Ink composition for writing instrument and writing instrument using the same

Abstract

To provide an ink composition for a writing instrument and a writing instrument using the same, which suppress corrosion of metal members of a writing instrument, such as a metal pen tip (ball) and a pen tip holder (tip body) that are in contact with the ink composition for a writing instrument, and a metal ink container and the like, thereby maintaining good writing performance and suppressing skipping of handwriting and line breakage.SOLUTION: An ink composition for a writing instrument comprises a colorant, a solvent, and an imidazole-based silane compound, where the imidazole-based silane compound is represented by general formula (Chemical Formula 1) or (Chemical Formula 2).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] Conventionally, writing instruments (ballpoint pens) have used metal nibs (balls) and nib holders (tip bodies) for their nibs, and metal ink reservoirs for their ink reservoirs. Metal corrodes and rusts when it comes into contact with moisture or solvents, and rust occurs when the ink composition for a writing instrument comes into contact with the nib (ball) and nib holder (tip body), causing resistance to the nib (ball) during writing, resulting in poor writing feel and the occurrence of smeared or skipped lines. Furthermore, metal ink reservoirs have had problems with the corrosion of their inner surfaces, resulting in the formation of pinholes and ink leakage.

[0003] Patent Documents 1 to 3 disclose that the occurrence of such corrosion can be suppressed by including in the aqueous ink composition a compound having a sulfide group, an amino derivative of benzotriazole. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] "JP 2004-115684 A" [Patent Document 2] "JP 2004-143338 A" [Patent Document 3] "Special Publication No. 49-45333" Summary of the Invention [Problem to be solved by the invention]

[0005] However, when the sulfide compound is added, depending on the structure of the compound, it may emit an odor or precipitate over a long period of time, making it difficult to obtain a sufficient corrosion inhibitory effect, etc. Furthermore, amino derivatives of benzotriazole have low solubility in aqueous media, so they lack dissolution stability in ink, and it is difficult to obtain a sufficient effect depending on the type of metal. As a result, both of these methods result in poor writing feel, and are insufficient to prevent writing problems such as blurred handwriting and skipped lines.

[0006] Therefore, as in Patent Documents 1 to 3, the selection of an anti-rust agent is extremely important, considering compatibility with the metal pen tip (ball) and pen tip holder (tip body) that come into contact with the ink composition for a writing instrument, as well as the metal ink reservoir.

[0007] An object of the present invention is to provide an ink composition for a writing instrument that can inhibit corrosion of metal components of the writing instrument and maintain good writing performance, and a writing instrument using the same. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention "1. An ink composition for a writing instrument comprising a colorant, a solvent, and an imidazole-based silane compound, wherein the imidazole-based silane compound is represented by the general formula (Chemical Formula 1) or (Chemical Formula 2). [ka] [ka] 2. The ink composition for a writing instrument according to item 1, wherein the content of the imidazole silane compound 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 item 1 or 2, wherein the solubility parameter of the organic solvent is 8 or more and 13 or less. 4. The ink composition for a writing instrument according to item 1 or 2, wherein the organic solvent is selected from the group consisting of alkylene glycol alkyl ether solvents, amide solvents, and alkylene oxide derivatives of glycerin. 5. A writing instrument containing the ink composition for a writing instrument according to item 1 or 2. 6. A ballpoint pen containing the ink composition for a writing instrument according to item 1 or 2. [Effects of the Invention]

[0009] The present invention inhibits corrosion of the metal components of a writing instrument, such as the metal nib (ball) and nib holder (tip body) that come into contact with the ink composition for a writing instrument, and the metal ink reservoir, thereby maintaining a good writing feel and inhibiting smearing of handwriting and skipped lines. DETAILED DESCRIPTION OF THE INVENTION

[0010]

[0023] In the present specification, the terms "parts," "%," "ratio," and the like, which indicate the composition, are based on mass unless otherwise specified, and the content is the mass % of the constituent components based on the mass of the ink composition.

[0011] The present invention is characterized in that the ink composition for a writing instrument contains a colorant, an organic solvent, and an imidazole-based silane compound having a chemical structure represented by general formula (Chemical Formula 1) or (Chemical Formula 2).

[0012] (Imidazole-based silane compounds) In the present invention, the imidazole-based silane compound having the chemical structure of the general formula (Chemical Formula 1) or (Chemical Formula 2) is contained, which inhibits corrosion of the metal components of the writing instrument, thereby maintaining a good writing feel and inhibiting smearing of handwriting and skipped lines, thereby achieving good writing performance. [ka] [ka]

[0013] By including an imidazole-based silane compound having a chemical structure represented by general formula (Chemical Formula 1) or (Chemical Formula 2), when metals such as stainless steel, brass, or nickel silver are used for the nib (ball) and nib holder (tip body) of a writing instrument component, or for the ink reservoir, the polar group of the imidazole is adsorbed to the metal surface to form an anti-rust coating, thereby inhibiting metal corrosion, maintaining a good writing feel, suppressing smeared handwriting, and preventing skipped lines, thereby achieving good writing performance. In particular, in an oil-based ink composition for a writing instrument, the imidazole-based silane compound is easily stabilized, making it easy to exhibit the effects of the present invention, maintaining a good writing feel, and preventing smeared handwriting and skipped lines.

[0014] Among the imidazole-based silane compounds, the general formula (Chemical Formula 1) is preferred because the polar group of imidazole is more easily adsorbed onto the metal surface, which makes it easier to inhibit metal corrosion, thereby maintaining a good writing feel and suppressing smeared handwriting and skipped lines. In particular, in an oil-based ink composition for a writing instrument, the general formula (Chemical Formula 1) makes it easier for the polar group of imidazole to be adsorbed onto the metal surface, allowing the formation of an anti-rust film, which makes it easier to achieve the effects of the present invention, thereby maintaining a good writing feel and suppressing smeared handwriting and skipped lines.

[0015] The content of the imidazole silane compound is more preferably 0.1 to 10% by mass 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 metal corrosion inhibitory effect, and if it exceeds 10% by mass, it is likely to affect the ink solubility. From this perspective, 0.5 to 8% by mass is more preferable, and even more preferably 1 to 6% by mass.

[0016] (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.

[0017] Examples of organic solvents 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 of 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.

[0018] Among these organic solvents, those that are prone to moisture absorption and accelerate corrosion of metal components are preferably selected from alkylene glycol alkyl ethers, amide solvents, and alkylene oxide derivatives of glycerin in order to more easily achieve the effects of the present invention, and more preferably alkylene glycol alkyl ethers or amide solvents.Furthermore, in order to be easily soluble in the imidazole-based silane compound and in consideration of ink stability, alkylene glycol alkyl ethers or β-alkoxypropionamide amide solvents are preferred, and from this perspective, alkylene glycol monoalkyl ethers are preferred.

[0019] Furthermore, with regard to the alkylene glycol monoalkyl ether, in consideration of ease of dissolution in the imidazole-based silane compound and ink stability, the number of carbon atoms in the alkylene glycol moiety of the alkylene glycol monoalkyl ether is preferably 3 to 8. In consideration of greater stability and ease of achieving the above-mentioned effects, the number of carbon atoms is preferably 4 to 6, and more preferably 5 to 6. Regarding the number of carbon atoms in the alkyl ether moiety of the alkylene glycol monoalkyl ether, the shorter the alkyl ether moiety, the easier it is to dissolve in the imidazole-based silane compound and the better the ink stability. Therefore, the number of carbon atoms is preferably 1 to 6, and from the viewpoint of greater stability and easier effect attainment, the number of carbon atoms is preferably 1 to 4, and more preferably 1 to 2.

[0020] In addition, the solubility parameter (SP value) of alkylene glycol alkyl ethers is 8 or more and 13 or less (cal / cm 3 ) 1 / 2 This is because the effect of the present invention is easily exhibited due to the compatibility with the imidazole-based silane compound, and from a more specific perspective, the solubility parameter (SP value) is preferably 9 or more and 12 or less (cal / cm 3 ) 1 / 2 Further, if considered, the solubility parameter (SP value) is preferably 10 or more and 11 or less (cal / cm 3 ) 1 / 2 It is preferable that: The solubility parameter (SP value) of a solvent used in this 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). The SP value is expressed in units of (cal / cm3)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).

[0021] Furthermore, it is preferable that the boiling point of alkylene glycol alkyl ethers is 170°C or higher. This is because if the boiling point is lower than 170°C, the alkylene glycol alkyl ethers tend to evaporate, the ink viscosity tends to increase, it becomes difficult to suppress line skipping and handwriting smearing, and the writing feel is likely to be affected, so from further consideration, it is preferable that the boiling point is 220°C or higher. On the other hand, if the boiling point is higher than 300°C, the drying property of the handwriting is likely to be affected, so it is preferable that the boiling point is 300°C or lower, and from further consideration, it is preferable that the boiling point is 280°C or lower.

[0022] Among the alkylene glycol alkyl ethers described above, triethylene glycol alkyl ether, propylene glycol alkyl ether, and diethylene glycol alkyl ether are preferred, considering that they are easily dissolved in the imidazole-based silane compound, maintain a good writing feel, and are likely to suppress blurred handwriting and skipped lines. From a more particular consideration, those containing triethylene glycol monomethyl ether, propylene glycol monomethyl ether, and diethylene glycol monobutyl ether are preferred, with triethylene glycol monomethyl ether being even more preferred.

[0023] Furthermore, in consideration of improving solubility, strike-through, handwriting drying properties, bleeding, etc., the content of the organic solvent is preferably 10% by mass or more and 90% by mass or less, and more preferably 25% by mass or more and 80% by mass or less, of the total amount of the ink composition.

[0024] In the present invention, the blending ratio of the imidazole silane compound to the organic solvent (organic compound / imidazole silane compound) is preferably 5 to 80 times, in consideration of the ease with which the imidazole silane compound is stabilized in the organic solvent and the effects of the present invention are easily exhibited, and more preferably 10 to 50 times. Furthermore, in consideration of maintaining a good writing feel and suppressing blurred handwriting and skipped lines, the blending ratio is preferably 10 to 40 times.

[0025] 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 slipperiness of the ball, maintains a good writing feel, and easily suppresses blurred handwriting and skipped lines, as well as uneven dots and smudges, thereby improving writing performance. This can be used effectively, particularly when used with a ballpoint pen.

[0026] The content of water is preferably 0.1% by mass or more and 20% by mass or less relative to the total amount of the ink composition. This is because, within this range, good writing feel is maintained, smearing of handwriting and skipped lines are easily suppressed, and dot unevenness and bleeding are suppressed, thereby improving writing performance. From further consideration, 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.

[0027] (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.

[0028] 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, salt-forming dyes formed from an acid dye and an organic amine, etc. Among these, salt-forming dyes are preferred in view of their stability with the imidazole-based silane compound. 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.).

[0029] 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.

[0030] Pigments used in oil-based ink compositions and water-based ink compositions include inorganic, organic, and processed pigments, and 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.

[0031] 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 enter the gap between the ball and the tip body, acting like a bearing, and suppressing metal contact improves lubricity, improves the writing feel, and makes it easier to suppress blurring and skipping of the handwriting, so it is preferable to use a pigment.Furthermore, the synergistic effect of the bearing action between the lubricating layer of the surfactant described below and the pigment particles makes it easier to maintain lubricity and improve the writing feel, so it is preferable.

[0032] The total content of the colorants is preferably 5 to 45% by mass relative to the total amount of the ink composition. This is because if it is less than 5% by mass, it is difficult to obtain thick handwriting, and if it exceeds 45% by mass, it is likely to affect the solubility in the ink. Taking this into consideration, a content of 7 to 35% by mass is more preferable, and even more preferably 10 to 30% by mass.

[0033] (surfactant) In the present invention, it is preferable to use a surfactant, because it further improves the lubricity of the writing tip, improves the writing feel, and suppresses blurred handwriting and line skipping, and in the case of a ballpoint pen, it improves the lubricity between the ball and the ball seat, reduces friction between the ball seat, and suppresses wear of the ball seat, which tends 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 out while the writing tip is left in the air. This is because the use of a surfactant tends to soften the coating that is 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, one or more surfactants selected from phosphate ester surfactants, fatty acids, and fatty acid esters are preferred. Considering these factors, phosphate ester surfactants and fatty acids are more preferred. In particular, it can be effectively used in ballpoint pens, and is preferably used as an oil-based ink composition for writing instruments, and more preferably as an oil-based ballpoint pen.

[0034] Furthermore, when a phosphate ester surfactant is used, the acid value is preferably 160 or less (mgKOH / g). This is because it makes it easier to exhibit the improved lubricity of the phosphate ester surfactant, improves the writing feel, and makes it easier to suppress blurred handwriting and line loss. Furthermore, taking into consideration stability and lubricity in the ink, 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.

[0035] 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, making it difficult to obtain the effects of the surfactant. On the other hand, an HLB value less than 6 tends to result in excessively strong lipophilicity, which is likely to affect compatibility with organic solvents and make the ink less stable 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.

[0036] 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.

[0037] 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.

[0038] (organic amine) In the present invention, when a surfactant such as a phosphate ester surfactant is used, neutralization is preferred because it stabilizes the solution in the ink, further improves the lubricity of the writing tip, improves the writing feel, and is likely to suppress blurred writing and line skipping, suppress wear of the ball seat, and improve 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 the solution stability in the ink. These may be used alone or in combination.

[0039] Furthermore, in consideration of stability with colorants, surfactants, 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-mentioned 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.

[0040] 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 imidazole-based silane compound, organic solvent, colorant, and other components, and the effects of the present invention are more likely to be obtained. From further consideration, the HLB value is more preferably 7 to 17, and even more preferably 9 to 16.

[0041] Considering the stability with the colorant, surfactant, and other components, the content of the organic amine is preferably 0.1 mass % or more and 10 mass % or less of the total amount of the ink composition, and further considering the neutralization of the surfactant described above, it is preferably 0.5 mass % or more and 5 mass % or less.

[0042] 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.

[0043] 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.

[0044] (writing implements, ballpoint pens) Materials for the ballpoint pen tip body, ink reservoir, etc. include metals such as stainless steel, nickel silver, brass, aluminum bronze, and aluminum, and resins such as polycarbonate, polyacetal, and ABS.

[0045] The ball of the ballpoint pen tip is not particularly limited, but cemented carbide balls whose main component is tungsten carbide use cobalt, nickel, etc. as their binder. The imidazole silane compound is resistant to corrosion by metals such as cobalt and nickel, so it is less likely to cause rotational resistance in the ball due to corrosion, and a good writing feel can be easily obtained, making it suitable for use with cemented carbide balls. The diameter of the ball is not particularly limited, but is generally about 0.2 mm to 2.0 mm.

[0046] (Example) The present invention will now be described with reference to examples. The ink composition for an oil-based ballpoint pen in Example 1 was prepared by weighing out the following ink components in predetermined amounts, heating them to 60°C, and then completely dissolving them using a disper stirrer. The specific blending amounts were as follows:

[0047] Example 1 (ink formulation) Colorant (salt-forming dye of acid dye and basic dye) 5.0% by mass Colorant (salt-forming dye of basic dye and organic acid) 10.0% by mass Pigment (pigment dispersion: pigment content 20%, average particle size 250 nm) 5.0% by mass Alkylene glycol alkyl ethers (solubility parameter (SP value): 10.5 (cal / cm3) 1 / 2 , boiling point: 249℃) 60.0% by mass Imidazole-based silane compound (general formula (chemical formula 1), R: methyl group) 2.0% by mass Phosphate ester surfactant 1.5% by mass Organic amine 0.5% by mass Polyvinyl butyral resin 5.0% by mass Ketone resin 10.0% by mass Spinnability imparting resin 1.0% by mass

[0048] Examples 2 to 16 As shown in Table 1, except for changing the ink components, ink compositions for writing instruments of Examples 2 to 16 were obtained in the same manner as in Example 1. The evaluation results are shown in the table.

[0049] Comparative Examples 1 to 3 As shown in the table, except that the ink components were changed, ink compositions for writing instruments of Comparative Examples 1 to 3 were obtained in the same manner as in Example 1. The evaluation results are shown in the table. [Table 1] [Table 2]

[0050] Testing and Evaluation Each of the ink compositions (1 g) for writing instruments prepared in Examples 1 to 16 and Comparative Examples 1 to 3 was filled into a refill for an oil-based ballpoint pen, which had a stainless steel ink reservoir and a stainless steel ballpoint pen tip body that rotatably held a cemented carbide ball with a ball diameter of 0.7 mm. The following tests and evaluations were carried out using JIS P3201 writing paper.

[0051] Writing feel: After leaving the pen for one month under conditions of 60°C and 80% humidity, a sensory test was conducted by handwriting on a writing test sheet to evaluate the writing feel. ◎ Very smooth ○ Smooth △: Slightly less smooth ×Heavy items

[0052] Writing performance test: After leaving the test piece for one month under conditions of 60°C and 80% humidity, handwriting was done on the test paper, and the handwriting condition was visually observed. ◎ No smearing occurred ○: Blurring occurred, but it was not a problem in practical use. ×: Blurring occurred, to the point that it was of concern in practical use.

[0053] Corrosion test: A metallic (nickel silver) ballpoint pen tip was immersed in the ink composition for writing instruments of each of the Examples and Comparative Examples at 80° C. for 3 days, and the state of corrosion of the ballpoint pen tip was observed under a microscope. ○···Metallic luster with no or very little discoloration △: Metallic gloss is slightly inferior and there is some discoloration ×: No metallic luster and discoloration

[0054] In Examples 1 to 16, good performance was obtained in the writing feel, writing performance test, and corrosion test. Furthermore, the ink compositions (1 g) for writing instruments prepared in Examples 1 to 4 were filled into oil-based ballpoint pen refills equipped with a stainless steel ink reservoir and a ballpoint pen tip body made of nickel silver that rotatably holds a cemented carbide ball with a ball diameter of φ0.7 mm, to prepare oil-based ballpoint pens. Tests of writing feel and writing performance were carried out in the same manner as in Examples 1 to 4, and good performance similar to that of Examples 1 to 4 was obtained.

[0055] In Comparative Examples 1 and 2, since no imidazole-based silane compound was used, the metal surface was discolored, the writing feel was heavy and scratchy, and smudges occurred. In Comparative Example 3, the metal surface was slightly discolored due to the use of a benzotriazole derivative, and the writing feel was slightly deteriorated.

[0056] In addition, in this example, for convenience, an oil-based ballpoint pen is exemplified in which an oil-based ballpoint pen refill in which an ink composition for a writing instrument is directly contained in the barrel is stored, but the writing instrument of the present invention may also be a writing instrument in the form of a direct-fill type ballpoint pen, marking pen, or felt-tip pen in which the barrel serves as an ink storage tube and the ink composition for a writing instrument is directly contained in the barrel. Furthermore, in this embodiment, for convenience, a ballpoint pen tip formed by cutting a wire material is exemplified, but a ballpoint pen tip formed by pressing a pipe material may also be used. [Industrial Applicability]

[0057] The present invention can be used as a writing instrument, and more specifically, can be widely used as a ballpoint pen, such as a cap-type or retractable writing instrument.

Claims

1. An ink composition for a writing instrument comprising a colorant, a solvent, and an imidazole-based silane compound, wherein the imidazole-based silane compound is represented by the general formula (Chemical Formula 1) or (Chemical Formula 2). 【Chemistry 1】 【Chemistry 2】

2. 2. The ink composition for a writing instrument according to claim 1, wherein the content of the imidazole silane compound 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, wherein the solubility parameter of the organic solvent is 8 or more and 13 or less.

4. 3. The ink composition for a writing instrument according to claim 1, wherein the organic solvent is selected from the group consisting of alkylene glycol alkyl ether solvents, amide solvents, and alkylene oxide derivatives of glycerin.

5. A writing instrument containing the ink composition for a writing instrument according to claim 1 or 2.

6. A ballpoint pen containing the ink composition for a writing instrument according to claim 1 or 2.

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