Ink composition for oil-based ballpoint pen and oil-based ballpoint pen

Abstract

To provide an ink composition for an oily ball point pen which has excellent pigment dispersibility even when reduced in viscosity, and can improve stability of an ink discharge amount of an oily ball point pen, and an oily ball point pen.SOLUTION: An ink composition for an oily ball point pen contains an organic solvent containing a water-soluble organic solvent, a resin, a coloring agent containing a pigment, a dispersant and water, wherein a percentage content of the water in the ink composition for the oily ball point pen is 3 to 10 mass%, the dispersant contains an aliphatic acid and aliphatic amine, and the resin contains at least one of a ketone resin and a maleic resin.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Ink compositions used in oil-based ballpoint pens generally have a high viscosity of 7,000 to 15,000 mPa·s at 25° C. For this reason, oil-based ballpoint pens using such ink compositions tend to write with a heavy feel, requiring a high writing pressure to transfer the ink to paper.

[0003] For this reason, in recent years, ink compositions with reduced viscosity have been proposed in order to achieve a light writing feel when using an oil-based ballpoint pen.

[0004] For example, Patent Document 1 below discloses an oil-based ballpoint pen ink composition containing an organic solvent, a colorant, a resin, and water, with the water content being 0.3% by weight or more and less than 3.0% by weight, and with a viscosity of 1000 to 7000 mPa·s at a shear rate of 5 / sec and at 25°C. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 4270628 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the oil-based ballpoint pen ink composition described in the above-mentioned Patent Document 1 has the following problems.

[0007] That is, the oil-based ballpoint pen ink composition described in Patent Document 1 still has a high viscosity, and therefore, in order to pursue an even lighter writing feel, it was necessary to further reduce the viscosity.

[0008] However, when the viscosity of the oil-based ballpoint pen ink composition is further decreased, the ink discharge amount may decrease or increase when the oil-based ballpoint pen is used for a long time, and the ink discharge amount of the oil-based ballpoint pen may decrease or increase, and there are cases where the line drawing property cannot be sufficiently improved.

[0009] In addition, when the viscosity of the oil-based ballpoint pen ink composition is decreased, if the colorant contains a pigment, the pigment may not be sufficiently dispersed, and color unevenness may occur in the line drawing when the oil-based ballpoint pen is used.

[0010] Therefore, there has been a demand for an ink composition for an oil-based ballpoint pen that has excellent pigment dispersibility even when the viscosity is reduced and can improve the stability of the ink discharge amount of the oil-based ballpoint pen.

[0011] The present invention has been made in view of the above circumstances, and an object thereof is to provide an ink composition for an oil-based ballpoint pen and an oil-based ballpoint pen that have excellent pigment dispersibility even when the viscosity is reduced and can improve the stability of the ink discharge amount of the oil-based ballpoint pen.

Means for Solving the Problems

[0012] As a result of repeated studies to solve the above problems, the present inventor has found that the above problems can be solved by using an organic solvent containing a water-soluble organic solvent as the organic solvent, setting the water content within a specific range, using a specific combination of compounds as the dispersant, and using a specific resin as the resin.

[0013] That is, the present invention is an ink composition for an oil-based ballpoint pen containing an organic solvent containing a water-soluble organic solvent, a resin, a colorant containing a pigment, a dispersant, and water, wherein the water content in the ink composition for an oil-based ballpoint pen is 3 to 10% by mass, the dispersant contains a fatty acid and an aliphatic amine, and the resin contains at least one of a ketone resin and a maleic resin.

[0014] Even when the viscosity of the ink composition for an oil-based ballpoint pen of the present invention is reduced, it has excellent pigment dispersibility and can improve the stability of the ink discharge amount of the oil-based ballpoint pen.

[0015] Regarding the reason why the above effects are obtained by the ink composition for an oil-based ballpoint pen of the present invention, the present inventor speculates as follows.

[0016] That is, generally, the dispersibility (storability) of the pigment deteriorates due to the reduction in the viscosity of the ink composition for an oil-based ballpoint pen. However, in the ink composition for an oil-based ballpoint pen of the present invention, the fatty acid contained in the dispersant, the aliphatic amine contained in the dispersant, and the ketone resin and maleic resin contained in the resin suppress the aggregation and sedimentation of the pigment, and it is considered that the dispersibility of the pigment is maintained well. In addition, when the viscosity of the ink composition for an oil-based ballpoint pen is reduced, generally, when the oil-based ballpoint pen is used for a long time, the ink discharge amount tends to decrease or increase. However, in the present invention, by containing 3 to 10% by mass of water, water molecules adsorb to the ball seat or the ball inside the tip, thereby reducing the contact between the ball seat and the ball. It is considered that it is possible to suppress the decrease or increase in the discharge amount of the ink composition for an oil-based ballpoint pen even when the oil-based ballpoint pen is used for a long time, and it is possible to improve the stability of the ink discharge amount of the oil-based ballpoint pen. From the above, the present inventor speculates that the above effects can be obtained by the ink composition for an oil-based ballpoint pen of the present invention.

[0017] The viscosity of the above ink composition for an oil-based ballpoint pen at 25°C and a shear rate of 7.5 / second is preferably less than 1000 mPa·s.

[0018] In this case, the viscosity of the ink composition can be reduced, and a light writing feel can be achieved when using an oil-based ballpoint pen. Further, even if the viscosity of the ink composition at 25°C and a shear rate of 7.5 / second is reduced to less than 1000 mPa·s, the ink composition of the present invention has better pigment dispersibility and can further improve the stability of the ink discharge amount of the oil-based ballpoint pen.

[0019] In the above ink composition for an oil-based ballpoint pen, it is preferable that the colorant contains a dye and the content of the water-soluble organic solvent in the organic solvent is 15% by mass or more and 80% by mass or less.

[0020] In this case, compared with the case where the content of the water-soluble organic solvent in the organic solvent is less than 15% by mass, it becomes possible to increase the water content, and the stability of the ink discharge amount can be further enhanced. Further, compared with the case where the content of the water-soluble organic solvent in the organic solvent exceeds 80% by mass, the solubility of the dye contained in the colorant in the organic solvent increases, and it is possible to maintain a state in which precipitation, sedimentation, and non-uniformity of the dye in the composition are less likely to occur, and it is possible to less likely generate undissolved solids. Further, the pigment dispersibility can be improved.

[0021] In the above ink composition for an oil-based ballpoint pen, it is preferable that the fatty acid is an unsaturated fatty acid and the aliphatic amine is an unsaturated aliphatic amine.

[0022] The ink composition for an oil-based ballpoint pen of the present invention can have better pigment dispersibility.

[0023] In the above ink composition for an oil-based ballpoint pen, it is preferable that the unsaturated fatty acid is oleic acid and the unsaturated aliphatic amine is oleylamine.

[0024] The ink composition for an oil-based ballpoint pen of the present invention can have particularly excellent pigment dispersibility.

[0025] Furthermore, the present invention relates to an oil-based ballpoint pen containing the above-described ink composition for an oil-based ballpoint pen.

[0026] This oil-based ballpoint pen contains the above-described ink composition for an oil-based ballpoint pen. The above-described ink composition for an oil-based ballpoint pen has excellent pigment dispersibility even when its viscosity is reduced, and can improve the stability of the ink discharge amount of the oil-based ballpoint pen. Therefore, according to the oil-based ballpoint pen of the present invention, during its use, it is possible to achieve a light writing feeling, suppress color unevenness, and improve the stability of the ink discharge amount.

Effects of the Invention

[0027] According to the present invention, there are provided an ink composition for an oil-based ballpoint pen and an oil-based ballpoint pen which have excellent pigment dispersibility even when their viscosities are reduced, and can improve the stability of the ink discharge amount of the oil-based ballpoint pen.

Modes for Carrying Out the Invention

[0028] Hereinafter, embodiments of the present invention will be described in detail.

[0029] <Ink Composition for Oil-Based Ballpoint Pen> The ink composition for an oil-based ballpoint pen of the present invention (hereinafter, may be simply referred to as "ink composition") contains an organic solvent containing a water-soluble organic solvent, a resin, a colorant containing a pigment, a dispersant, and water. Here, the water content in the ink composition is 3 to 10% by mass, and the dispersant contains a fatty acid and an aliphatic amine. The resin contains at least one of a ketone resin and a maleic resin.

[0030] The ink composition of the present invention has excellent pigment dispersibility even when its viscosity is reduced, can improve the stability of the ink discharge amount of the oil-based ballpoint pen, and can improve the line drawing property.

[0031] Hereinafter, the above ink composition will be described in detail.

[0032] (A) Organic Solvent (Organic solvent) The organic solvent includes water-soluble organic solvents. A water-soluble organic solvent refers to an organic solvent with a solubility in water of 10 g / 100 g or more at 25°C, and is used to increase the water content in the ink composition.

[0033] Examples of such water-soluble organic solvents include alcohols such as 3-methoxy-3-methyl-1-butanol, ethoxytriglycol, ethylene glycol, triethylene glycol, propylene glycol, polyethylene glycol, ethanol, methanol, t-butyl alcohol, isopropyl alcohol, 1-propanol, 2-propanol; and ethers such as propylene glycol monomethyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, dipropylene glycol methyl ether, dipropylene glycol monoethyl ether, diethylene glycol monobutyl ether, tripropylene glycol methyl ether, etc. Among them, 3-methoxy-3-methyl-1-butanol is preferred. When the water-soluble organic solvent is 3-methoxy-3-methyl-1-butanol, the ink composition can further improve the stability of the ink ejection amount of an oil-based ballpoint pen.

[0034] (Water-insoluble organic solvent) A water-insoluble organic solvent refers to an organic solvent with a solubility in water of less than 10 g / 100 g at 25°C.

[0035] Examples of such water-insoluble organic solvents include aromatic alcohols such as benzyl alcohol and phenyl glycol; aliphatic alcohols having 8 or more carbon atoms such as octanol; aromatic hydrocarbon solvents such as toluene, xylene, and ethylbenzene; aliphatic hydrocarbon solvents such as n-hexane, n-heptane, isoheptane, n-octane, and isooctane; and cycloparaffin solvents such as methylcyclohexane and ethylcyclohexane. These can be used alone or in combination of two or more. Among them, aromatic alcohols are preferred from the viewpoint of improving the solubility of the dye. Among the aromatic alcohols, benzyl alcohol is preferred. In this case, it is possible to maintain a state in which precipitation, sedimentation, and non-uniformity of the dye in the composition are less likely to occur, and it is possible to make it less likely to generate undissolved solids.

[0036] The content of the water-soluble organic solvent in the organic solvent is not particularly limited and is usually 0 to 80% by mass. The content of the water-soluble organic solvent in the organic solvent is preferably 15% by mass or more and 80% by mass or less, and more preferably 20 to 75% by mass. In this case, compared with the case where the content of the water-soluble organic solvent in the organic solvent is less than 15% by mass, it becomes possible to increase the water content, and it becomes possible to further improve the stability of the ink ejection amount. Therefore, when using an oil-based ballpoint pen, it is possible to achieve both a lighter writing feeling and the stability of the ink ejection amount. Further, compared with the case where the content of the water-soluble organic solvent in the organic solvent exceeds 80% by mass, the solubility of the dye contained in the colorant in the organic solvent increases, and it is possible to maintain a state in which precipitation, sedimentation, and non-uniformity of the dye in the composition are less likely to occur, and it is possible to make it less likely to generate undissolved solids.

[0037] (B) Resin The resin contains at least one of a ketone resin and a maleic resin. By the resin containing at least one of a ketone resin and a maleic resin, the ink composition can have excellent pigment dispersibility, and it is also possible to suppress emulsification even when the ink composition contains water.

[0038] Maleic resin is a resin containing structural units derived from maleic acid or maleic anhydride, and may be a homopolymer or a copolymer.

[0039] Ketone resin is a resin having a ketone group.

[0040] The content rates (unit: mass %) of the ketone resin and the maleic resin in the resin are not particularly limited, but are preferably 70 mass % or more.

[0041] In this case, compared with the case where the content rates of the ketone resin and the maleic resin in the resin are less than 70 mass %, the fastness of the handwriting strokes and the adhesiveness to the writing surface are further improved.

[0042] The content rate of the resin in the ink composition is not particularly limited, but is usually 20 mass % or less. The content rate of the resin in the ink composition is preferably 3 mass % or more. In this case, compared with the case where the content rate of the resin in the ink composition is less than 3 mass %, since the viscosity of the ink composition further increases, it is possible to suppress the dripping of the ink composition when using an oil-based ballpoint pen. Further, the content rate of the resin in the ink composition is preferably 15 mass % or less. In this case, compared with the case where the content rate of the resin in the ink composition exceeds 15 mass %, since it is possible to suppress the viscosity of the ink composition from increasing too much, it is possible to achieve a lighter writing feel when using an oil-based ballpoint pen.

[0043] (C) Colorant (Pigment) The pigment in the colorant is not particularly limited, and examples of the pigment include organic pigments and inorganic pigments. These can be used alone or in combination of two or more.

[0044] Examples of the organic pigment include insoluble azo pigments, phthalocyanine pigments, perylene pigments, quinacridone pigments, diketopyrrolopyrrole pigments, and the like.

[0045] Examples of the inorganic pigment include carbon black, titanium oxide, metal powder, and the like.

[0046] The content rate of the pigment in the colorant is not particularly limited and may be appropriately determined according to the desired color state. However, the present invention exhibits particularly excellent pigment dispersibility when the content rate of the pigment in the colorant is 1 to 5% by mass.

[0047] (Dye) The colorant may further contain a dye.

[0048] Examples of the dye include SPIRIT BLACK 61F, VALIFAST VIOLET 1701, VALIFAST VIOLET 1704, VALIFAST YELLOW1109, VALIFAST YELLOW 1151, VALIFAST YELLOW 1171, OIL YELLOW 107, VALIFAST BLUE 1605, VALIFAST BLUE 1621, VALIFAST BLUE 1623, VALIFAST BLUE 2620, OIL BLUE 613, VALIFAST RED 1308, VALIFAST RED 1320, VALIFAST RED 1364, VALIFAST RED 2320, VALIFAST BLACK 3830, VALIFAST BLACK 3870 (manufactured by Orient Chemical Industries, Ltd.), Aizen Spilon BLACK GHMSpecial, Aizen Spilon VIOLET C-RH, Aizen Spilon YELLOW C-GH new, Aizen Spilon BLUE C-RH, Aizen Spilon S.P.T.BLUE -111, Aizen Spilon S.P.T.BLUE -121 (manufactured by Hodogaya Chemical Co., Ltd.), and the like. These can be used alone or in combination of two or more.

[0049] The content rate of the dye in the colorant is not particularly limited and may be appropriately determined according to the desired color state.

[0050] (D) Dispersant The dispersant is used for dispersing pigments and contains fatty acids and aliphatic amines.

[0051] The fatty acid may be a saturated fatty acid or an unsaturated fatty acid, but an unsaturated fatty acid is preferred. In this case, the ink composition can have better pigment dispersibility than when the fatty acid is a saturated fatty acid.

[0052] The number of carbon atoms of the unsaturated fatty acid is not particularly limited, but is preferably 8 or more. In this case, higher pigment dispersibility can be obtained compared to the case where the number of carbon atoms is less than 8. The number of carbon atoms is more preferably 16 or more.

[0053] However, the number of carbon atoms is preferably 23 or less. In this case, the solubility of the unsaturated fatty acid in the organic solvent becomes higher compared to the case where the number of carbon atoms exceeds 23. The number of carbon atoms is more preferably 23 or less.

[0054] Specific examples of the fatty acid include saturated fatty acids such as caprylic acid, lauric acid, palmitic acid, margaric acid, stearic acid, arachidic acid, henicosylic acid, and behenic acid; and unsaturated fatty acids such as oleic acid, palmitoleic acid, sapienic acid, elaidic acid, vaccenic acid, gadoleic acid, eicosenoic acid, and erucic acid. Among them, oleic acid is preferred as the fatty acid. In this case, the ink composition can have particularly excellent pigment dispersibility.

[0055] The aliphatic amine may be either a saturated aliphatic amine or an unsaturated aliphatic amine, but an unsaturated aliphatic amine is preferred. In this case, the ink composition can have better pigment dispersibility than when the aliphatic amine is a saturated aliphatic amine.

[0056] The number of carbon atoms of the unsaturated aliphatic amine is not particularly limited, but is preferably 8 or more. In this case, higher pigment dispersibility can be obtained compared to the case where the number of carbon atoms is less than 16. The number of carbon atoms is more preferably 16 or more.

[0057] However, the number of carbon atoms is preferably 23 or less. In this case, the solubility of the aliphatic amine in the organic solvent is higher than that when the number of carbon atoms exceeds 23. More preferably, the number of carbon atoms is 23 or less.

[0058] The amino group of the aliphatic amine may be any of a primary amino group, a secondary amino group, or a tertiary amino group, but a primary amino group is preferred. In this case, the solubility of the aliphatic amine in the organic solvent becomes higher.

[0059] Specific examples of the aliphatic amine include saturated aliphatic amines such as cetylamine, stearylamine, and behenylamine; and unsaturated aliphatic amines such as oleylamine, ricinoleylamine, linoleylamine, and dimethyloleylamine. Among them, oleylamine is preferred as the aliphatic amine. In this case, the ink composition can have particularly excellent pigment dispersibility.

[0060] The content ratio R1 (unit: mass%) of the fatty acid in the total of the fatty acid and the aliphatic amine is not particularly limited, but is preferably 30 to 70 mass%. In this case, higher pigment dispersibility can be obtained compared to the case where R1 is less than 30 mass%. Also, higher lubricity can be obtained compared to the case where R1 exceeds 70 mass%.

[0061] The content ratio R2 (unit: mass%) of the fatty acid and the aliphatic amine in the ink composition is not particularly limited, but R2 is preferably 1 to 10 mass%. In this case, streaking during writing is less likely to occur compared to the case where R2 is less than 1 mass%. Also, the solubility of the fatty acid and the aliphatic amine in the organic solvent becomes higher compared to the case where R2 exceeds 1 mass%.

[0062] (E) Water The water may be either tap water or ion-exchanged water, but ion-exchanged water is preferred because of less contamination by impurities.

[0063] The water content in the ink composition is 3 to 10% by mass. In this case, compared with the case where the water content is less than 3% by mass, the stability of the ink ejection amount can be further enhanced. Also, compared with the case where the water content exceeds 10% by mass, even when the ink composition is made to have a lower viscosity, it has better pigment dispersibility, and since water can be solubilized in a liquid mixed with a solvent, dye, resin, etc., it is possible to maintain a state where precipitation, sedimentation, and non-uniformity of the dye hardly occur in the composition, and it is possible to make it difficult for undissolved solids to be generated.

[0064] It is preferable that the water content in the ink composition is 4% by mass or more. In this case, compared with the case where the water content in the ink composition is less than 4% by mass, it becomes possible to further improve the stability of the ink ejection amount of the ink composition.

[0065] More preferably, the water content in the ink composition is 5% by mass or more.

[0066] Also, it is preferable that the water content in the ink composition is 9% by mass or less. In this case, compared with the case where the water content in the ink composition exceeds 9% by mass, since water is more easily solubilized in a liquid mixed with a solvent, dye, resin, etc., it is possible to maintain a state where precipitation, sedimentation, and non-uniformity of the dye hardly occur in the composition, and it is possible to make it difficult for undissolved solids to be generated.

[0067] More preferably, the water content in the ink composition is 8% by mass or less.

[0068] The water content in the ink composition can be measured, for example, by a Karl Fischer moisture meter.

[0069] (F) Other components In addition to the above (A) to (E), the ink composition may contain, as necessary, known additives such as a thread-drawing property imparting agent, a lubricant, and a rust inhibitor, as long as the characteristics of the ink composition are not impaired.

[0070] (G) Viscosity of the ink composition The viscosity of the ink composition at 25°C and a shear rate of 7.5 / second is not particularly limited, but it is preferably less than 1000 mPa·s at 25°C and a shear rate of 7.5 / second.

[0071] In this case, the viscosity of the ink composition can be reduced, and a light writing feel can be achieved when using an oil-based ballpoint pen. Also, even if the viscosity of the ink composition at 25°C and a shear rate of 7.5 / second is reduced to less than 1000 mPa·s, the ink composition of the present invention has better pigment dispersibility and can further improve the stability of the ink discharge amount of the oil-based ballpoint pen.

[0072] More preferably, the viscosity of the ink composition is less than 700 mPa·s. In this case, the viscosity of the ink composition can be further reduced, and a lighter writing feel can be achieved when using an oil-based ballpoint pen. Also, even if the viscosity of the ink composition at 25°C and a shear rate of 7.5 / second is reduced to less than 700 mPa·s, the ink composition of the present invention has even better pigment dispersibility and can further improve the stability of the ink discharge amount of the oil-based ballpoint pen.

[0073] However, more preferably, the viscosity of the ink composition is 100 mPa·s or more. In this case, compared with the case where the viscosity is less than 100 mPa·s, dripping during the use of the oil-based ballpoint pen can be more suppressed, and the writing feel can be improved.

[0074] <Oil-based ballpoint pen> Next, the oil-based ballpoint pen of the present invention will be described. The oil-based ballpoint pen of the present invention contains the above-described ink composition.

[0075] According to this oil-based ballpoint pen, it contains the above-described ink composition for an oil-based ballpoint pen. The above-described ink composition for an oil-based ballpoint pen has excellent pigment dispersibility even when its viscosity is reduced, and can improve the stability of the ink discharge amount of the oil-based ballpoint pen. Therefore, according to the oil-based ballpoint pen of the present invention, it is possible to achieve a light writing feeling, suppress color unevenness, improve the stability of the ink discharge amount, and improve the line drawing property.

Examples

[0076] Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.

[0077] Specifically, the following organic solvents, resins, colorants, dispersants, water, lubricants, and drag reducing agents were used in the examples or comparative examples.

[0078] <Organic solvent> (Water-insoluble organic solvent) Benzyl alcohol Phenoxyethanol (Water-soluble organic solvent) 3-Methoxy-3-methyl-1-butanol Propylene glycol monomethyl ether Ethoxytriethylene glycol

[0079] <Resin> Ketone resin (trade name "TEGO (registered trademark) VariPlus SK", manufactured by Evonik Industries AG) Maleic resin (trade name "Markide No33", manufactured by Arakawa Chemical Industries, Ltd.) Terpene phenol resin (trade name "YS Polyster K125", manufactured by Yasuhara Chemical Co., Ltd.)

[0080] <Colorant> (Dye) VALIFAST VIOLET 10 (trade name, manufactured by Orient Chemical Industries Co., Ltd.) VALIFAST BLACK 3830 (Trade name, manufactured by Orient Chemical Industries, Ltd.) VALIFAST RED1308 (Trade name, manufactured by Orient Chemical Industries, Ltd.) OIL YELLOW107 (Trade name, manufactured by Orient Chemical Industries, Ltd.) (Pigment) Carbon black (Pigment Black 7) Organic pigment (Pigment Red 254)

[0081] <Dispersant> (Fatty acid) Oleic acid (Aliphatic amine) Oleylamine (Other dispersant) Polyvinyl butyral (PVB) resin (trade name "Esrec BL1", manufactured by Sekisui Chemical Co., Ltd.)

[0082] <Water> Ion-exchanged water

[0083] <Lubricant> Phosphate ester (trade name "PriSurf A207H", manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)

[0084] <Yarn-drawing property imparting agent> Polyvinyl pyrrolidone (trade name "PVP K-90", manufactured by Nippon Shokubai Co., Ltd.)

[0085] (Examples 1 to 10 and Comparative Examples 1 to 10) Using a reciprocating rotary stirrer agitator (manufactured by Shimazaki Engineering Co., Ltd.), an organic solvent, a resin, a colorant, a dispersant, water, a lubricant, and a yarn-drawing property imparting agent were mixed under heating at 50 Hz for 5 hours at 60 °C so as to have the contents shown in Tables 1 and 2 to obtain an ink composition.

[0086] <Evaluation of ink composition> Regarding the ink compositions obtained in Examples 1 to 10 and Comparative Examples 1 to 10, the state, viscosity, pigment dispersibility, and stability of ink discharge amount of the ink compositions were evaluated as follows.

[0087] (1) State of the ink composition The ink compositions obtained in Examples 1 to 10 and Comparative Examples 1 to 10 were observed at a magnification of 200 times using a transmission microscope. Then, based on the following criteria, the state of the ink composition was evaluated. (Criteria) 〇 ··· The ink composition is not in an emulsion state × ··· The ink composition is in an emulsion state

[0088] (2) Viscosity of the ink composition Regarding the ink compositions obtained in Examples 1 to 10 and Comparative Examples 1 to 10, the viscosity was measured at 25 °C and a shear rate of 7.5 / second using a digital viscometer (product name "DV-2+PRO", manufactured by Brookfield). The results are shown in Table 1 and Table 2.

[0089] (3) Dispersibility of the pigment Regarding the ink compositions obtained in Examples 1 to 10 and Comparative Examples 1 to 10, the dispersibility of the pigment was evaluated as follows.

[0090] That is, the ink compositions obtained in Examples 1 to 10 and Comparative Examples 1 to 10 were allowed to stand at room temperature for 7 days and then observed at a magnification of 200 times using a transmission microscope. Then, based on the following criteria, the dispersibility of the pigment in the ink composition was evaluated. The results are shown in Table 1 and Table 2. (Criteria) 〇 ··· No aggregation or sedimentation of the pigment is observed × ··· Aggregation or sedimentation of the pigment is observed

[0091] (4) Stability of the ink ejection volume Regarding the ink compositions obtained in Examples 1 to 10 and Comparative Examples 1 to 10, the stability of the ink ejection volume was evaluated as follows.

[0092] That is, first, a stainless steel ball (chip) with a ball diameter of 0.5 mm and a ballpoint pen refill were prepared. Then, the ink compositions obtained in Examples 1 to 10 and Comparative Examples 1 to 10 were filled into the ballpoint pen refills, and five ballpoint pen refills were prepared for each example or comparative example.

[0093] Next, in a thermo-hygrostat chamber at a temperature of 25 °C and a humidity of 60%, a continuous spiral writing test was conducted over 500 m at a load of 200 g, a writing angle of 70°, and a writing speed of 4.0 m / min. At this time, the writing test was performed while gradually rotating the ballpoint pen refill around the axis along its longitudinal direction, under the condition that the ballpoint pen refill makes one rotation every 5 m.

[0094] Then, the ink discharge amount (X) during writing from 0 to 100 m was calculated from the mass of the ballpoint pen refill measured with a precision balance at the time of writing 100 m and the mass of the ballpoint pen refill measured with a precision balance before writing. Similarly, the ink discharge amount (Y) during writing from 400 to 500 m was calculated from the mass of the ballpoint pen refill measured with a precision balance at the time of writing 500 m and the mass of the ballpoint pen refill measured with a precision balance at the time of writing 400 m, and Z (= Y - X) was calculated from the calculated values of X and Y. Then, the average value of "Z" for the five ballpoint pen refills was designated as "Z'".

[0095] Then, based on the following criteria, the stability of the ink discharge amount of the ballpoint pen refill using the ink composition was evaluated. The results are shown in Tables 1 and 2. (Criteria) 〇 ··· The absolute value of Z' is less than 5 mg × ··· The absolute value of Z' is 5 mg or more

[0096]

Table 1

[0097]

Table 2

[0098] From the results shown in Table 1 and Table 2, all of the ink compositions of Examples 1 to 10 were "〇" with respect to the dispersibility of the pigment and the stability of the ink ejection amount. On the other hand, in the ink compositions of Comparative Examples 1 to 10, at least one or more of the dispersibility of the pigment or the stability of the ink ejection amount was "×". Also, all of the ink compositions of Examples 1 to 10 had a sufficiently low viscosity.

[0099] From the above, it was confirmed that the ink composition for an oil-based ballpoint pen of the present invention has excellent pigment dispersibility even when the viscosity is lowered, and can improve the stability of the ink ejection amount of the oil-based ballpoint pen.

Claims

1. An organic solvent containing a water-soluble organic solvent, a resin, a colorant containing a pigment, a dispersant, and water to form an ink composition for an oil-based ballpoint pen, wherein the water content in the ink composition for an oil-based ballpoint pen is 3 to 10% by mass, the dispersant contains a fatty acid and an aliphatic amine, the fatty acid is oleic acid, the aliphatic amine is oleylamine, the content of the water-soluble organic solvent in the organic solvent is 15% by mass or more and 80% by mass or less, the content of the fatty acid in the total of the fatty acid and the aliphatic amine is 30 to 70% by mass, and the resin contains at least one of a ketone resin and a maleic resin, an ink composition for an oil-based ballpoint pen.

2. The ink composition for an oil-based ballpoint pen according to Claim 1, having a viscosity of less than 1000 mPa·s at 25°C and a shear rate of 7.5 / second.

3. An oil-based ballpoint pen containing the ink composition for an oil-based ballpoint pen according to Claim 1 or 2.

Images