Oil-based ballpoint pen

Abstract

To obtain an oil-based ballpoint pen which has improved writing feel, no faint marks or smudges in handwriting, and good writing properties.SOLUTION: The oil-based ballpoint pen includes an ink reservoir (2) containing an ink composition (10) for an oil-based ballpoint pen, the ink composition (10) including a colorant, an alkylene glycol alkyl ether, and a polyacrylic acid resin, and a ballpoint pen tip (4) rotatably holding a ball (3) at one end of the ink reservoir (2) in the extension direction (X). The ratio of the ink consumption (mg) per 100 m writing distance to the diameter (mm) of the ball (3) is 30 or more.SELECTED DRAWING: Figure 1

Description

[Technical Field] 【0001】 This invention relates to an oil-based ballpoint pen. [Background technology] 【0002】 Ballpoint pens are susceptible to frictional resistance between the ball and the tip during writing, which can affect the writing experience. In particular, unlike other types of writing instruments, ballpoint pens have a ballpoint pen tip consisting of a metal tip made of stainless steel or similar material at the end, and a transfer ball made of metal such as carbide held in the ball-receiving seat of the metal tip, which is then mounted in an ink reservoir. However, the rotation of the ball during writing can cause streaking, unevenness, poor writing quality, and ink buildup at the tip, resulting in a blob-like writing effect. 【0003】 To solve these problems, numerous oil-based ballpoint pen ink compositions have been proposed that use various lubricants and other additives to improve lubricity and suppress frictional resistance between the ball and the tip body. 【0004】 As an example of an oil-based ballpoint pen ink composition using such additives, an oil-based ballpoint pen ink using alkyl β-D-glucoside has been disclosed (see, for example, Patent Document 1). Also disclosed is an oil-based ballpoint pen ink composition using polyethylene glycol with an average molecular weight of 200 to 4,000,000 (see, for example, Patent Document 2). Furthermore, an oil-based ballpoint pen ink using N-acyl amino acids, N-acylmethyl tauric acid, and N-acylmethylalanine has been disclosed (see, for example, Patent Document 3). In addition, an oil-based ballpoint pen ink composition containing at least deca-macadamia nut oil fatty acid decaglyceryl and polyoxyethylene alkyl ether having 16 or more carbon atoms in the alkyl group and being solid at room temperature has been disclosed (see, for example, Patent Document 4). [Prior art documents] [Patent Documents] 【0005】 【Patent Document 1】 Japanese Patent Application Laid-Open No. 5-331403 【Patent Document 2】 Japanese Patent Application Laid-Open No. 7-196971 【Patent Document 3】 Japanese Patent Application Laid-Open No. 2007-176995 【Patent Document 4】 Japanese Patent Application Laid-Open No. 2008-88264 【Summary of the Invention】 【Problems to be Solved by the Invention】 【0006】 However, when using various additives such as those in Patent Documents 1 to 4, the frictional resistance between the ball and the chip body can be reduced to a certain extent, but the writing feel is not satisfactory. Moreover, writing properties such as streaks and blots in the handwriting cannot be improved, leaving room for improvement. Also, when using a new lubricant or the like, there is also compatibility with other ink components, and it is likely to affect the stability over time in the ink. 【0007】 An object of the present invention is to obtain an oil-based ballpoint pen that improves the writing feel, has no streaks or blots in the handwriting, and has good writing properties. 【Means for Solving the Problems】 【0008】 The present invention is to solve the above problems “1. An ink storage cylinder containing an ink composition for an oil-based ballpoint pen comprising a colorant, alkylene glycol alkyl ethers , a reactive acrylic resin, and water and a ballpoint pen tip that rotatably holds a ball at one end in the extending direction of the ink storage cylinder, provided with where the ratio of the ink consumption (mg) per 100 m of writing distance to the diameter (mm) of the ball is 30 or more, ​The ratio (E:F) of ink consumption Emg at the initial writing stage (0m to 100m) to ink consumption Fmg from 100m before ink depletion until ink depletion is in the range of 1:0.8 to 1:1.2. the law of nature, The ratio of water to the polyacrylic resin (water / polyacrylic resin) is 1 to 15 times by mass. The carboxyl group content in the polyacrylic acid resin is 40% by mass or more and 80% by mass or less. An oil-based ballpoint pen characterized by the following features. 2. The oil-based ballpoint pen according to paragraph 1, characterized in that the ratio is 65 or more and 100 or less. 3. The oil-based ballpoint pen according to paragraph 1 or 2, characterized in that the amount of movement of the ball in the stretching direction is greater than 3 μm and 25 μm or less. 4 The alkylene glycol alkyl ethers are characterized in that the alkylene glycol monoalkyl ethers are alkylene glycol monoalkyl ethers, paragraphs 1 to 1 3 An oil-based ballpoint pen as described in any one of the items. 5 The content of the alkylene glycol alkyl ethers is 50% or more of the total solvent content of the oil-based ballpoint pen ink composition, and the content of the alkylene glycol alkyl ethers is 30% by mass or more and 75% by mass or less of the total amount of the oil-based ballpoint pen ink composition, as described in paragraphs 1 to 2. 4 An oil-based ballpoint pen as described in any one of the items. 6 The polyacrylic acid resin content is characterized in that it is 0.1% by mass or more and 5.0% by mass or less based on the total amount of the oil-based ballpoint pen ink composition, paragraphs 1 to 1. 5 An oil-based ballpoint pen as described in any one of the items. 7. The oil-based ballpoint pen according to any one of paragraphs 1 to 6, characterized in that the content of the polyacrylic acid resin is 0.6% by mass or more and 1.8% by mass or less based on the total amount of the oil-based ballpoint pen ink composition. 8. An oil-based ballpoint pen according to any one of paragraphs 1 to 7, characterized in that the bulk density (g / ml) of the polyacrylic acid resin is 0.01 (g / ml) or more and 0.5 (g / ml) or less. 9. The oil-based ballpoint pen ink composition ,stomach An oil-based ballpoint pen according to any one of paragraphs 1 to 8, characterized in that the water content relative to the total amount of the ink composition is 1% by mass or more and 10% by mass or less. 10The blending ratio of alkylene glycol alkyl ethers to the polyacrylic acid resin (alkylene glycol alkyl ethers / polyacrylic acid resin) is 20 to 100 times, characterized in that paragraphs 1 to 1 9 An oil-based ballpoint pen as described in any one of the items. 11 The aforementioned oil-based ballpoint pen ink composition comprises a surfactant, The surfactant is characterized by being one or more selected from fatty acids, phosphate ester surfactants, and fatty acid esters, according to paragraphs 1 to 1 0 "An oil-based ballpoint pen as described in any one of the items." [Effects of the Invention] 【0009】 This invention has resulted in an oil-based ballpoint pen that provides a smooth writing experience, free from smudging or blotting, and offers excellent writing performance. [Brief explanation of the drawing] 【0010】 [Figure 1] Figure 1 is a cross-sectional view of an example of a ballpoint pen. [Figure 2] Figure 2 is a magnified cross-sectional view of an example of a ballpoint pen tip. [Modes for carrying out the invention] 【0011】 Embodiments of the present invention will be described in detail below. In this specification, unless otherwise specified, "parts," "%," and "ratio" used to indicate formulations are based on mass, and the content refers to the mass percentage of the constituent components based on the mass of the ink composition. 【0012】 The oil-based ballpoint pen of the present invention comprises an ink reservoir and a ballpoint pen tip. The ink reservoir contains an oil-based ballpoint pen ink composition comprising a colorant, alkylene glycol alkyl ethers, and polyacrylic acid resin. The ballpoint pen tip rotatably holds a ball at one end of the ink reservoir in the direction of extension. The oil-based ballpoint pen of the present invention is characterized in that the ratio of ink consumption (mg) per 100m of writing distance to the diameter (mm) of the ball is 30 or more. 【0013】 It has been found that by including alkylene glycol alkyl ethers and polyacrylic acid resin in the oil-based ballpoint pen ink composition, pseudoplasticity can be imparted, lowering the ink viscosity during writing and maintaining a good writing feel. This is because the polyacrylic acid resin swells and disperses within the alkylene glycol alkyl ethers, thereby imparting pseudoplasticity. Furthermore, it has been found that by using the oil-based ballpoint pen ink composition of the present invention, and by having a ratio of ink consumption (mg) per 100m of writing distance to the ball diameter (mm) of 30 or more, it is possible to improve writing performance by eliminating smudging and ink clumping. "Smudging" in "ink clumping" refers to the phenomenon where excess ink accumulates at the pen tip during writing. "Clumping" in "ink clumping" refers to the phenomenon where excess ink remains on the writing surface like a blob. 【0014】 The following provides a detailed description of each component contained in the oil-based ballpoint pen ink composition and of the oil-based ballpoint pen itself. First, the details of each component contained in the oil-based ballpoint pen ink composition will be described. In this embodiment, the oil-based ballpoint pen ink composition may be referred to as the ink composition or simply as ink. Also, the oil-based ballpoint pen may be simply referred to as a ballpoint pen. 【0015】 (Alkylene glycol alkyl ethers) The alkylene glycol alkyl ethers used in this invention are solvents that enable the imparting of pseudoplasticity to polyacrylic resins, which will be described later, by swelling and dispersing them. It has been found that by imparting pseudoplasticity, the viscosity of the ink during writing can be lowered, resulting in a better writing feel, and it is possible to maintain good writing performance by suppressing smudging and blotting of the writing line. In particular, when cross-linked polyacrylic resin is used, alkylene glycol alkyl ethers make it easier to form a three-dimensional network structure, and it is easier to form a denser cross-linked structure. Therefore, it is easy to impart pseudoplasticity, which is effective in improving writing feel and writing performance (suppression of smudging). Furthermore, it is effective because it is easier to suppress ink leakage from the gap between the ball and the tip (writing tip). In addition, since it is less likely to wet metal ballpoint pen tips, the ink does not crawl up from the tip, so no ink residue occurs, and it is possible to improve writing performance by suppressing smudging of the writing line. 【0016】 In particular, when using a ballpoint pen, strong shear stress is easily applied during writing, and the impact of shear stress on the ball during writing temporarily dissolves the pseudoplastic structure. As a result, the ink viscosity is reduced, making it possible to maintain good writing feel and writing performance (suppression of skipping and blotting), and thus it can be suitably used in ballpoint pens. 【0017】 In oil-based ballpoint pen ink compositions containing alkylene glycol alkyl ethers, it is preferable to use pigments as colorants. When pigments are used as colorants, the high-density three-dimensional network structure formed by the alkylene glycol alkyl ethers can improve pigment dispersibility. 【0018】 Examples of alkylene glycol alkyl ethers include alkylene glycol monoalkyl ethers and alkylene glycol dialkyl ethers. Among these, alkylene glycol monoalkyl ethers are preferred from the viewpoint of swelling dispersibility with polyacrylic acid resins, which will be discussed later. 【0019】 In addition, regarding the number of carbon atoms in the alkylene glycol moiety of the alkylene glycol monoalkyl ether, considering the ease of swelling and dispersion with the polyacrylic acid resin and the writing feel and writing properties (smearing and bleeding suppression), the number of carbon atoms is preferably 2 or more and 10 or less. Considering that it is more likely to be stable with the polyacrylic acid resin and the above effects are more 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. 【0020】 In addition, regarding the number of carbon atoms in the alkyl ether moiety of the alkylene glycol monoalkyl ether, considering the swelling dispersibility with the polyacrylic acid resin, the writing feel, and the writing properties (smearing and bleeding suppression), it is preferable that the alkyl ether moiety is shorter. For this reason, the number of carbon atoms is preferably 1 or more and 6 or less. Considering that it is more likely to be stable with the polyacrylic acid resin and the effects are more easily obtained, it is 1 or more and 4 or less, and further preferably 1 or more and 2 or less. 【0021】 In addition, for the alkylene glycol monoalkyl ether, the solubility parameter (SP value) is preferably 8 (cal / cm 3 ) 1 / 2 or more and 13 (cal / cm 3 ) 1 / 2 or less. This is because it improves the dissolution stability and dispersion stability of the colorant and is less likely to affect the swelling dispersibility with the polyacrylic acid resin. Further considering, the solubility parameter (SP value) is preferably 9 (cal / cm 3 ) 1 / 2 or more and 12 (cal / cm 3 ) 1 / 2 or less, and further preferably, considering, the solubility parameter (SP value) is 10 (cal / cm 3 ) 1 / 2 or more and 11 (cal / cm 3 ) 1 / 2 or less. 【0022】 In this invention, the solvent solubility parameter (SP value) 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 unit is (cal / cm³). 3 ) 1 / 2 This refers to the value at 25°C. 【0023】 For data that is not provided, it can be calculated using the method described in RFFedors, Polymer Engineering Science, 14, p147 (1967). 【0024】 Furthermore, regarding the boiling point of the alkylene glycol monoalkyl ether, it is preferable that the boiling point be 170°C or higher. This is because if the boiling point is below 170°C, the alkylene glycol monoalkyl ether tends to evaporate easily, which can affect the swelling and dispersibility with the polyacrylic resin over time and increase the ink viscosity. More precisely, it is preferable that the boiling point be 220°C or higher. On the other hand, if the boiling point exceeds 300°C, it tends to affect the drying properties of the ink. For this reason, it is preferable that the boiling point be 300°C or lower, and more precisely, 280°C or lower. 【0025】 Examples of alkylene glycol monoalkyl ethers include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monohexyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, tetraethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, those having a butylene glycol monomethyl ether structure, those having a butylene glycol monoethyl ether structure, and the like. These may be used individually or in combination of two or more. 【0026】 Examples of alkylene glycol dialkyl ethers include ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol ethyl methyl ether, diethylene glycol dibutyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol dibutyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, tetraethylene glycol dibutyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, those having a dibutylene glycol dimethyl ether structure, those having a dibutylene glycol diethyl ether structure, and others. These may be used individually or in combination of two or more. 【0027】 The content of alkylene glycol alkyl ethers is preferably 50% or more of the total solvent content in the oil-based ballpoint pen ink composition, and they are preferably used as the main solvent. This is because other solvents tend to inhibit the swelling and dispersion of the polyacrylic resin, making it difficult to impart pseudoplasticity to the ink and affecting the writing feel and writing performance (suppression of skipping and blotting). By using them as the main solvent, it is possible to prevent other solvents from affecting the swelling and dispersion. If writing performance is a priority, the content of alkylene glycol alkyl ethers is preferably 70% or more of the total solvent content. If writing performance and long-term stability in the ink are a priority, 90% or more is preferable. If these effects are considered to be even more beneficial, it is preferable to use only alkylene glycol alkyl ethers as the solvent. 【0028】 The content of the alkylene glycol alkyl ethers is preferably 10% by mass or more and 80% by mass or less, relative to the total amount of the ink composition. This is because if it is less than 10% by mass, the swelling and dispersion effect of the polyacrylic resin is difficult to obtain, the ink viscosity at rest does not increase easily, and ink leakage is difficult to suppress. If it exceeds 80% by mass, the ink's stability over time tends to be poor. Furthermore, considering the above effects, 20% by mass or more and 80% by mass or less is preferable, and if given even greater consideration, 30% by mass or more and 75% by mass or less is preferable. 【0029】 (Polyacrylic resin) The polyacrylic resin used in this invention is used as a thickening agent. Polyacrylic resin has an affinity for alkylene glycol alkyl ethers, and by swelling and dispersing, a stable thickening effect with pseudoplasticity can be obtained. Furthermore, considering the writing feel and writing performance (suppression of smudging and blotting of the ink), it is preferable to use a cross-linked polyacrylic resin. This is because the cross-linked polyacrylic resin itself has a cross-linked structure, and it is easier to form a more three-dimensional network structure with alkylene glycol alkyl ether solvents. Therefore, by forming a denser cross-linked structure, pseudoplasticity can be easily imparted, which lowers the ink viscosity during writing and improves the writing feel and writing performance (suppression of smudging and blotting). Carboxyvinyl polymer is particularly preferred. 【0030】 Furthermore, regarding the polyacrylic acid resin, the carboxyl group content in the polyacrylic acid resin is preferably 40% to 80% by mass, considering that a stable thickening effect can be obtained with alkylene glycol alkyl ethers. More preferably, it is 50% to 70% by mass. In particular, when alkylene glycol monoalkyl ether is used as the alkylene glycol alkyl ether, using a polyacrylic acid resin with a carboxyl group content of 55% to 65% by mass is preferable because it has excellent swelling dispersibility and imparts pseudoplasticity, thereby lowering the viscosity of the ink during writing and improving the writing feel. Furthermore, alkylene glycol monomethyl ether is even more preferable. 【0031】 Furthermore, the bulk density (g / ml) of the polyacrylic acid resin is preferably 0.5 (g / ml) or less. This is because it exhibits excellent swelling and dispersibility with alkylene glycol alkyl ethers and water, which further enhances the effects of the present invention. More specifically, it is preferable that it be 0.3 (g / ml) or less. On the other hand, if the bulk density (g / ml) of the polyacrylic acid resin is less than 0.01 (g / ml), it is difficult to swell and disperse, and the polyacrylic acid resin is more prone to aggregation. For this reason, it is preferable that it be 0.01 (g / ml) or more, and more specifically, 0.1 (g / ml) or more. 【0032】 Bulk density can be measured, for example, using a bulk density measuring instrument (Scott volume meter: manufactured by Tsutsui Rikagakukikai Co., Ltd.). 【0033】 If the polyacrylic resin content is less than 0.1% by mass relative to the total amount of ink composition, the swelling properties will not be sufficient and pseudoplasticity will not be obtained, making it difficult to improve writing feel. If it exceeds 5.0% by mass, the swelling dispersibility in the ink tends to be poor. Therefore, a content of 0.1% by mass or more and 5.0% by mass or less relative to the total amount of ink composition is preferable. Furthermore, if writing feel is given even greater consideration, 0.3% by mass or more and 3.0% by mass or less is preferable, and if even more consideration is given, 0.6% by mass or more and 1.8% by mass or less is preferable. 【0034】 In the present invention, the blending ratio of alkylene glycol alkyl ethers to polyacrylic acid resin (alkylene glycol alkyl ethers / polyacrylic acid resin) is preferably 5 to 150 times by mass, considering swelling dispersibility. More preferably, it is 10 to 120 times, considering more stable swelling dispersibility, and preferably 20 to 100 times. 【0035】 (Coloring agent) The coloring agent used in the present invention is not particularly limited to dyes, pigments, etc., and can be selected and used as appropriate. 【0036】 Examples of dyes include oil-soluble dyes, acid dyes, basic dyes, and metal-containing dyes, as well as various salt-forming types of these dyes, 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. These dyes may be used individually or in combination of two or more types. As dyes, considering the stability over time due to compatibility with alkylene glycol alkyl ethers, it is preferable to use at least salt-forming dyes, and further, considering that stability over time can be maintained by the stability of the salt-forming bond, it is preferable to use salt-forming dyes of basic dyes and organic acids, salt-forming dyes of acid dyes and basic dyes, and salt-forming dyes of acid dyes and organic amines. The above-mentioned salt-forming dyes have a solubility parameter (SP value) of 8 (cal / cm³). 3 ) 1 / 2 More than 13(cal / cm 3 ) 1 / 2 The following alkylene glycol monoalkyl ethers are preferred because they are easily soluble and stable. More specifically, the solubility parameter (SP value) of the alkylene glycol monoalkyl ether is 9 (cal / cm³). 3 ) 1 / 2 More than 12(cal / cm 3 ) 1 / 2 It is preferable that the following is 10 (cal / cm³) 3 ) 1 / 2 More than 11(cal / cm 3 ) 1 / 2 The following is even more preferable: 【0037】 Specifically, these include: Varifast Black 1802, Varifast Black 1805, Varifast Black 1807, Varifast Violet 1701, Varifast Violet 1704, Varifast Violet 1705, Varifast Blue 1601, Varifast Blue 1605, Varifast Blue 1613, Varifast Blue 1621, Varifast Blue 1631, Varifast Red 1320, Varifast Red 1355, Varifast Red 1360, Varifast Yellow 1101, Varifast 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 Industry Co., Ltd.), Eisenspiron Black GMH-Special, and Eisenspiron Violet. Examples include C-RH, Eisenspiron Blue GNH, Eisenspiron Blue 2BNH, Eisenspiron Blue C-RH, Eisenspiron Red C-GH, Eisenspiron Red C-BH, Eisenspiron Yellow C-GNH, Eisenspiron 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.). These may be used individually or in mixtures of two or more. 【0038】 Pigments include inorganic, organic, and processed pigments, but specifically include carbon black, aniline black, ultramarine, lead yellow, titanium dioxide, iron oxide, phthalocyanine, azo, quinacridone, diketopyrrolopyrrole, quinophthalone, surene, triphenylmethane, perinone, perylene, dioxazine, metallic pigments, pearl pigments, fluorescent pigments, and phosphorescent pigments. These may be used individually or in combination of two or more. 【0039】 As a coloring agent, it is preferable to use pigments. This is because, in the case of ballpoint pens, pigment particles can easily fill the gap between the ball and the tip body, creating a bearing-like effect that suppresses metal-to-metal contact, thereby improving lubrication, enhancing writing feel, and reducing wear on the ball seat. As in the present invention, by using alkylene glycol alkyl ethers or polyacrylic resins to impart pseudoplasticity, the viscosity of the ink during writing can be reduced, further improving writing feel. Therefore, using pigments is even more preferable. 【0040】 When using pigments as colorants, the synergistic effect of the bearing action between the lubricating layer provided by the surfactant and the pigment particles makes it easier to maintain lubrication and improve writing feel. Furthermore, considering the gap relationships inside the ballpoint pen tip, the average particle size of the pigment is preferably between 1 nm and 500 nm. More preferably between 30 nm and 350 nm, and even more preferably between 50 nm and 300 nm. 【0041】 The average particle diameter is determined by laser diffraction. Specifically, the average particle diameter can be determined by the particle diameter (D50) at 50% volume accumulation of the particle size distribution, measured using a laser diffraction particle size distribution analyzer (product name "MicrotracHRA9320-X100", Nikkiso Co., Ltd.) based on values ​​calibrated using standard samples and other measurement methods. 【0042】 Furthermore, since the pigment exerts the aforementioned effects depending on its dispersion state within the oil-based ballpoint pen ink composition, it is preferable to determine the particle size in the dispersed state. In addition, the pigment is less likely to redissolve even when wet with water or alcohol, and is less likely to be chemically decomposed even when exposed to light (sunlight), allowing the writing to be easily seen. For this reason, it is preferable to use a pigment as a coloring agent because it allows for the acquisition of an ink composition with excellent fastness. Fastness refers to water resistance, alcohol resistance, and light resistance. Moreover, it is preferable to use a pigment as a coloring agent because it also easily provides an ink leakage suppression effect. 【0043】 As a coloring agent, dyes and pigments may be used in combination. By using dyes and pigments in combination, it is possible to obtain vivid color development while maintaining good colorfastness, improving lubrication, enhancing writing feel, and suppressing wear of the ball bearing. Considering the above effects and ink stability over time, it is preferable to use salt-based dyes and pigments in combination. 【0044】 The total content of the colorant is preferably 5% by mass or more and 45% 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 not to produce dark writing, and if it exceeds 45% by mass, it tends to affect the solubility in the ink. Considering this tendency more carefully, 5% by mass or more and 35% by mass or less is preferred, and if further considered, 6% by mass or more and 30% by mass or less is preferred. 【0045】 Furthermore, in the present invention, it is preferable that the ink composition for oil-based ballpoint pens contains water. Although the reason is not entirely clear, water exhibits excellent affinity between alkylene glycol alkyl ethers and polyacrylic acid resins. Therefore, it can provide a higher viscosity and more stable swelling properties to the swelling dispersion of alkylene glycol alkyl ethers and polyacrylic acid resins. In addition, it can improve the slipperiness of the ball, improve ink discharge, suppress unevenness, blotting, and streaking, and thus improve writing performance. 【0046】 If the water content is less than 0.1% by mass relative to the total amount of ink composition, it tends to affect the ball's slipperiness and ink discharge. If it exceeds 20% by mass, solubility in the ink tends to be poor. For this reason, the water content relative to the total amount of ink composition is preferably 0.1% by mass or more and 20% by mass or less. Furthermore, considering solubility in the ink and writing performance (suppression of smudging and blotting), 1% by mass or more and 10% by mass or less is preferable, and if even more consideration is given, 2% by mass or more and 10% by mass or less is preferable. 【0047】 In this invention, the ratio of water to polyacrylic resin (water / polyacrylic resin) is preferably 0.1 to 20 times by mass, considering that a high viscosity is achieved by swelling and dispersion using alkylene glycol alkyl ethers and polyacrylic resin. More preferably, the water ratio is 1 to 15 times, and if further consideration is given, 1 to 10 times is preferable, as it is easier to improve writing feel and writing performance (suppression of skipping and blotting) in a well-balanced manner. 【0048】 (Organic amines) In this invention, it is preferable to use organic amines because neutralizing and stabilizing the polyacrylic acid resin with organic amines allows for sufficient swelling and dispersion, making it easier to obtain a stable thickening effect. Furthermore, even when using surfactants such as phosphate ester surfactants, neutralization is preferable because it allows for solubility and stabilization in the ink, improving writing feel and initial 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 distearylamine, dimethyl laurylamine, dimethyl stearylamine, and dimethyl octylamine; and alkanolamines, such as diethanolamine and triethanolamine. Among these, amines containing ethylene oxide are preferred when considering stability with polyacrylic acid resin. These may be used individually or in combination of two or more. 【0049】 The average number of moles of ethylene oxide added per amine molecule (EO number) of an amine containing ethylene oxide is preferably between 1 and 30, and more preferably between 4 and 20. By setting the EO number within the above range, the polyacrylic acid resin is neutralized and stabilized by the solubility with alkylene glycol alkyl ethers, making it easier to obtain a stable thickening effect. 【0050】 Furthermore, considering stability with alkylene glycol alkyl ethers, polyacrylic resins, colorants, 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, making it more likely to react with the above components, which tends to impair the long-term stability of the ink. Furthermore, considering stability with alkylene glycol alkyl ethers and polyacrylic resins, the total amine value is preferably 200 mgKOH / g or less, and more preferably 150 mgKOH / g or less. On the other hand, considering the above effects, the lower limit of the total amine value is preferably 30 mgKOH / g or more. 【0051】 The total amine value indicates the total amount of primary, secondary, and tertiary amines, and is expressed in milligrams of potassium hydroxide equivalent to the amount of hydrochloric acid required to neutralize 1 g of the sample. 【0052】 Regarding the HLB value of the organic amine, it is preferable that the HLB value is between 5 and 17. This is because a stable thickening effect can be obtained by neutralizing and stabilizing the polyacrylic acid resin and stabilizing the swelling dispersion with alkylene glycol alkyl ethers. If further consideration is given to neutralizing stability and improving swelling dispersibility, it is preferable that the HLB value is between 7 and 17, and if further consideration is given, it is preferable that the HLB value is between 9 and 16. 【0053】 In the present invention, the blending ratio of organic amine to polyacrylic resin (organic amine / polyacrylic resin) is preferably 0.1 to 10 times by mass, more preferably 0.3 to 5 times, and preferably 0.5 to 3 times. This is because a stable thickening effect can be obtained by neutralizing and stabilizing the polyacrylic resin and stabilizing the swelling dispersion with alkylene glycol alkyl ethers. 【0054】 Considering the neutralization stability with the polyacrylic acid resin and the phosphate ester surfactant described later, the content of the organic amine is preferably 0.1% to 10% by mass of the total amount of the ink composition. Furthermore, considering neutralization with the phosphate ester surfactant described later, the content of the organic amine in the total amount of the ink composition is preferably 0.1% to 8% by mass, and more preferably 1% to 6% by mass. 【0055】 (Surfactants) In this invention, it is preferable to use a surfactant to improve the writing feel by improving lubricity, and also to improve the writing performance when the tip of the pen tip dries out while left in the atmosphere. This is because the lubricating layer formed by the surfactant makes it easier to improve lubricity, and the surfactant also softens the film formed by the drying of the tip of the pen tip, making it easier to improve the writing performance. 【0056】 Examples of surfactants include fatty acids, silicone-based surfactants, fluorine-based surfactants, phosphate ester surfactants, surfactants containing acetylene bonds, fatty acid esters, polyalkylene alkyl ethers, alkylimidazolines, alkyl alkanolamides, and oxyethylene oxypropylene block copolymers. Among these, considering the effects described above, it is preferable to use one or more from fatty acids, phosphate ester surfactants, and fatty acid esters. 【0057】 In particular, when used in ballpoint pens, phosphate ester surfactants are preferable because their phosphate groups make them easily adsorbed to metal ballpoint pen tips and balls, thus providing a lubricating effect. Furthermore, when used in ballpoint pens, phosphate ester surfactants are preferable because they facilitate the creation of an extreme pressure effect between the metal ball and the ball seat, further improving lubrication. 【0058】 Regarding the HLB value of the surfactant, considering its compatibility with the alkylene glycol alkyl ethers and polyacrylic acid resin, it is preferable that the HLB value be between 5 and 17 so as not to inhibit the swelling and dispersibility with the alkylene glycol alkyl ethers and polyacrylic acid resin. If further improvement in swelling and dispersibility, lubricity, and writing performance is considered, it is preferable that the HLB value be between 6 and 14. Furthermore, considering lubricity, it is preferable that the HLB value be 12 or less, and it is preferable that the HLB value be between 6 and 12. 【0059】 The HLB value used in this invention can be determined by methods such as the Griffin method or the Kawakami method. In particular, in retractable writing instruments such as retractable writing instruments and twist-action writing instruments, the pen tip is always exposed to the outside, unlike capped writing instruments. For this reason, it is more preferable to use a surfactant with the above-mentioned HLB value, as it is easily affected by the writing performance when the writing tip is dry. 【0060】 Examples of surfactants include fatty acids such as oleic acid, stearic acid, and linoleic acid. Examples of silicone-based surfactants include dimethyl silicone, methylphenyl silicone, polyether-modified silicone, and higher fatty acid ester-modified silicone. Examples of fluorine-based surfactants include perfluoro group butyl sulfonates, perfluoro group-containing carboxylates, perfluoro group-containing phosphate esters, perfluoro group-containing phosphate ester type formulations, perfluoroalkyl betaines, and perfluoroalkylamine oxide compounds. Examples of phosphate ester-based surfactants include phosphate monoesters of polyoxyethylene alkyl ether or polyoxyethylene alkylaryl ether, phosphate diesters of polyoxyethylene alkyl ether or polyoxyethylene alkylaryl ether, phosphate triesters of polyoxyethylene alkyl ether or polyoxyethylene alkylaryl ether, alkyl phosphate esters, alkyl ether phosphate esters, or derivatives thereof. 【0061】 Among these, considering lubrication and thickening effects, it is preferable to use phosphate ester-based surfactants. 【0062】 When using a phosphate ester surfactant, the acid value is preferably 180 mgKOH / g or less. This is because it is easier to achieve improved lubricity due to the phosphate ester surfactant and to obtain the thickening effect of the polyacrylic resin. If lubricity and thickening effects are taken into consideration, the acid value is preferably 30 mgKOH / g to 170 mgKOH / g, and if these factors are taken into consideration even more, the acid value is preferably 70 mgKOH / g to 160 mgKOH / g. 【0063】 The acid value shall be expressed as the number of milligrams of potassium hydroxide required to neutralize the acidic components contained in 1 gram of the sample. 【0064】 Phosphate ester surfactants have a rust-preventive effect. Therefore, when the ball is made of metal, corrosion of the ball is suppressed, the writing quality is maintained well, and wear of the ball seat is suppressed, which is preferable. In particular, when the ball is made of an alloy containing cobalt, nickel, chromium, etc., these metals are less susceptible to corrosion over time due to the rust-preventive effect of the phosphate ester surfactant, which is preferable. This tendency is particularly pronounced and preferable when the ball material is a cemented carbide ball, especially when the ball material is a cemented carbide ball with tungsten carbide as the main component and cobalt, nickel, chromium, etc. as a binder. 【0065】 Furthermore, considering lubricity and ink stability over time, it is preferable to use a phosphate ester surfactant having an alkyl group, and in particular, it is preferable that the alkyl group has 8 to 18 carbon atoms. More preferably, the number of carbon atoms is 10 to 18, and even more preferably, it is 12 to 18. This is because if the number of carbon atoms in the alkyl group is too low, lubricity tends to be insufficient, and if the number of carbon atoms is too high, it tends to affect the ink's stability over time. 【0066】 The surfactant content is more 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 the amount is less than 0.1% by mass, it tends to be difficult to obtain the desired lubricity, and if it exceeds 5.0% by mass, the ink tends to become unstable over time. Considering this tendency, the surfactant content relative to the total amount of the ink composition is preferably 0.3% by mass or more and 3.0% by mass or less, and more preferably 0.5% by mass or more and 3.0% by mass or less, relative to the total amount of the ink composition. 【0067】 In the present invention, organic solvents other than alkylene glycol alkyl ethers may be used. Specifically, examples of organic solvents commonly used as oil-based inks include glycol solvents such as ethylene glycol monophenyl ether, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, butylene glycol, and ethylene glycol; and alcohol solvents such as benzyl alcohol, methanol, ethanol, 1-propanol, 2-propanol, isopropanol, isobutanol, t-butanol, propagyl alcohol, allyl alcohol, 3-methyl-1-butyne-3-ol, ethylene glycol monomethyl ether acetate, and other higher alcohols. 【0068】 Furthermore, considering improvements in solubility, drying properties, and smudging, the content of organic solvents is preferably 3% to 50% by mass relative to the total amount of the ink composition. Considering drying properties at the tip of the pen, 5% to 50% by mass is preferred, and more preferably 5% to 30% by mass. 【0069】 (resin) Furthermore, in this invention, resins may be used to improve ink viscosity modifiers, suppress ink leakage, improve writing feel, suppress brushstrokes and dot unevenness, and improve pigment dispersibility. Examples of resins 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 acid ester resin particles and amino resin particles. These may be used individually or in mixtures of two or more. Dot unevenness refers to the phenomenon in which writing lines are written intermittently as fine dots. 【0070】 Among these resins, it is preferable to use ketone resins and polyvinyl butyral resins, considering improvements in ink leakage suppression, writing feel, writing performance such as suppression of smudging and unevenness, and ease of improving pigment dispersibility. Furthermore, it is preferable to use ketone resins if improvements in writing feel, writing performance such as suppression of smudging and unevenness are considered. 【0071】 Polyvinyl butyral resin is produced by reacting polyvinyl alcohol (PVA) with butyraldehyde (BA), and has a structure containing butyral groups, acetyl groups, and hydroxyl groups. 【0072】 Among these resins, it is preferable that they contain resin particles, and more preferably that they contain acrylic ester resin particles and amino resin particles, considering the need to suppress ink leakage. This is because the resin particles create physical obstruction in the gap between the ball and the inner wall of the tip, thereby suppressing ink leakage. Furthermore, the particles partially deform and adhere closely to each other, creating a structure formed by weak aggregation. By forming a structure in the ink that has high resistance to ink leakage when stationary, high ink leakage suppression is possible. On the other hand, because the structure is formed by weak aggregation, the aggregated structure is broken down by physical actions such as the rotation of the ball during writing. Therefore, it is possible to write smoothly without hindering the flow of ink during writing, and to obtain a dark writing line. In addition, since the resin particles are stable against alkylene glycol alkyl ethers, they can be used suitably because they maintain the stability of the ink over time and also provide high solvent resistance and water resistance to the writing line. 【0073】 Regarding the average particle size of the resin particles, a smaller average particle size allows the particles to adhere more closely to each other, forming a weak aggregate structure and thus suppressing ink leakage. From this viewpoint, the average particle size of the resin particles is preferably 5 μm or less, and more preferably 3 μm or less. Furthermore, considering the dispersion stability of the resin particles in the ink (ink stability over time), the average particle size of the resin particles is preferably 2 μm or less, and more preferably less than 1 μm. On the other hand, if the average particle size is too small, the ink leakage suppression effect tends to be poor. For this reason, the average particle size of the resin particles is preferably 0.1 μm or more, and more preferably 0.3 μm or more. The average particle size of the resin particles can also be determined by the Coulter counter method. Specifically, using a Coulter Multisizer™3 (a measuring device manufactured by Beckman Coulter), the particle size (D50) at 50% volume accumulation of the particle size distribution, measured based on values ​​calibrated using standard samples or other measurement methods, is measured. The average particle size of the resin particles can be determined by this measurement. 【0074】 Furthermore, resin particles include acrylic acid ester resin particles (polyacrylic acid ester particles), such as acrylic acid esters and methacrylic acid esters (polyacrylic acid ester particles, polymethacrylic acid ester particles). More specifically, examples include acrylic acid ester resin particles (polyacrylic acid ester particles) such as methyl acrylate, ethyl acrylate, and butyl acrylate, and methacrylic acid ester resin particles (polymethacrylic acid ester particles) such as methyl methacrylate, isopropyl methacrylate, and butyl methacrylate. In addition, amino resin particles are a general term for resins obtained by the condensation reaction of a compound containing an amino group with an aldehyde, and examples include melamine resin particles, benzoguanamine resin particles, urea resin, and aniline aldehyde resin. 【0075】 Among these resin particles, acrylic ester resin particles are preferable when considering stability against alkylene glycol alkyl ethers in the ink and suppression of ink leakage. Furthermore, methacrylic ester resin particles are preferable when considering that they are more stable in the ink, thereby improving ink leakage suppression and ink stability over time. Moreover, a smaller number of carbon atoms in the alkyl group within the methacrylic ester resin particle structure makes them more stable in the ink. For this reason, it is preferable that the number of carbon atoms in the alkyl group is between 1 and 6, and more preferably between 1 and 4. When considering the effect of suppressing ink leakage even further, methyl methacrylate resin particles (polymethyl methacrylate particles) are preferable. 【0076】 These acrylic ester resin particles (polyacrylic ester particles) may be used individually, as a mixture of two or more types, or as a copolymer. Furthermore, the acrylic ester resin particles (polyacrylic ester particles) only need to contain at least acrylic ester resin particles, and may also be a mixture of acrylic ester resin particles and other resins, or a copolymer of acrylic ester resin particles and other resins. 【0077】 As for the acrylic ester resin particles (polyacrylic ester particles) mentioned above, it is preferable to use acrylic ester resin particles having a cross-linked structure, considering the suppression of ink leakage and improvement of ink stability over time. This is presumed to be because having a cross-linked structure forms a stable particle structure, making it easier to stabilize in ink, and further, it is easier to form a stable, weak aggregate structure between acrylic ester particles, thereby improving the suppression of ink leakage. It is preferable to use methacrylic ester having a cross-linked structure because it is easier to stabilize in ink, thereby improving the suppression of ink leakage and the stability of ink over time. 【0078】 Regarding the shape of the resin particles, spherical or irregularly shaped particles can be used, but spherical resin particles are preferred considering the ink leakage suppression effect due to the adhesion between the resin particles. The term "spherical resin particles" here is not limited to perfectly spherical particles, but may also refer to roughly spherical or roughly elliptical resin particles. 【0079】 Furthermore, regarding the content of the resin particles, it is preferable that it be 0.01% by mass or more and 10% by mass or less relative to the total amount of the ink composition. This is because if the content of the resin particles is less than 0.01% by mass, it is difficult to suppress ink leakage, and if it exceeds 10% by mass, the aggregated structure tends to become stronger, which can easily affect the ink's stability over time, writing feel, and initial writing performance. Moreover, considering further factors, it is preferable that the content of resin particles relative to the total amount of the ink composition be 0.1% by mass or more and 5% by mass or less, particularly preferably 0.3% by mass or more and 3% by mass or less, and most preferably 0.5% by mass or more and 3% by mass or less. 【0080】 The ink viscosity of the ballpoint pen ink composition of the present invention is not particularly limited, but when alkylene glycol alkyl ethers and polyacrylic resins are used, imparting pseudoplasticity makes it easier to lower the ink viscosity during writing and improve writing feel and writing performance such as skipping. For this reason, at 20°C and a shear rate of 100 sec, -1The ink viscosity (during writing) is preferably 5000 mPa·s or less. If writing feel and writing performance (preventing skipping) are considered, the ink viscosity is preferably 3000 mPa·s or less, and if further consideration is given, the ink viscosity is preferably 2000 mPa·s or less. On the other hand, if writing performance such as ink smudging, bleeding, show-through, and drying time of the ink is considered, the ink viscosity is preferably 100 mPa·s or more, if further consideration is given, preferably 200 mPa·s or more, and more preferably 400 mPa·s or more. 【0081】 Furthermore, considering ink-following properties, at 20°C and a shear rate of 0.18 sec, -1 The ink viscosity (at rest) is preferably 50,000 mPa·s or less, and more preferably 30,000 mPa·s or less. On the other hand, considering ink leakage suppression, the ink viscosity is preferably 1,000 mPa·s or more, more preferably 2,000 mPa·s or more, and more preferably 3,000 mPa·s or more. 【0082】 Furthermore, this method is effective for retractable writing instruments such as click-type and twist-type writing instruments, where ink leakage prevention needs to be given greater consideration. 【0083】 In the present invention, when alkylene glycol alkyl ethers and polyacrylic acid resins are used, the viscosity index n is S = αD n This refers to n in the viscosity equation shown. Note that S is the shear stress (dyn / cm²). 2 (=0.1Pa), D is the shear rate (s -1 ), α represents 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 (40mm cone plate, 2° angle). 【0084】 Regarding the viscosity index n, considering writing feel, ink blotting, and skipping, it is preferable that the viscosity index n be between 0.3 and 0.8. Considering the balance of writing feel, ink blotting, and skipping, it is preferable that the viscosity index n be between 0.35 and 0.7, and preferably between 0.4 and 0.7. 【0085】 (Ballpoint pen) Next, a ballpoint pen using the oil-based ballpoint pen ink composition of the present invention will be described. 【0086】 Figure 1 is a cross-sectional view of an example of the ballpoint pen 100 of this embodiment. The ballpoint pen 100 is an example of an oil-based ballpoint pen. 【0087】 The ballpoint pen 100 has an ink reservoir 2. The ink reservoir 2 is a long cylinder in the extension direction X. The extension direction X is the direction along the straight line passing through the center of the cross-section of the cylindrical ink reservoir 2. In other words, the extension direction X is the direction along the central axis of the cylindrical ink reservoir 2. 【0088】 The ink reservoir cylinder 2 contains an oil-based ballpoint pen ink composition 10. The oil-based ballpoint pen ink composition 10 is the oil-based ballpoint pen ink composition of the present invention as described above. As described above, in this embodiment, the oil-based ballpoint pen ink composition is described as an ink composition or simply ink. 【0089】 A ballpoint pen tip 4 is provided at one end of the ink reservoir 2 in the extension direction X. The ballpoint pen tip 4 is a component that rotatably holds the ball 3. That is, the ballpoint pen tip 4 holds the ball 3 at the tip portion, which is one end of the ink reservoir 2 in the extension direction X. 【0090】 Figure 2 is an enlarged cross-sectional view of an example of a ballpoint pen tip 4. The ballpoint pen tip 4 comprises a tip body 4A. The tip body 4A is provided with a coil spring 5, an ink flow hole 6, an ink flow groove 7, a ball seat 8, and a ball holding chamber 9. 【0091】 The ink flow hole 6 is a hole that penetrates in the stretching direction X and through which ink flows. The ink is an oil-based ballpoint pen ink composition 10. The ink flow groove 7 is a groove that extends radially from the ink flow hole 6. The ball holding chamber 9 is provided at the end of the ink flow hole 6 and has a ball seat 8 on which the ball 3 is placed. The ball seat 8 is provided with a coil spring 5 which presses the ball 3 placed on the ball seat 8 toward the inner wall of the tip T. When the ball 3 is placed on the ball seat 8, the ball 3 is rotatably held so that a portion of it protrudes from the tip T. 【0092】 When writing is performed using the ballpoint pen 100, the oil-based ballpoint pen ink composition 10 that flows out from the ink reservoir cylinder 2 is supplied from the ink flow hole 6 through the ink flow groove 7 to the ball 3 held in the ball holding chamber 9. The supply of ink to the ball 3 allows writing to occur on paper or other surfaces. 【0093】 The ink composition 10 for oil-based ballpoint pens, contained in the ink reservoir 2, comprises a colorant, alkylene glycol alkyl ethers, and polyacrylic acid resin, as described above. 【0094】 For a ballpoint pen 100 using an ink composition 10 containing alkylene glycol alkyl ethers and polyacrylic acid resin as the ink composition 10 for oil-based ballpoint pens, the ink consumption per 100m of writing distance is preferably greater than 20mg and less than or equal to 100mg. If the ink consumption per 100m is 20mg or less, ink smudging and unevenness are likely to occur, making it difficult to obtain a good writing feel. If the ink consumption per 100m of writing distance exceeds 100mg, ink leakage is likely to occur from the gap between the ball 3 and the tip T, and ink blobs are also likely to occur. Considering the above effects, the ink consumption per 100m of writing distance for the ballpoint pen 100 is preferably 25mg or more and 90mg or less, and more preferably 30mg or more and 80mg or less. 【0095】 Regarding ink consumption, a spiral writing test was conducted using five test samples at a writing speed of 4 m / min, under the conditions of 20°C, a writing angle of 70°, a writing load of 200 g, and on JIS P3201 writing paper. The average value of the ink consumption per 100 m of writing distance from the initial writing stage (0 m to 100 m) was defined as the ink consumption per 100 m. 【0096】 The diameter of ball 3 is not limited. For example, the diameter of ball 3 is in the range of 0.25 mm to 1.6 mm, preferably 0.5 mm to 1.6 mm, and more preferably 0.5 mm to 1.0 mm. Specifically, the diameter of ball 3 is 0.3 mm, 0.4 mm, 0.5 mm, 0.7 mm, 1.0 mm, 1.2 mm, or 1.6 mm. 【0097】 Furthermore, to improve writing quality, such as smooth writing, reduced skipping, uneven ink flow, and darker lines, as well as suppression of ink leakage and ink tracking, it is effective to consider the relationship between ink consumption and the diameter of the ballpoint pen. 【0098】 Specifically, the ratio of ink consumption (mg) per 100m of writing distance to the diameter (mm) of Ball 3 (ink consumption / diameter of Ball 3) is 30 or higher. By setting this ratio to 30 or higher, the writing feel is improved, and the writing becomes smoother without smudging or blotting. 【0099】 Furthermore, this ratio is preferably 150 or less. More specifically, from the viewpoint of improving writing feel, writing performance (suppression of skipping and blotting), ink followability, and ink leakage suppression, this ratio is preferably 40 to 140, more preferably 50 to 120, and particularly preferably 65 to 100. 【0100】 The amount of movement of the ball 3 of the ballpoint pen tip 4 in the stretching direction X is preferably greater than 3 μm and 25 μm or less. The amount of movement of the ball 3 in the stretching direction X refers to the distance that the ball 3 can move in the stretching direction X relative to the tip body 4A. This amount of movement is sometimes referred to as clearance. 【0101】 If the amount of movement of ball 3 in the extension direction X is 3 μm or less, it is likely to affect writing quality and feel, such as skipping, blotting, and uneven dots in the writing. Also, if the amount of movement exceeds 25 μm, it is likely to affect blotting, ink tracking performance, and ink leakage suppression. Furthermore, if the amount of movement of ball 3 is within the above range, it is easy to adjust the ratio of ink consumption (mg) per 100m of writing distance to the diameter (mm) of ball 3 to the above range of 30 to 150. 【0102】 More specifically, the amount of movement of ball 3 in the stretching direction X is preferably greater than 3 μm and 22 μm or less, more preferably between 5 μm and 20 μm, and more preferably between 7 μm and 18 μm. 【0103】 In this invention, the amount of movement of the ball 3 of the ballpoint pen tip 4 in the extension direction X represents the amount of movement of the ball 3 in the extension direction X in the ballpoint pen tip 4 in its initial state before writing begins. 【0104】 The arithmetic mean roughness (Ra) of the surface of the ball 3 of the ballpoint pen tip 4 is preferably between 0.1 nm and 12 nm. This is because if the arithmetic mean roughness (Ra) is less than 0.1 nm, it is difficult for sufficient ink to adhere to the surface of the ball 3, making it easy for streaking, uneven dots, and other problems to occur in the writing. Also, if the arithmetic mean roughness (Ra) exceeds 12 nm, the surface of the ball 3 is too rough, increasing the rotational resistance between the ball 3 and the ball seat 8. This tends to result in a poorer writing feel and is more likely to affect writing quality, such as streaking, blotting, and uneven dots. Furthermore, an arithmetic mean roughness (Ra) of 0.1 nm to 10 nm is preferable because it allows ink to adhere easily to the surface of the ball 3. Considering all these factors, the arithmetic mean roughness (Ra) of the ball 3 is preferably between 2 nm and 8 nm. The arithmetic mean roughness (Ra) of Ball 3 can be measured using a surface roughness measuring instrument (model name SPI3800N, manufactured by Seiko Epson). The arithmetic mean roughness (Ra) is calculated by taking a reference length from the roughness curve measured by this surface roughness measuring instrument, extracting a portion in the direction of the mean line, summing the absolute values ​​of the deviations from the mean line to the measurement curve in this extracted portion, and then averaging the results. 【0105】 Furthermore, while there are no particular limitations on the materials used for ball 3, 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. 【0106】 Furthermore, the material of the ballpoint pen tip 4 may include metal materials such as stainless steel, nickel silver, brass, aluminum bronze, and aluminum, as well as resin materials such as polycarbonate, polyacetal, and ABS. Considering the wear of the ball seat 8, long-term stability, and cost, it is preferable that the ballpoint pen tip 4 be made of a stainless steel tip body 4A. 【0107】 By using the oil-based ballpoint pen ink composition 10 of the present invention as the ink composition contained in the ink reservoir cylinder 2, the amount of ink consumed remains stable from the beginning of writing to the end of writing. Therefore, a good writing feel and writing performance (suppression of skipping and blotting) can be stably obtained. Specifically, the ratio of ink consumption Emg to ink consumption Fmg (E:F) is preferably within the following range. Ink consumption Emg is the amount of ink consumed (mg) at the beginning of writing, from 0m to 100m. Ink consumption Fmg is the amount of ink consumed (mg) at 100m before the ink runs out. 【0108】 A ratio (E:F) between 1:0.7 and 1:1.3 is preferable because it makes writing smoother and reduces the likelihood of skipping, blotting, and uneven dots in the handwriting, thus stably achieving good writing performance (suppression of skipping and blotting). More preferably, this ratio (E:F) is in the range of 1:0.8 to 1:1.2, and even more preferably in the range of 1:0.9 to 1:1.1. [Examples] 【0109】 The present invention will be described in detail below with reference to examples. However, the present invention is not limited to the following examples. 【0110】 Example 1 The oil-based ballpoint pen ink composition of Example 1 was prepared by taking alkylene glycol alkyl ethers, a colorant, water, a phosphate ester surfactant (HLB value: 10.5), and an organic amine, heating them to 60°C, and then dissolving them using a disperser stirrer to prepare a base ink. Subsequently, while heating the prepared base ink, polyacrylic acid resin was added and thoroughly mixed and stirred using a homogenizer stirrer until a uniform state was obtained to obtain the oil-based ballpoint pen ink composition of Example 1. 【0111】 The ratio of organic amine to polyacrylic resin (organic amine / polyacrylic resin) was 1.5 times. 【0112】 The specific proportions are as follows. Furthermore, when the viscosity of the ink in Example 1 was measured using a TA Instruments AR-G2 rheometer (40mm cone plate, 2° angle), the shear rate was 0.18 sec at 20°C. -1 Ink viscosity = 16500 mPa·s, under conditions of 20°C, shear rate 100 sec. -1 The ink viscosity was 800 mPa·s. The viscosity index n was 0.57. 【0113】 Example 1 (Ink formulation) Coloring agents (dyes, basic dyes and salt-forming dyes with organic acids) 10.0% by mass Coloring agent (dye, salt-forming dye with acid dye and organic amine) 10.0% by mass Alkylene glycol alkyl ethers (solubility parameter (SP value): 10.5 (cal / cm³) 3 ) 1 / 2 , boiling point: 249℃) 70.7% by mass Cross-linked polyacrylic acid resin 1.3% by mass Water 5.0% by mass Phosphate ester surfactant (HLB value: 10.5) 1.0% by mass Organic amine (HLB value: 15.4) 2.0% by mass 【0114】 Examples 2 to 43 As shown in Tables 1 to 4, oil-based ballpoint pen ink compositions 10 of Examples 2 to 43 were obtained using the same procedure as in Example 1, except that the ink components were changed. The measurement and evaluation results are shown in Tables 1 to 4. 【0115】 Comparative Examples 1 to 6 As shown in Table 4, oil-based ballpoint pen ink compositions for Comparative Examples 1 to 6 were obtained using the same procedure as in Example 1, except that the ink components were changed. The measurement and evaluation results are shown in Table 4. 【0116】 [Table 1] 【0117】 [Table 2] 【0118】 [Table 3] 【0119】 [Table 4] 【0120】 Testing and evaluation Tests and evaluations were conducted using the ballpoint pen 100 described with reference to Figures 1 and 2. Specifically, the oil-based ballpoint pen ink compositions (0.29 g) prepared in Examples 1 to 43 and Comparative Examples 1 to 6 were placed in an ink reservoir 2 (made of polypropylene). Then, a ballpoint pen tip 4, which rotatably holds a ball 3, was attached to one end of the ink reservoir 2 to create the ballpoint pen 100. 【0121】 As the ballpoint pen tip 4, a ballpoint pen tip 4 having a coil spring 5 that presses the ball 3 against the inner wall of the tip T was used (see Figure 2). The material of the ball 3 was a cemented carbide ball mainly composed of tungsten carbide (containing cobalt as a binder). The diameter of the ball 3 and the arithmetic mean roughness (Ra) of the surface of the ball 3 are shown in Tables 1 to 4, respectively. 【0122】 The following tests and evaluations were conducted using JIS P3201 writing paper as the written examination paper. Writing feel: Evaluated through a sensory test using handwriting. Extremely smooth ···◎ Smooth ···○ Slightly less smooth ···△ Heavy items ···× 【0123】 Smudge test (writing performance test 1): The handwriting was observed after a 100m writing test on a running test machine with a load of 200gf, a writing angle of 70°, and a speed of 4m / min. Handwriting with little or no smudging or unevenness ···◎ There are some slight smudges and unevenness in the handwriting, but it is at a level that does not affect practical use. The handwriting has smudges and uneven dots, which affect its practical use. ···△ Handwriting with many smudges and uneven dots... 【0124】 Crying-Bob Test (Writing Performance Test 2): Handwriting was observed after a 100m writing test on a running test machine with a load of 200gf, a writing angle of 70°, and a speed of 4m / min. Handwriting with little or no tear-shaped smudges ···◎ There are some slight smudges in the handwriting, but it's not at a level that would cause any practical problems. The handwriting has a smudged, tear-like appearance, which affects its practical use. ···△ Those whose handwriting contains many tear-streaked characters... 【0125】 Ink leak test: The pen was left with the tip facing downwards for 7 days in an environment of 30°C and 85% RH, and ink leakage from the tip of the pen was confirmed. No ink droplets on the tip of the pen ···◎ The ink droplet at the tip of the pen tip should be within 1 / 4 of the tapered section. The ink droplet at the tip of the pen tip extends beyond 1 / 4 of the tapered section but is less than 1 / 2 of it. ···△ Ink droplets at the tip of the pen tip that extend more than half the length of the tapered section... × 【0126】 In Examples 1 to 43, good performance was obtained in all aspects, including writing feel, skipping test (writing performance test 1), ink blotting test (writing performance test 2), and ink leakage test. 【0127】 In Examples 30 to 43, pigments were used as colorants, and they exhibited good pigment dispersibility and stability. Furthermore, when the fastness was examined, Examples 30 to 43, which used pigments, showed superior fastness compared to Examples 1 to 29, which did not use pigments. 【0128】 Furthermore, the ratio (E:F) of ink consumption Emg to ink consumption Fmg was measured for ballpoint pens 100 of Examples 1, 2, 3, 16, 25, 36, 37, 38, 39, and 42. As described above, ink consumption Emg is the ink consumption (mg) at the initial writing stage (0m to 100m). Ink consumption Fmg is the ink consumption (mg) at the last 100m before the ink runs out. 【0129】 The ratios (E:F) for each of Examples 1, 2, 3, 16, 25, 36, 37, 38, 39, and 42 were 50:52 (1:1.04), 53:54 (1:1.01), 48:45 (1:0.94), 52:56 (1:1.08), 48:44 (1:0.92), 63:57 (1:0.90), 71:66 (1:0.93), 90:87 (1:0.97), 100:95 (1:0.95), and 70:65 (1:0.93), respectively. 【0130】 Furthermore, the viscosity of the inks in Examples 2, 3, 5, 13, 30, and 31 was measured using a TA Instruments AR-G2 rheometer (40mm cone plate, 2° angle), and the viscosity index n was calculated. 【0131】 In Example 2, the shear rate was 0.18 sec in an environment of 20°C. -1 Ink viscosity = 8000 mPa·s, under conditions of 20°C, shear rate 100 sec. -1 The ink viscosity was 800 mPa·s, and the viscosity index n was 0.64. In Example 3, the shear rate was 0.18 sec in an environment of 20°C. -1Ink viscosity = 27000 mPa·s, under conditions of 20°C, shear rate 100 sec. -1 The ink viscosity was 1500 mPa·s, and the viscosity index n was 0.54. In Example 5, the shear rate was 0.18 sec in an environment of 20°C. -1 Ink viscosity = 22000 mPa·s, under conditions of 20°C, shear rate 100 sec. -1 The ink viscosity was 850 mPa·s, and the viscosity index n was 0.49. In Example 13, the shear rate was 0.18 sec in an environment of 20°C. -1 Ink viscosity = 10,000 mPa·s, under conditions of 20°C, shear rate 100 sec. -1 The ink viscosity was 700 mPa·s, and the viscosity index n was 0.58. In Example 30, the shear rate was 0.18 sec in an environment of 20°C. -1 Ink viscosity = 10,000 mPa·s, under conditions of 20°C, shear rate 100 sec. -1 The ink viscosity was 700 mPa·s, and the viscosity index n was 0.58. In Example 31, the shear rate was 0.18 sec in an environment of 20°C. -1 Ink viscosity = 4500 mPa·s, under conditions of 20°C, shear rate 100 sec. -1 The ink viscosity was 550 mPa·s, and the viscosity index n was 0.67. 【0132】 In Examples 1 to 43, good performance was obtained in all aspects, including writing feel, skipping test (writing performance test 1), ink blotting test (writing performance test 2), and ink leakage test. 【0133】 Furthermore, using ballpoint pen 100, which is an oil-based ballpoint pen as described in Examples 1 to 43, ink leakage suppression was tested by leaving the pen tip facing downwards in an environment of 30°C and 85% RH, and checking for ink leakage from the tip of the pen. The results showed that the level was at a level that did not pose a practical problem. 【0134】 Using ballpoint pen 100 and a comparative ballpoint pen, which are oil-based ballpoint pens from Examples 1 to 43, the ink consumption (mg) per 100m of writing distance was determined by the spiral writing test described above. The results are shown in Tables 1 to 4. Furthermore, the A / B value, where A (mg) is the ink consumption per 100m of writing distance and B (mm) is the diameter of ball 3, is shown in Tables 1 to 4. 【0135】 Furthermore, when the amount of movement of ball 3 in the stretching direction X of ballpoint pen 100, which is an oil-based ballpoint pen in Examples 1 to 43, and the comparative ballpoint pen was measured, the results shown in Tables 1 to 4 were obtained. In Tables 1 to 4, "Amount of ball movement" is the amount of movement of ball 3 in the stretching direction X. 【0136】 Furthermore, as shown in Tables 1 to 4, the order in which the effectiveness in suppressing ink leakage was obtained was: Example 25 and Example 26 (triethylene glycol monomethyl ether / acrylic acid ester resin particles), Example 1 (triethylene glycol monomethyl ether), Example 5 (propylene glycol monomethyl ether), Example 7 (diethylene glycol monobutyl ether) = Example 8 (triethylene glycol monobutyl ether). 【0137】 In Comparative Example 1, because alkylene glycol alkyl ethers were not used, the polyacrylic resin could not swell and disperse, and sufficient results were not obtained in the writing feel, ink blotting test (writing performance test 2), and ink leakage test. 【0138】 In Comparative Example 2, polyacrylic acid resin was not used, and in Comparative Example 3, fatty acid amide wax was used as a shear viscosity reducing agent. However, sufficient effects were not obtained in the writing feel, skipping test (writing performance test 1), ink blotting test (writing performance test 2), and ink leakage test. 【0139】 Comparative Example 4 did not contain alkylene glycol alkyl ethers, and therefore did not yield sufficient results in the writing feel, ink blotting test (writing performance test 2), and ink leakage test. 【0140】 Comparative Example 5, lacking polyacrylic acid resin, failed to achieve sufficient results in writing feel, skipping test (writing performance test 1), ink blotting test (writing performance test 2), and ink leakage test. 【0141】 Comparative Example 6 had an ink consumption ratio (mg) per 100m of writing distance to the ball diameter (mm) of less than 30, and therefore did not show sufficient effectiveness in the writing feel and skipping test (Writability Test 1). 【0142】 Furthermore, when using retractable writing instruments such as retractable writing instruments or twist-action writing instruments (retractable ballpoint pens), ink smudging is more likely to occur. For this reason, it is effective to use an oil-based ballpoint pen ink composition 10 containing alkylene glycol alkyl ethers and polyacrylic acid resin, as described in the present invention. 【0143】 Furthermore, in order to suppress ink leakage and improve writing performance (prevention of skipping), it is preferable that the ballpoint pen tip 4 be equipped with a valve mechanism. The valve mechanism is a mechanism that presses a ball 3, which is rotatably held in the tip T, against the inner wall of the tip edge directly or via a pressing body using a coil spring 5, thereby creating a gap between the inner wall of the tip edge and the ball 3 due to the pressure applied during writing, and allowing ink to flow out. It is preferable that the valve mechanism closes even the minute gap at the tip T when not in use. 【0144】 Furthermore, in this embodiment, for convenience, a direct-fill type ballpoint pen 100 in which the oil-based ballpoint pen ink composition 10 is directly contained in the ink reservoir 2 is shown as an example of an oil-based ballpoint pen. However, the oil-based ballpoint pen of the present invention may also be a writing instrument such as a marking pen or felt-tip pen in which the barrel is the ink reservoir 2 and the oil-based ballpoint pen ink composition 10 is directly contained in the barrel. Alternatively, the oil-based ballpoint pen of the present invention may also be a writing instrument in which a ballpoint pen refill in which the oil-based ballpoint pen ink composition 10 is directly contained in the ink reservoir 2 is used as the replacement core, and the replacement core is attached to the barrel (outer casing). 【0145】 Furthermore, in this embodiment, for convenience, a ballpoint pen tip 4 formed by cutting wire is shown as an example, but a ballpoint pen tip 4 formed by pressing pipe material may also be used. [Industrial applicability] 【0146】 The present invention can be used as a writing instrument, and more specifically, it can be widely used as a ballpoint pen, such as a capped or retractable pen. [Explanation of symbols] 【0147】 100 ballpoint pens 10. Ink composition for oil-based ballpoint pens 2 ink cartridges 3 balls 4 ballpoint pen tips

Claims

[Claim 1] An ink container containing an oil-based ballpoint pen ink composition comprising a colorant, alkylene glycol alkyl ethers, polyacrylic resin, and water, A ballpoint pen tip having a ball rotatably held at one end in the extension direction of the ink reservoir, Equipped with, The ratio of ink consumption (mg) per 100m of writing distance to the diameter (mm) of the ball is 30 or more. The ratio (E:F) of the ink consumption Emg at the initial writing stage (0m to 100m) to the ink consumption Fmg from 100m before ink depletion to ink depletion is in the range of 1:0.8 to 1:1.

2. The ratio of water to the polyacrylic resin (water / polyacrylic resin) is 1 to 15 times by mass. The carboxyl group content in the polyacrylic acid resin is 40% by mass or more and 80% by mass or less. An oil-based ballpoint pen characterized by the following features. [Claim 2] The oil-based ballpoint pen according to claim 1, characterized in that the ratio is 65 or more and 100 or less. [Claim 3] An oil-based ballpoint pen according to claim 1 or claim 2, characterized in that the amount of movement of the ball in the stretching direction is greater than 3 μm and 25 μm or less. [Claim 4] The oil-based ballpoint pen according to any one of claims 1 to 3, characterized in that the alkylene glycol alkyl ethers are alkylene glycol monoalkyl ethers. [Claim 5] The content of the alkylene glycol alkyl ethers is 50% or more of the total solvent content of the oil-based ballpoint pen ink composition. The content of the alkylene glycol alkyl ethers is 30% by mass or more and 75% by mass or less based on the total amount of the oil-based ballpoint pen ink composition. An oil-based ballpoint pen according to any one of claims 1 to 4, characterized in that... [Claim 6] The oil-based ballpoint pen according to any one of claims 1 to 5, characterized in that the content of the polyacrylic acid resin is 0.1% by mass or more and 5.0% by mass or less with respect to the total amount of the oil-based ballpoint pen ink composition. [Claim 7] The oil-based ballpoint pen according to any one of Claims 1 to 6, characterized in that the content of the polyacrylic acid resin is 0.6% by mass or more and 1.8% by mass or less with respect to the total amount of the oil-based ballpoint pen ink composition. [Claim 8] The oil-based ballpoint pen according to any one of Claims 1 to 7, characterized in that the bulk density (g / ml) of the polyacrylic resin is 0.01 (g / ml) or more and 0.5 (g / ml) or less. [Claim 9] An oil-based ballpoint pen according to any one of claims 1 to 8, characterized in that the water content of the oil-based ballpoint pen ink composition is 1% by mass or more and 10% by mass or less of the total amount of the ink composition. [Claim 10] An oil-based ballpoint pen according to any one of claims 1 to 9, characterized in that the blending ratio of alkylene glycol alkyl ethers to the polyacrylic acid resin (alkylene glycol alkyl ethers / polyacrylic acid resin) is 20 times or more and 100 times or less. [Claim 11] The aforementioned oil-based ballpoint pen ink composition contains a surfactant, The oil-based ballpoint pen according to any one of claims 1 to 10, characterized in that the surfactant is one or more selected from fatty acids, phosphate ester surfactants, and fatty acid esters.

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