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

Abstract

To provide an oil-based ballpoint pen ink composition that enables smooth writing through enhancement of lubricity at the writing tip, and that prevents wear of the ball seat and improves writing feel, and also to provide a writing instrument using the same.SOLUTION: An oil-based ballpoint pen ink composition comprises a colorant, an organic solvent, and a surfactant having an acetylenic bond in its structure. The oil-based ballpoint pen ink composition has an ink viscosity of 300 mPa s or more at 20°C and a shear rate of 200 sec-1.SELECTED DRAWING: None

Description

Technical Field

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

Background Art

[0002] Conventionally, oil-based ballpoint pens using ink have been known and are widely used by a wide range of age groups because they are easy to handle. These oil-based ballpoint pens contain a colorant, a solvent, a surfactant, etc., enabling good writing on paper. (Patent Document 1)

[0003] In the case of a ballpoint pen, when writing, it is difficult for the ink to sufficiently adhere to the ball, and the ball does not rotate sufficiently, resulting in skipping and blurred writing, so there is room for improvement. (Patent Document 1)

[0004] Furthermore, writing instruments are easily affected by writing resistance between the writing tip and the surface to be written on during writing, especially ballpoint pens. A ballpoint pen tip consists of a metal tip made of stainless steel or the like at the tip and a transfer ball made of a metal such as super steel held in the ball socket of the metal tip, and is mounted in an ink cartridge. During writing, wear occurs in the ball socket due to the rotation of the ball, resulting in problems such as skipping and blurring in the handwriting and a deterioration in writing feel, so there is room for improvement. Furthermore, in order to improve the writing feel, when the ink viscosity is set to a low viscosity or in the case of an applicator, a marking pen, or a signature pen, since the ink viscosity is low, bleeding occurs in the handwriting, so there is room for improvement.

[0005] To solve these problems, in order to suppress writing resistance between the writing tip and the surface to be written on during writing, many ink compositions for writing instruments using various lubricants have been proposed for the purpose of improving lubricity. (Patent Documents 2 to 5)

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, when various new lubricants are used, although the writing resistance between the writing tip and the writing surface can be reduced to a certain extent, it is very difficult for the ink to sufficiently adhere to the ball during writing. Furthermore, due to the load on the ball seat, wear of the ball seat causes poor writing, so there is room for improvement (Patent Documents 2 to 5).

[0008] An object of the present invention is to obtain an oil-based ballpoint pen ink composition capable of suppressing line skipping and ink trailing, suppressing wear of the ball seat, and providing good writing performance without bleeding through, and an oil-based ballpoint pen using the same.

Means for Solving the Problems

[0009] In order to solve the above problems, the present invention “1. An oil-based ballpoint pen ink composition comprising a colorant, an organic solvent, and a surfactant having an acetylene bond in its structure, wherein the ink viscosity of the ink composition for the oil-based ballpoint pen is 300 mPa·s or more at 20°C and a shear rate of 200 sec -1 -1. An oil-based ballpoint pen ink composition characterized by the above.” 2. The content of the surfactant having an acetylene bond in the structure is 0.1 to 10% by mass based on the total amount of the ink composition, and the oil-based ballpoint pen ink composition according to claim 1. 3. The oil-based ballpoint pen ink composition according to claim 1 or 2, characterized in that it is selected from phosphate ester surfactants, fatty acids, and fatty acid esters. 4. The oil-based ballpoint pen ink composition according to claim 1 or 2, characterized in that the colorant is a pigment. 5. The oil-based ballpoint pen ink composition according to claim 1 or 2, characterized in that the organic solvent is selected from alkylene oxide derivatives of glycerin, alkylene glycol alkyl ethers, and amide solvents. 6. 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 the oil-based ballpoint pen ink composition according to claim 1 or 2 in the ink containing cylinder.

Advantages of the Invention

[0010] The present invention can sufficiently place ink on the ball when writing, and by further improving the lubricity at the writing tip (between the ball and the ball seat of the tip body), it is possible to suppress ink splashing and blurred handwriting, suppress wear of the ball seat, and obtain a good writing property where the handwriting does not show through, and an oil-based ballpoint pen ink composition and an oil-based ballpoint pen using the same can be obtained.

Embodiments for Carrying Out the Invention

[0011] In this specification, "parts", "%", "ratio", etc. indicating formulation are based on mass unless otherwise specified.

[0012] The feature of the present invention is that an oil-based ballpoint pen ink composition containing a colorant, an organic solvent, and a surfactant having an acetylene bond in the structure is used, and the ink viscosity of the ink composition for the oil-based ballpoint pen is 20°C, shear rate 200 sec -1It is to be an oil-based ballpoint pen ink composition characterized by being 300 mPa·s or more. This is because it contains a surfactant having an acetylene bond in its structure, which suppresses ink splashing and ink streaks, provides good writing performance, and further improves the lubricity between the ball and the ball seat of the tip body, reduces the friction between the ball seats, and makes it possible to suppress the wear of the ball seats. Furthermore, the ink viscosity of the oil-based ballpoint pen ink composition is 20 °C, shear rate 200 sec -1 By being 300 mPa·s or more at, it has appropriate ink viscosity, which makes it easy to place the ink on the ball and suppresses the promotion of wear between the ball seats of the tip body. Therefore, it is effective in suppressing the wear of the ball seats and can provide good writing performance with no bleeding of the writing.

[0013] (Surfactant having an acetylene bond in its structure) Regarding the surfactant having an acetylene bond in its structure used in the present invention, by improving the wettability of the ink, the ink can be sufficiently placed on the ball during writing, ink splashing and ink streaks are suppressed, and further, by improving the lubricity at the writing tip (between the ball and the ball seat of the tip body), ink splashing and ink streaks are suppressed, providing good writing performance. Moreover, it improves the lubricity between the ball and the ball seat of the tip body, reduces the friction between the ball seats, and makes it possible to suppress the wear of the ball seats.

[0014] Also, the HLB value of the surfactant having an acetylene bond in its structure is preferably 4 to 14, more preferably 6 to 14, and particularly preferably 7 to 12. When it is within the above range, by improving the wettability of the ink, the ink can be sufficiently placed on the ball during writing, and it is easy to suppress ink splashing and ink streaks. Furthermore, by improving the lubricity, it is easy to suppress ink splashing and ink streaks, so it is preferable.

[0015] Moreover, for the surfactant having an acetylene bond in the structure, the dynamic surface tensions at 1 Hz and 10 Hz of a 0.1% by mass aqueous solution are preferably 50 mN / m or less, more preferably 15 to 50 mN / m, and even more preferably 20 to 45 mN / m. When within the above range, it is preferable because it is easy to suppress ink splashing and ink smear by improving the wettability of the ink. The dynamic surface tension was measured using a bubble pressure type dynamic surface tensiometer Kruss BP-100 (manufactured by KRUSS) for the values at 1 Hz and 10 Hz of a 0.1% by mass aqueous solution.

[0016] The surfactant having an acetylene bond in the structure used in the present invention is preferably mixed with a solvent. As the solvent, considering the stability over time with the surfactant having an acetylene bond in the structure, it is preferable to use a polyhydric alcohol solvent. More preferably, it is preferable to use propylene glycol or dipropylene glycol. Even more preferably considering the stability over time, it is preferable to use propylene glycol. These may be used alone or in combination of two or more.

[0017] Specific examples of the surfactant having an acetylene bond in the structure include the Orfin series (manufactured by Nissin Chemical Industry Co., Ltd.), the Surfynol series, the Dynol series, etc. (all manufactured by Air Products Japan Co., Ltd.).

[0018] The content of the surfactant having an acetylene bond in the structure is preferably 0.1% by mass or more based on the total amount of the ink composition. By setting it to 0.1% by mass or more, the effects of the present invention can be easily obtained. Considering the wettability and lubricity of the ink more, 0.3% by mass or more is preferable, and further 0.5% by mass or more is preferable. Also, since it hardly affects the stability of the ink over time and the effects of the present invention can be easily obtained, it is preferably 10% by mass or less. More preferably considering it, it is preferably 5% by mass or less, and preferably 4% by mass or less.

[0019] (Organic solvent) Examples of the organic solvent include alkylene oxide derivatives of glycerin such as polyoxyalkylene glyceryl ether, polyoxyalkylene alkyl glucoside, and polyoxypropylene alkyl ether; alkylene glycol alkyl ethers such as alkylene glycol monoalkyl ether and alkylene glycol dialkyl ether; amide solvents such as β-alkoxypropionamides such as 3-methoxy-N,N-dimethylpropanamide, 3-butoxy-N,N-dimethylpropanamide, and 3-ethoxy-N,N-dimethylpropanamide; glycol solvents such as diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, butylene glycol, and ethylene glycol; and alcohol solvents such as benzyl alcohol, methanol, ethanol, 1-propanol, 2-propanol, isopropanol, isobutanol, t-butanol, propargyl alcohol, allyl alcohol, 3-methyl-1-butyn-3-ol, ethylene glycol monomethyl ether acetate, and other higher alcohols.

[0020] Among these organic solvents, considering that the effects of the present invention are likely to be exhibited due to the compatibility with surfactants having an acetylene bond in the structure, it is preferable to select from alkylene oxide derivatives of glycerin, alkylene glycol alkyl ethers, amide solvents, and aromatic alcohols. This is because it can further improve the lubricity of the tip of the writing instrument, suppress ink splashing and streaks in the handwriting, improve the lubricity between the ball and the ball seat, reduce the friction with the ball seat, and easily suppress the wear of the ball seat. Further considering this, alkylene oxide derivatives of glycerin, alkylene glycol monoalkyl ether, and amide solvents of β-alkoxypropionamides are preferable, and more preferably, alkylene oxide derivatives of glycerin have good compatibility with surfactants having an acetylene bond in the structure, and considering stability, they are alkylene oxide derivatives of glycerin.

[0021] As an alkylene oxide derivative of glycerin, considering the suppression of skipping and ink smear on the writing stroke by improving slipperiness and the suppression of wear of the ball seat, polyoxyalkylene glyceryl ether is preferable.

[0022] In addition, polyoxyalkylene glyceryl ether is obtained by addition polymerization of alkylene oxide to glycerin or polyglycerin, and examples include polyoxyalkylene glyceryl ether, polyoxyalkylene diglyceryl ether, polyoxyalkylene triglyceryl ether, and the like.

[0023] Also, when using a pigment as a colorant, generally, the ink viscosity increases due to aggregation of the pigment over time, and the ink followability tends to decrease. However, the polar group in the structure of the alkylene oxide derivative of glycerin adsorbs on the pigment surface, and the pigment is stably dispersed in the ink. Therefore, by suppressing the increase in ink viscosity due to pigment aggregation, the ink followability can be improved, skipping and ink smear on the writing stroke can be suppressed, and good writing quality can be obtained. Therefore, considering pigment dispersion stability and ink followability, it is preferable to use polyoxyalkylene glyceryl ether, and among them, considering more, it is preferable to use polyoxyalkylene diglyceryl ether.

[0024] In addition, polyoxyalkylene glyceryl ether includes polyoxyethylene glyceryl ether, polyoxypropylene glyceryl ether, and the like. Among these, polyoxypropylene glyceryl ether has a propylene group, so it has excellent lipophilicity. By suppressing the moisture absorption of the ink composition for an oil-based ballpoint pen, the stability over time can be improved, and the effects of the present invention can be easily obtained. For this reason, it is preferable to use polyoxypropylene glyceryl ether.

[0025] By improving the lubricity, polyoxyalkylene glyceryl ether can suppress streakiness and ink smear, inhibit wear of the ball seat, and improve pigment dispersion stability and stability over time. Considering that it is easy to obtain the effects of the present invention, the average value of the number of moles of alkylene oxide added (average number of moles of alkylene oxide added) is preferably 1 or more and 30 or less. Further considering, it is preferably 1 or more and 30 or less. Considering improving lubricity and stability over time, the average number of moles of alkylene oxide added is preferably 1 or more and 20 or less, and more preferably 5 or more and 20 or less.

[0026] In particular, by improving the lubricity more, considering suppressing streakiness and ink smear, inhibiting wear of the ball seat, and improving the writing feel, the average number of moles of propylene oxide added is preferably 1 to 30, more preferably 1 or more and 20 or less, further preferably 5 or more and 20 or less, more preferably 1 or more and 12 or less, and particularly preferably 5 to 12. Also, considering that it is easy to exhibit the effects of the present invention, the structure of the polyoxyalkylene glyceryl ether is preferably a structure represented by the following formula (1) or (2).

Chemical formula

[0027] Among these, the polyoxyalkylene glyceryl ether represented by formula (1) has a large effect of improving stability over time, so the effects of the present invention are easily obtained and it is preferable.

[0028] In addition, the weight average molecular weight of the alkylene oxide derivative of glycerin is preferably 5000 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 for an oil-based ballpoint pen tends to increase, and it is likely to affect the handwriting due to ink followability. Considering more the stability over time and ink followability, the weight average molecular weight is preferably 3000 or less, more preferably 1500 or less, and still more preferably 1200 or less. Also, considering improving the slipperiness and obtaining good handwriting, 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 slipperiness and pigment dispersibility. Therefore, the weight average molecular weight is preferably 300 or more, and more preferably 500 or more when considering more. The weight average molecular weight is a value obtained in terms of polystyrene using GPC (gel permeation chromatography).

[0029] In addition, regarding the alkylene glycol monoalkyl ether, considering that it is likely to stably exhibit an effect with a surfactant having an acetylene bond in its structure, the number of carbon atoms in the alkylene glycol moiety of the alkylene glycol monoalkyl ether is preferably 2 or more and 10 or less. Considering more that it is more likely to be stable and the above effect is easily obtained, the number of carbon atoms is 3 or more and 8 or less, and further preferably 5 or more and 6 or less. Also, regarding the number of carbon atoms in the alkyl ether moiety of the alkylene glycol monoalkyl ether, considering that it is likely to stably exhibit an effect with a surfactant having an acetylene bond in its structure, a shorter alkyl ether moiety is preferred. For this reason, the number of carbon atoms is preferably 1 or more and 6 or less, more preferably 1 or more and 4 or less, and still more preferably 1 or more and 2 or less when considering more that it is more likely to be stable and the effect is easily obtained.

[0030] In addition, regarding the alkylene glycol monoalkyl ether, the solubility parameter (SP value) is 8 to 13 (cal / cm 3 ) 1 / 2It is preferably as follows. This is because, due to the compatibility with a surfactant having an acetylene bond in the structure, it is easier to exhibit the effects of the present invention. More specifically, the solubility parameter (SP value) is preferably 9 to 12 (cal / cm 3 ) 1 / 2 . Further, more specifically, the solubility parameter (SP value) is preferably 10 to 11 (cal / cm 3 ) 1 / 2 . The solubility parameter (SP value) of the solvent referred to in the present invention is a value represented by the square root of the molecular cohesion energy, which is described in Chapter IV Solubility Parameter Values of Polymer Handbook (Second Edition), and this value is used. The unit is (cal / cm3)1 / 2, and it refers to the value at 25°C. For those without data description, they can be calculated by the method described in R.F. Fedors, Polymer Engineering Science, 14, p147 (1967).

[0031] Also, for alkylene glycol monoalkyl ethers, the boiling point is preferably 170°C or higher. This is because if it is less than 170°C, the alkylene glycol monoalkyl ether is likely to evaporate, the ink viscosity is likely to increase, it is difficult to suppress wire drawing and ink smear, and it is likely to affect the writing feel. More specifically, it is preferably 220°C or higher. On the other hand, if the boiling point exceeds 300°C, it is likely to affect the drying property of the handwriting, so the boiling point is preferably 300°C or lower. More specifically, it is preferably 280°C or lower.

[0032] Also, for amide solvents, considering that they are likely to stably exhibit effects with surfactants having an acetylene bond in the structure, it is preferable to use 3-methoxy-N,N-dimethylpropanamide and 3-butoxy-N,N-dimethylpropanamide. More specifically, 3-methoxy-N,N-dimethylpropanamide is preferable.

[0033] In addition, considering the improvement of solubility, bleeding, drying of handwriting, bleeding, etc., the content of the organic solvent is preferably 10% by mass or more and 90% by mass or less, more preferably 25% by mass or more and 80% by mass or less, based on the total amount of the ink composition.

[0034] In the present invention, the oil-based ballpoint pen ink composition preferably contains water. By using water, the ink viscosity can be reduced, the slipperiness of the ball can be improved, the ink ejection property can be made good, stringing and bleeding of the handwriting can be suppressed, the writing feel can be easily improved, uneven dots, bleeding, etc. can be suppressed, and the writing property can be easily improved. In particular, when alkylene glycol alkyl ethers or amide solvents are used as the organic solvent, it is preferable because they are easily stabilized with water. As the water, conventional water such as ion-exchanged water, distilled water, and tap water can be used.

[0035] The content of the water is preferably 0.1% by mass or more and 20% by mass or less based on the total amount of the ink composition. When it is within the above range, the ink ejection property is good, stringing and bleeding of the handwriting are suppressed, the writing feel can be easily improved, uneven dots, bleeding, etc. are suppressed, and the writing property can be easily improved. Further considering, the content of water based on the total amount of the ink composition is preferably 1% by mass or more and 10% by mass or less, and more preferably 2% by mass or more and 10% by mass or less.

[0036] (Colorant) The colorant used in the oil-based ballpoint pen ink composition used in the present invention is not particularly limited, such as dyes and pigments, and can be appropriately selected and used. Dyes and pigments may be used in combination.

[0037] Examples of the dyes used in the oil-based ink composition 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 organic acids and basic dyes, and salt-forming dyes of acid dyes and organic amines. Among them, considering the stability with surfactants having an acetylene bond in the structure, it is preferable to use salt-forming dyes. Examples of the dyes include Vat Fast Black 1802, Vat Fast Black 1805, Vat Fast Black 1807, Vat Fast Violet 1701, Vat Fast Violet 1704, Vat Fast Violet 1705, Vat Fast Blue 1601, Vat Fast Blue 1605, Vat Fast Blue 1613, Vat Fast Blue 1621, Vat Fast Blue 1631, Vat Fast Red 1320, Vat Fast Red 1355, Vat Fast Red 1360, Vat Fast Yellow 1101, Vat Fast Yellow 1151, Nigrosine Base EXBP, Nigrosine Base EX, Base of Basic Dyes ROB-B, Base of Basic Dyes RO6G-B, Base of Basic Dyes VPB-B, Base of Basic Dyes VB-B, Base of Basic Dyes MVB-3 (all manufactured by Orient Chemical Industries, Ltd.), Iris Spiron Black GMH-Special, Iris Spiron Violet C-RH, Iris Spiron Blue GNH, Iris Spiron Blue 2BNH, Iris Spiron Blue C-RH, Iris Spiron Red C-GH, Iris Spiron Red C-BH, Iris Spiron Yellow C-GNH, Iris Spiron Yellow C-2GH, S.P.T. Blue 111, S.P.T. Blue GLSH-Special, S.P.T. Red 533, S.P.T. Orange 6, S.B.N. Yellow 510, S.B.N. Yellow 530, S.R.C-BH (all manufactured by Hodogaya Chemical Co., Ltd.), and the like. Examples of the pigments include inorganic, organic, and processed pigments. Specifically, examples include 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, and the like. These dyes and pigments may be used alone or in combination of two or more.

[0038] Also, as the colorant, it is preferable to use a pigment. This is because the pigment particles cause a physical obstacle in the gap between the ball and the inner wall of the tip in the case of a ballpoint pen, making it easier to suppress ink leakage. Further, the pigment is excellent in the fastness of the handwriting, especially in light resistance, so it is preferable. Furthermore, by using a pigment, in the case of a ballpoint pen, the pigment particles enter the gap between the ball and the tip body, making it easier for the action like that of a bearing to work. By suppressing metal contact, the lubricity is improved, splattering and streaking of the handwriting are suppressed, wear of the ball seat is suppressed, and an effect of improving the writing feel is easily obtained. Therefore, it is preferable to use a pigment. As in the present invention, when improving the slipperiness by using a surfactant having an acetylene bond in the structure, using a pigment is more effective. Further, due to the synergistic effect by the bearing action between the lubricating layer by the surfactant described later and the pigment particles, it is easy to maintain the lubricity, which is preferable.

[0039] Regarding the pigment, the average particle diameter is preferably 1 nm or more and 500 nm or less. More preferably, it is 30 nm or more and 350 nm or less, and still more preferably, it is 50 nm or more and 300 nm or less. By setting it within the above range, the slipperiness is further improved, splattering and streaking of the handwriting are suppressed, wear of the ball seat is suppressed, and an effect of improving the writing feel is easily obtained. Here, the average particle diameter can be determined by the laser diffraction method. Specifically, it is determined by the particle diameter (D50) at the time of 50% volume accumulation of the particle size distribution measured based on the numerical values calibrated using a standard sample and other measurement methods using a laser diffraction type particle size distribution analyzer (trade name "Microtrac HRA9320-X100", Nikkiso Co., Ltd.). In addition, since the above-described pigment exhibits the above-described action and effect in the dispersed state of the pigment in the ink composition for an oil-based ballpoint pen, it is preferable to determine the particle diameter in the dispersed state.

[0040] As the type of pigment, it is preferable to use from among carbon black, quinacridone-based, perylene-based, and diketopyrrolopyrrole-based pigments. Further, considering the suppression of bleeding and ink smears and the suppression of wear of the ball seat, it is preferable to use carbon black or diketopyrrolopyrrole-based pigments. More preferably, considering the suppression of bleeding and ink smears, diketopyrrolopyrrole-based pigments are preferred.

[0041] The content of the colorant is preferably 5% by mass or more and 30% by mass or less based on the total amount of the ink composition. This is because if it is less than 5% by mass, there is a tendency that it is difficult to suppress bleeding and ink smears, suppress wear of the ball seat, and obtain a dark handwriting. If it exceeds 30% by mass, it tends to affect the solubility in the ink. Considering this tendency more, it is preferably 7% by mass or more and 25% by mass or less, and further considering it, it is 10% by mass or more and 20% by mass or less.

[0042] (Surfactant) In the present invention, it is preferable to use a surfactant. This is because it can further improve the lubricity at the writing tip (between the ball and the ball seat of the tip body), suppress bleeding and ink smears, suppress wear of the ball seat, and more easily improve the writing feel. Furthermore, since an effect of more easily improving the writing performance when the writing tip (tip of the tip) dries in a state where the writing tip (tip of the tip) is left in the air can be obtained, it is preferable to use a surfactant. This is because when a surfactant is used, the formed film tends to be softened, the writing performance can be improved, and the lubricity can also be improved. Examples of the surfactant include silicone-based surfactants, fluorine-based surfactants, phosphate ester-based surfactants, polyoxyalkylene alkyl ethers, fatty acids, fatty acid esters, and the like. Among them, considering the above effects, it is preferably selected from among phosphate ester-based surfactants, fatty acids, and fatty acid esters. More preferably, it is selected from among phosphate ester-based surfactants and fatty acids, and most preferably, a phosphate ester-based surfactant is preferred.

[0043] As the phosphate ester surfactant, specifically, a phosphate ester having an alkoxyethyl group (C n H 2n+1 OCH2CH2O) or an alkoxy group (C m H 2m+1 O), a phosphoric acid monoester of polyoxyethylene alkyl ether or polyoxyethylene alkyl aryl ether, a phosphoric acid diester of polyoxyethylene alkyl ether or polyoxyethylene alkyl aryl ether, a phosphoric acid triester of polyoxyethylene alkyl ether or polyoxyethylene alkyl aryl ether, an alkyl phosphate ester, an alkyl ether phosphate ester or a derivative thereof, etc. may be mentioned.

[0044] Regarding the phosphate ester surfactant, specifically, phoslex series (manufactured by SC Organic Chemistry Co., Ltd.), JP series (manufactured by Johoku Chemical Industry Co., Ltd.), Plasurf series (manufactured by Daiichi Kogyo Co., Ltd.), Phosphanol series (manufactured by Toho Chemical Industry Co., Ltd.), NIKKOL series (manufactured by Nikko Chemicals Co., Ltd.), etc. can be mentioned.

[0045] Among the phosphate ester surfactants, considering improving the slipperiness, suppressing line skipping and writing trace streaks, suppressing wear of the ball seat, and improving the writing performance and writing feel, it is preferably selected from a phosphate ester having an alkoxyethyl group (C n H 2n+1 O-C2H4O) or an alkoxy group (C m H 2m+1 O), a phosphoric acid monoester of polyoxyethylene alkyl ether or polyoxyethylene alkyl aryl ether, and a phosphoric acid diester of polyoxyethylene alkyl ether or polyoxyethylene alkyl aryl ether.

[0046] Furthermore, among the phosphate ester surfactants, considering improving the slipperiness to suppress line skipping and writing trace streaks, suppressing wear of the ball seat, and improving the writing feel, an alkoxyethyl group (C n H 2n+1(O-C2H4O) or a phosphate ester surfactant having an alkoxy group (C m H 2m+1 O) is preferably used. More preferably, a phosphate ester surfactant having an alkoxyl group (C m H 2m+1 O) is preferably used.

[0047] Regarding the above phosphate ester surfactant, for the carbon chain (n, m) of the terminal alkyl group of the alkoxyethyl group (C n H 2n+1 (O-C2H4O) or an alkoxy group (C m H 2m+1 O), it is preferably 1 or more and 20 or less. Further, when the carbon chain (n, m) of the terminal alkyl group of the alkoxyethyl group (C n H 2n+1 (O-C2H4O) or an alkoxy group (C m H 2m+1 O) has an appropriate length, it is easier to maintain better slipperiness. Therefore, the carbon chain (n, m) of the terminal alkyl group is preferably 1 or more and 20 or less. More preferably, the carbon chain (n, m) is preferably 1 or more and 12 or less. The carbon chain (n, m) is preferably 2 or more and 12 or less, 3 or more and 8 or less, and 3 or more and 6 or less.

[0048] Furthermore, among phosphate ester surfactants, considering improving slipperiness to suppress wire skipping and ink smear, suppressing wear of the ball seat, and improving writing performance and writing feel, 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 or more and 18 or less, more preferably 10 or more and 18 or less, and even more preferably 12 or more and 18 or less. This is because when the number of carbon atoms in the alkyl group is excessively small, the slipperiness tends to be insufficient, and when the number of carbon atoms is excessively large, the stability over time tends to be affected. The above-mentioned alkoxyethyl group (C n H 2n+1 (O-C2H4O) or an alkoxy group (C m H2m+1 By using a combination of a phosphate surfactant having an O) and a phosphate surfactant having an alkyl group, the slipperiness is more likely to be improved due to the interaction, so the effect of the present invention is easily obtained, which is effective and preferable.

[0049] When using a phosphate surfactant, the acid value is preferably 150 (mgKOH / g) or less, more preferably 120 (mgKOH / g) or less, and even more preferably 100 or less. This is to make it easier to exhibit the improvement in slipperiness by the phosphate surfactant. Further, considering the stability and lubricity in the ink composition for an oil-based ballpoint pen, the acid value is preferably 30 (mgKOH / g) or more and 150 (mgKOH / g) or less, more preferably 40 (mgKOH / g) or more and 120 (mgKOH / g) or less, and even more preferably 40 (mgKOH / g) or more and 100 (mgKOH / g) or less. The above-mentioned alkoxyethyl group (C n H 2n+1 O-C2H4O) or a phosphate surfactant having an alkoxy group (C m H 2m+1 O), by the interaction of using them in combination with a phosphate surfactant having a specific acid value, the slipperiness is more likely to be improved, so the effect of the present invention is easily obtained, which is effective and preferable. Note that the acid value is represented by the number of mg of potassium hydroxide required to neutralize the acidic components contained in 1 g of the sample.

[0050] The content of the surfactant is more preferably 0.1% by mass or more and 5.0% by mass or less based on the total amount of the ink composition for an oil-based ballpoint pen. This is because if it is less than 0.1% by mass, it is difficult to obtain the improvement in slipperiness, suppression of line skipping and writing trace smearing, suppression of ball seat wear, and improvement of writing performance and writing feel. If it exceeds 5.0% by mass, the ink is likely to become unstable over time. Considering these more, the content of the surfactant based on the total amount of the ink composition for an oil-based ballpoint pen is preferably 0.3% by mass or more and 4.0% by mass or less, and more preferably 0.5% by mass or more and 3.0% by mass or less.

[0051] (Organic amine) In the present invention, when using a surfactant such as a phosphate ester surfactant, by neutralizing it, it can be stably dissolved in the ink, further improving the lubricity at the tip of the writing instrument, making it easier to suppress line skipping and writing streaks, suppressing wear of the ball seat, and easily obtaining the effect of improving the writing feel and writing performance. Therefore, it is preferable. Examples of organic amines include 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, and alkanolamines such as diethanolamine and triethanolamine. Among these, considering the dissolution stability in the ink, amines having ethylene oxide are preferable. These may be used alone or in admixture of two or more.

[0052] Furthermore, considering the stability with surfactants, colorants, surfactants, and other components having an acetylene bond in the structure, the total amine value of the organic amine is preferably 300 (mgKOH / g) or less. If it exceeds 300 (mgKOH / g), due to its strong reactivity, it is likely to affect the above components, thus easily affecting the stability of the ink over time. More preferably, the total amine value is 200 (mgKOH / g) or less, and even more preferably 150 (mgKOH / g) or less. On the other hand, considering the above effects, the lower limit value of the total amine value is preferably 30 (mgKOH / g) or more. Note that the total amine value indicates the total amount of primary, secondary, and tertiary amines, and is represented by the number of milligrams of potassium hydroxide equivalent to the hydrochloric acid required to neutralize 1 g of the sample.

[0053] Regarding the HLB value of the organic amine, the HLB value is preferably 5 to 17. This is because it is easy to be stable with surfactants, colorants, surfactants, resins and other components having an acetylene bond in the structure, and the effects of the present invention can be easily obtained. More preferably, the HLB value is 7 to 17, and further preferably, the HLB value is 9 to 16.

[0054] Regarding the content of the organic amine, considering the stability with surfactants, colorants, surfactants and other components having an acetylene bond in the structure, it is preferably 0.1% by mass or more and 10% by mass or less based on the total amount of the ink composition. Further considering the neutralization with the above-mentioned surfactant, it is preferably 0.5% by mass or more and 5% by mass or less.

[0055] (Resin) In the present invention, in order to improve the slipperiness, improve the adhesion of the handwriting to the paper surface, easily suppress the bleeding of the handwriting, and improve the suppression of ink leakage at the writing tip, it is preferably composed of a resin. Examples of the resin include polyvinyl butyral resin, ketone resin, amide resin, terpene phenol resin, rosin resin, alkyl phenol resin, styrene-maleic acid resin, ethylene-maleic acid resin, styrene-acrylic resin, acrylic resin, maleic acid resin, cellulose resin, petroleum resin, coumarone-indene resin, polyethylene oxide, polymethacrylate, ketone-formaldehyde resin, α- and β-pinene·phenol polycondensation resin, and the like. These may be used alone or in combination of two or more.

[0056] Among these resins, considering the improvement of slipperiness, improvement of the adhesion of the handwriting to the paper surface, easy suppression of ink splashing and bleeding of the handwriting, and suppression of ink leakage at the writing tip, it is preferably selected from polyvinyl butyral resin, ketone resin, terpene phenol resin, and rosin resin. Considering further improvement of the adhesion of the handwriting to the paper surface and suppression of ink splashing and bleeding of the handwriting, it is preferably selected from polyvinyl butyral resin, terpene phenol resin, and rosin resin. More preferably, it is selected from polyvinyl butyral resin and terpene phenol resin. Furthermore, for terpene phenol resin, by forming a strong handwriting film, the adhesion of the handwriting to the paper surface is improved. Moreover, by having an aromatic ring skeleton, between the ball and the ball seat, due to the cushioning effect, the slipperiness is improved, making it easier to suppress line skipping and handwriting streaks, and suppressing the resistance between the ball and the ball seat, making it easier to suppress wear of the ball seat, so it is preferable.

[0057] Regarding the weight average molecular weight of the terpene phenol resin, by forming a stronger handwriting film, the adhesion of the handwriting to the paper surface (writing property) is improved, the slipperiness is further improved, it is easier to suppress line skipping and handwriting streaks, and furthermore, considering that the dissolution stability in the ink is good and it is easier to obtain the effects of the present invention, the weight average molecular weight is preferably 200 or more and 1200 or less. Considering further improving the adhesion of the handwriting to the paper surface, suppressing handwriting streaks, and the dissolution stability in the ink, it is preferably 300 or more and 1000 or less, and preferably 400 or more and 800 or less. Furthermore, if the weight average molecular weight is too large, it is likely to affect the stability over time, and furthermore, the viscosity of the oil-based ballpoint pen ink composition is likely to increase, and it is likely to affect the handwriting due to ink followability, and it is likely to affect the line skipping and streaks in the handwriting. Note that the weight average molecular weight of the terpene phenol resin is measured by the GPC method (gel permeation chromatography method).

[0058] Regarding the softening point of the terpene phenol resin, by maintaining viscoelasticity and forming a stronger handwriting film, the adhesion of the handwriting to the paper surface (writing property) is improved, the slipperiness is further improved, it is easier to suppress line skipping and handwriting streaks, and furthermore, considering that the dissolution stability in the ink is good and it is easier to obtain the effects of the present invention, it is preferably 70°C or more and 150°C or less. Considering suppressing line skipping and handwriting streaks by maintaining viscoelasticity more, it is preferably 80°C or more and 130°C or less, and more preferably 90°C or more and 110°C or less. Here, the softening point of the resin is the value measured according to JIS K2207.

[0059] Regarding terpene phenol resins, generally, the hydroxyl value is controlled by the amount of phenolic moieties. Considering that by forming a stronger handwriting film, the adhesion of the handwriting to the paper surface (writing property) can be improved, the slipperiness can be enhanced, it is easier to suppress ink bleeding and handwriting streaks, and the dissolution stability in the ink can be improved, making it easier to obtain the effects of the present invention, the hydroxyl value of the terpene phenol resin is preferably 200 mgKOH / g or less. Further considering, the above hydroxyl value is preferably 30 mgKOH / g or more and 200 mgKOH / g or less, preferably 50 mgKOH / g or more and 200 mgKOH / g or less, preferably 50 mgKOH / g or more and 200 mgKOH / g or less, preferably 50 mgKOH / g or more and 100 mgKOH / g or less. Note that the hydroxyl value is the number of milligrams of potassium hydroxide required to neutralize acetic acid bonded to hydroxyl groups when 1 g of the resin is acetylated, and is defined as a value measured based on the potentiometric titration method specified in JIS K 0070.

[0060] Also, regarding the average degree of polymerization of polyvinyl butyral resin, considering the improvement of slipperiness and suppressing ink bleeding and handwriting streaks by the adhesion of the ink to the paper surface at the writing tip, the average degree of polymerization is preferably 100 or more and 2,000, and further considering, the average degree of polymerization is preferably 100 or more and 1,500 or less, more preferably 200 or more and 1,000 or less. Here, the average degree of polymerization refers to the number of basic units constituting one molecule of polyvinyl butyral resin, and a value measured based on the method specified in JIS K 6728 (2001 edition) can be adopted.

[0061] 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 less than 25 mol% has insufficient solubility in the alkylene glycol alkyl ether solvent, and it is difficult to obtain the effects of the present invention. Further considering, a polyvinyl butyral resin with a hydroxyl group content of 30 mol% or more is preferable. Moreover, it is preferable because it is easier to improve the slipperiness and writing feel. Also, when using a polyvinyl butyral resin with a hydroxyl group content exceeding 40 mol%, the moisture absorption amount tends to increase, and it is likely to affect the stability over time with the ink components. Therefore, a polyvinyl butyral resin with a hydroxyl group content of 40 mol% or less is preferable. For this reason, a polyvinyl butyral resin with a hydroxyl group content of 30 mol% or more and 40 mol% or less is preferable, and more preferably, a hydroxyl group content of 30 mol% or more and 36 mol% or less is preferable. Note that the hydroxyl group content (mol%) of the polyvinyl butyral resin indicates the content rate of hydroxyl groups (mol%) with respect to the total mol amount of butyral groups (mol%), acetyl groups (mol%), and hydroxyl groups (mol%).

[0062] Regarding rosin-based resins, examples include rosin, rosin esters, hydrogenated rosin esters, etc. Considering improving the adhesion of the handwriting to the paper surface and suppressing ink bleeding and smear of the handwriting, it is preferable to use rosin esters and hydrogenated rosin esters. Furthermore, since the ink film is also not likely to become strong, it is preferable to use them in combination with terpene phenol resins in order to easily improve the writing performance at the tip of the writing instrument.

[0063] Regarding the softening point of the rosin-based resin, considering improving the adhesion of the handwriting to the paper surface (writing property), suppressing ink bleeding and smear of the handwriting, and easily improving the writing property, it is preferably 50°C or higher and 150°C or lower. Further considering, it is preferably 60°C or higher and 130°C or lower, and more preferably 65°C or higher and 115°C or lower. Here, the softening point of the resin is a value measured according to JIS K2207.

[0064] If the total resin content is less than 3% by mass based on the total amount of the ink composition, it is difficult to obtain sufficient effects such as good ink adhesion to paper, slipperiness, and suppression of ink leakage. On the other hand, if the total resin content based on the total amount of the ink composition exceeds 40% by mass, the solubility in the ink tends to be poor, the ink viscosity becomes too high, which easily affects the reduction of ink consumption, writing feel, and writing performance. Therefore, the total resin content based on the total amount of the oil-based ballpoint pen ink composition is preferably 3% by mass or more and 40% by mass or less, more preferably 5% by mass or more and 30% by mass or less, and still more preferably 10% by mass or more and 25% by mass or less.

[0065] Also, in the present invention, a shear-thinning viscosity-imparting agent may be used. Examples of the shear-thinning viscosity-imparting agent include polyacrylic acid resin, xanthan gum, welan gum, succinoglycan, guar gum, locust bean gum, λ-carrageenan, cellulose derivatives, oxidized cellulose, diutan gum, fatty acid amide, hydrogenated castor oil, etc. By containing these, it is easy to form a three-dimensional network structure in the ink, which is effective in imparting pseudoplasticity, improving writing feel, and suppressing line skipping and ink bleeding of the handwriting, so it is preferable. Among them, when polyacrylic acid resin or polysaccharides are used, it is easy to form a three-dimensional network structure and easier to form a denser cross-linked structure, so it is preferable. More preferably, polyacrylic acid resin is used, and further preferably, cross-linked polyacrylic acid resin is used. The polyacrylic acid resin is used as a thickening agent. The polyacrylic acid resin has an affinity for alkylene glycol alkyl ethers and amide solvents, and by swelling and dispersing, a stable thickening action with pseudoplasticity can be obtained. Furthermore, considering the writing feel and writing properties (suppression of ink bleeding and blotting), it is preferable to use a cross-linked polyacrylic acid resin. Furthermore, considering that by forming a denser cross-linked structure, it is easy to impart pseudoplasticity, thereby reducing the ink viscosity during writing and easily improving the writing feel and writing properties (suppression of bleeding and blotting), carboxyvinyl polymer is preferable. In particular, when using alkylene glycol monoalkyl ethers or amide solvents of β-alkoxypropionamides as organic solvents, it is easier to form a more three-dimensional network structure, which is effective and preferable.

[0066] Regarding the polyacrylic acid resin, considering that a stable thickening effect can be obtained with alkylene glycol alkyl ethers, the carboxyl group content in the polyacrylic acid resin is preferably 40% by mass or more and 80% by mass or less. More preferably, it is 50% by mass or more and 70% by mass or less. In particular, when using alkylene glycol monoalkyl ether as the alkylene glycol alkyl ether, using a polyacrylic acid resin with a carboxyl group content of 55% by mass or more and 65% by mass or less is preferable because it has excellent swelling dispersibility and can impart pseudoplasticity, reducing the ink viscosity during writing and improving the writing feel. Furthermore, in the case of alkylene glycol monomethyl ether, it is more preferable.

[0067] If the content of the shear-thinning viscosity-imparting agent is less than 0.1% by mass based on the total amount of the ink composition, the swelling property is not sufficient and pseudoplasticity cannot be obtained, making it difficult to improve the writing feel. If it exceeds 5.0% by mass, the swelling dispersibility in the ink is likely to be poor. Therefore, based on the total amount of the ink composition, it is preferably 0.1% by mass or more and 5.0% by mass or less. Furthermore, considering the writing feel and the like more, it is preferably 0.3% by mass or more and 3.0% by mass or less, and more preferably 0.6% by mass or more and 1.8% by mass or less.

[0068] In addition, as others, a colorant stabilizer, a plasticizer, a chelating agent, etc. may be appropriately used. These can be used alone or in combination of two or more.

[0069] Also, at 20 °C, shear rate 200 sec -1(During writing), the ink viscosity is not particularly limited. Considering that the ink viscosity can make it easier to place the ink on the ball, suppress writing smears, and improve the writing feel, at 20 °C and a shear rate of 200 sec -1 (During writing), the ink viscosity is preferably 10,000 mPa·s or less, more preferably 8,000 mPa·s or less. Considering further, the ink viscosity is preferably 7,000 mPa·s or less. On the other hand, by having an appropriate ink viscosity, the wear promotion between the ball and the ball seat of the chip body can be suppressed. Further considering writing properties such as bleeding, blobbing, bleeding, and drying property of the writing, and pigment dispersibility, the ink viscosity is preferably 500 mPa·s or more. Considering further, it is preferably 800 mPa·s or more. Considering further, it is preferably 1,500 mPa·s or more, and preferably 2,000 mPa·s or more. Also, in retractable writing instruments such as click-type writing instruments and rotary feed writing instruments, it is necessary to consider ink leakage suppression more, so it is effective.

[0070] (Ball pen) Also, the ink consumption per 100 m of the ball pen is preferably 20 mg or more and 100 mg or less. This is because when the ink consumption per 100 m is within the above range, it can suppress line skipping and writing smears, improve the writing feel, and make it easier to obtain a thick writing. Considering further, it is preferably 25 mg or more and 90 mg or less, and preferably 40 mg or more and 80 mg or less. Regarding the ink consumption, on JIS P3201 writing paper at 20 °C, under the conditions of a writing angle of 70° and a writing load of 200 g, a spiral writing test is performed at a writing speed of 4 m / min using 5 test samples, and the average value of the ink consumption per 100 m is defined as the ink consumption per 100 m.

[0071] (Ball pen tip) Regarding the ballpoint pen tip, it is preferable to maintain lubricity between the ball and the tip body, suppress ink trailing and wear of the ball seat, improve the writing feel, and provide a substantially arcuate ball seat on the bottom wall of the ball holding chamber.

[0072] Also, regarding the arithmetic mean roughness (Ra) of the surface of the ball of the ballpoint pen tip used in the present invention, it is preferably 0.1 nm or more and 12 nm or less. This is because when the arithmetic mean roughness (Ra) is within the above range, it suppresses line skipping and ink trailing, improves the writing feel, and makes it easier to obtain a dark handwriting. Considering further, the arithmetic mean roughness (Ra) is preferably 0.1 nm or more and 10 nm or less, more preferably 1 nm or more and 8 nm or less. The surface roughness can be measured using (model name SPI3800N manufactured by Seiko Epson Corporation).

[0073] Also, the material used for the ball is not particularly limited, and 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, and zirconia, and ruby balls.

[0074] Also, the materials for the ballpoint pen tip include metal materials such as stainless steel, nickel silver, brass, aluminum bronze, and aluminum, and resin materials such as polycarbonate, polyacetal, and ABS. However, considering the wear of the ball seat and stability over time, it is preferable to use a stainless steel tip body.

[0075] Also, the movement amount of the ball of the ballpoint pen tip used in the present invention in the longitudinal axis direction is preferably 3 μm or more and 25 μm or less. This is because when it is within the above range, it increases the ink consumption, suppresses line skipping and ink trailing, improves the writing feel, and makes it easier to obtain a dark handwriting. Considering further, the movement amount of the ball of the ballpoint pen tip in the longitudinal axis direction is preferably 3 μm or more and 22 μm or less, more preferably 5 μm or more and 20 μm or less, and even more preferably 7 μm or more and 18 μm or less.

[0076] When directly storing ink in the ink storage cylinder, an ink backflow prevention body can also be filled at the rear end of the ink. The ink backflow prevention body composition consists of a non-volatile liquid or a hardly volatile liquid. Specifically, examples include petrolatum, spindle oil, castor oil, olive oil, refined mineral oil, liquid paraffin, polybutene, α-olefin, an oligomer or co-oligomer of α-olefin, dimethyl silicone oil, methylphenyl silicone oil, amino-modified silicone oil, polyether-modified silicone oil, fatty acid-modified silicone oil, etc., and one kind or two or more kinds can be used in combination.

[0077] It is preferable to add a thickening agent to the non-volatile liquid and / or hardly volatile liquid to thicken it to a suitable viscosity. Examples of the thickening agent include silica with a hydrophobic surface treatment, fine particle silica with a methylated surface treatment, aluminum silicate, swelling mica, clay-based thickening agents such as bentonite and montmorillonite with a hydrophobic treatment, fatty acid metal soaps such as magnesium stearate, calcium stearate, aluminum stearate, zinc stearate, tribenzylidene sorbitol, fatty acid amide, amide-modified polyethylene wax, hydrogenated castor oil, dextrin-based compounds such as fatty acid dextrin, and cellulose-based compounds. Furthermore, the liquid ink backflow prevention body and a solid ink backflow prevention body can also be used in combination. (Example)

[0078] Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples.

[0079] Example 1 The ink composition for an oil-based ballpoint pen of Example 1 was collected with a colorant, an organic solvent, an alkylene oxide derivative of glycerin, a phosphate ester surfactant, an organic amine, and a resin at 60°C using a dispersion stirrer, stirred and dissolved, and then cooled to room temperature to obtain an ink composition for an oil-based ballpoint pen. The specific blending amounts are as follows.

[0080] Pigment dispersion (carbon black, average particle diameter 150 nm, containing 35% pigment, containing 20% polyvinyl butyral) 30.0% by mass Alcohol solvent (benzyl alcohol) 36.5% by mass Polyoxyalkylene glyceryl ether (Formula (1), polyoxypropylene diglyceryl ether) 20.0% by mass Surfactant having an acetylene bond in the structure 2.0% by mass Phosphate ester surfactant having an alkoxyethyl group (CnH2n+1OCH2CH2O) 1.0% by mass Organic amine (polyoxyethylene alkylamine) 1.0% by mass Polyvinyl butyral resin 9.0% by mass Polyvinyl pyrrolidone 0.5% by mass

[0081] Examples 2 to 23 As shown in Table 1, except for changing the ink components, ink compositions for oil-based ballpoint pens of Examples 2 to were obtained in the same procedure as in Example 1. The measurement and evaluation results are shown in the table.

[0082] Comparative Examples 1 to 3 As shown in the table, except for changing the ink components, ink compositions for oil-based ballpoint pens of Comparative Examples 1 to 3 were obtained in the same procedure as in Example 1. The measurement and evaluation results are shown in the table.

[0083] Note that regarding the ink viscosity of the examples, in an environment of 20°C and a shear rate of 200 sec -1 using a viscometer manufactured by Brookfield Engineering Laboratories, Inc., viscometer RVDVII+Pro CP-52 spindle, the ink viscosity was measured, and the measured results are shown in the table.

[0084] Tests and evaluations The ink compositions for oil-based ballpoint pens prepared in Examples 1 to 23 and Comparative Examples 1 to 3 were used to attach a ballpoint pen tip to the tip of an ink storage cylinder (made of polypropylene). The ball of the ballpoint pen tip (φ0.7 mm, the amount of movement in the longitudinal axis direction of the ball: 12 μm), which was pressed against the inner wall of the tip edge by an elastic member, was rotatably held. At the same time, 0.3 g of the ink compositions for oil-based ballpoint pens prepared in Examples 1 to and Comparative Examples 1 to 3 were directly stored in the ink storage cylinder, and the ballpoint pen refills were installed in oil-based ballpoint pens manufactured by Pilot Corporation. Then, the following tests and evaluations were conducted using JIS P3201 writing paper as the writing test paper. When the ink consumption per 100 m at the initial stage of Examples 1, 3, and 14 was measured by performing a spiral writing test with an oil-based ballpoint pen, it was 55 mg / 100 m, 70 mg / 100 m, and 65 mg / 100 m, respectively. [Table 1] [Table 2] [Table 3]

[0085] Writing property test 1: The handwriting when writing by hand was observed. ◎ ··· Those without ink splashing or handwriting smearing ○ ··· Those with slightly ink splashing or handwriting smearing △ ··· Those with ink splashing or handwriting smearing but without practical problems × ··· Those with severe ink splashing or handwriting smearing

[0086] Wear resistance test (wear test of the ball seat): After the writing test, the wear of the ball seat was measured using a running test machine with a load of 200 gf, a writing angle of 70°, and a speed of 4 m / min. ◎ ··· Those with the wear of the ball seat less than 5 μm ○ ··· Those with the wear of the ball seat 5 μm or more and less than 10 μm △···The wear of the ball seat is 10 μm or more and less than 20 μm, but it is still writable. ×···The wear of the ball seat is severe and the writing becomes defective.

[0087] Writing property test 2 (ink bleeding test): After a 30 m writing test using a running tester with a load of 200 gf, a writing angle of 70°, and a speed of 4 m / min, the written traces were observed. ◎···There is no ink bleeding in the written traces. ○···There is some ink bleeding in the written traces, but it is at a level that does not cause practical problems. △···There is ink bleeding in the written traces, which has an impact on practical use. ×···There is a lot of ink bleeding in the written traces.

[0088] Writing feel: It was evaluated by a sensory test using handwriting. ◎···Very smooth. ○···Smooth. △···Somewhat less smooth. ×···Heavy.

[0089] In Examples 1 to 23, good performance was obtained in writing property test 1, wear resistance test (wear test of the ball seat), writing property test 2 (ink bleeding test), and writing feel. When comparing the written traces in writing property test 1 between Examples 1, 2 and Examples 8, 9, the written traces of Examples 8 and 9 containing diketopyrrolopyrrole - based pigments were much better. Also, after leaving the oil - based ball - pen ink compositions of the examples using pigments as colorants standing for 1 month and observing them under a microscope, the pigment dispersibility was good and stable.

[0090] In Comparative Examples 1 to 3, since a surfactant having an acetylene bond in its structure was not used, when handwriting was done in writing property test 1, skipping and trace blurring were severe. Furthermore, in the wear resistance test (wear test of the ball seat), the wear of the ball seat was also inferior. In Comparative Example 3, there were many voids in the handwriting, and in the wear resistance test (wear test of the ball seat), the wear of the ball seat was also inferior. Furthermore, when the ink composition for an oil-based ballpoint pen of Comparative Example 3 using a pigment as a colorant was observed under a microscope one month later, since the ink viscosity was low, pigment sedimentation was observed and the writing performance test was inferior.

[0091] In addition, in this Example, an oil-based ballpoint pen in which a ballpoint pen refill containing an ink composition for an oil-based ballpoint pen was disposed in a shaft cylinder was exemplified. However, the writing instrument of the present invention may be a writing instrument that uses the shaft cylinder itself as an ink storage cylinder and directly stores the ink composition for an oil-based ballpoint pen in the shaft cylinder, that is, a direct filling type ballpoint pen, or may have a structure in which the one containing the ink composition for an oil-based ballpoint pen (ballpoint pen refill) in the ink storage cylinder is used as a ballpoint pen as it is.

Industrial Applicability

[0092] 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 click type filled with the ink composition for an oil-based ballpoint pen.

Claims

1. An oil-based ballpoint pen ink composition comprising a colorant, an organic solvent, and a surfactant having an acetylene bond in its structure, wherein the ink viscosity of the oil-based ballpoint pen ink composition is 300 mPa·s or more at 20°C and a shear rate of 200 sec －１ -1. The oil-based ballpoint pen ink composition is characterized by this.

2. The oil-based ballpoint pen ink composition according to claim 1, wherein the content of the surfactant having an acetylene bond in its structure is 0.1 to 10% by mass based on the total amount of the ink composition.

3. The oil-based ballpoint pen ink composition according to claim 1 or 2, characterized in that a phosphate ester-based surfactant, a fatty acid, or a fatty acid ester is selected for the oil-based ballpoint pen ink composition.

4. The oil-based ballpoint pen ink composition according to claim 1 or 2, characterized in that the colorant is a pigment.

5. The oil-based ballpoint pen ink composition according to claim 1 or 2, characterized in that the organic solvent is selected from alkylene oxide derivatives of glycerin, alkylene glycol alkyl ethers, and amide solvents.

6. An oil-based ballpoint pen having a ballpoint pen tip that rotatably holds a ball at the tip of an ink storage cylinder, and containing the oil-based ballpoint pen ink composition according to claim 1 or 2 in the ink storage cylinder.

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