JP2019183042A - Water-based ink composition - Google Patents

Abstract

To provide a water-based ink composition good in black color development.SOLUTION: A water-based ink composition has an inorganic black pigment, a water soluble black dye, a resin emulsion and water. Content of the water soluble black dye is 0.1 mass% or more. Content of the resin emulsion is 1 mass% or more.SELECTED DRAWING: None

Description

  The present invention relates to a water-based ink composition.

  As an ink used for a ballpoint pen, an aqueous ink composition in which a colorant is added to water is known. For example, an aqueous ball-point pen ink composition containing carbon black as a colorant and an emulsion is disclosed in JP-A-8-92519 (Patent Document 1).

JP-A-8-92519

  Examples of the black colorant used in the water-based ink composition include pigments and dyes. Among black colorants, inorganic black pigments are inexpensive. In the water-based ink composition using such an inorganic black pigment, it is required that the color developability, that is, the color when the water-based ink composition is applied is made as black as possible. Note that the technique disclosed in Patent Document 1 cannot cope with the above case.

  Accordingly, an object of the present invention is to provide a water-based ink composition having good black color developability.

  The aqueous ink composition according to the present invention includes an inorganic black pigment, a water-soluble black dye, a resin emulsion, and water. The content of the water-soluble black dye is 0.1% by mass or more. The content of the resin emulsion is 1% by mass or more.

  Thus, according to the water-based ink composition of the present invention, the black color developability is good because the inorganic black pigment, the resin emulsion, and the water-soluble black dye are used in combination.

  In the aqueous ink composition, the content of the water-soluble black dye may be 3% by mass or less. Even if the water-soluble black dye is added in excess of 3% by mass, the effect of improving the color developability is saturated. Moreover, when water-soluble black dye is added exceeding 3 mass%, precipitation of a dye will arise and a color may change. For this reason, it is preferable that content of water-soluble black dye is 3 mass% or less.

  In the water-based ink composition, the content of the resin emulsion may be 7% by mass or less. By making content of a resin emulsion into 7 mass% or less, it can suppress that the viscosity of a water-based ink composition rises. Therefore, even if the water-based ink composition is used as the ink for the ballpoint pen, it is possible to suppress a decrease in the amount of the water-based ink composition that flows out when writing, and to suppress ink blur.

  In the water-based ink composition, the water-soluble black dye may be an acid dye. By using an acid dye in this way, black color developability can be further improved.

  In the water-based ink composition, the glass transition temperature of the resin emulsion may be 80 ° C. or higher. By using a resin emulsion having such a glass transition temperature, it is possible to suppress an increase in the viscosity of the water-based ink composition due to softening of the resin emulsion at room temperature (for example, 23 ° C.). Therefore, even when the water-based ink composition is used as ink for a ballpoint pen, the occurrence of defects when writing can be suppressed.

  In the water-based ink composition, the constituent resin of the resin emulsion may be an acrylate copolymer. By using such a resin emulsion, the dispersibility in the water-based ink composition can be improved.

  In the water-based ink composition, the inorganic black pigment may be carbon black, and the average particle size of the carbon black may be 10 μm or less. Carbon black is easy to handle and is suitable as a water-based ink composition. By using carbon black having an average particle size of 10 μm or less, the dispersibility in the aqueous ink composition can be improved.

  According to the water-based ink composition of the present invention, it is possible to provide a water-based ink composition with good black color developability.

It is a schematic sectional drawing at the time of apply | coating the water-based ink composition containing only an inorganic black pigment to paper. It is a schematic sectional drawing at the time of apply | coating the water-based ink composition containing only an inorganic black pigment and resin emulsion to paper. It is a schematic sectional drawing at the time of apply | coating the water-based ink composition containing only a water-soluble black dye to paper. It is a schematic sectional drawing at the time of apply | coating the water-based ink composition which concerns on this Embodiment to paper.

  Hereinafter, embodiments of the aqueous ink composition of the present invention will be described. The aqueous ink composition according to the present embodiment contains an inorganic black pigment, a water-soluble black dye, a resin emulsion, and water. The viscosity of the aqueous ink composition is, for example, 500 mPa · s to 10000 mPa · s. The viscosity is, for example, a value measured with an ELD viscometer (cone rotor type: 3 ° R14, rotation speed: 0.5 rpm, 20 ° C.).

[Inorganic black pigment]
As an inorganic black pigment in this Embodiment, it is a carbon black pigment, for example. By using an inorganic black pigment, a water-based ink composition having good water resistance and light resistance can be obtained. Inorganic black pigments are colored black by entering paper fibers. Examples of the carbon black pigment include carbon black, biotite, graphite powder, graphite powder and the like, and these can be used alone or in admixture of two or more. Among these, carbon black can be suitably used from the viewpoint of handleability. Examples of carbon black include acetylene black, ketjen black, furnace black, channel black, and thermal black.

  The lower limit of the content of the inorganic black pigment in the present embodiment is 2.5% by mass. By setting it as such a range, the black coloring property of an aqueous ink composition can be improved more. The lower limit of the content of the inorganic black pigment is preferably 2.6% by mass, and more preferably 2.8% by mass. The upper limit of the content of the inorganic black pigment is preferably 9% by mass. Even if the inorganic black pigment is added in excess of 9% by mass, the effect of black color developability is saturated. For this reason, it is preferable that content of an inorganic black pigment is 9 mass% or less. The upper limit of the content of the inorganic black pigment is more preferably 8.9% by mass, and still more preferably 8.7% by mass.

  The average particle size of the inorganic black pigment is preferably 10 μm or less, more preferably 5 μm or less, still more preferably 1 μm or less, and most preferably 0.1 μm or less. By setting it as such a range, the dispersibility in a water-based ink composition can be improved. The lower limit value of the average particle size of the inorganic black pigment is preferably 10 nm, more preferably 20 nm. The average particle diameter can be measured using, for example, a laser diffraction / scattering particle size distribution measuring apparatus.

[Water-soluble black dye]
Examples of the water-soluble black dye in the present embodiment include direct dyes, acid dyes, food dyes, and basic dyes. Among these, acidic dyes can further improve black color developability. Examples of the water-soluble black dye include disazo dyes, metal-containing azo dyes, anthraquinone dyes, monoazo dyes, hydroxyketone dyes, sulfur dyes, and the like. These may be used alone or in combination of two or more. it can. Among these, disazo dyes can be suitably used from the viewpoint of handleability.

  The lower limit of the content of the water-soluble black dye is 0.1% by mass. By containing the water-soluble black dye in such a range, the color developability of the water-based ink composition can be improved. In addition, the minimum of content of water-soluble black dye becomes like this. Preferably it is 0.2 mass%, More preferably, it is 0.4 mass%, More preferably, it is 0.7 mass%.

  The upper limit of the content of the water-soluble black dye in the present embodiment is 3% by mass. Even if the water-soluble black dye is added in excess of 3% by mass, the effect of improving the color developability is saturated. For this reason, it is preferable that content of water-soluble black dye is 3 mass% or less. In addition, the upper limit of the content of the water-soluble black dye is more preferably 2.8% by mass, and still more preferably 2.6% by mass.

[Resin emulsion]
The resin emulsion in the present embodiment is an aqueous dispersion of resin particles. The component resin of the resin emulsion is, for example, a copolymer of monomer components such as ethylenically unsaturated carboxylic acid, acrylic acid ester and methacrylic acid ester, vinyl aromatic compound, etc. Among them, acrylic acid from the viewpoint of dispersibility An ester copolymer can be suitably used. Examples of the ethylenically unsaturated carboxylic acid include acrylic acid, methacrylic acid, maleic acid and the like. Examples of the acrylic acid ester and methacrylic acid ester include ethyl acrylate, propyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, and butyl methacrylate. Examples of vinyl aromatic compounds include styrene and vinyl toluene.

  The lower limit of the content of the resin emulsion is 1% by mass. By containing the resin emulsion in such a range, the color developability of the water-based ink composition can be improved. In addition, the minimum of content of a resin emulsion becomes like this. Preferably it is 1.2 mass%, More preferably, it is 1.4 mass%, More preferably, it is 1.6 mass%. In addition, content of a resin emulsion is a content rate (mass%) of the solid content of the resin emulsion with respect to an aqueous ink composition.

  The upper limit of the content of the resin emulsion in the present embodiment is 7% by mass. By setting it as content of such a resin emulsion, it can suppress that the viscosity of a water-based ink composition rises. Therefore, even if the water-based ink composition is used as the ink for the ballpoint pen, it is possible to suppress a decrease in the amount of the water-based ink composition that flows out when writing, and to suppress ink blur. The upper limit of the content of the resin emulsion is preferably 7.8% by mass, more preferably 7.5% by mass, and further preferably 6.4% by mass.

  The glass transition temperature of the resin emulsion is preferably 80 ° C. or higher. By using a resin emulsion having such a glass transition temperature, it is possible to suppress an increase in the viscosity of the water-based ink composition due to softening of the resin emulsion at room temperature (for example, 23 ° C.). Therefore, even when the water-based ink composition is used as ink for a ballpoint pen, the occurrence of defects when writing can be suppressed. The glass transition temperature of the resin emulsion is more preferably 90 ° C. or higher, and further preferably 100 ° C. or higher. The glass transition temperature is, for example, a glass transition temperature obtained by the FOX equation based on the composition of the component resin of the resin emulsion.

[Medium]
The aqueous ink composition in the present embodiment contains water as a medium for dissolving or dispersing the above components. As water in this Embodiment, ion-exchange water, distilled water, ultrapure water etc. can be used, for example. The water content in the water-based ink composition is appropriately set in consideration of necessary characteristics such as ease of drying of the water-based ink composition. The water content in the aqueous ink composition is, for example, 50% by mass to 70% by mass.

[Other ingredients]
The water-based ink composition in the present embodiment further contains, as other components, conventional additives such as a viscosity modifier, a wetting agent, a lubricant, a pH adjuster, a dispersant, a preservative, and an antifungal agent. You may go out. These can be used alone or in combination of two or more.

[Viscosity modifier]
A viscosity modifier is mix | blended in order to adjust the viscosity of a water-based ink composition suitably. Examples of the viscosity modifier include natural water-soluble polymer polysaccharides and synthetic polymers. As the natural water-soluble polymer polysaccharide, for example, when a water-based ink composition is used as an ink for a ballpoint pen, those in which the viscosity of the water-based ink composition is reduced by rotation of the ball are preferable. Examples of the natural water-soluble polymer polysaccharide include rhamzan gum, xanthan gum, welan gum, gellan gum, pullulan, xanthan gum, guar gum, locust bean gum, pectin and the like. Among these, xanthan gum can be preferably used. Examples of the synthetic polymer include a cross-linked acrylic resin, an alkali swelling associative thickener, a nonionic associative thickener, and among them, a cross-linked acrylic resin can be preferably used. Content of a viscosity modifier becomes like this. Preferably it is 0.01 mass%-10 mass%, More preferably, it is 0.01 mass%-5 mass%.

[Wetting agent]
The humectant is formulated to prevent the aqueous ink composition from drying. Examples of the wetting agent include polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, and glycerin, glycol ethers such as propylene glycol monomethyl ether and dipropylene glycol monomethyl ether, and glycol ethers such as propylene glycol monomethyl ether acetate. Etc. Among these, glycerin or dipropylene glycol monomethyl ether can be preferably used.

[lubricant]
The lubricant is blended, for example, to improve the sliding of the ballpoint pen when the aqueous ink composition is used as the ink of the ballpoint pen. Examples of the lubricant include phosphate ester compounds.

[PH adjuster]
The pH adjuster is blended to adjust the pH value of the aqueous ink composition and prevent gelation of the aqueous ink composition. Examples of the pH adjuster include sodium hydroxide, triethanolamine, aminomethylpropanol, sodium carbonate and the like. Among these, sodium hydroxide can be preferably used.

[Dispersant]
The dispersant is blended in order to improve the dispersibility of the inorganic black pigment in the aqueous ink composition. Examples of the dispersant include styrene acrylic resins, styrene resins, acrylic resins, and the like.

[Anti-fungal and antiseptic]
An antifungal agent and an antiseptic agent are blended in order to suppress decay and generation of mold. Examples of fungicides and preservatives include chloroacetamide, 2-pyridinethiol-1-oxide sodium salt, sodium dehydroacetate, sodium benzoate, sodium sorbate, potassium sorbate, 2-bromo-2-nitropropane -1,3-diol, 3-iodo-2-propynylbutyl carbamate, 1,2-benzisothiazolin-3 (2H) -one, 5-chloro-2-methyl-4-isothiazolin-3-one, 2-methyl Examples include -4-isothiazoline-3-one thiabendazole, phenoxyethanol, sodium fluoride, 4- (2-nitrobutyl) morpholine, 1,3-dimorpholino-2-ethyl-2-nitripropane, and the like.

  Next, consider the case where a water-based ink composition is applied to a sheet. FIG. 1 is a schematic cross-sectional view when a water-based ink composition containing only an inorganic black pigment is applied to paper. FIG. 2 is a schematic cross-sectional view when a water-based ink composition containing only an inorganic black pigment and a resin emulsion is applied to paper. FIG. 3 is a schematic cross-sectional view when a water-based ink composition containing only a water-soluble black dye is applied to paper. FIG. 4 is a schematic cross-sectional view when a water-based ink composition according to the present embodiment containing an inorganic black pigment, a water-soluble black dye, and a resin emulsion is applied to paper. 1 to 4, the vertical direction is the Z-axis direction, and the horizontal direction is the X-axis direction. The Z-axis direction is the thickness direction of the paper.

  As shown in FIG. 1, when a water-based ink composition containing an inorganic black pigment 21 is applied to the paper 11, the inorganic black pigment 21 penetrates between the fibers of the paper 11 and penetrates in the paper thickness direction (Z-axis direction). Go. For this reason, the fibers of the paper 11 appear on the outermost surface 12 of the paper 11. This is the same even if the content of the inorganic black pigment 21 in the water-based ink composition is increased. Therefore, depending on the content of the inorganic black pigment 21 in the water-based ink composition, the color developability of the water-based ink composition is not sufficiently improved.

  As shown in FIG. 2, when the aqueous ink composition containing the inorganic black pigment 21 and the resin emulsion 41 is applied to the paper 11, the resin emulsion 41 enters between the fibers of the paper 11, as with the inorganic black pigment 21. By including the resin emulsion 41 having a content of 1% by mass or more in the aqueous ink composition, the penetration of the inorganic black pigment 21 in the thickness direction (Z-axis direction) of the paper 11 is suppressed. That is, the inorganic black pigment 21 can be kept in a region near the outermost surface 12 of the paper 11.

  As shown in FIG. 3, when the water-based ink composition containing the water-soluble black dye 31 is applied to the paper 11, the water-soluble black dye 31 can dye the fibers of the paper 11 black.

  As shown in FIG. 4, in the water-based ink composition containing the inorganic black pigment 21, the water-soluble black dye 31 and the resin emulsion 41 are used in combination so that the inorganic black pigment 21 is kept in a region near the outermost surface 12 of the paper 11. The fiber of the paper 11 can be dyed black. As a result, even if it is the water-based ink composition using the inorganic black pigment 21, black color developability can be improved.

  The water-based ink composition in the present embodiment can be suitably used as an ink composition used for a ballpoint pen. The ballpoint pen in which the water-based ink composition is used has the same structure as a general ballpoint pen. For example, a writing ball is rotatably held at the tip of the ballpoint pen. The water-based ink composition is stored in an ink storage tube of a water-based ballpoint pen. At the time of writing, the aqueous ink composition flows out from the ink storage tube, adheres to the surface of the ball, and is transferred to the paper by the rotation of the ball, thereby writing.

  The method for producing the water-based ink composition in the present embodiment is not particularly limited, and the water-based ink composition can be produced by a known method appropriately selected by those skilled in the art. For example, first, an inorganic black pigment is dispersed in water using a stirrer such as a bead mill to prepare a pigment base. Next, each component such as a pigment base, a dye, a resin emulsion, a viscosity modifier and water is mixed with a stirrer. Thereafter, the aqueous ink composition can be obtained by filtering using a mesh or the like and defoaming.

  Hereinafter, the present invention will be described more specifically with reference to examples. Note that the scope of the present invention is not construed as being limited by the description of these examples. In the examples, unless otherwise specified, “parts” and “%” are based on mass.

Example 1
In manufacturing the water-based ink composition according to Example 1, the following materials were prepared. Specifically, carbon black (trade name “Mitsubishi Carbon Black # 25”, manufactured by Mitsubishi Chemical Corporation) as an inorganic black pigment, disazo dye (trade name “Water Black 256-L”, Orient Chemical Industries, Ltd.) as a water-soluble black dye Acrylic ester copolymer aqueous emulsion (trade name “Movinyl 790”, manufactured by Nippon Synthetic Chemical Industry, glass transition temperature 100 ° C.) as resin emulsion, xanthan gum, viscosity modifier (2) as viscosity modifier (1) As a carboxyvinyl polymer (trade name “Carbopol 934”, manufactured by Lubrizol Advanced Materials), and a mixed solution of purified glycerin and dipropylene glycol methyl ether as a wetting agent (mixing ratio of glycerin 50 mass%, dipropylene glycol) (Mixing ratio of rumethyl ether 50% by mass), phosphoric acid ester compound as a lubricant (trade name “Phosphanol PE-510”, manufactured by Toho Chemical Industry Co., Ltd.)
Acrylic acid resin (trade name “Johncrill 683”, manufactured by BASF) as a dispersant, sodium hydroxide as a pH adjuster, benzoisothiazole-based compound (trade name “Proxel XL-2”, Lonza) as a preservative And an organic iodine compound (trade name “Coatside PH2”, manufactured by Osaka Gas Chemical Co., Ltd.) was prepared. First, a black pigment was dispersed in water by a bead mill to prepare a pigment base. The prepared pigment base, black dye, resin emulsion and other components were blended according to the ratio shown in Table 1, and mixed well with a stirrer. Then, the aqueous ink composition of Example 1 was produced by filtering through a mesh and defoaming.

(Example 2)
A water-based ink composition according to Example 2 was prepared in the same manner as in Example 1 except that the content ratio of the resin emulsion was changed to the blending ratio shown in Table 1.

(Example 3)
A water-based ink composition according to Example 3 was prepared in the same manner as in Example 1 except that the content ratio of the resin emulsion was changed to the blending ratio shown in Table 1.

Example 4
A water-based ink composition according to Example 4 was prepared in the same manner as in Example 1 except that the content ratio of the resin emulsion was changed to the blending ratio shown in Table 1.

(Example 5)
A water-based ink composition according to Example 5 was prepared in the same manner as in Example 1 except that the content ratio of the resin emulsion was changed to the blending ratio shown in Table 1.

(Example 6)
A water-based ink composition according to Example 6 was prepared in the same manner as in Example 2 except that the content ratio of the water-soluble black dye was changed to the blending ratio shown in Table 2.

(Example 7)
A water-based ink composition according to Example 7 was produced in the same manner as in Example 2 except that the content ratio of the water-soluble black dye was changed to the blending ratio shown in Table 2.

(Example 8)
A water-based ink composition according to Example 8 was prepared in the same manner as in Example 3 except that the content ratio of the water-soluble black dye was changed to the blending ratio shown in Table 2.

Example 9
A water-based ink composition according to Example 9 was produced in the same manner as in Example 7 except that the content ratio of the inorganic black pigment was changed to the blending ratio shown in Table 2.

(Example 10)
A water-based ink composition according to Example 10 was prepared in the same manner as in Example 7 except that the content ratio of the inorganic black pigment was changed to the blending ratio shown in Table 2.

(Comparative Example 1)
A water-based ink composition according to Comparative Example 1 was prepared according to the formulation shown in Table 3 in the same manner as in Example 1 except that the water-soluble black dye and the resin emulsion were removed.

(Comparative Example 2)
A water-based ink composition according to Comparative Example 2 was prepared in the same manner as Comparative Example 1 except that the water-soluble black dye was added and the content ratio of the water-soluble black dye was changed to the blending ratio shown in Table 3.

(Comparative Example 3)
A water-based ink composition according to Comparative Example 3 was produced in the same manner as Comparative Example 2 except that the content ratio of the water-soluble black dye was changed to the blending ratio shown in Table 3.

(Comparative Example 4)
A water-based ink composition according to Comparative Example 4 was prepared in the same manner as Comparative Example 2 except that the content ratio of the water-soluble black dye was changed to the blending ratio shown in Table 3.

(Comparative Example 5)
A water-based ink composition according to Comparative Example 5 was prepared in the same manner as Comparative Example 1 except that the resin emulsion was added and the content ratio of the resin emulsion was changed to the blending ratio shown in Table 3.

  About the water-based ink composition obtained by the Example and the comparative example, the blackness measurement and the blurring test were performed by the following method.

(1) Blackness Using the aqueous ink compositions obtained in Examples and Comparative Examples, a coating film sample having a thickness of about 20 μm was prepared on a white paper by a bar coater, and the blackness was measured by the following method. About the coating-film sample, Y value was measured with the colorimeter (Brand name "fluorescence spectral densitometer FD-5", Konica Minolta Japan Co., Ltd. product), and blackness My was computed with the following formulas. The blackness My is a numerical value indicating the degree of blackness that is not influenced by the hue of the coating film. When the blackness My was a value larger than 145, it was determined that the color development was good.
[My] = 100 × Log (100 / [Y])

(2) Scratch test The aqueous ink compositions obtained in Examples and Comparative Examples were filled as commercially available ballpoint pen inks to prepare ballpoint pen samples. About each ball-point pen sample, about 100 m was written on the blank paper (Kishu fine quality paper basic weight 64g / m < ² >), and the handwriting was confirmed visually. And the presence or absence of generation | occurrence | production of a blur was confirmed. The evaluation was “A” when there was no blur and “B” when the blur occurred.

  Tables 1 to 3 show the blackness and the blurring test results of Examples 1 to 10 and Comparative Examples 1 to 5.

  As the blackness My, for example, it is required that the numerical value of the blackness My is larger than 145 as one index. With reference to Table 1 and Table 2, about Example 1- Example 10, the numerical value of blackness My is a numerical value larger than 145, and has good coloring property. In Example 5, although the numerical value of the blackness My is a numerical value larger than 145, the blur test is evaluated as “B”. This is presumably because the viscosity of the water-based ink composition was increased by the resin emulsion, and the water-based ink composition did not easily flow out of the ballpoint pen. Therefore, when the water-based ink composition is used as the ink for the ballpoint pen, the content of the resin emulsion is preferably less than 8% by mass.

  On the other hand, looking at Comparative Examples 1 to 5, the numerical value of blackness My is 145 or less. Specifically, in Comparative Example 1 that does not include the water-soluble black dye and the resin emulsion, the numerical value of the blackness My is 131. Therefore, when it does not contain a water-soluble black dye and a resin emulsion, the color developability is insufficient. In Comparative Examples 2 to 4 containing only the water-soluble black dye, the numerical value of the blackness My is higher than that of Comparative Example 1, but is 145 or less. In Comparative Example 3 and Comparative Example 4 in which the content of the water-soluble black dye is 2.6% by mass or more, the numerical value of the blackness My is saturated without increasing. Therefore, when only a water-soluble black dye is included, the color developability is insufficient. Even in Comparative Example 5 including only the resin emulsion, the numerical value of the blackness My is higher than that of Comparative Example 1, but is 145 or less. Accordingly, when only the resin emulsion is included, the color developability is insufficient.

  From the above, it can be said that the water-based ink composition according to the present invention is a water-based ink composition having good black color developability.

  It should be understood that the embodiments and examples disclosed herein are illustrative in all respects and are not restrictive in any respect. The scope of the present invention is defined by the scope of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the scope of the claims.

  The water-based ink composition of the present application can be particularly advantageously applied in a field where a water-based ink composition with good black color developability is required.

  11 paper, 12 surface, 21 inorganic black pigment, 31 water-soluble black dye, 41 resin emulsion.

Claims (7)

An inorganic black pigment;
A water-soluble black dye,
A resin emulsion;
With water,
The content of the water-soluble black dye is 0.1% by mass or more,
The water-based ink composition, wherein the content of the resin emulsion is 1% by mass or more.   The water-based ink composition according to claim 1, wherein the content of the water-soluble black dye is 3% by mass or less.   The water-based ink composition according to claim 1 or 2, wherein the content of the resin emulsion is 7% by mass or less.   The water-based ink composition according to claim 1, wherein the water-soluble black dye is an acid dye.   The water-based ink composition according to any one of claims 1 to 4, wherein a glass transition temperature of the resin emulsion is 80 ° C or higher.   The water-based ink composition according to any one of claims 1 to 5, wherein a constituent resin of the resin emulsion is an acrylate copolymer. The inorganic black pigment is carbon black,
The water-based ink composition according to claim 1, wherein the carbon black has an average particle size of 10 μm or less.

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