JP2012220520A - Manufacturing method of liquid developer and liquid developer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid developer excellent in charging characteristics of positive charging, and further to provide a manufacturing method of the liquid developer capable easily.SOLUTION: A manufacturing method of a liquid developer according to the present invention includes: a pulverization step of pulverizing a toner material containing polyester resin and a charge control agent having a nitrogen functional group in insulating liquid and of obtaining a dispersion element in which resin fine particles dispersed in the insulating liquid; and a heating step of heating the dispersion element at a predetermined temperature and of obtaining a liquid developer in which toner particles dispersed in the insulating liquid. When the predetermined temperature in the heating step is represented by T(°C), a glass transition point of the polyester resin is represented by Tg(p)(°C) and a melting point of the charge control agent is represented by Tm(e)(°C), T, Tg(p) and Tm(e) satisfy the following expression: Tm(e)<T≤Tg(p)+10.

Description

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

As a developer used to develop the electrostatic latent image formed on the latent image carrier, a toner composed of a material containing a colorant such as a pigment and a binder resin is used as an electrically insulating carrier liquid (insulating property). Liquid developers dispersed in (liquid) are known.
In general, a polyester resin is widely used as a binder resin used for toner particles constituting such a liquid developer. The polyester resin has high transparency, and when used as a binder resin, it has characteristics that the resulting image has good color developability and high fixing characteristics.

By the way, as a liquid developer, a negatively chargeable liquid developer is generally used, but in recent years, development of a positively chargeable liquid developer has been advanced (for example, see Patent Document 1).
However, since the polyester resin conventionally used for toner particles generally has high negative chargeability, it has been difficult to apply it to positively charged toner particles (liquid developer). In addition, it is conceivable to add a charge control agent or a dispersing agent having a positive charging characteristic to toner particles using a conventional polyester resin as a binder resin, but it is difficult to obtain a sufficient charge amount. Met.

JP 2002-214849 A

  An object of the present invention is to provide a liquid developer excellent in positive charging characteristics, and to provide a method for producing a liquid developer capable of easily producing such a liquid developer. is there.

Such an object is achieved by the present invention described below.
The method for producing a liquid developer according to the present invention includes a dispersion in which a toner material containing a polyester resin and a charge control agent having a nitrogen-based functional group is pulverized in an insulating liquid, and resin fine particles are dispersed in the insulating liquid. Crushing step to obtain a body;
Heating the dispersion at a predetermined temperature to obtain a liquid developer in which toner particles are dispersed in the insulating liquid, and
When the predetermined temperature in the heating step is T [° C.], the glass transition point of the polyester resin is Tg (p) [° C.], and the melting point of the charge control agent is Tm (e) [° C.], Tm (e ) <T ≦ Tg (p) +10 is satisfied.
Accordingly, it is possible to provide a method for producing a liquid developer capable of easily producing a liquid developer having excellent positive charging characteristics.

In the method for producing a liquid developer according to the present invention, the charge control agent preferably has a pyrrolidone skeleton.
Thereby, it is possible to further improve the positively charged characteristics.
In the method for producing a liquid developer according to the present invention, the charge control agent preferably has a melting point of 35 ° C. or higher and 55 ° C. or lower.
As a result, the charge control agent can be more reliably present on the surface of the toner particles, and the positive charge characteristics can be further improved.

In the method for producing a liquid developer according to the present invention, the toner material is preferably a coarsely pulverized product obtained by roughly pulverizing a kneaded product containing the polyester resin and the charge control agent.
Thereby, the particle size of the fine particles (resin fine particles) can be reduced more effectively in the pulverization step. Further, by obtaining a coarsely pulverized product through the kneaded product, it is possible to reduce variations in the characteristics of the toner particles finally formed.

In the method for producing a liquid developer according to the aspect of the invention, it is preferable that a dispersing agent is included in the insulating liquid in the pulverization step.
As a result, the pulverization can be efficiently performed, and the dispersion stability of the obtained toner particles can be further increased.
In the method for producing a liquid developer of the present invention, the dispersant is preferably at least one selected from the group consisting of a graft copolymer of an acrylic polymer and polysiloxane, an amino-modified silicone, and a resin silicone. .
Thereby, the dispersion stability of the toner particles in the insulating liquid can be made particularly excellent.

In the method for producing a liquid developer according to the present invention, the insulating liquid is preferably composed of silicone oil.
Thereby, dissolution of the charge control agent into the insulating liquid can be prevented, and the charge control agent can be surely present on the surface of the toner particles.
In the method for producing a liquid developer of the present invention, the content of the charge control agent in the fine particles is preferably 0.05 parts by weight or more and 50 parts by weight or less with respect to 100 parts by weight of the polyester resin.
Thereby, it can be set as the liquid developer excellent in positive charging property.

The liquid developer of the present invention is obtained by pulverizing a toner material containing a polyester resin and a charge control agent having a nitrogen-based functional group in an insulating liquid to obtain a dispersion in which fine particles are dispersed in the insulating liquid. A pulverizing step, and a heating step of heating the dispersion at a predetermined temperature to obtain a liquid developer in which toner particles are dispersed in the insulating liquid. The predetermined temperature T [° C.] in the heating step is When the glass transition point of the polyester resin is Tg (p) [° C.] and the melting point of the charge control agent is Tm (e) [° C.], the relationship of Tm (e) <T ≦ Tg (p) +10 is established. It is manufactured by a satisfactory manufacturing method.
Accordingly, it is possible to provide a liquid developer that is particularly excellent in positive charging characteristics.

1 is a schematic diagram illustrating an example of an image forming apparatus to which a liquid developer of the present invention is applied. FIG. 2 is an enlarged view of a part of the image forming apparatus shown in FIG. 1.

Hereinafter, preferred embodiments of the present invention will be described in detail.
In the present invention, the liquid developer is one in which toner particles are dispersed in an insulating liquid.
<< Method for Producing Liquid Developer >>
First, a preferred embodiment of the method for producing a liquid developer according to the present invention will be described.
The liquid developer production method of the present embodiment includes a kneading step of kneading a polyester resin, a colorant, and a charge control agent having a nitrogen-based functional group to obtain a kneaded product, coarsely pulverizing the kneaded product, A coarse pulverization step for obtaining a pulverized product, a pulverization step for obtaining a dispersion in which resin fine particles are dispersed by pulverizing the coarse pulverized product in an insulating liquid containing a dispersant, and the dispersion at a predetermined temperature. And a heating step of heating.

  By the way, since the polyester resin conventionally used for the toner particles generally has high negative chargeability, it has been difficult to apply to the positively chargeable toner particles (liquid developer). In addition, it is conceivable to add a charge control agent or a dispersing agent having a positive charging characteristic to toner particles using a conventional polyester resin as a binder resin, but it is difficult to obtain a sufficient charge amount. Met.

  On the other hand, in the method for producing a liquid developer of the present invention, as described above, a toner material containing a polyester resin and a charge control agent having a nitrogen-based functional group is pulverized in an insulating liquid, and fine particles are obtained. A pulverizing step for obtaining a dispersion dispersed in an insulating liquid; and a heating step for heating the dispersion at a predetermined temperature to obtain a liquid developer in which toner particles are dispersed in the insulating liquid. When the predetermined temperature is T [° C.], the glass transition point of the polyester resin is Tg (p) [° C.], and the melting point of the charge control agent is Tm (e) [° C.], Tm (e) <T ≦ Tg ( p) It is characterized in that the relationship of +10 is satisfied. By having such characteristics, in the heating step, the charge control agent melted on the surface of the toner particles oozes out, and the charge control agent exists on the surface of the final toner particle surface. Since the charge control agent has a positive charge characteristic, the presence of such a charge control agent on the surface of the toner particles makes the liquid developer excellent in the positive charge characteristic. In addition, the heat treatment in the heating step makes it possible to make the corners of the toner particles to be close to a spherical shape, and to reduce the viscosity of the finally obtained liquid developer. As a result, a liquid developer having high dispersion stability of toner particles is obtained.

Hereinafter, each step will be described in detail.
<Kneading process>
In this step, toner constituent materials such as a polyester resin, a colorant, and a charge control agent having a nitrogen-based functional group are kneaded to obtain a kneaded product.
For kneading these materials, for example, various kneaders such as a biaxial kneading extruder, a kneader, a batch type triaxial roll, a continuous biaxial roll, a wheel mixer, and a blade type mixer can be used.

Hereinafter, each component will be described.
[Polyester resin]
The polyester resin has high transparency and can be suitably used as a resin material because it can enhance the color developability of an image obtained when used as a binder resin.
When the polyester resin is included, the acid value of the polyester resin is preferably 5 mgKOH / g or more and 20 mgKOH / g or less, and more preferably 5 mgKOH / g or more and 15 mgKOH / g or less.

The content of the polyester resin in the resin is preferably 50% by mass or more, and more preferably 60% by mass or more.
The glass transition temperature (Tg) of the resin used in the present invention is preferably 15 ° C. or higher and 70 ° C. or lower, and more preferably 20 ° C. or higher and 55 ° C. or lower. In this specification, the glass transition temperature is a measurement condition in a differential scanning calorimeter DSC-220C (manufactured by SII): measured in a sample amount of 10 mg, a heating rate of 10 ° C./min, and a measurement temperature range of 10 to 150 ° C. The temperature at the intersection of the base line extension below the glass transition temperature and the tangent that indicates the maximum slope from the peak rise to the peak apex.

  The softening point (T1 / 2) of the resin is not particularly limited, but is preferably 50 ° C. or higher and 130 ° C. or lower, more preferably 50 ° C. or higher and 120 ° C. or lower, and 60 ° C. or higher and 115 ° C. or lower. More preferably. In the present specification, the softening temperature is a measurement condition in a Koka type flow tester (manufactured by Shimadzu Corporation): temperature increase rate: 5 ° C./min, softening start temperature defined by a die hole diameter of 1.0 mm. Point to.

[Colorant]
The colorant used in the present invention is not particularly limited, and for example, known pigments and dyes can be used.
[Charge control agent]
As the charge control agent used as the toner material, one having a nitrogen-based functional group is used.

The charge control agent having a nitrogen-based functional group is not particularly limited, but a compound having a pyrrolidone skeleton is preferably used. Thereby, it is possible to further improve the positively charged characteristics.
Examples of such charge control agents having a pyrrolidone skeleton include polyvinyl pyrrolidone, α-olefin / vinyl pyrrolidone copolymers (ANTARON series, manufactured by ISP Japan), and vinyl acetate / vinyl pyrrolidone copolymers (PLASDONE series, ISP Japan). Manufactured) and the like.

The melting point of such a charge control agent is a temperature lower than the glass transition point of the polyester resin described above, and specifically, it is preferably 30 ° C. or higher and 55 ° C. or lower, and 35 ° C. or higher and 45 ° C. or lower. More preferably. As a result, the charge control agent can be more reliably present on the surface of the toner particles, and the positive charge characteristics can be further improved.
The amount of the charge control agent added in this step is preferably 0.05 parts by weight or more and 50 parts by weight or less, more preferably 1 part by weight or more and 30 parts by weight or less with respect to 100 parts by weight of the polyester resin. preferable. Thereby, it is possible to further improve the positively charged characteristics.

[Other ingredients]
Moreover, the kneaded material may contain components other than the above. Examples of such components include known waxes and magnetic powders.
In addition to the above materials, for example, zinc stearate, zinc oxide, cerium oxide, silica, titanium oxide, iron oxide, fatty acid, fatty acid metal salt, etc. are used as the constituent material (component) of the kneaded product. May be.

<Coarse grinding process>
Next, the kneaded product obtained in the above step is coarsely pulverized to obtain a coarsely pulverized product.
By using the coarsely pulverized product obtained by roughly pulverizing the kneaded material in this way, the particle size of the toner particles can be reduced more effectively in the pulverization step (fine pulverization step) described later.
The method of coarse pulverization is not particularly limited, and can be performed using, for example, various pulverizers and crushers such as a ball mill, a vibration mill, a jet mill, and a pin mill.
The average particle size of the coarsely pulverized product obtained in the coarse pulverization step is preferably 30 μm or more and 1000 μm or less.
The coarse pulverization step may be performed in multiple steps.

<Pulverization process (fine pulverization process)>
Next, the coarsely pulverized product obtained in the above step is wet-pulverized in an insulating liquid containing a dispersant (pulverization step). As a result, a dispersion in which resin fine particles containing the polyester resin and the charge control agent are dispersed in the insulating liquid is obtained. The dispersant may be added after wet pulverization.
The pulverization method in this step is not particularly limited, and can be performed using, for example, various pulverizers and crushers such as a ball mill, a vibration mill, a jet mill, and a pin mill.

Hereinafter, each component will be described.
[Insulating liquid]
The insulating liquid functions as a dispersion medium for dispersing the toner particles as described above.
The insulating liquid has a high insulating property in order to transfer charged toner particles during image formation.
The insulating liquid may be a liquid having a sufficiently high insulating property. Specifically, the electric resistance at room temperature (20 ° C.) is preferably 1 × 10 9 Ωcm or more, and preferably 1 × 1011 Ωcm or more. Is more preferably 1 × 10 13 Ωcm or more.
The dielectric constant of the insulating liquid is preferably 3.5 or less.

  As the insulating liquid, for example, KF-99, KF-96, KF-995 (Shin-Etsu Chemical Co., Ltd.), AK35, AK50, AK100, AK350, AK1000 (Such, Wacker Chemie AG), SH200, SH510, SH8400 ( As described above, dimethyl silicone oil such as Toray Dow Corning), silicone oil having a degree of polymerization greater than 20 such as hydrogen-modified silicone compound; cyclic siloxane compound such as cyclopentanesiloxane and decamethylcyclopentanesiloxane, and methyltris (trimethylsiloxy) silane Such as low molecular weight siloxane compounds having a polymerization degree of 20 or less; Isopar E, Isopar G, Isopar H, Isopar L (Isopar; trade name of Exxon Chemical Co., Ltd.), Cielsol 70, Cielsol 71 (Cie Lusol; trade name of Ciel Oil), Amsco OMS, Amsco 460 solvent (trade name of Amsco; Spirits), mineral oil (hydrocarbon liquid) such as low viscosity / high viscosity liquid paraffin (Wako Pure Chemical Industries); Fatty acid glycerides, fatty acid monoesters, fatty acid esters such as medium chain fatty acid esters or vegetable oils containing them; octane, isooctane, decane, isodecane, decalin, nonane, dodecane, isododecane, cyclohexane, cyclooctane, cyclodecane, benzene, toluene, xylene, Examples thereof include mesitylene, butyl acetate, and isopropanol, and one or more of these can be used in combination.

  In this step, it is preferable to use silicone oil as the insulating liquid among the above-mentioned ones. Thereby, the productivity of the liquid developer can be made particularly excellent, and the dispersion stability of the toner particles in the liquid developer can be made particularly excellent. Further, the charge control agent can be prevented from dissolving in the insulating liquid, and the charge control agent can be surely present on the surface of the toner particles.

[Dispersant]
In the pulverization step, the insulating liquid may contain a dispersant. As a result, the wet pulverization can be efficiently performed, and the dispersion stability of the obtained toner particles can be further increased.
Such a dispersant is not particularly limited, but it is preferable to use a graft copolymer of an acrylic polymer and polysiloxane (hereinafter referred to as an acrylic-polysiloxane graft copolymer). Thereby, the dispersion stability of the toner particles in the insulating liquid can be made particularly excellent. This is considered to be due to the following reasons.

  That is, the (meth) acryl moiety in the acrylic-polysiloxane graft copolymer has a relatively large polarity due to the carbonyl group in its skeleton. On the other hand, the polysiloxane portion has a relatively small polarity. For this reason, by having each of these parts, the acrylic-polysiloxane graft copolymer is such that the (meth) acrylic part has high affinity with the toner particles, and the polysiloxane part has affinity with the insulating liquid. It will be expensive. Further, since the acrylic-polysiloxane graft copolymer is present between the toner particles and the insulating liquid, the dispersion stability of the toner particles in the insulating liquid is excellent.

The monomer component constituting the acrylic polymer is not particularly limited, and examples thereof include acrylic acid, methacrylic acid; acrylic acid or methacrylic acid derivatives such as alkyl acrylate, alkyl methacrylate, etc. Among these, 1 Species or a combination of two or more can be used.
Moreover, as an acrylic polymer comprised by the monomer component mentioned above, it is 1 or more types of monomers chosen from acrylic acid, methacrylic acid, or those alkylesters, Comprising: Carbon number of the alkyl group is 4 Examples thereof include polymers composed of the following monomers (acrylates).
The acrylic-polysiloxane graft copolymer may include a plurality of types of acrylic polymers.

The acrylic polymer constituting the acrylic-polysiloxane graft copolymer is preferably acrylates and alkyl acrylates, more preferably acrylates and ethylhexyl acrylate. As a result, the effects of the acrylic-polysiloxane graft copolymer as described above can be obtained more remarkably, and the dispersion stability of the toner particles in the liquid developer can be made particularly excellent.
In addition, the acrylic polymer may include a monomer component other than the above.

  Further, the polysiloxane constituting the acrylic-polysiloxane graft copolymer is not particularly limited, and examples thereof include dialkylpolysiloxanes such as dimethylpolysiloxane, diarylpolysiloxanes such as diphenylpolysiloxane, and the like. One kind or a combination of two or more kinds can be used. Among the above, the polysiloxane preferably contains a dialkylsiloxane, more preferably dimethylpolysiloxane. As a result, the effects of the acrylic-polysiloxane graft copolymer as described above can be obtained more remarkably, and the dispersion stability of the toner particles in the liquid developer can be made particularly excellent.

The side chain or terminal of the polysiloxane constituting the acrylic-polysiloxane graft copolymer may be substituted with another functional group or the like. For example, acrylic acid or methacrylic acid may be added to the side chain or terminal of polysiloxane. In this case, the dispersion stability of the toner particles in the liquid developer can be made particularly excellent.
The polysiloxane may be linear or branched.

The acrylic-polysiloxane graft copolymer is obtained by graft polymerization of an acrylic polymer and polysiloxane. As a result, the acrylic-polysiloxane graft copolymer has many branched chains and is bulky. As a result, a portion having a relatively large polarity (acrylic polymer portion) and a portion having a relatively small polarity (polysiloxane portion) can sufficiently exhibit their functions.
More specifically, examples of the acrylic-polysiloxane graft copolymer as described above include KP-541, KP-575, KP-543, KP-545, KP-549, and the like. One or a combination of two or more can be used.

  The acrylic-polysiloxane graft copolymer is preferably contained in an amount of 1 to 40 parts by weight, preferably 1 to 20 parts by weight, based on 100 parts by weight of the toner base particles. More preferred. Thereby, the effect of the acrylic-polysiloxane graft copolymer can be sufficiently obtained, and the viscosity of the liquid developer can be made appropriate.

Moreover, as a dispersing agent, an amino modified silicone and a silicone resin can be used, for example.
Specific examples of the amino-modified silicone include a compound represented by the following general formula (1) having an amino group in the side chain of the polysiloxane, and a general formula (2) having an amino group at one end of the polysiloxane. A compound represented by the following general formula (3) having amino groups at both ends of the polysiloxane, and a general formula (4) having amino groups at both the side chain and both ends of the polysiloxane. And at least one compound selected from the group consisting of the represented compounds.

In the general formula (1), R1 to R9 each independently represent an alkyl group having 1 to 3 carbon atoms, m represents an integer of 1 to 40, and n represents an integer of 1 to 40. .
In the general formula (2), R10 to R16 each independently represents an alkyl group having 1 to 3 carbon atoms, and n represents an integer of 1 to 40.
Moreover, in said general formula (3), R17-R22 represents a C1-C3 alkyl group each independently, n shows the integer of 1-40.
In the general formula (4), R23 to R29 each independently represents an alkyl group having 1 to 3 carbon atoms, m represents an integer of 1 to 40, and n represents an integer of 1 to 40. Show.

  Among these compounds, when having an amino group at the terminal as in the general formula (2) or the general formula (3) due to a large amount of amino group in 1 mol of amino-modified silicone, etc. In the formula, the number of amino groups in one molecule is 1 to 2 regardless of the number of n, but when having an amino group in the side chain as in the general formula (1) or (4) In the formula, there are as many amino groups as n in the formula, and the change in the charging characteristics of the dispersed particles is efficiently suppressed. Therefore, it is preferable to use a side chain type amino-modified silicone oil having an amino group in the side chain as represented by the general formula (1) or the general formula (4).

  Specific examples of the above-mentioned amino-modified silicone include XF42-B8922, XF42-B1989, XF42-C0330, etc. (above Momentive Performance Materials Japan GK), FZ3785, BY16-205 (above Toray Dow Corning). Co., Ltd.) can be used, and among these, one or more can be used in combination.

  A silicone resin is a three-dimensional polymer obtained by co-hydrolysis of an organosilane compound and a subsequent condensation reaction. Regarding the production method and properties of the silicone resin, and the curing method of the resin and the physical properties of the cured product, There are many findings (Kunio Ito, Silicon Handbook P.468, Nikkan Kogyo Shimbun; Chemistry and Technology of Silicones, 2nd edition, P.409, Walter Noll Academic Press, Inc. (London) Ltd. 1968).

  The silicone resin is trifunctional (a silane compound having three hydrolyzable functional groups gives a siloxane unit called T unit) and bifunctional (also has two hydrolyzable functional groups). A silane compound gives a siloxane unit called D unit.) It is made by cohydrolysis of a hydrolyzable silane compound (so-called DT resin), and by hydrolysis of a trifunctional hydrolyzable silane compound. What is made (so-called polysilsesquioxane), monofunctional (also a silane compound having one hydrolyzable functional group to give a siloxane unit called M unit, see Table 1) and silicon tetrachloride All functional groups are made by co-hydrolysis of silane compounds that are hydrolyzable (4 functionalities = Q units are given, see Table 1) (so-called MQ resin) The or, and mixtures thereof. The M unit means -OSiR3, the D unit means (-O) 2SiR2, the T unit: (-O) 3SiRSi, and the Q unit: (O-) 4.

Specifically, TSF4600 (Momentive Performance Materials Japan GK), DC593 (Toray Dow Corning Co., Ltd.), etc. are mentioned, Among these, it can use 1 type or in combination of 2 or more types. .
In addition, in this process, you may add components (for example, external additive etc.) other than the component mentioned above.

<Heating process>
Next, the dispersion obtained in the above step is heated at a predetermined temperature as described above (heating step). By heating, the charge control agent contained in the resin fine particles oozes out to the surface, and the resin fine particles become toner particles, which are excellent in positive charging characteristics.
Such heating is preferably performed while stirring the dispersion. By performing the heat treatment while stirring, that is, by heating the fine particles while applying a shearing force, it is possible to more effectively prevent the toner particles from being aggregated by heating.

  In the present invention, when the predetermined temperature in the heating step is T [° C.], the glass transition point of the polyester resin is Tg (p) [° C.], and the melting point of the charge control agent is Tm (e) [° C.], Tm (E) Although the relationship of <T ≦ Tg (p) +10 is satisfied, it is more preferable that Tm (e) +5 <T ≦ Tg (p). As a result, the charge control agent can be oozed out more reliably on the toner particle surface while preventing the toner particles from aggregating, and the toner particles can be more effectively positively charged.

Note that the toner particle content in the finally obtained liquid developer is preferably 10 wt% or more and 60 wt% or less, and more preferably 20 wt% or more and 50 wt% or less.
In the above description, the wet pulverization step is performed after the coarse pulverization step. However, the present invention is not limited to this. For example, a resin material added with a basic compound is directly added to the insulating liquid. The liquid developer may be produced by wet pulverization.
In the above description, the kneaded material is roughly pulverized. However, the present invention is not limited to this, and the kneaded material may not be used.

≪Liquid developer≫
The liquid developer of the present invention is a liquid developer containing an insulating liquid and toner particles, and is produced by the production method as described above. Thereby, it is possible to provide a liquid developer which is excellent in positive charging characteristics and excellent in dispersibility of toner particles.
The content of the toner particles in the liquid developer is preferably 10 wt% or more and 60 wt% or less, and more preferably 20 wt% or more and 50 wt% or less.
The volume average particle diameter (D50) of the toner particles constituting the liquid developer is preferably 2 μm or more and 4 μm or less.

  In the present specification, the volume average particle diameter (D50) means “sphere-converted 50% average particle diameter (D50) by light scattering method” and is a value obtained as follows. That is, the particles in the dispersion medium are irradiated with light, and the generated diffracted scattered light is measured by detectors arranged in front, side, and rear of the dispersion medium. Using the measured value, assuming that the particles that are originally indefinite are spherical, a cumulative curve is obtained by setting the total volume of the particle population converted to a sphere equal to the volume of the particles as 100%, The point at which the cumulative value becomes 50% is defined as the volume average particle size. Examples of the measuring apparatus include a laser diffraction / scattering particle size analyzer Microtrac MT-3000 (manufactured by Nikkiso Co., Ltd.). In addition, the volume average particle diameter (D50) in the below-mentioned Example is the value measured by the said microtrack MT-3000.

  Further, the liquid developer may contain components other than those described above. Examples of such components include known waxes, magnetic particles, zinc stearate, zinc oxide, cerium oxide, silica, titanium oxide, iron oxide, fatty acids, fatty acid metal salts, dispersants, external additives, and known oxidation agents. An inhibitor etc. are mentioned. Such a component may be used in any step of the production method described above. That is, such a component may be included in, for example, particles that are subjected to a pulverization process, or may be added during the pulverization process, the heating process, or the mixing process. Also good.

≪Image forming device≫
Next, a preferred embodiment of an image forming apparatus to which the liquid developer of the present invention is applied will be described.
FIG. 1 is a schematic view showing a preferred example of an image forming apparatus to which the liquid developer of the present invention is applied, and FIG. 2 is an enlarged view of a part of the image forming apparatus shown in FIG.

As shown in FIGS. 1 and 2, the image forming apparatus 1000 includes four developing units 30Y, 30M, 30C, and 30K, a transfer unit (intermediate transfer unit 40 and a secondary transfer unit (secondary transfer unit) 60), and , A fixing unit (fixing device) F40 and four liquid developer replenishing units 90Y, 90M, 90C, and 90K.
The developing units 30Y, 30M, and 30C develop a latent image with a yellow liquid developer (Y), a magenta liquid developer (M), and a cyan liquid developer (C), respectively, and correspond to each color. It has a function of forming a single color image. The developing unit 30K has a function of developing a latent image with a black liquid developer (K) to form a black single color image.

Since the developing units 30Y, 30M, 30C, and 30K have the same configuration, the developing unit 30Y will be described below.
As shown in FIG. 2, the developing unit 30Y includes a photoconductor 10Y as an example of an image carrier, a charging roller 11Y, an exposure unit 12Y, a development unit 100Y, and a photoconductor along the rotation direction of the photoconductor 10Y. It includes a body squeeze device 101Y, a primary transfer backup roller 51Y, a charge removal unit 16Y, a photoreceptor cleaning blade 17Y, and a developer recovery unit 18Y.

The photoreceptor 10Y is formed on a cylindrical base material and an outer peripheral surface thereof, has a photosensitive layer made of a material such as amorphous silicon, and is rotatable about a central axis. Rotate clockwise as indicated by the arrow in FIG.
The photoreceptor 10Y is supplied with a liquid developer by a developing unit 100Y described later, and a layer of the liquid developer is formed on the surface.

The charging roller 11Y is a device for charging the photoconductor 10Y, and the exposure unit 12Y is a device for forming a latent image on the photoconductor 10Y charged by irradiating a laser. The exposure unit 12Y includes a semiconductor laser, a polygon mirror, an F-θ lens, and the like, and charges a modulated laser based on an image signal input from a host computer (not shown) such as a personal computer or a word processor. Irradiate onto the photoconductor 10Y.
The developing unit 100Y is a device for developing the latent image formed on the photoreceptor 10Y using the liquid developer of the present invention. Details of the developing unit 100Y will be described later.

  The photoconductor squeeze device 101Y is disposed on the downstream side in the rotation direction from the developing unit 100Y so as to face the photoconductor 10Y. The photoconductor squeeze roller 13Y and the photoconductor squeeze roller 13Y are pressed and slidably attached to the surface. The cleaning blade 14Y removes the liquid developer and the developer collection unit 15Y that collects the removed liquid developer. The photoreceptor squeeze device 101Y has a function of collecting excess carrier (insulating liquid) and originally unnecessary fog toner from the developer developed on the photoreceptor 10Y, and increasing the ratio of toner particles in the visible image.

The primary transfer backup roller 51Y is a device for transferring a single color image formed on the photoreceptor 10Y to an intermediate transfer unit 40 described later.
The neutralization unit 16Y is a device that removes residual charges on the photoreceptor 10Y after the intermediate transfer image is transferred onto the intermediate transfer unit 40 by the primary transfer backup roller 51Y.
The photoconductor cleaning blade 17Y is a rubber member that is in contact with the surface of the photoconductor 10Y, and remains on the photoconductor 10Y after the image is transferred onto the intermediate transfer portion 40 by the primary transfer backup roller 51Y. It has a function of scraping off and removing the liquid developer.

The developer recovery unit 18Y has a function of recovering the liquid developer removed by the photoconductor cleaning blade 17Y.
The intermediate transfer unit 40 is an endless elastic belt member, and is stretched around a belt driving roller 41 and a pair of driven rollers 44 and 45 to which a driving force of a motor (not shown) is transmitted. The intermediate transfer unit 40 is driven to rotate counterclockwise by the belt driving roller 41 while being in contact with the photoreceptors 10Y, 10M, 10C, and 10K by the primary transfer backup rollers 51Y, 51M, 51C, and 51K.

Further, the intermediate transfer unit 40 is applied with a predetermined tension by a tension roller 49 so that slack is removed. The tension roller 49 is disposed downstream of one driven roller 44 in the rotation (movement) direction of the intermediate transfer unit 40 and upstream of the other driven roller 45 in the rotation (movement) direction of the intermediate transfer unit 40. .
A single color image corresponding to each color formed by the developing units 30Y, 30M, 30C, and 30K is sequentially transferred to the intermediate transfer unit 40 by the primary transfer backup rollers 51Y, 51M, 51C, and 51K, and a single color corresponding to each color is transferred. The images are superimposed. As a result, a full-color developer image (intermediate transfer image) is formed on the intermediate transfer portion 40.

  In the intermediate transfer unit 40, the single-color images formed on the plurality of photoconductors 10Y, 10M, 10C, and 10K are secondarily transferred and superposed one after another. Secondary transfer is performed on a recording medium F5 such as paper, film, or cloth. Therefore, when the toner image is transferred to the recording medium F5 in the secondary transfer process, even if the surface of the recording medium F5 is a non-smooth sheet material due to fiber or the like, the secondary transfer characteristics follow the non-smooth sheet surface. An elastic belt member is employed as means for improving the above.

The intermediate transfer unit 40 is provided with a cleaning device including an intermediate transfer unit cleaning blade 46, a developer recovery unit 47, and a non-contact type bias applying member 48.
The intermediate transfer unit cleaning blade 46 and the developer recovery unit 47 are arranged on the driven roller 45 side.
The intermediate transfer unit cleaning blade 46 scrapes and removes the liquid developer adhering to the intermediate transfer unit 40 after the toner image is transferred onto the recording medium F5 by the secondary transfer unit (secondary transfer unit) 60. It has a function.
The developer recovery unit 47 has a function of recovering the liquid developer removed by the intermediate transfer unit cleaning blade 46.

  The non-contact type bias applying member 48 is disposed away from the intermediate transfer unit 40 at a position facing the tension roller 49. The non-contact type bias applying member 48 applies a bias voltage having a polarity opposite to that of the toner to the liquid developer toner (solid content) remaining on the intermediate transfer portion 40 after the secondary transfer. As a result, the toner is discharged, and the electrostatic adhesion force of the toner to the intermediate transfer unit 40 is reduced. In this example, a corona charger is used as the non-contact type bias applying member 48.

  The non-contact type bias applying member 48 is not necessarily disposed at a position facing the tension roller 49. For example, a position between the driven roller 44 and the tension roller 49, such as a position between the driven roller 44 and the intermediate transfer unit. It can be disposed at any position downstream in the movement direction and upstream of the driven roller 45 in the movement direction of the intermediate transfer unit. The non-contact type bias applying member 48 may be a known non-contact type charger other than the corona charger.

An intermediate transfer unit squeeze device 52Y is disposed downstream of the primary transfer backup roller 51Y in the moving direction of the intermediate transfer unit 40.
The intermediate transfer unit squeeze device 52Y is provided as a means for removing excess insulating liquid from the transferred liquid developer when the liquid developer transferred onto the intermediate transfer unit 40 has not reached the desired dispersion state. ing.

The intermediate transfer unit squeeze device 52Y is removed by the intermediate transfer unit squeeze roller 53Y, the intermediate transfer unit squeeze cleaning blade 55Y that presses and slides against the intermediate transfer unit squeeze roller 53Y, and the intermediate transfer unit squeeze cleaning blade 55Y. The developer collecting section 56Y collects the liquid developer.
The intermediate transfer unit squeeze device 52Y has a function of recovering excess insulating liquid from the developer primarily transferred to the intermediate transfer unit 40, increasing the toner particle ratio in the image, and recovering originally unwanted toner. Have.

  The secondary transfer unit 60 includes a pair of secondary transfer rollers that are spaced apart from each other by a predetermined distance along the transfer material movement direction. Of these pair of secondary transfer rollers, the secondary transfer roller disposed on the upstream side in the moving direction of the intermediate transfer unit 40 is the upstream secondary transfer roller 64. The upstream secondary transfer roller 64 can be pressed against the belt drive roller 41 via the intermediate transfer unit 40.

Of the pair of secondary transfer rollers, the secondary transfer roller disposed on the downstream side in the moving direction of the transfer material is the downstream secondary transfer roller 65. The downstream secondary transfer roller 65 can be brought into pressure contact with the driven roller 44 via the intermediate transfer unit 40.
That is, the upstream side secondary transfer roller 64 and the downstream side secondary transfer roller 65 bring the recording medium F5 into contact with the intermediate transfer unit 40 that is hung on the belt driving roller 41 and the driven roller 44, respectively. The intermediate transfer image formed by superimposing colors on 40 is secondarily transferred to the recording medium F5.

  In this case, the belt driving roller 41 and the driven roller 44 also function as backup rollers for the upstream side secondary transfer roller 64 and the downstream side secondary transfer roller 65, respectively. That is, the belt drive roller 41 is also used as an upstream backup roller disposed in the secondary transfer unit 60 on the upstream side of the driven roller 44 in the moving direction of the recording medium F5. The driven roller 44 is also used as a downstream backup roller disposed in the secondary transfer unit 60 on the downstream side in the moving direction of the recording medium F5 from the belt driving roller 41.

  Therefore, the recording medium F5 conveyed to the secondary transfer unit 60 is moved from the pressure contact start position (nip start position) between the upstream secondary transfer roller 64 and the belt drive roller 41 to the downstream secondary transfer roller 65 and the driven roller. In close contact with the intermediate transfer portion 40 in a predetermined movement region of the transfer material up to the press-contact end position (nip end position) with 44. As a result, the full-color intermediate transfer image on the intermediate transfer unit 40 is secondarily transferred to the recording medium F5 in close contact with the intermediate transfer unit 40 over a predetermined time, so that good secondary transfer is performed.

  The secondary transfer unit 60 includes a secondary transfer roller cleaning blade 66 and a developer recovery unit 67 with respect to the upstream side secondary transfer roller 64. The secondary transfer unit 60 includes a secondary transfer roller cleaning blade 68 and a developer recovery unit 69 with respect to the downstream side secondary transfer roller 65. The secondary transfer roller cleaning blades 66 and 68 are in contact with the secondary transfer rollers 64 and 65, respectively, and scrape and remove the liquid developer remaining on the surfaces of the secondary transfer rollers 64 and 65 after the secondary transfer. To do. Further, the developer collecting units 67 and 69 collect and store the liquid developer scraped off from the secondary transfer rollers 64 and 65 by the secondary transfer roller cleaning blades 66 and 68, respectively.

The toner image (transfer image) transferred onto the recording medium F5 by the secondary transfer unit 60 is sent to a fixing unit (fixing device) F40, and is heated and pressurized to be fixed on the recording medium F5.
Specifically, the fixing temperature (set temperature) is preferably 80 ° C. or higher and 160 ° C. or lower, more preferably 100 ° C. or higher and 150 ° C. or lower, and 100 ° C. or higher and 140 ° C. or lower. Further preferred.

Next, the developing units 100Y, 100M, 100C, and 100K will be described in detail. In the following description, the developing unit 100Y will be typically described.
As shown in FIG. 2, the developing unit 100Y includes a liquid developer storage unit 31Y, a coating roller 32Y, a regulating blade 33Y, a developer stirring roller 34Y, a communication unit 35Y, a recovery screw 36Y, and a developing roller 20Y. And a developing roller cleaning blade 21Y.

The liquid developer storage unit 31Y has a function of storing a liquid developer for developing the latent image formed on the photoreceptor 10Y. The supply unit 31aY supplies the liquid developer to the development unit, and the supply unit A recovery unit 31bY that recovers excess liquid developer generated at 31aY and the like, and a partition 31cY that partitions the supply unit 31aY and the recovery unit 31bY are provided.
The supply unit 31aY has a function of supplying the liquid developer to the application roller 32Y, and has a concave portion in which the developer stirring roller 34Y is installed. Further, the liquid developer is supplied from the liquid developer mixing tank 93Y to the supply unit 31aY through the communication unit 35Y.

The collection unit 31bY collects the liquid developer that is excessively supplied to the supply unit 31aY and excess liquid developer generated in the developer collection units 15Y and 24Y. The collected liquid developer is conveyed to a liquid developer mixing tank 93Y described later and reused. The recovery unit 31bY has a concave portion, and a recovery screw 36Y is installed near the bottom.
A wall-shaped partition 31cY is provided at the boundary between the supply unit 31aY and the recovery unit 31bY. The partition 31cY partitions the supply unit 31aY and the recovery unit 31bY and can prevent the recovered liquid developer from being mixed into the fresh liquid developer. Further, when an excessive liquid developer is supplied to the supply unit 31aY, the excess liquid developer can overflow from the supply unit 31aY to the recovery unit 31bY beyond the partition 31cY. For this reason, the amount of the liquid developer in the supply unit 31aY can be kept constant, and the amount of the liquid developer supplied to the application roller 32Y can be kept constant. For this reason, the image quality of the finally formed image becomes stable.

Further, the partition 31cY is provided with a notch, and the liquid developer can overflow from the supply part 31aY to the recovery part 31bY through the notch.
The coating roller 32Y has a function of supplying a liquid developer to the developing roller 20Y.
This application roller 32Y is a so-called anilox roller in which grooves are uniformly and spirally formed on the surface of a metallic roller such as iron and nickel-plated, and its diameter is about 25 mm. . In the present embodiment, a plurality of grooves are formed obliquely with respect to the rotation direction of the application roller 32Y by so-called cutting or rolling. The application roller 32Y contacts the liquid developer while rotating counterclockwise, thereby supporting the liquid developer in the supply unit 31aY in the groove and transporting the supported liquid developer to the development roller 20Y. To do.

  The regulating blade 33Y contacts the surface of the coating roller 32Y and regulates the amount of liquid developer on the coating roller 32Y. That is, the regulation blade 33Y plays a role of scraping off excess liquid developer on the application roller 32Y and measuring the liquid developer on the application roller 32Y supplied to the development roller 20Y. The restriction blade 33Y is made of urethane rubber as an elastic body, and is supported by a restriction blade support member made of metal such as iron. The regulating blade 33Y is provided on the side where the application roller 32Y rotates and advances from the liquid developer (that is, the right side in FIG. 2). The rubber hardness of the regulating blade 33Y is about 77 degrees according to JIS-A, and the hardness (about 77 degrees) of the contact portion of the regulating blade 33Y with the surface of the application roller 32Y is about the elasticity of the developing roller 20Y described later. It is lower than the hardness (about 85 degrees) of the press contact portion of the body layer to the surface of the application roller 32Y. Further, the excess liquid developer scraped off is collected in the supply unit 31aY and reused.

The developer stirring roller 34Y has a function of stirring the liquid developer in a uniformly dispersed state. Thus, even when a plurality of toner particles are aggregated, the toner particles can be suitably dispersed.
In the supply unit 31aY, the toner particles in the liquid developer have a positive charge, and the liquid developer is stirred by the developer stirring roller 34Y to be in a uniformly dispersed state, and the coating roller 32Y rotates. Thus, the liquid developer is stored in the liquid developer storage unit 31Y, and the amount of the liquid developer is regulated by the regulating blade 33Y and supplied to the developing roller 20Y. In addition, by being stirred by the developer stirring roller 34Y, the liquid developer can be stably overflowed to the collection unit 31bY side beyond the partition 31cY, and the liquid developer can be prevented from staying and being compressed. it can.

  Further, the developer stirring roller 34Y is provided in the vicinity of the communication portion 35Y. For this reason, the liquid developer supplied from the communication unit 35Y can quickly diffuse, and even when the liquid developer is supplied to the supply unit 31aY, the liquid level of the supply unit 31aY is stabilized. can do. By providing such a developer agitation roller 34Y in the vicinity of the communication portion 35Y, the communication portion 35Y has a negative pressure, and the liquid developer can be sucked up naturally.

The communication unit 35Y is provided in the vertical direction below the developer stirring roller 34Y, communicates with the liquid developer storage unit 31Y, and sucks the liquid developer from the liquid developer mixing tank 93Y to the supply unit 31aY.
By providing the communication portion 35Y below the developer stirring roller 34Y, the liquid developer supplied from the communication portion 35Y is stopped by the developer stirring roller 34Y, and the liquid top surface does not rise due to blowing, and the liquid The upper surface is held substantially constant, and the developer can be stably supplied to the coating roller 32Y.

The recovery screw 36Y provided in the vicinity of the bottom of the recovery unit 31bY is made of a cylindrical member, has a spiral rib on the outer periphery, and has a function of maintaining the fluidity of the recovered liquid developer. It has a function of promoting the conveyance of the developer to the liquid developer mixing tank 93Y.
The developing roller 20Y carries the liquid developer and conveys it to the developing position facing the photoconductor 10Y in order to develop the latent image carried on the photoconductor 10Y with the liquid developer.

The developing roller 20Y forms a liquid developer layer on its surface by supplying the liquid developer from the coating roller 32Y described above.
The developing roller 20Y includes a conductive elastic layer on the outer peripheral portion of an inner core made of metal such as iron, and has a diameter of about 20 mm. The elastic body layer has a two-layer structure. As the inner layer, urethane rubber having a rubber hardness of about 30 degrees JIS-A and a thickness of about 5 mm is used, and as the surface layer (outer layer), the rubber hardness is JIS. A urethane rubber having a thickness of about 30 μm at about 85 ° A is provided. The developing roller 20Y is in pressure contact with the coating roller 32Y and the photoreceptor 10Y in a state of being elastically deformed with the surface layer serving as a pressure contact portion.

  Further, the developing roller 20Y can rotate around its central axis, and the central axis is below the rotational central axis of the photoconductor 10Y. Further, the developing roller 20Y rotates in a direction (counterclockwise in FIG. 2) opposite to the rotation direction of the photoreceptor 10Y (clockwise in FIG. 2). When developing the latent image formed on the photoconductor 10Y, an electric field is formed between the developing roller 20Y and the photoconductor 10Y.

In the developing unit 100Y, the coating roller 32Y and the developing roller 20Y are separately driven by different power sources (not shown). And the quantity of the liquid developer supplied on the developing roller 20Y can be adjusted by changing the rotation speed (linear speed) ratio with the application roller 32Y and the developing roller 20Y.
The developing unit 100Y includes a rubber developing roller cleaning blade 21Y that is in contact with the surface of the developing roller 20Y, and a developer recovery unit 24Y. The developing roller cleaning blade 21Y is a device for scraping off and removing the liquid developer remaining on the developing roller 20Y after development is performed at the developing position. The liquid developer removed by the developing roller cleaning blade 21Y is collected in the developer collecting unit 24Y.

  As shown in FIGS. 1 and 2, the image forming apparatus 1000 includes liquid developer replenishing units 90Y, 90M, 90C, and 90K that replenish liquid developer to the developing units 30Y, 30M, 30C, and 30K. . These liquid developer replenishers 90Y, 90M, 90C, and 90K are respectively provided with liquid developer tanks 91Y, 91M, 91C, and 91K, insulating liquid tanks 92Y, 92M, 92C, and 92K, and a liquid developer mixing tank 93Y. , 93M, 93C, 93K.

  Each of the liquid developer tanks 91Y, 91M, 91C, and 91K stores a high concentration liquid developer corresponding to each color. Insulating liquid tanks 92Y, 92M, 92C, and 92K contain insulating liquids, respectively. Further, in each liquid developer mixing tank 93Y, 93M, 93C, 93K, a predetermined amount of each high-concentration liquid developer from each liquid developer tank 91Y, 91M, 91C, 91K, and each insulating liquid tank 92Y, A predetermined amount of each insulating liquid from 92M, 92C, and 92K is supplied.

  The liquid developer mixing tanks 93Y, 93M, 93C, and 93K are respectively mixed and stirred by the stirrers provided with the supplied high-concentration liquid developer and the insulating liquid, respectively, and the supply units 31aY. , 31aM, 31aC, and 31aK, a liquid developer corresponding to each color is prepared. The liquid developers prepared in the liquid developer mixing tanks 93Y, 93M, 93C, and 93K are supplied to the supply units 31aY, 31aM, 31aC, and 31aK, respectively.

Further, the liquid developer recovered by the recovery unit 31bY is recovered and reused in the liquid developer mixing tank 93Y. The same applies to the liquid developer mixing tanks 93M, 93C, and 93K.
In the image formation using the above apparatus, a plurality of single color images corresponding to the respective colors are applied to the photoreceptors 10Y, 10M, 10C, and 10K using a plurality of liquid developers having different colors (the liquid developer of the present invention). And a transfer step of transferring a plurality of single color images formed on the photosensitive member to the recording medium F5 and forming an unfixed toner image formed by superimposing the plurality of single color images on the recording medium F5. And a fixing step of fixing an unfixed toner image on the recording medium F5. By using such a method, an image excellent in color developability can be easily formed.

As mentioned above, although this invention was demonstrated based on suitable embodiment, this invention is not limited to these.
For example, the liquid developer of the present invention is not limited to that applied to the image forming apparatus as described above.
In the above-described embodiment, the configuration having the corona discharger as the image forming apparatus has been described. However, the corona discharger may be omitted.

[1] Production of Liquid Developer A liquid developer was produced as follows. About the process in which temperature is not described, it performed at room temperature (25 degreeC).
Example 1
[Kneading process, coarse pulverization process]
(Preparation of colorant masterbatch)
First, a polyester resin (glass transition point (Tg (p)): 60 ° C.): 60 parts by weight was prepared as a resin material.

Next, a mixture (mass ratio 50:50) of the resin material and a cyan pigment as a colorant (manufactured by Dainichi Seika Co., Ltd., Pigment Blue 15: 3) was prepared. These components were mixed using a 20 L type Henschel mixer to obtain a raw material for toner production.
Next, this raw material (mixture) was kneaded using a twin-screw kneading extruder. The kneaded product extruded from the extrusion port of the biaxial kneading extruder was cooled.
The kneaded material cooled as described above was coarsely pulverized to obtain a colorant master batch having an average particle size of 1.0 mm or less. A hammer mill was used for coarse pulverization of the kneaded product.

(Preparation of coarsely pulverized product)
Colorant master batch: 12 parts by weight, polyester resin: 68 parts by weight, α-olefin-vinylpyrrolidone copolymer as charge control agent A (PVP copolymer V220F, manufactured by ISP, melting point (Tm (e): 40 ° C)): 20 parts by weight were kneaded using a twin-screw kneading extruder. And the kneaded material extruded from the extrusion port of the biaxial kneading extruder was cooled. The obtained kneaded product was pulverized with a hammer mill to obtain a coarsely pulverized product.

[Wet grinding process]
Coarse pulverized product obtained by the above method: 20 parts by weight, acrylic-polysiloxane graft copolymer solution as a dispersant (KP-545, manufactured by Shin-Etsu Chemical Co., Ltd., copolymer component: alkyl acrylate / dimethyl poly Siloxane, solvent: decamethylcyclopentanesiloxane, solid content: 30 wt%): 5 parts by weight, dimethyl silicone oil as an insulating liquid (KF-96, manufactured by Shin-Etsu Chemical Co., Ltd., 50 cs): 75 parts by weight of ceramic pot (Inner volume: 600 ml), zirconia balls (ball diameter: 10 mm) were further placed in a ceramic pot so that the volume filling rate was 40%, and wet pulverization was performed in a tabletop pot mill at a rotational speed of 230 rpm for 48 hours. As a result, a dispersion in which the resin fine particles were dispersed in the insulating liquid was obtained.

[Heating process]
The obtained dispersion was put into a 500 ml flask, stirred while keeping the temperature of the oil bath at 60 ° C., and subjected to heat treatment (distillation under reduced pressure) for 30 minutes. Thereby, the water | moisture content in a dispersion was removed and the liquid developer was obtained.
The Dv (50) of the toner particles in the obtained liquid developer was 2.4 μm. The 50% volume particle diameter Dv (50) [μm] of the obtained toner particles was measured with Microtrac MT-3000 (manufactured by Nikkiso Co., Ltd.). Moreover, the particle diameter was similarly calculated | required about the particle | grains obtained by each Example and each comparative example demonstrated below.

  Further, the viscosity of the obtained liquid developer at 25 ° C. was 200 mPa · s. The viscosity of the obtained toner was measured with an E-type viscometer TVE-22 (manufactured by Toki Sangyo Co., Ltd.), and the dispersibility was evaluated according to the following criteria based on the magnitude of the viscosity. The shear rate during measurement was 1 (1 / s). Moreover, the viscosity was calculated | required similarly about the viscosity obtained by each Example and each comparative example demonstrated below.

(Example 2)
A liquid developer was produced in the same manner as in Example 1 except that the type of charge control agent, the content in the toner particles, the heating temperature and the like were changed as shown in Table 1.
(Comparative Examples 1 and 2)
A liquid developer was produced in the same manner as in Example 1 except that the type of charge control agent, the content in the toner particles, the heating temperature and the like were changed as shown in Table 1.

(Comparative Example 3)
A liquid developer corresponding to each color was produced in the same manner as in Example 1 except that no charge control agent was added.
As a result of analyzing the supernatant obtained by centrifuging the liquid developer of each example, it was confirmed that the dispersant was adsorbed on the surface of the toner base particles.

  For each of the above Examples and Comparative Examples, the content of the resin and the colorant in the toner base particles, the type of the charge control agent A and the content of the charge control agent A in the toner base particles, the dispersion in the liquid developer Table 1 shows the production conditions such as the content of the agent, the type of the charge control agent B, and the content of the charge control agent B in the liquid developer. In the table, α-olefin / vinylpyrrolidone copolymer as charge control agent A is “V220F”, polyvinylpyrrolidone (melting point: 50 ° C.) is “PVP50”, α-olefin / vinylpyrrolidone copolymer (PVP). Copolymer W660, manufactured by ISP, melting point (Tm (e): 63 ° C.) was indicated as “W660”. The glass transition point and melting point were measured using a differential scanning calorimeter DSC-220C (manufactured by Seiko Instruments Inc.).

[2] Evaluation Each liquid developer obtained as described above was evaluated as follows.
[2.1] Charging evaluation [2.1.1] Development efficiency Using the image forming apparatus as shown in FIG. 1 and FIG. 2, obtained in each of the above examples and comparative examples on the developing roller of the image forming apparatus. A liquid developer layer was formed from the obtained liquid developer. Next, the surface potential of the developing roller was set to 300V, the surface potential of the photoconductor was uniformly charged at 500V, the photoconductor was exposed, the charge on the surface of the photoconductor was attenuated, and the surface potential was set to 50V. The toner particles on the developing roller and the toner particles on the photosensitive member after the liquid developer layer passed between the photosensitive member and the developing roller were collected with a tape. Each tape used for sampling was affixed on a recording paper, and the concentration of each toner particle was measured. After the measurement, the value obtained by dividing the concentration of toner particles collected on the photoreceptor by the sum of the concentration of toner particles collected on the photoreceptor and the concentration of toner particles collected on the developing roller is multiplied by 100. Was determined as development efficiency, and evaluated according to the following four-stage criteria.
A: The development efficiency is 96% or more, and the development efficiency is particularly excellent.
B: The development efficiency is 90% or more and less than 96%, and the development efficiency is excellent.
C: The development efficiency is 80% or more and less than 90%, and there is no practical problem.
D: The development efficiency is less than 80% and the development efficiency is inferior.

[2.1.2] Transfer Efficiency Using an image forming apparatus as shown in FIGS. 1 and 2, a liquid developer obtained in each of the above-described embodiments and comparative examples is formed on the photoreceptor of the image forming apparatus. A developer layer was formed. Next, the toner particles on the photoconductor and the toner particles on the intermediate transfer portion after the liquid developer layer passed between the photoconductor and the intermediate transfer portion were collected with a tape. Each tape used for sampling was affixed on a recording paper, and the concentration of each toner particle was measured. After the measurement, a value obtained by dividing the concentration of the toner particles collected on the intermediate transfer portion by the sum of the concentration of the toner particles collected on the photoconductor and the concentration of the toner particles collected on the intermediate transfer portion is 100. A value obtained by multiplying by is obtained as transfer efficiency, and evaluated according to the following four criteria.
A: The transfer efficiency is 96% or more, and the transfer efficiency is particularly excellent.
B: The transfer efficiency is 90% or more and less than 96%, and the transfer efficiency is excellent.
C: The transfer efficiency is 80% or more and less than 90%, and there is no practical problem.
D: Transfer efficiency is less than 80% and inferior to transfer efficiency.

[2.2] Dispersion stability test The liquid developers obtained in the above Examples and Comparative Examples were subjected to viscosity measurement by the above-described viscosity measurement method, and the dispersibility was evaluated according to the following criteria.
A: 1 [mPa. s] or more and 300 [mPa.s] s] or less B: 300 [mPa.s] s] and 1000 [mPa.s]. s] or less C: 1000 [mPa.s] s] and greater than 3000 [mPa.s]. s] or less D: 3000 [mPa.s] greater than s]

[2.3] Environmental Stability The liquid developers obtained in the above Examples and Comparative Examples were left for 1 month in an environment of 40 ° C. and a relative humidity of 60%. Thereafter, the state of the liquid developer was observed, and changes in the viscosity, color, acid value, and electrical resistance value before and after being allowed to stand were evaluated according to the following five criteria. The acid value was measured according to JIS K2501. The change in color of the liquid developer was evaluated visually. The viscosity was measured according to JIS Z8809 using a vibration viscometer. In addition, the electric resistance value was measured using a universal electrometer MMAII-17B, a liquid electrode LP-05, and a shield box P-618 (manufactured by Kawaguchi Denki Seisakusho).

A: No change in viscosity / color / acid value / electric resistance value of the liquid developer is observed.
B: Almost no change in viscosity / color / acid value / electric resistance value of the liquid developer is observed.
C: Although the change of the viscosity / color / acid value / electric resistance value of the liquid developer is slightly observed, it is a range in which there is no problem as a liquid developer.
D: A change in viscosity / color / acid value / electric resistance value of the liquid developer is clearly recognized.
E: A change in the viscosity / color / acid value / electric resistance value of the liquid developer is noticeable.
These results are shown in Table 2.

  As is apparent from Table 2, the liquid developer of the present invention was excellent in charging characteristics (positive charging characteristics) and toner particle dispersion stability. Further, the liquid developer of the invention was excellent in environmental stability. On the other hand, satisfactory results were not obtained with the liquid developer of the comparative example.

  1000: Image forming apparatus 10Y, 10M, 10C, 10K ... Photoconductor 11Y ... Charging roller 12Y ... Exposure unit 13M, 13Y ... Photoconductor squeeze roller 14M, 14Y ... Cleaning blade 15M, 15Y ... Developer recovery unit 16Y ... Static elimination unit 17Y ... Photoconductor cleaning blade 18Y ... Developer collection unit 20Y, 20M, 20C, 20K ... Development roller 21Y ... Development roller cleaning blade 24Y ... Developer collection unit 30Y, 30M, 30C, 30K ... Development unit 31Y ... Liquid developer storage unit 31aY ... Supply unit 31bY ... Recovery unit 31cY ... Partition 32Y ... Applying roller 33Y ... Regulator blade 34Y ... Developer stirring roller 35Y ... Communication unit 36Y ... Recovery screw 40 ... Intermediate transfer unit 41 ... Belt drive roller 9: Tension roller 44, 45 ... Driven roller 46 ... Intermediate transfer unit cleaning blade 47 ... Developer recovery unit 48 ... Non-contact type bias applying member 51Y, 51M, 51C, 51K ... Primary transfer backup roller 52Y, 52M, 52C, 52K ... Intermediate transfer unit squeeze device 53Y ... Intermediate transfer unit squeeze roller 55Y ... Intermediate transfer unit squeeze cleaning blade 56Y ... Developer recovery unit 60 ... Secondary transfer unit 64 ... Upstream secondary transfer roller 65 ... Downstream secondary transfer roller 66, 68 ... Secondary transfer roller cleaning blade 67, 69 ... Developer recovery unit 90Y, 90M, 90C, 90K ... Liquid developer supply unit 91Y, 91M, 91C, 91K ... Liquid developer tank 92Y, 92M, 92C, 92K ... Insulating liquid tank 93Y, 93M, 93C, 93K ... liquid developer mixing tank 100Y ... developing unit 101Y ... photoreceptor squeeze device F 40 ... fixing portion (fixing device) F5 ... recording medium

Claims (9)

Crushing a toner material containing a polyester resin and a charge control agent having a nitrogen-based functional group in an insulating liquid to obtain a dispersion in which resin fine particles are dispersed in the insulating liquid;
Heating the dispersion at a predetermined temperature to obtain a liquid developer in which toner particles are dispersed in the insulating liquid, and
When the predetermined temperature in the heating step is T [° C.], the glass transition point of the polyester resin is Tg (p) [° C.], and the melting point of the charge control agent is Tm (e) [° C.], Tm (e ) <T ≦ Tg (p) +10 satisfying the relationship: a method for producing a liquid developer.   The method for producing a liquid developer according to claim 1, wherein the charge control agent has a pyrrolidone skeleton.   The method for producing a liquid developer according to claim 1, wherein the charge control agent has a melting point of 35 ° C. or higher and 55 ° C. or lower.   4. The method for producing a liquid developer according to claim 1, wherein the toner material is a coarsely pulverized product obtained by roughly pulverizing a kneaded product containing the polyester resin and the charge control agent.   The method for producing a liquid developer according to claim 1, wherein in the pulverizing step, the insulating liquid contains a dispersant.   6. The method for producing a liquid developer according to claim 5, wherein the dispersant is at least one selected from the group consisting of a graft copolymer of an acrylic polymer and polysiloxane, an amino-modified silicone, and a resin-based silicone.   The method for producing a liquid developer according to claim 1, wherein the insulating liquid is made of silicone oil.   8. The liquid developer according to claim 1, wherein the content of the charge control agent in the fine particles is 0.05 to 50 parts by weight with respect to 100 parts by weight of the polyester resin. Method.   A pulverizing step of pulverizing a toner material containing a polyester resin and a charge control agent having a nitrogen-based functional group in an insulating liquid to obtain a dispersion in which fine particles are dispersed in the insulating liquid; and And a heating step of obtaining a liquid developer in which toner particles are dispersed in the insulating liquid by heating at a predetermined temperature. The predetermined temperature T [° C.] in the heating step is a glass transition point of the polyester resin. Is Tg (p) [° C.], and the melting point of the charge control agent is Tm (e) [° C.], it is manufactured by a manufacturing method that satisfies the relationship of Tm (e) <T ≦ Tg (p) +10. A liquid developer characterized by that.

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