JP6484938B2 - Liquid developer and method for producing the same - Google Patents

Description

  The present invention relates to a liquid developer.

  Various liquid developers have been proposed for use in liquid development type image forming apparatuses. For example, Japanese Unexamined Patent Application Publication No. 2009-96994 (Patent Document 1) discloses a non-aqueous resin in which core-shell type resin particles (toner particles) composed of a shell layer and a core layer are dispersed in a non-aqueous organic solvent. Dispersions are disclosed.

JP 2009-96994 A

  By adopting the core / shell structure as described above, it is easy to obtain toner particles having a small particle size and a narrow particle size distribution. Conventionally, by reducing the toner particle size and sharpening the particle size distribution as described above, improvement in image uniformity and higher image quality have been achieved.

  However, if the toner particles having a core / shell structure are reduced in size, there is a problem that the chargeability of the toner particles is lowered, thereby lowering the uniformity of the image and the low-temperature fixability.

  The present invention has been made in view of the above situation, and an object thereof is to provide a liquid developer excellent in image uniformity and low-temperature fixability.

  The present inventor has conducted intensive research to solve the above problems. As a result, when the toner particles having a core / shell structure are reduced in size, the surface area of the shell layer is increased with respect to the core layer, and the charging of the toner particles is increased. And obtained a knowledge that the property and the charge retention rate have decreased, and further research based on the knowledge, by configuring the shell layer from a resin having a specific structural unit, while having a small particle size The inventors have found that toner particles having high chargeability and charge retention can be obtained, and have completed the present invention.

  That is, the liquid developer of the present invention is a liquid developer in which toner particles are dispersed in an insulating liquid, and the toner particles include a shell layer containing a first resin and a core layer containing a second resin. The first resin has a first structural unit derived from an amide monomer, a second structural unit derived from a monomer having a linear hydrocarbon group, and a branched hydrocarbon group. And a third structural unit derived from a monomer.

  Here, the first structural unit is preferably included in the first resin at a ratio of 0.1% by mass or more and 7% by mass or less.

  Moreover, it is preferable that the said 1st resin contains the said 2nd structural unit and the said 3rd structural unit in the range from which the total amount of both becomes 40 to 70 mass%.

  Moreover, it is preferable that the said 2nd structural unit occupies the ratio of 30 mass% or more and 90 mass% or less among the sum total of the said 2nd structural unit and the said 3rd structural unit.

  Further, the second resin preferably has an endothermic start temperature in differential scanning calorimetry of 50 ° C. or higher and 60 ° C. or lower.

  The liquid developer of the present invention is excellent in image uniformity and low-temperature fixability.

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

  Hereinafter, embodiments according to the present invention (hereinafter also referred to as “present embodiments”) will be described in more detail, but the present invention is not limited to these.

<Liquid developer>
The liquid developer according to the present embodiment includes an insulating liquid and toner particles. Such a liquid developer can contain other optional components as long as it contains an insulating liquid and toner particles. For example, as other components, a charge control agent, a thickener, a toner dispersant and the like may be included.

  Here, the content of the toner particles contained in the liquid developer is preferably 10 to 50% by mass, more preferably 15 to 45% by mass, from the viewpoint of the fixing property of the toner particles and the heat stability of the liquid developer. More preferably, it is 20-40 mass%.

  Such a liquid developer is useful as a developer for an electrophotographic image forming apparatus. Specifically, electrophotographic liquid developers, paints, electrostatic recording liquid developers, and inkjet printers used in electrophotographic image forming apparatuses such as copying machines, printers, digital printing machines, and simple printing machines. It can be used as oil-based ink or ink for electronic paper.

<Toner particles>
In the present embodiment, the toner particles contained in the liquid developer have a core / shell structure composed of a shell layer containing a first resin and a core layer containing a second resin. Here, the “first resin” means a first structural unit derived from an amide monomer, a second structural unit derived from a monomer having a linear hydrocarbon group, and a third structural unit derived from a monomer having a branched hydrocarbon group, , A resin containing

  In the present embodiment, the toner particles preferably have a volume average particle size of 0.5 μm or more and 5.0 μm or less. Such a volume average particle size is smaller than the particle size of toner particles of a conventional dry developer, which is one of the features of the present embodiment. This volume average particle size is less than 0.5 μm. In such a case, the particle size is too small, the mobility in the electric field is deteriorated, and the developability may be deteriorated. When the particle size exceeds 5 μm, the uniformity of the particle shape is deteriorated and the image quality may be deteriorated. A more preferable range of the volume average particle size is 0.5 μm or more and 2.0 μm or less.

  The volume average particle size of the toner particles is determined by a laser diffraction / scattering particle size distribution measuring device [for example, “LA-920” manufactured by Horiba, Ltd. or “Multisizer III” manufactured by Beckman Coulter, Inc., or a laser as an optical system. It can be measured using “ELS-800” (manufactured by Otsuka Electronics Co., Ltd.)] using the Doppler method. Here, when the volume average particle diameter is measured with a different measuring apparatus, if a difference occurs in the measured value, the measured value of “ELS-800” is adopted.

<Core / shell structure>
The “core / shell structure” in the present embodiment means that the shell layer (A) containing the first resin (a) is attached or coated on the surface of the core layer (B) containing the second resin (b). The following structure is shown. By adopting such a structure for the toner particles, it is possible to reduce the diameter of the toner particles, which contributes to high image quality. In the following description, the toner particles having such a core / shell structure may be referred to as “toner particles (C)”, and the liquid developer containing the toner particles (C) may be referred to as “liquid developer (X)”.

  In the toner particles (C) having a core / shell structure, the mass ratio [(A) :( B)] of the shell layer (A) and the core layer (B) is preferably 1:99 to 70:30. . From the viewpoint of the uniformity of the particle diameter of the toner particles (C) and the heat resistance stability of the liquid developer (X), the ratio [(A) :( B)] is more preferably 2:98 to 50:50. More preferably, it is 3: 97-35: 65. Hereinafter, the configurations of the shell layer (A) and the core layer (B) will be described.

<Shell layer (A) / first resin (a)>
The shell layer (A) in the present embodiment includes the first resin (a). The first resin (a) is derived from a first structural unit derived from an amide monomer (α1), a second structural unit derived from a monomer having a linear hydrocarbon group (α2), and a monomer having a branched hydrocarbon group. A third structural unit (α3). As long as the shell layer (A) includes the first resin (a), for example, vinyl resin, polyester resin, polyurethane resin, epoxy resin, polyamide resin, polyimide resin, silicon resin, phenol resin, melamine resin, urea resin, aniline. Resins, ionomer resins, polycarbonate resins, and the like can be included. The shell layer (A) may contain two or more of these resins.

  In the liquid developer (X) of the present embodiment, the first resin (a) containing each of the structural units described above is used as the resin constituting the shell layer (A), so that the toner particles (C) are highly charged. And excellent image uniformity and low-temperature fixability can be realized. Although the details of the reason why such characteristics are imparted to the toner particles (C) are not clear, the leakage of the first resin (a) and the solubility in the insulating liquid are adjusted by including each of the above structural units. It is estimated that Hereinafter, each structural unit will be described.

<First structural unit (α1)>
The first structural unit (α1) is a structural unit derived from an amide monomer. Here, the “amide monomer” is a monomer having an amide bond in the molecule, and preferably a monomer having an amide group and a polymerizable double bond. Examples of such amide monomers include (meth) acrylamide, N-methyl (meth) acrylamide, N-butyl (meth) acrylamide, N-aminoethyl (meth) acrylamide, diacetone (meth) acrylamide, N-methylol ( (Meth) acrylamide, N, N′-methylene-bis (meth) acrylamide, cinnamic acid amide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, hydroxyethyl (meth) acrylamide, N- Isopropyl (meth) acrylamide, N- [3- (dimethylamino) propyl] (meth) acrylamide, N, N-dibenzyl (meth) acrylamide, (meth) acrylformamide, morpholine (meth) acrylamide, N-methyl-N- Vinylacetoa Examples include Nido, N-vinylpyrrolidone and the like. In this specification, “(meth) acryl” means at least one of methacryl and acryl.

  The first structural unit (α1) is preferably contained in the first resin (a) at a ratio of 0.1% by mass to 7% by mass. This is because if the ratio of the first structural unit (α1) is less than 0.1% by mass, the fixability may be lowered, and if it exceeds 7% by mass, the chargeability may be impaired. Here, the first structural unit (α1) is more preferably contained in the first resin (a) at a ratio of 3 mass% to 7 mass%.

<Second structural unit (α2)>
The second structural unit (α2) is a structural unit derived from a monomer having a linear hydrocarbon group. Here, the “linear hydrocarbon group” is a hydrocarbon group having 2 to 30 carbon atoms and is linear. As long as such a hydrocarbon group is composed of carbon and hydrogen with a carbon-carbon bond as the main chain, a part of hydrogen may be substituted with another substituent (for example, halogen), or between carbon-carbon These bonds may partially contain double bonds.

  Examples of the monomer having a linear hydrocarbon group include a linear hydrocarbon having a polymerizable double bond, a mono-linear alkyl ester of an unsaturated monocarboxylic acid, and a mono-linear alkyl ester of an unsaturated dicarboxylic acid. Can be mentioned.

  Examples of the linear hydrocarbon having a polymerizable double bond include alkenes having 4 to 30 carbon atoms (for example, butene, pentene, heptene, octene, dodecene, octadecene, etc.), alkadienes having 4 to 30 carbon atoms. (Butadiene, isoprene, 1,4-pentadiene, 1,5-hexadiene, 1,7-octadiene, etc.) can be exemplified.

  Examples of the unsaturated monocarboxylic acid and unsaturated dicarboxylic acid include (meth) acrylic acid, maleic acid, fumaric acid, crotonic acid, itaconic acid, citraconic acid and the like, a carboxyl group-containing vinyl monomer having 3 to 24 carbon atoms, etc. Can be illustrated. Examples of linear alkyl esters obtained from these vinyl monomers include n-octyl (meth) acrylate, n-decyl (meth) acrylate, n-dodecyl (meth) acrylate, and (meth) acrylic. N-tridecyl acid, n-stearyl (meth) acrylate, n-behenyl (meth) acrylate, n-hexadecyl (meth) acrylate, n-heptadecyl (meth) acrylate and n-eicosyl (meth) acrylate, etc. Can be illustrated.

<Third structural unit (α3)>
The third structural unit (α3) is a structural unit derived from a monomer having a branched hydrocarbon group. In such a branched hydrocarbon group, as long as it is composed of carbon and hydrogen with a carbon-carbon bond as the main chain, a part of hydrogen may be substituted with another substituent (for example, halogen), or carbon- The bond between carbons may partially include a double bond, or part or all may be cyclized.

  Examples of the monomer having a branched hydrocarbon group include branched alkyl esters of unsaturated monocarboxylic acids and branched alkyl esters of unsaturated dicarboxylic acids. Such a branched alkyl ester can be obtained from the unsaturated monocarboxylic acid and unsaturated dicarboxylic acid exemplified in the second structural unit (α2) and an alcohol (or polyol) having a branched hydrocarbon group. Examples of such alcohols include 2-ethylhexanol, 2-decyltetradecinol, 2-octyldodecanol and the like. Further, ethers of these alcohols and polyols (for example, diethylene glycol) may be used.

  The monomer having a branched hydrocarbon group may be, for example, an ester of a branched unsaturated carboxylic acid and an alcohol. Examples of the branched unsaturated carboxylic acid include dimer acid and alkenyl succinic acid (for example, dodecenyl succinic acid, pentadecenyl succinic acid or octadecenyl succinic acid).

  Specific examples of such a monomer having a branched hydrocarbon group include (meth) acrylic acid 2-decyl tetradecyl, (meth) acrylic acid diethylene glycol mono 2-decyl tetradecyl ether, and the like.

  Here, the first resin (a) contains the first structural unit (α1), the second structural unit (α2), and the third structural unit (α3). Nuclear magnetic resonance (NMR) analysis And mass spectrometry (MS).

  The mass ratio of each structural unit of the first resin (a) was determined by 1H-NMR analysis using a Fourier transform nuclear magnetic resonance analyzer (FT-NMR) (trade name “Lambda400”, manufactured by JEOL Ltd.). The integration ratio can be determined. In this case, for example, a chloroform-d (deuterated chloroform) solvent is suitable as the measurement solvent.

  Here, the first resin (a) preferably contains the second structural unit (α2) and the third structural unit (α3) in a range where the total amount of both is 40% by mass or more and 70% by mass or less. If the total amount is less than 40% by mass, the lipophilicity of the first resin (a) may be lowered and the granulation property may be deteriorated. If it exceeds 70% by mass, the lipophilicity is excessively increased and cold offset is caused. This is because sex may deteriorate. Here, considering the granulation property and the cold offset property, the total amount of both is more preferably 40% by mass or more and 60% by mass or less, and particularly preferably 50% by mass or more and 60% by mass or less.

  Moreover, it is preferable that a 2nd structural unit ((alpha) 2) occupies the ratio of 30 mass% or more and 90 mass% or less among the sum total of a 2nd structural unit ((alpha) 2) and a 3rd structural unit ((alpha) 3). When the ratio of the second structural unit (α2) is less than 30% by mass, the content of the branched hydrocarbon group exhibiting high lipophilicity is excessively increased, so that the shell layer (A) is an insulating liquid (oil). This is because the low temperature fixability may be deteriorated by excessively adsorbing, and if it exceeds 90% by mass, the granulation property may be deteriorated. Here, considering the low-temperature fixability and the granulation property, the range occupied by the second structural unit (α2) in the total of the second structural unit (α2) and the third structural unit (α3) is more preferably 30 masses. % To 85% by mass, particularly preferably 30% to 75% by mass.

<Weight average molecular weight (Mw)>
The weight average molecular weight (hereinafter referred to as “Mw”) of the first resin (a) is preferably 40000 or more and 200000 or less, and more preferably 80000 or more and 120,000 or less. If the Mw is 40,000 or more, the amount of oligomer becomes a certain amount or less, so that it can have a good charge retention, and if the Mw is 200,000 or less, it can have good granulation properties and thus low temperature fixability. It is.

<Method of measuring weight average molecular weight (Mw) and number average molecular weight (Mn)>
In the present specification, the Mw and number average molecular weight (hereinafter referred to as “Mn”) of the resin are measured using gel permeation chromatography (GPC) for the soluble content of tetrahydrofuran (hereinafter referred to as “THF”). And measured under the following conditions.

Measuring device: “HLC-8120” manufactured by Tosoh Corporation
Column: “TSKgelGMHXL” (2) manufactured by Tosoh Corporation and “TSKgelMultiporeHXL-M” (1) manufactured by Tosoh Corporation
Sample solution: 0.25 mass% THF solution Injection amount of sample solution to the column: 100 μl
Flow rate: 1 ml / min Measurement temperature: 40 ° C
Detector: Refractive index detector Reference material: 12 standard polystyrene (TSK standard POLYSTYRENE) manufactured by Tosoh Corporation (Molecular weight: 500, 1050, 2800, 5970, 9100, 18100, 37900, 96400, 190000, 355000, 1090000, 2890000).

  Moreover, in this specification, Mn and Mw of a polyurethane resin are measured on condition of the following using GPC.

Measuring device: “HLC-8220GPC” manufactured by Tosoh Corporation
Column: “TSK guardcolumn α” (1) manufactured by Tosoh Corporation and “TSKgel α-M” (1) manufactured by Tosoh Corporation
Sample solution: 0.125 mass% dimethylformamide solution Injection amount of dimethylformamide solution to the column: 100 μl
Flow rate: 1 ml / min Measurement temperature: 40 ° C
Detector: Refractive index detector Reference material: 12 standard polystyrene (TSK standard POLYSTYRENE) manufactured by Tosoh Corporation (Molecular weight: 500, 1050, 2800, 5970, 9100, 18100, 37900, 96400, 190000, 355000, 1090000, 2890000).

<Core layer (B) / second resin (b)>
The second resin (b) of the present embodiment constitutes a core layer (B) having a core / shell structure. Examples of the second resin (b) 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, and polycarbonate resin. Can be illustrated. In the present embodiment, vinyl resin, polyester resin, and urethane resin are preferable from the viewpoint that desired thermophysical properties are easily obtained. Further, the second resin (b) may be a urethane-modified polyester resin obtained by chaining a polyester resin with an isocyanate. Such a urethane-modified polyester resin is preferable from the viewpoint of low-temperature fixability. The second resin (b) may contain two or more kinds of resins.

<Endothermic start temperature>
The second resin (b) may be a linear polymer or a non-linear polymer, but the endothermic start temperature in the differential scanning calorimetry of the second resin (b) is 50 ° C. or more and 60 ° C. or less. Preferably there is. This is because, when the endothermic start temperature of the second resin (b) occupies the above range, the chargeability of the toner particles tends to increase. The endothermic start temperature in differential scanning calorimetry can be measured using, for example, a conventionally known differential scanning calorimeter (for example, “DSC (Q2000)” manufactured by Seiko Instruments Inc.). As the measurement conditions, the endothermic start temperature can be measured with a measurement sample (5 mg) and a temperature increase rate of 10 ° C./min. Here, the endothermic start temperature of the second resin (b) is more preferably 50 ° C. or higher and 55 ° C. or lower.

<Number average molecular weight (Mn)>
The Mn of the second resin (b) is preferably 2000 or more and 20000 or less. This is because if Mn is less than 2000, the resin tends to be excessively soft and offset tends to occur, and if it exceeds 20000, the resin is difficult to melt and the fixing strength tends to decrease. Here, the Mn of the second resin (b) is more preferably 5000 or more and 10,000 or less.

<Other components contained in toner particles>
The toner particles (C) in the present embodiment preferably contain a colorant in at least one of the shell layer (A) and the core layer (B), and additives other than the colorant (for example, pigment dispersant, wax) , A charge control agent, a filler, an antistatic agent, a mold release agent, an ultraviolet absorber, an antioxidant, an antiblocking agent, a heat stabilizer, a flame retardant, and the like.

<Colorant>
The colorant is dispersed in at least one of the first resin (a) and the second resin (b). The volume average particle size of the colorant is preferably 0.3 μm or less. If the volume average particle size of the colorant exceeds 0.3 μm, dispersion may be deteriorated, resulting in a decrease in glossiness and the inability to achieve a desired color.

  As the colorant, conventionally known pigments and the like can be used without any particular limitation. For example, conventionally known black pigments, yellow pigments, magenta pigments, and cyan pigments can be used. Here, in terms of color configuration, basically colors other than black (color image) are toned by subtractive color mixture of yellow pigment, magenta pigment, and cyan pigment.

<Pigment dispersant>
The pigment dispersant has a function of uniformly dispersing the colorant (pigment) in the toner particles, and it is preferable to use a basic dispersant. Further, it is more preferable to select a pigment dispersant that does not dissolve in the insulating liquid (carrier liquid). For these reasons, it is preferable to use “Ajisper PB-821” (trade name), “Ajisper PB-822” (trade name), “Ajisper PB-881” (trade name), etc., manufactured by Ajinomoto Fine Techno Co., Ltd.

<Insulating liquid>
The insulating liquid contained in the liquid developer of the present embodiment may be one having a resistivity (about 10 ¹¹ to 10 ¹⁶ Ω · cm) that does not disturb the electrostatic latent image. Furthermore, a solvent having low odor and toxicity is preferable. In general, aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, polysiloxanes and the like can be mentioned. In particular, a normal paraffin solvent and an isoparaffin solvent are preferable from the viewpoint of odor, harmlessness, and cost. Specifically, Moresco White (trade name, manufactured by Matsumura Oil Research Co., Ltd.), Isopar (registered trademark, manufactured by ExxonMobil), Shellsol (trade name, manufactured by Shell Chemicals Japan Co., Ltd.), IP Solvent 1620, IP Solvent 2028, IP solvent 2835 (both are trade names, manufactured by Idemitsu Kosan Co., Ltd.) and the like.

<Method for producing liquid developer>
The liquid developer (X) according to this embodiment can be manufactured as follows. First, the first resin (a) and the second resin (b) are produced by a conventionally known method such as a dispersion polymerization method, an emulsion polymerization method, a soap-free emulsion polymerization method, a seed polymerization method or a suspension polymerization method. Next, a fine particle dispersion in which the first resin (a) is dispersed is prepared. Furthermore, the second resin (b) is dissolved in a good solvent to obtain a resin solution, and the resin solution is mixed with a fine particle dispersion of the first resin (a) in a poor solvent having an SP value different from that of the good solvent. The liquid developer (X) can be produced by volatilizing the good solvent after forming droplets by applying shear. The liquid developer (X) thus produced has a core / layer composed of a shell layer (A) containing the first resin (a) and a core layer (B) containing the second resin (b). Toner particles (C) having a shell structure can be included.

  Here, according to the above method, the volume average particle diameter of the toner particles can be controlled within a desired range by appropriately adjusting the method of applying shear, the difference in interfacial tension, and the like.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

<Production Example 1> [Production of polyester resin]
In a reaction vessel equipped with a stirrer, heating / cooling device, thermometer, cooling tube and nitrogen introduction tube, 286 parts by mass of dodecanedicarboxylic acid, 190 parts by mass of 1,6-hexanediol and titanium dihydroxybis (triethanolamino) as a condensation catalyst. Nate) 1 part by mass was added and reacted at 180 ° C. for 8 hours while distilling off the water produced under a nitrogen stream.

  Next, while gradually raising the temperature to 220 ° C., the reaction was performed for 4 hours while distilling off the generated water under a nitrogen stream, and the reaction was further performed for 1 hour under a reduced pressure of 0.007 to 0.026 MPa to obtain a polyester resin. . When Mn and Mw of this polyester resin were measured according to the above-mentioned method, Mn was 4900 and Mw was 10,000. Moreover, when the melting point of this polyester resin was measured by the method based on ASTM D3418-82 using the differential scanning calorimeter ("DSC20" by Seiko Instruments Inc.), the melting point was 68 degreeC. .

<Production Example 2> [Production of Fine Particle Dispersion (A1) of First Resin (a1)]
A fine particle dispersion (A1) in which fine particles made of the first resin (a1) were dispersed was produced as follows.

  100 parts by mass of THF was charged into 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. In a glass beaker, 45 parts by mass of n-octyl methacrylate, 15 parts by mass of 2-decyltetradecyl methacrylate, 3 parts by mass of N, N-diethylacrylamide (hereinafter referred to as “diethylacrylamide”), 15 parts by mass of methacrylic acid, 22 parts by mass of an equimolar reaction product of an isocyanate group-containing monomer (trade name “Karenz MOI” manufactured by Showa Denko KK) and the polyester resin obtained in Production Example 1, and 0.1 mass of azobismethoxydimethylvaleronitrile Part of the mixed solution was added and stirred and mixed at 20 ° C. to prepare a monomer solution, which was then added to the dropping funnel.

  After carrying out nitrogen substitution of the gas phase part of the reaction vessel, the monomer solution was added dropwise at 70 ° C. for 1 hour in a sealed state. 3 hours after the completion of the dropping, a mixture of 0.05 part by mass of azobismethoxydimethylvaleronitrile and 5 parts by mass of THF was added, reacted at 70 ° C. for 3 hours, cooled to room temperature, and then a copolymer solution. Got. While stirring 200 parts by mass of this copolymer solution, it was dropped into 300 parts by mass of an insulating liquid (“IP Solvent 2028”, manufactured by Idemitsu Kosan Co., Ltd.), and THF was distilled off at 40 ° C. under a reduced pressure of 0.039 MPa. Thus, a fine particle dispersion (A1) was obtained. When the Mw of the first resin (a1) contained in the fine particle dispersion (A1) was measured according to the above-described method, the Mw was 100,000. Hereinafter, Mw is measured by the same method.

  Here, in this production example, “diethylacrylamide” corresponds to “amide monomer”, “n-octyl methacrylate” corresponds to “monomer having a linear hydrocarbon group”, and “2-decyltetradecyl methacrylate” "Corresponds to" a monomer having a branched hydrocarbon group ".

<Production Example 3> [Production of Fine Particle Dispersion (A2) of First Resin (a2)]
A fine particle dispersion (A2) in which fine particles made of the first resin (a2) were dispersed was produced as follows.

  100 parts by mass of THF was charged into 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. In a glass beaker, 25 parts by mass of n-tridecyl methacrylate, 25 parts by mass of diethylene glycol mono2-decyl tetradecyl methacrylate, 7 parts by mass of morpholine acrylamide, 25 parts by mass of methacrylic acid, an isocyanate group-containing monomer (trade name “Karenz MOI ”, Made by Showa Denko KK) and 18 parts by mass of an equimolar reaction product of the polyester resin obtained in Production Example 1, and 0.1 parts by mass of azobismethoxydimethylvaleronitrile were charged at 20 ° C. The monomer solution was prepared by stirring and mixing at, and charged into a dropping funnel.

  After carrying out nitrogen substitution of the gas phase part of the reaction vessel, the monomer solution was added dropwise at 70 ° C. for 1 hour in a sealed state. 3 hours after the completion of the dropping, a mixture of 0.05 part by mass of azobismethoxydimethylvaleronitrile and 5 parts by mass of THF was added, reacted at 70 ° C. for 3 hours, cooled to room temperature, and then a copolymer solution. Got. While stirring 200 parts by mass of this copolymer solution, it was dropped into 300 parts by mass of an insulating liquid (trade name “IP Solvent 2028”, manufactured by Idemitsu Kosan Co., Ltd.), and THF was added at 40 ° C. under a reduced pressure of 0.039 MPa. Was distilled off to obtain a fine particle dispersion (A2). The Mw of the first resin (a2) contained in this fine particle dispersion (A2) was 90000.

  In this production example, “morpholine acrylamide” corresponds to “amide monomer”, “n-tridecyl methacrylate” corresponds to “monomer having a linear hydrocarbon group”, and “diethylene glycol mono-2-decyl methacrylate”. “Tetradecyl ether” corresponds to “a monomer having a branched hydrocarbon group”.

<Production Example 4> [Production of fine particle dispersion (A3) of first resin (a3)]
A fine particle dispersion (A3) in which fine particles made of the first resin (a3) were dispersed was produced as follows.

  100 parts by mass of THF was charged into 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. In a glass beaker, 12 parts by mass of n-octyl methacrylate, 28 parts by mass of 2-decyltetradecyl methacrylate, 1 part by mass of diethyl acrylamide, 15 parts by mass of methacrylic acid, an isocyanate group-containing monomer (trade name “Karenz MOI”, Showa A mixture of 44 parts by mass of an equimolar reaction product of the polyester resin obtained in Production Example 1 and 0.1 parts by mass of azobismethoxydimethylvaleronitrile was charged and stirred at 20 ° C. A monomer solution was prepared by mixing and charged into a dropping funnel.

  After carrying out nitrogen substitution of the gas phase part of the reaction vessel, the monomer solution was added dropwise at 70 ° C. for 1 hour in a sealed state. 3 hours after the completion of the dropping, a mixture of 0.05 part by mass of azobismethoxydimethylvaleronitrile and 5 parts by mass of THF was added, reacted at 70 ° C. for 3 hours, cooled to room temperature, and then a copolymer solution. Got. While stirring 200 parts by mass of this copolymer solution, it was dropped into 300 parts by mass of an insulating liquid (trade name “IP Solvent 2028”, manufactured by Idemitsu Kosan Co., Ltd.), and THF was added at 40 ° C. under a reduced pressure of 0.039 MPa. Was distilled off to obtain a fine particle dispersion (A3). The Mw of the first resin (a3) contained in this fine particle dispersion (A3) was 90000.

<Production Example 5> [Production of fine particle dispersion (A4) of first resin (a4)]
In the following manner, a fine particle dispersion (A4) in which fine particles made of the first resin (a4) were dispersed was produced.

  100 parts by mass of THF was charged into 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. In a glass beaker, 17 parts by mass of n-octyl methacrylate, 40 parts by mass of 2-decyltetradecyl methacrylate, 3 parts by mass of diethylacrylamide, 13 parts by mass of methacrylic acid, an isocyanate group-containing monomer (trade name “Karenz MOI”, Showa A mixture of 27 parts by weight of an equimolar reaction product of the polyester resin obtained in Production Example 1 and 0.1 parts by weight of azobismethoxydimethylvaleronitrile was charged and stirred at 20 ° C. A monomer solution was prepared by mixing and charged into a dropping funnel.

  After carrying out nitrogen substitution of the gas phase part of the reaction vessel, the monomer solution was added dropwise at 70 ° C. for 1 hour in a sealed state. 3 hours after the completion of the dropping, a mixture of 0.05 part by mass of azobismethoxydimethylvaleronitrile and 5 parts by mass of THF was added, reacted at 70 ° C. for 3 hours, cooled to room temperature, and then a copolymer solution. Got. While stirring 200 parts by mass of this copolymer solution, it was dropped into 300 parts by mass of an insulating liquid (trade name “IP Solvent 2028”, manufactured by Idemitsu Kosan Co., Ltd.), and THF was added at 40 ° C. under a reduced pressure of 0.039 MPa. Was distilled off to obtain a fine particle dispersion (A4). The Mw of the first resin (a4) contained in this fine particle dispersion (A4) was 110000.

<Production Example 6> [Production of fine particle dispersion (A5) of first resin (a5)]
In the following manner, a fine particle dispersion (A5) in which fine particles made of the first resin (a5) were dispersed was produced.

  100 parts by mass of THF was charged into 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. In a glass beaker, 30 parts by mass of n-octyl methacrylate, 10 parts by mass of 2-decyltetradecyl methacrylate, 3 parts by mass of diethylacrylamide, 10 parts by mass of methacrylic acid, an isocyanate group-containing monomer (trade name “Karenz MOI”, Showa A mixture of 47 parts by mass of an equimolar reaction product of the polyester resin obtained in Production Example 1 and 0.1 part by mass of azobismethoxydimethylvaleronitrile was charged and stirred at 20 ° C. A monomer solution was prepared by mixing and charged into a dropping funnel. After carrying out nitrogen substitution of the gas phase part of the reaction vessel, the monomer solution was added dropwise at 70 ° C. for 1 hour in a sealed state. 3 hours after the completion of dropping, a mixture of 0.05 part by mass of azobismethoxydimethylvaleronitrile and 5 parts by mass of THF was added, reacted at 70 ° C. for 3 hours, cooled to room temperature, and the copolymer solution was prepared. Obtained. While stirring 200 parts by mass of this copolymer solution, it was dropped into 300 parts by mass of an insulating liquid (trade name “IP Solvent 2028”, manufactured by Idemitsu Kosan Co., Ltd.), and THF was added at 40 ° C. under a reduced pressure of 0.039 MPa. Was distilled off to obtain a fine particle dispersion (A5). The Mw of the first resin (a5) contained in this fine particle dispersion (A5) was 95,000.

<Production Example 7> [Production of fine particle dispersion (A6) of first resin (a6)]
In the following manner, a fine particle dispersion (A6) in which fine particles made of the first resin (a6) were dispersed was produced.

  100 parts by mass of THF was charged into 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. In a glass beaker, 60 parts by mass of n-decyl methacrylate, 7 parts by mass of morpholine acrylamide, 15 parts by mass of methacrylic acid, an isocyanate group-containing monomer (trade name “Karenz MOI”, manufactured by Showa Denko KK) and Production Example 1 A mixed solution of 22 parts by mass of an equimolar reaction product with the obtained polyester resin and 0.1 part by mass of azobismethoxydimethylvaleronitrile was added, and the mixture was stirred and mixed at 20 ° C. to prepare a monomer solution. I put it in the funnel.

  After carrying out nitrogen substitution of the gas phase part of the reaction vessel, the monomer solution was added dropwise at 70 ° C. for 1 hour in a sealed state. 3 hours after the completion of the dropping, a mixture of 0.05 part by mass of azobismethoxydimethylvaleronitrile and 5 parts by mass of THF was added, reacted at 70 ° C. for 3 hours, cooled to room temperature, and then a copolymer solution. Got. While stirring 200 parts by mass of this copolymer solution, it was dropped into 300 parts by mass of an insulating liquid (trade name “IP Solvent 2028”, manufactured by Idemitsu Kosan Co., Ltd.), and THF was added at 40 ° C. under a reduced pressure of 0.039 MPa. Was distilled off to obtain a fine particle dispersion (A6). The Mw of the first resin (a6) contained in this fine particle dispersion (A6) was 80000.

  Here, this production example corresponds to an example in which the first resin (a) does not include the third structural unit (α3).

<Production Example 8> [Production of fine particle dispersion (A7) of first resin (a7)]
A fine particle dispersion (A7) in which fine particles made of the first resin (a7) were dispersed was produced as follows.

  100 parts by mass of THF was charged into 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. In a glass beaker, 40 parts by mass of n-tridecyl methacrylate, 30 parts by mass of diethylene glycol mono2-decyltetradecyl methacrylate, 3 parts by mass of diethylacrylamide, 25 parts by mass of methacrylic acid, an isocyanate group-containing monomer (trade name “Karenz MOI ”, Manufactured by Showa Denko KK) and a polyester resin obtained in Production Example 1 in an amount of 15 parts by mass, and a mixture of 0.1 part by mass of azobismethoxydimethylvaleronitrile was charged at 20 ° C. The monomer solution was prepared by stirring and mixing at, and charged into a dropping funnel.

  After carrying out nitrogen substitution of the gas phase part of the reaction vessel, the monomer solution was added dropwise at 70 ° C. for 1 hour in a sealed state. 3 hours after the completion of the dropping, a mixture of 0.05 part by mass of azobismethoxydimethylvaleronitrile and 5 parts by mass of THF was added, reacted at 70 ° C. for 3 hours, cooled to room temperature, and then a copolymer solution. Got. While stirring 200 parts by mass of this copolymer solution, it was dropped into 300 parts by mass of an insulating liquid (trade name “IP Solvent 2028”, manufactured by Idemitsu Kosan Co., Ltd.), and THF was added at 40 ° C. under a reduced pressure of 0.039 MPa. Was distilled off to obtain a fine particle dispersion (A7). The Mw of the first resin (a7) contained in this fine particle dispersion (A7) was 100,000.

<Production Example 9> [Production of fine particle dispersion (A8) of first resin (a8)]
A fine particle dispersion (A8) in which fine particles made of the first resin (a8) were dispersed was produced as follows.

  100 parts by mass of THF was charged into 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. In a glass beaker, 45 parts by mass of n-decyl methacrylate, 15 parts by mass of 2-decyltetradecyl methacrylate, 15 parts by mass of methacrylic acid, an isocyanate group-containing monomer (trade name “Karenz MOI”, manufactured by Showa Denko KK) And a mixed solution of 25 parts by mass of an equimolar reaction product of the polyester resin obtained in Production Example 1 and 0.1 part by mass of azobismethoxydimethylvaleronitrile were stirred and mixed at 20 ° C. to obtain a monomer solution. Was adjusted and put into a dropping funnel. After carrying out nitrogen substitution of the gas phase part of the reaction vessel, the monomer solution was added dropwise at 70 ° C. for 1 hour in a sealed state. 3 hours after the completion of the dropping, a mixture of 0.05 part by mass of azobismethoxydimethylvaleronitrile and 5 parts by mass of THF was added, reacted at 70 ° C. for 3 hours, cooled to room temperature, and then a copolymer solution. Got. While stirring 200 parts by mass of this copolymer solution, it was dropped into 300 parts by mass of an insulating liquid (trade name “IP Solvent 2028”, manufactured by Idemitsu Kosan Co., Ltd.), and THF was added at 40 ° C. under a reduced pressure of 0.039 MPa. Was distilled off to obtain a fine particle dispersion (A8). The Mw of the first resin (a8) contained in this fine particle dispersion (A8) was 110000.

  Here, this production example corresponds to an example in which the first resin (a) does not include the first structural unit (α1).

<Production Example 10> [Production of Fine Particle Dispersion (A9) of First Resin (a9)]
A fine particle dispersion (A9) in which fine particles made of the first resin (a9) were dispersed was produced as follows.

  100 parts by mass of THF was charged into 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. In a glass beaker, 45 parts by mass of n-decyl methacrylate, 15 parts by mass of diethylene glycol mono2-decyltetradecyl methacrylate, 7 parts by mass of diethylacrylamide, 16 parts by mass of methacrylic acid, an isocyanate group-containing monomer (trade name “Karenz MOI ”, Manufactured by Showa Denko KK) and the polyester resin obtained in Production Example 1, 17 parts by mass of an equimolar reaction product and 0.1 part by mass of azobismethoxydimethylvaleronitrile were charged at 20 ° C. The monomer solution was prepared by stirring and mixing at, and charged into a dropping funnel. After carrying out nitrogen substitution of the gas phase part of the reaction vessel, the monomer solution was added dropwise at 70 ° C. for 1 hour in a sealed state. 3 hours after the completion of the dropping, a mixture of 0.05 part by mass of azobismethoxydimethylvaleronitrile and 5 parts by mass of THF was added, reacted at 70 ° C. for 3 hours, cooled to room temperature, and then a copolymer solution. Got. While stirring 200 parts by mass of this copolymer solution, it was dropped into 300 parts by mass of an insulating liquid (trade name “IP Solvent 2028”, manufactured by Idemitsu Kosan Co., Ltd.), and THF was added at 40 ° C. under a reduced pressure of 0.039 MPa. Was distilled off to obtain a fine particle dispersion (A9). The Mw of the first resin (a9) contained in this fine particle dispersion (A9) was 100,000.

<Production Example 11> [Production of Fine Particle Dispersion (A10) of First Resin (a10)]
A fine particle dispersion (A10) in which fine particles made of the first resin (a10) were dispersed was produced as follows.

  100 parts by mass of THF was charged into 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. In a glass beaker, 60 parts by mass of diethylene glycol mono2-decyltetradecyl ether methacrylate, 7 parts by mass of morpholine acrylamide, 15 parts by mass of methacrylic acid, an isocyanate group-containing monomer (trade name “Karenz MOI”, manufactured by Showa Denko KK) And a mixed solution of 22 parts by mass of an equimolar reaction product of the polyester resin obtained in Production Example 1 and 0.1 part by mass of azobismethoxydimethylvaleronitrile were stirred and mixed at 20 ° C. to obtain a monomer solution. Was adjusted and put into a dropping funnel.

  After carrying out nitrogen substitution of the gas phase part of the reaction vessel, the monomer solution was added dropwise at 70 ° C. for 1 hour in a sealed state. 3 hours after the completion of the dropping, a mixture of 0.05 part by mass of azobismethoxydimethylvaleronitrile and 5 parts by mass of THF was added, reacted at 70 ° C. for 3 hours, cooled to room temperature, and then a copolymer solution. Got. While stirring 200 parts by mass of this copolymer solution, it was dropped into 300 parts by mass of an insulating liquid (trade name “IP Solvent 2028”, manufactured by Idemitsu Kosan Co., Ltd.), and THF was added at 40 ° C. under a reduced pressure of 0.039 MPa. Was distilled off to obtain a fine particle dispersion (A10). The Mw of the first resin (a10) contained in this fine particle dispersion (A10) was 80000.

  Here, this production example corresponds to an example in which the first resin (a) does not include the second structural unit (α2).

<Production Example 12> [Production of second resin (b1) solution]
A solution of the second resin (b1), which is a linear polyester resin, was produced as follows.

  In a reaction vessel equipped with a cooling pipe, a stirrer and a nitrogen introduction pipe, 701 parts by mass of 1,2-propylene glycol (hereinafter referred to as “propylene glycol”), 716 parts by mass of dimethyl terephthalate, 180 parts by mass of adipic acid, And 3 parts by mass of tetrabutoxy titanate was added as a condensation catalyst, and the reaction was carried out at 180 ° C. for 8 hours while distilling off the produced methanol under a nitrogen stream.

  Next, while gradually raising the temperature to 230 ° C., the reaction was performed for 4 hours while distilling off the generated propylene glycol and water in a nitrogen stream, and further, the reaction was performed for 1 hour under a reduced pressure of 0.007 to 0.026 MPa.

  Subsequently, it cooled to 180 degreeC, 10 mass parts of phthalic anhydride was added, and it was made to react for 2 hours under normal pressure sealing, Then, the produced | generated resin was taken out. A solution of the second resin (b1), which is a linear polyester resin, is placed in an autoclave reaction vessel equipped with a thermometer, a stirrer, and a nitrogen introduction tube together with 1800 parts by mass of acetone, and the resin is dissolved. Got. When Mn of this second resin (b1) was measured according to the method described above, Mn was 8000. Moreover, it was 55 degreeC when the endothermic start temperature of this 2nd resin (b1) was measured according to the above-mentioned method. Hereinafter, Mn and endothermic start temperature are measured by the same method.

<Production Example 13> [Production of second resin (b2) solution]
A solution of the second resin (b2), which is a nonlinear polyester resin, was produced as follows.

  In a reaction vessel equipped with a cooling tube, a stirrer and a nitrogen introduction tube, 557 parts by mass of propylene glycol, 569 parts by mass of dimethyl terephthalate, 184 parts by mass of adipic acid, and 3 parts by mass of tetrabutoxy titanate as a condensation catalyst were obtained. The reaction was carried out for 8 hours at 180 ° C. while distilling off the methanol produced under a nitrogen stream.

  Next, while gradually raising the temperature to 230 ° C., the reaction was performed for 4 hours while distilling off the generated propylene glycol and water in a nitrogen stream, and further, the reaction was performed for 1 hour under a reduced pressure of 0.007 to 0.026 MPa.

  Subsequently, it cooled to 180 degreeC, 6 mass parts of phthalic anhydride was added, and it was made to react under normal pressure sealing for 2 hours, Then, it was made to react at 220 degreeC under normal pressure. The softening point of the resin thus obtained was 180 ° C. The resin is taken out from the reaction tank, and the resin is placed in an autoclave reaction tank equipped with a thermometer, a stirrer, and a nitrogen introduction tube together with 1800 parts by mass of acetone, and the resin is dissolved, whereby the second resin which is a non-linear polyester resin A solution of (b2) was obtained. The Mn of the second resin (b2) was 8500, and the endothermic start temperature was 53 ° C.

<Production Example 14> [Production of second resin (b3) solution]
A solution of the second resin (b3) was obtained as follows.

  In a reaction vessel equipped with a cooling tube, a stirrer and a nitrogen introduction tube, 570 parts by mass of an ethylene oxide 2-mole adduct of bisphenol A and 217 parts by mass of terephthalic acid were placed and reacted at 230 ° C. for 8 hours under normal pressure. Furthermore, it was made to react under the reduced pressure of 0.013-0.20 MPa for 5 hours.

  Subsequently, it cooled to 180 degreeC, 4 mass parts of phthalic anhydrides were added, and it was made to react under normal pressure sealing for 2 hours, Then, produced | generated resin was taken out. The taken-out resin was put together with 1800 parts by mass of acetone in an autoclave reaction vessel equipped with a thermometer, a stirrer and a nitrogen introduction tube, and dissolved to obtain a solution of the second resin (b3). The Mn of the second resin (b3) was 2400, and the endothermic start temperature was 50 ° C.

<Production Example 15> [Production of Colorant Dispersion]
Into a beaker, 25 parts by mass of copper phthalocyanine, 4 parts by mass of a colorant dispersant (trade name “Azisper PB-822”, manufactured by Ajinomoto Fine Techno Co., Ltd.) and 75 parts by mass of acetone are stirred and uniformly dispersed. Thereafter, copper phthalocyanine was finely dispersed by a bead mill to obtain a colorant dispersion. When the volume average particle size of copper phthalocyanine contained in the colorant dispersion was measured using a laser diffraction / scattering particle size distribution analyzer (model “LA-920”, manufactured by Horiba, Ltd.), the volume average particle size was 0. .2 μm.

<Example 1> [Production of liquid developer (Z-1)]
In a beaker, 45 parts by mass of the second resin (b1) solution and 15 parts by mass of the colorant dispersion obtained in Production Example 14 were added, and a TK auto homomixer (product name, manufactured by Primix Co., Ltd.) at 25 ° C. Was stirred at 8000 rpm and dispersed uniformly to obtain a resin solution.

  In another beaker, 67 parts by mass of the insulating liquid (IP solvent 2028) and 6 parts by mass of the fine particle dispersion (A1) were charged and uniformly dispersed. Next, while stirring at 10,000 rpm using a TK auto homomixer at 25 ° C., 60 parts by mass of the resin solution was added and stirred for 2 minutes to obtain a mixed solution.

  Next, this mixed solution was put into a reaction vessel equipped with a stirrer, a heating / cooling device, a thermometer, and a solvent removal device. After the temperature was raised to 35 ° C., the acetone concentration was reduced to 0.039 MPa at a reduced pressure of 0.039 MPa. Acetone was distilled off until the content became 5% by mass or less to obtain a liquid developer (Z-1) according to Example 1. This liquid developer (Z-1) contains toner particles having a core / shell structure composed of a shell layer containing the first resin (a1) and a core layer containing the second resin (b1).

  Here, in the above operation, the concentration of acetone was quantified by gas chromatography equipped with a flame ion detector [product name “GC2010”, manufactured by Shimadzu Corporation].

  Further, when the solubility of the first resin (a1) in the insulating liquid (IP solvent 2028) at 25 ° C. was measured, the solubility was 3 mass%. This solubility was measured as follows.

  At 25 ° C., 10 g of the liquid developer (Z-1) was centrifuged at 10,000 rpm for 30 minutes, and the entire supernatant was recovered. 10 ml of insulating liquid was added to the remaining solid content, and the toner particles were dispersed again. Thereafter, the mixture was centrifuged at 10,000 ppm for 30 minutes at 25 ° C., and the entire supernatant was recovered. This operation was further repeated, and the supernatant was collected 3 times in total. The supernatant liquid was dried for 1 hour at the same temperature as the boiling point of the insulating liquid under a reduced pressure of 20 mmHg with a vacuum dryer, and the mass of the residue was weighed. And the percentage of the value which remove | divided the mass Y (g) of the residue at this time by the mass y (g) of 1st resin (a1) in 10 g of liquid developers (Z-1) is liquid developer (Z-1). The solubility (25 ° C.) of the first resin (a1) in the insulating liquid in FIG.

<Examples 2 to 10 and Comparative Examples 1 to 3> [Production of Liquid Developer]
As shown in Table 1, the liquid developers (Z-2) according to Examples 2 to 10 were used in the same manner as in Example 1 except that the types of the fine particle dispersion (A) and the second resin (b) were changed. ) To (Z-10) and liquid developers (Z′-1) to (Z′-3) according to Comparative Examples 1 to 3 were obtained. Here, the ratio [% by mass] of each structural unit of the first resin (a) shown in Table 1 is a value calculated from the charged amount of each monomer.

<Measurement of volume average particle diameter of toner particles>
The volume average particle diameter of toner particles contained in each liquid developer was measured using “LA-920” manufactured by Horiba. The results are shown in Table 1.

<Evaluation>
The chargeability, low-temperature fixing temperature and fixing strength of each liquid developer were evaluated as follows.

<Image forming apparatus>
First, the image forming apparatus used for evaluation will be described. FIG. 1 is a schematic conceptual diagram of an electrophotographic image forming apparatus. The process conditions and process outline of this apparatus are as follows.

  First, the liquid developer 6 is placed in the developing tank 5 of the image forming apparatus 100. The liquid developer 6 is pumped up by the anilox roller 22 and sent to the leveling roller 21. Excess liquid developer on the surface of the anilox roller 22 is scraped off by the anilox regulating blade 23 before reaching the leveling roller 21 so that the liquid developer becomes a thin layer having a uniform layer thickness. Adjusted. Next, the liquid developer is transferred from the leveling roller 21 to the developer carrier 24.

  The photoreceptor 1 is charged by the charging unit 7 and a latent image is formed by the exposure unit 8. The development charger 26 charges the toner particles contained in the liquid developer. The liquid developer 6 is developed on the photoconductor 1 corresponding to the latent image. The liquid developer 6 that has not transferred to the photoreceptor 1 is scraped off and collected by the cleaning blade 25 downstream of the developing unit. Although not shown, this apparatus includes a measuring instrument that can measure the surface potential of a thin layer made of a liquid developer 0.1 seconds and 1 second after the liquid developer is charged.

  The liquid developer developed on the photosensitive member 1 is electrostatically primary transferred to the intermediate transfer member 10 by the primary transfer unit 2. The liquid developer (toner particles) carried on the intermediate transfer member 10 is electrostatically secondary transferred to the recording material 12 in the secondary transfer unit 3. The liquid developer (toner particles) transferred to the recording material 12 is fixed by a fixing device 30 including a heating roller 31 and a pressure roller 32, and a printed image is completed.

  The liquid developer that cannot be completely transferred and remains on the photosensitive member 1 is scraped off by the cleaning blade 9 of the image carrier cleaning unit, and the photosensitive member 1 repeats charging, exposing, and developing steps to perform a printing operation. Similarly, the liquid developer that cannot be transferred and remains on the intermediate transfer member 10 is scraped off by the cleaning blade 11.

In the evaluation of each liquid developer, the toner particles were charged with a positive polarity by the development charger 26. The potential of the intermediate transfer member 10 was −400 V, the potential of the transfer roller 4 was −1200 V, and the conveyance speed was 400 mm / s. Coated paper (trade name: “OK Top Coat (registered trademark)” (128 g / m ² , manufactured by Oji Paper Co., Ltd.)) was used as the recording material.

<Evaluation of electrification>
The chargeability of the toner particles contained in each liquid developer was evaluated by measuring the charge amount and the charge retention rate as follows.

<Measurement of charge amount>
Using the image forming apparatus 100, a thin layer (a mass of toner particles per unit area: 1 g / m ² ) is formed on the developer carrier 24 and flows into the developer carrier. The thin layer was charged at a current of 0.2 mA / cm. Then, by measuring the surface potential of the thin layer 0.1 seconds after charging and dividing the surface potential by the mass of toner particles per unit area, the charge amount Vs 0.1 [unit: V · (g / m ² ) ⁻¹ ] was calculated.

<Measurement of charge retention>
Further, the surface potential of the thin layer 1 second after charging was measured, and the surface potential after 1 second was divided by the surface potential after 0.1 second to calculate the charge retention [unit:%]. These measurement results are shown in Table 1. In Table 1, the larger the numerical values shown in the “charge amount” and “charge retention” columns, the better the chargeability. The better the chargeability of the toner particles, the easier it is to obtain a uniform image.

<Evaluation of low-temperature fixability>
The low temperature fixability of each liquid developer was evaluated by measuring the low temperature fixing temperature and the fixing strength of each liquid developer as follows.

<Measurement of low-temperature fixing temperature>
Using the image forming apparatus 100, a solid pattern (10 cm × 10 cm, toner particle adhesion amount: 1.5 g / m ² ) is formed on a recording material (coated paper) with each liquid developer. Established. This operation was repeated while gradually decreasing the temperature of the heating roller 31 of the fixing device 30 from 200 ° C., and the temperature at which a cold offset (low temperature offset) occurs (nip time: 30 msec) was measured. The temperature at which cold offset occurs was defined as the low temperature fixing temperature. The results are shown in Table 1. In Table 1, the lower the low-temperature fixing temperature, the better the low-temperature fixing property.

<Measurement of fixing strength>
Further, the fixing strength was measured as follows. A tape (“Scotch Mending Tape” manufactured by Sumitomo 3M Co., Ltd.) was applied to the measurement target site on the coated paper on which the image was fixed, and then the tape was peeled off. Next, by using a reflection densitometer (trade name “X-Rite model 404” manufactured by X-Rite Co., Ltd.), the image density (ID) of the image peeled off the tape is obtained, and the image density becomes less than 0.1. The minimum temperature was measured. The results are shown in Table 1. This method indicates that the lower the image density of the peeled image, the harder the peeled image is peeled off by the tape. Therefore, it can be said that the lower the minimum temperature at which the image density is less than 0.1, the better the liquid developer is at low temperature fixability.

<Consideration of results>
As is apparent from Table 1, a liquid developer in which toner particles are dispersed in an insulating liquid, the toner particles comprising a shell layer containing a first resin and a core layer containing a second resin. The first resin has a core / shell structure, and the first resin includes a first structural unit derived from an amide monomer, a second structural unit derived from a monomer having a linear hydrocarbon group, and a monomer having a branched hydrocarbon group The liquid developer (Z-1 to Z-10) of Example, which is a resin including the third structural unit derived from, is a liquid developer (Z′-1 to Z ′) of Comparative Example that does not satisfy such conditions. 3), it was confirmed that excellent characteristics were exhibited in all evaluation items of charge amount, charge retention, low-temperature fixing temperature, and fixing temperature.

  Although the embodiments and examples of the present invention have been described above, it is also planned from the beginning to appropriately combine the configurations of the above-described embodiments and examples.

  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.

  DESCRIPTION OF SYMBOLS 1 Photoconductor, 2 Primary transfer part, 3 Secondary transfer part, 4 Transfer roller, 5 Developing tank, 6 Liquid developer, 7 Charging part, 8 Exposure part, 9 Cleaning blade, 10 Intermediate transfer body, 11 Cleaning blade, 12 recording material, 21 leveling roller, 22 anilox roller, 23 anilox regulating blade, 24 developer carrier, 25 cleaning blade, 26 developing charger, 30 fixing device, 31 heating roller, 32 pressure roller, 100 image forming apparatus.

Claims (9)

A liquid developer in which toner particles are dispersed in an insulating liquid,
The toner particles have a core / shell structure composed of a shell layer containing a first resin and a core layer containing a second resin,
The first resin includes a first structural unit derived from an amide monomer, a second structural unit derived from a monomer having a linear hydrocarbon group, and a third structural unit derived from a monomer having a branched hydrocarbon group. A liquid developer.   The liquid developer according to claim 1, wherein the first structural unit is contained in the first resin at a ratio of 0.1% by mass or more and 7% by mass or less.   3. The liquid according to claim 1, wherein the first resin includes the second structural unit and the third structural unit in a range in which the total amount of both is 40% by mass or more and 70% by mass or less. Developer.   The said 2nd structural unit occupies the ratio of 30 mass% or more and 90 mass% or less among the sum total of the said 2nd structural unit and the said 3rd structural unit. The liquid developer as described.   5. The liquid developer according to claim 1, wherein the second resin has an endothermic start temperature of 50 ° C. or more and 55 ° C. or less in differential scanning calorimetry.   The liquid developer according to claim 1, wherein the toner particles have a volume average particle size of 1.0 μm or more and 2.0 μm or less.   The liquid developer according to claim 1, wherein the second resin is a polyester resin. The charge amount Vs0.1 of toner particles is greater than ^{15.0V · (g / m 2)} -1, 18.9V · (g / m 2) is less than ^-1,
The toner particles have a charge retention of 50% or more and 68% or less.
The liquid developer according to claim 1.
(However, the charge amount Vs0.1 is such that a thin layer made of the liquid developer is formed on a developer carrier, and a current of 0.2 mA / cm is applied to the thin layer to charge the thin layer. Calculated by dividing the surface potential of the thin layer 0.1 seconds after charging by the mass of the toner particles,
The toner particles per unit area in the thin layer is 1 g / cm ² ;
The charge retention is calculated by dividing the surface potential after 1 second from charging by the surface potential after 0.1 second from charging. ) A method for producing a liquid developer in which toner particles are dispersed in an insulating liquid,
The toner particles have a core / shell structure composed of a shell layer containing a first resin and a core layer containing a second resin,
The first resin includes a first structural unit derived from an amide monomer, a second structural unit derived from a monomer having a linear hydrocarbon group, and a third structural unit derived from a monomer having a branched hydrocarbon group. And
The method for producing the liquid developer includes:
A fine particle dispersion in which fine particles of the first resin are dispersed and a resin solution in which the second resin is dissolved in a good solvent are mixed in a poor solvent different from the good solvent contained in the resin solution. Forming droplets of the resin solution,
Attaching the fine particles to the surface of the droplet;
and,
Forming the toner particles by volatilizing the good solvent contained in the droplets;
including,
A method for producing a liquid developer.

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