JP2007327003A - Ink composition for writing utensil - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an ink composition for writing utensil, which achieves all of writing feeling, light resistance of handwriting (handwriting fastness), handwriting intensity and handwriting stability with time at high levels. <P>SOLUTION: The ink composition for writing utensil is obtained by dispersing an aqueous component containing water, a polyhydric alcohol, a thixotropic agent and pigment into an oily component containing a polar solvent and an agent to impart stringiness. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ink composition for a writing instrument.

  Conventionally, dyes have been widely used as colorants for oil-based ballpoint pen inks. However, when a dye is used as a colorant, the light resistance of the handwriting tends to be insufficient. Therefore, in order to improve the light resistance of handwriting, it has been studied to disperse a pigment in oil-based ballpoint pen ink. However, when the pigment is dispersed in the oil-based ballpoint pen ink, other problems such as sedimentation and agglomeration of the pigment with time and writing becomes difficult, and wear of the ball seat occurs.

Among the problems when using such pigments, in order to suppress the wear of the ball seat, for example, in Patent Document 1 below, the pigment is dispersed in advance in an oily component, and an aqueous component containing a lubricant can be used there. An ink composition obtained by solubilization has been proposed.
JP 2004-115611 A

  However, in the ink composition described in the above-mentioned Patent Document 1, problems such as pigment aggregation and non-uniform pigment dispersion have not been sufficiently improved, and problems with stability over time remain. Has been. In addition to the above-mentioned Patent Document 1, various studies have been made on the suppression of the ball seat wear, but most of them increase the ink viscosity instead of suppressing the wear, and the writing density and handwriting concentration. Has the problem of lowering.

  The present invention has been made in view of the above-described problems of the prior art, and is a writing instrument ink that can achieve all of writing quality, light resistance of handwriting (handwriting fastness), handwriting density and stability over time. An object is to provide a composition.

  In order to achieve the above object, the present invention comprises an oily component containing a polar solvent and a spinnability imparting agent, and an aqueous component containing water, a polyhydric alcohol, a thixotropic agent and a pigment dispersed therein. An ink composition for a writing instrument is provided.

  Such an ink composition for writing instruments (hereinafter, simply referred to as “ink composition” in some cases) is prepared by previously containing a pigment in an aqueous component and mixing it with an oil component to form a water droplet comprising an aqueous component in which the pigment is dispersed. Can be obtained as a W / O emulsion ink dispersed in an oil component. According to such an ink composition, by including a pigment, the handwriting is clear and high light resistance can be obtained, and by setting the oily component and the aqueous component to the above-described composition, precipitation or aggregation of the pigment is achieved. Can be sufficiently suppressed, the temporal stability can be improved, and wear of the ball seat by the pigment can also be suppressed. Also, by adding thixotropy by adding thixotropy imparting agent to the aqueous component, the ink viscosity is high at the time of standing, the ink viscosity is lowered at the time of writing, and the smooth writing quality is sufficient while maintaining good temporal stability. Can achieve high handwriting density. Furthermore, since the ink composition contains an aqueous component, even if the viscosity is low, the ink composition does not break through, and it is possible to suppress the crying of the ink on the metal surface of the pen tip and the occurrence of the blur on the paper surface. Note that the ink crying and the blurring on the paper surface are suppressed because the polar solvent in the oily component tends to get wet on the metal surface, while the water in the aqueous component is easily repelled. This is considered to be because the wettability to the metal surface was controlled within an appropriate range.

  In the ink composition for a writing instrument of the present invention, the aqueous component preferably further contains a pigment dispersant. By adding a pigment dispersant to the aqueous component, the dispersibility of the pigment is improved, and the precipitation or aggregation of the pigment over time can be more sufficiently suppressed.

  In the ink composition for a writing instrument of the present invention, the aqueous component preferably further contains a lubricant. By adding a lubricant to the aqueous component, wear of the ball seat due to the pigment can be more sufficiently suppressed. Further, even when a lubricant is used, according to the ink composition of the present invention having the above-described configuration, aggregation of the pigment can be sufficiently suppressed, and good temporal stability can be obtained.

  In the ink composition for a writing instrument of the present invention, the oil component preferably further contains an oil-soluble dye. By adding an oil-soluble dye to the oil component, the handwriting can be made darker and clearer.

  In the ink composition for a writing instrument of the present invention, the ratio of the content of the oil component and the aqueous component is preferably in the range of 6: 4 to 7: 3 by mass ratio. By making the content ratio of the oily component and the aqueous component within the above range, the writing quality and stability over time can be improved, and the occurrence of blurring of the handwriting, crying, fluttering, etc. It can be sufficiently suppressed.

  Moreover, in the ink composition for writing instruments of the present invention, the content of the spinnability imparting agent is preferably 0.5 to 3.0% by mass based on the total amount of the ink composition for writing instruments. When the content of the spinnability imparting agent is within the above range, the emulsion can be further stabilized and the stability over time can be improved, and the ink can have appropriate viscoelasticity. Smooth writing can be achieved. Furthermore, it is possible to more sufficiently suppress the occurrence of blur at the time of writing and the occurrence of sagging at the time of standing.

  Furthermore, in the ink composition for a writing instrument of the present invention, the content of the thixotropic agent is preferably 0.1 to 2.0% by mass based on the total amount of the ink composition for a writing instrument. When the content of the thixotropic agent is within the above range, the ink composition can have an appropriate thixotropy, and a smoother writing feel can be realized. In addition, the emulsion can be further stabilized.

  ADVANTAGE OF THE INVENTION According to this invention, the ink composition for writing tools which can achieve all of writing taste, the light resistance (fastness) of handwriting, the density of handwriting, and stability with time can be provided.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings as the case may be. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant description is omitted.

  The ink composition for a writing instrument of the present invention is obtained by dispersing an aqueous component containing water, a polyhydric alcohol, a thixotropic agent and a pigment in an oily component containing a polar solvent and a spinnability imparting agent. is there. Hereinafter, each component constituting the ink composition will be described.

  The oil component contains at least a polar solvent and a spinnability imparting agent. Here, as a polar solvent, the polar solvent used for oil-based ink for writing instruments can be especially used without a restriction | limiting. Examples of the polar solvent include glycol ethers such as ethylene glycol monophenyl ether, propylene glycol monophenyl ether, propylene glycol dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monobutyl ether, and tripropylene glycol monomethyl ether. And alcohols such as benzyl alcohol, ethylene glycol, triethylene glycol, propylene glycol, and polyethylene glycol. These can be used alone or in combination of two or more. The content of the polar solvent in the oil component is preferably 20 to 60% by mass, more preferably 30 to 50% by mass based on the total amount of the ink composition.

  Examples of the spinnability-imparting agent include polyvinyl pyrrolidone, polyvinyl alcohol, polyethylene oxide, and hydroxypropyl cellulose. These can be used alone or in combination of two or more. By using the spinnability-imparting agent, it is possible to prevent dripping at the time of writing and dripping at the time of standing. Further, the effect of stabilizing the emulsion can be obtained, and the effect of smoothing the writing can be obtained since the ink has an appropriate viscoelasticity.

  The content of the spinnability imparting agent is preferably 0.5 to 3.0 mass%, more preferably 1.0 to 2.0 mass%, based on the total amount of the ink composition. When this content is less than 0.5% by mass, there is a tendency that writing or dripping at the time of standing tends to occur, and when it exceeds 3.0% by mass, the viscosity of the ink composition increases. There is a tendency that the handwriting is blurred or the writing quality is lowered.

  The oil component preferably further contains an oil-soluble dye. Known oil-soluble dyes can be used without particular limitation. Examples of such oil-soluble dyes include direct dyes, acid dyes, basic dyes, and the like. More specifically, for example, Spirit Black 61F, Bali First Violet 1701, Bali First Violet 1704, Bali First Yellow 1109, Bali First Blue 1605, Bali First Blue 1621, Bali First Blue 1623, Bali First Red 1320, Bali First Red 1360, Bali First Red 2320 (above, manufactured by Orient Chemical Industry Co., Ltd.), Eisenspiron Black GMH Special, Eisenspiron Violet C-RH, Eisenspiron Yellow C-GH new, Eisenspiron Blue C-RH Eisenspiron S. P. T. T. et al. Blue-111, Eisenspiron S. P. T. T. et al. Blue-121 (above, manufactured by Hodogaya Chemical Co., Ltd.) and the like. These can be used alone or in combination of two or more. By using an oil-soluble dye, the handwriting can be made dark and clear. Moreover, in the ink composition of this invention, even if it does not add viscosity adjustment resin, it is possible to adjust a viscosity with an oil-soluble dye.

  The content of the oil-soluble dye is preferably 20 to 50% by mass, more preferably 25 to 40% by mass based on the total amount of the ink composition. When the content is less than 20% by mass, the clarity of the handwriting tends to be lowered. When the content exceeds 50% by mass, the viscosity of the ink composition is increased, the writing quality is lowered, and the oil is gradually deteriorated. It tends to cause precipitation of soluble dyes.

  The oily component may further contain other additives in addition to the above materials. Examples of such additives include viscosity modifiers (resins and the like), lubricants, pigments, antioxidants and the like.

  Examples of the viscosity modifier include ketone resin, sulfoamide resin, maleic resin, xylene resin, amide resin, alkyd resin, phenol resin, rosin resin, terpene resin, butyral resin, and the like.

  As the lubricant, for example, higher fatty acids such as oleic acid, phosphate ester lubricants, and the like can be used.

  Examples of the pigment include carbon black, insoluble azo, azo lake, condensed azo, diketopyrrolopyrrole, phthalocyanine, quinacridone, anthraquinone, dioxazine, indigo, thioindigo, quinophthalone, and selenium. Ordinary organic pigments such as isoindolinone can be used.

  The aqueous component contains at least water, a polyhydric alcohol, a thixotropic agent, and a pigment. The conventional low-viscosity oil-based ink composition has a problem that handwriting easily penetrates into paper and easily causes breakthrough. However, according to the ink composition of the present invention, the occurrence of strikethrough is sufficiently caused by containing water. Can be prevented. Here, the content of water is preferably 5 to 30% by mass, more preferably 10 to 20% by mass based on the total amount of the ink composition. When this content is less than 5% by mass, the writing quality tends to decrease, and when it exceeds 30% by mass, the stability over time tends to decrease.

  Examples of the polyhydric alcohol include ethylene glycol, propylene glycol, glycerin, diethylene glycol, and polyethylene glycol. These can be used individually by 1 type or in combination of 2 or more types. By using a polyhydric alcohol, the emulsion can be kept stable.

  The content of the polyhydric alcohol is preferably 5 to 30% by mass, and more preferably 10 to 20% by mass based on the total amount of the ink composition. When the content is less than 5% by mass, the stability of the emulsion tends to decrease. When the content exceeds 30% by mass, the viscosity of the ink composition increases, the writing quality decreases, and the handwriting is blurred. It tends to occur.

  Examples of the thixotropic agent include xanthan gum, locust bean gum, welan gum, gellan gum, guar gum, pectin, carrageenan, carboxyvinyl polymer, gum arabic, tragacanth gum, ramzan gum, gelatin, sodium alginate, carboxymethyl cellulose and the like. These can be used alone or in combination of two or more. By using the thixotropic agent, the ink composition has thixotropy, and the effect of smoothing the writing quality can be obtained. Moreover, the effect which stabilizes an emulsion is also acquired.

  The content of the thixotropic agent is preferably 0.1 to 2.0% by mass, more preferably 0.1 to 0.5% by mass based on the total amount of the ink composition. When the content is less than 0.1% by mass, the thixotropy of the ink composition tends to be lowered and the writing quality tends to be lowered. When the content exceeds 2.0% by mass, the viscosity of the ink composition is increased. The writing taste tends to decrease.

  Known pigments can be used without particular limitation. Examples of such pigments include carbon black, insoluble azo, azo lake, condensed azo, diketopyrrolopyrrole, phthalocyanine, quinacridone, anthraquinone, dioxazine, indigo, thioindigo, quinophthalone, and sulene. Ordinary organic pigments such as isoindolinone can be used. These can be used alone or in combination of two or more. By using the pigment, the handwriting can be made dark and clear, and the light resistance of the handwriting can be made sufficient.

  The content of the pigment is preferably 0.5 to 10% by mass and more preferably 1 to 5% by mass based on the total amount of the ink composition. When the content is less than 0.5% by mass, the density, clarity and light resistance of the handwriting tend to decrease. When the content exceeds 10% by mass, the temporal stability decreases, and pigment aggregation and sedimentation occur. Tends to occur.

  The aqueous component preferably further contains a pigment dispersant. The pigment dispersant is not particularly limited as long as it can disperse the pigment, and for example, one kind of acrylic acid or an ester thereof, methacrylic acid or an ester thereof, maleic acid or an ester thereof is polymerized alone. Or a water-soluble resin obtained by neutralizing a resin copolymerized with styrene, acrylonitrile, vinyl acetate or the like with an alkali metal or an amine, an anionic surfactant, a nonionic surfactant, etc. Is mentioned. Among these, a water-soluble resin is preferable, and specifically, a styrene-maleic acid copolymer is particularly preferable. These can be used alone or in combination of two or more. By using a pigment dispersant, it is possible to suppress sedimentation and aggregation of the pigment over time, and good stability over time can be obtained.

  The content of the pigment dispersant is preferably 0.5 to 5.0% by mass, more preferably 1.0 to 2.0% by mass based on the total amount of the ink composition. When the content is less than 0.5% by mass, the pigment tends to be precipitated or aggregated over time. When the content exceeds 5.0% by mass, the viscosity of the ink composition increases and the writing quality is deteriorated. It tends to decrease.

  The aqueous component preferably further contains a lubricant. Examples of such lubricants include polyalkylene glycol derivatives, fatty acid salts, nonionic surfactants, and phosphate esters. Of these, fatty acid salts are preferred, and specifically potassium oleate is particularly preferred. These can be used alone or in combination of two or more. By using the lubricant, it is possible to suppress wear of the ball seat due to the pigment.

  The content of the lubricant is preferably 0.1 to 3.0% by mass, more preferably 0.3 to 1.0% by mass based on the total amount of the ink composition. When this content is less than 0.1% by mass, the wear-inhibiting effect of the ball seat tends to be reduced, and when it exceeds 3.0% by mass, the temporal stability of the ink composition tends to be reduced. .

  The aqueous component may further contain other additives in addition to the above materials. Examples of such additives include rust preventives, antibacterial agents, humectants, water-soluble dyes, pH adjusters, and the like.

  Examples of the rust inhibitor include benzotriazole, tolyltriazole, octyl phosphate, imidazole, benzimidazole, and ethylenediaminetetraacetate.

  Examples of the antibacterial agent include sodium pentachlorophenol, sodium benzoate, potassium sorbate, sodium dehydroacetate, 1,2-benzisothiazolin-3-one, 2,4-thiazolylbenzimidazole, and paraoxybenzoic acid. Esters can be used.

  As the humectant, for example, urea, thiourea, ethyleneurea and the like can be used.

  As said water-soluble dye, a direct dye, an acidic dye, a basic dye etc. can be used, for example. Among these, as direct dyes, the color index number (hereinafter abbreviated as CI) Direct Black 17, 19, 19, 38, 154, C.I. I. Direct Yellow 1, 4, 12, 29, C.I. I. Direct Orange 6, 8, 26, 29, C.I. I. Direct Red 1, 2, 4, 13, C.I. I. Direct Blue 2, 6, 15, 15, 78, and the like. Examples of acidic dyes include C.I. I. Acid Black 2, 31 and C.I. I. Acid Yellow 3, 17, 23, 73, C.I. I. Acid Orange 10, C.I. I. Acid Red 13, 14, 18, 27, 52, 73, 87, 92, C.I. I. Acid Blue 1, 9, 74, 90 and the like. Examples of basic dyes include C.I. I. Basic Yellow 2, 3 and C.I. I. Basic Red 1, 2, 8, 8, C.I. I. Basic Violet 1, 3, 10, C.I. I. Basic Blue 5, 9, 26 and the like.

  Examples of the pH adjuster include triethanolamine, diethanolamine, monoethanolamine, aqueous ammonia, sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, and the like.

  The ink composition of the present invention can be obtained as a W / O emulsion ink in which water droplets composed of an aqueous component are dispersed in an oily component by mixing the oily component and the aqueous component described above.

  Here, when the diameter of the water droplets dispersed in the oil component is too small, the writing quality tends to be lowered. Therefore, for example, when the ink composition is observed with an optical microscope or the like, the diameter of the water droplet is measured, and the average value of the arbitrary 10 points is set as the average particle diameter of the water droplet, the average particle diameter is 0.1 to 10. It is preferably 0.0 μm, and more preferably 1.0 to 6.0 μm. When the average particle diameter of the water drops is within the above range, particularly smooth writing can be realized. The average particle size of the water droplets can be adjusted mainly by changing the mixing conditions of the oily component and the aqueous component. Moreover, the average particle diameter of water droplets can also be adjusted by changing the respective compositions of the oil component and the aqueous component.

  In the ink composition of the present invention, the ratio of the content of the oil component to the aqueous component (oil component: aqueous component) is preferably in the range of 6: 4 to 7: 3 by mass ratio. If the ratio of the oily component is larger than the above range, it will be close to normal oil-based ink, and the writing quality will deteriorate, and it will tend to cause blurring of handwriting, ink crying, blurring on the paper surface, etc. . On the other hand, when the ratio of the oil component is smaller than the above range, the writing taste and the stability over time are lowered, and the handwriting tends to be blurred.

  The oily component and the aqueous component can be mixed using, for example, a stirrer such as a dissolver, a Henschel mixer, or a homomixer. The stirring conditions are not particularly limited. For example, emulsion ink in which water droplets having the above average particle diameter are uniformly dispersed in the oil component by stirring for 30 to 180 minutes at a rotational speed of 100 to 1000 rpm using a dissolver stirrer. Can be formed.

The ink composition of the present invention preferably has a viscosity of 300 to 2500 mPa · s, and 500 to 1500 mPa · s, measured using a cone CP40 at a temperature of 25 ° C. and a shear rate of 0.75 s ^−1. More preferably. When the viscosity is less than 300 mPa · s, leakage of the ink composition in a stationary state tends to occur, and the stability with time tends to decrease. When the viscosity exceeds 2500 mPa · s, the writing quality tends to decrease. It is in.

  Next, an embodiment of a ballpoint pen using the ink composition of the present invention will be described. FIG. 1 is a schematic cross-sectional view showing the ballpoint pen of the present embodiment. In the ballpoint pen 100 shown in FIG. 1, the ink composition 12 is filled in the ink containing tube 14. A ballpoint pen tip 20 is attached to one end of the ink containing tube 14. The ballpoint pen tip 20 is composed of a ball holder 24 and a ball 26, and is fixed to the ink containing tube 14 by a joint 22. In addition, a backflow preventer 16 is accommodated in the ink containing tube 14 on the side opposite to the ball-point pen tip 20 side of the ink composition 12 in a state adjacent to the ink composition 12. Here, the backflow prevention body 16 is arranged so that no gap is formed between the ink composition 12 and the backflow prevention body 16.

  In the ballpoint pen 100, the ink containing tube 14, the ballpoint pen tip 20, the ink composition 12, and the backflow preventer 16 constitute the core 10, and the core 10 is attached to the main body shaft 18, and further the main body shaft. A tail plug 28 having a vent hole is attached to the rear end of 18 (one end opposite to the ballpoint pen tip 20).

  Hereinafter, although the component of the ball-point pen 100 is demonstrated, the general structure used for a ball-point pen is applicable to structures other than the ink composition 12. FIG.

  As the ink containing tube 14, a resin made of polypropylene, polyethylene, polyethylene terephthalate, nylon, polyacetal, polycarbonate, or the like, or a metal can be used. Further, the shape of the ink containing tube 14 is not particularly limited, and may be a cylindrical shape, for example.

  The backflow prevention body 16 has a function of preventing the ink composition from flowing out (outflow prevention performance), a function of preventing the ink composition from drying up (sealing performance), and the like. Can be used without restriction. Such a backflow preventer 16 includes, for example, a base oil and a thickener. Examples of the base oil include mineral oil, polybutene, silicone oil, glycerin, polyalkylene glycol and the like. Moreover, as a thickener, a metal soap type thickener, an organic type thickener, an inorganic type thickener, etc. are mentioned.

  In addition, when the ball-point pen tip 20 is directed downward, the viscosity of the backflow preventing body 16 and the viscosity between the ink composition 12 and the backflow preventing body 16 are prevented so that the backflow preventing body 16 does not settle in the ink composition 12. It is important to adjust the specific gravity difference. It is important that the backflow preventer 16 has a composition that is incompatible with the ink composition 12.

  As the main body shaft 18 and the tail plug 28, for example, those made of a plastic material such as polypropylene can be used.

  As the joint 22, for example, a joint made of polypropylene, polyethylene, polyethylene terephthalate, nylon, polyacetal, polycarbonate or the like can be used.

  As the joint 22, the ball holder 24 and the ball 26 in the ballpoint pen tip 20, those used in a normal ballpoint pen can be used. The diameter of the ball 26 is preferably 0.3 to 1.2 mm.

  The ballpoint pen 100 of the present embodiment having the above-described configuration can be manufactured by a normal ballpoint pen manufacturing method.

  As mentioned above, although suitable embodiment of the ball-point pen using the ink composition of this invention was described, a ball-point pen is not limited to the said embodiment. For example, the ballpoint pen according to the present invention may not have the main body shaft 18, and the ink containing tube 14 may be the main body shaft as it is. Furthermore, the ballpoint pen according to the present invention is such that the ink composition 12 and the backflow preventer 16 in the ink containing tube 14 are pressurized from the rear end (one end opposite to the ballpoint pen tip 20). It may have a mechanism. Further, the ballpoint pen according to the present invention may not have the backflow prevention body 16.

  In addition, the ink composition of the present invention is not limited to those used for ballpoint pens, and can be used for marking pens including brush pens, writing instruments using a valve mechanism for the ink discharge part, and the like.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example.

(Examples 1-5 and Comparative Examples 1-5)
About an oily component and an aqueous component, each material shown to the following Tables 1-3 was mix | blended separately by the compounding quantity (mass part) shown to the table, and it prepared by mixing with a reciprocating rotary stirrer. Next, using a dissolver stirrer, the aqueous component is added while stirring the oil component, and water droplets composed of the aqueous component are dispersed in the oil component by stirring for 1 hour at room temperature (25 ° C.) and rotation speed of 300 rpm. W / O type emulsion ink compositions of Examples 1 to 5 and Comparative Examples 1 to 5 were obtained.

In addition, the detail of each material in Tables 1-3 is as follows.
Polyvinylpyrrolidone K-90 (trade name): Nippon Shokubai Co., Ltd., spinnability imparting agent.
Oleic acid: Lunac O-LL (trade name), manufactured by Kao Corporation, lubricant.
SPILIT BLACK 61F (trade name): Oil-soluble dye manufactured by Orient Chemical Industry Co., Ltd.
VALIFAST YELLOW 1109 (trade name): Oil-soluble dye, manufactured by Orient Chemical Industry Co., Ltd.
VALIFAST VIOLET 1704 (trade name): Oil-soluble dye, manufactured by Orient Chemical Industry Co., Ltd.
Xanthan gum: Monato gum GS (trade name), manufactured by Dainippon Pharmaceutical Co., Ltd., a thixotropic agent.
Welan gum: KELCO-CRETE (KIC376) (trade name), manufactured by Sanki Co., Ltd., a thixotropic agent.
Locust bean gum: GENUGUM type RL-200-J (trade name), manufactured by Sanki Co., Ltd., a thixotropic agent.
Carboxyvinyl polymer: Carbopol 941 (trade name), manufactured by BFGoodrich, a thixotropic agent.
Antirust agent: Colomin CB (trade name), manufactured by Kyrest Inc.
Antibacterial agent: Slout 99N (trade name), manufactured by Nippon Enviro Chemicals.
Potassium oleate: Nonsar OK-1 (trade name), manufactured by NOF Corporation.
Pigment dispersant (styrene-maleic acid copolymer): SMA1000H Solution (trade name), manufactured by SARTOMER.
AIZEN SPIRON BLACK GMH (trade name): manufactured by Hodogaya Chemical Co., Ltd., an oil-soluble dye.
VALIFAST VIOLET 1701 (trade name): Oil-soluble dye, manufactured by Orient Chemical Industry Co., Ltd.
Ketone resin: Synthetic Resin SK (trade name), manufactured by Huls.

[Measurement of viscosity]
For the ink compositions obtained in Examples 1 to 5 and Comparative Examples 1 to 5, using an E-type viscometer (manufactured by BROOKFIELD, cone: CP40), under conditions of a temperature of 25 ° C. and a shear rate of 0.75 s ⁻¹ . The viscosity was measured. The results are shown in Tables 4-5.

[Measurement of water droplet size]
About the ink composition obtained in Examples 1-5 and Comparative Examples 1-5, the dispersion state of the aqueous component in an oily component was observed using an optical microscope (magnification: 250 times), and the aqueous component was taken from the photograph taken. The diameter of the water droplet consisting of was measured. The diameters of 10 arbitrary water drops were measured, and the average value was determined as the average particle diameter. The results are shown in Tables 4-5.

<Production of ballpoint pen>
Examples 1 to 5 and Comparative Example were placed on a polypropylene cylindrical ink containing tube (inner diameter 4.0 mm) of a ballpoint pen similar to that shown in FIG. 1 having a ballpoint pen tip (ball diameter: 0.7 mm) at the tip. The ink composition obtained in 1-5 was accommodated. Next, 95% by mass of refined mineral oil and a thickener (metal soap, elastomer) on the side opposite to the ball-point pen tip in the ink containing tube (the rear end surface side of the ink composition) so as to be adjacent to the ink composition. A backflow prevention body consisting of 5% by mass was filled. Then, a tail plug was attached to the rear end of the main body shaft of the ballpoint pen to produce a ballpoint pen.

[Evaluation of writing quality]
Writing was performed freehand using the ballpoint pen produced as described above, and writing quality was evaluated based on the following evaluation criteria. The results are shown in Tables 4-5.
A: Very smooth,
B: Smooth
C: Heavy.

[Evaluation of handwriting density]
Using the ballpoint pen produced as described above, writing was performed freehand with a constant writing pressure, and the density of the handwriting was evaluated based on the following evaluation criteria. The results are shown in Tables 4-5.
A: Very dark and clear,
B: Dark and clear
C: Light and unclear.

[Evaluation of handwriting fastness (light resistance)]
Using the ballpoint pen made as described above, write freehand with a certain writing pressure, apply the writing line and the blue scale to direct sunlight, and check whether the writing line fades when the blue scale is grade 3 faded. The relative evaluation compared with the writing line not exposed to sunlight was evaluated by visual observation based on the following evaluation criteria. The results are shown in Tables 4-5.
A: Not fading,
B: Slightly faded,
C: Fading

[Evaluation of blur of handwriting]
The presence or absence of blurring of the handwriting when a loop was written freehand with a constant writing pressure using the ballpoint pen produced as described above was visually evaluated based on the following evaluation criteria. The results are shown in Tables 4-5.
A: No fading occurs at all, and the writing line is very clear.
B: It is hard to cause blur and the handwriting is clear.
C: Blurred and handwriting is unclear.

[Evaluation of crying and fluttering]
Using the ballpoint pen produced as described above, a loop was written by a writing tester (writing angle 70 °, load 200 g, writing speed 4 m / min), the state of the writing line (bottom) and the ink on the pen tip The degree of adhesion (crying out) was visually evaluated based on the following evaluation criteria. The results are shown in Tables 4-5. The term “bottom” means a state where ink at a portion not in contact with paper is gradually collected in the pen tip during writing and falls on the paper and the writing line becomes dirty.
A: There is no button and no ink is attached to the pen tip.
B: There is a slight blur and a small amount of ink is attached to the pen tip.
C: There is a noticeable button and a large amount of ink is attached to the pen tip.

[Evaluation of strikethrough]
Using the ballpoint pen produced as described above, write on the paper surface of the report paper (semi-B5, B ruled 6 mm, plus) with free hand pressure and observe the back of the paper after writing. Then, the write-through of the writing line was visually evaluated based on the following evaluation criteria. The results are shown in Tables 4-5.
A: No oozing,
B: Slightly exuding,
C: Exudation is conspicuous.

[Evaluation of stability over time]
The ball-point pen produced as described above was allowed to stand in an environment of 60 ° C. and 0% RH with the pen tip down. The temporal stability at this time was evaluated based on the following evaluation criteria. The results are shown in Tables 4-5.
A: Writing was possible even after 90 days.
B: Writing was possible from 60 days to less than 90 days,
C: Writing became difficult in less than 60 days.

  As is clear from the results shown in Tables 4 to 5, according to the ink compositions of the present invention (Examples 1 to 5), the writing taste, the darkness of the handwriting, and the handwriting, compared with Comparative Examples 1 to 5. It was confirmed that the properties of fastness, faint handwriting, crying / bottom, back-through, and stability over time can be achieved at a high level in a balanced manner. In addition, the ink composition of Comparative Example 1 was not added with a spinnability imparting agent, so that a smooth writing taste was not obtained, crying and fluttering occurred, and stability over time was also poor. The ink composition of Comparative Example 2 did not have a thixotropy imparting agent, so that a smooth writing feel was not obtained and the temporal stability was also poor. The ink composition of Comparative Example 3 had poor stability over time because no polyhydric alcohol was added. In the ink composition of Comparative Example 4, since no pigment was added, the handwriting was not clear and the light resistance was poor. The ink composition of Comparative Example 5 was prepared in accordance with Example 1 of Patent Document 1, but agglomeration of carbon black was observed over time, stability with time was inferior, and smooth writing Was not obtained. In addition, it is thought that the ink composition of the comparative example 5 has a water droplet particle size too small as a cause of inferior characteristics.

1 is a schematic cross-sectional view showing an embodiment of a ballpoint pen according to the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Center core, 12 ... Ink composition, 14 ... Ink storage pipe, 16 ... Backflow prevention body, 18 ... Main body axis | shaft, 20 ... Ball-point pen tip, 22 ... Joint, 24 ... Ball holder, 26 ... Ball, 28 ... Tail plug 100 ... A ballpoint pen.

Claims (7)

  An ink composition for a writing instrument, wherein an aqueous component containing water, a polyhydric alcohol, a thixotropic agent, and a pigment is dispersed in an oil component containing a polar solvent and a spinnability imparting agent.   The ink composition for a writing instrument according to claim 1, wherein the aqueous component further contains a pigment dispersant.   The ink composition for a writing instrument according to claim 1 or 2, wherein the aqueous component further contains a lubricant.   The ink composition for a writing instrument according to any one of claims 1 to 3, wherein the oil component further comprises an oil-soluble dye.   The ink composition for a writing instrument according to any one of claims 1 to 4, wherein the ratio of the content of the oil component and the aqueous component is in the range of 6: 4 to 7: 3 by mass ratio. object.   The ink for writing instruments as described in any one of Claims 1-5 whose content of the said spinnability imparting agent is 0.5-3.0 mass% on the basis of the ink composition whole quantity for writing instruments. Composition.   The ink composition for a writing instrument according to any one of claims 1 to 6, wherein the content of the thixotropic agent is 0.1 to 2.0% by mass based on the total amount of the ink composition for a writing instrument. object.

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