JP2008239805A - Purification method of liquid composition, production method of liquid composition, ink composition, image formation method and image formation apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a production method of a liquid composition which contains nanometer-sized pigment particulates of highly uniform size and is suitable for inkjet ink. <P>SOLUTION: The production method is the one of the liquid composition comprising the pigment particulates and a polymer compound, wherein the pigment particulates exist in a dispersed state. The production method comprises (1) a step of preparing a first solvent and a second solvent, provided that either one contains the polymer compound, (2) a step of obtaining a solution wherein a pigment is dissolved in the first solvent, (3) a step of preparing a mixture by mixing the solution and the second solvent and separating the pigment particulates in a dispersed state, (4) a step of separating or precipitating the polymer compound by adjusting the pH of the mixture to a range within which the particulates stay in a dispersed state and the polymer compound is hardly dissolved and (5) a step of removing the deposit or the precipitate of the polymer compound from the mixture. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for purifying a liquid composition, a method for producing pigment particles useful as an inkjet ink, a liquid composition containing pigment particles in a dispersed state, an image forming method using the liquid composition, and image formation It relates to the device.

  In recent years, digital printing technology has made great progress. Typical examples of this digital printing technology are electrophotographic technology and inkjet technology, but in recent years, its presence as an image forming technology in offices, homes, and the like has been increasing.

  Among them, the ink jet technology has a great feature of compactness and low power consumption as a direct recording method. In addition, the image quality is rapidly increasing due to the miniaturization of nozzles. An example of the ink jet technology is a method in which ink supplied from an ink tank is heated by a heater in a nozzle to evaporate and foam, and the ink is ejected to form an image on a recording medium. Another example is a method of ejecting ink from a nozzle by vibrating a piezo element.

  In these methods, water-soluble dye inks have been applied so far, but have problems with respect to bleeding, feathering, weather resistance and the like. In recent years, the use of pigment inks has been studied for the purpose of improving these (see Patent Document 1), and ink jet inks containing a pigment dispersion in an ink composition have also started to spread.

  However, pigment inks are often inferior to dye inks in terms of long-term storage stability and ejection stability from an inkjet head. Further, since light scattering and light reflection occur due to pigment particles, generally, an image formed with pigment ink tends to have lower color developability than an image formed with dye ink.

  Attempts have been made to make the pigment particles fine as one of the methods for improving the color developability of the pigment ink. Pigments refined to 100 nanometers or less (hereinafter referred to as pigment fine particles) are expected to have dye-like color developability because they are less affected by light scattering and the specific surface area is increased.

  The pigment particles are generally refined mechanically using a disperser such as a sand mill, a roll mill, or a ball mill. In these methods, it is the limit to make the pigment finer to the vicinity of the primary particles (about 100 nanometers), and when further finer is required, it not only requires a lot of time and cost but also is uniform. It becomes difficult to stably supply quality products (see Patent Document 2).

  On the other hand, in Patent Document 3 and Patent Document 4, after the pigment is dissolved in a solvent, the pigment solution and the poor solvent of the pigment are mixed and dispersed again in the presence of a dispersant to reprecipitate the pigment fine particles. An adjustment method has been proposed (hereinafter referred to as a reprecipitation method). The reprecipitation method overcomes the drawbacks of mechanical miniaturization such as a sand mill, but has a problem that a large amount of dispersant is required to produce nanometer-sized pigment fine particles.

  When an excessive amount of dispersant is contained in the dispersion of pigment fine particles, problems such as an increase in the viscosity of the dispersion and a decrease in the sucking property of the printed matter occur. For this reason, in order to apply the pigment fine particles produced by the reprecipitation method and the dispersion thereof as pigment ink, it is necessary to remove the dispersant from the dispersion.

  When an excessive amount of dispersant is contained in the pigment fine particle dispersion, a centrifugal separation method is generally used as a method for removing the dispersant. However, it is difficult to apply the centrifugal separation method when the cohesiveness of the pigment fine particles is large or when the size and specific gravity are small. As other methods, there are a dialysis method using a semipermeable membrane and an ultrafiltration method using a hollow fiber filter, but it is extremely applicable when the dispersant is a polymer compound as in the present invention. Have difficulty.

In view of the above background, a method for selectively removing only a high molecular weight compound from a dispersion of pigment fine particles containing a polymer compound as a dispersant has been required.
US Pat. No. 5,085,698 JP-A-10-110111 Japanese Examined Patent Publication No. 6-96679 JP 2004-91560 A

  The problem to be solved by the present invention is to apply the pigment fine particles produced by the reprecipitation method as an ink-jet ink, and for that reason, excessive polymer that causes the discharge characteristics and the sucking property of the printed matter to deteriorate. A method for selectively removing a compound from a dispersion is provided.

  That is, the present invention provides a method for purifying and producing a liquid composition containing nanometer-order pigment fine particles with high size uniformity, which is suitable as an inkjet ink.

  The present invention also provides an ink composition containing the liquid composition, an image forming method and an image forming apparatus using the ink composition.

  As a result of intensive studies to solve the above problems, the present inventors have found that in a liquid composition containing dispersed pigment fine particles and a dissolved polymer compound, the dispersibility of the pigment fine particles and the polymer compound We focused on the factors affecting the solubility. And it discovered that a high molecular compound could be selectively removed from the dispersion liquid, without impairing the dispersibility of pigment fine particles, and resulted in this invention.

  A method for purifying a liquid composition that solves the above problem is a method for purifying a liquid composition that removes a polymer compound from a liquid composition containing dispersed fine particles and a polymer compound in a dissolved state, 1) a step of preparing the liquid composition in a pH range in which the fine particles maintain a dispersed state and the polymer compound is hardly soluble, and depositing or precipitating the polymer compound, (2) the polymer compound And a step of removing the precipitate or the precipitate from the liquid composition.

  A method for producing a liquid composition that solves the above-mentioned problem is a method for producing a liquid composition containing pigment fine particles and a polymer compound, wherein the pigment fine particles are present in a dispersed state, wherein (1) A step of preparing a first solvent and a second solvent containing a molecular compound, (2) a step of obtaining a solution in which a pigment is dissolved in the first solvent, (3) the solution and the second solvent (4) preparing the mixed liquid in a pH range in which the fine particles maintain the dispersed state and the polymer compound is hardly soluble. And a step of precipitating or precipitating the polymer compound, and (5) a step of removing the precipitate or precipitate of the polymer compound from the mixed solution.

An ink composition for ink jet recording that solves the above-described problems contains the liquid composition produced by the above method.
An image forming method that solves the above-described problems includes a step of recording an image by applying the ink composition for ink jet recording to a medium.

  An image forming apparatus that solves the above-described problems has means for recording an image by applying the ink composition for inkjet recording to a medium.

  ADVANTAGE OF THE INVENTION According to this invention, the refinement | purification method and manufacturing method of a liquid composition containing the pigment fine particle of nanometer order with a high size uniformity suitable as an inkjet ink can be provided.

  Further, the present invention can provide an ink composition containing the liquid composition, an image forming method and an image forming apparatus using the ink composition.

Hereinafter, the present invention will be described in detail.
The method for purifying a liquid composition of the present invention is a method for purifying a liquid composition that removes a polymer compound from a liquid composition containing dispersed fine particles and a polymer compound in a dissolved state. A step of preparing a liquid composition in a pH range in which the fine particles maintain a dispersed state and the polymer compound is hardly soluble, and depositing or precipitating the polymer compound; (2) a precipitate of the polymer compound or Removing the precipitate from the liquid composition.

The polymer compound in the present invention will be described.
The polymer compound in the present invention is a chargeable polymer compound that is charged positively or negatively or both in a certain pH range. Examples of polymer compounds charged by pH include compounds containing charged functional groups that change their degree of dissociation depending on pH typified by carboxyl groups and amino groups, and those functional groups in the main chain or side chain Polymers can be used. Since the dissociation of the carboxyl group is promoted at high pH, the polymer compound containing the carboxyl group is negatively charged. Conversely, dissociation of amino groups is promoted at low pH, so that the polymer compound containing amino groups is positively charged. In addition, a polymer compound containing both a carboxyl group and an amino group is negatively charged in a high pH region and positively charged in a low pH region with an isoelectric point determined by the content of each functional group as a boundary. However, the chargeable functional group contained in the chargeable polymer compound in the present invention is not limited to a carboxyl group or an amino group, and any chargeable functional group can be applied as long as the object of the present invention can be achieved. It is.

  Furthermore, the polymer compound of the present invention is a polymer compound whose solubility in water or an aqueous solution changes depending on pH from hardly soluble to soluble or from soluble to hardly soluble. Examples of this polymer compound include a compound containing a charged functional group that changes its degree of dissociation depending on pH, a polymer having such a main chain or side chain, and a compound having a hydrophobic structure, or Examples thereof include a copolymer with a polymer having such a main chain or side chain. Such a polymer compound is soluble in water or an aqueous solution in a pH range where the chargeable functional group is satisfactorily dissociated. Conversely, in a pH range where the dissociation degree of the charged functional group is low or does not dissociate, it becomes hardly soluble in water or an aqueous solution. However, the polymer compound in the present invention is not limited to the copolymer as described above, and the solubility in water or an aqueous solution changes from slightly soluble to soluble or from soluble to hardly soluble depending on pH. Any polymer compound can be applied.

The fine particles in the present invention will be described.
The dispersibility of the fine particles in the liquid composition is determined by the charge and potential on the surface of the fine particles (inkjet latest technology, p116, 2004, issued by Information Technology Co., Ltd.). This is explained by the DLVO theory, which is a theory that quantitatively discusses the stability of hydrophobic colloidal particles from the interaction between particles and the diffusion electric double layer. According to this theory, when two particles approach each other, the influence of attractive force based on van der Waals force increases as the distance between the particles decreases. However, when the fine particles are charged, the surroundings of the fine particles are covered with a cloud of counter ions (called a diffusion electric double layer). Force is generated. In other words, the dispersion stability of fine particles is determined by the balance between attractive force based on van der Waals force and electrical repulsive force. The larger the absolute value of the surface potential of fine particles (hereinafter referred to as zeta potential), the better the dispersion stability. . Conversely, when the absolute value of the zeta potential is small, the dispersion stability is poor, and when the absolute value of the zeta potential is 0 mV, it is extremely difficult to maintain the dispersion stability.

  The fine particles in the present invention are fine particles having a charged functional group on the surface. As the chargeable functional group, a carboxyl group or an amino group can be applied. Since these functional groups change the degree of dissociation depending on the pH, the fine particles having these functional groups on the surface change the zeta potential depending on the pH. For example, fine particles having a carboxyl group on the surface promote dissociation at high pH, and therefore have a large absolute value of zeta potential and exhibit good dispersion stability. On the other hand, at low pH, the dissociation of the carboxyl group is suppressed, the absolute value of the zeta potential becomes small, and the dispersed state cannot be maintained. In contrast, fine particles having amino groups on the surface promote dissociation at low pH, so that the absolute value of the zeta potential is large and shows good dispersion stability. On the other hand, dissociation of amino groups occurs at high pH. It is suppressed and the absolute value of the zeta potential becomes small, and the dispersed state cannot be maintained. However, the chargeable functional group on the surface of the fine particle in the present invention is not limited to a carboxyl group or an amino group, and any functional group that can provide charge to the fine particle and can achieve the object of the present invention can be applied. It is. Further, the functional group does not need to be one kind, and can be applied within a range in which the object of the present invention can be achieved even when plural kinds of functional groups exist on the surface of the fine particles.

  In the present invention, the dissociation degree of the chargeable functional group possessed by the fine particles and the dissociation degree of the chargeable functional groups possessed by the polymer compound are determined based on the dissociation degree in which the microparticles maintain a dispersed state and the polymer compound is hardly soluble. The pH of the liquid composition is adjusted so that This is characterized in that only the polymer compound is selectively aggregated and precipitated. That is, the combination of the fine particles and the polymer compound in the present invention is a combination in which the fine particles maintain a dispersed state in a certain pH region and the polymer compound exhibits physical properties that are hardly soluble.

  The pH at which the fine particles in the present invention maintain a dispersed state means a pH region in which the absolute value of the zeta potential of the fine particles is greater than 0 mV. More preferably, the absolute value of the zeta potential of the fine particles is 5 mV or more, more preferably the absolute value of the zeta potential is 20 mV or more. The zeta potential of the fine particles can be measured according to a known method. Examples of the measuring device include devices such as ZEECOM (Microtech Nichion), ELS-3000 (Otsuka Electronics), and ZetaPALS (Brookhaven).

  The pH at which the polymer compound in the present invention is hardly soluble is determined by the solubility test of the polymer compound described below. The polymer composition is mixed with the liquid composition adjusted to a predetermined pH so that its concentration is 3 wt%, shaken at a predetermined temperature for 24 hours, and then allowed to stand for 24 hours. A case where the mixed state exists as a uniform state is defined as soluble, and a case where the mixed state exists as an incomplete dissolution exhibiting a gel or granular appearance or clear turbidity is defined as hardly soluble. However, in the present invention, a so-called insoluble state in which no interaction is observed between the polymer compound and the liquid composition is included in the hardly soluble state. When it is difficult to judge solubility visually, it can also be used as a solubility index by measuring the transmittance of a liquid composition in which a polymer compound is dissolved or dispersed. In this case, in the present invention, the case where the transmittance is 99% or more is defined as soluble, and the case where the transmittance is less than 99% is defined as hardly soluble. The transmittance can be measured by a known method. In the present invention, the transmittance at 500 nm measured using a U-2001 type double beam spectrophotometer (Hitachi, Ltd.) is used as an evaluation standard.

  The present invention can be preferably used when the dispersed fine particles and the dissolved polymer compound contained in the liquid composition are charged with the same sign. On the other hand, when the dispersed fine particles are negatively charged and the dissolved high molecular compound is positively charged, it is possible to separate the fine particles and the high molecular compound by an alternative method such as electrophoresis. Alternatively, as in the flotation technique, a substance (such as foam or salt) that selectively collects and collects only the polymer compound can be added to the liquid composition to selectively remove the polymer compound. However, when the dispersed fine particles and the dissolved polymer compound are charged with the same sign, it is difficult to selectively separate only the fine particles or only the polymer compound by these alternative methods. Only applicable. However, the present invention is not limited to the case where the dispersed fine particles and the dissolved polymer compound contained in the liquid composition are charged with the same sign, and within the scope of achieving the object of the present invention. The present invention can also be applied to cases where charging is performed with different signs.

  As a method for adjusting the pH of the liquid composition, a desalting treatment such as dialysis or ultrafiltration is preferably used in addition to a treatment of adding a known pH adjusting agent such as acid or alkali, pH buffering agent or salt. be able to. In particular, desalting by dialysis, ultrafiltration, or the like is preferable because it can suppress a rapid change in pH and reduce the possibility of causing aggregation of fine particles due to a solvent shock or the like. However, the method for adjusting the pH of the liquid composition in the present invention is not limited to these methods, and any method can be applied as long as the object of the present invention can be achieved.

  In the present invention, in the purification method for selectively separating only the polymer compound from the dispersed fine particles and the dissolved polymer compound, it is possible to remove all or part of the polymer compound, and the purification thereof. The degree of can be appropriately determined according to the purpose.

  The present invention is used for the purpose of selectively removing a polymer compound from a liquid composition containing pigment fine particles having a pigment and a polymer compound as constituents in a dispersed state and containing the polymer compound in a dissolved state. be able to.

  That is, the present invention is a method for producing a liquid composition containing pigment fine particles and a polymer compound, wherein the pigment fine particles are present in a dispersed state. A step of preparing the solvent and the second solvent, (2) a step of obtaining a solution in which the pigment is dissolved in the first solvent, and (3) mixing the solution and the second solvent into a mixed solution, (4) precipitating the pigment fine particles in a dispersed state; and (4) precipitating or precipitating the polymer compound in a pH range where the fine particles maintain the dispersed state and the polymer compound is hardly soluble. And (5) a step of removing the precipitate or precipitate of the polymer compound from the mixed solution.

The polymer compound of the present invention is a polymer compound that can impart dispersion stability to pigment fine particles in water or an aqueous solution.
In the present invention, for the purpose of imparting dispersion stability to pigment fine particles in water or an aqueous solution, a polymer compound containing a repeating structure of a monomer unit having hydrophilicity (hereinafter referred to as a hydrophilic site) is provided. Use. Examples of the hydrophilic portion include a structure having a repeating unit structure such as a structure containing a large amount of carboxylic acid, carboxylate salt, or hydrophilic oxyethylene unit, and a structure having a hydroxyl group. Specific examples include acrylic acid and methacrylic acid, carboxylates such as inorganic salts and organic salts thereof, polyethylene glycol macromonomers, and hydrophilic monomers such as vinyl alcohol and 2-hydroxyethyl methacrylate. A structure having a repeating unit structure. However, the hydrophilic portion contained in the polymer compound of the present invention is not limited to these, and any substance can be used as long as the object of the present invention can be achieved. Further, in the present invention, a copolymer structure having a repeating structure composed of a plurality of hydrophilic monomers even if it is a repeating unit structure represented by one kind of hydrophilic monomer as the hydrophilic portion contained in the polymer compound Even so, it is applicable. Furthermore, the copolymer structure may be a random copolymer structure or a block copolymer structure, and can be suitably used as long as the object of the present invention can be achieved.

  In the present invention, for the purpose of imparting affinity to the pigment, a polymer compound containing a repeating structure of a monomer unit having hydrophobicity (hereinafter referred to as a hydrophobic site) is used as a dispersant. Specific examples of the hydrophobic site include a structure containing a repeating unit structure having a hydrophobic unit such as an isobutyl group, a t-butyl group, a phenyl group, a biphenyl group, and a naphthyl group. More specifically, the structure has a hydrophobic monomer such as styrene or t-butyl methacrylate as a repeating unit. However, the hydrophobic site contained in the polymer chain of the present invention is not limited to these, and any substance can be used as long as the object of the present invention can be achieved. Further, in the present invention, a copolymer structure having a repeating structure composed of a plurality of hydrophobic monomers, even if it is a repeating unit structure represented by one kind of hydrophobic monomer as a hydrophobic site contained in the polymer chain Even so, it is applicable. Further, the copolymer structure may be a random copolymer structure or a block copolymer structure, and can be suitably used as long as the object of the present invention can be achieved.

  As described above, it is an essential requirement that the polymer compound of the present invention is a polymer compound containing the hydrophilic part and the hydrophobic part as described above. The hydrophilic part and the hydrophobic part can be applied within the range in which the object of the present invention can be achieved regardless of whether they are contained in a random copolymer structure or a block copolymer structure in a polymer compound. is there.

  The weight average molecular weight of the polymer compound in the present invention is 500 or more and 1000000 or less, and the range preferably used is 1000 or more and 1000000 or less. If the molecular weight exceeds 1,000,000, the entanglement between the polymer compounds becomes too large. On the other hand, when the molecular weight is less than 500, the molecular weight is small and the polymer compound does not easily function as a dispersant. Cannot provide good dispersion stability. The weight average molecular weight can be measured by a light scattering method, an X-ray micronucleus scattering method, a sedimentation equilibrium method, a diffusion method, an ultracentrifugation method, or various chromatographies. It is a weight average molecular weight in terms of polystyrene measured by a gel permeation chromatography) method.

  The high molecular compound in this invention can be used individually by 1 type or in combination of 2 or more types. The proportion of the polymer compound used is not particularly limited, but it is used in the range of 0.05 parts by mass or more with respect to 1 part by mass of the pigment and 50 parts by mass or less with respect to 100 parts by mass of the aprotic solvent. Is preferred. When the polymer compound is more than 50 parts by mass with respect to 100 parts by mass of the aprotic solvent, it may be difficult to completely dissolve the polymer compound, and 0.05 part by mass with respect to 1 part by mass of the organic pigment If it is less, a sufficient dispersion effect may not be obtained.

  The polymer compound in the present invention needs to be soluble in at least one of the first solvent and the second solvent. If the dispersant is insoluble in either the first solvent or the second solvent, the polymer compound cannot efficiently diffuse and adsorb on the pigment particles, and only the coarse pigment particles can be absorbed. Can't get. More specifically, when the polymer compound is contained in the first solvent, the polymer compound needs to be soluble in at least the first solvent. In this case, the polymer compound may be soluble or insoluble in the second solvent, but in the case of being insoluble, the pigment formed by mixing the first solvent and the second solvent. Since the deposition rate of the polymer compound on the particles increases, it is advantageous for the formation of nanometer-order pigment fine particles with high size uniformity. Next, when a high molecular compound is contained in the second solvent, the high molecular compound must be soluble in at least the second solvent. In this case, any compound can be used as long as the object of the present invention can be achieved, regardless of whether the polymer compound is soluble or unnecessary in the first solvent.

  The pigment used in the present invention is soluble in the first solvent, and any pigment that can achieve the object of the present invention can be used. More preferably, a stable organic pigment that does not exhibit reactivity under dissolution conditions is preferable. Specifically, organic pigments used in printing inks and paints can be used. For example, azo, disazo, condensed azo, anthraquinone, dianslaquinonyl, anthrapyridine, ansan Throne, thioindigo, naphthol, benzimidazolone, pyranthrone, phthalocyanine, flavanthrone, quinacridone, dioxazine, diketopyrrolopyrrole, indanthrone, isoindolinone, isoindoline, There are quinophthalone, perinone and perylene pigments, vat dye pigments, metal complex pigments, basic dye pigments, fluorescent pigments and daylight fluorescent pigments. Examples include C.I. I. Pigment Yellow 1, 3, 12, 13, 13, 17, 42, 55, 62, 73, 74, 81, 83, 93, 95, 97, 108, 109, 110, 128, 130, 151, 155, 158, 139, 147, 154, 168, 173, 180, 184, 191, 199, C. I. Pigment Red 2, 4, 5, 22, 23, 31, 48, 53, 57, 88, 112, 122, 144, 146, 150, 166, 171, 175, 176, 177, 181, 183, 183, 184, 185, 202, 206, 207, 208, 209, 213, 214, 220, 254, 255, 264, 272, C.I. I. Pigment Blue 16, 25, 26, 56, 57, 60, 61, 66, C.I. I. Pigment Violet 19, 23, 29, 37, 38, 42, 43, 44, C.I. I. Pigment Orange 16, 34, 35, 36, 61, 64, 66, 71, 73, C.I. I. Pigment Brown 23 and 38. These organic pigments can be used alone or in combination of two or more. In addition, organic pigment derivatives in which a substituent is introduced into the basic skeleton of the organic pigment can also be used as long as the object of the present invention can be achieved.

  An aprotic solvent is preferable as the first solvent used in the present invention. Among these, those having a solubility in the second solvent of 5% or more are preferably used, and those that are freely mixed with the second solvent are preferred. When the pigment is solubilized using a solvent having a solubility in the second solvent of less than 5%, it is disadvantageous in that the pigment-containing particles are difficult to precipitate when mixed with water and are likely to become coarse particles. It is also disadvantageous in that it tends to adversely affect the dispersion stability of the resulting pigment fine particles. Specifically, the first solvent is dimethyl sulfoxide, dimethylimidazolidinone, sulfolane, N-methylpyrrolidone, dimethylformamide, acetonitrile, acetone, dioxane, tetramethylurea, hexamethylphosphoramide, hexamethylphosphorotriamide, Pyridine, propionitrile, butanone, cyclohexanone, tetrahydrofuran, tetrahydropyran, ethylene glycol diacetate, γ-butyrolactone and the like are mentioned as preferred solvents, among which dimethyl sulfoxide, N-methylpyrrolidone, dimethylformamide, dimethylimidazolidinone, sulfolane, Acetone, acetonitrile or tetrahydrofuran is preferred. Moreover, these can be used individually by 1 type or in combination of 2 or more types. The proportion of the aprotic solvent used is not particularly limited, but it is possible to further improve the dissolved state of the organic pigment, the ease of forming the desired fine particle diameter, and the color density of the aqueous dispersion. From the viewpoint of making it favorable, it is preferably used in the range of 2 to 500 parts by mass, more preferably 5 to 100 parts by mass with respect to 1 part by mass of the organic pigment. When it is difficult to dissolve the organic pigment only with the aprotic solvent, the solubility of the organic pigment can be enhanced by adding an alkali described below. The first solvent is preferably a mixed solvent of an aprotic solvent and an alkali.

  As the alkali used in the present invention, an organic pigment can be dissolved in an aprotic solvent, and any substance that can achieve the object of the present invention can be used. Alkali metal alkoxides, alkaline earth metal hydroxides, alkaline earth metal alkoxides and strong organic bases are preferred because of their high solubilizing ability of organic pigments. Specifically, lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, potassium tert-butoxide, potassium methoxide, potassium ethoxide, sodium methoxide, sodium ethoxide, tetramethylammonium hydroxide, tetra Use quaternary ammonium compounds such as butylammonium hydroxide, 1,8-diazabicyclo [5,4,0] -7-undecene, 1,8-diazabicyclo [4,3,0] -7-nonene, guanidine, etc. I can do it. Moreover, these alkalis can be used individually by 1 type or in combination of 2 or more types. Although the usage-amount of the said alkali is not specifically limited, It is preferable to use in 0.01 to 1000 mass parts with respect to 1 mass part of organic pigments. If the alkali is less than 0.01 parts by weight with respect to 1 part by weight of the organic pigment, it may be disadvantageous in that it tends to be difficult to completely dissolve the organic pigment together with the polymer compound in the aprotic solvent. is there. If the amount is more than 1000 parts by mass, it may be disadvantageous in that the alkali becomes difficult to dissolve in the aprotic solvent and the increase in solubility of the organic pigment cannot be expected.

  In order to completely dissolve the alkali in the aprotic solvent, a solvent having high solubility with respect to the alkali, such as some water and lower alcohol, can be added to the aprotic solvent. These act as an alkali-soluble auxiliary agent, increase the solubility of the alkali in the aprotic solvent, and facilitate the dissolution of the organic pigment. However, when the addition rate is 50% by mass or more based on the total amount of the solvent, it is disadvantageous in that the solubility of the organic pigment is lowered. Therefore, the addition rate of about 0.5 to 30% by mass is usually most effective. This is because only an aprotic solvent has a relatively low alkali solubility. Specifically, water, methanol, ethanol, n-propanol, isopropanol, butyl alcohol, or the like can be used. When dissolving the organic pigment, the alkali is used as a solution such as water or lower alcohol in order to minimize the amount of alkali used and quickly dissolve the organic pigment. It is better to add until the pigment is dissolved in the solvent. At this time, since the pigment is in the form of a solution, it is possible to easily remove foreign substances. In selecting these alkali-soluble auxiliary agents, it is important to ensure compatibility with the polymer compound.

  When dissolving an organic pigment in an aprotic solvent, in addition to the organic pigment and the polymer compound, the aprotic solvent contains at least one kind of crystal growth inhibitor, ultraviolet absorber, antioxidant, resin additive, and the like. Can be added as needed.

  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.

  As the second solvent used in the present invention, any solvent can be used as long as it is compatible with the first solvent to be used and can achieve the object of the present invention. It is preferable that

  The water or aqueous solution to be used can contain additives. Any additive can be used as long as it is compatible with water or an aqueous solution and can achieve the object of the present invention. For example, there are known pH adjusting agents and salts including the alkalis and pH buffering agents described above. Further, for the purpose of enhancing the compatibility between the first solvent and water or an aqueous solution, it is possible to contain an organic solvent such as alcohol. In this case, the organic solvent to be contained is not limited to alcohol, and any organic solvent can be used as long as the object of the present invention can be achieved.

  In order to obtain pigment fine particles of nanometer order with high size uniformity, it is preferable to mix the first solvent and the second solvent as quickly as possible, such as an ultrasonic vibrator, a full zone stirring blade, an internal circulation Any conventionally known apparatus such as a mixing stirrer, an external circulation stirrer, a flow rate and an ion concentration controller, and the like used for stirring, mixing, dispersion, and stagnation can be applied as the mixing mode. Moreover, you may mix in the water which flows continuously. As a method for charging the pigment solution into water, any of the conventionally known liquid injection methods can be used, but it is preferable that the pigment solution is injected from water or water as a jet flow from a nozzle such as a syringe, needle, or tube. In addition, in order to throw in in a short time, it can also throw in from several nozzles. In order to increase the mixing efficiency of the first solvent and the second solvent, the shape and size of the mixing container can be devised. For example, it is preferable to mix the first solvent and the second solvent in a microspace such as a microreactor because the mixing efficiency of the two liquids is large and microparticles are easily formed.

  Further, these temperatures are not particularly specified when the first solvent and the second solvent are mixed, but the temperature of the solution at the time of mixing greatly affects the size of the organic pigment to be deposited. In order to obtain pigment fine particles, the temperature of the solution should be adjusted in the range of -50 ° C to 500 ° C, more preferably in the range of -30 ° C to 100 ° C, more preferably in the range of -20 ° C to 50 ° C. 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 solution.

  The liquid composition containing the pigment fine particles obtained in the present invention can be used as it is, but it can be used for various applications by concentrating and purifying as necessary. As a concentration / purification method, any conventionally known apparatus used for concentration / purification, such as a centrifugal separator, an evaporator, or an ultrafiltration apparatus, can be used.

  In the present invention, the charged functional group derived from the polymer compound possessed by the pigment fine particles and the charged functional group possessed by the dissolved polymer compound maintain the dispersed state of the pigment fine particles, and the polymer compound is hardly soluble. The dissolved polymer compound can be removed from the liquid composition by selectively aggregating and precipitating the dissolved polymer compound by adjusting the pH of the liquid composition so as to achieve a dissociation degree of it can.

  In the present invention, the pH at which the pigment fine particles maintain a dispersed state means a pH region in which the absolute value of the zeta potential of the pigment fine particles is greater than 0 mV. More preferably, the absolute value of the zeta potential of the pigment fine particles is 5 mV or more, more preferably 20 mV or more. The zeta potential of the pigment fine particles can be measured according to a known method. Examples of the measuring device include devices such as ZEECOM (Microtech Nichion), ELS-3000 (Otsuka Electronics), and ZetaPALS (Brookhaven).

  The pH at which the polymer compound in the present invention is hardly soluble is determined by the solubility test of the polymer compound described below. The polymer composition is mixed with the liquid composition adjusted to a predetermined pH so that its concentration is 3 wt%, shaken at a predetermined temperature for 24 hours, and then allowed to stand for 24 hours. A case where the mixed state exists as a uniform state is defined as soluble, and a case where the mixed state exists as an incomplete dissolution exhibiting a gel or granular appearance or clear turbidity is defined as hardly soluble. However, in the present invention, a so-called insoluble state in which no interaction is observed between the polymer compound and the liquid composition is included in the hardly soluble state. When it is difficult to judge solubility visually, it can also be used as a solubility index by measuring the transmittance of a liquid composition in which a polymer compound is dissolved or dispersed. In this case, in the present invention, the case where the transmittance is 99% or more is defined as soluble, and the case where the transmittance is less than 99% is defined as hardly soluble. The transmittance can be measured by a known method. In the present invention, the transmittance at 500 nm measured using a U-2001 type double beam spectrophotometer (Hitachi, Ltd.) is used as an evaluation standard.

  As a method for adjusting the pH of the liquid composition, a desalting treatment such as dialysis or ultrafiltration is preferably used in addition to a treatment of adding a known pH adjusting agent such as acid or alkali, pH buffering agent or salt. be able to. In particular, desalting treatment such as dialysis or ultrafiltration is preferable because it can suppress a rapid change in pH and reduce the possibility of causing aggregation of pigment fine particles due to solvent shock or the like. However, the method for adjusting the pH of the liquid composition in the present invention is not limited to these methods, and any method can be applied as long as the object of the present invention can be achieved.

  When the liquid composition of the present invention is used as an ink composition for inkjet recording, various additives, auxiliaries and the like can be added as necessary. One additive is a dispersion stabilizer that stably disperses a pigment in a solvent. The pigment fine particles contained in the liquid composition of the present invention are dispersed and stabilized by the polymer compound constituting the pigment fine particles. However, when the dispersion is insufficient, other dispersion stabilizers are added. May be.

  As another dispersion stabilizer, it is possible to use a resin or a surfactant having both hydrophilic and hydrophobic portions. Examples of the resin having both hydrophilic and hydrophobic parts include a copolymer of a hydrophilic monomer and a hydrophobic monomer.

  Hydrophilic monomers include acrylic acid, methacrylic acid, maleic acid, fumaric acid, or the above carboxylic acid monoesters, vinyl sulfonic acid, styrene sulfonic acid, vinyl alcohol, acrylamide, methacryloxyethyl phosphate, etc. Styrene derivatives such as styrene and α-methylstyrene, vinylcyclohexane, vinylnaphthalene derivatives, acrylic acid esters, and methacrylic acid esters. Copolymers having various configurations such as random, block, and graft copolymers can be used. Of course, both hydrophilic and hydrophobic monomers are not limited to those shown above.

  As the surfactant, an anionic, nonionic, cationic or amphoteric surfactant can be used. Anionic activators include fatty acid salts, alkyl sulfate esters, alkylaryl sulfonates, alkyl diaryl ether disulfonates, dialkyl sulfosuccinates, alkyl phosphates, naphthalene sulfonic acid formalin condensates, polyoxyethylene alkyls. Examples thereof include phosphate ester salts and glycerol borate fatty acid esters. Nonionic activators include polyoxyethylene alkyl ethers, polyoxyethyleneoxypropylene block copolymers, sorbitan fatty acid esters, glycerin fatty acid esters, polyoxyethylene fatty acid esters, polyoxyethylene alkylamines, fluorine-based, silicon-based and the like. It is done. Examples of the cationic activator include alkylamine salts, quaternary ammonium salts, alkylpyridinium salts, alkylimidazolium salts and the like. Examples of amphoteric activators include alkylbetaines, alkylamine oxides, phosphadylcholines, and the like. Similarly, the surfactant is not limited to the above.

  Furthermore, an aqueous solvent can be added to the ink composition for inkjet recording of the present invention, if necessary. In particular, when used in an inkjet ink, the aqueous solvent is used to prevent drying at the nozzle portion of the ink and solidification of the ink, and can be used alone or in combination. As the aqueous solvent, those described above are applied as they are. In the case of ink, the content is 0.1 mass% or more and 60 mass% or less, preferably 1 mass% or more and 40 mass% or less of the total weight of the ink.

  As other additives, for example, in the case of use as an ink, a pH adjuster for obtaining stability of the ink and stability of the ink pipe in the recording apparatus, the penetration of the ink into the recording medium, and the appearance Penetrating agent that accelerates drying of the ink, antifungal agent that prevents the occurrence of wrinkles in the ink, sequestering metal ions in the ink, precipitating metal at the nozzle and insoluble matter in the ink, etc. Add chelating agents to prevent, anti-foaming agents, antioxidants, anti-fungal agents, viscosity modifiers, conductive agents, UV absorbers, etc. to prevent the generation and generation of bubbles during recording liquid circulation and movement can do.

  The ink composition of the present invention can be prepared by mixing the liquid composition of the present invention and the above-described components and uniformly dissolving or dispersing them. Further, when an excessive amount of a polymer compound or additive is contained in the adjusted ink composition, the ink composition can be readjusted by a known method such as centrifugation or dialysis, and the ink composition can be readjusted. it can.

  The composition 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, when using a liquid composition, it can be used for the liquid provision method for forming a fine pattern in the inkjet method etc. or administering a medicine.

  The image forming method of the present invention is a method for forming an excellent image with the composition of the present invention. The image forming method of the present invention is preferably an image forming method in which recording is performed by ejecting the ink composition of the present invention from an ink ejecting portion and applying it onto a recording medium. For image formation, a method using an ink jet method in which thermal energy is applied to the ink to discharge the ink is preferably used.

  Furthermore, according to the present invention, bleeding and feathering on a recording medium can be suppressed by using together with stimulation by a polyvalent cation. The block polymer compound of the present invention is characterized by containing a repeating unit having an organic acid composed of a polycyclic aromatic group as described above. An organic acid composed of polycyclic aromatics easily interacts with a polyvalent cation due to its strong hydrophobicity, and easily causes aggregation through the polyvalent cation. For this reason, when polyvalent cations are present on the recording medium, the ink composition quickly causes aggregation, and the ink composition with improved bleeding and feathering on the recording medium, and the liquid application method, liquid It is also possible to provide an application device. As the polyvalent cation, preferably, the metal cation includes a divalent cation such as Ca, Cu, Mg, Ni, Zn, Fe, Co, and a trivalent cation such as Al, Nd, Y, Fe, La, and the like. Non-metal cations include, but are not limited to, diammonium cations and triammonium cations. In addition, as a method for applying the polyvalent cation to the recording medium, a recording medium on which the polyvalent cation has been applied in advance may be used, or the polyvalent cation may be applied over the entire region where an image is formed by an inkjet head. A driving method may be used.

  Various methods can be applied to the method of applying the stimulus. As a preferred embodiment, a method for applying a stimulus when the stimulus is a polyvalent cation will be described. For example, as described in JP-A-64-63185, a polyvalent cation can be implanted over the entire area where an image is formed by an inkjet head. It is also preferable to apply a polyvalent cation to the recording medium in advance.

  As an inkjet printer using the inkjet ink composition of the present invention, various inkjet recording apparatuses such as a piezo inkjet system using a piezoelectric element and a bubble jet (registered trademark) system that records by foaming by applying thermal energy are used. Applicable to.

The outline of the ink jet recording apparatus will be described below with reference to FIG. However, FIG. 1 is merely an example of the configuration and does not limit the present invention.
FIG. 1 is a block diagram showing the configuration of the ink jet recording apparatus.

  FIG. 1 shows a case where recording is performed on a recording medium by moving the head. In FIG. 1, an X direction drive motor 56 and a Y direction drive motor 58 for driving the head 70 in the XY directions include an X motor drive circuit 52 and a Y motor drive circuit 54 for the CPU 50 that controls the overall operation of the manufacturing apparatus. Connected through. In accordance with an instruction from the CPU, the X direction drive motor 56 and the Y direction drive motor 58 are driven through the X motor drive circuit 52 and the Y motor drive circuit 54, and the position of the head 70 with respect to the recording medium is determined.

  As shown in FIG. 1, a head driving circuit 60 is connected to the head 70 in addition to the X direction driving motor 56 and the Y direction driving motor 58, and the CPU 50 controls the head driving circuit 60. Drive, that is, discharge ink jet ink or the like. Further, an X encoder 62 and a Y encoder 64 for detecting the head position are connected to the CPU 50, and position information of the head 70 is input. A control program is also input into the program memory 66. The CPU 50 moves the head 70 based on this control program and the positional information of the X encoder 62 and the Y encoder 64, disposes the head at a desired position on the recording medium, and ejects ink for inkjet. In this way, desired drawing can be performed on the recording medium. Further, in the case of an image recording apparatus capable of loading a plurality of ink jet inks, desired drawing can be performed on a recording medium by performing the above-described operation for each ink jet ink a predetermined number of times.

  In addition, after ejecting the ink jet ink, the head 70 is moved to a position where removing means (not shown) for removing excess ink adhering to the head is arranged, if necessary. It can also be cleaned by wiping or the like. As a specific method of cleaning, a conventional method can be used as it is.

When drawing is completed, the drawn recording medium is replaced with a new recording medium by a recording medium conveyance mechanism (not shown).
It should be noted that the present invention can be modified or modified without departing from the spirit of the present invention. For example, in the above description, the example in which the head 70 is moved in the XY axis direction is shown. However, the head 70 is moved only in the X axis direction (or Y axis direction), and the recording medium is moved in the Y axis direction (or X axis). The drawing may be performed while moving in the axial direction) and interlocking these.

  The present invention includes a head (for example, an electrothermal converter or a laser beam) that generates thermal energy as energy used for ejecting ink jet ink, and ejects ink jet ink by the heat energy. Has an excellent effect. According to this method, high definition of drawing can be achieved. By using the ink-jet ink composition of the present invention, further excellent drawing can be performed.

  As for the typical configuration and principle of the apparatus provided with the means for generating the heat energy, for example, the basic principle disclosed in US Pat. Nos. 4,723,129 and 4,740,796 is used. What to do is preferred. This method can be applied to both the so-called on-demand type and the continuous type. In particular, in the case of the on-demand type, the liquid is retained and electrothermal conversion is arranged corresponding to the flow path. At least one drive signal is applied to the body that corresponds to the ejection information and provides a rapid temperature rise above nucleate boiling. As a result, heat energy is generated in the electrothermal transducer, and film boiling occurs on the heat acting surface of the head. As a result, bubbles in the liquid corresponding one-to-one with this drive signal can be formed, which is effective. is there. By the growth and contraction of the bubbles, the liquid is discharged through the discharge opening to form at least one droplet. It is more preferable that the drive signal has a pulse shape, because the bubble growth and contraction is performed immediately and appropriately, and thus it is possible to achieve liquid discharge particularly excellent in responsiveness. As this pulse-shaped drive signal, those described in US Pat. Nos. 4,463,359 and 4,345,262 are suitable. In addition, when the conditions described in US Pat. No. 4,313,124 of the invention relating to the temperature increase rate of the heat acting surface are adopted, further excellent discharge can be performed.

  As the configuration of the head, in addition to the combination configuration (straight liquid channel or right-angle liquid channel) of the discharge port, the liquid channel, and the electrothermal transducer as disclosed in each of the above-mentioned specifications, The configuration arranged in the bent region is also included in the present invention. For example, configurations using US Pat. No. 4,558,333 and US Pat. No. 4,459,600 are also included in the present invention. In addition, the effect of the present invention is effective even in a configuration based on Japanese Patent Laid-Open No. 59-123670 that discloses a configuration in which a common slit is used as a discharge portion of the electrothermal transducer for a plurality of electrothermal transducers It is. The effect of the present invention is also effective as a configuration based on Japanese Patent Laid-Open No. 59-138461 which discloses a configuration in which an opening that absorbs a pressure wave of thermal energy is made to correspond to a discharge portion. In other words, regardless of the form of the head, according to the present invention, it is possible to reliably and efficiently discharge ink jet ink.

  Further, the present invention can be effectively applied to a full-line type head having a length corresponding to the maximum width of a recording medium in the image forming apparatus of the present invention. As such a head, either a configuration satisfying the length by a combination of a plurality of heads or a configuration as a single integrally formed head may be used.

  In addition, a serial type head that is fixed to the main body of the apparatus or mounted on the main body of the apparatus can be electrically connected to the main body of the apparatus and ink can be supplied from the main body. The present invention is also effective when a chip-type head is used.

Furthermore, the apparatus of the present invention may further include a droplet removing unit. When such means is provided, a further excellent discharge effect can be realized.
In addition, it is preferable to add preliminary auxiliary means or the like as the configuration of the apparatus of the present invention because the effects of the present invention can be further stabilized. Specific examples thereof include a capping unit for the head, a pressurizing or suction unit, an electrothermal converter, or a heating element different from this. Alternatively, a preliminary heating unit that performs heating using a combination of these, a preliminary ejection unit that performs ejection other than the ejection of ink, and the like can be given.

The most effective for the present invention is to execute the above-described film boiling method.
In the apparatus of the present invention, the amount of ink ejected from each ejection port of the ejection head for inkjet ink is preferably in the range of 0.1 picoliter to 100 picoliter.

  The ink composition of the present invention can also be used in an indirect recording apparatus using a recording method in which ink is printed on an intermediate transfer member and then transferred to a recording medium such as paper. Also, the present invention can be applied to an apparatus using an intermediate transfer member by a direct recording method.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these Examples.
<Example 1>
Styrene and methacrylic acid were weighed into a four-necked flask, and toluene was added to dissolve. A stirring seal, a stirring rod, a cooling tube, and a nitrogen introduction tube were set, and nitrogen substitution was performed for 1 hour while stirring at 200 rpm in a thermostatic bath at 60 ° C. Thereafter, a toluene solution of AIBN was prepared in a separate container and injected into a four-necked flask using a syringe to initiate polymerization. One hour after the start of the polymerization, oxygen was introduced into the four-necked flask to stop the polymerization reaction, and the reaction solution was poured into a large amount of methanol to purify the product. When evaluated by gel permeation chromatography (GPC), it was confirmed that a styrene / methacrylic acid copolymer (polySt-r-MAc) having a weight average molecular weight of 11700 and a molecular weight distribution of 2.79 was obtained. As a result of observing the solubility of the synthesized poly (St-r-MAc) in water, it was hardly soluble in water or an aqueous solution (a mixture of water and pH-adjusting KOH or HCl) in a pH range lower than pH 9.

  20 parts by mass of the synthesized poly (St-r-MAc) was dissolved in 100 parts by mass of tetrahydrofuran, and C.I. I. 5 parts by mass of Pigment Red 122 magenta pigment was suspended in a container for 2 hours. Next, a potassium hydroxide aqueous solution was dropped little by little to dissolve the magenta pigment. This pigment solution is quickly put into distilled water stirred with a stirrer while being ultrasonically treated using a syringe to precipitate magenta pigment, dispersed pigment fine particles and dissolved polySt-r-MAc. A liquid composition containing When the average particle diameter of the pigment fine particles was measured in distilled water at 25 ° C. using DLS-7000 (manufactured by Otsuka Electronics Co., Ltd.), it was confirmed to be 32.2 nm. The zeta potential of the pigment fine particles was measured and found to be 0 mV at pH 2 (salt concentration of 0.01 N), 3 mV at pH 3, 18 mV at pH 4, and 22 mV at pH 8.

  The liquid composition produced as described above is a dispersion having a pH of 11.5, and contains pigment fine particles and dissolved polySt-r-MAc. This liquid composition was desalted using an ultrafiltration system (Microza R-UF pencil type module, manufactured by Asahi Kasei) to adjust the pH to 8. It was observed that the pH 8 liquid composition was allowed to stand for a predetermined time to produce a precipitate. When the precipitate was removed from the liquid composition by decantation and the removed precipitate was evaluated by IR and GPC, it was confirmed to be polySt-r-MAc. From the results as described above, it is confirmed that, in a liquid composition containing pigment fine particles and a dissolved polymer compound, the dissolved polymer compound can be selectively removed from the liquid composition by adjusting its pH. It was done.

  As a comparative experiment, when the liquid composition was adjusted to pH 2, both pigment fine particles and polySt-r-MAc were precipitated, and only polySt-r-MAc could not be removed from the liquid composition.

As a comparative experiment, when the liquid composition was adjusted to pH 3, it was observed that only polySt-r-MAc was precipitated / precipitated, but the pigment fine particles were also slightly aggregated.
As a comparative experiment, when the liquid composition was adjusted to pH 4, it was observed that only polySt-r-MAc was precipitated / precipitated, and the dispersion stability of the pigment fine particles was maintained well.

<Example 2>
Styrene and p-nitrophenyl acrylate were weighed into a four-necked flask and dissolved by adding toluene. A stirring seal, a stirring rod, a cooling tube, and a nitrogen introduction tube were set, and nitrogen substitution was performed for one hour while stirring at 200 rpm in a thermostatic bath at 60 ° C. Thereafter, a toluene solution of AIBN was prepared in a separate container and injected into a four-necked flask using a syringe to initiate polymerization. Three hours after the start of the polymerization, oxygen was introduced into the four-necked flask to stop the polymerization reaction, and the reaction solution was poured into a large amount of methanol to purify the product. Next, the product and hexamethylenediamine were dissolved in toluene, the active ester group derived from p-nitrophenyl acrylate and hexamethylenediamine were reacted for a predetermined time, and the reaction solution was poured into a large amount of methanol to purify the product. When evaluated by gel permeation chromatography (GPC), it was confirmed that an amino group-containing polymer compound having a weight average molecular weight of 11100 and a molecular weight distribution of 3.27 was obtained. As a result of observing the solubility of the synthesized amino group-containing polymer in water, it was hardly soluble in water or an aqueous solution (a mixture of water and KOH or HCl for adjusting pH) in a pH range higher than pH 4.

  20 parts by mass of the synthesized amino group-containing polymer compound was dissolved in 100 parts by mass of tetrahydrofuran, and C.I. I. 5 parts by weight of Pigment Yellow 128 yellow pigment was suspended in a container for 2 hours. Next, a potassium hydroxide aqueous solution was dropped little by little to dissolve the yellow pigment. This pigment solution is rapidly treated using a syringe into a pH 1 aqueous solution (prepared using distilled water and hydrochloric acid) stirred with a stirrer while ultrasonically treating the pigment solution to precipitate a yellow pigment. A liquid composition containing pigment fine particles and a dissolved amino group-containing polymer compound was obtained. When the average particle diameter of the pigment fine particles was measured at 25 ° C. in distilled water using DLS-7000 (manufactured by Otsuka Electronics Co., Ltd.), it was confirmed to be 42.2 nm. The zeta potential of the pigment fine particles was measured and found to be 10 mV at pH 3 (salt concentration of 0.01 N), 5 mV at pH 5, 2 mV at pH 8, and 0 mV at pH 11.

  The liquid composition produced as described above is a dispersion having a pH of 3 and contains pigment fine particles and a dissolved amino group-containing polymer compound. This liquid composition was desalted using an ultrafiltration system (Microza R-UF pencil type module, manufactured by Asahi Kasei) to adjust the pH to 5. It was observed that the pH 8 liquid composition was allowed to stand for a predetermined time to produce a precipitate. When the precipitate was removed from the liquid composition by decantation and the removed precipitate was evaluated by IR and GPC, it was confirmed to be an amino group-containing polymer compound. From the results as described above, it is confirmed that, in a liquid composition containing pigment fine particles and a dissolved polymer compound, the dissolved polymer compound can be selectively removed from the liquid composition by adjusting its pH. It was done.

  As a comparative experiment, when the liquid composition was adjusted to pH 11, both the pigment fine particles and the amino group-containing compound were precipitated, and only the amino group-containing compound could not be removed from the liquid composition.

As a comparative experiment, when the liquid composition was adjusted to pH 8, it was observed that only the amino group-containing compound was precipitated and precipitated, but the pigment fine particles were also slightly agglomerated.
<Preparation of ink composition>
In Example 1, the liquid composition in which polySt-r-MAc in a dissolved state at pH 8 was selectively removed was concentrated using an evaporator to obtain a concentrated liquid having a pigment content of 10%. The ink composition was prepared by mixing 50 parts by mass of this concentrated liquid, 7.5 parts by mass of diethylene glycol, 5 parts by mass of glycerin, 5 parts by mass of trimethylolpropane, 0.2 parts by mass of acetylenol EH, and 32.3 parts by mass of ion-exchanged water. Was prepared.

<Print evaluation>
The prepared ink composition was mounted on an ink jet printer BJF800 (trade name, manufactured by Canon Inc.), and solid image ink jet recording was performed on plain paper. When the recorded matter was visually evaluated, it was confirmed that it had a clear hue.

  The prepared ink composition was mounted on an ink jet printer BJF800 (trade name, manufactured by Canon Inc.), and character images were ink jet recorded on plain paper, and the ejection stability was evaluated. With regard to ejection stability, 1 million alphanumeric characters are printed continuously, and the obtained printed matter is visually observed, so that it can be printed neatly without causing problems such as blurring or non-ejection. there were.

  INDUSTRIAL APPLICABILITY Since the present invention can provide a liquid composition containing nanometer-order pigment fine particles with high size uniformity suitable as an ink-jet ink, an ink-jet ink composition, an image forming method using the ink composition, and It can be used for an image forming apparatus.

It is a block diagram which shows the structure of an inkjet recording device.

Explanation of symbols

20 Inkjet device 50 CPU
52 X motor drive circuit 54 Y motor drive circuit 56 X direction drive motor 58 Y direction drive motor 60 Head drive circuit 62 X encoder 64 Y encoder 66 Program memory 70 Head

Claims (13)

  A method for purifying a liquid composition by removing a polymer compound from a liquid composition containing dispersed fine particles and a dissolved polymer compound, wherein: (1) the fine particles maintain the dispersed state in the liquid composition And a step of precipitating or precipitating the polymer compound in a pH range where the polymer compound is hardly soluble, and (2) a step of removing the precipitate or precipitate of the polymer compound from the liquid composition; A method for purifying a liquid composition, comprising:   The method for purifying a liquid composition according to claim 1, wherein an absolute value of a zeta potential of the fine particles is larger than 0 mV in the pH range.   The method for purifying a liquid composition according to claim 1 or 2, wherein an absolute value of a zeta potential of the fine particles is 5 mV or more in the pH range.   The method for purifying a liquid composition according to any one of claims 1 to 3, wherein the polymer compound is a charged polymer compound.   5. The method for purifying a liquid composition according to claim 1, wherein the fine particles and the polymer compound are charged with the same sign in the liquid composition.   A method for producing a liquid composition comprising pigment fine particles and a polymer compound, wherein the pigment fine particles exist in a dispersed state, wherein (1) the first solvent and the second solvent containing the polymer compound in any one of (2) obtaining a solution in which the pigment is dissolved in the first solvent, (3) mixing the solution and the second solvent to obtain a mixed solution, and dispersing the pigment fine particles (4) a step of precipitating or precipitating the polymer compound in a pH range in which the fine particles maintain a dispersed state and the polymer compound is hardly soluble; And a step of removing the precipitate of the polymer compound or the precipitate from the mixed solution.   The method for producing a liquid composition according to claim 6, wherein the first solvent is an aprotic solvent.   The method for producing a liquid composition according to claim 6 or 7, wherein the first solvent is a mixed solvent of an aprotic solvent and an alkali.   The method for producing a liquid composition according to any one of claims 6 to 8, wherein the second solvent is water or an aqueous solution.   The method for producing a liquid composition according to claim 6, wherein the polymer compound is a charged polymer compound.   An ink composition for ink jet recording, comprising the liquid composition produced by the method according to any one of claims 6 to 10.   An image forming method comprising a step of recording an image by applying the ink composition according to claim 11 to a medium.   An image forming apparatus comprising means for recording an image by applying the ink composition according to claim 11 to a medium.

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