JP2000160044A - Aqueous organic pigment and its preparation, organic pigment dispersion and water-base ink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve dispersion stability of an organic pigment in an aqueous medium and to enhance fluidity and storage stability of an organic pigment dispersion and a water-base ink in which the organic pigment is used by bonding a hydrophilic modifier group to the surface of the organic pigment. SOLUTION: The aqueous organic pigment has at least one hydrophilic modifier group represented by formula I or II bonded to its surface. In formulae I and II, X is a 1-4C alkylene group or alkylene oxide group of formula III (wherein R1 is a 1-4C alkylene group; and (n) is 1-3) and these groups may contain a hydroxy group; Y1 is a group selected from NH, NHCO, O and the like; Y2 is a group selected from formula IV and formula V; Z1, Z2 and Z3 are each an aryl or a 1-4C alkyl group having a hydrophilic group, or a group of formula VI (wherein R2 is H or a 1-6C alkyl group; and (m) is an integer of 1-50). The hydrophilic group contained in Z1 to Z3 is hydroxy, carboxyl, sulfonic acid group or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous organic pigment, a method for producing the same, and an organic pigment dispersion and an aqueous ink. The characteristic feature is that the dispersion stability of the organic pigment in the ink is improved, and the fluidity and storage stability of the organic pigment dispersion using the organic pigment and the aqueous ink are improved.

[0002]

2. Description of the Related Art In recent years, in the fields of inks and paints, pigments dispersed in an aqueous medium have been used from the viewpoint of easy handling and safety.

In dispersing a pigment in an aqueous medium as described above, a highly polar pigment such as titanium oxide is easily dispersed in an aqueous medium such as highly polar water, but an organic pigment having a strong hydrophobicity is used. Does not disperse well in aqueous media, this organic pigment is easily separated, and when used in inks and paints, its fluidity and storage stability deteriorate, and when this ink or paints is applied In addition, there is a problem that the gloss and the color of the coating film deteriorate and the durability also deteriorates.

In recent years, various methods have been developed to sufficiently disperse the organic pigment in an aqueous medium. For example, a method of treating the surface of the organic pigment with rosin or a surfactant, a method of treating the surface of the organic pigment, Plasma treatment method,
A method of encapsulating an organic pigment using a hydrophilic polymer, a method of polymerizing a vinyl monomer with radical species on the surface of the organic pigment, and the like have been proposed.

[0005] However, each of the above methods is suitable for dispersing a specific organic pigment in an aqueous medium, but is not necessarily effective for various kinds of organic pigments. There was a problem in point.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems in an organic pigment used by being dispersed in an aqueous medium. The problem is to improve the surface stability of each organic pigment used, improve the dispersion stability of the organic pigment in an aqueous medium, and improve the fluidity and storage stability of an organic pigment dispersion using an organic pigment and an aqueous ink. It is assumed that.

[0007]

According to the first aspect of the present invention, in the aqueous organic pigment according to the first aspect of the present invention, in order to solve the above-mentioned problems, the surface of the organic pigment is coated with the general formula (1) At least one type of hydrophilic modifying group represented by (2) is bonded.

Here, the general formula (1),
The hydrophilic modifying group represented by (2) is appropriately bonded to the surface of any organic pigment, and the hydrophilic modifying group is bonded to the surface of the organic pigment, whereby the organic pigment in an aqueous medium is Dispersibility is improved.

Here, as the organic pigment, known pigments generally used can be used, for example, azo pigments such as azo lake, insoluble azo and condensed azo; phthalocyanine, perylene, berynone, anthraquinone And polycyclic pigments such as quinacridone and dioxazine.

In the hydrophilic modifying group to be bonded to the surface of the organic pigment, the above-mentioned general formula (1),
The hydrophilic groups of Z ₁ , Z ₂ and Z ₃ in (2) are
At least one selected from a hydroxyl group, a carboxyl group and salts thereof, a sulfonic acid group and salts thereof, and an amino group
It is preferably a seed group.

In producing the aqueous organic pigment according to the first aspect, as described in the third aspect,
After treating the surface of the organic pigment with a silane coupling agent having a reactive group, a compound having a hydrophilic group and a group reacting with a reactive group in the silane coupling agent may be reacted. As shown, after reacting a silane coupling agent having a reactive group with a compound having a reactive group and a hydrophilic group in the silane coupling agent, the reaction product is used to form an organic pigment. Allow the surface to be treated.

Here, as the silane coupling agent having a reactive group, those represented by the following general formula (5) can be used. Y'-X-Si (OR) ₃ (5)

In the general formula (5), Y ′
Is a reactive group, for example, an amino group, an epoxy group, an isocyanate group and the like. X has 1 carbon atom.
To 4 or an alkylene oxide group shown in Chemical formula 2 above, and these groups may have a hydroxyl group. R is a lower alkyl group such as a methyl group and an ethyl group.

Examples of the silane coupling agent having a reactive group as described above include γ-glycidoxymethoxysilane, γ-glycidoxytriethoxysilane, glycidyltrimethoxysilane, glycidyltriethoxysilane, -Aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 2-aminoethylaminoethyltrimethoxysilane, 2-aminoethylaminoethyltriethoxysilane, 3-isocyanatopropyltrimethoxysilane, 3-isocyanatopropyltri Ethoxysilane or the like can be used.

On the other hand, as the compound having a group which reacts with a reactive group and a hydrophilic group in the silane coupling agent, a compound represented by the following general formula 5 can be used.

[0016]

Embedded image

In the above formula, A is a group that reacts with the reactive group of the silane coupling agent.
Examples thereof include a hydroxyl group, a carboxyl group, an amino group, an acid anhydride group, an epoxy group and the like. R ₂ is hydrogen or an alkyl group having 1 to 6 carbon atoms, and m is an integer of 1 to 50.

The above-mentioned compound having a group which reacts with a reactive group and a hydrophilic group in the silane coupling agent includes, for example, oxycarboxylic acids such as malic acid, dimethylolpropionic acid and hydroxycaproic acid; glutamic acid; Amino acids such as lecithin and salts thereof; aminoalkylsulfonic acids and salts thereof such as aminoethanesulfonic acid and aminopropanesulfonic acid; succinic anhydride, maleic anhydride, phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, etc. Acid anhydrides; epoxy compounds such as glycidol and epichlorohydrin, monoethanolamine,
Alkanolamines such as diethanolamine and triethanolamine can be used.

In treating the surface of the organic pigment with a silane coupling agent having a reactive group, any of a dry method and a wet method may be used. it can. In the case of the dry method, an organic pigment and a silane coupling agent are added to a mixer and mixed. Here, when adding the silane coupling agent, the silane coupling agent is added as it is in a stock solution or dissolved in an appropriate solvent.
In addition, in performing the above-described mixing treatment, the treatment is usually performed at a temperature of room temperature to 130 ° C. for 30 to 90 minutes. On the other hand, in the case of the wet method, an organic pigment and a silane coupling agent are mixed in an organic solvent such as an ester or an aromatic hydrocarbon.

Further, in the above-mentioned claim 3, when reacting a compound having a group which reacts with a reactive group of the silane coupling agent and a compound having a hydrophilic group, a dry method,
Any of the wet methods can be used. In the case of the dry method, the above compound is added to the organic pigment treated with the silane coupling agent as described above, and the mixture is reacted at a temperature of usually 30 to 120 ° C. for 2 to 5 hours with stirring. To In the case of the dry method, there is no need to remove the solvent after the treatment, and the operation is easy. In the case of the wet method, there is an advantage that uniform treatment can be performed.

Further, as described in claim 4 above, a silane coupling agent having a reactive group is reacted with a compound having a group reactive with the reactive group and a compound having a hydrophilic group in the silane coupling agent. After treating the surface of the organic pigment with the reaction product,
In this case, the order of the reaction is merely changed.First, a compound having a group reactive with the reactive group of the silane coupling agent and a compound having a hydrophilic group is reacted with the silane coupling agent. The surface of the organic pigment is treated with the silane coupling agent.

Here, in obtaining the aqueous organic pigment as described above, if the amount of the silane coupling agent is small,
While it is not possible to sufficiently impart dispersion stability in an aqueous medium to the organic pigment, if the amount of the silane coupling agent is too large, the cost increases and impurities are easily generated, so that the Weight ratio of silane coupling agent (silane coupling agent / organic pigment)
Is preferably in the range of 1/1000 to 2/10, and more preferably in the range of 1/100 to 1/10.

When the amount of the compound having a group which reacts with the reactive group of the silane coupling agent and the hydrophilic group is too small, the organic pigment may have sufficient dispersion stability in an aqueous medium. Therefore, the molar ratio of this compound to the silane coupling agent (compound / silane coupling agent) is preferably set to 1/10 or more.

Further, in the organic pigment dispersion according to claim 7 of the present invention, the aqueous organic pigment obtained as described above is dispersed in an aqueous medium.

Here, when dispersing the aqueous organic pigment in the aqueous medium, the aqueous organic pigment is dispersed using a ball mill, a roll mill, a bead mill, a dissolver, a homogenizer, or the like.

Further, in the aqueous ink according to claim 8 of the present invention, the organic pigment dispersion and the binder are contained.

Here, as the binder, for example, water-soluble resins such as polyvinyl alcohol, hydroxycellulose, carboxycellulose, casein; rosin / maleic acid, (meth) acrylic copolymer, styrene /
An alkali-soluble resin such as a maleic acid copolymer, a styrene / (meth) acrylic acid copolymer, and a styrene / α-methylstyrene / acrylic acid copolymer can be used.

Examples of the alkali for solubilizing the alkali-soluble resin include, for example, alkylamines such as ammonia, triethylamine and tripropylamine;
Alkanolamines such as monoethanolamine, diethanolamine and triethanolamine; inorganic alkalis such as sodium hydroxide and potassium hydroxide can be used.

In the aqueous ink, in addition to the organic pigment dispersion and the binder, for example, an antiblocking agent, a humectant, a lubricant, a preservative, an antioxidant, etc. are added according to the use. You can also.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an aqueous organic pigment and an organic pigment dispersion according to an embodiment of the present invention will be described, and in the organic pigment dispersion and the aqueous ink using the organic pigment dispersion in this embodiment, an organic pigment will be described. Are sufficiently dispersed to show excellent fluidity and storage stability with reference to Comparative Examples.

(Embodiment 1) In this embodiment, 50
In a 0 ml beaker, 40 parts by weight of cyanine blue as an organic pigment, 200 parts by weight of ethyl acetate, and 2 parts by weight of 3-isocyanatopropyltrimethoxysilane as a silane coupling agent were added at room temperature using a homogenizer. After dispersing for 1 hour, 3 parts by weight of diethanolamine as a compound having a group reactive with the reactive group of the silane coupling agent and a hydrophilic group was added thereto, and the mixture was reacted for 1 hour.

Thereafter, the above-mentioned ethyl acetate was removed, and the treated cyanine blue was dried under reduced pressure at room temperature for 4 hours to obtain an aqueous organic pigment to which a hydrophilic modifying group represented by the following chemical formula 6 was bonded.

[0033]

Embedded image

Then, the aqueous organic pigment obtained as described above was added to water, and this was dispersed with a homogenizer to obtain an organic pigment dispersion having a pigment concentration of 15% by weight.

(Example 2) In this example, only the reaction sequence was changed from that of the above-mentioned Example 1, and the silane coupling agent, 3-isocyanatopropyltrimethoxysilane, and this silane coupling agent In the case of Example 1 above, the surface of the organic pigment cyanine blue was treated with the reaction product in advance by reacting with diethanolamine which is a compound having a group reactive with the reactive group and a hydrophilic group. In the same manner as in the above, an aqueous organic pigment having the hydrophilic modifying group shown in Chemical formula 6 was obtained.

Also in this example, the aqueous organic pigment obtained as described above was added to water, and this was dispersed with a homogenizer to obtain an organic pigment dispersion having a pigment concentration of 15% by weight. .

EXAMPLE 3 In this example, as in Example 1, 40 parts by weight of cyanine blue as an organic pigment, 200 parts by weight of ethyl acetate, and 3-isocyanate as a silane coupling agent were used. Natopropyltrimethoxysilane was added at a ratio of 2 parts by weight, and these were dispersed with a homogenizer at room temperature for 1 hour. Then, 3 parts by weight of polyethylene glycol having a molecular weight of 400 was added as a compound having a group that reacts with the reactive group of the silane coupling agent and a hydrophilic group, and the mixture was reacted for 4 hours while refluxing.

Thereafter, the above-mentioned ethyl acetate was removed, and the treated cyanine blue was air-dried at room temperature for 24 hours to obtain an aqueous organic pigment having a hydrophilic modifying group shown in Chemical Formula 7 below.

[0039]

Embedded image

In the hydrophilic modifying group shown in Chemical formula 7, m was 9 or 10.

Also in this example, the aqueous organic pigment obtained as described above was added to water, and this was dispersed with a homogenizer to obtain an organic pigment dispersion having a pigment concentration of 15% by weight. .

Example 4 In this example, the silane coupling agent used in Example 1 was used
An aqueous organic pigment to which a hydrophilic modifying group represented by the following chemical formula 8 was bonded was obtained in the same manner as in Example 1 except that glycidoxypropyltrimethoxysilane was used.

[0043]

Embedded image

Also in this example, the aqueous organic pigment obtained as described above was added to water, and this was dispersed with a homogenizer to obtain an organic pigment dispersion having a pigment concentration of 15% by weight. .

Example 5 In this example, the silane coupling agent used in Example 1 was changed to γ-glycidoxypropyltrimethoxysilane, the same as in Example 4, and Sodium aminoethanesulfonate is used as a compound having a group that reacts with the reactive group of the silane coupling agent and a hydrophilic group, and otherwise is shown in the following chemical formula 9 in the same manner as in Example 1 above. An aqueous organic pigment having a hydrophilic modifying group bonded thereto was obtained.

[0046]

Embedded image

Also in this example, the aqueous organic pigment obtained as described above was added to water, and this was dispersed with a homogenizer to obtain an organic pigment dispersion having a pigment concentration of 15% by weight. .

Example 6 In this example, the silane coupling agent used in Example 1 was changed to γ-glycidoxypropyltrimethoxysilane, which was the same as in Example 4, and Phthalic acid is used as a compound having a group that reacts with a reactive group of the silane coupling agent and a hydrophilic group, and the other conditions are the same as in Example 1 described above, except for the hydrophilic modification represented by Chemical Formula 10 below. An aqueous organic pigment having attached groups was obtained.

[0049]

Embedded image

Also in this example, the aqueous organic pigment obtained as described above was added to water, and this was dispersed with a homogenizer to obtain an organic pigment dispersion having a pigment concentration of 15% by weight. .

Example 7 In this example, the silane coupling agent used in Example 1 was
Along with changing to aminopropyltrimethoxysilane,
Epichlorohydrin was used as a compound having a group that reacts with the reactive group of the silane coupling agent and a hydrophilic group, and the other conditions were the same as in Example 1 described above except for the hydrophilic modification shown in Chemical Formula 11 below. An aqueous organic pigment having attached groups was obtained.

[0052]

Embedded image

Also in this example, the aqueous organic pigment obtained as described above was added to water, and this was dispersed with a homogenizer to obtain an organic pigment dispersion having a pigment concentration of 15% by weight. .

Example 8 In this example, the silane coupling agent used in Example 1 was changed to the same 3-aminopropyltrimethoxysilane as in Example 7, and Succinic anhydride is used as a compound having a group that reacts with a reactive group of the silane coupling agent and a hydrophilic group. An aqueous organic pigment to which a modifying group was bonded was obtained.

[0055]

Embedded image

Also in this example, the aqueous organic pigment obtained as described above was added to water, and this was dispersed with a homogenizer to obtain an organic pigment dispersion having a pigment concentration of 15% by weight. .

(Example 9) In this example, the organic pigment used in Example 1 was changed to quinacridone magenta, and the other conditions were the same as in Example 1 above. Thus, an aqueous organic pigment to which the hydrophilic modifying group shown in No. 6 was bonded was obtained.

Also in this example, the aqueous organic pigment obtained as described above was added to water, and this was dispersed with a homogenizer to obtain an organic pigment dispersion having a pigment concentration of 15% by weight. .

(Example 10) In this example, the organic pigment used in Example 1 was changed to chromophthal yellow, and otherwise, the organic pigment used in Example 1 was changed.
In the same manner as in the case of the above, an aqueous organic pigment to which the hydrophilic modifying group shown in Chemical formula 6 was bonded was obtained.

Also in this example, the aqueous organic pigment obtained as described above was added to water, and this was dispersed with a homogenizer to obtain an organic pigment dispersion having a pigment concentration of 15% by weight. .

Example 11 In this example, the ratio of 3-isocyanatopropyltrimethoxysilane used as the silane coupling agent in Example 1 was 0.04 parts by weight, The ratio of diethanolamine used as the compound having a group that reacts with the reactive group and the hydrophilic group was changed to 0.06 parts by weight, and the other conditions were the same as in Example 1 above. Thus, an aqueous organic pigment to which the hydrophilic modifying group shown in No. 6 was bonded was obtained.

Also in this example, the aqueous organic pigment obtained as described above was added to water, and this was dispersed with a homogenizer to obtain an organic pigment dispersion having a pigment concentration of 15% by weight. .

Comparative Example 1 In this comparative example, 3-isocyanatopropyltrimethoxysilane used as a silane coupling agent in Example 1 was not used. The organic pigment cyanine blue was treated in the same manner as in the above. In addition,
No hydrophilic modifying group was bonded to the surface of cyanine blue treated in this way.

Also in this comparative example, the organic pigment obtained as described above was added to water, and this was dispersed with a homogenizer to obtain an organic pigment dispersion having a pigment concentration of 15% by weight.

Comparative Example 2 In this comparative example, the silane coupling agent used in Example 1 was changed to 3-aminopropyltrimethoxysilane, which was the same as in Example 7, while Avoid using a compound having a group that reacts with the reactive group of the coupling agent and a hydrophilic group, and otherwise use the above Example 1
In the same manner as in the above case, an organic pigment having a group represented by the following chemical formula 13 was obtained.

[0066]

Embedded image

Also in this comparative example, the organic pigment obtained as described above was added to water, and this was dispersed with a homogenizer to obtain an organic pigment dispersion having a pigment concentration of 15% by weight.

Comparative Example 3 In this comparative example, glass beads having a diameter of 2 mm were placed in a 200-ml bottle, 15 parts by weight of quinacridone magenta was used as an organic pigment, and a styrene-maleic acid-based pigment dispersant was used. 5 parts by weight and 48 parts by weight of water are added, and they are mixed by a paint conditioner. Thereafter, water is added to the mixture so that the total amount becomes 100 parts by weight, and the mixture is mixed for 10 minutes to disperse the organic pigment. I got a body.

Comparative Example 4 In this comparative example, 40 parts by weight of cyanine blue, 200 parts by weight of ethyl acetate, and 0.5 parts by weight of 3-isocyanatopropyltrimethoxysilane as a silane coupling agent were used as organic pigments. And these were dispersed for 1 hour at room temperature with a homogenizer. Then, 25 parts by weight of polyethylene glycol having a molecular weight of 4000 was added as a compound having a group that reacts with the reactive group of the silane coupling agent and a hydrophilic group, and the mixture was reacted for 4 hours while being refluxed.

Thereafter, the ethyl acetate was removed, and the treated cyanine blue was air-dried at room temperature for 24 hours.
An aqueous organic pigment to which a hydrophilic modifying group was bonded was obtained.

In this comparative example, the value of m in Chemical Formula 7 is about 90, and m is 1
The above condition of the present invention of an integer of ５０50 was not satisfied.

Also in this comparative example, the aqueous organic pigment obtained as described above was added to water, and this was dispersed with a homogenizer to obtain an organic pigment dispersion having a pigment concentration of 15% by weight. .

Next, the above Examples 1 to 11 and Comparative Example 1
60 parts by weight of each of the organic pigment dispersions of Nos. 1 to 4, 30 parts by weight of a 30% aqueous solution obtained by neutralizing a styrene-α-methylstyrene-acrylic acid copolymer (acid value 220) with ammonia water as a binder, These were mixed and stirred in a ratio of parts by weight to prepare aqueous inks using the organic pigment dispersions of Examples 1 to 11 and Comparative Examples 1 to 4.

The storage stability and fluidity of each of the organic pigment dispersions and aqueous inks of Examples 1 to 11 and Comparative Examples 1 to 4 prepared as described above were evaluated. 1 is shown.

Here, regarding the storage stability, the degree of sedimentation of the organic pigment after visually preparing each of the organic pigment dispersions and the aqueous ink described above and allowing to stand for 24 hours was evaluated. The case where slight sedimentation was observed was indicated by ○, the case where sedimentation was partially observed was indicated by △, and the case where sedimentation was completely occurred was indicated by ×.

The fluidity of the organic pigment dispersion and the aqueous ink was measured using a BL viscometer under an environment of 25 ° C. and a rotor rotation speed of 30 rpm.
At a rotor speed of 60 rpm (ρ2), and the ratio of these viscosities (ρ1)
1 / ρ 2), and when the ratio is 1.0 or more and less than 1.1, ○, when the ratio is 1.1 or more and less than 1.3, Δ1.3
The above cases are indicated by x. Note that this ratio (ρ1 / ρ2)
As the value approaches 1, the dispersibility of the organic pigment increases and the fluidity increases.

[0077]

[Table 1]

As is apparent from the results, as shown in Examples 1 to 11, the hydrophilic modifying groups represented by the general formulas (1) and (2) are bonded to the surface of the organic pigment. When using the aqueous organic pigments described above, when using the organic pigments of Comparative Examples 1 and 3 to which the hydrophilic modifying group is not bonded as described above, or when the conditions of the general formulas (1) and (2) are used. The dispersion stability of the organic pigment in the aqueous medium is improved as compared with the case of using the organic pigments of Comparative Examples 2 and 4 in which unsatisfied groups are bonded, and the aqueous organic pigments of Examples 1 to 11 are used. The storage stability and fluidity of the organic pigment dispersion and the aqueous ink were improved.

In the case of Example 11 described above, the amount of the silane coupling agent used, the group reactive with the reactive group of the silane coupling agent, and the compound having a hydrophilic group was reduced. The storage stability and fluidity of the organic pigment dispersion and the aqueous ink were lower than those of the other examples.

[0080]

As described above in detail, in the aqueous organic pigment according to the present invention, the above-mentioned compound (1) is formed on the surface of the organic pigment.
Since the hydrophilic modifying groups represented by the general formulas (1) and (2) shown in (1) are bonded, the dispersion stability of the organic pigment in an aqueous medium is improved by the hydrophilic modifying groups.
In addition, the hydrophilic modifying group was appropriately bonded to the surface of any organic pigment, and the dispersion stability of various kinds of organic pigments in an aqueous medium could be improved.

As a result, when an organic pigment dispersion or an aqueous ink is obtained using the aqueous organic pigment to which the hydrophilic modifying group is bonded, the fluidity and storage stability of the organic pigment dispersion and the aqueous ink are reduced. Improved.

Claims (8)

[Claims] 1. An aqueous organic material comprising at least one hydrophilic modifying group represented by the following general formula (1) or (2) bonded to the surface of an organic pigment. Pigment. Embedded image In the hydrophilic modifying groups represented by the general formulas (1) and (2), X is an alkylene group having 1 to 4 carbon atoms or an alkylene oxide group represented by the following chemical formula 2, and these groups are hydroxyl groups. May be provided. Y ₁ is -NH-, -N
HCO-, -O-, -OCO-, -NHCOO-, -N
It is at least one group selected from HCONH-. Y ₂ is a group selected from the following general formulas (3) and (4). Z ₁ , Z ₂ , and Z ₃ are an aryl group having a hydrophilic group, an alkyl group having 1 to 4 carbon atoms, or a group represented by the following chemical formula 4, respectively. Embedded image In the formula shown in Chemical Formula 2, R ₁ has 1 to ₁ carbon atoms.
4 represents an alkylene group, and n represents an integer of 1 to 3. Embedded image Embedded image In the formula, R ₂ represents hydrogen or an alkyl group having 1 to 6 carbon atoms, and m represents an integer of 1 to 50. 2. The aqueous organic pigment according to claim 1, wherein the hydrophilic groups represented by Z ₁ , Z ₂ and Z _{3 in} the hydrophilic modifying groups represented by the general formulas (1) and (2) are the same. An aqueous organic pigment characterized in that it is at least one group selected from the group consisting of hydroxyl group, carboxyl group and salts thereof, sulfonic acid group and salts thereof, and amino group. 3. The method according to claim 1, wherein the surface of the organic pigment is treated with a silane coupling agent having a reactive group, and then a compound having a reactive group and a compound having a hydrophilic group in the silane coupling agent are reacted. A method for producing an aqueous organic pigment. 4. After reacting a silane coupling agent having a reactive group with a compound having a hydrophilic group and a group reactive with the reactive group in the silane coupling agent,
A method for producing an aqueous organic pigment, comprising treating the surface of the organic pigment with the reaction product. 5. The method for producing an aqueous organic pigment according to claim 3, wherein the reactive group in the silane coupling agent is at least one selected from an amino group, an epoxy group, and an isocyanate group. A method for producing an aqueous organic pigment, which is a base. 6. The method for producing an aqueous organic pigment according to claim 3, wherein the group that reacts with the reactive group of the silane coupling agent is a hydroxyl group, an amino group, a carboxyl group, or an acid anhydride. A method for producing an aqueous organic pigment, comprising at least one group selected from groups. 7. An organic pigment dispersion, wherein the aqueous organic pigment according to claim 1 or 2 is dispersed in an aqueous medium. 8. An aqueous ink comprising at least the organic pigment dispersion according to claim 7 and a binder.