JP2017119839A - Water-based ink composition for writing utensil and writing utensil using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water-based ink composition for writing utensils, which has good redispersibility without forming a hard cake and excellent stability with lapse of time and exhibits good writing property, color developability and brilliancy on permeable and non-permeable recording medium, and writing utensils using the above composition.SOLUTION: The water-based ink composition for writing utensils comprises silica-coated metal pigment particles, an aggregation controlling agent and a solvent, in which a compounding ratio of the aggregation controlling agent is 0.01 to 5.0 times on a mass basis with respect to the silica-coated metal pigment particles. Writing utensils using the above composition are also disclosed.SELECTED DRAWING: None

Description

  The present invention relates to a water-based ink composition for a writing instrument, and a writing instrument using the same.

  Conventionally, as a water-based ink composition for a writing instrument capable of leaving a writing line having glitter, an ink composition containing a metal powder such as aluminum, a gelling agent and spherical resin particles as in Patent Document 1 is known. Yes.

  As a similar water-based ink composition for writing instruments, Patent Document 2 discloses an ink composition containing metal pigment particles coated with water, a water-soluble solvent, and silicate.

  However, in the conventional ink composition as described above, since the specific gravity of the pigment that brings about glitter such as metal powder and metal pigment particles is large, the pigment settles with time and forms a so-called hard cake. As a result, there was a problem that the pigment was not redispersed even when shaken. In particular, in a low-viscosity ink composition, since the pigment tends to settle out, it has been a big problem to prevent this hard cake formation and to redisperse the pigment. In order to solve such problems, Patent Document 3 proposes an ink composition containing a plate-like pigment whose surface is coated with a water-insoluble substance such as cellulose. However, it has not been sufficiently solved in terms of preventing the ink composition from becoming a hard cake and redispersibility of the pigment.

  In addition, when a conventional ink composition such as the above-mentioned Patent Documents 1 to 3 is used for a writing instrument and written on a non-permeable recording medium such as a film, the writing line is blurred or contracted. In addition, there is room for improvement in writability with respect to a non-permeable recording medium such that a good writing line cannot be obtained.

  Furthermore, since the writing line formed using the conventional ink composition as in Patent Documents 1 to 3 described above has low abrasion resistance, there is a high possibility that the writing line will be peeled off due to friction or the like. The scuff resistance of the writing line on the recording medium was low. Therefore, further improvement in abrasion resistance is demanded.

JP 2010-126715 A JP 2014-231553 A JP2013-124360A

  The present inventor can prevent the ink composition from becoming a hard cake by blending specific components into the water-based ink composition containing metal pigment particles, and easily redisperse the pigment after a lapse of time. Furthermore, the present inventors have found that the writability with respect to a permeable recording medium such as paper and a non-permeable recording medium such as a film can be improved.

  The present invention is based on such knowledge, and its purpose is not to form a hard cake, good redispersibility, excellent stability over time, and writing properties for both permeable and non-permeable recording media, An object of the present invention is to provide an ink composition having good color developability and brightness.

  The water-based ink composition for a writing instrument according to the present invention comprises silica-coated metal pigment particles, an aggregation control agent, and a solvent, and the mixing ratio of the aggregation control agent to the silica-coated metal pigment particles is based on mass. It is 0.01 to 5.0 times.

  The writing instrument according to the present invention is characterized by containing the above-mentioned water-based ink composition for a writing instrument.

  According to the present invention, an ink composition that does not form a hard cake, has good redispersibility, has excellent temporal stability, and has good writing properties, color developability, and glitter for both permeable and non-permeable recording media. Can be provided.

  In the present specification, “part”, “%”, “ratio” and the like indicating the composition are based on mass unless otherwise specified.

  A water-based ink composition for a writing instrument according to the present invention (hereinafter sometimes referred to as “water-based ink composition”) comprises silica-coated metal pigment particles, an agglomeration control agent, and a solvent. The pigment particles and the aggregation control agent are set at a specific ratio. Hereafter, each component which comprises the water-based ink composition by this invention is demonstrated.

(Silica-coated metal pigment particles)
Silica-coated metal pigment particles are those in which metal pigment particles are coated with silica. By covering the metal pigment particles with silica, the metal pigment particles in the water-based ink composition are prevented from settling with time to form a hard cake, and the redispersibility of the metal pigment particles is improved. be able to. Silica has low reactivity with the solvent and high stability. Therefore, when silica-coated metal pigment particles are used, the generation of bubbles caused by the reaction between the metal pigment particles and a solvent can be suppressed, and an aqueous ink composition having excellent temporal stability can be obtained. Among the silica-coated metal pigment particles, in view of excellent stability over time, it is preferable that the surface of the metal pigment particles is coated with silica.

  The material of the metal pigment particles is not particularly limited, and examples thereof include aluminum, brass, stainless steel, bronze, and alloys thereof. Among these, aluminum is preferable because it has a small specific gravity and can prevent sedimentation of the metal pigment particles and the resulting hard cake and a decrease in redispersibility.

  The shape of the metal pigment particles can be arbitrarily selected, but is preferably needle-like, plate-like, or rectangular because it can diffuse light more and improve the glitter.

  The coating amount of the metal pigment particles with silica, that is, the ratio of the mass of the silica to 100 mass parts of the metal pigment particles is preferably 3 to 20 parts by mass, and more preferably 11 to 20 parts by mass. When the coating amount is within the above numerical range, the hard ink cake of the water-based ink composition can be sufficiently prevented without impairing the glitter of the metal pigment particles.

  The average particle diameter of the silica-coated metal pigment particles is preferably 1 to 30 μm, more preferably 3 to 20 μm, and further preferably 3 to 10 μm. If the average particle diameter of the metal pigment particles is within the above numerical range, it is possible to maintain the glitter of a water-based ink composition and a writing line formed using the same, and the metal pigment particles are water-based inks. Even when it settles in the composition, its redispersibility can be improved. Moreover, when the water-based ink composition containing the metal pigment particles having an average particle diameter within the above numerical range is used for a writing instrument such as a marking pen, ink ejection properties can be improved. The average particle size of the metal pigment particles is 50% when the volume cumulative particle size distribution is measured by a laser diffraction method using a laser diffraction particle size distribution analyzer (trade name “Microtrac HRA9320-X100”, Nikkiso Co., Ltd.). The particle size (D50) can be measured. In this specification, the “average particle diameter” of the silica-coated metal pigment particles refers to the volume-based average particle diameter unless otherwise specified.

  When the average particle diameter of the silica-coated metal pigment particles is D μm and the average thickness is d μm, the aspect ratio (D / d) of the metal pigment particles is preferably 1 to 100, and preferably 10 to 50. Is more preferable. When the aspect ratio (D / d) of the metal pigment particles is within the above numerical range, high glitter of the metal pigment particles can be imparted to the water-based ink composition and a writing line formed using the same. In addition, when the water-based ink composition is used for a writing instrument such as a marking pen, ink clogging at the pen tip can be suppressed.

  The content of the silica-coated metal pigment particles in the aqueous ink composition is preferably 1 to 15% by mass and more preferably 2 to 8% by mass based on the total mass of the aqueous ink composition. When a water-based ink composition in which the content of the metal pigment particles is within the above numerical range is used for a writing instrument, it is possible to prevent a decrease in ink dischargeability from the pen tip, and a water-based ink composition, and The glitter of the writing line formed by using can be maintained.

(Aggregation control agent)
The water-based ink composition comprises an aggregation control agent. The aggregation control agent can prevent the water-based ink composition from forming a hard cake and can improve the redispersibility of the silica-coated metal pigment particles. As the aggregation control agent, for example, an elastic polymer, a cellulose derivative, or the like can be used, and it is particularly preferable to use two or more of these in combination.

  The blending ratio of the aggregation control agent to the silica-coated metal pigment particles is 0.01 to 5.0 times on a mass basis. More preferably, it is 0.1-2.5 times, More preferably, it is 0.5-2.0 times. If the blending ratio is within the above numerical range, a hard cake of the water-based ink composition is prevented, and agglomerated state capable of easily redispersing the metal pigment particles is created by shaking and stirring. As a result, the redispersibility of the metal pigment particles can be improved. Furthermore, if the blending ratio is within the above numerical range, the aggregation control agent does not block the glitter of the metal pigment particles, and the glitter of the water-based ink composition and the writing line formed using the same are high. Can be given. In addition, since the fixability of the metal pigment particles to the impermeable recording medium can be improved, the scuff resistance of the writing line can also be improved.

The content of the aggregation control agent in the water-based ink composition is preferably 0.01 to 25% by weight, more preferably 0.1 to 20% by weight, based on the total weight of the water-based ink composition. More preferably, it is 0.1-10 mass%. If the content of the aggregation control agent is within the above numerical range, the aqueous ink composition can be prevented from forming a hard cake and the redispersibility of the metal pigment particles can be improved. Furthermore, if the content of the aggregation control agent is within the above numerical range, the viscosity of the water-based ink composition can be easily set to 1 to 50 mPa · s at 20 ° C., a shear rate of 380 sec ⁻¹ , and a rotational speed of 100 rpm. When the ink composition is used in a writing instrument such as a marking pen, the time until the ink composition is supplied to the writing tip of the pen tip is shortened, and the ink ejection properties are improved. Therefore, it is possible to improve the writing property with respect to both the permeable and non-permeable recording media.

(Elastic polymer)
By containing an elastic polymer in the water-based ink composition, redispersibility of the silica-coated metal pigment particles can be improved. In addition, the elastic polymer improves the fixability of the water-based ink composition, and the scuff resistance of writing lines formed using the water-based ink composition, in particular, the scuff resistance of writing lines to a non-permeable recording medium such as a film. Can be further improved.

  In the present invention, the elastic polymer refers to a polymer having elasticity when in a solid state. Such polymers include styrene and styrene-olefin elastomers, olefin elastomers, acrylic elastomers, styrene-acrylics composed of styrene and olefins such as butadiene, isoprene, ethylene butylene, ethylene propylene, and vinyl isoprene. Elastomers, urethane elastomers, polyester elastomers, polyamide elastomers, vinyl acetate elastomers, vinyl chloride elastomers, fluorine elastomers and other elastomers, synthetic rubbers such as natural rubber and silicon rubber, ethylene monomers such as ionomer resins Resin etc. are mentioned. Of these, styrene-butadiene elastomer and acrylic elastomer are preferably used. It is more preferable to use a styrene-butadiene elastomer because even if the written recording medium is bent and the written recording medium is bent, an effect of easily suppressing the writing line cracking (bending strength) can be imparted. Further, the elastic polymer may be contained in the ink as it is, or may be contained as an emulsion that has been stably dispersed in a solvent in advance.

For the styrene-butadiene elastomer, the average particle diameter of the styrene-butadiene elastomer is preferably 300 nm or less, considering the redispersibility of the metal pigment particles, the fixability of the water-based ink composition and the stability over time. Preferably it is 200 nm or less. The average particle diameter of the styrene-butadiene elastomer can be measured by a dynamic light scattering method.
The pH of the styrene-butadiene elastomer is preferably 5 to 10, and more preferably 6 to 9. If the pH of the styrene butadiene elastomer is within the above numerical range, the metal pigment particles can be prevented from being corroded or dispersible.
When the styrene-butadiene elastomer is used as an emulsion in which the styrene-butadiene elastomer is stably dispersed in a solvent, the viscosity of the styrene-butadiene elastomer emulsion is preferably 100 to 350 mPa · s at 25 ° C. If the viscosity of the styrene-butadiene elastomer emulsion is within the above numerical range, when the water-based ink composition is used for a writing instrument such as a marking pen, the ink composition is supplied to the writing tip of the pen tip. Therefore, the ink ejection property is improved, and the writing property on both the permeable and non-permeable recording media can be improved. Further, the content of styrene is preferably 60 mol% or less, more preferably 50 mol% or less, based on the total amount constituting the styrene-butadiene elastomer.

  The molecular weight of the elastic polymer is not particularly limited, and preferably has a weight average molecular weight of 1,000 or more, for example, depending on the physical properties of the target aqueous ink composition. On the other hand, those having a weight average molecular weight of 1,000,000 or less can be used.

  The glass transition temperature (Tg) of the elastic polymer is preferably 1 to 70 ° C, more preferably 2 to 60 ° C, and further preferably 2 to 20 ° C. If the glass transition temperature of the elastic polymer is within the above numerical range, the glittering property of the water-based ink composition and the writing line formed using the same and the scuff resistance of the writing line can be improved. The Tg of the elastic polymer can be obtained by differential scanning calorimetry.

  The content of the elastic polymer in the water-based ink composition is preferably 0.1 to 15.0% by weight, and preferably 0.1 to 8.0% by weight, based on the total weight of the water-based ink composition. More preferably, it is 0.1 to 6.5%. If the content of the elastic polymer is within the above numerical range, the aqueous ink composition can be prevented from forming a hard cake and the redispersibility of the metal pigment particles can be improved. In addition, when the water-based ink composition having the above blending ratio is used for a writing instrument such as a marking pen, it improves the writing property with respect to a non-permeable recording medium such as a film, and also improves the fixing property and bending strength of the writing line. be able to.

(Cellulose derivative)
Examples of the cellulose derivative include carboxymethylcellulose, methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, hydroxypropylethylcellulose, and salts thereof. Of these, carboxymethylcellulose is preferred because it can further prevent the aqueous ink composition from forming a hard cake and the redispersibility of the silica-coated metal pigment particles from being lowered. This is considered to be because the carboxyl group contained in carboxymethylcellulose is easily adsorbed on the metal pigment particles and inhibits aggregation of the metal pigment particles. Furthermore, carboxymethyl cellulose is preferable because it has good solubility in a water-based ink composition.

Furthermore, in consideration of making the water-based ink composition into a hard cake and preventing the redispersibility of the metal pigment particles from being lowered, it is preferable that the weight average molecular weight of the carboxymethyl cellulose is 50,000 or less. In this case, the weight average molecular weight is preferably 35,000 or less. Furthermore, regarding the average degree of polymerization of the cellulose chain of the cellulose derivative, the average degree of polymerization is 50 to 300 in consideration of writing properties, hard cake formation of the water-based ink composition, and redispersibility of the metal pigment particles. Is preferred. When the average degree of polymerization is 300 or less, it is possible to prevent the ink viscosity from being easily increased, and to maintain good writing properties for both the permeable and non-permeable recording media. When the average degree of polymerization is 50 or more, the aqueous ink composition can be prevented from forming a hard cake, and the redispersibility of the metal pigment particles can be kept good. Considering the above, the average degree of polymerization is preferably 100 to 250.
In view of dissolution stability in the ink, it is preferable to use a carboxymethyl cellulose having a degree of etherification of 0.65 to 0.0.85.

  The content of the cellulose derivative in the water-based ink composition is preferably 0.1 to 10.0% by weight, and preferably 0.5 to 5.0% by weight, based on the total weight of the water-based ink composition. Is more preferable, and it is further more preferable that it is 0.5-3.5 mass%. If the content of the cellulose derivative is within the above numerical range, the aqueous ink composition can be prevented from forming a hard cake and the redispersibility of the metal pigment particles can be improved. In addition, when the ink composition of the above blending ratio is used for a writing instrument such as a marking pen, in both permeable and non-permeable recording media, it is possible to obtain a good writing line without being colored or faded, The scuff resistance of the writing line with respect to the non-permeable recording medium can be improved.

As the aggregation control agent, it is particularly preferable to use an elastic polymer and a cellulose derivative in combination. In the water-based ink composition in which the elastic polymer and the cellulose derivative are used in combination, the hard ink cake of the water-based ink composition can be prevented, and the redispersibility of the metal pigment particles can be further improved. When used for a writing instrument such as a marking pen, it is possible to further improve the writing property with respect to a permeable and non-permeable recording medium.
The blending ratio of the elastic polymer to the cellulose derivative is preferably 0.1 to 10 times, more preferably 0.3 to 5 times, and further preferably 1 to 3 times on a mass basis. is there. If the blending ratio of the elastic polymer to the cellulose derivative is within the above numerical range, when the water-based ink composition is used for a writing instrument such as a marking pen, the abrasion resistance of the writing line to the non-permeable recording medium is improved. Can be made.

(solvent)
Examples of the solvent include water and a mixed solvent of water and an organic solvent. Conventional water such as ion exchange water, distilled water, and tap water can be used as the water. When a mixed solvent of water and an organic solvent is used, ethanol, propanol, isopropyl alcohol, glycerin, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, polyethylene glycol, mineral spirit, etc. may be used as the organic solvent. it can. In addition, it is preferable that it is 30 mass% or less with respect to the total mass of a solvent, and, as for the content rate of an organic solvent, it is more preferable that it is 20 mass% or less.

  The content of the solvent in the aqueous ink composition is preferably 20 to 90 mass%, more preferably 30 to 80 mass%, based on the total mass of the aqueous ink composition. If content of a solvent is in the said numerical range, while being able to maintain the stability of the said water-based ink composition, favorable writability can be obtained.

(Surfactant)
The water-based ink composition preferably contains a surfactant. Examples of the surfactant include a surfactant having an acetylene bond in the structure, a fluorine-based surfactant, a silicone-based surfactant, and a succinic acid-based surfactant, and the surfactant includes acetylene. It is preferable to select and use one or more of surfactants having a bond in the structure, fluorosurfactants, silicone surfactants, and succinic surfactants. By incorporating the surfactant as described above into the water-based ink composition, the surface tension is lowered, the wettability of the water-based ink composition with respect to a non-permeable recording medium such as a film is improved, and the non-permeable recording Writability with respect to the medium can be improved.

Among the surfactants, it is preferable to include a surfactant having an acetylene bond in the structure. This is because a surfactant having an acetylene bond in the structure is very stable, and continuously exerts an improvement effect on wettability, and it is easy to improve the writing property on a non-permeable recording medium. It is. In addition, when there is already an ink composition as a writing line on the recording medium, even if the ink composition is overwritten from above, the writing line is faded, faded, mixed in color, This is preferable because it can be written well without causing shrinkage or the like (overwriting performance is improved).
Furthermore, as other surfactants, fluorosurfactants can easily reduce surface tension with a small amount of the above surfactants, and more effectively improve wettability. Easy to improve. Silicone surfactants are chemically stable, do not invade other substances, have excellent stability over time, and have good environmental safety, but can improve wettability and improve overwriting performance. Easy to improve. For this reason, in the present invention, it is preferable to include a fluorine-based surfactant that easily exhibits an effect when contained in a small amount, and a silicone-based surfactant that has good temporal stability and environmental safety.
Therefore, in the present invention, in view of improving wettability, improving writability and overwriting performance with respect to a non-permeable recording medium, and considering stability in a water-based ink composition, at least an acetylene bond is structured. It is preferable to use a surfactant having in the inside, and further, a combination of the surfactant having the acetylene bond in the structure and a fluorine-based surfactant that easily exerts an effect in a small amount, or It is more preferable to use the surfactant having the acetylene bond in the structure in combination with a silicone surfactant having good temporal stability and environmental safety.

Examples of the surfactant having an acetylene bond in the structure include an acetylene alcohol surfactant and an acetylene glycol surfactant. In particular, an acetylene glycol-based surfactant is preferable because it has excellent volatility of the writing line after writing, that is, excellent drying properties, and can impart abrasion resistance in a short time.
Furthermore, the HLB value of the surfactant having an acetylene bond in the structure is preferably an HLB value of 7 or more in consideration of further improving the wettability. Further, when the HLB value is 10 or more, the hydrophilic property in the water-based ink composition becomes strong, and it tends to dissolve in water, and the stability over time tends to be stable, and the acetylene bond is incorporated into the structure for a long time. It is preferable because the effect of the surfactant that is included can be maintained.

  Fluorosurfactants include, for example, perfluoro group butyl sulfonate, perfluoro group-containing carboxylate, perfluoro group-containing phosphate ester, perfluoro group-containing phosphate ester type compound, perfluoroalkylethylene oxide addition Perfluoro group / hydrophilic group / lipophilic group-containing oligomer, perfluoro group / hydrophilic group-containing oligomer, perfluoro group / lipophilic group-containing oligomer, perfluoroalkyl betaine, perfluoroalkylamine oxide compound, etc. It is done. Among them, when ethylene oxide is present in the structural formula of the fluorosurfactant, it tends to be highly hydrophilic, easily dissolved in water, and highly stable over time. This is preferable because it can be maintained. In particular, in the present invention, it is more preferable to use a perfluoroalkylethylene oxide adduct that easily reduces the surface tension and easily improves the overwriting performance by exhibiting the effect of improving wettability.

In consideration of the writing property and overwriting property with respect to the non-permeable recording medium, the HLB value of the fluorosurfactant obtained by the Griffin method is preferably 5 to 15, and more preferably, The HLB value of the system surfactant is more preferably 5-9. In addition, the HLB value calculated | required by the Griffin method is defined by "20 * sum total of the formula weight of a hydrophilic part / molecular weight".
Moreover, it is preferable that the surface tension of 0.1% aqueous solution of a fluorosurfactant is 20 mN / m or less. The surface tension can be measured by the Wilhelmy method at 23 ° C.

  The content of the fluorosurfactant in the water-based ink composition lowers the surface tension of the water-based ink composition, improves the wettability with respect to the non-permeable recording medium, In consideration of improving the overwriting property, it is preferably 0.005 to 1.5% by mass based on the total mass of the water-based ink composition. If it considers, it is more preferable that it is 0.005-0.5 mass%, and if it considers more, it is preferable that it is 0.005-0.3 mass%.

  Examples of silicone surfactants include reactive silicone oils and non-reactive silicone oils. Among these, non-reactive silicone oils having excellent stability over time are preferably used. Further, the non-reactive silicone oil includes dimethyl silicone oil, methylphenyl silicone oil, alkyl-modified silicone oil, alkyl-aralkyl-modified silicone oil, alkyl-polyether-modified silicone oil, polyether-modified silicone oil, higher fatty acid ester-modified silicone. In particular, in the present invention, the polyether-modified silicone oil is excellent in solubility in water and stability over time, and also in environmental safety, and is easy to improve overwriting performance. It is preferable to select and use.

  Moreover, when further considering writability and overwriting properties with respect to a non-permeable recording medium, the HLB value of the silicone surfactant is preferably 10 to 18, and more preferably 10 to 15. It is preferable.

  The content of the silicone surfactant in the water-based ink composition reduces the surface tension of the water-based ink composition and improves the wettability with respect to the non-permeable recording medium. In consideration of improving the writability, the content is preferably 0.1 to 3% by mass based on the total mass of the water-based ink composition. If it is, it is more preferable that it is 0.1-1 mass%.

  Examples of the succinic surfactant include dialkylsulfosuccinic acid, alkylsulfosuccinic acid that is dialkylsulfosuccinate, and alkylsulfosuccinate.

  If the total content of the surfactant in the water-based ink composition is considered to improve the wettability with respect to the non-permeable recording medium and improve the writing property and overwriting property with respect to the non-permeable recording medium, It is preferable that it is 0.01-3 mass% on the basis of the total mass of a water-based ink composition, and when the improvement of overwriting property and ink aging stability are considered, it is 0.1-1.5 mass%. More preferably, it is more preferably 0.1 to 1.2% by mass in consideration.

(Polyolefin resin particles)
The water-based ink composition preferably comprises a polyolefin resin. When the water-based ink composition contains a polyolefin resin, when the water-based ink composition is used for a writing instrument such as a marking pen, writing is performed with respect to the formed writing line and accompanying it. High abrasion resistance can be imparted. In particular, it is effective for improving the scuff resistance of the writing line on the non-permeable recording medium. Further, the aggregation control agent used in the present invention is also preferable because it has the effect of improving the fixability of the writing line and can be used in combination with the polyolefin resin particles to further improve the abrasion resistance of the writing line.
Examples of the material of the polyolefin resin particles include polyolefins such as polyethylene and polypropylene, and mixtures thereof. When polyethylene is used, low density polyethylene, linear low molecular weight polyethylene, high density polyethylene, modified polyethylene, modified high density polyethylene and the like can be used. Although the molecular weight of these polyolefin is not specifically limited, For example, the polyolefin whose weight average molecular weight is 500-10000 is preferable, and it is more preferable that the weight average molecular weight is 3000-8000. If the weight average molecular weight of the polyolefin resin particles is within the above numerical range, when this water-based ink composition is used for a writing instrument such as a marking pen and writing is performed, it has higher lubricity with respect to the formed writing line. The high abrasion resistance accompanying it can be provided. The polyolefin resin particles may contain a material other than polyolefin as required.

  The shape of the polyolefin resin particles is not particularly limited, and can take any shape such as a spherical shape, a needle shape, a plate shape, a square shape, and the spherical shape tends to reduce the frictional resistance. Since it is easy to give high slipperiness to a writing line, it is preferable that it is spherical.

  The average particle diameter of the polyolefin resin particles is preferably 0.1 to 35 μm. If the average particle diameter of the polyolefin resin particles is within the above numerical range, when this water-based ink composition is used for a writing instrument such as a marking pen, writing is performed with respect to the formed writing line. The high abrasion resistance accompanying it can be provided. Moreover, from the viewpoint of maintaining the glitter of the water-based ink composition and the writing line while imparting high scratch resistance, it is more preferably 0.1 to 20 μm, and 0.5 to 10 μm. Is more preferable, and it is especially preferable that it is 0.5-5 micrometers. The average particle diameter of the polyolefin resin particles can be measured by a Coulter counter method.

  The content of the polyolefin resin particles in the water-based ink composition is preferably from 0.01 to 10% by weight, more preferably from 0.1 to 2% by weight, based on the total weight of the water-based ink composition. More preferably, it is 0.1-1.5 mass%. If the content of the polyolefin resin particles is within the above numerical range, it is possible to maintain the ink dischargeability from the pen tip and the water-based ink composition, and the glitter of the writing line formed using the ink composition. Higher slipperiness can be imparted to the line.

  Further, the blending ratio of the polyolefin resin particles to the silica-coated metal pigment particles is preferably 0.01 to 1.0 times, more preferably 0.05 to 0.5 times on a mass basis. If the blending ratio is within the above numerical range, it is possible to maintain the glitter of the water-based ink composition and the writing line formed using the same, and to impart higher slipperiness to the writing line. Can do.

(Water-soluble acrylic polymer)
The water-based ink composition preferably comprises a water-soluble acrylic polymer. In the present invention, the water-soluble acrylic polymer contains acrylic acid or methacrylic acid in the repeating unit and has a water-soluble group in the side chain. This water-soluble group may be a carboxyl group derived from acrylic acid or methacrylic acid, or may be other water-soluble groups. By containing a water-soluble acrylic polymer in the water-based ink composition, the fixability of the water-based ink composition can be improved, and the scuff resistance of writing lines formed using the water-based ink composition can be further improved. Furthermore, the water-soluble acrylic polymer preferably has a carboxyl group. This is because such a water-soluble acrylic polymer is adsorbed on the silica-coated metal pigment particles and inhibits the aggregation of the metal pigment particles, so that it is possible to prevent the formation of a hard cake and a decrease in redispersibility. . In particular, the combined use of the above-described aggregation control agent and a water-soluble acrylic polymer is preferable because the effect is strongly expressed.

  As the water-soluble acrylic polymer, a water-soluble acrylic resin, a water-soluble styrene-acrylic resin, or the like can be used. Although the molecular weight of these polymers is not particularly limited, for example, those having a weight average molecular weight of 1000 to 100,000 are preferable.

  The content of the water-soluble acrylic polymer in the water-based ink composition is preferably 0.1 to 7% by mass, more preferably 0.3 to 5% by mass, based on the total mass of the water-based ink composition. Preferably, it is 0.3-3 mass%.

(Complementary color pigment)
The water-based ink composition may contain a complementary color pigment in order to adjust the color of the writing line to be obtained. The complementary color pigment is not particularly limited, and pigments of various colors such as red, blue, yellow, green, white, and black can be used. Examples of the complementary color pigment include SP4359, SP5658, and SP9604 (manufactured by Fuji Dye Co., Ltd.).

  The content of the complementary color pigment in the aqueous ink composition is preferably 0.1 to 10% by mass, more preferably 1 to 5% by mass, based on the total mass of the aqueous ink composition.

(Defoamer)
The water-based ink composition preferably contains an antifoaming agent. This is because when the metal pigment particles are used as in the present invention, the shape of the metal powder of the metal pigment particles is a needle shape, plate shape, square shape, etc. This is because pinholes are likely to occur when bubbles remain in the handwriting. Examples of the antifoaming agent include silicone-based, polyether-based, acetylene glycol-based, and acrylic polymer-based systems, but it is preferable to include a polyether-based or silicone-based antifoaming agent. Furthermore, it is more preferable to include a silicone-based antifoaming agent that has a low surface tension and interfacial tension with water, easily enters the foam film, diffuses, and easily exhibits an excellent defoaming effect.

  The content of the antifoaming agent in the water-based ink composition is preferably 0.0001 to 0.1% by mass, and 0.0005 to 0.05% by mass based on the total mass of the water-based ink composition. More preferably, the content is 0.001 to 0.01% by mass. If the content of the antifoaming agent is within the above numerical range, even if bubbles are entrained in the ink, the defoaming effect works effectively, no bubbles remain on the writing line, and a good writing line is obtained. be able to.

(Other)
Moreover, the water-based ink composition may contain a fungicide, a rust inhibitor, a pH adjuster, a shear thinning agent, a viscosity adjuster, and the like as necessary.

(Water-based ink composition for writing instruments)
The viscosity of the water-based ink composition according to the present invention is preferably 1 to 50 mPa · s, more preferably 3 to 30 mPa · s at 20 ° C., a shear rate of 380 sec ⁻¹ , and a rotational speed of 100 rpm. If the viscosity of the water-based ink composition is within the above numerical range, when used for a writing instrument such as a marking pen, the time until the ink composition is supplied to the writing tip of the pen tip is shortened. Dischargeability can be improved. In particular, in view of improvement in writing properties for non-permeable recording media such as films, it is more preferably 5 to 15 mPa · s. The viscosity can be measured using an E-type rotational viscometer (manufactured by Brookfield).

The viscosity index n at 20 ° C. of the water-based ink composition according to the present invention is preferably 0.7 to 1.0, more preferably 0.80 to 1.00, and further 0.85 to 0.98. It is preferable that Here, the viscosity index n refers to n in the viscosity equation represented by S = αD ⁿ . S represents a shear stress (dyn / cm ² = 0.1 Pa), D represents a shear rate (s ⁻¹ ), and α represents a viscosity coefficient. The viscosity index n can be calculated by measuring the ink viscosity using an E-type rotational viscometer (DV-II + Pro, cone-type rotor CPE-42, manufactured by Brookfield). If the viscosity index n of the water-based ink composition is within the above numerical range, it is possible to improve the ink ejection properties when used for a writing instrument such as a marking pen, and in particular, the writing property to a non-permeable recording medium such as a film. Can be improved.

  The pH of the water-based ink composition is preferably 6.0 to 10.0, and more preferably 7.0 to 9.0. If the pH of the water-based ink composition is within the above numerical range, when silica-coated metal pigment particles are used, the metal pigment particles are prevented from being corroded or dispersible. Can do. In the present invention, the pH value can be measured at 20 ° C., for example, with an IM-40S type pH meter (manufactured by Toa DKK Corporation).

The surface tension of the water-based ink composition is preferably 10 to 35 mN / m in a 20 ° C. environment. If it is 35 mN / m or less, it tends to prevent blurring of writing lines and back-through to paper, and if it is 10 mN / m or more, when writing on a non-permeable recording medium, There is no fading or color fading, and a good writing line can be obtained and the drying property of the writing line tends to be improved. In consideration of the tendency, the surface tension of the water-based ink composition is preferably 22 to 33 mN / m. In particular, in the present invention, a surfactant having an acetylene bond in the structure and a fluorosurfactant are used in combination, or a surfactant having an acetylene bond in the structure and a silicone surfactant are used in combination. By doing so, the value of the surface tension of the water-based ink composition can be easily set in the above range, which is more preferable.
The surface tension is determined by measuring by a vertical plate method using a platinum plate with a surface tension measuring instrument manufactured by Kyowa Interface Science Co., Ltd. in a 20 ° C. environment.

(Method for producing water-based ink composition)
The water-based ink composition for a writing instrument of the present invention can be produced by any conventionally known method. Specifically, it can be produced by blending the necessary amounts of the above components and mixing them with various agitators such as propeller agitation, homodisper, or homomixer, and various dispersers such as a bead mill.

(Writing instrument)
The water-based ink composition of the present invention is used for a writing pen such as a fountain pen using a marking pen, a ball-point pen, or a metal pen point, such as a fiber tip, a felt tip, a plastic tip, or a pen tip or a ball-point tip. Can do. Among them, the pen core is preferably a fiber chip or a felt chip in order to improve the writing property for a non-permeable recording medium such as a film. In particular, it is preferably used for a marking pen. The porosity of the pen core is preferably 50 to 80%. When the porosity of the pen core is within the above numerical range, the silica-coated metal pigment particles are not clogged, and an appropriate ink discharge amount and writing line glitter can be maintained.
In particular, the pen core has a porosity of 50 to 80%, and the water-based ink composition has a surfactant having an acetylene bond in the structure, a fluorosurfactant, a silicone surfactant, and a succinic acid interface. In the case where the viscosity of the water-based ink composition is ^{1 to} 50 mPa · s at 20 ° C., a shear rate of 380 sec ⁻¹ , and a rotation speed of 100 rpm, the water-based ink composition is selected and used from among the activators. However, it is preferable because the time until the supply reaches the writing tip of the nib is shortened and the writing property with respect to the permeable and non-permeable recording medium can be improved.

  The writing instrument of the present invention may be configured to be directly filled with a water-based ink composition, or may be provided with an ink container or ink occlusion body that can be filled with a water-based ink composition. Further, in order to redisperse the silica-coated metal pigment particles, it is preferable to incorporate a stirring body such as a stirring ball for stirring the ink in the ink container. Furthermore, examples of the shape of the stirring body include a spherical body and a rod-shaped body. The material of the stirrer is not particularly limited, but specific examples include metal, ceramic, resin, glass, etc. Among them, stirring power for redispersing the silica-coated metal pigment particles In consideration of the above, it is preferable to use a metal material, and considering the cost, it is preferable to use a glass material. In addition, you may use multiple types and several types of materials for a stirring body.

  The writing instrument of the present invention is not particularly limited, and may be a cap-type writing instrument provided with a cap that covers the pen tip, or a retractable writing instrument that can accommodate the pen tip in the shaft tube. Examples of the pen mechanism of the pen tool include a knock type, a rotary type, and a slide type.

  Further, the ink supply mechanism in the writing instrument is not particularly limited, for example, (1) a mechanism for supplying an ink guide core composed of a fiber bundle or the like as an ink flow rate adjusting member, and supplying a water-based ink composition to the pen tip; (2) A comb groove-shaped ink flow rate adjusting member is provided, and a mechanism for interposing the ink flow rate adjusting member to supply the water-based ink composition to the pen tip. (3) An ink flow rate adjusting member by a valve mechanism is provided. Examples thereof include a mechanism for supplying the ink composition first, and (4) a mechanism for supplying the water-based ink composition directly to the pen tip from the ink container or the shaft cylinder provided with the pen tip.

  In one embodiment, the writing instrument is a marking pen, and the nib is not particularly limited, and may be, for example, a fiber chip, a felt chip, a plastic chip, or the like. It may be a brush pen type.

  In one embodiment, it is preferable that the writing instrument is a ballpoint pen and includes an ink backflow preventer.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.

(Example 101)
A water-based ink composition for a writing instrument was obtained by mixing and dissolving with the following raw materials and blending amounts at 25 ° C. for 20 minutes using a stirrer. The viscosity of the obtained water-based ink composition was measured with an E-type rotational viscometer (DV-II + Pro, cone-type rotor CPE-42, manufactured by Brookfield). Specifically, the viscosity at 20.degree. C. and a shear rate of 380 sec.sup.- ¹ (rotation speed of 100 rpm) was 9.05 mPa.s, and the viscosity at a shear rate of 456 sec.sup.- ¹ (rotation speed of 120 rpm) was 8.85 Pa.s. . From these viscosities, the viscosity index was calculated to be 0.88. Furthermore, as a result of measuring the pH of the aqueous ink composition at 20 ° C. using an IM-40S type pH meter (manufactured by Toa DKK Co., Ltd.), the pH was 8.0.
The blending ratio of the aggregation control agent to the silica-coated metal pigment particles of Example 101 was 1.1 times on a mass basis.
Further, the surface tension of the obtained water-based ink composition was measured by a surface tension measuring instrument (in a 20 ° C. environment, a vertical plate method, manufactured by Kyowa Interface Science Co., Ltd.), and was 26.6 mN / m.

・ Silica-coated metal pigment particles 12% by mass
(Silica-coated plate-like aluminum particles, average particle diameter: 7 μm, aspect ratio: 25, silica coating amount: 14 parts by mass, solid content: 40%, manufactured by Toyo Aluminum Co., Ltd., trade name: EMR-D6390)
・ Elastic polymer 7.5% by mass
(Styrene-butadiene elastomer, solid content: 46%, Tg: 5 ° C, manufactured by Asahi Kasei Chemicals Corporation, trade name: L-1924)
-Cellulose derivative 1.75% by mass
(Carboxymethylcellulose, solid content: 100%, degree of etherification: 0.70 to 0.80, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., trade name: Serogen 5A)
・ Polyolefin resin particles 1% by mass
(Low molecular polyethylene, spherical particles, average particle size: 1 μm, solid content: 40%, weight average molecular weight: 6000, manufactured by Mitsui Chemicals, trade name: Chemipearl W401)
・ Water-soluble acrylic polymer 3% by mass
(Solid content: 30%, manufactured by Fuji Pigment Co., Ltd., trade name: A-29 NH3)
・ Surfactant 1% by mass
(Acetylene glycol surfactant, manufactured by Nissin Chemical Industry Co., Ltd., trade name: Olfine EXP4200, active ingredient 75%)
・ Bactericide 0.5% by mass
(Lonza Japan Co., Ltd., trade name: Proxel XL-2)
-Antifoaming agent 0.005 mass%
(Toray Dow Corning, trade name: Antifoam 013A, active ingredient 25%)
・ Tap water 74.245% by mass

(Examples 102 to 134, Comparative Examples 101 to 103)
The ink compositions of Examples 102 to 134 and Comparative Examples 101 to 103 were obtained by changing the types and addition amounts of the components to be blended as shown in Tables 1 to 5 with respect to Example 101. Details of the materials used in these examples are as follows.
Moreover, the viscosity of the water-based ink composition obtained in Examples 102, 111, and 117 was measured with an E-type rotational viscometer (DV-II + Pro, cone-type rotor CPE-42, manufactured by Brookfield) in the same manner as in Example 101. It was measured.
Example 102: The viscosity at a shear rate of 380 sec ⁻¹ (rotation speed of 100 rpm) was 9.22 mPa · s, and the viscosity at a shear rate of 456 sec ⁻¹ (rotation speed of 120 rpm) was 9.00 mPa · s. From these viscosities, the viscosity index was calculated to be 0.87.
Example 111: The viscosity at a shear rate of 380 sec ⁻¹ (rotation speed of 100 rpm) was 2.13 mPa · s, and the viscosity at a shear rate of 456 sec ⁻¹ (rotation speed of 120 rpm) was 2.13 mPa · s. From these viscosities, the viscosity index was calculated to be 1.00.
Example 117: The viscosity at a shear rate of 380 sec ⁻¹ (rotation speed of 100 rpm) was 8.13 mPa · s, and the viscosity at a shear rate of 456 sec ⁻¹ (rotation speed of 120 rpm) was 7.95 mPa · s. From these viscosities, the viscosity index was calculated to be 0.88.
Further, the surface tension of the water-based ink compositions obtained in Examples 128 and 130 was measured by a surface tension measuring instrument (in a 20 ° C environment, a vertical plate method, manufactured by Kyowa Interface Science Co., Ltd.) in the same manner as in Example 101. As a result, Example 128 was 16.1 mN / m, and Example 130 was 29.6 mN / m.

<Metallic pigment particles>
Rotosafe Aqua 260 003 Silver (manufactured by Ecart Co., Ltd., solid content 95%, active agent treatment, average particle size: 10 μm)
<Complementary color pigment>
SP4359 (Fuji Pigment Co., Ltd., solid content: 23%)
SP5658 (Fuji Pigment Co., Ltd., solid content: 23%)
<Elastic polymer>
A-7535 (Asahi Kasei Chemicals Corporation, styrene-butadiene elastomer, Tg: 17 ° C., solid content: 46%)
L-1432 (manufactured by Asahi Kasei Chemicals Corporation, styrene-butadiene elastomer, Tg: 18 ° C., solid content: 46%)
Jonkrill PDX-734 1 (manufactured by BASF Japan Ltd., acrylic elastomer, Tg: 15 ° C., solid content: 49%)
AE986B (Etec Co., Ltd., acrylic elastomer, Tg: 2 ° C., solid content: 35%)
Jonkrill 352D (manufactured by BASF Japan Ltd., acrylic elastomer, Tg: 56 ° C., solid content: 45%)
AE986B (Etec Co., Ltd., acrylic elastomer, Tg: 2 ° C., solid content: 35%)
<Cellulose derivative>
Sun Heck L (Sanki Co., Ltd., hydroxyethyl cellulose, solid content 100%)
Crucell L (manufactured by Sankisha Co., Ltd., hydroxypropylcellulose, solid content 100%) <surfactant>
Megafac F444 (manufactured by DIC, perfluoroalkylethylene oxide adduct fluorine-based surfactant, active ingredient: 100%, HLB value: 8.5, surface tension 16.8 mN / m)
TSF4440 (manufactured by Momentive Performance Materials, silicone surfactant (polyether-modified silicone oil), active ingredient: 100%, HLB value: 14)
FZ-2105 (manufactured by Dow Corning Toray, silicone surfactant (polyether-modified silicone oil), active ingredient: 100%, HLB value: 11)
Aerosol OT-100 (manufactured by Cytec Industry Japan, dioctyl sodium sulfosuccinate, active ingredient: 100%)

<Aging test>
The water-based ink compositions of Examples 101 to 134 and Comparative Examples 101 to 103 were put in a tightly opened and closed glass test tube having a diameter of 15 mm and left at room temperature for 14 days. Thereafter, the glass test tubes once settled were shaken up and down, and the re-dispersed state of the water-based ink composition was visually observed. The aggregation state was evaluated according to the following criteria. The obtained evaluation results are summarized in Tables 1 to 5. The evaluation criteria were as follows.
A: The silica-coated metal pigment particles are easily redispersed by shaking.
B: Silica-coated metal pigment particles re-dispersed by shaking
C: The silica-coated metal pigment particles are redispersed over time by shaking.
D: Silica-coated metal pigment particles are not sufficiently redispersed even when shaken

<Ink reachability test at the tip of the pen tip>
A spherical stirrer made of a metal material having a diameter of 8 mm is incorporated in the ink holder of a marking pen equipped with a nib and filled with the aqueous ink composition obtained in Examples 101 to 134 and Comparative Examples 101 to 103. Then, the ink arrival time to the tip of the pen tip when the water-based ink composition was soaked into the pen tip was evaluated according to the following criteria. The evaluation results are summarized in Tables 1 to 5. The pen tip was a bullet-type polyester fiber core with a porosity of 65%.
A: The ink easily reached the writing tip of the nib.
B: The ink reached the writing tip of the nib
C: The ink reached the writing tip of the nib over time.
D: The ink did not reach the writing tip of the nib

<Writing test>
Writing was performed on a writing test paper and a polypropylene sheet with the marking pen used in the ink reachability test on the writing tip of the pen tip, and each writing line was visually evaluated according to the following criteria. The evaluation results are summarized in Tables 1 to 5. JISP3201 writing paper A was used as a writing test paper.
A: Written lines are faint, faint, not faded B: Written lines are faint, faint, faint, but have no practical problems
C: Written lines are faint, faint, faint, but practical
D: Written lines are faint, pale, or discolored, but there are practical concerns E: Ink does not come out of the pen tip and cannot be written

(Example 201)
A water-based ink composition for writing instruments was obtained in the same manner as in Example 101 except that the following raw materials and blending amounts were changed as follows.

・ Silica-coated metal pigment particles 12% by mass
(Silica-coated plate-like aluminum particles, average particle diameter: 7 μm, aspect ratio: 25, silica coating amount: 14 parts by mass, solid content: 40%, manufactured by Toyo Aluminum Co., Ltd., trade name: EMR-D6390)
・ Elastic polymer 7.5% by mass
(Styrene-butadiene elastomer, solid content: 46%, Tg: 5 ° C, manufactured by Asahi Kasei Chemicals Corporation, trade name: L-1924)
-Cellulose derivative 1.75% by mass
(Carboxymethylcellulose, solid content: 100%, degree of etherification: 0.70 to 0.80, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., trade name: Serogen 5A)
・ Polyolefin resin particles 1% by mass
(Low molecular polyethylene, spherical particles, average particle size: 1 μm, solid content: 40%, weight average molecular weight: 6000, manufactured by Mitsui Chemicals, trade name: Chemipearl W401)
・ Water-soluble acrylic polymer 3% by mass
(Solid content: 30%, manufactured by Fuji Pigment Co., Ltd., trade name: A-29 NH3)
・ Surfactant 1% by mass
(Acetylene glycol surfactant, manufactured by Nissin Chemical Industry Co., Ltd., trade name: Olfine EXP4200, active ingredient 75%)

・ Bactericide 0.5% by mass
(Lonza Japan Co., Ltd., trade name: Proxel XL-2)
-Antifoaming agent 0.005 mass%
(Product name: Antifoam 013A, active ingredient 25%, manufactured by Toray Dow Corning)
・ Tap water 74.245% by mass

(Examples 202 to 219, Comparative Example 201 to Comparative Example 202)
The ink composition of Examples 202 to 219 and Comparative Examples 201 to 202 is obtained by changing the types and addition amounts of the components to be blended as shown in Tables 6 to 8 with respect to Example 201. It was. Details of the materials used in these examples are as follows.

<Metallic pigment particles>
Rotosafe Aqua 260 003 Silver (manufactured by Ecart Co., Ltd., solid content 95%, active agent treatment, average particle size: 10 μm)
<Complementary color pigment>
SP4359 (Fuji Pigment Co., Ltd., solid content: 23%)
SP5658 (Fuji Pigment Co., Ltd., solid content: 23%)
<Elastic polymer>
A-7535 (Asahi Kasei Chemicals Corporation, styrene-butadiene elastomer, Tg: 17 ° C., solid content: 46%)
L-1432 (manufactured by Asahi Kasei Chemicals Corporation, styrene-butadiene elastomer, Tg: 18 ° C., solid content: 46%)
Jonkrill PDX-7341 (manufactured by BASF Japan Ltd., acrylic elastomer, Tg: 15 ° C., solid content: 49%)
AE986B (Etec Co., Ltd., acrylic elastomer, Tg: 2 ° C., solid content: 35%)
Jonkrill 352D (manufactured by BASF Japan Ltd., acrylic elastomer, Tg: 56 ° C., solid content: 45%)
AE986B (Etec Co., Ltd., acrylic elastomer, Tg: 2 ° C., solid content: 35%)
<Cellulose derivative>
Sun Heck L (Sanki Co., Ltd., hydroxyethyl cellulose, solid content 100%)
Crucell L (manufactured by Sanki Co., Ltd., hydroxypropylcellulose, solid content 100%
<Surfactant>
MegaFuck F444 (manufactured by DIC, perfluoroalkylethylene oxide adduct fluorosurfactant)
TSF4440 (Momentive Performance Materials, silicone surfactant (polyether-modified silicone oil))
FZ-2105 (manufactured by Dow Corning Toray, silicone surfactant (polyether-modified silicone oil))
Aerosol OT-100 (Cytech Industry Japan, Dioctyl sodium sulfosuccinate)

<Abrasion resistance test>
A spherical stirring body made of a metal material having a diameter of 8 mm is incorporated in an ink container of a marking pen equipped with a nib, and the water-based ink compositions obtained in Examples 201 to 219 and Comparative Examples 201 to 202 are used. After filling, the pen tip was soaked with the water-based ink composition. As the pen tip, a bullet-type polyester fiber core pen core having a porosity of 65% was used. With this marking pen, writing was performed on a writing test paper and a polypropylene sheet. After leaving this writing line for one day, using a Gakushin type friction fastness tester (manufactured by Tester Sangyo Co., Ltd.), rubbing 50 strokes under a load of 200 g with a cotton cloth, and the writing line after rubbing is the initial writing line. In comparison, the abrasion resistance was evaluated according to the following criteria. The evaluation results are also summarized in Tables 6 to 8. JISP3201 writing paper A was used as a writing test paper.
The evaluation criteria were as follows.
A: No writing line peeling
B: There is no problem in practical use although there is some peeling of the writing line
C: Written lines are peeled off but are practical
D: Written lines are peeled off and there are practical concerns
E: There are many peeling of writing lines, and there are very practical concerns

<Overwriteability test>
Write on a polypropylene sheet using a commercially available water-based pigment marking pen (white ink marking pen), and overwrite the resulting writing line with the marking pen used for the abrasion resistance test. When the obtained writing line was confirmed by visual observation, overwriting was performed with a marking pen filled with the aqueous ink composition of Example 201 using only the surfactant having an acetylene bond in the structure as the surfactant. The writing lines obtained by overwriting with the marking pen filled with the water-based ink composition of Example 213 to Example 219 are mixed in color or contracted compared to the writing lines obtained in the above. Good handwriting was obtained without causing any problems. Among them, the aqueous ink compositions of Example 215 and Examples 217 to 219, in which a surfactant having an acetylene bond in the structure, and a fluorine-based surfactant or a silicone-based surfactant were used, were filled. The writing line obtained by overwriting with a marking pen was particularly good.

Claims (10)

  It comprises silica-coated metal pigment particles, an aggregation control agent, and a solvent, and the mixing ratio of the aggregation control agent to the silica-coated metal pigment particles is 0.01 to 5.0 times on a mass basis. A water-based ink composition for a writing instrument, The composition according to claim 1, wherein the viscosity is 1 mPa · s to 50 mPa · s at 20 ° C., a shear rate of 380 sec ⁻¹ , and a rotation speed of 100 rpm.   The composition according to claim 1 or 2, wherein the aggregation control agent is selected from one or more elastic polymers or cellulose derivatives.   The composition according to any one of claims 1 to 3, wherein the aggregation control agent comprises an elastic polymer, and the glass transition temperature (Tg) of the elastic polymer is 1 ° C to 70 ° C.   The composition according to any one of claims 1 to 4, wherein the aggregation control agent comprises an elastic polymer, and the elastic polymer is a styrene-butadiene elastomer.   The composition according to any one of claims 1 to 5, wherein the aggregation control agent comprises a cellulose derivative, and the cellulose derivative is carboxymethylcellulose.   A surfactant further comprising at least one surfactant selected from a surfactant having an acetylene bond in the structure, a fluorosurfactant, a silicone surfactant, and a succinic surfactant. The composition according to any one of claims 1 to 6, which is selected.   The composition according to any one of claims 1 to 7, further comprising an antifoaming agent.   The composition according to any one of claims 1 to 8, wherein the metal pigment particles are aluminum pigment particles. A writing instrument comprising the composition according to any one of claims 1 to 9.