JP5090338B2 - Method for producing liquid developer and liquid developer obtained by the method - Google Patents

Description

The present invention relates to a method for producing a liquid developer for electrophotography or electrostatic recording used in printing machines, copiers, printers, facsimiles, and the like, and a liquid developer obtained by the method.

The liquid developer is generally obtained by dispersing colored resin particles (toner particles) enclosing a colorant such as a pigment in a highly insulating organic medium. In the electrophotographic method or electrostatic recording method using this liquid developer, development is performed by utilizing the phenomenon that toner particles are electrophoresed in an organic medium by applying an electric field. In practice, the developer is stored or applied on one side of the opposite electrode, and an electric field corresponding to the electric latent image is applied between the opposite electrode and the toner receiving the force of the electric field. Development is performed by selectively migrating only the particles and attaching them to the image area.

Today, there is a demand for faster development speeds and higher-definition images. For this reason, first, the colorant is well dispersed in the resin constituting the toner particles, and the toner particles are also organic media. Must be well dispersed in. If the dispersibility is good in both the colorant and the toner particles, it is expected to increase the development speed and improve the image quality by improving the coloring power, lowering the viscosity of the developer, and improving the migration property of the toner particles. Is done.

At present, almost all pigments are used as colorants, but attempts have been made to improve the dispersibility of pigments and toner particles in a liquid developer in order to realize the above-mentioned demand. For example, as a method for improving the dispersibility of toner particles that particularly has a great influence on the development performance, a method using poly (hydroxycarboxylic acid ester) or a material having a polar group such as a base at its terminal (for example, Patent Document 1). Reference). However, the dispersant cannot sufficiently improve the dispersibility, and when the terminal has a polar group such as a base, the insulation property of the organic medium derived from the polar group component is deteriorated or the charging property of the toner is deteriorated. There is also a problem that good image quality cannot be obtained.

Furthermore, when pigment-encapsulated colored resin particles obtained by a general method are made fine particles by a wet pulverization method, they are often crushed at the pigment-resin interface, and the pigment is exposed on the surface of the obtained toner particles. Become. However, the charging characteristics of the color pigments used and the charging characteristics of the resin and the pigment are different. As a result, when the electric field is applied, the charging characteristics are deteriorated, the migration properties of the toner particles are deteriorated, and the toner particles are different for each color and depending on the amount of the pigment exposed on the surface even for the same color. Different charging characteristics make it more difficult to obtain good image quality.
As described above, it is currently inadequate to use toner particles obtained by a known wet pulverization method to achieve both maintenance of insulation and charging characteristics and dispersibility of pigments and toner particles. is there.
Japanese Patent Laid-Open No. 05-273792

The present invention improves the dispersibility of the pigment and the dispersion stability of the toner particles in a liquid developer for electrophotography or electrostatic recording, and minimizes adverse effects on the electrical resistance of the liquid developer and the charging characteristics of the toner particles. It is an object of the present invention to provide a method for producing a liquid developer suppressed to a low level and a liquid developer obtained by the method.

As a result of intensive studies to solve the above problems, the present inventors have improved the dispersibility of the pigment and the dispersion stability of the toner particles by using a pigment previously treated with a specific carbodiimide compound, The inventors have found that adverse effects on the charging characteristics of toner particles formed by the wet pulverization method and the electric resistance of the liquid developer can be minimized, and the present invention has been completed.
That is, in the present invention, (1) as a dispersant, a pigment treated with a carbodiimide compound satisfying the following condition 1 is dispersed in a resin to obtain a pigment resin composite, and then the pigment resin composite is obtained. The present invention relates to a method for producing a liquid developer, which comprises wet pulverization in a dispersion medium to disperse pigment-encapsulated colored resin particles in the dispersion medium.
Condition 1: A carbodiimide compound having a chain introduced by reacting a compound having a group that reacts with a carbodiimide group with a carbodiimide group.
The present invention also provides (2) a carbodiimide system in which the dispersant is introduced with at least one chain selected from the group consisting of a polyester chain, a polyacryl chain, and a polysiloxane chain through a reaction with a carbodiimide group. 2. The method for producing a liquid developer according to claim 1, wherein the liquid developer is a compound.
The present invention also relates to (3) the method for producing a liquid developer according to (1) or (2) above, wherein a carbodiimide compound having a carbodiimide equivalent of 100 to 50000 is used as the dispersant.
The present invention also relates to (4) the method for producing a liquid developer according to any one of (1) to (3) above, wherein a carbodiimide-based compound having a basic nitrogen-containing group is used as the dispersant.
The present invention also relates to (5) the method for producing a liquid developer according to (4), wherein a carbodiimide compound having a basic nitrogen-containing group in the main chain is used as the dispersant.
The present invention also relates to (6) the method for producing a liquid developer according to (4) or (5) above, wherein the basic nitrogen-containing group is a tertiary amino group.
The present invention also provides (7) a carbodiimide compound in which the number average molecular weight of at least one chain selected from the group consisting of a polyester chain, a polyacryl chain, and a polysiloxane chain is 200 to 10,000 as the dispersant. It is related with the manufacturing method of the liquid developer of any one of said (1)-(6) used .

Hereinafter, the liquid developer of the present invention will be described in detail.
Examples of the pigment used in the present invention include inorganic pigments and organic pigments. Specifically, inorganic pigments such as acetylene black, graphite, bengara, yellow lead, ultramarine, carbon black, azo pigments, lake pigments, and phthalocyanine pigments. Organic pigments such as isoindoline pigments, anthraquinone pigments and quinacridone pigments.

When the carbodiimide-based compound described later has a basic nitrogen-containing group, the pigment preferably has an adsorption part with a basic nitrogen-containing group, and the adsorption part with the basic nitrogen-containing group is as follows: Typically, it is an acid group, preferably a functional group capable of reacting with a basic nitrogen-containing group such as a carboxyl group or a sulfonic acid group. As a method for introducing carboxyl groups and sulfonic acid groups even in pigments that have not been adsorbed with basic nitrogen-containing groups in an untreated state, introduction of normal functional groups such as pigment surface derivative treatment and sulfonation treatment It can be processed and used by the method.

When the carbodiimide-based compound described later has a carbodiimide group, the pigment is preferably a pigment having a functional group that can react with a carbodiimide group. Here, the functional group capable of reacting with the carbodiimide group is preferably at least one functional group selected from the group consisting of a carboxyl group, a hydroxyl group, a phosphoric acid group and an amino group. Even if the pigment does not have a functional group capable of reacting with a carbodiimide group, the functional group can be introduced by surface treatment. In addition to the above-described derivative treatment and sulfonation treatment, for example, “pigment dispersion stabilization” And surface treatment technology / evaluation ", first edition, Technical Information Association (published), December 25, 2001, p. The functional group capable of reacting with the carbodiimide group can be introduced by plasma treatment described in 76 to 85, oxygen / ultraviolet treatment, low-temperature plasma method described in JP-A-58-217559, and the like.
In the present invention, the pigment content is not particularly limited, but is preferably 0.5 to 40% by mass in the final liquid developer from the viewpoint of image density.

Next, as a dispersing agent used by this invention, the carbodiimide type compound which has the chain | strand introduce | transduced in the molecule | numerator by making the compound which has the group which reacts with a carbodiimide group react with a carbodiimide group is mentioned.
The “carbodiimide compound” in the present specification is a compound obtained by reacting a compound having a carbodiimide group (carbodiimide compound) and a compound having a group that reacts with a carbodiimide group with each other. In addition to those having a carbodiimide group in the molecule of the obtained compound, those having no carbodiimide are also included.

Hereinafter, in the present invention, regardless of the size of the chain structure, the portion derived from the compound having a carbodiimide group is referred to as a “main chain”, and the reaction between the carbodiimide group and the compound having a group that reacts with the carbodiimide group. All the chains introduced by are referred to as “side chains”.
Examples of the side chain include polyester chain, polyether chain, polyacryl chain, basic nitrogen-containing chain, pigment derivative chain, pigment intermediate chain, dye derivative chain, dye intermediate chain, chain having ultraviolet sensitizing ability, radical Examples thereof include at least one selected from the group consisting of an initiating chain, a chain having an amide group, a polybutadiene chain, and a polysiloxane chain. The side chain is preferably at least one selected from the group consisting of a polyester chain, a polyacryl chain, and a polysiloxane chain.

As the carbodiimide-based compound, preferably, at least one selected from the group consisting of a polyester chain, a polyacryl chain, and a polysiloxane chain is used as a molecule by utilizing a reaction between a carbodiimide group and a functional group capable of reacting with the carbodiimide group. The compounds introduced in can be used. In the present invention, such a reaction between a carbodiimide group and a functional group may be referred to as a grafting reaction. A side chain introduced by the method is referred to as a grafted side chain, for example, an introduced polyester side chain is referred to as a grafting side chain. Sometimes called grafted polyester side chain.

The carbodiimide compound having a grafted side chain is first composed of a polyester side chain, a polyacryl side chain, and a polysiloxane side chain by a grafting reaction based on a compound having one or more carbodiimide groups in the molecule. Mention may be made of compounds obtained by a method of adding at least one side chain selected from the group.

As the compound having one or more carbodiimide groups in the molecule, for example, a compound obtained by carbodiimidizing a diisocyanate compound by decarboxylation in the presence of a carbodiimidization catalyst in an organic solvent can be used. Examples of the diisocyanate compound to be decarboxylated include aliphatics such as hexamethylene diisocyanate, isophorone diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, cyclohexane diisocyanate, dicyclohexylmethane diisocyanate, xylylene diisocyanate, tetramethylene diisocyanate, and tetramethylxylylene diisocyanate. Mention may be made of cyclic, aromatic and araliphatic diisocyanate compounds.

Further, usable organic solvents are those having a high boiling point and no active hydrogen that reacts with an isocyanate compound or a compound having a carbodiimide group to be generated. Specifically, toluene, xylene, diethylbenzene Aromatic hydrocarbons such as: diethylene glycol diacetate, dipropylene glycol dibutyrate, hexylene glycol diacetate, glycol diacetate, methyl glycol acetate, ethyl glycol acetate, butyl glycol acetate, ethyl diglycol acetate, butyl diglycol acetate, etc. Glycol ether esters; ketones such as ethyl butyl ketone, acetophenone, propiophenone, diisobutyl ketone, cyclohexanone; amyl acetate, propyl propionate And aliphatic esters such as ethyl butyrate and the like.
Examples of the carbodiimidization catalyst that can be used include phospholenes and phospholene oxides. Specifically, 1-ethyl-3-methyl-3-phospholene oxide, 1-phenyl-3-methyl- Examples include 3-phospholene oxide and 1-phenyl-3-methyl-2-phospholene oxide.

As a method for performing a decarboxylation reaction of an isocyanate group using these materials, a known method can be used. For example, the reaction can be performed at a reaction temperature of 100 to 200 ° C. in a nitrogen atmosphere. Examples of other methods for obtaining the above compound having a carbodiimide group include methods such as US Pat. No. 2,941,956, Japanese Patent Publication No. 47-33279, Japanese Patent Application Laid-Open No. 5-178954, and Japanese Patent Application Laid-Open No. 6-56950. Is mentioned.

Using such a method, for example, a compound obtained by decarboxylation of K (≧ 2) moles of a diisocyanate compound can be represented by the following general formula (1).

In the above general formula, A is a residue excluding the isocyanate group of the diisocyanate compound used for the synthesis of the carbodiimide compound.
As a commercial product of the compound having a carbodiimide group represented by the general formula (1), carbodiimide made of tetramethylxylylene diisocyanate as a raw material, carbodilite V-03, V-05, etc. (both trade names, manufactured by Nisshinbo Co., Ltd.) ) And the like.

The compound represented by the general formula (1) has an isocyanate group in the molecule, but when the carbodiimide compound used in the present invention is synthesized, the isocyanate group is first eliminated by a reaction, It may be preferable to carry out the reaction with a carbodiimide group. Especially when the component that forms a side chain by grafting described later has a functional group that can react with an isocyanate group in addition to a functional group that can react with a carbodiimide group, and the reaction to an isocyanate group compared to a carbodiimide group When having a functional group having the same or better properties, it is preferable that the isocyanate group has disappeared.
In such a case, the molecule that is low in reactivity with the remaining carbodiimide group and that forms the carbodiimide compound of the present invention by reacting the compound that selectively reacts with the isocyanate group with the isocyanate group first. It can also be used as a compound having one or more carbodiimide groups.

The carbodiimide compound that is the dispersant of the present invention preferably has a basic nitrogen-containing group in the molecule. The above-mentioned “basic nitrogen-containing group” includes not only a group containing nitrogen that forms a quaternary ammonium ion in water but also a group containing nitrogen that acts as a Lewis base. Is an amino group or a nitrogen-containing heterocyclic group. The amino group includes a tertiary amino group. As the basic nitrogen-containing group, a tertiary amino group is preferable.
As a method for obtaining such a carbodiimide-based compound, it is a preferable method to introduce a basic nitrogen-containing group into the carbodiimide group-containing compound by utilizing the reaction with the isocyanate group. And when introducing a basic nitrogen-containing group into a carbodiimide group-containing compound, from the above conditions, a reaction with a hydroxyl group suitable as a functional group that can selectively react with an isocyanate group, and a carbodiimide group or an isocyanate group. It is preferable to use a compound having a non-participating tertiary amino group or basic nitrogen-containing heterocyclic group.

Specifically, examples of the compound having one hydroxyl group and a tertiary amino group include N, N-dialkylalkanolamine compounds such as N, N-dimethylethanolamine and N, N-diethylethanolamine; Examples thereof include an ethylene oxide adduct of a compound, a reaction product of a secondary amine compound and an epoxy compound, and the like. Examples of the compound having two hydroxyl groups and a tertiary amino group include N-alkyl dialkanolamine compounds such as N-methyldiethanolamine and N-ethyldiethanolamine; ethylene oxide adducts of primary amine compounds, primary amine compounds, and the like. The reaction material with an epoxy compound etc. can be mentioned.

Further, examples of the compound having a hydroxyl group and a basic nitrogen-containing heterocyclic group include, for example, a heterocyclic ring containing tertiary basic nitrogen such as hydroxypyridine, pyridinemethanol, pyridineethanol, pyridine, pyrazine, triazine, quinoline and the like. And a compound having a hydroxyl group can be used. Moreover, even a heterocyclic compound containing secondary basic nitrogen such as piperidine or piperazine can be used by alkylating and tertiaryizing to contain a hydroxyl group.

Then, 2 moles of the compound having one hydroxyl group may be reacted with 1 mole of the compound represented by the general formula (1) to introduce a basic nitrogen-containing group at the end of the main chain. A basic nitrogen-containing group may be introduced into the main chain by allowing the compound represented by the general formula (1) to react with the compound represented by the general formula (1) in an amount in which the isocyanate group is in excess of the hydroxyl group. A compound in which a basic nitrogen-containing group is introduced into such a main chain is a more preferable compound.

Further, a compound having no basic nitrogen-containing group can also be used in the reaction. For example, it contains a low molecular monoalcohol compound such as methanol or ethanol, a monoalkyl ester compound of (poly) alkylene glycol, and one hydroxyl group described later. A polyester compound, a polyacryl compound, etc. can be mentioned.

A polyester side chain, a polyacryl side chain and / or a polysiloxane side chain can be further introduced into the compound having one or more carbodiimide groups in the molecule obtained by the above method by grafting reaction.

As a typical method for introducing these side chains into the molecule by grafting reaction, a functional group capable of reacting with a carbodiimide group, for example, a carboxyl group, a sulfonic acid group, a phosphoric acid group, a hydroxyl group, an amino group, etc. The method of making the polyester compound, polyacryl compound, and polysiloxane chain containing compound which have it react with the carbodiimide group of a carbodiimide compound can be utilized.

As the polyester compound having the functional group, first,
(1) Ring-opening polymerization compound of cyclic ester compound using oxycarboxylic acid, monoalcohol, low molecular diol compound or the like as an initiator (for example, lactic acid, caproic acid, 12-hydroxystearic acid, dimethylolpropionic acid, dimethylolbutane) Mono- or polyoxycarboxylic acid such as acid is used as an initiator, and ε-caprolactone, γ-butyrolactone, 2-methylcaprolactone, 4-methylcaprolactone, β-propiolactone, δ-valerolactone, β-methyl-δ- A polyester compound containing a carboxyl group and a hydroxyl group obtained by ring-opening polymerization of a cyclic ester compound such as valerolactone; a ring-opening polymerization of the cyclic ester compound using a low-molecular monool compound such as methanol or ethanol as an initiator. Polyester monoester containing hydroxyl groups Lumpur compounds, ethylene glycol, used as the initiator of low molecular weight diol compounds such as propylene glycol, and polyester diol compounds) having a hydroxyl group obtained by ring-opening polymerization of the cyclic ester compound.

(2) Self-polycondensation compound of oxycarboxylic acid (for example, polyester compound containing carboxyl group and hydroxyl group obtained by polycondensation of monooxycarboxylic acid such as lactic acid, caproic acid, 12-hydroxystearic acid, etc.) Can be mentioned.
(3) Compounds obtained by polycondensation of low molecular diol compounds and low molecular dicarboxylic acid compounds (for example, ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol) Low molecular weight diol compound components such as linear glycols such as 1,2-propanediol, neopentyl glycol, branched glycols such as 3-methyl-1,5-pentanediol, ethylbutylpropanediol, and succinic acid A low molecular weight diol compound in the presence of an excess of a low molecular weight diol compound such as adipic acid, azelaic acid, sebacic acid, maleic acid and other saturated and unsaturated aliphatic dicarboxylic acids, and aromatic dicarboxylic acid such as phthalic acid. And polyester diol compounds containing a hydroxyl group obtained by reaction with

And (4) a phosphate ester compound of a ring-opening polymer of a cyclic ester compound using a monoalcohol as an initiator (for example, containing a phosphate group obtained by esterifying the polyester monool compound with phosphoric acid). Polyester diol compounds, etc.), (5) ring-opening polymerization compounds of cyclic ester compounds using an amino group-containing sulfonic acid compound as an initiator (for example, an amino group-containing sulfonic acid compound such as taurine as an initiator, And polyester diol compounds containing sulfonic acid groups obtained by ring-opening polymerization.

(6) A sulfurous acid gas adduct of a ring-opening polymer of a cyclic ester compound using a monoalcohol as an initiator (for example, a polyester diol containing a sulfonic acid group obtained by adding sulfurous acid gas to the polyester monool compound) Compounds). The polyester compound having a phosphoric acid group or a sulfonic acid group is preferably a compound having a polyester chain obtained by ring-opening polymerization of polycaprolactone.

Next, the polyacrylic compound having the functional group is at least selected from a (meth) acrylic monomer having at least one selected from the group consisting of a carboxyl group, a sulfonic acid group, a phosphoric acid group, a hydroxyl group and an amino group. A (meth) acrylic polymer obtained by polymerizing a monomer component containing one kind is preferred. As such, for example, a (meth) acrylic monomer having a carboxyl group: (meth) acrylic acid, crotonic acid, maleic acid, fumaric acid, cytocoranoic acid, itaconic acid, etc .; having a sulfonic acid group (meth) Acrylic monomers: (meth) acrylic acid sulfoethyl, (meth) acrylic acid sulfopropyl, etc .; (meth) acrylic monomers having a phosphate group: 2-methacryloyloxyethyl acid phosphate, trisacryloyloxyethyl phosphate, etc .; (Meth) acrylic monomer having: (meth) acrylic acid hydroxyalkyl ester such as 2-hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate and hydroxypentyl (meth) acrylate; (meth) acrylic mono having an amino group -: (Meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-propyl (meth) acrylamide, N-butyl (meth) acrylamide, N-hexyl (meth) acrylamide, N-octyl At least one selected from monomers such as (meth) acrylamide, N, N-dimethylaminoethyl (meth) acrylamide, N, N-diethylaminoethyl (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide and the like. (Meth) acrylic polymers obtained by polymerizing various monomer components and known monomers such as alkyl esters and styrene monomers generally used as reaction components for acrylic resins other than the above, if necessary be able to.

In addition, you may use the polyacryl compound which has the said functional group, and also has a polyester chain, for example, the polyacryl compound obtained using the (meth) acrylic-type monomer which contains a polyester chain in a molecule | numerator can be mentioned, for example. .

Among these polyester compounds and polyacryl compounds, it is advantageous to have a carboxyl group, a sulfonic acid group, and a phosphoric acid group from the viewpoint of reactivity with a carbodiimide group.

In addition, when the original compound having a carbodiimide group further has an isocyanate group, the compound having a hydroxyl group reacts with the isocyanate group prior to the carbodiimide group, making it difficult to control the reaction. Compounds having more than one can crosslink and cause gelation during the grafting reaction.
Therefore, for a compound having only a hydroxyl group, a polyester compound or polyacryl compound containing one carboxyl group is obtained by further reacting with an acid anhydride such as phthalic anhydride, maleic anhydride, or succinic anhydride. After that, it is desirable to carry out a grafting reaction.
Among polyester compounds or polyacrylic compounds introduced into the carbodiimide compound molecule as a side chain, those having a basic nitrogen-containing group can introduce a basic nitrogen-containing group into the carbodiimide compound simultaneously with the side chain. become.
About the correspondence in case a functional group is only a hydroxyl group, and the point which has a basic nitrogen containing group, it is the same also about other compounds used for introduction | transduction of a side chain other than a polyester compound and a polyacryl compound.

Next, as the polysiloxane chain-containing compound having the functional group used for introducing the polysiloxane chain, for example, the following materials can be used.
(1) Specific examples of a compound obtained by reacting an acid anhydride with a polysiloxane polyol include acid anhydrides such as phthalic anhydride, maleic anhydride, succinic anhydride, benzoic anhydride, and styrene-maleic anhydride resin. A compound obtained by reacting a product.
(2) Polysiloxane chain-containing polymer having an acid group at one end As a polysiloxane chain-containing compound having a functional group that reacts with a carbodiimide group, in the presence of an acid group-containing chain transfer agent, a radical polymerizable unsaturated at the end A polysiloxane chain-containing polymer having an acid group at one end obtained by polymerizing an acid group-free radically polymerizable compound containing at least one acid group-free polysiloxane having a bond can be used.

Examples of the acid group-containing chain transfer agent include chain transfer agents having a carboxyl group such as mercaptoacetic acid, 2-mercaptopropionic acid, 3-mercaptopropionic acid, mercaptobenzoic acid; 2-chloroethanesulfonic acid, sodium 2-chloroethanesulfonate , 4-chlorophenylsulfoxide, 4-chlorobenzenesulfonamide, p-chlorobenzenesulfonic acid, sodium p-chlorobenzenesulfonate, sodium 2-bromoethanesulfonate, sodium 4- (bromomethyl) benzenesulfonate, etc. Agents and the like. Among these acid group-containing chain transfer agents, thiol-based acid group-containing chain transfer agents are preferable, and mercaptoacetic acid, 2-mercaptopropionic acid, 3-mercaptopropionic acid, and mercaptobenzoic acid are more preferable.

Examples of the acid group-free polysiloxane having a radical polymerizable unsaturated bond at the terminal include an acid group-free polydimethylsiloxane monomer having a methacryloyl group at the terminal, a silicone macromonomer, and the like.
In addition, if necessary, an acid group-free radically polymerizable unsaturated monomer can be used in combination as long as the performance does not deteriorate.
Specific examples include alkyl (meth) acrylate monomers (for example, methyl methacrylate), (meth) acrylate monomers having an aromatic ring (for example, allyl acrylate, allyl methacrylate, benzyl acrylate, benzyl methacrylate, etc.) ) (Meth) acrylic acid ester compounds; styrene monomers such as styrene and α-methylstyrene.

When such a component is used to synthesize a polysiloxane chain-containing polymer having an acid group at one end, a commonly used initiator such as an azo-nitrile compound: 2,2′-azo-bis-isobuty Ronitrile, 1,1′-azo-bis-1-cyclobutanenitrile, 2,2′-azo-bis-2methylbutyronitrile, etc., azo compounds: 2,3-diaza-bicyclo [2,2,1] Heptene, 2,2,2'-azo-bis-propane, 1,1'-azo-bis-1-phenylethane, peroxide compounds: t-butyl peroxide, benzoyl peroxide, t-butyl hydroperoxide , Cumene hydroperoxide and the like can be used.
The polysiloxane chain-containing polymer having an acid group at one end is synthesized from a material having no acid group capable of reacting with a carbodiimide group other than the acid group-containing chain transfer agent, and the functional group capable of reacting with the carbodiimide group is a molecule. There is only one acid group at one end.

The polysiloxane chain-containing polymer having an acid group at one end of the molecule can be prepared by using a polymerization method such as bulk polymerization, solution polymerization, and suspension polymerization as necessary. According to the method, it can be synthesized by reacting at a reaction temperature of not less than the decomposition temperature of the initiator, usually 70 to 170 ° C. for 1 to 8 hours. In this polymerization, by using an acid group-containing chain transfer agent as the chain transfer agent, a polysiloxane chain-containing polymer having an acid group at one end can be obtained.

The compound in which at least one polyester compound or the like exemplified above is introduced into the molecule by grafting may have 0 carbodiimide groups, preferably one or more. For example, the above general formula (1) When a side chain is introduced into the polycarbodiimide compound represented by formula (1) by a grafting reaction, carbodiimide compounds represented by the following general formulas (2) and (3) can be obtained.

Here, A is a residue excluding the isocyanate group of the diisocyanate compound used for the synthesis of the polycarbodiimide compound. X is the same or different, and a trivalent linking group obtained by reacting a carbodiimide group and a functional group capable of reacting with it, Y is the same or different, such as a polyester chain, polyacryl chain, polysiloxane chain, etc. It is a chain, and l, m, and n represent an integer of 1 or more. In the compound of the general formula (2) and the compound of the general formula (3), Y may have a basic nitrogen-containing group, and a basic nitrogen-containing group is introduced into the side chain. It will be.
On the other hand, in the general formula (2), when Y does not contain a basic nitrogen-containing group, an amino acid or a compound having a hydroxyl group and a basic nitrogen-containing group is further grafted to the remaining carbodiimide group. Thus, a basic nitrogen-containing group can be introduced into the molecule for use.

In addition, as a trivalent coupling group represented by said X, for example, the coupling group formed from the reaction of a carbodiimide group and a carboxyl group includes the following general formulas (4) and (5), carbodiimide group and hydroxyl group: The linking group formed from the reaction of the following general formulas (6) and (7), the linking group formed from the reaction of the carbodiimide group and the amino group is the following general formula (8), carbodiimide group and sulfone The linking group formed from the reaction with the acid group is represented by the following general formula (9), and the linking group formed from the reaction between the carbodiimide group and the phosphoric acid group is represented by the following general formula (10).

In the above general formula, R represents a hydrogen atom or a hydrocarbon group having 1 or more carbon atoms.

Further, the carbodiimide compounds represented by the general formulas (2) and (3) have an isocyanate group in the molecule, but react with a compound having a functional group capable of reacting with the isocyanate group in the same manner as described above. As a result, the same compound as that obtained when a component having a side chain is reacted with a compound having a carbodiimide group from which an isocyanate group has been eliminated can be obtained.

For example, a carbodiimide compound obtained by reacting a compound having one hydroxyl group with isocyanate groups at both ends of the carbodiimide compound represented by the general formulas (2) and (3) is represented by the following general formula (11), This compound can also be used as a carbodiimide compound in the present invention.

In the above general formula, Z ¹ and Z ² each independently represent a residue other than the functional group of a compound having a functional group capable of reacting with an isocyanate group, which may have a different structure. A is a residue excluding the isocyanate group of the diisocyanate compound used for the synthesis of the polycarbodiimide compound. X is the same or different, a trivalent linking group obtained by reacting a carbodiimide group and a functional group capable of reacting with it, Y is the same or different, and is a chain such as a polyester chain, polyacryl chain, polysiloxane chain, etc. And l, m, and n represent an integer of 1 or more. And in the compound of the general formula (11) and the compound of the general formula (12), any of Z ¹ , Z ² , and Y may have a basic nitrogen-containing group, and the above Z ¹ , Z the backbone having ² as the basic nitrogen-containing group, those with a basic nitrogen-containing group as the Y will be a basic nitrogen-containing groups are introduced into the side chain.
On the other hand, in the general formula (11), when none of Z ¹ , Z ² and Y contains a basic nitrogen-containing group, an amino acid or the above hydroxyl group and a basic nitrogen-containing group are further added to the remaining carbodiimide group. It is possible to introduce a basic nitrogen-containing group into the molecule and use it by grafting the compound having the same.

In addition, the reaction mentioned above, ie, the ring-opening reaction of the cyclic ester compound using the hydroxyl group-containing compound as an initiator, the polycondensation reaction of oxycarboxylic acid, the polycondensation reaction of the low-molecular diol compound and the low-molecular dicarboxylic acid compound Conventional methods can be used for the ring-opening reaction of a hydroxyl group-containing ester compound and an acid anhydride, the reaction of a carbodiimide group with a carboxyl group or a hydroxyl group, and the reaction of an isocyanate group with a hydroxyl group or the like.
In addition, even if the order of reacting the materials used for the grafting reaction is different, the obtained carbodiimide-based compound does not have different performance as long as the finally obtained compound has the same molecular structure.

Accordingly, in the compounds of the general formulas (11) and (12), for example, in order to introduce a polyester side chain by grafting, a polyester compound containing a functional group capable of reacting with a carbodiimide group is synthesized first, and carbodiimide Although the method of reacting with a group to form a side chain has been described, as another method, a compound having a functional group capable of reacting with a carbodiimide group is reacted with a carbodiimide group, and then a polyester chain is introduced into the molecule. The side chain can also be introduced.

That is, when a grafted polyester side chain is introduced, for example, an oxycarboxylic acid is first reacted with a carbodiimide group, a hydroxyl group is introduced into the molecule of the carbodiimide compound, and then the cyclic polyester compound is subjected to ring-opening polymerization. Alternatively, a method of grafting polyester chains may be used. In the case of introducing a grafted polyacryl chain, for example, a compound having a radical polymerizable unsaturated double bond and a functional group capable of reacting with a carbodiimide group such as an acid group or a hydroxyl group is first converted into a carbodiimide. Alternatively, a method may be used in which a radical polymerizable unsaturated double bond is introduced into a carbodiimide compound molecule by reacting with a group, and then an acrylic monomer is polymerized to graft a polyacryl chain. And about the order of these reaction, it is desirable to synthesize | combine on the conditions that there are few undesirable side reaction products.

When synthesizing a compound having at least one carbodiimide group (a compound represented by general formula (2) or general formula (11)) as a preferred form of the carbodiimide compound having a grafted side chain in the molecule, There is a possibility that both a compound having no grafted side chain in the molecule (m = 0) and a compound having no carbodiimide group in the molecule (l = 0) are produced.
Therefore, as a method of synthesizing only a compound having one or more grafted side chains and carbodiimide groups in the molecule, the compound represented by the above general formula (1) and all of the carbodiimide groups are grafted polyester chains, The following method based on the compound represented by the above general formula (3), which is a chain such as a grafted polyacryl chain and a grafted polysiloxane chain, can be mentioned.

First, using a compound represented by the general formula (1) or a compound represented by the general formula (3), a diol compound is reacted with an isocyanate group at both ends to obtain a compound having hydroxyl groups at both ends. For example, a compound obtained by reacting 1 mol of the compound represented by the general formula (1) and 2 mol of the diol compound is represented by the following general formula (13), while represented by the general formula (3). A compound obtained by reacting 1 mol of a compound with 2 mol of a diol compound is represented by the following general formula (14).

In said general formula, G is the same or different and represents the residue except the hydroxyl group which reacted with the isocyanate group of the diol compound.
Then, a diisocyanate compound having a chain such as a grafted polyester chain, a grafted polyacryl chain, or a grafted polysiloxane chain (general) with respect to the diol compound having the carbodiimide group (the compound represented by the general formula (13)). A compound obtained by reacting a compound represented by the formula (3), and conversely, a diol compound having a grafted side chain (a compound represented by the general formula (14)), which has a carbodiimide group. A compound obtained by reacting a diisocyanate compound (a compound represented by the general formula (1)) is a compound having at least one grafted side chain and a carbodiimide group. Further, when a diol compound having a basic nitrogen-containing group in the molecule is used in this method, it is preferable because a basic nitrogen-containing group can be introduced into the molecule at the same time.

As described above, when the grafting reaction is used, the side chain can be easily introduced into the carbodiimide compound, but the side chain of the carbodiimide compound can also be introduced by a method other than the grafting reaction. For example, the method of extending | stretching the polycarbodiimide compound represented by the said General formula (1) using the chain extender which has a polyester chain or a polyacryl chain, etc. can be utilized.

Examples of such chain extenders include compounds obtained by ring-opening polymerization of the cyclic ester compound to a polyol compound having three or more hydroxyl groups such as trimethylolpropane and pentaerythritol, having a polyester chain, A compound obtained by polycondensation with a low molecular dicarboxylic acid and a diol monocarboxylic acid such as dimethylolpropionic acid, partially combined with a molecular diol compound and a triol compound, reacts with an epoxy compound having a polyester chain in the molecule. The compound etc. which are made to let it be mentioned can be mentioned. As what has a polyacryl chain, the compound etc. which are obtained by making the (meth) acrylic-type polymer which has a carboxyl group react with the said polyol compound can be mentioned.

When the carbodiimide compound has a basic nitrogen-containing group, the amount of the basic nitrogen-containing group per 1 g of the carbodiimide compound is preferably 0.02 to 4 mmol, more preferably 0.05 to 3 mmol. is there. When the amount of the basic nitrogen-containing group per 1 g of the carbodiimide compound is in the above range, good dispersion stability can be obtained.

In the carbodiimide compound, a chain such as a polyester chain, a polyacryl chain, or a polysiloxane chain introduced as a side chain has an effect of improving the dispersion stability of the pigment-encapsulated colored resin particles in the dispersion medium. Although not particularly limited, the number average molecular weight is preferably 200 or more and 10,000 or less. More preferably, it is 300 or more and 5000 or less. The number average molecular weight of the present invention is obtained on the basis of gel permeation chromatography method (GPC method) <polystyrene conversion>, as a device Water 2690 (manufactured by Waters), and as a column PLgel 5μ MIXED-D. (Polymer Laboratories) is used.

When the carbodiimide compound has one or more carbodiimide groups in the molecule, the carbodiimide equivalent is preferably from 100 to 50,000, and more preferably from 200 to 10,000. When the carbodiimide equivalent is in the above range, the effect of improving the dispersion stability is enhanced. The carbodiimide equivalent means a number represented by (molecular weight of carbodiimide compound) / (number of carbodiimide groups in carbodiimide compound molecule).

The number average molecular weight of the carbodiimide compound used in the present invention is preferably 1000 or more and 100000 or less, more preferably 1000 or more and 50000 or less. When the number average molecular weight of the carbodiimide compound exceeds 100,000, it becomes difficult to obtain a liquid developer having an appropriate viscosity, which is not preferable when a high-concentration composition is required. On the other hand, if the number average molecular weight is less than 1000, the dispersion stability is lowered, which is not preferable.

The amount of the carbodiimide compound of the present invention is preferably 0.1 to 200% by mass with respect to the pigment in the liquid developer. When the amount of the carbodiimide compound of the present invention is less than 0.1% by mass, dispersibility may be insufficient, and when it exceeds 200% by mass, a liquid developer having an appropriate viscosity is obtained. It is not preferable because it is difficult.
The said carbodiimide type compound can use 1 type (s) or 2 or more types. In addition, the kind of the said carbodiimide type compound can be suitably selected according to the kind of dispersion medium.

Next, the resin used for forming pigment-encapsulated colored resin particles that become toner particles in the present invention will be described. As the resin, a thermoplastic resin having fixing properties to an adherend such as printing paper is preferable. Specifically, a polyolefin resin is modified to introduce a carboxyl group, ethylene- (meth) acrylic acid copolymer Polymers, ethylene-vinyl acetate copolymers, partially saponified ethylene-vinyl acetate copolymers, olefin resins such as ethylene- (meth) acrylate copolymers, polyethylene resins, polypropylene resins; thermoplastic saturated polyester resins; Styrene resins such as styrene-acrylic copolymer resins and styrene-acrylic modified polyester resins; alkyd resins, phenolic resins, epoxy resins, rosin-modified phenolic resins, rosin-modified maleic resins, rosin-modified fumaric acid resins, (meth) acrylic Acrylic resin such as acid ester resin, vinyl chloride Le resins, vinyl acetate resins, vinylidene chloride resins, fluorine resins, polyamide resins, and polyacetal resins. These can use 1 type (s) or 2 or more types.
In addition, 5-50 mass% is preferable, and, as for the total ratio with the pigment, a dispersing agent, and resin which occupy in the liquid developer of this invention, More preferably, it is 10-40 mass%. When the amount is less than 5% by mass, a liquid developer having a sufficient concentration may not be obtained. When the amount is more than 50% by mass, the viscosity of the liquid developer may increase excessively.
The pigment-encapsulated colored resin particles are obtained by dispersing in a resin a pigment that has been treated in advance using a carbodiimide compound that is a dispersant, and the average particle size in the liquid developer is 0.1 to 10%. Those having a thickness of 0.0 μm are preferable. The average particle diameter of the pigment-encapsulated colored resin particles can be measured by a particle size distribution meter (dynamic light scattering method).

As the dispersion medium constituting the liquid developer of the present invention, one having a resistance value (about 10 ¹¹ to 10 ¹⁶ Ω · cm) that does not disturb the electrostatic latent image is used. For example, in addition to silicone dispersion media such as silicone oil, aliphatic hydrocarbons such as normal paraffin hydrocarbons and isoparaffin hydrocarbons; alicyclic hydrocarbons such as cycloparaffin hydrocarbons; aromatic hydrocarbons, halogenated Hydrocarbons and the like can be used, but in the present invention, a silicone-based dispersion medium is preferable. Examples of the silicone dispersion medium include silicone oils such as low-viscosity synthetic dimethylpolysiloxane and cyclic methylpolysiloxane.

In addition to these materials, the liquid developer of the present invention may further contain a charge control agent as necessary, and is roughly classified into the following two types (1) and (2).
(1) A type in which the surface of toner particles is coated with a substance that can ionize or adsorb ions. As this type, oils and fats such as linseed oil and soybean oil; alkyd resins, halogenated polymers, aromatic polycarboxylic acids, acidic group-containing water-soluble dyes, and oxidative condensates of aromatic polyamines are suitable.
(2) A type that coexists with a substance capable of exchanging toner particles and ions by dissolving in an insulating hydrocarbon organic solvent. Cobalt naphthenate, nickel naphthenate, iron naphthenate, zinc naphthenate, octyl Metal soaps such as cobalt acid, nickel octylate, zinc octylate, cobalt dodecylate, nickel dodecylate, zinc dodecylate, cobalt 2-ethylhexanoate; petroleum metal sulfonates, metal salts of sulfosuccinates, etc. Suitable are sulfonic acid metal salts; phospholipids such as lecithin; salicylic acid metal salts such as t-butyl salicylic acid metal complex; polyvinylpyrrolidone resin, polyamide resin, sulfonic acid-containing resin, hydroxybenzoic acid derivative and the like.
In addition, other additives can be blended as necessary.

Next, a method for producing the liquid developer of the present invention will be described.
In the present invention, a pigment treated with the carbodiimide compound is used as a dispersant. Here, the pigment treatment (pigment surface treatment step) is carried out by dispersing the composition containing the pigment, the carbodiimide compound as a dispersant and a solvent with a paint shaker, Eiger mill or the like, and then removing the solvent by evaporating or the like. It can be performed by the method of doing.

Next, in the present invention, a step of dispersing the treated pigment obtained in the pigment surface treatment step in the resin to obtain a pigment resin composite (pigment resin composite formation step) is performed. In the pigment resin complexing step, the resin is added to the treated pigment, heated and kneaded at a temperature higher than the softening point of the resin with a three-roll mill, a twin screw extruder, or the like, and cooled as necessary. , Etc.

In the present invention, subsequently, the step of wet-pulverizing the pigment resin composite obtained in the pigment resin composite formation step in a dispersion medium to disperse the pigment-encapsulated colored resin particles in the dispersion medium (tonerization step) Is done. In the toner forming step, the obtained pigment resin composite is further added with a dispersant as necessary, and in the dispersion medium, such as attritor, sand mill, dyno mill, ball mill, DCP mill, apex mill, pearl mill, etc. Wet with wet type pulverizers such as media type dispersers, media type pulverizers such as media type dispersers, ultimateizer (manufactured by Sugino Machine), nanomizer (manufactured by nanomizer), micro full dither (manufactured by Mizuho Kogyo Co.) This can be done by grinding. Prior to the dispersing step, the obtained pigment resin composite may be dry pulverized using a pulverizer such as a hammer mill, a jet mill, a pin mill, a turbo mill, a cutter mill, or a ball mill. The liquid developer of the present invention can be obtained by the manufacturing method described above.
Further, the pigment resin composite may be formed after the pigment, the dispersant and the resin are simultaneously added and heated and kneaded with a three-roll mill, a twin screw extruder or the like.
Note that the charge control agent that can be added to the liquid developer as necessary can be added during wet pulverization and / or after wet pulverization.

By using the production method of the present invention, it can be applied to a liquid developer using any pigment, the dispersibility of the pigment and the dispersion stability of the toner particles are improved, and the electric resistance of the liquid developer and the toner particles A liquid developer can be obtained in which adverse effects on charging characteristics are minimized.

Hereinafter, the liquid developer of the present invention will be described in more detail by way of examples. However, the present invention is not limited to these examples without departing from the spirit and scope of application. In the following description, unless otherwise specified, “part” and “%” mean “part by mass” and “% by mass”, respectively.
(Synthesis Example 1)
<Dispersant 1> (Polyester side chain-containing carbodiimide compound)
In a four-necked flask equipped with a reflux condenser, a nitrogen gas inlet tube, a stirrer, and a thermometer, 132.6 parts of a toluene solution of a polycarbodiimide compound having a carbodiimide equivalent of 316 having an isocyanate group (solid content 50%), N- 12.8 parts of methyldiethanolamine was charged and maintained at about 100 ° C. for 3 hours to react an isocyanate group with a hydroxyl group. Next, 169.3 parts of a 12-hydroxystearic acid self-polycondensate having a number average molecular weight of 1600 having a carboxyl group at the end was charged and held at about 80 ° C. for 2 hours to react a carbodiimide group with a carboxyl group, Toluene was distilled off under reduced pressure to obtain Dispersant 1 (100% solid content) having a number average molecular weight of about 9300, an amine number of 23.5, and a carbodiimide equivalent of 2400.

(Synthesis Example 2)
<Dispersant 2> (polysiloxane side chain-containing carbodiimide compound)
(A) A four-necked flask equipped with a reflux condenser, a nitrogen gas inlet tube, a stirrer, and a thermometer, 45 parts of toluene, 10 parts of 3-mercaptopropionic acid, and a molecular weight of 1000 having a methacryloyl group at one end 180 parts of dimethylsiloxane was charged and the temperature was raised to 85 ° C. While maintaining the internal temperature at about 85 ° C., a mixture of 80 parts of toluene and 1.9 parts of azobisisobutyronitrile was added dropwise over 2 hours. Thereafter, the mixture was stirred for 2 hours while maintaining the internal temperature at about 85 ° C. to obtain a carboxyl group-containing polysiloxane resin 1 having a solid content of 60% and a number average molecular weight of about 2000.
(B) A toluene solution of a polycarbodiimide compound having a carbodiimide equivalent of 316 having an isocyanate group (solid content 50%) 114.8 parts in a four-necked flask equipped with a reflux condenser, a nitrogen gas inlet tube, a stirring rod, and a thermometer. Then, 11.1 parts of methyldiethanolamine was charged and maintained at about 100 ° C. for 3 hours to react an isocyanate group with a hydroxyl group. Next, 306.5 parts of the polysiloxane resin 1 obtained in the above (a) was charged and held at about 80 ° C. for 2 hours to react the carbodiimide group and the carboxyl group, and then toluene was distilled off under reduced pressure. Thus, Dispersant 2 (solid content: 100%) having a number average molecular weight of about 11,000 and a carbodiimide equivalent of 2774 was obtained.

(Synthesis Example 3)
<Resin>
Styrene (St) 76.7 parts, stearyl methacrylate (SMA) 14.7 parts, dimethylacrylamide (DMAA) 8.6 parts, toluene 160 parts and azobisisobutyronitrile 1.5 parts as an initiator, Radical polymerization was performed at 80 ° C. for 10 hours. The obtained resin solution was further heated under reduced pressure at 150 ° C. and 70 cmHg (≈93 kPa) for 8 hours to distill off toluene, unreacted monomers and low molecular weight oligomers, thereby obtaining a resin. The obtained resin had a composition (St: SMA: DMAA = 85: 5: 10, molar ratio), a weight average molecular weight of 45800, and a melting point of 92 ° C.

Example 1
10 parts by mass of carbon black (MA285, manufactured by Mitsubishi Chemical), 10 parts by mass of dispersant 1, and 80 parts by mass of methyl ethyl ketone (hereinafter abbreviated as MEK) are pre-dispersed in a paint shaker, and then filled with 0.5 mmΦ zirconia beads. The Eiger mill (trade name: D-50) was dispersed. Thereafter, the dispersion was charged into a four-necked flask equipped with a stirrer, a thermometer, a cooling tube, etc., and then MEK was distilled off while heating and stirring under reduced pressure to obtain a surface-treated pigment. Next, after cooling the kneaded material obtained by melt-kneading 50 parts by mass of the surface-treated pigment and 50 parts by mass of the resin obtained in Synthesis Example 3 at 160 ° C. using three hot rolls, Micronized with a mill. Thereafter, 20 parts by mass of the fine powder, 1 part by mass of the dispersant 2, and 79 parts by mass of carrier liquid SH200 (manufactured by Toray Dow Corning Silicone, polydimethylpolysiloxane) were filled with zirconia beads of 0.5 mmΦ. Using an Eiger mill (trade name: M-250), wet pulverization was performed at a temperature of 40 ° C. for about 90 minutes to obtain a liquid developer of Example 1.

(Example 2)
10 parts by weight of carbon black (MA285, manufactured by Mitsubishi Chemical), 4 parts by weight of dispersant 1 and 86 parts by weight of methyl ethyl ketone (hereinafter abbreviated as MEK) are pre-dispersed in a paint shaker and filled with 0.5 mmΦ zirconia beads. The Eiger mill (trade name: D-50) was dispersed. Thereafter, the dispersion was charged into a four-necked flask equipped with a stirrer, a thermometer, a cooling tube, etc., and then MEK was distilled off while heating and stirring under reduced pressure to obtain a surface-treated pigment. Next, after cooling the kneaded material obtained by melting and kneading 35 parts by mass of the surface-treated pigment and 65 parts by mass of the resin obtained in Synthesis Example 3 at 160 ° C. using three hot rolls, Micronized with a mill. Thereafter, 20 parts by mass of the fine powder, 1 part by mass of the dispersant 2, and 79 parts by mass of carrier liquid SH200 (manufactured by Toray Dow Corning Silicone, polydimethylpolysiloxane) were filled with zirconia beads of 0.5 mmΦ. Using an Eiger mill (trade name: M-250), wet pulverization was performed at a temperature of 40 ° C. for about 90 minutes to obtain a liquid developer of Example 2.

(Example 3)
10 parts by weight of carbon black (MA285, manufactured by Mitsubishi Chemical), 2 parts by weight of dispersant 1 and 88 parts by weight of methyl ethyl ketone (hereinafter abbreviated as MEK) are pre-dispersed in a paint shaker and filled with 0.5 mmΦ zirconia beads. The Eiger mill (trade name: D-50) was dispersed. Thereafter, the dispersion was charged into a four-necked flask equipped with a stirrer, a thermometer, a cooling tube, etc., and then MEK was distilled off while heating and stirring under reduced pressure to obtain a surface-treated pigment. Next, after cooling the kneaded material obtained by melting and kneading 30 parts by mass of the surface-treated pigment and 70 parts by mass of the resin obtained in Synthesis Example 3 at 160 ° C. using three hot rolls, Micronized with a mill. Thereafter, 20 parts by mass of the fine powder, 1 part by mass of the dispersant 2, and 79 parts by mass of carrier liquid SH200 (manufactured by Toray Dow Corning Silicone, polydimethylpolysiloxane) were filled with zirconia beads of 0.5 mmΦ. Using an Eiger mill (trade name: M-250), wet pulverization was performed at a temperature of 40 ° C. for about 90 minutes to obtain a liquid developer of Example 3.

Example 4
10 parts by mass of carbon black (MA285, manufactured by Mitsubishi Chemical), 1 part by mass of dispersant 1 and 89 parts by mass of methyl ethyl ketone (hereinafter abbreviated as MEK) are pre-dispersed in a paint shaker, and then filled with 0.5 mmΦ zirconia beads. The Eiger mill (trade name: D-50) was dispersed. Thereafter, the dispersion was charged into a four-necked flask equipped with a stirrer, a thermometer, a cooling tube, etc., and then MEK was distilled off while heating and stirring under reduced pressure to obtain a surface-treated pigment. Next, 27.5 parts by mass of the surface-treated pigment and 72.5 parts by mass of the resin obtained in Synthesis Example 3 were melt-kneaded at 160 ° C. using three hot rolls. After cooling, it was pulverized by a jet mill. Thereafter, 20 parts by mass of the fine powder, 1 part by mass of the dispersant 2, and 79 parts by mass of carrier liquid SH200 (manufactured by Toray Dow Corning Silicone, polydimethylpolysiloxane) were filled with zirconia beads of 0.5 mmΦ. Using an Eiger mill (trade name: M-250), wet pulverization was performed at a temperature of 40 ° C. for about 90 minutes to obtain a liquid developer of Example 4.

(Example 5)
After predispersing 10 parts by mass of carbon black (MA285, manufactured by Mitsubishi Chemical), 0.1 part by mass of dispersant 1 and 89.9 parts by mass of methyl ethyl ketone (hereinafter abbreviated as MEK) with a paint shaker, 0.5 mmΦ The mixture was dispersed using an Eiger mill (trade name: D-50) filled with zirconia beads. Thereafter, the dispersion was charged into a four-necked flask equipped with a stirrer, a thermometer, a cooling tube, etc., and then MEK was distilled off while heating and stirring under reduced pressure to obtain a surface-treated pigment. Next, a paste obtained by melt-kneading 25.25 parts by mass of the surface-treated pigment and 74.75 parts by mass of the resin obtained in Synthesis Example 3 at 160 ° C. using three hot rolls. After cooling, it was pulverized by a jet mill. Thereafter, 20 parts by mass of the fine powder, 1 part by mass of the dispersant 2, and 79 parts by mass of carrier liquid SH200 (manufactured by Toray Dow Corning Silicone, polydimethylpolysiloxane) were filled with zirconia beads of 0.5 mmΦ. A liquid developer of Example 5 was obtained by wet pulverization for about 90 minutes at a temperature of 40 ° C. using an Eiger mill (trade name: M-250).

(Example 6)
10 parts by weight of carbon black (MA285, manufactured by Mitsubishi Chemical), 4 parts by weight of dispersant 2 and 86 parts by weight of methyl ethyl ketone (hereinafter abbreviated as MEK) are pre-dispersed in a paint shaker and then filled with 0.5 mmΦ zirconia beads. The Eiger mill (trade name: D-50) was dispersed. Thereafter, the dispersion was charged into a four-necked flask equipped with a stirrer, a thermometer, a cooling tube, etc., and then MEK was distilled off while heating and stirring under reduced pressure to obtain a surface-treated pigment. Next, after cooling the kneaded material obtained by melting and kneading 35 parts by mass of the surface-treated pigment and 65 parts by mass of the resin obtained in Synthesis Example 3 at 160 ° C. using three hot rolls, Micronized with a mill. Thereafter, 20 parts by mass of the fine powder, 1 part by mass of the dispersant 2, and 79 parts by mass of carrier liquid SH200 (manufactured by Toray Dow Corning Silicone, polydimethylpolysiloxane) were filled with zirconia beads of 0.5 mmΦ. Using an Eiger mill (trade name: M-250), wet pulverization was performed at a temperature of 40 ° C. for about 90 minutes to obtain a liquid developer of Example 6.

(Example 7)
After pre-dispersing 10 parts by weight of phthalocyanine blue (127EPS, manufactured by Dainichi Seika), 4 parts by weight of dispersant 1 and 86 parts by weight of methyl ethyl ketone (hereinafter abbreviated as MEK) with a paint shaker, 0.5 mmΦ zirconia beads are added. It disperse | distributed using the filled Eiger mill (brand name: D-50). Thereafter, the dispersion was charged into a four-necked flask equipped with a stirrer, a thermometer, a cooling tube, etc., and then MEK was distilled off while heating and stirring under reduced pressure to obtain a surface-treated pigment. Next, after cooling the kneaded material obtained by melting and kneading 35 parts by mass of the surface-treated pigment and 65 parts by mass of the resin obtained in Synthesis Example 3 at 160 ° C. using three hot rolls, Micronized with a mill. Thereafter, 20 parts by mass of the fine powder, 1 part by mass of the dispersant 2, and 79 parts by mass of carrier liquid SH200 (manufactured by Toray Dow Corning Silicone, polydimethylpolysiloxane) were filled with zirconia beads of 0.5 mmΦ. Using an Eiger mill (trade name: M-250), wet pulverization was performed at a temperature of 40 ° C. for about 90 minutes to obtain a liquid developer of Example 7.

(Comparative Example 1)
A kneaded product obtained by melt-kneading 25 parts by mass of carbon black (MA285, manufactured by Mitsubishi Chemical) and 75 parts by mass of resin at 160 ° C. using three hot rolls was cooled and then pulverized. Thereafter, 20 parts by mass of the finely pulverized product, 1 part by mass of the above-mentioned dispersant 2, 79 parts by mass of carrier liquid SH200 (manufactured by Toray Dow Corning Silicone, polydimethylpolysiloxane), Eiger mill filled with 0.5 mmφ zirconia beads (Trade name: M-250) was used and wet pulverized at a temperature of 40 ° C. for about 90 minutes to obtain a liquid developer of Comparative Example 1.

(Comparative Example 2)
A kneaded product obtained by melt-kneading 25 parts by mass of carbon black (MA285, manufactured by Mitsubishi Chemical) and 75 parts by mass of resin at 160 ° C. using three hot rolls was cooled and then pulverized. Thereafter, an Eiger mill (trade name: M-250) in which 20 parts by mass of finely pulverized product, 80 parts by mass of carrier liquid SH200 (made by Toray Dow Corning Silicone, polydimethylpolysiloxane) and 0.5 mmφ zirconia beads were filled. A liquid developer of Comparative Example 2 was obtained by wet pulverization at a temperature of 40 ° C. for about 90 minutes.

<Evaluation method>
Each liquid developer was evaluated by the following evaluation method. The results are shown in Table 1.
(Chargeability and electrophoretic properties)
Particles were observed using an electrophoresis cell (conditions: distance between electrodes: 80 μm, applied voltage: 200 V). The electrophoretic properties were evaluated as follows.
○: The particles migrate smoothly without agglomeration Δ: The particles migrate while forming an aggregate ×: The particles aggregate between the electrodes and do not move

Regarding the charging property, when 90% or more of the toner particles migrate to the negative electrode side when voltage is applied to the migration cell, the charging property is “+”, and 90% or more of the toner particles migrate to the positive electrode side. In this case, the chargeability was evaluated as “−”, and other cases were evaluated as “±”.
In Comparative Example 2, the chargeability could not be evaluated due to severe aggregation.

(Average particle size)
The average particle size was measured by a particle size distribution meter (dynamic light scattering method), and Microtrac 9340-UPA (Nikkiso Co., Ltd.) was used as a measuring device.
(Dispersibility)
The dispersibility after standing at room temperature for 1 week was visually evaluated.
○: No sedimentation ×: There is sedimentation

By using the production method of the present invention, it can be applied to a liquid developer using any pigment, the dispersibility of the pigment and the dispersion stability of the toner particles are improved, and the electric resistance of the liquid developer and the toner particles are improved. A liquid developer can be obtained in which adverse effects on charging characteristics are minimized.

Claims (7)

As a dispersant, a pigment treated with a carbodiimide compound that satisfies the following condition 1 is dispersed in a resin to obtain a pigment resin composite, and then the pigment resin composite is wet-ground in a dispersion medium, A method for producing a liquid developer, comprising dispersing pigment-encapsulated colored resin particles in a dispersion medium.
Condition 1: A carbodiimide compound having a chain introduced by reacting a compound having a group that reacts with a carbodiimide group with a carbodiimide group. The dispersing agent is a carbodiimide compound into which at least one chain selected from the group consisting of a polyester chain, a polyacryl chain, and a polysiloxane chain is introduced through a reaction with a carbodiimide group. Item 2. A method for producing a liquid developer according to Item 1. The method for producing a liquid developer according to claim 1, wherein a carbodiimide compound having a carbodiimide equivalent of 100 to 50,000 is used as the dispersant. The method for producing a liquid developer according to claim 1, wherein a carbodiimide compound having a basic nitrogen-containing group is used as the dispersant. 5. The method for producing a liquid developer according to claim 4, wherein a carbodiimide compound having a basic nitrogen-containing group in the main chain is used as the dispersant. 6. The method for producing a liquid developer according to claim 4, wherein the basic nitrogen-containing group is a tertiary amino group. 7. The carbodiimide compound having a number average molecular weight of at least one chain selected from the group consisting of a polyester chain, a polyacryl chain, and a polysiloxane chain of 200 to 10,000 as the dispersant. A method for producing a liquid developer according to claim 1 .