 degrees to 110 degrees, more preferably 60 degrees to 95 degrees, and for example, 80 degrees.

[0083] Also, the inner diameter of the ball holding chamber can generally be 101 to 120% of the ball diameter, for example, 104%, and the diameter of the ball seat 9 can generally be 70 to 95% of the ball diameter, for example, 86%. By being in such a range, the ink consumption per 100 m can be adjusted to an appropriate value.

[0084] In such a ball 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, etc., and ruby balls. Among them, cemented carbide balls that are less likely to crack and have good workability and productivity are preferred, cemented carbide balls mainly composed of tungsten carbide are preferred, and furthermore, considering the bonding stability, it is also preferable to use a cemented carbide containing cobalt as a binder.

[0085] In addition, a single metal such as steel, copper, aluminum, or nickel may be used, or an alloy such as brass or stainless steel may be used. Further, carbides, oxides, nitrides, borides, silicides, etc. of metals, etc. can also be used. As the carbide, carbides of titanium, vanadium, chromium, tantalum, niobium, molybdenum, boron, zirconium, tungsten, or silicon, etc. can be used. As the oxide, oxides of aluminum, chromium, magnesium, silicon, beryllium, thorium, titanium, calcium, or zirconium, etc. can be used. As the nitride, nitrides of titanium, boron, silicon, silicon, or aluminum, etc. can be used. As the boride, borides of zirconium, chromium, or titanium, etc. can be used.

[0086] The ball 3 generally has a diameter in the range of 0.25 mm to 1.6 mm, preferably 0.5 mm to 1.6 mm, and more preferably 0.5 mm to 1.0 mm. Specifically, a plurality of sizes of the ball 3 are prepared according to the desired writing line width. For example, balls 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 are adopted.

[0087] Also, 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 the ink to sufficiently adhere to the ball surface, and it is difficult to obtain a dark handwriting during writing. Lines and smudges are likely to occur in the handwriting. If the arithmetic mean roughness (Ra) exceeds 12 nm, the ball surface is too rough, and the rotational resistance between the ball and the ball seat is large. Therefore, the ball seat is likely to wear and the writing feel is inferior. Furthermore, it is likely to affect the writing performance such as smudges, lines, and line unevenness in the handwriting. Also, when the arithmetic mean roughness (Ra) is 0.1 to 10 nm, when an ink composition as in the present invention is used, it is more preferable because the writing feel is improved and the ink adheres easily to the ball surface. Considering the writing feel more, 2 to 8 nm is preferable. Regarding the arithmetic mean roughness of the ball surface, the arithmetic mean roughness (Ra) can be obtained from the roughness curve measured by a surface roughness measuring instrument (SPI3800N, trade name, manufactured by Seiko Epson Corporation). Specifically, it is a value obtained by extracting a reference length in the direction of the average line of the roughness curve, summing the absolute values of the deviations from the average line of this extracted part to the measured roughness curve, and averaging them.

[0088] Also, the material of the ball pen tip body is not particularly limited. For example, it may be various metals alone or alloys, ceramics, resins, etc. Specifically, a single metal such as steel, copper, aluminum, or nickel may be used, or an alloy such as brass or stainless steel may be used. It is preferable to use a brass tip body because it can improve the writing feel and has high workability such as cutting. Or, it is preferable to use a stainless steel tip body because of high wear resistance of the ball seat and high stability over time. Among these, ferritic stainless steel is preferable.

[0089] Also, for the ballpoint pen tip, the movable amount (clearance) of the ball of the ballpoint pen tip in the longitudinal axis direction is preferably 3 to 30 μm. This is because if it is excessively small, it is likely to affect the writing quality such as streaks, blots, and dot unevenness in the handwriting, and if it is excessively large, it is likely to affect blots, ink followability, and ink leakage suppression. The movable amount is more preferably 3 to 25 μm, even more preferably 5 to 25 μm, and particularly preferably 7 to 20 μm in consideration of handwriting drying property, ink followability, and handwriting streaks.

[0090] In the present invention, regarding the movable amount of the ball of the ballpoint pen tip in the longitudinal axis direction, it is in the form of the ballpoint pen tip of the ballpoint pen in the initial state before the start of writing.

[0091] The ink consumption per 100 m of the ballpoint pen is preferably 20 to 150 mg. This is because if the ink consumption per 100 m is less than 20 mg, handwriting streaks and dot unevenness are likely to occur, and it is difficult to obtain thick handwriting and good writing feel. If the ink consumption per 100 m exceeds 150 mg, it will affect ink followability and ink leakage is likely to occur from the gap between the ball and the tip of the tip, and handwriting drying property and blots are also likely to occur. The ink consumption per 100 m of the ballpoint pen is more preferably 25 to 140 mg, preferably 30 to 130 mg, and even more preferably 40 to 110 mg.

[0092] Regarding the ink consumption, a spiral writing test is performed using 5 test samples at a writing speed of 4 m / min under the conditions of 20 °C, a writing angle of 70° on JIS P3201 writing paper, and a writing load of 200 g, and the average value of the ink consumption per 100 m is defined as the ink consumption per 100 m.

[0093] In addition, to improve darker handwriting, writing feel, ink followability, and ink leakage suppression, it is effective to consider not only setting the ink consumption but also the relationship with the ball diameter. Specifically, regarding the ratio of the ball diameter (mm) to the ink consumption (mg) per 100 m of an oil-based ballpoint pen, by setting the relationship of (ball diameter: ink consumption) to 1:40 to 1:140, it is easier to obtain darker handwriting, writing feel, ink followability, ink leakage suppression, and handwriting dryness. The ratio of ball diameter: ink consumption is more preferably 1:50 to 1:130, and even more preferably 1:60 to 1:120.

[0094] By using an ink composition for an oil-based ballpoint pen containing polyoxyalkylene glyceryl ether as in the present invention, wear of the ball seat can be suppressed. Therefore, from the beginning to the end of writing, the ink consumption is stable, and it is preferable because good writing performance such as writing feel, less streaking in the handwriting, and darker handwriting can be stably obtained. Specifically, when the ink consumption E mg at the initial 0 to 100 m and the ink consumption F mg in the last 100 m before the end of ink are considered, regarding the ratio of the ink consumption F mg in the last 100 m before the end of ink to the ink consumption E mg at the initial 0 to 100 m, (E:F) being 1:0.7 to 1:1.3 is preferable because it is less likely to have streaking in the writing feel and handwriting, and good writing performance can be stably obtained. 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] (Example) Next, the present invention will be described by showing examples. For the ink composition for an oil-based ballpoint pen of Example 1, an organic solvent, a pigment, and a pigment dispersant were added in advance and dispersed using a three-roll disperser to prepare a pigment dispersion. Then, a pigment dispersion, a dye, an organic solvent, polyoxyalkylene glyceryl ether, a nonionic surfactant, polyvinylpyrrolidone, and a polyvinyl butyral resin were adopted, weighed in a predetermined amount, heated to 60°C, and then completely dissolved using a dispersing stirrer to obtain an ink composition for an oil-based ballpoint pen. The specific blending amounts are as follows.

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

[0097] Example 1 Pigment dispersion (carbon black, average particle diameter 150 nm, containing 20% pigment, containing 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 to 34 As shown in the table, except for changing each component, the ink was formulated in the same procedure as in Example 1 to obtain the ink compositions for oil-based ballpoint pens of Examples 2 to 34. Also, in Examples 18, 22, 28 to 34, the arithmetic mean roughness of the ball surface or the longitudinal movement amount of the ball in the ballpoint pen tip was changed. The evaluation results are shown in the table.

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

[0100] In the same manner as in Example 1, for Examples 3, 21, 25, and 31, at a shear rate of 5 sec under an environment of 20°C -1When measuring the ink viscosity at (rotation speed 2.5 rpm), it was found that for 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, containing 20% pigment content, containing 20% polyvinyl butyral resin 2 Manufactured by Fuji Pigment Co., Ltd., diketopyrrolopyrrole-based pigment, average particle size 250 nm), containing 20% pigment content, containing 20% polyvinyl butyral resin 3 Manufactured by Orient Chemical Co., Ltd. 4 SC-P750 (trade 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 (trade 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 (trade name) manufactured by Sakamoto Pharmaceutical Co., Ltd., average number of moles of propylene oxide added (m + n + o + p) = 14 7 SC-P1600 (trade name) manufactured by Sakamoto Pharmaceutical Co., Ltd., average number of moles of propylene oxide added (m + n + o + p) = 24 8 SC-E2000 (trade 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 Manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Solgen 40 (trade name), number of carbon atoms in the alkyl group = 18 Manufactured by Kao Corporation, Liondor TW-S320V (trade name), number of carbon atoms in the alkyl group = 18 Manufactured by Kao Corporation, Liondor SP-P10 (trade name), number of carbon atoms in the alkyl group = 16 12 PS-5S (trade name) manufactured by Sakamoto Yakuhin Kogyo Co., Ltd. 13 Manufactured by Kao Corporation 14 Neugen TDS-120 (trade name) manufactured by Daiichi Kogyo Seiyaku Co., Ltd. 15 Phosphanol (trade name) series manufactured by Toho Chemical Industry Co., Ltd. 16 Pricerf (trade name) series manufactured by Daiichi Kogyo Seiyaku Co., Ltd. 17 Farmine DM2098 (trade name) manufactured by Kao Corporation, tertiary amine 18 Nimine (trade name) manufactured by NOF Corporation, secondary amine 19 PVP K-90 (trade name) manufactured by IBS Japan Co., Ltd. 20 Manufactured by Sekisui Chemical Co., Ltd. 21 Manufactured by Hitachi Chemical Co., Ltd.

[0104] Tests and evaluations The ink compositions for oil-based ballpoint pens prepared in Examples 1 to 34 and Comparative Examples 1 to 3 were placed at the tip of an ink storage cylinder (made of polypropylene), and a ball (φ0.7 mm, arithmetic mean roughness (Ra) of the ball surface: 7 nm), material: cemented carbide ball mainly composed of tungsten carbide (including cobalt as a binder)) was rotatably held by a ballpoint pen tip (having a coil spring that directly presses the ball against the inner wall at the tip edge of the chip inside the chip, axial movement of the ball: 12 μm, material: ferritic stainless steel). At the same time, 0.2 g of the oil-based ballpoint pen ink of Example 1 was directly stored in the ink storage cylinder, and the ballpoint pen refill was installed in an oil-based ballpoint pen (trade name: Super Grip (registered trademark)) manufactured by Pilot Corporation, and the following tests and evaluations were carried out according to JIS P3201 for the writing paper as the writing test paper.

[0105] The ink compositions of Example 1, Example 3, Example 21, Example 25, and Example 31 were disposed in an oil-based ballpoint pen, and a spiral writing test was conducted. As a result, the ink consumption per 100 m at the start of writing was 70 mg / 100 m, 75 mg / 100 m, 60 mg / 100, 50 mg / 100 m, and 98 mg / 100, respectively.

[0106] Also, the ratios of the ink consumption (mg) per 100 m at the start of writing to the ball diameter (mm) of these oil-based ballpoint pens (ball diameter: ink consumption) were 1:100, 1:107, 1:86, 1:71, and 1:140, respectively.

[0107] In addition, when the ink consumption Emg at the time of 0 to 100 m at the start of writing and the ink consumption Fmg from 100 m before the end of writing to the end of writing of the oil-based ballpoint pens in which the ink compositions of Example 1, Example 3, Example 21, Example 25, and Example 31 were disposed were used, the ratios of the ink consumption 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 (wear test of the ball seat): The wear of the ball seat after the writing test was measured with a running tester at a load of 400 gf, a writing angle of 70°, and a speed of 4 m / min. A: Those with wear of the ball seat less than 5 μm B: Those with wear of the ball seat of 5 μm or more and less than 10 μm C: Those with wear of the ball seat of 10 μm or more and less than 20 μm but still capable of writing D: Those with severe wear of the ball seat resulting in poor writing

[0109] Writing feel: Evaluated by a sensory test by handwriting. A: Those that are very smooth B: Those that are smooth C: Those with a smoothness at a practically acceptable level D: Those that are heavy

[0110] Writing performance test: After handwritten note-taking, with the tip of the chip extended, it was left in an environment of 20°C and 65% RH for 24 hours. Then, note-taking was carried out under the following note-taking conditions in a running test, and the length of the smear of the handwriting during writing was measured. <Note-taking conditions> Evaluation was carried out by performing straight-line writing on a running tester under the conditions of a note-taking load of 200 gf, a note-taking angle of 70°, and a note-taking speed of 4 m / min. A: Those with a smear length of less than 5 mm B: Those with a smear length of 5 mm or more and less than 10 mm C: Those with a smear length of 10 mm or more and less than 20 mm D: Those with a smear length of 20 mm or more

[0111] Ink aging test: After one month in an environment of 50°C, the ink inside the chip was observed under a microscope. A: Those with no precipitate and in good condition B: Those with slightly generated precipitate C: Those with precipitate generated but with no practical problems D: Those with precipitate generated and causing smears or poor note-taking

[0112] Ink follow-up performance test: After one month in an environment of 50°C, continuous fast handwritten note-taking was carried out for 10 seconds. A: Those with no smear or skipping of the line B: Those with slightly smeared or skipped lines but at a level with no practical problems C: Those with smeared or skipped lines D: Those with severely smeared or skipped lines

[0113] Water resistance test: After drying the spiral handwriting on the note paper, it was immersed in water for 10 seconds, and the state of the handwriting was observed. A: Those with good handwriting B: Those with faded handwriting but still distinguishable C: Those with unreadable handwriting

[0114] Light resistance test: On the notepaper, under the conditions of a writing angle of 70° and a writing load of 150 g, a spiral writing test was carried out at a writing speed of 4.5 m / min. After leaving it for 1 hour, using a xenon fade meter X15F (manufactured by Suga Test Instruments Co., Ltd.), it was irradiated until the blue scale faded to grade 3, and the handwriting was observed. A: No fading B: Fading can be seen, but it can still be distinguished C: Obvious fading

[0115] In Examples 1 to 34, good performance was obtained in the abrasion resistance test (ball seat abrasion test), writing feel, writing start performance test, ink aging test, ink follow-up performance test, water resistance test, and light resistance test. In Examples 1 to 17 and 19 to 34, pigments were used as colorants, and the pigment dispersibility was good and stable.

[0116] Also, in Comparative Examples 1 to 3, since polyoxyalkylene glyceryl ether was not used, the abrasion resistance test (ball seat abrasion test) was poor, and furthermore, the ink follow-up property test was inferior.

[0117] Also, when using retractable oil-based ball pens such as knock-type oil-based ball pens and rotary feed oil-based ball pens, since writing start performance is one of the important performances, it is effective to use the ink composition according to the present invention.

[0118] The ink composition according to the present invention is preferably used for a ball pen tip having a valve mechanism that directly or through a pressing body presses a ball rotatably held at the tip of the ball pen tip against the inner wall of the tip edge by an elastic member (such as a coil spring) in order to suppress ink leakage and improve writing start performance, and gives a gap between the inner wall of the tip edge and the ball by the pressing force during writing to allow the ink to flow out. It is preferable that such a ball pen tip having such a structure closes even the minute gap at the tip of the tip when not in use.

[0119] In addition, in this embodiment, an oil-based ballpoint pen in which a ballpoint pen refill containing an oil-based ballpoint pen ink composition is disposed in a shaft cylinder was exemplified. However, the oil-based ballpoint pen according to the present invention may be an oil-based ballpoint pen in which the shaft cylinder itself is an ink storage cylinder and the oil-based ballpoint pen ink composition is directly stored in the shaft cylinder, that is, a straight-fill type ballpoint pen. It may also have a structure in which a ballpoint pen refill containing an oil-based ballpoint pen ink composition in an ink storage cylinder is used as a ballpoint pen as it is.

Industrial Applicability

[0120] The present invention can be used as an ink composition for an oil-based ballpoint pen. More specifically, it can be widely used as an oil-based ballpoint pen such as a cap type or a knock type filled with the ink composition for an oil-based ballpoint pen.

Explanation of Symbols

[0121] 1 Ballpoint pen refill 2 Ink storage cylinder 3 Ball 4 Ballpoint pen tip 5 Tip tip 6 Ball holding chamber 7 Ink flow hole 8 Ink flow groove 9 Ball seat 10 Ink for oil-based ballpoint pen H Ball out α Caulking angle

Claims

1. The oil-based ballpoint pen has a ballpoint pen tip at the tip of an ink reservoir tube, the ball tip rotatably holding a ball, and contains an ink composition containing a colorant, an organic solvent, and a polyoxyalkylene glyceryl ether in the ink reservoir tube.

2. 2. The oil-based ballpoint pen according to claim 1, wherein the arithmetic mean roughness (Ra) of the surface of the ball is 0.1 to 12 nm.

3. 3. The oil-based ballpoint pen according to claim 1, wherein the ink consumption per 100 m of the oil-based ballpoint pen is 20 to 150 mg.

4. The oil-based ballpoint pen according to any one of claims 1 to 3, wherein the amount of movement of the ball in the ballpoint pen tip in the longitudinal direction is 3 to 30 µm.

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