JP2021075660A - Pigment dispersion - Google Patents

Abstract

To provide a pigment dispersion useful as various colorants which has low viscosity, exhibits good coloring performance, and is excellent in dispersion stability of a pigment and long-term preservability.SOLUTION: The pigment dispersion contains a pigment, an organic solvent, and a polymer dispersant. The polymer dispersant is a polymer satisfying the following requirements (1)-(4): (1) the polymer is an A-B block copolymer containing 90 mass% or more of a methacrylate-based monomer unit; (2) a polymer chain A is a polymer block having an amine value of 0.5 mg KOH/g or less and a number average molecular weight of 3,000-15,000; (3) a polymer chain B is a polymer block containing a methacrylate-based monomer unit (b) with a specific quaternary ammonium base and having an amine value of 0-150 mg KOH/g; and (4) the content of the methacrylate-based monomer unit (b) is 30-80 mass% based on the whole polymer.SELECTED DRAWING: None

Description

The present invention relates to a pigment dispersion liquid using a polymer having a specific structure as a pigment dispersant.

As information devices, next-generation displays such as liquid crystal displays, organic EL displays, and quantum dot displays have been developed in recent years. Further, with the rapid development of technology, there is a demand for a color filter which is a member constituting a liquid crystal display panel having higher image quality and excellent cost performance, and a colorant for manufacturing such a color filter. There is. Further, for organic EL displays and quantum dot displays, there is a demand for a colorant having excellent dispersibility of pigments, which can form a bank material for dividing the pixels of the light emitting layer.

The pigment dispersion liquid used as a colorant used as a material for producing a color filter or the like contains extremely fine pigments (pigment fine particles) in a finely dispersed state. In such a pigment dispersion liquid, the surface tension is high 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, various colorants for color filters that are easily alkaline-developed using a pigment dispersant having good heat resistance have been proposed (Patent Documents 1 to 3).

Japanese Unexamined Patent Publication No. 2008-298967 Japanese Unexamined Patent Publication No. 2011-068865 Japanese Unexamined Patent Publication No. 2013-032441

As for colorants for next-generation displays, pigments are becoming finer. In order to stably exhibit high coloring performance while containing finely divided pigments, the pigments do not aggregate and the finely dispersed state is maintained even when stored for a long period of time under high temperature conditions. It is required to be. However, conventional colorants have not always been able to satisfy these requirements.

The present invention has been made in view of the problems of the prior art, and the problems thereof are low viscosity, good coloring performance, and dispersion stability of the pigment. An object of the present invention is to provide a pigment dispersion having excellent long-term storage stability and useful as various colorants.

That is, according to the present invention, the pigment dispersion liquid shown below is provided.
[1] A pigment dispersion liquid containing a pigment, an organic solvent, and a polymer dispersant, wherein the polymer dispersant is a polymer satisfying the following requirements (1) to (4).
(1) An AB block copolymer having a polymer chain A and a polymer chain B containing 90% by mass or more of a methacrylate-based monomer unit.
(2) The polymer chain A is a polymer block having an amine value of 0.5 mgKOH / g or less and a polystyrene-equivalent number average molecular weight of 3,000 to 15,000 as measured by a gel permeation chromatograph.
(3) The polymer chain B is a polymer block having an amine value of 0 to 150 mgKOH / g, which contains a methacrylate-based monomer unit (b) having a functional group represented by the following general formula (1).
(4) The content of the methacrylate-based monomer unit (b) is 30 to 80% by mass based on the entire polymer.

（前記一般式（１）中、Ｒ_１、Ｒ_２、及びＲ_３は、相互に独立に、炭素数１〜１８のアルキル基、アルケニル基、又はアリルメチル基を示し、Ｘ_１及びＸ_２は、相互に独立に、フッ素原子又は炭素数１〜８のフッ化アルキル基を示す）

(In the general formula (1), R ₁ , R ₂ , and R ₃ independently represent an alkyl group, an alkenyl group, or an allylmethyl group having 1 to 18 carbon atoms, and X ₁ and X ₂ are Independently of each other, they indicate a fluorine atom or an alkyl fluoride group having 1 to 8 carbon atoms).

[2] The pigment dispersion liquid according to the above [1], wherein the organic solvent is an aprotic solvent having a relative permittivity of 20 or less.
[3] The pigment dispersion according to the above [1] or [2], wherein the pigment is a pigment having at least one acidic group of a carboxy group, a sulfonic acid group, and a phosphoric acid group on its surface.
[4] The pigment dispersion liquid according to any one of the above [1] to [3], wherein the pigment is a nanocarbon substance.
[5] The pigment dispersion liquid according to the above [4], wherein the nanocarbon substance is at least one of carbon nanotubes and nanographenes.
[6] The content of the polymer dispersant is 10 to 200 parts by mass with respect to 100 parts by mass of the pigment, and the content of the pigment is 0.5 to 30% by mass with respect to the entire dispersion liquid. The pigment dispersion liquid according to any one of the above [1] to [5].

According to the present invention, it is possible to provide a pigment dispersion liquid that has low viscosity, exhibits good coloring performance, and is excellent in dispersion stability and long-term storage stability of pigments, and is useful as various colorants. .. The pigment dispersion liquid of the present invention is useful as a colorant for color filters, oil-based inkjet inks, ultraviolet curable inkjet inks, other paints, gravure inks, coating agents, and the like. Further, the polymer dispersant used in the pigment dispersion of the present invention can stably disperse nanocarbon substances such as carbon nanotubes and nanographenes, which are poorly dispersible black pigments, in an organic solvent. .. Therefore, according to the present invention, it is also possible to provide a pigment dispersion having a high degree of blackness and jet-blackness in which the above-mentioned nanocarbon substance, which is a pigment, is stably dispersed at a high concentration.

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

<Pigment dispersion>
The pigment dispersion of the present invention is a so-called "oil-based" pigment dispersion containing a pigment, an organic solvent, and a polymer dispersant. The polymer dispersant for dispersing the pigment in the organic solvent is a polymer that satisfies the following requirements (1) to (4). Hereinafter, the details of the pigment dispersion liquid of the present invention will be described.
(1) An AB block copolymer having a polymer chain A and a polymer chain B containing 90% by mass or more of a methacrylate-based monomer unit.
(2) The polymer chain A is a polymer block having an amine value of 0.5 mgKOH / g or less and a polystyrene-equivalent number average molecular weight of 3,000 to 15,000 as measured by a gel permeation chromatograph.
(3) The polymer chain B is a polymer block having an amine value of 0 to 150 mgKOH / g, which contains a methacrylate-based monomer unit (b) having a functional group represented by the following general formula (1).
(4) The content of the methacrylate-based monomer unit (b) is 30 to 80% by mass based on the entire polymer.

（一般式（１）中、Ｒ_１、Ｒ_２、及びＲ_３は、相互に独立に、炭素数１〜１８のアルキル基、アルケニル基、又はアリルメチル基を示し、Ｘ_１及びＸ_２は、相互に独立に、フッ素原子又は炭素数１〜８のフッ化アルキル基を示す）

(In the general formula (1), R ₁ , R ₂ , and R ₃ independently represent an alkyl group, an alkenyl group, or an allylmethyl group having 1 to 18 carbon atoms, and X ₁ and X ₂ represent each other. Independently indicates a fluorine atom or an alkyl fluoride group having 1 to 8 carbon atoms)

(Polymer dispersant)
A polymer dispersant (pigment dispersant), which is a component that functions as a dispersant for dispersing pigments having various shapes such as fine particles, fibrous, scaly, or rod-like substances in an organic solvent (pigment dispersion liquid) , A block copolymer having a quaternary ammonium base with a specific counter anion in its molecular structure. The quaternary ammonium base is adsorbed on the pigment by an electric action of the pigment on the particle surface or the like. As a result, the dispersion stability of the fine particle pigment in the pigment dispersion liquid can be enhanced, and the viscosity of the pigment dispersion liquid is less likely to change with time, so that long-term storage stability is exhibited. Further, when an amino group is further present in the molecular structure of the polymer dispersant, it ionic bonds with an acidic group such as a carboxy group, a sulfonic acid group, or a phosphoric acid group on the particle surface of the pigment, so that the pigment and the polymer are dispersed. Adsorption with the agent is improved, and the dispersion stability of the pigment is further improved.

The polymer used as the polymer dispersant is an AB block copolymer having a polymer chain A and a polymer chain B containing 90% by mass or more of a methacrylate-based monomer unit (requirement (1)). The AB block copolymer is a polymer whose structure is precisely controlled, and can be produced by living polymerization, especially living radical polymerization. In particular, in the case of living radical polymerization using an organic iodide as a starting compound, it is preferable that the iodine atom, which is a terminal growth group, is bonded to a tertiary carbon atom. Therefore, the AB block copolymer contains 90% by mass or more of methacrylate-based monomer units.

The methacrylate-based monomer unit is formed, for example, by polymerizing a methacrylate-based monomer. When the content of the methacrylate-based monomer unit is large, the glass transition temperature of the AB block copolymer becomes high, and the thermal properties such as heat resistance are improved. Among them, the AB block copolymer preferably has a content of a methacrylate-based monomer unit of 100% by mass.

As the methacrylate-based monomer, a conventionally known methacrylate-based monomer can be used. Methacrylate monomers include, for example, methacrylate; methyl, ethyl, propyl, butyl, hexyl, 2-ethylhexyl, octyl, decyl, dodecyl, tridecyl, hexadecyl, octadecyl, isostearyl, behenyl, cyclohexyl, trimethylcyclohexyl, t-butyl. Cyclohexyl, benzyl, methoxyethyl, butoxyethyl, phenoxyethyl, nonylphenoxyethyl, isobornyl, dicyclopentanyl, dicyclopentenyl, dicyclopentenyloxyethyl, glycidyl, 2-hydroxyethyl, 2-hydroxypropyl, 4-hydroxy Examples thereof include monofunctional methacrylate having substituents such as butyl, dimethylaminoethyl, diethylaminoethyl, polyethylene glycol, polypropylene glycol, polyethylene gucholyl monomethyl ether, polypropylene glycol monomethyl ether, polyepsilon caprolactone, and polydimethylsiloxane.

Polymer chain A (hereinafter, also simply referred to as “A chain”) has an amine value of 0.5 mgKOH / g or less and a polystyrene-equivalent number average molecular weight of 3,000 to 15 as measured by gel permeation chromatography (GPC). 000 polymer blocks (requirement (2)). The polymer chain A is a polymer block that can be dissolved in an organic solvent, and has a function of making the pigment compatible with the organic solvent and suppressing reaggregation of the pigment dispersed in the organic solvent due to its steric repulsion and electrical repulsion.

The amine value of the polymer chain A is 0.5 mgKOH / g or less, preferably 0.1 mgKOH / g or less, and more preferably 0 mgKOH / g. When the amine value is 0 mgKOH / g, it means that the polymer chain A has substantially no amino group. On the other hand, the polymer chain B (hereinafter, also simply referred to as “B chain”) has an amino group or a quaternary ammonium base. The polymer chain B is adsorbed on the pigment by these amino groups and quaternary ammonium bases adsorbing to the pigment by ionic bonding, electrical action, hydrogen bonding, π-π stacking, hydrophobic interaction, etc. It is thought that. However, when the polymer chain A has an amino group exceeding a certain amount, the polymer chain A also tends to be positively adsorbed on the pigment, so that the dispersibility and storage stability tend to decrease.

The polystyrene-equivalent number average molecular weight (Mn) of the polymer chain A measured by GPC is 3,000 to 15,000, preferably 4,000 to 10,000. Of the polymer blocks constituting the AB block copolymer, the polymer chain B is adsorbed on the pigment, and the polymer chain A is compatible and soluble in the organic solvent. As a result, the pigment can be dispersed in the organic solvent. The polymer chain A needs to be a polymer block having a molecular weight capable of exerting a function of suppressing reaggregation of pigments due to its steric repulsion or the like. Therefore, if the number average molecular weight of the polymer chain A is less than 3,000, the steric repulsion and the like are insufficient, and the dispersion stability becomes insufficient. On the other hand, if the number average molecular weight of the polymer chain A is more than 15,000, the viscosity of the dispersion may become excessively high or it may be difficult to dissolve in an organic solvent.

The polymer chain B is a polymer block having an amine value of 0 to 150 mgKOH / g, which contains a methacrylate-based monomer unit (b) having a functional group represented by the following general formula (1) (requirement (3)). The content of the polymer chain B in the polymer dispersant (AB block copolymer) is preferably 50 to 80% by mass.

（一般式（１）中、Ｒ_１、Ｒ_２、及びＲ_３は、相互に独立に、炭素数１〜１８のアルキル基、アルケニル基、又はアリルメチル基を示し、Ｘ_１及びＸ_２は、相互に独立に、フッ素原子又は炭素数１〜８のフッ化アルキル基を示す）

(In the general formula (1), R ₁ , R ₂ , and R ₃ independently represent an alkyl group, an alkenyl group, or an allylmethyl group having 1 to 18 carbon atoms, and X ₁ and X ₂ represent each other. Independently indicates a fluorine atom or an alkyl fluoride group having 1 to 8 carbon atoms)

The functional group represented by the general formula (1) is a quaternary ammonium base containing a specific counter anion. This functional group is ionic and acts to be adsorbed on the pigment surface by electronic action. This quaternary ammonium base has low water solubility and is easily dissolved in an organic solvent, especially a low to medium polar organic solvent. In the general formula (1), when the _{number of carbon atoms of the alkyl fluoride group represented by X 1} and X ₂ is more than 8, the water repellency of the alkyl fluoride group (perfluoroalkyl group) becomes too high, so that it is used. The type of organic solvent may be limited. _{The alkyl fluoride group represented by X 1} and X ₂ in the general formula (1) preferably has 1 to 4 carbon atoms. When the alkyl fluoride group has 1 to 4 carbon atoms, it is easily dissolved in a low-polarity organic solvent and further an aprotic organic solvent even though it is an ionic quaternary ammonium salt. Further, by using such an ionic quaternary ammonium salt, it becomes easy to be adsorbed on the pigment by an electric action or an ionic action, and the dispersibility of the pigment can be improved.

Examples of the counter anion of the quaternary ammonium cation include bis (fluorosulfonyl) imide anion, (fluorosulfonyl) (trifluoromethyl sulfone) imide anion, bis (trifluoromethyl sulfone) imide anion, and bis (2,2,2-). Trifluoroethyl sulfone) imide anion, bis (perfluoroethyl sulfone) imide anion, bis (perfluoropropyl sulfone) imide anion, bis (perfluorobutyl sulfone) imide anion, bis (perfluorooctyl sulfone) imide anion, 1, 1,2,2,3,3-hexafluoropropane-1,3-disulfonimide anion and the like can be mentioned. Among them, an anion having a perfluoroalkyl group having a small number of carbon atoms is preferable from the viewpoint of solubility in an organic solvent and availability, and bis (trifluoromethylsulfone) imide anion and bis (perfluoro) are preferable. Butyl sulfone) imide anion is more preferred.

The polymer chain B is a polymer block containing a methacrylate-based monomer having a functional group represented by the general formula (1) as a constituent component. The functional group represented by the general formula (1) is bonded to an arbitrary organic group. The above-mentioned methacrylate-based monomer is formed by reacting an amino group of an amino group-containing methacrylate such as dimethylaminoethyl methacrylate or diethylaminoethyl methacrylate with a quaternary agent to make the amino group a quaternary ammonium base. .. For example, by reacting dimethylaminoethyl methacrylate with benzyl chloride, a chloride salt of benzyldimethyl-2-methacloyloxyethylammonium can be obtained.

The quaternary ammonium base can also be formed by a method other than the above. Specifically, the methods (i) to (iii) shown below can be mentioned.
(I) A compound having a primary or secondary amino group and a tertiary amino group is reacted with methacrylate or isocyanatoethyl methacrylate having a glycidyl group to introduce a tertiary amino group, and then the tertiary amino group is introduced. A tertiary amino group is used as a quaternary ammonium base.
(Ii) A tertiary amine is reacted with a methacrylate having a glycidyl group to obtain a quaternary ammonium base.
(Iii) A tertiary amine is reacted with a methacrylate having an alkyl halide group such as 3-chloro-2-hydroxypropyl methacrylate to obtain a quaternary ammonium base.

In the general formula (1), the ^{quaternary ammonium cation represented by "-N +} (-R ₁ ) _{(-R 2} ) (-R ₃ )" includes trimethylammonium cation, butyldimethylammonium cation, and diethylmethyl. Ammonium cation, butyl diethylammonium cation, dipropylmethylammonary cation, dibutylmethylammonium cation, benzyldimethylammonium cation, benzyldiethylammonium cation, benzyldipropylammonium cation, benzyldibutylammonium cation, dimethyl (naphthylmethyl) ammonium cation, dimethyl Anthracenylmethyl) ammonium cations, dimethyl (pyrenemethyl) ammonium cations and the like can be mentioned.

The content of the methacrylate-based monomer unit (b) having a functional group represented by the general formula (1) is 30 to 80% by mass based on the entire polymer (requirement (4)). Low polarity by setting the content of the methacrylate-based monomer unit (b) having a functional group represented by the general formula (1) (hereinafter, also simply referred to as “content of unit (b)”) in the above range. It becomes easy to dissolve in the organic solvent and the aprotic organic solvent of the above, and it becomes easy to be adsorbed on the pigment, and the dispersibility of the pigment can be improved. The content of the unit (b) is more preferably 50 to 70% by mass based on the entire polymer.

The polymer chain B may be substantially composed of only the methacrylate-based monomer unit (b), or may further have a structural unit (other structural unit) other than the methacrylate-based monomer unit (b). Examples of other structural units include structural units derived from the above-mentioned methacrylate-based monomers. Among them, the polymer chain B preferably further contains a structural unit derived from a methacrylate-based monomer having an amino group. When an amino group is introduced into the polymer chain B, the adsorptivity with the pigment can be further enhanced, and the dispersion stability of the pigment can be further improved. In particular, when used in combination with a pigment having an acidic group such as a carboxy group, a sulfonic acid group, or a phosphoric acid group on its surface, ionic bonds are formed with these acidic groups, so that the adsorptivity between the pigment and the polymer dispersant is improved. At the same time, the desorption of the polymer (polymer dispersant) from the pigment is suppressed, so that the dispersion stability of the pigment can be further improved.

The amine value of the polymer chain B is 0 to 150 mgKOH / g, preferably 100 mgKOH / g or less, and more preferably 50 mgKOH / g or less. When the amine value of the polymer chain B is more than 150 mgKOH / g, the amount of amino groups is too large, so that the polymer chain B tends to be hydrophilic. In addition, since the polymer is easily adsorbed across the particles of the adjacent pigment, it may function as a coagulant and may cause problems such as coloring.

The molecular weight of the polymer chain B may be designed in consideration of the content of the quaternary ammonium base in the polymer chain B, the molecular weight of the polymer chain A, and the like. Specifically, the polystyrene-equivalent number average molecular weight Mn of the polystyrene-equivalent polymer chain B measured by GPC is preferably 500 to 15,000, and more preferably 1,000 to 10,000.

The AB block copolymer used as a polymer dispersant can be produced according to a conventionally known method. Among them, it can be produced by living anionic polymerization, living cationic polymerization, living radical polymerization, and is preferably produced by living radical polymerization from the viewpoint of conditions, materials, equipment and the like. Living radical polymerization includes, for example, atomic transfer radical polymerization (ATRP method), nitroxide-mediated radical polymerization (NMP method), reversible addition cleavage chain transfer polymerization (RAFT method), and organic tellurium-based living radical polymerization (TERP method). ), Reversible mobile catalytic polymerization (RTCP method), reversible catalyst-mediated polymerization (RCMP method) and the like. Of these, the RTCP method and the RCMP method, in which an organic compound is used as a catalyst and an organic iodide is used as a starting compound, are preferable. Although these methods use relatively safe commercially available compounds, they are advantageous in terms of cost because they do not use heavy metals or special compounds, and are also advantageous in terms of ease of purification and processing. is there. Furthermore, since the iodine atom, which is a terminal growth group, is bonded to a tertiary carbon atom, it is possible to accurately and easily produce an AB block copolymer having a specific block structure with general equipment. Is preferable.

The AB block copolymer may be produced by any polymerization form such as solvent-free, solution polymerization, and emulsion polymerization. Of these, solution polymerization is preferable. The solvent used in the solution polymerization is preferably the same as the organic solvent used in the pigment dispersion. This is because the AB block copolymer solution after polymerization can be used as it is in the pigment dispersion liquid without taking out the AB block copolymer. The above RTCP method and RCMP method can be carried out in the organic solvent used for the pigment dispersion liquid.

Either the polymer block of the polymer chain A or the polymer chain B may be polymerized first, but it is preferable to polymerize the polymer chain A first and then the polymer chain B later. This is because when the polymer chain B is polymerized first, if the polymerization rate is less than 100%, the structural units derived from the remaining monomers may be introduced into the polymer chain A to be polymerized later. .. A quaternary ammonium base can be introduced into the polymer chain B by polymerizing a methacrylate having a quaternary ammonium base. A quaternary ammonium base can also be introduced into the polymer chain B by polymerizing a methacrylate having an amino group and then reacting with a quaternary agent. Further, by forming a quaternary ammonium salt in which the counter anion is a halide ion and adding a metal salt having a specific counter anion for ion exchange, the quaternary ammonium base can be added to the polymer chain B. Can be introduced.

(Pigment)
As the pigment, conventionally known inorganic pigments and organic pigments can be used. Examples of the inorganic pigment include carbon black such as thermal black, ketjen black, and acetylene black, as well as titanium oxide, zinc oxide, petals, ocher, and composite oxide pigments. Among them, since a polymer dispersant having a basic group is used, it is preferable to use a pigment having an acidic surface. For example, as the carbon black, it is preferable to use so-called acidic carbon black. Titanium oxide is preferably treated with silica or an acidic silane coupling agent to make the surface acidic. Organic pigments include quinacridone pigments, anthracinone pigments, diketopyrrolopyrrole pigments, perylene pigments, phthalocyanine blue pigments, phthalocyanine green pigments, isoindolinone pigments, indigo / thioindigo pigments, dioxazine pigments, and quinophthalones. Examples thereof include pigments, nickel azo pigments, insoluble azo pigments, soluble azo pigments, high molecular weight azo pigments, and organic black pigments. In addition, nanocarbon substances that can be used as black colorants such as carbon nanotubes, graphite, and nanographenes can be mentioned.

Examples of pigments for image recording such as inkjet ink include Color Index Number (CI) Pigment Blue-15: 3, 15: 4, C.I. I. Pigment Red-122, 269, C.I. I. Pigment Violet-19, C.I. I. Pigment Yellow-74, 155, 180, 183, C.I. I. Pigment Green-7, 36, 58, C.I. I. Pigment Orange-43, C.I. I. Pigment Black-7, C.I. I. Pigment White-6 and the like. The average primary particle size of these pigments is preferably less than 350 nm.

C. I. Pigment Blue-15: 3, 15: 4, C.I. I. Pigment Red-122, 269, C.I. I. Pigment Violet-19, C.I. I. Pigment Yellow-74, 155, 180, 183, C.I. I. Pigment Green-7, 36, 58, C.I. I. Pigment Orange-43, and C.I. I. The average primary particle size of Pigment Black-7 is preferably less than 150 nm. In addition, C.I. I. The average primary particle size of Pigment White-6 is preferably less than 300 nm. Considering the clogging of the recording head of the inkjet recording apparatus, the sharpness of the recorded image, and the like, it is preferable that the particle size of the pigment is small. So-called treated pigments that have been surface-treated or encapsulated with a surface-treating agent such as a coupling agent or a surfactant, a synergist, a resin, or the like can also be used.

As the pigment for displaying an image such as a color filter, it is preferable to use an organic pigment or an inorganic pigment for black matrix. Examples of the red pigment include Color Index (CI) Pigment Red (PR) 56, 58, 122, 166, 168, 176, 177, 178, 224, 242, 254, 255 and the like. Examples of the green pigment include C.I. I. Pigment Green (PG) 7, 36, 58, poly (14-16) bromed copper phthalocyanine, poly (12-15) brominated-poly (4-1) chlorinated copper phthalocyanine and the like. Examples of the blue pigment include C.I. I. Pigment Blue 15: 1, 15: 3, 15: 6, 60, 80 and the like.

Examples of complementary color pigments or multicolor pixel pigments for the above pigments include the following. Examples of the yellow pigment include C.I. I. 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, C .. I. Pigment Violet (PV) 19, 23 and the like. Further, as a black pigment for a black matrix, C.I. I. Pigment Black (PBK) 6, 7, 11, 26, copper / manganese / iron-based composite oxides and the like can be mentioned. The surface of these pigments may be treated with a pigment derivative (surface modifier) called synergist, a surfactant, or the like.

The number average particle size of carbon black and the organic pigment in the pigment dispersion is preferably 10 to 200 nm, more preferably 20 to 150 nm. The number average particle size of the inorganic pigment such as titanium oxide in the pigment dispersion is preferably 50 to 300 nm, more preferably 100 to 250 nm. The number average particle size of the pigment can be observed, measured and calculated using a transmission electron microscope (TEM). The pigment dispersion liquid containing the pigment finely divided in this way is useful as a colorant that imparts high color development, high image quality, high gloss, high printability, and the like.

Further, by using the above-mentioned polymer dispersant, the nanocarbon substance, which is a poorly dispersible black pigment, can be stably dispersed in an organic solvent. Examples of the nanocarbon substance include carbon nanotubes, graphite, graphene, carbon nanohorns, carbon nanoribbons, carbon fullerene, carbon-based quantum dots, and nanodiamonds. Among them, at least one of carbon nanotubes and nanographenes is preferable because it has excellent blackness.

Carbon nanotubes are nanocarbon substances composed of graphene sheets curled into a cylindrical shape. Examples of carbon nanotubes include single-walled carbon nanotubes (SWNTs) made of one-layer cylindrical graphene sheets, and multi-walled carbon nanotubes (MWNTs) in which a plurality of cylindrical graphene sheets are concentrically laminated. Further, the nanographenes are nano-sized graphene sheets themselves, and there are one graphene sheet, a laminated sheet in which a plurality of graphene sheets are laminated, and the like. The shape, size, manufacturing method, etc. of the nanocarbon substance are not particularly limited. The nanocarbon material may be doped with a metal such as platinum or palladium or a metal salt.

The pigment is preferably a pigment having at least one acidic group of a carboxy group, a sulfonic acid group, and a phosphoric acid group on its surface. When the polymer dispersant is an AB block copolymer having an amino group in its molecular structure, the acidic group on the particle surface of the pigment is ionic bonded to the amino group, so that the polymer dispersant is adsorbed on the pigment. It will be easier. As a result, the affinity between the polymer dispersant and the pigment is improved, so that the removal of the polymer dispersant from the pigment is suppressed, the dispersion stability of the pigment is further improved, and the reaggregation of the pigment is further suppressed. can do.

The acidic group can be introduced into the surface of the pigment by a conventionally known method. Specifically, the surface of the pigment is (i) oxidized; (ii) surface-treated with a treatment agent such as a silane coupling agent having an acidic group; (iii) the surface is treated with an aromatic diazonium salt or the like having an acidic group. The acidic group can be introduced into the surface of the pigment by a method such as coupling treatment; (iv) surface treatment with a synergist (dye derivative) having an acidic group;

As the synergist for surface-treating the pigment (combined with the pigment), a compound having a pigment skeleton having at least one acidic group of a carboxy group, a sulfonic acid group, and a phosphoric acid group can be used. Among them, a synergist having a sulfonic acid group is preferable because it is easily adsorbed by ionic bonding with the above-mentioned polymer dispersant.

(Organic solvent)
As the organic solvent, a conventionally known organic solvent can be used. The organic solvent may contain a small amount of water. Examples of the organic solvent 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. , Ester solvents such as butyl acetate, amyl acetate, dimethyl succinate, dimethyl adipate, methyl lactate, dimethyl lactate; ether solvents such as dipropyl ether, tetrahydrofuran, dioxane; carbonates such as dimethyl carbonate, ethylene carbonate, propylene carbonate System solvent; amides such as N, N-dimethylformamide, N, N-dimethylacetamide, pyrrolidone, N-methylpyrrolidone, 3-methoxy-N, N-dimethylpropanamide, 3-butoxy-N, N-dimethylpropanamide, etc. Solvents: Urea solvents such as tetramethylurea and dimethylimidazolidinone; Sulfoxide solvents such as dimethylsulfoxide; ethylene glycol, propylene glycol, diethylene glycol, ethylene glycol methyl ether, ethylene glycol butyl ether, diethylene glycol methyl ether, diethylene glycol monobutyl ether, tri Glycol monoether solvents such as ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether; ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, dipropylene glycol dimethyl ether, etc. Glycoldiether-based solvent; a glycol ether monoether ester solvent such as ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether acetate, and propylene glycol monobutyl ether acetate; and the like.

Further, a reactive monomer such as a (meth) acrylic monomer, a vinyl ether monomer, an epoxy compound, or an oxetane compound can be used as the organic solvent. By using the reactive monomer as an organic solvent, it is possible to obtain a dispersion liquid applicable to ultraviolet curable or electron beam curable inks and coating agents.

As the organic solvent, it is preferable to use an aprotic solvent. Furthermore, the organic solvent contains an aprotic low-polarity solvent and an aprotic non-polar solvent, but preferably contains substantially no protic solvent. An aprotic solvent is a solvent that does not have a hydrogen atom that ^{becomes a proton (H +).} Further, the polarity of the aprotic solvent can be defined by the relative permittivity under the temperature condition of 20 to 25 ° C. The relative permittivity of the aprotic solvent is preferably 20 or less, and more preferably 10 or less. Examples of the aprotic solvent having a relative permittivity of 20 or less include ethyl acetate (6.0), butyl acetate (5.0), cyclohexanone (18.3), methyl ethyl ketone (18.5), and tetrahydrofuran (7.5). ), Tetrahydrofuran (2.4), propylene glycol monomethyl ether acetate (8.0), 3-methoxy-3-methyl-1-butanol (13), butyl acrylate (5.1) and the like (. The numbers in parentheses indicate the relative permittivity at 25 ° C.). The relative permittivity of the aprotic solvent may be an actually measured value, or may be a value described in a manufacturer's catalog or information, documents such as a solvent pocket book, a chemical handbook, a chemical dictionary, or the like. ..

A general polymer having a quaternary ammonium base as an ionic group is difficult to dissolve in an aprotic solvent, particularly an aprotic low-polarity solvent and an aprotic non-polar solvent. Therefore, a protic polar solvent is usually used to dissolve a general polymer having a quaternary ammonium base. On the other hand, the polymer used as the polymer dispersant in the pigment dispersion of the present invention has a quaternary ammonium base having a specific counter anion, so that it is easily dissolved in an aprotic solvent and stabilizes the pigment. It can be dispersed in this state. Further, by using an aprotic solvent, it is possible to improve the drying property, hygroscopicity, workability, etc. of inks and paints, and there are advantages such as easy mixing with other reactive substances. ..

(Other ingredients)
The pigment dispersion liquid can further contain components (other components) such as conventionally known additives and resins. Examples of the additive include a dye, a resin, a light stabilizer, an ultraviolet absorber, a leveling agent, an antifoaming agent, a photopolymerization initiator and the like.

As the resin, a photosensitive or non-photosensitive resin varnish or the like can be used. The photosensitive resin varnish includes a photosensitive cyclized rubber resin, a photosensitive phenol resin, a photosensitive polyacrylate resin, a photosensitive polyamide resin, a photosensitive polyimide resin, an unsaturated polyester resin, and a polyester acrylate resin. Examples thereof include varnishes such as resins, polyepoxy acrylate resins, polyurethane acrylate resins, polyether acrylate resins, and polyol acrylate resins. Further, a varnish in which a monomer as a reactive diluent is added to these varnishes can also be used.

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

The pigment dispersion liquid can be prepared, for example, by blending each of the above-mentioned components and dispersing the pigment in an organic solvent with a polymer dispersant. A resin-treated pigment may be prepared by adding a polymer dispersant when the pigment base is pigmented, or by adding a polymer dispersant when the pigment is made finer (micronized). .. The content of the pigment in the pigment dispersion is preferably 0.1 to 70% by mass, more preferably 0.5 to 30% by mass, and 5 to 20% by mass, based on the entire dispersion. Is particularly preferable. If the content of the pigment is less than 0.5% by mass, the coloring property may be insufficient. On the other hand, if the content of the pigment is more than 30% by mass, the viscosity of the pigment dispersion liquid may become excessively high. The content of the polymer dispersant in the pigment dispersion is preferably 5 to 100 parts by mass, more preferably 10 to 200 parts by mass with respect to 100 parts by mass of the pigment.

A polymer dispersant, a pigment, and an organic solvent are mixed, and if necessary, various additives and the like are further mixed, and then dispersion treatment is performed using a disperser or the like until the pigment has fine particles having a desired particle size. By doing so, a pigment dispersion can be obtained. A pigment dispersion can also be obtained by mixing a polymer dispersant, a pigment, and an organic solvent, premixing them if necessary, and then performing a dispersion treatment using a disperser or the like. As the disperser, various conventionally known dispersers can be used. Examples of the disperser include a kneader, an attritor, a ball mill, a sand mill using glass, zircon, etc., a horizontal media disperser, a colloid mill, and the like. In order to increase the reliability of the obtained pigment dispersion, it is preferable to perform further treatment using a centrifuge, an ultracentrifuge, or a filter after the dispersion treatment to remove a small amount of coarse particles present. ..

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 colorant to be blended in conventional inks, paints, and the like. Furthermore, colorants for oil-based inkjet inks, colorants for UV-curable inks, colorants for UV-curable inkjet inks, colorants for display members for color filters, colorants for suspension or emulsion polymerization toners. It can also be used as an agent or the like. Further, a pigment dispersion liquid using a nanocarbon substance as a pigment is useful as a colorant for applications requiring jet blackness, such as cars, musical instruments, and design displays.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples as long as the gist thereof is not exceeded. Unless otherwise specified, those described as "parts" and "%" regarding the amount of components are based on mass.

<Synthesis of quaternary ammonium base-containing polymer (polymer dispersant)>
(Synthesis Example 1)
A stirrer, a backflow condenser, a thermometer, and a reaction device in which a nitrogen introduction tube was attached to a separable flask were prepared. In this reactor, 438 parts of diethylene glycol monobutyl ether (BDG), 4.1 parts of iodine, 2,2-azobis (2,4-dimethylvaleronitrile) (trade name "V-65", manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) ) (V-65) 11.9 parts, diphenylmethane (DPM) 0.7 parts, methyl methacrylate (MMA) 80 parts, butyl methacrylate (BMA) 80 parts, and 2-ethylhexyl methacrylate (EHMA) 80. Part was added, nitrogen was stirred while bubbling, and the mixture was heated to 60 ° C. and polymerized for 4.5 hours to synthesize a polymer (A chain). The solid content measured by sampling a part of the reaction solution was 36.8%, and the polymerization rate calculated based on this was about 100%. The polystyrene-equivalent number average molecular weight (Mn) of the A chain was 4,500 and the dispersity (PDI) was 1.22 as measured by GPC using tetrahydrofuran (THF) as a developing solvent. Mn was measured by a differential refractive index detector of GPC.

Then, 5.4 parts of V-65 and 180 parts of 2- (dimethylamino) ethyl methacrylate (DMAEMA) were added, and the mixture was heated to 60 ° C. and polymerized for 4 hours. As a result, a polymer (B chain) was formed, and a polymer solution containing polymer BP-1, which is a block copolymer, was obtained. The solid content measured by sampling a part of the reaction solution was 49.9%, and the polymerization rate calculated based on this was about 100%. The Mn of the polymer BP-1 was 7,700, the PDI was 1.26, and the amine value (actual measurement) was 153.2 mgKOH / g. The amine value (actual measurement) of the polymer was measured using a potential difference automatic titrator using a 0.1 mol / L 2-propanol solution of hydrochloric acid as a titration solution after diluting the sample with toluene and 2-propanol.

After cooling the polymer BP-1 to room temperature, a mixed solution of 144.9 parts of benzyl chloride (BzCl) and 144.9 parts of BDG was added dropwise over 30 minutes. The temperature was raised to 80 ° C. and the reaction was carried out for 5 hours, and the amino group derived from DMAEMA was quaternary ammonium chloride to obtain a solution of polymer PP-1 (prepolymer) having a solid content of 49.8%. The amine value (actual measurement) of the polymer PP-1 was about 0 mgKOH / g, and it was confirmed that all the amino groups in the polymer BP-1 became quaternary ammonium bases. The counter anion of the quaternary ammonium cation in the polymer PP-1 is chloride ion (Cl ⁻ ).

276.4 parts of polymer PP-1 and 2487.6 parts of water were placed in a vat equipped with a stirrer and stirred to obtain a transparent solution. When a mixed solution of 82.2 parts of bis (trifluoromethanesulfonyl) imidelithium (TFSILi) and 739.8 parts of water was added dropwise, the system became cloudy and a precipitate was formed. It is presumed that a precipitate was formed due to the high hydrophobicity of the quaternary ammonium salt having a bis (trifluoromethanesulfonyl) imide anion (TFSI) as a counterion produced by salt exchange. The precipitate was suction-filtered, washed with water, and dried to obtain a quaternary ammonium base-containing polymer (polymer SIB-1) as a white solid. Since the amine value of the polymer SIB-1 is 0 mgKOH / g, the amine value of the B chain is also 0 mgKOH / g.

(Synthesis Examples 2 and 3)
Polymers SIB-2 and SIB-, which are quaternary ammonium base-containing polymers, are the same as in Synthesis Example 1 described above, except that raw materials such as monomers of the type and amount (unit: part) shown in Table 1 are used. I got 3. The meanings of the abbreviations in Table 1 are as shown below.
-BzMA: benzyl methacrylate-PME200: poly (n≈4) ethylene glycol monomethyl ether methacrylate-DMQ: quaternary ammonium salt produced by reacting DMAEMA with BzCl-DMTFSI: Chloride ion of DMQ was exchanged for TFSI. Quaternary ammonium salt

The amine value (calculation) of the B chain of the polymer SIB-3 obtained in Synthesis Example 3 was calculated as follows, with the molecular weight of DMAEMA being 157.1 and the molecular weight of KOH being 56.1. That is, since the B chain is composed of DMAEMA and DMTFSI, the DMAEMA content of the B chain is "23.9 / (23.9 + 40.1) x 100 = 0.3734", and the amine value of the B chain (calculation). ) Is "(0.3734 / 157.1) x 56.1 = 133.3 mgKOH / g".

(Synthesis Example 4)
225 parts of polymer PP-3 and 2137.5 parts of water were put into a vat equipped with a stirrer and stirred to obtain a transparent solution (resin: about 5%). When a mixed solution of 74.7 parts of bis (nonafluorobutanesulfonyl) imidelithium (NFSILi) and 672.3 parts of water was added dropwise, the system became cloudy and a precipitate was formed. It is presumed that a precipitate was formed due to the high hydrophobicity of the quaternary ammonium salt having a bis (nonaflatebutanesulfonyl) imide anion (NFSI) as a counterion produced by salt exchange. The precipitate was suction-filtered, washed with water, and dried to obtain a quaternary ammonium base-containing polymer (polymer SIB-4) as a white solid.

(Synthesis Example 5)
A quaternary salt having a bis (fluorosulfonyl) imide anion (FSI) as a counterion is used in the same manner as in Synthesis Example 4 described above, except that the raw materials of the type and amount (unit: part) shown in Table 2 are used. An ammonium base-containing polymer (polymer SIB-5) was obtained. The meanings of the abbreviations in Table 2 are as shown below.
・ FSILi: Bis (fluorosulfonyl) imide lithium ・ DMNFSI: Quaternary ammonium salt in which chloride ion of DMQ is exchanged for NFSI ・ DMFSI: Quaternary ammonium salt in which chloride ion of DMQ is exchanged for FSI

(Comparative Synthesis Examples 1 and 2)
Type shown in Tables 3 and amount: except for using raw materials (unit portion), in the same manner as in Synthesis Example 4 above, tetrafluoroborate anion (BF 4 ^_-) and hexafluorophosphate anion (PF ₆ ^-) to obtain a quaternary ammonium salt group-containing polymer as a counter ion, respectively (polymer HB-1 and HB-2). The meanings of the abbreviations in Table 3 are as shown below.
· NaBF _4: sodium tetrafluoroborate · NaPF _6: hexafluorophosphate Sodium · DMBF _4: quaternary ammonium salt · DMPF ₆ of chloride ions DMQ is replaced with tetrafluoroborate: DMQ of chloride ions Quaternary ammonium salt in which is replaced with hexafluorophosphate

Table 4 shows the physical characteristics of the quaternary ammonium base-containing polymer obtained in Synthesis Examples 1 to 5 and Comparative Synthesis Examples 1 and 2 and the solubility in various solvents and acrylic monomers. The meanings of the abbreviations in Table 4 are as shown below.
-MEK: Methyl ethyl ketone-THF: tetrahydrofuran-PGMAc: Propylene glycol monomethyl ether acetate-PEA: Phenyl ethyl acrylate-BzA: Benzyl acrylate

The evaluation criteria for "solubility" in Table 4 are as shown below.
◯: Soluble (transparent solution)
Δ: Translucent solution ×: Insoluble (precipitated)

As shown in Table 4, the counter anion of the quaternary ammonium cation is BF ₄ ^- or PF ₆ ^- Polymer HB-1 and HB-2 is is difficult to dissolve in various organic solvents such. Therefore, it can be seen that even if the polymers HB-1 and HB-2 are used, it is practically impossible to disperse the pigments and nanocarbons in these organic solvents.

<Preparation of pigment dispersion (1)>
(Examples 1 to 3)
(A) Pigment miniaturization treatment PR254, PG58, and PB15-6 were prepared as pigments for color filters. 100 parts of pigment, 400 parts of sodium chloride, and 130 parts of diethylene glycol were placed in a kneader equipped with a pressure lid (a pressure kneader manufactured by Moriyama Co., Ltd.). After premixing until a uniformly moistened mass was formed in the kneader, the pressure 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 product.} The obtained pyroclastic material was put into 3,000 parts of 2% sulfuric acid and stirred for 1 hour. After removing sodium chloride and diethylene glycol by filtration, the mixture was thoroughly washed with water, and then dried and pulverized to obtain each pigment powder. The number average particle size of the pigment powder measured and calculated by observing with a transmission electron microscope (TEM) was about 30 nm.

(B) Preparation of Polymer Dispersant Solution 50 parts of polymers SIB-13 and 116.7 parts of PGMAc were placed in a beaker, respectively. Further, a stirrer was added, and the mixture was stirred using a magnetic stirrer until the polymer was completely dissolved to obtain polymer dispersant solutions SIB-1S, SIB-2S, and SIB-3S. The solid content of the obtained polymer dispersant solution was 30.0% (SIB-1S), 29.9% (SIB-2S), and 29.9% (SIB-3S), respectively.

(C) Preparation of Pigment Dispersion Solution Each component of the type and amount (unit: part) shown in the upper part of Table 5 was mixed and stirred using a dissolver for 2 hours. After confirming that the pigment lumps had disappeared, dispersion treatment was performed using a horizontal media disperser to prepare a pigment dispersion liquid. In Table 5, "Synagisto 1" is a compound (dye derivative) represented by the following formula (I), "Synagisto 2" is a compound represented by the following formula (II), and "Synagisto 3" is the following. It is a compound represented by the formula (III). As the "acrylic resin" in Table 5, a polymer having a monomer composition of BzMA / MAA = 80/20 (mass ratio), Mn5,500, and PDI2.02 was used. The Mn of the polymer was measured using a PGMAc solution having a solid content of 30%.

(D) Evaluation of pigment dispersion liquid The number average particle size (nm) of the pigment in the pigment dispersion liquid, the initial viscosity (mPa · s) of the pigment dispersion liquid, and the pigment dispersion liquid after storage at 45 ° C. for 3 days. The measurement results of viscosity (viscosity after storage; mPa · s) are shown in the lower part of Table 5. The number average particle size of the pigment was measured using a dynamic light scattering type particle size distribution measuring device. The viscosity of the pigment dispersion was measured using an E-type viscometer under the conditions of 60 rpm and 25 ° C.

<Application to resists for color filters>
(Application Examples 1 to 3)
(A) Preparation of resist ink for color filter The components of the type and amount (unit: part) shown in Table 6 are mixed and sufficiently mixed using a mixer to obtain a resist ink for color filter of each color. It was. The "photosensitive acrylic resin varnish" in Table 6 is an acrylic resin (Mn6, 100, PT14, 400, PDI 2.39, acid value 111 mgKOH / g) obtained by reacting a BzMA / MAA copolymer with glycidyl methacrylate. ) Is contained in the varnish. The meanings of the abbreviations in Table 6 are as shown below.
-TMPTA: Trimethylolpropane triacrylate-HEMPA: 2-Hydroxyethyl 2-methylpropionic acid-DEAP: 2,2-diethoxyacetophenone

(B) Evaluation of Resist Ink for Color Filter A glass substrate treated with a silane coupling agent was set in a spin coater. The resist inks of each color were spin-coated on the glass substrate under the conditions of 300 rpm and 5 seconds. After prebaking at 80 ° C. for 10 minutes, the glass substrate of each color (red glass substrate-1, green glass substrate-1, and blue glass substrate-1) is exposed to light at ^{100 mJ / cm 2 using an ultra-high pressure mercury lamp.} Manufactured.

The obtained glass substrates of each color had excellent spectral curve characteristics and were also excellent in robustness such as light resistance and heat resistance. In addition, all the glass substrates were excellent in optical characteristics such as light transmission and contrast ratio.

<Preparation of pigment dispersion (2)>
(Examples 4 to 8)
(A) Preparation of polymer dispersant solution 50 parts each of polymers SIB-4 and SIB-5 and 116.7 parts of PEA were placed in a beaker. Further, a stirrer was added, and the mixture was stirred using a magnetic stirrer until the polymer was completely dissolved to obtain polymer dispersant solutions SIB-4S and SIB-5S. The solid content of the obtained polymer dispersant solution was 29.9% (SIB-4S) and 30.0% (SIB-5S), respectively.

(B) Preparation of Pigment Dispersion Solution Each component of the type and amount (unit: part) shown in the upper part of Table 7 was mixed and stirred using a dissolver for 2 hours. After confirming that the pigment lumps had disappeared, dispersion treatment was performed using a horizontal media disperser to prepare a pigment dispersion liquid. In Table 7, "Synagisto 4" is a compound (dye derivative) represented by the following formula (IV). In Table 7, the trade name “Levasclin Yellow” (manufactured by LANXESS) was used as “PY-150”. Further, as "PR-122" and "PB-15: 4", pigments manufactured by Dainichiseika Kogyo Co., Ltd. were used. Further, the product name "MB-1000" (manufactured by Mitsubishi Chemical Corporation) was used as "carbon black", and the product name "JR-405" (manufactured by TAYCA Corporation) was used as "titanium oxide".

(C) Evaluation of Pigment Dispersion Liquid Number average particle size (nm) of pigment in initial pigment dispersion liquid, number average particle size (nm) of pigment in pigment dispersion liquid after storage at 70 ° C. for 1 week, pigment The measurement results of the initial viscosity (mPa · s) of the dispersion and the viscosity (mPa · s) of the pigment dispersion after storage at 70 ° C. for 1 week are shown in the lower part of Table 7.

As shown in Table 7, the pigment dispersions of the respective colors of Examples 4 to 8 are suitable as colorants for ultraviolet curable inks because the pigments are highly dispersed and the storage stability is high. .. Among them, since the pigment is stably dispersed in the state of fine particles for a long period of time with almost no aggregation, it is particularly suitable as a colorant for ultraviolet curable inkjet inks that require ejection stability and high-speed printability. is there.

<Preparation of pigment dispersion (3)>
(Examples 9 to 11)
(A) Preparation of polymer dispersant solution 50 parts of polymer SIB-2 to 4 and 116.7 parts of 3-methoxy-3-methyl-1-butyl acetate (trade name "Solfit AC", manufactured by Kuraray Co., Ltd.) Was put in a beaker. Further, a stirrer was added, and the mixture was stirred using a magnetic stirrer until the polymer was completely dissolved to obtain polymer dispersant solutions SIB-2A, SIB-3A, and SIB-4A. The solid content of the obtained polymer dispersant solution was 29.8% (SIB-2A), 29.8% (SIB-3A), and 30.1% (SIB-4A), respectively.

(B) Preparation of Pigment Dispersion Liquid (Nanocarbon Dispersion Liquid) Each component of the type and amount (unit: part) shown in the upper part of Table 8 was mixed and stirred using a dissolver for 2 hours. After confirming that the nanocarbon lumps had disappeared, dispersion treatment was performed using a horizontal media disperser to prepare a nanocarbon dispersion liquid. In Table 8, the trade name “N006-P” (manufactured by Ishihara Chemical Co., Ltd.) was used as “graphene”. Further, as "graphite", the trade name "xGnP-M-5" (manufactured by XG Science Co., Ltd.) was used. Further, as "CNT", the trade name "AMC" (manufactured by Ube Industries, Ltd.) was used.

(C) Evaluation of pigment dispersion liquid (nanocarbon dispersion liquid) Measurement results of the initial viscosity (mPa · s) of the pigment dispersion liquid and the viscosity (mPa · s) of the pigment dispersion liquid after storage at 70 ° C. for 1 week. Is shown in the lower part of Table 8.

The pigment dispersion liquid of the present invention is suitable as a colorant for an image display material such as a color filter and a colorant for an image recording material such as an inkjet ink.

Claims (6)

Contains pigments, organic solvents, and polymer dispersants,
A pigment dispersion liquid in which the polymer dispersant is a polymer that satisfies the following requirements (1) to (4).
(1) An AB block copolymer having a polymer chain A and a polymer chain B containing 90% by mass or more of a methacrylate-based monomer unit.
(2) The polymer chain A is a polymer block having an amine value of 0.5 mgKOH / g or less and a polystyrene-equivalent number average molecular weight of 3,000 to 15,000 as measured by a gel permeation chromatograph.
(3) The polymer chain B is a polymer block having an amine value of 0 to 150 mgKOH / g, which contains a methacrylate-based monomer unit (b) having a functional group represented by the following general formula (1).
(4) The content of the methacrylate-based monomer unit (b) is 30 to 80% by mass based on the entire polymer.

(In the general formula (1), R ₁ , R ₂ , and R ₃ independently represent an alkyl group, an alkenyl group, or an allylmethyl group having 1 to 18 carbon atoms, and X ₁ and X ₂ are Independently of each other, they indicate a fluorine atom or an alkyl fluoride group having 1 to 8 carbon atoms). The pigment dispersion liquid according to claim 1, wherein the organic solvent is an aprotic solvent having a relative permittivity of 20 or less. The pigment dispersion according to claim 1 or 2, wherein the pigment is a pigment having at least one acidic group of a carboxy group, a sulfonic acid group, and a phosphoric acid group on its surface. The pigment dispersion liquid according to any one of claims 1 to 3, wherein the pigment is a nanocarbon substance. The pigment dispersion liquid according to claim 4, wherein the nanocarbon substance is at least one of carbon nanotubes and nanographenes. The content of the polymer dispersant with respect to 100 parts by mass of the pigment is 10 to 200 parts by mass.
The pigment dispersion liquid according to any one of claims 1 to 5, wherein the content of the pigment is 0.5 to 30% by mass based on the entire dispersion liquid.