Ink composition for writing implements and writing implements using the same

Abstract

To provide an ink composition for writing instruments that improves the lubricity of the pen tip on the prints formed with print inks such as toner, facilitating good writing, whereby the wear on the ball seat is suppressed, resulting in improved the writing feel; and to provide a writing instrument including the ink composition.SOLUTION: An ink composition for writing instruments includes a colorant, an organic solvent, and a diglycerin / dilinoleic acid / hydroxystearic acid copolymer.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an ink composition for a writing instrument and a writing instrument using the same. [Background technology]

[0002] Writing implements using ink have been known for some time and are used by people of all ages because they are easy to use. These writing implements contain colorants, solvents, surfactants, etc., which enable them to write well on paper (Patent Document 1).

[0003] During normal use, it is possible to write well on paper, but when writing on prints made with printing ink such as toner, the handwriting becomes blurred and smudged, making it difficult to write well. This is because, in the case of ballpoint pens, the ball slides over the print when writing, preventing the ball from rotating sufficiently, resulting in blurred lines and smudged handwriting, and there is room for improvement (Patent Document 1).

[0004] Furthermore, writing instruments are prone to affecting the writing feel of ballpoint pens, marking pens, and the like due to the writing resistance that occurs between the writing tip and the surface being written on when writing. Ballpoint pens in particular have a configuration in which a ballpoint pen tip is attached to an ink reservoir, and the ball tip consists of a metal tip made of stainless steel or the like at the tip and a transfer ball made of metal such as carbide that is held in a ball receiving seat of the metal tip. When writing, the rotation of the ball causes wear to the ball seat, resulting in problems such as skipped lines and smudges in the handwriting and a poor writing feel, leaving room for improvement. Furthermore, when writing for a long period of time, since the ink storage tube is made of a material such as polyolefin resin, it has a strong affinity with the writing instrument ink, and as the ink moves inside the ink storage tube, the ink tends to adhere to the inner wall, making it difficult to see the remaining ink (visibility of remaining ink), which was a problem and left room for improvement.

[0005] To solve these problems, many ink compositions for writing instruments using various lubricants have been proposed to improve lubricity and reduce the writing resistance between the writing tip and the surface being written on (Patent Documents 2 to 5). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 8-41406 [Patent Document 2] Japanese Patent Application Publication No. 5-331403 [Patent Document 3] Japanese Patent Application Laid-Open No. 2007-176995 [Patent Document 4] Japanese Patent Application Laid-Open No. 2013-151594 [Patent Document 5] Japanese Patent Application Laid-Open No. 2014-88486 Summary of the Invention [Problem to be solved by the invention]

[0007] However, when various new lubricants are used, although it is possible to reduce the writing resistance between the writing tip and the surface being written on to some extent, it is not sufficient, and the load on the ball seat causes wear on the ball seat, which can lead to poor writing, so there is room for improvement (Patent Documents 2 to 5).

[0008] The object of the present invention is to provide an ink composition for a writing instrument, which improves the lubricity of the writing tip, thereby enabling good writing on prints formed with printing ink such as toner, suppressing wear on the ball seat, improving writing feel, and allowing the remaining ink to be visually confirmed, and a writing instrument using the same. [Means for solving the problem]

[0009] In order to solve the above problems, the present invention "1. An ink composition for a writing instrument, comprising a colorant, an organic solvent, and a (diglycerin / dilinoleic acid / hydroxystearic acid) copolymer. 2. The ink composition for a writing instrument according to item 1, wherein the content of the (diglycerin / dilinoleic acid / hydroxystearic acid) copolymer is 0.1 to 10% by mass based on the total amount of the ink composition. 3. The ink composition for a writing instrument according to any one of items 1 and 2, characterized in that the ink composition for a writing instrument contains a surfactant. 4. The ink composition for a writing instrument according to item 3, wherein the HLB value of the surfactant is 6 or more and 14 or less. 5. A writing instrument containing the ink composition for a writing instrument according to any one of items 1 to 4. 6. An oil-based ballpoint pen, characterized in that it has a ballpoint pen tip that rotatably holds a ball at the tip of an ink reservoir, and the ink composition for a writing instrument described in any one of items 1 to 4 is contained in the ink reservoir. [Effects of the Invention]

[0010] The present invention has made it possible to obtain an ink composition for a writing instrument, and a writing instrument using the same, which can suppress line skipping and smearing of handwriting by improving the lubricity of the writing tip on prints made with printing ink such as toner, thereby achieving good writing properties, and further suppressing wear on the ball seat, improving writing feel, and preventing the ink from adhering to the inner wall as it moves inside the ink reservoir, thereby making it possible to visually check the amount of ink remaining (visible remaining ink amount). DETAILED DESCRIPTION OF THE INVENTION

[0011] In this specification, "parts," "%," "ratio," and the like indicating the composition are based on mass unless otherwise specified.

[0012] A feature of the present invention is an ink composition for a writing instrument comprising a (diglycerin / dilinoleic acid / hydroxystearic acid) copolymer. The inclusion of the (diglycerin / dilinoleic acid / hydroxystearic acid) copolymer improves the lubricity of the writing tip, thereby suppressing line skipping and smearing of handwriting even on prints made with printing inks such as toner, resulting in good writing performance and an improved writing feel. In the case of a ballpoint pen, the copolymer improves the lubricity between the ball and the ball seat of the tip body, reducing friction between the ball seat and the seat, thereby suppressing wear on the ball seat and further improving the writing feel. Furthermore, the copolymer can be effectively used in ballpoint pens, and considering the suppression of line skipping and smearing of handwriting even on prints made with printing inks such as toner, it is preferable to use the copolymer as an oil-based ink composition for a writing instrument, and preferably as an oil-based ballpoint pen. Furthermore, by preventing ink from adhering to the inner wall as it moves through the ink reservoir, the remaining ink amount can be visually checked, improving visibility. This eliminates the need to apply a surfactant or other coating to the inner surface of the ink reservoir, reducing the number of production steps and achieving cost savings.

[0013] (Diglycerin / Dilinoleic Acid / Hydroxystearic Acid Copolymer) The (diglycerin / dilinoleic acid / hydroxystearic acid) copolymer used in the present invention is a copolymer of diglycerin, dilinoleic acid, and hydroxystearic acid, which improves the lubricity of the writing tip and suppresses line skipping and blurring of handwriting even on prints made with printing inks such as toner, resulting in good writing properties and an improved writing feel.In the case of ballpoint pens, it improves the lubricity between the ball and ball seat and reduces friction between the ball seat, thereby suppressing wear on the ball seat, further improving the writing feel, and making it possible to improve the visibility of the remaining ink. The (diglycerin / dilinoleic acid / hydroxystearic acid) copolymer is a copolymer of diglycerin, dilinoleic acid, and hydroxystearic acid. Specifically, there is the Lithocasta HSDA manufactured by High Alcohol Corporation.

[0014] The content of the (diglycerin / dilinoleic acid / hydroxystearic acid) copolymer is preferably 0.1% by mass or more relative to the total amount of the ink composition. This is because a content of 0.1% by mass or more makes it easier to achieve the effects of the present invention, and from a more specific perspective, 0.5% by mass or more is preferable, and 1% by mass or more is more preferable. Furthermore, since this does not affect the ink stability over time and makes it easier to achieve the effects of the present invention, the content is preferably 10% by mass or less, and from a more specific perspective, 5% by mass or less is preferable, and 4% by mass or less is more preferable.

[0015] (solvent) The solvent used in the ink composition for a writing instrument used in the present invention may be water, an organic solvent, or a mixed solvent of water and an organic solvent.

[0016] Examples of the organic solvent 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, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, triethylene glycol dimethyl ether, 3-methoxybutanol, and 3-methoxy-3-methylbutanol; 3-methoxy-N,N-dimethylpropanamide; and 3-butoxy-N,N-dimethylpropanamide. Examples of organic solvents commonly used in inks for writing instruments include amide solvents of β-alkoxypropionamides such as 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.

[0017] Among these organic solvents, glycol ether solvents or amide solvents are preferred because they are compatible with diglycerin / dilinoleic acid / hydroxystearic acid copolymers, which facilitate the effective delivery of the effects of the present invention. This is because they further improve the lubricity of the writing tip, suppress line skipping and smearing even on prints made with printing inks such as toner, and facilitate an improved writing experience. In the case of ballpoint pens, they improve the lubricity between the ball and ball seat, reduce friction between the ball seat, and inhibit wear on the ball seat, thereby further improving the writing experience. Furthermore, alkylene glycol monoalkyl ethers and amide solvents of β-alkoxypropionamides are preferred because they stabilize the ink over time even during long-term storage, thereby facilitating the effective delivery of the effects of the present invention. Furthermore, they can be effectively used in ballpoint pens, and are preferred as oil-based ink compositions for writing instruments, particularly oil-based ballpoint pens, because they suppress line skipping and smearing even on prints made with printing inks such as toner.

[0018] Furthermore, in consideration of the ease with which the alkylene glycol moiety of the alkylene glycol monoalkyl ether can stably exhibit its effect together with the (diglycerin / dilinoleic acid / hydroxystearic acid) copolymer, the number of carbon atoms is preferably 2 or more and 10 or less. In consideration of the ease with which the effect can be more stably exhibited and the effect can be more easily obtained, the number of carbon atoms is preferably 3 or more and 8 or less, and more preferably 5 or more and 6 or less. Furthermore, the number of carbon atoms in the alkyl ether moiety of the alkylene glycol monoalkyl ether is preferably shorter, since it is easier to stably exert its effect together with the (diglycerin / dilinoleic acid / hydroxystearic acid) copolymer. Therefore, the number of carbon atoms is preferably 1 to 6, and from the viewpoint of greater stability and easier effect attainment, it is preferably 1 to 4, and more preferably 1 to 2.

[0019] In addition, the solubility parameter (SP value) of alkylene glycol monoalkyl ether is 8 to 13 (cal / cm 3 )1 / 2 This is because the effects of the present invention are easily exhibited due to the compatibility with the (diglycerin / dilinoleic acid / hydroxystearic acid) copolymer, and from a more specific perspective, the solubility parameter (SP value) is preferably 9 to 12 (cal / cm 3 ) 1 / 2 Further, if one takes into consideration, the solubility parameter (SP value) is preferably 10 to 11 (cal / cm 3 ) 1 / 2 It is preferable that: The solubility parameter (SP value) of a solvent in the present invention is a value expressed as the square root of the molecular cohesive energy, and is described in Chapter IV, Solubility Parameter Values, of the Polymer Handbook (Second Edition), and this value was used. The unit is (cal / cm 3 ) 1 / 2 and refers to the value at 25°C. For those for which no data is given, the values ​​can be calculated by the method described in RF Fedors, Polymer Engineering Science, 14, p. 147 (1967).

[0020] Furthermore, the boiling point of the alkylene glycol monoalkyl ether is preferably 170°C or higher. This is because if the boiling point is lower than 170°C, the alkylene glycol monoalkyl ether is likely to evaporate, the ink viscosity is likely to increase, and it is difficult to suppress line skipping and blurred handwriting on prints formed with printing ink such as toner, which is likely to affect the writing feel. From this perspective, a boiling point of 220°C or higher is preferable. On the other hand, if the boiling point exceeds 300°C, the drying properties of the handwriting are likely to be affected, so a boiling point of 300°C or lower is preferable, and from this perspective, a boiling point of 280°C or lower is more preferable.

[0021] Furthermore, the content of the organic solvent is preferably 10% by mass or more and 70% by mass or less of the total amount of the ink composition, in consideration of improving solubility, handwriting drying property, bleeding, etc. Furthermore, the content of the alcohol solvent is preferably 30% by mass or more and 90% by mass or less of the total organic solvent, in consideration of drying property at the tip end.

[0022] As the water, conventional water such as ion-exchanged water, distilled water, and tap water can be used. In the present invention, the ink composition for a writing instrument preferably contains water. This is because the use of water reduces the ink viscosity, improves the ball's slipperiness, improves ink dischargeability, suppresses line skipping and blurred handwriting even on prints formed with printing inks such as toner, improves the writing feel, suppresses dot unevenness and bleeding, and easily improves writing performance. Water can be used effectively, particularly when used with a ballpoint pen.

[0023] The content of water is preferably 0.1% by mass or more and 20% by mass or less, based on the total amount of the ink composition. This is because, within this range, ink discharge properties are improved, line skipping and blurred handwriting are suppressed even on prints formed with printing inks such as toner, the writing feel is easily improved, and dot unevenness, bleeding, etc. are suppressed, making it easy to improve writing properties. From a more specific perspective, the content of water relative to the total amount of the ink composition is preferably 1% by mass or more and 10% by mass or less, and even more preferably 2% by mass or more and 10% by mass or less.

[0024] (coloring agent) The colorant used in the water-based ink composition for a writing instrument and the oil-based ink composition for a writing instrument used in the present invention is not particularly limited and may be a dye, a pigment, or the like, and may be appropriately selected and used. Dyes and pigments may also be used in combination.

[0025] Dyes that can be used in oil-based ink compositions include oil-soluble dyes, acid dyes, basic dyes, metal-containing dyes, and various salt-forming dyes thereof, such as salt-forming dyes formed from an acid dye and a basic dye, salt-forming dyes formed from an organic acid and a basic dye, and salt-forming dyes formed from an acid dye and an organic amine. Among these, salt-forming dyes are preferred in view of their stability with the (diglycerin / dilinoleic acid / hydroxystearic acid) copolymer. Dyes include Balifast Black 1802, Balifast Black 1805, Balifast Black 1807, Balifast Violet 1701, Balifast Violet 1704, Balifast Violet 1705, Balifast Blue 1601, Balifast Blue 1605, Balifast Blue 1613, Balifast Blue 1621, Balifast Blue 1631, Balifast Red 1320, Balifast Red 1355, Balifast Red 1360, Balifast Yellow 1101, Balifast Yellow 1151, Nigrosine Base EXBP, Nigrosine Base EX, BASE OF BASIC DYES ROB-B, BASE OF BASIC DYES RO6G-B, BASE OF BASIC DYES VPB-B, BASE OF BASIC DYES VB-B, BASE OF BASIC DYES MVB-3 (all manufactured by Orient Chemical Industries Co., Ltd.), Aizen Spiron Black GMH-Special, and Aizen Spiron Violet C-RH, Aizenspiron Blue GNH, Aizenspiron Blue 2BNH, Aizenspiron Blue C-RH, Aizenspiron Red C-GH, Aizenspiron Red C-BH, Aizenspiron Yellow C-GNH, Aizenspiron Yellow C-2GH, SPT Blue 111, SPT Blue GLSH-Special, SPT Red 533, SPT Orange 6, SBN Yellow 510, SBN Yellow 530, SRC-BH (all manufactured by Hodogaya Chemical Co., Ltd.). Examples of pigments include inorganic, organic, and processed pigments. Specific examples include carbon black, aniline black, ultramarine, yellow lead, titanium oxide, iron oxide, phthalocyanine-based, azo-based, quinacridone-based, diketopyrrolopyrrole-based, quinophthalone-based, threne-based, triphenylmethane-based, perinone-based, perylene-based, dioxazine-based, metallic pigments, pearl pigments, fluorescent pigments, and phosphorescent pigments. These dyes and pigments may be used alone or in combination of two or more.

[0026] As the dyes used in the aqueous ink composition, direct dyes, acid dyes, basic dyes, metal-containing dyes, various salt-forming dyes, etc. can be used. (a) Direct dyes include Direct Yellow 4, 26, 44, 50, and 85; Direct Red 1, 2, 4, 23, 31, 37, 39, 75, 80, 81, 83, 225, 226, and 227; Direct Blue 1, 3, 15, 41, 71, 86, 106, and 119; and Direct Orange 6. (b) Acid dyes include The colors are Acid Black 1, 2, 24, 26, 31, 52, 107, Acid Orange 56, Acid Yellow 3, 7, 17, 19, 23, 42, 49, 61, 92, Acid Red 8, 9, 14, 18, 51, 52, 73, 87, 92, 94, Acid Blue 1, 7, 9, 22, 62, 90, 103, Acid Green 3, 9, 16, 25, 27, Acid Violet 15, 17, etc.; (c) Basic dyes include CI Basic Yellow 1, 2, 21, 7, 40, CI Basic Orange 2, 14, 32, CI Basic Red 1, 1:1, 2, 9, 14, CI Basic Violet 1, 3, 7, 10, 11:1, CI Basic Blue 3, 7, 26, Basic Green 4, CI Basic Brown 12, CI Basic Black 2, methyl violet, Victoria Blue FB, malachite green, and rhodamine series; (d) Other dyes include disperse dyes such as Disperse Yellow 82, 121, and Disperse Blue 7.

[0027] It is also preferable to use a pigment as the colorant, because in the case of a ballpoint pen, the pigment particles create a physical obstacle in the gap between the ball and the inner wall of the tip, which makes it easy to suppress ink leakage. Pigments are also preferred because they provide excellent handwriting durability, especially excellent light resistance. Furthermore, in the case of a ballpoint pen, the use of a pigment allows the pigment particles to penetrate into the gap between the ball and the tip body, acting like a bearing, and by suppressing metal contact, it is possible to improve lubricity, improve the writing feel, and reduce wear on the ball seat, making it preferable to use a pigment. When using a (diglycerin / dilinoleic acid / hydroxystearic acid) copolymer to improve lubricity, as in the present invention, the use of a pigment is more effective. Furthermore, the synergistic effect of the bearing action of the lubricating layer formed by the surfactant (described below) and the pigment particles makes it easier to maintain lubricity and improve the writing feel, making it preferable.

[0028] The content of the colorant is preferably 5% by mass or more and 30% by mass or less relative to the total amount of the ink composition. This is because if it is less than 5% by mass, it tends to be difficult to obtain thick handwriting, and if it exceeds 30% by mass, it tends to affect the solubility in the ink. Taking these tendencies into consideration, the content is preferably 7% by mass or more and 25% by mass or less, and even more preferably 10% by mass or more and 20% by mass or less.

[0029] (surfactant) In the present invention, it is preferable to use a surfactant, because it improves the lubricity of the writing tip, suppresses line skipping and blurring of handwriting even on prints made with printing ink such as toner, and is likely to improve the writing feel, and in the case of a ballpoint pen, it improves the lubricity between the ball and ball seat, reduces friction between the ball seat, and suppresses wear of the ball seat, which is likely to further improve the writing feel. Furthermore, the use of a surfactant is preferred because it facilitates improved writing performance when the writing tip (tip tip) dries when left in the air. This is because the use of a surfactant tends to soften the coating formed, improving writing performance and lubricity. Examples of surfactants include silicone surfactants, fluorine-based surfactants, phosphate ester surfactants, polyoxyalkylene alkyl ethers, fatty acids, and fatty acid esters. Considering the above effects, it is preferable to use one or more surfactants selected from phosphate ester surfactants, polyoxyalkylene alkyl ethers, fatty acids, and fatty acid esters. Considering these advantages, it is more preferable to use two or more surfactants. In particular, it is preferable to use a phosphate ester surfactant and a polyoxyalkylene alkyl ether in combination to ensure good writing even on prints made with printing inks such as toner. In particular, when used in a ballpoint pen, it can be used effectively, and further, considering that it suppresses line skipping and blurring of handwriting even on prints formed with printing ink such as toner, it is preferably used as an oil-based ink composition for a writing instrument, and preferably in an oil-based ballpoint pen.

[0030] Furthermore, when a phosphate ester surfactant is used, the acid value is preferably 160 or less (mgKOH / g). This is because the improved lubricity of the phosphate ester surfactant is easily exhibited, and it is easy to write well on characters printed with printing ink such as toner. Furthermore, taking into consideration stability in the ink and lubricity, the acid value is preferably 30 or more and 160 or less, and more preferably 70 or more and 120 or less (mgKOH / g). The acid value is expressed as the number of milligrams of potassium hydroxide required to neutralize the acidic components contained in 1 g of sample. When a polyoxyalkylene alkyl ether is used, the alkyl group preferably has 10 to 20 carbon atoms. This is because the alkyl group chain of the polyoxyalkylene alkyl ether has a length suitable for maintaining stable performance of the (diglycerin / dilinoleic acid / hydroxystearic acid) copolymer in a solvent and allows for good writing even on prints formed with printing inks such as toner. In consideration of the length of the alkyl group chain, the alkyl group preferably has 12 to 18 carbon atoms. Furthermore, in consideration of maintaining stable performance in a solvent, the alkyl group is preferably a lauryl group, an oleyl group, a stearyl group, or a cetyl group, and more preferably a lauryl group.

[0031] The surfactant preferably has an HLB value of 6 or more and 14 or less. This is because an HLB value exceeding 14 tends to result in strong hydrophilicity, which tends to result in poor solubility in oil-based inks, making it difficult to obtain the effects of the surfactant and to maintain stable performance in the solvent, which is likely to affect the effects of the present invention. Furthermore, an HLB value of less than 6 tends to result in excessively strong lipophilicity, which tends to affect compatibility with organic solvents and makes it difficult for the ink to stabilize over time. Furthermore, in consideration of the effects of the surfactant, the HLB value is preferably 12 or less, and an HLB value of 6 or more and 12 or less is preferable. In consideration of better ink performance over time, an HLB value of 7 or more and 12 or less is preferable. The HLB can be determined by the Griffin method, the Kawakami method, or the like, and as an example, it can be determined from the general formula HLB=7+11.7log(Mw / Mo), where Mw is the molecular weight of the hydrophilic group and Mo is the molecular weight of the lipophilic group. In particular, in retractable writing instruments such as knock-type writing instruments and rotary-type writing instruments, unlike cap-type writing instruments, the pen tip is always exposed to the outside, which is likely to affect the writing performance when the writing tip dries, so it is more preferable to use a surfactant with the above HLB value.

[0032] Specific examples of the surfactant include fatty acids such as oleic acid and linoleic acid; fatty acid esters include fatty acid esters obtained by esterifying a fatty acid with a monohydric alcohol and fatty acid esters obtained by esterifying a fatty acid with an alcohol such as a polyhydric alcohol; silicone surfactants include dimethyl silicone, methylphenyl silicone, polyether-modified silicone, and higher fatty acid ester-modified silicone; fluorine-based surfactants include perfluoro group-containing butyl sulfonate salts, perfluoro group-containing carboxylate salts, perfluoro group-containing phosphate esters, perfluoro group-containing phosphate ester-type compounds, perfluoroalkyl betaines, and perfluoroalkylamine oxide compounds; phosphate ester surfactants include polyoxyethylene alkyl ether or polyoxyethylene alkylaryl ether phosphate monoesters, polyoxyethylene alkyl ether or polyoxyethylene alkylaryl ether phosphate diesters, polyoxyethylene alkyl ether or polyoxyethylene alkylaryl ether phosphate triesters, alkyl phosphate esters, alkyl ether phosphate esters, and derivatives thereof; and polyoxyalkylene alkyl ethers include polyoxyethylene alkyl ethers and polyoxypropylene alkyl ethers.

[0033] The content of the surfactant is preferably 0.1% by mass or more and 5.0% by mass or less relative to the total amount of the ink composition. This is because if it is less than 0.1% by mass, it is difficult to obtain the desired lubricity, and if it exceeds 5.0% by mass, the ink tends to become unstable over time. Taking this into consideration, the content is preferably 0.3% by mass or more and 3.0% by mass or less, and even more preferably 0.5% by mass or more and 3.0% by mass or less relative to the total amount of the ink composition.

[0034] (organic amine) In the present invention, when a surfactant such as a phosphate ester surfactant is used, neutralization stabilizes the solution in the ink, further improves the lubricity of the writing tip, and helps prevent line skipping and blurring of handwriting even on prints made with printing inks such as toner. This neutralization is preferred because it reduces wear on the ball seat and improves the writing feel and writing performance. Examples of organic amines include amines containing ethylene oxide, such as oxyethylene alkylamines and polyoxyethylene alkylamines; alkylamines, such as laurylamine and stearylamine; aliphatic amines, such as dimethyl alkylamines, distearylamine, dimethyl laurylamine, dimethyl stearylamine, and dimethyl octylamine; and alkanolamines, such as diethanolamine and triethanolamine. Among these, amines containing ethylene oxide or dimethyl alkylamines are preferred, considering their solubility in the ink. These may be used alone or in combination.

[0035] Furthermore, in consideration of the stability with the (diglycerin / dilinoleic acid / hydroxystearic acid) copolymer, colorant, surfactant, and other components, the total amine value of the organic amine is preferably 300 (mgKOH / g) or less. This is because if it exceeds 300 (mgKOH / g), the reactivity is strong and it is likely to affect the above components, which is likely to affect the ink stability over time. From this perspective, the total amine value is preferably 200 (mgKOH / g) or less, and even more preferably 150 (mgKOH / g) or less. On the other hand, in consideration of the above effects, the lower limit of the total amine value is preferably 30 (mgKOH / g) or more. The total amine value indicates the total amount of primary, secondary, and tertiary amines, and is expressed as the number of milligrams of potassium hydroxide equivalent to the amount of hydrochloric acid required to neutralize 1 g of sample.

[0036] The HLB value of the organic amine is preferably 5 to 17. This is because the organic amine is more likely to be stable with the (diglycerin / dilinoleic acid / hydroxystearic acid) copolymer, colorant, surfactant, resin, and other components, and the effects of the present invention are more likely to be achieved. From further consideration, the HLB value is more preferably 7 to 17, and even more preferably 9 to 16. In particular, when a polyacrylic acid resin is used, it is preferable to neutralize it and stabilize its swelling dispersion with the solvent, since this will provide a stable thickening effect.

[0037] The content of the organic amine is preferably 0.1% by mass or more and 10% by mass or less of the total amount of the ink composition, taking into consideration the stability with the (diglycerin / dilinoleic acid / hydroxystearic acid) copolymer, colorant, surfactant, and other components, and furthermore, taking into consideration the neutralization of the surfactant described above, it is preferably 0.5% by mass or more and 5% by mass or less.

[0038] In the present invention, a resin may be used as an ink viscosity modifier. 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, polyvinylpyrrolidone resin, ethylene oxide polymer, and resin particles such as acrylic ester resin particles and amino resin particles. These may be used alone or in combination of two or more.

[0039] In addition, in the present invention, it is preferable to use a shear thinning agent. Examples of shear thinning agents include polyacrylic acid resin, xanthan gum, welan gum, succinoglycan, guar gum, locust bean gum, λ-carrageenan, cellulose derivatives, oxidized cellulose, and diutan gum. The inclusion of these agents is preferable because they form a three-dimensional network structure in the ink, which easily imparts pseudoplasticity and is effective in improving the writing feel and writing performance (suppression of handwriting smearing). Among these, polyacrylic acid resin is preferable because it easily forms a three-dimensional network structure and easily forms a denser crosslinked structure. From this perspective, crosslinked polyacrylic acid resin is preferred. Polyacrylic acid resin is used as a thickener. Polyacrylic acid resin has affinity with alkylene glycol alkyl ethers, and by swelling and dispersing, it achieves pseudoplasticity and stable thickening action. Furthermore, from the perspective of writing feel and writing performance (suppression of handwriting smearing and smearing), crosslinked polyacrylic acid resin is preferred. Furthermore, carboxyvinyl polymers are preferred because they form a denser crosslinked structure, which makes it easier to impart pseudoplasticity, thereby reducing the ink viscosity during writing and improving the writing feel and writing performance (suppressing smearing and bleeding). In particular, it is effective and preferable to use an amide solvent such as alkylene glycol monoalkyl ether or β-alkoxypropionamide as the organic solvent, since it is easy to form a more three-dimensional network structure. In particular, when used in a ballpoint pen, it can be used effectively, and further, considering that it suppresses line skipping and blurring of handwriting even on prints formed with printing ink such as toner, it is preferably used as an oil-based ink composition for a writing instrument, and preferably in an oil-based ballpoint pen.

[0040] Furthermore, in the case of polyacrylic acid resins, the carboxyl group content in the polyacrylic acid resin is preferably 40% by mass or more and 80% by mass or less, considering that a stable thickening effect can be obtained together with alkylene glycol alkyl ethers. Even more preferably, it is 50% by mass or more and 70% by mass or less. In particular, when alkylene glycol monoalkyl ethers are used as alkylene glycol alkyl ethers, polyacrylic acid resins having a carboxyl group content of 55% by mass or more and 65% by mass or less are preferred, since they have excellent swelling and dispersibility and impart pseudoplasticity, thereby lowering the ink viscosity during writing and improving the writing feel. Furthermore, alkylene glycol monomethyl ethers are even more preferred.

[0041] If the content of the polyacrylic acid resin is less than 0.1% by mass relative to the total amount of the ink composition, the swelling is insufficient and pseudoplasticity is not obtained, making it difficult to improve the writing feel, while if it exceeds 5.0% by mass, the swelling and dispersibility in the ink is likely to be poor, so the content is preferably 0.1% by mass or more and 5.0% by mass or less relative to the total amount of the ink composition. Furthermore, taking into consideration the writing feel, etc., the content 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.

[0042] In addition, as viscosity modifiers, pseudoplasticity imparting agents such as fatty acid amides and hydrogenated castor oil, colorants, stabilizers, plasticizers, chelating agents, etc. may be used as appropriate. These may be used alone or in combination of two or more.

[0043] The ink viscosity of the ink composition for a writing instrument of the present invention is not particularly limited, but considering that the ink viscosity during writing is reduced, ink consumption is increased, and line skipping and blurring of handwriting are suppressed even on prints formed with printing ink such as toner, and the writing feel is easily improved, the ink viscosity is preferably set to 20°C, a shear rate of 24 sec -1The ink viscosity (during writing) is preferably 7000 mPa·s or less, and even more preferably 6000 mPa·s or less, and even more preferably 5000 mPa·s or less. On the other hand, taking into consideration writing properties such as bleeding, bleed-through, and drying of handwriting, the ink viscosity is preferably 100 mPa·s or more, and even more preferably 200 mPa·s or more, and even more preferably 400 mPa·s or more.

[0044] In addition, when using polyacrylic acid resin, by imparting pseudoplasticity, the ink viscosity during writing is lowered, ink consumption is increased, and line skipping and blurring of handwriting are suppressed even on prints made with printing inks such as toner, making it easier to improve the writing feel. In this regard, it is recommended to use a temperature of 20°C and a shear rate of 200 sec. -1 The ink viscosity (when writing) is preferably 1500 mPa·s or less, and more preferably 1000 mPa·s or less. Taking this into consideration, an ink viscosity of 900 mPa·s or less is preferable. On the other hand, taking into consideration writing performance such as blobbing, bleeding, show-through, and drying of handwriting, an ink viscosity of 100 mPa·s or more is preferable, and taking this into consideration, an ink viscosity of 200 mPa·s or more is preferable, and 400 mPa·s or more is more preferable.

[0045] In addition, considering ink followability, 20°C, shear rate 0.18 sec -1 The ink viscosity (when stationary) is preferably 50,000 mPa·s or less, and even more preferably 30,000 mPa·s or less. On the other hand, in consideration of suppressing ink leakage, the ink viscosity is preferably 1,000 mPa·s or more, and even more preferably 2,000 mPa·s or more, and even more preferably 3,000 mPa·s or more. This is also effective for retractable writing instruments such as knock-type writing instruments and rotary-propelling writing instruments, in which it is necessary to give greater consideration to preventing ink leakage.

[0046] When a shear thinning agent is used as in the present invention, the viscosity index n is expressed as S=αD n where S is the shear stress (dyn / cm 2=0.1 Pa), D is the shear rate (s -1 ), and α is the viscosity coefficient. The viscosity index n can be calculated by measuring the ink viscosity at 20°C using a TA Instruments AR-G2 rheometer (cone plate 40 mm, angle 2°). The viscosity index n is preferably 0.3 or more and 0.8 or less, in order to suppress line skipping and blurring of handwriting even on prints formed with printing ink such as toner, and in consideration of writing performance such as smooth writing, smearing, and blurring. Considering the balance of writing performance such as smooth writing, smearing, and blurring, the viscosity index n is preferably 0.35 or more and 0.7 or less, and more preferably 0.4 or more and 0.7 or less. It can be used particularly effectively when used in a ballpoint pen.

[0047] (ballpoint pen) Furthermore, the ink consumption per 100 m of a ballpoint pen is preferably 20 mg or more and 100 mg or less. This is because, when the ink consumption per 100 m is within this range, line skipping and blurring of handwriting are suppressed even on prints formed with printing inks such as toner, improving the writing feel and making it easier to produce thick handwriting. From further consideration, the ink consumption is preferably 25 mg or more and 90 mg or less, and more preferably 40 mg or more and 80 mg or less. Regarding ink consumption, a spiral writing test was conducted using five test samples at a writing speed of 4 m / min on JIS P3201 writing paper at a writing angle of 70° and a writing load of 200 g at 20°C, and the average ink consumption per 100 m was defined as the ink consumption per 100 m.

[0048] (ballpoint pen tip) For ballpoint pen tips, it is preferable to maintain lubricity between the ball and the tip body, prevent blurred handwriting, and reduce wear on the ball seat, improving the writing feel, and to provide a ball seat with an approximately arc-shaped surface on the bottom wall of the ball holding chamber.

[0049] Furthermore, the arithmetic mean roughness (Ra) of the ball surface of the ballpoint pen tip used in the present invention is preferably 0.1 nm or more and 12 nm or less. This is because when the arithmetic mean roughness (Ra) is in the above range, line skipping and handwriting smearing are suppressed even on prints formed with printing ink such as toner, improving the writing feel and making it easier to produce thick handwriting. From further consideration, the arithmetic mean roughness (Ra) is preferably 0.1 nm or more and 10 nm or less, and more preferably 1 nm or more and 8 nm or less. Surface roughness can be measured using a Seiko Epson SPI3800N.

[0050] The material used for the balls 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, and zirconia, and ruby ​​balls.

[0051] In addition, materials for ballpoint pen tips include metals such as stainless steel, nickel silver, brass, aluminum bronze, and aluminum, and resins such as polycarbonate, polyacetal, and ABS, but considering wear of the ball seat and stability over time, it is preferable to use a tip body made of stainless steel.

[0052] Furthermore, the amount of movement of the ball in the ballpoint pen tip used in the present invention along the vertical axis is preferably 3 μm or more and 25 μm or less. This is because, within this range, ink consumption is increased, preventing line skipping and blurring of handwriting even on prints made with printing ink such as toner, improving the writing feel and making it easier to produce thick handwriting. From a more specific perspective, the amount of movement of the ball in the ballpoint pen tip along the vertical axis 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. (Example)

[0053] The present invention will be described in more detail below with reference to examples, although the present invention is not limited to the following examples.

[0054] The present invention will now be described with reference to examples. The oil-based ink composition for writing instruments in Example 1 was prepared by adding a pigment and a pigment dispersant to an organic solvent and dispersing them in a disperser, and then using a pigment dispersion, dye, organic solvent, ketone resin, organic amine, surfactant, and resin, weighing out predetermined amounts of these, heating them to 60°C, and then completely dissolving them in a disper stirrer to obtain an oil-based ink composition for writing instruments. The specific blending amounts are as follows:

[0055] Example 1 Coloring agents (dyes, salt-forming dyes of acid dyes and basic dyes) 10.0% by mass Coloring agent (dye, salt-forming dye of basic dye and organic acid) 5.0% by mass Pigment dispersion (pigment content 20%) 15.0% by mass Alcohol solvent (benzyl alcohol) 28.5% by mass Glycol ether solvent (ethylene glycol monophenyl ether) 20.0% by mass (Diglycerin / Dilinoleic Acid / Hydroxystearic Acid) Copolymer 1.0% by mass Surfactant (phosphate ester surfactant) 2.0% by mass Surfactant (polyoxyalkylene alkyl ether) 2.0% by mass Organic amine (HLB value: 15.4) 1.0% by mass Polyvinyl butyral resin (hydroxyl group content: 36 mol%) 5.0 mass% Ketone resin (ketone resin with aromatic ring) 10.0% by mass Spinnability-imparting resin (polyvinylpyrrolidone resin) 0.5% by mass

[0056] Examples 2 to 4 As shown in the table, except for changing each component, inks were formulated in the same manner as in Example 1 to obtain oil-based ink compositions for writing instruments of Examples 2 to 4. The table shows the measurement and evaluation results.

[0057] Example 5 The oil-based ink composition for a writing instrument of Example 5 was prepared by adding a pigment and a pigment dispersant to an organic solvent and dispersing them in a disperser, then using a colorant, organic solvent, surfactant, and organic amine, weighing out predetermined amounts, heating to 60°C, and dissolving them using a disper stirrer to prepare a base ink. Thereafter, while heating the prepared base ink, a polyacrylic acid resin was added and thoroughly mixed and stirred using a homogenizer stirrer until a uniform state was achieved, thereby obtaining the oil-based ink composition for a writing instrument of Example 5.

[0058] Examples 6 to 18 As shown in the table, except for changing the components and tip specifications, inks were formulated in the same manner as in Example 5 to obtain oil-based ink compositions for writing instruments of Examples 6 to 18. The table shows the measurement and evaluation results.

[0059] The ink viscosity of Examples 1 and 2 was measured at a shear rate of 500 sec in an environment of 20°C. -1 The ink viscosities of Examples 1 and 2 were measured using a Brookfield Viscometer RVDVII+Pro CP-52 spindle, and the ink viscosity was 4500 mPa·s in both cases. Similarly, the ink viscosity of Example 5 was measured at a shear rate of 0.18 sec under an environment of 20°C. -1 Ink viscosity = 10,000 mPa·s, 20°C environment, shear rate 200 sec -1 The ink viscosity was 700 mPa·s and the viscosity index n was 0.58. The ink viscosity of Example 8 was measured in the same manner under a 20°C environment at a shear rate of 0.18 sec. -1 Ink viscosity = 4500 mPa·s, 20°C environment, shear rate 200 sec -1 The ink viscosity was 550 mPa·s and the viscosity index n was 0.67.

[0060] Comparative Examples 1-2 As shown in the table, except for changing the components and tip specifications, an oil-based ink composition for a writing instrument of Comparative Example 1 was obtained in the same manner as in Example 1. Furthermore, an oil-based ink composition for a writing instrument of Comparative Example 2 was obtained in the same manner as in Example 5. The measurement and evaluation results are shown in the table.

[0061] Testing and Evaluation A ballpoint pen tip was attached to the tip of an ink reservoir (made of polypropylene) and rotatably held a ball (φ0.7 mm) of the ballpoint pen tip, with the ball pressed against the inner wall of the tip end edge by a resilient member. 0.3 g of the oil-based ink compositions for writing instruments (made in Examples 1 to 18 and Comparative Examples 1 to 2) was directly placed in the ink reservoir, and the ballpoint pen refill was placed in an oil-based ballpoint pen manufactured by Pilot Corporation to prepare an oil-based ballpoint pen. JIS P3201 writing paper was used as the writing test paper, and the following tests and evaluations were carried out. When a spiral writing test was conducted using an oil-based ballpoint pen, the ink consumption per initial 100 m of Examples 1, 2, 5, and 15 was 44 mg / 100 m, 40 mg / 100 m, 70 mg / 100 m, and 80 mg / 100 m, respectively. [Table 1] [Table 2] [Table 3]

[0062] Writability test 1 (writing test on toner-printed paper): The handwriting was observed when writing by hand on a paper surface that had been printed with toner. ◎ No broken lines or blurred handwriting ○ · · · Some missing lines or blurred handwriting △: There are some broken lines or smudged handwriting, but it is still usable. ×...Severely broken lines or blurred handwriting

[0063] Abrasion resistance test (ball seat abrasion test): The abrasion of the ball seat after the writing test was measured using a running test machine with a load of 350 gf, a writing angle of 70°, and a speed of 4 m / min. ◎ Ball seat wear is less than 5μm ○...Ball seat wear is 5μm or more and less than 10μm △: Wear of the ball seat is 10 μm or more but less than 20 μm, but writing is still possible × The ball seat is badly worn, causing poor writing.

[0064] Writing feel: Evaluation was carried out by a sensory test using handwriting. ◎ Very smooth ○ Smooth △: Smooth enough to cause no problems in practical use ×Heavy items

[0065] Writability test 2 (crying / blobbing test): The handwriting was observed after a 100m writing test using a running test machine with a load of 200gf, a writing angle of 70°, and a speed of 4m / min. ◎ No or minimal bleeding or blobbing in the handwriting ○: There are some tears or smudges in the handwriting, but it is not a problem for practical use. △: The handwriting is blurred or smudged, affecting its practical use. ×...Handwriting with many tears or blobs

[0066] In Examples 1 to 18, good performance was obtained in all of the writability test 1 (writing test on toner-printed paper), abrasion resistance test (ball seat abrasion test), writing feel, and writability test 2 (crying / blobbing test). When comparing Example 1 and Example 12 in writability test 1 (writing test on toner-printed paper), Example 5, which contains a phosphate ester surfactant, produced significantly better handwriting. Furthermore, in Examples 1 to 18, a writing test was conducted using a running tester with a load of 200 gf, a writing angle of 70°, and a speed of 4 m / min until the ink ran out. The remaining ink in the ink reservoir could be confirmed throughout the test, and the visibility of the remaining ink was good.

[0067] In Comparative Examples 1 and 2, the (diglycerin / dilinoleic acid / hydroxystearic acid) copolymer was not used, and therefore, in the writing test 1 (writing test on toner-printed paper), when handwriting was performed on the paper surface printed with toner, there was severe line skipping and smearing of handwriting. Furthermore, in the abrasion resistance test (abrasion test of the ball seat), the abrasion of the ball seat was also poor.

[0068] Furthermore, in this example, an oil-based ballpoint pen in which a ballpoint pen refill containing an oil-based ink composition for a writing instrument in an ink storage tube is disposed within the barrel has been exemplified, but the writing instrument of the present invention may be a writing instrument in which the barrel itself serves as the ink storage tube and the oil-based ink composition for a writing instrument is directly stored within the barrel, such as a direct-fill type ballpoint pen, marking pen, or felt-tip pen, or may have a structure in which an ink storage tube containing an oil-based ink composition for a writing instrument (ballpoint pen refill) is used as a ballpoint pen as is. [Industrial Applicability]

[0069] The present invention can be used as an ink composition for writing instruments, and more specifically, can be widely used as a cap-type, knock-type or other oil-based ballpoint pen, a marking pen, or a felt-tip pen filled with the ink composition for writing instruments.

Claims

1. An ink composition for a writing instrument, comprising a colorant, a solvent, and a (diglycerin / dilinoleic acid / hydroxystearic acid) copolymer.

2. 2. The ink composition for a writing instrument according to claim 1, wherein the content of the (diglycerin / dilinoleic acid / hydroxystearic acid) copolymer is 0.1 to 10% by mass based on the total amount of the ink composition.

3. 3. The ink composition for a writing instrument according to claim 1, further comprising a surfactant.

4. 4. The ink composition for a writing instrument according to claim 3, wherein the HLB value of the surfactant is 6 or more and 14 or less.

5. A writing instrument containing the ink composition for a writing instrument according to claim 1.

6. A ballpoint pen having a ballpoint pen tip rotatably holding a ball at the tip of an ink reservoir, and containing the ink composition for a writing instrument according to claim 1 in the ink reservoir.

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