Pigment dispersion, and ink for ink jet

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Conventional technology]

Inkjet recording is for recording images, characters, etc. by flying minute droplets of ink according to various operating principles and adhering them to a recording medium, but it is relatively fast, low noise, and easy to multicolor. It has the advantage of.

【0002】

In addition, due to recent technological advances, high image quality and low price of equipment, which are close to those of silver halide photographs of inkjet prints using dye ink, are accelerating their widespread use. Generally, the dye used in the dye ink is soluble in the ink solvent, and the dye molecules are colored in the molecular state or the cluster state. Therefore, since the environment of each molecule is similar even after recording on the recording medium, its absorption spectrum is sharp and exhibits high purity and clear color development. Further, since it has no particle nature and does not generate scattered light or reflected light, it is possible to obtain an image with good reproducibility even for an image having high brightness and saturation.

【0003】

However, on the other hand, when the molecules are destroyed by a photochemical reaction or the like, the decrease in the number of molecules is directly reflected in the coloring concentration, resulting in poor light resistance. Inkjet recorded images using dye inks have high image quality, but the image quality deteriorates significantly due to storage over time, and the current situation is that no technology that surpasses silver halide photography has emerged from the viewpoint of image preservation.

【0004】

Pigment inks that use pigments with good light resistance as colorants are used as inks for applications that require images that are resistant to fading due to light, as opposed to dye inks.

【0005】

However, compared to dyes, pigments are more susceptible to light scattering than dyes, and give images with poor reproducibility of brightness and saturation. Therefore, pigments are inferior to dyes in terms of color reproducibility. was there.

【0006】

Further, the pigment for this purpose is required to have a smaller particle size and higher dispersion stability than commonly used paints in order to prevent clogging of the inkjet recording head and ensure stable injection stability. To. In order to ensure a high degree of dispersion stability with this small particle size, the pigment has been mechanically dispersed by using a dispersant such as a surfactant or a polymer dispersant, such as sandmill dispersion. Since the surface is hydrophobic, the surfactant and the polymer dispersant are not sufficiently adsorbed on the pigment surface, so that a sufficient small particle size and dispersion stability have not been ensured.

【0007】

The surface of the pigment by reforming, small attempts trying to improve the dispersibility and particle diameter is in the field of high water-based paints of the polymer compound, for example, by using a quinacridone pigment derivative having an amino group, the pigment surface Has been known to be modified to be cationic to improve the dispersion in the polymer compound.

【0008】

For aqueous dispersions for inkjet, an organic pigment and a pigment derivative having a sulfonic acid group are acid-pasted in JP-A-11-049974, the whole is positively charged with a salt, and then a polymer dispersant is added to the ink. An example of using as is described. However, in this technique, when the pigment has a small particle size, the dispersion stability deteriorates, so that the polymer dispersant must be increased, and as a result, the ink ejection stability decreases due to the increase in the viscosity of the ink. Therefore, it has not been possible to solve the basic problem of inkjet ink.

【0009】

Further, a method of adsorbing a pigment derivative having a sulfonic acid or the like on a pigment surface to obtain an aqueous dispersion is described in JP-A-2000-273383 and JP-A-2000-303014. However, the compounds described in these are those in which a sulfonic acid group and a carboxylic acid group are directly introduced into the phthalocyanine matrix, and even if these are used, the prevention of aggregation due to the smaller particle size of the pigment can be solved. Was not enough.

【0010】

In addition, as an attempt to modify the surface of the pigment surface using a direct chemical reaction, as described in US5, 922, and 118, the organic pigment is reacted with the diazonium salt of sulfanilic acid under dispersion to form a sulfophenyl group. A method for improving dispersion stability by using a pigment in which is introduced is described. However, even in this technique, it is necessary to use a reaction that requires attention to ensure safety, such as reacting a pigment with a diazonium salt at 80 ° C, which is a disadvantageous method in terms of versatility.

【0011】

[Problems to be Solved by the Invention]

An object to be solved by the present invention is to provide an aqueous pigment dispersion in which the primary particles of the pigment are small and the dispersion stability is good in the pigment dispersion in which the pigment is dispersed in a hydrophilic medium. Furthermore, it is an object of the present invention to provide an ink jet ink and an image forming method which can obtain an image having excellent dispersion stability, high brightness and saturation, and can obtain an image having high color reproducibility.

【0012】

[Means for solving problems]

The above issue is (1) A pigment dispersion characterized in that a compound represented by the general formula (1) is contained in a dispersion in which a pigment is dispersed in a hydrophilic medium.

【0013】

[Chemical 2]

<img file="JP2002201401A_D0001.tif" />【0014】

(Pig in the formula represents the pigment matrix. X represents the divalent linking group. Y represents the carbon atom or aromatic or heterocyclic residue to which Z is bonded. Z represents the sulfonic acid group or sulfonate. , A carboxylic acid group or a carboxylate. P represents 1, 2 or 3. n represents a positive number.) (2) The pigment dispersion of (1), wherein the Pig is a quinacridone mother nucleus. (3) The pigment dispersion according to (1), wherein the Pig is a phthalocyanine mother nucleus. (4) The pigment dispersion according to (1), wherein the Pig is a diketopyrrolopyrrole pigment mother nucleus. (5) The pigment dispersion according to (1), wherein the pigment has a pigment matrix represented by Pig of the general formula (1). (6) The pigment dispersion according to (1), wherein Z is a sulfonic acid or a salt thereof. (7) The pigment dispersion according to (1), wherein X is a residue of an amide group, a sulfonamide group, a carbamoyl group, and an aminosulfonyl group. (8) An inkjet ink containing at least a hydrophilic medium and a pigment, which contains a compound represented by the general formula (1). (9) The inkjet ink according to (8), wherein the Pig is a quinacridone mother nucleus. (10) The inkjet ink according to (8), wherein the Pig is a phthalocyanine mother nucleus. (11) The inkjet ink according to (8), wherein the Pig is a diketopyrrolopyrrole mother nucleus. (12) The ink jet ink according to (8) to (11), wherein the primary particle size of the pigment is 5 to 50 nm. (13) The ink jet ink according to (12), wherein the primary particle size of the pigment is 5 to 40 nm. (14) The inkjet ink according to (8) to (13), wherein the dispersed particle size of the pigment is 5 to 200 nm, and the proportion of particles having a particle size of 300 nm or more is 5% by weight or less of the total pigment. (15) The inkjet ink according to (14), wherein the dispersed particle size of the pigment is 30 to 150 nm, and the proportion of particles having a particle size of 300 nm or more is 5% by weight or less of the total pigment. (16) An image forming method characterized in that an image is formed by ejecting the inks of (8) to (15) onto a recording medium. (17) It can be solved by a method for producing pigment particles, which comprises dissolving a pigment in a solvent together with a compound represented by the general formula (1) and pasting it in a poor solvent of the pigment.

【0015】

BEST MODE FOR CARRYING OUT THE INVENTION

The pigment used in the present invention refers to a pigment having a color, and an organic pigment is preferably used. Specifically, quinacridone pigments, phthalocyanine pigments, 1,4-diketopyrolol pigments, azo pigments, perylene pigments, anthraquinone pigments, dioxazine pigments, indantron pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, flavantrons. Examples thereof include polycyclic pigments such as pigments and pyranthron pigments, dye lakes such as basic dye type rakes and acidic dye type rakes, and organic pigments such as nitro pigments, nitroso pigments, aniline blacks and daylight fluorescent pigments.

【0016】

Specific organic pigments are illustrated below. Pigments for magenta or red include CI Pigment Red 2, CI Pigment Red 3, CI Pigment Red 5, CI Pigment Red 6, CI Pigment Red 7, CI Pigment Red 15, CI Pigment Red 16, CI Pigment Red 48: 1. , CI Pigment Red 53: 1, CI Pigment Red 57: 1, CI Pigment Red 122, CI Pigment Red 123, CI Pigment Red 139, CI Pigment Red 144, CI Pigment Red 149, CI Pigment Red 166, CI Pigment Red 177, CI Pigment Red 178, CI Pigment Red 222, CI Pigment Red 254 and the like can be mentioned.

【0017】

Pigments for orange or yellow include CI Pigment Orange 31, CI Pigment Orange 43, CI Pigment Yellow 12, CI Pigment Yellow 13, CI Pigment Yellow 14, CI Pigment Yellow 15, CI Pigment Yellow 17, CI Pigment Yellow 93, CI Pigment Yellow 94, CI Pigment Yellow 138 and the like.

【0018】

Pigments for green or cyan include CI Pigment Blue 15, CI Pigment Blue 15: 2, CI Pigment Blue 15: 3, CI Pigment Blue 16, CI Pigment Blue 60, CI Pigment Green 7, and the like.

【0019】

In the compound represented by the general formula (1), the pigment mother nucleus represented by Pig is the mother nucleus of an organic pigment having a color, and is a quinacridone-based pigment, a phthalocyanine-based pigment, a perylene pigment, and a 1,4-diketopyrrol pigment. , Anthraquinone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments and other organic pigments.

【0020】

The divalent linking group represented by X is a divalent organic group, which is an alkylene group (for example, a substituted or unsubstituted alkylene group from C1 to C20) and an alkelene group (for example, from C1 to C20). Substituent or unsubstituted alkerene group), arylene group (for example, C6 to C12 substituted or unsubstituted arylene group), ether group, sulfone residue, sulfonamide residue, sulfamoyl residue Carbonyl residue, ester, oxycarbonyl residue Amino residue, amide residue, carbamoyl residue Examples thereof include divalent linking groups such as thio and thiocarbonyl residues, and divalent groups in which these groups are continuously linked.

【0021】

Preferred examples of X include sulfonamide residue, sulfamoyl residue, sulfamoylmethyl residue, amide residue, carbamoyl residue, carbamoylmethyl residue, ester group and oxycarbonyl residue.

【0022】

Y represents a carbon atom or aromatic or heterocyclic residue to which Z is bonded. Examples of aromatic residues include phenyl residues and naphthalene residues, and examples of heterocyclic residues include triazine residues and benzothiazole residues.

【0023】

Z refers to sulfonic acid groups, carboxylic acid groups, or salts thereof. These salts refer to ions having a positive charge that neutralizes sulfonic acid ions and carboxylate ions, and specifically, monovalent inorganic salts (lithium ion, sodium ion, potassium ion, ammonium ion, etc.), Refers to divalent or higher inorganic salts (magnesium ion, calcium ion, aluminum ion, nickel ion, etc.) and organic ammonium ion (pyridinium ion, diethanolammonium ion, triethanolammonium ion, n-butylammonium ion, triethylammonium ion, etc.) , Preferably monovalent ions.

【0024】

The quinacridone mother nucleus refers to quinacridone having a substituent or unsubstituted quinacridone, and examples of the substituent include a halogen atom (for example, chlorine bromine), an alkyl group (for example, methyl, ethyl, propyl group) and an alkyloxy group (for example, methyl, ethyl, propyl group). For example, methoxy, ethoxy group) and the like can be mentioned.

【0025】

The phthalocyanine mother nucleus is a substituted or unsubstituted phthalocyanine in which hydrogen or a metal is coordinated. This metal is not particularly limited as long as it is a metal that can coordinate with the phthalocyanine matrix, but nickel, copper, aluminum, iron, titanium, and cobalt are preferable.

【0026】

The diketopyrrol mother nucleus refers to a substituted or unsubstituted diketopyrrol. The above-mentioned compound used in the present invention is polar with a chlorsulfonyl compound obtained by reacting a compound having a pigment matrix with a chlorosulfonic acid or reacting a pigment having a sulfonic acid with a chlorating agent such as phosphorus oxychloride. Amine having a polar group and an amine having a polar group obtained by reacting a nucleophilic reagent such as an amine or alcohol having a group or reacting a pigment having a carboxylic acid with a chlorating agent such as phosphorus oxychloride. Aminomethyl groups obtained by reacting such a nucleophilic reagent or by reacting a pigment with phthalimide and formaldehyde to hydrolyze a phthalimide group, and an ester having a sulfonic acid carboxylic acid, a parent such as chloride. It can be easily obtained by reacting with an electronic reagent or the like.

【0027】

Examples of the compound represented by the general formula (1) are given below, but the present invention is not limited thereto.

【0028】

[Chemical 3]

<img file="JP2002201401A_D0002.tif" />【0029】

[Chemical 4]

<img file="JP2002201401A_D0003.tif" />【0030】

[Chemical 5]

<img file="JP2002201401A_D0004.tif" />【0031】

[Chemical 6]

<img file="JP2002201401A_D0005.tif" />【0032】

[Chemical 7]

<img file="JP2002201401A_D0006.tif" />【0033】

[Chemical 8]

<img file="JP2002201401A_D0007.tif" />【0034】

[Chemical 9]

<img file="JP2002201401A_D0008.tif" />【0035】

[Chemical 10]

<img file="JP2002201401A_D0009.tif" />【0036】

The compound used in the present invention is stable in dispersion even when an existing disperser such as a ball mill, a sand mill, a paint shaker, an atrater, a pearl mill, or a homogenizer is dispersed together with a pigment using zirconia beads, alumina beads, magnetic beads, styrene beads, or the like. Properties are obtained, but preferably a method known as the paste method, ie, the pigment is sulfuric acid, a sulfonic acid solvent (chlorsulfonic acid, methanesulfonic acid), or an alkaline aprotonic solvent (DMF, DMSO, acetonitrile). Etc.) The compound of the present invention is dissolved in a solution obtained by dissolving the pigment in a solvent in which the pigment dissolves, and then crystals are formed in a poor solvent for the pigment such as water to form a pigment having small primary particles. After obtaining the particles, it is preferable to disperse them with the above-mentioned disperser.

【0037】

The size of the primary particles varies depending on the pigment concentration at the time of pasting, stirring speed, and temperature, but in order to obtain a dispersion having a dispersed particle size of a small particle size, 5 nm to 50 nm is preferable, and 5 to 40 nm is particularly preferable. preferable. If it is larger than 5 nm, it is easier to disperse, and if it is 50 nm or less, it is easier to obtain a dispersion having a small particle size. Further, it is easy to obtain a dispersion having a small particle size of 40 nm or less. Here, the primary particles in the present invention refer to 1000 pigment particles whose major axis is measured with a transmission electron microscope and the average value (number average) thereof.

【0038】

The dispersion of the present invention and the compound represented by the general formula (1) in the ink for inkjet are preferably contained in a proportion of 0.1 mol% or more and 50 mol% or less with respect to the pigment. The dispersion of the present invention is particularly suitable for ink jet inks because a dispersion having a small particle size can be obtained. In this case, the average scattering intensity of the dispersed particle size is preferably 5 nm or more and 200 nm or less from the viewpoint of light resistance and color transparency. Further, it is preferable to reduce the amount of dispersed particles of 300 nm or more to 2% or less from the viewpoint of clogging. The dispersed particle size is more preferably 30 to 150 nm. Here, the dispersed particle size in the present invention refers to the average particle size of the scattering intensity performed by the light scattering method and the laser scattering method.

【0039】

The zeta potentials of these dispersions can be measured by known methods, the values of which are in the range of -20 to -70 mV, with preferred dispersions being -30 to -70 mV. The hydrophilic medium of the present invention refers to a solvent having a solubility in water of 0.1% by mass or more.

【0040】

Examples of these solvents are alcohols (eg, methanol, ethanol, 1-propanol, 2-propanol, butanol, iso-butanol, sec-butanol, tert-butanol, pentanol, hexanol, cyclohexanol, benzyl alcohol. Etc.), polyhydric alcohols (eg, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, thiodiglycol, etc. ), Polyhydric alcohol ethers (eg, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monophenyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol dimethyl ether, propylene glycol Monomethyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, triethylene glycol dimethyl ether, dipropylene glycol monopropyl ether, tripropylene glycol dimethyl ether, etc. ), Minerals (eg, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholin, N-ethylmorpholin, ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, Pentamethyldiethylenetriamine, tetramethylpropylenediamine, etc.), amides (eg, formamide, N, N-dimethylformamide, N,N-dimethylacetamide, etc.), heterocyclics (eg, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-cyclohexyl-2-pyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone, etc.) , Sulfoxides (eg, dimethyl sulfoxide, etc.), sulfones (eg, sulfolane, etc.), sulfonates (eg, 1-butane sulfonic acid sodium salt, etc.), urea, acetonitrile, acetone, and the like.

【0041】

The pigment dispersion of the present invention may contain a surfactant and a polymer dispersant, if necessary. The types of surfactants and polymer dispersants are not particularly limited, but anionic surfactants and polymer dispersants having the same charge as the compounds of the present invention or nonionic surfactants and polymer dispersants having no electric charge are preferably used. Preferred surfactants include, for example, anionic surfactants such as dialkyl sulfosuccinates, alkylnaphthalene sulfonates, fatty acid salts, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, and acetylene glycol. Examples thereof include nonionic surfactants such as polyoxyethylene / polyoxypropylene block copolymers. Examples of the polymer dispersant include polystyrene-acrylic acid copolymers.

【0042】

As the hydrophilic medium used in the ink of the present invention, a water-soluble organic solvent is preferable, and specifically, alcohols (for example, methanol, ethanol, 1-propanol, 2-propanol, n-butanol, i-butanol, etc. sec-butanol, tert-butanol, pentanol, hexanol, cyclohexanol, benzyl alcohol, etc.), polyhydric alcohols (eg, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, etc. Butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, thiodiglycol, etc.), polyhydric alcohol ethers (eg, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monophenyl ether, Diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol dimethyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether , Triethylene glycol dimethyl ether, dipropylene glycol monopropyl ether, tripropylene glycol dimethyl ether, etc.), amines (eg, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholin, N-ethylmorpholin , Ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine, etc.), amides (eg, formami)Do, N, N-dimethylformamide, N, N-dimethylacetamide, etc.), heterocyclics (eg 2-pyrrolidone, N-methyl-2-pyrrolidone, N-cyclohexyl-2-pyrrolidone, 2-oxazolidone, 1, 3-Dimethyl-2-imidazolidinone etc.), sulfoxides (eg dimethyl sulfoxide etc.), sulfones (eg sulfolane etc.), sulfonates (eg 1-butane sulfonic acid sodium salt etc.), urea, acetonitrile, Examples include acetone.

【0043】

These hydrophilic media (ink solvents) may be used alone or in combination. In the ink of the present invention, latex may be added to the ink. Examples thereof include latexes such as styrene-butadiene copolymers, polystyrenes, acrylonitrile-butadiene copolymers, acrylic acid ester copolymers, polyurethanes, silicon-acrylic copolymers and acrylic modified fluororesins.

【0044】

The latex used in the present invention may be one in which polymer particles are dispersed using an emulsifier, or one in which polymer particles are dispersed without using an emulsifier. Surfactants are often used as emulsifiers, but polymers having a water-soluble group such as a sulfonic acid group or a carboxylic acid group (for example, a polymer having a solubilizing group grafted on it, or a simple polymer having a solubilizing group). It is also preferable to use a polymer obtained from a dimer and a monomer having an insoluble moiety).

【0045】

Further, it is particularly preferable to use soap-free latex in the ink of the present invention. The soap-free latex of the present invention is a latex that does not use an emulsifier, and a polymer having a water-soluble group such as a sulfonic acid group or a carboxylic acid group (for example, a polymer in which a solubilizing group is graft-bonded). It refers to a latex that uses (a polymer obtained from a monomer having a solubilizing group and a monomer having an insoluble moiety) as an emulsifier.

【0046】

In recent years, as latex polymer particles, in addition to latex in which polymer particles having uniform as a whole are dispersed, there is also latex in which core-shell type polymer particles having different compositions at the center and outer edges of the particles are dispersed. However, in the present invention, this type of latex can also be preferably used.

【0047】

In the ink of the present invention, from the viewpoint of image glossiness, water resistance, and scratch resistance, a range in which the average particle size of the polymer particles in the latex is 10 nm or more and 100 nm or less is preferably used, and 10 nm or more and 50 nm or less is particularly advantageous. Used for.

【0048】

The average particle size of the polymer particles in the latex can be determined by a commercially available particle size measuring device using a light scattering method, an electrophoresis method, or a laser Doppler method. In the ink of the present invention, latex is added so that the amount of solid content added is 0.1% by weight or more and 10% by weight or less with respect to the total weight of the ink from the viewpoint of water resistance, storage stability and the like. It is preferable, and it is particularly preferable that the content is 0.5% by weight or more and 3% by weight or less.

【0049】

In addition to this, the pigment ink of the present invention may contain a preservative, an antifungal agent, a viscosity regulator and the like, if necessary. An electric conductivity adjusting agent can also be used in the ink of the present invention, and examples thereof include inorganic salts such as potassium chloride, ammonium chloride, sodium sulfate, sodium nitrate and sodium chloride, and aqueous amines such as triethanolamine.

【0050】

In the ink of the present invention, a viscosity modifier, a resistivity adjuster, and a film forming agent are further applied according to the purpose of ejection stability, print head or ink cartridge compatibility, storage stability, image storage stability, and other performance improvements. Agents, UV absorbers, antioxidants, anti-fading agents, rust inhibitors, preservatives and the like can also be added.

【0051】

The recording medium used in the present invention includes plain paper, coated paper, swelling type inkjet recording paper provided with an ink receiving layer that absorbs and swells the ink liquid, and void type inkjet having a porous ink receiving layer. A recording paper or one using a resin support such as a polyethylene terephthalate film instead of the base paper can also be used. However, the void-type inkjet recording paper or the void-type inkjet film exhibits the best performance.

【0052】

The void-type inkjet recording paper or the void-type inkjet film refers to a recording medium provided with a void layer having an ink absorbing ability, and the void layer is mainly formed by soft aggregation of a hydrophilic binder and inorganic fine particles. Is to be done.

【0053】

As for the method of providing the void layer, various methods for forming voids in the film are known. For example, a uniform coating liquid containing two or more kinds of polymers is applied onto a support, and these are applied in a drying process. A method of phase-separating polymers from each other to form voids, a coating solution containing solid microparticles and a hydrophilic or hydrophobic binder is applied onto the support, and after drying, the inkjet recording paper contains water or a suitable organic solvent. A method of creating voids by immersing in a liquid to dissolve solid fine particles, and after applying a coating liquid containing a compound that has the property of foaming during film formation, this compound is foamed during the drying process to create voids in the film. Method of forming, method of applying a coating liquid containing porous solid tail particles and a hydrophilic binder on a support to form voids in or between the porous fine particles, approximately equal to or more than the amount of the hydrophilic binder. Examples thereof include a method in which solid fine particles having a volume (preferably 1.0 times or more) and / or a coating liquid containing fine particle oil droplets and a hydrophilic binder are applied onto a support to create voids between the solid fine particles. , In using the ink of the present invention, good results can be obtained even if any of them is provided by a method.

【0054】

The inkjet head for ejecting ink used in the image forming method of the present invention may be an on-demand method or a continuous type. The discharge method includes an electric-mechanical conversion method (for example, single cavity type, double cavity type, bender type, piston type, shared mode type, shared wall type, etc.) and an electric-heat conversion method (for example, thermal). Specific examples include an inkjet type, a bubble jet (registered trademark) type, etc.), an electrostatic attraction method (for example, an electric field control type, a slit jet type, etc.) and a discharge method (for example, a spark jet type, etc.). However, any discharge method can be used.

【0055】

[Example]

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

【0056】

In the examples, (%) indicates mass% unless otherwise specified. Example 1 Put 60 g of chlorosulfuric acid in a 300 ml three-necked flask and cool with ice. After adding 5 g of quinacridone at 5 to 15 ° C, it was heated at 40 ° C for 2 hours. After cooling, the mixture was placed in 300 ml of ice water, and the precipitated crystals were filtered and washed with water to obtain sulfonylquinacridone chloride.

【0057】

The obtained sulfonylquinacridone chloride was added to a mixture of 300 ml of acetone, 30 ml of pyridine and 2.9 g of sulfanilic acid, and the mixture was heated at 60 ° C. for 4 hours. After cooling, hydrochloric acid was added to make it acidic, and then filtration was performed. The obtained red substance was washed with saturated brine until it became neutral, further washed with ion-exchanged water, and dried to obtain 3.5 g of sulfophenylaminosulfonyl quinacridone (compound (1)).

【0058】

Other compounds of the present invention can also be synthesized by the same method from known carbonyl quinacridone chloride, aminomethyl quinacridone and the like. (Preparation of Pigment Dispersion 1) 200 ml of water and 7.5 g of acetic acid compound (1) 1.65 g (2.9 mmol) are added to a 1 l three-necked flask, and the mixture is ice-cooled.

【0059】

A solution prepared by dissolving 10 g (29 mmol) of PR (CI Pigment Red) 122 in a mixed solvent of 150 ml of DMSO and 50 ml of a 10% aqueous sodium hydroxide solution is slowly added dropwise thereto.

【0060】

After completion of the dropwise addition, 2 liters of methanol was added, the supernatant was removed by centrifugation, 500 ml of water was added, and sand mill dispersion was performed for 24 hours. A dispersion liquid (pigment dispersion 1) of PR122 5% was obtained through a 0.45 μm membrane filter. ..

【0061】

In order to determine the primary particle size of this dispersion, the average major axis of 1000 particles was calculated with an electron microscope and found to be 28 nm. Further, when the dispersed particle size was determined using Zetasizer 1000 (manufactured by Malvern), the average scattering intensity was 93 nm, and the number of particles of 300 nm or more was 5% or less.

【0062】

Hereinafter, as shown in Table 1, the compounds of the present invention and the following comparative compounds (a) and (b) were used, and the same procedure was used as above except that the compounds and amounts were changed. I got 18 ~ 20.

【0063】

(Preparation of Pigment Dispersion 11) In the method for preparing the dispersion 1, the dispersion 11 was obtained by the same method as that for the dispersion 1 except that the dispersion was not passed through a 0.45 μm membrane filter. The dispersed particle size was 93 nm, and 8% of the particles were 300 nm or more.

【0064】

(Preparation of Pigment Dispersion 12) HOSTAPERM PINK EB TRANS (manufactured by Clariant, PR122 primary particle size 40 nm) 10 g, compound 1 1.65 g, and ion-exchanged water 500 ml were added and sand mill dispersion was performed for 24 hours. (Pigment dispersion 2) was obtained. The primary particle size of this dispersion was 40 nm, and the dispersed particle size was 130 nm.

【0065】

(Synthesis Example 2) 2.9 g of the obtained copper phthalocyanine sulfonyl chloride was added to a mixture of 300 ml of acetone, 30 ml of pyridine and 2.9 g of sulfanilic acid, and the mixture was heated at 60 ° C. for 12 hours. After cooling, hydrochloric acid was added to make it acidic, and then filtration was performed. The obtained blue substance was washed with saturated brine until it became neutral, further washed with ion-exchanged water, and dried to obtain 3.5 g of sulfophenylaminosulfonyl copper phthalocyanine sodium salt (compound (25)).

【0066】

(Adjustment of dispersions 13 and 14) After dissolving 0.5 g of copper phthalocyanine, 50 g of concentrated sulfuric acid, and 0.5 g of sulfophenylaminosulfonyl copper phthalocyanine sodium salt (compound (25)), the liquid temperature is placed in 1000 ml of strongly stirred water. Was dropped while paying attention to the dropping speed so that the temperature was 15 ° C or less.

【0067】

After completion of the dropwise addition, after washing with water, 500 ml of methanol was added, the supernatant was removed by centrifugation, 100 ml of water was added, and sandmill dispersion was carried out for 24 hours to obtain a dispersion liquid (pigment dispersion 13) having a PB of 15: 3.

【0068】

In order to determine the primary particle size of this dispersion, the average major axis of 1000 particles was calculated with an electron microscope and found to be 24 nm. Similarly, dispersion 14 was prepared using the compounds listed in Table 1.

【0069】

(Synthesis Example 3) 3.4 g of the obtained diketopyrrolopyrrole sulfonyl chloride was added to a mixture of 300 ml of acetone, 30 ml of pyridine, and 2.9 g of sulfanilic acid, and the mixture was heated at 60 ° C. for 12 hours. After cooling, hydrochloric acid was added to make it acidic, and then filtration was performed. The obtained blue substance was washed with saturated brine until it became neutral, further washed with ion-exchanged water, and dried to obtain 2.8 g of sulfophenylaminosulfonyl diketopyrrole sodium salt (Compound 29).

【0070】

(Adjustment of dispersion 15) After dissolving 5 g of PR254, 50 g of concentrated sulfuric acid, and sodium sulfophenylaminosulfonyl diketopyrrolol sodium salt (Compound 29), the liquid temperature is 15 ° C or less in 1000 ml of strongly stirred water. The dropping was carried out while paying attention to the dropping speed.

【0071】

After completion of the dropping, after washing with water, 500 ml of methanol was added, the supernatant was removed by centrifugation, 100 ml of water was added, and sandmill dispersion was carried out for 24 hours to obtain a dispersion liquid of PR254 (pigment dispersion 15).

【0072】

In order to determine the primary particle size of this dispersion, the average major axis of 1000 particles was calculated with an electron microscope and found to be 29 nm. (Preparation of dispersion 16) Add 500 ml of water and 7.5 g of acetic acid, 1.65 g (2.9 mmol) of compound 1 to a 1 l three-necked flask, and cool with ice to bring the liquid temperature to 5 ° C.

【0073】

A solution prepared by dissolving 10 g (29 mmol) of PR122 in a mixed solvent of 450 ml of DMSO and 50 ml of a 10% sodium hydroxide aqueous solution is slowly added dropwise thereto.

【0074】

After completion of the dropwise addition, 2 liters of methanol was added, the supernatant was removed by centrifugation, 500 ml of water was added, and sand mill dispersion was performed for 24 hours. A dispersion liquid of PR122 5% (pigment dispersion liquid 16) was obtained through a 0.45 μm membrane filter. ..

【0075】

In order to determine the primary particle size of this dispersion, the average major axis of 1000 particles was calculated with an electron microscope and found to be 8 nm. Further, when the dispersed particle size was determined using Zetasizer 1000 (manufactured by Malvern), the average scattering intensity was 38 nm, and the number of particles of 300 nm or more was 5% or less. (Preparation of dispersion 17) Add 350 ml of water and 7.5 g of acetic acid, 1.65 g (2.9 mmol) of compound 1 to a 1 l three-necked flask, and cool with ice to bring the liquid temperature to 5 ° C.

【0076】

A solution prepared by dissolving 10 g (29 mmol) of PR122 in a mixed solvent of 350 ml of DMSO and 50 ml of a 10% sodium hydroxide aqueous solution is slowly added dropwise thereto.

【0077】

After completion of the dropwise addition, 2 liters of methanol was added, the supernatant was removed by centrifugation, 500 ml of water was added, and sandmill dispersion was performed for 24 hours to obtain a PR122 5% dispersion (pigment dispersion 17) through a 0.45 μm membrane filter. ..

【0078】

In order to determine the primary particle size of this dispersion, the average major axis of 1000 particles was calculated with an electron microscope and found to be 18 nm. Further, when the dispersed particle size was determined using Zetasizer 1000 (manufactured by Malvern), the average scattering intensity was 48 nm, and the number of particles of 300 nm or more was 5% or less.

【0079】

(Ink preparation method) Pigment dispersion 2 160g Diethylene glycol 180g Glycerin 80g Perex OT-P (manufactured by Kao Corporation) 5g Proxel GXL (manufactured by Zeneca) 2g The above was finished to 1000 g with ion-exchanged water, and a 1-micron millipore filter was passed twice to prepare a pigment ink. In the same manner, inks using the dispersions shown in Table 1 were prepared, and recording was performed on a recording medium using the inks.

【0080】

(Recording on recording medium) Equipped with a piezo type head with a nozzle particle size of 20 μm, a drive frequency of 12 kHz, a nozzle number of 128 per color, and a nozzle density of the same color of 180 dpi (dpi represents the number of dots per 2.54 cm). Using an on-demand inkjet with a maximum recording density of 720 x 720 dpi (dpi stands for the number of dots per 2.54 cm), a uniform image pattern was created to give 1.0 reflection density to the inkjet transparency.

【0081】

(Evaluation of Discharge Stability) The image obtained after continuous recording on the recording medium for 1 hour was visually evaluated. A three-level evaluation was performed, with a small number of nozzles being marked as , a large number of nozzles being marked as x, and a medium number being marked as .

【0082】

(Evaluation of dispersion stability) Place 100 ml of ink in a sealed sample bottle to prevent evaporation, leave it in a constant temperature bath at 60 ° C for 1 week, and use Zetasizer 1000 (manufactured by Malvern) to grain. The rate of change in diameter was calculated and evaluated on a three-point scale of , , and ×. : Particle size change rate is 10% or less Δ: Particle size change rate is 10 to 50% ×: Particle size change rate is 50% or more (Evaluation of image reproducibility) The obtained image pattern was visually evaluated and evaluated on a 5-point scale with the highest reproducibility as 5 points and the worst as 1 point.

【0083】

As described above, the pigment dispersion prepared by using the compound of the present invention had a small primary particle size and a dispersed particle size, and was excellent in dispersion stability. Further, it can be seen that the inkjet ink produced using this dispersion is excellent in dispersion stability, and the image produced using the ink is excellent in image reproducibility.

【0084】

[table 1]

<img file="JP2002201401A_D0010.tif" />【0085】

[Chemical 11]

Comparative compound (a)<img file="JP2002201401A_D0011.tif" />【0086】

[Chemical 12]

Comparative compound (b)<img file="JP2002201401A_D0012.tif" />【0087】

[Effect of the invention]

According to the present invention, in a pigment dispersion in which a pigment is dispersed in a hydrophilic medium, an aqueous pigment dispersion having a small primary particle size of the pigment and good dispersion stability can be obtained. Further, an ink jet ink having excellent dispersion stability, excellent reproducibility of brightness and saturation, and an image having good color reproducibility was obtained.