JP7148488B2 - Pigment dispersant, method for producing pigment dispersant, and pigment dispersion - Google Patents

Description

The present invention relates to pigment dispersants, methods of making pigment dispersants, pigment dispersions, and uses of pigment dispersions.

As information equipment, next-generation displays such as liquid crystal displays, organic EL displays, and quantum dot displays have been developed in recent years. In addition, with the rapid development of technology, there is a demand for a color filter, which is a component of a liquid crystal display panel with high image quality and excellent cost performance, and a coloring agent for manufacturing such a color filter. there is Furthermore, for organic EL displays and quantum dot displays, there is a demand for a colorant with excellent pigment dispersibility that can constitute a bank material that divides the pixels of the light-emitting layer.

A pigment dispersion liquid used as a coloring agent, which is a material for manufacturing a color filter or the like, contains extremely fine pigments (pigment fine particles) in a finely dispersed state. Such a pigment dispersion liquid has a high surface tension because the pigment is finely divided, and the pigment tends to aggregate easily. Therefore, it is necessary to devise a pigment dispersion liquid to maintain the dispersion stability of the pigment dispersed in the state of fine particles. For example, there have been proposed various colorants for color filters that use a pigment dispersant with good heat resistance and are easily developed with an alkali (Patent Documents 1 to 3).

JP 2008-298967 A JP 2011-068865 A JP 2013-32441 A

As for colorants for next-generation displays, finer particles of pigments are progressing further. In order to stably exhibit high coloring performance while containing such finely divided pigments, it is necessary to maintain a finely dispersed state without aggregating the pigments even when stored at high temperatures for a long period of time. required to be present. However, it cannot be said that conventional colorants can always satisfy these requirements.

The present invention has been made in view of the problems of the prior art, and its object is to provide a low viscosity, good coloring performance, dispersion stability and long-term storage of the pigment. To provide a pigment dispersant capable of preparing a pigment dispersion having excellent properties and useful as a material for a colorant for color filters. Further, an object of the present invention is to provide a method for producing the above-mentioned pigment dispersant, a pigment dispersion obtained by using the above-mentioned pigment dispersant, and a method for producing an image display device member using this pigment dispersion. to provide use as a coloring agent.

That is, according to the present invention, the following pigment dispersant is provided.
[1] A pigment dispersant that is a polymer that satisfies the following requirements [1] to [3].
[1] A structural unit (1) derived from a monomer 1 represented by the following general formula (1), a structural unit (2) derived from a monomer 2 represented by the following general formula (2), and the following general formula ( It has a structural unit (3) derived from the monomer 3 represented by 3-1) or (3-2).

（前記一般式（１）中、Ｒ_１は水素原子又はメチル基を示し、Ｒ_２は炭素数２～４のアルキレン基を示し、ｎは５～２０の数（平均値）を示す。前記一般式（２）、（３－１）、及び（３－２）中、Ｒ_３は水素原子又はメチル基を示し、Ｒ_４は炭素数２～４のアルキレン基を示す）

(In general formula (1), R ₁ represents a hydrogen atom or a methyl group, R ₂ represents an alkylene group having 2 to 4 carbon atoms, and n represents a number (average value) of 5 to 20. In formulas (2), (3-1), and (3-2), R ₃ represents a hydrogen atom or a methyl group, and R ₄ represents an alkylene group having 2 to 4 carbon atoms.)

[2] The total content of the structural units (1) to (3) is 80% by mass or more, and the content of the structural unit (1) is 50 to 70% by mass.
[3] It has a polystyrene equivalent number average molecular weight of 5,000 to 20,000 and an acid value of 30 to 130 mgKOH/g as measured by gel permeation chromatography.
[2] The pigment dispersant according to [1], which is a polymer composed only of the structural units (1) to (3).
[3] In the general formula (1), R ₁ is a methyl group and R ₂ is an ethylene group, and in the general formulas (2), (3-1) and (3-2), R ₃ is methyl The pigment dispersant according to the above [1] or [2], wherein the group _R4 is an ethylene group.
[4] The pigment dispersant according to any one of [1] to [3], which is used for dispersing a pigment in an aprotic organic solvent having a dielectric constant of 20 or less at room temperature.

Further, according to the present invention, there is provided the following method for producing a pigment dispersant.
[5] A method for producing a pigment dispersant according to any one of [1] to [4], comprising: an aromatic tricarboxylic acid anhydride; reacting moles of said monomer 2 to obtain a monomer mixture containing said monomer 2 and said monomer 3; and reacting said monomer mixture with said monomer 1; is trimellitic anhydride or naphthalenetricarboxylic anhydride.
[6] The method for producing a pigment dispersant according to [5], wherein the aromatic tricarboxylic acid anhydride and the monomer 2 are reacted in an aprotic organic solvent having a dielectric constant of 20 or less at room temperature.
[7] The aromatic tricarboxylic anhydride and the monomer 2 are combined at 30° C. or less using 0.01 to 10 mol % of 4-dimethylaminopyridine as a catalyst with respect to the aromatic tricarboxylic anhydride. The method for producing a pigment dispersant according to [5] or [6], wherein the pigment dispersant is reacted.

Furthermore, according to the present invention, the following pigment dispersion is provided.
[8] A pigment dispersion containing an organic solvent, a pigment, and a pigment dispersant for dispersing the pigment in the organic solvent, wherein the pigment dispersant is any of the above [1] to [4] A pigment dispersion liquid which is the pigment dispersant described above, and the content of the pigment dispersant is 5 to 50 parts by mass with respect to 100 parts by mass of the pigment.
[9] The pigment dispersion according to [8], wherein the organic solvent is an aprotic organic solvent having a dielectric constant of 20 or less at room temperature.
[10] The pigment dispersion according to [8] or [9], which further contains 5 to 20 parts by mass of a dye derivative having a basic group with respect to 100 parts by mass of the pigment.

Further, according to the present invention, use of the pigment dispersion liquid shown below is provided.
[11] Use of the pigment dispersion according to any one of [8] to [10] as a colorant for producing a member for an image display device.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to prepare a pigment dispersion that has low viscosity, exhibits good coloring performance, is excellent in pigment dispersion stability and long-term storage stability, and is useful as a material for colorants for color filters. can provide a pigment dispersant capable of Further, according to the present invention, there are provided a method for producing the pigment dispersant, a pigment dispersion obtained by using the pigment dispersant, and a coloring agent for producing a member for an image display device using the pigment dispersion. provided for use as

Embodiments of the present invention will be described below, but the present invention is not limited to the following embodiments. In addition, unless otherwise specified, various physical property values in this specification are values at room temperature (25° C.).

<Pigment Dispersant>
The pigment dispersant of the present invention is a polymer that satisfies the following requirements [1] to [3]. Details of the pigment dispersant of the present invention are described below.
[1] A structural unit (1) derived from a monomer 1 represented by the following general formula (1), a structural unit (2) derived from a monomer 2 represented by the following general formula (2), and the following general formula ( It has a structural unit (3) derived from the monomer 3 represented by 3-1) or (3-2).

（前記一般式（１）中、Ｒ_１は水素原子又はメチル基を示し、Ｒ_２は炭素数２～４のアルキレン基を示し、ｎは５～２０の数（平均値）を示す。前記一般式（２）、（３－１）、及び（３－２）中、Ｒ_３は水素原子又はメチル基を示し、Ｒ_４は炭素数２～４のアルキレン基を示す）

(In general formula (1), R ₁ represents a hydrogen atom or a methyl group, R ₂ represents an alkylene group having 2 to 4 carbon atoms, and n represents a number (average value) of 5 to 20. In formulas (2), (3-1), and (3-2), R ₃ represents a hydrogen atom or a methyl group, and R ₄ represents an alkylene group having 2 to 4 carbon atoms.)

[2] The total content of the structural units (1) to (3) is 80% by mass or more, and the content of the structural unit (1) is 50 to 70% by mass.
[3] It has a polystyrene equivalent number average molecular weight of 5,000 to 20,000 and an acid value of 30 to 130 mgKOH/g as measured by gel permeation chromatography.

(Requirement [1])
The polymer, which is a pigment dispersant, comprises a structural unit (1) derived from the monomer 1 represented by the general formula (1), a structural unit (2) derived from the monomer 2 represented by the general formula (2), and general It has a structural unit (3) derived from a monomer 3 represented by formula (3-1) or (3-2).

[Constituent unit (1)]
Structural unit (1) is a unit derived from monomer 1 represented by general formula (1) below.

（一般式（１）中、Ｒ_１は水素原子又はメチル基を示し、Ｒ_２は炭素数２～４のアルキレン基を示し、ｎは５～２０の数（平均値）を示す）

(In general formula (1), R ₁ represents a hydrogen atom or a methyl group, R ₂ represents an alkylene group having 2 to 4 carbon atoms, and n represents a number of 5 to 20 (average value).)

Monomer 1 is a so-called macromonomer having a polycaprolactone chain in its molecular structure. That is, since the pigment dispersant of the present invention is a polymer having a polycaprolactone chain introduced into its molecular structure, it dissolves in an organic solvent to cause steric repulsion between particles, thereby finely dispersing the pigment and dispersing it. Stability can be maintained.

The repeating number (n) of the polycaprolactone chain is a value calculated from NMR with a (meth)acryloyl group as 1 mol. For example, the average molecular weight of a polycaprolactone chain when n=5 is 570, and the average molecular weight of a polycaprolactone chain when n=20 is 2,280. If the value of n is less than 5, the steric repulsion will be insufficient and the dispersion stability will be insufficient. On the other hand, when the value of n exceeds 20, the polycaprolactone chain tends to crystallize and become waxy. As a result, the pigment dispersion tends to solidify, and when the temperature of the pigment dispersion drops, the polymer tends to crystallize and precipitate out in some cases. The value of n in general formula (1) is preferably 6-15. That is, the average molecular weight of the polycaprolactone chain is preferably about 700-1,800.

Examples of the group represented by R ₂ in general formula (1) include ethylene, propyne, (methyl)ethylene, butylene, (methyl)propylene, and dimethylethylene. Among them, ethylene, methylethylene and butylene are preferred.

Monomer 1 is produced by, for example, ring-opening polymerization of ε-caprolactone using hydroxyalkyl (meth)acrylate as a starting compound in the presence of a metal compound such as tetrabutyl titanate and tin dilaurate as a catalyst. be able to. After the ring-opening polymerization, the macromonomer solution may be taken out as it is, but since it may solidify in a waxy state, it is preferable to dilute it with an organic solvent to obtain a macromonomer solution without any particular purification.

Examples of hydroxyalkyl (meth)acrylates include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate and the like. .

[Constituent unit (2)]
A structural unit (2) is a unit derived from a monomer 2 represented by the following general formula (2).

（一般式（２）中、Ｒ_３は水素原子又はメチル基を示し、Ｒ_４は炭素数２～４のアルキレン基を示す）

(In general formula (2), R ₃ represents a hydrogen atom or a methyl group, and R ₄ represents an alkylene group having 2 to 4 carbon atoms)

By introducing the structural unit (2) derived from the monomer 2, a high concentration of hydroxyl groups can be introduced into the main chain of the pigment dispersant (polymer). It is believed that this makes it easier for the polymer to adsorb to the pigment through hydrogen bonding. Monomer 2 includes hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. be able to.

[Constituent unit (3)]
Structural unit (3) is a unit derived from monomer 3 represented by general formula (3-1) or (3-2) below.

（一般式（３－１）及び（３－２）中、Ｒ_３は水素原子又はメチル基を示し、Ｒ_４は炭素数２～４のアルキレン基を示す）

(In general formulas (3-1) and (3-2), R ₃ represents a hydrogen atom or a methyl group, and R ₄ represents an alkylene group having 2 to 4 carbon atoms)

By introducing the structural unit (3) derived from the monomer 3, an acidic group (carboxy group) can be introduced into the molecular structure of the pigment dispersant (polymer). That is, since the pigment dispersant of the present invention is a polymer having an acidic group in its molecular structure, it easily adsorbs a pigment (especially a pigment having a basic group) through hydrogen bonding or ionic bonding. In addition, since it is a structural unit derived from the monomer 3 having two carboxy groups in one molecule, and the carboxy groups located at the meta-position and para-position of the ester bond have high acidity, it is a pigment dispersant (polymer). It is possible to reduce the amount of monomer required to obtain the desired acid value. Further, by containing a large amount of the structural unit (3), it is possible to obtain a pigment dispersant having a high acid value and excellent adsorptivity to pigments. Therefore, the pigment dispersant of the present invention is suitable as a dispersant for dispersing a pigment in a medium.

Monomer 3 can be obtained by reacting aromatic tricarboxylic anhydride such as trimellitic anhydride or naphthalenetricarboxylic anhydride with monomer 2 in a low polar solvent. When monomer 3 is a compound obtained by reacting an aromatic tricarboxylic acid anhydride with monomer 2, it is represented by R ₃ and R ₄ in general formulas (3-1) and (3-2). All groups are the same as the groups represented by R ₃ and R ₄ in general formula (2).

Monomer 3 can also be obtained by reacting trimellitic acid or trimellitic acid halide with monomer 2, but it is necessary to use a solvent that dissolves trimellitic acid or trimellitic acid halide, and Purification by removal of halides is also required. Furthermore, when the monomer 2 is used as a solvent for dehydration condensation of trimellitic acid, the monomer 2 may be polymerized by heat or unexpected coloration may occur, so a purification step may be required. Therefore, it is preferable to obtain the monomer 3 by reacting the aromatic tricarboxylic anhydride with the monomer 2 in large excess with respect to the aromatic tricarboxylic anhydride. As a result, the reaction solution containing the monomers 2 and 3 can be directly used in subsequent polymerization reactions without purification.

Trimellitic anhydride forms an anhydride with the 1- and 2-position carboxy groups. Therefore, when trimellitic anhydride and monomer 2 are reacted, a compound represented by the following general formula (3-1-1) may be obtained, or a compound represented by the following general formula (3-1-2) may be obtained. In some cases, the compound obtained is obtained. However, since the 1-carboxy group, which has less steric hindrance, is likely to be esterified, the compound represented by the following general formula (3-1-1) is considered to be the main component. As the monomer 3, a mixture of positional isomers of carboxy groups may be used.

As the monomer 3, 1-[2-(meth)acryloyloxyethyl]-1,2,4-benzenetricarboxylic acid ester, 2-[2-(meth)acryloyloxyethyl]-1,2,4-benzenetricarboxylic acid acid ester, 1-[2-(meth)acryloyloxypropyl]-1,2,4-benzenetricarboxylic acid ester, 2-[2-(meth)acryloyloxypropyl]-1,2,4-benzenetricarboxylic acid ester , 1-[2-(meth)acryloyloxybutyl]-1,2,4-benzenetricarboxylic acid ester, 2-[2-(meth)acryloyloxybutyl]-1,2,4-benzenetricarboxylic acid ester, etc. preferable.

Both R ₁ in general formula (1) and R ₃ in general formulas (2), (3-1) and (3-2) are preferably methyl groups. Further, both R ₂ in general formula (1) and R ₄ in general formulas (2), (3-1) and (3-2) are preferably ethylene groups. In other words, all of monomers 1 to 3 are preferably methacrylate monomers. Methacrylate-based monomers are preferred because they cause relatively little skin irritation and are easy to handle. In addition, methacrylate-based monomers are slightly inferior to acrylate-based monomers in polymerizability, and are therefore preferable because they are unlikely to cause unexpected polymerization due to light or heat. Furthermore, when hydroxyethyl methacrylate is used as the monomer 2, it is preferable because it is easily available as a commercial product and the primary hydroxyl group easily reacts with the aromatic tricarboxylic acid anhydride.

(Requirement [2])
The polymer used as the pigment dispersant has a total content of the structural units (1) to (3) of 80% by mass or more, preferably 90% by mass or more, and particularly preferably 100% by mass. That is, it is particularly preferable that the pigment dispersant (polymer) is a polymer substantially composed only of structural units (1) to (3). In addition, the content of the structural unit (1) in the pigment dispersant (polymer) is 50 to 70% by mass, preferably 55 to 65% by mass. A large number of graft chains can be introduced into the polymer by containing the largest number of structural units (1). As a result, the acidic groups of the main chain are adsorbed to the pigment through ionic bonding or the like, and the numerous graft chains promote repulsion of the pigment particles due to steric hindrance, so that the pigment can be dispersed in a favorable state. If the content of the structural unit (1) is less than 50% by mass, the dispersion stability of the pigment will be insufficient. On the other hand, when the content of the structural unit (1) is more than 70% by mass, the content of the structural unit (2) and the structural unit (3) is relatively small, so that the polymer becomes difficult to adsorb to the pigment, Insufficient dispersion stability of the pigment.

[Other structural units]
The pigment dispersant (polymer) may have structural units (other structural units) other than the above structural units (1) to (3). Monomers constituting other structural units (other monomers) may be radically polymerizable monomers. Other monomers include aromatic and heterocyclic vinyl monomers such as styrene, vinyltoluene, vinylnaphthalene, vinylcarbazole and vinylpyridine; Cyclic, aromatic carboxylic acid vinyl ester monomer; methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, (meth) ) 2-ethylhexyl acrylate, decyl (meth)acrylate, cyclohexyl (meth)acrylate, polyethylene glycol monomethyl ether methacrylate and other (meth)acrylic acid monomers; (meth)acrylamide, dimethyl (meth)acrylamide, (meth) Acryloylmorpholine, amide monomers such as N-methylol (meth)acrylamide; (meth)acrylonitrile; N-vinylpyrrolidone; maleic anhydride, maleic acid, maleic acid mono-lower alcohol ester, maleic acid di-lower alcohol ester, N -maleic acids such as phenylmaleimide and N-cyclohexylmaleimide; Furthermore, if necessary, carboxylic acid-containing monomers such as (meth)acrylic acid and maleic acid may be copolymerized. The content of other structural units in the pigment dispersant (polymer) is usually 20% by mass or less, preferably 10% by mass or less.

(Requirement [3])
The polymer used as the pigment dispersant has a polystyrene-equivalent number average molecular weight (Mn) measured by gel permeation chromatography (GPC) of 5,000 to 20,000, preferably 6,000 to 18,000. More preferably 8,000 to 15,000. If the Mn of the polymer is less than 5,000, the dispersion stability of the pigment will be insufficient. On the other hand, when the Mn of the polymer exceeds 20,000, it is necessary to add a large amount of the pigment dispersant, which may excessively increase the viscosity of the pigment dispersion. The molecular weight distribution (PDI=weight average molecular weight (Mw)/number average molecular weight (Mn)) of the polymer is preferably 1.5 to 2.5.

The acid value of the polymer that is the pigment dispersant is 30-130 mgKOH/g, preferably 50-100 mgKOH/g. If the acid value of the polymer is less than 30 mgKOH/g, the adsorptivity to the pigment is insufficient, and the dispersibility of the pigment cannot be improved. On the other hand, when the acid value of the polymer is more than 130 mgKOH/g, the amount of hydrophilic groups becomes excessive, which may result in deterioration of water resistance or yellowing. The acid value of a resin such as a polymer is expressed by the amount (mg) of potassium hydroxide required to neutralize 1 g of the resin. The acid value of the resin is obtained by titrating a resin dissolved in an organic solvent (e.g., toluene/ethanol = 1/1 mass ratio) with 0.1N potassium hydroxide/ethanol as a titrant and a phenolphthalein solution as an indicator. It is the obtained value (unit: mgKOH/g).

The acid value of the polymer is theoretically the sum of the acid value derived from the acidic group (carboxy group) of monomer 3 and the acid value derived from the acidic groups of other monomers used as necessary. However, the acid value of the polymer used as the pigment dispersant is preferably the acid value derived from the monomer 3. It is believed that the acidic group of monomer 3 (the carboxy group bonded to the aromatic ring) acts effectively on the pigment. For this reason, if the acid value derived from the monomer 3 is small, the adsorption to the pigment may tend to decrease.

<Method for producing pigment dispersant>
Next, a method for producing the above-described pigment dispersant will be described. The method for producing a pigment dispersant of the present invention comprises reacting an aromatic tricarboxylic anhydride with 2 to 8 mol of a monomer 2 with respect to 1 mol of an aromatic tricarboxylic anhydride to obtain a monomer 2 and a monomer 3. It has a step of obtaining a monomer mixture (step (1)) and a step of reacting the monomer mixture and the monomer 1 (step (2)). And the aromatic tricarboxylic anhydride is trimellitic anhydride or naphthalenetricarboxylic anhydride.

Polymers used as high-performance pigment dispersants are usually designed with structures such as block copolymers and graft copolymers that clearly separate performance. Such block copolymers and graft copolymers are often produced by living radical polymerization. However, in the case of living radical polymerization, operations such as purification of various components (compounds) such as monomers and removal of impurities derived from catalysts, initiator compounds, etc. are required, so there is a problem in terms of production costs. In contrast, the method for producing a pigment dispersant of the present invention does not require a step such as purification, and is advantageous in that a highly functional pigment dispersant (polymer) can be produced in one pot at low cost. is.

(Step (1))
In step (1), an aromatic tricarboxylic acid anhydride such as trimellitic anhydride is reacted with a large excess of monomer 2 relative to the aromatic tricarboxylic acid anhydride. That is, the monomer 2 is used not only as a monomer but also as a solvent. Therefore, the monomer 2 used in excess remains and the monomer 3 is produced by the reaction, so that a monomer mixture containing the monomer 2 and the monomer 3 can be obtained. Since the aromatic tricarboxylic acid anhydride is reacted with a large excess of the monomer 2, it does not substantially remain in the obtained monomer mixture. Therefore, it is not necessary to remove the aromatic tricarboxylic acid anhydride by purifying the resulting monomer mixture, which contributes to process shortening and cost reduction.

In step (1), 2 to 8 mol, preferably 3 to 6 mol of monomer 2 is reacted with 1 mol of aromatic tricarboxylic acid anhydride. If the amount of monomer 2 is less than 2 mols per 1 mol of the aromatic tricarboxylic anhydride, the aromatic tricarboxylic anhydride may remain. On the other hand, if the amount of monomer 2 is more than 8 mol per 1 mol of the aromatic tricarboxylic anhydride, the concentration of monomer 3 in the resulting monomer mixture will decrease, so The amount of introduced structural unit (3) is reduced.

A case where 2-hydroxyethyl methacrylate (HEMA, molecular weight 130) is used as the monomer 2 and trimellitic anhydride (molecular weight 192) is used as the aromatic tricarboxylic acid anhydride will be described as an example. When HEMA and trimellitic anhydride are reacted at a molar ratio of 4:1, the amount of HEMA is 520 parts by mass and the amount of trimellitic anhydride is 192 parts by mass. Through the reaction, 322 parts by weight of 1-[2-(meth)acryloyloxyethyl]-1,2,4-benzenetricarboxylic acid ester (molecular weight: 322), which is the monomer 3, is produced, and 390 parts by weight of HEMA remains. That is, a monomer 2 solution containing 45.2% by mass of monomer 3 can be obtained.

When reacting the aromatic tricarboxylic acid anhydride and the monomer 2, an organic solvent other than the monomer 2 may be used together. As the organic solvent, it is preferable to use an aprotic organic solvent having a dielectric constant of 20 or less at room temperature. If a protic organic solvent is used, it may react with the aromatic tricarboxylic acid anhydride. The amount of the organic solvent is preferably equal to or less than the amount of the monomer 2. If the amount of the organic solvent is too large, the aromatic tricarboxylic anhydride becomes difficult to dissolve in the system and may remain without reacting.

If necessary, the aromatic tricarboxylic anhydride and the monomer 2 may be heated to 100° C. or higher to react. In addition, the aromatic tricarboxylic acid anhydride and the monomer 2 can be reacted in the presence of a basic catalyst such as diazabicycloundecane, but this may result in coloration or polymerization of the produced monomer by heating. Therefore, the aromatic tricarboxylic anhydride and the monomer 2 are reacted at 30° C. or less using 0.01 to 10 mol % of 4-dimethylaminopyridine as a catalyst with respect to the aromatic tricarboxylic anhydride. is preferred. As a result, a monomer mixture containing the monomers 2 and 3 can be easily obtained without causing coloration or polymerization of the monomers.

The progress of the reaction was monitored by analysis using an infrared spectrophotometer (IR) and the aromatic tricarboxylic anhydride was added until the anhydride peak (1,780-1,800 cm ⁻¹ ) disappeared. and the monomer 2 are preferably reacted. Also, by measuring the acid value of the monomers in the resulting monomer mixture, it is possible to confirm whether the reaction has proceeded stoichiometrically.

(Step (2))
In step (2), the monomer mixture obtained in step (1) and monomer 1 are reacted. Thereby, the intended pigment dispersant (polymer) can be obtained. The monomer mixture and monomer 1 are preferably radically polymerized in an organic solvent. As the organic solvent, it is preferable to use an aprotic organic solvent. Aprotic organic solvents include hydrocarbon solvents such as hexane, toluene and xylene; ketone solvents such as acetone, methyl ethyl ketone, diethyl ketone and isobutyl methyl ketone; ester solvents such as ethyl acetate, butyl acetate and amyl acetate; Glycol ether monoether ester solvents such as propylene glycol monomethyl ether acetate and propylene glycol monobutyl ether acetate can be used.

Among the aprotic organic solvents, it is preferable to use an aprotic organic solvent with a lower polarity. The polarity of an aprotic organic solvent can be defined by the dielectric constant at room temperature (25°C). The dielectric constant (25° C.) of the aprotic organic solvent is preferably 20 or less, more preferably 10 or less. Aprotic organic solvents having a dielectric constant of 20 or less include ethyl acetate (6.0), butyl acetate (5.0), cyclohexanone (18.3), methyl ethyl ketone (18.5), tetrahydrofuran (7.5). ), toluene (2.4), propylene glycol monomethyl ether acetate (8.0), etc. (the numerical value in parentheses indicates the dielectric constant at 25° C.). The dielectric constant of the aprotic organic solvent may be an actually measured value, or may be a value described in manufacturer's catalogs and information, literature such as solvent pocketbooks, chemical handbooks, chemical encyclopedias, etc. good.

A pigment dispersant (polymer) can be obtained by heating the monomer mixture obtained in the step (1) and the monomer 1 in the presence of the above organic solvent for solution polymerization. Polymerization initiators such as azo-based radical polymerization initiators and peroxide-based radical polymerization initiators, chain transfer agents, and the like may also be used. The polymerization time may be, for example, 3 to 12 hours, preferably 5 to 8 hours. In the solution polymerization, each component such as an organic solvent, a monomer, a polymerization initiator, and a chain transfer agent may be charged all at once for polymerization, or the monomer may be added dropwise to allow the polymerization reaction to proceed. Since the use of a chain transfer agent makes it difficult to generate heat, it is possible to sufficiently control the temperature even if each component is charged all at once. Solution polymerization is preferably carried out in a reaction system such that the polymer solution obtained by polymerization has a solid content concentration of 20 to 80% by mass.

<Pigment dispersion>
The pigment dispersion of the present invention contains an organic solvent, a pigment, and a pigment dispersant that disperses the pigment in the organic solvent. And the pigment dispersant is the above-mentioned pigment dispersant (polymer).

(Organic solvent)
The pigment dispersion of the present invention is an oily pigment dispersion containing an organic solvent as a dispersion medium. Examples of organic solvents include hydrocarbon solvents such as hexane, toluene and xylene; alcohol solvents such as methanol, ethanol, isopropanol, butanol and dodecanol; ketone solvents such as acetone, methyl ethyl ketone, diethyl ketone and isobutyl methyl ketone; ethyl acetate. , butyl acetate, amyl acetate, dimethyl succinate, dimethyl adipate, methyl lactate, dimethyl lactate and other ester solvents; dipropyl ether, tetrahydrofuran, dioxane and other ether solvents; dimethyl carbonate, ethylene carbonate, propylene carbonate and other carbonates amide solvents such as dimethylformamide, dimethylacetamide, pyrrolidone and N-methylpyrrolidone; urea solvents such as tetramethylurea and dimethylimidazolidinone; sulfoxide solvents such as dimethylsulfoxide; ethylene glycol, propylene glycol, diethylene glycol, Glycol monoethers such as ethylene glycol methyl ether, ethylene glycol butyl ether, diethylene glycol methyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, and dipropylene glycol monomethyl ether Solvent; Glycol diether solvent such as ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, dipropylene glycol dimethyl ether; Glycol such as ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol monobutyl ether acetate Ether monoether ester solvents and the like can be mentioned. Among them, as the organic solvent, it is preferable to use an aprotic organic solvent having a dielectric constant of 20 or less at room temperature (25° C.).

(pigment)
As the pigment, conventionally known inorganic pigments and organic pigments can be used. Examples of inorganic pigments include carbon black such as thermal black, ketjen black, and acetylene black, as well as titanium oxide, zinc oxide, red iron oxide, ocher, and composite oxide pigments. Titanium oxide is preferably treated with silica or a silane coupling agent to make the surface basic. Inorganic oxide pigments can be easily adsorbed through hydrogen bonding with the carboxyl group of the pigment dispersant (polymer), so that the dispersibility can be improved.

Examples of organic pigments include quinacridone pigments, anthraquinone pigments, diketopyrrolopyrrole pigments, perylene pigments, phthalocyanine blue pigments, phthalocyanine green pigments, isoindolinone pigments, indigo/thioindigo pigments, dioxazine pigments, and quinophthalone. Pigments, nickel azo pigments, insoluble azo pigments, soluble azo pigments, high molecular weight azo pigments, organic black pigments and the like can be mentioned.

When the pigment dispersion is used as a colorant for producing a color filter (colorant for color filters (colorant for CF)), it is preferable to use an organic pigment as the pigment, and a dye derivative having a basic group (so-called synergist) is preferably further contained. As the organic pigment, conventional pigments of each color that constitute a color filter can be used. Examples of red pigments include Color Index (C.I.) Pigment Red (PR) 56, 58, 122, 166, 168, 176, 177, 178, 224, 242, 254, and 255. Examples of green pigments include Pigment Green (PG) 7, 36, 58, 59, poly(14-16) bromocopper phthalocyanine, poly(12-15) bromo-poly(4-12) chlorocopper phthalocyanine, and the like. can be mentioned. Examples of blue pigments include Pigment Blue (PB) 15:1, 15:3, 15:6, 60 and 80. Complementary color pigments for each of these color pigments and multicolor pixel pigments can also be used. Specifically, pigment yellow (PY) 12, 13, 14, 17, 24, 55, 60, 74, 83, 90, 93, 126, 128, 138, 139, 150, 154, 155, 180, 185, 216, 219; Pigment Violet (PV) 19, 23;

When the pigment dispersion liquid is used as a material for forming the partition wall that constitutes the organic EL, a white pigment or a black pigment is used. Examples of white pigments include titanium oxide and zinc oxide. Examples of black pigments include carbon black, titanium black, black inorganic composite oxides, and organic black pigments. Among them, it is preferable to use an organic black pigment that does not have conductivity. Examples of organic black pigments include aniline black, perylene black, lactam black, lignin black, azomethine azo black, cyanine black, and indigoid black.

The pigment is preferably a finely divided pigment in order to provide color characteristics such as transparency, brightness, and contrast of the color filter. The number average particle size (primary particle size) of the pigment is preferably 10 to 100 nm, more preferably 20 to 80 nm, particularly preferably 20 to 50 nm. When the number average particle size of the pigment is less than 10 nm, the crystallinity of the pigment tends to be broken, and the pigment tends to decompose or dissolve at high temperatures, which may reduce the heat resistance. On the other hand, when the number average particle size of the pigment is more than 100 nm, the particle size is too large, and the transparency and brightness may tend to decrease. The number average particle size of the pigment can be observed, measured and calculated using a transmission electron microscope (TEM). The pigment content in the CF colorant is preferably 5 to 30% by mass, more preferably 8 to 25% by mass.

As a method for making the pigment finer, for example, a method of kneading the pigment, an inorganic salt, and an organic solvent such as diethylene glycol, which is used as necessary, with a kneader or the like to make it finer; After that, a method of precipitating in water to form fine crystal particles; When the shape of the finely divided pigment crystals is nearly spherical, light scattering due to irregular reflection is less likely to occur, and the contrast tends to be improved, which is preferable. A narrower particle size distribution of the finely divided pigment is preferable because light scattering due to irregular reflection is less likely to occur, and color developability and contrast tend to be improved. By using a CF colorant prepared using a pigment dispersion obtained by dispersing a finely divided pigment with a specific pigment dispersant (polymer), high color development, high image quality, high transparency, and high Contrasting color filters can be produced.

(dye derivative)
Generally, in a pigment dispersion containing an organic solvent as a dispersion medium, the pigment and the organic solvent are oily, and the pigment dispersant dissolved in the organic solvent is also oily. Therefore, the pigment dispersant adsorbed to the pigment is soluble in an organic solvent, and is easily detached from the pigment, making it difficult to stably maintain the dispersed state of the pigment. Therefore, in the case of oil-based pigment dispersions, an acidic group (or basic group) is introduced to the surface of the pigment, and a pigment dispersant with a basic group (or acidic group) is used to By ionically bonding the groups, the pigment dispersant is adsorbed to the pigment. Since the ionic bond is difficult to dissociate in a low-polarity organic solvent, the pigment dispersant is difficult to detach from the pigment. Thereby, the dispersed state of the pigment can be stably maintained.

However, it is difficult to introduce an acidic group or a basic group (functional group) to the surface of a finely divided pigment. Therefore, it is possible to further contain a compound (dye derivative) having a specific functionality and the same structure, a similar structure, or a structure that is likely to interact with the pigment (dye derivative), and to adsorb this dye derivative to the surface of the pigment. traditionally done. Dye derivatives having such specific functional groups are also called pigment treatment agents or synergists.

Since the aforementioned pigment dispersant is a polymer having an acidic group, it is preferable to introduce a basic group to the surface of the pigment in order to stably maintain the dispersed state of the pigment. However, as described above, it is difficult to introduce basic groups into finely divided pigments. Therefore, a dye derivative (synergist) having a basic group is used. Basic groups include primary amino groups, secondary amino groups, tertiary amino groups, alkyl amino groups, heterocyclic amino groups, and the like. Among them, a tertiary amino group is preferred. Tertiary amino groups include dimethylamino, diethylamino, dipropylamino, dibutylamino, dibenzylamino, pyridinyl and imidazolinyl groups.

Examples of the dye derivative main body (part other than the basic group) include a compound that is a raw material for the pigment, a compound that has the same structure as the pigment, and the like. In addition, since general pigments have an aromatic ring skeleton, aromatic compounds, polycyclic compounds, heterocyclic compounds, and the like can also be used. The acidic group may be directly bonded to the dye derivative body, or may be bonded via a linking group. Examples of linking groups include alkyl groups, alkenyl groups, aryl groups, alkyl ester groups, alkyl ether groups, alkylamide groups, alkylurethane groups, alkylurea groups, and sulfonamide groups. Examples of dye derivatives include azo dye derivatives, phthalocyanine dye derivatives, anthraquinone dye derivatives, triazine dye derivatives, acridine dye derivatives, perylene dye derivatives, and diketopyrrolopyrrole dye derivatives. , dioxazine violet-based dye derivatives, and the like.

In the pigment dispersion, the content of the dye derivative having a basic group is preferably 5 to 20 parts by mass, more preferably 7 to 15 parts by mass, based on 100 parts by mass of the pigment. If the content of the dye derivative is less than 5 parts by mass with respect to 100 parts by mass of the pigment, the amount of the basic group introduced to the surface of the pigment is small, so the amount of the pigment dispersant adsorbed to the pigment becomes insufficient. In some cases, dispersion stability may be unsatisfactory. On the other hand, if the content of the dye derivative exceeds 20 parts by mass with respect to 100 parts by mass of the pigment, the color of the dye derivative itself tends to be expressed, and the desired hue of the pigment may be difficult to exhibit. Furthermore, heat resistance and weather resistance may deteriorate. The dye derivative not only adsorbs to the pigment to introduce a functional group such as a basic group to the surface of the pigment, but also suppresses crystal growth of the pigment due to heat by adsorbing to the pigment. Furthermore, it is also possible to prevent the crystals of the pigment from being broken by heat, or from being melted and leached out.

A pigment derivative can be blended and dispersed together with the pigment when producing the pigment dispersion. However, it is preferable to prepare a treated pigment by previously treating the pigment with a dye derivative. Further, it is preferable to prepare a treated pigment by micronizing the pigment and then treating the micronized pigment with a dye derivative. Methods of treating a pigment with a dye derivative include, for example, a method of synthesizing a pigment in the presence of a dye derivative; a method in which a pigment derivative is added at the time of conversion, and the pigment is finely divided and treated with the pigment derivative at the same time; Further, the pigment is deflocculated with water, and the basic group of the pigment derivative is neutralized with an acidic substance such as acetic acid to make it compatible with, disperse, or dissolve in water. There is also a method in which a basic substance is added to adjust the pH to make the dye derivative insoluble in water so that the dye derivative is adsorbed on the surface of the pigment.

(other ingredients)
In addition to the components described above, the pigment dispersion may further contain conventionally known additives and resins. Examples of additives include coloring agents other than the pigments described above, light stabilizers, ultraviolet absorbers, leveling agents, antifoaming agents, photopolymerization initiators, and the like. Examples of coloring agents other than pigments include various dyes such as acid dyes, basic dyes, disperse dyes, reactive dyes, direct dyes, and fluorescent dyes.

As the resin, a photosensitive resin varnish and a non-photosensitive resin varnish can be used.
Examples of photosensitive resin varnishes include photosensitive cyclized rubber resins, photosensitive phenolic resins, photosensitive polyacrylate resins, photosensitive polyamide resins, photosensitive polyimide resins, unsaturated polyester resins, and polyester acrylate resins. Varnishes such as resins, polyepoxyacrylate-based resins, polyurethane acrylate-based resins, polyether acrylate-based resins, and polyol acrylate-based resins can be used. Furthermore, varnishes obtained by adding a monomer as a reactive diluent to these varnishes can also be used.

Non-photosensitive resin varnishes include cellulose acetate resins, nitrocellulose resins, styrene (co)polymers, polyvinyl butyral resins, amino alkyd resins, polyester resins, amino resin-modified polyester resins, and polyurethane resins. Resin, acrylic polyol urethane resin, soluble polyamide resin, soluble polyimide resin, soluble polyamideimide resin, soluble polyesterimide resin, hydroxyethyl cellulose, water-soluble salt of styrene-maleic acid ester copolymer, (meth) Varnishes such as water-soluble salts of acrylic ester (co)polymers, water-soluble aminoalkyd resins, water-soluble aminopolyester resins, and water-soluble polyamide resins can be mentioned.

(Pigment dispersion)
The pigment dispersion can be prepared, for example, by blending the components described above and dispersing the pigment in an organic solvent. The resin-treated pigment may be prepared by adding a pigment dispersant when converting a raw pigment into a pigment, or adding a pigment dispersant when making the pigment finer (fine particles). The content of the pigment dispersant in the pigment dispersion is 5 to 50 parts by weight, preferably 10 to 30 parts by weight, per 100 parts by weight of the pigment. If the content of the pigment dispersant is less than 5 parts by mass with respect to 100 parts by mass of the pigment, the dispersion stability of the pigment will be insufficient. On the other hand, if the content of the pigment dispersant is more than 50 parts by mass with respect to 100 parts by mass of the pigment, the viscosity of the pigment dispersion increases too much and the concentration of the pigment relatively decreases, resulting in a decrease in the coloring density. do. The content of the pigment in the pigment dispersion is preferably 5-70% by mass, more preferably 10-60% by mass.

A pigment dispersant, a pigment, and an organic solvent as a liquid medium are mixed, and if necessary, various additives are further mixed. A pigment dispersion can be obtained by carrying out the dispersion treatment until the A pigment dispersion can also be obtained by mixing a pigment, a pigment dispersant, and an organic solvent, premixing the mixture if necessary, and then subjecting the mixture to dispersion treatment using a disperser or the like. As the dispersing machine, conventionally known various dispersing machines can be used. Examples of dispersing machines include kneaders, attritors, ball mills, sand mills using glass or zircon, horizontal media dispersing machines, colloid mills, and the like. In order to improve the reliability of the pigment dispersion, it is preferable to further treat it using a centrifugal separator, an ultracentrifuge, or a filter after the dispersion treatment to remove coarse particles slightly present.

The number average particle size (primary particle size) of the inorganic pigment in the pigment dispersion is preferably 100 to 300 nm. Further, when the pigment dispersion is used as a CF colorant, the number average particle size (primary particle size) of the organic pigment in the pigment dispersion is preferably 10 to 100 nm, more preferably 20 to 80 nm. More preferred.

The pigment dispersion liquid can disperse the pigment into fine particles, and is excellent in storage stability, transparency as a coating film, and high color reproducibility, and therefore can be used as a coloring agent for members for image display devices. Recent image display devices are required to have high performance, high image quality, and high functionality, and the requirements for these colorants are also very large. Examples of image display devices include liquid crystal displays, organic EL displays, quantum dot displays, micro LED displays, and the like. It is very useful as a black matrix for panels and a colorant for solid-state imaging devices such as CCDs. The printing method can be applied to a spin coating method, a slit coating method, or an inkjet printing method, and is not particularly limited.

Since the pigment dispersion liquid of the present invention is a so-called "oil-based" dispersion liquid in which a pigment is dispersed in an organic solvent, it can be used as a coloring agent blended in conventional inks, paints, and the like. In addition, coloring agents for oil-based inkjet inks, coloring agents for UV-curable inks, coloring agents for UV-curable inkjet inks, coloring agents for display members for color filters, and coloring agents for suspension or emulsion polymerization toners. It can also be used as an agent. In addition, the pigment dispersion liquid of the present invention has a highly dispersed pigment in the form of fine particles and is excellent in storage stability. Furthermore, since it can form a coating film with excellent transparency and color reproducibility, it is used for image display devices such as color filters and partition materials such as liquid crystal displays, organic EL displays, quantum dot displays, and micro LED displays. It is useful as a coloring agent for manufacturing parts.

EXAMPLES The present invention will be specifically described below based on Examples, but the present invention is not limited to these Examples. "Parts" and "%" in Examples and Comparative Examples are based on mass unless otherwise specified.

<Synthesis of Monomer 3>
(Synthesis example 1)
520 parts of 2-hydroxyethyl methacrylate (HEMA) and 192 parts of trimellitic anhydride (TA) were placed in a separable flask equipped with a condenser, a stirrer, and a thermometer, and stirred at 25° C. (room temperature). When 0.1 part of 4-dimethylaminopyridine (DMAP) (0.08 mol % with respect to TA) was added to start the reaction, TA gradually dissolved and became almost transparent in 1 hour. After further reacting for 3 hours, a portion of the reaction solution was sampled and measured with an infrared spectrophotometer to find that the acid anhydride peak (1,780 cm ⁻¹ ) had disappeared. The acid value measured and calculated by titration was 157.1 mgKOH/g. That is, it is believed that almost all of the acid anhydride (TA) reacted to produce 1-[2-methacryloyloxyethyl]-1,2,4-benzenetricarboxylic acid ester (TRIHEMA). 92 parts of HEMA was added to the reaction solution to obtain a TRIHEMA solution in which TRIHEMA was dissolved in HEMA. The content of TRIHEMA in the obtained TRIHEMA solution was 40.0%.

(Synthesis Examples 2-5)
A monomer 3 solution was obtained in the same manner as in Synthesis Example 1 described above, except that the formulation shown in Table 1 was used. The details of the monomers and the like in Table 1 are shown below. In any synthesis example, no acid anhydride remained, and a solution of monomer 3 (mixture of monomers 2 and 3) could be obtained. These results show that any concentration of Monomer 3 solution can be prepared.
・HEMA: 2-hydroxyethyl methacrylate ・HEA: 2-hydroxyethyl acrylate ・HPMA: 2-hydroxypropyl methacrylate ・HPA: 2-hydroxypropyl acrylate ・HBA: 4-hydroxybutyl acrylate ・TA: trimellitic anhydride ・PGMAc: propylene Glycol monomethyl ether acetate (dielectric constant 8)
・TRIHEMA: 1-[2-methacryloyloxyethyl]-1,2,4-benzenetricarboxylic acid ester ・TRIHEA: 1-[2-acryloyloxyethyl]-1,2,4-benzenetricarboxylic acid ester ・TRIHPMA: 1 -[2-methacryloyloxypropyl]-1,2,4-benzenetricarboxylic acid ester TRIHPA: 1-[2-acryloyloxypropyl]-1,2,4-benzenetricarboxylic acid ester TRIHBA: 1-[4- Acryloyloxybutyl]-1,2,4-benzenetricarboxylic acid ester

<Synthesis of Monomer 1>
(Synthesis Example 6)
130 parts of HEMA, 1,141 parts of ε-caprolactone (CPL), and 0.5 parts of tetrabutyl titanate (TBT) were placed in a separable flask equipped with a stirrer, reflux condenser, thermometer, and nitrogen inlet tube. After the temperature was raised to 170° C. over 1 hour while blowing nitrogen gas, the temperature was maintained for 5 hours. The blowing of nitrogen gas was stopped, a decompression device was attached, and the pressure was gradually reduced to 10 mmHg for 30 minutes to distill off unreacted HEMA to obtain Monomer 1 (FM10). The obtained FM10 had a number average molecular weight (Mn) of 1,300 and a molecular weight distribution (PDI=weight average molecular weight (Mw)/number average molecular weight (Mn)) of 1.11. Mn and Mw of Monomer 1 are polystyrene-equivalent values measured by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as a developing solvent and equipped with a differential refractive index detector. The obtained FM10 is a monomer in which 10 mol of CPL is added to 1 mol of HEMA.

(Synthesis Example 7)
Monomer 1 (F20) was obtained in the same manner as in Synthesis Example 6 described above, except that 116 parts of HEA was used instead of HEMA and the amount of CPL was changed to 2,282 parts. The resulting F20 had an Mn of 2,500 and a PDI of 1.15. The obtained F20 is a monomer in which 20 mol of CPL is added to 1 mol of HEA.

In addition, as a monomer in which 5 mol of CPL was added to 1 mol of HEMA, trade name "PLAXEL FM5" (manufactured by Daicel Corporation) was prepared. This monomer is referred to as "FM5". The Mn of FM5 was 800 and the PDI was 1.04.

Table 2 summarizes the physical properties and the like of Monomer 1.

<Production of graft copolymer>
(Example 1)
80.5 parts of TRIHEMA solution (TRIHEMA/HEMA = 32.2 parts/48.3 parts), 334 parts of PGMAc, 200 parts of FM5, 53 parts of methyl methacrylate (MMA), 4.5 parts of a chain transfer agent (thioglycerol (TGL)), and a polymerization initiator (dimethyl 2,2'-azobis (2-methylpropionate) (trade name "V- 601", manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) (V-601) was added and polymerized at 80° C. for 8 hours while bubbling nitrogen gas to obtain a solution of graft copolymer TMG-1.

A part of the solution was sampled and measured, and the solid content was 50.3%, and the polymerization rate was about 100%. The Mn of the graft copolymer TMG-1 was 5,500 and the PDI was 1.72. After diluting a portion of the sampled solution with toluene and 2-propanol, the acid value of the graft copolymer TMG-1 measured by titration with a 0.1 mol/L ethanolic potassium hydroxide solution was 33.2 mgKOH/g. Met.

(Examples 2-5)
Solutions of graft copolymers TMG-2 to 5 were obtained in the same manner as in Example 1, except that the formulations shown in Table 3 were used.

(Comparative example 1)
80.5 parts of TRIHEMA solution (TRIHEMA/HEMA = 32.2 parts/48.3 parts), 334 parts of PGMAc, 200 parts of FM3, 53 parts of MMA, 4.5 parts of TGL and 0.3 parts of V-601 were added and polymerized at 80° C. for 8 hours while bubbling nitrogen gas to obtain a solution of graft copolymer HG-1. The above "FM3" is a monomer in which 3 mol of CPL is added to 1 mol of HEMA (trade name "PLAXEL FM3", manufactured by Daicel Corporation). FM3 had an Mn of 500 and a PDI of 1.03.

A part of the solution was sampled and measured, and the solid content was 50.1%, and the polymerization rate was about 100%. The Mn of the graft copolymer HG-1 was 5,100 and the PDI was 1.69. The acid value of the graft copolymer TMG-1 was 32.9 mgKOH/g.

(Comparative Examples 2-4)
Solutions of graft copolymers HG-2 to HG-4 were obtained in the same manner as in Comparative Example 1, except that the formulations shown in Table 4 were used. Details of the monomers in Table 4 are shown below.
・PAMA: 2-methacryloyloxyethyl phthalate

<Preparation of pigment dispersion>
(Examples 6-7, Comparative Examples 5-7)
(a) Refining Treatment of Pigments PR254, PR177, and black pigment (trade name “Chromo Fine Black A1103” manufactured by Dainichiseika Kogyo Co., Ltd.) (A1103) were prepared as pigments for color filters.
100 parts of a pigment, 400 parts of sodium chloride, and 130 parts of diethylene glycol were placed in a kneader equipped with a pressurized lid (pressurized kneader manufactured by Moriyama Co., Ltd.). After pre-mixing in the kneader until a uniformly moist mass was formed, the pressurized lid was closed, and the contents were kneaded and ground for 7 hours while pressing the contents at a pressure of 6 kg/cm ² to obtain a ground material. The resulting ground product was added to 3,000 parts of 2% sulfuric acid and stirred for 1 hour. After removing sodium chloride and diethylene glycol by filtration, the product was thoroughly washed with water, dried and pulverized to obtain each pigment powder. When the number average particle size of the pigment powder obtained by observation with a transmission electron microscope (TEM) was measured and calculated, it was about 30 nm for PR254 and PR177, and about 90 nm for A1103.

(b) Preparation of Pigment Dispersion The types and amounts (unit: part) of each component shown in Table 5 were mixed and stirred for 2 hours using a dissolver. After confirming that there were no lumps of the pigment, a dispersion treatment was performed using a horizontal media dispersing machine to prepare a pigment dispersion. In Table 5, "Synergist 1" is a compound (dye derivative) represented by the following formula (I), "Synergist 2" is a compound represented by the following formula (II), and "Synergist 3" is the following It is a compound represented by formula (III). As the "acrylic resin" in Table 5, a polymer having a monomer composition of BzMA/MAA = 80/20 (mass ratio), Mn 5,500, and PDI 2.02 was used. The Mn of the polymer was measured using a PGMAc solution with a solid content of 30%.

(c) Evaluation of pigment dispersion The number average particle diameter (nm) of the pigment in the pigment dispersion, the initial viscosity (mPa s) of the pigment dispersion, and the pigment dispersion after storage at 45 ° C. for 3 days Table 6 shows the measurement results of viscosity (viscosity after storage; mPa·s). The number average particle size of the pigment was measured using a dynamic light scattering particle size distribution analyzer. The viscosity of the pigment dispersion was measured using an E-type viscometer under the conditions of 60 rpm and 25°C.

<Application to color filter resist>
(Application examples 1 and 2)
(a) Preparation of color filter resist ink The types and amounts (unit: part) of each component shown in Table 7 are blended and thoroughly mixed using a mixer to obtain a color filter (CF) resist of each color. got the ink. "Photosensitive acrylic resin varnish" in Table 7 is an acrylic resin obtained by reacting a BzMA/MAA copolymer with glycidyl methacrylate (Mn 6,100, PT 14,400, PDI 2.39, acid value 111 mgKOH/g ) is a varnish containing Abbreviations in Table 7 have the following meanings.
・TMPTA: trimethylolpropane triacrylate ・HEMPA: 2-hydroxyethyl 2-methylpropionic acid ・DEAP: 2,2-diethoxyacetophenone

(b) Evaluation of Color Filter Resist Ink A glass substrate treated with a silane coupling agent was set on a spin coater. Each color resist ink was spin-coated on the glass substrate at 300 rpm for 5 seconds. After pre-baking at 80° C. for 10 minutes, it was exposed to light of 100 mJ/cm ² using an ultra-high pressure mercury lamp to produce glass substrates of each color (red glass substrate-1 and black glass substrate-1).

The resulting red glass substrate-1 had excellent spectral curve characteristics and excellent fastness such as light resistance and heat resistance. In addition, optical properties such as light transmittance and contrast ratio were excellent.

The obtained black glass substrate-1 has a light transmittance of 20% from long wavelengths in the visible light region to around 670 nm, a light transmittance of 80% or more at 780 nm, and a light transmittance in the wavelength region of 780 nm or more. gradually rose to equilibrium. In particular, the light transmittance in the vicinity of 580 to 625 nm was extremely low and was 5% or less. In addition, the volume resistivity of the formed black coating film was 10 ¹⁴ Ω·cm or more, indicating that it was a highly insulating coating film.

<Application to black matrix (BM) pattern for color filter>
(Application example 3)
A glass substrate treated with a silane coupling agent was set on a spin coater. The black pigment ink-1 obtained in Application Example 2 was spin-coated on a glass substrate at 300 rpm for 5 seconds. After pre-baking at 80° C. for 10 minutes, it was exposed to light of 100 mJ/cm ² using an extra-high pressure mercury lamp. After developing with an alkaline developer, the film was washed with water and dried to form a BM pattern. Since the film (BM film) that constitutes the formed BM pattern is a highly insulating coating film, it can be used, for example, as a BM film that maintains the thickness of the liquid crystal layer. Liquid crystals can be constructed. In addition, since it sufficiently absorbs visible light up to the long wavelength region, it can also be used as a BM of an LCD panel employing an LED backlight.

<Production of colorant for UV curable inkjet ink>
(Examples 9 and 10, Comparative Examples 8 and 9)
(a) Preparation of Pigment Dispersion The types and amounts (unit: part) of each component shown in Table 8 were blended and stirred for 2 hours using a dissolver. After confirming that there were no lumps of the pigment, a horizontal media dispersing machine was used to carry out a dispersion treatment to obtain white pigment dispersions-1 to -4. As the white pigment, titanium oxide (trade name “JR-405”, manufactured by Tayca) (JR-405) was used.

(b) Evaluation of Pigment Dispersion For the obtained pigment dispersion, the number average particle diameter of the initial pigment, the number average particle diameter of the pigment after storage (the number average particle diameter of the pigment after being left at 70 ° C. for one week, ), initial viscosity, and viscosity after storage (viscosity after standing at 70° C. for one week) were measured. Table 9 shows the results. The number average particle size of the pigment was measured using a dynamic light scattering particle size distribution analyzer. The viscosity was measured at 60 rpm and 25° C. using an E-type viscometer.

White pigment dispersions-1 and 2 are placed in a light-shielded glass bottle and stored in a constant temperature bath at 60 ° C. for 1 month, and the change in viscosity, the change in the particle size of the pigment, the generation of supernatant, and the generation of sediment , and confirmed whether or not the sediment disappeared by shaking. As a result, the number average particle diameters of the pigment before and after storage were 238 nm and 237 nm, respectively, and no aggregation of the pigment was observed during storage, confirming that a high degree of dispersion stability was maintained. Also, no supernatant was generated by storage. When scraped with a spatula, a slightly viscous sediment was observed, but upon shaking, the sediment disappeared and returned to the original dispersed state. The number average particle diameters of the pigments in the dispersion that returned to the original dispersed state were 245 nm and 247 nm, respectively. In other words, it was confirmed that although the particle size of the pigment slightly increased due to the occurrence of sediment, it returned to a good dispersed state after redispersion.

On the other hand, when the white pigment dispersions-3 and 4 were placed in light-shielded glass bottles and stored in a constant temperature bath at 60°C for 1 month, a nearly transparent supernatant was formed and almost all the pigments settled. did. Even if the sediment was scraped with a spatula, it was very hard and could not be returned to the original dispersion.

Both white pigment dispersions-1 and 2 are suitable as UV curable inks because the pigments are highly dispersed and the dispersion stability is also high. In particular, the pigment is difficult to agglomerate, is dispersed in the form of fine particles, and can be easily redispersed even if it settles, making it suitable for UV-curable inkjet inks that require ejection stability and high-speed printing. It is considered to be

By using the pigment dispersant of the present invention, it is possible to prepare a pigment dispersion and a pigment colorant having low viscosity and excellent long-term storage stability. In addition, the resulting pigment dispersion has excellent coating properties and developability, so it can be used for images such as color filters and partition walls that have excellent optical properties such as fineness, color density, light transmittance, and contrast. It is useful as a material for producing members for display devices.

Claims (11)

A pigment dispersant that is a polymer that satisfies the following requirements [1] to [3].
[1] A structural unit (1) derived from a monomer 1 represented by the following general formula (1), a structural unit (2) derived from a monomer 2 represented by the following general formula (2), and the following general formula ( It has a structural unit (3) derived from the monomer 3 represented by 3-1) or (3-2).

(In general formula (1), R ₁ represents a hydrogen atom or a methyl group, R ₂ represents an alkylene group having 2 to 4 carbon atoms, and n represents a number (average value) of 5 to 20. In formulas (2), (3-1), and (3-2), R ₃ represents a hydrogen atom or a methyl group, and R ₄ represents an alkylene group having 2 to 4 carbon atoms.)
[2] The total content of the structural units (1) to (3) is 80% by mass or more, and the content of the structural unit (1) is 50 to 70% by mass.
[3] It has a polystyrene equivalent number average molecular weight of 5,000 to 20,000 and an acid value of 30 to 130 mgKOH/g as measured by gel permeation chromatography. 2. The pigment dispersant according to claim 1, which is a polymer composed only of the structural units (1) to (3). In the general formula (1), R ₁ is a methyl group and R ₂ is an ethylene group,
3. The pigment dispersant according to claim 1, wherein R ₃ is a methyl group and R ₄ is an ethylene group in the general formulas (2), (3-1) and (3-2). The pigment dispersant according to any one of claims 1 to 3, which is used for dispersing a pigment in an aprotic organic solvent having a dielectric constant of 20 or less at room temperature. A method for producing a pigment dispersant according to any one of claims 1 to 4,
a step of reacting an aromatic tricarboxylic anhydride with 2 to 8 mol of the monomer 2 per 1 mol of the aromatic tricarboxylic anhydride to obtain a monomer mixture containing the monomer 2 and the monomer 3;
and reacting the monomer mixture with the monomer 1;
A method for producing a pigment dispersant, wherein the aromatic tricarboxylic anhydride is trimellitic anhydride or naphthalenetricarboxylic anhydride. 6. The method for producing a pigment dispersant according to claim 5, wherein the aromatic tricarboxylic acid anhydride and the monomer 2 are reacted in an aprotic organic solvent having a dielectric constant of 20 or less at room temperature. The aromatic tricarboxylic anhydride and the monomer 2 are reacted at 30° C. or less using 0.01 to 10 mol % of 4-dimethylaminopyridine with respect to the aromatic tricarboxylic anhydride as a catalyst. Item 7. A method for producing a pigment dispersant according to Item 5 or 6. A pigment dispersion containing an organic solvent, a pigment, and a pigment dispersant for dispersing the pigment in the organic solvent,
The pigment dispersant is the pigment dispersant according to any one of claims 1 to 4,
A pigment dispersion containing 5 to 50 parts by mass of the pigment dispersant with respect to 100 parts by mass of the pigment. 9. The pigment dispersion according to claim 8, wherein the organic solvent is an aprotic organic solvent having a dielectric constant of 20 or less at room temperature. 10. The pigment dispersion according to claim 8, further comprising 5 to 20 parts by mass of a dye derivative having a basic group with respect to 100 parts by mass of the pigment. Use of the pigment dispersion according to any one of claims 8 to 10 as a colorant for producing a member for an image display device.