JP4940699B2 - Liquid developer, method for producing liquid developer, and image forming apparatus - Google Patents

Description

The present invention relates to a liquid developer, a method for producing a liquid developer, and an image forming apparatus .

A dry toner method in which a toner composed of a material containing a colorant such as a pigment and a binder resin is used in a dry state as a developer used to develop the electrostatic latent image formed on the latent image carrier. And a method using a liquid developer in which toner 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, since the insulating liquid that has been used in conventional liquid developers is mainly composed of petroleum-based hydrocarbons, it adversely affects the environment when, for example, it goes out of an image forming apparatus or the like. There was concern.
In general, in a liquid developer, an insulating liquid adheres to the surface of toner particles during fixing. In the conventional liquid developer, there is also a problem that the insulating liquid adhering to the surface of the toner particles decreases the fixing strength. In order to improve the fixing strength of the toner, it may be possible to fix the toner particles by heating at a relatively high temperature for a long time, but it satisfies the recent demand for higher speed and energy saving of image formation. It was difficult.

In order to solve the above problems, there is an attempt to use natural fats and oils as the insulating liquid (see, for example, Patent Document 1).
The liquid developer described in Patent Document 1 uses an oxidative polymerization reaction of natural fats and oils to improve fixability. However, natural fats and oils have low permeability to recording media and have sufficiently high fixing strength. It was difficult to get.

Japanese Patent Laid-Open No. 11-212035

An object of the present invention is to provide a liquid developer that is excellent in fixing characteristics of toner particles to a recording medium and is environmentally friendly, and that can efficiently produce such a liquid developer. Another object of the present invention is to provide a method for producing an agent 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 comprises toner particles in which fatty acid monoesters are unevenly distributed on the surface;
And an insulating liquid containing an unsaturated fatty acid triglyceride .
As a result, it is possible to provide a liquid developer that is excellent in fixing characteristics of toner particles onto a recording medium and that is environmentally friendly.

In the liquid developer of the present invention, the fatty acid monoester preferably has a viscosity of 10 mPa · s or less.
Accordingly, it is possible to more suitably permeate the recording medium, and to more surely promote the penetration of the toner particles and unsaturated fatty acid triglyceride melted by the heat at the time of fixing into the recording medium.
In the liquid developer of the present invention, the fatty acid monoester is preferably an ester of a saturated fatty acid having 8 to 18 carbon atoms.
Thereby, the fatty acid monoester can be unevenly distributed on the toner particle surface.

In the liquid developer of the present invention, the resin material of the toner particles is preferably a polyester resin.
Thereby, the dispersibility of the toner particles in the liquid developer can be made particularly excellent. Moreover, the polyester resin has high transparency, and when used as a binder resin, the color developability of the obtained image can be made high.

The method for producing a liquid developer of the present invention is a method for producing a liquid developer having an insulating liquid containing toner particles in which fatty acid monoesters are unevenly distributed on the surface and unsaturated fatty acid triglycerides ,
In the fatty acid monoester, a pulverizing step of pulverizing a toner material including a resin material to obtain a pulverized dispersion;
A mixing step of mixing the pulverized dispersion and the liquid containing the unsaturated fatty acid triglyceride ;
It is characterized by having.
In this way, in the liquid developer finally obtained by pulverizing the constituent material of the toner particles in the fatty acid monoester, the toner particles are unevenly distributed (attached) to the surface of the toner particles. It becomes.
In the method for producing a liquid developer of the present invention, in the pulverizing step, the toner material is preferably pulverized in a state where a dispersant is contained in the fatty acid monoester.
As a result, the dispersant acts as a pulverization aid, and the toner material can be pulverized more efficiently and the dispersibility of the resulting toner particles can be made higher.

The method for producing a liquid developer of the present invention is a method for producing a liquid developer having an insulating liquid containing toner particles in which fatty acid monoesters are unevenly distributed on the surface and unsaturated fatty acid triglycerides ,
A step of associating fine particles having a resin material to obtain associated particles;
Crushing the associated particles in the fatty acid monoester to obtain the toner particles;
It said toner particles, characterized by having a a dispersion step of dispersing in a liquid containing the unsaturated fatty acid triglyceride.
Thus, by crushing the associated particles in the fatty acid monoester, the toner particles are unevenly distributed (attached) near the surface of the toner particles in the finally obtained liquid developer. That is, the fatty acid monoester can be unevenly distributed on the surface of the toner particles by applying a large shearing force of crushing.
An image forming apparatus according to the present invention includes a liquid developer storage unit that stores a liquid developer having an insulating liquid containing toner particles in which fatty acid monoesters are unevenly distributed on the surface and unsaturated fatty acid triglycerides,
A developing unit for developing using the liquid developer supplied from the liquid developer storage unit;
An image carrier for carrying an image developed in the developing unit;
A transfer unit that transfers the image developed by the developing unit to a recording medium;
A fixing unit that heat-fixes the recording medium onto which the image has been transferred;
It is characterized by providing.

Hereinafter, preferred embodiments of a liquid developer, a method for producing a liquid developer, and an image forming apparatus according to the present invention will be described in detail.
<Liquid developer>
First, the liquid developer of the present invention will be described.
In the liquid developer of the present invention, toner particles in which fatty acid monoesters are unevenly distributed near the surface are dispersed in an insulating liquid containing unsaturated fatty acid triglycerides.

<Insulating liquid>
First, the insulating liquid will be described.
The insulating liquid used in the present invention contains an unsaturated fatty acid triglyceride.
Unsaturated fatty acid triglycerides are oils and fats derived from plants and are environmentally friendly components. Accordingly, 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.

Unsaturated fatty acid triglycerides are components that can contribute to improving the fixing property of toner particles to a recording medium. More specifically, the unsaturated fatty acid triglyceride is a component having a function of curing itself and improving the fixing property of toner particles by oxidative polymerization (by oxidative polymerization at a fixing temperature at the time of fixing). .
However, since unsaturated fatty acid triglycerides have low permeability to a recording medium, it is difficult to obtain sufficient fixing characteristics when an insulating liquid containing unsaturated fatty acid triglycerides is simply used.

Therefore, as a result of intensive studies, the present inventors have used, as a liquid developer, toner particles in which fatty acid monoesters are unevenly distributed in the vicinity of the surface are dispersed in an insulating liquid containing unsaturated fatty acid triglycerides. The present inventors have found that toner particles can be firmly fixed on a recording medium.
More specifically, since the fatty acid monoester is a component that easily penetrates into the recording medium, the fatty acid monoester unevenly distributed in the vicinity of the surface of the toner particles is applied to the recording medium when the toner particles come into contact with the recording medium during fixing. Quickly penetrate. Along with the permeation of the fatty acid monoester, 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, an anchor effect works, and the fixing strength is improved. . Further, along with the penetration of the fatty acid monoester, a part of the unsaturated fatty acid triglyceride existing near the surface of the toner particle also penetrates, and the toner particles are fixed more firmly by oxidative polymerization in this state.

In addition, since fatty acid monoesters have high affinity with unsaturated fatty acid triglycerides, dispersibility of toner particles can be improved by using toner particles in which fatty acid monoesters are unevenly distributed near the surface as in the present invention. As a result, it is possible to effectively prevent toner particles from being settled or aggregated during storage. That is, the liquid developer has high storage stability.
Further, by using a monoester of saturated fatty acid, the storage stability of the liquid is superior to the case of using an unsaturated monoester.

  Examples of the fatty acid monoester unevenly distributed on the surface of the toner particles include oleic acid, palmitoleic acid, linoleic acid, α-linolenic acid, γ-linolenic acid, arachidonic acid, docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), and the like. Alkyl (methyl, ethyl, propyl, butyl, etc.) monoesters, butyric acid, caproic acid, caprylic acid, capric acid, lauric acid, myristylic acid, palmitic acid, stearic acid, arachidic acid, behenic acid represented by And alkyl (methyl, ethyl, propyl, butyl, etc.) monoesters of saturated fatty acids typified by lignoceric acid and the like, and one or more selected from these can be used in combination.

Among the above, the fatty acid monoester is preferably an ester of a saturated fatty acid having 8 to 18 carbon atoms. Thereby, the fatty acid monoester can be unevenly distributed on the toner particle surface.
The viscosity of the fatty acid monoester as described above is preferably 10 mPa · s or less, and more preferably 5 mPa · s or less. Accordingly, it is possible to more suitably permeate the recording medium, and to more surely promote the penetration of the toner particles and unsaturated fatty acid triglyceride 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.

  The fatty acid monoester as described above is not only unevenly distributed on the surface of the toner particles, but may also be contained in the toner particles or in the insulating liquid. When fatty acid monoester is contained inside the toner particles, the toner particles are crushed at the time of fixing, and at the same time, the toner particles can be squeezed out and more effectively promote the penetration of the melted toner particles into the recording medium. can do. Further, when the fatty acid monoester is contained in the insulating liquid, the viscosity of the insulating liquid can be made moderate.

  Examples of unsaturated fatty acid triglycerides include monounsaturated fatty acid triglycerides represented by oleic acid, palmitoleic acid, ricinoleic acid, linoleic acid, α-linolenic acid, γ-linolenic acid, arachidonic acid, docosahexaenoic acid (DHA). ), Polyunsaturated fatty acid triglycerides represented by eicosapentaenoic acid (EPA) and the like, and one or more of them can be used.

Among the above-mentioned, polyunsaturated fatty acid triglycerides are preferably used, and among polyunsaturated fatty acid triglycerides, those having a conjugated unsaturated bond (conjugated unsaturated fatty acid triglyceride) are more preferably used. Thereby, the oxidative polymerization reaction can proceed more effectively.
As such a conjugated unsaturated fatty acid triglyceride, any one having a conjugated unsaturated bond may be used. For example, a synthesized one may be used, or one extracted directly from vegetable oil or the like. May be used, and those obtained by conjugating unsaturated fatty acid triglycerides may be used.

  Unsaturated fatty acid triglycerides as described above are, for example, dehydrated castor oil, tung oil, safflower oil, linseed oil, sunflower oil, corn oil, cottonseed oil, soybean oil, sesame oil, corn oil, cannabis oil, evening primrose oil, blackcurrant oil, borage It is a component contained in naturally derived fats and oils such as oils (borage oil), sardine oil, mackerel oil, herring oil, and other plant-derived fats and oils derived from various animals.

Among the above-mentioned, dehydrated castor oil can be suitably used because it contains a large amount of conjugated linoleic acid triglyceride (conjugated unsaturated fatty acid triglyceride).
The content of unsaturated fatty acid triglyceride in the insulating liquid is preferably 64 wt% or less, and more preferably 48 wt% or less. As a result, the oxidative polymerization reaction can proceed more effectively at the time of fixing, with a particularly low environmental load.

The insulating liquid may contain, for example, saturated fatty acid triglycerides as shown below in addition to the components described above.
Saturated fatty acid triglyceride is a component having a function of maintaining high chemical stability of the liquid developer. Therefore, when saturated fatty acid triglyceride is contained in the insulating liquid, the chemical change of the liquid developer can be effectively prevented, and as a result, the storage stability and long-term stability of the obtained liquid developer are higher. It can be.
Saturated fatty acid triglycerides have a function of maintaining high electrical insulation. Therefore, when saturated fatty acid triglyceride is contained in the insulating liquid, the electric resistance of the liquid developer can be maintained at a higher level.

  Examples of saturated fatty acids constituting such saturated fatty acid triglycerides include butyric acid (C4), caproic acid (C6), caprylic acid (C8), capric acid (C10), lauric acid (C12), and myristylic acid (C14). , Palmitic acid (C16), stearic acid (C18), arachidic acid (C20), behenic acid (C22), lignoceric acid (C24) and the like, and one or more selected from these are used in combination. be able to. 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 triglyceride composed of such saturated fatty acids, the effects as described above are further prominent.

The saturated fatty acid triglycerides as described above are, for example, naturally-derived oils and fats such as oils derived from plants such as palm oil (particularly palm kernel oil), coconut oil, and coconut oil, and oils and fats derived from various animals (such as butter). Can be obtained efficiently.
The electrical resistance of the insulating liquid as described above at room temperature (20 ° C.) is preferably 1 × 10 ⁹ Ωcm or more, more preferably 1 × 10 ¹¹ Ωcm or more, and 1 × 10 ¹³ Ωcm or more. More preferably.
The dielectric constant of the insulating liquid is preferably 3.5 or less.

<Toner particles>
Next, toner particles will be described.
[Component material of toner particles]
The toner particles (toner) constituting the liquid developer of the present invention include at least a resin material.

1. Resin Material The toner constituting the liquid developer is composed of a material containing a resin material as a main component.
In the present invention, the resin (binder resin) is not particularly limited, and for example, polystyrene, poly-α-methylstyrene, chloropolystyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene copolymer. Polymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, styrene-maleic acid copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-acrylic acid ester -Styrene resins such as methacrylic acid ester copolymer, styrene-α-chloroacrylic acid methyl copolymer, styrene-acrylonitrile-acrylic acid ester copolymer, styrene-vinyl methyl ether copolymer, etc. A homopolymer or copolymer, Polyester resin, epoxy resin, urethane modified epoxy resin, silicone modified epoxy resin, vinyl chloride resin, rosin modified maleic acid resin, phenyl resin, polyethylene resin, polypropylene, ionomer resin, polyurethane resin, silicone resin, ketone resin, ethylene-ethyl Examples include acrylate copolymers, xylene resins, polyvinyl butyral resins, terpene resins, phenol resins, aliphatic or alicyclic hydrocarbon resins. One or more of these can be used in combination. Among these, when a polyester resin is used, the dispersibility of the toner particles in the liquid developer can be made particularly excellent. Moreover, the polyester resin has high transparency, and when used as a binder resin, the color developability of the obtained image can be made high.

  Although the softening temperature of resin (resin material) is not specifically limited, It is preferable that it is 50-130 degreeC, It is more preferable that it is 50-120 degreeC, It is further more preferable that it is 60-115 degreeC. In the present specification, the softening temperature is a measurement condition in a Koka type flow tester (manufactured by Shimadzu Corporation): temperature increase rate: 5 ° C./min, softening start temperature defined by a die hole diameter of 1.0 mm. Point to.

2. Colorant The toner may contain a colorant. Examples of the colorant that can be used include pigments and dyes. Examples of such pigments and dyes include carbon black, spirit black, lamp black (CI No. 77266), magnetite, titanium black, chrome lead, cadmium yellow, mineral fast yellow, navel yellow, and naphthol yellow S. , Hansa Yellow G, Permanent Yellow NCG, Chrome Yellow, Benzidine Yellow, Quinoline Yellow, Tartrazine Lake, Red Mouth Lead, Molybdenum Orange, Permanent Orange GTR, Pyrazolone Orange, Benzidine Orange G, Cadmium Red, Permanent Red 4R, Watching Red Calcium salt, eosin lake, brilliant carmine 3B, manganese purple, fast violet B, methyl violet lake, bitumen, cobalt blue, al Reblue Lake, Victoria Blue Lake, First Sky Blue, Indanthrene Blue BC, Ultramarine, Aniline Blue, Phthalocyanine Blue, Calco Oil Blue, Chrome Green, Chrome Oxide, Pigment Green B, Malachite Green Lake, Phthalocyanine Green, Final Yellow Green G, Rhodamine 6G, quinacridone, rose bengal (C.I. No. 45432), C.I. I. Direct Red 1, C.I. I. Direct Red 4, C.I. I. Acid Red 1, C.I. I. Basic Red 1, C.I. I. Modern Tread 30, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 184, C.I. I. Direct Blue 1, C.I. I. Direct Blue 2, C.I. I. Acid Blue 9, C.I. I. Acid Blue 15, C.I. I. Basic Blue 3, C.I. I. Basic Blue 5, C.I. I. Modern Blue 7, C.I. I. Pigment blue 15: 1, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 5: 1, C.I. I. Direct Green 6, C.I. I. Basic Green 4, C.I. I. Basic Green 6, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 97, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 180, C.I. I. Pigment yellow 162, nigrosine dye (CI No. 50415B), metal complex dye, silica, aluminum oxide, magnetite, maghemite, various ferrites, cupric oxide, nickel oxide, zinc oxide, zirconium oxide, titanium oxide, Examples thereof include metal oxides such as magnesium oxide and magnetic materials containing magnetic metals such as Fe, Co, and Ni, and one or more of these can be used in combination.

3. Other Components The toner may contain components other than those described above. Examples of such components include waxes, charge control agents, magnetic powders, and the like.
Examples of the wax include hydrocarbon waxes such as ozokerite, cercin, paraffin wax, microwax, microcrystalline wax, petrolatum, Fischer-Tropsch wax, carnauba wax, rice wax, methyl laurate, methyl myristate, palmitic acid. Methyl, methyl stearate, butyl stearate, candelilla wax, cotton wax, wood wax, beeswax, lanolin, montan wax, fatty acid ester ester wax, polyethylene wax, polypropylene wax, oxidized polyethylene wax, oxidized polypropylene wax Olefin waxes such as 12-hydroxy stearamide, stearamide, phthalic anhydride amide wax, Lauro , Ketone waxes such as stearone, ether waxes, and the like, can be used singly or in combination of two or more of them.

Examples of the charge control agent include benzoic acid metal salt, salicylic acid metal salt, alkyl salicylic acid metal salt, catechol metal salt, metal-containing bisazo dye, nigrosine dye, tetraphenylborate derivative, quaternary ammonium salt, alkyl Examples include pyridinium salts, chlorinated polyesters, and nitrofunic acid.
Examples of the magnetic powder include magnetite, maghemite, various ferrites, cupric oxide, nickel oxide, zinc oxide, zirconium oxide, titanium oxide, magnesium oxide, and other metal oxides, and magnetic materials such as Fe, Co, and Ni. The thing etc. which were comprised with the magnetic material containing a metal are mentioned.
In addition to the above materials, for example, zinc stearate, zinc oxide, cerium oxide, silica, titanium oxide, iron oxide, fatty acid, fatty acid metal salt, etc. are used as the constituent material (component) of the kneaded product. May be.

[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 particle diameter of the toner particles composed of the above materials is preferably 0.1 to 5 μm, more preferably 0.1 to 4 μm, and further preferably 0.5 to 3 μm. preferable. When the average particle diameter of the toner particles is a value within the above range, the resolution of an image formed by the liquid developer (toner) can be sufficiently increased.

The average value (average circularity) of the circularity R represented by the following formula (I) for the toner particles constituting the liquid developer is preferably 0.94 to 0.99, and 0.96. More preferably, it is -0.99.
R = L ₀ / L ₁ (I)
(Where, L ₁ [μm] is the circumference of the projected image of the toner particles to be measured, and L ₀ [μm] is 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 content ratio of the toner particles in the liquid developer is preferably 10 to 60 wt%, and more preferably 20 to 50 wt%.

  Further, the viscosity of the liquid developer is preferably 20 to 300 mPa · s, and more preferably 30 to 250 mPa · s. When the viscosity of the liquid developer is in such a range, the dispersibility of the toner particles can be increased, and in the image forming apparatus P1 as described later, the liquid developer is applied to the application roller P12. The liquid can be supplied more uniformly, and dripping of the liquid developer from the application roller P12 and the like can be more effectively prevented.

<< Method for Producing Liquid Developer >>
Next, a preferred embodiment of the method for producing a liquid developer of the present invention will be described.
<First Embodiment>
First, a first embodiment of a method for producing a liquid developer according to the present invention will be described.
In the method for producing a liquid developer of the present embodiment, a pulverizing step of pulverizing a toner material mainly composed of a resin material in a fatty acid monoester to obtain a pulverized dispersion, a pulverized dispersion, and an unsaturated fatty acid A mixing step of mixing a liquid containing triglycerides.

[Crushing process]
In this step, the constituent material (toner material) of the toner particles as described above is wet pulverized in a fatty acid monoester to obtain a pulverized dispersion.
In the present embodiment, the toner particles are unevenly distributed (adsorbed) in the vicinity of the surface in the liquid developer finally obtained by pulverizing the toner material in the fatty acid monoester. It will be. On the other hand, the fatty acid monoester cannot be unevenly distributed near the surface of the toner particles simply by dispersing the toner particles in the fatty acid monoester. That is, the fatty acid monoester can be unevenly distributed on the surface of the toner particles for the first time by applying a large shearing force called pulverization.

  Further, the fatty acid monoester has a relatively low viscosity, has a high degree of freedom of movement of the toner material in the fatty acid monoester, and has a low resistance of the fatty acid monoester, so that the coarsely pulverized product can be efficiently pulverized. Further, since the fatty acid monoester has a high affinity with the above-described resin material and has a relatively low viscosity, the fatty acid monoester can enter a minute crack or the like of the toner material caused by pulverization or the like. As a result, it can be efficiently pulverized and toner particles having a small particle diameter can be formed efficiently. Further, the pulverization rate can be improved. Further, by grinding in a fatty acid monoester having a relatively low viscosity, the energy added for grinding can be used efficiently for grinding the toner material, thus preventing the temperature of the fatty acid monoester from rising. be able to. As a result, even if the resin material constituting the toner material has a low melting point, it can be efficiently pulverized.

Further, as the toner material used in this step, it is preferable to use a coarsely pulverized product obtained by roughly pulverizing the kneaded product as described above. Thus, by using the coarsely pulverized product obtained by roughly pulverizing the kneaded product, the particle size of the toner particles can be reduced more effectively in this step.
The method of wet pulverization is not particularly limited, and can be performed using various pulverizers and crushers such as a ball mill, a vibration mill, a jet mill, and a pin mill.
The wet pulverization step may be performed in multiple steps.

Note that a dispersant (surfactant) may be added to the fatty acid monoester before mixing the fatty acid monoester with the toner material. As a result, the dispersant acts as a pulverization aid, and the toner material can be pulverized more efficiently and the dispersibility of the resulting toner particles can be made higher.
In addition, when the toner material is pulverized in a state where the fatty acid monoester contains the dispersant, it becomes easier for the dispersant to adhere to the surface of the toner particles, thereby improving the charging characteristics of the finally obtained liquid developer. Can be made.

  Examples of the dispersant include polyvinyl alcohol, carboxymethyl cellulose, polyethylene glycol, Solsperse (trade name of Nippon Lubrizol), polycarboxylic acid and its salt, polyacrylic acid metal salt (for example, sodium salt), polymethacrylic acid, and the like. 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 salt) Etc.), polymer dispersants such as polyamine aliphatic polycondensation polymers, viscosity minerals, silica, tricalcium phosphate, metal tristearate (eg, aluminum salt), metal distearate (eg, aluminum salt, barium salt) Etc.), metal stearate (for example, calcium sulfate) 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.), olein 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 the above-mentioned dispersants, when a polymer dispersant is used, the grinding efficiency can be effectively increased. In addition, when a polymer dispersant is present when pulverizing with a fatty acid monoester, the polymer dispersant can be suitably present on the surface of the toner particles (so as to be entangled). When mixed with the liquid containing the fatty acid monoester, the fatty acid monoester can be more effectively retained near the surface of the toner particles. As a result, the dispersibility of the toner particles in the finally obtained liquid developer can be further improved, and the fixing characteristics can be further improved. In particular, among the polymer dispersants, when Solsperse is used, the above-described effects become more remarkable.

[Mixing process]
Next, the obtained pulverized material dispersion is mixed with the liquid containing the unsaturated fatty acid triglyceride as described above (mixing step).
As described above, the liquid developer of the present invention is obtained in which toner particles in which fatty acid monoesters are unevenly distributed in the vicinity of the surface are dispersed in an insulating liquid containing unsaturated fatty acid triglycerides.

Second Embodiment
Next, a second embodiment of the method for producing a liquid developer according to the present invention will be described.
The method for producing a liquid developer according to the present embodiment includes a process for forming an associated particle by associating resin fine particles mainly composed of a resin material to obtain an associated particle, pulverizing the associated particle in a fatty acid monoester, And a dispersion step of dispersing the obtained toner particles in a liquid containing an unsaturated fatty acid triglyceride.

[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.
Any method may be used to prepare the associated particles, but in this embodiment, the dispersoid mainly composed of a resin material (toner constituent material) in an aqueous dispersion medium composed of an aqueous liquid. An aqueous emulsion in which (fine particles) are dispersed is obtained, and the dispersoids in the aqueous emulsion are associated to obtain associated particles.

(Aqueous emulsion)
First, the aqueous emulsion used in this embodiment will be described.
The aqueous emulsion obtained in the aqueous emulsion preparation step described below has a structure in which dispersoids (fine particles) are finely dispersed in an aqueous dispersion medium composed of an aqueous liquid.

-Aqueous dispersion medium (aqueous liquid)-
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.

  Further, the aqueous dispersion medium (aqueous liquid) is preferably one having low compatibility with a high insulating liquid described later (for example, one having a solubility in 100 g of the high insulating liquid at 25 ° C. of 0.01 g or less). . As a result, the shape of the dispersoid can be suitably maintained in the liquid mixture obtained in the liquid mixture preparation step described later, and the shape of the toner particles in the finally obtained liquid developer can be made more uniform. can do.

  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.

-Dispersoid (fine particles)-
The dispersoid contains the components constituting the toner particles as described above.
The dispersoid may contain a solvent that dissolves at least a part of the components. Thereby, for example, the fluidity of the dispersoid in the aqueous emulsion can be increased, and the dispersoid in the aqueous emulsion can have a relatively small particle size and small variation in size. it can. 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.

Any solvent may be used as long as it dissolves at least a part of the components constituting the dispersoid, 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 dispersoid 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 composition of the resin and the colorant described above, the composition of the aqueous dispersion medium, and the like.

  Examples of the solvent include inorganic solvents such as carbon disulfide and carbon tetrachloride, methyl ethyl ketone (MEK), acetone, diethyl ketone, methyl isobutyl ketone (MIBK), methyl isopropyl ketone (MIPK), cyclohexanone, 3-heptanone, 4 -Ketone solvents such as heptanone, methanol, ethanol, n-propanol, isopropanol, n-butanol, i-butanol, t-butanol, 3-methyl-1-butanol, 1-pentanol, 2-pentanol, n- Alcohol solvents such as hexanol, cyclohexanol, 1-heptanol, 1-octanol, 2-octanol, 2-methoxyethanol, allyl alcohol, furfuryl alcohol, phenol, diethyl ether, dipropyl ether, diisopropyl Ether solvents such as ether, dibutyl ether, 1,2-dimethoxyethane (DME), 1,4-dioxane, tetrahydrofuran (THF), tetrahydropyran (THP), anisole, diethylene glycol dimethyl ether (diglyme), 2-methoxyethanol, Cellosolve solvents such as methyl cellosolve, ethyl cellosolve, phenyl cellosolve, aliphatic hydrocarbon solvents such as hexane, pentane, heptane, cyclohexane, methylcyclohexane, octane, didecane, methylcyclohexene, isoprene, toluene, xylene, benzene, ethylbenzene, Aromatic hydrocarbon solvents such as naphthalene, pyridine, pyrazine, furan, pyrrole, thiophene, 2-methylpyridine, 3-methylpyridine, 4-methylpyridine, fluoro Aromatic heterocyclic compound solvents such as furyl alcohol, amide solvents such as N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMA), dichloromethane, chloroform, 1,2-dichloroethane, trichloroethylene, chlorobenzene Halogenated solvents such as acetylacetone, ethyl acetate, methyl acetate, isopropyl acetate, isobutyl acetate, isopentyl acetate, ethyl chloroacetate, butyl chloroacetate, isobutyl chloroacetate, ethyl formate, isobutyl formate, ethyl acrylate, methyl methacrylate, Ester solvents such as ethyl benzoate, amine solvents such as trimethylamine, hexylamine, triethylamine and aniline, nitrile solvents such as acrylonitrile and acetonitrile, nitromethane, nitroethane, etc. Organic solvents such as aldehyde solvents such as nitro solvents, acetaldehyde, propionaldehyde, butyraldehyde, pentanal, acrylic aldehyde, etc., and a mixture of one or more selected from these may be used. it can.

Further, the aqueous emulsified liquid may contain an emulsifying dispersant.
When an emulsifying dispersant is used, the dispersibility of the dispersoid is improved, and the dispersion of the dispersoid in the aqueous emulsion is relatively easily reduced in size and size. Can be substantially spherical. As a result, the final liquid developer can be obtained as a toner composed of toner particles having a substantially spherical shape, a uniform shape, and a uniform size. Here, examples of the emulsifying dispersant include emulsifiers, dispersants, and dispersion aids.

  Examples of the dispersant include inorganic dispersants such as clay minerals, silica, and tricalcium phosphate, nonionic organic dispersants such as polyvinyl alcohol, carboxymethyl cellulose, polyethylene glycol, and hydroxy stearates, and metal tristearate ( For example, aluminum salts, etc.), distearic acid metal salts (eg, aluminum salts, barium salts, etc.), stearic acid metal salts (eg, calcium salts, lead salts, zinc salts, etc.), linolenic acid metal salts (eg, cobalt salts, Manganese salt, lead salt, zinc salt, etc.), octanoic acid metal salt (eg, aluminum salt, calcium salt, cobalt salt etc.), oleic acid metal salt (eg, calcium salt, cobalt salt etc.), palmitic acid metal salt (eg. , Zinc salts, etc.), naphthenic acid metal salts (eg calcium salts, cobalt salts) Manganese salt, lead salt, zinc salt, etc.), resinate metal salt (eg calcium salt, cobalt salt, manganese lead salt, zinc salt etc.), polyacrylic acid metal salt (eg sodium salt etc.), 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 salt) ) And other cationic organic dispersants such as quaternary ammonium salts. Among these, nonionic organic dispersants or anionic organic dispersants are particularly preferable.

The content of the dispersant in the aqueous emulsion is not particularly limited, but is preferably 3.0 wt% or less, and more preferably 0.01 to 1.0 wt%.
Examples of the dispersion aid include anions, cations, and nonionic surfactants.
The dispersing aid is preferably used in combination with a dispersing agent. When the aqueous emulsion contains a dispersant, the content of the dispersion aid in the aqueous emulsion is not particularly limited, but is preferably 2.0 wt% or less, and is 0.005 to 0.5 wt%. Is more preferable.

In the aqueous emulsion, components other than the dispersoid may be dispersed as an insoluble matter. For example, inorganic fine powders such as silica, titanium oxide, and iron oxide, and organic fine powders such as fatty acids and fatty acid metal salts may be dispersed in the aqueous emulsion.
In the aqueous emulsion used in the present embodiment as described above, since the dispersoid is liquid, the dispersoid tends to have a shape with a high degree of circularity (sphericity) due to its surface tension. Therefore, the finally obtained toner particles in the liquid development have a particularly high degree of circularity, and the variation in shape among the particles is particularly small.

The content of the dispersoid in the aqueous emulsion 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 reliably preventing the dispersoids from binding (aggregating) in the aqueous emulsion.
The average particle size of the dispersoid (liquid dispersoid) in the aqueous emulsion 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.

(Aqueous emulsion preparation process)
The aqueous emulsion as described above can be prepared, for example, as follows (aqueous emulsion preparation step).
First, an aqueous solution in which a dispersant is added to the aqueous liquid as necessary is prepared.
On the other hand, a resin liquid containing a resin as a main component of the toner as described above or a precursor thereof (hereinafter collectively referred to as “resin material”) is prepared. For the preparation of the resin liquid, for example, the above-described solvent may be used in addition to the resin material. The resin liquid may be a molten liquid obtained by heating a resin material. Further, for the preparation of the resin liquid, for example, a kneaded product obtained by kneading a toner material such as a resin material and 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.

  Next, an aqueous emulsion in which the dispersoid containing the resin material is dispersed in the aqueous dispersion medium is obtained by gradually adding the resin liquid to the stirred aqueous solution while dropping. By preparing an aqueous emulsion by such a method, the circularity of the dispersoid in the aqueous emulsion can be further increased. As a result, the finally obtained toner particles in liquid development have a particularly high degree of circularity, and the variation in shape among the particles is particularly small. In addition, when dripping a resin liquid, you may heat an aqueous solution and / or a resin liquid. In addition, when a solvent is used for the preparation of the resin liquid, for example, after the dropwise addition as described above, the obtained aqueous emulsion is heated or placed in a reduced-pressure atmosphere to be contained in the dispersoid. At least a part of the solvent may be removed.

(Association particle formation process)
Next, an electrolyte is added to the aqueous emulsion 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 emulsion. 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 with each other and coarse particles may be generated, and there is a possibility that the size of finally obtained toner particles 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 is obtained.
In addition, in this way, in the liquid developer finally obtained by crushing the associated particles in the fatty acid monoester, the toner particles are unevenly distributed (adsorbed) near the surface of the toner particles. It becomes. That is, the fatty acid monoester can be unevenly distributed on the surface of the toner particles by applying a large shearing force of crushing.
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, since the obtained toner particles have irregularities derived from the fine particles (dispersoid) on the surface thereof, 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.

[Dispersion process]
Next, the toner particle dispersion obtained as described above and a liquid containing unsaturated fatty acid triglycerides are mixed to disperse the toner particles in the insulating liquid (dispersing step).
As described above, the liquid developer of the present invention is obtained in which toner particles in which fatty acid monoesters are unevenly distributed in the vicinity of the surface are dispersed in an insulating liquid containing unsaturated fatty acid triglycerides.

Next, a preferred embodiment of a liquid developing apparatus to which the liquid developer of the present invention as described above is applied will be described.
FIG. 1 shows an example of a contact-type liquid developing apparatus to which the liquid developer of the present invention is applied. The liquid developing device P1 has a drum of a cylindrical photosensitive member P2, and after the surface is uniformly charged by a charger P3 made of epichlorohydrin rubber or the like, information to be recorded by a laser diode or the like In accordance with the exposure P4, an electrostatic latent image is formed.

  The developing device P10 includes a coating roller P12 and a developing roller P13, part of which is immersed in a developer container P11. The application roller P12 is, for example, a metal gravure roller such as stainless steel, and rotates to face the developing roller P13. Further, a liquid developer coating layer P14 is formed on the surface of the coating roller P12, and the thickness thereof is kept constant by the metering blade P15.

  Then, the liquid developer is transferred from the coating roller P12 to the developing roller P13. The developing roller P13 has a low hardness silicone rubber layer on a roller core P16 made of metal such as stainless steel, and a conductive PFA (polytetrafluoroethylene-perfluorovinyl ether copolymer) resin on the surface thereof. A layer is formed, and rotates at the same speed as the photosensitive member P2 to transfer the liquid developer to the latent image portion. The liquid developer remaining on the developing roller P13 after being transferred to the photoreceptor P2 is removed by the developing roller cleaning blade P17 and collected in the developer container P11.

Further, after the transfer of the toner image from the photoconductor to the intermediate transfer roller, the photoconductor is neutralized by the neutralizing light P21, and the residual transfer toner remaining on the photoconductor is a cleaning made of urethane rubber or the like. It is removed by the blade P22.
Similarly, the transfer residual toner remaining on the intermediate transfer roller P18 after being transferred from the intermediate transfer roller P18 to the recording medium F5 such as paper is removed by a cleaning blade P23 made of urethane rubber or the like.
After the toner image formed on the photoreceptor P2 is transferred to the intermediate transfer roller P18, a transfer current is passed through the secondary transfer roller P19, and the image is transferred to the recording medium F5 passing between the two. Then, the toner image on the recording medium F5 is fixed using a fixing device as will be described later.

  FIG. 2 shows an example of a non-contact type liquid developing apparatus to which the liquid developer of the present invention is applied. In the non-contact method, the developing roller P13 is provided with a charging blade P24 made of a phosphor bronze plate having a thickness of 0.5 mm. The charging blade P24 has a function of making frictional charging in contact with the liquid developer layer, and since the application roller P12 is a gravure roll, a developer layer corresponding to the unevenness of the surface of the gravure roll is formed on the development roller P13. Therefore, it functions to uniformly level the unevenness, and the arrangement direction may be either the counter direction or the trail direction with respect to the rotation direction of the developing roller, and may be a roller shape instead of a brate shape.

Further, an interval of 200 μm to 800 μm is provided between the developing roller P13 and the photosensitive member P2, and a frequency of 500 to 3000 Vpp superimposed on a direct current voltage of 200 to 800 V is applied between the developing roller P13 and the photosensitive member P2. An AC voltage of 50 to 3000 Hz is preferably applied. The rest is the same as the liquid developing apparatus described with reference to FIG.
In FIGS. 1 and 2, the image formation using one color liquid developer has been described. However, when forming an image using a plurality of color toners, each color image is formed using a plurality of color developing devices. Thus, a color image can be formed.

FIG. 3 is a cross-sectional view showing an example of a fixing device to which the liquid developer of the present invention is applied.
As shown in FIG. 3, the fixing device 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.

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.

  In addition, two columnar halogen lamps F1a and F1a constituting a heating source are built in the heat fixing roller F1, 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 disposed so as to face the heat fixing roller F1, and is configured to apply pressure to a recording medium F5 on which an unfixed toner image is formed via a heat-resistant belt F3 described later. ing. By applying pressure, the insulating liquid can be more efficiently penetrated into the recording medium F5. As a result, the transesterified oil and fat in the insulating liquid can be hardened more reliably inside the recording medium F5 by heat and ultraviolet irradiation, which will be described later, and the toner image F5a is more firmly formed on the recording medium F5 by the anchor effect. It can be fixed.

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.
The aforementioned elastic body F1c of the heat fixing roller F1 and the elastic body F2c of the pressure roller F2 are subjected to substantially uniform elastic deformation to form a so-called horizontal nip. In addition, 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, with respect to the peripheral speed of the heat fixing roller F1, 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 device F40, a recording medium F5 on which an unfixed toner image F5a is formed using an image forming apparatus as will be described later enters the fixing nip portion from the initial nip position and enters the heat resistant belt F3 and the heat fixing roller F1. , And exiting from the nip end position, the unfixed toner image F5a formed on the recording medium F5 is thermally fixed, and then the pressing portion of the pressure roller F2 to the heat fixing roller F1 is pressed. It is discharged in the tangential direction L.

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.

  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.
The fixing temperature when fixing the unfixed toner image is preferably 80 to 200 ° C, more preferably 80 to 180 ° C.

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, the aqueous emulsion is obtained, and the association particles are obtained by adding an electrolyte to the aqueous emulsion. However, the present invention is not limited to this. For example, associating particles are prepared by dispersing a colorant, a monomer, a surfactant, and a polymerization initiator in an aqueous liquid, preparing an aqueous emulsion by emulsion polymerization, and adding an electrolyte to the aqueous emulsion and associating. What was prepared using the emulsion polymerization association method may be used, and the associated particle | grains may be obtained by spray-drying the obtained aqueous emulsion.

[1] Production of liquid developer (Example 1)
First, 80 parts by weight of a polyester resin (softening temperature: 99 ° C.) and 20 parts by weight of a cyan pigment as a coloring agent (Pigment Blue 15: 3 manufactured by Dainichi Seika Co., Ltd.) were 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 (coarse pulverized product) having an average particle size of 1.0 mm or less. A hammer mill was used for coarse pulverization of the kneaded product.
Next, the coarsely pulverized product obtained as described above: 100 parts by weight, methyl laurate (manufactured by Nippon Oil & Fats Co., Ltd.): 100 parts by weight, and polyamine aliphatic polycondensate (Nippon Lubrizol Co., Ltd.) as a dispersant. Product, trade name “Solsperse 11200”): 10 parts by weight and magnesium stearate as a charge control agent: 1.0 part by weight were prepared. The viscosity of methyl laurate at 25 ° C. was 3 mPa · s.

These components were put into a ball mill and wet pulverized for 200 hours to obtain a pulverized dispersion.
Thereafter, the obtained pulverized dispersion liquid: 100 parts by weight and rapeseed oil (manufactured by Nisshin Oilio Co., Ltd.): 150 parts by weight were mixed to obtain a liquid developer. The viscosity of rapeseed oil at 19 ° C. was 75 mPa · s.
In the obtained liquid developer, the average particle diameter of the toner particles was 1.2 μm, and the standard deviation of the particle diameter between the toner particles was 0.62 μm. Further, the viscosity of the liquid developer at room temperature (20 ° C.) was 120 mPa · s.

(Example 2)
A liquid developer was produced in the same manner as in Example 1 except that methyl laurate was changed to methyl stearate. The viscosity of methyl stearate at 25 ° C. was 8 mPa · s.
(Example 3)
A liquid developer was produced in the same manner as in Example 1 except that the rapeseed oil was changed to soybean oil (manufactured by Nisshin Eulio). The viscosity of soybean oil at 19 ° C. was 67 mPa · s.
Example 4
A liquid developer was produced in the same manner as in Example 1 except that the polyester resin was changed to an epoxy resin (Epicoat 1004, softening temperature: 128 ° C.).

(Example 5)
First, 80 parts by weight of a polyester resin (softening temperature: 99 ° C.) and 20 parts by weight of a cyan pigment as a coloring agent (Pigment Blue 15: 3 manufactured by Dainichi Seika Co., Ltd.) were 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 (coarse pulverized product) having an average particle size of 1.0 mm or less. A hammer mill was used for coarse pulverization of the kneaded product.

Next, 100 parts by weight of the coarsely pulverized product of the kneaded product was added to 250 parts by weight of toluene, and the polyester resin of the kneaded product was dissolved by treating with an ultrasonic homogenizer (output: 400 μA) for 1 hour. A solution was obtained. In this solution, the pigment was uniformly finely dispersed.
On the other hand, an aqueous liquid in which sodium dodecylbenzenesulfonate as a dispersant: 1 part by weight and ion-exchanged water: 700 parts by weight were uniformly mixed was prepared.

The aqueous liquid was stirred with a homomixer (made by Tokushu Kika Kogyo Co., Ltd.) while adjusting the stirring rotation speed.
The above solution (a kneaded toluene solution) was dropped into the agitated aqueous liquid. As a result, an aqueous emulsion in which the dispersoid having an average particle diameter of 0.5 μm was uniformly dispersed was obtained. The solid content (dispersoid) concentration in the obtained aqueous emulsion was 20 wt%.

Next, with respect to the obtained aqueous emulsion: 100 parts by weight, a nonionic surfactant (Daiichi Kogyo Seiyaku Co., Ltd., trade name “Epan 450”): 0.35 parts by weight is added with stirring. did.
Next, while adjusting the stirring speed and setting the temperature to 30 ° C., 35 parts by weight of 3% aqueous ammonium sulfate solution was added dropwise to 100 parts by weight of the aqueous emulsion. As a result, an associated particle dispersion in which associated particles are dispersed was obtained.
The associated particles were separated from the obtained associated particle dispersion by a centrifugal separator, washed, and then dried by a vacuum dryer to obtain associated particles. The average particle size of the obtained associated particles was 5.2 μm.

Next, 4 mm carbon chromium beads are put into a 500 mL container, and then methyl caprylate (manufactured by Lion Corporation): 50 parts by weight and a polyamine aliphatic polycondensation polymer (manufactured by Nippon Lubrizol Co., Ltd., product) Name “Solsperse 11200”): 10 parts by weight were charged. The viscosity of methyl caprylate was 3 mPa · s.
Next, 50 parts by weight of the obtained associating particles are added and mixed for 10 minutes by a ball mill. Thereafter, 0.5 part by weight of magnesium stearate as a charge control agent is further added, and the mixture is dissolved by a ball mill for 200 hours. Crushing to obtain a toner dispersion.

After crushing, 150 parts by weight of rapeseed oil was added to disperse the toner particles. Dispersion was carried out for 24 hours with 4 mm beads using a ball mill. As a result, a liquid developer was obtained.
In the obtained liquid developer, the average particle diameter of the toner particles was 1.3 μm, and the standard deviation of the particle diameter between the toner particles was 0.50 μm. Further, the viscosity of the liquid developer at room temperature (20 ° C.) was 95 mPa · s.

(Example 6)
A liquid developer was produced in the same manner as in Example 5 except that the fatty acid monoester was changed to methyl stearate (manufactured by NOF Corporation). The viscosity of methyl stearate at 25 ° C. was 8 mPa · s.
(Example 7)
A liquid developer was produced in the same manner as in Example 5 except that the rapeseed oil was changed to soybean oil (Nisshin Oilio Co., Ltd.). The viscosity of soybean oil at 19 ° C. was 67 mPa · s.
(Example 8)
A liquid developer was produced in the same manner as in Example 5 except that the polyester resin was changed to an epoxy resin (Epicoat 1004, softening temperature: 128 ° C.).

(Comparative Example 1)
A coarsely pulverized product was obtained in the same manner as in Example 1.
Next, the obtained coarsely pulverized product: 100 parts by weight, soybean oil (manufactured by Nisshin Oilio Co., Ltd., viscosity (19 ° C.): 67 mPa · s): 100 parts by weight, and polyoxyethylene alkyl ether as a dispersant: 10 parts by weight and magnesium stearate as a charge control agent: 1.0 part by weight were prepared.

These components were put into a ball mill and wet pulverized for 400 hours to obtain a pulverized dispersion.
Thereafter, 100 parts by weight of the obtained pulverized material dispersion and 150 parts by weight of methyl laurate were mixed to obtain a liquid developer.
The average particle size of the toner particles in the obtained liquid developer was 1.5 μm, and the standard deviation of the particle size between the toner particles was 0.92 μm. Further, the viscosity of the liquid developer at room temperature (20 ° C.) was 72 mPa · s.

(Comparative Example 2)
A coarsely pulverized product was obtained in the same manner as in Example 1.
Next, the obtained coarsely pulverized product: 100 parts by weight, soybean oil (manufactured by Nisshin Oilio Co., Ltd., viscosity (19 ° C.): 67 mPa · s): 100 parts by weight, and polyoxyethylene alkyl ether as a dispersant: 10 parts by weight and magnesium stearate as a charge control agent: 1.0 part by weight were prepared.
These components were put into a ball mill and wet-ground for 300 hours. However, the toner particles could not be made sufficiently large.

(Comparative Example 3)
Associated particles were obtained in the same manner as in Example 5.
Next, 4 mm carbon chromium beads are put into a 500 mL container, and then soybean oil (manufactured by Nisshin Oilio Co., Ltd., viscosity (19 ° C.): 67 mPa · s): 50 parts by weight, and polyamine aliphatic as a dispersant. Polycondensation polymer (trade name “Solsperse 11200” manufactured by Nippon Lubrizol Co., Ltd.): 5 parts by weight was charged.

Next, 50 parts by weight of the obtained associating particles are added and mixed for 10 minutes by a ball mill. Thereafter, 0.5 part by weight of magnesium stearate as a charge control agent is further added, and the mixture is dissolved by a ball mill for 200 hours. Crushing to obtain a toner dispersion.
After crushing, 150 parts by weight of methyl laurate was added to disperse the toner particles. Dispersion was carried out for 24 hours with 4 mm beads using a ball mill. As a result, a liquid developer was obtained.
The average particle size of the toner particles in the obtained liquid developer was 1.8 μm, and the standard deviation of the particle size between the toner particles was 0.85 μm. The viscosity of the liquid developer at room temperature (20 ° C.) was 83 mPa · s.
Table 1 shows the manufacturing conditions of the liquid developer for each of the above Examples and Comparative Examples.

[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 a liquid developer obtained in each of the examples and the comparative examples was recorded on a recording paper (manufactured by Seiko Epson Corporation, It was formed on fine paper LPCPPA4). Thereafter, the image formed on the recording paper was thermally fixed by an oven. This heat fixing was performed under the condition of 120 ° C. × 30 minutes.

Thereafter, 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.) with a pressing load kgf, and the residual ratio of the image density is determined as X -Measured according to "X-Rite model 404" manufactured by Rite Inc, and evaluated according to the following five-step criteria.
A: Image density residual ratio is 95% or more.
A: Image density residual ratio is 90% or more and less than 95%.
○: Image density remaining rate is 80% or more and less than 90%.
Δ: Image density remaining rate is 70% or more and less than 80%.
X: Image density remaining rate is less than 70%.

[2.2] Dispersion stability test 10 mL of the liquid developer obtained in each example and each comparative example was placed in a centrifuge tube, centrifuged at 1000 G for 10 minutes, and then 200 μL of the supernatant was collected. The sample was diluted 100-fold with the insulating liquid used in each example and each comparative example to prepare a sample.
The absorption wavelength of each sample was measured using an ultraviolet-visible spectrophotometer (manufactured by JASCO Corporation, V-570).

Evaluation was performed according to the following four-stage criteria from the absorbance value in the absorption range (685 nm) of the cyan pigment.
A: Absorbance is 1.50 or more (no precipitation is observed).
○: Absorbance is 1.00 or more and less than 1.50 (almost no sedimentation is observed).
Δ: Absorbance of 0.50 or more and less than 1.00 (precipitation is confirmed).
X: Absorbance is less than 0.50 (sedimentation is remarkable and sedimentation starts even when left standing).

[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 floating or coagulation sedimentation of toner particles is observed.
A: Floating toner particles and coagulation sedimentation are hardly observed.
○: Slight floating or coagulation sedimentation of toner particles is observed, but as a liquid developer
There is no problem.
Δ: Floating or coagulating sedimentation of toner particles is clearly observed.
X: Remarkably floating and coagulating sedimentation of toner particles are observed.

[2.4] Evaluation of uneven distribution of fatty acid monoester For each of the examples and comparative examples, the liquid obtained after 1 hour of ball milling (in the case of Examples 5 to 8 and Comparative Example 2) and finally obtained The obtained liquid developer was centrifuged, the supernatant was removed, and the solid content was taken out.
The solid content was heated to 50 ° C., the weight change was measured with a precision balance, and the presence or absence of the fatty acid monoester on the toner particle surface was evaluated according to the following criteria.
○: The weight is 0.005 g or more, and fatty acid monoesters are unevenly distributed near the surface of the toner particles.
X: Change in weight is smaller than 0.005 g, and fatty acid monoester is not unevenly distributed near the surface of the toner particles.
These results are shown in Table 2 together with the viscosity of the liquid developer, the volume-based average particle diameter of the toner particles, and the particle diameter standard deviation.

As apparent from Table 2, the liquid developer of the present invention was excellent in fixing strength, dispersion stability, and storage stability. On the other hand, satisfactory results were not obtained with the liquid developers of the comparative examples. In addition, it was confirmed that fatty acid monoesters are unevenly distributed on the surface of the toner particles in the liquid developer obtained in each example. On the other hand, in the comparative example, the uneven distribution of the fatty acid monoester could not be confirmed.
In addition, the liquid developer was manufactured and evaluated in the same manner as described above except that Pigment Red 122, Pigment Yellow 180, and Carbon Black (Printex L, manufactured by Degussa) were used as the colorant instead of the cyan pigment. As a result, the same result as above was obtained.

1 is a cross-sectional view illustrating an example of a contact-type liquid developing apparatus to which a liquid developer of the present invention is applied. 1 is a cross-sectional view illustrating an example of a non-contact type image forming apparatus to which a liquid developer of the present invention is applied. FIG. 3 is a cross-sectional view illustrating an example of a fixing device to which the liquid developer of the present invention is applied.

Explanation of symbols

  P1 ... Liquid developing device P2 ... Photoconductor P3 ... Charger P4 ... Exposure P10 ... Developer P11 ... Developer container P12 ... Application roller P13 ... Development roller P14 ... Liquid developer application layer P15 ... Metering blade P16 ... Roller core P17 ... developing roller cleaning blade P18 ... intermediate transfer roller P19 ... secondary transfer roller P21 ... static light P22 ... cleaning blade P23 ... cleaning blade P24 ... charging blade F40 ... fixing device F1 ... heat fixing roller (fixing roller) F1a ... column-shaped halogen Lamp F1b ... Roller base material F1c ... Elastic body 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 ... Recess F5 ... Recording medium F5a ... toner image 6 ... cleaning member F7 ... frame F9 ... spring

Claims (8)

Toner particles in which fatty acid monoesters are unevenly distributed on the surface;
And an insulating liquid containing an unsaturated fatty acid triglyceride .   The liquid developer according to claim 1, wherein the fatty acid monoester has a viscosity of 10 mPa · s or less.   The liquid developer according to claim 1, wherein the fatty acid monoester is a saturated fatty acid ester having 8 to 18 carbon atoms. The liquid developer according to claim 1, wherein a resin material of the toner particles is a polyester resin. A method for producing a liquid developer having an insulating liquid containing toner particles in which fatty acid monoesters are unevenly distributed on the surface and unsaturated fatty acid triglycerides ,
In the fatty acid monoester, a pulverizing step of pulverizing a toner material including a resin material to obtain a pulverized dispersion;
A mixing step of mixing the pulverized dispersion and the liquid containing the unsaturated fatty acid triglyceride ;
A method for producing a liquid developer, comprising:   The method for producing a liquid developer according to claim 5, wherein, in the pulverizing step, the toner material is pulverized in a state where a dispersant is contained in the fatty acid monoester. A method for producing a liquid developer having an insulating liquid containing toner particles in which fatty acid monoesters are unevenly distributed on the surface and unsaturated fatty acid triglycerides ,
A step of associating fine particles having a resin material to obtain associated particles;
Crushing the associated particles in the fatty acid monoester to obtain the toner particles;
Wherein the toner particles, the method for producing a liquid developer, characterized in that it comprises a and a dispersion step of dispersing in a liquid containing an unsaturated fatty acid triglyceride.   A liquid developer reservoir for storing a liquid developer having an insulating liquid containing toner particles in which fatty acid monoesters are unevenly distributed on the surface and unsaturated fatty acid triglycerides;
  A developing unit for developing using the liquid developer supplied from the liquid developer storage unit;
  An image carrier for carrying an image developed in the developing unit;
  A transfer unit that transfers the image developed by the developing unit to a recording medium;
  A fixing unit that heat-fixes the recording medium onto which the image has been transferred;
  An image forming apparatus comprising:

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