JP2016170251A - Method for producing liquid developer, and liquid developer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent occurrence of streak-like noise in a formed image.SOLUTION: In a method for producing a liquid developer, a volume average particle diameter of shell particles in a state where a dispersion liquid for a shell and a solution for a core are mixed is 50 nm or more and 300 nm or less. A shell resin is produced by reaction of a mixture containing a first vinyl monomer containing a linear hydrocarbon chain having 12 or more and 27 or less carbon atoms, a second vinyl monomer containing a branched hydrocarbon chain having 12 or more and 27 or less carbon atoms, and a third vinyl monomer containing at least one of a hydroxyl group and a carboxyl group. When an amount of the first vinyl monomer to be mixed is represented by M1, an amount of the second vinyl monomer to be mixed is represented by M2, and an amount of the third vinyl monomer to be mixed is represented by M3, a relationship of {M3/(M1+M2)}≤0.05 is satisfied.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing a liquid developer and a liquid developer.

  As a method of forming an image using an electrophotographic method, there are a method of forming an image using a dry developer and a method of forming an image using a liquid developer. The dry developer contains toner particles containing a binder resin and a colorant such as a pigment in a dry state. The liquid developer contains toner particles dispersed in an electrically insulating carrier liquid (hereinafter referred to as “insulating liquid”).

  In general, a method of forming an image using a dry developer is used. However, since this method handles toner particles in a powder state, there are problems such as contamination due to scattering of toner particles. In addition, since there is a concern that the toner particles in the powder state adversely affect the human body, the lower limit of the particle size of the toner particles is about 5 to 6 μm, and the lower limit cannot be made smaller than 5 to 6 μm. Therefore, it is difficult to form a high-resolution toner image.

  On the other hand, in the method of forming an image using a liquid developer, the particle diameter of the toner particles can be 5 μm or less. Therefore, the reproducibility of the fine line image is good, the reproducibility of the gradation (the degree of change in shading in the image) is good, and an image with higher resolution can be formed. In particular, by setting the particle size of the toner particles to 1 to 3 μm and increasing the content ratio of the colorant in the toner particles, at least a desired image density can be obtained with an adhesion amount of the toner particles. Therefore, the image quality at the offset printing level is obtained. As toner particles contained in the liquid developer, toner particles having a core / shell structure are known (for example, Patent Document 1).

JP 2009-96994 A

  In toner particles having a core / shell structure, it is said that the particle size of the toner particles can be controlled by controlling the particle size of the shell particles. Here, toner particles having a core / shell structure can be obtained by mixing a dispersion of shell particles containing a shell resin and a solution of the core resin. Therefore, it has been considered that toner particles having a desired particle diameter can be obtained by mixing a dispersion of shell particles having a controlled particle diameter and a core resin solution.

  However, when the particle size of the shell particles is reduced because the shell particles are dissolved in a solvent (for example, a solvent contained in the core resin solution) at the time of mixing the dispersion of the shell particles and the solution of the core resin, It was found that toner particles having an extremely small particle size (hereinafter referred to as “fine powder toner particles”) were produced. For example, Patent Document 1 describes an example in which the volume average particle diameter of shell particles in liquid paraffin is 40 nm to 60 nm. When mixing a dispersion of shell particles and a solution of a core resin, the particles of shell particles are described. It is considered that the diameter is further reduced. Therefore, the obtained toner particles may contain fine powdery toner particles (for example, toner particles having a particle size of less than 0.5 μm) that are difficult to detect with an apparatus for measuring the particle size of the toner particles. .

  Incidentally, in an image forming apparatus using an electrophotographic system, a cleaning device is usually provided in the vicinity of the photoconductor for collecting the developer remaining on the photoconductor after development. As a cleaning device, a method using a roller or a blade is known, but a blade cleaning method (an elastic contact plate (hereinafter referred to as a “cleaning blade”) is arranged so as to contact the surface of the photoconductor. In many cases, the cleaning blade is used to scrape off the developer remaining on the photoreceptor.

  When an image is formed using a liquid developer containing finely divided toner particles, when the liquid developer remaining on the photoreceptor is collected, the finely powdered toner particles easily pass through the gap between the photoreceptor and the cleaning blade. Become. Therefore, it is difficult to collect the fine powdery toner particles contained in the liquid developer remaining on the photoreceptor, and streaky noise may occur in the formed image.

  Further, if fine powdery toner particles that have passed through the gap adhere to the surface of the cleaning blade (contamination of the cleaning blade), a cleaning failure occurs in the cleaning blade. This also causes streak noise in the formed image.

  The present invention has been made in view of such a point, and an object thereof is to prevent the occurrence of streak-like noise in a formed image.

  The method for producing a liquid developer according to the present invention includes a core / shell structure including a core particle including a core resin and a shell resin that is provided on at least a part of the surface of the core particle and is a resin different from the core resin This is a method for producing a liquid developer comprising particles and an insulating liquid in which toner particles are dispersed and containing a first solvent. The method for producing a liquid developer of the present invention is a solvent different from the first solvent and the step of preparing a dispersion for shell having shell particles dispersed in the first solvent and containing shell resin, and the first solvent. A step of preparing a core solution having a second solvent, a core resin dissolved in the second solvent, and a colorant dispersed in the second solvent, and mixing the shell dispersion and the core solution A granulation step of producing particles. The volume average particle size of the shell particles in a state where the shell dispersion and the core solution are mixed is 50 nm or more and 300 nm or less.

  In the method for producing a liquid developer according to the present invention, the first vinyl monomer including a linear hydrocarbon chain having 12 to 27 carbon atoms and the first hydrocarbon monomer having a branched hydrocarbon chain having 12 to 27 carbon atoms. A shell resin is made by reacting a mixture comprising a 2 vinyl monomer and a third vinyl monomer containing at least one of hydroxyl and carboxyl groups. When the blending amount of the first vinyl monomer is represented as M1, the blending amount of the second vinyl monomer is represented as M2, and the blending amount of the third vinyl monomer is represented as M3, {M3 / (M1 + M2)} ≦ 0.05 Fulfill.

  The “shell resin that is a resin different from the core resin” means that at least one of the chemical structure and the molecular weight is different between the core resin and the shell resin. “Vinyl monomer” means a monomer having a polymerizable double bond.

  The “volume average particle diameter of shell particles” means the median diameter D50 when the particle size distribution of shell particles is measured on a volume basis. The “volume average particle diameter of toner particles” described later means a median diameter D50 when the particle size distribution of toner particles is measured on a volume basis.

  It is preferable to preliminarily disperse the shell dispersion before the granulation step. In the granulation step, it is preferable to mechanically disperse the shell dispersion and the core solution.

  The first solvent is preferably at least one of a normal paraffin solvent and an isoparaffin solvent.

  The liquid developer of the present invention is produced according to the method for producing a liquid developer of the present invention.

  In the present invention, it is possible to prevent the occurrence of streak noise in the formed image.

1 is a schematic conceptual diagram of a part of an electrophotographic image forming apparatus.

  Hereinafter, embodiments of the present invention (hereinafter referred to as “present embodiments”) will be described with reference to the drawings. In the drawings of the present invention, the same reference numerals represent the same or corresponding parts. In addition, dimensional relationships such as length, width, thickness, and depth are changed as appropriate for clarity and simplification of the drawings, and do not represent actual dimensional relationships.

[Manufacture of liquid developer]
The method for producing a liquid developer according to the present embodiment is a method for producing a liquid developer including an insulating liquid containing a first solvent and toner particles dispersed in the insulating liquid. The toner particles have a core / shell structure. The core / shell structure includes core particles including a core resin and a shell resin that is provided on at least a part of the surface of the core particles and is a resin different from the core resin. The produced liquid developer is an electrophotographic liquid developer, paint, or electrostatic recording liquid developer used in an electrophotographic image forming apparatus (described later) such as a copying machine, a printer, a digital printing machine, or a simple printing machine. It is useful as an agent, an oil-based ink for an ink jet printer, or an ink for electronic paper.

  Conventionally, a pulverization method or a granulation method is known as a method for producing a liquid developer. In the pulverization method, a resin and a colorant such as a pigment are melt-kneaded and then pulverized. Such pulverization may be performed in a dry state or in a wet state such as in an insulating liquid. On the other hand, the granulation method includes a suspension polymerization method, an emulsion polymerization method, a particle aggregation method, a method in which a poor solvent is added to a resin solution, a spray drying method, For example, the toner particle resin may have a core / shell structure using two different types of resins.

  The method for producing the liquid developer of this embodiment may be either a pulverization method or a granulation method, but it is preferable to adopt a granulation method rather than a pulverization method. Thereby, toner particles having a small diameter and a uniform particle diameter can be obtained. Specifically, a resin having a high melting property or a resin having a high crystallinity is difficult to be crushed because it is soft even at room temperature. Therefore, when toner particles are produced by a pulverization method using such a resin, it is difficult to obtain toner particles having a small diameter and a uniform particle diameter. On the other hand, in the granulation method, toner particles having a small diameter and a uniform particle diameter can be obtained even when a resin having a high melting property or a resin having a high crystallinity is used.

  Among the granulation methods, it is preferable to prepare toner particles by the following method. The core solution is prepared by dissolving the resin in a good solvent. The core solution is mixed with an interfacial tension adjusting agent (toner dispersant) in a poor solvent having a SP value different from that of the good solvent to give shear. Thereby, a droplet is produced. Thereafter, when the good solvent is volatilized, toner particles are produced. If toner particles are prepared by this method, the particle size of the toner particles and the shape of the toner particles can be improved by appropriately adjusting the shearing method, the difference in interfacial tension, or the material of the interfacial tension adjusting agent (toner dispersant). Can be controlled. Therefore, toner particles having a desired particle size distribution and a desired shape can be obtained.

  Specifically, the method for producing a liquid developer according to the exemplary embodiment includes a preparation step of a dispersion liquid for a shell, a preparation step of a solution for a core, and toner particles are prepared by mixing the dispersion liquid for shell and the core solution. A granulating step (hereinafter simply referred to as “granulating step”). The prepared dispersion for shell has a first solvent (the first solvent is included in the insulating liquid) and shell particles dispersed in the first solvent and containing a shell resin. The prepared core solution has a second solvent that is a solvent different from the first solvent, a core resin dissolved in the second solvent, and a colorant dispersed in the second solvent. The volume average particle diameter of the shell particles in a state where the shell dispersion and the core solution are mixed is 50 nm or more and 300 nm or less.

  When the shell dispersion and the core solution are mixed, core particles made of the core resin are produced, and at the same time, the shell resin adheres to the surface of the core particles (production of toner particles having a core / shell structure). Since the shell resin adheres to the surface of the core particles by mixing the shell dispersion and the core solution in this way, toner particles having a core / shell structure (hereinafter referred to as “toner particles of this embodiment”). Can be prevented. Further, the toner particles of the present embodiment can be prevented from being divided even under high shear conditions (conditions in which the toner particles are easily sheared).

  In the present embodiment, the volume average particle diameter of the shell particles in the mixed state of the shell dispersion and the core solution is 50 nm or more. It has now been found that this makes it difficult to produce finely divided toner particles. Therefore, when collecting the liquid developer remaining on the photoconductor, it is possible to prevent toner particles contained in the liquid developer remaining on the photoconductor from passing through the gap between the photoconductor and the cleaning blade. Therefore, the toner particles contained in the liquid developer remaining on the photoreceptor can be collected. Therefore, it is possible to prevent streak noise from occurring in the formed image.

  In addition, since the toner particles contained in the liquid developer remaining on the photoreceptor can be prevented from slipping through the gap, the toner particles can be prevented from adhering to the surface of the cleaning blade. As a result, it is possible to prevent the occurrence of cleaning failure in the cleaning blade, and it is therefore possible to prevent the occurrence of streak-like noise in the formed image. As described above, when the volume average particle diameter of the shell particles in the mixed state of the shell dispersion and the core solution is 50 nm or more, it is possible to prevent the generation of streak noise in the formed image.

  Furthermore, the volume average particle size of the shell particles in the mixed state of the shell dispersion and the core solution is 300 nm or less. Thereby, it is possible to prevent the volume average particle diameter of the toner particles of the present embodiment from becoming much larger than a desired value (for example, 1 μm to 3 μm). The volume average particle diameter of the shell particles in the mixed state of the shell dispersion and the core solution is preferably 60 nm or more and 280 nm or less, more preferably 60 nm or more and 250 nm or less.

  When the shell dispersion and the core solution are mixed, the dispersed phase composed of the shell dispersion and the oil phase composed of the core solution may be partially compatible. Specifically, a first solvent (for example, an insulating liquid) that is a medium of a dispersed phase and a second solvent (for example, acetone) that is a medium of an oil phase are partially compatible, and the second solvent is mixed with the dispersed phase. Sometimes. In this case, the second solvent is distributed into the dispersed phase and the oil phase. In the present specification, the medium of the dispersed phase after the second solvent is distributed into the dispersed phase and the oil phase may be referred to as “granulation medium”.

  In this specification, the volume average particle diameter of the shell particles (shell particles in the granulation medium) in a mixed state of the shell dispersion and the core solution is an ultrasonic particle size distribution measuring device (a product manufactured by Dispersion Technology). The value measured under the following conditions using the name “DT1200”).

(Preparation of measurement solution)
A measurement solution having a composition close to that of the granulation medium is prepared. Specifically, about 3 g of the shell dispersion, about 17 g of the first solvent (eg, “IP Solvent 2028” manufactured by Idemitsu Kosan Co., Ltd.), 13.35 g of the second solvent (eg, acetone), and 0.13 g A solution for measurement is prepared by mixing with water. At this time, the blending amount of the first solvent is adjusted so that the concentration of the shell particles in the measurement solution is 1.1% by mass. However, the solid content concentration of the shell dispersion varies from sample to sample and is, for example, 9 to 13% by mass. Therefore, it is preferable to appropriately adjust the blending amount of the first solvent according to the solid content concentration of the shell dispersion.

(Measurement)
The temperature of the prepared measurement solution is adjusted to 50 ° C. (temperature at the time of granulation of toner particles) using a water bath, and then returned to room temperature (23 to 25 ° C.). The measurement solution (about 25 cm ³ ) is put into the chamber of the ultrasonic particle size distribution measuring apparatus, and the volume average particle size of the shell particles in the mixed state of the shell dispersion and the core solution is measured. Measurement is carried out while confirming that the temperature of the solution for measurement is room temperature using a non-contact thermometer (product number “830-T2” manufactured by Testo Co., Ltd.).

(analysis)
Assuming that the particle size distribution of the shell particles is monodisperse, the obtained results are analyzed. At the time of analysis, a mixed liquid of the first solvent, the second solvent, and water is used as a blank liquid. In addition, it is preferable that the mixing | blending ratio of the said 1st solvent in the blank liquid, the said 2nd solvent, and water is respectively the same as these mixing | blending ratios in the solution for a measurement.

<Preparation of dispersion for shell>
In the step of preparing the shell dispersion, it is preferable to disperse the shell particles in the first solvent. The method for dispersing the shell particles in the first solvent is not particularly limited, and a conventionally known method can be used as a method for dispersing the resin particles in the organic solvent. For example, it is preferable to disperse the shell particles in the first solvent using a conventionally known dispersion apparatus.

(First solvent)
The first solvent is not particularly limited as long as it can disperse the shell particles, but it is preferable that the toner particles of this embodiment can be dispersed. That is, the first solvent preferably has a resistance value (resistance value of 10 ¹¹ Ω · cm or more and 10 ¹⁶ Ω · cm or less) that does not disturb the electrostatic latent image, and in addition, has low odor and toxicity. Is more preferable. For example, the first solvent is preferably at least one of an aliphatic hydrocarbon, an alicyclic hydrocarbon, an aromatic hydrocarbon, a halogenated hydrocarbon, and a polysiloxane.

  The first solvent is preferably at least one of a normal paraffinic solvent (linear aliphatic saturated hydrocarbon) and an isoparaffinic solvent (branched aliphatic saturated hydrocarbon). Thereby, a solvent with low odor, toxicity and cost can be used as the first solvent. In addition, since the affinity between the shell particles and the first solvent can be increased, the granulation of the toner particles of the present embodiment is stabilized, and thus the peak appearing in the particle size distribution of the toner particles of the present embodiment is sharp. Become.

  Commercially available products of normal paraffin solvents or isoparaffin solvents include, for example, “Moresco White” (trade name) manufactured by Matsumura Oil Co., Ltd., “Isopar H” (trade name), “Isopar L” manufactured by ExxonMobil. (Product name) or “Isopar M” (product name), “Shellsol TK” (product name) or “Shellsol TM” (product name) manufactured by Showa Shell Sekiyu KK, or “Isemitsu Kosan Co., Ltd.” “IP solvent 1620” (trade name) or “IP solvent 2028” (trade name) can be used. Two or more of these may be mixed and used as the first solvent.

  The first solvent is preferably composed of at least one of a normal paraffin solvent and an isoparaffin solvent. However, the first solvent may contain 10% by mass or less of at least one of alicyclic hydrocarbon, aromatic hydrocarbon, and polysiloxane.

(Shell particles)
The shell particles include a shell resin, preferably made of a shell resin.

  It is preferable to appropriately adjust the volume average particle diameter of the shell particles contained in the shell dispersion so that the volume average particle diameter of the toner particles of the present embodiment falls within a desired range. The volume average particle diameter of the shell particles is preferably 0.0005 μm or more and 3 μm or less. The upper limit of the volume average particle diameter of the shell particles is more preferably 2 μm, and even more preferably 1 μm. The lower limit of the volume average particle diameter of the shell particles is more preferably 0.01 μm, still more preferably 0.02 μm, still more preferably 0.04 μm. For example, when it is desired to obtain toner particles having a volume average particle diameter of 1 μm, the volume average particle diameter of the shell particles contained in the shell dispersion liquid is preferably 0.5 nm or more and 300 nm or less, more preferably 1 nm. It is 200 nm or less. When it is desired to obtain toner particles having a volume average particle size of 10 μm, the volume average particle size of the shell particles contained in the shell dispersion is preferably 5 nm or more and 3 μm or less, more preferably 50 nm or more and 2 μm. It is as follows.

  For example, the volume average particle diameter of the shell particles contained in the shell dispersion can be measured using a flow type particle image analyzer (trade name “FPIA-3000S” manufactured by Sysmex Corporation). In this analyzer, it is possible to use the solvent as a dispersion medium as it is. Therefore, by using this analyzer, it is possible to measure the state of the shell particles in a state closer to the actual dispersed state than to measure in an aqueous system.

  The shell particles are preferably produced, for example, by any one of the following [1] to [7]. From the viewpoint of easy preparation of shell particles, it is preferable to prepare shell particles by the method [4], [6] or [7], and to prepare shell particles by the method [6] or [7]. Is more preferable.

[1] The shell resin is pulverized dry using a known dry pulverizer such as a jet mill. [2] The shell resin powder is dispersed in an organic solvent, and a known wet disperser such as a bead mill or a roll mill is used. [3] Spray the shell resin solution using a spray dryer and dry it. [4] Add a poor solvent to the shell resin solution or cool it to supersaturate the shell resin and precipitate. [5] Disperse the shell resin solution in water or an organic solvent. [6] Polymerize the precursor of the shell resin in water by emulsion polymerization, soap-free emulsion polymerization, seed polymerization or suspension polymerization. [7] The shell resin precursor is polymerized in an organic solvent by dispersion polymerization or the like.

(Shell resin)
The shell resin may be a thermoplastic resin or a thermosetting resin. Examples of the shell resin include vinyl resin, polyester resin, polyurethane resin, epoxy resin, polyamide resin, polyimide resin, silicon resin, phenol resin, melamine resin, urea resin, aniline resin, ionomer resin, or polycarbonate resin. It is done. As the shell resin, any of these resins may be used, or two or more of these resins may be used in combination.

  From the viewpoint of easily obtaining toner particles having a small diameter and a uniform particle diameter, the shell resin is preferably at least one of a vinyl resin, a polyester resin, a polyurethane resin, and an epoxy resin. More preferably, it is a resin.

  The shell resin is required to have a function of dispersing toner particles in an insulating liquid. Therefore, it is preferable that the shell resin has a portion having a high affinity for the first solvent (parent oil portion) and a portion having a high affinity for the core resin (parent core portion) in the molecule. If the shell resin is a vinyl resin, the shell resin can be designed by adjusting the blending ratio of the vinyl monomers or the composition of the vinyl monomers. Therefore, the shell resin is preferably a vinyl resin.

  For example, a first vinyl monomer containing a linear hydrocarbon chain having 12 to 27 carbon atoms, a second vinyl monomer containing a branched hydrocarbon chain having 12 to 27 carbon atoms, a hydroxyl group and a carboxyl group A shell resin is produced by reacting (for example, polymerization reaction) a mixture containing a third vinyl monomer containing at least one of the above. Further, when the blending amount of the first vinyl monomer is represented as M1, the blending amount of the second vinyl monomer is represented as M2, and the blending amount of the third vinyl monomer is represented as M3, {M3 / (M1 + M2)} ≦ 0. 05 is satisfied. Thereby, since the diameter reduction of the shell particles in the granulation medium is prevented, the volume average particle diameter of the shell particles in the granulation medium can be controlled to 50 nm or more and 300 nm or less. Therefore, it is considered that the production of fine powder toner particles is prevented. Therefore, it is possible to prevent streak noise from occurring in the formed image.

  Specifically, since the shell resin is produced by reacting not only the second vinyl monomer but also a mixture further containing the first vinyl monomer and the third vinyl monomer, the produced shell resin is appropriate for the first solvent. Will have a good affinity. Thereby, since the diameter reduction of the shell particles in the dispersion liquid for shell is prevented, the diameter reduction of the shell particles in the granulation medium is prevented. Therefore, the volume average particle diameter of the shell particles in the granulation medium can be controlled to 50 nm or more and 300 nm or less. Therefore, since it is considered that the production of fine powder toner particles is prevented, it is possible to prevent the generation of streaky noise in the formed image. The present inventors consider that it is preferable to use the first vinyl monomer as a monomer constituting the shell resin in order to prevent the diameter of the shell particles from being reduced in the shell dispersion.

  Further, since {M3 / (M1 + M2)} ≦ 0.05 is satisfied, the manufactured shell resin has an appropriate affinity for the core resin. This optimizes the adsorptivity of the shell particles to the core particles in the granulation medium. This also prevents the shell particles in the granulation medium from being reduced in size, so that the volume average particle diameter of the shell particles in the granulation medium can be controlled to 50 nm or more and 300 nm or less. Therefore, since it is considered that the production of fine powder toner particles is prevented, it is possible to prevent the generation of streak-like noise in the formed image.

  Furthermore, since the shell resin is produced by reacting not only the first vinyl monomer but also a mixture further containing the second vinyl monomer and the third vinyl monomer, the produced shell resin has an appropriate affinity for the first solvent. It will have sex. Thereby, since the increase in the diameter of the shell particles in the dispersion liquid for shell is prevented, the increase in the diameter of the shell particles in the granulation medium is prevented. Accordingly, it is possible to prevent the volume average particle size of the toner particles of the present embodiment from significantly exceeding a desired value, and thus toner particles having a desired volume average particle size can be produced. The present inventors consider that it is preferable to use a second vinyl monomer as a monomer constituting the shell resin in order to prevent an increase in the diameter of the shell particles in the shell dispersion.

  Since the shell resin is prepared by reacting a mixture containing the first vinyl monomer, the second vinyl monomer, and the third vinyl monomer, the shell resin is composed of a linear hydrocarbon chain having 12 to 27 carbon atoms and carbon. And a branched hydrocarbon chain having a number of 12 or more and 27 or less. When the first solvent is at least one of a normal paraffin solvent and an isoparaffin solvent, the linear hydrocarbon chain and the branched hydrocarbon chain have a high affinity for the first solvent. Therefore, the shell particles are stably dispersed in the first solvent.

(First vinyl monomer)
The first vinyl monomer includes a linear hydrocarbon chain having 12 to 27 carbon atoms, and preferably includes a linear hydrocarbon chain having 16 to 25 carbon atoms.

  Examples of the first vinyl monomer include mono-linear alkyl esters of unsaturated monocarboxylic acids or mono-linear alkyl esters of unsaturated dicarboxylic acids. Such a first vinyl monomer is obtained by reacting an unsaturated monocarboxylic acid or unsaturated dicarboxylic acid with an alcohol containing a linear hydrocarbon chain having 12 to 27 carbon atoms. Therefore, the mono linear alkyl corresponds to a linear hydrocarbon chain having 12 to 27 carbon atoms.

  Examples of the unsaturated monocarboxylic acid include vinyl monomers containing one carboxyl group in the molecule and having 3 to 24 carbon atoms, and (meth) acrylic acid or crotonic acid is preferred. In this specification, “(meth) acrylic acid” means at least one of acrylic acid and methacrylic acid.

  Examples of the unsaturated dicarboxylic acid include vinyl monomers containing two carboxyl groups in the molecule and having 3 to 24 carbon atoms, such as maleic acid, fumaric acid, itaconic acid, or citraconic acid. preferable.

  Specific examples of the first vinyl monomer include, for example, stearyl (meth) acrylate, dodecyl (meth) acrylate, behenyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, or ( (E.g., meta) eicosyl acrylate.

(Second vinyl monomer)
The second vinyl monomer includes a branched hydrocarbon chain having 12 to 27 carbon atoms, and preferably includes a branched hydrocarbon chain having 16 to 25 carbon atoms.

  Examples of the second vinyl monomer include mono-branched alkyl esters of unsaturated monocarboxylic acids or mono-branched alkyl esters of unsaturated dicarboxylic acids. Such a second vinyl monomer is obtained by reacting an unsaturated monocarboxylic acid or unsaturated dicarboxylic acid with an alcohol containing a branched hydrocarbon chain having 12 to 27 carbon atoms. Therefore, the mono-branched alkyl corresponds to a branched hydrocarbon chain having 12 to 27 carbon atoms.

  Examples of the unsaturated monocarboxylic acid include vinyl monomers containing one carboxyl group in the molecule and having 3 to 24 carbon atoms, and (meth) acrylic acid or crotonic acid is preferred.

  Examples of the unsaturated dicarboxylic acid include vinyl monomers containing two carboxyl groups in the molecule and having 3 to 24 carbon atoms, such as maleic acid, fumaric acid, itaconic acid, or citraconic acid. preferable.

  Specific examples of the second vinyl monomer include 2-decyl tetradecyl (meth) acrylate or 2-octyl tetradecyl (meth) acrylate.

(Third vinyl monomer)
The third vinyl monomer contains at least one of a hydroxyl group and a carboxyl group.

  Examples of the vinyl monomer containing a hydroxyl group include unsaturated alcohols having 1 to 10 carbon atoms [for example, (meth) allyl alcohol, crotyl alcohol, isocrotyl alcohol, 1-buten-3-ol, 2-buten-1-ol, 2-butene-1,4-diol, propargyl alcohol, hydroxystyrene, etc.] or unsaturated acrylate having a hydroxyl group [for example, hydroxyethyl (meth) acrylate, hydroxypropyl (Meth) acrylate or polyethylene glycol mono (meth) acrylate]], unsaturated amide having a hydroxyl group [for example, N-methylol (meth) acrylamide, etc.], or having a hydroxyl group. Unsaturated ether [ A example, if 2-hydroxyethyl propenyl ether, or sucrose allyl ether, etc.] may be.

  The vinyl monomer containing a carboxyl group may be, for example, an unsaturated monocarboxylic acid [for example, (meth) acrylic acid, crotonic acid, isocrotonic acid, or cinnamic acid] having 3 to 15 carbon atoms. An unsaturated dicarboxylic acid (anhydride) having 3 to 30 carbon atoms [for example, (anhydrous) maleic acid, fumaric acid, itaconic acid, (anhydrous) citraconic acid, mesaconic acid, etc.] Monoalkyls of unsaturated dicarboxylic acids having 3 to 10 carbon atoms (with 1 to 10 carbon atoms) [for example, maleic acid monomethyl ester, maleic acid monodecyl ester, fumaric acid monoethyl ester, itaconic acid Monobutyl ester or citraconic acid monodecyl ester, etc.].

  As used herein, “unsaturated dicarboxylic acid (anhydride)” means at least one of an unsaturated dicarboxylic acid and an unsaturated dicarboxylic anhydride. Similarly, “(maleic anhydride)” means at least one of maleic acid and maleic anhydride. Further, “(anhydrous) citraconic acid” means at least one of citraconic acid and citraconic anhydride.

({M3 / (M1 + M2)})
More preferably, 0 <{M3 / (M1 + M2)} ≦ 0.04 is satisfied. This makes it easy to optimize the adsorptivity of the shell particles with respect to the core particles in the granulation medium, thereby further preventing the reduction in the diameter of the shell particles in the granulation medium. Therefore, it is considered that the production of fine powdery toner particles can be further prevented, and therefore it is possible to further prevent the generation of streaky noise in the formed image. More preferably, it satisfies 0.01 ≦ {M3 / (M1 + M2)} ≦ 0.035.

  As long as {M3 / (M1 + M2)} ≦ 0.05 is satisfied, in the manufactured shell resin, the structural unit derived from the first vinyl monomer, the structural unit derived from the second vinyl monomer, and the third The arrangement order of the structural units derived from the vinyl monomer is not limited. Further, the blending amounts of the first vinyl monomer, the second vinyl monomer, and the third vinyl monomer are not limited. For example, a mixture containing a first vinyl monomer of 20% by weight to 40% by weight, a second vinyl monomer of 20% by weight to 40% by weight, and a third vinyl monomer of 0.05% by weight to 5% by weight. It is preferable to produce a shell resin by reacting.

  The shell resin may have 10% by mass or less of a resin different from the resin obtained by reacting a mixture containing the first vinyl monomer, the second vinyl monomer, and the third vinyl monomer. Even in such a case, the above effects can be obtained.

  A shell resin is produced by reacting (for example, a polymerization reaction) a mixture further containing a vinyl monomer different from any of the first vinyl monomer, the second vinyl monomer, and the third vinyl monomer (hereinafter referred to as “fourth vinyl monomer”). You may do it. In this case, the blending amount of the fourth vinyl monomer is preferably 10% by mass or less.

(4th vinyl monomer)
The fourth vinyl monomer may be any of the following vinyl monomers, or two or more of the following vinyl monomers may be used in combination.

(1) Hydrocarbon having a polymerizable double bond (1-1) Aliphatic hydrocarbon having a polymerizable double bond (1-1-1) Chained aliphatic hydrocarbon having a polymerizable double bond Polymerization Chain aliphatic hydrocarbons having an ionic double bond include, for example, alkenes having 2 to 30 carbon atoms (for example, ethylene, propylene, butene, isobutylene, pentene, heptene, diisobutylene, octene, dodecene, octadecene, etc.) Or an alkadiene having 4 to 30 carbon atoms (for example, butadiene, isoprene, 1,4-pentadiene, 1,5-hexadiene, 1,7-octadiene, etc.).

(1-1-2) Cyclic aliphatic hydrocarbon having a polymerizable double bond Cyclic aliphatic hydrocarbon having a polymerizable double bond is, for example, a monocycloalkene having 6 to 30 carbon atoms or a dicycloalkene. A cycloalkene (such as cyclohexene, vinylcyclohexene or ethylidenebicycloheptene), or a monocycloalkadiene or dicycloalkadiene having 5 to 30 carbon atoms (such as monocyclopentadiene or dicyclopentadiene) Preferably there is.

(1-2) Aromatic hydrocarbon having a polymerizable double bond The aromatic hydrocarbon having a polymerizable double bond is, for example, styrene or a hydrocarbyl of styrene (for example, an alkyl having 1 to 30 carbon atoms). , Cycloalkyl, aralkyl or alkenyl) substituted (for example, α-methylstyrene, vinyltoluene, 2,4-dimethylstyrene, ethylstyrene, isopropylstyrene, butylstyrene, phenylstyrene, cyclohexylstyrene, benzylstyrene, crotylbenzene, Divinylbenzene, divinyltoluene, divinylxylene, trivinylbenzene, etc.) or vinylnaphthalene is preferred.

(2) Monomers having a sulfo group and a polymerizable double bond and salts thereof (3) Monomers having a phosphono group and a polymerizable double bond and salts thereof Specific examples of the above (2) to (3) Although not listed, it can be used as the fourth vinyl monomer.

(4) Nitrogen-containing monomer having a polymerizable double bond (4-1) Monomer having an amino group and a polymerizable double bond A monomer having an amino group and a polymerizable double bond is, for example, aminoethyl (meta ) Acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, t-butylaminoethyl methacrylate, N-aminoethyl (meth) acrylamide, (meth) allylamine, morpholinoethyl (meth) acrylate, 4-vinylpyridine 2-vinylpyridine, crotylamine, N, N-dimethylaminostyrene, methyl-α-acetaminoacrylate, vinylimidazole, N-vinylpyrrole, N-vinylthiopyrrolidone, N-arylphenylenediamine, aminocarbazole, aminothiazole Aminoindole, aminopyrrole, it is preferable that in such aminoimidazole or amino mercaptothiazole.

  Instead of the monomer having an amino group and a polymerizable double bond, or together with the monomer having an amino group and a polymerizable double bond, a salt of a monomer having an amino group and a polymerizable double bond can be used.

(4-2) Monomer having amide group and polymerizable double bond Monomers having amide group and polymerizable double bond are, for example, (meth) acrylamide, N-methyl (meth) acrylamide, N-butylacrylamide , Diacetone acrylamide, N-methylol (meth) acrylamide, N, N′-methylene-bis (meth) acrylamide, cinnamic acid amide, N, N-dimethylacrylamide, N, N-dibenzylacrylamide, methacrylformamide, N— Methyl-N-vinylacetamide or N-vinylpyrrolidone is preferred.

(4-3) Monomers having 3 to 10 carbon atoms having nitrile groups and polymerizable double bonds Monomers having 3 to 10 carbon atoms having nitrile groups and polymerizable double bonds are, for example, (meta ) Acrylonitrile, cyanostyrene or cyanoacrylate is preferred.

(4-4) Monomer having 8 to 12 carbon atoms having nitro group and polymerizable double bond Monomer having 8 to 12 carbon atoms having nitro group and polymerizable double bond is, for example, nitrostyrene And the like.

(5) Monomer having 6 to 18 carbon atoms having epoxy group and polymerizable double bond (6) Monomer having 2 to 16 carbon atoms having halogen element and polymerizable double bond Above (5) to ( Although a specific example is not enumerated about 6), it can be used as the fourth vinyl monomer.

(7) Ester having 4 to 16 carbon atoms having a polymerizable double bond Ester having 4 to 16 carbon atoms having a polymerizable double bond includes, for example, vinyl acetate, vinyl propionate, vinyl butyrate, diallyl phthalate , Diallyl adipate, isopropenyl acetate, vinyl methacrylate, methyl-4-vinyl benzoate, cyclohexyl methacrylate, benzyl methacrylate, phenyl (meth) acrylate, vinyl methoxyacetate, vinyl benzoate, ethyl-α-ethoxy acrylate, 1 to 11 carbon atoms Alkyl (meth) acrylates having the following alkyl groups [for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate or 2-ethylhexyl ( Meth) acrylates, etc.], dialkyl fumarate (the two alkyl groups are straight, branched or alicyclic alkyl groups having 2 to 8 carbon atoms), dialkyl maleates (2 Each alkyl group is a straight chain alkyl group having 2 to 8 carbon atoms, a branched alkyl group or an alicyclic alkyl group), poly (meth) allyloxyalkanes (for example, diaryloxyethane, Triaryloxyethane, tetraallyloxyethane, tetraallyloxypropane, tetraallyloxybutane or tetrametaallyloxyethane), a monomer having a polyalkylene glycol chain and a polymerizable double bond [eg, polyethylene glycol (Mn = 300) Mono (meth) acrylate, polypropylene glycol (Mn = 500) monoacrylate , Methyl alcohol ethylene oxide (hereinafter, “ethylene oxide” is referred to as “EO”) 10 mol adduct (meth) acrylate or lauryl alcohol EO 30 mol adduct (meth) acrylate, etc.], or poly (meth) acrylates { For example, poly (meth) acrylates of polyhydric alcohols [for example, ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate or polyethylene Glycol di (meth) acrylate and the like]} and the like. As used herein, “(meth) arylo” means at least one of alilo and metallillo.

  The fourth vinyl monomer may be at least one of a vinyl monomer having a fluoroalkyl chain having 4 to 20 carbon atoms and a vinyl monomer having a polydimethylsiloxane chain. The difference in SP value between the fluoroalkyl chain or polydimethylsiloxane chain contained in the fourth vinyl monomer and the first solvent is preferably 2 or less. In the present specification, the “SP value” is a method according to Fedors [Polym. Eng. Sci. 14 (2) 152, (1974)].

  The melting point of the shell resin is preferably 50 ° C. or higher and 100 ° C. or lower, more preferably 50 ° C. or higher and 80 ° C. or lower. If the melting point of the shell resin is 50 ° C. or higher, the shell resin is maintained in a high aggregation resistance, so that the shell particles are stably dispersed in the first solvent. If the melting point of the shell resin is 100 ° C. or lower, the toner particles can be fixed to the recording medium at a low temperature. In this specification, the melting point is measured in accordance with the method described in ASTM D3418-82 using a differential scanning calorimeter (eg, trade name “DSC20” manufactured by Seiko Instruments Inc.). is there.

  The number average molecular weight (hereinafter referred to as “Mn”) of the shell resin is preferably 100 or more and 5000000 or less, more preferably 200 or more and 5000000 or less, and further preferably 500 or more and 500000 or less. The Mn of the shell resin can be measured by GPC (Gel Permeation Chromatography).

The SP value of the shell resin is preferably 7 to 18 (cal / cm ³ ) ^1/2 , more preferably 8 to 14 (cal / cm ³ ) ^1/2 .

<Preparation of core solution>
In the step of preparing the core solution, the core resin is preferably dissolved in the second solvent, and the colorant is preferably dispersed in the second solvent. The method for dissolving the core resin in the second solvent is not particularly limited, and a conventionally known method can be used as a method for dissolving the resin particles in the organic solvent. For example, it is preferable to dissolve the core resin in the second solvent using a conventionally known dispersion apparatus. The same applies to the method of dispersing the colorant in the second solvent. In the prepared core solution, components different from the core resin and the colorant (for example, a pigment dispersant, a wax, or a charge control agent) may be dispersed in the second solvent.

(Second solvent)
The second solvent is not particularly limited as long as the core resin can be dissolved at room temperature or under heating. However, considering that the second solvent is removed after mixing the shell dispersion and the core solution, the second solvent preferably has a boiling point of 100 ° C. or lower, more preferably 90 ° C. or lower. Thereby, the odor of a 2nd solvent can also be suppressed low. For example, the second solvent is preferably at least one of THF (tetrahydrofuran), toluene, acetone, methyl ethyl ketone and ethyl acetate, and more preferably at least one of acetone and ethyl acetate.

(Core resin)
As the core resin, a conventionally known resin can be used as the binder resin for the toner particles without particular limitation. For example, a vinyl resin (a vinyl resin having a different chemical structure and molecular weight from a shell resin), A polyester resin, a urethane-modified polyester resin (polyester resin chain-chained by an isocyanate group), a polyurethane resin, an epoxy resin, or the like can be used. The core resin is preferably a polyester resin, more preferably a mixture of an aliphatic polyester resin and an aromatic polyester resin.

  Since the aliphatic polyester resin tends to exhibit crystallinity (described later), toner particles can be fixed to the recording medium at a low temperature by using the aliphatic polyester resin as the core resin. However, the hardness of the aliphatic polyester resin is low. For this reason, when an aliphatic polyester resin is used as the main component of the binder resin of toner particles, the hardness of the toner particles is lowered, which causes aggregation of the toner particles in the image forming apparatus.

  On the other hand, when the aromatic polyester resin is used as the main component of the binder resin of the toner particles, the softening point of the aromatic polyester resin is lowered if the molecular weight of the aromatic polyester resin is reduced. It can be fixed on the medium at low temperature. However, if the molecular weight of the aromatic polyester resin is reduced, not only the softening point of the aromatic polyester resin but also the glass transition point of the aromatic polyester resin is lowered. Therefore, the heat resistance of the toner particles is reduced.

  However, as a result of research by the present inventors, if a small amount of an aliphatic polyester resin is mixed with an aromatic polyester resin, the softening point of the aromatic polyester resin is lowered while maintaining high heat resistance of the toner particles. I understood. Preferably, the core resin contains 5% by mass or more and 40% by mass or less of an aliphatic polyester resin, and contains 60% by mass or more and 95% by mass or less of an aromatic polyester resin.

The content of the aliphatic polyester resin and the content of the aromatic polyester resin were determined by ¹ H-NMR analysis using a Fourier transform nuclear magnetic resonance apparatus (FT-NMR) (trade name: “Lambda400”, manufactured by JEOL Ltd.). And can be determined from the integration ratio. As the measurement solvent, a chloroform-d (deuterated chloroform) solvent can be used. In the structural unit derived from the aliphatic monomer in both the structural unit derived from the alcohol component and the structural unit derived from the acid component (described later), and the structural unit derived from the alcohol component and the acid component The content ratio (described later) of the structural unit derived from the aromatic monomer in both structural units with the derived structural unit can also be measured by the same method.

  Further, studies by the present inventors have found that the acid value of the mixture of the aliphatic polyester resin and the aromatic polyester resin is preferably 20 mgKOH / g or more and 100 mgKOH / g or less. When the acid value of such a mixture is 20 mgKOH / g or more, it is possible to ensure adhesion between the toner particles and the recording medium in a state dispersed in the insulating liquid. Thereby, the fixing strength of the toner particles on the recording medium can be secured. More preferably, the acid value of the mixture is 30 mgKOH / g or more. In addition, it is difficult to make the acid value of the said mixture larger than 100 mgKOH / g. In the present specification, “the acid value of the above mixture” is described in JIS K 0070: 1992 (acid acid value, saponification value, ester value, iodine value, hydroxyl value, and unsaponified test method for chemical products). It means the acid value of the mixture measured according to the method and corresponds to the amount of carboxyl groups contained in the mixture.

  The polyester resin is synthesized by a polycondensation reaction between a carboxylic acid (a structural unit derived from an acid component) and an alcohol (a structural unit derived from an alcohol component). Therefore, the part derived from carboxylic acid becomes a structural unit derived from the acid component, the part derived from alcohol becomes the structural unit derived from the alcohol component, and the polyester resin is configured by repeating these structural units.

  The term “aliphatic polyester resin” means that the content of the structural unit derived from the aliphatic monomer in both the structural unit derived from the alcohol component and the structural unit derived from the acid component is 90% by mass or more. Means. Since the aliphatic polyester resin has linearity, it exhibits crystallinity.

  The “structural unit derived from the alcohol component” means a unit in which a hydrogen atom is removed from the hydroxyl group of the alcohol, and includes a unit in which a hydrogen atom is removed from at least one hydroxyl group contained in the alcohol. The “structural unit derived from the acid component” means a unit in which a hydroxyl group is removed from the carboxyl group of the carboxylic acid, and includes a unit in which the hydroxyl group is removed from at least one carboxyl group contained in the carboxylic acid. “Aliphatic monomers” include aliphatic carboxylic acids, lower alkyl esters of aliphatic carboxylic acids, acid anhydrides of aliphatic carboxylic acids, and aliphatic alcohols. “Aliphatic carboxylic acid” means a carboxylic acid having no aromatic ring in the molecule. “Aliphatic alcohol” means an alcohol having no aromatic ring in the molecule.

  "Aromatic polyester resin" means that the content ratio of the structural unit derived from the aromatic monomer in both the structural unit derived from the alcohol component and the structural unit derived from the acid component is 90% by mass or more. Means. Aromatic polyester resins have non-linearity and are therefore less likely to exhibit crystallinity (amorphous).

  “Aromatic monomers” include aromatic carboxylic acids, lower alkyl esters of aromatic carboxylic acids, acid anhydrides of aromatic carboxylic acids, and aromatic alcohols. “Aromatic carboxylic acid” means a carboxylic acid having an aromatic ring in the molecule. “Aromatic alcohol” means an alcohol having an aromatic ring in the molecule.

  Examples of the aliphatic monomer serving as a structural unit derived from the acid component include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelic acid, sebacic acid, and 1,9-nonane. Dicarboxylic acid, 1,10-decanedicarboxylic acid, 1,11-undecanedicarboxylic acid, 1,12-dodecanedicarboxylic acid, 1,13-tridecanedicarboxylic acid, 1,14-tetradecanedicarboxylic acid, 1,16-hexadecanedicarboxylic acid Examples thereof include acid or 1,18-octadecanedicarboxylic acid. These lower alkyl esters may be used, and these acid anhydrides may be used. In terms of promoting the crystallinity of the polyester resin, it is more preferable to use adipic acid, sebacic acid, 1,10-decanedicarboxylic acid, or 1,12-dodecanedicarboxylic acid. As such an aliphatic monomer, any one of the above may be used alone, or two or more of the above may be used in combination.

  Examples of the aliphatic monomer serving as a structural unit derived from the alcohol component include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1 , 7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, , 14-tetradecanediol, 1,18-octadecanediol, 1,20-eicosanediol, and the like. From the viewpoint of promoting the crystallinity of the polyester resin, it is preferable to use ethylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,9-nonanediol, or 1,10-decanediol. . As such an aliphatic monomer, any one of the above may be used alone, or two or more of the above may be used in combination.

  Examples of the aromatic monomer serving as a structural unit derived from the acid component include an aromatic polyvalent carboxylic acid, a lower alkyl ester of an aromatic polyvalent carboxylic acid, or an acid anhydride of an aromatic polyvalent carboxylic acid. Can do. Specifically, terephthalic acid, isophthalic acid, orthophthalic acid, 5-tert-butylisophthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4′-biphenyldicarboxylic acid, or trimellitic acid (with 3 functional groups) ) And the like. From the viewpoint of availability, terephthalic acid, isophthalic acid, or 5-tert-butylisophthalic acid is preferably used.

  An aromatic polyhydric alcohol etc. can be mentioned as an aromatic monomer used as the structural unit derived from an alcohol component. Specific examples include an alkylene oxide adduct of bisphenol A represented by the following chemical formula (I).

In the chemical formula (I), R ¹ and R ² each independently represents an alkylene group having 2 or 3 carbon atoms. m and n each independently represent 0 or a positive integer. The sum of m and n is 1 or more and 16 or less.

  The Mn of the polyester resin (mixture of aliphatic polyester resin and aromatic polyester resin) is preferably 1000 or more and 25000 or less, and the mass average molecular weight (Mw) of the polyester resin is preferably 2000 or more and 200000 or less. The Mn and Mw of the polyester resin can be measured by GPC.

  The core resin may contain less than 10% by mass of a resin other than the aliphatic polyester resin and the aromatic polyester resin. Examples of the resin other than the aliphatic polyester resin and the aromatic polyester resin include styrene-acrylic resin, urethane resin, and epoxy resin. When the content is 10% by mass or more, it may be difficult to regularly arrange the molecular chains of the polyester resin.

(Crystalline and amorphous)
The shell resin preferably has crystallinity. The core resin preferably contains a crystalline resin (for example, an aliphatic polyester resin). As a result, an image with excellent gloss can be obtained even when the toner particles of the present embodiment are fixed on a recording medium at a low temperature.

  In the present specification, “crystallinity” means a ratio (Tm / Ta) between a softening point of a resin (hereinafter referred to as “Tm”) and a maximum peak temperature of heat of fusion (hereinafter referred to as “Ta”) of the resin. It means that it is 0.8 or more and 1.55 or less, and the result obtained by differential scanning calorimetry (DSC) has a clear endothermic peak instead of showing a stepwise endothermic amount change. Means that. In the present specification, “amorphous” means that the ratio of Tm to Ta (Tm / Ta) is larger than 1.55. Tm and Ta can be measured by the following method.

  Tm can be measured using a Koka type flow tester (for example, “CFT-500D” manufactured by Shimadzu Corporation). Specifically, while a 1 g measurement sample is heated at a heating rate of 6 ° C./min, a load of 1.96 MPa is applied to the measurement sample by a plunger, and the measurement sample is pushed out from a nozzle having a diameter of 1 mm and a length of 1 mm. . Then, the relationship between “plunger descent amount (flow value)” and “temperature” is drawn on a graph. The temperature at which the plunger descending amount is ½ of the maximum value of the descending amount is read from the graph, and this value (temperature when half of the measurement sample is pushed out of the nozzle) is defined as Tm.

  Ta can be measured using a differential scanning calorimeter (for example, product number “DSC210” manufactured by Seiko Instruments Inc.). Specifically, first, a sample used for measuring Ta is pretreated. After the sample is melted at 130 ° C., the temperature is lowered from 130 ° C. to 70 ° C. at a rate of 1.0 ° C./minute, and then the temperature is lowered from 70 ° C. to 10 ° C. at a rate of 0.5 ° C./minute. Next, the sample is heated at a heating rate of 20 ° C./min by DSC method to measure the endothermic change of the sample, and the relationship between the “endothermic amount” and “temperature” is plotted on a graph. At this time, the temperature of the endothermic peak observed at 20 to 100 ° C. is Ta ′. When there are a plurality of endothermic peaks, the temperature of the peak with the largest endothermic amount is defined as Ta '. Then, the sample is stored at (Ta′-10) ° C. for 6 hours, and then stored at (Ta′-15) ° C. for 6 hours.

  When the pretreatment for the sample is completed, the sample subjected to the pretreatment is cooled to 0 ° C. at a temperature drop rate of 10 ° C./min by the DSC method, and then heated at a temperature rise rate of 20 ° C./min. The relationship between the “heat absorption / heat generation amount” and “temperature” is drawn on the graph from the change in heat absorption / exotherm thus measured. The temperature at which the endotherm takes the maximum value is taken as the maximum peak temperature (Ta) of heat of fusion.

(Coloring agent)
The colorant preferably has a particle size of 0.3 μm or less. If the particle size of the colorant is 0.3 μm or less, the dispersibility of the colorant can be further increased, so that the glossiness of the image can be further increased, and thus the desired color can be easily realized. Become.

  As the colorant, conventionally known pigments and the like can be used without any particular limitation, but the following pigments are preferably used from the viewpoints of cost, light resistance, and colorability. In terms of color composition, these pigments are usually classified into black pigments, yellow pigments, magenta pigments, and cyan pigments. Basically, colors other than black (color image) are toned by a subtractive color mixture of a yellow pigment, a magenta pigment, or a cyan pigment. The pigments shown below may be used alone, or two or more of the pigments shown below may be used in combination as required.

  As the pigment (black pigment) contained in the black colorant, for example, carbon black such as furnace black, channel black, acetylene black, thermal black, or lamp black may be used, or biomass-derived carbon black may be used. Alternatively, magnetic powder such as magnetite or ferrite may be used. Nigrosine (azine compound), which is a purple black dye, may be used alone or in combination. Nigrosine includes C.I. I. Solvent Black 7 or C.I. I. Solvent black 5 or the like can be used.

  Examples of the pigment (magenta pigment) contained in the magenta colorant include C.I. I. Pigment red 2, C.I. I. Pigment red 3, C.I. I. Pigment red 5, C.I. I. Pigment red 6, C.I. I. Pigment red 7, C.I. I. Pigment red 15, C.I. I. Pigment red 16, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 139, C.I. I. Pigment red 144, C.I. I. Pigment red 149, C.I. I. Pigment red 166, C.I. I. Pigment red 177, C.I. I. Pigment red 178, or C.I. I. And CI Pigment Red 222.

  Examples of the pigment (yellow pigment) contained in the yellow colorant include C.I. I. Pigment orange 31, C.I. I. Pigment orange 43, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 15, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. Pigment yellow 138, C.I. I. Pigment yellow 155, C.I. I. Pigment yellow 180, or C.I. I. And CI Pigment Yellow 185.

  Examples of the pigment (cyan pigment) contained in the cyan colorant include C.I. I. Pigment blue 15, C.I. I. Pigment blue 15: 2, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 15: 4, C.I. I. Pigment blue 16, C.I. I. Pigment blue 60, C.I. I. Pigment blue 62, C.I. I. Pigment blue 66 or C.I. I. And CI Pigment Green 7.

(Pigment dispersant)
The pigment dispersant has a function of uniformly dispersing the colorant (pigment) in the toner particles, and is preferably a basic dispersant. A basic dispersing agent means what is defined below. That is, 0.5 g of pigment dispersant and 20 ml of distilled water were placed in a glass screw tube, and the glass screw tube was shaken for 30 minutes using a paint shaker and then filtered. The pH of the filtrate thus obtained is measured by a pH meter (trade name: “D-51”, manufactured by Horiba, Ltd.).
When the pH is higher than 7, the basic dispersant is used. In addition, when the pH is smaller than 7, it shall call an acidic dispersing agent.

  The kind of such basic dispersant is not particularly limited. Basic dispersants are, for example, amine groups, amino groups, amide groups, pyrrolidone groups, imine groups, imino groups, urethane groups, quaternary ammonium groups, ammonium groups, pyridino groups, pyridium groups, imidazolino groups, or imidazoliums. A compound having a functional group such as a group in the molecule is preferred. In addition, as a dispersing agent, what is called surfactant which has a hydrophilic part and a hydrophobic part in a molecule | numerator normally corresponds. However, as long as it has an action of uniformly dispersing the colorant (pigment) in the toner particles, it is not limited to the surfactant, and various compounds can be used.

  As a commercial item of such a basic dispersant, for example, “Ajisper PB-821” (trade name), “Azisper PB-822” (trade name) or “Azisper PB-881” manufactured by Ajinomoto Fine Techno Co., Ltd. (Trade name) may be used, or “Solspers 28000” (trade name), “Solspurs 32000” (trade name), “Solspurs 32500” (trade name), “Solspurs 35100” manufactured by Nippon Lubrizol Co., Ltd. (Trade name) or “Solspers 37500” (trade name) may be used.

  It is more preferable to select a pigment dispersant that does not dissolve in the first solvent. In consideration of this point, use “Ajisper PB-821” (trade name), “Ajisper PB-822” (trade name) or “Ajisper PB-881” (trade name) manufactured by Ajinomoto Fine Techno Co., Ltd. Is more preferable. Although the detailed mechanism is unknown, it is easy to obtain toner particles having a desired shape by using such a pigment dispersant.

  Such a pigment dispersant is preferably added in an amount of 1 to 100% by mass, more preferably 1 to 40% by mass, based on the colorant (pigment). If the added amount of the pigment dispersant is 1% by mass or more, the dispersibility of the colorant (pigment) can be secured, so that the necessary ID (image density) can be achieved, and the fixing strength of the toner particles on the recording medium. Can be secured. If the addition amount of the pigment dispersant is 100% by mass or less, since the addition amount of the pigment dispersant can be prevented from being excessive, it is possible to prevent the excess of the pigment dispersant from being dissolved in the first solvent. The chargeability of the toner particles or the fixing strength of the toner particles can be maintained in a good state. The pigment dispersant may be used alone, or two or more of the pigment dispersants may be used in combination as necessary.

<Preliminary dispersion>
It is preferable to pre-disperse the shell dispersion before mixing the shell dispersion and the core solution. Pre-dispersion means crushing the aggregate of shell particles contained in the shell dispersion before mixing the shell dispersion and the core solution. The method for preliminarily dispersing the shell dispersion liquid is not particularly limited, and examples thereof include a method of irradiating the shell dispersion liquid with ultrasonic waves. An aggregate of shell particles is taken out from the dispersion for shell, and the aggregate (aggregate of shell particles taken out from the dispersion for shell) is pulverized in a dry state using a known dry pulverizer such as a jet mill. The shell particles after pulverization may be returned to the original shell dispersion. The aggregate of shell particles contained in the shell dispersion may be pulverized in a wet state using a known wet disperser such as a bead mill or a roll mill.

  If the shell dispersion is pre-dispersed before mixing the shell dispersion and the core solution, the aggregates of the shell particles contained in the shell dispersion are crushed, so that they appear in the particle size distribution of the shell particles. The peak becomes sharp. Thereby, it becomes easy to control the volume average particle diameter of the shell particles (shell particles in the granulation medium) in a mixed state of the shell dispersion and the core solution to 50 nm or more and 300 nm or less. Therefore, it is possible to prevent the volume average particle diameter of the toner particles of the present embodiment from significantly exceeding a desired value, thereby further improving the fog resistance.

<Mixing of shell dispersion and core solution (granulation process)>
The method for mixing the shell dispersion and the core solution is not particularly limited, and examples thereof include a method of mechanically dispersing the shell dispersion and the core solution. “Mechanically disperse the shell dispersion and the core solution” means a conventionally known apparatus (for example, a homogenizer (for example, manufactured by IKA Japan Co., Ltd.)) This means that the shell dispersion and the core solution are mixed using a dar (trade name, manufactured by Ebara Manufacturing Co., Ltd.) or a microfluidizer (for example, manufactured by Mizuho Kogyo Co., Ltd.).

  When the shell dispersion and the core solution are mixed, core particles made of the core resin are produced, and at the same time, the shell resin adheres to the surface of the core particles. In this way, the toner particles of the present embodiment are produced. Therefore, toner particles having a desired particle size distribution and a desired shape are obtained.

  For example, toner particles having a volume average particle size of 0.5 μm or more and 5.0 μm or less can be produced. This volume average particle size is smaller than the particle size of toner particles contained in a conventional dry developer, and is one of the features of this embodiment. If toner particles having a volume average particle size of 0.5 μm or more can be produced, the mobility of the toner particles in an electric field is improved, so that developability can be improved. If toner particles having a volume average particle size of 5.0 μm or less can be produced, the dispersibility of the toner particles can be ensured, and the image quality can be improved. More preferably, toner particles having a volume average particle diameter of 1 μm or more and 3 μm or less are produced.

  In addition, toner particles having an average circularity of 0.85 to 0.95 can be prepared, and toner particles having a standard deviation of the circularity of 0.01 to 0.1 can be manufactured. Thereby, transferability is improved. The “circularity” means a numerical value obtained by dividing the perimeter of a circle having the same area as the particle area projected in two dimensions by the perimeter of the particle. “Average circularity” means an arithmetic average value of the calculated circularity.

  For example, by using a flow type particle image analyzer (product number “FPIA-3000S” manufactured by Sysmex Corporation) or the like, the volume average particle diameter of the toner particles, the average circularity of the toner particles, and the standard deviation of the circularity of the toner particles Can be measured. In this analyzer, it is possible to use the solvent as a dispersion medium as it is. Therefore, by using this analyzer, it is possible to measure the state of the toner particles in a state closer to the actual dispersed state than measured in the aqueous system.

  Further, toner particles having a volume-based particle size distribution variation coefficient of 1% to 100% can be produced. Thereby, the peak appearing in the particle size distribution of the toner particles becomes sharp. That is, toner particles having a uniform particle size can be obtained. Therefore, the production of fine powder toner particles is easily prevented. “Variation coefficient of toner particle volume-based particle size distribution” means the ratio (%) of the standard deviation of the volume average particle size of toner particles to the volume average particle size of toner particles. For example, the variation coefficient of the volume-based particle size distribution of the toner particles can be obtained using a laser type particle size distribution measuring device (product number “LA-920” manufactured by Horiba, Ltd.).

  As described above, in this embodiment, the volume average particle size of the shell particles (shell particles in the granulation medium) in the mixed state of the shell dispersion and the core solution is 50 nm or more and 300 nm or less. As a result, it is considered that the production of fine powdery toner particles can be prevented, so that it is possible to prevent the occurrence of streaky noise in the formed image.

<Removal of second solvent>
It is preferable to remove the second solvent after mixing the shell dispersion and the core solution. As a result, the shell resin easily adheres to the surface of the core particles, so that the volume average particle diameter of the toner particles of the present embodiment is easily converged to a constant value. Therefore, the peak appearing in the particle size distribution of the toner particles of the present embodiment becomes even sharper.

  Preferably, the content of the second solvent in the mixture of the shell dispersion and the core solution is 1% by volume or less, more preferably the content of the second solvent in the mixture is 0.5% by volume. The second solvent is removed so that: For example, it is preferable to remove the second solvent at a pressure of 20 mmHg or more and 500 mmHg or less (under reduced pressure) at a temperature of 20 ° C. or more and the boiling point of the second solvent or less. A part of the first solvent may be removed together with the second solvent.

[Configuration of liquid developer]
The liquid developer of this embodiment is manufactured according to the above-described method. That is, the liquid developer of the present embodiment includes an insulating liquid containing a first solvent and toner particles dispersed in the insulating liquid. The toner particles have a core / shell structure. The shell resin constitutes shell particles having a volume average particle diameter of 50 nm or more and 300 nm or less on at least a part of the surface of the core particles. Thereby, the volume average particle diameter of the toner particles of the present embodiment can be controlled to a desired value (for example, 1 μm or more and 3 μm or less), so that it is possible to prevent the occurrence of streak noise in the formed image.

  In the present specification, the volume average particle diameter of the shell particles existing on the surface of the core particles is obtained by observing a scanning electron microscope (SEM) image of the toner particles. The volume average particle diameter of the shell particles present on the surface of the core particles can also be obtained by observing a cryo SEM (Cryo-SEM) image of the toner particles (an SEM image of the toner particles in a frozen state).

[Image forming apparatus]
FIG. 1 is a schematic diagram illustrating a configuration of an image forming apparatus according to the present exemplary embodiment. In the image forming apparatus shown in FIG. 1, the liquid developer 21 is pumped up from the developing tank 22 by the anilox roller 23. Excess liquid developer 21 on the anilox roller 23 is scraped off by the anilox regulating blade 24, and the remaining liquid developer 21 is sent to the leveling roller 25. On the leveling roller 25, the liquid developer 21 is adjusted to have a uniform and thin thickness.

  The liquid developer 21 on the leveling roller 25 is sent to the developing roller 26. The liquid developer 21 on the developing roller 26 is charged by the developing charger 28 and developed on the photoconductor 29, and excess liquid developer is scraped off by the developing cleaning blade 27. Specifically, the surface of the photoconductor 29 is uniformly charged by the charging unit 30, and the exposure unit 31 disposed around the photoconductor 29 emits light based on predetermined image information on the surface of the photoconductor 29. Irradiate. As a result, an electrostatic latent image based on predetermined image information is formed on the surface of the photoreceptor 29. By developing the formed electrostatic latent image, a toner image is formed on the photoreceptor 29. The excess liquid developer on the photoconductor 29 is scraped off by the cleaning blade 32.

  The toner image formed on the photosensitive member 29 is primarily transferred to the intermediate transfer member 33 in the primary transfer unit 37, and the liquid developer transferred to the intermediate transfer member 33 is recorded in the recording medium 40 (for example, high-quality paper) in the secondary transfer unit 38. ) Is secondarily transferred. The liquid developer remaining on the intermediate transfer member 33 without being subjected to the secondary transfer is scraped off by the intermediate transfer member cleaning unit 34.

  An unused liquid developer (a liquid developer that has never been used for image formation) may be supplied from the storage tank 61 to the storage tank 22 through the first conveyance path 60 as necessary.

  The liquid developer 21 scraped off by the developing cleaning blade 27 is transported to the storage tank 63 through the second transport path 62 when the image formation is completed, and stored in the storage tank 63. Thereafter, the liquid developer is transported to the density adjustment tank 65 through the third transport path 64. In the density adjusting tank 65, the density of toner particles contained in the liquid developer collected from the developing roller 26 after development is adjusted. The liquid developer whose toner particle concentration is adjusted in the density adjusting tank 65 is conveyed to the storage tank 22 through the fourth conveying path 66 and used for image formation.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to the following.
<Production Example 1> [Production of Shell Dispersion (S-1)]
In a glass beaker, 26.5 parts by mass of methacryloylated polymethyl methacrylate oligomer (trade name “AA-6”, Mn = 6000, manufactured by Toagosei Co., Ltd.) and 2-decyltetradecyl methacrylate (second vinyl) Monomer) 35 parts by mass, behenyl methacrylate (first vinyl monomer) 35 parts by mass, acrylic acid (third vinyl monomer) 3.5 parts by mass and azobismethoxydimethylvaleronitrile 0.1 part by mass, and 20 ° C. Stir with. Thereby, a monomer solution was obtained. In this production example, M3 / (M1 + M2) = 3.5 / (35 + 35) = 0.050.

  A reaction vessel equipped with a stirrer, a heating / cooling device, a thermometer, a dropping funnel, a solvent removal device, and a nitrogen introduction tube was prepared. 100 parts by mass of THF was placed in this reaction vessel, and the monomer solution was placed in a dropping funnel. After the gas phase part of the reaction vessel was replaced with nitrogen, the monomer solution was added dropwise to THF at 70 ° C. for 1 hour in a sealed state. Three hours after the completion of dropping of the monomer solution, a mixture of 0.05 parts by mass of azobismethoxydimethylvaleronitrile and 5 parts by mass of THF was added to the monomer solution. After reacting at 70 ° C. for 3 hours, the mixture was cooled to room temperature. Thereby, a copolymer solution was obtained.

  200 parts by mass of the obtained copolymer solution was dropped into 300 parts by mass of an insulating liquid under stirring (trade name “IP Solvent 2028” manufactured by Idemitsu Kosan Co., Ltd.), and then at 40 ° C. under a reduced pressure of 0.039 MPa. THF was distilled off. In this way, a dispersion for shell (S-1) was obtained. When Mn of the shell resin contained in the dispersion liquid for shell (S-1) and the volume average particle diameter of the shell particles contained in the dispersion liquid for shell (S-1) were measured according to the method described above, Mn was The volume average particle size was 40000.

<Production Example 2> [Production of Shell Dispersion (S-2)]
In a glass beaker, 28 parts by mass of methacryloylated polymethyl methacrylate oligomer (trade name “AA-6”, Mn = 6000, manufactured by Toagosei Co., Ltd.) and 2-decyltetradecyl methacrylate (second vinyl monomer) 35 parts by mass, 35 parts by mass of behenyl methacrylate (first vinyl monomer), 2 parts by mass of acrylic acid (third vinyl monomer) and 0.1 part by mass of azobismethoxydimethylvaleronitrile were added and stirred at 20 ° C. Thereby, a monomer solution was obtained. In this production example, M3 / (M1 + M2) = 2 / (35 + 35) = 0.029.

  A reaction vessel equipped with a stirrer, a heating / cooling device, a thermometer, a dropping funnel, a solvent removal device, and a nitrogen introduction tube was prepared. 100 parts by mass of THF was placed in this reaction vessel, and the monomer solution was placed in a dropping funnel. After the gas phase part of the reaction vessel was replaced with nitrogen, the monomer solution was added dropwise to THF at 70 ° C. for 1 hour in a sealed state. Three hours after the completion of dropping of the monomer solution, a mixture of 0.05 parts by mass of azobismethoxydimethylvaleronitrile and 5 parts by mass of THF was added to the monomer solution. After reacting at 70 ° C. for 3 hours, the mixture was cooled to room temperature. Thereby, a copolymer solution was obtained.

  200 parts by mass of the obtained copolymer solution was dropped into 300 parts by mass of an insulating liquid under stirring (trade name “IP Solvent 2028” manufactured by Idemitsu Kosan Co., Ltd.), and then at 40 ° C. under a reduced pressure of 0.039 MPa. THF was distilled off. In this way, a dispersion for shell (S-2) was obtained. When Mn of the shell resin contained in the dispersion liquid for shell (S-2) and the volume average particle diameter of the shell particles contained in the dispersion liquid for shell (S-2) were measured according to the method described above, Mn was The volume average particle size was 40000.

<Production Example 3> [Production of Shell Dispersion (S-3)]
In a glass beaker, 29 parts by mass of methacryloylated polymethyl methacrylate oligomer (trade name “AA-6”, Mn = 6000, manufactured by Toagosei Co., Ltd.) and 2-decyltetradecyl methacrylate (second vinyl monomer) 35 parts by mass, 35 parts by mass of behenyl methacrylate (first vinyl monomer), 1 part by mass of acrylic acid (third vinyl monomer) and 0.1 part by mass of azobismethoxydimethylvaleronitrile were added and stirred at 20 ° C. Thereby, a monomer solution was obtained. In this production example, M3 / (M1 + M2) = 1 / (35 + 35) = 0.014.

  A reaction vessel equipped with a stirrer, a heating / cooling device, a thermometer, a dropping funnel, a solvent removal device, and a nitrogen introduction tube was prepared. 100 parts by mass of THF was placed in this reaction vessel, and the monomer solution was placed in a dropping funnel. After the gas phase part of the reaction vessel was replaced with nitrogen, the monomer solution was added dropwise to THF at 70 ° C. for 1 hour in a sealed state. Three hours after the completion of dropping of the monomer solution, a mixture of 0.05 parts by mass of azobismethoxydimethylvaleronitrile and 5 parts by mass of THF was added to the monomer solution. After reacting at 70 ° C. for 3 hours, the mixture was cooled to room temperature. Thereby, a copolymer solution was obtained.

  200 parts by mass of the obtained copolymer solution was dropped into 300 parts by mass of an insulating liquid under stirring (trade name “IP Solvent 2028” manufactured by Idemitsu Kosan Co., Ltd.), and then at 40 ° C. under a reduced pressure of 0.039 MPa. THF was distilled off. In this way, a dispersion for shell (S-3) was obtained. When Mn of the shell resin contained in the dispersion liquid for shell (S-3) and the volume average particle diameter of the shell particles contained in the dispersion liquid for shell (S-3) were measured according to the above-described method, Mn was 40000, and the volume average particle diameter was 280 nm.

<Production Example 4> [Production of Shell Dispersion (S-4)]
In a glass beaker, 23 parts by mass of one-end methacryloylated polymethyl methacrylate oligomer (trade name “AA-6”, Mn = 6000, manufactured by Toagosei Co., Ltd.) and 2-decyltetradecyl methacrylate (second vinyl monomer) 35 parts by mass, 35 parts by mass of behenyl methacrylate (first vinyl monomer), 7 parts by mass of acrylic acid (third vinyl monomer) and 0.1 part by mass of azobismethoxydimethylvaleronitrile were added and stirred at 20 ° C. Thereby, a monomer solution was obtained. In this production example, M3 / (M1 + M2) = 7 / (35 + 35) = 0.1.

  A reaction vessel equipped with a stirrer, a heating / cooling device, a thermometer, a dropping funnel, a solvent removal device, and a nitrogen introduction tube was prepared. 100 parts by mass of THF was placed in this reaction vessel, and the monomer solution was placed in a dropping funnel. After the gas phase part of the reaction vessel was replaced with nitrogen, the monomer solution was added dropwise to THF at 70 ° C. for 1 hour in a sealed state. Three hours after the completion of dropping of the monomer solution, a mixture of 0.05 parts by mass of azobismethoxydimethylvaleronitrile and 5 parts by mass of THF was added to the monomer solution. After reacting at 70 ° C. for 3 hours, the mixture was cooled to room temperature. Thereby, a copolymer solution was obtained.

  200 parts by mass of the obtained copolymer solution was dropped into 300 parts by mass of an insulating liquid under stirring (trade name “IP Solvent 2028” manufactured by Idemitsu Kosan Co., Ltd.), and then at 40 ° C. under a reduced pressure of 0.039 MPa. THF was distilled off. In this way, a dispersion for shell (S-4) was obtained. When Mn of the shell resin contained in the dispersion liquid for shell (S-4) and the volume average particle diameter of the shell particles contained in the dispersion liquid for shell (S-4) were measured according to the method described above, Mn was 40000, and the volume average particle diameter was 30 nm.

<Production Example 5> [Production of dispersion liquid for shell (S-5)]
In a glass beaker, 27 parts by mass of methacryloylated polymethyl methacrylate oligomer (trade name “AA-6” manufactured by Toagosei Co., Ltd., Mn = 6000) and 70 parts by mass of behenyl methacrylate (first vinyl monomer) 3 parts by mass of acrylic acid (third vinyl monomer) and 0.1 part by mass of azobismethoxydimethylvaleronitrile were added and stirred at 20 ° C. Thereby, a monomer solution was obtained.

  A reaction vessel equipped with a stirrer, a heating / cooling device, a thermometer, a dropping funnel, a solvent removal device, and a nitrogen introduction tube was prepared. 100 parts by mass of THF was placed in this reaction vessel, and the monomer solution was placed in a dropping funnel. After the gas phase part of the reaction vessel was replaced with nitrogen, the monomer solution was added dropwise to THF at 70 ° C. for 1 hour in a sealed state. Three hours after the completion of dropping of the monomer solution, a mixture of 0.05 parts by mass of azobismethoxydimethylvaleronitrile and 5 parts by mass of THF was added to the monomer solution. After reacting at 70 ° C. for 3 hours, the mixture was cooled to room temperature. Thereby, a copolymer solution was obtained.

  200 parts by mass of the obtained copolymer solution was dropped into 300 parts by mass of an insulating liquid under stirring (trade name “IP Solvent 2028” manufactured by Idemitsu Kosan Co., Ltd.), and then at 40 ° C. under a reduced pressure of 0.039 MPa. THF was distilled off. In this way, a dispersion for shell (S-5) was obtained. When Mn of the shell resin contained in the dispersion liquid for shell (S-5) and the volume average particle diameter of the shell particles contained in the dispersion liquid for shell (S-5) were measured according to the method described above, Mn was The volume average particle size was 40000.

<Production Example 6> [Production of dispersion liquid for shell (S-6)]
In a glass beaker, 27 parts by mass of methacryloylated polymethyl methacrylate oligomer (trade name “AA-6”, Mn = 6000, manufactured by Toagosei Co., Ltd.) and 2-decyltetradecyl methacrylate (second vinyl monomer) 70 parts by mass, 3 parts by mass of acrylic acid (third vinyl monomer) and 0.1 part by mass of azobismethoxydimethylvaleronitrile were added and stirred at 20 ° C. Thereby, a monomer solution was obtained.

  A reaction vessel equipped with a stirrer, a heating / cooling device, a thermometer, a dropping funnel, a solvent removal device, and a nitrogen introduction tube was prepared. 100 parts by mass of THF was placed in this reaction vessel, and the monomer solution was placed in a dropping funnel. After the gas phase part of the reaction vessel was replaced with nitrogen, the monomer solution was added dropwise to THF at 70 ° C. for 1 hour in a sealed state. Three hours after the completion of dropping of the monomer solution, a mixture of 0.05 parts by mass of azobismethoxydimethylvaleronitrile and 5 parts by mass of THF was added to the monomer solution. After reacting at 70 ° C. for 3 hours, the mixture was cooled to room temperature. Thereby, a copolymer solution was obtained.

  200 parts by mass of the obtained copolymer solution was dropped into 300 parts by mass of an insulating liquid under stirring (trade name “IP Solvent 2028” manufactured by Idemitsu Kosan Co., Ltd.), and then at 40 ° C. under a reduced pressure of 0.039 MPa. THF was distilled off. In this way, a dispersion for shell (S-6) was obtained. When Mn of the shell resin contained in the dispersion liquid for shell (S-6) and the volume average particle diameter of the shell particles contained in the dispersion liquid for shell (S-6) were measured according to the method described above, Mn was 40000, and the volume average particle diameter was 40 nm.

<Production Example 7> [Synthesis of an adduct formed by adding PO (propylene oxide) to bisphenol A]
Bisphenol A (228 g) and potassium hydroxide (2 g) were placed in an autoclave equipped with stirring and temperature control functions, and the temperature was raised to 135 ° C. Thereafter, propylene oxide (139 g) was introduced under a pressure condition of 0.1 to 0.4 MPa and allowed to react for 3 hours. An adsorbent (trade name “KYOWARD 600” manufactured by Kyowa Chemical Industry Co., Ltd.) (16 g) was added to the reaction product thus obtained, and the mixture was aged by stirring for 30 minutes while maintaining at 90 ° C. Thereafter, filtration was performed to obtain the above adduct (an adduct formed by adding PO to bisphenol A). The resulting adduct is a mixture of a compound in which the sum (m + n) of m and n in the chemical formula (I) is 2 and a compound in which the sum (m + n) of m and n in the chemical formula (I) is 3. Met.

<Production Example 8> [Production of core solution (C-1)]
A four-necked flask equipped with a stirring bar, a partial condenser, a nitrogen gas inlet tube and a thermometer is mixed with the propylene oxide adduct (alcohol) of bisphenol A and terephthalic acid (carboxylic acid) produced in Production Example 7. Was added at about 1: 1, and nitrogen gas was added while stirring. Thereafter, a polycondensation reaction was carried out at about 170 ° C. for 5 hours. In the obtained polyester resin, Mn was 2500, Mw was 7000, and the glass transition point was 60 ° C. 100 parts by mass of the obtained polyester resin and 150 parts by mass of acetone were mixed to obtain a core solution (C-1).

<Production Example 9> [Production of Colorant Dispersion]
In a beaker, 20 parts by mass of copper phthalocyanine (trade name “Fastogen Blue FDB-14” manufactured by DIC Corporation) (colorant (pigment)) and a pigment dispersant (trade name “Ajisper PB-821 manufactured by Ajinomoto Fine Techno Co., Ltd.) “) 5 parts by mass and 75 parts by mass of acetone were added and stirred to uniformly disperse the copper phthalocyanine. Copper phthalocyanine was finely dispersed using a bead mill to obtain a colorant dispersion. The volume average particle diameter of copper phthalocyanine in the colorant dispersion was 0.2 μm.

<Example 1> [Production of liquid developer (1)]
In a beaker, 40 parts by mass of the core resin forming solution (C-1) and 20 parts by mass of the colorant dispersion were added. The obtained solution was stirred at 8000 rpm at 25 ° C. using a TK auto homomixer (manufactured by PRIMIX Corporation). In this way, a resin solution in which the colorant was uniformly dispersed was obtained.

  In another beaker, 67 parts by mass of an insulating liquid (trade name “IP Solvent 2028” manufactured by Idemitsu Kosan Co., Ltd.) and 11 parts by mass of the shell dispersion (S-1) were added. While stirring the obtained solution at 10000 rpm using CLEARMIX (M Technique Co., Ltd.) at 25 ° C., 60 parts by mass of the resin solution was added and stirred for 2 minutes. According to the method described above, the volume average particle diameter of the shell particles in a state where the shell dispersion liquid (S-1) and the core solution (C-1) were mixed was measured.

  The obtained mixed liquid was put into a reaction vessel equipped with a stirring device, a heating / cooling device, a thermometer, and a solvent removal device, and the temperature was raised to 35 ° C. At the same temperature, acetone was removed from the mixed solution under a reduced pressure of 0.039 MPa until the acetone concentration became 0.5% by mass or less. As a result, a liquid developer was obtained.

<Examples 2-3 and Comparative Examples 1-3>
A liquid developer was prepared according to the method described in Example 1 except that the shell dispersion liquid shown in Table 1 was used instead of the shell dispersion liquid (S-1).

<Evaluation of granulation property of toner particles>
In accordance with the method described above, the volume average particle size of the toner particles contained in the obtained liquid developer was determined. In accordance with the method described above, the coefficient of variation of the volume-based particle size distribution of the toner particles was determined. The results are shown in Table 1.

  In Table 1, when the volume average particle size of the toner particles is 3 μm or less and the variation coefficient of the volume-based particle size distribution of the toner particles is 50% or less, “A1” is described. When the volume average particle diameter of the toner particles is larger than 3 μm, or when the variation coefficient of the volume-based particle size distribution of the toner particles is larger than 50%, “C1” is described. If the volume average particle size of the toner particles is 3 μm or less, it can be said that toner particles having a desired volume average particle size were obtained. Further, if the variation coefficient of the volume-based particle size distribution of the toner particles is 50% or less, it can be said that the toner particles have a uniform particle size.

<Evaluation of cleaning properties>
First, a solid image was printed on 5000 sheets of A4 paper using the image forming apparatus shown in FIG. In this embodiment, the surface of the photosensitive member 29 is positively charged by the charging unit 30, the potential of the intermediate transfer member 33 is −400 V, and the potential of the secondary transfer roller 35 is −1200 V. The conveyance speed of the recording medium 40 was 400 mm / s.

  Next, it was examined whether or not streaky noise was generated on the surface of the photoconductor 29 and whether or not streaky noise was generated in the formed image. The results are shown in Table 1.

  In Table 1, when no streak-like noise occurs on both the surface of the photoconductor 29 and the formed image, it is indicated as “A2”, and it is applied not only to the surface of the photoconductor 29 but also to the formed image. When streaky noise is generated, it is described as “C2”.

In Table 1, “dispersion liquid for shell ^{* 11} ” indicates the volume average particle diameter of the shell particles contained in the dispersion liquid for shell, and “granulation medium ^{* 12} ” indicates the shell particles contained in the granulation medium. The volume average particle diameter is described. In “CV (%) ^{* 13} ”, the coefficient of variation of the volume-based particle size distribution of the toner particles is described. In “shell particles (μm) ^{* 14} ”, the volume average particle diameter of the shell particles present on the surface of the core particles, which is obtained according to the above-described method, is described. “Compound (1)” means behenyl methacrylate and “compound (2)” means 2-decyltetradecyl methacrylate.

<Discussion>
In Examples 1 to 3, since toner particles having a volume average particle diameter of 3 μm or less were obtained, it can be said that toner particles having a desired volume average particle diameter were obtained. In addition, toner particles having a volume-based particle size distribution variation coefficient of 50% or less were obtained, so it can be said that toner particles having a uniform particle size were obtained. Further, no streak-like noise occurred on both the surface of the photoreceptor 29 and the formed image.

  In Comparative Example 1, streaky noise was generated in the image formed on the surface of the photoconductor 29 as well. The reason can be considered as follows. In Comparative Example 1, {M3 / (M1 + M2)} = 0.1. Therefore, it is difficult to optimize the adsorptivity of the shell particles with respect to the core particles in the granulation medium, and accordingly, the diameter of the shell particles is reduced in the granulation medium (30 nm). As a result, the production of fine powdery toner particles could not be prevented, and streaky noise was generated in the image formed on the surface of the photoreceptor 29 as well.

  In Comparative Example 2, toner particles having a volume average particle diameter exceeding 3 μm were obtained. The reason can be considered as follows. In Comparative Example 2, the shell resin is synthesized without using the second vinyl monomer. For this reason, the increase in the diameter of the shell particles in the shell dispersion liquid cannot be prevented, and thus the increase in the diameter of the shell particles occurred in the granulation medium (500 nm). As a result, the volume average particle diameter of the toner particles is larger than 4 μm.

  In Comparative Example 3, streaky noise was generated in the image formed on the surface of the photoreceptor 29 as well. The reason can be considered as follows. In Comparative Example 3, the shell resin is synthesized without using the first vinyl monomer. For this reason, the reduction in the diameter of the shell particles in the shell dispersion could not be prevented, and the reduction in the diameter of the shell particles occurred in the granulation medium (40 nm). As a result, the production of fine powdery toner particles could not be prevented, and streaky noise was generated in the image formed on the surface of the photoreceptor 29 as well.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  21 Liquid developer, 22, 61, 63 Developer tank, 23 Anilox roller, 24 Anilox regulating blade, 25 Leveling roller, 26 Developer roller, 27 Developer cleaning blade, 28 Developer charger, 29 Photoconductor, 30 Charger, 31 Exposure Part, 32 cleaning blade, 33 intermediate transfer body, 34 intermediate transfer body cleaning part, 35 secondary transfer roller, 37 primary transfer part, 38 secondary transfer part, 40 recording medium, 60 first transport path, 62 second transport path 64 3rd conveyance path, 65 Density adjustment tank, 66 4th conveyance path.

Claims (5)

A toner particle having a core / shell structure including a core particle including a core resin and a shell resin which is provided on at least a part of a surface of the core particle and is different from the core resin; and the toner particles are dispersed. And a method for producing a liquid developer comprising an insulating liquid containing a first solvent,
Preparing a dispersion for shell having the first solvent and shell particles dispersed in the first solvent and containing the shell resin;
Preparing a core solution having a second solvent, which is a solvent different from the first solvent, the core resin dissolved in the second solvent, and a colorant dispersed in the second solvent;
A granulation step of preparing the toner particles by mixing the shell dispersion and the core solution;
The shell particles in a state where the shell dispersion and the core solution are mixed have a volume average particle size of 50 nm to 300 nm,
Of the first vinyl monomer containing a linear hydrocarbon chain having 12 to 27 carbon atoms, the second vinyl monomer containing a branched hydrocarbon chain having 12 to 27 carbon atoms, a hydroxyl group and a carboxyl group The shell resin is produced by reacting a mixture containing a third vinyl monomer containing at least one of
When the blending amount of the first vinyl monomer is represented as M1, the blending amount of the second vinyl monomer is represented as M2, and the blending amount of the third vinyl monomer is represented as M3, {M3 / (M1 + M2)} ≦ 0 Manufacturing method of liquid developer satisfying .05.   The method for producing a liquid developer according to claim 1, wherein the shell dispersion is preliminarily dispersed before the granulation step.   3. The method for producing a liquid developer according to claim 1, wherein in the granulation step, the shell dispersion and the core solution are mechanically dispersed.   The method for producing a liquid developer according to claim 1, wherein the first solvent is at least one of a normal paraffin solvent and an isoparaffin solvent.   The liquid developer manufactured according to the method in any one of Claims 1-4.

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