JP2010083925A - Dispersion of poorly soluble compound and method for producing the same, recording liquid, ink set, printed matter, image forming method and image forming apparatus using the same - Google Patents

Abstract

Disclosed is a dispersion in which primary particles of a slightly soluble organic compound or water-insoluble colorant are made into very fine nanometer size particles and contained as columnar particles of a predetermined shape, and a method for producing the same. In addition, the present invention provides a dispersion containing the columnar fine particles that have very high dispersion stability and storage stability and can be stored for a long time while maintaining desired performance, and a production method for efficiently obtaining the dispersion.
A sparingly soluble organic substance having columnar particles having an aspect ratio of 3 or more and a major axis length of 50 nm to 300 nm and a volume average particle diameter of 50 nm or less by dynamic light scattering measurement of a 0.5 mass% liquid. A sparingly soluble organic compound dispersion containing fine particles of a compound.
[Selection figure] None

Description

  The present invention relates to a dispersion of a poorly soluble organic compound and a production method thereof, a recording liquid using the same, an ink set, a printed matter, an image forming method, and an image forming apparatus.

As a method for obtaining a dispersion of a hardly soluble organic compound or a similar water-insoluble colorant, these are added alone or in combination to an aqueous solvent or an organic solvent, and a dispersing machine such as a sand mill, a bead mill, or a ball mill is used. The method of pulverizing and refining the pigment particle diameter is employed (see Patent Documents 1 and 2). In addition, it has been proposed to make a pigment into a solid solution in consideration of improvement in coloring power and weather resistance (see Patent Document 3).
In addition, a method of preparing a pigment dispersion by mixing an organic pigment and a polymer dispersant, or a polymer compound as a dispersant in an aprotic organic solvent in the presence of an alkali, and then mixing this solution with water (Hereinafter, the above method will be referred to as a build-up method), and predetermined polymer compounds used therein have been studied (see Patent Documents 4 to 7). However, the pigment dispersions prepared by these methods are likely to increase in primary or secondary particle diameter during storage and cannot be said to have sufficient storage stability, and further improvement in storage stability has been desired.

JP 2006-57044 A JP 2006-328262 A JP-A-60-35055 JP 2003-26972 A JP 2004-43776 A JP 2006-342316 A JP 2007-119586 A

  An object of the present invention is to provide a dispersion in which primary particles of a hardly soluble organic compound or water-insoluble colorant are made into extremely fine nanometer size particles and further included as columnar particles of a predetermined shape, and a method for producing the same And The present invention also provides a dispersion containing the columnar fine particles that has very high dispersion stability and storage stability, can be stored for a long time while maintaining desired performance, and a production method for efficiently obtaining the dispersion. For the purpose of provision. Another object of the present invention is to provide a recording liquid, an ink set, an image forming method, and an image forming apparatus using the dispersion having the above-described excellent characteristics, in particular, an aqueous dispersion of the water-insoluble colorant.

The above problems have been achieved by the following means.
(1) A sparingly soluble organic compound having columnar particles having an aspect ratio of 3 or more and a major axis length of 50 nm to 300 nm and a volume average particle diameter of 50 nm or less by dynamic light scattering measurement of a 0.5 mass% liquid A sparingly soluble organic compound dispersion comprising:
(2) The dispersion according to (1), wherein the hardly soluble organic compound is a water-insoluble colorant.
(3) The dispersion according to (1) or (2), wherein the fine particles contained in the dispersion are a water-insoluble colorant dispersed by a coexisting polymer compound.
(4) The dispersion according to any one of (1) to (3), wherein the dispersion medium of the dispersion is an aqueous medium.
(5) The polymer compound is an acid group-containing polymer compound having at least one acid group selected from the group consisting of a carboxylic acid group, a sulfonic acid group, a phosphoric acid group, and a hydroxyl group. The dispersion according to (3) or (4).
(6) The tough organic compound is an organic pigment selected from the group consisting of quinacridone organic pigments, diketopyrrolopyrrole organic pigments, and monoazo yellow organic pigments. The dispersion according to any one of the above.
(7) The number of the fine particles of the hardly soluble compound having the particle diameter, the aspect ratio, and the long axis length is 80% by number or more of the total primary fine particles of the hardly soluble organic compound in the dispersion. The dispersion according to any one of 6).
(8) (1) Step (2) in which an organic or inorganic base or organic or inorganic acid is co-dissolved in an organic solvent (2) The solution obtained in (1) Step (3) in which fine particles of a hardly soluble organic compound are mixed and dispersed in an aqueous medium to disperse the hardly soluble organic compound dispersion obtained in (2) by applying a predetermined temperature to heat the primary particles. Grown, at least 80% or more of all primary particles are columnar particles having an aspect ratio of 3 or more and a major axis length of 50 nm to 300 nm, and a volume average particle diameter by dynamic light scattering measurement of 0.5% by mass liquid. Forming a dispersion having a thickness of 50 nm or less,
A method for producing an aqueous dispersion of a sparingly soluble organic compound, comprising:
(9) The method for producing an aqueous dispersion according to (8), wherein the hardly soluble organic compound is a water-insoluble colorant.
(10) In the step (1) of co-dissolving the water-insoluble colorant and the polymer compound, the base used is represented by the following general formula (I) or (II): The method for producing an aqueous dispersion according to 8) or (9).
(Wherein R _{1 to} R ₅ are each independently an unsubstituted straight chain or branched alkyl having 1 to 3 carbon atoms, and n is an integer of 1 to 4).
(11) Any of (8) to (10), wherein the hardly soluble organic compound is an organic pigment selected from the group consisting of quinacridone organic pigments, diketopyrrolopyrrole organic pigments, and monoazo yellow organic pigments 2. A method for producing an aqueous dispersion of a water-insoluble colorant according to item 1.
(12) A dispersion obtained by the production method according to any one of (8) to (11).
(13) The fine particle of the hardly soluble organic compound in the dispersion according to any one of (1) to (7) and (12) is contained in an amount of 0.1 to 15% by mass of the total mass of the recording liquid. Recording liquid.
(14) The recording liquid according to (13), wherein the recording liquid is an inkjet recording liquid.
(15) An ink set using the inkjet recording liquid according to (13) or (14).
(16) A printed matter in which an image is recorded by means of applying the recording liquid to the medium using the recording liquid according to (13) or (14) or the ink set according to (15), Has a function of adjusting the application amount or density of the recording liquid, and the printed matter in which the density of the printed matter is adjusted by the means.
(17) A step of recording an image by applying the recording liquid to the medium using the recording liquid according to (13) or (14) or the ink set according to (15). Image forming method.
(18) A recording liquid according to (13) or (14) or an ink set according to (15) is used to apply a recording liquid to a medium, thereby having means for recording an image. An image forming apparatus.

The dispersion of the present invention contains a sparingly soluble organic compound or water-insoluble compound as nanometer-sized extremely fine and columnar fine particles, and therefore has unique properties that cannot be achieved by conventional spherical or irregular fine particles. The dispersion can be applied to a recording liquid using the dispersion. Further, the dispersion containing the columnar fine particles of the hardly soluble organic compound or water-insoluble compound of the present invention has very high dispersion stability and storage stability, and can be stored for a long time while maintaining desired performance. Excellent operational effects.
Furthermore, according to the production method of the present invention, it is possible to efficiently produce a dispersion having the above-described excellent characteristics, and a recording liquid using this has high transparency and good ejection properties, A high-performance ink set, printed matter, image forming method, and image forming apparatus can be provided.

  Hereinafter, the dispersion of the present invention will be described in detail based on preferred embodiments thereof. First, the hardly soluble organic compound used in the present invention will be described.

  Examples of the hardly soluble organic compounds in the present invention include chitin / chitosan which is insoluble due to strong hydrogen bonding and a strong crystal structure, and poorly soluble polysaccharides and derivatives thereof such as cellulose, which is a main component such as cotton, and hydrogen bonding. In addition, organic pigments that are sparingly soluble due to strong π-π conjugation interactions, sparingly soluble compounds that can be used as pharmaceuticals, etc. Examples of sparingly soluble pharmaceuticals include antifungal agents (such as itraconazole), dihydropyridine antihypertensive agents (nifedipine) , Nilvadipine, nicardipine hydrochloride, benidipine hydrochloride, manidipine hydrochloride, nisoldipine, nitrendipine, varnidipine hydrochloride, amlodipine besylate, efonidipine hydrochloride, felodipine, etc.), fibrate hyperlipidemia agents (fenofibrate, etc.) and the like. The hardly soluble organic compound preferably used in the present invention is a water-insoluble colorant, and an organic pigment is more preferable, but the present invention is not limited to this.

  The organic pigment suitably used in the dispersion of the present invention is not particularly limited in terms of hue or structure. For example, perylene compound pigment, perinone compound pigment, quinacridone compound pigment, quinacridone quinone compound pigment, anthraquinone compound pigment, Anthanthrone compound pigment, benzimidazolone compound pigment, disazo condensation compound pigment, disazo compound pigment, azo compound pigment, indanthrone compound pigment, indanthrene compound pigment, quinophthalone compound pigment, quinoxalinedione compound pigment, metal complex azo compound pigment, Phthalocyanine compound pigment, triarylcarbonium compound pigment, dioxazine compound pigment, aminoanthraquinone compound pigment, diketopyrrolopyrrole compound pigment, naphthol AS compound pigment, thioin Gore compound pigments, isoindoline compound pigments, isoindolinone compound pigments, pyranthrone compound pigments, isoviolanthrone compound pigment, or a mixture thereof.

  More specifically, for example, C.I. I. Pigment red 179, C.I. I. Pigment red 190, C.I. I. Pigment red 224, C.I. I. Perylene compound pigments such as C.I. Pigment Violet 29; I. Pigment orange 43, or C.I. I. Perinone compound pigments such as CI Pigment Red 194; I. Pigment violet 19, C.I. I. Pigment violet 42, C.I. I. Pigment red 122, C.I. I. Pigment red 192, C.I. I. Pigment red 202, C.I. I. Pigment red 207 or C.I. I. Pigment Red 209 quinacridone compound pigment, C.I. I. Pigment red 206, C.I. I. Pigment orange 48, or C.I. I. Quinacridonequinone compound pigments such as C.I. Pigment Orange 49; I. Anthraquinone compound pigments such as C.I. Pigment Yellow 147; I. Anthanthrone compound pigments such as C.I. Pigment Red 168; I. Pigment brown 25, C.I. I. Pigment violet 32, C.I. I. Pigment yellow 180, C.I. I. Pigment yellow 181, C.I. I. Pigment orange 36, C.I. I. Pigment orange 62, or C.I. I. Benzimidazolone compound pigments such as CI Pigment Red 185; I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. Pigment yellow 95, C.I. I. Pigment yellow 128), C.I. I. Pigment yellow 166, C.I. I. Pigment orange 34, C.I. I. Pigment orange 13, C.I. I. Pigment orange 31, C.I. I. Pigment red 144 (C.I. No. 20735), C.I. I. Pigment red 166, C.I. I. Pigment yellow 219, C.I. I. Pigment red 220, C.I. I. Pigment red 221, C.I. I. Pigment red 242, C.I. I. Pigment red 248, C.I. I. Pigment red 262, or C.I. I. Disazo condensation compound pigments such as C.I. Pigment Brown 23; I. Pigment yellow 13, C.I. I. Pigment yellow 83, or C.I. I. Disazo compound pigments such as C.I. Pigment Yellow 188; I. Pigment red 187, C.I. I. Pigment red 170, C.I. I. Pigment yellow 74, C.I. I. Pigment red 48, C.I. I. Pigment red 53, C.I. I. Pigment orange 64, or C.I. I. Azo compound pigments such as C.I. Pigment Red 247; I. Indanthrone compound pigments such as C.I. Pigment Blue 60; I. Indanthrene compound pigments such as C.I. Pigment Blue 60; I. Quinophthalone compound pigments such as C.I. Pigment Yellow 138; I. Quinoxalinedione compound pigments such as CI Pigment Yellow 213; I. Pigment yellow 129, or C.I. I. Pigment Yellow 150 and other metal complex azo compound pigments, C.I. I. Pigment green 7, C.I. I. Pigment green 36, C.I. I. Pigment green 37, C.I. I. Pigment blue 16, C.I. I. Pigment blue 75, or C.I. I. Phthalocyanine compound pigments such as C.I. Pigment Blue 15 (including 15: 1, 15: 6, etc.); I. Pigment blue 56 or C.I. I. Triarylcarbonium compound pigments such as C.I. Pigment Blue 61; I. Pigment violet 23, or C.I. I. Dioxazine compound pigments such as C.I. Pigment Violet 37; I. Aminoanthraquinone compound pigments such as C.I. Pigment Red 177; I. Pigment red 254, C.I. I. Pigment red 255, C.I. I. Pigment red 264, C.I. I. Pigment red 272, C.I. I. Pigment orange 71, or C.I. I. Diketopyrrolopyrrole compound pigments such as C.I. Pigment Orange 73; I. Pigment red 187, or C.I. I. Naphthol AS compound pigments such as C.I. Pigment Red 170; I. Thioindigo compound pigments such as CI Pigment Red 88; I. Pigment yellow 139, C.I. I. Pigment Orange 66 and other isoindoline compound pigments, C.I. I. Pigment yellow 109, C.I. I. Pigment yellow 110, or C.I. I. Pigment Orange 61 and other isoindolinone compound pigments, C.I. I. Pigment orange 40, or C.I. I. A pyranthrone compound pigment such as C.I. Pigment Red 216; I. And isoviolanthrone compound pigments such as CI Pigment Violet 31.

  Among them, in the present invention, quinacridone organic pigments, diketopyrrolopyrrole organic pigments, and monoazo yellow organic pigments are preferable.

The dispersion of the present invention is preferably a dispersion in which columnar fine particles of a hardly soluble organic compound described later are dispersed by a coexisting polymer compound, and more preferably from a carboxylic acid group, a sulfonic acid group, and a phosphoric acid group. It is preferable to be dispersed by a polymer compound having one or more kinds selected from the group as a hydrophilic site. Specifically, styrene, styrene derivatives, vinyl naphthalene, vinyl naphthalene derivatives, aliphatic alcohol esters of α, β-ethylenically unsaturated carboxylic acids, acrylic acid, acrylic acid derivatives, methacrylic acid, methacrylic acid derivatives, maleic acid, Maleic acid derivative, alkenylsulfonic acid, vinylamine, allylamine, itaconic acid, itaconic acid derivative, fumaric acid, fumaric acid derivative, vinyl acetate, vinylphosphonic acid, vinylpyrrolidone, acrylamide, N-vinylacetamide, N-vinylformamide and derivatives thereof A block copolymer composed of at least two monomers selected from the group consisting of at least one monomer having a functional group that becomes one of a carboxylic acid group, a sulfonic acid group, and a phosphoric acid group. Polymer or random copolymer, Examples include raft copolymers, modified products thereof, and salts thereof.
As the acid group, carboxylic acid or sulfonic acid is more preferable, and carboxylic acid is more preferable. Moreover, this high molecular compound can be used individually by 1 type or in combination of 2 or more types. Furthermore, the more preferable range of the acid value which these acid group containing polymers have is 100 mgKOH / g-300 mgKOH / g, More preferably, they are 140 mgKOH / g-240 mgKOH / g.

  More specifically, the polymer compound in the present invention is preferably composed of a hydrophilic group site and a hydrophobic site, and a copolymer obtained by copolymerizing a hydrophilic monomer component and a hydrophobic monomer component is used. It is preferable. The hydrophilicity is a property that has a high affinity for water and is easily dissolved in water, and the hydrophobic property is a property that has a low affinity for water and is difficult to dissolve in water.

  For example, the hydrophobic monomer component includes a monomer component having a hydrophobic unit such as a long-chain alkyl group having 8 or more carbon atoms, a t-butyl group, a phenyl group, a biphenyl group, or a naphthyl group as a structural unit. From the viewpoint of imparting high dispersion stability to the water-insoluble colorant, a block segment having styrene, stearylmethacrylamide or the like as a repeating unit as a hydrophobic monomer is preferred, but the hydrophobic monomer component is not limited thereto.

  Examples of the hydrophilic monomer component include acrylic acid ester / methacrylic acid ester having an alkylene oxide group, N-vinylpyrrolidone, N-vinylimidazole, and the like, but the hydrophilic monomer component of the present invention is limited to this. It is not a thing.

In the present invention, it is also preferable to use a polymerizable compound (polymerizable compound [i]) that has an acid group and forms a hydrophilic portion (a repeating unit having a hydrophilic group) after polymerization. Specifically, acrylic acid, acrylic acid derivative, methacrylic acid, methacrylic acid derivative, maleic acid, maleic acid derivative, alkenyl sulfonic acid, itaconic acid, itaconic acid derivative, fumaric acid, fumaric acid derivative, vinylphosphonic acid, phenol and And derivatives thereof. However, the acid group in the present invention is not limited to this, and general functional groups that can be ionized and ionized in water by sodium hydroxide or potassium hydroxide, which are generally used as strong bases, are used as acid groups. May be.
The acid group is more preferably a carboxylic acid group or a sulfonic acid group, and even more preferably a carboxylic acid group. Furthermore, the more preferable range of the acid value of the acid group-containing polymer compound having the heterocyclic structure of the present invention is 100 mgKOH / g to 300 mgKOH / g, and more preferably 140 mgKOH / g to 240 mgKOH / g.

The amount of the specific polymer compound contained in the dispersion of the present invention is not particularly limited, but is preferably 10 to 100 parts by mass with respect to 100 parts by mass of the hardly soluble organic compound or the water-insoluble colorant. More preferably, it is 50 mass parts.
Although the molecular weight of the polymer compound is not particularly limited, the mass average molecular weight is preferably 5,000 to 100,000, and more preferably 10,000 to 50,000. In the present invention, the term “molecular weight” means a weight average molecular weight, and the weight average molecular weight is an average molecular weight in terms of polystyrene measured by gel permeation chromatography (carrier: tetrahydrofuran) unless otherwise specified.

  The dispersion medium in the dispersion of the present invention is composed of, for example, water or an aqueous solution of water and a water-soluble organic solvent (aqueous medium), and a water-soluble / water-insoluble organic solvent in which two or more types may be mixed. Specific water-soluble organic solvents include acetone, methyl ethyl ketone, tetrahydrofuran, acetonitrile, methanol, ethanol, isopropanol, glycerin, (mono / di / tri) ethylene glycol or monoalkyl ethers thereof, and the like. PGMEA, ethyl lactate, ethyl acetate, toluene, t-butyl methyl ether, dimethyl sulfoxide, N-methyl pyrrolidone and the like are exemplified, but the present invention is not limited thereto. These can be used alone or in combination of two or more. In addition, the amount of water in the aqueous medium is preferably 99 to 20% by mass, more preferably 95 to 30% by mass. The amount of the water-soluble organic solvent in the dispersion is preferably 50 to 0.1% by mass, more preferably 30 to 0.05% by mass.

  The hardly soluble organic compound dispersion of the present invention is obtained by co-dissolving a hardly soluble organic compound and a polymer compound in an organic solvent in the presence of an inorganic / organic base or an inorganic / organic acid, and then dissolving the solution (hereinafter referred to as “slightly soluble”). The organic compound solution is sometimes referred to as “organic compound solution.”) Is mixed with an aqueous medium to produce the hardly soluble organic compound fine particles.

  As the organic solvent used in the production method of the present invention, any kind of an aprotic organic solvent and a protic organic solvent can be used. However, the organic solvent for dissolving the water-insoluble colorant and the polymer compound in the presence of alkali is preferably an aprotic organic solvent, more preferably dimethyl sulfoxide, N-methylpyrrolidone, dimethylformamide, dimethylacetamide, sulfolane, etc. It is. Moreover, these can be used individually by 1 type or in combination of 2 or more types.

  Examples of the base used in the present invention include inorganic or organic bases. This inorganic or organic base is preferably a phase transfer base from the viewpoint of solubility / dispersibility, and specifically, preferred examples include alkylammonium derivatives, alkylsulfonium derivatives, and alkylphosphonium derivatives. As the phase transfer type base, one having a structure in which the ClogP value is negative is preferable, and more preferable is negative than −2. Here, the ClogP value refers to a common logarithm value of 1-octanol / water partition coefficient P indicating the ratio between the equilibrium concentrations of the compound in 1-octanol and in water. This ClogP value is determined by a fragment approach based on the chemical structure of the compound (A. Leo, Comprehensive Medical Chemistry, Vol. 4; C. Hansch, P. G. Sammens, J. B. Taylor and C. A. Ramden. , P. 295, Pergramon Press, 1990), etc., and can be defined by values calculated with the “CLOGP” program available from Daylight Chemical Information Systems.

  As the phase transfer base, those represented by the general formula (I) or (II) are preferable. Particularly preferred are choline hydroxide, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide and the like, but the phase transfer base used in the present invention is not limited thereto.

  Examples of the inorganic / organic acid suitably used in the production method of the present invention include sulfuric acid, fuming sulfuric acid, nitric acid, fuming nitric acid and the like, and examples of the organic acid include methanesulfonic acid, chlorosulfonic acid, and polyfluorinated alkylsulfonic acid. Sulfuric acid is more preferable.

  The use ratio of the inorganic / organic base or the inorganic / organic acid is not particularly limited, but is preferably 1.0 to 100 molar equivalents in terms of a molar ratio with the hardly soluble organic compound or the water-insoluble colorant, It is more preferably 1.5 to 50 molar equivalents, and particularly preferably 2.0 to 20 molar equivalents. Moreover, it is preferable that it is 0.5-10 molar equivalent with respect to 1 mol equivalent of acid groups which this polymer has with respect to the said specific high molecular compound in a dispersion, 0.8-5 molar equivalent It is more preferable that it is 0.9 to 1.5 molar equivalent.

  In the dispersion of the present invention, the content of the hardly soluble organic compound in the dispersion is not particularly limited, and is preferably, for example, 0.01 to 30% by mass when considering use as an ink. More preferably, it is -20 mass%, and it is especially preferable that it is 1.1-15%. In addition, the dispersion medium of the hardly soluble organic compound of the present invention may be an aqueous solvent. When the content is referred to as the water content, for example, when considering use as an ink, 0.01 to 30% by mass It is preferable that it is 1.1-15 mass%.

  The dispersion in the present invention can maintain the dispersion at a low viscosity even at a high concentration. For example, when used as a recording liquid, the dispersion of the present invention is preferably used as a recording liquid because the degree of freedom of the types and amounts of additives that can be used in the recording liquid increases even if the concentration is low. Can do.

  The content of the organic solvent in the hardly soluble organic compound solution is not particularly limited, but when making the hardly soluble organic compound in a better dissolved state, 2 to 500 parts by mass with respect to 1 part by mass of the hardly soluble organic compound. Furthermore, it is preferable to use in the range of 5 to 100 parts by mass.

  In the production method of the present invention, a hardly soluble organic compound or a water-insoluble colorant is dissolved in an organic solvent together with the specific polymer compound. In addition, the organic solvent contains a crystal growth inhibitor, an ultraviolet absorber, At least one of an antioxidant, a resin additive, a surfactant and the like can be added as necessary.

  Examples of the crystal growth inhibitor include phthalocyanine derivatives and quinacridone derivatives that are well known in the art. For example, phthalocyanine phthalimidomethyl derivatives, phthalocyanine sulfonic acid derivatives, phthalocyanine N- (dialkylamino) methyl derivatives, phthalocyanines N- (dialkylaminoalkyl) sulfonic acid amide derivatives, phthalimidomethyl derivatives of quinacridone, sulfonic acid derivatives of quinacridone, N- (dialkylamino) methyl derivatives of quinacridone, N- (dialkylaminoalkyl) sulfonic acid amide derivatives of quinacridone, etc. Is mentioned.

  UV absorbers include metal oxides, aminobenzoate UV absorbers, salicylate UV absorbers, benzophenone UV absorbers, benzotriazole UV absorbers, cinnamate UV absorbers, nickel chelate UV absorbers, hindered amines. UV absorbers such as UV absorbers, urocanic acid UV absorbers and vitamin UV absorbers.

  Examples of the antioxidant include hindered phenol compounds, thioalkanoic acid ester compounds, organic phosphorus compounds, and aromatic amines.

  Examples of the resin additive include anion-modified polyvinyl alcohol, cation-modified polyvinyl alcohol, polyurethane, carboxymethylcellulose, polyester, polyallylamine, polyvinylpyrrolidone, polyethyleneimine, polyaminesulfone, polyvinylamine, hydroxyethylcellulose, hydroxypropylcellulose, melamine resin, or these resins. Examples include synthetic resins such as modified products. These crystal growth inhibitors, ultraviolet absorbers, and resin additives can be used alone or in combination of two or more.

  Surfactants include alkyl benzene sulfonates, alkyl naphthalene sulfonates, higher fatty acid salts, higher fatty acid ester sulfonates, higher alcohol ether sulfates, higher alcohol ether sulfonates, higher alkyl sulfonamides. Anionic surfactants such as alkyl carboxylates and alkyl phosphates, polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, ethylene oxide adducts of acetylene glycol, ethylene of glycerin Nonionic surfactants such as oxide adducts and polyoxyethylene sorbitan fatty acid esters, as well as amphoteric surfactants such as alkylbetaines and amidebetaines, Recon surfactant, including such fluorine-based surfactant, can be appropriately selected from surfactants and derivatives thereof are known.

  In the production method of the present invention, a hardly soluble organic compound solution or a water-insoluble colorant solution is mixed with an aqueous medium to produce water-insoluble colorant fine particles. From the viewpoint of further improving the dispersion stability and further improving the color density of the dispersion, 0.5 to 1000 parts by mass is preferable with respect to 1 part by mass of the water-insoluble colorant solution, and 1 to 100 parts by mass. Part is more preferred.

  In the production method of the present invention, the temperature when mixing the water-insoluble colorant pigment solution and the aqueous medium is preferably in the range of −50 ° C. to 100 ° C., and is adjusted in the range of −20 ° C. to 50 ° C. It is more preferable. The temperature of the solution at the time of mixing may greatly affect the size of the fine particles of the water-insoluble colorant to be generated, and the liquid temperature is −50 ° C. to 100 ° C. in order to obtain a dispersion of fine particles of nanometer order. It is preferable to make it into a range. At this time, a known freezing point depressant such as ethylene glycol, propylene glycol or glycerin can be added to the water to be mixed in order to ensure the fluidity of the liquid.

  Furthermore, in order to obtain nanometer-order fine particles having a uniform particle size, it is preferable to mix the sparingly soluble organic compound solution and the aqueous medium as quickly as possible. Any of the devices used for stirring, mixing, dispersion, and crystallization, such as an internal circulation type stirring device, an external circulation type stirring device, a flow rate and ion concentration control device, and the like can be used. Moreover, you may mix in the water which flows continuously. As a method for adding the hardly soluble organic compound solution to the aqueous medium, any of the usual liquid injection methods can be used. However, it is possible to use the injection flow from a nozzle such as a syringe, a needle, or a tube in water or from above the water. preferable. In addition, in order to throw in in a short time, it can also throw in from several nozzles. Furthermore, in order to stably prepare the aqueous dispersion of the hardly soluble organic compound fine particles, an additive such as an alkali and a dispersing agent can be added to the aqueous medium to be mixed with the hardly soluble organic compound solution.

Hereinafter, the characteristics of the columnar fine particles in the dispersion of the present invention and the formation thereof will be described.
It is considered that a hardly soluble organic compound such as a pigment dissolved in an organic solvent is rapidly crystallized by mixing with an aqueous medium to form an amorphous-like aggregate. In the present invention, the aqueous solution containing the amorphous-like fine particles thus formed is heated by applying a specific temperature to each hardly soluble organic compound, thereby forming fine columnar particles having high monodispersity. be able to.

  The temperature applied in the heating step described above varies depending on each hardly soluble organic compound. Specifically, for example, quinacridone (PV-19) and dimethylquinacridone (PR-122), which are widely used as insoluble colorants, preferably have a temperature of about 80 ° C to 150 ° C, more preferably 90 ° C to 130 ° C, and even more preferably. 100 ° C to 120 ° C. The same is true for dichlorodiketopyrrolopyrrole (PR-254), but the appropriate heating temperature for monoazo yellow pigments is about 60 ° C. to 90 ° C., and the compound dependency is large. As a method for determining the specific temperature, the aqueous solution containing the above-mentioned amorphous-like fine granular particles is heated at a specific temperature for 3 hours, and then the primary particle shape is observed by SEM imaging, and the primary particle shape becomes columnar. An operation for finding the lower limit of temperature is given. Thereby, the specific temperature suitable for heating can be prescribed | regulated and the manufacturing conditions suitable for each compound can be set.

  The dispersion of the present invention thus produced preferably contains fine particles whose primary particle structure is stabilized in a columnar state as a result of being ignited, and as a result exhibits very high storage stability, It can be used as a material exhibiting strong anisotropic orientation, which is preferable. In the present invention, it is preferable to adopt the columnar particle formation step by heating as described above, but the present invention is not limited to this, and columnar particle formation that can be produced under reaction conditions such as magnetic field, ultrasonic wave, UV exposure, etc. Includes general.

The sparingly soluble organic compound or aqueous water-insoluble colorant dispersion of the present invention can be used in various applications, for example, inkjet inks, as they are or by adjusting the colorant concentration as necessary.
When the aqueous water-insoluble colorant dispersion is applied to ink jet ink, the colorant concentration may be low. Although the concentration can be increased by concentrating the dispersion medium of the dispersion, it is not practical industrially. On the other hand, the dispersion of the present invention first takes out the hardly soluble organic compound fine particles as a powder or paste, and then imparts dispersibility to water, so that the water-insoluble fine particles can be efficiently redispersed in an aqueous medium. it can. Therefore, an aqueous dispersion having a desired color material concentration can be efficiently prepared.

In the present invention, it is preferable to use the dispersion obtained in the above-described step and further form an aggregate of fine particles of the hardly soluble organic compound contained in the dispersion.
In the present invention, the term “fine particles of a hardly soluble organic compound” includes fine particles comprising only a hardly soluble organic compound and fine particles made of a hardly soluble organic compound and other components. For example, a slightly soluble organic compound and / or other compounds may form the core of particles, and adsorb so that the dispersant (polymer compound, surfactant, etc.) covers them to form fine particles. In the dispersion of the present invention, it is particularly preferable that the specific polymer compound is coated and adsorbed on the fine particles of the hardly soluble organic compound. This coating adsorption state can be confirmed by, for example, X-ray crystal structure analysis (XRD).

  For the formation of the agglomerates of fine particles of the hardly soluble organic compound, treatment by adding an organic acid / inorganic acid is preferably used. The treatment using an acid preferably includes a step of agglomerating fine particles of a hardly soluble organic compound with an acid, separating it from a solvent (dispersion medium), and performing concentration, desolvation and desalting (deoxidation). By making the system acidic, the electrostatic repulsion force by the acidic hydrophilic portion is reduced, and the hardly soluble organic compound fine particles are aggregated. In general, even when the pigment dispersion is agglomerated with an acid and then subjected to an alkali treatment, the fine particles are hardly redispersed and an increase in the primary particle size may be observed. On the other hand, according to the dispersion of the present invention, when an aqueous dispersion of fine particles of a hardly soluble organic compound material such as a pigment is prepared, and this is aggregated with an acid to redisperse the fine particles, the primary particle diameter increases. Can be greatly reduced. As described above, this is presumed to be due to the strengthening of the crystal structure by heating.

  As an acid used for agglomerating fine particles of a poorly soluble organic compound, the particles contained in the aqueous dispersion, which are fine particles that are difficult to precipitate, are agglomerated to form a slurry, paste, powder, granule, cake (lump), or sheet. It is preferable to use a short fiber, flake, or the like that can be efficiently separated from the solvent by a normal separation method. More preferably, in order to separate the alkali used in the step of dissolving the hardly soluble organic compound simultaneously with the solvent, it is preferable to use an acid that forms a water-soluble salt with the alkali such as the phase transfer base used. Also preferred are those having high solubility in water. In order to efficiently perform desalting, the amount of acid to be added is preferably as small as possible within the range in which the fine particles aggregate. Specific examples include hydrochloric acid, sulfuric acid, nitric acid, acetic acid, phosphoric acid, trifluoroacetic acid, dichloroacetic acid, methanesulfonic acid and the like, with hydrochloric acid, acetic acid and sulfuric acid being particularly preferred. The aqueous dispersion of water-insoluble colorant fine particles that can be easily separated by an acid can be easily separated by a centrifugal separator, a filtration device, a slurry solid-liquid separation device, or the like. At this time, the degree of desalting and solvent removal can be adjusted by adding dilution water or increasing the number of decantations and washings.

  Furthermore, in the step of obtaining the hardly soluble organic compound aggregate, the filterability can be improved by adding an organic solvent, which is a useful process. As the preferred solvent, any kind of aprotic organic solvent and protic organic solvent can be used, and specifically, polar solvents such as ethyl acetate, ethyl lactate, acetone, methyl ethyl ketone, acetonitrile, methanol ethanol, isopropanol are preferred. . Although the amount is not particularly limited, it is preferably 1 to 100 parts by mass, more preferably 5 to 50 parts by mass with respect to 100 parts by mass of the water-insoluble colorant dispersion.

  The agglomerates thus obtained can be used as a paste or slurry with a high water content, but as necessary, such as spray drying, centrifugal drying, filtration drying or freeze drying. It can also be used as a fine powder by a drying method. Moreover, it is also possible to obtain primary particles which have been exposed to a solvent and further grown in a crystal structure by adding an aggregate into an organic solvent such as acetone, tetrahydrofuran, or methanol and filtering. The growth of the crystal structure can be easily observed by XRD (crystal structure analysis) analysis.

  In a preferred embodiment of the dispersion of the present invention, an aggregate is prepared from a primary dispersion (aqueous dispersion, reprecipitation liquid) obtained by mixing a hardly soluble organic compound solution and an aqueous medium. It is preferable to add an aqueous medium or an organic solvent to the aggregate and redisperse the fine particles to obtain a secondary dispersion (redispersion liquid). At the time of this redispersion, it is more preferable to carry out an alkali treatment with an aqueous medium. That is, in this step including the alkali treatment, the acid groups coexisting by treating the fine particles of the water-insoluble colorant aggregated with, for example, an acid in the step of obtaining the aggregate with an alkali and adsorbing the fine particles, for example. It is possible to neutralize the polymer compound having a function as a dispersant and effectively re-disperse the hardly soluble organic compound in the aqueous medium. In dispersion under an organic solvent, the dispersion step proceeds due to steric hindrance between the polymer compounds contained therein, so that alkali addition is not necessary and redispersion is performed as it is.

In the above preferred embodiment of the present invention, since desalting and solvent removal have already been performed in the aggregate formation step, it is possible to obtain a concentrated base of a fine particle dispersion of a sparingly soluble organic compound such as a pigment with few impurities. it can. When the aqueous medium is used, any alkali can be used as long as it serves as a neutralizing agent for the dispersant having an acidic hydrophilic portion and the solubility in water is enhanced. Here, “alkali” has the same meaning as the “base” described above. As alkali, specifically, hydroxide of alkali metal such as sodium hydroxide, lithium hydroxide, potassium hydroxide, ammonia, aminomethylpropanol, dimethylaminopropanol, dimethylethanolamine, diethyltriamine, monoethanolamine, Examples include various organic amines such as diethanolamine, triethanolamine, butyldiethanolamine, and morpholine, and the above phase transfer bases. More specifically, ammonium compounds represented by the general formula (I) or (II) can be mentioned, and choline hydroxide, tetramethylammonium hydroxide, tetraethylammonium hydroxide and the like are more preferable. Moreover, these 1 type (s) or 2 or more types can be used in combination.
The amount of alkali used is not particularly limited as long as the aggregated particles can be stably redispersed in an aqueous medium, but when used in applications such as printing ink and ink for inkjet printers, corrosion of various members. Therefore, the pH is preferably 6-12, more preferably 7-11.

  In the above step of redispersing the aggregated hardly soluble organic compound particles in an aqueous medium or an organic solvent, a stirring, mixing, and dispersing device can be used as necessary. In particular, when using a paste or slurry of a poorly soluble organic compound having a high water content, it is not necessary to add water. Furthermore, heating, cooling, distillation or the like can be performed for the purpose of increasing the efficiency of redispersion and for removing unnecessary water-soluble organic solvent or excess alkali.

  The recording liquid of the present invention can be prepared by using the above-described dispersion of the present invention and mixing, for example, predetermined components such as a polymer compound, a surfactant, and an aqueous solvent, and uniformly dissolving or dispersing them. The recording liquid of the present invention preferably contains 0.1 to 15% by mass of the hardly soluble organic compound. In addition, when the prepared ink contains an excessive amount of a polymer compound or additive, the ink composition can be re-prepared by removing them appropriately by a method such as centrifugation or dialysis. The recording liquid of the present invention may be used alone, but may be combined with another ink to form the ink set of the present invention.

  The recording liquid of the present invention can be used in various image forming methods and apparatuses such as various printing methods, ink jet methods, and electrophotographic methods, and can be drawn by an image forming method using this device. Moreover, a fine pattern can be formed by this ink jet method, or a drug can be administered.

  The recording liquid of the present invention is preferably an inkjet recording liquid, and an ink set using the same is preferable. The recording liquid or ink set of the present invention is preferably used as a printed matter in which an image is recorded by means for applying the recording liquid to the medium, and the means adjusts the application amount or concentration of the recording liquid. It is preferable that the printed matter has a density adjusted by the means. Further, the recording liquid or ink set is preferably used in an image forming method having a step of recording an image by applying the recording liquid to a medium. Furthermore, in this invention, it can be set as the image forming apparatus which has a means for recording an image by providing a recording liquid to a medium using the said recording liquid or ink set.

  The dispersion of the present invention having the above-described excellent characteristics has a high density that is comparable to the current offset printing or letterpress printing that expresses the color tone by area ratio (area gradation) when ink is used.・ High-definition image recording can be realized.

  In the hardly soluble organic compound dispersion of the present invention, the average particle size of the hardly soluble organic compound or water-insoluble colorant fine particles is 50 nm or less, preferably 5 to 50 nm, more preferably 10 to 45 nm. It is preferably 15 to 40 nm, particularly preferably. Thus, it is especially preferable from the viewpoint of coexistence of transparency of the dispersion, dispersion stability in the dispersion, and light resistance, by making the hardly soluble organic compound into nanometer-sized fine particles. If the average particle size is too small, it may be difficult to maintain a stable dispersion state in the dispersion for a long time, and good light resistance may not be obtained. On the other hand, if it is too large, the transparency of the dispersion may not be obtained. In the present invention, the particles of the hardly soluble organic compound may contain two or more kinds of pigments, or may be composed of only pigments or may contain compounds other than pigments. At this time, it is preferable that the solid solution of 2 or more types of pigment comprises the particle | grains. However, a portion having a crystal structure and a portion not having a crystal structure may be mixed in the particles. In addition, pigments and / or other compounds may form particles by adsorbing so that the core of the particles is coated with the dispersant (polymer compound, surfactant, etc.).

In the present invention, the dispersion is diluted with ion-exchanged water so that the average particle diameter of the dispersion by dynamic light scattering is 0.5% by mass, and then LB-500 (product of Horiba, Ltd.) Name) Value measured using a dynamic light scattering meter. At this time, the number average particle diameter Mn can be measured in addition to the volume average particle diameter Mv of each dispersion. Hereinafter, the average particle diameter measured by the dynamic light scattering measuring instrument is referred to as “dynamic light scattering average particle diameter”.
When measuring and evaluating the average particle diameter by observation with a transmission electron microscope (TEM) instead of the dynamic light scattering measurement, a dispersion diluted in Cu200 mesh with a carbon film attached is dropped and dried. From the image magnified 100,000 times with TEM (JEOL 1200EX (trade name)), the major axis of 300 independent particles that do not overlap is measured, and the average value is calculated as the average particle size.

  The dispersion of the present invention is a columnar particle having an aspect ratio of 3 or more and a major axis length of 50 nm to 300 nm, and a volume average particle diameter by dynamic light scattering measurement of a 0.5 mass% solution is 50 nm or less. Contains fine particles of poorly soluble organic compounds. The volume average particle diameter is as described above, and the aspect ratio is preferably 4 or more and 10 or less, and the major axis length is preferably 70 nm to 250 nm.

  The dispersion of the present invention preferably contains 80% by number, more than 90% by number, of columnar fine particles that satisfy the above average particle size and dimensional condition with respect to the total number of primary particles in the dispersion. More preferred. In the present invention, the total primary particles of the dispersion are evaluated by representatively 300 particles observed under the above TEM measurement conditions. That is, out of 300 total particles observed from the TEM image of the dispersion sample, the aspect ratio of 240 or more (80% by number or more) primary particles is 3 or more and the major axis length is 50 to 300 nm. A dispersion showing a dynamic light scattering result of a 0.5 mass% solution of 50 nm or less is preferred. The aspect ratio and the major axis length can be measured by a two-dimensional image of each particle being imaged. The major axis length is the length of the longest part (major axis) of the two-dimensional image of the particle. The aspect ratio is calculated as a ratio (major axis length / minor axis length) to a length (minor axis length, minor axis) in a direction orthogonal to the major axis length. Speaking of the needle-like or columnar fine particles as a right circular cylinder, the major axis length corresponds to the generatrix length, and the minor axis length corresponds to the diameter of a circle forming the upper base or the lower base.

The dispersion of the present invention contains fine columnar fine particles of nanometer size, has very high dispersion stability and storage stability, and can be stored for a long time while maintaining desired performance. It can be suitably used as a coloring material.
In addition, the dispersion of the present invention is preferably prepared as containing fine columnar particles having a uniform size. Using this unique particle property, for example, anisotropic orientation with respect to magnetic field or electric field application Therefore, it can be used as a material that meets the demand for producing a deflecting color filter. This deflection color filter can be made thinner by unifying the functions of the two-layer film structure consisting of a color filter and a deflection plate, which has been widely adopted in the conventional full-color liquid crystal display method, and has a low transmittance loss. As a technology for producing a small number of products, there are great expectations for their practical application.

The present invention will be described below in more detail based on examples, but the present invention is not limited to these examples. In the text, “parts” and “%” are based on mass unless otherwise specified.
(Example 1 and Comparative Example 1)
Example 1
C. I. Pigment Red 122 13.2 parts by mass, styrene / methacrylic acid copolymer (acid value 200 mg KOH / g, Mw = 18000) 6.6 parts by mass, dimethyl sulfoxide 160 parts by mass, tetramethylammonium hydroxide (Alfa Aesar 25) % Methanol solution) (logP: -4.586) [base for co-dissolution] 39 parts by mass were mixed, heated to 60 ° C., and stirred for 2 hours, whereby the pigment and styrene / methacrylic acid copolymer ( Dispersant A, acid value 200 mgKOH / g, Mw = 18000) were co-dissolved to obtain a deep blue-violet pigment solution.

  After ultrasonically treating this pigment solution, it is rapidly injected into 2000 parts by mass of ion-exchanged water (water temperature of 12 ° C. by an ice bath) stirred with a stirrer using a liquid feed pump at 100 ml / min. As a result, a reddish pigment dispersion (reprecipitation liquid) was obtained. The volume average particle size of the pigment dispersion obtained by the dynamic light scattering method is 35.4 nm (TEM average particle size: 28.3 nm), and the dispersion containing fine pigment fine particles is suppressed while suppressing the progress of the aggregation state. It was possible to get There was no change in the particle size after storage for 2 weeks, and no sediment was observed. Furthermore, this was a kinetically formed loose aggregation state, and could be refined to a volume average particle size of 31.2 nm with an ultrasonic homogenizer or with a time of one month.

  Next, this pigment dispersion was put into a 3 L flask, heated to a liquid temperature of 90 ° C., and stirred for 3 hours to form fine particles in a columnar shape. Next, after cooling to room temperature, 11 ml of hydrochloric acid was added dropwise to adjust the pH to about 3, and the pigment particles were aggregated from the pigment dispersion. Thereafter, 200 ml of ethyl acetate was further added and stirred for 2 hours, followed by filtration under reduced pressure using a membrane filter having an average pore size of 0.2 μm, washing with ion exchange water twice, and vacuum drying (45 ° C.) for one day. Then, a desalted and desolvated PR-122 (quinacridone organic pigment) / styrene / methacrylic acid copolymer aggregated powder was obtained.

  To 10 parts by weight of the obtained agglomerated powder, 100 parts by weight of acetone was added and stirred at room temperature for 1 hour. This was filtered under reduced pressure using a membrane filter having an average pore diameter of 0.2 μm, washed with acetone, and dried to obtain 8 parts by weight of an aggregated powder for redispersion.

  Next, 0.5 parts by mass of tetramethylammonium hydroxide (15% by mass aqueous solution) [redispersion base] is added to this powder part by mass, and ion-exchanged water [redispersion aqueous medium] so that the pigment content becomes 10%. After that, redispersion treatment by ultrasonic treatment was performed to obtain a pigment dispersion (redispersion). This pigment dispersion had a volume average particle diameter of 39.6 nm according to the dynamic light scattering method, and a high-concentration dispersion containing pigment fine particles having very high monodispersibility was obtained. There was no change in the particle size after storage for 2 weeks, and no sediment was observed. Moreover, the dispersion liquid was imaged with TEM (JEOL 1200EX (trade name)), and the TEM image of FIG. 1 was obtained. Thereafter, the aspect ratio and the major axis length were calculated for all the primary particles, and it was confirmed that the dispersion satisfies the specified conditions of the present invention.

(Comparative Example 1)
C. I. Pigment Red 122 13.2 parts by mass, styrene / methacrylic acid copolymer (acid value 200 mg KOH / g, Mw = 18000) 6.6 parts by mass, dimethyl sulfoxide 160 parts by mass, tetramethylammonium hydroxide (Alfa Aesar 25) % Methanol solution) [base for co-dissolution] 39 parts by mass, heated to 60 ° C., and stirred for 2 hours, whereby the pigment and the styrene / methacrylic acid copolymer (dispersant A, acid value 200 mgKOH / g, Mw = 18000) were co-dissolved to obtain a dark blue-violet pigment solution.

  After ultrasonically treating this pigment solution, it is rapidly injected into 2000 parts by mass of ion-exchanged water (water temperature of 12 ° C. by an ice bath) stirred with a stirrer using a liquid feed pump at 100 ml / min. As a result, a reddish pigment dispersion (reprecipitation liquid) was obtained. The volume average particle size of the pigment dispersion obtained by the dynamic light scattering method is 35.4 nm (TEM average particle size: 28.3 nm), and the dispersion containing fine pigment fine particles is suppressed while suppressing the progress of the aggregation state. It was possible to get There was no change in the particle size after storage for 2 weeks, and no sediment was observed. Furthermore, this was a kinetically formed loose aggregation state, and could be refined to a volume average particle size of 31.2 nm with an ultrasonic homogenizer or with a time of one month.

  Next, this pigment dispersion was put into a 3 L flask and stirred at room temperature (about 28 ° C.) for 3 hours without heating for columnar formation of fine particles. Thereafter, 11 ml of hydrochloric acid was added dropwise to adjust the pH to about 3, and the pigment particles were aggregated from the pigment dispersion. Thereafter, 200 ml of ethyl acetate was further added and stirred for 2 hours, followed by filtration under reduced pressure using a membrane filter having an average pore size of 0.2 μm, washing with ion exchange water twice, and vacuum drying (45 ° C.) for one day. Then, a desalted and desolvated PR-122 (quinacridone organic pigment) / styrene / methacrylic acid copolymer aggregated powder was obtained.

  To 10 parts by weight of the obtained agglomerated powder, 100 parts by weight of acetone was added and stirred at room temperature for 1 hour. This was filtered under reduced pressure using a membrane filter having an average pore diameter of 0.2 μm, washed with acetone, and dried to obtain 8 parts by weight of an aggregated powder for redispersion.

Next, 0.5 parts by mass of tetramethylammonium hydroxide (15% by mass aqueous solution) [redispersion base] is added to this powder part by mass, and ion-exchanged water [redispersion aqueous medium] so that the pigment content becomes 10%. After that, redispersion treatment by ultrasonic treatment was performed to obtain a pigment dispersion (redispersion). A high concentration dispersion having a volume average particle diameter of 41.6 nm by a dynamic light scattering method of this pigment dispersion was obtained. The dispersion liquid was imaged by TEM in the same manner as in Example 1 to obtain the TEM image shown in FIG.
This indicates that the crystal structure is not columnarized and does not grow, and the particle diameter increases due to dynamic light scattering after two weeks, and it is confirmed that the storage stability is not sufficient.

[Table 1]
--------------------------------------
Columnar heating Average particle diameter Columnar particle abundance Aspect ratio Long axis length Temperature (° C) (nm) (Number%) (nm)
--------------------------------------
Example 1 90 35.4 85% 8 150
Comparative Example 1 Room temperature 41.6 1% or less 1.1 20
--------------------------------------

Each word in the table has the following meaning.
Average particle size: Dynamic light scattering method measured using a LB-500 (trade name) dynamic light scattering meter manufactured by HORIBA, Ltd. after the dispersion was diluted with ion-exchanged water to 0.5% by mass. Volume average particle size (Mv)
-Columnar fine particle ratio: The ratio (number%) of those recognized as columnar fine particles out of 300 sample particles by TEM image analysis
-Aspect ratio: average value of 500 aspect ratios among 300 sample particles by TEM image analysis, which were recognized as columnar fine particles-long axis length: columnar among 300 sample particles by TEM image analysis The average value of the long axis length of 500 particles recognized as fine particles

(Example 2 and Comparative Example 2)
(Adjustment of ink composition)
Next, 50 parts by mass of the pigment dispersion (redispersion liquid) obtained in Example 1 and Comparative Example 1 was used, respectively, 7.5 parts by mass of diethylene glycol, 5 parts by mass of glycerin, 5 parts by mass of trimethylolpropane, acetylenol EH ( The product was mixed with 0.2 parts by mass (trade name, manufactured by Kawaken Fine Chemical Co., Ltd.) and 32.3 parts by mass of ion-exchanged water, and then subjected to ultrasonic treatment to obtain ink compositions.

[Evaluation of storage stability]
For the obtained ink composition, first, the dynamic light scattering average particle diameter (initial particle diameter) on the day of preparation was measured. Next, the ink composition was subjected to forced aging for one week under heating at 60 ° C., and then the average particle size (particle size after heating aging) by dynamic light scattering was measured again. The particle diameter variation rate at this time is shown in the table. If this particle diameter variation rate is low, it can be said that the ink composition has high storage stability. The average particle size was measured using a LB-500 (trade name) dynamic light scattering meter manufactured by Horiba, Ltd. after diluting the dispersion with ion-exchanged water so that the dispersion became 0.5% by mass. It is a volume average particle diameter (Mv) by a dynamic light scattering method.

[Table 2]
------------------------------------
Ink liquid / storage stability evaluation
Initial particle size Heated particle size Particle size variation rate (%)
------------------------------------
Example 2 39.7 nm 40.3 nm 1.5
Comparative Example 2 42.9 nm 58.9 nm 37.3
------------------------------------

As the results of Tables 1 and 2 show, the dispersion liquid of the comparative example was easy to agglomerate the pigment fine particles contained therein, and the storage stability was low. Thus, it can be seen that the dispersion of the comparative example cannot satisfy the practically required level when it is used as an ink.
In contrast, the dispersion of the present invention (Example) contains columnar fine particles having a predetermined aspect ratio and an average particle size of nanometer size, and contains fine pigment fine particles in both the redispersion liquid / ink liquid. In addition, it was found that the dispersion stability was high and the storage stability after ink formation was high, and it was found that there was a remarkable effect in suppressing secondary aggregation.

(Evaluation of ejection properties)
The prepared ink composition is packed in a cartridge of an ink jet printer (PX-G930 (trade name), manufactured by Epson Corporation), and is placed on an ink jet paper (photo paper <gloss> (trade name) manufactured by Epson Corporation). A solid image (reflection density is 1.0) was printed on the entire surface, the number of white streaks was measured, and the ejection property was evaluated according to the following criteria.

3: No white streak, which is an unprinted part, is generated on the entire printing surface. 2: Slight white streaking is observed, but is practically acceptable. 1: Many white streaks occur on the entire printing surface. Table 3 shows the evaluation results, which are unacceptable quality for practical use.

[Evaluation of transparency]
Each of the above ink compositions was coated on a polyethylene terephthalate (PET) sheet having a thickness of 60 μm with a bar coater and dried, and then the transparency was visually evaluated.
2: Good 1: Bad

[Table 3]
--------------------
Ink composition ^* Dischargeability Transparency --------------------
Example 2 3 2
Comparative Example 2 2 1
--------------------
* Indicated by the numbers of the examples and comparative examples in which the pigment dispersions used in the preparation of the ink composition were prepared.

  As can be seen from Table 3 above, it can be seen that the ink compositions prepared using the pigment dispersions of the examples are excellent in ejection properties. Further, a printed material using the ink composition of the present invention is excellent in transparency even at a high concentration, and is useful as an ink composition.

  From the above results, it can be seen that in the dispersion containing the columnar fine particles of the present invention, the fine pigment particles contained therein can be kept fine for a long period without excessive secondary aggregation. For this reason, it is possible to obtain an ink composition that has high ejection stability when converted into ink, high transparency even in a high concentration region, and high color reproducibility.

2 is a TEM image of the dispersion sample prepared in Example 1. FIG. 4 is a TEM image of the dispersion sample prepared in Example 2.

Claims (18)

  Particles of a hardly soluble organic compound having columnar particles having an aspect ratio of 3 or more and a major axis length of 50 nm to 300 nm and a volume average particle diameter of 50 nm or less by dynamic light scattering measurement of a 0.5 mass% liquid. A sparingly soluble organic compound dispersion characterized by containing.   The dispersion according to claim 1, wherein the hardly soluble organic compound is a water-insoluble colorant.   The dispersion according to claim 1 or 2, wherein the fine particles contained in the dispersion are a water-insoluble colorant dispersed by a coexisting polymer compound.   The dispersion medium according to any one of claims 1 to 3, wherein the dispersion medium of the dispersion is an aqueous medium.   The polymer compound is an acid group-containing polymer compound having at least one acid group selected from the group consisting of a carboxylic acid group, a sulfonic acid group, a phosphoric acid group, and a hydroxyl group. The dispersion according to 3 or 4.   6. The organic pigment selected from the group consisting of quinacridone organic pigments, diketopyrrolopyrrole organic pigments, and monoazo yellow organic pigments, according to any one of claims 1 to 5. The dispersion described.   The number of fine particles of the hardly soluble compound having the particle diameter, aspect ratio, and major axis length is 80% by number or more of all the primary fine particles of the hardly soluble organic compound in the dispersion. The dispersion according to item 1. (1) A step of co-dissolving a poorly soluble organic compound and a polymer compound in an organic solvent using an organic or inorganic base or an organic or inorganic acid. (2) The solution obtained in (1) is an aqueous medium. Step (3) to produce and disperse fine particles of a hardly soluble organic compound, and (3) the hardly soluble organic compound dispersion obtained in (2) is heated at a predetermined temperature to grow primary particles. At least 80% or more of all primary particles are columnar particles having an aspect ratio of 3 or more and a major axis length of 50 nm to 300 nm, and a volume average particle diameter by dynamic light scattering measurement of 0.5% by mass of liquid is 50 nm or less. Forming a dispersion which is
A method for producing an aqueous dispersion of a sparingly soluble organic compound, comprising:   The method for producing an aqueous dispersion according to claim 8, wherein the hardly soluble organic compound is a water-insoluble colorant. In the step (1) of co-dissolving the water-insoluble colorant and the polymer compound, the base to be used is represented by the following general formula (I) or (II): 10. The method for producing an aqueous dispersion according to item 9.
(Wherein R _{1 to} R ₅ are each independently an unsubstituted straight chain or branched alkyl having 1 to 3 carbon atoms, and n is an integer of 1 to 4).   The said hardly soluble organic compound is an organic pigment chosen from the group which consists of a quinacridone organic pigment, a diketopyrrolopyrrole organic pigment, and a monoazo yellow organic pigment, The any one of Claims 8-10 characterized by the above-mentioned. A method for producing an aqueous dispersion of a water-insoluble colorant.   The dispersion obtained by the manufacturing method of any one of Claims 8-11.   A recording liquid comprising 0.1 to 15% by mass of the hardly soluble organic compound fine particles in the dispersion according to any one of claims 1 to 7 and 12, based on the total mass of the recording liquid.   The recording liquid according to claim 13, wherein the recording liquid is an inkjet recording liquid.   An ink set using the inkjet recording liquid according to claim 13 or 14.   15. A printed matter in which an image is recorded by means for applying a recording liquid to a medium using the recording liquid according to claim 13 or 14, or the ink set according to claim 15, wherein the means applies the recording liquid. A print having a function of adjusting the amount or density, and the density of the print being adjusted by the means.   An image forming method comprising a step of recording an image by applying a recording liquid to a medium using the recording liquid according to claim 13 or 14 or the ink set according to claim 15.   An image forming apparatus comprising means for recording an image by applying the recording liquid to the medium using the recording liquid according to claim 13 or 14 or the ink set according to claim 15. .