JP5763895B2 - Method for producing pigment dispersion for color filter - Google Patents

Description

  The present invention relates to a method for producing a pigment dispersion for a color filter.

In recent years, liquid crystal display devices have been developed not only as monitors for personal computers but also as monitors for televisions, and color filters are used for color development. At present, the colored layers of color filters are mainly manufactured by a pigment dispersion method using a pigment having excellent light resistance and heat resistance. Generally, if the pigment can be dispersed as fine and stable particles, the scattering with respect to visible light is reduced.
As a method for dispersing a pigment, a method is known in which particles are pulverized and pulverized using a media mill disperser by a shearing force / friction force by stirring and mixing, an impact force between media, and the like.
However, the finer the pigment is, the easier it is for the dispersed particles to re-agglomerate, resulting in an increase in particle diameter and viscosity, which makes it difficult to stabilize the dispersion state.

Until now, in order to improve the quality of color filters (higher brightness, higher contrast, etc.), optimization of pigments and pigment dispersants, refinement of pigments contained in colored layers, and the like have been studied.
Patent Documents 1 to 3 disclose a method in which coarse pigment particles that cause light scattering and cause a decrease in contrast ratio are removed from a color filter dispersion by centrifugation.
However, Patent Documents 1 and 2 do not describe a method for reducing the viscosity or improving the storage stability only by removing the coarse particles and defining the particle size distribution of the pigment particles in the dispersion.
Moreover, since the viscosity of a dispersion liquid is quite high, patent document 3 is a method of removing a coarse particle by centrifugation after diluting with a low boiling-point solvent, and removing a solvent after that. In this method, the centrifugal separation conditions are too weak, and coarse particles that affect the contrast ratio cannot be sufficiently removed.
Patent Document 4 discloses a method of removing colored polymer by forming pigmented particles by high-speed ultracentrifugation after forming colored fine particles composed of a colorant and a polymer for stabilizing the discharge of water-based inkjet ink. Patent Document 5 discloses a method in which a part of the dispersant is removed by centrifugation or ultrafiltration for stabilizing the dispersion of the solution containing metal colloid particles.
However, Patent Documents 4 and 5 relate to water-based inks, which are different from non-aqueous pigment dispersions and do not describe a method for removing coarse particles.

Japanese Patent No. 3073769 JP 2008-250023 A Japanese Patent No. 2951347 Japanese Patent Laid-Open No. 11-302586 WO2002 / 094954

  An object of the present invention is to provide a method for producing a pigment dispersion for a color filter having a low viscosity, excellent storage stability, and extremely few coarse pigment particles.

That is, this invention provides the manufacturing method of the pigment dispersion for color filters which has the following process (1)-(3).
Step (1): A step of dispersing a mixed liquid containing a pigment, a water-insoluble dispersant, and an organic solvent and having a viscosity of 10 to 55 mPa · s to obtain a pigment dispersion Step (2): In Step (1) Step of obtaining the pigment dispersion by subjecting the obtained pigment dispersion to centrifugation treatment under conditions of 300,000 to 30 million G · min Step (3): To the pigment dispersion obtained in Step (2), Purify the pigment dispersion by applying a cross-flow filtration treatment (i) using a microfiltration membrane of 100 μm or less or an ultrafiltration membrane with a molecular weight cut off of 100,000 or more, or a condition of 50 million G · min or more. The step of purifying the pigment dispersion by redispersing the solid content obtained by performing the centrifugal separation treatment (ii) below

  According to the present invention, it is possible to efficiently produce a pigment dispersion for a color filter having a low viscosity, excellent storage stability, and extremely few coarse pigment particles.

The manufacturing method of the pigment dispersion for color filters of this invention has the following process (1)-(3), It is characterized by the above-mentioned.
Step (1): A step of dispersing a mixed liquid containing a pigment, a water-insoluble dispersant, and an organic solvent and having a viscosity of 10 to 55 mPa · s to obtain a pigment dispersion Step (2): In Step (1) Step of obtaining the pigment dispersion by subjecting the obtained pigment dispersion to centrifugation treatment under conditions of 300,000 to 30 million G · min Step (3): To the pigment dispersion obtained in Step (2), Purify the pigment dispersion by applying a cross-flow filtration treatment (i) using a microfiltration membrane of 100 μm or less or an ultrafiltration membrane with a molecular weight cut off of 100,000 or more, or a condition of 50 million G · min or more. Step of purifying the pigment dispersion by redispersing the solid content obtained by performing the centrifugal treatment (ii) below Hereinafter, each component and each step used in the present invention will be described.

<Pigment>
As the pigment used in the present invention, both inorganic pigments and organic pigments can be used. If necessary, they can be used in combination with extender pigments.
The hue is not particularly limited, and chromatic pigments such as red, yellow, blue, orange, green, violet, and white pigments can be used.
Examples of the inorganic pigment include carbon black, metal oxide, metal sulfide, and metal chloride. As the inorganic black pigment, carbon black is preferable, and examples thereof include furnace black, thermal lamp black, acetylene black, and channel black.
Examples of extender pigments include silica, calcium carbonate, and talc.
Examples of the organic pigment include azo pigments, diazo pigments, phthalocyanine pigments, quinacridone pigments, isoindolinone pigments, dioxazine pigments, perylene pigments, perinone pigments, thioindigo pigments, anthraquinone pigments, and quinophthalone pigments.
Examples of red organic pigments include azo pigments, diazo pigments, condensed azo pigments, azo lake pigments, quinacridone pigments, perylene pigments, anthraquinone pigments, diketopyrrolopyrrole pigments, and the like.
More specifically, compounds classified as Pigment in the Color Index (published by The Society of Dyersand Colorists, 1997 edition) can be mentioned.
Among these, diketopyrrolopyrrole pigments such as CI Pigment Red 254 and 255 are particularly preferred from the viewpoint of more effectively expressing the effects of the present invention. .

(Wherein, X ¹ and X ² each independently represent a hydrogen atom or a halogen atom, and Y ¹ and Y ² each independently represent a hydrogen atom or a —SO ₃ H group.)
Examples of the halogen atom of X ¹ and X ² in the general formula (1) include a fluorine atom and a chlorine atom.
There is no restriction | limiting in particular in the manufacturing method of the diketopyrrolopyrrole pigment represented by General formula (1). For example, it is produced by reacting benzonitrile or halogenated benzonitrile with a halogenated acetate such as bromoacetate in the presence of a reducing agent such as zinc powder, or by further sulfonating the obtained compound. be able to.
The above pigments can be used alone or in combination of two or more.
In addition, from the viewpoint of increasing the affinity with an organic solvent for the pigment surface and enhancing the dispersion stability, a pigment that has been previously surface-treated with a resin, a polymer, a pigment derivative, or the like may be used. It may be contained in the dispersion treatment.

<Water-insoluble dispersant>
The water-insoluble dispersant used in the present invention is not particularly limited as long as it can disperse the pigment in an organic solvent stably in a finely divided state, and a known polymer dispersant can be used. The water-insoluble dispersant is considered to have a function as a binder when forming a color filter or the like.
Here, the water-insoluble dispersant is 10 g or less, preferably 5 g or less, more preferably when the dispersant is dried at 105 ° C. for 2 hours and then dissolved in 100 g of water at 25 ° C. A dispersant that is 1 g or less. When the dispersant has a salt-forming group, the dissolution amount is a dissolution amount when the salt-forming group of the dispersant is 100% neutralized with acetic acid or sodium hydroxide depending on the type.
Examples of the water-insoluble dispersant include an amide skeleton in the main chain described in JP-A-3-277673, JP-A-10-339949, JP-T-2003-517063, etc., and the side chain is methacrylic. Graft polymer comprising macromonomer by acid ester; polyester oligomer having aliphatic hydroxycarboxylic acid residue described in JP-B-7-96654, JP-A-7-207178, etc .; organosiloxane polymer (Shin-Etsu Chemical Co., Ltd.) (Meth) acrylic acid-based (co) polymer (manufactured by Kyoei Yushi Chemical Co., Ltd., Polyflow No. 75, 90, 95, etc.); other commercially available products manufactured by Nippon Lubrizol Co., Ltd. Solsperse 3000, 5000, 9000, 12000, 13240, 13940, 7000, 20000, 24000, 26000, 28000, etc., various Solsperse dispersants, Ajinomoto Fine Techno Co., Ltd. Ajisper PB-821, PB-822, PB-881 [Composition (weight ratio): polyallylamine / polycaprolactone = 5 / 95, Mw: 8,000], Isonet S-20 manufactured by Sanyo Chemical Co., Ltd., DISPERBYK-161, DISPERBYK-2001 manufactured by Big Chemie Japan Co., Ltd., and the like.

In particular, a graft polymer composed of a structural unit containing at least a monomer having an adsorptivity to a pigment and a structural unit containing a monomer having an affinity for an organic solvent is preferable from the viewpoint of improving dispersion stability. These can be appropriately selected and used depending on the pigment and the organic solvent species.
For example, when the diketopyrrolopyrrole pigment is used as the pigment and the organic solvent is diethylene glycol monobutyl ether acetate (BCA), a graft polymer having an amide group in the main chain and a macromonomer in the side chain is preferable. Is a graft polymer (x) having a structural unit derived from a monomer having an amide group in the main chain and having a structural unit derived from a macromer of a methacrylic ester in the side chain, or a structural unit derived from a methacrylic ester macromer in the main chain And a graft polymer (y) having a structural unit derived from polyoxazoline in the side chain is preferred.
Among these, the graft polymer (x) is more preferable.

[Graft polymer (x)]
The graft polymer (x) is particularly preferably one having the following main chain and side chain.
Main chain: Containing structural unit (a) derived from N-vinyl-2-pyrrolidone and structural unit (b) derived from a hydroxyl group-containing monomer, and content of structural unit (a) in graft polymer (x) Is 2 to 30% by weight, and the content of the structural unit (b) is 5 to 30% by weight.
Side chain: contains a structural unit (c) derived from an alkyl (meth) acrylate macromer having a number average molecular weight of 800 to 4,000, and the content of the structural unit (c) in the graft polymer (x) is 65 ~ 92% by weight.
The contents of the structural units (a), (b) and (c) in the graft polymer (x) are the same as those in the structural units (a), (b) and (c) when the graft polymer (x) is produced. This corresponds to the charge amount of the corresponding monomer.

  When the main chain of the graft polymer (x) contains the structural unit (a) derived from N-vinyl-2-pyrrolidone, the dispersibility of the pigment is considered to be excellent. From this viewpoint, the content of the structural unit (a) in the graft polymer (x) is 2 to 30% by weight, preferably 5 to 25% by weight, and more preferably 10 to 20% by weight. When the content of the structural unit (a) is 2% by weight or more, the structural unit (a) can be sufficiently adsorbed to the pigment, can contribute to improvement of the dispersibility of the pigment, and the structural units (b) and (c). From the standpoint of balance, the effect of the present invention can be effectively exhibited if the upper limit is 30% by weight or less.

Examples of the hydroxyl group-containing monomer that forms the structural unit (b) contained in the main chain of the graft polymer (x) include compounds represented by the following formula (2).
^{_{CH 2 = C (R 4)}} COO (R 5 O) n H (2)
(In the formula, R ⁴ is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, R ⁵ is a divalent hydrocarbon group having 1 to 30 carbon atoms which may have a hetero atom, and n is an average added mole number. And is a number from 1 to 60.)
In the formula (2), preferred examples of R ⁴ include a methyl group, an ethyl group, and an (iso) propyl group. Examples of the hetero atom of R ⁵ include a nitrogen atom, an oxygen atom, a halogen atom, and sulfur. Atom. n is preferably a number from 1 to 30.
Preferred examples of the R ⁵ O group include an oxyethylene group, an oxytrimethylene grave, an oxypropane-1,2-diyl group, an oxytetramethylene group, an oxyheptamethylene group, an oxyhexamethylene group, and two or more kinds thereof. Examples thereof include oxyalkanediyl groups having 2 to 7 carbon atoms (oxyalkylene groups).

  Specific examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, polyethylene glycol (n = 2 to 30, n represents the average number of moles of oxyalkylene group added. The same)) (meth) acrylate, polypropylene glycol (n = 2-30) (meth) acrylate, poly (ethylene glycol (n = 1-15) / propylene glycol (n = 1-15)) (meth) acrylate, etc. Can be mentioned. Among these, from the viewpoint of excellent viscosity stability of the pigment dispersion, 2-hydroxyethyl (meth) acrylate, polyethylene glycol monomethacrylate, and polypropylene glycol methacrylate are preferable, and 2-hydroxyethyl (meth) acrylate is particularly preferable.

  It is considered that the viscosity stability of the pigment dispersion is improved when the main chain of the graft polymer (x) contains the structural unit (b) derived from the hydroxyl group-containing monomer. From this viewpoint, the content of the structural unit (b) in the graft polymer (x) is 5 to 30% by weight, preferably 5 to 25% by weight, and more preferably 10 to 20% by weight. If content of this structural unit (b) is 5 weight% or more, it can contribute to sufficient viscosity stability, and the upper limit is 30 from a viewpoint of the balance of structural unit (b) and (c). The effect of the present invention can be effectively expressed if it is not more than wt%.

  In addition, the side chain of the graft polymer (x) contains the structural unit (c) derived from an alkyl (meth) acrylate macromer having a number average molecular weight of 800 to 4000, so that the dispersibility of the organic pigment (A) can be improved. It is thought that it can improve and contribute to lowering the viscosity of the pigment dispersion. From this viewpoint, the content of the structural unit (c) in the graft polymer (x) is 65 to 92% by weight, preferably 65 to 85% by weight, and more preferably 65 to 80% by weight. If the content of the structural unit (c) is 65% by weight or more, (A) the organic pigment can be sufficiently dispersed, and the upper limit thereof from the viewpoint of the balance between the structural units (b) and (c). If it is 92 weight% or less, the effect of this invention can be expressed effectively.

The alkyl (meth) acrylate-based macromer that forms the structural unit (c) contained in the side chain of the graft polymer of the present invention has a structural unit derived from alkyl (meth) acrylate, and has a polymerizable functional group at one end thereof. It is what has. The side chain containing the structural unit (c) derived from the alkyl (meth) acrylate macromer can be obtained by copolymerizing an alkyl (meth) acrylate macromer having a polymerizable functional group at one end, As for the structural unit (c), one or more structural units may be contained in the side chain.
Specific examples thereof include a homopolymer of alkyl (meth) acrylate having a polymerizable functional group at one end, or a copolymer of an alkyl (meth) acrylate having a polymerizable functional group at one end and another monomer. Coalescence is mentioned.

The alkyl (meth) acrylate is preferably a straight chain having 1 to 8 carbon atoms, more preferably 1 to 6 carbon atoms, and particularly preferably 1 to 3 carbon atoms, from the viewpoint of promoting a reduction in viscosity of the pigment dispersion. Those having a branched alkyl group are preferred. Specifically, methyl (meth) acrylate, ethyl (meth) acrylate, (iso) propyl (meth) acrylate, (iso or tertiary) butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (iso) octyl (Meth) acrylate etc. are mentioned. Among these, methyl (meth) acrylate, ethyl (meth) acrylate, and (iso) propyl (meth) acrylate are particularly preferable. These alkyl (meth) acrylates can be used individually by 1 type or in mixture of 2 or more types.
In the present specification, “(iso or tertiary)” and “(iso)” mean both the case where these groups are present and the case where these groups are not present, and these groups are not present. In the case, it indicates normal. “(Meth) acrylate” means both acrylate and methacrylate.

The polymerizable functional group of the alkyl (meth) acrylate macromer is preferably an acryloyloxy group or a methacryloyloxy group.
Examples of other monomers copolymerized with alkyl (meth) acrylate include styrene monomers such as styrene, α-methylstyrene, vinyltoluene, and benzyl (meth) acrylate. In the alkyl (meth) acrylate-based macromer, the content of the structural unit derived from the alkyl (meth) acrylate is preferably 80% by weight or more, more preferably 90% by weight or more, and particularly preferably substantially 100% by weight. “Substantially” means that it may contain constituent units derived from other monomers in the amount of impurities.

The number average molecular weight of the alkyl (meth) acrylate macromer is 800 to 4,000, preferably 1,000 to 3,500, more preferably 1 from the viewpoint of promoting the reduction of the viscosity of the pigment dispersion. , 500 to 3,000. If the number average molecular weight is 800 or more, sufficient steric repulsion can be generated to improve the dispersibility, and if it is 4,000 or less, it is suitable for lowering the viscosity of the pigment dispersion.
The number average molecular weight of the alkyl (meth) acrylate macromer should be measured using polystyrene as a standard substance by gel chromatography (GPC) method using chloroform containing 1 mmol / L lauryldimethylamine as a solvent. Can do.

[Production of graft polymer (x)]
The graft polymer (x) is preferably obtained by copolymerizing a monomer mixture (hereinafter referred to as “monomer mixture”) containing N-vinyl-2-pyrrolidone, a hydroxyl group-containing monomer, and an alkyl (meth) acrylate macromer. . The monomer mixture may further contain alkyl (meth) acrylate and the like within a range not impairing the present invention.
The content of N-vinyl-2-pyrrolidone in the monomer mixture is 2 to 30% by weight, preferably 5 to 25% by weight, from the viewpoint of dispersion stability of the (A) organic pigment in the pigment dispersion. Yes, more preferably 10 to 20% by weight.
The content of the hydroxyl group-containing monomer in the monomer mixture is from 5 to 30% by weight, preferably from 5 to 25% by weight, more preferably from the viewpoint of dispersion stability of the organic pigment (A) in the pigment dispersion. Is 10 to 20% by weight.
The content of the alkyl (meth) acrylate macromer in the monomer mixture is 65 to 92% by weight, preferably 65 to 85% from the viewpoint of improving the dispersion stability of the (A) organic pigment in the pigment dispersion. %, More preferably 65 to 80% by weight.

The graft polymer (x) can be produced by copolymerizing the monomer mixture by a known polymerization method such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method or an emulsion polymerization method. Among these polymerization methods, the solution polymerization method is preferable from the viewpoint of using an organic solvent for the pigment dispersion.
As the organic solvent used in the solution polymerization method, an organic solvent having a high affinity with the graft polymer is preferable, and the above organic solvents can be used.
In the polymerization, azo compounds such as 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), tert-butyl peroxyoctoate, dibenzoyl peroxide, etc. Known radical polymerization initiators such as organic peroxides can be used.
The amount of the radical polymerization initiator is preferably 0.001 to 5 mol, more preferably 0.01 to 2 mol, per mol of the monomer mixture.
In the polymerization, a known polymerization chain transfer agent such as mercaptans such as octyl mercaptan and 2-mercaptoethanol and thiuram disulfide can be further added.
Although the polymerization conditions of the monomer mixture vary depending on the type of polymerization initiator, monomer, and organic solvent used, the polymerization temperature is usually 30 to 100 ° C., preferably 50 to 80 ° C., and the polymerization time is the polymerization temperature, etc. However, it is usually about 1 to 20 hours. The polymerization atmosphere is preferably an inert gas atmosphere such as nitrogen gas or argon.
After completion of the polymerization reaction, the produced dispersant can be isolated from the reaction solution by a known method such as reprecipitation or solvent distillation. The obtained dispersant can be purified by repeating reprecipitation or removing unreacted monomers by membrane separation, chromatography, extraction, or the like.

  The weight average molecular weight (Mw) of the obtained graft polymer (x) is from 5,000 to 200,000 from the viewpoint of improving the dispersion stability of the (A) organic pigment, particularly the diketopyrrolopyrrole pigment, in the pigment dispersion. 000 is preferable, 5,000 to 100,000 is more preferable, and 6,000 to 70,000 is particularly preferable. In addition, the weight average molecular weight of a polymer is measured using polystyrene as a standard substance by gel chromatography (GPC) method using chloroform containing 1 mmol / L lauryldimethylamine as a solvent.

<Organic solvent>
The organic solvent is not particularly limited as long as it is a liquid organic solvent under the conditions for the dispersion treatment.
Preferable examples of the organic solvent include, for example, a lower alcohol having 1 to 4 carbon atoms such as ethanol and isopropyl alcohol; a ketone such as acetone and methyl ethyl ketone; and toluene and xylene from the viewpoint of dispersibility between the pigment and the polymer dispersant. In addition to aliphatic hydrocarbons such as cyclohexane; polyhydric alcohols such as propylene glycol; ethers such as ethylene glycol diethyl ether, etc., ethyl acetate, silicone oil, higher alcohols, oils and fats, and the following general formula (3 ) And the like.

(In the formula, R ¹ and R ² each independently represent a linear or branched alkyl group having 1 to 4 carbon atoms, and R ³ represents a hydrogen atom or a methyl group.)
In the general formula (3), the linear or branched alkyl group having 1 to 4 carbon atoms of R ¹ and R ² is methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl. Groups, sec-butyl groups, and tert-butyl groups. In these, a methyl group and an ethyl group are preferable.
Said organic solvent can be used individually or in combination of 2 or more types.

The amount of the pigment in the dispersion is preferably 1% by weight or more, more preferably 5% by weight or more, and still more preferably 10% by weight or more from the viewpoint of improving productivity during dispersion. Further, from the viewpoint of ensuring handling properties at the time of dispersion, it is preferably 60% by weight or less, more preferably 50% by weight or less, and still more preferably 40% by weight or less.
The amount of the polymer dispersant in the dispersion is preferably an addition amount that does not become deficient in the dispersion treatment process from the viewpoint of improving dispersion stability. Specifically, it is 5% by weight or more, preferably 7% by weight or more, more preferably 10% by weight or more based on the pigment weight. Further, from the viewpoint of obtaining an appropriate viscosity of the dispersion, it is 200% by weight or less, preferably 100% by weight or less, and more preferably 80% by weight or less based on the pigment weight.
The amount of the organic solvent in the dispersion is the amount excluding the pigment concentration, polymer dispersant, and other additives, and is 30% by weight or more, preferably 50% by weight or more from the viewpoint of improving the operability during the dispersion treatment. More preferably, it is 70% by weight or more.

<Manufacture of pigment dispersion for color filter>
In the method for producing a pigment dispersion for a color filter of the present invention, the following steps (1) to (3) are performed.
Step (1): A step of dispersing a mixed liquid containing a pigment, a water-insoluble dispersant, and an organic solvent and having a viscosity of 10 to 55 mPa · s to obtain a pigment dispersion Step (2): In Step (1) Step of obtaining the pigment dispersion by subjecting the obtained pigment dispersion to centrifugation treatment under conditions of 300,000 to 30 million G · min Step (3): To the pigment dispersion obtained in Step (2), Purify the pigment dispersion by applying a cross-flow filtration process using a microfiltration membrane of 100 μm or less or an ultrafiltration membrane with a molecular weight cut off of 100,000 or more (i), or a condition of 50 million G · min or more The step of purifying the pigment dispersion by redispersing the solid content obtained by performing the centrifugal separation treatment (ii) below

[Step (1)]
In the step (1), a mixed liquid (hereinafter also simply referred to as “mixed liquid”) having a viscosity of 10 to 55 mPa · s containing a pigment, a water-insoluble dispersant, and an organic solvent is subjected to a dispersion treatment to obtain a pigment dispersion. It is a process to obtain. The viscosity of the mixed solution is preferably 10 to 55 mPa · s, preferably 12 to 50 mPa · s, more preferably 13 to 45 mPa · s, and further preferably 15 to 35 mPa · s, from the viewpoint of atomization of the pigment.
Although the average particle diameter of the pigment can be atomized only by the main dispersion until the desired particle diameter is reached, it is preferably pre-dispersed (primary dispersion) and then further subjected to shear stress to form the main dispersion (secondary dispersion). (Third order dispersion) is preferably performed so that the average particle diameter of the pigment is controlled to a desired particle diameter.
For example, the average particle size (D50: 50% passing particle size in the volume average particle size distribution) of the pigment after the pre-dispersion is preferably adjusted to 0.2 μm or less, more preferably 0.15 μm or less.
Further, from the viewpoint of reducing the content of coarse particles, D90 (90% passing particle diameter in the volume average particle size distribution) after completion of preliminary dispersion is preferably 1 μm or less, more preferably 0.6 μm or less. More preferably, the thickness is 0.4 μm or less. The average particle size (D50) and D90 can be measured by a dynamic light scattering particle size distribution meter or a laser Doppler particle size distribution meter that can measure the particle size range.
The mixing order of the pigment, the organic solvent, and the water-insoluble dispersant is not particularly limited, but from the viewpoint of increasing the productivity in consideration of the bulk specific gravity of the pigment and the ease of mixing the pigment and the organic solvent, It is preferable to add a pigment to the solvent. The water-insoluble dispersant is preferably added before and after the pigment is added.
Further, when the mixed liquid is dispersed, two or more preliminary dispersion treatments or different preliminary dispersion treatments may be combined from the viewpoint of reducing the content of coarse particles after completion of the preliminary dispersion. The number of preliminary dispersion treatments is preferably 10 times or less, more preferably 5 times or less, from the viewpoint of complexity and productivity.

(Preliminary dispersion)
As a mixing device used for preliminary dispersion, a commonly used mixing and stirring device such as an anchor blade can be used. Among the mixing and stirring devices, Ultra Disper (Iwata Iron Works Co., Ltd., trade name), Ebara Milder (Ebara Manufacturing Co., Ltd., trade name), TK homomixer, TK pipeline mixer, TK homojetter, TK homomic line flow, Philmix (above, Primix Co., Ltd., trade name), Ultra Turrax, DISPAX-REACTOR, Colloid Mill, CMS, MHD (IKA Japan Co., Ltd., trade name), Clear Mix (M Technique Co., Ltd., trade name), A high-speed stirring and mixing apparatus such as KD Mill (Kinetic Dispersion, trade name) is preferred.
In addition, after the mixed liquid is predispersed in the step (1), when the obtained predispersion has a large number of coarse particles, a desired shearing force is applied to the desired particle size by applying a shearing force stronger than the stirring force as necessary. Atomization can also be performed until.
As the atomization treatment method, one pass is performed by a media mill having a high effect atomization effect, for example, a media particle having a particle size of 0.1 mm or more, preferably a media particle having a particle size of 0.2 mm or more, a high-pressure homogenizer, or the like. The method of performing the above continuous dispersion processing etc. are mentioned. Commercially available media mills using media particles with high atomization effect include dyno mill (manufactured by Shinmaru Enterprises, trade name: 0.6L-ECM), SC mill (Nippon Coke Industrial Co., Ltd., trade name), paint shaker (Iwata Iron Works Co., Ltd., trade name).

(Distributed)
Examples of the mixing apparatus used for the dispersion include a kneader such as a roll mill, a kneader, and an extruder, a star mill (Ashizawa Finetech Co., Ltd., trade name), an ultra apex mill (Koto Kogyo Co., Ltd., trade name), a paint shaker, Media mills such as Picomill (Iwata Tekko Co., Ltd., trade name), MicroMedia, DCP Superflow, Cosmo (Buhler Co., Ltd., trade name), MSC Mill (Nippon Coke Industries Co., Ltd., trade name), high pressure homogenizer [Izumi Co., Ltd. Food machinery, trade name], Homovalve type high pressure homogenizer represented by minilab 8.3H type (Rannie, trade name), Microfluidizer [Microfluidics, trade name], Nanomizer [Nanomizer, trade name], Star Burst [Sugino Machine Co., Ltd., Name], Genus PY (white water Chemical Co., Ltd., trade name), DeBEE2000 (Japan Biii CO., LTD., Trade name), and the chamber type high-pressure homogenizer or the like of such.
Among these, from the viewpoint of atomization of the pigment contained in the mixed liquid, a media mill is preferable as the secondary dispersion apparatus that is the main dispersion, and a high-pressure homogenizer is preferable as the tertiary dispersion apparatus.

When a media mill is used for preliminary dispersion and main dispersion in step (1), it is preferable that the media diameter to be used is smaller in the main dispersion process than in the pre-dispersion process because the dispersion can be made more efficient. The media diameter used during the preliminary dispersion treatment varies depending on the size of the coarse particles of the pigment to be used, but is preferably 5 to 200 times, more preferably 10 to 100 times the D90 of the raw material pigment, and 0.1 mm or more as described above Is preferable, and 0.2 mm or more is more preferable. The media diameter used during the dispersion treatment is preferably 0.1 mm or less, more preferably 0.05 mm or less, and the upper limit is preferably 0.005 mm or more from the viewpoint of efficiently promoting dispersion.
On the other hand, when a media mill is used for preliminary dispersion and main dispersion in step (1), it is preferable that the dispersion processing time is longer in the main dispersion process than in the preliminary dispersion process. If the dispersion time during the preliminary dispersion treatment is too long, re-aggregation of the dispersion tends to occur, and the dispersion tends to increase in particle size, increase in viscosity, decrease in heat resistance, and the like. On the other hand, if the dispersion time during this dispersion treatment is too short, the amount of coarse particles in the dispersion will not be reduced, making it difficult to obtain the desired contrast ratio.

The amount of the organic solvent during the dispersion treatment in the step (1) is preferably 50 to 90% by weight, and more preferably 60 to 90% by weight. By setting the amount of the organic solvent to 50% by weight or more, it is possible to reduce the viscosity of the dispersion during the dispersion treatment, to efficiently impart a dispersion force, and to atomize the pigment. On the other hand, by setting the amount of the organic solvent to 90% by weight or less, it is possible to suppress excessive dispersion force and prevent re-aggregation of the dispersion, increase in viscosity of the dispersion, and deterioration of storage stability. .
In addition, the pigment dispersion obtained in the step (1) may be directly subjected to the centrifugal treatment in the step (2). From the viewpoint of increasing the efficiency of the centrifugal treatment, the pigment dispersion is further subjected to organic treatment before the centrifugal treatment. A solvent may be added to adjust the viscosity to preferably 3 to 40 mPa · s, more preferably 3 to 30 mPa · s, and even more preferably 3 to 20 mPa · s.

[Step (2)]
Step (2) is a step of obtaining the pigment dispersion by subjecting the pigment dispersion obtained in step (1) to centrifugal separation under the conditions of 300,000 to 30 million G · min. By performing step (2), coarse particles of 100 nm or more in the pigment dispersion can be removed, and a pigment dispersion for a color filter having a uniform particle size and a high contrast ratio can be obtained.
In the centrifugation process of the step (2), the supernatant liquid free from coarse particles after the centrifugation is collected. The sediment containing coarse particles remains on the side wall of the centrifuge or the bottom of the centrifuge tube. Therefore, when recovering the supernatant, a careful operation is required so as not to collect the separated coarse particles. As this operation method, for example, the supernatant portion is gradually recovered in several times, the particle size of each recovered portion is measured and it is confirmed that coarse particles are not contained, and then the supernatant liquid divided and recovered again is collected. And the like.
There are no particular limitations on the centrifuge that can be used. For example, the centrifugal sedimentation tube type described in Maruzen Co., Ltd., published by Chemical Society of Japan, “Chemical Equipment Handbook”, Second Revised Second Edition (see page 798), etc. , Cylindrical type, separator plate type, basket type, screw decanter type and the like. Among these, a cylindrical centrifuge is preferable from the viewpoint that the supernatant liquid can be discharged continuously together with operability such as easy washing at the time of product changeover, and thus efficient centrifugation is possible. .
Examples of commercially available cylindrical centrifuges include KS type manufactured by Kansai Centrifuge Co., Ltd. and ASM type centrifuge manufactured by Sakai Kogyo Co., Ltd.

The operation method of the centrifuge includes (i) a continuous type in which the separation liquid layer is discharged while supplying the raw liquid dispersion, and (ii) the separation liquid layer is formed after the supply of the raw liquid dispersion. Any of the batch operation methods for discharging the liquid layer may be used. From the viewpoint that a dispersion containing no coarse particles is continuously obtained, the operation method using the continuous centrifuge of (i) is preferable.
Factors that determine the processing conditions for centrifugation include centrifugal acceleration (G) and centrifugation processing time (min). Of these, the centrifugal acceleration uses a value obtained by dividing the a value obtained based on Equation (4) by the gravitational acceleration (9.8 m / s ² ).
a [m / s ² ] = N ² × π ² × r / 900 (4)
[In the formula, N represents the rotational speed (min ⁻¹ ), r represents the rotational radius (m), and π represents the circumference]
The product of the centrifugal acceleration and the treatment time is preferably 300,000 to 30 million G · min, preferably 500,000 to 250,000,000 as the centrifugal separation condition capable of removing coarse particles of 100 nm or more from the dispersion in the viscosity range. G · min is more preferable, and 1 million to 20 million G · min is more preferable.
From the viewpoint that the contrast ratio tends to be higher when the amount of coarse particles of 100 nm or more after the completion of the step (2) is less, the cumulative amount of coarse particles in the volume average particle size distribution is preferably 5% or less, more preferably 3% or less. 1% or less is more preferable. The lower limit is not particularly limited, but is preferably 0.01% or more from the viewpoint of productivity and storage stability.

[Step (3)]
In step (3), the pigment dispersion obtained in step (2) is subjected to a cross-flow filtration treatment (i) using a microfiltration membrane of 100 μm or less or an ultrafiltration membrane having a molecular weight cut off of 100,000 or more. Purify the pigment dispersion by re-dispersing the solid content obtained by purifying the pigment dispersion by centrifuging or subjecting it to centrifugation (ii) under conditions of 50 million G · min or more. It is a process to do. By this cross flow filtration treatment (i) or centrifugal separation treatment (ii), the content of the unstable water-insoluble dispersant not adsorbed on the pigment generated in step (1) and step (2) can be reduced. And a pigment dispersion having a low viscosity and good storage stability can be obtained.
In the step (2), when an organic solvent is added and diluted to increase the centrifugal separation efficiency, the organic solvent can be removed by performing the step (3), and the solid content of the pigment dispersion is optimized. It is also possible to adjust the concentration.
The solid content of the pigment dispersion obtained in the step (3) is preferably higher than the solid content of the pigment dispersion obtained in the step (2).

(Cross flow filtration (i))
The unstable water-insoluble dispersant that is not adsorbed to the pigment can be removed by circulating the pigment dispersion through the cross-flow filter by the cross-flow filtration treatment (i). The pore size of the filtration membrane used for the cross-flow filtration treatment (i) is set to a size that allows the water-insoluble dispersant in the pigment dispersion to permeate and does not permeate the pigment in the pigment dispersion.
The pore size of the microfiltration membrane (MF membrane) is 100 nm (0.1 μm) or less, preferably 80 nm (0.08 μm) or less, more preferably 50 nm (0.05 μm) or less. In the ultrafiltration membrane (UF membrane), the molecular weight cutoff is 100,000 or more, preferably 100,000 to 1,000,000, more preferably 100,000 to 800,000, and still more preferably 100,000 to 500,000.
The filtration membrane used is not particularly limited as long as it does not deteriorate depending on the organic solvent and the use temperature. For example, inorganic films using alumina, zirconia, titania, etc. as base materials, metal films using 304 and 316 stainless steel as base materials, cellulose, bleached cotton, polysulfone (PS), polypropylene (PP), polyethersal Examples thereof include polymer films using von (PES), polyethylene terephthalate (PET), polyvinylidene fluoride (PVDF), polycarbonate (PCTE), polytetrafluoroethylene (PTFE) and the like as a base material. Among these, an inorganic film, a polysulfone (PS) film, a polytetrafluoroethylene (PTFE) film, and a polyethersulfone (PES) film are preferable, and a polyethersulfone (PES) film is more preferable.

Examples of the shape of the membrane include a tube type, a flat plate type, a monolith type, and the like, and the method of flowing the dispersion may be an internal pressure filtration method or an external pressure filtration method.
Among the above, a crus flow filtration method using an ultrafiltration membrane is more preferable, and among them, a diafiltration method that performs cross flow filtration while adding an organic solvent is more preferable.
Increasing the filtration temperature reduces the viscosity of the dispersion and increases the filtration efficiency. The filtration temperature may be within the range of application of the membrane to be used and within a range capable of maintaining dispersion stability, preferably 10 to 150 ° C, more preferably 15 to 100 ° C, more preferably 20 to 60 ° C, and more preferably 35 to 35 ° C. More preferred is 60 ° C.

(Centrifuge separation (ii))
Centrifugation treatment (ii) is carried out under a centrifugal separation condition (G · min) stronger than the centrifugation treatment in step (2), whereby the pigment dispersion obtained in step (2) is converted into a liquid component and a solid content. Separated, the formed liquid (supernatant) is removed to recover the solid, and the resulting solid is redispersed to purify the pigment dispersion.
Since water-insoluble dispersants that are not adsorbed to the pigment are present in the liquid (organic solvent), they are not adsorbed to the pigment by removing all or part of the liquid during or after centrifugation. The water-insoluble dispersant can be removed appropriately. The recovered solid content is mainly composed of particles in which the water-insoluble dispersant is adsorbed on the pigment, and becomes a slurry or cake after centrifugation and remains on the side wall or bottom of the centrifuge. Can be recovered. Further, by redispersing the obtained solid content, the pigment aggregate can be further crushed and stabilized. As the organic solvent used in the redispersion treatment, the same organic solvent as used in the step (1) can be used.

The centrifuge that can be used is not particularly limited, and may be the same as or different from the step (2). From the viewpoint of operability such as easy washing at the time of product type change, a cylindrical centrifuge is preferable, and a cylindrical centrifuge that can automatically discharge solids is more preferable. As a commercial item of an automatic discharge cylindrical centrifuge, for example, an AF type manufactured by Sakai Kogyo Co., Ltd. may be mentioned. In addition, from the viewpoint of efficiently recovering solids, a basket-type centrifuge is preferable, a non-porous wall-type centrifuge is more preferable, in particular, as described in JP-A-2003-93811, A basket type centrifuge having a function of inserting a nozzle into the supernatant liquid and discharging the supernatant liquid (skimming function) is preferable because it can perform centrifugal separation efficiently. Examples of commercially available non-perforated wall basket type centrifuges include KBS type manufactured by Kansai Centrifugal Machinery Co., Ltd. and S type centrifuge manufactured by Tanabe Wiltech Co., Ltd.
There is no particular limitation on the operation method of the centrifuge. Either (i) a continuous type in which the separated liquid layer is discharged while supplying the raw liquid dispersion, and (ii) a batch type in which the liquid layer is discharged when the separated liquid layer is formed after supplying the raw liquid dispersion. It may be a driving method. From the viewpoint that the solid content can be separated and recovered efficiently, continuous centrifugal treatment is preferred.
The product (G · min) of the centrifugal acceleration and the processing time is 50 million G · min or more from the viewpoint of reliably separating the dispersion obtained in the step (2) into a liquid and a solid. From the viewpoint of improving the separation processing efficiency and enhancing the durability of the centrifuge, 50 to 500 million G · min is more preferable, and 50 to 200 million G · min is more preferable.
Also in the centrifugal treatment (ii) of the step (3), the same organic solvent used in the step (1) is added to the pigment dispersion obtained in the step (2) in order to increase the efficiency of the centrifugal treatment. Thus, the viscosity of the dispersion can be reduced and the centrifugal separation can be performed.

A homogenizer can be used for the redispersion treatment. The homogenizer reduces the coarse particles (pigment aggregates) by pulverizing the pigment aggregates and suppressing reaggregation by expressing the cavitation phenomenon with its high impact force and instantaneous high pressure. It is believed that the particles can be stabilized.
Examples of the homogenizer include an ultrasonic homogenizer and a high-pressure homogenizer. When using an ultrasonic homogenizer, it is desirable to carry out dispersion treatment after evacuation, defoaming, and deaeration. Moreover, a high-pressure homogenizer is more preferable from the viewpoint of use efficiency of the dispersed energy to be input.
Commercially available high-pressure homogenizers that can be used include those described above.
From the viewpoint of suppressing reaggregation of pigment particles and achieving dispersion stabilization, the dispersion pressure is preferably 20 MPa or more, and more preferably 50 MPa or more. From the same point of view, the number of processing passes is at least 1 pass or more, preferably 3 passes or more, more preferably 5 passes or more. As the operation method for passing, like the media-type disperser in the second step, there are a circulation method and a continuous method, and a continuous method is more preferable from the viewpoint of hardly generating a pass number distribution.
Although the temperature at the time of redispersion processing is not specifically limited, 5-80 degreeC is preferable.

  In step (3), the water-insoluble dispersant not adsorbed on the pigment is removed by the crossflow filtration treatment (i) or the centrifugal separation treatment (ii). From the viewpoint of enhancing the storage stability, the pigment in the dispersion The concentration of the water-insoluble dispersant that is not adsorbed on the surface is preferably 1.8% by weight or less, more preferably 1.5% by weight or less, and even more preferably 1% by weight or less, and there is no unadsorbed dispersant. More preferably. The lower limit is not particularly limited, but is preferably 0.01% by weight or more from the viewpoint of productivity and storage stability. The amount of the dispersant not adsorbed on the pigment can be measured by the method described in the examples.

For the viscosity of the final pigment dispersion obtained in step (3), when cross-flow filtration (i) is used in step (3), by adjusting the amount of organic solvent removed in the filtration step, The viscosity of the dispersion can be adjusted to a desired value. When using the centrifugation (ii), the viscosity is adjusted to the desired viscosity according to the amount of organic solvent added in the redispersion step after the centrifugation. be able to.
Regarding the storage stability such as the particle size change rate and the viscosity change rate, the particle size or viscosity does not change before and after storage of the pigment dispersion. It is preferable from the viewpoint of stabilization. In that respect, the particle size change rate is preferably 1.2 or less, more preferably 1.1 or less, still more preferably 1.0, and the viscosity change rate is preferably 1.5 or less, more preferably 1.3 or less, 1.1 or less is more preferable.

<Pigment dispersion for color filter>
The pigment dispersion for a color filter obtained by the production method of the present invention has a low viscosity, excellent storage stability, and extremely few coarse pigment particles, so that the contrast ratio as a color filter is high. Therefore, it is particularly useful as a coloring composition for a color filter produced by an ink jet method. That is, it can be used as a color filter coloring composition (color resist coloring material) by adding and mixing various binders, polyfunctional monomers, photopolymerization initiators, solvents, additives and the like.
Examples of the binder include a copolymer of (meth) acrylic acid and (meth) acrylic ester, a styrene / maleic anhydride copolymer, a reaction product of a styrene / maleic anhydride copolymer and an alcohol, and the like. Can do. The weight average molecular weight is preferably 5000 to 200,000. The content of the binder is preferably 20 to 80% by weight with respect to the total solid content in the pigment dispersion composition.
Examples of the polyfunctional monomer include (meth) acrylic acid ester, urethane (meth) acrylate, (meth) acrylic acid amide, allyl compound, and vinyl ester having two or more ethylenically unsaturated double bonds. The content of the polyfunctional monomer is preferably 10 to 60% by weight with respect to the total solid content in the pigment dispersion composition.
Examples of the photopolymerization initiator include aromatic ketones, lophine dimers, benzoin, benzoin ethers, and polyhalogens. In particular, a combination of 4,4′-bis (diethylamino) benzophenone and 2- (o-chlorophenyl) -4,5-diphenylimidazole dimer, 4- [pN, N-di (ethoxycarbonylmethyl) -2, 6-di (trichloromethyl) -s-triazine] is preferred. A photoinitiator can be used individually or in combination of 2 or more types. The content of the photopolymerization initiator is preferably 0.2 to 10% by weight with respect to the total solid content in the pigment dispersion composition.

In the following production examples, examples and comparative examples, “parts” and “%” are “parts by weight” and “% by weight” unless otherwise specified.
Measurement of water-insoluble dispersant (hereinafter also referred to as “pigment non-adsorbing dispersant”), solid content, coarse particle amount, and viscosity not adsorbed to the pigment in the pigment dispersions obtained in Examples and Comparative Examples The storage stability (viscosity change rate, particle size change rate) was evaluated by the following method.

(1) Measurement of concentration of non-pigmented dispersant 40 parts of pigment dispersion was diluted with 80 parts of diethylene glycol monobutyl ether acetate (hereinafter referred to as “BCA”; organic solvent) and centrifuged (cooled centrifuge manufactured by Kubota Corporation). 3K30C) was centrifuged for 24 hours (79,200,000 G · min) at 55,000 G (rotor: S12158), and then the solid content in the supernatant was measured by the following method.
The supernatant liquid is precisely weighed in an aluminum cup, and the solid content in the supernatant liquid is obtained from the following formula (5) from the total weight after drying in a vacuum oven at 150 ° C. for 12 hours.
Solid content in supernatant (% by weight) = [(total weight after drying−aluminum cup weight) / (sample weight before drying)] × 100 (5)
From the solid content of the supernatant, the pigment non-adsorbed dispersant concentration can be calculated from the following equation.
Non-pigmented dispersant concentration (% by weight) = solid content in the supernatant liquid × 3 (6)

(2) Measurement of coarse particle amount The particle size distribution of the pigment dispersion was measured using a Zeta Sizer (particle size, zeta potential, molecular weight measuring device) manufactured by Malvern, and the cumulative particle size distribution of 100 nm or more was determined as the coarse particle amount ( Volume%).
(3) Measurement of viscosity The viscosity was measured using an E-type viscometer [measurement temperature: 20 ° C., measurement time: 1 minute, rotation speed: 20 rpm, standard rotor (1 ° 34 ′ × R24)].
(4) Evaluation of viscosity stability The viscosity immediately after preparing the target pigment dispersion (pigment dispersion obtained in step (3)) (before storage) was measured according to (3) above. Similarly, the viscosity of the pigment dispersion after storage at 40 ° C. for 1 week was measured, and the viscosity change before and after storage was compared to obtain the rate of change in viscosity by the following formula (7). evaluated.
Viscosity change rate = viscosity after 1 week storage / viscosity immediately after preparation (before storage) (7)
(5) Evaluation of particle size stability The particle size immediately after preparation of the target pigment dispersion (pigment dispersion obtained in step (3)) (before storage) is the same as the above-mentioned Zeta Sizer manufactured by Malvern. It measured using. Similarly, the average particle diameter (D50) after storing the pigment dispersion at 40 ° C. for one week was measured, and the change of the average particle diameter (D50) before and after storage was compared, and the following calculation formula (8) Was used to determine the rate of change in particle size and storage stability was evaluated.
Change rate of particle size = average particle size after storage for 7 days / average particle size immediately after preparation (before storage) (8)

Production Example 1 (Production of polymer dispersant)
In a reaction vessel equipped with a nitrogen introduction tube, 50 parts of methyl methacrylate, 25 parts of BCA, and 5 parts of 3-mercaptopropionic acid (chain transfer agent) were weighed and heated to 75 ° C. while being sealed with nitrogen. Next, a mixture of 200 parts of methyl methacrylate, 100 parts of BCA, 16.7 parts of the chain transfer agent, and 2 parts of 2,2′-azobis (2,4-dimethylvaleronitrile) (polymerization initiator) was added dropwise over 3 hours. did. Thereafter, a mixture of 125 parts of BCA, 0.9 part of the chain transfer agent and 2 parts of the polymerization initiator was added dropwise over 1 hour, and further aged for 2 hours. The number average molecular weight was 2,080 and the weight average molecular weight was 3,350. A methyl methacrylate macromer precursor was synthesized.
Subsequently, the nitrogen introduction tube was switched to an air introduction tube, and air was blown into the obtained macromer precursor with a gas pump. 23.3 parts of glycidyl methacrylate, 7.9 parts of tetrabutylammonium bromide, 0.8 parts of p-methoxyphenol And 17 parts of BCA were added and reacted at 90 ° C. for 10 hours to obtain a methyl methacrylate macromer having a number average molecular weight of 2,200, a weight average molecular weight of 3,500, and a solid content of 60%.

In a reaction vessel equipped with a nitrogen introduction tube, 10 parts of BCA was measured, and the temperature was raised to 80 ° C. while sealing with nitrogen. 72.5 parts of methyl methacrylate macromer obtained in this reaction vessel as a solid content, 12.8 parts of N-vinyl-2-pyrrolidone, 14.7 parts of 2-hydroxyethyl methacrylate, 230 parts of a mixed solution of 120 parts of BCA, 2 parts of the polymerization initiator and 0.4 part of 2-mercaptoethanol (chain transfer agent) are added dropwise over 2 hours, and after completion of the addition, the reaction is further performed for 3 hours to obtain a graft polymer having a solid content of 40% (polymer dispersion). Agent) solution.
As a result of measuring polystyrene as a standard substance by gel chromatography (GPC) method of the obtained dispersant, it was number average molecular weight (Mn) 5,200 and weight average molecular weight (Mw) 28,000.

Example 1
(1) Production of Pigment Dispersion (1) Diketopyrrolopyrrole pigment (A) (Ciba Specialty Chemicals, CI Pigment Red 254, trade name “IRGAPHOR BK-CF”, average primary 10 parts of particle size 30 nm (catalog value)), 67.5 parts of BCA, 22.5 parts of the polymer dispersant (40%) obtained in Production Example 1 and 200 parts of φ0.3 mm zirconia beads are placed in a polybin and pre-dispersed. Shake for 3 hours in a paint shaker (manufactured by Iwata Tekko Co., Ltd.) as a processing step, and then add 80 parts of the dispersion and 160 parts of zirconia beads of φ0.05 mm to a polybin. The mixture was shaken for 24 hours to obtain a pigment dispersion (1) (viscosity: 20 mPa · s).
(2) Production of pigment dispersion (2) 80 parts of the obtained pigment dispersion (1) were put into a centrifugal settling tube (rotor: S12158), and a centrifugal separator (manufactured by Kubota Corporation, cooling centrifuge 3K30C). Was centrifuged for 1 hour under the conditions of a temperature of 20 ° C. and 20,000 G. Confirm that sediment is visually observed. Thereafter, only the supernatant was slowly recovered so as not to mix the settled solids, thereby obtaining a pigment dispersion (2).
(3) Production of pigment dispersion (3) A pigment dispersion obtained by diluting 40 parts of the obtained pigment dispersion (2) with 80 parts of BCA was placed in a centrifugal settling tube (rotor: S12159), and the same centrifugal separator as above. After centrifugation at a temperature of 20 ° C. and 55,000 G for 24 hours, the supernatant (the supernatant was visually transparent) was discarded to obtain a sediment.
BCA is added to the obtained sediment so that the dispersion is 40 parts, and re-dispersion treatment is performed by ultrasonic irradiation using an ultrasonic homogenizer (SILENTSONIC UT-204, manufactured by Sharp Corporation) to disperse the pigment. A body (3) (viscosity: 16 mPa · s) was obtained. The evaluation results are shown in Table 1.

Example 2
(1) Production of pigment dispersion (4) Diketopyrrolopyrrole pigment (A) (Ciba Specialty Chemicals, CI Pigment Red 254, trade name “IRGAPHOR BK-CF”, average primary (Particle size 30 nm (catalog value)) 12.1 parts, BCA 60.7 parts, polymer dispersant (40%) 27.3 parts obtained in Production Example 1 and φ0.3 mm zirconia beads 200 parts are put in a polybin. Shake for 3 hours in a paint shaker (manufactured by Iwata Tekko Co., Ltd.) as a preliminary dispersion treatment step, and then add 80 parts of the dispersion and 160 parts of zirconia beads having a diameter of 0.05 mm to a polybin. The mixture was shaken with a shaker for 24 hours to obtain a pigment dispersion (4) (viscosity: 40 mPa · s).
(2) Production of Pigment Dispersion (5) 80 parts of the obtained pigment dispersion (4) was put in a centrifugal settling tube (rotor: S12159), and a centrifuge (manufactured by Kubota Corporation, cooling centrifuge 3K30C). Was centrifuged for 5.5 hours under the conditions of a temperature of 20 ° C. and 38,000 G. Confirm that sediment is visually observed. Thereafter, only the supernatant was slowly recovered so that the precipitated solid content was not mixed to obtain a pigment dispersion (5).
(3) Production of Pigment Dispersion (6) A pigment dispersion obtained by diluting 40 parts of the obtained pigment dispersion (5) with 80 parts of BCA was used at the temperature of 20 ° C. and 55,000 G using the same centrifuge. After centrifugation for 48 hours under the conditions, the supernatant (the supernatant was visually transparent) was discarded to obtain a sediment.
BCA is added to the obtained sediment so that the dispersion is 40 parts, and re-dispersion treatment is performed by ultrasonic irradiation using an ultrasonic homogenizer (SILENTSONIC UT-204, manufactured by Sharp Corporation) to disperse the pigment. A body (6) (viscosity: 22 mPa · s) was obtained. The evaluation results are shown in Table 1.

Example 3
(1) Production of pigment dispersion (7) Centrifugal sedimentation of a dispersion (viscosity: 5 mPa · s) obtained by diluting 40 parts of the pigment dispersion (1) obtained in Example 1 (1) with 40 parts of BCA It put into the pipe | tube (rotor: S12158), and it centrifuged for 0.25 hours on the conditions of temperature 20 degreeC and 20,000G using the centrifuge (the Kubota Corporation make, cooling centrifuge 3K30C). Confirm that sediment is visually observed. Thereafter, only the supernatant was slowly recovered so that the precipitated solid content was not mixed to obtain a pigment dispersion (7).
(2) Production of Pigment Dispersion (8) 80 parts of the obtained pigment dispersion (7) was placed in a centrifugal settling tube (rotor: S12159), and using the same centrifuge as described above, the temperature was 20 ° C., 55 After centrifuging for 18 hours under the condition of 1,000,000 G, the supernatant (the supernatant is visually transparent) was discarded to obtain a sediment.
BCA is added to the obtained sediment so that the dispersion is 40 parts, and re-dispersion treatment is performed by ultrasonic irradiation using an ultrasonic homogenizer (SILENTSONIC UT-204, manufactured by Sharp Corporation) to disperse the pigment. A body (8) (viscosity: 13 mPa · s) was obtained. The evaluation results are shown in Table 1.

Example 4
(1) Production of Pigment Dispersion (9) 80 parts of the pigment dispersion (1) obtained in Example 1 (1) above was added to a basket type centrifuge (KBS-10, manufactured by Kansai Centrifuge Co., Ltd.). ) Was centrifuged for 13 hours under the condition of 1,500 G. Thereafter, a pigment dispersion (9) was obtained in which only the supernatant was slowly skimmed and recovered so that the settled solid content was not mixed.
(2) Production of Pigment Dispersion (10) A pigment dispersion obtained by diluting 40 parts of the obtained pigment dispersion (9) with 80 parts of BCA was used as a continuous centrifuge (manufactured by Kansai Centrifuge Co., Ltd., KS- 1-L), after centrifugation at 20,000 G for 50 hours, the rotation was stopped, the supernatant was discarded, and the sediment deposited inside the rotor was collected.
BCA is added to the obtained sediment so that the dispersion is 40 parts, and re-dispersion treatment is performed by ultrasonic irradiation using an ultrasonic homogenizer (SILENTSONIC UT-204, manufactured by Sharp Corporation) to disperse the pigment. A body (10) (viscosity: 17 mPa · s) was obtained. The evaluation results are shown in Table 1.

Comparative Example 1
(1) Production of Pigment Dispersion (11) Diketopyrrolopyrrole Pigment (A) (Ciba Specialty Chemicals Co., Ltd., CI Pigment Red 254, trade name “IRGAPHOR BK-CF”, average primary 5 parts of particle size 30 nm (catalog value)) 83.75 parts of BCA, 11.25 parts of polymer dispersant (40%) obtained in Production Example 1 and 200 parts of φ0.3 mm zirconia beads are placed in a polybin and pre-dispersed. Shake for 3 hours in a paint shaker (manufactured by Iwata Tekko Co., Ltd.) as a processing step, and then add 80 parts of the dispersion and 160 parts of zirconia beads of φ0.05 mm to a polybin. The mixture was shaken for 24 hours to obtain a pigment dispersion (11) (viscosity: 6 mPa · s).
(2) Production of pigment dispersion (12) 80 parts of the pigment dispersion (11) obtained were put into a centrifugal settling tube (rotor: S12158), and a centrifuge (manufactured by Kubota Corporation, cooling centrifuge 3K30C). Was centrifuged at 20,000 G under the conditions of a temperature of 20 ° C. and 20,000 G for 0.25 hour. Confirm that sediment is visually observed. Thereafter, only the supernatant liquid was slowly recovered so as not to mix the precipitated solid content, thereby obtaining a pigment dispersion (12).
(3) Production of Pigment Dispersion (13) 80 parts of the pigment dispersion (12) obtained were put into a centrifugal settling tube (rotor: S12159), and the same centrifuge as described above was used. After centrifuging for 18 hours under the condition of 1,000,000 G, the supernatant (the supernatant is visually transparent) was discarded to obtain a sediment.
BCA is added to the obtained sediment so that the dispersion is 40 parts, and re-dispersion treatment is performed by ultrasonic irradiation using an ultrasonic homogenizer (SILENTSONIC UT-204, manufactured by Sharp Corporation) to disperse the pigment. A body (13) (viscosity: 19 mPa · s) was obtained. The evaluation results are shown in Table 1.

Comparative Example 2
(1) Production of Pigment Dispersion (14) 80 parts of the pigment dispersion (1) obtained in Example 1 (1) above was placed in a centrifugal settling tube (rotor: S12158) and a centrifuge (Kubota Co., Ltd.). Using a cooling centrifuge 3K30C manufactured by Seisakusho, centrifugation was performed for 1 hour under conditions of a temperature of 20 ° C. and 2500 G. As a result of visual confirmation, no sediment was confirmed. What was collect | recovered from the centrifugal settling tube was made into the pigment dispersion liquid (14).
(2) Production of Pigment Dispersion (15) A pigment dispersion obtained by diluting 40 parts of the obtained pigment dispersion (14) with 80 parts of BCA was placed in a centrifugal settling tube (rotor: S12159), and the same centrifugal separation as described above. Using a machine, the mixture was centrifuged for 24 hours under conditions of a temperature of 20 ° C. and 55,000 G, and then the supernatant (the supernatant was visually transparent) was discarded to obtain a sediment.
BCA is added to the obtained sediment so that the dispersion is 40 parts, and re-dispersion treatment is performed by ultrasonic irradiation using an ultrasonic homogenizer (SILENTSONIC UT-204, manufactured by Sharp Corporation) to disperse the pigment. A body (15) (viscosity: 16 mPa · s) was obtained. The evaluation results are shown in Table 1.

Comparative Example 3
(1) Production of Pigment Dispersion (16) A pigment dispersion obtained by diluting 40 parts of the pigment dispersion (2) obtained in Example 1 (2) above with 80 parts of BCA was centrifuged into a settling tube (rotor: S12158). And centrifuged for 1 hour under the conditions of a temperature of 20 ° C. and 20,000 G using the same centrifuge as described above. A clear supernatant layer was not formed and almost no sediment was formed. Since almost no sediment was generated, the sediment was collected together with the pigment dispersion, and redispersed by ultrasonic irradiation using an ultrasonic homogenizer (manufactured by Sharp Corporation, SILENTSONIC UT-204). (16) (Viscosity: 4 mPa · s) was obtained. Since the supernatant could not be discarded with this dispersion, the concentration of the final dispersion was considerably thin at 5.8%. The evaluation results are shown in Table 1.

  From Table 1, the pigment dispersions of Examples 1 to 4 have less coarse particles of 100 nm or more than the pigment dispersions of Comparative Examples 1 to 3, the amount of non-pigmented dispersant is small, and the viscosity after storage. It can be seen that the rate of change and the rate of change in particle size are small and the storage stability is excellent.

Example 5
(1) Production of Pigment Dispersion (17) A pigment dispersion obtained by diluting 100 parts of the pigment dispersion (2) obtained in Example 1 (2) above with 100 parts of BCA was converted into an ultrafiltration membrane device (Millipore Corporation, Using Pericon II, Biomax, material: PES, molecular weight cut off 500,000, membrane area 0.1 m ² ), the permeate side is first returned to the circulating fluid side until the permeate becomes transparent visually. After confirming that the sample becomes transparent, a sample for measuring the concentration of the non-pigmented dispersant is continuously fed from the circulating fluid side while performing cross-flow filtration using a diafiltration method in which BCA is continuously dropped at the same flow rate as the permeation flow rate. Sampled with a dropper. The pigment non-adsorbed dispersant concentration was appropriately measured, and the filtration was continued until the non-adsorbed dispersant concentration on the permeate side became almost zero. Thereafter, the dropping of BCA was stopped, and filtration was performed until the amount of permeated liquid of BCA reached 100 parts to obtain a pigment dispersion (17) (viscosity: 16 mPa · s) on the circulating liquid side. The evaluation results are shown in Table 2.

Example 6
(1) Production of Pigment Dispersion (18) Pigment dispersion obtained by diluting 100 parts of pigment dispersion (5) obtained in Example 2 (2) above with 200 parts of BCA was used as an ultrafiltration membrane device (manufactured by Millipore). , Pericon II, Biomax, material: PES, molecular weight cut off 500,000, membrane area 0.1 m ² ), until the concentration of the unadsorbed dispersant on the permeate side becomes almost zero as in Example 5. Filtration was continued. Thereafter, dropping of BCA was stopped, and filtration was performed until the amount of permeated liquid of BCA reached 200 parts, and a pigment dispersion (18) (viscosity: 23 mPa · s) on the circulating liquid side was obtained. The evaluation results are shown in Table 2.

Example 7
(1) Production of Pigment Dispersion (19) 200 parts of the pigment dispersion (7) obtained in Example 3 (1) above was subjected to ultrafiltration membrane device (Millipore, Pericon II, Biomax, Material: PES). In the same manner as in Example 5, filtration was continued until the concentration of the unadsorbed dispersant on the permeate side became almost zero, using a molecular weight cut-off of 500,000 and a membrane area of 0.1 m ² ). Thereafter, dropping of BCA was stopped, and filtration was performed until the amount of permeated liquid of BCA reached 100 parts to obtain a circulating liquid side pigment dispersion (19) (viscosity: 16 mPa · s). The evaluation results are shown in Table 2.

Example 8
(1) Production of Pigment Dispersion (20) 80 parts of the pigment dispersion (1) obtained in Example 1 (1) above was added to a continuous centrifuge (manufactured by Kansai Centrifuge Co., Ltd., KS-1). -L) was centrifuged at 18,000 G for 1 hour. Thereafter, the rotation was stopped and the supernatant was recovered to obtain a pigment dispersion (20).
(2) Production of Pigment Dispersion (21) A pigment dispersion obtained by diluting 100 parts of the obtained pigment dispersion (20) with 100 parts of BCA was used as an ultrafiltration membrane device (Millipore, Pericon II, Biomax, material: Using PES, a molecular weight cut-off of 500,000, and a membrane area of 0.1 m ² ), filtration was continued until the concentration of the unadsorbed dispersant on the permeate side became almost zero, as in Example 5. Thereafter, dropping of BCA was stopped, and filtration was performed until the amount of permeated liquid of BCA reached 100 parts to obtain a circulating liquid-side pigment dispersion (21) (viscosity: 18 mPa · s). The evaluation results are shown in Table 2.

Example 9
(1) Production of Pigment Dispersion (22) A pigment dispersion obtained by diluting 100 parts of the pigment dispersion (20) obtained in Example 8 (1) above with 100 parts of BCA was used as an ultrafiltration membrane device (manufactured by Millipore). , Pericon II, Biomax, material: PES, molecular weight cut off 500,000, membrane area 0.1 m ² ), until the concentration of the unadsorbed dispersant on the permeate side becomes almost zero as in Example 5. Filtration was continued. Thereafter, dropping of BCA was stopped, and filtration was performed until the amount of permeated liquid of BCA reached 100 parts to obtain a circulating liquid-side pigment dispersion (22) (viscosity: 16 mPa · s). At this time, the dispersion temperature was raised to 40 ° C. (actual measurement was 43 ° C.), followed by filtration. The evaluation results are shown in Table 2.

Example 10
(1) Production of Pigment Dispersion (23) A pigment dispersion obtained by diluting 100 parts of the pigment dispersion (20) obtained in Example 8 (1) above with 100 parts of BCA was used as a microfiltration membrane device (manufactured by Tetratec Corporation). In the same manner as in Example 5, the filtration was continued until the concentration of the unadsorbed dispersant on the permeate side became substantially zero, using PTFE, pore diameter 0.05 μm, membrane area 0.05 m ² ). At this time, the permeate side was not transparent, and was very light red (light pink). Thereafter, dropping of BCA was stopped, and filtration was performed until the amount of permeated liquid of BCA reached 100 parts to obtain a circulating liquid-side pigment dispersion (23) (viscosity: 15 mPa · s). The evaluation results are shown in Table 2.

Example 11
(1) Production of pigment dispersion (24) 67.5 parts of BCA and 22.5 parts of the polymer dispersant (40%) obtained in Production Example 1 were mixed with a homomixer (manufactured by IKA Japan, Ultra Turrax) While stirring at 17,000 rpm, 10 parts of diketopyrrolopyrrole pigment (manufactured by Ciba Specialty Chemicals Co., Ltd., PR254: trade name “IRGAPHOR BT-CF”) was added as a pigment, and stirred for 30 minutes. The primary preliminary dispersion was obtained by mixing.
The resulting mixture was stirred with a dyno mill (manufactured by Shinmaru Enterprises Co., Ltd., trade name, model 0.6 L-ECM) filled with zirconia beads having a diameter of 0.3 mm and a stirring peripheral speed of 8 m / s, and a residence time. Under a condition of 5 minutes, 3 passes were processed by a continuous method to disperse coarse particles of several μm, and a secondary preliminary dispersion was obtained.
Next, an ultra apex mill filled with φ0.05 mm zirconia beads (filling rate 64 vol%) (internal volume 0.17 L, manufactured by Kotobuki Kogyo Co., Ltd., trade name of media-type disperser, model UAM-05) was stirred. Under the conditions of a speed of 6 m / s and a residence time of 0.6 minutes, 50-pass main dispersion treatment was performed by a continuous method to obtain a pigment dispersion (24) (viscosity: 25 mPa · s).
(2) Production of Pigment Dispersion (25) Using 80 parts of the obtained pigment dispersion (24), a continuous centrifuge (manufactured by Kansai Centrifuge Co., Ltd., KS-1-L) was used. Centrifugation treatment was performed for 1 hour under the condition of 1,000 G. Thereafter, the rotation was stopped and the supernatant was collected to obtain a pigment dispersion (25).
(3) Production of Pigment Dispersion (26) A pigment dispersion obtained by diluting 100 parts of the obtained pigment dispersion (25) with 100 parts of BCA was used as an ultrafiltration membrane device (Millipore, Pericon II, Biomax, Material : PES, molecular weight cut off 500,000, membrane area 0.1 m ² ), and filtration was continued until the concentration of the unadsorbed dispersant on the permeate side became almost zero as in Example 5. Thereafter, dropping of BCA was stopped, and filtration was performed until the amount of permeated liquid of BCA reached 100 parts to obtain a pigment dispersion (26) (viscosity: 17 mPa · s) on the circulating liquid side. The evaluation results are shown in Table 2.

Comparative Example 4
(1) Production of Pigment Dispersion (27) 200 parts of Pigment Dispersion (12) obtained in Comparative Example 1 (2) above was subjected to ultrafiltration membrane device (Millipore, Pericon II, Biomax, Material: PES). Using a molecular weight cut off of 500,000 and a membrane area of 0.1 m ² ), the permeate side was first returned to the circulating liquid side until the permeate became transparent visually, and after confirming that the permeate became transparent, A sample for measuring the pigment non-adsorbed dispersant concentration was continuously sampled with a dropper from the circulating liquid side while performing cross-flow filtration by a diafiltration method in which BCA was continuously dropped at the same flow rate as the permeation flow rate. The pigment non-adsorbed dispersant concentration was appropriately measured, and the filtration was continued until the non-adsorbed dispersant concentration on the permeate side became almost zero. Thereafter, dropping of BCA was stopped, and filtration was performed until the amount of permeated liquid of BCA reached 100 parts, whereby a pigment dispersion (27) (viscosity: 23 mPa · s) on the circulating liquid side was obtained. The evaluation results are shown in Table 2.

Comparative Example 5
(1) Production of Pigment Dispersion (28) Diketopyrrolopyrrole pigment (A) (Ciba Specialty Chemicals, Inc., CI Pigment Red 254, trade name “IRGAPHOR BK-CF”, average primary Particle size 30 nm (catalog value) 21 parts, BCA 31.75 parts, polymer dispersant (40%) 47.25 parts obtained in Production Example 1 and φ0.3 mm zirconia beads 200 parts are placed in a polybin and pre-dispersed. Shake for 3 hours in a paint shaker (manufactured by Iwata Tekko Co., Ltd.) as a processing step, and then add 80 parts of the dispersion and 160 parts of zirconia beads of φ0.05 mm to a polybin. Shake for 24 hours. A pigment dispersion (28) (viscosity: 60 mPa · s) having a solid content of 40.0% (pigment concentration: 21.0%, dispersant: 19.0%) was obtained.
(2) Production of Pigment Dispersion (29) 80 parts of the obtained pigment dispersion (28) was put into a centrifugal settling tube (rotor: S12159), and a centrifuge (manufactured by Kubota Corporation, cooling centrifuge 3K30C). Was centrifuged for 25 hours under the conditions of a temperature of 20 ° C. and 20,000 G. Confirm that sediment is visually observed. Thereafter, only the supernatant liquid was slowly recovered so as not to mix the precipitated solid content, thereby obtaining a pigment dispersion (29).
(3) Production of Pigment Dispersion (30) A pigment dispersion obtained by diluting 100 parts of the obtained pigment dispersion (29) with 100 parts of BCA was used as an ultrafiltration membrane device (Millipore, Pericon II, Biomax, Material : Using PES, molecular weight cut-off 500,000, membrane area 0.1 m ² ), the permeate side is first returned to the circulating liquid side until the permeate is visually transparent, and the permeate is confirmed to be transparent. Thereafter, a sample for measuring the pigment non-adsorbed dispersant concentration was continuously sampled with a dropper from the circulating liquid side while performing cross-flow filtration with a diafiltration method in which BCA was continuously dropped at the same flow rate as the permeation flow rate. The pigment unadsorbed dispersant concentration was appropriately measured, and an attempt was made to continue the filtration until the concentration of the unadsorbed dispersant on the permeate side became substantially zero. However, the filtration treatment time was about 3 times that of Example 5, and was stopped. Thereafter, dropping of BCA was stopped, and filtration was performed until the amount of permeated liquid of BCA reached 100 parts to obtain a pigment dispersion (30) (viscosity: 41 mPa · s) on the circulating liquid side. Since the viscosity of the final dispersion was considerably high, the filter membrane was easily clogged. The evaluation results are shown in Table 2.

Comparative Example 6
(1) Production of Pigment Dispersion (31) A pigment dispersion obtained by diluting 100 parts of the pigment dispersion (2) obtained in Example 1 (2) above with 100 parts of BCA was used as an ultrafiltration membrane device (manufactured by Millipore). , Pericon II, Biomax, Material: PES, molecular weight cut off 50,000, membrane area 0.1 m ² ), the permeate side is returned to the circulating fluid side until the permeate becomes transparent at first. After confirming that the liquid is transparent, continuously circulate the sample for measuring the concentration of non-pigmented dispersant while performing cross-flow filtration using a diafiltration method that continuously drops BCA at the same flow rate as the permeation flow rate. Sampling was performed from the liquid side with a dropper. The pigment non-adsorbed dispersant concentration was appropriately measured, and the filtration was continued until the non-adsorbed dispersant concentration on the permeate side became almost zero. Thereafter, dropping of BCA was stopped, and filtration was performed until the amount of permeated liquid of BCA reached 100 parts to obtain a circulating liquid-side pigment dispersion (31) (viscosity: 22 mPa · s). The evaluation results are shown in Table 2.

Comparative Example 7
(1) Production of pigment dispersion (32) 200 parts of pigment dispersion (7) obtained in Example 3 (1) above were collected using a rotary evaporator until the recovered BCA amount reached 100 parts. The BCA solvent was removed (topping) to obtain a pigment dispersion (32) (viscosity: 20 mPa · s). The evaluation results are shown in Table 2.

  From Table 2, the pigment dispersions of Examples 5 to 11 have fewer coarse particles of 100 nm or more, less pigment non-adsorbed dispersant, and viscosity after storage than the pigment dispersions of Comparative Examples 4 to 7. It can be seen that the rate of change and the rate of change in particle size are small and the storage stability is excellent.

  According to the present invention, it is possible to efficiently produce a pigment dispersion for a color filter having a low viscosity, excellent storage stability, and extremely few coarse pigment particles. Moreover, since the obtained pigment dispersion for color filters is excellent in heat resistance and contrast ratio, it can be suitably used as a color material for color filters such as liquid crystal display elements and solid-state imaging elements.

Claims (6)

The manufacturing method of the pigment dispersion for color filters which has following process (1)-(3).
Step (1): Step of obtaining a pigment dispersion having a viscosity of 10 to 55 mPa · s by dispersing a mixed solution containing an organic pigment, a water-insoluble dispersant, and an organic solvent. Step (2): Step (1) Step of obtaining the pigment dispersion by centrifuging the pigment dispersion obtained in step 300 to 30 million G · min. Step (3): To the pigment dispersion obtained in step (2) , Purifying the pigment dispersion by applying a cross-flow filtration treatment (i) using a microfiltration membrane of 100 μm or less or an ultrafiltration membrane with a molecular weight cut off of 100,000 or more The manufacturing method of the pigment dispersion for color filters which has following process (1), (2-1), (2-2), and (3-2) .
Step (1): A step of obtaining a pigment dispersion having a viscosity of 10 to 55 mPa · s by dispersing a mixed solution containing an organic pigment, a water-insoluble dispersant, and an organic solvent.
Step (2-1): Step of obtaining a pigment dispersion in which an organic solvent is added to the pigment dispersion obtained in Step (1) and the viscosity is adjusted to a range of 3 to 40 mPa · s.
Step (2-2): A step of obtaining a pigment dispersion by subjecting the pigment dispersion obtained in the step (2-1) to a centrifugal separation treatment under conditions of 300,000 to 30 million G · min.
Step (3-2): Cross flow filtration treatment (i) using a microfiltration membrane of 100 μm or less or an ultrafiltration membrane having a molecular weight cut off of 100,000 or more to the pigment dispersion obtained in Step (2-2). Purifying the pigment dispersion by applying The manufacturing method of the pigment dispersion for color filters of Claim 1 or 2 whose said crossflow filtration process (i) is a diafiltration process. The manufacturing method of the pigment dispersion for color filters in any one of Claims 1-3 whose temperature of the said crossflow filtration process (i) is 35-60 degreeC.   The pigment dispersion for a color filter according to any one of claims 1 to 4, wherein the water-insoluble dispersant is a graft polymer (x), and the weight average molecular weight of the graft polymer (x) is 5,000 to 200,000. Body manufacturing method. Cross flow filtration treatment (i) so that the concentration of the water-insoluble dispersant not adsorbed to the pigment in the pigment dispersion obtained in the step (3) or the step (3-2) is 0.01 to 1.8% by weight. The manufacturing method of the pigment dispersion for color filters of Claim 1 or 2 which gives).