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] The present invention relates to an oil-based ballpoint pen. [Background technology]

[0002] The writing feel of a ballpoint pen is easily affected by friction between the ball and the tip body during writing. In particular, unlike other types of writing implements, ballpoint pens have a configuration in which a ballpoint pen tip is attached to an ink reservoir, and the tip is made of a metal tip such as stainless steel at the tip and a transfer ball made of a metal such as carbide, which is held in the ball seat of the metal tip. However, the rotation of the ball during writing can cause smearing and uneven dots in the handwriting, a poor writing feel, and blobbing due to ink remaining at the tip.

[0003] In order to solve these problems, many ink compositions for oil-based ballpoint pens have been proposed that use additives such as various lubricants to improve lubricity and reduce frictional resistance between the ball and the tip body.

[0004] As an ink composition for oil-based ballpoint pens using such additives, an ink for oil-based ballpoint pens using alkyl β-D-glucoside has been disclosed (see, for example, Patent Document 1). Also, an ink composition for oil-based ballpoint pens using polyethylene glycol with an average molecular weight of 200 to 4,000,000 has been disclosed (see, for example, Patent Document 2). Also, an ink for oil-based ballpoint pens using N-acylamino acid, N-acylmethyl tauric acid, or N-acylmethyl alanine has been disclosed (see, for example, Patent Document 3). Also, an oil-based ink composition for ballpoint pens containing at least deca-macadamia nut oil fatty acid decaglyceryl and a polyoxyethylene alkyl ether whose alkyl group has 16 or more carbon atoms and is 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 Publication No. 5-331403 [Patent Document 2] Japanese Patent Application Publication 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 [Problem to be solved by the invention]

[0006] However, when various additives such as those described in Patent Documents 1 to 4 are used, the frictional resistance between the ball and the tip body can be reduced to some extent, but the writing feel is not satisfactory, and furthermore, writing performance such as smearing and blobbing of handwriting cannot be improved, so there is room for improvement. Furthermore, when a new lubricant is used, compatibility with other ink components can also be a factor, which can easily affect stability over time in the ink.

[0007] An object of the present invention is to provide an oil-based ballpoint pen which has an improved writing feel, is free from smearing or bleeding in handwriting, and has good writing properties. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention "1. An ink reservoir containing an ink composition for an oil-based ballpoint pen, the ink composition comprising a colorant, an alkylene glycol alkyl ether, and a polyacrylic acid resin; An oil-based ballpoint pen comprising: a ballpoint pen tip that rotatably holds a ball at one end of the extension direction of the ink reservoir tube; wherein the ratio of ink consumption (mg) per 100 m of writing distance to the diameter (mm) of the ball is 30 or more; and the ratio (E:F) of ink consumption E mg at the beginning of writing, from 0 m to 100 m, to ink consumption F mg from 100 m before the end of ink consumption to the end of ink consumption, is in the range of 1:0.8 to 1:1.2. 2. The oil-based ballpoint pen described in item 1, characterized in that the ratio is 65 or more and 100 or less. 3. The oil-based ballpoint pen described in item 1 or 2, characterized in that the amount of movement of the ball in the extension direction is greater than 3 μm and not more than 25 μm. 4. The oil-based ballpoint pen according to any one of items 1 to 3, characterized in that the ink consumption (mg) per 100 m writing distance is greater than 20 mg and less than 100 mg. 5. The oil-based ballpoint pen according to any one of items 1 to 4, wherein the alkylene glycol alkyl ether is an alkylene glycol monoalkyl ether. 6. The oil-based ballpoint pen according to any one of items 1 to 5, wherein the alkylene glycol moiety of the alkylene glycol alkyl ether has 3 or more and 8 or less carbon atoms. 7. The oil-based ballpoint pen according to any one of items 1 to 6, characterized in that the content of the alkylene glycol alkyl ethers is 50% or more relative to the total solvent content of the ink composition for the oil-based ballpoint pen, and the content of the alkylene glycol alkyl ethers is 30% by mass or more and 75% by mass or less relative to the total amount of the ink composition for the oil-based ballpoint pen. 8. The oil-based ballpoint pen according to any one of items 1 to 7, wherein the content of the polyacrylic acid resin is 0.1% by mass or more and 5.0% by mass or less relative to the total amount of the ink composition for the oil-based ballpoint pen. 9. An oil-based ballpoint pen according to any one of items 1 to 8, characterized in that the ink composition for the oil-based ballpoint pen contains water, and the content of water relative to the total amount of the ink composition is 1% by mass or more and 10% by mass or less. 10. The oil-based ballpoint pen according to item 9, characterized in that the blending ratio of water to the polyacrylic acid resin (water / polyacrylic acid resin) is 0.1 to 20 times by mass. 11. An oil-based ballpoint pen described in any one of items 1 to 10, 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. 12. The oil-based ballpoint pen according to any one of items 1 to 11, wherein the carboxyl group content in the polyacrylic acid resin is 40% by mass or more and 80% by mass or less. 13. The oil-based ballpoint pen according to any one of items 1 to 12, wherein the ink composition for the oil-based ballpoint pen contains a surfactant, and the surfactant is one or more selected from the group consisting of fatty acids, phosphate ester surfactants, and fatty acid esters. [Effects of the Invention]

[0009] The present invention has made it possible to obtain an oil-based ballpoint pen that has a good writing feel, is free from smearing or bleeding in handwriting, and has good writing properties. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view of an example of a ballpoint pen. [Figure 2] FIG. 2 is an enlarged cross-sectional view of an example of a ballpoint pen tip. DETAILED DESCRIPTION OF THE INVENTION

[0011]

[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.

[0012] The oil-based ballpoint pen of the present invention comprises an ink reservoir and a ballpoint pen tip. The ink reservoir contains an ink composition for an oil-based ballpoint pen, comprising a colorant, an alkylene glycol alkyl ether, and a polyacrylic acid resin. The ballpoint pen tip rotatably holds a ball at one end of the ink reservoir in the extension direction. The oil-based ballpoint pen of the present invention is characterized in that the ratio of ink consumption (mg) per 100 m writing distance to the ball diameter (mm) is 30 or more.

[0013] It has been found that by including alkylene glycol alkyl ethers and polyacrylic acid resins in an ink composition for oil-based ballpoint pens, pseudoplasticity can be imparted, reducing the ink viscosity during writing and maintaining a good writing feel. This is because the polyacrylic acid resin swells and disperses in the alkylene glycol alkyl ethers, imparting pseudoplasticity. It has also been found that by using the ink composition for oil-based ballpoint pens of the present invention and ensuring that the ratio of ink consumption (mg) per 100 m of writing distance to the ball diameter (mm) is 30 or more, writing performance can be improved without blurring or blobbing. The "blobbing" in "blobbing" refers to the phenomenon in which excess ink accumulates at the pen tip during writing. The "blobbing" in "blobbing" refers to the phenomenon in which excess ink remains as clumps on the writing surface during writing.

[0014] Hereinafter, the details of each component contained in the ink composition for an oil-based ballpoint pen and the oil-based ballpoint pen will be described in detail. First, the details of each component contained in the ink composition for an oil-based ballpoint pen will be described. In this embodiment, the ink composition for an oil-based ballpoint pen may be referred to as an ink composition or ink. In addition, the oil-based ballpoint pen may be referred to simply as a ballpoint pen.

[0015] (Alkylene glycol alkyl ethers) The alkylene glycol alkyl ethers used in the present invention are solvents that swell and disperse the polyacrylic acid resin described below, thereby imparting pseudoplasticity. It has been found that imparting pseudoplasticity reduces the ink viscosity during writing, improving the writing feel, and suppressing smearing and bleeding of handwriting, thereby maintaining good writing performance. In particular, when a crosslinked polyacrylic acid resin is used, alkylene glycol alkyl ethers facilitate the formation of a three-dimensional network structure, which in turn facilitates the formation of a denser crosslinked structure. This facilitates the impartation of pseudoplasticity, which is effective in improving the writing feel and writing performance (suppression of bleeding of handwriting). Furthermore, this is effective because it easily suppresses ink leakage from the gap between the ball and the tip end (writing tip). Furthermore, since they do not easily wet metal ballpoint pen tips, the ink does not creep up from the tip end, preventing ink residue and suppressing bleeding of handwriting, thereby improving writing performance.

[0016] In particular, when using a ballpoint pen, strong shear is likely to be applied during writing, and the pseudoplastic structure temporarily dissolves due to the impact of shearing from the ball during writing, which reduces the ink viscosity and makes it possible to maintain good writing feel and writing performance (suppression of smearing and bleeding), making it suitable for use in ballpoint pens.

[0017] In the ink composition for oil-based ballpoint pens containing alkylene glycol alkyl ethers, it is preferable to use a pigment as a colorant. When a pigment is used as a colorant, the high-density three-dimensional network structure of the alkylene glycol alkyl ethers can improve the pigment dispersibility.

[0018] Examples of alkylene glycol alkyl ethers include alkylene glycol monoalkyl ethers, alkylene glycol dialkyl ethers, etc. Among these, it is preferable to use alkylene glycol monoalkyl ethers from the viewpoint of swelling and dispersibility with the polyacrylic acid resin described below.

[0019] Furthermore, the number of carbon atoms in the alkylene glycol moiety of the alkylene glycol monoalkyl ether is preferably 2 to 10 in consideration of ease of swelling and dispersion with the polyacrylic acid resin and writing feel and writing performance (suppression of smearing and blobbing).In consideration of greater stability with the polyacrylic acid resin and easier achievement of the above-mentioned effects, the number of carbon atoms is preferably 3 to 8, more preferably 5 to 6.

[0020] Regarding the number of carbon atoms in the alkyl ether moiety of the alkylene glycol monoalkyl ether, in consideration of swelling dispersibility with polyacrylic acid resin, writing feel, and writing performance (suppression of smearing and blobbing), the shorter the alkyl ether moiety, the better. Therefore, the number of carbon atoms is preferably 1 to 6, and in consideration of being more stable with polyacrylic acid resin and being more effective, it is preferably 1 to 4, and more preferably 1 to 2.

[0021] In addition, the solubility parameter (SP value) of alkylene glycol monoalkyl ether is 8 (cal / cm 3 ) 1 / 2 More than 13(cal / cm 3 ) 1 / 2 It is preferable that the solubility parameter (SP value) is 9 (cal / cm or less). This is because the dissolution stability and dispersion stability of the colorant are improved and the swelling and dispersibility with the polyacrylic acid resin is less affected. 3 ) 1 / 2 More than 12(cal / cm 3 ) 1 / 2 It is preferable that the solubility parameter (SP value) is 10 (cal / cm 3 ) 1 / 2 More than 11(cal / cm 3 ) 1 / 2 It is preferable that:

[0022] The solubility parameter (SP value) of a solvent in the present invention is a value expressed as the square root of the molecular cohesive energy, and is described in Chapter IV, Solubility Parameter Values, of the Polymer Handbook (Second Edition), and this value was used. The unit is (cal / cm 3 ) 1 / 2 and refers to the value at 25°C.

[0023] 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).

[0024] Furthermore, the boiling point of the alkylene glycol monoalkyl ether is preferably 170°C or higher. This is because if the boiling point is lower than 170°C, the alkylene glycol monoalkyl ether is likely to evaporate, which can affect the swelling and dispersibility with the polyacrylic acid resin over time and increase the ink viscosity. From a more specific perspective, a boiling point of 220°C or higher is preferable. On the other hand, if the boiling point exceeds 300°C, the drying property of the handwriting is likely to be affected. For this reason, a boiling point of 300°C or lower is preferable, and from a more specific perspective, a boiling point of 280°C or lower is preferable.

[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, etc. These may be used alone 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, etc. These may be used alone or in combination of two or more.

[0027] The content of the alkylene glycol alkyl ethers is preferably 50% or more of the total solvent content in the ink composition for oil-based ballpoint pens, and is preferably used as the main solvent. This is because other solvents tend to inhibit the swelling and dispersion of the polyacrylic acid resin, making it difficult to impart pseudoplasticity to the ink and affecting the writing feel and writing performance (preventing smearing and blobbing). Using the alkylene glycol alkyl ethers as the main solvent prevents other solvents from affecting the swelling and dispersion. In terms of better writing performance, the content of the alkylene glycol alkyl ethers is preferably 70% or more of the total solvent content. In terms of better writing performance and stability over time in the ink, 90% or more is preferred. In consideration of these effects, 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, based on the total amount of the ink composition. This is because if it is less than 10% by mass, it is difficult to obtain the swelling and dispersion effect of the polyacrylic acid resin, it is difficult to increase the viscosity of the ink when stationary, and it is difficult to suppress ink leakage. If it exceeds 80% by mass, the ink stability over time is likely to deteriorate. Furthermore, taking the above effects into consideration, the content is preferably 20% by mass or more and 80% by mass or less, and more preferably 30% by mass or more and 75% by mass or less.

[0029] (Polyacrylic acid resin) The polyacrylic acid resin used in the present invention is used as a thickener. Polyacrylic acid resins have affinity with alkylene glycol alkyl ethers, and by swelling and dispersing, they exhibit pseudoplasticity and stable thickening properties. Furthermore, considering the writing feel and writing performance (suppression of smearing and blobbing of handwriting), it is preferable to use a crosslinked polyacrylic acid resin. This is because the crosslinked polyacrylic acid resin itself has a crosslinked structure, and it is easy to form a more three-dimensional network structure with the alkylene glycol alkyl ether solvent. Therefore, by forming a denser crosslinked structure, it is easy to impart pseudoplasticity, which reduces the ink viscosity during writing and tends to improve the writing feel and writing performance (suppression of smearing and blobbing). Carboxyvinyl polymers are particularly preferred.

[0030] Furthermore, in the case of polyacrylic acid resins, the carboxyl group content in the polyacrylic acid resin is preferably 40% by mass or more and 80% by mass or less, considering that a stable thickening effect can be obtained together with alkylene glycol alkyl ethers. Even more preferably, it is 50% by mass or more and 70% by mass or less. In particular, when alkylene glycol monoalkyl ethers are used as alkylene glycol alkyl ethers, polyacrylic acid resins having a carboxyl group content of 55% by mass or more and 65% by mass or less are preferred, since they have excellent swelling and dispersibility and impart pseudoplasticity, thereby lowering the ink viscosity during writing and improving the writing feel. Furthermore, alkylene glycol monomethyl ethers are even more preferred.

[0031] Furthermore, the bulk density (g / ml) of the polyacrylic acid resin is preferably 0.5 (g / ml) or less. This is because the effects of the present invention are more readily exhibited by having excellent swelling and dispersibility in alkylene glycol alkyl ethers and water, and from a more particular perspective, it is preferably 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), swelling and dispersion are difficult, and the polyacrylic acid resin is more likely to aggregate. For this reason, it is preferably 0.01 (g / ml) or more, and from a more particular perspective, it is preferably 0.1 (g / ml) or more.

[0032] The bulk density can be measured, for example, by a bulk density measuring device (Scott volume meter, manufactured by Tsutsui Scientific Instruments Co., Ltd.).

[0033] If the content of the polyacrylic acid resin is less than 0.1% by mass relative to the total amount of the ink composition, the swelling is insufficient and pseudoplasticity is not obtained, making it difficult to improve the writing feel, while if it exceeds 5.0% by mass, the swelling and dispersibility in the ink is likely to be poor, so the content is preferably 0.1% by mass or more and 5.0% by mass or less relative to the total amount of the ink composition. Furthermore, taking into consideration the writing feel, etc., the content is preferably 0.3% by mass or more and 3.0% by mass or less, and more preferably 0.6% by mass or more and 1.8% by mass or less.

[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 in consideration of swelling and dispersibility. In consideration of more stable swelling and dispersibility, it is more preferably 10 to 120 times, and from further consideration, it is more preferably 20 to 100 times.

[0035] (coloring agent) The colorant 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.

[0036] Examples of dyes include oil-soluble dyes, acid dyes, basic dyes, metal-containing dyes, and various salt-forming dyes thereof, such as salt-forming dyes formed between an acid dye and a basic dye, salt-forming dyes formed between an organic acid and a basic dye, and salt-forming dyes formed between an acid dye and an organic amine. These dyes may be used alone or in combination of two or more. Considering stability over time due to compatibility with alkylene glycol alkyl ethers, it is preferable to use at least a salt-forming dye. Furthermore, considering that stability over time can be maintained due to the stable salt-forming bond, it is preferable to use a salt-forming dye formed between a basic dye and an organic acid, a salt-forming dye formed between an acid dye and a basic dye, or a salt-forming dye formed between an acid dye and an organic amine. The above-mentioned salt-forming dyes have a solubility parameter (SP value) of 8 (cal / cm 3 ) 1 / 2 More than 13(cal / cm 3 ) 1 / 2 It is preferable because it is easy to dissolve and stabilize in the alkylene glycol monoalkyl ether below. From a more specific viewpoint, it is preferable that the solubility parameter (SP value) of the alkylene glycol monoalkyl ether is 9 (cal / cm 3 ) 1 / 2 More than 12(cal / cm 3 ) 1 / 2 It is preferable that the value is 10 (cal / cm 3 ) 1 / 2 More than 11(cal / cm 3 ) 1 / 2 It is even more preferable that:

[0037] Specifically, 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 Industry Co., Ltd.), Aizen Spiron Black GMH-Special, 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.). These may be used alone or in combination of two or more.

[0038] Examples of pigments 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 may be used alone or in combination of two or more.

[0039] It is preferable to use a pigment as the colorant, because in the case of a ballpoint pen, pigment particles can get into the gap between the ball and the tip body, acting like a bearing, and by suppressing metal contact, it is possible to improve lubricity, improve the writing feel, and reduce wear of the ball seat. As in the present invention, by imparting pseudoplasticity using alkylene glycol alkyl ethers or polyacrylic acid resins, it is possible to lower the ink viscosity during writing and improve the writing feel, making it more preferable to use a pigment.

[0040] When a pigment is used as a colorant, the synergistic effect of the bearing action between the lubricating layer of the surfactant and the pigment particles makes it easier to maintain lubricity and improve the writing feel. Furthermore, taking into account the gaps inside the ballpoint pen tip, the average particle diameter of the pigment is preferably 1 nm or more and 500 nm or less. It is more preferably 30 nm or more and 350 nm or less, and even more preferably 50 nm or more and 300 nm or less.

[0041] The average particle size can be determined by a laser diffraction method. Specifically, the average particle size can be determined by the particle size at 50% cumulative volume (D50) of the particle size distribution measured using a laser diffraction particle size distribution analyzer (trade name "MicrotracHRA9320-X100", Nikkiso Co., Ltd.) based on values calibrated using standard samples or other measurement methods.

[0042] It is preferable to determine the particle size of the pigment in the dispersed state, since the pigment exerts the above-mentioned effects when dispersed in the ink composition for an oil-based ballpoint pen. Furthermore, pigments are unlikely to redissolve even when wet with water or alcohol, and are unlikely to be chemically decomposed when exposed to light (sunlight), allowing handwriting to be visible. This makes them suitable in that an ink composition with excellent fastness can be obtained. Fastness refers to water resistance, alcohol resistance, and light resistance. Furthermore, it is preferable to use a pigment as a colorant because it is likely to provide an ink leakage suppression effect.

[0043] As the colorant, a dye and a pigment may be used in combination. By using a dye and a pigment in combination, vivid color development can be obtained, fastness can be improved, lubricity can be improved, writing feel can be improved, and wear of the ball seat can be suppressed. In consideration of the above effects and the ink stability over time, it is preferable to use a salt-forming dye in combination with a pigment.

[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 the content is less than 5% by mass, it tends to be difficult to obtain thick handwriting, and if the content is more than 45% by mass, it tends to affect the solubility in the ink. Taking this tendency into consideration, the content is preferably 5% by mass or more and 35% by mass or less, and even more preferably 6% by mass or more and 30% by mass or less.

[0045] In addition, in the present invention, the ink composition for an oil-based ballpoint pen preferably contains water. The reason for this is unclear, but water has excellent affinity with alkylene glycol alkyl ethers and polyacrylic acid resins. This allows water to impart a stronger thickening effect and stable swelling properties to the swelling dispersion of alkylene glycol alkyl ethers and polyacrylic acid resins. Furthermore, water improves the slipperiness of the ball while improving ink ejection, suppressing uneven dots, bleeding, and smearing, thereby improving writing performance.

[0046] If the water content is less than 0.1% by mass relative to the total amount of the ink composition, it is likely to affect the ball's sliding properties and ink ejection properties. If it exceeds 20% by mass, it is likely to result in poor solubility in the ink. For this reason, the water content relative to the total amount of the ink composition is preferably 0.1% by mass or more and 20% by mass or less. Furthermore, in consideration of solubility in the ink and writing properties (prevention of smearing and bleeding), it 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.

[0047] In the present invention, the blending ratio of water to polyacrylic acid resin (water / polyacrylic acid resin) is preferably 0.1 to 20 times by mass, considering that a high thickening effect is achieved by swelling and dispersion of the alkylene glycol alkyl ethers and the polyacrylic acid resin. In consideration of a better balance between improved writing feel and writing performance (prevention of smearing and blobbing), the blending ratio of water is more preferably 1 to 15 times, and even more preferably 1 to 10 times.

[0048] (organic amine) In the present invention, the use of an organic amine is preferred because neutralizing and stabilizing the polyacrylic acid resin with an organic amine allows for sufficient swelling and dispersion, resulting in a stable thickening effect. Furthermore, even when a surfactant such as a phosphate ester surfactant is used, neutralization is preferred because it stabilizes dissolution in the ink and improves the writing feel and start-up 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 are preferred in terms of stability with the polyacrylic acid resin. These may be used alone or in combination.

[0049] The average number of moles of ethylene oxide added (per amine molecule) (EO number) of the amine having ethylene oxide is preferably 1 or more and 30 or less, and more preferably 4 or more and 20 or less. By setting the EO number within the above range, the polyacrylic acid resin is neutralized and stabilized due to the stable dissolution with the alkylene glycol alkyl ether, and a stable thickening effect is easily obtained.

[0050] Furthermore, in consideration of stability with alkylene glycol alkyl ethers, polyacrylic acid 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 organic amine is highly reactive and easily reacts with the above-mentioned components, which tends to deteriorate the ink's stability over time. Furthermore, in consideration of stability with alkylene glycol alkyl ethers and polyacrylic acid resins, 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.

[0051] 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.

[0052] The HLB value of the organic amine is preferably 5 or more and 17 or less. This is because a stable thickening effect can be obtained by neutralizing and stabilizing the polyacrylic acid resin and stabilizing the swelling and dispersion with the alkylene glycol alkyl ether. In consideration of further neutralization stability and improved swelling and dispersion properties, the HLB value is preferably 7 or more and 17 or less, and further taking into consideration the above, the HLB value is preferably 9 or more and 16 or less.

[0053] In the present invention, the blending ratio of the organic amine to the polyacrylic acid resin (organic amine / polyacrylic acid resin) is preferably 0.1 to 10 times by mass, more preferably 0.3 to 5 times, and more preferably 0.5 to 3 times. This is because the polyacrylic acid resin is neutralized and stabilized, and swelling and dispersion with the alkylene glycol alkyl ethers are stabilized, thereby achieving a stable thickening effect.

[0054] The content of the organic amine is preferably 0.1% by mass or more and 10% by mass or less of the total amount of the ink composition, taking into consideration the neutralization stability with the polyacrylic acid resin and the phosphate ester surfactant described below. Furthermore, taking into consideration the neutralization with the phosphate ester surfactant described below, the content of the organic amine is preferably 0.1% by mass or more and 8% by mass or less of the total amount of the ink composition, and more preferably 1% by mass or more and 6% by mass or less.

[0055] (surfactant) In the present invention, it is preferable to use a surfactant, since improving lubricity improves the writing feel and also improves the writing performance when the tip of the pen is left in the air and the tip dries. This is because the lubricating layer formed by the surfactant makes it easier to improve lubricity, and the surfactant also softens the coating formed by drying the tip of the pen, making it easier to improve the writing performance.

[0056] Examples of surfactants include fatty acids, silicone surfactants, fluorine surfactants, phosphate ester surfactants, surfactants having an acetylene bond, fatty acid esters, polyalkylene alkyl ethers, alkylimidazolines, alkylalkanolamides, oxyethyleneoxypropylene block copolymers, etc. Among these, in consideration of the above-mentioned effects, it is preferable to use one or more of fatty acids, phosphate ester surfactants, and fatty acid esters.

[0057] In particular, when used in a ballpoint pen, a phosphate ester surfactant is preferably used because the phosphate group makes it easy for the surfactant to be adsorbed to a ballpoint pen tip or ball made of metal or the like, and therefore a lubricating effect can be easily obtained.Furthermore, when used in a ballpoint pen, a phosphate ester surfactant is preferable because it easily obtains an extreme pressure effect between the metal ball and the ball seat, and therefore it is easy to further improve lubricity.

[0058] Regarding the HLB value of the surfactant, in consideration of compatibility with the alkylene glycol alkyl ethers and polyacrylic acid resin, the HLB value is preferably 5 or more and 17 or less, since swelling and dispersibility with the alkylene glycol alkyl ethers and polyacrylic acid resin is less likely to be inhibited. In consideration of further improving swelling and dispersibility, lubricity, and writing performance, the HLB value is preferably 6 or more and 14 or less. Furthermore, in consideration of lubricity, the HLB value is preferably 12 or less, and an HLB value of 6 or more and 12 or less is more preferred.

[0059] The HLB value used in the present invention can be determined by the Griffin method, the Kawakami method, or the like. In particular, in retractable writing instruments such as knock-type writing instruments and rotary-type writing instruments, the pen tip is always exposed to the outside, unlike cap-type writing instruments. Therefore, since the writing performance when the writing tip is dry is easily affected, it is more preferable to use a surfactant with the above HLB value.

[0060] Specific examples of the surfactant include fatty acids such as oleic acid, stearic acid, and linoleic acid. Silicone surfactants include dimethyl silicone, methylphenyl silicone, polyether-modified silicone, and higher fatty acid ester-modified silicone. Fluorine-based surfactants include perfluorobutyl sulfonate, perfluorocarboxylate, perfluorophosphate, perfluorophosphate-containing compounds, perfluoroalkyl betaine, and perfluoroalkylamine oxide compounds. Phosphate surfactants include polyoxyethylene alkyl ether or polyoxyethylene alkylaryl ether phosphate monoester, polyoxyethylene alkyl ether or polyoxyethylene alkylaryl ether phosphate diester, polyoxyethylene alkyl ether or polyoxyethylene alkylaryl ether phosphate triester, alkyl phosphate ester, alkyl ether phosphate ester, and derivatives thereof.

[0061] Among these, it is preferable to use a phosphate ester surfactant in consideration of lubrication and thickening effects.

[0062] When a phosphate ester surfactant is used, the acid value is preferably 180 (mgKOH / g) or less. This is because the phosphate ester surfactant is more likely to improve lubricity and also more likely to thicken the polyacrylic acid resin. Taking lubricity and thickening effects into consideration, the acid value is preferably 30 (mgKOH / g) or more and 170 (mgKOH / g) or less, and more preferably 70 (mgKOH / g) or more and 160 (mgKOH / g) or less.

[0063] 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.

[0064] Phosphate ester surfactants have a rust-preventing effect. Therefore, when the ball is made of metal, corrosion of the ball is suppressed, maintaining a good writing feel and suppressing wear of the ball seat, which is preferable. In particular, when the ball is made of an alloy containing cobalt, nickel, chromium, or the like, the rust-preventing effect of the phosphate ester surfactant makes these metals less susceptible to corrosion over time, which is preferable. This tendency is particularly pronounced and preferable when the ball material is a cemented carbide ball, particularly when the ball material is a cemented carbide ball containing tungsten carbide as the main component and cobalt, nickel, chromium, or the like as a binder.

[0065] Furthermore, in consideration of lubricity and ink stability over time, it is preferable to use a phosphate ester surfactant having an alkyl group, and it is particularly preferable that the number of carbon atoms contained in the alkyl group be 8 to 18. Taking further consideration into account, it is more preferable that the number of carbon atoms be 10 to 18, and even more preferable that the number of carbon atoms be 12 to 18. This is because if the number of carbon atoms in the alkyl group is too small, lubricity tends to be insufficient, and if the number of carbon atoms is too large, it tends to affect the ink stability over time.

[0066] The content of the surfactant is more preferably 0.1% by mass or more and 5.0% by mass or less, based on the total amount of the ink composition. This is because if it 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. Taking this tendency into consideration, the content of the surfactant 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 even more preferably 0.5% by mass or more and 3.0% by mass or less.

[0067] In the present invention, organic solvents other than alkylene glycol alkyl ethers may be used, specifically, examples of organic solvents commonly used in 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, propargyl alcohol, allyl alcohol, 3-methyl-1-butyn-3-ol, ethylene glycol monomethyl ether acetate, and other higher alcohols.

[0068] Furthermore, the content of the organic solvent is preferably 3% by mass or more and 50% by mass or less of the total amount of the ink composition in consideration of improving solubility, handwriting drying properties, bleeding, etc. In consideration of drying properties at the tip end, it is preferably 5% by mass or more and 50% by mass or less, and more preferably 5% by mass or more and 30% by mass or less.

[0069] (resin) In addition, in the present invention, a resin may be used as an ink viscosity adjuster, to improve ink leakage suppression, improve writing feel, suppress handwriting smearing and dot unevenness, and facilitate improved pigment dispersibility. Examples of resins include polyvinyl butyral resins, ketone resins, polyacetal resins, polyvinyl alcohol resins, cellulose resins, terpene resins, alkyd resins, phenoxy resins, polyvinyl acetate resins, polyvinylpyrrolidone resins, ethylene oxide polymers, 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. Dot unevenness refers to the phenomenon in which a written line is written intermittently as fine dots.

[0070] Among these resins, ketone resins and polyvinyl butyral resins are preferred in consideration of improving ink leakage suppression, improving writing feel, and improving writing performance such as suppressing smeared handwriting and uneven dots, as well as facilitating improved pigment dispersibility. Furthermore, ketone resins are preferred in consideration of improving writing feel and improving writing performance such as suppressing smeared handwriting and uneven dots.

[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, resin particles are preferred for suppressing ink leakage, and acrylic ester resin particles and amino resin particles are also preferred. This is because the resin particles create a physical barrier in the gap between the ball and the inner wall of the tip, thereby suppressing ink leakage. Furthermore, particles partially deform and adhere to each other, resulting in a structure formed by weak aggregation. Forming a structure in the ink that is highly resistant to ink leakage when left stationary enables high ink leakage suppression. Meanwhile, 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, ink fluidity is not impaired during writing, allowing for smooth writing and thick handwriting. Furthermore, resin particles are stable against alkylene glycol alkyl ethers, and therefore are preferably used because they can maintain the ink's stability over time while also imparting high solvent resistance and water resistance to handwriting.

[0073] The smaller the average particle diameter of the resin particles, the more easily the particles adhere to each other, forming a weakly aggregated structure and suppressing ink leakage. From this perspective, the average particle diameter of the resin particles is preferably 5 μm or less, 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 diameter of the resin particles is preferably 2 μm or less, and even more preferably less than 1 μm. On the other hand, if the average particle diameter is too small, the ink leakage suppression effect tends to be poor. Therefore, the average particle diameter of the resin particles is preferably 0.1 μm or more, more preferably 0.3 μm or more. The average particle diameter of the resin particles can be determined by the Coulter Counter method. Specifically, using a Coulter Multisizer™3 (a measuring device manufactured by Beckman Coulter, Inc.), the particle diameter at 50% cumulative volume (D50) of the particle size distribution is measured based on values calibrated using standard samples and other measurement methods. This measurement allows the average particle diameter of the resin particles to be determined.

[0074] Furthermore, examples of resin particles include acrylic acid ester resin particles (polyacrylic acid ester particles) such as acrylic acid ester and methacrylic acid ester (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. Furthermore, amino resin particles are a general term for resins obtained by a condensation reaction between a compound containing an amino group and an aldehyde, and examples include melamine resin particles, benzoguanamine resin particles, urea resin, and aniline aldehyde resin.

[0075] Among these resin particles, it is preferable to use acrylic acid ester resin particles in consideration of stability against alkylene glycol alkyl ethers in the ink and suppression of ink leakage. Furthermore, it is preferable to use methacrylic acid ester resin particles in consideration of the fact that they are more stable in the ink, thereby more easily suppressing ink leakage and improving the ink's stability over time. Furthermore, the alkyl group in the methacrylic acid ester resin particle structure has a small number of carbon atoms, which makes them more stable in the ink. For this reason, it is preferable that the alkyl group has 1 to 6 carbon atoms, and more preferably the alkyl group has 1 to 4 carbon atoms. It is preferable to use methyl methacrylate resin particles (polymethyl methacrylate particles) in consideration of a better ink leakage suppression effect.

[0076] These acrylic acid ester resin particles (polyacrylic acid ester particles) may be used alone or in the form of a mixture or copolymer of two or more kinds. Furthermore, the acrylic acid ester resin particles (polyacrylic acid ester particles) may contain at least acrylic acid ester resin particles, and may be a mixture of acrylic acid ester resin particles and other resins, or a copolymer of acrylic acid ester resin particles and other resins.

[0077] As the acrylic ester resin particles (polyacrylic ester particles), it is preferable to use acrylic ester resin particles having a crosslinked structure, considering the suppression of ink leakage and the improvement of ink stability over time. This is presumably because the crosslinked structure forms a stable particle structure, which makes it easier to stabilize in the ink, and furthermore, it makes it easier to form a stable, weak aggregation structure between the acrylic ester particles, which makes it easier to improve ink leakage suppression. It is preferable to use a methacrylic ester having a crosslinked structure, because it is easier to stabilize in the ink, which makes it easier to improve ink leakage suppression and ink stability over time.

[0078] The resin particles may be spherical or irregularly shaped, but spherical resin particles are preferred in view of the ink leakage suppression effect due to the adhesion between the resin particles. The spherical resin particles referred to here are not limited to true spheres, and may be approximately spherical resin particles or approximately oval spherical resin particles.

[0079] Furthermore, the content of the resin particles is preferably 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 prevent ink leakage, and if it exceeds 10% by mass, the aggregate structure tends to become stronger, which is likely to affect the ink's stability over time, writing feel, and writing performance. Furthermore, taking into consideration the above, the content of the resin particles relative to the total amount of the ink composition is preferably 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 ink composition for ballpoint pens of the present invention is not particularly limited, but when alkylene glycol alkyl ethers or polyacrylic acid resins are used, pseudoplasticity is imparted to the ink, which reduces the ink viscosity during writing and improves writing feel and writing performance such as smearing. -1An ink viscosity of 5000 mPa·s or less (when writing) is preferred. If consideration is given to the writing feel and writing performance (smearing), an ink viscosity of 3000 mPa·s or less is preferred, and even more preferably, an ink viscosity of 2000 mPa·s or less is preferred. On the other hand, if consideration is given to writing performance such as blobbing, bleeding, bleed-through, and drying of handwriting, an ink viscosity of 100 mPa·s or more is preferred, and even more preferably, 200 mPa·s or more is preferred, with 400 mPa·s or more being more preferred.

[0081] In addition, considering ink followability, 20°C, shear rate 0.18 sec -1 The ink viscosity (when stationary) is preferably 50,000 mPa·s or less, and even more preferably 30,000 mPa·s or less. On the other hand, in consideration of suppressing ink leakage, the ink viscosity is preferably 1,000 mPa·s or more, and even more preferably 2,000 mPa·s or more, and even more preferably 3,000 mPa·s or more.

[0082] This is also effective for retractable writing instruments such as knock-type writing instruments and rotary-propelling writing instruments, in which it is necessary to give greater consideration to preventing ink leakage.

[0083] When alkylene glycol alkyl ethers and polyacrylic acid resins are used as in the present invention, the viscosity index n is expressed as S=αD n where S is the shear stress (dyn / cm 2 =0.1 Pa), D is the shear rate (s -1 ), and α is the viscosity coefficient. The viscosity index n can be calculated by measuring the ink viscosity at 20°C using a TA Instruments AR-G2 rheometer (cone plate 40 mm, angle 2°).

[0084] Regarding the viscosity index n, taking into consideration writing performance such as writing feel, smudging, and smearing, it is preferable that the viscosity index n is 0.3 or more and 0.8 or less. Taking into consideration the balance of writing performance such as writing feel, smudging, and smudging, it is preferable that the viscosity index n is 0.35 or more and 0.7 or less, and more preferably 0.4 or more and 0.7 or less.

[0085] (ballpoint pen) Next, a ballpoint pen using the oil-based ballpoint pen ink composition of the present invention will be described.

[0086] 1 is a cross-sectional view of an example of a ballpoint pen 100 according to 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 cylindrical and elongated in an extension direction X. The extension direction X is a direction along a straight line passing through the center of a cross section of the cylindrical ink reservoir 2. In other words, the extension direction X is a direction along the central axis of the cylindrical ink reservoir 2.

[0088] An ink composition 10 for an oil-based ballpoint pen is contained inside the ink reservoir 2. The ink composition 10 for an oil-based ballpoint pen is the ink composition for an oil-based ballpoint pen of the present invention described above. As described above, in this embodiment, the ink composition for an oil-based ballpoint pen is referred to as an ink composition or 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 member that rotatably holds the ball 3. That is, the ballpoint pen tip 4 holds the ball 3 at the tip end, which is one end of the ink reservoir 2 in the extension direction X.

[0090] 2 is an enlarged cross-sectional view of an example of the ballpoint pen tip 4. The ballpoint pen tip 4 includes 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 ink composition 10 for an oil-based ballpoint pen. 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. A coil spring 5 is provided in the ball seat 8, which presses the ball 3 placed on the ball seat 8 toward the inner wall of the tip end 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 end T.

[0092] When writing is performed using the ballpoint pen 100, the ink, which is the oil-based ballpoint pen ink composition 10 that flows out of the ink reservoir 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. By supplying the ink to the ball 3, writing is performed with the ink on paper or the like.

[0093] The ink composition, which is the ink composition 10 for an oil-based ballpoint pen contained in the ink reservoir 2, contains a colorant, alkylene glycol alkyl ethers, and a polyacrylic acid resin, as described above.

[0094] In a ballpoint pen 100 using an ink composition 10 for an oil-based ballpoint pen containing alkylene glycol alkyl ethers and a polyacrylic acid resin, the ink consumption per 100 m of writing distance is preferably greater than 20 mg and less than 100 mg. If the ink consumption per 100 m is 20 mg or less, smeared handwriting and uneven dots are likely to occur, making it difficult to achieve a good writing feel. If the ink consumption per 100 m of writing distance exceeds 100 mg, ink is likely to leak from the gap between the ball 3 and the tip end T, and bleeding is also likely to occur. Taking the above effects into further consideration, the ink consumption per 100 m of the ballpoint pen 100 is preferably 25 mg or more and 90 mg or less, and more preferably 30 mg or more and 80 mg or less.

[0095] Regarding ink consumption, a spiral writing test was conducted using five test samples at a writing speed of 4 m / min on JIS P3201 writing paper at a writing angle of 70° and a writing load of 200 g at 20°C. The average ink consumption per 100 m of writing distance from the initial point of writing, between 0 m and 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] In addition, in order to improve writing performance such as writing feel, blurred handwriting, blobs, uneven dots, and thick handwriting, as well as ink leakage prevention and ink tracking, it is effective to consider the relationship between ink consumption and the diameter of the ball 3.

[0098] Specifically, the ratio of ink consumption (mg) per 100 m writing distance to the diameter (mm) of the ball 3 (ink consumption / diameter of ball 3) is 30 or more. By making this ratio 30 or more, the writing feel is improved, and handwriting is free of smearing or blobbing, resulting in good writing performance.

[0099] Furthermore, this ratio is preferably not more than 150. In particular, from the viewpoint of improving the writing feel, writing performance (suppression of smearing and blobbing), ink tracking ability, and ink leakage suppression, this ratio is preferably from 40 to 140, more preferably from 50 to 120, and particularly preferably from 65 to 100.

[0100] The amount of movement of the ball 3 of the ballpoint pen tip 4 in the extension direction X is preferably greater than 3 μm and less than 25 μm. The amount of movement of the ball 3 in the extension direction X means the distance that the ball 3 can move in the extension direction X relative to the tip body 4A. The amount of movement is sometimes referred to as clearance.

[0101] If the movement amount of the ball 3 in the stretching direction X is 3 μm or less, it is likely to affect writing performance and writing feel, such as blurred handwriting, smudges, and uneven dots. Furthermore, if the movement amount exceeds 25 μm, it is likely to affect smudges, ink tracking performance, and ink leakage prevention. Furthermore, if the movement amount of the ball 3 is within the above range, it is easy to adjust the ratio of ink consumption (mg) per 100 m of writing distance to the diameter (mm) of the ball 3 to the above range of 30 to 150.

[0102] Considering further, the movement amount of the ball 3 in the extension direction X is preferably more than 3 μm and not more than 22 μm, more preferably 5 μm or more and 20 μm or less, and even more preferably 7 μm or more and 18 μm or less.

[0103] In the present invention, the amount of movement of the ball 3 of the ballpoint pen tip 4 in the extension direction X refers to the amount of movement of the ball 3 in the extension direction X of the ballpoint pen tip 4 in the initial state before starting writing.

[0104] The arithmetic mean roughness (Ra) of the surface of the ball 3 of the ballpoint pen tip 4 is preferably 0.1 nm or more and 12 nm or less. This is because if the arithmetic mean roughness (Ra) is less than 0.1 nm, ink does not adhere sufficiently to the surface of the ball 3, and handwriting tends to become smeared and uneven. Furthermore, if the arithmetic mean roughness (Ra) exceeds 12 nm, the surface of the ball 3 becomes too rough, increasing the rotational resistance of the ball 3 and the ball seat 8. This tends to result in a poor writing feel and can further affect writing performance, such as smeared handwriting, blobbing, and uneven handwriting. Furthermore, an arithmetic mean roughness (Ra) of 0.1 nm or more and 10 nm or less is preferable because it allows ink to adhere easily to the surface of the ball 3. Considering this, the arithmetic mean roughness (Ra) of the ball 3 is preferably 2 nm or more and 8 nm or less. The arithmetic mean roughness (Ra) of the ball 3 can be measured using a surface roughness measuring instrument (model SPI3800N manufactured by Seiko Epson Corporation). The arithmetic mean roughness (Ra) is calculated by extracting a reference length from the roughness curve measured with the surface roughness measuring instrument in the direction of the mean line, and averaging the absolute values of the deviations from the mean line of this extracted portion to the measured curve.

[0105] The material used for ball 3 is not particularly limited, but examples include cemented carbide balls mainly composed of tungsten carbide, metal balls such as stainless steel, ceramic balls such as silicon carbide, silicon nitride, alumina, silica, and zirconia, and ruby balls.

[0106] The material of the ballpoint pen tip 4 may be metal, such as stainless steel, nickel silver, brass, aluminum bronze, or aluminum, or resin, such as polycarbonate, polyacetal, or ABS. Considering the wear of the ball seat 8, stability over time, and cost, it is preferable that the ballpoint pen tip 4 have a tip body 4A made of stainless steel.

[0107] By using the ink composition 10 for an oil-based ballpoint pen of the present invention as the ink composition contained in the ink reservoir 2, ink consumption is stable from the beginning to the end of writing. As a result, good writing feel and writing performance (suppression of smearing and blobbing) can be stably obtained. Specifically, the ratio (E:F) of ink consumption E mg to ink consumption F mg is preferably in the following range. Ink consumption E mg is the ink consumption (mg) at the beginning of writing, from 0 m to 100 m. Ink consumption F mg is the ink consumption (mg) 100 m before the end of writing.

[0108] When this ratio (E:F) is in the range of 1:0.7 or more and 1:1.3 or less, it is preferable because it is easy to stably obtain good writing performance (suppression of smearing and smearing) with a good writing feel and handwriting that is less likely to have smearing, blobbing, or uneven dots. From further consideration, this ratio (E:F) is preferably in the range of 1:0.8 or more and 1:1.2 or less, and more preferably in the range of 1:0.9 or more and 1:1.1 or less. [Example]

[0109] The present invention will be described in more detail below with reference to examples, although the present invention is not limited to the following examples.

[0110] Example 1 The ink composition for an oil-based ballpoint pen of Example 1 was prepared by collecting alkylene glycol alkyl ethers, colorant, water, a phosphate ester surfactant (HLB value: 10.5), and an organic amine, heating them to 60°C, and dissolving them using a disper mixer to prepare a base ink. Thereafter, while heating the prepared base ink, a polyacrylic acid resin was added and the mixture was thoroughly mixed and stirred using a homogenizer mixer until a uniform state was achieved, thereby obtaining the ink composition for an oil-based ballpoint pen of Example 1.

[0111] The compounding ratio of the organic amine to the polyacrylic acid resin (organic amine / polyacrylic acid resin) was 1.5 times.

[0112] The specific blending amounts are as follows: When the ink viscosity of Example 1 was measured using a TA Instruments AR-G2 rheometer (cone plate 40 mm, angle 2°), it was found to be 0.18 sec-1 at a shear rate of 0.18 sec-1 in an environment of 20°C. -1 Ink viscosity = 16,500 mPa·s, 20°C environment, shear rate 100 sec -1 The ink viscosity was 800 mPa·s, and the viscosity index n was 0.57.

[0113] Example 1 (ink formulation) Coloring agent (dye, salt-forming dye of basic dye and organic acid) 10.0% by mass Coloring agent (dye, acid dye and organic amine salt-forming dye) 10.0% by mass Alkylene glycol alkyl ethers (solubility parameter (SP value): 10.5 (cal / cm 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, except for changing the ink components, ink compositions 10 for oil-based ballpoint pens of Examples 2 to 43 were obtained in the same manner as in Example 1. Tables 1 to 4 show the measurement and evaluation results.

[0115] Comparative Examples 1 to 6 As shown in Table 4, oil-based ballpoint pen ink compositions of Comparative Examples 1 to 6 were obtained in the same manner as in Example 1, except that the ink components were changed. Table 4 shows the measurement and evaluation results.

[0116] [Table 1]

[0117] [Table 2]

[0118] [Table 3]

[0119] [Table 4]

[0120] Testing and Evaluation Tests and evaluations were carried out using the ballpoint pen 100 described with reference to Figures 1 and 2. Specifically, the ink compositions (0.29 g) for oil-based ballpoint pens 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 rotatably holding a ball 3 was attached to one end of the ink reservoir 2, thereby preparing the ballpoint pen 100.

[0121] The ballpoint pen tip 4 used had a coil spring 5 that pressed the ball 3 against the inner wall of the tip tip T (see Figure 2). The material of the ball 3 was a cemented carbide ball (containing cobalt as a binder) whose main component was tungsten carbide. The diameter of the ball 3 and the arithmetic mean roughness (Ra) of the surface of the ball 3 were as shown in Tables 1 to 4, respectively.

[0122] The following tests and evaluations were carried out using JIS P3201 writing paper as the written test paper. Writing feel: Evaluation was carried out by a sensory test using handwriting. Very smooth... Smooth ○ Slightly less smooth...△ Heavy items ×

[0123] Blurring test (writing test 1): The handwriting was observed after a 100m writing test using a running test machine with a load of 200gf, a writing angle of 70°, and a speed of 4m / min. There are few or no smudges or uneven dots in the handwriting. There are some faint marks and uneven spots in the writing, but they are not a problem for practical use. The handwriting is smudged or uneven, affecting practical use. There are many smudges and uneven marks in the handwriting... ×

[0124] Crying blob test (writing test 2): The handwriting was observed after a 100m writing test using a running test machine with a load of 200gf, a writing angle of 70°, and a speed of 4m / min. There is little or no blob in the handwriting. There are some blemishes in the writing, but it is not a problem for practical use. There are smudges in the handwriting that affect its practical use. There are many tears in the handwriting... ×

[0125] Ink leakage test: The pen was left in an environment of 30°C and 85% RH with the tip facing downwards for 7 days, and ink leakage from the tip was confirmed. No ink droplets at the tip end... The ink droplet at the tip end is within 1 / 4 of the tapered section. The ink droplet at the tip tip is more than 1 / 4 but less than 1 / 2 of the tapered section. The ink droplet at the tip is more than half the size of the tapered part. ×

[0126] In Examples 1 to 43, good performance was obtained in the writing feel, the blur test (writing test 1), the tear-stain test (writing test 2), and the ink leakage test.

[0127] In Examples 30 to 43, pigments were used as colorants, and the pigment dispersibility was good and stable. Furthermore, when fastness was confirmed, Examples 30 to 43, which used pigments, had better fastness than Examples 1 to 29, which did not use pigments.

[0128] Furthermore, the ratio (E:F) of ink consumption amount E mg to ink consumption amount F mg was measured for the ballpoint pens 100 of Examples 1, 2, 3, 16, 25, 36, 37, 38, 39, and 42. As described above, ink consumption amount E mg is the ink consumption amount (mg) from the beginning of writing, 0 m to 100 m. Ink consumption amount F mg is the ink consumption amount (mg) 100 m before the ink runs out.

[0129] The ratios (E:F) 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] In addition, the ink viscosities of Examples 2, 3, 5, 13, 30, and 31 were measured using a TA Instruments AR-G2 viscometer (cone plate 40 mm, angle 2°), 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, 20°C environment, 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, 20℃ environment, 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, 20℃ environment, 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, 20°C environment, 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, 20°C environment, 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, 20°C environment, 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 the writing feel, the blur test (writing test 1), the tear-stain test (writing test 2), and the ink leakage test.

[0133] In addition, using ballpoint pen 100, which is an oil-based ballpoint pen of Examples 1 to 43, ink leakage suppression was checked by leaving the pen tip facing downward in an environment of 30°C and 85% RH, and ink leakage from the tip end was found to be at a level that was not problematic for practical use.

[0134] The ink consumption (mg) per 100 m of writing distance was determined by the spiral writing test described above using the ballpoint pens 100 and the comparative ballpoint pens of Examples 1 to 43. The results obtained are shown in Tables 1 to 4. Tables 1 to 4 also show the A / B ratio, where A (mg) is the ink consumption per 100 m of writing distance and B (mm) is the diameter of the ball 3.

[0135] Furthermore, when the movement amount of the ball 3 in the extension direction X of the ball point pens 100, which are oil-based ball point pens of Examples 1 to 43, and the comparative ball point pens, was measured, the results shown in Tables 1 to 4 were obtained. In Tables 1 to 4, the "ball movement amount" is the movement amount of the ball 3 in the extension direction X.

[0136] Furthermore, as shown in Tables 1 to 4, the order of effectiveness in suppressing ink leakage 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, alkylene glycol alkyl ethers were not used, so the polyacrylic acid resin could not swell and disperse, and sufficient effects were not obtained in the writing feel, the tearing blobbing test (writing property test 2), and the ink leakage test.

[0138] In Comparative Example 2, no polyacrylic acid resin was used, and in Comparative Example 3, fatty acid amide wax was used as a shear thinning agent, but sufficient effects were not obtained in the writing feel, smear test (Writability Test 1), weeping blob test (Writability Test 2), and ink leakage test.

[0139] Comparative Example 4 did not contain any alkylene glycol alkyl ethers, and therefore did not provide sufficient effects in the writing feel, the tear-staining test (writing property test 2), and the ink leakage test.

[0140] Comparative Example 5, which does not contain polyacrylic acid resin, did not achieve sufficient effects in the writing feel, blur test (writing test 1), weeping blob test (writing test 2), and ink leakage test.

[0141] In Comparative Example 6, the ratio of ink consumption (mg) per 100 m writing distance to ball diameter (mm) was less than 30, and sufficient effects were not obtained in the writing feel and blur test (writing performance test 1).

[0142] In addition, when using a retractable writing instrument (retractable ballpoint pen) such as a knock-type writing instrument or a rotary-type writing instrument, the influence of blurred handwriting is likely to occur. For this reason, it is effective to use the ink composition 10 for an oil-based ballpoint pen containing the alkylene glycol alkyl ether and polyacrylic acid resin as in the present invention.

[0143] Furthermore, in order to prevent ink leakage and improve writing performance (reduction of smudged handwriting), the ballpoint pen tip 4 is preferably equipped with a valve mechanism. The valve mechanism presses the ball 3, which is rotatably held at the tip tip T, against the inner wall of the tip tip edge by a coil spring 5 directly or via a pressing body, and the pressing force during writing creates a gap between the inner wall of the tip tip edge and the ball 3, allowing ink to flow out. It is preferable that the valve mechanism closes even the minute gap at the tip tip T when not in use.

[0144] For convenience, the present examples show an example of a direct-fill type ballpoint pen 100 in which the ink composition 10 for an oil-based ballpoint pen is directly contained in the ink reservoir 2. However, the oil-based ballpoint pen of the present invention may also be a writing instrument such as a marking pen or a felt-tip pen in which the barrel is the ink reservoir 2 and the ink composition 10 for an oil-based ballpoint pen is directly contained in the barrel. The oil-based ballpoint pen of the present invention may also be a writing instrument in which a ballpoint pen refill in which the ink composition 10 for an oil-based ballpoint pen is directly contained in the ink reservoir 2 serves as a refill, and the refill is attached to the barrel (exterior).

[0145] Furthermore, for convenience, the present embodiment illustrates the ballpoint pen tip 4 formed by cutting a wire material, but the ballpoint pen tip 4 may be formed by pressing a pipe material. [Industrial Applicability]

[0146] The present invention can be used as a writing instrument, and more specifically, can be widely used as a ballpoint pen, which is a writing instrument of a cap type, a retractable type, or the like. [Explanation of symbols]

[0147] 100 ballpoint pens 10. Ink composition for oil-based ballpoint pens 2 Ink reservoir 3 balls 4 Ballpoint pen tips

Claims

1. an ink reservoir containing an ink composition for an oil-based ballpoint pen, the ink composition comprising a colorant, an alkylene glycol alkyl ether, and a polyacrylic acid resin; a ballpoint pen tip that rotatably holds a ball at one end of the ink reservoir in the extending direction; Equipped with the ratio of ink consumption (mg) per 100 m writing distance to the ball diameter (mm) is 30 or more; The ratio (E:F) of the ink consumption amount E mg at the beginning of writing, from 0 m to 100 m, to the ink consumption amount F mg from 100 m before the end of ink consumption to the end of ink consumption, is in the range of 1:0.8 to 1:1.

2. An oil-based ballpoint pen characterized by:

2. 2. The oil-based ballpoint pen according to claim 1, wherein the ratio is 65 or more and 100 or less.

3. 3. The oil-based ballpoint pen according to claim 1, wherein the amount of movement of the ball in the extension direction is greater than 3 μm and not more than 25 μm.

4. 4. The oil-based ballpoint pen according to claim 1, wherein the ink consumption (mg) per 100 m of writing distance is greater than 20 mg and less than or equal to 100 mg.

5. 5. The oil-based ballpoint pen according to claim 1, wherein the alkylene glycol alkyl ether is an alkylene glycol monoalkyl ether.

6. The oil-based ballpoint pen according to any one of claims 1 to 5, wherein the alkylene glycol moiety of the alkylene glycol alkyl ether has 3 or more and 8 or less carbon atoms.

7. the content of the alkylene glycol alkyl ethers is 50% or more of the total solvent content of the ink composition for oil-based ballpoint pens, 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 ink composition for oil-based ballpoint pens. The oil-based ballpoint pen according to any one of claims 1 to 6,

8. The oil-based ballpoint pen according to any one of claims 1 to 7, characterized in that the content of the polyacrylic acid resin is 0.1% by mass or more and 5.0% by mass or less relative to the total amount of the ink composition for the oil-based ballpoint pen.

9. The oil-based ballpoint pen according to any one of claims 1 to 8, characterized in that the ink composition for the oil-based ballpoint pen contains water, and the content of water relative to the total amount of the ink composition is 1% by mass or more and 10% by mass or less.

10. 10. The oil-based ballpoint pen according to claim 9, wherein the blending ratio of water to the polyacrylic acid resin (water / polyacrylic acid resin) is 0.1 to 20 times by mass.

11. The oil-based ballpoint pen according to any one of claims 1 to 10, characterized in that the blending ratio of the 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.

12. The oil-based ballpoint pen according to any one of claims 1 to 11, characterized in that the carboxyl group content in the polyacrylic acid resin is 40% by mass or more and 80% by mass or less.

13. The ink composition for an oil-based ballpoint pen contains a surfactant, The oil-based ballpoint pen according to any one of claims 1 to 12, wherein the surfactant is one or more selected from the group consisting of fatty acids, phosphate ester surfactants, and fatty acid esters.

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