JP2000239594A - Aqueous pigment dispersion, and aqueous recording liquid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an aqueous pigment dispersion which has excellent dispersibility and dispersion stability and improves storage stability, color- rendering property, and transparency, when used for recording liquids, by adding C.I. pigment yellow 74 pigment and an anionic group-containing organic polymer compound in a specific ratio. SOLUTION: This aqueous pigment dispersion contains at least (A) 100 pts.wt. of C.I. pigment yellow 74 pigment and (B) 5-25 pts.wt., preferably 10-20 pts.wt., of an anionic group-containing organic polymer compound. The anionic group- containing organic polymer compound preferably contains at least one or more compounds selected from the group consisting of (meth)acrylic acid 3-5C alkyl esters or the (meth)acrylic acid 3-5C alkyl esters and styrene as components. The pigment is preferably coated with the anionic group-containing organic polymer compound, and the aqueous pigment dispersion is preferably used to prepare aqueous recording liquids.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an aqueous pigment dispersion,
And an aqueous recording liquid using the pigment dispersion.

[0002]

2. Description of the Related Art Conventionally, dyes have been used as coloring materials for writing instruments such as felt-tip pens and water-based markers and inks for ink jet printers. Recording liquids using dyes are excellent in coloring power and sharpness, but have problems in light resistance, water resistance and the like.

[0003] Japanese Patent Application Laid-Open No. 2-276874 specifies the weight ratio of a pigment to an organic polymer compound, and describes that any of various series of pigments can be used.

In order to solve the problems of light fastness and water fastness,
In recent years, conversion of colorants from dyes to pigments has been actively studied in the application fields described above. The use of pigments as colorants in this field, especially in the field of ink-jet inks, requires very high levels of dispersibility and dispersion stability in solid-liquid two-phase pigment dispersions. As means for achieving such a high degree of dispersibility and dispersion stability, JP-A-9-151342 discloses a microencapsulated pigment dispersion in which a pigment is coated with an anionic group-containing organic polymer compound.

[0005]

However, the technical idea described in JP-A-2-276874 does not universally apply to any kind of pigments, and the pigments can be used in a suitable manner. The reality is that the amount range varies. JP-A-9-151342
Also, the microencapsulated pigment dispersion described in JP-A No. 2000-135, in particular, for yellow and red pigments, may not be sufficiently satisfactory in all aspects such as dispersion attained level, dispersion stability, and dispersion viscosity.

In particular, relatively excellent coloring power and sharpness,
C. which exhibits light fastness and has well-balanced color characteristics. I. Pigment Yellow 74 pigment was difficult to make a stable dispersion.

[0007]

Means for Solving the Problems The present inventors have made intensive studies to solve the above problems, and as a result, C.I. I. In the case where Pigment Yellow 74 pigment is used, it has been found that the above-mentioned various requirements are satisfied by setting the weight ratio of the pigment and the anionic group-containing organic polymer compound to a specific range, thereby completing the present invention.

[0008]

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to at least C.I. I. An aqueous pigment dispersion containing CI Pigment Yellow 74 pigment and an anionic group-containing organic polymer compound, wherein C.I.
I. An aqueous pigment dispersion characterized in that the amount of the anionic group-containing organic polymer compound used is more than 5 parts by weight and less than 25 parts by weight based on 100 parts by weight of Pigment Yellow 74 pigment.

The anionic group-containing organic polymer compound used in the aqueous pigment dispersion of the present invention is not particularly limited as long as it has an anionic group. Examples thereof include a carboxyl group, a sulfone group, a phospho group and a thiol group. One or more monomers containing an anionic group such as a carboxyl group and an anionic group-containing organic polymer compound obtained by copolymerizing other monomers that can be copolymerized with these anionic group-containing monomers, Considering the availability of raw material monomers, price, and the like, an anionic group-containing organic polymer compound containing a carboxyl group or a sulfone group is preferable, and the coexistence range of the electric neutral state and the anionic state can be widely controlled. And an anionic group-containing organic polymer compound containing a carboxyl group.

The organic polymer compound containing an anionic group used in the aqueous pigment dispersion of the present invention includes, for example, an organic polymer compound having an anionic group which may have a crosslinked portion.

Representative examples of the organic polymer compound having an anionic group which can be used in the present invention include an acrylate polymer having a crosslinked portion, an acrylate polymer having no crosslinked portion, and a polymer having a crosslinked portion. Examples thereof include a methacrylate polymer and a methacrylate polymer having no cross-linking portion. In the present invention, both (meth) acrylate and methacrylate are referred to as (meth) acrylate. The (meth) acrylate-based polymer means a polymer obtained by polymerizing (meth) acrylate as a main component.

The most suitable organic polymer compound having an anionic group is an organic polymer compound having an anionic group in which the anionic group contains both a carboxyl group and a carboxylate group.

Examples of the monomer having a carboxyl group include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, crotonic acid, itaconic acid and 4-vinylbenzoic acid; vinyl succinate, allyl maleate And polybasic unsaturated esters such as vinyl terephthalate and allyl trimellitate. Examples of monomers containing a sulfonic acid group include unsaturated sulfo-substituted alkyl or aryl esters such as 2-sulfoethyl acrylate and 4-sulfophenyl methacrylate; unsaturated sulfocarboxylic acids such as vinyl sulfosuccinate; Sulfostyrenes such as styrene-4-sulfonic acid;

Examples of other monomers which can be copolymerized with the anionic group-containing monomer include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, acrylic T-butyl acid, 2-ethylhexyl acrylate, n-octyl acrylate, dodecyl acrylate, octadecyl acrylate, cyclohexyl acrylate, isobornyl acrylate, benzyl acrylate, 2,3-epoxypropyl acrylate, 2,2 acrylate 3
-Epoxybutyl, 2,3-epoxycyclohexyl acrylate, vinyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate , 2-ethylhexyl methacrylate, n-octyl methacrylate,
Dodecyl methacrylate, octadecyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate, benzyl methacrylate, 2,3-epoxypropyl methacrylate, 2,3-epoxybutyl methacrylate,
2,3-epoxycyclohexyl methacrylate, vinyl methacrylate, dimethyl maleate, diethyl maleate, dimethyl fumarate, diethyl fumarate, ethyl itaconate, benzyl itaconate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-aminoethyl acrylate, 2-aminopropyl acrylate, 3-aminopropyl acrylate, 2- (methylamino) ethyl acrylate, 2-acrylate (Methylamino) propyl, 2- (ethylamino) ethyl acrylate, 2- (ethylamino) acrylate
Propyl, 2- (dimethylamino) ethyl acrylate,
Unsaturated fatty acid esters such as 3- (dimethylamino) propyl acrylate; acrylamide, N-methylacrylamide, N-ethylacrylamide, N-propylacrylamide, N-dimethylacrylamide, N-diethylacrylamide, N-dipropylacrylamide , N- (2-aminoethyl) acrylamide, N-
(2-aminopropyl) acrylamide, N- (3-aminopropyl) acrylamide, N- [2- (methylamino) ethyl] acrylamide, N- [2- (methylamino) propyl] acrylamide, N- [3- ( Methylamino) propyl] acrylamide, N- [2- (dimethylamino) ethyl] acrylamide, N- [2- (dimethylamino) propyl] acrylamide, N- [3-
(Dimethylamino) propyl] acrylamide, methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, N-propylmethacrylamide, N
-Dimethyl methacrylamide, N-diethyl methacrylamide, N-dipropyl methacrylamide, N- (2-
Aminoethyl) methacrylamide, N- (2-aminopropyl) methacrylamide, N- (3-aminopropyl) methacrylamide, N- [2- (methylamino) ethyl] methacrylamide, N- [2- (methylamino) )
Propyl] methacrylamide, N- [3- (methylamino) propyl] methacrylamide, N- [2- (dimethylamino) ethyl] methacrylamide, N- [2- (dimethylamino) propyl] methacrylamide, N- [ 3
-(Dimethylamino) propyl] methacrylamide, maleamide, N, N-dimethylmaleamide, fumaramid,
Unsaturated fatty acid amides such as N, N-dimethyl fumamide; unsaturated nitriles such as acrylonitrile, methacrylonitrile; vinyl acetate, vinyl propionate, vinyl butanoate, vinyl hexanoate, vinyl 2-ethylhexanoate Carboxylic acid unsaturated esters such as octadecanoate, vinyl benzoate, allyl acetate, allyl propionate, allyl hexanoate and allyl decanoate; ethyl vinyl ether, butyl vinyl ether, 2-polyoxyethylene-2- (4- Unsaturated ethers such as nonylphenoxy) methylethyl allyl ether; styrene, α
-Methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, pt-butylstyrene, 4-methoxystyrene, 4-chlorostyrene, and other styrenes; ethylene, propylene, 1-butene, 1- Unsaturated hydrocarbons such as octene, vinylcyclohexane and 4-vinylcyclohexene; unsaturated halogenated hydrocarbons such as vinyl chloride, vinylidene chloride, tetrafluoroethylene and 3-chloropropylene; 4-vinylpyridine, N- Vinyl-substituted heterocyclic compounds such as vinylcarbazole, N-vinylpyrrolidone, etc .; monomers having a substituent having an active hydrogen such as a carboxyl group, a hydroxyl group, or an amino group in the above-exemplified monomers, and ethylene oxide, propylene oxide, and cyclohexene oxide Reaction products with epoxides; Hydroxyl group of the serial exemplified in the monomer,
A monomer containing a substituent having an amino group or the like and acetic acid,
Reaction products with carboxylic acids such as propionic acid, butanoic acid, hexanoic acid, decanoic acid and dodecanoic acid can be mentioned.

When the anionic group-containing organic polymer compound is selected from (meth) acrylic ester copolymers, it is preferably selected from the group consisting of at least acrylic acid and methacrylic acid alkyl esters having 3 to 5 carbon atoms. A copolymer obtained by polymerizing one or more selected compounds as constituent elements and other monomers is selected, or at least an alkyl ester of acrylic acid having 3 to 5 carbon atoms and a methacrylic acid having 3 to 5 carbon atoms. And one or more compounds selected from the group consisting of alkyl esters of
It is preferable in terms of performance to select a copolymer containing styrene as a constituent element.

Such an anionic group-containing organic polymer compound can be synthesized by various conventionally known reaction methods such as bulk polymerization, solution polymerization, suspension polymerization and emulsion polymerization.

The weight average molecular weight of the anionic group-containing organic polymer compound used in the present invention is from 2,000 to 100,
5,000, preferably 5,000 to 5
It is particularly preferred that it is in the range of 000. If the weight-average molecular weight is too small, the dispersion stability of the aqueous pigment dispersion itself decreases, and if it is too large, not only the viscosity of the dispersion increases but also the dispersibility tends to decrease. If the weight average molecular weight is too small or too large, for example, when applied to an ink for an ink jet printer, it adversely affects the printing characteristics and makes it difficult to perform stable printing for a long period of time.

The acid value and the glass transition point of the organic polymer having an anionic group used in the present invention are preferably in the range of 30 to 220 mgKOH / g and -20 to 60 ° C., respectively. If the acid value is too low, the dispersibility and dispersion stability of the aqueous pigment dispersion will decrease, and the printing stability when applied to inks for inkjet printers will deteriorate. If the acid value is too high, the water resistance of the image will decrease when applied to an ink for an inkjet printer. If the glass transition point is too high, stable printing is difficult to obtain, and if it is too low, image storability such as abrasion resistance and bar-stacking resistance tends to decrease.

The anionic group-containing organic polymer compound in the aqueous pigment dispersion of the present invention has a dispersibility and a dispersion stability in which at least a part of the anionic group is ionized by a basic substance. Is preferred in terms of expression of The optimal ratio of the ionized group among the anionic groups is determined by the composition of the used anionic group-containing organic polymer compound,
Although it is not uniquely limited because it changes depending on the molecular weight, the acid value, and the like, it may be within a range in which desired dispersibility and dispersion stability are exhibited, and usually 30 to 100%, particularly 70 to 100%.
Preferably, it is set in the range of 100%. The ratio of the ionized group does not mean the molar ratio between the anionic group and the basic substance, but takes into account dissociation equilibrium. For example, when the anionic group is a carboxyl group, the proportion of the group (carboxylate group) ionized by the dissociation equilibrium is less than 100% even when a stoichiometrically equivalent amount of a strong basic substance is used, and Group and carboxyl group.

As described above, examples of the basic substance used to ionize at least a part of the anionic group of the anionic group-containing organic polymer compound include known and commonly used substances. Preferred are compounds selected from the group consisting of primary, secondary or tertiary organic amines (including basic nitrogen-containing heterocyclic compounds) and alkali metal hydroxides. By ionizing at least a portion of the anionic group with these exemplified suitable basic substances, the counter ion of the carboxylate group is
It is a cation selected from the group consisting of ammonium ions (including protonated cations of basic nitrogen-containing heterocyclic compounds) and alkali metal ions. And so on.

C. used in the present invention. I. Pigment
The yellow 74 pigment may be a powdery, granular or massive dry pigment, or may be a wet cake or slurry.

In the present invention, C.I. I. Pigment
The amount of the anionic group-containing organic polymer compound used is more than 5 parts by weight and less than 25 parts by weight, preferably 10 to 20 parts by weight, based on 100 parts by weight of the yellow 74 pigment.

The aqueous pigment dispersion of the present invention contains at least C.I. I. Pigment Yellow 74 pigment, an anionic group-containing organic polymer compound, a basic substance, and water.

Examples of the steps other than the dispersing step which can be incorporated into the process for producing the aqueous pigment dispersion of the present invention include a preliminary dispersing step, a dissolving step, a dilution step, a distillation step, a centrifugal separation step, an acid precipitation step, a filtration step, Redispersion step, pH adjustment step,
And a filling step.

Examples of the pre-dispersing step include a step of mixing and dispersing a resin and a pigment in a solution state or a molten state to form a slurry, a paste, or a solid state called a masterbatch or a chip. Examples of the dissolving step include a step of dissolving a solid anionic group-containing organic polymer compound in an organic solvent, preferably a water-soluble organic solvent, or an aqueous medium containing a basic substance, or an anionic group-containing organic compound. There is a step of dissolving a water-soluble organic solvent solution of the polymer compound in an aqueous medium containing a basic substance.

In the present invention, it is preferable to include a step of dispersing a mixture comprising a pigment, an organic polymer compound having an anionic group, a basic substance and water as essential components. The mixture preferably contains a water-soluble organic solvent. More specifically, it is preferable to include a step of dispersing at least a mixture of a pigment, an anionic group-containing organic polymer compound, a basic substance, a water-soluble organic solvent, and water.

In the aqueous dispersion of the present invention, in order to exhibit more excellent characteristics in all aspects of the attained dispersion level, the required dispersion time, and the dispersion stability, the pigment is preferably prepared by using an anionic group-containing organic polymer compound. It is preferred that the coated, encapsulated pigment be dispersed in the aqueous dispersion.
In order to form such a state, in a state where the pigment is dispersed in a liquid medium containing the anionic group-containing organic polymer compound, the anionic group-containing organic polymer in a dissolved state is used as the post-process. It is preferable to incorporate a step of coating the compound on the pigment surface.

The step of coating the surface of the pigment with the anionic group-containing organic polymer compound in a dissolved state is performed by acidifying the anionic group-containing organic polymer compound dissolved in the alkaline aqueous solution. The step of precipitating is preferred.

Examples of the distillation step include a step of removing an organic solvent when it is used in the dispersion step, and a step of removing excess water to obtain a desired solid content concentration. Examples of the centrifugation step include a step of removing coarse particles in the dispersion that adversely affect the suitability for use as an aqueous recording liquid.

In the example of the acid precipitation step, the aqueous dispersion obtained in the dispersion step is acidified by adding an acid such as hydrochloric acid, sulfuric acid or acetic acid.
A step of forming a salt with a base to precipitate an anionic group-containing organic polymer compound in a dissolved state on the surface of pigment particles. By this step, the interaction between the pigment and the organic polymer compound having an anionic group can be enhanced. As a result, the pigment is coated with the anionic group-containing organic polymer compound, so-called microencapsulated pigment can be in the form of being dispersed in the aqueous dispersion, and as the aqueous dispersion, the dispersion reaching level and More excellent properties can be exhibited in terms of physical properties such as dispersion stability and usability such as solvent resistance.

Examples of the filtration step include a step of removing coarse particles in the dispersion with a cartridge filter or a membrane filter in the same manner as the centrifugal separation step, a step of filtering the solid content after the above-mentioned acid precipitation step by a filter press, a Nutsche type filtration device,
There is a step of filtering with a pressure filtration device or the like. Examples of the redispersion step include a step of adding a basic substance and, if necessary, water and additives to the solid obtained by the acid precipitation step and the filtration step to obtain a dispersion again. Thereby, the counter ion of the ionized anionic group in the anionic group-containing organic polymer compound can be changed from that used in the dispersion step.

Further, in the dispersion step, a water-soluble organic solvent can be used in combination, whereby the liquid viscosity in the dispersion step can be sometimes reduced. Examples of the water-soluble organic solvent include ketones such as acetone, methyl ethyl ketone, methyl butyl ketone and methyl isobutyl ketone; methanol, ethanol, 2-propanol and 2-ketone.
Alcohols such as methyl-1-propanol, 1-butanol and 2-methoxyethanol; tetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane,
Ethers; amides such as dimethylformamide and N-methylpyrrolidone; and the use of compounds selected from the group consisting of ketones having 3 to 6 carbon atoms and alcohols having 1 to 5 carbon atoms. preferable. These water-soluble organic solvents may be used as an anionic group-containing organic polymer compound solution, or may be separately and independently added to the dispersion mixture.

As the dispersing device that can be used in the dispersing step, devices according to various known systems can be used and are not particularly limited. Examples thereof include steel, stainless steel, zirconia, alumina, silicon nitride, and the like.
A method using the kinetic energy of a spherical dispersion medium made of glass or the like having a diameter of about 0.1 to 10 mm, a method using a shearing force by mechanical stirring, a pressure change of a high-speed supplied distribution bundle, a flow path A dispersion method such as a method using a force generated by a change or a collision can be adopted.

In the present invention, when the anionic group-containing organic polymer compound contains a crosslinkable group, for example, 2,3-epoxypropyl acrylate, 2,3-epoxybutyl acrylate, 2,3-epoxybutyl acrylate Epoxycyclohexyl, 2,3-epoxypropyl methacrylate, 2,3-epoxybutyl methacrylate, 2,3-methacrylic acid
In the case of a copolymer containing a monomer composed of at least one unsaturated fatty acid having an epoxy group such as epoxycyclohexyl, a ring-opening reaction can be performed in the aqueous dispersion production process to crosslink.

The crosslinking step can be carried out at any stage after the dispersion step. However, in order to sufficiently exhibit the high dispersion stability characteristic of the aqueous pigment dispersion of the present invention, storage, transportation and actual processing are carried out. When used, the crosslinking reaction is preferably completed, and particularly preferably completed before the step of removing coarse particles in the aqueous dispersion by centrifugation or the like.
The ring opening reaction temperature is preferably about 80 to 140 ° C. When the reaction temperature is too low, the reaction rate is low and a long time is required for completing the reaction, so that the pigment particles are likely to fuse with each other to form an aggregate. If the reaction temperature is too high, fusion of the pigment particles and growth of the pigment particles themselves occur, which is not preferable in any case. When the reaction temperature becomes higher than the boiling point of the dispersion, it is necessary to use a pressurized reactor.

The aqueous pigment dispersion of the present invention can be used for any of known and commonly used applications. For example, an aqueous recording liquid containing the same is one of the most preferable applications.

The recording liquid of the present invention contains at least C.I. I. It is prepared by mixing an aqueous pigment dispersion containing Pigment Yellow 74 pigment and an anionic group-containing organic polymer compound with a water-soluble organic solvent, water and the like. If necessary, a surfactant, a water-soluble resin, a preservative, a viscosity adjuster, a pH adjuster, a chelating agent and the like can be added.

Examples of the water-soluble organic solvent that can be used for preparing the recording liquid include methanol, ethanol, 1-
Propanol, 2-propanol, 2-methyl-1-propanol, 1-butanol, 2-methoxyethanol, 2-butoxyethanol, 2- (2-methoxyethoxy) ethanol, 2- (2-butoxyethoxy) ethanol, 2- [2- (2-methoxyethoxy) ethoxy] ethanol, 2- [2- (2-butoxyethoxy)
Ethoxy] alcohols such as ethanol; 1,2-ethanediol, 1,2-propanediol, 1,2-butanediol, 2,3-butanediol, 2,2′-oxybisethanol, 2,2′- Ethylenedioxybis (ethanol), thiodiethanol, glycerin, 1,
Polyhydric alcohols such as 2,6-hexanetriol; amides such as dimethylformamide, dimethylacetamide, N-methyl-pyrrolidone, 1,3-dimethyl-2-imidazolidinone; acetone, methyl ethyl ketone, methyl n-butyl ketone; Ketones such as methyl isobutyl ketone; tetrahydrofuran, 1,4-dioxane,
1,2-dimethoxyethane, 1,2-diethoxyethane, 2,2′-oxybis (2-methoxyethane),
2,2′-oxybis (2-ethoxyethane), 2,
2′-ethylenedioxybis (2-methoxyethane),
Ethers such as 2,2′-ethylenedioxybis (2-methoxyethane) are exemplified. The content of the water-soluble organic solvent in the recording liquid is preferably 50% by weight or less,
A range of 40% by weight is particularly preferred.

Surfactants which may be added to the recording liquid of the present invention include anionic, cationic, zwitterionic,
Any nonionic activator may be used.

Examples of anionic surfactants include fatty acid salts such as sodium stearate, potassium oleate, and sodium hydrogenated tallow fatty acid; sodium dodecyl sulfate, tri (2-hydroxyethyl) ammonium dodecyl sulfate, sodium octadecyl sulfate. Alkyl sulfates such as sodium nonylbenzenesulfonate, sodium dodecylbenzenesulfonate, sodium octadecylbenzenesulfonate, sodium dodecyldiphenyletherdisulfonate; sodium dodecylnaphthalenesulfonate;
Naphthalene sulfonic acid salts such as naphthalene sulfonic acid formalin condensate; sulfosuccinate ester salts such as sodium dododecyl sulfosuccinate and dioctadecyl sodium sulfosuccinate; sodium polyoxyethylene dodecyl ether sulfate, polyoxyethylene dodecyl ether sulfate Ethyl) ammonium, sodium polyoxyethylene octadecyl ether sulfate, sodium polyoxyethylene dodecyl phenyl ether sulfate and the like; and polyoxyethylene sulfate salts such as potassium dodecyl phosphate and sodium octadecyl phosphate.

Examples of the cationic surfactant include alkylamine salts such as octadecyl ammonium acetate and coconut oil amine acetate; dodecyltrimethylammonium chloride, octadecyltrimethylammonium chloride, dioctadecyldimethylammonium chloride, dodecylbenzyldimethylammonium chloride and the like. Quaternary ammonium salts.

Examples of zwitterionic activators include alkyl betaines such as dodecyl betaine and octadecyl betaine; and amine oxides such as dodecyl dimethyl amine oxide.

Examples of the nonionic surfactant include polyoxyethylene alkyl ethers such as polyoxyethylene dodecyl ether, polyoxyethylene hexadecyl ether, polyoxyethylene octadecyl ether and polyoxyethylene (9-octadecenyl) ether. Polyoxyethylene phenyl ethers such as polyoxyethylene octyl phenyl ether and polyoxyethylene nonyl phenyl ether; oxirane polymers such as polyethylene oxide and co-polyethylene oxide propylene oxide; sorbitan dodecanoate and sorbitan hexadecanoate Sorbitan octadecanoate, sorbitan (9-octadecenoate) ester, sorbitan (9-octadecenoate) triester, polyoxyethylene sorbita Dodecanoic acid ester, polyoxyethylene sorbitan hexadecanoic ester, polyoxyethylene sorbitan octadecanoic ester, polyoxyethylene sorbitan octadecanoic acid triester,
Polyoxyethylene sorbitan (9-octadecenoic acid)
Esters, sorbitan fatty acid esters such as polyoxyethylene sorbitan (9-octadecenoic acid) triester; sorbitol fatty acid esters such as polyoxyethylene sorbitol (9-octadecenoic acid) tetraester; glycerin octadecanoate, glycerin (9-octadecene) Glycerin fatty acid esters such as (acid) esters. Among these nonionic surfactants, those having an HLB of 14 or more are particularly preferred.

Examples of the water-soluble resin which may be added to the aqueous recording liquid of the present invention include glue, gelatin, casein,
Albumin, gum arabic, fish gleu, alginic acid, methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, polyethylene oxide,
Polyvinyl alcohol, polyacrylamide, polyacrylic acid, polyvinyl ether, polyvinylpyrrolidone,
Styrene-maleic acid copolymer, styrene-acrylic acid copolymer, acrylate-acrylic acid copolymer and the like can be mentioned.

The water-soluble resin is used as needed for the purpose of improving the fixing property, adjusting the viscosity and drying quickly.
When used in the recording liquid, the content of the water-soluble resin in the recording liquid is preferably from 0 to 30% by weight, particularly preferably from 0 to 20% by weight.

The aqueous recording liquid of the present invention can be suitably used as an ink for stationery such as a felt-tip pen, a marker, etc., and various printers and plotters. It can be suitably used as an ink for use.

The present invention includes the following specific embodiments. 1. At least C.I. I. An aqueous pigment dispersion containing CI Pigment Yellow 74 pigment and an anionic group-containing organic polymer compound, wherein C.I. I. Pigment Yellow 7
(4) An aqueous pigment dispersion, wherein the amount of the anionic group-containing organic polymer compound used is more than 5 parts by weight and less than 25 parts by weight based on 100 parts by weight of the pigment.

2. The organic polymer compound containing an anionic group contains at least one compound selected from the group consisting of an alkyl ester of acrylic acid having 3 to 5 carbon atoms and an alkyl ester of methacrylic acid having 3 to 5 carbon atoms as a constituent element. 2. The aqueous pigment dispersion according to the above 1, which is an organic polymer compound containing an anionic group.

3. The anionic group-containing organic polymer compound comprises at least one compound selected from the group consisting of an alkyl ester of acrylic acid having 3 to 5 carbon atoms and an alkyl ester of methacrylic acid having 3 to 5 carbon atoms, and styrene. 2. The aqueous pigment dispersion according to the above 1, wherein the aqueous pigment dispersion is an anionic group-containing organic polymer compound.

4. 4. The aqueous pigment dispersion according to any one of the above 1 to 3, wherein the pigment is coated with an anionic group-containing organic polymer compound.

5. An aqueous recording liquid comprising the aqueous yellow pigment dispersion according to any one of the above items 1 to 4.

[0052]

The present invention will be described below in more detail with reference to Examples and Comparative Examples. In the following Examples and Comparative Examples,
“Parts” and “%” represent “parts by weight” and “% by weight”.

<Synthesis Example 1> (Synthesis of Organic Polymer Compound Containing Anionic Group) An automatic polymerization reaction apparatus having a reaction vessel equipped with a stirring device, a dropping device, a temperature sensor, and a reflux device having a nitrogen introduction device on the top. (Polymerization tester DSL-2AS type, manufactured by Todoroki Sangyo Co., Ltd.)
Then, the reaction vessel was purged with nitrogen while stirring. After raising the temperature to 75 ° C. while maintaining the inside of the reaction vessel in a nitrogen atmosphere, n-butyl methacrylate 350 was added from a dropping device.
Parts, n-butyl acrylate 100 parts, methacrylic acid 2-
A mixture of 150 parts of hydroxyethyl, 200 parts of methacrylic acid, 200 parts of styrene and 80 parts of “perbutyl O” (active ingredient t-butyl peroxy 2-ethylhexanoate, manufactured by NOF Corporation) was added dropwise over 2 hours. . After completion of the dropwise addition, the reaction was further continued at the same temperature for 15 hours,
An anionic group-containing organic polymer compound solution having an acid value of 130, a glass transition temperature (calculated value) of 47 ° C., and a weight average molecular weight of 21,200 was obtained. After completion of the reaction, the nonvolatile content of the resin solution is reduced to 5
It was adjusted to 0%.

<Example 1> An anionic group-containing organic polymer compound obtained in Synthesis Example was placed in a mixing tank provided with a cooling jacket,
20% aqueous sodium hydroxide, water and C.I. I. Pigment Yellow 74 pigment (Shimler Fast Yellow 4190; manufactured by Dainippon Ink and Chemicals, Inc.)
Stir and mix. Here, each charged amount is C.I. I.
Pigment Yellow 74 pigment is 1,000 parts, and the anionic group-containing organic polymer compound is C.I. I. Pigment Yellow 74 pigment in an amount that gives a predetermined ratio, 20% aqueous sodium hydroxide is used to neutralize the acid value of the anionic group-containing organic polymer compound by 90%, and water is used to reduce the nonvolatile content of the mixed solution by 30%. Is the amount needed to

A dispersing device (SC mill SC100 / 32 type, in which the mixed solution was filled with zirconia beads having a diameter of 0.3 mm,
(Mitsui Mining Co., Ltd.), and dispersed for 6 hours by a circulation method. The rotation speed of the dispersing device was set to 2700 rpm, and the temperature of the dispersion liquid was kept at 40 ° C. or lower by passing cold water through a cooling jacket.

After the completion of the dispersion, the undiluted dispersion was taken out of the mixing tank, and then the mixing tank and the dispersing apparatus channel were washed with 10,000 parts of water. The diluted dispersion was placed in a glass distillation apparatus, and the entire amount of methyl ethyl ketone and a part of water were distilled off to obtain a concentrated dispersion.

After cooling to room temperature, 10% hydrochloric acid was added dropwise to the concentrated dispersion while stirring to adjust the pH to 3.5, and the solid content was filtered with a Nutsche filter and washed with water. The cake is placed in a container, and a 20% aqueous solution of potassium hydroxide and 200 parts of water are added in such an amount that the acid value of the anionic group-containing organic polymer compound is 95% neutralized, and a dispersion stirrer (TK homodisper 20) is added.
Mold, manufactured by Tokushu Kika Kogyo Co., Ltd.). After removing coarse particles with a centrifuge (50A-IV, Sakuma Seisakusho), the nonvolatile content was adjusted to 20%.
A water-based pigment dispersion was obtained. This aqueous pigment dispersion was excellent in dispersion stability over time.

<Example 2> (Evaluation of stability of aqueous recording liquid for ink jet printer) Using the aqueous pigment dispersion obtained in Example 1, JP-A-7-22
An ink for an ink jet printer was prepared with reference to Example 1 described in JP-A-8808. The ink composition is shown below.

Aqueous pigment dispersion 25 parts Triethylene glycol monobutyl ether 10 parts Diethylene glycol 15 parts Ethanol 5 parts Surfynol 465 (manufactured by Air Products) 0.8 parts Water 49.2 parts

The ink thus prepared was evaluated for dispersion stability and average particle size. The dispersion stability is 70 ° C,
The degree of varnish separation after storage for 3 days was used as a scale, and expressed as a ratio of the translucent portion of the upper layer caused by sedimentation of the pigment to the total dispersion height. The average particle diameter was defined as the median diameter measured with a laser Doppler particle size analyzer Microtrac (UPA150, manufactured by Leeds & Northrop).

[0061]

[Table 1] Table 1

As can be seen from Table 1, the amount of the organic polymer compound having an anionic group per 100 parts of the pigment was 10 to 10 parts.
When the amount is 20 parts by weight, the dispersion of the pigment microcapsules has a small change in particle diameter even after the ink is formed into an aqueous recording liquid, and the dispersion stability is excellent because there is no varnish separation. Is evident. This is a particularly advantageous effect in ink-jet printer ink applications in which ink is ejected from fine nozzles for flying recording.

[0063]

According to the present invention, C.I. I. Pigment Yellow 74 pigment aqueous dispersion is C.I. I. Since the amount of the anionic group-containing organic polymer compound used is more than 5 parts by weight and less than 25 parts by weight based on 100 parts by weight of Pigment Yellow 74 pigment, the dispersibility and the dispersion stability are excellent,
When used for a recording liquid such as an ink for an ink jet printer, a recording liquid having excellent storage stability, color rendering properties, and transparency can be provided, and a clear image can be formed.

Continued on the front page F term (reference) 4J037 AA30 CC13 CC14 CC15 CC16 CC17 DD24 EE03 FF07 FF09 FF15 FF22 FF23 4J039 AD03 AD04 AD10 AD11 AD12 AD13 AD14 AD23 AE07 BE01 BE22 CA06 DA02 EA17 EA35 EA42 EA44 GA24

Claims (5)

[Claims] At least C.I. I. An aqueous pigment dispersion containing CI Pigment Yellow 74 pigment and an anionic group-containing organic polymer compound, wherein C.I. I. An aqueous pigment dispersion, wherein the amount of the anionic group-containing organic polymer compound used is more than 5 parts by weight and less than 25 parts by weight based on 100 parts by weight of CI Pigment Yellow 74 pigment. 2. An organic polymer compound having an anionic group,
An anionic group-containing organic polymer compound containing, as a constituent, at least one compound selected from the group consisting of at least an alkyl ester of acrylic acid having 3 to 5 carbon atoms and an alkyl ester of methacrylic acid having 3 to 5 carbon atoms. The aqueous pigment dispersion according to claim 1. 3. An organic polymer compound having an anionic group,
Organic polymer containing anionic group containing at least one compound selected from the group consisting of alkyl esters of acrylic acid having 3 to 5 carbon atoms and alkyl esters of methacrylic acid having 3 to 5 carbon atoms and styrene as constituent elements The aqueous pigment dispersion according to claim 1, which is a compound. 4. The aqueous pigment dispersion according to claim 1, wherein the pigment is coated with an anionic group-containing organic polymer compound. 5. An aqueous recording liquid comprising the aqueous yellow pigment dispersion according to claim 1. Description: