JPH11189739A - Aqueous pigment ink composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an aqueous pigment ink composition excellent in discharge stability and discharge responsiveness when used in ink jet recording, capable of printing without causing clogging in orifice of a head and exhibiting sufficient printing concentration and capable of smoothly writing from fine pen tip when used as aqueous ink for writing tools, having good water resistance and light resistance as well as high printing concentration, free from unevenness of writing and capable of providing clear recording image having good hue. SOLUTION: In this aqueous pigment ink composition containing at least aqueous solution medium and a colored pigment, the colored pigment is obtained by subjecting an organic pigment exhibiting chromatic color to wet oxidation with a gypohalous acid and/or its salt. At least a part of an acidic hroup formed (or provided) on surface part of the colored pigment is preferably an ammonium salt, an amine salt or an alkali metal salt.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous pigment ink composition containing a color pigment, and more particularly to an aqueous pigment ink composition containing an oxidized organic pigment having undergone an oxidation treatment as a color pigment.

[0002]

2. Description of the Related Art Conventionally, a dye-containing aqueous ink has been mainly used as a coloring agent in recording liquids for writing instruments and ink jet printers. In particular, chromatic inks other than black are still mainly used for dyes in writing instruments and ink jet printers. A chromatic dye has a clear hue and can provide high-quality printing, but the light resistance and water resistance of a recorded image are not sufficient. In recent years, the demand for robustness for recorded images has been increasing, and aqueous pigment ink compositions using pigments have been receiving attention.

[0003] In general, pigments do not exhibit hydrophilicity, and therefore are difficult to disperse alone in water. Therefore, in the presence of a dispersant, various types of dispersers are used to stabilize the dispersion of the pigment in an aqueous medium. However, since the above-mentioned ink does not have sufficient dispersion stability of the pigment, it can be used as a general-purpose writing instrument, but is sufficiently satisfactory as a writing instrument or an ink jet recording ink that requires high-precision stability over time. is not.

[0004] As an attempt of an aqueous pigment ink composition using such a pigment exhibiting a chromatic color, an ink composition for erasable writing implements containing spherical resin particles in a pigment (chromatic pigment), a binder and a liquid medium has been proposed. Product (JP-A-63-145)
No. 383); an aqueous pigment ink composition for a non-absorbable writing material comprising a pigment, a dispersant, and an aqueous medium (Japanese Patent Application Laid-Open No. H05-208, JP-A-Hei-5).
JP-A-51550); an inkjet ink containing water, an organic pigment having a particle size of 5 μm or less, and a water-soluble binding resin (JP-A-7-310038);
Aqueous pigment dispersion containing an alkali-soluble resin dispersant and a surfactant and a method for producing the same (Japanese Patent Application Laid-Open No. H8-7378)
No. 7); an ink-jet ink composition containing water, a pigment, a polymer dispersant having a carboxyl group, a hydroxide of an alkali metal and an alcoholamine having at least one hydroxyl group (JP-A-8-253719). Gazette) and the like.

In general, in order to generate droplets stably from a fine tip of an ink jet recording head or to write smoothly with a thin pen tip of an aqueous ballpoint pen, solidification due to drying at an orifice of an ink jet recording head or a ballpoint pen tip is required. It is necessary to prevent aggregation and sedimentation of the organic pigment.

However, when a dispersant is used as in the above-described water-based pigment ink composition, the resin forming the dispersant is not redissolved after adhering to the orifice or the like.
Clogging and non-ejection of droplets may occur. In addition, since the aqueous pigment ink composition containing a dispersant has a viscous tone, when performing continuous ejection and high-speed printing for a long time, resistance occurs in the path to the nozzle tip, and ejection becomes unstable, and smooth recording is difficult. Become. Further, the aqueous pigment ink composition has a disadvantage that the pigment concentration cannot be sufficiently increased in order to secure ejection stability, and the print density is insufficient as compared with the aqueous dye ink.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems. It is an object of the present invention to provide excellent ejection stability and ejection responsiveness when used in ink jet recording, and to cause clogging at an orifice of a head. It is an ink that can print easily and shows sufficient print density, and even when used as a water-based ink for writing implements, it can write smoothly from a thin pen tip, and has good water resistance and light resistance, high print density, writing It is an object of the present invention to provide a water-based pigment ink composition from which a clear and good hue-recorded image without unevenness is obtained.

[0008]

According to the present invention, there is provided an aqueous pigment ink composition containing at least an aqueous liquid medium and a colored pigment, wherein the colored pigment is an organic pigment exhibiting a chromatic color, which is composed of hypohalous acid and / or It is intended to provide an aqueous pigment ink composition which is obtained by wet oxidation using the salt,
Thereby, the above object is achieved.

That is, in the aqueous pigment ink composition containing the aqueous liquid medium of the present invention and an organic pigment exhibiting a chromatic color, the oxidized organic pigment exhibiting a chromatic color comprises (a) an organic pigment exhibiting a chromatic color. Finely dispersing the pigment in water, (b) oxidizing with an oxidizing agent (eg, hypohalous acid and / or a salt thereof), and (c) after the steps (a) and (b). Purification and concentration to obtain an aqueous dispersion having a pigment concentration of 10 to 30% by weight.

After the above-mentioned steps (a) and (b), a step of neutralizing a part of the acidic groups formed (or provided) on the surface of the organic pigment particles exhibiting a chromatic color with a basic compound. Further, it may be produced by a method including the above.

[0011] The inventors of the present invention provide hypohalous acid and / or
Alternatively, the organic pigments exhibiting chromatic colors oxidized by using the salts thereof have an increased number of carboxyl groups and hydroxyl groups, so that the dispersibility (partially solubility) ) Is improved, and the viscosity of the ink is appropriately adjusted by preparing the aqueous pigment ink composition, the ejection stability and ejection response are excellent, the stability over time during long-term storage is good, and no clogging occurs. That is, the aqueous ink composition of the present invention was completed.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The coloring pigment used in the present invention has a high surface active hydrogen content and has many hydroxyl groups and carboxyl groups having active hydrogen on the surface (part) of the pigment particles, so that the pigment itself has a hydrophilic property. (Surface-active hydrogen means a hydrogen atom at the terminal of a substituent added to the surface of organic pigment particles exhibiting a chromatic color by an oxidation treatment.)
In addition, the oxygen content of the above-mentioned coloring pigments is clearly increased due to an increase in oxygen-containing functional groups such as a carboxyl group and a hydroxyl group, as compared with the organic pigment exhibiting a chromatic color before the oxidation treatment.

Further, by subjecting the coloring pigment of the present invention to an oxidation treatment, water-soluble groups such as a carboxyl group and a hydroxyl group increase, and the surface has chemical dispersibility as if it were an acidic dye. In addition, the inside has retained the characteristics of organic pigments showing chromatic colors before oxidation treatment,
The light resistance and the heat resistance are the same as those of a conventional chromatic organic pigment.

The oxidizable organic pigment of the present invention has a chromatic color such as yellow, orange, red, brown, green, blue or violet. The structure of the organic pigment is not particularly limited. Phthalocyanine pigment, azo pigment, naphthol azo pigment, azo lake pigment, azomethine pigment, anthraquinone pigment, quinacridone pigment, dioxazine pigment, diketopyrrolopyrrole pigment, anthrapyridine pigment, anthanthrone pigment, Isoindolinone pigments, indanthrone pigments, flavanthrone pigments, perinone pigments, perylene pigments, indigo pigments, thioindigo pigments, quinophthalone pigments, quinoline pigments, benzimidazolone pigments, triphenyl methane pigments Organic pigments such as pigments can be used. Preferred are phthalocyanine pigments, azo pigments, perylene pigments, quinacridone pigments, and diketopyrrolopyrrole pigments.

The oxidizable organic pigments of the present invention having chromatic colors are exemplified below for each color.

(1) Yellow organic pigments are insoluble azo organic pigments, and Hansa Yellows are C.I. I. P
Ignition Yellow 1, 2, 3, 4,
5, 5, 6, 10, etc .; Benzidine yellows include C.I. I. Pigment Yellow 12,
13, 13 and 15, and 17 and the like.

The isoindolinone-based organic pigments include:
C. I. Pigment Yellow 109, 11
0 and 137.

The benzimidazolone-based organic pigments include:
C. I. Pigment Yellow 120, 15
4 and the like.

The anthraquinone organic pigments include C.I.
I. Pigment Yellow 23, 24, 9
9, 123, and 147.

Examples of the condensed azo organic pigment include C.I. I. P
i.g., Yellow 93, 95 and 128.

The insoluble azomethine-based organic pigments include
C. I. Pigment Yellow 101, 12
9 and the like. As quinophthalone organic pigments,
C. I. Pigment Yellow 138 and the like.

Examples of quinoline organic pigments include C.I. I. P
and the like.

(2) Among the orange organic pigments, insoluble azo organic pigments include C.I. I. Pigment Ora
nge1, same 2, same 3, same 5, same 13, same 14,
15, 15, 16, 17, 18, 19, 22, 24, 32, 33, 34, 36, 38, 4
4, same 46, same 50, same 54, same 55, same 56, same 5
7, 58, 62, 63 and the like. Examples of anthraquinone-based organic pigments include C.I. I. Pigment
Orange 40, 43 and the like. Examples of quinacridone organic pigments include C.I. I. Pigment Or
angel47 and the like.

The isoindolinone-based organic pigments include
C. I. Pigment Orange 42 and 61.

The benzimidazolone organic pigments include:
C. I. Pigment Orange 60 and the like.

(3) Among the red organic pigments, insoluble azo organic pigments include C.I. I. Pigment Red
2, 3, 4, 5, 6, 7, 8, 9, 9
0, 11, 11, 12, 13, 14, 15, 1
6, 17, 18, 19, 21, 22, 22
3, 30, 30, 31, 32, 37, 38, 3
9, 112, 114, 146, 150, 17
0, 176, 185, 187, and 208.

Examples of anthraquinone-based organic pigments include C.I.
I. Pigment Red 83, 84, 85, 89 and the like.

As the perylene organic pigment, C.I. I. P
imag. Red 123, 149, 178, 179, 190 and the like.

The quinacridone organic pigments include C.I.
I. Pigment Red 122, 192, 19
4, 195 and 202.

The insoluble azomethine organic pigments include
C. I. Pigment Red 205 and the like.

(4) Among purple organic pigments, insoluble azo organic pigments include C.I. I. Pigment Vio
let8, 17, 25, 32, 41, 50 and the like.

The quinacridone organic pigments include C.I.
I. Pigment Violet 19, 30 and the like.

Examples of the dioxazine-based organic pigment include C.I.
I. Pigment Violet 23, 34, 3
5, and 37, 42, and the like.

As the triphenylmethane-based organic pigment,
C. I. Pigment Violet 3, 4 and 2
8 and the like.

As the anthraquinone organic pigment, C.I.
I. Pigment Violet 5, 6, 7, 8, 12, 12, 26, 31, 33, and the like.

As the perylene organic pigment, C.I. I. P
and the like.

(5) Among the blue organic pigments, insoluble azo organic pigments include C.I. I. Pigment Bl
ue25, 26, 27, 32, 41, 50 and the like.

Examples of the phthalocyanine organic pigment include C.I.
I. Pigment Blue 15, 16 and 17,
68 and 70.

As the indanthrene organic pigment, C.I.
I. Pigment Blue 60 and 64, C.I. I.
Vat Blue 4, 6 and the like.

The triallylmethane organic pigments include
C. I. Pigment Blue 12, 18, 18
9, 28, 53, 56, 57, 67 and the like.

As the triphenylmethane-based organic pigment,
C. I. Pigment Blue 1, 2, 3, 9, 9, 10, 11, 14, 24, 59, and 6
1, and 62.

Examples of the anthraquinone-based organic pigment include C.I.
I. Pigment Blue 21, 22 and 52,
64 and 65, and the like.

(6) Green organic pigments include phthalocyanine organic pigments such as C.I. I. Pigment Gr
een7, 13, 13, 25, 36, 37 and the like.

Examples of the anthraquinone-based organic pigment include C.I.
I. Pigment Green 47 and the like.

The triphenylmethane organic pigments include
C. I. Pigment Green 1, 2 and 4,
49 and the like.

(7) Among the brown organic pigments, insoluble azo organic pigments include C.I. I. Pigment Br
own1,2,3,5,23,25,3
2, 36 and the like.

As the perylene organic pigment, C.I. I. P
Pigment Brown 26 and the like.

The anthraquinone organic pigments include C.I.
I. Pigment Brown 28 and 30.

In the present invention, a general oxidizing method (for example, an oxidizing method by air contact,
Gas phase oxidation by reaction with nitrogen oxides and ozone, low-temperature plasma oxidation using oxides such as carbon dioxide, oxidizing agents such as nitric acid, potassium permanganate, potassium dichromate, hydrogen peroxide, and aqueous ozone More carboxyl groups or hydroxyl groups can be increased than in the oxidation method such as the liquid phase oxidation method used, and the most effective high surface active hydrogen content can be imparted. Specific examples of the hypohalite include sodium hypochlorite and potassium hypochlorite, and sodium hypochlorite is particularly preferred in terms of reactivity.

The oxidation of organic pigments exhibiting chromatic colors is generally carried out by
The effective halogen concentration is 10 based on the weight of the above-mentioned organic pigment.
~ 30% of a hypohalite (e.g. sodium hypochlorite) is charged into a suitable amount of water and allowed to react for 3 hours or more, preferably about 5 to 15 hours at room temperature. The reaction temperature can be appropriately adjusted in consideration of the above. Generally, the amount of hypohalite is from 5 to 300% by weight in terms of 100% based on the weight of the organic pigment exhibiting a chromatic color.

It is preferable that the chromatic organic pigment used as the raw material before oxidation is finely dispersed, that is, oxidized in a finely dispersed state. That is, fine dispersion is performed using a mill medium and a pulverizer before the oxidation treatment. Alternatively, fine dispersion may be performed by stirring or pulverizing together with an oxidation treatment in an aqueous solution of hypohalite or the like.

The fine dispersion is carried out when the organic pigment particles have an average particle size of 30.
The process is performed until the particle size becomes 0 nm or less, preferably 150 nm or less, 100 nm or less, and more preferably primary particles. The fine dispersion of the pigment is generally vertical sand mill, horizontal sand mill, ball mill, roll mill, and any other dispersing machine.
It may be used in consideration of the state of the pigment and the oxidation step.

Next, the product is filtered, and by-product salts are removed by washing with ion-exchanged water. If necessary, desalting and purification may be performed using a separation membrane having a fine pore size such as a reverse osmosis membrane or an ultrafiltration membrane. After acidification with a mineral acid such as hydrochloric acid, the mixture may be neutralized with an appropriate amount of a basic compound such as aqueous ammonia, purified again, and then concentrated. Purification and concentration are performed using a separation membrane having a fine pore size, such as a reverse osmosis membrane or an ultrafiltration membrane. The obtained pigment dispersion can be used as it is as an aqueous pigment ink composition, but in that case, the concentration of the organic pigment is preferably adjusted to 1 to 20% by weight.

The concentrated pigment dispersion may be further dried to obtain a powdery pigment, or the pigment dispersion may be further concentrated to a pigment concentration of 50%.
A pigment paste of about weight% may be used. Thereafter, these are dispersed in an aqueous medium and adjusted to an appropriate concentration to obtain the aqueous pigment ink composition of the present invention. In order to disperse the pigment or the pigment composition in the dispersion or solution of the water-soluble resin, it is preferable to use a disperser such as a dissolver, a high-speed mixer, a homomixer, a sand mill, and an attritor.

Since the aqueous pigment ink composition of the present invention has been sufficiently desalted and purified, corrosion of writing instruments and ink jet printers does not occur. Furthermore, since most or a part of the carboxyl group on the surface of the organic pigment is an alkali metal salt derived from hypohalite used as an oxidizing agent, there is no need to particularly adjust the pH. However, in order to impart good dispersion stability to the aqueous pigment ink composition of the present invention over a long period of time, it is necessary to adjust the pH to slightly acidic to alkaline (pH 8 to 10) as in the case of ordinary aqueous dye ink. preferable. Or, before or during the membrane treatment, adjust the pH of the solution to acidic with an acid such as hydrochloric acid and finish the membrane treatment to make it a carboxylic acid, and adjust the pH and stability with ammonia or amine during ink formation It is also possible.

Examples of the basic compound that can be used in the aqueous pigment ink composition composition of the present invention include ammonia water and water-soluble aliphatic amines substituted with an alkyl group having 1 to 3 carbon atoms (eg, methylamine, trimethylamine). Alkanolamine substituted with an alkanol group having 1 to 3 carbon atoms (eg, ethanolamine, diethanolamine, triethanolamine); an alkyl group having 1 to 3 carbon atoms and an alkanol having 1 to 3 carbon atoms Alkyl alkanolamines substituted with a group; hydroxides of alkali metals such as sodium hydroxide, potassium hydroxide and lithium hydroxide, and basic solvents. In addition, quaternary ammonium can be added.

The chromatic organic pigment of the present invention is generally contained in an amount of 0.1 to 50% by weight, preferably 1 to 30% by weight, based on the total amount of the aqueous pigment ink composition. . If the content of the pigment is less than 1% by weight, the printing or writing density becomes insufficient, and if it exceeds 30% by weight, the pigment is liable to agglomerate, causing precipitation during long-term storage, and poor discharge stability. .

The average particle size of the pigment in the aqueous pigment ink composition of the present invention is 300 nm or less, particularly 150 nm or less.
Further, the thickness is preferably 100 nm or less. If the average particle size of the pigment exceeds 300 nm, sedimentation of the pigment is likely to occur.

The aqueous liquid medium used in the aqueous ink composition of the present invention contains water as a main component, but may also contain an organic solvent compatible with water. (Water, a water-miscible organic solvent or a mixture thereof is referred to as an aqueous liquid medium in this specification.) Examples of suitable organic solvents having compatibility with water include alcohols, polyhydric alcohols, and cellosolves. And carbitols.

Examples of the water-miscible organic solvent include, for example, methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol,
C1-C4 alkyl alcohols such as sec-butyl alcohol and isobutyl alcohol; ketones or ketone alcohols such as acetone and diacetone alcohol; ethers such as tetrahydrofuran (THF) and dioxane; ethylene glycol, propylene glycol, diethylene glycol And polyalkylene glycols such as polyethylene glycol and polypropylene glycol; polyhydric alcohols such as ethylene glycol monoethyl ether, propylene glycol monomethyl ether, diethylene glycol monomethyl ether and triethylene glycol monoethyl ether. Lower alkyl ether; polyethylene glycol monomethyl ether Lower alkyl ether acetates such as Seteto; glycerol; and pyrrolidones such as 2-methylpyrrolidone and N- methyl-2-pyrrolidone. The use amount of these organic solvents is not particularly limited, but generally ranges from 3 to 50% by weight.

Further, the aqueous pigment ink composition of the present invention requires a known material used in an aqueous ink as an additive as long as the intended object of the present invention can be achieved and the effect can be exhibited. Depending on the situation, it can be appropriately selected and used in an appropriate amount. Such additives include, for example, dispersants (surfactants), anti-settling aids, surface tension adjusters, wetting agents, viscosity adjusters, pH adjusters, slow drying agents, preservatives, fungicides And an antifoaming agent.

As the dispersant, any of anionic, cationic, nonionic and amphoteric dispersants can be used.

Specifically, examples of the anionic dispersant include fatty hydrochloric acid, alkyl sulfate, alkyl aryl sulfonate, alkyl naphthalene sulfonate, dialkyl sulfonate, dialkyl sulfosuccinate, alkyl diaryl ether disulfonate. , Alkyl phosphate, polyoxyethylene alkyl ether sulfate, polyoxyethylene alkyl aryl ether sulfate, naphthalenesulfonic acid formalin condensate, polyoxyethylene alkyl phosphate ester salt, glycerol borate fatty acid ester, polyoxyethylene glycerol Examples thereof include fatty acid esters.

Examples of the nonionic dispersant include polyoxyethylene alkyl ether, polyoxyethylene alkyl aryl ether, polyoxyethylene oxypropylene block copolymer, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, and glycerin. Examples thereof include fatty acid esters, polyoxyethylene fatty acid esters, polyoxyethylene alkylamines, fluorine-based, and silicon-based nonionic activators.

Examples of the cationic dispersant include an alkylamine salt, a quaternary ammonium salt, an alkylpyridinium salt, an alkylimidazolinium salt and the like.

Examples of the zwitterionic dispersant include alkyl betaine, alkyl amine oxide, phosphadyl choline and the like.

The aqueous pigment ink composition of the present invention may optionally contain a water-soluble resin in order to impart gloss or the like to printed matter or written characters, or to impart an appropriate fixing property to the ink.
(For example, a low-condensate of vinylpyrrolidone, a water-soluble alkyd resin or a water-soluble acrylic resin), and an alcohol-soluble resin (for example, a phenol resin, an acrylic resin, a styrene-maleic acid resin or a ketone resin) can also be added.

In consideration of the water resistance of a printed image, it is preferable that the above resin is an ammonium salt. The water-soluble or alcohol-soluble resin is, in terms of the weight ratio from the viewpoint of the discharge stability of the aqueous pigment ink composition and the like, 1 to 1 of the organic pigment.
It is preferably set to 1/10 or less.

[0069]

According to the present invention, a commercially available organic pigment as a colorant has a strong lipophilic property and, when dispersed in water, requires a dispersing resin and a dispersing agent. On the other hand, the oxidized organic pigment provides an organic pigment excellent in water dispersibility. In this organic pigment, the amount of polar groups (for example, phenolic hydroxyl groups and carboxyl groups) on the surface is increased, and at the same time, the surface is ionically activated. Therefore, the recording liquid of the present invention is excellent in long-term dispersion stability without adding a pigment-dispersing resin or a surfactant or the like, or without performing a mechanical dispersion treatment. No sinking at

Further, the aqueous pigment ink composition of the present invention comprises
Even when used as a recording ink by an ink jet system or a writing ink such as a water-based ballpoint pen, the recording / writing characteristics are good and high-speed printing can be performed.

Furthermore, the robustness (light fastness and water fastness) of the characters and figures recorded on the paper surface is excellent, the pigment does not flow out even when immersed again in water, and has water fastness, and even when exposed to sunlight. Excellent light fastness without discoloration unlike dye ink. Since the organic pigment used in the present invention can be contained in the aqueous ink at a high concentration, the density of the printed matter is excellent, and an optical density equal to or higher than that of the water-soluble dye can be provided.

[0072]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but it should be understood that the present invention is by no means limited to these. In the following description, “parts by weight” is replaced by “parts”.
Abbreviated.

Example 1 Preparation of Pigment Dispersion Commercially available organic red pigment Shinkasha Red B RT-790
D (CI Pigment Violet 19: CI
BA-GEIGY (trade name) 300 g in water 1000
Then, the mixture was dispersed in a horizontal sand mill for 5 hours. Add sodium hypochlorite (effective chlorine concentration 12
%) Was added dropwise, and the mixture was stirred at 50 to 60 ° C for 15 hours. The obtained slurry was filtered with filter paper No. 2 (manufactured by Toyo Advantic) and washed with water until pigment particles leaked. The pigment wet cake was redispersed in 3000 ml of water, and the filtrate was desalted to a conductivity of 70 μS using a reverse osmosis membrane. Further, the pigment dispersion adjusted to pH = 9.5 with aqueous ammonia was concentrated to a pigment concentration of 10% by weight. The resulting pigment dispersion exhibited stable dispersibility.

Example 2 Preparation of aqueous pigment ink composition To 50 g of the pigment dispersion obtained in Example 1 was added ethanol 5
g and 2-methylpyrrolidone 5 g, and water was further added to make the total amount 100 g, whereby an aqueous pigment ink composition was obtained. The viscosity of this ink was 2 cps / 25 ° C. or less, and the average particle size of the pigment was 150 nm. The average particle size was measured using a laser light diffusion type particle size distribution analyzer (trade name: LPA3000 / 3100, manufactured by Otsuka Electronics Co., Ltd.).

Next, when the above ink was set in an ink jet recording apparatus (trade name: HG5130, manufactured by Epson Corporation) and printed, the ink ejection was stable and printing was carried out promptly. The pigment did not flow even when immersed in water, and the water resistance was good. The nozzle used was for a general aqueous dye ink, but the ink did not solidify, and there was no ejection failure in a printing test several hours later. Even if this ink is stored at 50 ° C. for one month, no sediment is generated, the average particle diameter and the viscosity are not changed, and the ink ejection is stable even if the printing test is performed again. Was. Macbeth densitometer TR-92
The optical density of the solid printed portion was measured at 7 (manufactured by Colmorgen) and found to be 1.34, which was sufficiently satisfactory.

Comparative Example 1 (a) Preparation of Pigment Dispersion Commercially available organic red pigment Shinkasha Red B RT-790
D (CI Pigment Violet 19: C
300 g of water (trade name, manufactured by IBA-GEIGY)
After mixing well to 0 ml, the mixture was dispersed in a horizontal sand mill for 5 hours.

(B) Preparation of aqueous pigment ink composition To 25 g of the dispersion obtained in (a) was added 5 g of ethanol and 2 g of ethanol.
A water-based pigment ink composition was obtained by adding 5 g of methylpyrrolidone and further adding water to make the total amount 100 g. The viscosity of this ink was 15 cps / 25 ° C. or less, and the average particle size of the pigment was 270 nm.

Example 3 Preparation of Pigment Dispersion A commercially available blue pigment Cyanine Blue BNRS (CI Pi
gment Blue 15: trade name of Toyo Ink Co., Ltd.)
After 300 g was well mixed with 1000 ml of water, the mixture was dispersed in a horizontal sand mill for 2 hours. 1000 g of sodium hypochlorite (effective chlorine concentration 12%) was added dropwise to this dispersion,
Stir at 20 ° C. for 12 hours. The obtained slurry was filtered with Toyo Filter Paper No. 2 and washed with water until pigment particles leaked. The pigment wet cake was redispersed in 3000 ml of water, and the filtrate was desalted to a conductivity of 70 μS using a reverse osmosis membrane. Further, this pigment dispersion was concentrated to a pigment concentration of 10% by weight. The resulting pigment dispersion exhibited stable dispersibility.

Example 4 Preparation of aqueous pigment ink composition 50 g of the pigment dispersion obtained in Example 3 was added to ethanol 5
g and 2 g of 2-methylpyrrolidone, and water was further added to make the total amount 100 g, whereby an aqueous pigment ink composition was obtained. The viscosity of this ink was 1.8 cps / 25 ° C. or less, and the average particle size was 100 nm. Next, when this ink was set in an ink jet recording apparatus and printed in the same manner as in Example 2, the ink was discharged stably and quickly, and the printed matter showed that the pigment flowed even when immersed in water after drying. No, and the water resistance was good. The nozzle used was for a general aqueous dye ink. However, the ink did not solidify, and there was no ejection failure in a print test several hours later. Even if this ink is stored at 50 ° C. for one month, no sediment is generated, the average particle diameter and the viscosity are not changed, and the ink ejection is stable even if the printing test is performed again. Was.

Comparative Example 2 (a) Preparation of Pigment Concentrated Dispersion Commercially available blue pigment Cyanine Blue BNRS (CI Pi
gment Blue 15: trade name of Toyo Ink Co., Ltd.)
After 300 g was well mixed with 1000 ml of water, the mixture was dispersed in a horizontal sand mill for 2 hours.

(B) Preparation of aqueous pigment ink composition To 25 g of the pigment dispersion obtained in (a), 5 g of ethanol and 5 g of 2-methylpyrrolidone were added, and the total amount was made 100 g with water to obtain an aqueous pigment ink composition. Viscosity 10 cps / 2
At 5 ° C., the dispersion stability was good. When this ink was set in an ink jet recording apparatus and printed, no ink was ejected.

Comparative Example 3 (a) Preparation of Pigment Concentrated Dispersion Commercially available blue pigment Cyanine Blue BNRS (CI Pi
gment Blue 15: trade name of Toyo Ink Co., Ltd.)
After thoroughly mixing 300 g with 300 g of John Krill 62 (aqueous styrene acrylic resin: trade name, manufactured by Johnson Polymer Co.) and 1000 ml of water, 10 g was mixed with a horizontal sand mill.
Time dispersed. The average particle size was 100 nm.

(B) Preparation of aqueous pigment ink composition 5 g of ethanol was added to 20 g of the pigment dispersion obtained in (a).
5 g of 2-methylpyrrolidone and 70 g of water were added to obtain an aqueous pigment ink composition. When this ink was set in an ink jet recording apparatus and printing was performed, a little printing could be performed at first, but the density gradually decreased, and finally printing became impossible.

Example 5 Preparation of aqueous pigment ink composition To 30 g of a 20% aqueous solution of oxidized carbon black wet-oxidized with sodium hypochlorite and 10 g of the pigment dispersion obtained in Example 3, 5 g of ethanol, An aqueous pigment ink composition was obtained by adding 5 g of methylpyrrolidone and 1 g of triethanolamine, and further adding water to make the total amount 100 parts. The viscosity of this ink is 2.0 cps
/ 25 ° C or less, and the average particle size was 60 nm.

Next, when this ink was set and printed in an ink jet recording apparatus in the same manner as in Example 1, the ink was discharged stably and quickly, and the printed matter had a vivid bluish black color. The pigment did not flow even when immersed in water after drying, and the water resistance was good. The nozzle used was for a general aqueous dye ink. However, the ink did not solidify, and there was no ejection failure in a print test several hours later. Even if this ink is stored at 50 ° C. for one month, no sediment is generated, the average particle diameter and the viscosity are not changed, and the ink ejection is stable even if the printing test is performed again. Was.

Claims (7)

[Claims] An aqueous pigment ink composition containing at least an aqueous liquid medium and a color pigment, wherein the color pigment is
An aqueous pigment ink composition obtained by wet oxidizing an organic pigment exhibiting a chromatic color with hypohalous acid and / or a salt thereof. 2. The aqueous pigment ink according to claim 1, wherein at least a part of the acidic group formed (or provided) on the surface of the color pigment is an ammonium salt, an amine salt, or an alkali metal salt. Composition. 3. The aqueous pigment ink composition according to claim 1, wherein the average particle size of the color pigment is 300 nm or less. 4. The organic pigment exhibiting a chromatic color is selected from the group consisting of azo organic pigments, perylene organic pigments, quinacridone organic pigments, phthalocyanine organic pigments, and diketopyrrolopyrrole pigments. The aqueous pigment ink composition according to claim 1, 5. The aqueous pigment ink composition according to claim 1, wherein the content of the color pigment is 0.1 to 50% by weight based on the total amount of the aqueous pigment ink composition. 6. An aqueous pigment ink for inkjet recording, comprising the aqueous pigment ink composition according to claim 1. 7. A water-based pigment ink for a writing implement, comprising the water-based pigment ink composition according to claim 1.