JP2009047863A - Method of manufacturing toner particle for liquid developer, toner particle for liquid developer, method of manufacturing liquid developer, and liquid developer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing toner particle for liquid developer having a sufficiently small scope of distribution of grain size and excellent charging characteristics. <P>SOLUTION: The method of manufacturing the toner particle for the liquid developer has: a dispersion liquid preparing step of preparing a dispersion liquid having a dispersoid containing an organic solvent and a resin material having the predetermined acid value and dispersed in an aqueous dispersion medium; a joining step of joining a plurality of dispersoids to prepare joined particles; a solvent eliminating step of removing the organic solvent and obtaining resin particles; a first washing step of washing the resin particles, an alkaline treatment process for preparing a resin particle dispersed liquid containing the resin particles dispersed in an aqueous liquid and adjusting pH of the resin particle dispersed liquid to the predetermined pH; and a second washing step of washing the resin particles in the resin particle dispersed liquid by using the aqueous liquid. The electric conductivity of the resin particle dispersed liquid before adjusting its pH in the alkaline treatment process is in the predetermined scope. In the second washing step, washing is continued until the electric conductivity of the dispersed liquid when the resin particles are dispersed in water to obtain the predetermined concentration of solid reaches the predetermined scope. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

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

For the developer used for developing the electrostatic latent image formed on the latent image carrier, a dry toner using a toner composed of a material containing a colorant such as a pigment and a binder resin in a dry state; And a liquid developer in which toner is dispersed in an electrically insulating carrier liquid.
The dry toner is usually produced by a dry pulverization method in which a material containing a colorant and a binder resin is pulverized in a dry state. However, since the dry toner handles toner in a solid state, there are concerns about adverse effects on the human body and the like due to powder, but there are also problems such as contamination due to toner scattering. Also, with dry toners, particle aggregation tends to occur during storage, and it is difficult to sufficiently reduce the size of toner particles, and it is difficult to form a high-resolution toner image. . In addition, when the size of the toner particles is relatively small, the problem due to the powder as described above becomes more remarkable.

On the other hand, since the liquid developer uses an insulating liquid as a medium, the problem of aggregation of toner particles in the liquid developer during storage is less likely to occur compared to dry toner, and fine toner particles should be used. it can. As a result, the liquid developer has better fine line image reproducibility, better gradation reproducibility, better color reproducibility, and better image formation at high speed than dry toner. It has the feature of being.
As a method for producing such a liquid developer, a wet pulverization method for producing a liquid developer by pulverizing a material containing a colorant and a resin in an electrically insulating liquid (insulating liquid) (for example, patent literature) 1) is known.

However, the conventional method for producing a liquid developer has the following problems.
That is, it is difficult to pulverize the toner particles to a sufficiently small size by the wet pulverization method. To make the toner particles sufficiently small, a very large pulverization energy is required for a very long time. In short, the productivity of the liquid developer was extremely low. Further, in the method as described above, the particle size distribution of the toner particles tends to be wide (particle size variation is large). In this case, it has been difficult to obtain a liquid developer having sufficiently high dispersibility of toner particles. As described above, when the dispersibility of the toner particles is poor, there is a problem in that the toner particles settle when left standing for a long time, and the toner particles aggregate. In addition, once the particles settle and agglomerate, the toner particles are difficult to disperse even if they are stirred again to disperse, and the toner particles can be supplied uniformly during image formation. There was a problem that it was impossible.
Further, when image formation is performed using a liquid developer, the quality of the formed image is greatly affected by the charging characteristics of the toner particles. However, when the particle size distribution of the toner particles is wide, the variation in charging characteristics among the toner particles tends to be large. When an image is formed using a liquid developer containing such toner particles, there is a problem that it is difficult to obtain a clear image.

JP 2007-41027 A

  An object of the present invention is to provide a method for producing toner particles for liquid developer having a sufficiently narrow particle size distribution and excellent charging characteristics, and to provide toner particles for liquid developer produced by such a production method. Another object of the present invention is to provide a method for producing a liquid developer containing toner particles for a liquid developer having a sufficiently narrow particle size distribution and excellent charging characteristics, and a liquid developer produced by such a production method.

Such an object is achieved by the present invention described below.
The method for producing toner particles for a liquid developer according to the present invention is a dispersion for preparing a dispersion in which a dispersoid containing an organic solvent and a resin material having an acid value of 5.0 to 20 KOHmg / mg is dispersed in an aqueous dispersion medium. A liquid preparation step;
Coalescing a plurality of the dispersoids to obtain coalesced particles; and
Removing the organic solvent contained in the coalesced particles to obtain resin particles; and
A first cleaning step of cleaning the resin particles with an aqueous liquid;
An alkali treatment step of preparing a resin particle dispersion in which the resin particles are dispersed in an aqueous liquid and adjusting the pH of the resin particle dispersion to 8.0 to 12.0;
A second washing step of washing the resin particles in the resin particle dispersion with an aqueous liquid,
The electric conductivity at 25 ° C. of the resin particle dispersion before adjusting the pH of the resin particle dispersion in the alkali treatment step is 50 μS / cm or less,
In the second washing step, washing is performed until the electrical conductivity at 25 ° C. of the dispersion when the resin particles are dispersed in water so that the solid content concentration is 10 wt% is 50 μS / cm or less. It is characterized by that.

In the method for producing toner particles for a liquid developer of the present invention, it is preferable that in the alkali treatment step, a base defined by Arrhenius is mixed with the resin particle dispersion.
In the method for producing toner particles for liquid developer according to the present invention, the base is mixed with the resin particle dispersion in an aqueous solution state,
The concentration of the base in the aqueous solution is preferably 0.5 to 1.5 N.

In the method for producing toner particles for a liquid developer of the present invention, the resin material preferably contains a styrene-acrylic acid ester copolymer or a polyester resin.
In the method for producing toner particles for a liquid developer of the present invention, in the dispersion preparation step, a resin solution preparation process for preparing a resin liquid containing the resin material and the organic solvent;
It is preferable to have a dispersoid forming process for forming the dispersoid by adding an aqueous liquid to the resin solution.
The toner particles for liquid developer of the present invention are manufactured by the method for manufacturing toner particles for liquid developer of the present invention.

The method for producing a liquid developer according to the present invention includes a dispersion preparation step of preparing a dispersion in which a dispersoid containing an organic solvent and a resin material having an acid value of 5.0 to 20 KOHmg / mg is dispersed in an aqueous dispersion medium. When,
Coalescing a plurality of the dispersoids to obtain coalesced particles; and
Removing the organic solvent contained in the coalesced particles to obtain resin particles; and
A first cleaning step of cleaning the resin particles with an aqueous liquid;
An alkali treatment step of preparing a resin particle dispersion in which the resin particles are dispersed in an aqueous liquid, and adjusting the pH of the resin particle dispersion to 8.0 to 12.0;
A second washing step of obtaining toner particles for liquid developer by washing the resin particles in the resin particle dispersion with an aqueous liquid;
A dispersion step of dispersing the toner particles for liquid developer in an insulating liquid,
The electric conductivity at 25 ° C. of the resin particle dispersion before adjusting the pH of the resin particle dispersion in the alkali treatment step is 50 μS / cm or less,
In the second washing step, washing is performed until the electric conductivity at 25 ° C. of the dispersion in which the resin particles are dispersed in water so that the solid content concentration is 10 wt% is 50 μS / cm or less. Features.
The liquid developer of the present invention is manufactured by the method for manufacturing a liquid developer of the present invention.
The liquid developer of the present invention includes the toner particles for liquid developer of the present invention.

  By satisfying the above configuration, a method for producing toner particles for liquid developer having a sufficiently narrow particle size distribution and excellent charging characteristics is provided, and toner particles for liquid developer produced by such a production method. A method for producing a liquid developer containing toner particles for a liquid developer having a sufficiently narrow particle size distribution and excellent charging characteristics, and a liquid developer produced by such a production method. it can.

Hereinafter, preferred embodiments of the present invention will be described in detail.
<< Liquid Developer Toner Particles and Liquid Developer Manufacturing Method >>
First, the toner particles for liquid developer (hereinafter also simply referred to as toner particles) and the method for producing the liquid developer of the present invention will be described.
The method for producing toner particles for a liquid developer according to the present invention includes a dispersion preparation step of preparing a dispersion in which a dispersoid containing an organic solvent and a resin material having a predetermined acid value is dispersed in an aqueous dispersion medium, A coalescence step of coalescing the dispersoids, a coalescence step of obtaining coalesced particles, a solvent removal step of removing the organic solvent contained in the coalesced particles to obtain resin particles, and a first step of washing the resin particles with an aqueous liquid A washing step, an alkali treatment step of preparing a resin particle dispersion in which resin particles are dispersed in an aqueous liquid, and adjusting the pH of the resin particle dispersion under a basic condition, and the resin particles in the resin particle dispersion in an aqueous system A second cleaning step of cleaning with a liquid. In this embodiment, the toner particle obtained in the second cleaning step is dried. Further, the method for producing a liquid developer of the present invention includes a dispersion step of dispersing the toner particles thus produced in the insulating liquid.

In the method for producing toner particles for a liquid developer of the present invention, a plurality of dispersoids present in the dispersion are combined to form a combined particle. It is considered that the particle size and particle size distribution of the obtained toner particles greatly depend on the particle size and particle size distribution of the coalesced particles.
The present inventors have found that the dispersion stability of the dispersoid and the coalesced particles in the dispersion can be controlled by setting the acid value of the resin material contained in the dispersoid within a predetermined range, It has been found that toner particles having a narrow particle size distribution can be obtained.

  On the other hand, examples of the liquid developer include a liquid developer having a negatively chargeable property and a positively chargeable liquid developer in which toner particles are included. When the resin material has an acid value as described above, the toner particles are negatively charged on the particle surface. In general, when a negatively chargeable liquid developer is used, ozone is likely to be generated inside the image forming apparatus when an image is formed. Ozone is a compound having a strong oxidizing power and has problems such as adverse effects on the liquid developer and peripheral components in the image forming apparatus. In order to solve this problem, it is conceivable to add a charge control agent to the toner particles using the resin material having an acid value as described above as the resin material to make the toner particles positively charged. It is difficult to obtain a charge amount. Further, the charge control agent attached to the surface of the toner particles is easily detached from the surface of the toner particles when the toner particles come into contact with each other. In this case, the chargeability varies among the toner particles.

Therefore, the present inventors have further intensively studied, and as a result, have arrived at the invention. That is, by using a resin material having a predetermined acid value to form coalesced particles having a narrow particle size distribution, and further, treating the coalesced particles in the presence of a base under certain conditions (alkali treatment step), It has been found that toner particles that are easily charged positively, have excellent charging characteristics, and have a sufficiently narrow particle size distribution can be obtained.
Hereafter, each process which comprises the manufacturing method of a toner particle is demonstrated in detail.

[Dispersion Preparation Step (Aqueous Dispersion Preparation Step)]
First, a dispersion (aqueous dispersion) is prepared.
The aqueous dispersion may be prepared by any method. For example, a resin material, a constituent material of toner particles such as a colorant (toner material) is dissolved and dispersed in an organic solvent, and the resin liquid is obtained. Obtained (resin liquid preparation treatment), by adding an aqueous dispersion medium composed of an aqueous liquid to the resin liquid, a dispersoid containing the toner material (liquid dispersoid) is formed in the aqueous liquid, and the dispersoid is dispersed. The obtained dispersion liquid (aqueous dispersion liquid) is obtained (dispersoid formation treatment).

(Resin liquid preparation process)
First, a resin liquid in which a resin material having a predetermined acid value is dissolved or dispersed in an organic solvent is prepared.
The prepared resin liquid contains the constituent material of the dispersoid in the dispersion preparation step described later, and includes the constituent material of the toner particles.
The resin liquid can be obtained, for example, by mixing a material containing a resin material and an organic solvent with a stirrer or the like. Examples of the stirrer that can be used for preparing the resin liquid include DESPA (manufactured by Asada Tekko Co., Ltd.), T.C. K. Robotics / T. K. Examples thereof include a high-speed stirrer such as a homodisper 2.5-type blade (manufactured by Primex).

Moreover, it is preferable that the material temperature at the time of stirring is 20-60 degreeC, and it is more preferable that it is 30-50 degreeC.
Although the content rate of solid content in a resin liquid is not specifically limited, It is preferable that it is 40-75 wt%, it is more preferable that it is 50-73 wt%, and it is further more preferable that it is 50-70 wt%. When the solid content is within the above range, the dispersoid constituting the dispersion liquid (aqueous dispersion liquid) described later can have a higher sphericity (a shape close to a true sphere). The shape of the toner particles finally obtained can be made more surely suitable.
In the preparation of the resin liquid, all the components of the resin liquid to be prepared may be mixed at the same time, or a part of the components of the resin liquid to be prepared may be mixed in advance to prepare a mixture (master). After that, the mixture (master) may be mixed with other components.

  For example, after a colorant and a resin material are kneaded to obtain a colorant master as a kneaded product, a resin liquid is obtained by mixing the colorant master, a resin material as an additional resin, and an organic solvent. It may be prepared. Thereby, the resin liquid in which each component was uniformly mixed can be obtained more reliably. By using such a kneaded product, each component in the kneaded product obtained by kneading even if the constituent material of the toner particles contains components that are difficult to disperse or compatible with each other. Is sufficiently compatible and finely dispersed. In particular, when a pigment (coloring agent) having a relatively low dispersibility in the solvent as described above is used, the resin material or the like is effective around the pigment particles by being kneaded in advance before being dispersed in the solvent. This improves the dispersibility of the pigment in the organic solvent (especially facilitates fine dispersion in the organic solvent) and improves the color developability of the finally obtained toner particles.

Hereinafter, each component which comprises a resin liquid is demonstrated.
1. Resin Material The resin material (resin component) that can be used in the present invention is not particularly limited as long as it has an acid value as described later. For example, one or more known resin materials may be combined. Can be used. Such a resin material preferably contains a polyester resin or a styrene-acrylic acid ester copolymer. As a result, the particle size distribution is particularly narrow, toner particles of a desired size can be more reliably produced, and the dispersibility and charging characteristics of the toner particles in the liquid developer described later are particularly excellent. Can do. Of these, the polyester resin has high transparency, and when used as a resin material, the color developability of an image formed using the manufactured toner particles can be increased. In addition, as such a polyester resin, it is preferable that it is a condensate of diol and dicarboxylic acid.

  In the present invention, the acid value of the resin material is 5 to 20 KOHmg / g. When the acid value of the resin material is within the above range, it is possible to easily control the growth rate of the coalesced particles while more effectively preventing the generation of coarse particles in the coalescing step described later. For this reason, coalesced particles having a narrow particle size distribution and a desired size can be reliably obtained. Further, the productivity in toner production can be made particularly excellent. Further, when the acid value of the resin material is within such a range, the toner particles that have undergone the alkali treatment step described later are likely to be positively charged and have excellent chargeability.

  On the other hand, if the acid value of the resin material is less than the lower limit, in the coalescing step described later, the dispersion cannot stably exist, and the coalescing rate of the dispersoid becomes excessively fast. Will progress unevenly. For this reason, the obtained toner particles have many coarse particles and have a wide particle size distribution. Further, it is difficult to control the particle size of the coalesced particles, and it becomes difficult to obtain toner particles having a desired size. On the other hand, when the acid value of the resin material exceeds the upper limit, the effect of improving the chargeability of the surface of the toner particles in the alkali treatment step described later becomes insufficient. As a result, the chargeability of the manufactured toner particles is inferior. Moreover, the rate of coalescence of the dispersoids becomes excessively slow, resulting in poor productivity.

The acid value of the resin material may be within the above-described range, but is preferably 7 to 15 KOH mg / g, and more preferably 8 to 13 KOH mg / g. Thereby, the effects as described above can be obtained more remarkably.
The weight average molecular weight Mw of the resin material is not particularly limited, but is preferably 10,000 to 180,000, and more preferably 20,000 to 150,000. As a result, the liquid developer using the produced toner particles can more effectively prevent the occurrence of offset in the high temperature region.

  The resin material preferably has a glass transition temperature Tg of 35 to 60 ° C, more preferably 40 to 55 ° C. As a result, the liquid developer containing toner particles to be produced is more reliably prevented from agglomerating and fusing between the toner particles during storage, and the storage stability of the liquid developer is further improved. Further, the toner particles can be more suitably fixed on the recording medium at a low temperature.

The softening temperature Tf of the resin material is preferably 60 to 180 ° C, more preferably 80 to 120 ° C. As a result, the liquid developer containing toner particles to be produced is more reliably prevented from aggregating and fusing toner particles during storage, and the storage stability of the liquid developer becomes better.
In this specification, the glass transition temperature Tg is a measurement condition in a differential scanning calorimeter DSC-220C (manufactured by SII): sample amount 10 mg, temperature rising rate 10 ° C./min, measurement temperature range 10 to 150 ° C. When measured, it refers to the temperature at the intersection of an extension of the baseline below the glass transition point and a tangent that indicates the maximum slope from the peak rise to the peak apex.
The softening temperature refers to a softening start temperature defined by measurement conditions in a Koka flow tester (manufactured by Shimadzu Corporation): temperature rising rate: 5 ° C./min and die hole diameter 1.0 mm.
Moreover, as a constituent material (component) of the resin liquid, a precursor (for example, a prepolymer, a monomer, a dimer, a trimer, an oligomer, or the like) of the resin material described above may be included.

2. Organic Solvent Any organic solvent may be used as long as it dissolves at least a part of the resin material, but it is preferable to use an organic solvent having a boiling point lower than that of the aqueous liquid described later. Thereby, the organic solvent can be easily removed.
The organic solvent is preferably one having low compatibility with an aqueous dispersion medium (aqueous liquid) described later (for example, one having a solubility in 100 g of the aqueous dispersion medium at 25 ° C. of 30 g or less). Thereby, the toner material can be finely dispersed in a stable state in the aqueous emulsion.
Further, the composition of the organic solvent can be appropriately selected according to, for example, the resin material, the composition of the colorant, the composition of the aqueous dispersion medium, and the like as described above.
Such an organic solvent is not particularly limited, and examples thereof include ketone solvents such as MEK and aromatic hydrocarbon solvents such as toluene.

3. Colorant The resin solution may contain a colorant. The colorant is not particularly limited, and for example, known pigments and dyes can be used.
Moreover, it is preferable that content of the coloring agent in solid content of a resin liquid is 3-20 wt%, and it is more preferable that it is 8-15 wt%. As a result, it is possible to make the viscosity characteristic of the resin liquid suitable easily and reliably while improving the color reproducibility of the obtained toner. For this reason, the generation of coarse particles during production is particularly small. Further, the obtained toner particles have a particularly narrow particle size distribution and are particularly excellent in transferability and chargeability.

4). Others The resin liquid may contain components other than those described above. Examples of such components include known emulsifiers, waxes, magnetic powders, and the like.
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 resin liquid. May be.

(Dispersoid formation processing)
Next, an aqueous dispersion (dispersion) is prepared.
By adding an aqueous dispersion medium composed of an aqueous liquid to the resin liquid, a dispersoid containing the toner material (liquid dispersoid) is formed in the aqueous liquid, and the dispersion in which the dispersoid is dispersed (aqueous dispersion) Get.

The aqueous dispersion medium is composed of an aqueous liquid.
As the aqueous liquid, a liquid mainly composed of water can be used.
The aqueous liquid may contain, for example, a solvent having excellent compatibility with water (for example, a solvent having a solubility in 100 parts by weight of water at 25 ° C. of 50 parts by weight or more).
Further, an emulsifying dispersant (emulsifier) may be added to the aqueous dispersion medium as necessary. By adding an emulsifying dispersant, an aqueous emulsion can be prepared more easily.

The emulsifying dispersant is not particularly limited, and for example, a known emulsifying dispersant can be used.
In preparing the aqueous dispersion, for example, a neutralizing agent may be used. As a result, for example, the functional group (carboxyl group) of the resin material can be neutralized, and the shape, size uniformity, and dispersibility of the dispersoid in the aqueous dispersion prepared are particularly excellent. Can be. For this reason, the obtained toner particles have a particularly narrow particle size distribution.

For example, the neutralizing agent may be added to the resin liquid or may be added to the aqueous liquid.
Further, the neutralizing agent may be added in a plurality of times in the preparation of the aqueous dispersion.
As the neutralizing agent, a basic compound can be used. More specifically, for example, inorganic bases such as sodium hydroxide, potassium hydroxide, and ammonia, and organic bases such as diethylamine, triethylamine, and isopropylamine are used. 1 type selected from these, or 2 or more types can be used in combination. The neutralizing agent may be an aqueous solution containing the above compound.

  Moreover, the usage-amount of a basic compound has the preferable amount (1-3 equivalent) equivalent to 1-3 times the amount required in order to neutralize all the carboxyl groups which a resin material has, and is equivalent to 1-2 times The amount (1 to 2 equivalents) is more preferred. Thereby, it is possible to effectively prevent the formation of irregular dispersoids, and it is possible to make the particle size distribution of the particles obtained in the coalescence step described in detail later sharper.

The aqueous liquid may be added to the resin liquid by any method, but it is preferable to add the aqueous liquid containing water to the resin liquid while stirring the resin liquid. That is, it is performed by gradually adding (dropping) the aqueous liquid into the resin liquid while shearing the resin liquid with a stirrer or the like, and finally the aqueous system in which the dispersoid derived from the resin liquid is dispersed in the aqueous liquid. It is preferable to obtain a dispersion. As a result, the dispersoid can be easily and reliably formed as a uniform and fine particle, and the generation of coarse particles during production is particularly small.
Examples of the stirrer that can be used for the preparation of the aqueous dispersion include DESPA (manufactured by Asada Tekko Co., Ltd.), T.C. K. Robotics / T. K. Examples thereof include a high-speed stirrer such as a homodisper 2.5-type blade (manufactured by Primics), a slasher (manufactured by Mitsui Mining Co., Ltd.), a Cavitron (manufactured by Eurotech), or a high-speed disperser.

  Further, at the time of adding the aqueous liquid to the resin liquid, stirring is preferably performed so that the blade tip speed is 10 to 20 m / sec, and more preferably 12 to 18 m / sec. When the blade tip speed is a value within the above range, an aqueous dispersion can be obtained efficiently, and the dispersion of the shape and size of the dispersoid in the aqueous dispersion can be made particularly small. In particular, the uniform dispersibility of the dispersoid can be made excellent while preventing the generation of fine dispersoids and coarse particles.

The solid content in the aqueous dispersion is not particularly limited, but is preferably 5 to 55 wt%, and more preferably 10 to 50 wt%. Thereby, the productivity of toner particles can be made particularly excellent while preventing unintentional aggregation of the dispersoids in the aqueous dispersion more reliably.
The average particle size of the dispersoid in the aqueous dispersion is not particularly limited, but is preferably 0.01 to 1.0 μm, and more preferably 0.05 to 0.5 μm. As a result, the finally obtained toner particles have a particularly narrow particle size distribution. In the present specification, “average particle diameter” refers to an average particle diameter based on volume.
Moreover, it is preferable that the material temperature in this process is 20-60 degreeC, and it is more preferable that it is 20-50 degreeC.

[Joint process]
Next, a plurality of dispersoids are coalesced to obtain coalesced particles (a coalescence step). The coalescence of dispersoids usually proceeds as a result of collision of dispersoids containing an organic solvent so that they are integrated.
The coalescence of a plurality of dispersoids is performed by adding an electrolyte to the dispersion while stirring the dispersion. Thereby, coalesced particles can be obtained easily and reliably. Moreover, the particle diameter and particle size distribution of the coalesced particles can be controlled easily and reliably by adjusting the amount of electrolyte added.

It does not specifically limit as electrolyte, Well-known organic and inorganic water-soluble salt etc. can be used 1 type or in combination of 2 or more types.
The electrolyte is preferably a monovalent cation salt. Thereby, the particle size distribution of the obtained coalesced particles can be narrowed. In addition, by using a monovalent cation salt, it is possible to reliably prevent generation of coarse particles in this step.

Moreover, among the above-mentioned, it is preferable that electrolyte is a sulfate (for example, sodium sulfate, ammonium sulfate) or carbonate, and it is especially preferable that it is a sulfate. Thereby, the particle diameter of the coalesced particles can be controlled particularly easily.
The amount of the electrolyte added in this step is preferably 0.5 to 3 parts by weight, preferably 1 to 2 parts by weight, based on 100 parts by weight of the solid content in the dispersion to which the electrolyte is added. Is more preferable. As a result, the particle diameter of the coalesced particles can be controlled particularly easily and reliably, and the generation of coarse particles can be reliably prevented.
The electrolyte is preferably added in the form of an aqueous solution. As a result, the electrolyte can be quickly diffused throughout the dispersion, and the amount of electrolyte added can be easily and reliably controlled. As a result, coalesced particles having a desired particle size and a particularly narrow particle size distribution can be obtained.

  Moreover, when adding electrolyte in the state of aqueous solution, it is preferable that the density | concentration of the electrolyte in aqueous solution is 2-10 wt%, and it is more preferable that it is 2.5-6 wt%. As a result, the electrolyte can be diffused through the entire dispersion particularly quickly, and the amount of electrolyte added can be easily and reliably controlled. Further, by adding such an aqueous solution, the content of water in the dispersion when the addition of the electrolyte is completed becomes suitable. For this reason, the growth rate of the coalesced particles after the addition of the electrolyte can be made moderately slow to the extent that productivity does not decrease. As a result, the particle diameter of the final coalesced particles can be controlled more reliably, and unintentional coalescence of the coalesced particles can be reliably prevented.

  When the electrolyte is added as an aqueous solution, the rate of addition of the aqueous electrolyte solution is 0.5 to 10 parts by weight / minute with respect to 100 parts by weight of the solid content in the dispersion to which the aqueous electrolyte solution is added. Is preferable, and it is more preferable that it is 1.5-5 weight part / min. As a result, it is possible to prevent the uneven concentration of the electrolyte from occurring in the dispersion, and reliably prevent the generation of coarse particles. Further, the particle size distribution of the coalesced particles is particularly narrow. Furthermore, by adding the electrolyte at such a rate, the coalescing rate can be controlled particularly easily, the average particle size of the coalesced particles can be controlled particularly easily, and the toner productivity is particularly excellent. Can be.

The addition of the electrolyte may be performed in a plurality of times. As a result, coalescent particles having a desired size can be obtained easily and reliably, and the circularity of the obtained coalescent particles can be surely made sufficiently large.
Moreover, this process is performed in the state which stirred the dispersion liquid. Thereby, coalesced particles with particularly small variations in shape and size among the particles can be obtained.

  For stirring the dispersion, for example, an agitation blade such as an anchor blade, a turbine blade, a fiddler blade, a full zone blade, a max blend blade, or a half moon blade may be used, and among these, a max blend blade or a full zone blade is preferable. As a result, the added electrolyte can be quickly and uniformly dispersed and dissolved to reliably prevent the uneven concentration of the electrolyte from occurring. In addition, it is possible to more reliably prevent the coalesced particles once formed from collapsing while efficiently coalescing the dispersoid. As a result, coalesced particles with small variations in shape and particle size among the particles can be obtained efficiently.

The blade tip speed of the stirring blade is preferably from 0.1 to 10 m / second, more preferably from 0.2 to 8 m / second, and even more preferably from 0.2 to 6 m / second. When the blade tip speed is a value within the above range, the added electrolyte can be uniformly dispersed and dissolved, and the occurrence of uneven concentration of the electrolyte can be reliably prevented. In addition, it is possible to more reliably prevent the coalesced particles once formed from collapsing while more efficiently coalescing the dispersoid.
The average particle size of the obtained coalesced particles is preferably 0.1 to 7 μm, and more preferably 0.5 to 3 μm. Thereby, the particle diameter of the toner particles finally obtained can be made moderate.

[Desolvation (desolvation) step]
Thereafter, the organic solvent contained in the dispersion is removed. Thereby, resin particles dispersed in the dispersion are obtained.
The removal of the organic solvent may be performed by any method, but can be performed, for example, under reduced pressure. Thereby, the organic solvent can be efficiently removed while sufficiently preventing the modification of the constituent material such as the resin material.

Moreover, it is preferable that the process temperature in this process is temperature lower than the glass transition point (Tg) of the resin material which comprises coalesced particle.
Moreover, you may perform this process in the state which added the antifoamer to the dispersion liquid. Thereby, an organic solvent can be removed efficiently.
Antifoaming agents include, for example, mineral oil-based antifoaming agents, polyether-based antifoaming agents, silicone-based antifoaming agents, lower alcohols, higher alcohols, fats and oils, fatty acids, fatty acid esters, phosphoric acid Esters can be used.
Although the usage-amount of an antifoamer is not specifically limited, It is preferable that it is 20-300 ppm by weight ratio with respect to the solid content contained in a dispersion liquid, and it is more preferable that it is 30-100 ppm.

In this step, at least a part of the aqueous liquid may be removed together with the organic solvent.
In this step, it is not always necessary to remove all of the organic solvent (the total amount of the organic solvent contained in the dispersion). Even in such a case, the remaining organic solvent can be sufficiently removed in other steps described later.

[First cleaning step]
Next, the resin particles are washed using an aqueous liquid.
The resin particles are washed by separating the resin particles by solid-liquid separation (separation from the aqueous dispersion medium), and then redispersing (reslurry) the solid content (resin particles) in the aqueous liquid and solid-liquid separation (aqueous system). By separating the toner particles from the liquid). By removing this aqueous liquid by solid-liquid separation, the organic solvent and other impurities in the resin particles can be removed.

Solid-liquid separation is not particularly limited. For example, a suction filter, a centrifugal separator (for example, a basket type, a DeLaval type, a shear press type, a decanter type, a cooling method, etc.), a filter press, a drum dryer, a single plate filter, etc. It can carry out using the apparatus of.
Further, the redispersion and solid-liquid separation of the solid content (resin particles) in the aqueous liquid may be repeated a plurality of times.

[Alkali treatment process]
Next, a resin particle dispersion in which resin particles are dispersed in an aqueous liquid is prepared, and the pH of the resin particle dispersion is set to a predetermined alkaline range (alkali treatment).
When resin particles are prepared using a resin material having an acid value as described above, the resin particles can release hydrogen ions from a functional group such as a carboxyl group and are negatively charged. For this reason, when the resin particles are dispersed as they are in the insulating liquid as they are and used in the liquid developer, the toner particles are negatively charged on the particle surface. In general, when a negatively chargeable liquid developer is used, ozone tends to be generated inside the image forming apparatus when an image is formed. Ozone is a compound having a strong oxidizing power, and has problems such as adversely affecting liquid developers and peripheral components in the image forming apparatus. In order to solve this problem, it is conceivable to add a charge control agent to the toner particles using the resin material having an acid value as described above as a resin material to make the toner particles positively charged. It is difficult to obtain a charge amount.

  However, in the present invention, by performing such an alkali treatment on the resin particles, toner particles that are easily positively charged and excellent in charging characteristics can be obtained. More specifically, in the alkali treatment, the functional groups capable of releasing hydrogen ions such as carboxyl groups of the resin particles (hereinafter also referred to as acid sites) are neutralized, that is, the hydrogen ions at the acid sites are exchanged with other cations. Replace. At this time, in the acid site, the cation and the anion portion of the acid site are polarized. For this reason, the surface of the resin particles is likely to be positively charged because the surface is covered with cations. Such cations generally have a larger ionic radius than hydrogen ions. For this reason, the surface part of the resin particle can be efficiently covered with the cation, and the variation in the charging characteristics of the surface within the resin particle is small. As a result, the resulting toner particles are easily positively charged and have excellent charging characteristics.

The alkali treatment of the resin particles is performed by adjusting the pH of the resin particle dispersion in which the resin particles are dispersed with an aqueous liquid.
The resin particle dispersion may be prepared by any method. For example, the solid content (resin particles) obtained by the individual liquid separation in the first washing step is redispersed (reslurry) in the aqueous liquid. Obtainable.

  Further, the electric conductivity of the resin particle dispersion at 25 ° C. is 50 μS / cm or less. Thus, if the electrical conductivity in the resin particle dispersion is sufficiently low, the electrolyte and other impurities in the resin particle dispersion are sufficiently small, and the effect of the alkali treatment is more easily obtained. Has excellent charging characteristics. On the other hand, when the electrical conductivity of the resin particle dispersion is large, the electrolyte and the other impurities in the resin particle dispersion are large, and the resin particles cannot sufficiently obtain the effect of the alkali treatment. For this reason, the toner particles obtained are inferior in charging characteristics.

  The electrical conductivity of the resin particle dispersion before adjusting the pH may be within the above-mentioned range, but is preferably 45 μS / cm or less, and more preferably 25 μS / cm or less. Thereby, the effects as described above can be obtained more remarkably. The electrical conductivity of the resin particle dispersion may be sufficiently low, for example, by repeating redispersion of solid content (resin particles) in an aqueous liquid and solid-liquid separation in the first washing treatment. it can.

  In this step, the concentration of the solid content in the resin particle dispersion before the alkali treatment is not particularly limited, but is preferably 1 to 25 wt%, and more preferably 3 to 20 wt%. Thereby, the concentration unevenness of cations or the like in the resin particle dispersion during pH adjustment can be further suppressed, and variation in charging characteristics between the resin particles can be further reduced. Further, the charging characteristics on the surface of the resin particles can be made particularly excellent. Moreover, the effect of the alkali treatment can be sufficiently obtained while reducing the amount of the base to be described later.

  Moreover, the pH of the resin particle dispersion during the alkali treatment is 8.0 to 12.0. When the pH of the resin particle dispersion is within the above range, the acid sites on the surface of the resin particles are sufficiently neutralized, and hydrogen ions at the acid sites are more reliably replaced with other cations. For this reason, the obtained toner particles have excellent chargeability. On the other hand, if the pH of the resin particle dispersion is less than the lower limit, the acid sites on the surface of the resin particles are not sufficiently neutralized, and the resulting toner particles are inferior in charging characteristics. On the other hand, if the pH of the resin particle dispersion exceeds the above upper limit, the constituent materials such as resin materials and pigments of the resin particles may be altered, and as a result, the charging characteristics of the obtained toner particles are excellent. It can not be. In addition, as a result of alteration of the constituent material of the resin particles, aggregation or deformation of the resin particles may occur. In addition, in the second cleaning step described later, the cleaning time is extremely long, and the productivity is poor. The pH of the resin particle dispersion during the alkali treatment may be within the above-described range, but is preferably 8.5 to 11.5, more preferably 9.0 to 11.0. The effect as described above can be obtained more remarkably.

The pH of the resin particle dispersion may be adjusted by any method, but it is preferable to mix a base defined by Arrhenius with the resin particle dispersion. As a result, the pH can be adjusted more reliably, and the resulting toner particles have particularly excellent charging characteristics.
Moreover, it does not specifically limit as a base which can be used for adjustment of pH, A well-known basic compound can be used, For example, barium hydroxide, calcium hydroxide, sodium hydroxide, sodium carbonate, sodium hydrogencarbonate Inorganic bases such as potassium hydroxide, potassium carbonate and ammonia, and organic bases such as diethylamine, triethylamine and isopropylamine can be used alone or in combination of two or more.

The base described above is preferably mixed with the resin particle dispersion in the form of an aqueous solution. Thereby, the pH of the resin particle dispersion can be easily and reliably adjusted, and the charging characteristics of the obtained toner particles can be made particularly excellent.
In this case, the concentration of the base in the aqueous solution is preferably 0.5 to 1.5 N, and more preferably 0.6 to 1.3 N. Thereby, the pH of the resin particle dispersion can be adjusted particularly easily, and the charging characteristics of the obtained toner particles can be made particularly excellent.

[Second cleaning step]
Next, the alkali-treated resin particles are washed using an aqueous liquid. Thereby, toner particles are obtained. Further, such toner particles are usually dried in a drying step described later and used for a liquid developer.
The resin particles can be washed by the same method as in the first washing step.

  In this step, washing is performed until the electric conductivity at 25 ° C. of the dispersion obtained by dispersing the resin particles in water so that the solid content concentration is 10 wt% is 50 μS / cm or less. By sufficiently washing the resin particles in this way, the toner particles obtained are less contaminated with electrolytes and impurities generated in the alkali treatment step. For this reason, moisture can be reliably removed in the drying step described later, and mixing of water into the liquid developer described later can be prevented. As a result, the manufactured liquid developer can prevent a decrease in electrical conductivity due to a component in which water is dissolved, and the charging characteristics of toner particles in the liquid developer are excellent. In addition, it is possible to reliably prevent deterioration of the liquid developer and the like, and the liquid developer is excellent in environmental stability.

  On the other hand, when the washing is finished in a state where the electrical conductivity of the dispersion liquid is large, the obtained toner particles are much contaminated with electrolytes and impurities generated in the alkali treatment process. For this reason, water cannot be sufficiently removed from the toner particles in the drying step described later. For this reason, water is mixed into the liquid developer described later. When water is mixed in the liquid developer, the electrical conductivity is lowered due to the components dissolved in the water, and the charging characteristics of the toner particles in the liquid developer are not excellent. Further, the obtained liquid developer is easily deteriorated and has poor environmental stability.

Moreover, the electrical conductivity of the dispersion liquid described above may be within the above-described range, but is preferably 45 μS / cm or less, and more preferably 25 μS / cm or less. Thereby, the effects as described above can be obtained more remarkably.
In this step, it is preferable to perform washing until the pH of the dispersion liquid in which the resin particles are dispersed in water so that the solid content concentration is 10 wt% is 7.5 to 9.5. This ensures that cations are retained at the acid sites on the surface of the resin particles. For this reason, the obtained toner particles have excellent charging characteristics. Further, alteration of the constituent material of the obtained toner particles can be reliably prevented.

[Drying process]
Thereafter, by performing a drying treatment, dried toner particles can be obtained (drying step).
The drying step can be performed using, for example, a vacuum dryer (for example, ribocorn (manufactured by Okawara Seisakusho), nauter (manufactured by Hosokawa Micron) etc.), fluidized bed dryer (manufactured by Okawara Seisakusho), etc.
The treatment temperature in this step is preferably lower than the glass transition point (Tg) of the resin component of the toner particles.

[Dispersion process]
Next, the toner particles are dispersed in an insulating liquid. Thereby, a liquid developer is obtained.
The toner particles can be dispersed in the insulating liquid by any method, for example, by mixing the insulating liquid and the toner particles with a bead mill, a ball mill, or the like.
In addition, components other than the insulating liquid and toner particles may be mixed during the dispersion. Thereby, for example, an additive such as a charge control agent can be more efficiently attached to the toner particles.

Further, the dispersion of the toner particles in the insulating liquid may be performed by using the whole amount of the insulating liquid constituting the finally obtained liquid developer, or by using a part of the insulating liquid. It may be a thing.
Further, when the toner particles are dispersed using a part of the insulating liquid, the same liquid as the liquid used for the dispersion may be added as the insulating liquid after the dispersion, or after the dispersion, Alternatively, a liquid different from the liquid used for dispersion may be added as an insulating liquid. In the latter case, characteristics such as the viscosity of the finally obtained liquid developer can be easily adjusted.

Hereinafter, each component to be mixed in this step will be described. The description of the toner particles described above is omitted.
(Insulating liquid)
The insulating liquid is not particularly limited, and a known liquid can be used. Specifically, KF96, KF4701, KF965, KS602A, KS603, KS604, KF41, KF54, FA630 (manufactured by Shin-Etsu Silicone), TSF410, TSF433, TSF434, TSF451, TSF437, (Momentive Performance Materials Japan GK) ), SH200 (manufactured by Toray Industries, Inc.), etc. Silicone oil, Isopar E, Isopar G, Isopar H, Isopar L (Exxon Chemical), Cosmo White P-60, Cosmo White P-70, Cosmo White P-120 ( Cosmo Oil Lubricants), Dyna Fresia W-8, Daphne Oil CP, Daphne Oil KP, Transformer Oil H, Transformer Oil G, Transformer Oil A, Transformer Oil B Transformer oil S (manufactured by Idemitsu Kosan), Cielsol 70, Cielsol 71 (manufactured by Ciel Oil), Amsco OMS, Amsco 460 solvent (manufactured by Spirits), low viscosity / high viscosity liquid paraffin (manufactured by Wako Pure Chemical Industries), octane , Isooctane, decane, isodecane, decalin, nonane, dodecane, isododecane, cyclohexane, cyclooctane, cyclodecane and other aliphatic hydrocarbons, fatty acid triglycerides, and fatty acid diglycerides, fatty acid monoglycerides, fatty acid triglycerides and other degradation products, fatty acids Examples include monoesters, synthetic ester liquids such as Prifer 6813 (manufactured by UNIQUEMA), benzene, toluene, xylene, mesitylene, fatty acid monoesters, etc., and one or more of these In combination it can be used.

Among the liquids described above, the insulating liquid preferably contains a fatty acid monoester that is an ester between a fatty acid and a monohydric alcohol. Such a fatty acid monoester is represented by the general formula R—COO—R ′ (where R and R ′ are alkyl groups).
Fatty acid monoesters are naturally derived components and are environmentally friendly components. Therefore, it is possible to reduce the load on the environment of the insulating liquid due to leakage of the insulating liquid to the outside of the image forming apparatus and disposal of the used liquid developer. As a result, an environmentally friendly liquid developer can be provided.

In addition, the fatty acid monoester is a liquid having a relatively low viscosity and is excellent in affinity with the resin material as described above. Therefore, when the insulating liquid contains the fatty acid monoester, the dispersibility of the toner particles in the liquid developer becomes excellent, and the storage stability and long-term stability of the liquid developer can be improved.
The fatty acid monoester has a property of easily entering between the molecular complexes of the resin material constituting the toner particles, and the fatty acid monoester incorporated into the resin material in this manner is the toner particle (resin material). ) Has a plasticizing effect. Therefore, the toner particles incorporating the fatty acid monoester can be easily melted and fixed on the recording medium even at a relatively low temperature. Further, the plasticized toner particles can be fixed more closely to the recording medium, and the fixing strength of the obtained toner image is particularly excellent. For example, when paper is used as the recording medium, the toner particles can easily enter the gap between the paper fibers. Then, a part of the toner particles (resin material constituting the toner particles) melted by heat at the time of fixing penetrates into the inside of the recording medium, and in this state, the toner particles are allowed to cool and harden, whereby the anchor effect is obtained. The toner particles can be firmly fixed on the paper. Therefore, the liquid developer containing such toner particles has improved low-temperature fixability and excellent fixing strength of the toner particles to the recording medium.

  The fatty acid component constituting such a fatty acid monoester is represented by a general formula of R—COOH (where R is an alkyl group), and is not particularly limited. For example, oleic acid, palmitoleic acid, linoleic acid, α-linolene Unsaturated fatty acids such as acid, γ-linolenic acid, arachidonic acid, docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), butyric acid, lauric acid, caproic acid, caprylic acid, capric acid, myristic acid, palmitic acid , Saturated fatty acids represented by stearic acid, arachidic acid, behenic acid, lignoceric acid and the like, and one or more selected from these can be used in combination.

  Among these, when the fatty acid monoester contains a saturated fatty acid as a fatty acid component, the fatty acid monoester is hardly deteriorated (oxidation, decomposition, etc.) and becomes chemically particularly stable. For this reason, the insulating liquid containing such a fatty acid monoester reliably prevents deterioration phenomena such as viscosity increase, discoloration, and decrease in electric resistance over a long period of time, and the storage stability and long-term stability of the liquid developer are prevented. The property is particularly excellent. At the time of fixing, the fatty acid monoester is also transferred to the paper together with the toner particles, and the saturated fatty acid monoester is contained in the formed toner image. As described above, the saturated fatty acid monoester is a component that is not easily deteriorated, and even if the toner image is exposed to the external environment (light, heat, oxygen, etc.), it is reliably prevented from being discolored, and a toner image that is formed. Will be clear for a long time.

  Moreover, when a fatty acid monoester contains a saturated fatty acid as a fatty acid component, it is preferable that a C8-C20 fatty acid is included as a saturated fatty acid. Thereby, the plasticizing effect of the fatty acid monoester is expressed more suitably, and the storage stability and low-temperature fixability of the liquid developer can be made particularly excellent. Further, even when a part of such fatty acid monoester remains together with the toner particles on the recording medium, it is more reliably prevented from being deteriorated by the influence of the external environment such as light (ultraviolet rays) and heat. The color of the toner image can be made clearer over a long period of time.

  Further, such a fatty acid monoester is an ester of a fatty acid and a monohydric alcohol, and this alcohol is represented by a general formula of R—OH (where R is an alkyl group), and R has 1 carbon atom. It is preferably ~ 4. Such fatty acid monoesters suitably penetrate into the toner particles and suitably plasticize the toner particles. As a result, the storage stability and low-temperature fixability of the liquid developer are particularly excellent. Further, the chemical stability of the liquid developer is excellent, and the long-term stability of the liquid developer is further excellent. Further, the viscosity of the insulating liquid can be made favorable, and the penetration of the liquid developer into the recording medium can be made more suitable. Examples of such alcohol include methanol, ethanol, propanol, butanol, isobutanol and the like.

The fatty acid monoester may be produced by a transesterification reaction between a vegetable oil and a monohydric alcohol as described above. That is, the insulating liquid used in the present invention may include a fatty acid monoester obtained by combining one or more selected from fatty acids and alcohols as described above.
Examples of vegetable oils used for transesterification include soybean oil, rapeseed oil, dehydrated castor oil, tung oil, safflower oil, linseed oil, sunflower oil, corn oil, cottonseed oil, sesame oil, corn oil, cannabis oil, evening primrose oil, palm oil (Especially palm kernel oil), coconut oil, coconut oil and the like.

In addition, the content of the fatty acid monoester in the insulating liquid is preferably 10 to 60 wt%, more preferably 15 to 55 wt%, and even more preferably 30 to 50 wt%. Thereby, the dispersibility of the toner particles in the liquid developer is particularly excellent, and the toner particles are more suitably plasticized. As a result, the storage stability and low-temperature fixability of the liquid developer are particularly excellent.
The electrical resistance of the insulating liquid as described above at room temperature (20 ° C.) is preferably 1 × 10 ⁹ Ωcm or more, more preferably 1 × 10 ¹¹ Ωcm or more, and 1 × 10 ¹² Ωcm or more. More preferably.
The dielectric constant of the insulating liquid is preferably 3.5 or less.

(Dispersant)
Examples of the dispersant include polyglycerin fatty acid ester, polyurethane derivative, sorbitan fatty acid ester, polyoxyethylene alkyl ether, alkyl ether type nonionic surfactant, sorbitan derivative nonionic surfactant, polyvinyl alcohol, carboxymethylcellulose, polyethylene glycol Solsperse 3000, 5000, 11200, 12000, 13240, 13650, 13940, 16000, 17000, 18000, 20000, 21000, 22000SC, 24000GR (trade name of Nippon Lubrizol), polycarboxylic acid and salts thereof, polyacrylic Acid metal salt (for example, sodium salt), polymethacrylic acid metal salt (for example, sodium salt), polymaleic acid metal salt (for example, Sodium salts, etc.), acrylic acid-maleic acid copolymer metal salts (eg, sodium salts, etc.), polystyrene sulfonic acid metal salts (eg, sodium salts, etc.), polyamine fatty acid polycondensate polymer dispersants, viscosity minerals, etc. , Silica, tricalcium phosphate, metal tristearate (eg, aluminum salt), metal distearate (eg, aluminum salt, barium salt), stearic acid metal salt (eg, calcium salt, lead salt, zinc salt) ), Linolenic acid metal salts (eg, cobalt salts, manganese salts, lead salts, zinc salts, etc.), octanoic acid metal salts (eg, aluminum salts, calcium salts, cobalt salts, etc.), oleic acid metal salts (eg, calcium Salts, cobalt salts, etc.), palmitic acid metal salts (for example, zinc salts), dodecylbenzenesulfonic acid metal salts (for example, Sodium salts, etc.), naphthenic acid metal salts (eg, calcium salts, cobalt salts, manganese salts, lead salts, zinc salts, etc.), resinic acid metal salts (eg, calcium salts, cobalt salts, manganese lead salts, zinc salts, etc.) Etc.

Among such dispersants, those containing a polymer dispersant are preferable. In the present specification, the polymer dispersant means a polymer dispersant having a molecular weight of 1000 or more.
Such a polymer dispersant is a component that easily adheres to the surface of the toner particles, among the various dispersants described above, and has a function of further improving the dispersibility of the toner particles in the liquid developer. And also has a function of further improving the charging characteristics of the liquid developer. This is considered as follows. As described above, the acid particles on the surface of the toner particles of the present invention are polarized by the alkali treatment. On the other hand, the polymer dispersant is generally one in which a part of its skeleton is polarized. For this reason, the polymer dispersant adheres firmly to the toner particles by attaching the plurality of polarized portions of the polymer dispersant to the acid sites of the toner particles, respectively. Therefore, the dispersibility of the toner particles in the liquid developer is particularly excellent, the toner particles are more reliably prevented from aggregating and fusing with each other, and the storage stability of the liquid developer is further improved. Become. In addition, it is considered that the charging properties of the toner particles are particularly excellent depending on the polarized part of the polymer dispersant. Further, since the polymer dispersant released in the insulating liquid is small, the electrical resistance of the entire liquid developer can be increased.

Among the polymer dispersants as described above, Solsperse has an ester group in its skeleton, and can particularly firmly adhere to the surface of toner particles composed of the resin material as described above. . Solsperse is a dispersant having positive chargeability, and toner particles to which Solsperse adheres have high positive chargeability.
The content of the dispersant as described above in the liquid developer is preferably 1.0 to 10.0 parts by weight, and 2.5 to 8.0 parts by weight with respect to 100 parts by weight of the toner particles. Is more preferable. As a result, the dispersant can be evenly adhered or adsorbed on the surface of each toner particle, and the aggregation of the toner particles can be more reliably prevented, and the storage stability of the liquid developer can be further improved. Furthermore, when a polymer dispersant is used as the dispersant, the charging characteristics of the entire toner can be further improved.

(Charge control agent)
Examples of the charge control agent include metal oxides such as zinc oxide, aluminum oxide, magnesium oxide, metal salts of benzoic acid, metal salts of salicylic acid, metal salts of alkyl salicylic acid, metal salts of catechol, metal-containing bisazo dyes, nigrosine Examples thereof include dyes, tetraphenylborate derivatives, quaternary ammonium salts, alkylpyridinium salts, chlorinated polyesters, and nitrofunnic acid.
Further, other components may be mixed when the toner particles are dispersed in the insulating liquid. Examples of such components include antioxidants and viscosity modifiers.

≪Toner particles for liquid developer≫
Since the toner particles for toner (toner particles) of the present invention are produced by the production method as described above, the particle size distribution is narrow and the variation in characteristics among the toner particles is small. Further, the toner particles are easily charged positively on the surface and have excellent charging characteristics.
When the 50% volume particle size of the toner particles is Dv (50) [μm], Dv (50) [μm] is preferably 0.1 to 5 μm, and preferably 0.1 to 4 μm. More preferably, it is 0.5-3 micrometers. When Dv (50) [μm] is a value within the above range, the variation in characteristics among the toner particles is particularly small, and the reliability of the entire liquid developer is particularly high, while the liquid developer is particularly high. The resolution of the image formed by (toner) can be made sufficiently high.

  When the 50% volume particle diameter of the toner particles is Dv (50) [μm] and the 50% number particle diameter is Dn (50) [μm], the value of Dv (50) / Dn (50) is It is preferably 1.00 to 1.15, and more preferably 1.00 to 1.10. As a result, the variation in characteristics among the toner particles is particularly reduced, and the reliability of the entire liquid developer is further improved.

Further, the average value of the circularity R (average circularity) of the toner particles represented by the following formula (I) is preferably 0.92 or more, more preferably 0.95 to 0.99. preferable.
R = L ₀ / L ₁ (I)
(Where, L ₁ [μm] is the circumference of the projected image of the toner particles to be measured, and L ₀ [μm] is a perfect circle having an area equal to the area of the projected image of the toner particles to be measured (completely Represents the perimeter of a geometric circle)

  As described above, when the circularity of the toner particles is sufficiently large, the transfer efficiency of the toner particles can be made sufficiently excellent. Further, since the circularity of the toner particles is sufficiently large, the toner particles are irreversible even when stress is applied to the toner particles for a long period of time in an image forming apparatus (particularly, a developing device). Can be prevented. As a result, the toner can exhibit stable characteristics over a long period of time.

≪Liquid developer≫
The liquid developer of the present invention is obtained by dispersing toner particles as described above in an insulating liquid. As described above, the toner particles manufactured by the above manufacturing method are easily positively charged, have excellent charging characteristics, and have a narrow particle size distribution. For this reason, the liquid developer is excellent in developability and transferability. More specifically, toner particles having a narrow particle size distribution tend to have uniform charging characteristics among the particles. Therefore, during development, each toner particle can migrate in the liquid developer at a uniform speed. Furthermore, since each toner particle has excellent charging characteristics, it can be transferred and developed efficiently and uniformly, and an image formed using a liquid developer has a clear and high color density. It becomes.

In addition, since the toner particles of the liquid developer are uniform in both charging characteristics and particle diameter, a phenomenon in which only toner particles having a part of particle diameter and charging characteristics are used for development during development (so-called selective development). Therefore, it is possible to form a stable, clear image with high color density over a long period of time.
Further, since the toner particle has a narrow particle size distribution, a gap is easily formed between the toner particles, and the dispersion stability in the insulating liquid is excellent. Further, in an image forming apparatus as described later, once aggregated toner particles can be easily redispersed in the insulating liquid by gentle stirring or the like. Therefore, the liquid developer has excellent toner particle recyclability.

The toner particle content in the liquid developer is preferably 10 to 60 wt%, and more preferably 20 to 50 wt%. Thereby, the viscosity of the liquid developer can be made appropriate, and conditions such as heating during fixing can be made particularly gentle.
The electrical resistance of the liquid developer at room temperature (20 ° C.) is preferably 1 × 10 ⁹ Ωcm or more, more preferably 1 × 10 ¹¹ Ωcm or more, and 1 × 10 ¹² Ωcm or more. Is more preferable.

  Further, the viscosity of the liquid developer is preferably 20 to 300 mPa · s, and more preferably 30 to 250 mPa · s. When the viscosity of the liquid developer is in such a range, the dispersibility of the toner particles can be increased, and the liquid developer is more evenly distributed on the coating roller in a liquid developing apparatus as described later. In addition, dripping of the liquid developer from the application roller or the like can be more effectively prevented. Moreover, in this specification, a viscosity is measured based on JISZ8809 using a vibration viscometer at 25 degreeC.

≪Image forming device≫
Next, a preferred embodiment of the image forming apparatus using the liquid developer as described above will be described. The image forming apparatus forms a color image on a recording medium using the liquid developer of the present invention as described above.
1 is a schematic view showing an example of an image forming apparatus to which the 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, and FIG. 3 is a developing roller. FIG. 4 is a cross-sectional view illustrating an example of a fixing device applied to the image forming apparatus illustrated in FIG. 1. FIG. 4 is a schematic diagram illustrating a state of toner particles in the upper liquid developer layer.

As shown in FIGS. 1 and 2, the image forming apparatus 1000 includes four developing units 30Y, 30M, 30C, and 30K, an intermediate transfer unit 40, a secondary transfer unit (secondary transfer unit) 60, and a fixing unit. (Fixing device) F40 and four liquid developer supply portions 80Y, 80M, 80C, and 80K are provided.
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. The image forming apparatus 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 has a cylindrical base material and a photosensitive layer formed on the outer peripheral surface thereof, and can rotate around a central axis. In this embodiment, as shown by an arrow in FIG. Rotate clockwise.
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 of the developing unit 100Y in the rotation direction 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, is wound around a belt driving roller 41 and a tension roller 42, and is stretched by the primary transfer backup rollers 51Y, 51M, 51C, and 51K. It is rotationally driven by the driving roller 41 while contacting with 10M, 10C, 10K.

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, and recorded on paper, film, cloth, and the like in a lump. Secondary transfer is performed on the medium F5. 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 sheet material that is not smooth due to fiber or the like, the secondary transfer characteristics follow the surface of the non-smooth sheet material. An elastic belt member is employed as means for improving the above.

A cleaning device including an intermediate transfer unit cleaning blade 46 and a developer recovery unit 47 is disposed on the tension roller 42 side that stretches the intermediate transfer unit 40 together with the belt drive roller 41.
The intermediate transfer portion cleaning blade 46 has a function of scraping and removing the liquid developer adhering to the intermediate transfer portion 40 after the image is transferred onto the recording medium F5 by the secondary transfer roller 61.

The developer recovery unit 47 has a function of recovering the liquid developer removed by the intermediate transfer unit cleaning blade 46.
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 includes an intermediate transfer unit squeeze roller 53Y, an intermediate transfer unit squeeze backup roller 54Y disposed opposite to the intermediate transfer unit squeeze roller 53Y with the intermediate transfer unit 40 interposed therebetween, and an intermediate transfer unit squeeze roller 53Y. It comprises an intermediate transfer unit squeeze cleaning blade 55Y that cleans the surface by pressing and sliding, and a developer recovery unit 15M.

  The intermediate transfer unit squeeze device 52Y has a function of recovering excess carrier from the developer primarily transferred to the intermediate transfer unit 40, increasing the toner particle ratio in the visible image, and recovering originally unwanted toner. . The developer recovery unit 15M uses a mechanism for recovering the carrier recovered by the cleaning blade 14M of the magenta photosensitive member squeeze roller disposed downstream in the moving direction of the intermediate transfer unit 40. The developer transfer unit squeeze the intermediate transfer unit squeeze roller 53Y. This is also used for the cleaning blade 55Y. In this way, in the developer collection units 15M, 15C, and 15K (developer collection units 15C and 15K are not shown) of the image carrier squeeze device for the second and subsequent colors, the primary transfer backup roller 51 of the previous color ( Y, M, C) is used as a developer recovery unit of the intermediate transfer unit squeeze device 52 (Y, M, C) disposed downstream of the intermediate transfer unit 40 in the moving direction, so that the interval between them is constant. It can be regulated, and the structure can be simplified and the size can be reduced.

The secondary transfer unit 60 includes a cleaning device including a secondary transfer roller 61 facing the belt driving roller 41 with the intermediate transfer unit 40 interposed therebetween, and a cleaning device including a cleaning blade 62 and a developer recovery unit 63 of the secondary transfer roller 61. Be placed.
In the secondary transfer unit 60, the recording medium F5 is conveyed and supplied in accordance with the timing at which the intermediate transfer image formed on the intermediate transfer unit 40 by overlapping colors reaches the transfer position of the secondary transfer unit 60. The intermediate transfer image is secondarily transferred to the recording medium F5.

The toner image (transfer image) F5a transferred onto the recording medium F5 by the secondary transfer unit 60 is sent to a fixing unit F40, which will be described later, and is fixed.
The cleaning blade 62 has a function of scraping and removing the liquid developer adhering to the secondary transfer roller 61 after the image is transferred onto the recording medium F5 by the secondary transfer roller 61.
The developer recovery unit 63 has a function of recovering the liquid developer removed by the cleaning blade 62.

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 developing roller 20Y, a developing roller cleaning blade 21Y, and a developing unit. And an agent compression roller (compression means) 22Y.

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 coating roller 32Y has a function of supplying a liquid developer to the developing roller 20Y.
The 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 has a diameter of 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 clockwise, thereby supporting the liquid developer in the liquid developer storage section 31Y in the groove, and the supported liquid developer is transferred to the developing roller 20Y. Transport to.

  The regulating blade 33Y is in contact with 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 the 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. Further, the regulating blade 33Y is provided on the side where the coating roller 32Y rotates and advances from the liquid developer as viewed from the vertical surface A (that is, the left side in FIG. 2 as viewed from the vertical surface A). The rubber hardness of the regulation blade 33Y is about 77 degrees according to JIS-A, and the hardness (about 77 degrees) of the contact portion of the regulation blade 33Y with the surface of the coating roller 32Y is about the elasticity of the developing roller 20Y described later. It is lower than the hardness (about 85 degrees) of the pressure 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 liquid developer storage unit 31Y 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 1 are aggregated, the toner particles 1 can be suitably dispersed. In particular, the toner particles 1 can be suitably dispersed even when the liquid developer once used is reused.
In the liquid developer storage unit 31Y, the toner particles 1 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. , The liquid developer is stored in the liquid developer reservoir 31Y, and the amount of liquid developer is regulated by the regulating blade 33Y and supplied to the developing roller 20Y.

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 201Y on the surface thereof 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 layer has a two-layer structure. As an inner layer thereof, urethane rubber having a rubber hardness q degree of about 30 degrees and a thickness of about 5 mm is used as a surface layer (outer layer) of rubber hardness. Is provided with urethane rubber having a JIS-A of about 85 degrees and a thickness of about 30 μm. 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.

The developer compression roller 22Y is a device having a function of compressing the liquid developer toner carried on the development roller 20Y. In other words, the developer compression roller 22Y applies an electric field having the same polarity as the toner particles 1 to the liquid developer layer 201Y described above, thereby developing the liquid developer layer 201Y in the liquid developer layer 201Y as shown in FIG. This is a device having a function of unevenly distributing the toner particles 1 near the surface of the roller 20Y. By unevenly distributing the toner particles in this way, the development density (development efficiency) can be improved, and as a result, a clear image with high quality can be obtained.
The developer compression roller 22Y is provided with a cleaning blade 23Y.
The cleaning blade 23Y has a function of removing the liquid developer adhering to the developer compression roller 22Y. The liquid developer removed by the cleaning blade 23Y is collected in the liquid developer reservoir 31Y and reused.

  The developing unit 100Y includes a rubber developing roller cleaning blade 21Y that is in contact with the surface of the developing roller 20Y. 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 liquid developer reservoir 31Y and reused.

As shown in FIGS. 1 and 2, the image forming apparatus 1000 includes liquid developer replenishing sections 80Y, 80M, 80C, and 80K that replenish liquid developer to the developing section 30Y. Since the configurations of the liquid developer supply portions 80Y, 80M, 80C, and 80K are the same, the liquid developer supply portion 80Y will be described below.
The liquid developer supply unit 80Y includes a recovered liquid developer storage unit 81Y, a supply liquid developer storage unit 82Y, transport means 83Y and 84Y, a pump 85Y, and a filter 86Y.

  The recovered liquid developer storage unit 81Y mainly stores the recovered liquid developer recovered by the developer recovery unit 18Y, and supplies the recovered liquid developer to the liquid developer storage unit 31Y of the developing unit 30Y by the transport unit 83Y. . In addition, the liquid developer is stored in the replenishment liquid developer storage portion 82Y, and the liquid developer is supplied to the liquid developer storage portion 31Y by the transport means 84Y. The composition of the liquid developer stored in the replenishment liquid developer storage portion 82Y and the composition of the recovered liquid developer stored in the recovered liquid developer storage portion 81Y are the same as the liquid developer stored in the liquid developer storage portion 31Y. It may be different or different.

Further, the liquid developer collected in the developer collecting unit 18Y is supplied to the liquid developer replenishing unit 80Y through the conveyance path 70Y.
The transport path 70Y is provided with a pump 85Y. The pump 85Y transports the liquid developer recovered by each developer recovery section to the recovered liquid developer storage section 81Y.
Further, a filter 86Y is provided in the conveyance path 70Y, and coarse particles, foreign matter, and the like can be removed from the collected liquid developer. Solid content such as coarse particles and foreign matter removed by the filter 86Y is detected by a filter state detection means (not shown). Then, the filter 86Y is replaced based on the detection result. Thereby, the filtering function of the filter 86Y can be stably maintained.

Next, the fixing unit will be described.
The fixing unit F40 fixes the unfixed toner image F5a formed in the above-described developing unit, transfer unit, and the like on the recording medium F5.
As shown in FIG. 4, the fixing unit F40 includes a heat fixing roller F1, a pressure roller F2, a heat-resistant belt F3, a belt stretching member F4, a cleaning member F6, a frame F7, and a spring F9. is doing.

The heat fixing roller (fixing roller) F1 includes a roller base material F1b made of a pipe material, an elastic body F1c covering the outer periphery thereof, and a columnar halogen lamp F1a as a heating source inside the roller base material F1b. It can be rotated counterclockwise as indicated by an arrow in the figure.
Inside the heat fixing roller F1, two columnar halogen lamps F1a and F1a constituting a heating source are incorporated, and the heating elements of these columnar halogen lamps F1a and F1a are arranged at different positions. Yes. Then, by selectively lighting each columnar halogen lamp F1a, F1a, a fixing nip portion where a heat-resistant belt F3, which will be described later, is wound around the heat-fixing roller F1, and a belt stretching member F4, which will be described later, are attached to the heat-fixing roller F1. The temperature controller is easily performed under different conditions from the sliding contact portion, different conditions between the wide recording medium and the narrow recording medium, or the like.

The pressure roller F2 is arranged to face the heat fixing roller F1, and is configured to apply pressure to the recording medium F5 on which the unfixed toner image F5a is formed via a heat-resistant belt F3 described later. Has been.
The pressure roller F2 includes a roller base material F2b made of a pipe material and an elastic body F2c covering the outer periphery thereof, and is rotatable in the clockwise direction indicated by an arrow in the drawing.

  A PFA layer is provided on the surface layer of the elastic body F1c of the heat fixing roller F1. As a result, the elastic bodies F1c and 2c have different thicknesses, but the elastic bodies F1c and 2c are substantially uniformly elastically deformed to form a so-called horizontal nip, and with respect to the peripheral speed of the heat fixing roller F1. Since there is no difference in the conveyance speed of the heat-resistant belt F3 or the recording medium F5, which will be described later, extremely stable image fixing is possible.

The heat-resistant belt F3 is an endless annular belt that is stretched around the outer periphery of the pressure roller F2 and the belt stretching member F4 and is movable, and is sandwiched between the heat fixing roller F1 and the pressure roller F2. is there.
The heat-resistant belt F3 has a thickness of 0.03 mm or more, and its front surface (the surface on which the recording medium F5 comes into contact) is formed of PFA, and the rear surface (the pressure roller F2 and the belt stretching member F4 is in contact). The side surface is formed of a seamless tube having a two-layer structure formed of polyimide. The heat-resistant belt F3 is not limited to this, and can be formed of other materials such as a metal tube such as a stainless steel tube or a nickel electroformed tube, or a heat-resistant resin tube such as silicone.

The belt stretching member F4 is disposed upstream of the fixing nip portion between the heat fixing roller F1 and the pressure roller F2 in the conveyance direction of the recording medium F5, and has an arrow P around the rotation axis F2a of the pressure roller F2. It is arranged so that it can swing in the direction.
The belt stretching member F4 is configured to stretch the heat-resistant belt F3 in the tangential direction of the heat fixing roller F1 in a state where the recording medium F5 does not pass through the fixing nip portion. If the fixing pressure is large at the initial position where the recording medium F5 enters the fixing nip portion, the entry may not be smoothly performed and the recording medium F5 may be fixed in a state where the tip of the recording medium F5 is broken. By adopting a configuration in which F3 is stretched in the tangential direction of the heat fixing roller F1, an inlet port of the recording medium F5 through which the recording medium F5 enters smoothly can be formed, and the stable fixing nip portion of the recording medium F5 can be formed. Can enter.

The belt stretching member F4 is fitted into the inner periphery of the heat-resistant belt F3 and cooperates with the pressure roller F2 to apply a tension f to the heat-resistant belt F3 (a heat-resistant belt F3 is a belt). Sliding on the tension member F4). This belt stretching member F4 is disposed at a position where the heat-resistant belt F3 is wound around the heat fixing roller F1 side from the pressing portion tangent L between the heat fixing roller F1 and the pressure roller F2 to form a nip. The protruding wall F4a protrudes from one end or both ends of the belt stretching member F4 in the axial direction. The protruding wall F4a is formed by the heat-resistant belt F3 when the heat-resistant belt F3 approaches one of the axial ends. The contact to the end of the heat-resistant belt F3 is regulated by contacting the wall F4a. A spring F9 is contracted between the end of the protruding wall F4a opposite to the heat fixing roller F1 and the frame, and the protruding wall F4a of the belt stretching member F4 is lightly pressed by the heat fixing roller F1, so that the belt tension is increased. The frame member F4 is positioned in sliding contact with the heat fixing roller F1.
The position where the belt stretching member F4 is lightly pressed against the heat fixing roller F1 is the nip initial position, and the position where the pressure roller F2 is pressed against the heat fixing roller F1 is the nip end position.

  In the fixing portion F40, the recording medium F5 on which the unfixed toner image F5a is formed enters the fixing nip portion from the nip initial position and passes between the heat-resistant belt F3 and the heat fixing roller F1, and the nip end position. As a result, the unfixed toner image F5a formed on the recording medium F5 is fixed, and then discharged in the tangential direction L of the pressing portion of the pressure roller F2 to the heat fixing roller F1.

The cleaning member F6 is disposed between the pressure roller F2 and the belt stretching member F4.
The cleaning member F6 is in sliding contact with the inner peripheral surface of the heat-resistant belt F3 to clean foreign matter, abrasion powder, and the like on the inner peripheral surface of the heat-resistant belt F3. By cleaning the foreign matter, wear powder, and the like in this way, the heat-resistant belt F3 is refreshed, and the above-described factor of instability of the friction coefficient is removed. Further, the belt stretching member F4 is provided with a recess F4f, and is configured to store foreign matter, abrasion powder, and the like removed from the heat-resistant belt F3.

The fixing unit F40 has a removing blade (removing means) F12 that removes the insulating liquid adhering (remaining) to the surface of the heat fixing roller F1 after fixing the toner image F5a on the recording medium F5. . The removing blade F12 can remove the insulating liquid and simultaneously remove the toner and the like that have moved onto the heat fixing roller F1 during fixing.
In order to stably drive the heat-resistant belt F3 by the pressure roller F2 and the belt stretching member F4 and stably drive the pressure roller F2, the friction coefficient between the pressure roller F2 and the heat-resistant belt F3 is determined by the belt tension. It is good to set larger than the friction coefficient of the frame member F4 and the heat-resistant belt F3. However, the friction coefficient is such that foreign matter enters between the heat-resistant belt F3 and the pressure roller F2 or between the heat-resistant belt F3 and the belt stretching member F4, or the heat-resistant belt F3, the pressure roller F2, and the belt stretching member. It may become unstable due to wear of the contact portion with F4.

  Therefore, the belt tension member F4 and the heat-resistant belt F3 have a winding angle smaller than the winding angle of the pressure roller F2 and the heat-resistant belt F3, and the diameter of the belt stretching member F4 is smaller than the diameter of the pressure roller F2. Set as follows. As a result, the length that the heat-resistant belt F3 slides on the belt stretching member F4 is shortened, which can be avoided from instability factors such as changes with time and disturbances, and the heat-resistant belt F3 is driven stably by the pressure roller F2. Will be able to.

  Specifically, the heat (fixing temperature) applied by the heat fixing roller F1 is preferably 80 to 200 ° C, more preferably 100 to 180 ° C, and further preferably 100 to 150 ° C. Since the liquid developer of the present invention is excellent in fixability at a low temperature, the toner image can be firmly fixed on the recording medium even when the fixing temperature is such a relatively low temperature.

As mentioned above, although this invention was demonstrated based on suitable embodiment, this invention is not limited to these.
For example, the toner particles for liquid developer of the present invention are not limited to those produced by the production method as described above. For example, an arbitrary process and process may be performed in the manufacturing method as described above.

  In the above-described embodiment, a resin liquid containing a resin material and an organic solvent is prepared, and the dispersion liquid is adjusted by adding an aqueous dispersion medium to the resin liquid. However, the present invention is not limited to this. For example, the dispersion liquid may be prepared by adding a resin liquid to the aqueous dispersion medium. Further, for example, a dispersion may be prepared by mixing each material without using a resin liquid.

For example, the liquid developer of the present invention is not limited to those manufactured by the manufacturing method as described above. For example, an arbitrary process and process may be performed in the manufacturing method as described above.
In the above-described embodiment, the toner particles for liquid developer are described as being dispersed in the insulating liquid. However, for example, the toner particles may be crushed at the time of dispersion.
Further, the toner particles for liquid developer of the present invention are not limited to those applied to the liquid developer as described above.
Further, the liquid developer of the present invention is not limited to those applied to the liquid developing device and the fixing device as described above.

[1] Production of liquid developer (Example 1)
First, toner particles were manufactured. In addition, about the process in which temperature is not described, it performed at room temperature (25 degreeC).
<Dispersion adjustment process>
≪Preparation of colorant master solution≫
First, a polyester resin (acid value: 10.0 KOH mg / g, weight average molecular weight Mw: 45,600, glass transition temperature Tg: 48 ° C., softening temperature Tf: 108 ° C.) and a cyan pigment (Daiichi Seisen as a colorant) A mixture (mass ratio R1: cyan pigment = 50: 50) with Pigment Blue 15: 3) manufactured by Kasei Co., Ltd. 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 product cooled as described above was coarsely pulverized to obtain a powder having an average particle size of 1.0 mm or less. A hammer mill was used for coarse pulverization of the kneaded product.
Methyl ethyl ketone was added to the obtained kneaded powder so that the solid content was 30% by mass, and wet dispersion was performed with an Eiger motor mill (manufactured by Eiger, USA: M-1000) to prepare a colorant master solution.

≪Resin preparation process≫
The above colorant master solution: 139.2 parts by weight, methyl ethyl ketone: 3.4 parts by weight, polyester resin R1: 97.4 parts by weight, and Neogen SC-F as an emulsifier (Daiichi Kogyo Seiyaku Co., Ltd.): 1.1 parts by weight A resin solution was prepared by mixing with a high-speed disperser (manufactured by Primics Co., Ltd., TK Robotics / TK homodisper type 2.5 blade). In this solution, the pigment was uniformly finely dispersed. At this time, the solid content of the resin liquid was 58%.

≪Dispersoid formation processing≫
Next, 25.1 parts by weight of 1.0 N ammonia water was added to the resin liquid in the container, and then a high-speed disperser (Primics Co., Ltd., TK Robotics / TK homodisper type 2.5 blade) was used. The stirring blade is sufficiently stirred at a blade tip speed of 7.5 m / s, the temperature of the solution in the flask is adjusted to 25 ° C., and then the stirring blade blade speed is 14.7 m / s while stirring. 170 parts by weight of deionized water was added dropwise to cause phase inversion emulsification. While continuing stirring, 70 parts by weight of deionized water was further added to the resin solution. As a result, an aqueous dispersion in which the dispersoid containing the resin material was dispersed was obtained.

<Joint process>
Next, the aqueous dispersion was transferred to a stirring vessel having a Max Blend blade, and the temperature of the aqueous dispersion was adjusted to 25 ° C. while stirring at a blade tip speed of 1.0 m / s.
Next, while maintaining the same temperature and stirring conditions, 83.5 parts by weight of a 5.0% ammonium sulfate aqueous solution was dropped, and the dispersoids were coalesced to form coalesced particles. After the dropping, stirring was continued until the 50% volume particle diameter Dv (50) [μm] of the coalesced toner particles grew to 2.5 μm. When the Dv (50) of the coalesced particles reached 2.5 μm, 200 parts by weight of deionized water was added to complete the coalescence.

<Desolvation process>
With respect to the obtained unitary particle dispersion, the organic solvent was distilled off under reduced pressure until the solid content was 23 wt%, to obtain a slurry of resin particles.
<First cleaning step>
Next, solid-liquid separation was performed on the slurry, and further redispersion in water (reslurry) and solid-liquid separation were repeated to obtain a wet cake of resin particles.

<Alkali treatment process>
Next, 170 parts by weight of the obtained wet cake was dispersed in 500 parts by weight of water to obtain a resin particle dispersion. The solid content concentration of the resin particle dispersion at this time was 24.4 wt%. Further, the electric conductivity of this resin particle dispersion at 25 ° C. was 15 μS / cm. Moreover, electrical conductivity was performed using Lacom Tester desktop type conductivity meter PC6000.
Next, a 1.0 N aqueous sodium hydroxide solution is added to the resin particle dispersion so that the pH of the resin particle dispersion is 10.0, and the mixture is gently stirred for 30 minutes so as to mix uniformly. went. Stirring was performed using a Max Blend blade and a blade tip speed of 1.0 m / s. The temperature of the resin particle dispersion at this time was 25 ° C. (room temperature).

<Second cleaning step>
Next, the resin particle dispersion subjected to the alkali treatment was subjected to solid-liquid separation, and further redispersion in water (reslurry) and solid-liquid separation were repeatedly performed for washing.
At this time, the electrical conductivity at 25 ° C. of the dispersion in which resin particles are dispersed in water so that the solid content concentration is 10 wt% is 18 μS / cm, and the pH of the dispersion at this time is 9. 2.
After washing, solid-liquid separation was performed to obtain an alkali-treated resin particle wet cake.

<Drying process>
Thereafter, the obtained wet cake was dried using a vacuum dryer to obtain toner particles. Further, Dv (50) is 2.2 μm and Dv (Dv (50) when the 50% volume particle diameter of the toner particles is Dv (50) [μm] and the 50% number particle diameter is Dn (50) [μm]. 50) / Dn (50) was 1.07.
In each example and comparative example, the 50% volume particle size of each particle is Dv (50) [μm], and the 50% number particle size is Dn (50) [μm], which is a Mastersizer 2000 particle analyzer (Malvern Instruments). Ltd.).

<Dispersing process>
Toner particles obtained by the above method: 40 parts by weight, soybean oil transesterification liquid produced by a transesterification reaction between soybean oil and methanol (viscosity 5.1 mPa · s, manufactured by Nisshin Oilio Co., Ltd., trade name “Large” Soybean oil fatty acid methyl "): 60 parts by weight, high oleic rapeseed oil (manufactured by Nisshin Oillio Co., Ltd., trade name" high oleic rapeseed oil "): 90 parts by weight, dispersant (Solsperse 13940, manufactured by Nippon Lubrizol Co., Ltd.): 2.0 parts by weight In addition, 3.0 parts by weight of aluminum stearate (Nihon Yushi Co., Ltd.) as a charge control agent is placed in a ceramic pot (internal volume 600 ml), and zirconia balls (ball diameter: 3 mm) have a volume filling rate of 30%. In a ceramic pot, dispersion was carried out for 8 hours at a rotational speed of 220 rpm in a desktop pot mill to produce a liquid developer.

In the obtained liquid developer, Dv (50) of the toner particles was 2.2 μm, and Dv (50) / Dn (50) was 1.07.
Moreover, the viscosity of the liquid developer measured according to JIS Z8809 using a vibration viscometer at 25 ° C. was 270 mPa · s. The electric resistance of the liquid developer was 2.7 × 10 ¹² Ωcm.

(Examples 2 to 10)
In the same manner as in Example 1 except that the types of pigment and resin were changed as shown in Table 1, and the conditions in the alkali treatment step and the second washing step were changed as shown in Table 1. A liquid developer was produced. In each example, the electrical conductivity of the resin particle dispersion and the dispersion at the end of the second washing step is the solid-liquid separation in the first washing step and the second washing step, respectively. Adjusted by changing the number of times. The styrene acrylate copolymer of Example 10 has an acid value of 12.6 [KOHmg / g], a weight average molecular weight Mw of 3000, a glass transition temperature Tg of 103 ° C., and a softening temperature Tf of 108 ° C. A thing was used.

(Example 11)
<Dispersion adjustment process>
First, polyester resin R2 (acid value: 6) instead of polyester resin R1 (acid value: 10.0 KOH mg / g, weight average molecular weight Mw: 45,600, glass transition temperature Tg: 48 ° C., softening temperature Tf: 108 ° C.) A resin solution was prepared in the same manner as in Example 1, except that 3 KOH mg / g, weight average molecular weight Mw: 49,300, glass transition temperature Tg: 52 ° C., softening temperature Tf: 115 ° C. were used.

≪Dispersoid formation processing≫
Next, 15.1 parts by weight of 1.0 N ammonia water was added to the resin solution in the container, and a high-speed disperser (manufactured by Primics Co., Ltd., TK Robotics / TK homodisper type 2.5 blade) The stirring blade was sufficiently stirred at a blade tip speed of 7.5 m / s. Next, 240 parts by weight of deionized water was prepared. The deionized water was stirred at a blade tip speed of 14.7 m / s with a high-speed disperser (Primics Co., Ltd., TK Robotics / TK Homodisper 2.5 blade). While the above resin solution was added dropwise to deionized water. As a result, an aqueous dispersion in which the dispersoid containing the resin material was dispersed was obtained.
Thereafter, toner particles and a liquid developer were produced in the same manner as in Example 1 except that the conditions in the alkali treatment step and the second washing step were changed as shown in Table 1.

Example 12
<Dispersion preparation process>
≪Wax master adjustment≫
First, polyester resin R1 (acid value: 10.0 KOH mg / g, weight average molecular weight Mw: 45,600, glass transition temperature Tg: 48 ° C., softening temperature Tf: 108 ° C.): 75 parts by weight, carnauba wax: 25 weights Parts, GRAFTER-4001 (manufactured by Nippon Seiki Co., Ltd.): 5 parts by weight and methyl ethyl ketone: 195 parts by weight were mixed, and carnauba wax was dispersed in methyl ethyl ketone with a bead mill to obtain a wax master.

≪Preparation of colorant master solution≫
Next, a colorant master solution was prepared in the same manner as in Example 1 except that the amount of methyl ethyl ketone used was changed. The resulting colorant master solution had a solid content of 40 wt%.

≪Resin preparation process≫
The above-mentioned colorant master solution: 103.5 parts by weight, wax master: 49.7 parts by weight, polyester resin R1: 79.2 parts by weight, and Neogen SC-F as an emulsifier (Daiichi Kogyo Seiyaku Co., Ltd.): 1.1 Part by weight was added and mixed with a high-speed disperser (manufactured by Primics Co., Ltd., TK Robotics / TK homodisper type 2.5 blade) to prepare a resin liquid. In this solution, the pigment was uniformly finely dispersed. At this time, the solid content of the resin liquid was 57.5%.
Thereafter, an aqueous dispersion was prepared and toner particles and a liquid developer were produced in the same manner as in Example 1 except that the conditions for the alkali treatment were changed as shown in Table 1. In the alkali treatment step, a 1.0 N potassium hydroxide aqueous solution was used instead of the sodium hydroxide aqueous solution.

(Comparative Example 1)
First, polyester resin R1 (acid value: 10.0 KOH mg / g, weight average molecular weight Mw: 45,600, glass transition temperature Tg: 48 ° C., softening temperature Tf: 108 ° C.): 40 parts by weight, cyan as a colorant A mixture of 50 parts by weight of a pigment (manufactured by Dainichi Seika Co., Ltd., Pigment Blue 15: 3) and 10 parts by weight of a dispersant (manufactured by Ajinomoto Co., Inc., trade name: Ajisper PB821) was prepared. These components were mixed using a 20 L type Henschel mixer to obtain a raw material for a colorant master.

Next, this raw material was kneaded using a biaxial kneading extruder heated to 120 ° C. to obtain a kneaded product. Next, the kneaded product extruded from the extrusion port of the biaxial kneading extruder was cooled.
The kneaded product cooled as described above was coarsely pulverized to obtain a powder having an average particle size of 1.0 mm or less to obtain a colorant master (pulverized product). A hammer mill was used for coarse pulverization of the kneaded product.
Next, the pulverized product thus obtained: 50 parts by weight and polyester resin R1: 50 parts by weight were kneaded using a biaxial kneading extruder heated to 120 ° C., and after cooling, coarsely pulverized and averaged A powdery colored raw material having a particle size of 1.0 mm or less was obtained.

Next, the coloring material obtained by the above method: 40 parts by weight, soybean oil transesterification liquid produced by transesterification reaction between soybean oil and methanol (viscosity 5.1 mPa · s, manufactured by Nisshin Oilio Co., Ltd., commercial product) Name “soybean oil fatty acid methyl”): 60 parts by weight, high oleic rapeseed oil (manufactured by Nisshin Oilio Co., Ltd., trade name “high oleic rapeseed oil”): 90 parts by weight, dispersant (Solsperse 13940, manufactured by Nihon Lubrizol): 2.0 Part by weight, and aluminum stearate as a charge control agent (Nippon Yushi Co., Ltd.): 3.0 parts by weight are placed in a ceramic pot (internal volume 600 ml), and zirconia balls (ball diameter: 1 mm) are filled in a volume of 30. % In a ceramic pot, and pulverized in a desktop pot mill at a rotational speed of 220 rpm for 48 hours. To produce a body developer.
In the obtained liquid developer, Dv (50) of the toner particles was 2.2 μm, and Dv (50) / Dn (50) was 1.23.

(Comparative Example 2)
The above comparison except that a positively chargeable amide resin (acid value: 10.8 KOH mg / g, weight average molecular weight Mw: 276000, glass transition temperature Tg: 68 ° C., softening temperature Tf: 183 ° C.) was used as the resin material. Toner particles and a liquid developer were produced in the same manner as in Example 1.
(Comparative Example 3)
Toner particles and a liquid developer were produced in the same manner as in Example 1 except that the first washing step and the alkali washing step were not performed.

(Comparative Examples 4 to 8)
Toner particles and liquid development were carried out in the same manner as in Example 1 except that the resin type was changed as shown in Table 1 and the conditions in the alkali treatment step and the second washing step were changed as shown in Table 1. An agent was produced. In each example, the electrical conductivity of the resin particle dispersion and the dispersion at the end of the second washing step is the solid-liquid separation in the first washing step and the second washing step, respectively. Adjusted by changing the number of times.
In Comparative Example 7, coalesced particles could not be produced, and toner particles and liquid developer could not be obtained.

  Table 1 shows the types of pigments and resins used in each example and each comparative example, and the production conditions of the toner particles. In the table, “PB15: 3” is pigment blue 15: 3, “PR238” is pigment red 238, “PBk7” is pigment black 7, “PY180” is pigment yellow 180, “PEs” is polyester resin, “ “StAc” represents a styrene acrylate copolymer, and “amide” represents an amide resin.

[2] Evaluation Each liquid developer obtained as described above was evaluated as follows.
[2.1] Development efficiency Monochromatic liquid developer using the liquid developer obtained in each of the embodiments and comparative examples on the developing roller of the image forming apparatus using an image forming apparatus as shown in FIG. A layer was formed. Next, the developer roller potential is set to 300 V, the surface of the photosensitive member is uniformly charged at 500 V, and the toner particles on the developing roller after the liquid developer layer passes between the photosensitive member and the developing roller; The toner particles on the photoreceptor 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. The value X was determined and evaluated according to the following five-stage criteria. In general, it is considered that toner particles have better charging characteristics, and the narrower the particle size distribution, the better the development efficiency.

A: X ≧ 95
B: 90 ≦ X <95
C: 85 ≦ X <90
D: 80 ≦ X <85
E: X <80

[2.2] Transfer efficiency Using an image forming apparatus as shown in FIG. 2, a monochromatic liquid developer using the liquid developer obtained in each of the above examples and comparative examples on the developing roller of the image forming apparatus. A layer was formed. Next, the potential of the developing roller was set to 300V, and the surface of the photoconductor was uniformly charged at 500V to form a solid toner image on the photoconductor. After the toner image passed between the photoreceptor and the intermediate transfer portion, the toner particles on the photoreceptor and the toner particles on 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 intermediate transfer portion and the concentration of the toner particles collected on the photoreceptor is 100. The value Y (transfer efficiency) multiplied by is determined and evaluated according to the following five-step criteria. In general, it is considered that toner particles have better charging characteristics, and the narrower the particle size distribution, the better the transfer efficiency.

A: Y ≧ 95
B: 90 ≦ Y <95
C: 85 ≦ Y <90
D: 80 ≦ Y <85
E: Y <80

[2.3] Positively Charged Amount The potential difference of the liquid developer obtained in each example and each comparative example was measured using a “microscopic laser zeta electrometer” ZC-2000 manufactured by Microtic Nichion. The evaluation was made according to the following five criteria.
The measurement is performed by diluting the liquid developer with a diluting solvent, putting it in a 10 mm transparent cell, applying a voltage of 300 V at 9 mm between the electrodes, and simultaneously observing the moving speed of the particles in the cell with a microscope. The calculation was performed by calculating the zeta potential from the value.

A: The potential difference is +100 mV or more (very good).
B: Potential difference is +85 mV or more and less than +100 mV (good).
C: The potential difference is +70 mV or more and less than +85 mV (normal).
D: The potential difference is +50 mV or more and less than +70 mV (somewhat bad).
E: Potential difference is less than +50 mV (very bad).

[2.4] Selective Development Using an image forming apparatus as shown in FIG. 1, a toner image of a predetermined pattern of a single color with the liquid developer obtained in each of the examples and comparative examples was recorded on a recording paper (manufactured by Seiko Epson Corporation). , High quality paper LPCPPA4). After the toner image forming operation is repeated 1000 times, the 50% volume particle size of the toner particles in the liquid developer in the liquid developer storage tank is changed to Dv (50) ₁₀₀₀ [μm] by the Mastersizer 2000 particle analyzer (Malvern Instruments Ltd.). Next, the ratio (Dv (50) ₀ / Dv (50) between Dv (50) ₁₀₀₀ [μm] and 50% volume particle size Dv ₀ (50) [μm] in the liquid developer before forming an image. ) ₁₀₀₀ ), and the selective development was evaluated according to the following criteria. Toner particles having some particle size and charging characteristics as the average particle size of the toner particles in the liquid developer reservoir after image formation is closer to the average particle size of the toner particles of the liquid developer before image formation However, it is considered that a phenomenon (so-called selective development) used only for development does not occur, and an image having a clear and high color density can be formed stably over a long period of time.

A: Dv (50) ₀ / Dv (50) ₁₀₀₀ ≧ 95
B: 90 ≦ Dv (50) ₀ / Dv (50) ₁₀₀₀ <95
C: 85 ≦ Dv (50) ₀ / Dv (50) ₁₀₀₀ <90
D: 80 ≦ Dv (50) ₀ / Dv (50) ₁₀₀₀ <85
E: Dv (50) ₀ / Dv (50) ₁₀₀₀ <80

[2.5] Preservability The liquid developers obtained in the respective Examples and Comparative Examples were allowed to stand for 6 months in an environment of a temperature of 20 to 35 ° C. Thereafter, the state of the toner in the liquid developer was visually confirmed and evaluated according to the following five-step criteria.
A: No toner particle floating or coagulation sedimentation is observed.
B: Floating and coagulation sedimentation of toner particles are hardly observed.
C: Slight floating or coagulation sedimentation of toner particles is observed, but as a liquid developer
There is no problem.
D: Floating or coagulation sedimentation of toner particles is clearly observed.
E: Suspension and coagulation sedimentation of toner particles are remarkably observed.

  These results are shown in Table 2 together with the average particle size and particle size distribution of the toner particles. The 50% volume particle diameter of the toner particles is represented by Dv (50) [μm], and the 50% number particle diameter of the toner particles is represented by Dn (50) [μm]. These values are represented by a Mastersizer 2000 particle analyzer (Malvern Instruments Ltd.). Measurement). The particle size distribution of the toner particles is shown as Dv (50) / Dn (50). The toner particle has a narrower particle size distribution as Dv (50) / Dn (50) is smaller.

  As apparent from Table 2, the liquid developer of the present invention had a sufficiently narrow particle size distribution, excellent charging characteristics, and high development efficiency and transfer efficiency. In the liquid developer of the present invention, selective development is suitably prevented, and toner particles are aggregated over a long period of time. On the other hand, satisfactory results were not obtained with the liquid developer of the comparative example.

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. FIG. 6 is a schematic diagram illustrating a state of toner particles in a liquid developer layer on a developing roller. FIG. 2 is a cross-sectional view illustrating an example of a fixing device applied to the image forming apparatus illustrated in FIG. 1.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Toner particle 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 collection part 16Y Destaticizing unit 17Y ... Photoconductor cleaning blade 18Y ... Developer collection unit 20Y, 20M, 20C, 20K ... Developing roller 201Y ... Liquid developer layer 21Y ... Developing roller cleaning blade 22Y ... Developer compression roller 23Y ... Roller cleaning blade 30Y, 30M, 30C, 30K ... developing part 31Y ... liquid developer storage part 32Y ... application roller 33Y ... regulator blade 34Y ... developer stirring roller 40 ... intermediate transfer part 41 ... belt drive roller 42 ... tension roller 4 ... Intermediate transfer part cleaning blade 47 ... Developer recovery part 51Y, 51M, 51C, 51K ... Primary transfer backup roller 52Y, 52M, 52C, 52K ... Intermediate transfer part squeeze device 53Y ... Intermediate transfer part squeeze roller 54Y ... Intermediate transfer part Squeeze backup roller 55Y ... Intermediate transfer unit squeeze cleaning blade 60 ... Secondary transfer unit 61 ... Secondary transfer roller 62 ... Cleaning blade 63 ... Developer recovery unit 70Y ... Conveyance path 80Y, 80M, 80C, 80K ... Liquid developer supply unit 81Y ... recovered liquid developer reservoir 82Y ... replenishment liquid developer reservoir 83Y, 84Y ... transport means 85Y ... pump 86Y ... filter 100Y ... development unit 101Y ... photoconductor squeeze device F40 ... fixing unit (fixing device) F1 ... heat Forming roller (heating roller) F1a ... Column halogen lamp F1b ... Roller base material F1c ... Elastic body F12 ... Removal blade F2 ... Pressure roller F2a ... Rotating shaft F2b ... Roller base material F2c ... Elastic body F3 ... Heat-resistant belt F4 ... Belt tension Mounting member F4a ... Projection wall F4f ... Recess F5 ... Recording medium F5a ... Toner image F6 ... Cleaning member F7 ... Frame F9 ... Spring

Claims (9)

A dispersion preparation step of preparing a dispersion in which a dispersoid containing an organic solvent and a resin material having an acid value of 5.0 to 20 KOHmg / mg is dispersed in an aqueous dispersion medium;
Coalescing a plurality of the dispersoids to obtain coalesced particles; and
Removing the organic solvent contained in the coalesced particles to obtain resin particles; and
A first cleaning step of cleaning the resin particles with an aqueous liquid;
An alkali treatment step of preparing a resin particle dispersion in which the resin particles are dispersed in an aqueous liquid and adjusting the pH of the resin particle dispersion to 8.0 to 12.0;
A second washing step of washing the resin particles in the resin particle dispersion with an aqueous liquid,
The electric conductivity at 25 ° C. of the resin particle dispersion before adjusting the pH of the resin particle dispersion in the alkali treatment step is 50 μS / cm or less,
In the second washing step, washing is performed until the electric conductivity at 25 ° C. of the dispersion liquid when the resin particles are dispersed in water so that the solid content concentration is 10 wt% is 50 μS / cm or less. A method for producing toner particles for a liquid developer.   The method for producing toner particles for liquid developer according to claim 1, wherein in the alkali treatment step, a base defined by Arrhenius is mixed with the resin particle dispersion. The base is mixed with the resin particle dispersion in an aqueous solution state,
The method for producing toner particles for a liquid developer according to claim 2, wherein the concentration of the base in the aqueous solution is 0.5 to 1.5 N.   4. The method for producing toner particles for liquid developer according to claim 1, wherein the resin material contains a styrene-acrylic acid ester copolymer or a polyester resin. In the dispersion liquid preparation step, a resin solution preparation process for preparing a resin liquid containing the resin material and the organic solvent;
5. The method for producing toner particles for liquid developer according to claim 1, further comprising a dispersoid forming process for forming the dispersoid by adding an aqueous liquid to the resin solution.   6. A toner particle for liquid developer produced by the method for producing toner particles for liquid developer according to claim 1. A dispersion preparation step of preparing a dispersion in which a dispersoid containing an organic solvent and a resin material having an acid value of 5.0 to 20 KOHmg / mg is dispersed in an aqueous dispersion medium;
Coalescing a plurality of the dispersoids to obtain coalesced particles; and
Removing the organic solvent contained in the coalesced particles to obtain resin particles; and
A first cleaning step of cleaning the resin particles with an aqueous liquid;
An alkali treatment step of preparing a resin particle dispersion in which the resin particles are dispersed in an aqueous liquid, and adjusting the pH of the resin particle dispersion to 8.0 to 12.0;
A second washing step of obtaining toner particles for liquid developer by washing the resin particles in the resin particle dispersion with an aqueous liquid;
A dispersion step of dispersing the toner particles for liquid developer in an insulating liquid,
The electric conductivity at 25 ° C. of the resin particle dispersion before adjusting the pH of the resin particle dispersion in the alkali treatment step is 50 μS / cm or less,
In the second washing step, washing is performed until the electric conductivity at 25 ° C. of the dispersion in which the resin particles are dispersed in water so that the solid content concentration is 10 wt% is 50 μS / cm or less. A method for producing a liquid developer.   A liquid developer produced by the method for producing a liquid developer according to claim 7.   A liquid developer comprising the toner particles for liquid developer according to claim 8.

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