Oil-based ballpoint pen

Abstract

To provide an oil-based ballpoint pen writable on a non-permeable surface while allowing thick handwriting, and capable of preventing ink leakage (weighted ink leakage prevention) to achieve an excellent writing quality.SOLUTION: An oil-based ballpoint pen includes a ballpoint pen tip at a tip of an ink housing cylinder, and an ink composition for an oil-based ballpoint pen is housed in the ink housing cylinder. An ink consumption of the oil-based ballpoint pen per 100 m is 80 mg or more. The ink composition for an oil-based ballpoint pen includes a colorant, an organic solvent, a fatty amide and a cellulose derivative.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an oil-based ballpoint pen. [Background technology]

[0002] 2. Description of the Related Art A ballpoint pen, which is provided with a ballpoint pen tip that rotatably holds a ball at the tip of an ink tube, is well known as a writing instrument capable of writing on a permeable surface such as paper.

[0003] On the other hand, as a writing instrument capable of writing on non-permeable surfaces such as plastic materials and craft tape, a marking pen whose brush tip is generally formed of a fiber bundle is known. Marking pens are widely used when writing on the non-permeable surfaces. However, these marking pens have various problems and there is room for improvement.

[0004] A marking pen has a brush tip that is very susceptible to breakage and deformation because it is made of a fiber bundle. When the brush tip is made of a fiber bundle, it comes into surface contact with the writing surface, making it possible to write in bold. Furthermore, when writing on a non-permeable surface, ink can be sufficiently applied according to the movement of the brush tip, since writing does not depend on the rotation of the ball as with a typical ballpoint pen. However, the tip of a fiber bundle is easily broken or deformed by writing, and a constant writing width cannot be guaranteed over long-term use. In particular, when writing on non-permeable surfaces such as plastic materials and craft tape, the brush tip made of a fiber bundle is easily deformed. (Patent Documents 1 and 2)

[0005] In order to solve these problems with marking pens, various attempts have been made to form the brush end not as a fiber bundle but with a ballpoint pen tip made of metal or resin like a ballpoint pen. However, simply changing the brush end from a marking pen structure to a ballpoint pen structure and using a ballpoint pen tip made of metal or resin like a conventional oil-based ballpoint pen (Patent Document 3) does not completely solve the problems on non-permeable surfaces such as plastic materials and craft tape, and new problems arise.

[0006] In addition, with ballpoint pen inks that are set to consume 32 to 47 mg of ink per 200 m (16 to 23.5 mg per 100 m), writing is possible on paper, but the thickness of the writing is not sufficient, and when writing on a non-permeable surface (such as a plastic surface), the ink does not adhere to the non-permeable surface and is not sufficient, resulting in various problems (Patent Document 4). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] "JP Patent Publication No. 2006-056946" [Patent Document 2] "JP Patent Publication No. 2003-176438" [Patent Document 3] "Unexamined Japanese Patent Publication No. 10-95948" [Patent Document 4] "JP 2011-153199 A" Summary of the Invention [Problem to be solved by the invention]

[0008] In light of these issues, even if the ink consumption per 100 m was increased compared to before, simply increasing the ink ejection volume meant that ink leakage (ink dripping) was likely to occur from the gap between the ball and the tip tip, so there was room for improvement. On the other hand, in order to solve the ink leakage problem, if the ink viscosity is increased, the ink consumption is reduced, and the thick handwriting cannot be obtained on paper, and writing on non-permeable surfaces (such as plastic surfaces) is not sufficient. Furthermore, the writing feel is also poor, so there is room for improvement.

[0009] Incidentally, when a ballpoint pen is displayed in a display case, a user takes the ballpoint pen out of the display case, tests it for writing or checks the knock operation, and then returns the ballpoint pen to the display case. At this time, in the case of a ballpoint pen in a cap-off state such as a retractable ballpoint pen, when the ballpoint pen tip is returned to the display case with the ballpoint pen tip protruding, the ball of the ballpoint pen tip abuts against the bottom of the ballpoint pen display case. In this way, as ballpoint pens that have been used for test writing or the like are repeatedly returned to the same display case, many ballpoint pens are piled up on top of the ballpoint pen that was returned first, and as a result, due to the weight of the multiple ballpoint pens piled up, the ball receives the impact when the tip of the ballpoint pen abuts against the bottom of the ballpoint pen display case and moves toward the bottom wall of the ball holding chamber, creating a gap between the ball and the inner wall of the tip, causing ink to drip from the gap, causing ink leakage, soiling the display case, and also soiling the ballpoint pens in other cases. There was a problem that it was necessary to improve the ink leakage suppression when more weight is applied to the ballpoint pen (weighted ink leakage suppression).

[0010] The object of the present invention is to provide an oil-based ballpoint pen that can write on non-permeable surfaces while maintaining a thick handwriting, and that suppresses ink leakage (suppression of ink leakage under weight) even when the ballpoint pen is under weight, such as in the display case described above, thereby providing a good writing feel. [Means for solving the problem]

[0011] In order to solve the above problems, the present invention "1. An oil-based ballpoint pen having a ballpoint pen tip at the tip of an ink reservoir and containing an ink composition for an oil-based ballpoint pen in said ink reservoir, characterized in that the ink consumption of said oil-based ballpoint pen per 100 m is 80 mg or more, and said ink composition for an oil-based ballpoint pen contains a colorant, an organic solvent, a fatty acid amide, and a cellulose derivative. 2. The oil-based ballpoint pen according to claim 1, wherein the organic solvent is a lower alcohol. 3. The oil-based ballpoint pen according to claim 1 or 2, wherein the cellulose derivative is selected from the group consisting of alkyl cellulose, hydroxyalkyl cellulose, and hydroxyalkyl alkyl cellulose. 4. The oil-based ballpoint pen according to any one of items 1 to 3, wherein the ink composition for the oil-based ballpoint pen contains a surfactant. 5. The oil-based ballpoint pen described in item 4, wherein the HLB value of the surfactant is 12 or less. 6. The oil-based ballpoint pen according to any one of items 1 to 5, wherein the amount of movement of the ball in the ballpoint pen tip in the vertical axis direction is 10 to 50 μm. 7. The ink viscosity of the ink composition for oil-based ballpoint pens is 20°C and a shear rate of 200 sec -1 7. The oil-based ballpoint pen according to any one of claims 1 to 6, wherein the viscosity of the ink is 300 mPa·s or less. 8. The oil-based ballpoint pen according to any one of items 1 to 7, wherein the ink composition for the oil-based ballpoint pen has a viscosity index of 0.3 to 0.8. Effect of the Invention

[0012] It is possible to provide an oil-based ballpoint pen that can write not only on paper but also on non-porous surfaces while increasing ink consumption and maintaining a thick handwriting, suppresses ink leakage from the gap between the ball and the tip end (suppression of weighted ink leakage), and provides a good writing feel. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The feature of the present invention is that, in order to produce thick handwriting and enable writing on non-permeable surfaces, even when the ink consumption of the oil-based ballpoint pen is increased to 80 mg or more per 100 m, the ink composition for the oil-based ballpoint pen contains fatty acid amide and cellulose derivative, thereby suppressing ink leakage from the gap between the ball and the tip end (suppression of weighted ink leakage), thereby making it possible to provide a good writing feel.

[0014] In the present invention, it has been found that the combined use of fatty acid amide and cellulose derivative makes it possible to suppress ink leakage from the gap between the ball and the tip end. This is because fatty acid amide imparts pseudoplasticity through interaction with organic solvents and the like, forming a three-dimensional network structure, and further combined use of cellulose derivatives allows the fatty acid amides to be entangled with each other to form a denser three-dimensional network structure, allowing the ink viscosity at rest to be set high, and the ink flow is suppressed, thereby suppressing the ink from seeping out from the gap between the ball and the tip end. Furthermore, the coating formed at the tip end by the cellulose derivative is more effective in suppressing ink leakage, which is particularly effective. In particular, it is possible to obtain the effect of suppressing ink leakage (weighted ink leakage suppression) even when weight is applied to the ballpoint pen, as in the display case described above. In addition, the three-dimensional network structure of the fatty acid amide and cellulose derivative is easily formed into a relatively weak aggregate structure by the cellulose derivative, so that the gel structure is easily dissolved temporarily by impact such as shearing during writing. By lowering the ink viscosity, the ink consumption can be increased, and the ink consumption per 100 m of the ballpoint pen can be made 80 mg or more compared to conventional oil-based ballpoint pens, while at the same time maintaining a good writing feel. Furthermore, when a pigment is used as the colorant, the pigment dispersibility is easily improved due to a high-density three-dimensional network structure, and therefore the colorant can be used more preferably, which is preferable.

[0015] (Fatty acid amide) The fatty acid amide used in the present invention can impart pseudoplasticity and form a three-dimensional network structure through interaction with an organic solvent, etc., thereby increasing the ink viscosity at rest and setting the ink viscosity at writing low. The fatty acid amide can be obtained by reacting a carboxylic acid having 2 to 22 carbon atoms with a diamine having 2 to 12 carbon atoms or a monoamine having 2 to 22 carbon atoms. Examples of monocarboxylic acids having 2 to 22 carbon atoms include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, 12-hydroxystearic acid, oleic acid, behenic acid, etc. These may be used alone or in combination of two or more. Examples of diamines having 2 to 12 carbon atoms include ethylenediamine, 1,4-diaminobutane, hexamethylenediamine, metaxylylenediamine, 1,10-decamethylenediamine, 1,11-undecamethylenediamine, 1,12-dodecamethylenediamine, etc., and examples of monoamines having 2 to 22 carbon atoms include ethylamine, monoethanolamine, propylamine, butylamine, pentylamine, hexylamine, octylamine, decylamine, laurylamine, myristylamine, cetylamine, stearylamine, behenylamine, etc. These may be used alone or in combination of two or more.

[0016] For the fatty acid amide used in the present invention, it is preferable to use a compatible hydrocarbon solvent or alcohol solvent in consideration of stability over time, and more preferably, it is preferable to use an aliphatic hydrocarbon or a lower alcohol (having 1 to 5 carbon atoms). In consideration of stability over time, it is preferable to use an aliphatic hydrocarbon or a lower alcohol having 1 to 3 carbon atoms, more preferably, it is preferable to use an aliphatic cyclohexane or a lower alcohol having 1 to 3 carbon atoms, and it is preferable to use a mixed solution of these. These may be used alone or in combination of two or more kinds. Furthermore, it is preferable to use the fatty acid amide in advance by mixing it with the above-mentioned solvent, swelling it, and making it into a paste in consideration of stability over time. Specific examples of fatty acid amides include the Disparlon series (Kusumoto Chemical Industries, Ltd.) and the Talen series (Kyoeisha Chemical Industries, Ltd.).

[0017] Furthermore, if the content of the fatty acid amide is less than 0.1% by mass, relative to the total amount of the ink composition, it is difficult to form the desired three-dimensional network structure and the effect of suppressing ink leakage cannot be obtained. If it exceeds 5% by mass, the ink viscosity increases, resulting in less ink consumption and a decrease in the darkness of the written lines. Therefore, the content is preferably 0.1 to 5% by mass, and from further consideration, 0.1 to 3% by mass is more preferable, and from further consideration, 0.2 to 1% by mass is more preferable.

[0018] (Cellulose derivatives) The cellulose derivative is preferably selected from alkyl cellulose, hydroxyalkyl cellulose, and hydroxyalkyl alkyl cellulose. Among these, hydroxyalkyl cellulose is preferred in consideration of forming a denser three-dimensional network structure, easily maintaining high ink viscosity at rest, making the gel structure easy to dissolve by the shear of the ball during writing, keeping the ink consumption of 80 mg or more per 100 m of the ballpoint pen, making thick handwriting, making it easy to write on non-permeable surfaces, suppressing ink leakage, and making writing feel good, and more particularly, hydroxypropyl cellulose is preferred in consideration of easily forming a stable three-dimensional network structure in the ink. Among cellulose derivatives, the mass average molecular weight is preferably 2 million or less. If it exceeds the above range, the ink viscosity is likely to be high, making it difficult to maintain the ink consumption amount, and affecting the thick handwriting, writing ability on non-permeable surfaces, and writing feel. From a more detailed consideration, the mass average molecular weight is preferably 1.5 million or less, and more preferably 1.3 million or less. Also, the mass average molecular weight is preferably 100,000 or more. If it is lower than the above range, it is difficult to obtain the desired ink viscosity, which is likely to affect the suppression of ink leakage. From a more detailed consideration, the mass average molecular weight is preferably 300,000 or more, and more preferably 500,000 or more. The mass average molecular weight was determined by GPC using pullulan as a molecular weight standard.

[0019] Furthermore, examples of the cellulose derivatives used in the present invention include hydroxyalkyl celluloses such as carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, and hydroxypropyl ethyl cellulose. Considering that the effects of the present invention can be easily obtained, hydroxypropyl cellulose and hydroxypropyl methyl cellulose are preferred, with hydroxypropyl cellulose being even more preferred. Specific examples of the cellulose derivatives include the HPC series (manufactured by Nippon Soda Co., Ltd.), the Crucel series, and the Sanheck series (manufactured by Sansho Co., Ltd.).

[0020] The content of the cellulose derivative is more preferably 0.01 to 3% by mass based on the total amount of the ink composition. This is because if the content of the cellulose derivative is less than 0.01% by mass, it is difficult to prevent ink leakage, and if it exceeds 3% by mass, the ink viscosity is likely to be high, the ink consumption is insufficient, and the writing performance and writing feel on thick handwriting and non-permeable surfaces are likely to be affected. From further consideration, the content is preferably 0.01 to 1.5% by mass, particularly preferably 0.1 to 1.0% by mass, and further preferably 0.1 to 0.5% by mass.

[0021] When the content of the fatty acid amide relative to the total amount of the ink composition is X and the content of the cellulose derivative relative to the total amount of the ink composition is Y, in consideration of a well-balanced improvement in dark handwriting, writeability on non-permeable surfaces, and ink leakage suppression, the relationship is preferably 0.1≦Y / X≦10, and more preferably 1≦Y / X≦10, and further preferably 4≦X / Y≦10.

[0022] (Ballpoint pen) In addition, the ink consumption of the ballpoint pen per 100 m must be 80 mg or more. The reason for making the ink consumption per 100 m 80 mg or more is to enable thick handwriting and writing on non-permeable surfaces, and a good writing feel can also be obtained. From a more specific perspective, it is preferable to make it 100 mg or more, and more preferably 110 mg or more. In addition, the ink consumption is preferably 300 mg or less, because it is likely to affect the suppression of ink leakage from the gap between the ball and the tip end, and handwriting bleed-through and weeping are likely to occur. From a more specific perspective, the ink consumption is preferably 200 mg or less, and more preferably 180 mg or less. Considering the balance of the above effects, the ink consumption is preferably 100 to 200 mg, and from a consideration of achieving both thicker handwriting, writing on non-permeable surfaces, and suppression of ink leakage, it is preferably 110 to 180 mg. Regarding ink consumption, a spiral writing test is 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 100 g at 20°C. The average ink consumption per 100 m is defined as the ink consumption per 100 m.

[0023] In the present invention, in order to produce thick handwriting while also being able to write on non-permeable surfaces, suppress ink leakage, and improve all aspects of writing performance such as writing feel, handwriting smearing, bleed-through, weeping, bleeding, and drying, it is not sufficient to simply increase the ink consumption, and it is preferable to consider the relationship between the ink consumption A (mg) of the ballpoint pen and the ball diameter B (mm). If the ink consumption per 100 m is A (mg) and the ball diameter is B (mm), ​Regarding the relationship of 100 < A / B < 600 in the present invention, when A / B < 100, the ink consumption is not sufficient with respect to the ball diameter. When writing thick strokes or on non-permeable surfaces, streakiness, repellency of the strokes occur, and a good writing feel cannot be obtained. When A / B > 600, bleeding, blotting, and smudging occur, the drying property of the strokes is also inferior, and ink leakage is likely to occur from the gap between the ball and the tip of the chip. Considering suppressing thicker strokes, writability on non-permeable surfaces, ink leakage, and making the writing feel, streakiness, blotting, smudging, drying property, etc. of the strokes good, it is preferable to have a relationship of 120 ≤ A / B ≤ 450. To balance and achieve the above effects well, 150 ≤ A / B ≤ 400 is preferable, and 180 ≤ A / B ≤ 400 is preferable. Regarding the ball diameter, although not particularly limited, it is set to a ball diameter of about 0.1 to 2.0 (mm). In the present invention, it is preferable to have a ball diameter in the range of 0.3 to 1.6 (mm).

[0024] Also, the movement amount of the ball of the ballpoint pen tip used in the present invention in the longitudinal axis direction of the ball is preferably 10 to 50 μm. This is because when the movement amount of the ball in the longitudinal axis direction is less than 10 μm, it is difficult to ensure the desired ink consumption, and it becomes difficult to obtain thick strokes, writability on non-permeable surfaces, and a good writing feel. On the other hand, when the movement amount of the ball in the longitudinal axis direction exceeds 50 μm, it is likely to affect ink leakage suppression. Further considering this, it is preferably 20 to 50 μm, and more preferably 25 to 45 μm. In the present invention, regarding the movement amount of the ball of the ballpoint pen tip in the longitudinal axis direction of the ball, it is in the form of the ballpoint pen tip of the ballpoint pen in the initial state before writing starts.

[0025] The arithmetic mean roughness (Ra) of the ball surface of the ballpoint pen tip used in the present invention is preferably 0.1 to 12 nm. If the arithmetic mean roughness (Ra) is less than 0.1 nm, the ink is difficult to apply sufficiently to the ball surface, making it difficult to obtain thick handwriting during writing, and line skipping and smearing are likely to occur in the handwriting. If the arithmetic mean roughness (Ra) exceeds 12 nm, the ball surface is too rough, and the rotation resistance of the ball and the ball seat is large, so the writing feel is likely to be poor, and further, the writing performance is likely to be affected by smearing, line skipping, and line unevenness in the handwriting. If the arithmetic mean roughness (Ra) is 0.1 to 10 nm, it is easy to maintain the writing ability on non-permeable surfaces, and more preferably 0.1 to 8 nm. The surface roughness can be measured using a Seiko Epson Corporation model (model name SPI3800N).

[0026] The material used for the balls is not particularly limited, but examples include cemented carbide balls mainly composed of tungsten carbide, metal balls such as stainless steel, ceramic balls such as silicon carbide, silicon nitride, alumina, silica, and zirconia, and ruby ​​balls. Examples of materials for the ballpoint pen tip include metal materials such as stainless steel, nickel silver, brass, aluminum bronze, and aluminum, and resin materials such as polycarbonate, polyacetal, and ABS.

[0027] (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 for use. A dye and a pigment may be used in combination. Examples of dyes include oil-soluble dyes, acid dyes, basic dyes, metal-containing dyes, nigrosine dyes, and various salt-forming dyes thereof, such as salt-forming dyes made from acid dyes and basic dyes, salt-forming dyes made from organic acids and basic dyes, salt-forming dyes made from acid dyes and organic amines, etc. These dyes may be used alone or in combination of two or more kinds. Among these, in consideration of obtaining a dark handwriting, it is preferable to select from among metal complex dyes, nigrosine dyes, and salt forming dyes, and further, in consideration of stability with fatty acid amides and cellulose derivatives, it is preferable to use metal complex dyes and salt forming dyes. Specific examples of dyes include Balifast Black 1802, Balifast Black 1805, Balifast Black 1807, Balifast Violet 1701, Balifast Violet 1704, Balifast Violet 1705, Balifast Blue 1601, Balifast Blue 1605, Balifast Blue 1613, Balifast Blue 1621, Balifast Blue 1631, Balifast Red 1320, Balifast Red 1355, Balifast Red 1360, Balifast Yellow 1101, Balifast Yellow 1151, Nigrosine Base EXBP, Nigrosine Base EX, BASE OF BASIC DYES ROB-B, BASE OF BASIC DYES RO6G-B, BASE OF BASIC DYES VPB-B, BASE OF BASIC DYES VB-B, BASE OF BASIC DYES MVB-3 (manufactured by Orient Chemical Industry Co., Ltd.), Aizen Spiron Black GMH-Special, Aizen Spiron Violet C-RH, Aizen Spiron Blue GNH, Aizen Spiron Blue 2BNH, Aizen Spiron Blue C-RH, Aizen Spiron Red C-GH, Aizen Spiron Red C-BH, Aizen Spiron Yellow C-GNH, Aizen Spiron Yellow C-2GH, SPT Blue 111, SPT Blue GLSH-Special, SPT Red 533, SPT Orange 6, SBN Violet 510, SBN Yellow 530, SRC-BH (manufactured by Hodogaya Chemical Co., Ltd.), and the like.

[0028] As for the pigment, examples thereof include inorganic, organic, and processed pigments, and specific examples thereof 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.

[0029] The content of the colorant is preferably 3.0 to 30.0% by mass based on the total amount of the ink composition. This is because if it is less than 3.0% by mass, it tends to be difficult to obtain thick handwriting, and if it exceeds 30.0% by mass, it tends to affect the solubility in the ink. Taking this tendency into consideration, the content is preferably 5.0 to 25.0% by mass, and more preferably 5.0 to 20.0% by mass.

[0030] (Organic solvent) Examples of the organic solvent used in the present invention include organic solvents that are generally used as inks for oil-based ballpoint pens, such as glycol ether solvents such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol dimethyl ether, ethylene glycol monophenyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, diethylene glycol dimethyl ether, 3-methoxybutanol, and 3-methoxy-3-methylbutanol; glycol solvents such as diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, and ethylene glycol; and alcohol solvents such as benzyl alcohol, methanol, ethanol, 1-propanol, isopropanol, isobutanol, butanol, propargyl alcohol, allyl alcohol, 3-methyl-1-butyn-3-ol, ethylene glycol monomethyl ether acetate, and other higher alcohols.

[0031] Among these organic solvents, it is preferable to use an alcohol solvent, considering that fatty acid amides and cellulose derivatives maintain a stable three-dimensional network structure in the ink. Also, considering the drying property of the ink, it is preferable to use an alcohol solvent with a boiling point of 140°C or less. This is effective because the handwriting drying property is easily improved when writing on a non-permeable surface, and furthermore, it makes it easier to dry the tip of the ballpoint pen tip, and it is easy to suppress ink leakage from the gap between the ball and the tip tip, so from further consideration, an alcohol solvent with a boiling point of 120°C or less is preferable. From further consideration, lower alcohols (5 or less carbon atoms in the molecule) are preferable, and from further consideration, lower alcohols with 3 or less carbon atoms in the molecule are preferable. In order to easily obtain the above-mentioned effects, the content of the alcohol solvent is preferably 50% or more of the total organic solvent content in the ink composition for an oil-based ballpoint pen, and from further consideration, it is preferably 70% or more, and more preferably 90% or more.

[0032] The organic solvent preferably contains an organic solvent having a boiling point of 160°C or more. This is because the high boiling point makes it difficult to volatilize, improves the writing performance of the tip of the ballpoint pen tip, and makes it easy to suppress whitening of handwriting. In particular, when an alcohol solvent having a boiling point of 140°C or less is used as the main agent, the handwriting may be whitened due to rapid drying, so using an organic solvent having a boiling point of 160°C or more is effective in preventing rapid drying. From a more detailed perspective, an organic solvent having a boiling point of 170°C or more is preferable, and a boiling point of 200°C or more is more preferable. Therefore, in order to achieve a good balance between the drying properties of handwriting on non-permeable surfaces, the prevention of ink leakage, writing performance, and the prevention of whitening of handwriting, it is preferable to use a combination of an alcohol solvent with a boiling point of 140°C or less and an organic solvent with a boiling point of 170°C or higher. In order to easily obtain the above-mentioned effects, the content of organic solvents having a boiling point of 160°C or higher is preferably less than 20% of the total organic solvent content in the oil-based ballpoint pen ink composition, and from a more careful consideration, it is preferably less than 10%, and more preferably less than 5%.

[0033] Regarding organic solvents, taking the above into consideration, in order to achieve a good balance between handwriting drying properties on non-permeable surfaces, inhibition of ink leakage, writing performance, and inhibition of handwriting whitening, it is preferable to use a combination of an alcohol solvent with a boiling point of 140°C or less and an organic solvent with a boiling point of 160°C or higher, and it is also preferable to use a combination of a lower alcohol (5 or less carbon atoms in the molecule) and an organic solvent with a boiling point of 170°C or higher.

[0034] In addition, in consideration of improving solubility, handwriting drying properties, writing performance, etc., the content of the organic solvent is preferably 10.0 to 90.0 mass %, preferably 20.0 to 90.0 mass %, and more preferably 40.0 to 70.0 mass %, relative to the total amount of the ink composition.

[0035] (resin) In addition, it is preferable that the ink viscosity adjuster contains a resin to improve adhesion (writing ability) to non-permeable surfaces. Examples of the resin include ketone resins, amide resins, rosin-modified resins, rosin-modified phenolic resins, and other rosin resins, terpene phenolic resins, alkylphenolic resins, polyvinyl butyral resins, styrene-maleic acid resins, ethylene-maleic acid resins, styrene-acrylic resins, acrylic resins, maleic acid resins, cellulose resins, petroleum resins, coumarone-indene resins, polyethylene oxide, polymethacrylic acid esters, ketone-formaldehyde resins, α- and β-pinene-phenol polycondensation resins, and the like. These may be used alone or in combination of two or more.

[0036] Among these resins, when using fatty acid amides or cellulose derivatives, taking into consideration the adhesion of the ink to non-permeable surfaces (writing properties) and the suppression of ink leakage, it is preferable to select from terpene phenol resins, rosin resins, styrene-maleic acid resins, styrene-acrylic resins, and acrylic resins, and from these considerations, terpene phenol resins and styrene-acrylic resins are preferred.

[0037] Regarding the terpene phenol resin, in consideration of the adhesion of the ink to the non-permeable surface and the dissolution stability in the ink, the hydroxyl value of the terpene phenol resin is preferably 300 mgKOH / g or less, and more preferably 30 to 300 mgKOH / g, more preferably 80 to 250 mgKOH / g, and more preferably 100 to 200 mgKOH / g. Here, the "hydroxyl value" means the number of milligrams (mg) of potassium hydroxide equivalent to the hydroxyl groups in 1 g of sample. Moreover, the softening point of the terpene phenol resin is preferably 100 to 160° C. in consideration of the adhesion of the ink to a non-permeable surface and the dissolution stability in the ink, and more preferably 110 to 150° C. Here, the softening point of the terpene phenol resin (C) is a value measured in accordance with JIS K2207. In addition, for styrene-maleic acid resin, styrene-acrylic resin, and acrylic resin, taking into consideration the adhesion of the ink to non-permeable surfaces, the dissolution stability in the ink, and the drying properties of the ink, the acid value is preferably 300 mgKOH / g or more, and from further consideration, the acid value is preferably 50 to 300 mgKOH / g, and more preferably 100 to 250 mgKOH / g. Specific examples of these resins include the YS Polystar U, T, G, S, N, K, and TH series (manufactured by Yasuhara Chemical Co., Ltd.), and the Tamanol series (manufactured by Arakawa Chemical Industries, Ltd.).

[0038] If the total resin content is less than 3% by mass relative to the total amount of the ink composition, it is difficult to obtain sufficient adhesion (writing ability) to non-permeable surfaces and sufficient effect in suppressing ink leakage. If it exceeds 40% by mass, the solubility in the ink is likely to be poor and the ink viscosity will become too high, which will reduce ink consumption and affect the writing feel and writing performance. Therefore, the content is preferably 3 to 40% by mass relative to the total amount of the ink composition, and from further considerations, it is preferably 5 to 30% by mass, and more preferably 10 to 25% by mass.

[0039] In addition to the above-mentioned resins, a stringiness imparting agent may be appropriately used. In particular, polyvinylpyrrolidone resin is preferably contained since it is easy to suppress the generation of excess ink at the tip end by blending polyvinylpyrrolidone resin. If the content of the polyvinylpyrrolidone resin is less than 0.01% by mass relative to the total amount of the ink composition, it is difficult to suppress the generation of excess ink, and if it exceeds 3.0% by mass, the solubility in the ink is easily deteriorated, so it is preferably 0.01 to 3.0% by mass relative to the total amount of the ink composition. Considering the above reasons, it is preferably 0.1 to 2.0% by mass. Specifically, PVP series (manufactured by ISP Japan Co., Ltd.) can be mentioned. These may be used alone or in combination of two or more kinds.

[0040] (Surfactant) In the present invention, in order to enable writing not only on paper but also on non-permeable surfaces, it is preferable to use a surfactant, considering that it improves wettability to non-permeable surfaces, lubricity, and writing performance when the tip of the tip is left in the air and dries. The surfactant is preferably selected from phosphate ester surfactants, silicone surfactants, fluorine surfactants, fatty acids, and fatty acid esters.

[0041] Among surfactants, it is preferable to use a phosphate surfactant or a silicone surfactant, in order to improve wettability to a non-permeable surface, thereby suppressing handwriting repellency, allowing good writing on a non-permeable surface, and improving writing performance.Furthermore, a phosphate surfactant is preferable because it has an effect of easily improving the writing feel, and it is preferable to use a phosphate surfactant and a silicone surfactant in combination.

[0042] Specific examples of phosphate surfactants include those having an alkoxyethyl group (C n H 2n+1 OCH 2 CH 2 O) or alkoxy group (C m H 2m+1O), a phosphate ester having the formula (I) or (II), a phosphate monoester of a polyoxyethylene alkyl ether or a polyoxyethylene alkylaryl ether, a phosphate diester of a polyoxyethylene alkyl ether or a polyoxyethylene alkylaryl ether, a phosphate triester of a polyoxyethylene alkyl ether or a polyoxyethylene alkylaryl ether, an alkyl phosphate ester, an alkyl ether phosphate ester, or a derivative thereof. Specific examples of phosphate ester surfactants include the phoslex series (manufactured by SC Organic Chemical Co., Ltd.), the JP series (manufactured by Johoku Chemical Industry Co., Ltd.), the Plasurf series (manufactured by Daiichi Kogyo Co., Ltd.), the Phosphanol series (manufactured by Toho Chemical Industry Co., Ltd.), and the NIKKOL series (manufactured by Nikko Chemicals Co., Ltd.).

[0043] Among the phosphate ester surfactants, alkoxyethyl groups (C l H 2l+1 O.C. 2 H 4 O) or alkoxy group (C m H 2m+1 O), a phosphoric acid ester of a polyoxyethylene alkyl ether or a polyoxyethylene alkylaryl ether, or a phosphoric acid diester of a polyoxyethylene alkyl ether or a polyoxyethylene alkylaryl ether. Furthermore, among the phosphate ester surfactants, in order to improve the writing performance on non-permeable surfaces and improve the writing feel, alkoxyethyl groups (C l H 2l+1 O.C. 2 H 4 O) or alkoxy group (C m H 2m+1 It is preferable to use a phosphate ester surfactant having an alkoxy group (C m H 2m+1 It is preferable to use a phosphate ester surfactant having the formula (I) or (II).

[0044] The phosphate ester surfactant has an alkoxyethyl group (C l H 2l+1 O.C. 2 H 4 O) or alkoxy group (C m H 2m+1 The carbon chain (l, m) of the terminal alkyl group of the alkoxyethyl group (C l H 2l+1 O.C. 2 H 4 O) or alkoxy group (C m H 2m+1 When the carbon chain (l, m) of the terminal alkyl group of O) has an appropriate length, it is easy to maintain good writing performance on a non-permeable surface, so the carbon chain (l, m) of the terminal alkyl group is preferably 4 to 20, and from a more particular consideration, the carbon chain (l, m) is preferably 12 to 18.

[0045] Specific examples of the silicone surfactant include dimethyl silicone, methylphenyl silicone, polyether-modified silicone, higher fatty acid ester-modified silicone, etc. Among the silicone surfactants, polyether-modified silicone is preferably used in consideration of improving wettability to non-permeable surfaces. Specific examples of silicone surfactants include the BYK series (manufactured by BYK Japan K.K.), the L series, the FZ series (manufactured by Dow Corning Toray Co., Ltd.), the KF series (manufactured by Shin-Etsu Chemical Co., Ltd.), the Silface series (manufactured by Nissin Chemical Industry Co., Ltd.), and the Disparlon series (manufactured by Kusumoto Chemical Co., Ltd.).

[0046] Regarding the HLB value of the surfactant, in consideration of improving wettability to non-permeable surfaces, writing performance, and writing feel, the HLB value is preferably 12 or less, and more preferably 9 or less. Furthermore, in consideration of ink stability over time, the HLB value is preferably 3 or more, and more preferably 5 or more. The HLB value used in the present invention can be determined by the Griffin method, Kawakami method, or the like.

[0047] The content of the surfactant is more preferably 0.1 to 5.0% by mass relative to 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 wettability and lubricity to non-permeable surfaces, and if it exceeds 5.0% by mass, the ink tends to become unstable over time. Taking this tendency into consideration, the content is preferably 0.3 to 4.0% by mass relative to the total amount of the ink composition, and even more preferably 0.5 to 3.0% by mass.

[0048] (Organic amine) In the present invention, in consideration of the stability of the ink components in the ink, it is preferable to use an organic amine. Examples of the organic amine include amines having ethylene oxide such as oxyethylene alkylamines and polyoxyethylene alkylamines, alkyl amines such as laurylamine and stearylamine, and aliphatic amines such as dimethyl alkyl amines such as distearylamine, dimethyl laurylamine, dimethyl stearylamine, and dimethyl octylamine, and among them, in consideration of the stability in the ink, amines having ethylene oxide and dimethyl alkyl amines are preferable. In particular, when a phosphate surfactant is used, it is preferable because it is stabilized in the ink by neutralization, and the effect of the phosphate surfactant is easily obtained.

[0049] Regarding the reactivity of the organic amines with other components in the ink, primary amines are the most reactive, followed by secondary amines and tertiary amines, and therefore, in consideration of the ink stability over time, it is preferable to use secondary amines or tertiary amines. These may be used alone or in combination of two or more kinds.

[0050] Furthermore, the total amine value of the organic amine is preferably 70 to 300 (mgKOH / g) in consideration of the stability with the fatty acid amide, cellulose derivative, colorant and other components. If it exceeds 300 (mgKOH / g), the reactivity is strong and it easily reacts with the above components, so the ink stability over time is likely to be poor. If the total amine value is less than 70 (mgKOH / g), the ink stability over time is likely to be affected. If the stability with the above components is more important, the range of 100 to 300 (mgKOH / g) is preferable, and if the stability is more important, the range of 150 to 300 (mgKOH / g) is preferable. 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.

[0051] The content of the organic amine is preferably 0.1 to 10.0 mass% based on the total amount of the ink composition, taking into consideration the stability with the ink components, and furthermore, taking into consideration the neutralization of surfactants such as phosphate ester surfactants, the content is preferably 0.1 to 5.0 mass%, and more preferably 0.3 to 3.0 mass%.

[0052] In addition, other additives such as a colorant stabilizer, a plasticizer, a chelating agent, an antifoaming agent, water, etc. may be used as appropriate. These may be used alone or in combination of two or more kinds.

[0053] The ink viscosity of the ink composition for ballpoint pens of the present invention is not particularly limited. However, when a fatty acid amide or a cellulose derivative is used, the ink viscosity during writing can be reduced by imparting pseudoplasticity, and the ink consumption can be set to 80 mg or more, making it possible to write thick lines or on non-permeable surfaces, providing a good writing feel, and making it easy to improve writing properties such as blurring. In this regard, the ink viscosity is preferably set to 20° C. and a shear rate of 200 sec. -1The ink viscosity (when writing) is preferably 300 mPa s or less, and considering darker handwriting and the ability to write on non-permeable surfaces, the ink viscosity is preferably 200 mPa s or less, and even more preferably 150 mPa s or less. Considering writing properties such as handwriting drying speed, prevention of handwriting bleed-through, and bleeding, the ink viscosity is preferably 10 mPa s or more, and even more preferably 20 mPa s or more. In addition, when using fatty acid amides and cellulose derivatives, taking into consideration the suppression of ink leakage and ink tracking (setting a large amount of ink consumption), it is recommended to use a temperature of 20°C and a shear rate of 1.0 sec. -1 The ink viscosity (at rest) is preferably 300 mPa·s or more, and from further consideration, 800 mPa·s or more is preferable, and 1000 mPa·s or more is more preferable. This is also effective for retractable writing instruments such as knock-type writing instruments and rotary-type writing instruments, in which it is necessary to give special consideration to preventing ink leakage.

[0054] In the case of using fatty acid amides and cellulose derivatives as in the present invention, the viscosity index n is 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 viscometer, RVDVII+Pro CP-42 spindle, manufactured by Brookfield Corporation. With regard to the viscosity index n, taking into consideration writing properties such as thick handwriting, writing ability on non-permeable surfaces, writing feel, handwriting bleed-through, and smearing, the viscosity index n is preferably 0.3 to 0.8, and taking into consideration the balance of the above effects, the viscosity index n is preferably 0.4 to 0.7, and more preferably 0.4 to 0.6.

[0055] Example 1 The ink composition for an oil-based ballpoint pen in Example 1 uses a dye as a colorant, a lower alcohol, ethylene glycol monophenyl ether, a fatty acid amide, and a cellulose derivative as an organic solvent, a phosphate ester surfactant having an alkoxyl group, a polyether-modified silicone, an organic amine, and a terpene phenol resin as a surfactant, and a predetermined amount of these was weighed out and heated to 60°C, and then completely dissolved using a Disper stirrer to obtain an ink composition for an oil-based ballpoint pen. The specific blending amounts are as follows:

[0056] Example 1 (ink formulation) Colorant (metallic dye) 10.0% by mass Lower alcohol (mixture of ethanol (boiling point 79°C) and isopropyl alcohol (boiling point 82°C)) 64.5% by mass Organic solvent (ethylene glycol monophenyl ether, boiling point 245°C) 3.0% by mass Fatty acid amide (active ingredient: 20%, fatty acid amide previously swollen in a mixture of aliphatic hydrocarbon and lower alcohol having 1 to 3 carbon atoms) 5.0% by mass Cellulose derivative (hydroxyalkyl cellulose, mass average molecular weight: 1 million) 0.2% by mass Phosphate ester surfactant (alkoxyl group (C m H 2m+1 O): Phosphate ester surfactant having m=18) 1.0% by mass Silicone surfactant (polyether modified silicone, HLB value: 6) 0.3% by mass Organic amine (polyoxyethylene alkylamine) 2.0% by mass Terpene phenol resin (hydroxyl value: 160 mg KOH / g) 14.0% by mass

[0057] Examples 2 to 22 As shown in Table 1, except for changing the ink components, oil-based ballpoint pen ink compositions of Examples 2 to 22 were obtained in the same manner as in Example 1. The measurement and evaluation results are shown in the table. The measurements were performed using a Brookfield Viscometer RVDVII+Pro CP-42 spindle at a shear rate of 1.0 sec at 20°C. -1 , shear rate 200sec -1 The ink viscosities of Examples 1 to 7 were measured and the viscosity index n was calculated, with the following results being obtained. Example 1 Shear rate 1.0sec -1 Ink viscosity = 1400mPa·s Shearing rate 200sec -1 Ink viscosity = 110 mPa s Viscosity index n = 0.52 Example 2 Shear rate 1.0sec -1 Ink viscosity = 2400mPa·s Shearing rate 200sec -1 Ink viscosity = 110 mPa s Viscosity index n = 0.42 Example 3 Shear rate 1.0sec -1 Ink viscosity = 1800mPa·s Shearing rate 200sec -1 Ink viscosity = 96 mPa s Viscosity index n = 0.45 Example 4 Shear rate 1.0sec -1 Ink viscosity = 1800mPa·s Shearing rate 200sec -1 Ink viscosity = 94 mPa s Viscosity index n = 0.44 Example 5 Shear rate 1.0sec -1 Ink viscosity = 750 mPa·s Shearing rate 200sec -1 Ink viscosity = 45 mPa s Viscosity index n = 0.46 Example 6 Shear rate 1.0sec -1 Ink viscosity = 400mPa·s Shearing rate 200sec -1 Ink viscosity = 95 mPa s Viscosity index n = 0.73 Example 7 Shear rate 1.0sec -1 Ink viscosity = 600mPa·s Shearing rate 200sec -1 Ink viscosity = 170 mPa s Viscosity index n = 0.76

[0058] Comparative Examples 1 to 6 As shown in the table, except that the ink components were changed, the ink compositions for oil-based ballpoint pens of Comparative Examples 1 to 6 were obtained in the same manner as in Example 1. The measurement and evaluation results are shown in the table. The measurements were performed using a Brookfield Viscometer RVDVII+Pro CP-42 spindle at a shear rate of 1.0 sec at 20°C. -1 , shear rate 200sec -1 The ink viscosities of Comparative Examples 1 to 3 were measured and the viscosity index n was calculated, yielding the following results. Comparative Example 1 Shear rate 1.0sec -1 Ink viscosity = 10 mPa·s Shearing rate 200sec -1 Ink viscosity = 15 mPa·s Comparative Example 2 Shear rate 1.0sec -1 Ink viscosity = 1250 mPa·s Shearing rate 200sec -1 Ink viscosity = 50 mPa s Viscosity index n = 0.39 Comparative Example 3 Shear rate 1.0sec -1 Ink viscosity = 3000mPa·s Shearing rate 200sec -1 Ink viscosity = 80 mPa s Viscosity index n = 0.31 [Table 1] [Table 2] [Table 3]

[0059] Testing and Evaluation The ink compositions (1.0 g) for oil-based ballpoint pens prepared in Example 1 and Comparative Example 1 were filled into refills for oil-based ballpoint pens equipped with ballpoint pen tips (movement of ball in the vertical axis direction: 35 μm, arithmetic mean roughness (Ra) of ball surface: 1 nm) that rotatably hold a ball with a ball diameter of φ0.38 mm in an ink storage tube (polypropylene), to prepare oil-based ballpoint pens. Similarly, in Examples 2 to 22 and Comparative Examples 2 to 6, the ink compositions (1.0 g) for oil-based ballpoint pens prepared were filled into refills for oil-based ballpoint pens equipped with ballpoint pen tips with tip specifications changed as shown in the table in an ink storage tube (polypropylene), to prepare oil-based ballpoint pens. The following tests and evaluations were performed using JIS P3201 writing paper as the writing test paper. The ink consumption per 100 m of Example 1 was 120 mg / 100 m when a spiral writing test was carried out with an oil-based ballpoint pen.

[0060] Darkness of handwriting: JIS P3201 writing paper was used as the writing test paper, and handwritten marks were visually evaluated. Thick and clear handwriting...◎ Thick handwriting: ○ The handwriting is thick enough that it does not cause any problems for practical use. Light handwriting: ×

[0061] Weighted ink leakage prevention test: A 40g weight was attached to the ballpoint pen, with the ballpoint pen tip protruding and pointing downwards, and the ball of the ballpoint pen tip was kept in contact with the bottom of a ballpoint pen display case. The pen was left for one day in an environment of 20°C and 65% RH, and any ink leakage from the tip was confirmed. Almost no ink leakage from the tip end...◎ Ink leakage from the tip tip is not a problem in practice. Ink leakage from the tip end is a practical problem... ×

[0062] Test for writing on non-permeable surface: A handwritten mark was written on a polyethylene terephthalate (PET) sheet, and the mark was visually evaluated. The writing lines are slightly chipped or faded, but still have no problems in practical use. The writing lines are chipped or faded, but still usable. The written lines are repelled or discolored, and there are concerns about their practical use. ×

[0063] Test for bleed-through of handwriting: JIS P3201 writing paper was used as the test paper, and handwritten characters were visually evaluated. No bleed-through...◎ There is some bleed through, but no practical problems. There is bleed-through and there are concerns about practical use... ×

[0064] Writing feel: Evaluation was performed by a sensory test using handwriting. Very smooth...◎ Something that is smooth Slightly inferior smoothness: △ Heavy objects ×

[0065] In Examples 1 to 22, good performance was obtained in terms of thickness of writing, weighted ink leakage inhibition test, writing ability test on non-permeable surface, writing strike-through test, and writing feel. In particular, good performance was obtained in the weighted ink leakage inhibition test, which is a stricter condition than the conventional ink leakage inhibition test. In Examples 1 to 22, as a writing performance test, after handwriting, the pen was left in an environment of 20 or 65% RH for 30 minutes with the tip end protruding, and then handwriting was performed again. Good performance was obtained. Furthermore, the pigment dispersibility of the pigment ink of Example 22 was practically satisfactory.

[0066] In Comparative Examples 1 to 4, the fatty acid amide and the cellulose derivative were not used in combination, and therefore the ink leakage suppression was poor. In Comparative Example 5, gelation did not proceed smoothly and ink could not be produced, so that testing and evaluation were not possible. In Comparative Example 6, the ink consumption was as low as less than 80 mg, so the thickness of the handwriting was insufficient, and the writing feel was poor in the writing test on the non-permeable surface.

[0067] Furthermore, when using a retractable oil-based ballpoint pen (retractable ballpoint pen) such as a knock-type oil-based ballpoint pen or a twist-type oil-based ballpoint pen, ink leakage suppression performance is one of the most important performance characteristics, so it is effective to use an ink composition for oil-based ballpoint pens containing a fatty acid amide and a cellulose derivative as in the present invention, which can suppress ink leakage from the gap between the ball and the tip end and achieve good ink leakage suppression performance as in the present invention.

[0068] In order to prevent ink leakage and improve writing performance (reduction in smudges), it is preferable to provide a valve mechanism in which the ball, which is rotatably held at the tip of the ballpoint pen tip, is pressed against the inner wall of the tip edge by a coil spring directly or via a pressing body, creating a gap between the ball and the inner wall of the tip edge by the pressing force during writing, allowing ink to flow out, and to close the tiny gap at the tip when not in use.

[0069] In addition, in this embodiment, for convenience, an oil-based ballpoint pen in which an oil-based ballpoint pen refill in which an ink composition for an oil-based ballpoint pen is directly accommodated in the barrel is exemplified, but the oil-based ballpoint pen of the present invention may be a direct-loading type ballpoint pen or an oil-based ballpoint pen in which the barrel is an ink-accommodating barrel and the ink composition for an oil-based ballpoint pen is directly accommodated in the barrel. In addition, in this embodiment, for convenience, a ballpoint pen tip formed by cutting a wire material is exemplified, but a ballpoint pen tip formed by pressing a pipe material may also be used.

[0070] In addition, in this embodiment, an oil-based ballpoint pen in which a ballpoint pen refill containing an ink composition for an oil-based ballpoint pen in an ink holding tube is disposed in the barrel has been exemplified, but the oil-based ballpoint pen of the present invention may be a direct-loading type oil-based ballpoint pen in which the barrel itself is the ink holding tube and the ink composition for an oil-based ballpoint pen is directly held in the barrel, or may have a structure in which the ink holding tube contains an ink composition for an oil-based ballpoint pen (ballpoint pen refill) and is used as is as a ballpoint pen. [Industrial Applicability]

[0071] INDUSTRIAL APPLICABILITY The present invention can be used as an oil-based ballpoint pen, and more specifically, can be widely used as an oil-based ballpoint pen such as a cap type or a retractable type.

Claims

1. An oil-based ballpoint pen having a ballpoint pen tip at the tip of an ink reservoir, and an ink composition for an oil-based ballpoint pen contained in the ink reservoir, wherein the ink consumption of the oil-based ballpoint pen per 100 m is 80 mg or more, and the ink composition for an oil-based ballpoint pen comprises a colorant, an organic solvent, a fatty acid amide, a cellulose derivative, and a terpene phenol resin having a hydroxyl value of 80 to 250 mgKOH / g, and wherein the content of the fatty acid amide relative to the total amount of the ink composition is X and the content of the cellulose derivative relative to the total amount of the ink composition is Y, such that the relationship between the fatty acid amide content and the cellulose derivative content satisfies 4≦X / Y≦10.

2. 2. The oil-based ballpoint pen according to claim 1, wherein the organic solvent is a lower alcohol.

3. 3. The oil-based ballpoint pen according to claim 1, wherein the cellulose derivative is selected from the group consisting of alkyl cellulose, hydroxyalkyl cellulose, and hydroxyalkyl alkyl cellulose.

4. 4. The oil-based ballpoint pen according to claim 1, wherein the ink composition for the oil-based ballpoint pen contains a phosphate ester surfactant.

5. 5. The oil-based ballpoint pen according to claim 4, wherein the HLB value of the surfactant is 12 or less.

6. The oil-based ballpoint pen according to any one of claims 1 to 5, characterized in that the amount of movement of the ball of the ballpoint pen tip in the vertical axis direction is 10 to 50 µm.

7. The ink viscosity of the ink composition for oil-based ballpoint pens is 20° C. at a shear rate of 200 sec. －１ 7. The oil-based ballpoint pen according to claim 1, wherein the viscosity of the ink is 300 mPa·s or less.

8. 8. The oil-based ballpoint pen according to claim 1, wherein the ink composition for the oil-based ballpoint pen has a viscosity index of 0.3 to 0.8.

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