JP7166532B2 - Coloring material dispersion - Google Patents

Description

TECHNICAL FIELD The present invention relates to a coloring material dispersion containing a specific block polymer, which can be suitably used for inkjet water-based ink.

Background Art Conventionally, many pigments have been used as colorants for inkjet recording inks, writing instrument inks, and the like, due to their excellent fastness such as water resistance and light resistance. In water-based inks using pigments, pigments are not soluble in water, so when used in ink compositions, it is important to stably disperse the pigments in water as fine particles. However, there is a problem of denaturation of the recording liquid due to aggregation and sedimentation of the pigment, that is, so-called storage stability. In addition, it should have excellent color characteristics such as color development and gloss, should not clog nozzles with ink, and should quickly recover from nozzle clogging after a long period of inactivity, in other words, should have excellent ink ejection stability. , is required.

The reason for the decrease in ejection stability is often that the medium in the ink evaporates and the solid components of the ink precipitate or crystallize at the air/liquid interface. Particularly for water-based colorant inks, changes in solvent composition caused by evaporation can cause the dispersed colorant to agglomerate. Aggregates precipitated at that time need to be easily redispersed in the head cleaning operation.

In order to solve these problems, it has been proposed to improve the storage stability by using a block polymer that is superior in pigment adsorption to a random polymer. For example, in Patent Document 1, it is proposed to achieve both dispersibility and gloss by using a block polymer having a gradient copolymer structure with a gradient of hydrophilicity and hydrophobicity. , monomers with one aromatic ring such as styrene, benzyl methacrylate, etc. are used in the hydrophobic segment.

Further, Patent Document 2 proposes a method for improving storage stability, ejection stability and redispersibility by using a block polymer and a pigment derivative. Specifically, as in Patent Document 1, a hydrophobic segment composed of a monomer having one aromatic ring is used, but by using a derivative, storage stability, ejection stability, and redispersibility are improved. I'm trying to let

In addition to using a block polymer, for example, in Patent Document 3, a water-insoluble polymer dispersant is used to coat (encapsulate) a colorant to cope with deterioration of storage stability.

JP-A-2008-195769 JP 2011-225834 A JP 2016-26256 A

However, the present inventors have found that even when the block polymer described in Patent Document 1 is used, redispersibility related to ejection stability is not sufficient.
Moreover, it has been found that the use of a pigment derivative as described in Patent Document 2 causes a problem of color deterioration, and the problem of color characteristics cannot be solved.
Further, in the method using a water-insoluble polymer as in Patent Document 3, the high hydrophobicity of the dispersant causes the problem of poor redispersibility during head cleaning operation.

The present invention has been made in view of the problems of the prior art, and by using a block polymer having a hydrophobic segment derived from a specific monomer, excellent storage stability and redispersibility can be obtained. and capable of adjusting an ink composition that achieves color characteristics.

As a result of intensive studies aimed at achieving the above object, the present inventors have found that the above object can be solved by using a block polymer having a specific structure containing a specific skeleton as a dispersant. That is, according to the present invention, the following dispersant and coloring material dispersion are provided.

That is, the present invention
[1] A coloring material comprising at least a water-insoluble coloring material, an aqueous medium, and a block polymer having a hydrophobic segment and a hydrophilic segment, wherein the hydrophobic segment has a biphenyl group. dispersion,
[2] The coloring material dispersion according to [1] above, wherein the coloring material is a pigment or a water-insoluble dye.
[3] The coloring material dispersion according to [1] or [2], wherein the mass ratio of the hydrophobic segment to the hydrophilic segment is 25:75 to 65:35,
[4] The coloring material dispersion according to any one of [1] to [3], wherein the hydrophilic segment contains a structural unit derived from (meth)acrylic acid,
[5] The coloring material dispersion according to any one of [1] to [4], wherein the block polymer has an acid value of 120 mgKOH/g or more and 170 mgKOH/g or less.
[6] The coloring material dispersion according to any one of [1] to [5], wherein the peak top molecular weight of the block polymer is 3000 or more and 16000 or less.

[7] Any one of the above [1] to [6], wherein the structural unit derived from a biphenyl group-containing (meth)acrylate constituting the hydrophobic segment includes one having a logP of 3.00 or more and 5.00 or less. a coloring material dispersion according to
[8] Any one of [1] to [7], wherein the weight ratio of biphenyl group-containing (methacrylate) to other monomers in the hydrophobic segment is 10/90 or more. a coloring material dispersion according to
[9] The aqueous colorant dispersion according to any one of [1] to [8], wherein at least part of the hydrophilic segment is neutralized with an alkaline compound.
is.

The present invention was completed based on the discovery that the above-described problems can be solved by incorporating a specific block polymer. That is, it is a dispersion containing a block polymer which has a hydrophilic segment and a hydrophobic segment as a block polymer, and which contains a structural unit derived from a biphenyl group-containing (meth)acrylate in the hydrophobic segment.

By containing such a specific polymer, it is possible to obtain a coloring material dispersion that has excellent storage stability and redispersibility, and that allows adjustment of an ink composition that achieves color characteristics. .

Hereinafter, the present invention will be described in detail based on its preferred embodiments.

(water-insoluble coloring material)
In the coloring material dispersion of the present invention, a water-insoluble coloring material is used. They are typically pigments or water-insoluble dyes. The term "water-insoluble" as used herein also includes so-called water-insoluble substances that are difficult to completely dissolve in water.
As pigments, for example, C.I. I. Pigment yellow 1, 2, 3, 12, 14, 16, 17, 73, 74, 75, 83, 93, 95, 97, 98, 109, 110, 114, 128, 129, 138, 139, 147, 150, 151, 154, 155, 180, 185, etc., and one or more of these can be used.

Further, as a pigment for magenta ink, for example, C.I. I. Pigment Red 5, 7, 12, 48 (Ca), 48 (Mn), 57 (Ca), 57: 1, 112, 122, 123, 168, 184, 202, 209; I. pigment violet 19, etc., and one or more of these can be used.
As a pigment for cyan ink, for example, C.I. I. Pigment Blue 1,2,3,15:3,15:4,16,22,60; C.I. I. Bat Blue 4, 60 and the like are included, and one or more of these can be used.
Examples of black ink pigments include carbon blacks (C.I. Pigment Black 7) such as furnace black, lamp black, acetylene black and channel black, inorganic pigments such as iron oxide pigments; aniline black (C.I. Examples include organic pigments such as pigment black 1).

Among the above pigments, those having a structure in which aromatic rings are linked, such as anthracene, quinacridone, and biphenyl structures, are particularly effective in storage stability. It is presumed that the π-π interaction between the aromatic ring of the pigment and the biphenyl group of the polymer described below contributes to further stabilization. Examples of such pigments include Pigment Yellow 74, 114, 147, 150, Pigment Red 5, 7, 12, 48, 57, 112, 122, 123, 168, 184, 202, 209, Pigment Violet 19, Pigment Blue 1, 2, 22, 60, Pigment Black 7 and the like.

The above various pigments may be pigments kneaded with a dispersant.

Further, the dispersion liquid of the present invention may contain a disperse dye as a water-insoluble coloring material. Disperse dyes are compounds that are sparingly soluble or insoluble in water.
Specific examples of disperse dyes include the following.
Yellow disperse dyes include, but are not limited to, C.I. I. Disperse Yellow 3, 4, 5, 7, 9, 13, 23, 24, 30, 33, 34, 42, 44, 49, 50, 51, 54, 56, 58, 60, 63, 64, 66, 68 , 71, 74, 76, 79, 82, 83, 85, 86, 88, 90, 91, 93, 98, 99, 100, 104, 108, 114, 116, 118, 119, 122, 124, 126, 135 , 140, 141, 149, 160, 162, 163, 164, 165, 179, 180, 182, 183, 184, 186, 192, 198, 199, 202, 204, 210, 211, 215, 216, 218, 224 , 227, 231, 232.

Examples of the orange disperse dye include, but are not limited to, C.I. I. Disperse Orange 1, 3, 5, 7, 11, 13, 17, 20, 21, 25, 29, 30, 31, 32, 33, 37, 38, 42, 43, 44, 45, 46, 47, 48 , 49, 50, 53, 54, 55, 56, 57, 58, 59, 61, 66, 71, 73, 76, 78, 80, 89, 90, 91, 93, 96, 97, 119, 127, 130 , 139, 142.
Examples of red disperse dyes include, but are not limited to, C.I. I. disperse thread 1, 4, 5, 7, 11, 12, 13, 15, 17, 27, 43, 44, 50, 52, 53, 54, 55, 56, 58, 59, 60, 65, 72, 73, 74, 75, 76, 78, 81, 82, 86, 88, 90, 91, 92, 93, 96, 103, 105, 106, 107, 108, 110, 111, 113, 117, 118, 121, 122, 126, 127, 128, 131, 132, 134, 135, 137, 143, 145, 146, 151, 152, 153, 154, 157, 159, 164, 167, 169, 177, 179, 181, 183, 184, 185, 188, 189, 190, 191, 192, 200, 201, 202, 203, 205, 206, 207, 210, 221, 224, 225, 227, 229, 239, 240, 257, 258, 277, 278, 279, 281, 288, 298, 302, 303, 310, 311, 312, 320, 324, 328.

Violet disperse dyes include, but are not limited to, C.I. I. Disperse Violet 1, 4, 8, 23, 26, 27, 28, 31, 33, 35, 36, 38, 40, 43, 46, 48, 50, 51, 52, 56, 57, 59, 61, 63 , 69, 77.
Examples of green disperse dyes include, but are not limited to, C.I. I. Disperse Green 9 is mentioned.
Examples of blue disperse dyes include, but are not limited to, C.I. I. Disperse Blue 3, 7, 9, 14, 16, 19, 20, 26, 27, 35, 43, 44, 54, 55, 56, 58, 60, 62, 64, 71, 72, 73, 75, 79 , 81, 82, 83, 87, 91, 93, 94, 95, 96, 102, 106, 108, 112, 113, 115, 118, 120, 122, 125, 128, 130, 139, 141, 142, 143 , 146, 148, 149, 153, 154, 158, 165, 167, 171, 173, 174, 176, 181, 183, 185, 186, 187, 189, 197, 198, 200, 201, 205, 207, 211 , 214, 224, 225, 257, 259, 267, 268, 270, 284, 285, 287, 288, 291, 293, 295, 297, 301, 315, 330, 333, 359, 360.
Examples of the black disperse dye include, but are not limited to, C.I. I. Disperse Black 1, 3, 10, 24 can be mentioned.
One or more of the above pigments or water-insoluble dyes can be appropriately selected and used.

(block polymer)
[Each segment of the block polymer]
The coloring material dispersion of the present invention contains a specific block polymer. That is, block polymers containing at least one hydrophobic segment and at least one hydrophilic segment.
When each segment is composed of two or more monomers, the shape of the segment may be a random copolymer, a block copolymer within the segment, an alternating copolymer, or the like, but is not particularly limited in the present invention.
Two or more of each of the hydrophobic segment and the hydrophilic segment may be provided, but sufficient effect can be obtained with one of each.

[About the hydrophobic segment]
A hydrophobic segment refers to a portion containing a hydrophobic functional group. The present invention is particularly characterized by having a biphenyl group. In the hydrophobic segment, the hydrophobic functional group functions as an adsorption group to the coloring material. In the present invention, the biphenyl group functions as the hydrophobic functional group, and other hydrophobic functional groups may be present. do not have.
A hydrophobic segment having a biphenyl group can be easily obtained by preparing a polymer using a biphenyl group-containing (meth)acrylate as a monomer.

The hydrophobic segment in the present invention can be typically represented by the following formula (1). Ph2 represents a biphenyl group, and in addition to the unsubstituted biphenyl skeleton, it has a substituent such as a hydroxyl group, a methyl group, a carbonyl group, Cl, Br, etc. at positions X1 to 9 in the following formula (2). may An unsubstituted biphenyl skeleton is particularly preferred. That is, the biphenyl group is present on the side chain. The structure represented by this formula (1) is repeated to form the hydrophobic segment.

In addition, Y is not limited, but a single bond, an alkylene group having 1 to 12 carbon atoms, a (poly)ethyleneoxy group having 1 to 20 repeating units, and a (poly)propyleneoxy group having 1 to 20 repeating units A typical example is a divalent linking group consisting of at least one selected from groups. Among them, an ethyleneoxy group is preferred.
The position of Y is also not limited, and any position in formula (2) can be selected. Especially preferred is the position o- to the bond of the two benzene rings of the biphenyl group.

To form the hydrophobic segment in the block polymer, a monomer having a hydrophobic functional group and a polymerizable functional group is generally polymerized. In the present invention, a hydrophobic segment having a biphenyl group can be obtained by using a monomer having at least a biphenyl group and a polymerizable functional group. Specifically, it is the following formula (3). In the formula, Ph2 and Y are the same as in formula (1).

A typical polymerizable group is a vinyl group. When Y is an ethyleneoxy group, it becomes a monomer represented by the following formula (4).

Again, the biphenyl group may be substituted or unsubstituted. As for the position of Y, any position can be selected as in formula (1). Specifically, they are compounds represented by the following formulas (5) to (7).

Specific examples of such monomers include biphenyl group-containing compounds having a vinyl group as a polymerizable functional group such as 4-vinylbiphenyl and 4,4′-divinylbiphenyl, and 2-(biphenyl 2-yloxy)ethyl acrylate. , diphenyl-2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate and the like. Among these, 2-(biphenyl-2-yloxy)ethyl acrylate, diphenyl-2-acryloyloxyethyl phosphate, and diphenyl-2-methacryloyloxyethyl phosphate are preferred, and 2-(biphenyl-2-yloxy)ethyl is more preferred. = acrylate, ethoxylated o-phenylphenol acrylate.

As such a hydrophobic monomer having a biphenyl group, various commercially available products, for example, compounds listed in the following formula (8) (when m = 1, Log P: 3.98. For example, "A-LEN-10" (trade name Shin-Nakamura Chemical Co., Ltd. ethoxylated o-phenylphenol acrylate)), when m = 1 to 2, for example, "New Frontier OPPE" (trade name, ethylene oxide-modified orthophenylphenol acrylate manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) . Others "Aronix M-108" (trade name: o-phenylphenol ethylene oxide modified acrylate manufactured by Toagosei Co., Ltd.), "MR-260" (trade name: diphenyl-2-methacryloyloxyethyl manufactured by Daihachi Chemical Industry Co., Ltd.) phosphate.) and the like.

Among these monomers, those having a LogP of 3.00 to 5.00 are particularly preferred. These are highly hydrophobic and can be expected to have a high effect due to the π stack. Note that the measurement of LogP here is the measurement of the partition coefficient (Partition Coefficient) according to "OECD GUIDELINE FOR TESTING OF CHEMICALS," Partition Coefficient (n-octanol/water), High Performance Liquid Chromatography (HPLC) Method", Adopted by the Council on 30th March 1989.”. Other methods that can obtain equivalent values may also be used.

As the monomer used for forming the hydrophobic segment, a monomer other than the biphenyl group-containing monomer described above may be used in combination. For example tert-butyl acrylate, tert-butyl methacrylate, n-hexyl acrylate, n-hexyl methacrylate, n-octyl acrylate, n-octyl methacrylate, iso-octyl acrylate, iso-octyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate , decyl acrylate, decyl methacrylate, lauryl acrylate, lauryl methacrylate, stearyl acrylate, stearyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, phenyl acrylate, phenyl methacrylate, isobornyl acrylate, nonylphenyl acrylate, nonylphenyl methacrylate, benzyl acrylate, benzyl methacrylate , dicyclopentenyl acrylate, dicyclopentenyl methacrylate, styrene, methylstyrene, vinyltoluene, and the like.
As for these monomers, those having a LogP of 3.00 to 5.00 are particularly preferred. Specific examples include benzyl acrylate (log P: 2.37), benzyl methacrylate (log P: 2.72), styrene (log P: 2.67), and methylstyrene (log P: 2.84). .

The blending ratio of the hydrophobic monomer having the biphenyl group described above and the other monomer is 10/90 or more, more preferably 25/75 or more, further preferably 50/50 or more. This is because if the amount of the hydrophobic monomer having a biphenyl group is less than that, the adsorptive power to the pigment will be weak, and the storage stability will be low.

[About the hydrophilic segment]
The hydrophilic segment contains at least a functional group that has an affinity for water. For this purpose, a functional group having affinity for water and a monomer having a polymerizable functional group may be polymerized.

Examples of monomers having affinity for water include (meth)acrylic acid, maleic acid, itaconic acid, vinylphosphonic acid, vinylsulfonic acid and the like. Among these, acrylic acid is preferred because of its good storage stability.

[About synthesis method]
A block polymer having at least one hydrophilic segment and at least one hydrophobic segment is formed by polymerizing the above monomers.

The method for producing (synthesizing) the block polymer is not particularly limited. Various methods generally known as block polymer production methods, for example, using a metal complex such as copper or ruthenium as a catalyst, and using an organic halide as an initiating compound, atom transfer radical polymerization by redox; nitroxide; nitroxide method in which the —N—O radical of is transferred; reversible addition-fragmentation chain transfer polymerization using a dithiocarboxylic acid ester or the like; and iodine transfer polymerization.
It is common to form a hydrophobic segment by these well-known living radical polymerization methods and add a hydrophilic segment by adding a monomer having a hydrophilic functional group.

(initiator)
As initiators, general azo initiators azobis (isobutyronitrile) (AIBN), azobis (2,4-dimethylvaleronitrile) (V65), 2,2'-azobis (4-methoxy-2 ,4-dimethylvaleronitrile) (V70), peroxide-based initiators benzoyl peroxide, dicumyl peroxide, t-butyl peroxybenzoate (BPB), di (4-tert-butylcyclohexyl) peroxydicarbonate (PERKADOX16), peroxide Potassium disulfate oxide can be used without restriction. AIBN is particularly preferred.

(Neutralizer)
A dispersant can be obtained by neutralizing the block polymer described above with an alkaline compound. Specific examples of alkaline compounds include KOH, NaOH, triethylamine, triethanolamine, ammonia and the like.
The amount of the alkaline compound to be added should be such that it can neutralize 20% to 200% of the acid value of the resin. It is preferably 40-180%, more preferably 60-150%. This is because if the neutralization rate is lower than that, the resin will precipitate over time, and if the neutralization rate is higher, there is a possibility that printer head members and the like will be damaged due to an increase in pH.

[Resin characteristics]
The mass ratio of the hydrophobic segment to the entire block polymer is preferably 5-70%, more preferably 25-65%, and particularly preferably 40-60%. That is, the weight ratio of the hydrophobic segment to the hydrophilic segment is preferably in the range of 25:75 to 65:35. If the proportion of the hydrophobic segment is smaller than this, the pigment adsorption performance tends to be low and the stability tends to be low. On the other hand, if the proportion of the hydrophobic segment is too high, it may become insoluble in the solvent.
These ratios can be adjusted by the ratios of the monomers described above. Further, when the obtained resin is analyzed and confirmed, ¹ H-NMR, GPC, acid value titration, or the like can be used.

The block polymer used in the present invention has a peak top molecular weight of 3,000 to 16,000, preferably 4,000 to 14,000, more preferably 5,000 to 12,000. When the peak top molecular weight is less than 3,000, steric hindrance and charge repulsion are reduced, and storage stability cannot be maintained. On the other hand, when the peak top molecular weight is 16,000 or more, the viscosity of the ink increases and the adsorption speed slows down, resulting in poor dispersion. Moreover, the water solubility of the polymer itself may be remarkably lowered.
The conditions for measuring the peak top molecular weight are as described in Examples.

The acid value of the block polymer is preferably 120 mgKOH/g or more and 170 mgKOH/g or less. If it exceeds 170 mgKOH/g, the affinity to the aqueous medium becomes too high, and the adsorption performance to the pigment may deteriorate, making dispersion difficult. Conversely, if the acid value is reduced to less than 120 mgKOH/g, the water solubility will drop, and redispersibility may deteriorate.
The acid value is the mg amount of KOH required to neutralize 1 g of resin. Specifically, it can be measured by titrating a solution obtained by dissolving the resin in methoxypropanol with a 1N NaOH aqueous solution.
Although the mechanism by which a coloring material dispersion having excellent performance is obtained by the block polymer used in the present invention described above is not completely clear, biphenyl group-containing (meth)acrylates have high hydrophobicity as indicated by LogP and the like. It is presumed that the excellent storage stability is obtained because of the strong adsorption to the coloring material in the aqueous medium due to the hydrophilic/hydrophobic interaction.

In particular, when the coloring material has an aromatic ring as described above, the π-π interaction is also expressed, which is considered to work more favorably for storage stability. Since it is a block polymer, the hydrophobicity of the hydrophobic segment is high and it is likely that it is easily adsorbed to the coloring material, further enhancing the π-π interaction. At the same time, since the hydrophilic segment is also localized, strong charge repulsion is obtained in the aqueous medium, which is presumed to contribute to the improvement of storage stability. It is also presumed that due to the localization of the hydrophilic segment, it can be easily re-dispersed by re-contacting the ink even in an environment where the solvent has evaporated.
Thus, by containing the specific polymer described above, storage stability and redispersibility are excellent, so there is no need to use a pigment derivative. Therefore, the coloring material dispersion of the present invention has excellent color properties.

(aqueous medium)
As the aqueous medium used in the coloring material dispersion of the present invention, water is usually used, but a water-soluble organic solvent may be used as necessary. Examples of water-soluble organic solvents include 1,2-hexanediol, 1,6-hexanediol, 1,5-pentanediol, 2-pyrrolidone, N-methylpyrrolidone, triethylene glycol monobutyl ether, ethylene glycol, propylene glycol. , triethylene glycol, glycerin, and the like.
Among these, 1,2-hexanediol, 2-pyrrolidone and triethylene glycol monobutyl ether are particularly preferred.

(Additive)
If necessary, activators such as acetylene glycol-based and silicone-based active agents and preservatives may be added. Commercially available products can be used, for example, Olfine Y, Surfynol 82, 440, 465, STG, E1010 for acetylene glycol-based compounds, and BYK348 (manufactured by BYK-Chemie Japan) for polysiloxane-based compounds. can be used.

(Dispersion process)
In order to obtain the coloring material dispersion of the present invention, each of the above components may be dispersed by a known method. Specifically, each of the above components is put into a bead mill or other wet dispersing machine and dispersed.

(Cross-linking treatment)
In order to achieve both stability and redispersibility, the dispersion of the present invention is preferably subjected to cross-linking treatment after dispersion.
As the cross-linking agent, an epoxy resin having a glycidyl ether skeleton, a resin having an oxazoline group, or the like can be used.
The amount of the cross-linking agent is preferably in the range of 0.5% to 60% with respect to the resin. If it is less than this, the stabilizing effect by crosslinking cannot be exhibited, and if it is more than this, the redispersibility may deteriorate. Cross-linking can be carried out by adding a cross-linking agent to the coloring material dispersion that has undergone the above-described dispersion step and heating the mixture to around 80°C.

(ultrafiltration)
The coloring material dispersion of the present invention is preferably subjected to an impurity removal step by ion exchange treatment or ultrafiltration treatment. Ionic substances such as cations and anions (divalent metal ions, etc.) can be removed by ion exchange treatment, and impurities dissolved substances (residual substances during pigment synthesis, excess components in dispersion composition, etc.) can be removed by ultrafiltration treatment. , resin not adsorbed to the organic pigment, contaminants, etc.) can be removed.

The coloring material dispersion of the present invention containing each of the components described above may contain other components depending on the application. In addition, the term "dispersion" means that a water-insoluble coloring material is dispersed in an aqueous medium. It also includes a state in which a coloring material is dispersed in an aqueous medium.
To prepare the ink, it is preferable to previously prepare a dispersion liquid in which each component described above is dispersed. The composition in this case is 1 to 60 parts by weight, preferably 3 to 40 parts by weight, more preferably 5 to 25 parts by weight of the coloring material when the entire dispersion is 100 parts by weight. The content of the block polymer is 0.1-30 parts by weight, preferably 0.3-20 parts by weight, more preferably 1-15 parts by weight.
To prepare an ink from such a dispersion liquid, for example, in the case of an inkjet ink, the following method can be adopted.

(Inkjet ink)
When an inkjet ink is produced using the dispersion described above, other components such as an organic solvent, a resin, and an antiseptic may be added.
Examples of organic solvents include, but are not limited to, polyhydric alcohols and pyrrolidones. Examples of polyhydric alcohols include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, trimethylolpropane and glycerin. Polyhydric alcohols have effects such as enhancing wettability of ink to paper and preventing drying in head nozzles to enhance moisture retention. When polyhydric alcohols are contained, they can be contained in an amount of 2% by mass or more and 30% by mass or less with respect to the total mass of the ink.
Resins have the function of increasing fixability, such as acrylic resins, fluorene resins, urethane resins, olefin resins, rosin-modified resins, terpene resins, ester resins, amide resins, epoxy resins, and vinyl chloride. resins, vinyl chloride-vinyl acetate copolymers, ethylene vinyl acetate resins, and the like. These resins can be used singly or in combination of two or more. As the resin, an emulsion type resin or a solution type resin may be used. When resin is contained, the content can be 0.1% by mass or more and 6% by mass or less.

Examples of antiseptics and antifungal agents include sodium benzoate, pentachlorophenol sodium, 2-pyridinethiol-1-oxide sodium, sodium sorbate, sodium dehydroacetate, 1,2-dibenzisothiazolin-3-one (Zeneca Proxel CRL, Proxel BDN, Proxel GXL, Proxel XL.2, Proxel TN, Proxel LV), 4-chloro-3-methylphenol (Bayer's Preventol CMK, etc.).

(Example)
EXAMPLES The present invention will be described in more detail below with reference to examples. "Parts" means "parts by weight".
[Synthesis example]
(Preparation of aqueous resin)
"A-LEN-10" (trade name, Shin-Nakamura Chemical Co., Ltd. ethoxylated o-phenylphenol acrylate, specific gravity 1.135 (25 ° C), viscosity 150 mPa s (25 ° C), refractive index: 1.577, molecular weight 268, log P = 3.98) 420 parts, methacrylic acid 87.5 parts, acrylic acid 73.5 parts S-benzyl-S-dodecyltrithiocarbonate (polymerization modifier) 51.6 parts, azobisisobutyronitrile (radical initiator) 11.5 parts, methoxypropanol (Reaction solvent) 700 parts were charged into a 2 L stainless steel separable flask, the temperature of the system was raised to 70100°C in an oil bath while nitrogen bubbling and stirring were performed, and the reaction was allowed to proceed for 6 hours after the temperature was raised, Polymer block A was synthesized. Then, the temperature in the system was raised to 170° C., the pressure in the system was reduced, the solvent was distilled off, and the content was taken out. A small amount of the sample was sampled and subjected to GPC measurement. Next, 119 parts of "ALEN10" and 420 parts of methoxypropanol were added to the flask, and the mixture was reacted at 70°C for 8 hours with nitrogen bubbling and stirring. A sample of the contents was subjected to GPC measurement, and the peak top molecular weight was 5000, Mw/Mn=1.29.

A block copolymer (I) was taken out. GPC measurement of the obtained block copolymer (I) revealed a peak top molecular weight of 5,000 and an Mw/Mn ratio of 1.30. Moreover, the acid value was 143 mgKOH/g.

After ion-exchanged water and KOH were added to the synthesized resin, the resin solution 1 was obtained by stirring/dissolving with a dissolver at 80° C. for 2 hours.
The resin concentration was set to 10%, and KOH was added in an amount capable of 100% neutralizing oxidation of the resin.

(resin melt 2-9)
Resin solutions 2 to 9 were obtained by changing the monomer types and ratios as shown in Table 2 in the same procedure as for resin solution 1.

(resin melt 10)
420 parts of "A-LEN-10", 87.5 parts of methacrylic acid, 73.5 parts of acrylic acid, 11.5 parts of azobisisobutyronitrile (radical initiator), 700 parts of methoxypropanol (reaction solvent) in a 2L stainless steel separable The mixture was placed in a flask, heated to 100° C. in an oil bath with nitrogen bubbling and stirring, and reacted for 6 hours after the temperature was raised to synthesize a polymer. Then, the temperature in the system was raised to 170° C., the pressure in the system was reduced, the solvent was distilled off, and the content was taken out. When a small amount of the sample was sampled and GPC measurement was performed, the peak top molecular weight was 10500 and Mw/Mn was 6.2. Moreover, the acid value was 143 mgKOH/g.
After ion-exchanged water and KOH were added to the synthesized resin, the resin solution 10 was obtained by stirring/dissolving with a dissolver at 80° C. for 2 hours.
The resin concentration was 10%, and KOH was added in an amount capable of neutralizing the acid value of the resin by 100%.

GPC measurement was performed under the following conditions.
Equipment: HLC-8220GPC (manufactured by Tosoh Corporation)
Detector: RI (Differential Thermal Refractive Index Detector)
Solvent: degassed THF
Column: Gelpack GL-R400M, GL-R440, GL-R450, used in conjunction with a guard column Measurement concentration: 10mg/ml
Flow rate: 2.0ml/min.
Injection volume: 150 μL/min
Column temperature: 40℃

Table 2 shows the physical properties (acid value, Mp, Mw/Mn) of each resin.

(Example 1)
Mix 20g of "Inkjet yellow 5GXW" (trade name: Clariant, PY74), 140g of resin solution, (1.40g?) 7g of 1,2-hexanediol, and 33g of water. was dispersed for 5 hours using Furthermore, 0.1 mm zirconia beads were used and dispersed for 12 hours with a paint shaker.
Next, 0.24% of an epoxy resin having a glycidyl ether skeleton (epoxy equivalent weight: 143) was added to the recovered dispersion, and crosslinked at 80°C for 2 hours to obtain a crosslinked preparation 1. The resulting crosslinked preparation 1 was centrifuged at 16300 rpm for 10 minutes, and then subjected to ultrafiltration to concentrate/remove impurities to obtain a pigment dispersion. Each of the following evaluations was performed on the pigment dispersion, and the results are shown in Table 3.

(Examples 2-4, Comparative Examples 1-6)
A pigment dispersion was prepared in the same manner as in Example 1, except that the resin was changed as shown in Table 3. Each of the following evaluations was performed on the pigment dispersion, and the results are shown in Table 3.

(Evaluation of storage stability)
A dispersion liquid prepared using each of the above dispersion liquids was made into an ink according to the composition shown in Table 1, left at 70° C. for one week, and the difference in viscosity and particle size from the initial stage was examined. A cone rotor type rotational viscometer (“TV25 type” manufactured by Toki Sangyo Co., Ltd.) was used as a viscosity measuring device, and “Nanotrac wave II EX-150” (manufactured by Nikkiso Co., Ltd.) was used as a particle size measuring device.
○: Change rate less than 5% △: Change rate 5 or more and less than 10% ×: 10% or more

(Evaluation of redispersibility)
The dispersion liquid was dropped onto the petri dish and dried in an oven at 70° C. for 1 hour. After that, the petri dish was filled with ink component liquids other than the ink dispersion liquid, and re-dispersion was confirmed visually.
○: Completely redispersed △: Although redispersed, some aggregates can be seen ×: Not redispersed

(Evaluation of color characteristics)
The ink mixed according to the composition shown in Table 1 was dripped onto a laser copy paper "Xerox4200" and coated using a bar coater. After drying for 30 minutes at room temperature, the OD value of the applied portion was measured using a Macbeth densitometer "RD-918" (manufactured by Sakata Inx).
○: 1.00 or more △: 0.95 or more to less than 1.00 ×: less than 0.95

It can be seen that Comparative Example 1, in which a resin containing structural units not derived from a biphenyl group-containing methacrylate is used as the hydrophobic segment, has insufficient stability and redispersibility.
In addition, it can be seen that in Comparative Example 6, in which the same monomer as in Example 1 was used, but Resin 10, which is a random polymer rather than a block polymer, was used, the stability and redispersibility were not sufficient.

On the other hand, in Examples 1 to 4, which are the inks of the present invention using a block polymer containing a structural unit derived from a biphenyl group-containing methacrylate as a hydrophobic segment, the performance balance of stability, redispersibility, and color characteristics It can be seen that the

As described above, according to the present invention, it is possible to obtain an inkjet ink having excellent performance or a coloring material dispersion having excellent performance as a material thereof.

Claims (8)

A coloring material dispersion containing at least a water-insoluble coloring material, an aqueous medium, and a block polymer having a hydrophobic segment and a hydrophilic segment, wherein the hydrophobic segment has a biphenyl group, wherein the hydrophilic A coloring material dispersion, wherein the segment contains a structural unit derived from (meth)acrylic acid . 2. The coloring material dispersion according to claim 1, wherein the coloring material is a pigment or a water-insoluble dye. 3. The coloring material dispersion liquid according to claim 1, wherein the weight ratio of the hydrophobic segment to the hydrophilic segment is 25:75 to 65:35. 4. The coloring material dispersion liquid according to claim 1 , wherein the block polymer has an acid value of 120 mgKOH/g or more and 170 mgKOH/g or less. 5. The coloring material dispersion liquid according to claim 1 , wherein the block polymer has a peak top molecular weight of 3000 or more and 16000 or less. 6. The coloring material according to any one of claims 1 to 5 , wherein the structural unit derived from a biphenyl group-containing (meth)acrylate constituting the hydrophobic segment includes a structural unit having a logP of 3.00 or more and 5.00 or less. dispersion. 7. The coloring material according to any one of claims 1 to 6 , wherein the weight ratio of biphenyl group-containing (methacrylate) to other monomers in the hydrophobic segment is 10/90 or more. dispersion. The coloring material dispersion according to any one of claims 1 to 7 , wherein at least part of said hydrophilic segment is neutralized with an alkaline compound.