JP2009042729A - Liquid developer and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid developer that is harmless to the environment and has superior preservability and storage stability and superior fixing characteristics at a low temperature, and to provide an image forming apparatus using such a liquid developer. <P>SOLUTION: The liquid developer includes an insulation liquid containing fatty acid monoester and toner particles comprised of a resin material, the resin material containing a first resin component and a second resin component of which weight-average molecular weight Mw is larger than a weight-average molecular weight of the first resin component. The weight-average molecular weight Mw of the first resin component is 3,000-12,000, the weight-average molecular weight Mw of the second resin component is 20,000-400,000, and when a content of the first resin component in the resin material is defined as A (wt.%) and a content of the second resin component in the resin material is defined as B (wt.%), A and B satisfy a relation: 1.0≤A/B≤9.0. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a liquid developer and an image forming apparatus.

  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 There is a liquid developer (liquid toner) in which a toner as shown in Patent Document 1 is dispersed in an electrically insulating carrier liquid (insulating liquid).

  The method using dry toner handles solid-state toner, so there are advantages in handling, but there are concerns about adverse effects on the human body due to powder, as well as contamination due to scattering of toner, and when toner is dispersed There is a problem with uniformity. Further, the dry toner has a problem that the particles are likely to aggregate and it is difficult to sufficiently reduce the size of the toner particles, and it is difficult to form a toner image with high resolution. 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, in the method using the liquid developer, the toner particles are effectively prevented from aggregating in the liquid developer, so that it is possible to use fine toner particles, and the binder resin has a low softening point. (Low softening temperature) can be used. As a result, in the method using a liquid developer, fine line image reproducibility is good, gradation reproducibility is good, color reproducibility is excellent, and it is also excellent as a high-speed image forming method. It has characteristics.

  However, although the conventional liquid developer improves the dispersibility of the toner particles as compared with the dry toner, the affinity between the insulating liquid and the toner particles is low, and it is difficult to maintain a good dispersion state for a long time. there were. As a result, it has been difficult to ensure sufficient storage stability and long-term stability of the liquid developer. Further, there has been a problem that offset (low temperature offset) and the like frequently occur in fixing at a low temperature accompanying recent energy saving.

JP 2006-251253 A

  An object of the present invention is to provide a liquid developer that is environmentally friendly and excellent in storage stability and low-temperature fixability, and to provide an image forming apparatus using such a liquid developer.

Such an object is achieved by the present invention described below.
The liquid developer of the present invention has an insulating liquid containing a fatty acid monoester and toner particles containing a resin material,
The resin material includes a first resin component and a second resin component having a weight average molecular weight Mw larger than that of the first resin component,
The weight average molecular weight Mw of the first resin component is 3000 to 12000,
The weight average molecular weight Mw of the second resin component is 20,000 to 400,000,
When the content of the first resin component in the resin material is A [wt%] and the content of the second resin component is B [wt%], 1.0 ≦ A / B ≦ 9 0.0 is satisfied.

  In the liquid developer of the present invention, in the liquid developer, at least a part of the fatty acid monoester permeates the toner particles, and the differential scanning calorific value of the toner particles does not permeate the fatty acid monoester. It is preferable that the glass transition temperature Tg measured by measurement DSC is lowered by 10 to 30 ° C.

In the liquid developer of the present invention, the glass transition temperature Tg of the first resin component is 30 to 55 ° C., and
The glass transition temperature Tg of the second resin component is preferably 45 to 70 ° C.
In the liquid developer of the present invention, it is preferable that the first resin component and the second resin component have an ester bond in a chemical structure.

In the liquid developer of the present invention, each of the first resin component and the second resin component has ethylene glycol (EG) and / or neopentyl glycol (NPG) as a constituent monomer component,
The ethylene glycol content in all constituent monomers used when synthesizing each resin component is W (EG) [wt%], and the neopentyl glycol content is W (NPG) [wt%]. The weight ratio W (EG) / W (NPG) of the EG and the NPG used when synthesizing the first resin component is 0 to 1.1, and the second resin The value of the weight ratio W (EG) / W (NPG) between the EG and the NPG used when synthesizing the components is preferably 1.2 to 3.0.

（ただし、ｌは９〜１２の整数、ｍは３〜６の整数、ｎは５〜８の整数、Ｒは−ＯＨ、Ｒ’はＨ−またはＣＨ_３（ＣＨ_２）_ｐＣＯ−であり、ｐは１５〜１８の整数である。） In the liquid developer of the present invention, the content of the fatty acid monoester in the insulating liquid is preferably 10 to 60 wt%.
The liquid developer of the present invention preferably contains a polymer dispersant.
In the liquid developer of the present invention, the polymer dispersant preferably has a structure represented by the following general formula (I).

(However, l is 9-12 integer, m is an integer of 3 to 6, n represents 5-8 integer, R represents -OH, R 'is H- or _CH 3 _{(CH 2)} a p CO-, p is an integer of 15-18.)

In the liquid developer of the present invention, the content of the polymer dispersant in the liquid developer is preferably 1.0 part by weight to 10.0 parts by weight with respect to 100 parts by weight of the toner particles.
The liquid developer of the present invention has an insulating liquid containing a fatty acid monoester and toner particles containing a resin material,
As a result of analyzing the molecular weight distribution of the resin material contained in the toner particles taken out from the liquid developer by a size exclusion chromatography method, the first is derived from the resin component and has a weight average molecular weight of 2800 to 11000. A peak and a second peak derived from the resin component and having a weight average molecular weight of 18000 to 380000 are detected,
The content of the resin component derived from the first peak in the toner particles calculated from the peak area is C [wt%], and the content of the resin component derived from the second peak in the toner particles is D. When [wt%] is satisfied, the relationship 1.1 ≦ C / D ≦ 9.2 is satisfied.

The image forming apparatus of the present invention, using a plurality of liquid developers of different colors, a plurality of developing units that form the single color image corresponding to the plurality of liquid developers,
An intermediate transfer unit that sequentially transfers a plurality of the single-color images formed by the plurality of developing units, and forms an intermediate transfer image formed by superimposing the transferred single-color images;
A secondary transfer unit that transfers the intermediate transfer image to a recording medium and forms an unfixed color image on the recording medium;
A fixing unit for fixing the unfixed color image on the recording medium,
The liquid developer includes an insulating liquid containing a fatty acid monoester, a first resin component having a weight average molecular weight Mw of 3000 to 12000, and a second resin component having a weight average molecular weight Mw of 20000 to 400000. Toner particles containing the resin material, and the content of the first resin component in the resin material is A [wt%] and the content of the second resin component is B [wt%]. When satisfied, the relationship of 1.0 ≦ A / B ≦ 9.0 is satisfied.

In the image forming apparatus of the present invention, the developing unit includes a supply unit that supplies the liquid developer for forming the monochrome image, and a recovery unit that recovers excess liquid developer in the supply unit, A partition provided between the recovery unit and the supply unit;
It is preferable that the excess liquid developer in the supply unit is recovered by the recovery unit through the partition.
By satisfying the above configuration, it is possible to provide a liquid developer that is environmentally friendly and excellent in storage stability and low-temperature fixability, and to provide an image forming apparatus using such a liquid developer. it can.

Hereinafter, preferred embodiments of the present invention will be described in detail.
<Liquid developer>
The liquid developer of the present invention is one in which toner particles mainly composed of a resin material are dispersed in an insulating liquid.
<Toner particles>
First, toner particles will be described.

[Component material of toner particles (toner material)]
The toner particles (toner) constituting the liquid developer of the present invention include at least a resin material.
1. Resin Material The resin material constituting the toner particles includes a first resin component having a weight average molecular weight Mw of 3000 to 12000 and a second resin component having a weight average molecular weight Mw of 20000 to 400000. Thus, since the resin material constituting the toner particles includes both the low molecular weight first resin component and the high molecular weight second resin component, the toner particles are aggregated during storage. This can be surely prevented, and at the time of fixing, the toner particles can be fixed on the recording medium at a relatively low temperature. In the resin material constituting the toner particles, when the content of the first resin component is A [wt%] and the content of the second resin component is B [wt%], 1.0 ≦ A This satisfies the relationship of /B≦9.0.

  The following excellent effects can be obtained with a liquid developer having toner particles containing a resin material that satisfies the above conditions as a constituent and an insulating liquid containing a fatty acid monoester as described below. As will be described in detail later, the fatty acid monoester is a component having a plasticizing effect for plasticizing the resin material constituting the toner particles. That is, in such a liquid developer, the fatty acid monoester suitably enters the resin material constituting the toner particles, and the toner particles are plasticized. Such a resin material includes a second resin component having a high molecular weight, so that when the toner particles thus plasticized come into contact with each other in the liquid developer, they are aggregated or fused. Is reliably prevented. Therefore, the storage stability of the liquid developer is excellent. In particular, even when such a liquid developer is stored at a high temperature, unintentional aggregation and fusion between toner particles can be surely prevented, and the liquid developer has excellent high-temperature storage stability. Become. At the time of fixing, the first resin component having a low molecular weight is a component that can be melted at a relatively low temperature, and the toner particles are plasticized including a fatty acid monoester, so that the toner particles melt. It is possible to reduce the amount of heat required for this. As a result, the toner particles can be suitably fixed to the recording medium at a low temperature. In addition, since the amount of heat required for melting the toner particles can be reduced, the liquid developer can be suitably adapted to high-speed image formation.

  As described above, in the liquid developer of the present invention, the resin material constituting the toner particles includes a predetermined amount of the low-molecular-weight first resin component and the high-molecular-weight second resin component as an insulating liquid. It is characterized by containing a fatty acid monoester, and thereby an excellent effect is obtained. On the other hand, when the liquid developer does not have the above-described configuration, the above excellent effects cannot be obtained.

  More specifically, in the resin material constituting the toner particles, when the content of the first resin component having a low molecular weight is too small and the A / B value is less than the lower limit value, There is a problem. That is, since the toner particles have a high content of the second resin component having a high molecular weight, the storage stability of the liquid developer can be sufficiently increased, but the fatty acid monoester penetrates suitably in the toner particles. I can't let you. As a result, the toner particles cannot be sufficiently plasticized, and the low-temperature fixability of the liquid developer cannot be made sufficient.

  Further, if the content of the high molecular weight second resin component is too small in the resin material constituting the toner particles and the A / B value is larger than the upper limit value, the following problems occur. is there. That is, since the toner particles contain a large amount of the low-molecular-weight first resin component, the toner particles can be fixed to the recording medium at a relatively low temperature. During storage, they will aggregate and fuse with each other. As a result, the storage stability of the liquid developer cannot be made sufficient.

  Further, when the weight average molecular weight Mw of the first resin component having a low molecular weight as described above is less than the above lower limit value, when the fatty acid monoester penetrates into the toner particles, the first resin component is extracted from the toner particles. Dissolves in insulating liquid. Such toner particles are likely to aggregate with each other, resulting in poor storage stability of the liquid developer. Further, the shape of the toner particles becomes unstable, and the particle size tends to vary. As a result, the characteristics (electrical characteristics, etc.) of the toner in the liquid developer become unstable, making it difficult to perform stable development and transfer. On the other hand, when the weight average molecular weight Mw of the first resin component having a low molecular weight is larger than the upper limit, the plastic effect of the fatty acid monoester is not sufficiently exhibited, and the toner particles are fixed to the recording medium at a low temperature. It becomes difficult.

  Further, when the weight average molecular weight Mw of the high molecular weight second resin component as described above is less than the above lower limit value, the fatty acid monoester permeates and the plasticized toner particles easily aggregate. Therefore, the storage stability of the liquid developer cannot be made sufficient. On the other hand, when the weight average molecular weight Mw of the high molecular weight second resin component is larger than the upper limit, the plasticity effect of the fatty acid monoester is not sufficiently exhibited, and the toner particles are fixed to the recording medium at a low temperature. It becomes difficult.

  A / B, which is the content ratio between the content of the first resin component and the content of the second resin component, in the resin material constituting such toner particles is 1.0 ≦ A / B ≦ 9. 0.0 relationship is satisfied, but 1.5 ≦ A / B ≦ 6.0 is preferable, and 2.0 ≦ A / B ≦ 5.0 is more preferable. Thereby, the fatty acid monoester described later penetrates more favorably into the toner particles, and the toner particles are more suitably plasticized. In addition, the toner particles thus plasticized are more reliably prevented from aggregating and fusing. As a result, the storage stability and low-temperature fixability of the liquid developer are particularly excellent.

  Moreover, although the weight average molecular weight Mw of the low molecular weight 1st resin component as mentioned above is 3000-12000, it is preferable that it is 4000-10000, and it is more preferable that it is 5000-7000. Thereby, the storage stability of the toner particles can be made sufficiently excellent. Further, the toner particles infiltrated with the fatty acid monoester and plasticized can be more stably fixed on the recording medium at a low temperature. Further, such a liquid developer can be more suitably applied to image formation at high speed. Furthermore, when the toner particles contain a colorant as described later together with the resin material as described above, the distribution of the colorant in the toner particles can be made more uniform. As a result, the formed toner image becomes clearer.

  Moreover, although the weight average molecular weight Mw of the high molecular weight 2nd resin component as mentioned above is 20000-400000, it is preferable that it is 50000-300000, and it is more preferable that it is 100,000-250,000. As a result, during storage, the fatty acid monoester permeates and the plasticized toner particles are more reliably prevented from aggregating with each other, and the storage stability of the liquid developer is particularly excellent. Further, at the time of fixing, the toner particles can be more preferably fixed at a low temperature. Further, the fixed toner particles are further improved in adhesion to the recording medium and weather resistance, and the obtained toner image has particularly excellent durability.

Further, when the resin material contained in the toner particles taken out from the liquid developer of the present invention produced using the resin material as described above is analyzed by size exclusion chromatography, the resin material is as follows. Satisfy the relationship.
As a result of analyzing the molecular weight distribution of the resin material contained in the toner particles taken out from the liquid developer by a size exclusion chromatography method, the first is derived from the resin component and has a weight average molecular weight of 2800 to 11000. A peak and a second peak derived from the resin component and having a weight average molecular weight of 18,000 to 380000 are detected. That is, the toner particles in the liquid developer include a resin component having a weight average molecular weight of 2800 to 11000 and a resin component having a weight average molecular weight of 18000 to 380000.

  As described above, in the liquid developer, the toner particles are suitably plasticized because the resin material of the toner particles contains a resin component having a relatively low weight average molecular weight. In addition, since the resin material of the toner particles in the liquid developer contains a resin component having a relatively high weight average molecular weight, the toner particles in the liquid developer can be easily maintained in shape. When they come into contact with each other, aggregation or fusion is suppressed.

The content of the resin component derived from the first peak in the toner particles calculated from the peak area is C [wt%], and the content of the resin component derived from the second peak in the toner particles is D. When [wt%] is satisfied, the relationship 1.1 ≦ C / D ≦ 9.2 is satisfied. As a result, the toner particles are more reliably prevented from aggregating and fusing with each other while the toner particles are maintained in a more suitably plasticized state. As a result, the storage stability and low-temperature fixability of the liquid developer are excellent.
As described above, the molecular weight and composition of the resin component used as the constituent material of the toner particles and the resin component of the toner particles taken out from the manufactured liquid developer are different from those of monoester as described later. This is probably because the acid component of the part is liberated and the resin component is decomposed, or a part of the resin component is dissolved in the insulating liquid.

Further, the weight average molecular weight of the resin component derived from the first peak may be within the range as described above, but is preferably 3800 to 95000, more preferably 4800 to 7500, as described above. Effects can be obtained more remarkably.
Further, the weight average molecular weight of the resin component derived from the first peak may be in the range as described above, but is preferably 35000 to 280000, more preferably 95000 to 240000, as described above. Effects can be obtained more remarkably.
Further, C / D is not limited as long as it satisfies the above-mentioned relationship, but preferably 1.6 ≦ C / D ≦ 6.1, and 2.2 ≦ C / D ≦ 5.1. It is more preferable that the effects as described above can be obtained more remarkably.

  The measurement of the molecular weight distribution as described above is performed by size exclusion chromatography, but can be performed by, for example, gel permeation chromatography. Further, in this case, the detected peak can be obtained from the peak area based on a calibration curve prepared with a standard substance, the content of the resin component and the weight average molecular weight. Moreover, as a standard substance which can be used for such a measurement, polystyrene is mentioned, for example.

(First resin component)
The first resin component is not particularly limited as long as the above-described conditions are satisfied. For example, a known resin can be used, and such a resin includes an ester bond in the chemical structure. Those having the following are preferred. A toner composed of a resin that satisfies such conditions has a high affinity for an insulating liquid due to the similarity in chemical structure with a fatty acid monoester described later. Therefore, the dispersibility of the toner particles in the liquid developer can be made particularly excellent, the aggregation of the toner particles during storage can be more effectively prevented, and the storage stability and long-term stability of the liquid developer can be prevented. The property can be made particularly excellent. In addition, toner particles containing such a resin as a constituent component reliably retain the fatty acid monoester permeating into the toner particles, and the toner particles are more suitably plasticized. Thereby, the low temperature fixability of the liquid developer is further improved.

Examples of the resin having an ester bond in the chemical structure include polyester resins, styrene-acrylic acid ester copolymers, and styrene-methacrylic acid ester copolymers. Among these, the polyester resin has high transparency, and when used as a binder resin, the color developability of the obtained image can be increased.
Moreover, when using a polyester resin as a 1st resin component, it is preferable that such a polyester resin has ethylene glycol (EG) and / or neopentyl glycol (NPG) as a structural monomer component. In addition, when synthesizing such a polyester resin, the content of EG in all constituent monomers is W (EG) [wt%], and the content of NPG is W (NPG) [wt%]. The value of the weight ratio W (EG) / W (NPG) between EG and NPG is preferably 0 to 1.1, and more preferably 0.8 to 1.0. As a result, the storage stability of the toner particles can be made sufficiently excellent. Further, the toner particles infiltrated with the fatty acid monoester and plasticized can be more stably fixed on the recording medium at a low temperature. Further, such a liquid developer can be more suitably applied to image formation at high speed.

Moreover, it is preferable that it is 30-55 degreeC, and, as for the glass transition temperature Tg of a 1st resin component, it is more preferable that it is 35-50 degreeC. By using the first resin component satisfying the above conditions as a constituent material of the toner particles, aggregation and fusion of the toner particles are more reliably suppressed during storage, and the storage stability of the liquid developer is superior. It becomes. Further, the toner particles can be more suitably fixed on the recording medium at a low temperature.
Moreover, it is preferable that it is 60-120 degreeC, and, as for the softening temperature Tf of a 1st resin component, it is more preferable that it is 80-110 degreeC. By using a resin material that satisfies the above conditions as a constituent material of the toner particles, during storage, aggregation and fusion of the toner particles are more reliably suppressed, and the storage stability of the liquid developer becomes better. . Further, at the time of fixing, the toner particles can be melted with a smaller amount of heat. Thereby, the toner particles can be fixed more stably at a low temperature. Further, such a liquid developer is more suitably adapted to high-speed image formation.

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.
Further, the content of the first resin component in the resin material constituting the toner particles is preferably 50 to 90 wt%, and more preferably 60 to 80 wt%. As a result, the storage stability and low-temperature fixability of the liquid developer are particularly excellent.

(Second resin component)
The second resin component is not particularly limited as long as the above-described conditions are satisfied. For example, a known resin can be used, and such a resin includes an ester bond in the chemical structure. Those having the following are preferred. A toner composed of a resin that satisfies such conditions has a high affinity for an insulating liquid due to the similarity in chemical structure with a fatty acid monoester described later. Therefore, the dispersibility of the toner particles in the liquid developer can be made particularly excellent, the aggregation of the toner particles during storage can be more effectively prevented, and the storage stability and long-term stability of the liquid developer can be prevented. The property can be made particularly excellent. In addition, toner particles containing such a resin as a constituent component reliably retain the fatty acid monoester permeating into the toner particles, and the toner particles are more suitably plasticized. Thereby, the low temperature fixability of the liquid developer is further improved.

Examples of the resin having an ester bond in the chemical structure include polyester resins, styrene-acrylic acid ester copolymers, and styrene-methacrylic acid ester copolymers. Among these, the polyester resin has high transparency, and when used as a binder resin, the color developability of the obtained image can be increased.
Moreover, when using a polyester resin as a 2nd resin component, it is preferable that such a polyester resin has ethylene glycol (EG) and / or neopentyl glycol (NPG) as a structural monomer component. In addition, when synthesizing such a polyester resin, the content of EG in all constituent monomers is W (EG) [wt%], and the content of NPG is W (NPG) [wt%]. The value of the weight ratio W (EG) / W (NPG) between EG and NPG is preferably 1.2 to 3.0, more preferably 1.5 to 2.0. During storage, the fatty acid monoester permeates and the plasticized toner particles are more reliably prevented from agglomerating with each other, and the storage stability of the liquid developer is particularly excellent. Further, at the time of fixing, the toner particles can be more preferably fixed at a low temperature. Further, the fixed toner particles are further excellent in adhesion to the recording medium and weather resistance, and the obtained toner image has particularly excellent durability.

  Moreover, it is preferable that it is 45-70 degreeC, and, as for the glass transition temperature Tg of a 2nd resin component, it is more preferable that it is 50-65 degreeC. By using the first resin component satisfying the above conditions as a constituent material of the toner particles, aggregation and fusion of the toner particles are more reliably suppressed during storage, and the storage stability of the liquid developer is superior. It becomes. In particular, even when the liquid developer is stored at a high temperature, the toner particles are more reliably prevented from aggregating with each other, and the liquid developer is particularly excellent in high-temperature storage. Further, the toner particles can be more suitably fixed on the recording medium at a low temperature.

  Moreover, it is preferable that it is 60-220 degreeC, and, as for the softening temperature Tf of a 2nd resin component, it is more preferable that it is 80-190 degreeC. By using a resin material that satisfies the above conditions as a constituent material of the toner particles, during storage, aggregation and fusion of the toner particles are more reliably suppressed, and the storage stability of the liquid developer becomes better. . Further, at the time of fixing, the toner particles can be fixed more firmly on the recording medium at a low temperature.

The glass transition temperature Tg of the resin material containing the first resin component and the second resin component as described above is preferably 35 to 60 ° C, and more preferably 40 to 50 ° C. By using the first resin component satisfying the above conditions as a constituent material of the toner particles, aggregation and fusion of the toner particles are more reliably suppressed during storage, and the storage stability of the liquid developer is superior. It becomes. Further, the toner particles can be more suitably fixed on the recording medium at a low temperature.
In addition, the content of the second resin component in the resin material constituting the toner particles is preferably 10 to 50 wt%, and more preferably 20 to 40 wt%. As a result, the storage stability and low-temperature fixability of the liquid developer are particularly excellent.

2. Colorant The toner may contain a colorant. The colorant is not particularly limited, and for example, known pigments and dyes can be used.
3. Other Components The toner may contain components other than those described above. Examples of such components include known waxes and magnetic powders.
In addition to the materials described above, for example, zinc stearate, zinc oxide, cerium oxide, silica, titanium oxide, iron oxide, fatty acid, fatty acid metal salt, and the like are used as toner constituent materials (components). Also good.

[Toner particle shape, etc.]
As the toner particles applied to the liquid developer of the present invention, those having fine irregularities on the surface are preferably used. By having such minute irregularities, the above-described fatty acid monoester can be effectively unevenly distributed (adsorbed) near the surface of the toner particles.
The average value (average circularity) of the circularity R represented by the following formula (II) for the toner particles constituting the liquid developer is preferably 0.94 to 0.99, and preferably 0.96 to 0 More preferred is .99.

R = L ₀ / L ₁ (II)
(Where, L ₁ [μm] is the circumference of the projected image of the toner particles to be measured, and L ₀ [μm] is the circumference of a perfect circle having an area equal to the area of the projected image of the toner particles to be measured) Represents length)
When the average circularity of the toner particles is within such a range, the insulating liquid can be appropriately contained in the unfixed toner image transferred onto the recording medium, and the fixing strength of the toner particles is higher. Can be.

The average particle size of the toner particles composed of the above materials is preferably 0.7 to 3 μm, more preferably 0.8 to 2.5 μm, and 0.8 to 2 μm. More preferably. When the average particle diameter of the toner particles is within the above range, the variation in characteristics among the toner particles is small, and the liquid developer as a whole is made highly reliable while being formed with the liquid developer. The resolution of the toner image can be made sufficiently high. Further, it is possible to improve the dispersion of the toner particles in the insulating liquid and to improve the storage stability of the liquid developer.
The content ratio of the toner particles in the liquid developer is preferably 10 to 60 wt%, and more preferably 20 to 50 wt%.

<Insulating liquid>
Next, the insulating liquid will be described.
The insulating liquid used in the present invention 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. As a result, the plastic effect of the fatty acid monoester on the toner particles can be expressed more suitably, and the liquid developer has particularly excellent fixing characteristics. In addition, aggregation of toner particles during storage can be reliably prevented.

  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. Thereby, the chemical stability of the liquid developer is excellent, and the storage stability and long-term stability of the liquid developer are further improved. 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 further 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.

  Further, the viscosity of such a fatty acid monoester is preferably 10 mPa · s or less, and more preferably 5 mPa · s or less. Accordingly, it is possible to more suitably infiltrate the recording medium, and to more surely promote the penetration of the toner particles melted by the heat at the time of fixing into the recording medium. In addition, for example, when producing a liquid developer by a method as described later, toner particles having a uniform particle diameter can be suitably obtained. In the present specification, unless otherwise specified, the viscosity is a viscosity measured at 25 ° C. using a vibration viscometer in accordance with JIS Z8809.

  The insulating liquid may contain a known liquid as the insulating liquid in addition to the fatty acid monoester as described above. 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 Co., Ltd.), 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, fatty acid diglycerides, fatty acid monoglycerides, glycerin, fatty acid triglyceride degradation products, Prifer 6813 Synthetic ester liquids such as (manufactured by UNIQUEMA), benzene, toluene, xylene, mesitylene, fatty acid monoester, etc. are used, and one or more of these are used in combination. Door can be.

  Among these, the following effects can be obtained when the insulating liquid contains a fatty acid triglyceride. The fatty acid triglyceride is a triester (triglyceride) of glycerin and a fatty acid. That is, the fatty acid triglyceride is a component having excellent affinity with the toner particles and the fatty acid monoester as described above, and a component having a relatively higher viscosity than the fatty acid monoester. Therefore, the insulating liquid containing fatty acid triglyceride in addition to the fatty acid monoester has a more suitable viscosity, and the amount of the fatty acid monoester that penetrates into the toner particles is more suitable. As a result, the toner particles are more suitably plasticized. Further, a liquid developer having such an insulating liquid has better storage stability. This is considered as follows. In other words, in such a liquid developer, the viscosity of the insulating liquid becomes more suitable. As a result, the number of times the toner particles contact and collide with each other is reduced, so that the aggregation of the toner particles is more reliably prevented. This is thought to be due to Further, since fatty acid triglyceride is an environmentally friendly component, 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.

  Further, when an unsaturated fatty acid is included as the fatty acid component constituting the fatty acid triglyceride, the fixing strength of the toner particles on the recording medium can be improved. More specifically, the unsaturated fatty acid component is a component having a function of being cured by being oxidized (by being oxidized at the fixing temperature at the time of fixing) and improving the fixing strength of the toner particles. . Thereby, the fixing strength of the toner particles on the recording medium can be made excellent. Further, since the unsaturated fatty acid component is cured, the fixed toner image can be easily and reliably added with an aqueous ballpoint pen.

The unsaturated fatty acid constituting the fatty acid triglyceride is not particularly limited, but monounsaturated fatty acids such as crotonic acid, myristoleic acid, palmitoleic acid, oleic acid, elaidic acid, vaccenic acid, gadoleic acid, erucic acid, nervonic acid, Polyunsaturated fatty acids such as linoleic acid, α-linolenic acid, γ-linolenic acid, arachidonic acid, eleostearic acid, stearidonic acid, arachidonic acid, succinic acid, docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), etc. These unsaturated fatty acids and their derivatives can be used, and one or more selected from these can be used in combination.
Such unsaturated fatty acid triglycerides are derived from various animal origins such as safflower oil, rice oil, rice bran oil, rapeseed oil, olive oil, canola oil, soybean oil, flaxseed oil, castor oil, etc. It can be efficiently obtained from naturally derived fats and oils such as fats and oils.

Moreover, the saturated fatty acid component may be contained in the fatty acid triglyceride. By including the saturated fatty acid component, it is possible to keep the chemical stability of the liquid developer and the electrical insulation of the insulating liquid even higher.
Examples of the saturated fatty acid constituting such a saturated fatty acid component include butyric acid, caproic acid, caprylic acid, capric acid, lauric acid, myristylic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, lignoceric acid and the like. These can be used alone or in combination of two or more. Among the saturated fatty acids as described above, the number of carbon atoms in the molecule is preferably 6-22, more preferably 8-20, and even more preferably 10-18. . By including a saturated fatty acid component composed of such a saturated fatty acid, the effects as described above are exhibited more significantly.

  Further, when the insulating liquid contains the aliphatic hydrocarbon as described above, the following effects can be obtained. Aliphatic hydrocarbons generally have high electrical resistance and are chemically stable. For this reason, the liquid developer using the aliphatic hydrocarbon has particularly excellent developability and transferability, and the resulting toner image is clear with few defects and the like. Aliphatic hydrocarbons are liquids that absorb less moisture. For this reason, when an aliphatic hydrocarbon is contained in an insulating liquid, it can prevent suitably that an insulating liquid absorbs moisture at the time of a preservation | save, and can prevent suitably that an insulating liquid denatures (deteriorates).

  Further, when the insulating liquid contains the silicone oil as described above, the following effects can be obtained. Silicone oil is an organic compound having a siloxane bond as a skeleton. Silicone oil generally has a high electrical resistance. For this reason, when silicone oil is used as the insulating liquid, the liquid developer has a particularly high electric resistance, and the toner image has excellent transferability and developability. Moreover, since the silicone oil has various viscosities depending on the type, the viscosity of the liquid developer can be made particularly suitable by selecting the silicone oil. Silicone oil is generally a substance that is chemically stable and has little influence on the human body. For this reason, the liquid developer can suitably prevent deterioration of the insulating liquid during storage, and has excellent environmental stability. Even when the insulating liquid leaks out of the image forming apparatus, a safe liquid developer can be obtained.

Further, the liquid developer (insulating liquid) may contain a dispersant that improves the dispersibility of the toner particles.
As such a dispersant, for example, polyvinyl alcohol, carboxymethyl cellulose, polyethylene glycol, Solsperse (trade name of Nippon Lubrizol Co., Ltd.), polycarboxylic acid and its salt, polyacrylic acid metal salt (for example, sodium salt), Polymethacrylic acid metal salt (for example, sodium salt), polymaleic acid metal salt (for example, sodium salt), acrylic acid-maleic acid copolymer metal salt (for example, sodium salt), polystyrene sulfonic acid metal salt (for example, , Sodium salts, etc.), polymer dispersants such as polyamine fatty acid condensation polymers, viscosity minerals, silica, tricalcium phosphate, tristearic acid metal salts (for example, aluminum salts), distearic acid metal salts (for example, aluminum salts, Barium salts), metal stearates (e.g. Calcium salt, lead salt, zinc salt, etc.), linolenic acid metal salt (eg, cobalt salt, manganese salt, lead salt, zinc salt, etc.), octanoic acid metal salt (eg, aluminum salt, calcium salt, cobalt salt, etc.), Oleic acid metal salts (for example, calcium salts, cobalt salts, etc.), palmitic acid metal salts (for example, zinc salts), dodecylbenzenesulfonic acid metal salts (for example, sodium salts), naphthenic acid metal salts (for example, calcium salts) , Cobalt salts, manganese salts, lead salts, zinc salts, etc.), resinic acid metal salts (for example, calcium salts, cobalt salts, manganese lead salts, zinc salts, etc.) and the like.

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. Further, as described above, in the liquid developer of the present invention, the toner particles are suitably plasticized by permeation of the fatty acid monoester. By the presence of the polymer dispersant as described above on the surface of such toner particles, 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. It will be a thing.
Among such polymer dispersants, those having a structure represented by the following general formula (I) are preferable.

（ただし、ｌは９〜１２の整数、ｍは３〜６の整数、ｎは５〜８の整数、Ｒは−ＯＨ、Ｒ’はＨ−またはＣＨ_３（ＣＨ_２）_ｐＣＯ−であり、ｐは１５〜１８の整数である。）

(However, l is 9-12 integer, m is an integer of 3 to 6, n represents 5-8 integer, R represents -OH, R 'is H- or _CH 3 _{(CH 2)} a p CO-, p is an integer of 15-18.)

  The polymer dispersant represented by the general formula (I) as described above has an ester bond in the molecule, and is excellent in affinity with the above-described fatty acid monoester. Therefore, the polymer dispersant having such a structure is uniformly dispersed in the insulating liquid containing the fatty acid monoester and more uniformly adheres to the surface of each toner particle in the liquid developer. In addition, since such a polymer dispersant has a relatively long molecular chain and a branched chain, there are many opportunities for contact with the surface of the toner particles, and the polymer dispersant is firmly attached or adsorbed. As described above, when the dispersant suitably adheres to the surface of the toner particles, the dispersant having the structure described above is interposed between adjacent toner particles, and aggregation of the toner particles is more reliably prevented. In particular, the polymer dispersant having the structure represented by the general formula (I) is a component having a high affinity with the fatty acid monoester, but is a component that does not easily contain the fatty acid monoester in the molecule, and swells. It is a component that is difficult to be plasticized. Therefore, the toner particles to which such a polymer dispersant adheres have a suitable surface hardness, and aggregation of the toner particles can be more reliably prevented. As a result, the storage stability of the liquid developer can be further improved. Further, since such a polymer dispersant is uniformly and firmly attached or adsorbed to each toner particle, the charging characteristics of the entire toner are made more uniform, and the developability and transferability of the liquid developer are improved. Further improve. As a result, it becomes a liquid developer capable of stably forming a clear toner image over a long period of time.

  In the present invention, in the general formula (I), l may be an integer of 9 to 12, but is preferably 10 to 11. As a result, the polymer dispersant can be firmly adhered or adsorbed to the toner particles, and aggregation of the toner particles can be prevented more reliably. Further, the developability and transferability of the liquid developer are further improved, and the liquid developer can be formed stably over a long period of time.

  In the present invention, in the above general formula (I), m may be an integer of 3 to 6, but is preferably 4 to 5. As a result, the polymer dispersant can be firmly adhered or adsorbed to the toner particles, and aggregation of the toner particles can be prevented more reliably. Further, the developability and transferability of the liquid developer are further improved, and the liquid developer can be formed stably over a long period of time.

  In the present invention, in the general formula (I), n may be an integer of 5 to 8, but is preferably 7 to 8. As a result, the polymer dispersant is easily entangled with the toner particles, and aggregation of the toner particles is more reliably prevented. Further, the developability and transferability of the liquid developer are further improved, and the liquid developer can be formed stably over a long period of time.

In the present invention, R ′ constituting the general formula (I) is H— or CH ₃ (CH ₂ ) _p CO—, and p may be an integer of 15-18, but 16-17 Is preferred. As a result, the polymer dispersant can be firmly adhered or adsorbed to the toner particles, and aggregation of the toner particles can be prevented more reliably. Further, the developability and transferability of the liquid developer are further improved, and the liquid developer can be formed stably over a long period of time.

  The content of the polymer 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. It is more preferable that As a result, the polymer dispersant can be evenly adhered or adsorbed on the surface of each toner particle, the toner particles are more reliably prevented from agglomerating, and the storage stability of the liquid developer is further improved. . Further, the charging characteristics of the entire toner can be further improved.

The insulating liquid may contain an antioxidant.
The liquid developer (insulating liquid) may contain a 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.

The electric resistance of the insulating liquid at room temperature (20 ° C.) is preferably 1.0 × 10 ¹¹ Ωcm or more, more preferably 1.0 × 10 ¹² Ωcm or more, and 2.0 × 10 ^12. More preferably, it is at least Ωcm.
The dielectric constant of the insulating liquid is preferably 3.5 or less.
Further, in the liquid developer, the toner particles as described above have a glass transition measured by differential scanning calorimetry DSC more than the toner particles in which the fatty acid monoester does not penetrate due to the penetration of the fatty acid monoester. The temperature Tg is preferably 10 to 30 ° C lower, more preferably 15 to 28 ° C lower, still more preferably 20 to 25 ° C lower. As a result, even when the fatty acid monoester permeates and the plasticized toner particles come into contact with each other, aggregation and fusion are more reliably prevented, and the storage stability of the liquid developer is further improved. . Further, the toner particles can be more stably fixed at a low temperature. Further, by satisfying the configuration of the liquid developer of the present invention, the toner particles are more reliably reduced in glass transition temperature within the above-described range.

The viscosity of the liquid developer composed of each component as described above (viscosity measured at 25 ° C. using a vibration viscometer in accordance with JIS Z8809) is 20 to 900 mPa · s. Is more preferable, 30 to 800 mPa · s is more preferable, and 50 to 500 mPa · s is still more preferable. Thereby, since the penetration of the liquid developer into the recording medium becomes more suitable, the fixing characteristics of the toner particles to the recording medium become more excellent. In addition, the image obtained on the recording medium becomes clear with no unevenness, and is particularly suitable as a liquid developer suitable for image formation at high speed.
In addition, the electrical resistance at room temperature (20 ° C.) of the liquid developer composed of the components as described above is preferably 1.0 × 10 ¹¹ Ωcm or more, and 1.0 × 10 ¹² Ωcm or more. More preferably.

≪Liquid developer manufacturing method≫
Next, an example of a method for producing the liquid developer of the present invention will be described.
The production method to be described mainly involves associating resin fine particles composed of a resin material having a first resin component and a second resin component having a weight average molecular weight Mw larger than that of the first resin component. A process for forming an associated particle to be obtained, and a mixture in which the associated particles are pulverized in the fatty acid monoester, and the toner particle dispersion in which the toner particles are dispersed in the fatty acid monoester and the other components constituting the insulating liquid are mixed. Process.

[Preparation of associated particles]
First, an example of a method for preparing associated particles in which resin fine particles mainly composed of a resin material are associated will be described.
The association particles may be prepared by any method, but in this embodiment, a dispersoid (fine particles) mainly composed of a resin material (toner material) in an aqueous dispersion medium composed of an aqueous liquid. ) Is dispersed, and the dispersoids in the aqueous emulsion are associated to obtain associated particles.

(Preparation of aqueous dispersion)
Hereinafter, the preparation of the aqueous dispersion will be described.
The aqueous dispersion may be prepared by any method, but in this embodiment, first, the toner material as described above is dissolved in a solvent to obtain a toner material solution, and the toner material solution, By mixing with an aqueous dispersion medium composed of an aqueous liquid, an aqueous emulsion in which the dispersoid (liquid dispersoid) containing the toner material is dispersed is obtained, and then at least one of the solvents contained in the aqueous emulsion is obtained. An aqueous dispersion is obtained by removing the part.

The aqueous emulsion can be prepared, for example, as follows (aqueous emulsion preparation step).
First, an aqueous dispersion medium is prepared.
The aqueous dispersion medium is composed of an aqueous liquid.
In the present invention, the “aqueous liquid” refers to a liquid that is excellent in water and / or water compatibility (for example, a liquid having a solubility in 100 g of water at 25 ° C. of 30 g or more). As described above, the aqueous liquid is composed of water and / or a liquid having excellent compatibility with water, but is preferably composed mainly of water. In particular, the water content is 70 wt%. % Or more is preferable, and 90% by weight or more is more preferable. By using such a material, for example, the dispersibility of the dispersoid in the aqueous dispersion medium can be improved, and the dispersoid in the aqueous emulsion can have a relatively small particle size and a variation in size. It can be less. As a result, the toner particles in the finally obtained liquid developer have a small variation in size and shape between the particles, and have a high degree of circularity.

  Specific examples of the aqueous liquid include, for example, water, alcohol solvents such as methanol, ethanol and propanol, ether solvents such as 1,4-dioxane and tetrahydrofuran (THF), and aromatic heterocycles such as pyridine, pyrazine and pyrrole. Compound solvents, amide solvents such as N, N-dimethylformamide (DMF) and N, N-dimethylacetamide (DMA), nitrile solvents such as acetonitrile, and aldehyde solvents such as acetaldehyde.

Further, an emulsifying dispersant 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.
On the other hand, the toner material as described above is dissolved in a solvent to prepare a toner material solution.
Any solvent can be used as long as it dissolves at least a part of the toner material, but it is preferable to use a solvent having a boiling point lower than that of the aqueous liquid described above. Thereby, a solvent can be removed easily.

Moreover, it is preferable that a solvent is a thing with low compatibility with the aqueous dispersion medium (aqueous liquid) mentioned above (for example, a thing with the solubility with respect to 100 g of aqueous dispersion media at 25 degreeC is 30 g or less). Thereby, the toner material can be finely dispersed in a stable state in the aqueous emulsion.
Moreover, the composition of the 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 a solvent is not particularly limited, and examples thereof include ketone solvents such as MEK and aromatic hydrocarbon solvents such as toluene.
In preparing the toner material solution, for example, a kneaded material obtained by kneading a toner material such as a resin material or a colorant may be used. By using such a kneaded product, each component in the kneaded product obtained by kneading can be obtained even when the constituent materials of the toner contain components that are hardly dispersed or compatible with each other. It can be in a sufficiently compatible and finely dispersed state. In particular, when a pigment (colorant) having a relatively low dispersibility in the solvent as described above is used, the resin component or the like is effective around the pigment particles by being kneaded in advance before being dispersed in the solvent. Thus, the dispersibility of the pigment in the solvent is improved (particularly fine dispersion in the solvent is possible), and the color developability of the finally obtained toner is also improved. For this reason, in the case where the constituent material of the toner contains a component that is poor in dispersibility in the aqueous dispersion medium of the aqueous emulsion or a component inferior in solubility in the solvent contained in the dispersion medium of the aqueous emulsion. Even so, the dispersibility of the dispersoid in the aqueous emulsion can be made particularly excellent.

  In addition, as the kneaded material as described above, it is preferable to use a kneaded material obtained by kneading a low molecular weight first resin component and a colorant, and then adding a high molecular weight second resin component. . As a result, the colorant is more uniformly dispersed in the kneaded product. Further, since the first resin component having a low molecular weight and higher dispersibility in the solvent is preferentially adhered to the colorant surface over the second resin component, the dispersibility of the colorant in the solvent. Is further improved, and the color developability of the toner particles finally obtained is further improved.

Next, the toner material solution is gradually added dropwise to the stirred aqueous dispersion medium to obtain an aqueous emulsion in which the dispersoid containing the toner material is dispersed in the aqueous dispersion medium. It is done. Note that when the toner material solution is dropped, the aqueous dispersion medium and / or the toner material solution may be heated.
Further, instead of the above operation, the aqueous dispersion medium may be added while gradually dropping into the stirred toner material solution. Thus, by adding the aqueous dispersion medium to the toner material solution, the toner material solution undergoes phase inversion emulsification, and the aqueous dispersion medium contains the toner material in the same manner as the aqueous emulsion obtained by the above operation. An aqueous emulsion in which the dispersoid is dispersed can be obtained.

Thereafter, the obtained aqueous emulsion is heated or placed in a reduced-pressure atmosphere to remove at least a part of the solvent contained in the dispersoid, and the dispersoid (fine particles) composed of the toner material is dispersed. An aqueous dispersion is obtained.
The content of the dispersoid 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 (liquid developer) can be made particularly excellent while more surely preventing unintentional aggregation of dispersoids in the aqueous dispersion.
The average particle size of the dispersoid in the aqueous dispersion is not particularly limited, but is preferably 0.01 to 3 μm, and more preferably 0.1 to 2 μm. Thereby, the size of the toner particles finally obtained can be optimized. In the present specification, “average particle diameter” refers to an average particle diameter based on volume.

(Association particle formation process)
Next, an electrolyte is added to the aqueous dispersion obtained as described above, and the dispersoid is associated to form associated particles (associated particle forming step).
Examples of the electrolyte to be added include acidic substances such as hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid, and oxalic acid, sodium sulfate, ammonium sulfate, potassium sulfate, magnesium sulfate, sodium phosphate, sodium dihydrogen phosphate, sodium chloride, and chloride. Organic and inorganic water-soluble salts such as potassium, ammonium chloride, calcium chloride, and sodium acetate can be used, and one or more of these can be used in combination. Among these, monovalent cation sulfates such as sodium sulfate and ammonium sulfate can be preferably used for promoting uniform association.

In addition, before adding electrolyte etc., you may add inorganic dispersion stabilizers, such as a hydroxyapatite, and an ionic and nonionic surfactant as a dispersion stabilizer. By adding an electrolyte in the presence of a dispersion stabilizer (emulsifier), non-uniform association can be prevented.
Examples of such a dispersion stabilizer include polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene alkyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene Examples include ethylene sorbitan fatty acid esters, various pluronic nonionic surfactants, alkyl sulfate salt type anionic surfactants, quaternary ammonium salt type cationic surfactants, and the like. Among these, anionic and nonionic surfactants are effective in dispersion stability even when added in a small amount, and can be suitably used. The cloud point of the nonionic surfactant is preferably 40 ° C. or higher.

The amount of the electrolyte added is preferably 0.5 to 15 parts by weight, more preferably 1 to 12 parts by weight, with respect to 100 parts by weight of the solid content in the aqueous dispersion. More preferably. If the amount of electrolyte added is less than the lower limit, dispersoid association may not proceed sufficiently. Further, when the amount of electrolyte added exceeds the upper limit, dispersoids are not uniformly associated, and coarse particles may be generated, and there is a possibility that the size of toner particles finally obtained may vary. is there.
Then, after associating, the associated particles are obtained by performing filtration, washing, drying and the like.
The average particle size of the associated particles obtained 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.

[Crushing process]
Next, the associated particles obtained as described above are crushed in a fatty acid monoester (pulverization step). Thereby, a toner particle dispersion liquid in which toner particles are dispersed in a fatty acid monoester liquid is obtained.
As described above, the fatty acid monoester is a component having a high affinity with the resin materials (first resin component and second resin component) constituting the toner particles. For this reason, when the associated particles are crushed in the fatty acid monoester, the fatty acid monoester is likely to enter between the fine particles (dispersoid) constituting the associated particle, and the associated particles can be efficiently crushed with less energy. Can do. Further, fatty acid monoesters are preferably easily penetrated into the surface of the pulverized associated particles (toner particles), and the toner particles in the liquid developer are suitably plasticized. As a result, the produced liquid developer is excellent in both storage stability and low-temperature fixability.

In addition, since it is pulverized in a liquid called fatty acid monoester, it is possible to prevent generation of toner particles coarsened due to aggregation or the like.
Further, the obtained toner particles have irregularities derived from the fine particles (dispersoid) on the surface thereof, so that the fatty acid monoester can be reliably retained on the irregularities.
Further, in this embodiment, toner particles are obtained by crushing the associated particles, so finer particles (particles that are extremely smaller than particles of a target size) compared to conventional pulverization methods and wet pulverization methods. Generation | occurrence | production can be prevented effectively. As a result, it is possible to effectively prevent a decrease in charging characteristics of the liquid developer due to fine powder.
In addition, since the fatty acid monoester has a relatively low viscosity, it easily enters between the fine particles (dispersoids) constituting the associated particles, and the associated particles can be suitably crushed.

[Mixing process]
Next, the toner particle dispersion liquid obtained as described above and other components constituting the insulating liquid are mixed to disperse the toner particles in the insulating liquid (mixing step).
As described above, the liquid developer of the present invention in which toner particles are dispersed in an insulating liquid containing a fatty acid monoester is obtained.
In the above description, the present embodiment has been described as having a step of crushing the obtained associated particles in a fatty acid monoester (crushing step). However, the obtained associated particles are crushed. Alternatively, the liquid developer may be produced by dispersing in the components constituting the insulating liquid.

<< First Embodiment of Image Forming Apparatus >>
Next, a first embodiment of the image forming apparatus of the present invention will be described. The image forming apparatus of the present invention forms a color image on a recording medium using the liquid developer of the present invention as described above.
FIG. 1 is a schematic view showing a first embodiment 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. FIG. 4 is a schematic view showing a state of toner particles in the liquid developer layer on the developing roller, and FIG. 4 is a cross-sectional view showing an example of a fixing device applied to the image forming apparatus shown in FIG.

As shown in FIGS. 1 and 2, the image forming apparatus 1000 includes four developing units 30Y, 30M, 30C, and 30K, 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, in transferring the toner image 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 the 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 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 at a relatively low fixing temperature.

<< Second Embodiment of Image Forming Apparatus >>
Next, a second embodiment of the image forming apparatus of the present invention will be described.
FIG. 5 is a schematic view showing a second embodiment of an image forming apparatus to which the liquid developer of the present invention is applied, and FIG. 6 is an enlarged view of a part of the image forming apparatus shown in FIG.
As shown in FIGS. 5 and 6, 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 ′, a fixing unit (fixing device) F40 ′, and four liquid developer replenishing units 90Y ′, 90M ′, 90C ′, and 90K ′.

The developing units 30Y ′, 30M ′, and 30C ′ develop the latent image with a yellow liquid developer (Y), a magenta liquid developer (M), and a cyan liquid developer (C), respectively. Has a function of forming a monochrome image of a color corresponding to the above. 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. 6, the developing unit 30Y ′ includes a photoconductor 10Y ′ as an example of an image carrier, a charging roller 11Y ′, an exposure unit 12Y ′, and a developer along the rotation direction of the photoconductor 10Y ′. It has a unit 100Y ′, a photoreceptor 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 photoconductor 10Y ′ is formed on a cylindrical base material and an outer peripheral surface thereof, and has a photosensitive layer made of a material such as amorphous silicon, and is rotatable about a central axis. Rotates clockwise as indicated by the arrow in FIG.
The photoreceptor 10Y ′ is supplied with a liquid developer by a developing unit 100Y ′, which will be 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 a modulated laser is generated based on an image signal input from a host computer (not shown) such as a personal computer or a word processor. Irradiation is performed on the charged 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 photoreceptor squeeze device 101Y ′ is disposed on the downstream side of the developing unit 100Y ′ in the rotation direction so as to face the photoreceptor 10Y ′, and presses and slides on the photoreceptor squeeze roller 13Y ′ and the photoreceptor squeeze roller 13Y ′. The cleaning blade 14Y ′ that removes the liquid developer that comes in contact with the surface and the developer collecting unit 15Y ′ that collects the removed liquid developer are configured. 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 portion 40 ′ by the primary transfer backup roller 51Y ′.
The photoreceptor cleaning blade 17Y ′ is a rubber member in contact with the surface of the photoreceptor 10Y ′, and after the image is transferred onto the intermediate transfer portion 40 ′ by the primary transfer backup roller 51Y ′, the photoreceptor 10Y. 'Has the function of scraping off and removing the liquid developer remaining on the top.

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

Further, the intermediate transfer section 40 ′ is applied with a predetermined tension by a tension roller 49 ′ so that slack is removed. The tension roller 49 ′ is downstream of one driven roller 44 ′ in the rotation (movement) direction of the intermediate transfer unit 40 ′ and upstream of the other driven roller 45 ′ in the rotation (movement) direction of the intermediate transfer unit 40 ′. It is arranged.
Single-color images corresponding to the respective colors formed by the developing units 30Y ′, 30M ′, 30C ′, and 30K ′ by the primary transfer backup rollers 51Y ′, 51M ′, 51C ′, and 51K ′ are formed on the intermediate transfer unit 40 ′. The images are sequentially transferred, and single color images corresponding to the respective colors 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 photoreceptors 10Y ′, 10M ′, 10C ′, and 10K ′ are successively transferred and superposed on the intermediate transfer unit 40 ′. At 60 ', the images are collectively transferred to a recording medium F5' such as paper, film, cloth, or the like. Therefore, when the toner image is transferred to the recording medium F5 ′ in the secondary transfer process, even if the surface of the recording medium F5 ′ is a non-smooth sheet material due to the fiber or the like, the secondary follows the surface of the non-smooth sheet material. An elastic belt member is employed as means for improving transfer characteristics.
The intermediate transfer unit 40 ′ is provided with a cleaning device including an intermediate transfer unit cleaning blade 46 ′, a developer recovery unit 47 ′, and a non-contact type bias applying member 48 ′.

The intermediate transfer portion cleaning blade 46 ′ and the developer recovery portion 47 ′ are arranged on the driven roller 45 ′ side.
The intermediate transfer portion cleaning blade 46 ′ scrapes off the liquid developer adhering to the intermediate transfer portion 40 ′ after the image is transferred onto the recording medium F5 ′ by the secondary transfer unit (secondary transfer portion) 60 ′. It has a function to remove.

The developer recovery unit 47 ′ has a function of recovering the liquid developer removed by the intermediate transfer unit cleaning blade 46 ′.
The non-contact type bias applying member 48 ′ is disposed away from the intermediate transfer portion 40 at a position facing the tension roller 49 ′. The non-contact type bias applying member 48 ′ applies a bias voltage having a polarity opposite to that of the toner to the liquid developer toner (solid content) remaining on the intermediate transfer portion 40 ′ after the secondary transfer. As a result, the toner is discharged, and the electrostatic adhesion force of the toner to the intermediate transfer portion 40 ′ is reduced. In this example, a corona charger is used as the non-contact type bias applying member 48 ′.

  Note that the non-contact type bias applying member 48 ′ is not necessarily disposed at a position facing the tension roller 49 ′. For example, the position between the driven roller 42 and the tension roller 49 ′ is less than the driven roller 44 ′. It can be disposed at any position downstream of the intermediate transfer portion in the moving direction and upstream of the driven roller 45 ′ in the moving direction of the intermediate transfer portion. As the non-contact type bias applying member 48 ′, a known non-contact type charger other than the corona charger can be used.

Further, an intermediate transfer unit squeeze device 52Y ′ is arranged downstream of the primary transfer backup roller 51Y ′ in the moving direction of the intermediate transfer unit 40 ′.
This intermediate transfer portion squeeze device 52Y ′ is a means for removing excess insulating liquid from the transferred liquid developer when the liquid developer transferred onto the intermediate transfer portion 40 ′ has not reached the desired dispersion state. Is provided.

The intermediate transfer unit squeeze device 52Y ′ includes an intermediate transfer unit squeeze roller 53Y ′, an intermediate transfer unit squeeze cleaning blade 55Y ′ that presses and slides against the intermediate transfer unit squeeze roller 53Y ′, and an intermediate transfer unit squeeze cleaning blade. The developer collecting unit 56Y ′ collects the liquid developer removed at 55Y ′.
The intermediate transfer unit squeeze device 52Y ′ collects excess insulating liquid from the developer primarily transferred to the intermediate transfer unit 40 ′, increases the toner particle ratio in the image, and collects originally unnecessary fog toner. It has a function.

  The secondary transfer unit 60 ′ includes a pair of secondary transfer rollers arranged at a predetermined interval along the transfer material moving direction. Of the pair of secondary transfer rollers, the secondary transfer roller disposed on the upstream side in the moving direction of the intermediate transfer portion 40 ′ is the upstream secondary transfer roller 64 ′. The upstream secondary transfer roller 64 'can be brought into pressure contact with the belt driving roller 41' via the intermediate transfer portion 40 '.

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

  In this case, the belt driving roller 41 ′ and the driven roller 44 ′ also function as backup rollers for the upstream side secondary transfer roller 64 ′ and the downstream side secondary transfer roller 65 ′, respectively. That is, the belt driving roller 41 'is also used as an upstream backup roller disposed upstream of the driven roller 44' in the moving direction of the recording medium F5 'in the secondary transfer unit 60'. The driven roller 44 ′ is also used as a downstream backup roller disposed in the secondary transfer unit 60 ′ on the downstream side in the moving direction of the recording medium F <b> 5 ′ from the belt driving roller 41 ′.

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

  Further, the secondary transfer unit 60 ′ includes a secondary transfer roller cleaning blade 66 ′ and a developer recovery unit 67 ′ with respect to the upstream secondary transfer roller 64 ′. Further, the secondary transfer unit 60 ′ includes a secondary transfer roller cleaning blade 68 ′ and a developer recovery unit 69 ′ with respect to the downstream secondary transfer roller 65 ′. Each of the secondary transfer roller cleaning blades 66 ′ and 68 ′ is in contact with the secondary transfer rollers 64 ′ and 65 ′, respectively, and the liquid development remaining on the surfaces of the secondary transfer rollers 64 ′ and 65 ′ after the secondary transfer. Scrape off the agent. Further, the developer collecting sections 67 ′ and 69 ′ collect the liquid developer scraped off from the secondary transfer rollers 64 ′ and 65 ′ by the secondary transfer roller cleaning blades 66 ′ and 68 ′, respectively. Store.

The toner image (transfer image) F5a ′ transferred onto the recording medium F5 ′ by the secondary transfer unit 60 ′ is sent to a fixing unit (fixing device) F40 ′ to be described later and fixed.
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. 6, the developing unit 100Y ′ includes a liquid developer storage unit 31Y ′, a coating roller 32Y ′, a regulating blade 33Y ′, a developer stirring roller 34Y ′, a communication unit 35Y ′, and a recovery screw 36Y. ', A developing roller 20Y', a developing roller cleaning blade 21Y ', and a corona discharger (compression means) 25Y'.

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

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

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

  The regulating blade 33Y 'contacts the surface of the coating roller 32Y' and regulates the amount of liquid developer on the coating roller 32Y '. In other words, the regulation blade 33Y 'plays a role of scraping off excess liquid developer on the application roller 32Y' and measuring the liquid developer on the application roller 32Y 'supplied to the development roller 20Y'. The regulation blade 33Y 'is made of urethane rubber as an elastic body, and is supported by a regulation blade support member made of metal such as iron. The regulation blade 33Y 'is provided on the side where the application roller 32Y' rotates and advances from the liquid developer (that is, the right side in FIG. 6). 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 application roller 32Y ′ (about 77 degrees) is described later. It is lower than the hardness (about 85 degrees) of the pressure contact portion of the 20Y ′ elastic body layer to the surface of the application roller 32Y ′. Further, the excess liquid developer thus scraped off is collected in the supply unit 31aY 'and reused.

The developer stirring roller 34Y ′ has a function of stirring the liquid developer in a uniformly dispersed state. Thus, even when a plurality of toner particles 1 are aggregated, the toner particles 1 can be suitably dispersed.
In the supply unit 31aY ′, 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 the liquid developer is regulated by the regulating blade 33Y ′ and supplied to the developing roller 20Y ′. Further, by stirring by the developer stirring roller 34Y ′, the liquid developer can be stably overflowed to the recovery unit 31bY ′ side beyond the partition 31cY ′, and the liquid developer stays and is compressed. Can be prevented.

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

The communication portion 35Y ′ is provided in the vertical direction below the developer stirring roller 34Y ′, communicates with the liquid developer storage portion 93Y ′, and sucks the liquid developer from the liquid developer mixing tank 93Y ′ to the supply portion 31aY ′. It is.
By providing the communication portion 35Y ′ below the developer stirring roller 34Y ′, the liquid developer supplied from the communication portion 35Y ′ is stopped by the developer stirring roller 34Y ′, and the liquid top surface rises due to blowing. In other words, the upper surface of the liquid is held almost constant, and the developer can be stably supplied to the coating roller 32Y ′.

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

The developing roller 20Y ′ has a liquid developer layer 201Y ′ formed on the surface thereof by supplying the liquid developer from the coating roller 32Y ′.
The developing roller 20Y ′ includes a conductive elastic layer on the outer periphery of an inner core made of metal such as iron, and has a diameter of about 20 mm. The elastic body layer has a two-layer structure. As the inner layer, urethane rubber having a rubber hardness of about 30 degrees JIS-A and a thickness of about 5 mm is used, and as the surface layer (outer layer), the rubber hardness is JIS. A urethane rubber having a thickness of about 30 μm at about 85 ° A is provided. The developing roller 20Y ′ is in pressure contact with the coating roller 32Y and the photoreceptor 10Y ′ in a state of being elastically deformed with the surface layer serving as a pressure contact portion.

  Further, the developing roller 20Y 'can rotate around its central axis, and the central axis is below the rotational central axis of the photoconductor 10Y'. Further, the developing roller 20Y ′ rotates in a direction (counterclockwise in FIG. 6) opposite to the rotation direction (clockwise in FIG. 6) of the photoconductor 10Y ′. 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 corona discharger (compression unit) 25'Y is a device having a function of bringing the liquid developer toner carried on the developing roller 20Y 'into a compressed state. In other words, the corona discharger 25Y ′ applies an electric field having the same polarity as that of the toner particles 1 to the liquid developer layer 201Y ′, as shown in FIG. 3, in the liquid developer layer 201Y ′. The apparatus has a function of unevenly distributing the toner particles 1 in the vicinity of the surface of the developing 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.

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

  As shown in FIGS. 5 and 6, the image forming apparatus 1000 ′ includes liquid developer supply units 90Y ′, 90M ′, which supply liquid developer to the developing units 30Y ′, 30M ′, 30C ′, 30K ′. 90C 'and 90K' are provided. These liquid developer replenishers 90Y ′, 90M ′, 90C ′, and 90K ′ are respectively provided with liquid developer tanks 91Y ′, 91M ′, 91C ′, and 91K ′, and insulating liquid tanks 92Y ′, 92M ′, and 92C. ', 92K' and liquid developer mixing tanks 93Y ', 93M', 93C ', 93K'.

  Each liquid developer tank 91Y ', 91M', 91C ', 91K' contains a high concentration liquid developer corresponding to each color. Insulating liquid tanks 92Y ', 92M', 92C ', and 92K' each contain an insulating liquid. Further, each liquid developer mixing tank 93Y ′, 93M ′, 93C ′, 93K ′ has a predetermined amount of each high-concentration liquid developer from each liquid developer tank 91Y ′, 91M ′, 91C ′, 91K ′. A predetermined amount of each insulating liquid is supplied from each insulating liquid tank 92Y ′, 92M ′, 92C ′, 92K ′.

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

Further, the liquid developer recovered by the recovery unit 31bY ′ is recovered and reused in the liquid developer mixed layer 93Y ′. The same applies to the liquid developer mixing tanks 93M ′, 93C ′, and 93K ′.
Since the fixing unit F40 ′ is the same as that in the above-described embodiment, the description thereof is omitted.
As mentioned above, although this invention was demonstrated based on suitable embodiment, this invention is not limited to these.

For example, the liquid developer of the present invention is not limited to those applied to the liquid developing device and the fixing device as described above.
Further, the liquid developer of the present invention is not limited to those produced by the production method as described above.
In the above-described embodiment, it has been described that an aqueous dispersion is obtained and an association particle is obtained by adding an electrolyte to the aqueous emulsion. However, the present invention is not limited to this. For example, the associating particles are prepared by dispersing a colorant, a monomer, a surfactant, and a polymerization initiator in an aqueous liquid, preparing an aqueous dispersion by emulsion polymerization, and adding an electrolyte to the aqueous dispersion to be associated. It may be prepared using an emulsion polymerization association method, or may be obtained by spray-drying the obtained aqueous dispersion to obtain associated particles.

In the above-described embodiment, the association particles are described as being crushed in the fatty acid monoester. However, as the liquid for pulverizing the association particles, a mixture of the fatty acid monoester and other components constituting the insulating liquid is used. A solution may be used. Even if the associated particles are pulverized in such a mixed solution, the above-described effects can be obtained.
In the above-described embodiment, the insulating liquid has been described as including a fatty acid monoester and other components. However, when the insulating liquid is composed only of a fatty acid monoester, The liquid developer can be produced by omitting the mixing step of the embodiment.

[1] Production of liquid developer (Example 1)
<Preparation of colorant master solution>
First, polyester resin L1 (weight average molecular weight Mw: 5,200, glass transition temperature Tg: 46 ° C., softening temperature Tf: 95 ° C.) as a first resin component, and cyan pigment (Daiichi Seika) as a colorant Pigment Blue 15: 3) (mass ratio L1: cyan pigment = 50: 50) 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.

<Preparation of resin solution>
Colorant master solution: 33 parts by weight methyl ethyl ketone: 200 parts by weight and polyester resin L1: 57.4 parts by weight, polyester resin H1 as a second resin component (weight average molecular weight Mw: 237,000, glass transition temperature Tg: 63 ° C., softening temperature Tf: 182 ° C.): 15.6 parts by weight were added and mixed with an Eiger motor mill (Migrated by Eiger, USA: M-1000) to prepare a resin solution. In this solution, the pigment was uniformly finely dispersed.

<Preparation of aqueous emulsion>
500 parts by weight of the above resin liquid and 45.5 parts by weight of methyl ethyl ketone were placed in a cylindrical 2 L separable flask having a Max blend stirring blade, and the solid content of the resin liquid was 55%.

  Next, 11.7 ammonia water: 41.7 parts by weight (the molar equivalent ratio with respect to the total amount of carboxyl groups of the polyester resin is 1.1) is added to the resin liquid in the flask, and three-one motor (manufactured by Shinto Kagaku Co., Ltd.) is used. The rotation speed of the stirring blade was set to 210 rpm (peripheral speed of stirring blade: 0.71 m / s), and the mixture was sufficiently stirred, and then 133 parts by weight of deionized water was added while maintaining stirring. While adjusting the temperature of the solution in the flask to 25 ° C. and continuing stirring, 133 parts by weight of deionized water was dropped into the resin liquid to cause phase inversion emulsification, and the dispersoid containing the resin material was dispersed. An aqueous emulsion was obtained.

<Production of associated particles by association>
Next, while continuing stirring in the flask, 285 parts by weight of deionized water was added to the aqueous emulsion so that the total amount of 1N ammonia water and water was 593 parts by weight. Subsequently, 2.6 parts by weight of Emul 0 (manufactured by Kao Corporation), which is an anionic emulsifier, was diluted to 30 parts by weight of deionized water and added to the aqueous emulsion.

Thereafter, while maintaining the temperature of the aqueous emulsion at 25 ° C., the rotation speed of stirring was 150 rpm (peripheral speed of stirring blade: 0.54 m / s), and 3.5% ammonium sulfate aqueous solution: 300 parts by weight was dropped. The particle size of the dispersoid aggregate was 3.5 μm. After dropping, stirring was continued until the particle size of the dispersoid aggregates grew to 5.0 μm, and the association operation was completed.
The resulting aggregate dispersion was dried by distilling off the organic solvent under reduced pressure to obtain associated particles.
In addition, the average particle diameter of each particle in each example and comparative example is a volume-based average particle diameter, and the average particle diameter and particle size distribution of these particles are obtained from a Mastersizer 2000 particle analyzer (manufactured by Malvern Instruments Ltd.). And measured. Further, when the glass transition temperature Tg of the associated particles obtained as described above was measured using a differential scanning calorimeter DSC as described later, the glass transition temperature Tg was 47 ° C.

<Preparation of liquid developer>
Associated particles obtained by the above method: 37.5 g, 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 g, dispersant represented by the following structural formula (III): 0.94 g is put in a ceramic pot (internal volume 600 ml), and zirconia balls (ball diameter: 1 mm) are further filled in a volume of 30 % In a ceramic pot, and pulverized for 24 hours at a rotational speed of 220 rpm in a desktop pot mill.

  Thereafter, 90 g of high oleic rapeseed oil (manufactured by Nisshin Oilio Co., Ltd., trade name “High oleic rapeseed oil”) was added, and further diluted and dispersed for 24 hours at a rotation speed of 220 rpm using the desktop pot mill to obtain a liquid developer.

The average particle diameter of the toner particles in the obtained liquid developer was 1.5 μm, and the standard deviation of the particle diameter between the toner particles was 0.65 μm. Moreover, the viscosity of the liquid developer measured in accordance with JIS Z8809 using a vibration viscometer at 25 ° C. was 230 mPa · s. Further, the electric resistance of the liquid developer was 2.5 × 10 ¹² Ωcm. The liquid developer thus obtained was filtered, and the glass transition temperature Tg of the toner particles was measured using a DSC as described later. The Tg was 25 ° C.
The same as above except that magenta pigment: pigment red 122, yellow pigment: pigment yellow 180, black pigment: carbon black (Printex L, manufactured by Degussa) was used instead of cyan pigment. Thus, a magenta liquid developer, a yellow liquid developer, and a black liquid developer were produced.

(Examples 2 to 13)
A liquid developer corresponding to each color was produced in the same manner as in Example 1 except that the resin material used and the type and content of the insulating liquid were configured as shown in Table 1.
(Comparative Examples 1-6)
A liquid developer corresponding to each color was produced in the same manner as in Example 1 except that the resin material used and the type and content of the insulating liquid were configured as shown in Table 1.
The ratio of terephthalic acid (TPA) to isophthalic acid (IPA), ethylene glycol (EG) and neopentyl in all the monomer components used when synthesizing the resins used in the above Examples and Comparative Examples. Table 1 shows the ratio with glycol (NPG) and the physical properties of each resin. In each example and each comparative example, the weight average molecular weight Mw, the glass transition temperature Tg, the softening temperature Tf, the content in the resin material of the first resin component and the second resin component used, in the liquid developer And the glass transition temperature Tg (Tg (1)) of the associated particles before being crushed in the insulating liquid, and the Tg (Tg (2) of the toner particles dispersed in the liquid developer. ΔTg (= Tg (2) −Tg (1)) which is a difference from)), the type of fatty acid monoester, the alcohol component, the content, the type of main components other than the fatty acid monoester, in the insulating liquid Table 2 shows the contents and the like.

Table 3 shows the analysis results of the resin components contained in the toner particles of the liquid developer obtained in each Example and each Comparative Example.
Further, the evaluation of the glass transition temperature Tg of the resin material and toner particles in Table 1 was carried out using DSC (DSC-220C manufactured by SII) as a measuring device, taking about 10 mg of the resin material in an aluminum pan, and the rate of temperature rise: Measurement was performed under the conditions of 10 ° C./min, measurement temperature range: 30 to 150 ° C. In addition, the measurement used the data measured on the same conditions for the 2nd time, raising / lowering temperature (10 degreeC-150 degreeC-10 degreeC).

Moreover, the softening temperature Tf of the resin material in Table 1 was measured using a Koka flow tester (manufactured by Shimadzu Corporation) as a measuring device under conditions of a temperature rising rate: 5 ° C./min and a die hole diameter of 1.0 mm. did.
In Table 1, ethyl laurate refers to a monoester of lauric acid produced by a transesterification reaction between lauric acid and ethanol, and coconut oil fatty acid isobutyl refers to transesterification between coconut oil and isobutanol. The palm oil transesterification liquid produced | generated by reaction means a soybean oil fatty-acid octyl means the soybean oil transesterification liquid produced | generated by the transesterification reaction of a soybean oil and n-octyl alcohol. In Table 1, the polyester resin L1 as the first resin component is “L1”, the polyester resin L2 is “L2”, the polyester resin L3 is “L3”, and the polyester resin H1 as the second resin component is “H1”. ”, Polyester resin H2 as“ H2 ”, polyester resin H3 as“ H3 ”, polyester resin H4 as“ H4 ”, methanol as MeOH, ethanol as EtOH, isobutanol as i-BuOH, n-octyl alcohol as OctOH, and fat High oleic rapeseed oil (manufactured by Nissin Oillio Co., Ltd.) a, Cosmo White P-60 (viscosity 15 mPa · s, manufactured by Cosmo Oil Lubricants Co.) as an aliphatic hydrocarbon, b, Dynaflecia W-8 (viscosity 14 mPa · s, Idemitsu Kosan Co., Ltd.) is represented by c, and the dispersant represented by the structural formula (III) is represented by d.

  Moreover, in Table 3, the analysis of the resin component was performed as follows. First, 20 ml of liquid developer was placed in a 50 ml centrifuge tube made of polypropylene, solid-liquid separation was performed with a centrifuge (relative centrifugal acceleration: 890 G × 3 min), and the supernatant was removed by decantation. Isopar H was added to the residue so that the total amount was 50 ml, sufficiently stirred and mixed with a spatula, and the residue was obtained again by centrifugation and decantation. The above operation was repeated twice, and the insulating liquid was replaced with Isopar H.

  Next, after the residue was naturally dried for 24 hours, the residue was dissolved in tetrohydrofuran and separated into a pigment-derived component (residue) and a resin component solution in which the resin component was dissolved by a centrifuge. Tetrohydrofuran was added to the resin component solution so that the sample concentration (solid content concentration) was 1 mg / ml. The diluted resin component solution was allowed to stand overnight, and then filtered with a syringe filter having a pore size of 0.2 μm, and the resulting filtered solution was used as a sample solution.

Next, the molecular weight distribution of the resin component contained in this sample solution was measured by gel permeation chromatography. For analysis, Tosoh Corporation high-speed GPC system (RI / UV-8220 with built-in HLC-8220 GPC) was used as the apparatus, TSKgel SuperHZM-M (inner diameter: 4.6 mm, length: 15 cm) was used as the column, and column temperature: The measurement was performed under the conditions of 40 ° C. and injection amount: 20 μl. Further, from the obtained molecular weight distribution chart, the standard substance was standard polystyrene (manufactured by Tosoh Corporation), and the weight average molecular weight of the resin component and the content in the toner particles were determined based on the peak area.
In Table 3, “C” is the content of the resin component in the toner particles obtained from the peak area of the first peak, and “D” is the peak area of the second peak. This is the content of the required resin component in the toner particles.

[2] Evaluation Each liquid developer obtained as described above was evaluated as follows.
[2.1] Fixing Strength Using an image forming apparatus as shown in FIG. 1, an image of a predetermined pattern using the liquid developer obtained in each of the above examples and comparative examples was recorded on a recording paper (quality paper manufactured by Seiko Epson Corporation). LPCPPA4). Thereafter, heat fixing was performed using a fixing device as shown in FIG.
Then, after confirming the non-offset area, the fixed image on the recording paper is erased twice (rubber eraser “LION 261-11” manufactured by Lion Business Machine Co., Ltd.) twice with a pressing load of 1.2 kgf, and the remaining ratio of image density Was measured by “X-Rite model 404” manufactured by X-Rite Inc, and evaluated according to the following five-step criteria.
A: Image density residual ratio is 95% or more (very good).
B: Image density remaining rate is 90% or more and less than 95% (good).
C: Image density remaining rate is 80% or more and less than 90% (normal).
D: Image density residual ratio is 70% or more and less than 80% (slightly bad).
E: Image density residual ratio is less than 70% (very bad).

[2.2] Low-temperature fixability Using an image forming apparatus as shown in FIG. 1, images of a predetermined pattern with the liquid developer obtained in each of the examples and comparative examples were recorded on a recording paper (manufactured by Seiko Epson Corporation). , High quality paper LPCPPA4). Thereafter, using a fixing device as shown in FIG. 4, heat fixing was performed at three set temperatures of 110 ° C., 130 ° C., and 150 ° C. for the heat fixing roller.
Then, after confirming the non-offset area, a Scotch mending tape 10 mm width 810-1-18 was applied to the fixed image on the recording paper obtained at each level, and 5 cm / s in a direction of 170 ° with respect to the recording paper surface. The tape was peeled off at a speed of 5 mm, and the residual ratio of the image density was measured by “X-Rite model 528” manufactured by X-Rite Inc. The evaluation was made according to the following five criteria.
A: Image density remaining rate is 95% or more.
B: Image density remaining ratio is 90% or more and less than 95%.
C: Image density remaining rate is 80% or more and less than 90%.
D: Image density remaining ratio is 70% or more and less than 80%.
E: Image density remaining rate is less than 70%.

[2.3] Preservability The liquid developers obtained in the respective Examples and Comparative Examples were allowed to stand for 6 months in an environment at a temperature of 15 to 25 ° 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.

[2.4] Environmental stability of liquid developer (long-term stability)
The liquid developers obtained in the respective Examples and Comparative Examples were allowed to stand for 6 months in an environment of 35 ° C. and a relative humidity of 65%. Thereafter, the state of the liquid developer was observed, and changes in the viscosity, color, acid value, and electrical resistance value before and after being allowed to stand were evaluated according to the following five criteria. The acid value was measured according to JIS K2501. The change in color of the liquid developer was evaluated visually. The viscosity was measured according to JIS Z8809 using a vibration viscometer. In addition, the electrical resistance value was measured using a universal electrometer MMAII-17B, a liquid electrode LP-05, and a shield box P-618 (manufactured by Kawaguchi Electric Manufacturing Co., Ltd.).

A: No change in viscosity / color / acid value / electric resistance value of the liquid developer is observed.
B: Almost no change in viscosity / color / acid value / electric resistance value of the liquid developer is observed.
C: A slight change in viscosity / color / acid value / electric resistance value of the liquid developer is observed, but it is in a range where there is no problem as a liquid developer.
D: A change in viscosity / color / acid value / electric resistance value of the liquid developer is clearly recognized.
E: A change in the viscosity / color / acid value / electric resistance value of the liquid developer is noticeable.
These results are shown in Table 2 together with the average particle diameter, viscosity and electric resistance of the toner particles. The viscosity and electrical resistance were expressed according to the following four-stage criteria.

<Viscosity>
Very good (A): 50 mPa · s or more and 500 mPa · s or less.
Good (B): 30 mPa · s or more and 800 mPa · s or less. (Except 50mPa · s or more and 500mPa · s or less)
Allowable range (C): 20 mPa · s or more and 900 mPa · s or less. (Except for 30mPa · s or more and 800mPa · s or less)
Poor (D): Less than 20 mPa · s or more than 900 mPa · s.

<Electrical resistance>
Very good (A): 2.0 × 10 ¹² Ωcm or more.
Good (B): 1.5 × 10 ¹² Ωcm or more and less than 2.0 × 10 ¹² Ωcm.
Tolerable range (C): 1.0 × 10 ¹² Ωcm or more and less than 1.5 × 10 ¹² Ωcm.
Poor (D): Less than 1.0 × 10 ¹² Ωcm.

[2.5] Durability Using an image forming apparatus as shown in FIG. 5, images of a predetermined pattern with the liquid developer obtained in each of the examples and comparative examples were printed on 5000 sheets of recording paper (Seiko Epson). Using a fixing device as shown in FIG. 4, the heat fixing roller was set at 130 ° C. and heat-fixed. Regarding the image density ODs of the image on the recording paper printed on the first sheet and the image density ODe of the image on the recording paper printed on the 5000th sheet, “X-Rite model 528” manufactured by X-Rite Inc. And measured. Then, an image density maintenance ratio (ODe / ODs × 100) as an index of durability was obtained and evaluated according to the following five-step criteria.

A: Image density maintenance rate is 90% or more.
B: Image density maintenance rate is 80% or more and less than 90%.
C: Image density maintenance rate is 70% or more and less than 80%.
D: Image density maintenance rate is 60% or more and less than 70%.
E: Image density remaining rate is less than 60%.
These results are shown in Table 4.

  As is apparent from Table 4, the liquid developer of the present invention is suitable for low-temperature fixing, and the formed toner image is firmly fixed on the recording medium even when fixing is performed at a relatively low temperature. Was. Further, the liquid developer of the present invention was excellent in storage stability and long-term stability. On the other hand, satisfactory results were not obtained with the liquid developer of the comparative example.

1 is a schematic diagram illustrating a first embodiment 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. It is a schematic diagram showing a second embodiment of an image forming apparatus to which the liquid developer of the present invention is applied. FIG. 6 is an enlarged view of a part of the image forming apparatus shown in FIG. 5.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Toner particle 1000, 1000 '... Image forming apparatus 10Y, 10M, 10C, 10K, 10Y', 10M ', 10C', 10K '... Photoconductor 11Y, 11Y' ... Charging roller 12Y, 12Y '... Exposure unit 13M, 13Y, 13M ', 13Y' ... photosensitive squeeze rollers 14M, 14Y, 14M ', 14Y' ... cleaning blades 15M, 15Y, 15M ', 15Y' ... developer recovery unit 16Y, 16Y '... static elimination units 17Y, 17Y' ... Photoconductor cleaning blades 18Y, 18Y '... developer recovery unit 20Y, 20M, 20C, 20K, 20Y', 20M ', 20C', 20K '... developing roller 201Y, 201Y' ... liquid developer layer 21Y, 21Y '... development Roller cleaning blade 22Y ... Developer compression roller 23Y ... Image compression roller cleaning blade 24Y '... developer recovery unit 25Y' ... corona discharger (compression means) 30Y, 30M, 30C, 30K, 30Y ', 30M', 30C ', 30K' ... development units 31Y, 31Y '... Liquid developer storage unit 31aY '... supply unit 31bY' ... collection unit 31cY '... partition 32Y, 32Y' ... application roller 33Y, 33Y '... regulator blade 34Y, 34Y' ... developer stirring roller 35Y '... communication unit 36Y' ... Recovery screw 40, 40 '... Intermediate transfer portion 41, 41' ... Belt drive roller 42, 49 '... Tension roller 44', 45 '... Driven roller 46, 46' ... Intermediate transfer portion cleaning blade 47, 47 '... Developer Collection unit 48 '... non-contact type bias applying member 51Y, 51M, 51C, 51K, 51Y' 51M ', 51C', 51K '... Primary transfer backup roller 52Y, 52M, 52C, 52K, 52Y', 52M ', 52C', 52K '... Intermediate transfer unit squeeze device 53Y, 53Y' ... Intermediate transfer unit squeeze roller 54Y ... Intermediate transfer unit squeeze backup roller 55Y, 55Y '... Intermediate transfer unit squeeze cleaning blade 56Y' ... Developer recovery unit 60,60 '... Secondary transfer unit 61 ... Secondary transfer roller 62 ... Roller cleaning blade 63 ... Developer recovery Portion 64 '... Upstream side secondary transfer roller 65' ... Downstream side secondary transfer roller 66 ', 68' ... Secondary transfer roller cleaning blades 67 ', 69' ... Developer recovery unit 70Y ... Conveyance paths 80Y, 80M, 80C , 80K ... Liquid developer supply unit 81Y ... Recovered liquid developer storage Part 82Y ... replenishment liquid developer storage part 83Y, 84Y ... conveying means 85Y ... pump 86Y ... filter 90Y ', 90M', 90C ', 90K' ... liquid developer replenishment part 91Y ', 91M', 91C ', 91K' ... Liquid developer tanks 92Y ', 92M', 92C ', 92K' ... Insulating liquid tanks 93Y ', 93M', 93C ', 93K' ... Liquid developer mixing tanks 100Y, 100Y '... Development units 101Y, 101Y' ... Photosensitive Body squeeze device F40, F40 '... Fusing unit (fixing device) F1 ... Heat fixing roller (heating roller) F1a ... Column halogen lamp F1b ... Roller base material F1c ... Elastic body F12 ... Removing blade F2 ... Pressure roller F2a ... Rotating shaft F2b ... Roller base material F2c ... Elastic body F3 ... Heat-resistant belt F4 ... Belt stretch member F4a ... Projection wall F4f ... concave portion F5, F5 '... recording medium F5a ... toner image F6 ... cleaning member F7 ... frame F9 ... spring

Claims (12)

An insulating liquid containing a fatty acid monoester, and toner particles containing a resin material;
The resin material includes a first resin component and a second resin component having a weight average molecular weight Mw larger than that of the first resin component,
The weight average molecular weight Mw of the first resin component is 3000 to 12000,
The weight average molecular weight Mw of the second resin component is 20,000 to 400,000,
When the content of the first resin component in the resin material is A [wt%] and the content of the second resin component is B [wt%], 1.0 ≦ A / B ≦ 9 A liquid developer satisfying the relationship of 0.0.   In the liquid developer, at least a part of the fatty acid monoester is infiltrated into the toner particles, and the glass transition measured by differential scanning calorimetry DSC is more than the toner particles in the state where the fatty acid monoester is not infiltrated. The liquid developer according to claim 1, wherein the temperature Tg is 10 to 30 ° C. lower. The glass transition temperature Tg of the first resin component is 30 to 55 ° C., and
3. The liquid developer according to claim 1, wherein the glass transition temperature Tg of the second resin component is 45 to 70 ° C. 4.   The liquid developer according to claim 1, wherein the first resin component and the second resin component have an ester bond in a chemical structure. Each of the first resin component and the second resin component has ethylene glycol (EG) and / or neopentyl glycol (NPG) as a constituent monomer component,
The ethylene glycol content in all constituent monomers used when synthesizing each resin component is W (EG) [wt%], and the neopentyl glycol content is W (NPG) [wt%]. The weight ratio W (EG) / W (NPG) of the EG and the NPG used when synthesizing the first resin component is 0 to 1.1, and the second resin The value of the weight ratio W (EG) / W (NPG) of the EG and the NPG used when synthesizing components is 1.2 to 3.0. Liquid developer.   The liquid developer according to claim 1, wherein the content of the fatty acid monoester in the insulating liquid is 10 to 60 wt%.   The liquid developer according to claim 1, wherein the liquid developer contains a polymer dispersant. The liquid developer according to claim 7, wherein the polymer dispersant has a structure represented by the following general formula (I).

(However, l is 9-12 integer, m is an integer of 3 to 6, n represents 5-8 integer, R represents -OH, R 'is H- or _CH 3 _{(CH 2)} a p CO-, p is an integer of 15-18.)   The liquid developer according to claim 7 or 8, wherein a content of the polymer dispersant in the liquid developer is 1.0 to 10.0 parts by weight with respect to 100 parts by weight of the toner particles. An insulating liquid containing a fatty acid monoester, and toner particles containing a resin material;
As a result of analyzing the molecular weight distribution of the resin material contained in the toner particles taken out from the liquid developer by a size exclusion chromatography method, the first is derived from the resin component and has a weight average molecular weight of 2800 to 11000. A peak and a second peak derived from the resin component and having a weight average molecular weight of 18000 to 380000 are detected,
The content of the resin component derived from the first peak in the toner particles calculated from the peak area is C [wt%], and the content of the resin component derived from the second peak in the toner particles is D. A liquid developer characterized by satisfying a relationship of 1.1 ≦ C / D ≦ 9.2 when [wt%] is satisfied. Using a plurality of liquid developers having different colors, a plurality of developing units that form the single-color images corresponding to the plurality of liquid developers;
An intermediate transfer unit that sequentially transfers a plurality of the single-color images formed by the plurality of developing units, and forms an intermediate transfer image formed by superimposing the transferred single-color images;
A secondary transfer unit that transfers the intermediate transfer image to a recording medium and forms an unfixed color image on the recording medium;
A fixing unit for fixing the unfixed color image on the recording medium,
The liquid developer includes an insulating liquid containing a fatty acid monoester, a first resin component having a weight average molecular weight Mw of 3000 to 12000, and a second resin component having a weight average molecular weight Mw of 20000 to 400000. Toner particles containing a resin material, and the content of the first resin component in the resin material is A [wt%] and the content of the second resin component is B [wt%]. The image forming apparatus satisfies the relationship of 1.0 ≦ A / B ≦ 9.0. The developing unit includes a supply unit that supplies the liquid developer for forming the monochromatic image, a recovery unit that recovers excess liquid developer in the supply unit, the recovery unit, and the supply unit. And a partition provided between
The image forming apparatus according to claim 11, wherein excess liquid developer in the supply unit is collected by the collection unit through the partition.

Images