JP4983090B2 - Method for refining pigment, and coloring composition using fine pigment obtained by the method - Google Patents

Description

  The present invention relates to a method for refining a pigment, which is a solvent salt milling method, which is one of the methods for refining pigments, to obtain a finer pigment with less coarse particles and a finer particle diameter distribution.

  Various methods for refining pigments are known. Taking phthalocyanine pigment as an example, a crude pigment with a coarse particle diameter after synthesis is once dissolved by an acid pasting method or an acid slurry method, and then reprecipitated under appropriate conditions to extract fine pigment particles. A method of dry crushing a crude pigment with an attritor filled with a powder and applying a physical impact to refine the pigment, a pigment composition containing a crude pigment, a water-soluble inorganic salt, a water-soluble organic solvent, a crystal growth inhibitor, etc. A solvent salt milling method in which a pigment is refined by kneading a product (hereinafter referred to as a dough) with a kneader or the like, and a method in which these pigment refinement methods are combined, for example, after acid pasting, solvent salt milling A method of making the pigment finer is known.

When the crystal type of the pigment changes with the miniaturization process, the crystal type control is performed together with the particle size control of the pigment by changing the miniaturization condition or performing an additional process. In the case of the above phthalocyanine pigment, α-type crystals are obtained by an acid slurry method or a dry pulverization method, and when changing to β-type, solvent treatment or the like is performed.
For pigments, it is important to narrow the particle size distribution (increase the sized particle size) in addition to miniaturization and crystal form control. For example, the dispersibility, viscosity, storage stability, gloss, etc. in printing inks are better for pigments with higher particle size. Also, in color resist inks and inkjet ink applications where pigments with fine particle sizes are required, if the average particle size of the pigment is sufficiently small and the coarse particle size is low and coarse particles are contained, these coarse particles will have an adverse effect. For example, a color resist leads to a decrease in quality such as a decrease in contrast ratio and an increase in viscosity. Therefore, in recent years, there has been a strong demand for pigments to increase the particle size at the same time as miniaturization.

Patent Document 1 discloses that by adding a small amount of a crude pigment and an organic solvent having a crystal growth action and pulverizing, the finer pulverization and the crystal growth by the organic solvent are balanced to achieve grain size control. Yes. However, this method is not superior to the general solvent salt milling method, although the particle size is improved as compared with the general dry pulverization method.
The solvent salt milling method is a miniaturization method having a high particle size among the above-mentioned various pigment miniaturization methods. In the solvent salt milling method, in order to obtain a finer pigment, a method using a fine abrasive, a method using a large amount of the abrasive (Patent Document 2), a method of kneading with a crystal growth inhibitor, and the like are taken. .

  The finer the pigment in the solvent salt milling method, the more the shearing force applied to the pigment is, the more the dough becomes harder by adjusting the amount of water-soluble inorganic salt or water-soluble organic solvent. However, when the dough is hardened, the degree of micronization of the pigment is advanced, but due to the fact that the dough is hard, it adheres and stays on the dead space, the inner wall, and the stirring blade of the kneader, thereby leaving a coarse material. The problem occurs. In applications where fine pigments are required, there are many cases in which these coarse products are a very small part, and the quality is greatly deteriorated by mixing them. Conventionally, a method of kneading for a long time has been taken in order to avoid the residue of these coarse products. However, this method is extremely inefficient, and the residue of coarse materials cannot be sufficiently eliminated.

JP 2004-244563 A Japanese Patent Laid-Open No. 2002-121420

Accordingly, an object of the present invention is to provide a method for refining a pigment, which is capable of obtaining a finer pigment having a small size and a fine particle size distribution.
Another object of the present invention is to provide a coloring composition that is excellent in dispersibility, viscosity, and storage stability, is excellent in gloss, and can form a coating film having a high contrast ratio.

The method for refining a pigment of the present invention includes a first pigment refining step of kneading a pigment composition containing a pigment, a water-soluble inorganic salt, and a water-soluble organic solvent with a kneader, and the pigment obtained in the step A step of discharging the kneaded material from the kneading machine, and a second pigment refining step of charging the pigment kneaded material discharged in the step into the kneader and kneading again, The amount of the water-soluble organic solvent in the composition to be kneaded in the forming step is 0.10 to 0.25 times by weight with respect to the total weight of the pigment and the water-soluble inorganic salt.
In addition, the refined pigment of the present invention is obtained by the refinement method of the present invention.
Moreover, the coloring composition of the present invention is characterized by containing a fine pigment and a pigment carrier obtained by the fine method of the present invention.

According to the method for refining a pigment of the present invention, the amount of the water-soluble organic solvent relative to the total weight of the pigment and the water-soluble inorganic salt is small, and it is obtained in the first pigment refining step despite kneading hard dough. The pigment kneaded product is once discharged from the kneader, and the discharged pigment kneaded material is put into the kneader and kneaded again, so that no coarse pigment remains. In the solvent salt milling method, the reason why the coarse product is difficult to disappear is because the adhering matter to the dead space, the inner wall, and the stirring blade of the kneader is not replaced for a long time, and there is a part that is not kneaded or kneaded. The tendency is remarkable when the dough is hardened for the purpose of miniaturization. However, according to the method for refining a pigment of the present invention, the degree of refining and the particle size of pigment particles are increased as compared with the conventional method, and the kneading time can be shortened.
In addition, since the coloring composition of the present invention uses a finer pigment having a high degree of fineness and a finely sized particle size, when prepared as a printing ink, it has excellent dispersibility, viscosity, storage stability and gloss. When prepared as a color resist, a coating film having a high contrast ratio can be formed.

The method for refining a pigment of the present invention includes a first pigment refining step of kneading a pigment composition containing a pigment, a water-soluble inorganic salt, and a water-soluble organic solvent with a kneader, and the pigment obtained in the step A step of discharging the kneaded material from the kneader, and a second pigment refining step of charging the pigment kneaded material discharged in the step into the kneader and kneading again. The amount of the water-soluble organic solvent in the composition to be kneaded in the first and second pigment refining steps is 0.10 to 0.25 times the total weight of the pigment and the water-soluble inorganic salt. Is double.
In the pigment refinement method of the present invention, in the first and second pigment refinement steps, crystal type control is performed along with the refinement and size regulation of the pigment.

  The method for refining the pigment of the present invention is a copper phthalocyanine blue pigment, more specifically C.I. I. Pigment Blue 15, C.I. I. Pigment Blue 15: 1, C.I. I. Pigment Blue 15: 2, C.I. I. Pigment Blue 15: 3, C.I. I. Pigment Blue 15: 4, C.I. I. Pigment Blue 15: 6, especially C.I. I. This is useful for making Pigment Blue 15: 6 fine.

The water-soluble inorganic salt used in the first and second pigment refining steps serves as an abrasive and is kneaded with the pigment to advance the refining of the pigment. Examples of the water-soluble inorganic salt include sodium chloride, potassium chloride, calcium chloride, sodium sulfate, aluminum sulfate, sodium hydrogen carbonate and the like, and sodium chloride is preferable. These water-soluble inorganic salts can be pulverized. These water-soluble inorganic salts can be used alone or in a mixture of two or more.
The amount of the water-soluble inorganic salt is 2.5 to 20 times, more preferably 4 to 10 times the weight of the pigment.

  The water-soluble organic solvent serves as a linking agent for the pigment and the water-soluble inorganic salt, and gives the dough firmness and viscosity, and promotes the crystal growth and crystal transition of the pigment. Examples of water-soluble organic solvents include alkylene glycols such as ethylene glycol and propylene glycol, condensates of alkylene glycols such as diethylene glycol, triethylene glycol, dipropylene glycol, polyethylene glycol, and polyethylene-propylene glycol, methoxyethanol, polyethylene glycol monomethyl ether, and the like Alkyl ethers of (poly) alkylene glycol, glycerin and the like can be used. These water-soluble organic solvents can be used alone or in a mixture of two or more.

  If the amount of the water-soluble organic solvent is too small, dough is not formed and the shearing force applied to the pigment is weakened. Even if it is excessive, the dough becomes too soft and the shearing force applied to the pigment is weakened. The optimum amount varies depending on the amount of the pigment, the amount of the water-soluble inorganic salt, the temperature, the pigment particle diameter, the characteristics of the kneading machine used, etc., but in many cases, the amount is 0.10% with respect to the total weight of the pigment and the water-soluble inorganic salt. Times to 0.25 times by weight, more preferably 0.12 to 0.20 times by weight.

The kneading machine only needs to be capable of kneading a composition (dough) composed of a pigment, a water-soluble inorganic salt, and a water-soluble organic solvent, and a double-arm kneader, a flasher, a planetary mixer, or the like can be used. For miniaturization, a double-arm kneader having a strong shearing force is more preferable.
The temperature at the time of kneading is set according to the temperature dependence and crystal transition of the crystal growth rate of the pigment. In general, the lower the temperature, the lower the crystal growth rate. On the other hand, the wettability of the water-soluble organic solvent to the pigment surface and the penetration rate of the water-soluble organic solvent into the pigment mass are faster as the temperature is higher. The sizing of the pigment progresses by a balance between both fineness and crystal growth, and in many cases, 0 ° C to 120 ° C is preferable, and 10 ° C to 100 ° C is more preferable.

In the step of discharging the pigment kneaded material obtained in the first pigment refinement step from the kneader, the pigment kneaded material adheres to the inner wall of the kneader and the stirring blade and is hardly kneaded, or the kneading efficiency is in other places. Take out the inferior dough compared to. The pigment kneaded product obtained in the first pigment refinement step is discharged from the kneader and then kneaded again in the second pigment refinement step, whereby the kneading efficiency can be made uniform.
In the second pigment refinement step, a water-soluble inorganic salt or a water-soluble organic solvent can be added in accordance with the progress of pigment refinement and granulation.

  In addition, when the pigment kneaded material once discharged in the second pigment refinement step is kneaded again, the pigment kneaded material does not only indicate the dough that has been discharged from the kneader, but also the purified product. Including. That is, in the second pigment refinement step, the pigment kneaded product obtained in the first pigment refinement step is discharged from the kneader, purified, dried, isolated pigment, water-soluble inorganic salt and water-soluble It also includes putting the organic solvent into a kneader and kneading again. The discharge and re-kneading of the pigment kneaded material is not limited to once, and may be performed a plurality of times.

In the first and / or second pigment refinement step, crystal transition can be performed together with the refinement of the pigment. In the first and / or second pigment refinement step, a known pigment derivative or a surface treatment agent may be added in order to refine the pigment, control the crystal type, and further provide appropriateness in a practical system. it can.
The pigment kneaded product (dough) kneaded in the second pigment refinement step is purified by a known purification method such as washing with water, acid, or alkali, and the refined pigment is isolated.

  In the first pigment refinement step, it is preferable that the average primary particle size is 10 nm to 50 nm and the pigment is refined and sized so that the variation coefficient of the primary particle size distribution is 0.70 or less. In the first pigment refinement step, the kneaded composition in which the pigment is refined until the average primary particle size and the variation coefficient of the primary particle size distribution are obtained is once discharged from the kneader and then passed through the second pigmentation step. Thus, a finely sized pigment having an average primary particle size of 10 nm to 30 nm and a variation coefficient of primary particle size distribution of 0.35 or less can be obtained.

  The primary particle diameter of the pigment referred to in the present invention is a particle diameter determined by a method of directly measuring the size of primary particles from an electron micrograph of the pigment. Specifically, the short axis diameter and the long axis diameter of the primary particles of each pigment are measured, the area is obtained from the particle image, and the diameter of a circle having the same area is defined as the primary particle diameter. The short axis diameter and the long axis diameter are measured for 500 primary particles of the pigment, and the average value of the primary particle diameters calculated from the results is defined as the average primary particle diameter. The variation coefficient of the primary particle size distribution is obtained by dividing the standard deviation of the primary particle size calculated for 500 particle sizes by the average value.

  The refined pigment obtained by the pigment refinement method of the present invention is dispersed in a pigment carrier to form a colored composition, and used as a printing ink, inkjet ink, paint, toner, color resist ink for color filters, and the like. Can do.

For the pigment carrier of printing ink, a resin can be used to improve the dispersibility in the ink. Examples of the resin include rosin-modified phenol resin, petroleum resin, rosin-modified maleic resin, rosin alkyd, Examples include rosin ester, polymerized rosin, disproportionated rosin, polyamide resin, nitrocellulose-based resin, urethane resin, and acrylic resin. The pigment carrier can be used in an amount of 10 to 250 parts by weight with respect to 100 parts by weight of the fine pigment.
The printing ink may contain a solvent such as a high boiling point petroleum solvent, an aliphatic hydrocarbon solvent, a higher alcohol solvent, or vegetable oil.

  Resin can be used for the pigment carrier of inkjet ink in order to improve the fixability to paper and the water resistance of an ink coating film. Resins used in water-based inkjet inks can be broadly classified into water-soluble resins and water-dispersible resins. Acrylic resins, styrene-acrylic resins, vinyl acetate resins, polyester resins, polyamide resins, polyurethane resins, epoxy resins, Examples thereof include water-soluble resins and water-dispersible resins such as butadiene-based resins, petroleum-based resins, and fluorine-based resins. The pigment carrier can be used in an amount of 10 to 150 parts by weight with respect to 100 parts by weight of the fine pigment.

  The aqueous inkjet ink can also contain an aqueous solvent. Examples of such aqueous solvents include ethylene glycol, diethylene glycol, propylene glycol, 1,3-propanediol, triethylene glycol, polyethylene glycol, glycerin, tetra Ethylene glycol, dipropylene glycol, ketone alcohol, diethylene glycol monobutyl ether, ethylene glycol monobutyl ether, triethylene glycol monobutyl ether, ethylene glycol monoethyl ether, 1,2-hexanediol, N-methyl-2-pyrrolidone, 2,4, Examples thereof include 6-hexanetriol, tetrafurfuryl alcohol, 4-methoxy-4-methylpentanone and the like.

Resins used in oil-based inkjet inks include acrylic resins, styrene-acrylic resins, styrene-maleic acid resins, rosin resins, rosin ester resins, ethylene-vinyl acetate resins, petroleum resins, coumarone indenes. Resin, isoprene resin, terpene phenol resin, phenol resin, urethane resin, melamine resin, urea resin, epoxy resin, cellulose resin, vinyl chloride resin, xylene resin, alkyd resin, aliphatic hydrocarbon resin, butyral Resin, maleic acid resin, fumaric acid resin and the like can be mentioned. The pigment carrier can be used in an amount of 10 to 150 parts by weight with respect to 100 parts by weight of the fine pigment.
For oil-based inkjet inks, aliphatic hydrocarbon solvents, carbitol solvents, cellosolve solvents, higher fatty acid ester solvents, higher alcohol solvents, higher fatty acid solvents, aromatic hydrocarbon solvents, etc. Can also be included.

Resin such as melamine resin, acrylic resin, urethane resin, alkyd resin, epoxy resin, polyamide resin, and phthalic acid resin can be used for the pigment carrier of the paint. The pigment carrier can be used in an amount of 10 to 250 parts by weight with respect to 100 parts by weight of the fine pigment.
The paint may contain a solvent such as toluene, alcohols, esters, and alcohol ethers.

  For the toner pigment carrier, a resin having good fixability and excellent transparency, for example, polyester, acrylic, styrene-acrylic, and epoxy resins can be used as the toner binder resin. Of these, a non-linear resin is more preferable, and a polyester resin is particularly preferable, and a bisphenol derivative represented by a bisphenol A-alkylene oxide adduct or a substituted product thereof is used alone for the diol component, or It is used in combination with an aliphatic dialcohol, and these diol components and divalent or higher carboxylic acids, for example, carboxylic acid components such as fumaric acid, terephthalic acid, trimellitic acid, etc. may be condensed or co-condensed. it can. The pigment carrier can be used in an amount of 10 to 250 parts by weight with respect to 100 parts by weight of the fine pigment.

  The pigment carrier of the color resist ink is composed of a transparent resin, a precursor thereof, or a mixture thereof. The transparent resin is a resin having a transmittance of preferably 80% or more, more preferably 95% or more in the entire wavelength region of 400 to 700 nm in the visible light region. Transparent resins include thermoplastic resins, thermosetting resins, and active energy ray curable resins, and precursors thereof include monomers or oligomers that are cured by irradiation with active energy rays to form transparent resins. These can be used alone or in admixture of two or more. The pigment carrier can be used in an amount of 10 to 250 parts by weight with respect to 100 parts by weight of the fine pigment.

  Thermoplastic resins include butyral resin, styrene-maleic acid copolymer, chlorinated polyethylene, chlorinated polypropylene, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, polyurethane resin, polyester resin, acrylic resin Resin, alkyd resin, polystyrene resin, polyamide resin, rubber resin, cyclized rubber resin, cellulose, polyethylene (high density, low density), polybutadiene, polyimide resin and the like. Examples of thermosetting resins include epoxy resins, benzoguanamine resins, rosin-modified maleic acid resins, rosin-modified fumaric acid resins, melamine resins, urea resins, and phenol resins.

  As the active energy ray-curable resin, a (meth) acryl having a reactive substituent such as an isocyanate group, an aldehyde group or an epoxy group on a linear polymer having a reactive substituent such as a hydroxyl group, a carboxyl group or an amino group. A resin in which a photocrosslinkable group such as a (meth) acryloyl group or a styryl group is introduced into the linear polymer by reacting a compound or cinnamic acid is used. Further, a linear polymer containing an acid anhydride such as a styrene-maleic anhydride copolymer or an α-olefin-maleic anhydride copolymer is converted into a (meth) acrylic compound having a hydroxyl group such as hydroxyalkyl (meth) acrylate. Half-esterified products are also used.

  Monomers and oligomers that are precursors of transparent resins include methyl (meth) acrylate, ethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, cyclohexyl (meta ) Acrylate, β-carboxyethyl (meth) acrylate, polyethylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, triethylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, Trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, 1,6-hexanediol diglycidyl ether di (meth) acrylate, bisphenol A diglycidyl ether di (meth) Acrylate, neopentyl glycol diglycidyl ether di (meth) acrylate, dipentaerythritol hexa (meth) acrylate, tricyclodecanyl (meth) acrylate, ester acrylate, (meth) acrylic acid ester of methylolated melamine, epoxy (meth) Various acrylates and methacrylates such as acrylate and urethane acrylate, (meth) acrylic acid, styrene, vinyl acetate, hydroxyethyl vinyl ether, ethylene glycol divinyl ether, pentaerythritol trivinyl ether, (meth) acrylamide, N-hydroxymethyl ( (Meth) acrylamide, N-vinylformamide, acrylonitrile, etc. are mentioned, and these may be used alone or in combination of two or more. it can.

  The color resist ink may contain a solvent in order to sufficiently disperse the pigment in the pigment carrier. Solvents include cyclohexanone, ethyl cellosolve acetate, butyl cellosolve acetate, 1-methoxy-2-propyl acetate, diethylene glycol dimethyl ether, ethylbenzene, ethylene glycol diethyl ether, xylene, ethyl cellosolve, methyl-n-amyl ketone, propylene glycol monomethyl ether toluene, methyl ethyl ketone , Ethyl acetate, methanol, ethanol, isopropyl alcohol, butanol, isobutyl ketone, petroleum solvent and the like, and these are used alone or in combination.

Hereinafter, the present invention will be described more specifically with reference to examples. In the following, “part” represents “part by weight”.
[Example 1]
Copper phthalocyanine blue pigment “Heliogen blue L6700F” (CI Pigment Blue 15: 6, manufactured by BASF, average primary particle size 95.0 nm, coefficient of variation of primary particle size distribution 0.49, average aspect ratio 5.16) 1 .000 parts, 7.500 parts of sodium chloride, and 1.300 parts of diethylene glycol were charged into a 500 L double-arm kneader to form a dough and kneaded at a material temperature of 100 ° C. for 8 hours. Next, all the dough was discharged. A sample was collected, purified and dried by the method described below, and the particle size was measured. The average primary particle size was 30.5 nm, the primary particle size distribution variation coefficient was 0.26, and the average aspect ratio was 1.84. 9.800 parts of the discharged dough was again charged into the kneader, and 2.500 parts of sodium chloride and 0.350 parts of diethylene glycol were added and kneaded at a material temperature of 100 ° C. for 10 hours. The obtained dough was reslurried in about 10 times the weight of the dough, stirred for 1.5 hours at 70 ° C., and then filtered. The slurry was reslurried again, washed with filtered water to obtain a paste pigment, and dried in a heating oven at 80 ° C. for 48 hours.

[Example 2]
Copper phthalocyanine blue pigment “Heliogen blue L6700F” (CI Pigment Blue 15: 6, manufactured by BASF, average primary particle size 95.0 nm, coefficient of variation of primary particle size distribution 0.49, average aspect ratio 5.16) 1 .000 parts, 7.500 parts of sodium chloride, and 1.300 parts of diethylene glycol were charged into a 500 L double-arm kneader to form a dough and kneaded at a material temperature of 100 ° C. for 8 hours. Next, after the entire amount of the dough was discharged, it was purified and dried in the same manner as in Example 1. When the particle diameter of the obtained pigment was measured, the average primary particle diameter was 30.5 nm, the primary particle diameter distribution coefficient of variation was 0.26, and the average aspect ratio was 1.84. 1.500 parts of the obtained dry pigment, 10.000 parts of sodium chloride, and 1.650 parts of diethylene glycol were charged into a 500 L double-arm kneader, formed a dough, and then kneaded at a material temperature of 100 ° C. for 10 hours. The obtained dough was purified and dried in the same manner as in Example 1.

[Comparative Example 1]
Copper phthalocyanine blue pigment “Heliogen blue L6700F” (CI Pigment Blue 15: 6, manufactured by BASF, average primary particle size 95.0 nm, coefficient of variation of primary particle size distribution 0.49, average aspect ratio 5.16) 1 .000 parts, 7.500 parts of sodium chloride, and 1.300 parts of diethylene glycol were charged into a 500 L double-arm kneader to form a dough and kneaded at a material temperature of 100 ° C. for 8 hours. Next, 2.500 parts of sodium chloride and 0.350 parts of diethylene glycol were added and kneaded at a material temperature of 100 ° C. for 10 hours. The obtained dough was purified and dried in the same manner as in Example 1.

[Example 3]
Copper phthalocyanine blue pigment “Heliogen blue L6700F” (CI Pigment Blue 15: 6, manufactured by BASF, average primary particle size 95.0 nm, coefficient of variation of primary particle size distribution 0.49, average aspect ratio 5.16) 1 .000 parts, 10.000 parts of sodium chloride, and 1.100 parts of diethylene glycol were charged into a 500 L double-arm kneader to form a dough, and then kneaded at a material temperature of 100 ° C. for 6 hours. Next, all the dough was discharged. A sample was collected, purified and dried in the same manner as in Example 1, and the particle size was measured. The average primary particle size was 35.0 nm, the primary particle size distribution coefficient of variation was 0.33, and the average aspect ratio was 1.80. . 12.100 parts of the discharged dough was charged into the kneader again, 0.050 part of diethylaminopropylaminosulfonylated copper phthalocyanine was added, and the mixture was kneaded at a material temperature of 100 ° C. for 6 hours. The obtained dough was purified and dried in the same manner as in Example 1.

[Comparative Example 2]
Copper phthalocyanine blue pigment “Heliogen blue L6700F” (CI Pigment Blue 15: 6, manufactured by BASF, average primary particle size 95.0 nm, coefficient of variation of primary particle size distribution 0.49, average aspect ratio 5.16) 1 .000 parts, 12.000 parts of sodium chloride and 1.100 parts of diethylene glycol were charged into a 500 L double-arm kneader, formed a dough, and then kneaded at a material temperature of 100 ° C. for 6 hours. Next, all the dough was discharged. A sample was collected, purified and dried in the same manner as in Example 1, and the particle size was measured. The average primary particle size was 40.0 nm, the primary particle size distribution coefficient of variation was 0.55, and the average aspect ratio was 1.90. . 14.100 parts of the discharged dough was charged again into the kneader, 0.050 part of diethylaminopropylaminosulfonylated copper phthalocyanine was added, and the mixture was kneaded at a material temperature of 100 ° C. for 6 hours. The obtained dough was purified and dried in the same manner as in Example 1.

[Comparative Example 3]
Copper phthalocyanine blue pigment “Heliogen blue L6700F” (CI Pigment Blue 15: 6, manufactured by BASF, average primary particle size 95.0 nm, coefficient of variation of primary particle size distribution 0.49, average aspect ratio 5.16) 1 .000 parts, 5.000 parts of sodium chloride, and 1.600 parts of diethylene glycol were charged into a 500 L double-arm kneader to form a dough, and then kneaded at a material temperature of 100 ° C. for 6 hours. Next, all the dough was discharged. A sample was collected, purified and dried in the same manner as in Example 1, and the particle size was measured. The average primary particle size was 48.0 nm, the primary particle size distribution coefficient of variation was 0.63, and the average aspect ratio was 1.90. . 7.600 parts of the discharged dough was charged again into the kneader, 0.050 part of diethylaminopropylaminosulfonylated copper phthalocyanine was added, and the mixture was kneaded at a material temperature of 100 ° C. for 6 hours. The obtained dough was purified and dried in the same manner as in Example 1.

[Example 4]
Crude copper phthalocyanine blue pigment (CI Pigment Blue 15: 3 crude manufactured by Phthalo Color, Inc .; crude pigment containing many primary particles having a major axis of 2 μm or more and an aspect ratio of 3.00 or more), 1.000 parts, laurylaminosulfonylated 0.050 parts of copper phthalocyanine, 5.250 parts of sodium chloride and 1.300 parts of diethylene glycol were charged into a 500 L double-arm kneader, and after forming a dough, they were kneaded at a material temperature of 95 ° C. for 4 hours. Next, all the dough was discharged. A sample was collected, purified and dried in the same manner as in Example 1, and the particle size was measured. The average primary particle size was 47.1 nm, the primary particle size distribution coefficient of variation was 0.53, and the average aspect ratio was 1.72. . The discharged dough was charged again into the kneader, 0.080 parts of diethylaminopropylaminosulfonylated copper phthalocyanine, 1.750 parts of sodium chloride and 0.300 parts of diethylene glycol were added and kneaded at a material temperature of 95 ° C. for 4 hours. The obtained dough was purified and dried in the same manner as in Example 1.

[Comparative Example 4]
Crude Copper Phthalocyanine Blue Pigment (CI Pigment Blue 15: 3 crude manufactured by Phthalo Color, Inc .; Crude pigment containing many particles having a major axis of 2 μm or more and an aspect ratio of 3.00 or more) 1.000 parts, laurylaminosulfonylated copper 0.050 part of phthalocyanine, 5.250 parts of sodium chloride and 1.300 parts of diethylene glycol were charged into a 500 L double-arm kneader, and after forming a dough, they were kneaded at a material temperature of 95 ° C. for 4 hours. Next, 0.080 part of diethylaminopropylaminosulfonylated copper phthalocyanine, 1.750 parts of sodium chloride and 0.300 part of diethylene glycol were added and kneaded at a material temperature of 95 ° C. for 4 hours. The obtained dough was purified and dried in the same manner as in Example 1.

Table 1 shows the average primary particle size, the coefficient of variation of the primary particle size distribution, and the average aspect ratio of the refined pigments obtained in Examples and Comparative Examples. These measurements were performed by the following method.
The average primary particle diameter of the pigment was measured by reading an image from a transmission electron micrograph and using image analysis software “Mac-View phase 3” (manufactured by Mountec). More specifically, an image read from a photograph with a scanner or the like is used to manually recognize the contour of each particle using software, measure the major axis diameter and minor axis diameter, and determine the area from the particle image. The diameter of a circle with the same area was taken as the primary particle size. The short axis diameter and the long axis diameter of 500 primary particles of the pigment were measured, and the average primary particle diameter calculated from the results was defined as the average primary particle diameter. The variation coefficient of the primary particle size distribution was calculated by dividing the standard deviation of the primary particle size calculated for 500 particle sizes by the average value. The aspect ratio is calculated by dividing the major axis diameter by the minor axis diameter, and the average aspect ratio is an average value of 500 primary particles.

  Further, color resist inks were prepared using the finer pigments obtained in Examples and Comparative Examples, and the contrast ratio, viscosity, and thixo index, which are representative qualities, were measured. The resist ink was produced by the following method.

(Manufacture of acrylic resin solution for resist ink)
The reaction vessel was charged with 800.0 parts of cyclohexanone and heated to 100 ° C. while injecting nitrogen gas into the vessel. At the same temperature, 60.0 parts of styrene, 60.0 parts of methacrylic acid, 65.0 parts of methyl methacrylate, A mixture of 65.0 parts of butyl methacrylate and 10.0 parts of azobisbutyronitrile was added dropwise over 1 hour to carry out polymerization.
After the dropwise addition, the mixture was further reacted at 100 ° C. for 3 hours, then 2.0 parts of azobisisobutylnitrile dissolved in 50 parts of cyclohexanone was added, and the reaction was further continued for 1 hour, and the weight average molecular weight was about 40,000. An acrylic resin solution (GPC measurement) was obtained.
After cooling to room temperature, a part of the resin solution was sampled and heated and dried at 180 ° C. for 20 minutes to measure the nonvolatile content, and cyclohexanone was added to the obtained resin solution so that the nonvolatile content was 20% by weight. To prepare an acrylic resin solution.

(Manufacture of pigment dispersion)
After uniformly stirring and mixing the mixture having the composition shown below, the mixture is dispersed for 5 hours with an Eiger mill (“Mini Model M-250 MKII” manufactured by Eiger Japan) using zirconia beads having a diameter of 1 mm, and filtered through a 5 μm filter. Thus, a pigment dispersion was prepared. The derivatives include N, N′-diethylaminopropylaminosulfonylated copper phthalocyanine for Examples 1 to 5 and Comparative Examples 1 to 4, and Japanese Patent Publication No. 5-9469 for Example 6 and Comparative Example 5. The following compounds described were used.

Refined pigment 10.0 parts Derivative 0.5 parts Phosphate ester pigment dispersant ("BYK111" manufactured by Big Chemie) 8.0 parts Acrylic resin solution 33.5 parts Solvent (cyclohexanone) 48.0 parts Total 100.0 Part

(Manufacture of resist ink)
Next, a mixture of the following composition containing the obtained pigment dispersion pair was stirred and mixed so as to be uniform, and then filtered through a 1 μm filter to obtain an alkali developing blue resist.
Trimethylolpropane triacrylate as a monomer, “Irgacure 907” (manufactured by Ciba Specialty Chemicals) as a photopolymerization initiator, “EAB-F” (manufactured by Hodogaya Chemical Co.) as a sensitizer, solvent Cyclohexanone was used.
Pigment dispersion 47.0 parts Acrylic resin solution 5.0 parts Monomer 5.6 parts Photopolymerization initiator 2.0 parts Sensitizer 0.2 parts Solvent 40.2 parts Total 100.0 parts

About the obtained resist, the viscosity in 20 rpm was measured using the E-type viscosity meter "ELD type viscometer" (made by Toki Sangyo Co., Ltd.). Furthermore, the viscosity at 6 rpm and 60 rpm was measured, and the ratio between 6 rpm and 60 rpm (referred to as the thixo index, the higher the value, the higher the thixotropic property and the lower the better). If the dispersion system is constant, the higher the particle size of the dispersed pigment, the smaller the thixo index generally.
Further, the obtained resist was applied by using a spin coater so as to change the rotation speed so that the dry film thickness was about 1 μm, thereby preparing a three-point coated substrate. After coating, the film was dried in a hot air oven at 80 ° C. for 30 minutes, and then the film thickness and the contrast ratio were measured, and the contrast ratio at a film thickness of 1 μm was determined from the three points of data by the primary correlation method.
The results are shown in Table 1.

(Contrast ratio measurement method)
As shown in FIG. 1, the light emitted from the backlight unit for liquid crystal display (7) passes through the polarizing plate (6), is polarized, and is applied onto the glass substrate (5). 4) to reach the polarizing plate (3). If the polarization planes of the polarizing plate (6) and the polarizing plate (3) are parallel, light passes through the polarizing plate (3), but if the polarization planes are orthogonal, the light is transmitted by the polarizing plate (3). Blocked. However, when the light polarized by the polarizing plate (6) passes through the dry resist coating (4) of the resist, scattering by pigment particles or the like occurs, and if a part of the polarization plane is displaced, the polarizing plate becomes parallel. In this case, the amount of light transmitted through the polarizing plate (3) is reduced, and when the polarizing plate is orthogonal, a part of the light is transmitted through the polarizing plate (3). This transmitted light was measured as the luminance on the polarizing plate, and the ratio (contrast ratio) between the luminance when the polarizing plate was parallel and the luminance when it was orthogonal was calculated.
(Contrast ratio) = (Luminance when parallel) / (Luminance when orthogonal)

Accordingly, when scattering occurs due to the pigment in the dry coating film (4) of the resist, the brightness in the parallel case decreases and the brightness in the orthogonal direction increases, so the contrast ratio decreases. The larger the particle size of the pigment, the greater the scattering and the lower the contrast ratio. Accordingly, the finer and sized the pigment in the dried resist coating film (4), the higher the contrast ratio.
As a luminance meter, a color luminance meter “BM-5A” (manufactured by Topcon Corporation) was used, and as a polarizing plate, “NPF-G1220DUN” (manufactured by Nitto Denko Corporation) was used. In the measurement, in order to block unnecessary light, a black mask (2) having a 1 cm square hole was applied to the measurement portion.

It is a conceptual diagram of the measuring apparatus for measuring a contrast ratio.

Explanation of symbols

1: Luminance meter 2: Mask (black)
3: Polarizing plate (1)
4: Resist dry coating film 5: Glass substrate 6: Polarizing plate (2)
7: Backlight unit

Claims (7)

  A first pigment refinement step of kneading a pigment composition containing a pigment, a water-soluble inorganic salt, and a water-soluble organic solvent in a kneader; and a step of discharging the pigment kneaded product obtained in the step from the kneader. And a second pigment refining step in which the pigment kneaded product discharged in the step is put into a kneader and kneaded again, and water in the composition kneaded in the first and second pigment refining steps The method for refining a pigment, wherein the amount of the organic solvent is 0.10 to 0.25 times by weight based on the total weight of the pigment and the water-soluble inorganic salt.   2. The pigment according to claim 1, wherein the average primary particle size of the pigment obtained in the first pigment refinement step is 10 nm to 50 nm, and the coefficient of variation of the primary particle size distribution is 0.70 or less. Refinement method.   The average primary particle diameter of the pigment obtained in the second pigment refinement step is 10 nm to 30 nm, and the coefficient of variation of the primary particle diameter distribution is 0.35 or less. Pigment refinement method.   4. The method for refining a pigment according to claim 1, wherein the kneader used in the first pigment refining step is a double arm kneader.   5. The method according to claim 1, wherein the pigment is a copper phthalocyanine blue pigment.   A refined pigment obtained by the refinement method according to claim 1. A coloring composition comprising the finely divided pigment according to claim 6 and a pigment carrier.

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