JP4844037B2 - Method for producing liquid developer - Google Patents

Description

The present invention relates to the production how the liquid developer.

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

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

  However, in recent years, with the further increase in resolution of formed images, further miniaturization of toner particles has been demanded, and it is difficult to pulverize toner particles to a sufficiently small size by the conventional liquid developer manufacturing method. In order to make the size of the toner particles sufficiently small, a very long grinding energy is required for a very long time, and the productivity of the liquid developer is extremely low. Further, in the method as described above, the particle size distribution of the toner particles tends to be wide (particle size variation is large). As a result, variation in characteristics (for example, charging characteristics) among the toner particles tends to increase. On the other hand, dry pulverization as described above is also conceivable, but in such a case, it is very difficult to obtain fine particles as required for the toner particles of the liquid developer, and aggregation or the like proceeds, and the comparison It was difficult to obtain small toner particles.

  Further, in the conventional wet pulverization method, it has been difficult to obtain a liquid developer having sufficiently high dispersibility of toner particles. When the dispersibility of the toner particles is poor, there is a problem that when left for a long time, the toner particles settle, and the toner particles aggregate. In addition, once the particles settle and agglomerate, the toner particles are difficult to disperse even if they are stirred again to disperse, and the toner particles can be supplied uniformly during image formation. There was a problem that it was impossible.

JP-A-8-36277

An object of the present invention is to provide a liquid developer in which sufficiently small toner particles are stably dispersed, and to produce a liquid developer capable of efficiently producing such a liquid developer. there is a way in and provides child.

Such an object is achieved by the present invention described below.
The method for producing a liquid developer of the present invention includes a wet pulverization step in which a colorant and a resin material are pulverized in a first liquid to obtain a pulverized dispersion.
A mixing step of mixing the pulverized dispersion obtained in the wet pulverization step with a second liquid having a higher viscosity than the first liquid ;
It is characterized by having.
This makes it possible to efficiently produce a liquid developer in which sufficiently small toner particles are stably dispersed.

In the method for producing a liquid developer of the present invention, the viscosity V ₁ of the first liquid is preferably 0.5 to 30 mPa · s.
Thereby, toner particles having a sufficiently small particle diameter can be obtained more efficiently.
In the method for producing a liquid developer of the present invention, the viscosity V ₂ of the second liquid is preferably 30 to 1000 mPa · s.
As a result, the viscosity of the insulating liquid (liquid developer) can be made more suitable and the dispersibility of the toner particles can be made higher.

In the method for producing a liquid developer of the present invention, the V ₁ [mPa · s] and the V ₂ [mPa · s]
0.0005 ≦ V ₁ / V ₂ ≦ 1
It is preferable to have the following relationship.
Thereby, toner particles having a sufficiently small particle diameter can be obtained more efficiently, and the dispersibility of the toner particles can be further increased.

In the liquid developer producing method of the present invention, the first liquid and the second liquid is preferably a nonpolar liquid.
Thereby, the compatibility between the first liquid and the second liquid can be improved while increasing the electrical resistance (insulating property) of the insulating liquid. As a result, the storage stability as a liquid developer is improved.

In the method for producing a liquid developer of the present invention, in the pulverizing step, it is preferable that the colorant and the resin material are pulverized in a state where a dispersant is contained in the first liquid.
As a result, the dispersant acts as a pulverization aid, whereby toner particles having a sufficiently small particle diameter can be obtained more efficiently, and the dispersibility of the resulting toner particles can be made higher.

In the method for producing a liquid developer of the present invention, it is preferable that the first liquid and the dispersant are mixed before mixing the first liquid, the colorant, and the resin material .
As a result, the charging characteristics of the finally obtained liquid developer can be improved.
In the liquid developer producing method of the present invention, the first liquid is preferably a mineral oil.
Thereby, toner particles having a sufficiently small particle diameter can be obtained more efficiently. Further, the mineral oil has a high affinity with the toner particles, and when mixed with the second liquid, the toner particles can be suitably wrapped. As a result, the dispersibility of the toner particles is further improved, and a liquid developer having higher storage stability can be obtained.

In the liquid developer producing method of the present invention, the second liquid is preferably a vegetable oil.
Thereby, an environmentally friendly liquid developer can be provided. Further, the dispersibility of the toner particles can be made higher, and the storage stability of the obtained liquid developer can be made higher.

In the method for producing a liquid developer according to the aspect of the invention, it is preferable that the resin material includes at least one of an epoxy resin and a polyester resin.
Thereby, toner particles having a sufficiently small particle diameter can be obtained more efficiently, and the dispersibility of the toner particles in the liquid developer can be made higher .

Hereinafter, a preferred embodiment of manufacturing how the liquid developer of the present invention will be described in detail.
The liquid developer used in the present invention is one in which toner particles are dispersed in an insulating liquid.
The insulating liquid includes a first liquid and a second liquid having a higher viscosity than the first liquid.

Hereinafter, the method for producing the liquid developer of the present invention will be described in detail.
The method for producing a liquid developer of the present invention includes a pulverizing step of pulverizing a toner material containing a colorant and a resin material in a first liquid to obtain a pulverized dispersion, and a pulverized dispersion and a second A mixing step of mixing the liquid.
<Preparation of toner material>
First, an example of a toner material preparation method will be described.
FIG. 1 is a longitudinal sectional view schematically showing an example of the configuration of a kneader and a cooler for producing a kneaded material used for adjusting the toner material.
-Toner material-
First, the configuration of the toner material used for manufacturing the liquid developer will be described.
The toner material contains at least a resin material (resin) and a colorant.

1. Resin material (binder resin)
In the present invention, the resin material (binder resin) is not particularly limited. For example, polystyrene, poly-α-methylstyrene, chloropolystyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene. Copolymer, 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 Styrene or styrene substitution with styrenic resins such as ester-methacrylic acid ester copolymer, styrene-α-methyl chloroacrylate copolymer, styrene-acrylonitrile-acrylic acid ester copolymer, styrene-vinyl methyl ether copolymer Homopolymer or copolymer containing Body, 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 acrylate copolymer, xylene resin, polyvinyl butyral resin, terpene resin, phenol resin, aliphatic or alicyclic hydrocarbon resin and the like. One or more of these can be used in combination.

  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 material contains 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 material 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 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.

(Kneading process)
In this embodiment, the toner material is adjusted by kneading the above-described components.
The raw material K5 used for kneading contains the components as described above. In particular, in a composition containing a colorant, since the colorant easily embeds air, air tends to remain in the composition. However, by kneading in this step, air contained in the raw material K5 ( In particular, air entrained by the colorant can be efficiently removed, and bubbles can be effectively prevented from being mixed (residual) inside the toner particles. The raw material K5 used for kneading is preferably a mixture of these components.

This embodiment demonstrates the structure which uses a biaxial kneading extruder as a kneading machine.
The kneading machine K1 includes a process part K2 for kneading while conveying the raw material K5, a head part K3 for extruding the kneaded raw material (kneaded material K7) into a predetermined cross-sectional shape, and a raw material K5 in the process part K2. And a feeder K4 to be supplied.
The process part K2 includes a barrel K21, a screw K22 and a screw K23 inserted into the barrel K21, and a fixing member K24 for fixing the head part K3 to the tip of the barrel K21.
In the process part K2, when the screw K22 and the screw K23 rotate, a shearing force is applied to the raw material K5 supplied from the feeder K4, and a uniform kneaded material K7 is obtained.

  The total length of the process part K2 is preferably 50 to 300 cm, and more preferably 100 to 250 cm. If the total length of the process part K2 is less than the lower limit, it may be difficult to mix the components in the raw material K5 sufficiently uniformly. On the other hand, when the total length of the process part K2 exceeds the upper limit, depending on the temperature in the process part K2, the number of rotations of the screw K22, the screw K23, and the like, the material K5 is easily denatured by heat, and finally obtained. It may be difficult to sufficiently control the physical properties of the liquid developer (toner).

  Moreover, although the raw material temperature at the time of kneading | mixes changes with compositions etc. of the raw material K5, it is preferable that it is 80-260 degreeC, and it is more preferable that it is 90-230 degreeC. Note that the raw material temperature in the process part K2 may be uniform or may vary depending on the part. For example, the process unit K2 includes a first region having a relatively low set temperature and a second region that is provided on the base end side from the first region and whose set temperature is higher than the first region. You may have.

  In addition, the residence time (time required for passage) of the raw material K5 in the process part K2 is preferably 0.5 to 12 minutes, and more preferably 1 to 7 minutes. If the residence time in the process part K2 is less than the lower limit, it may be difficult to mix the components in the raw material K5 sufficiently uniformly. On the other hand, if the residence time in the process part K2 exceeds the upper limit, the production efficiency is reduced. Depending on the temperature in the process part K2, the rotational speed of the screw K22, the screw K23, etc., the heat of the raw material K5 Modification is likely to occur, and it may be difficult to sufficiently control the physical properties of the finally obtained liquid developer (toner).

  The number of rotations of the screw K22 and the screw K23 varies depending on the composition of the binder resin and the like, but is preferably 50 to 600 rpm. If the rotational speeds of the screws K22 and K23 are less than the lower limit, it may be difficult to mix the components in the raw material K5 sufficiently uniformly. On the other hand, when the rotation speed of the screw K22 and the screw K23 exceeds the upper limit value, the molecular chain of the resin may be cut by shearing, and the resin characteristics may be deteriorated.

  Further, in the kneader K1 used in the present embodiment, the inside of the process unit K2 is connected to the pump P via the deaeration port K25. Thereby, the inside of the process part K2 can be degassed, and an increase in the pressure in the process part K2 due to heating or heat generation of the raw material K5 (kneaded material K7) can be prevented. As a result, the kneading process can be performed safely and efficiently. Further, since the inside of the process part K2 is connected to the pump P via the deaeration port K25, it is possible to effectively prevent bubbles (particularly relatively large bubbles) from being contained in the obtained kneaded material K7. And the properties of the liquid developer (toner) finally obtained can be made more excellent.

(Extrusion process)
The kneaded material K7 kneaded in the process part K2 is pushed out of the kneader K1 through the head part K3 by the rotation of the screw K22 and the screw K23.
The head part K3 has an internal space K31 into which the kneaded material K7 is fed from the process part K2, and an extrusion port K32 from which the kneaded material K7 is extruded.

  The temperature of the kneaded material K7 in the internal space K31 (at least in the vicinity of the extrusion port K32) is not particularly limited, but is preferably a temperature equal to or higher than the softening temperature of the resin material contained in the raw material K5. As a result, the toner particles can be obtained as a mixture of the constituent components more uniformly, and variations in characteristics (charging characteristics, fixing properties, etc.) among the toner particles can be particularly reduced.

The specific temperature of the kneaded material K7 in the internal space K31 (at least the temperature near the extrusion port K32) is not particularly limited, but is preferably 80 to 150 ° C, more preferably 90 to 140 ° C. preferable. When the temperature of the kneaded material K7 in the internal space K31 is a value within the above range, the kneaded material K7 does not solidify in the internal space K31 and is easily extruded from the extrusion port K32.
In the illustrated configuration, the internal space K31 has a cross-sectional area gradually decreasing portion K33 in which the cross-sectional area gradually decreases in the direction of the extrusion port K32. By having such a cross-sectional area gradually decreasing portion K33, the extrusion amount of the kneaded material K7 extruded from the extrusion port K32 is stabilized, and the cooling rate of the kneaded material K7 in the cooling step described later is stabilized. As a result, the toner produced using the toner has a small variation in characteristics among the toner particles, and has excellent overall characteristics.

(Cooling process)
The softened kneaded material K7 extruded from the extrusion port K32 of the head portion K3 is cooled and solidified by the cooler K6.
The cooler K6 includes rolls K61, K62, K63, and K64, and belts K65 and K66.
The belt K65 is wound around a roll K61 and a roll K62. Similarly, the belt K66 is wound around the roll K63 and the roll K64.

  The rolls K61, K62, K63, and K64 rotate around the rotation axes K611, K621, K631, and K641 in the directions indicated by e, f, g, and h in the drawing. Thereby, the kneaded material K7 extruded from the extrusion port K32 of the kneading machine K1 is introduced between the belt K65 and the belt K66. The kneaded material K7 introduced between the belt K65 and the belt K66 is cooled while being formed into a plate shape having a substantially uniform thickness. The cooled kneaded material K7 is discharged from the discharge portion K67. The belts K65 and K66 are cooled by a method such as water cooling or air cooling. When such a belt type is used as the cooler, the contact time between the kneaded product extruded from the kneader and the cooling body (belt) can be increased, and the cooling efficiency of the kneaded product is particularly excellent. Can be.

  By the way, in the kneading process, since shearing force is applied to the raw material K5, phase separation (particularly macrophase separation) is sufficiently prevented, but the kneaded product K7 that has finished the kneading process is not subjected to shearing force. Therefore, depending on the constituent materials of the kneaded product, phase separation (macrophase separation) or the like may occur again if left for a long period of time. Therefore, it is preferable to cool the kneaded material K7 obtained as described above as soon as possible. Specifically, the cooling rate of the kneaded material K7 (for example, the cooling rate when the kneaded material K7 is cooled to about 60 ° C.) is preferably −3 ° C./second or more, and is preferably −5 to −100 ° C. / More preferably it is seconds. Further, the time required from the end of the kneading step (when the shearing force is no longer applied) to the completion of the cooling step (for example, the time required for cooling the temperature of the kneaded product K7 to 60 ° C. or lower) is 20 seconds. Or less, more preferably 3 to 12 seconds.

In the present embodiment, the configuration using a continuous biaxial kneading extruder as the kneading machine has been described, but the kneading machine used for kneading the raw materials is not limited to this. For kneading the raw materials, for example, various kneaders such as a kneader, a batch type triaxial roll, a continuous biaxial roll, a wheel mixer, and a blade type mixer can be used.
In the illustrated configuration, a kneader having two screws has been described. However, the number of screws may be one or three or more. Further, the kneading apparatus may have a disc (kneading disc) portion.

Further, in the present embodiment, the configuration using one kneader has been described, but kneading may be performed using two kneaders. In this case, the heating temperature of the raw material, the rotational speed of the screw, and the like may be different between one kneader and the other kneader.
In the present embodiment, a configuration using a belt type as the cooler has been described. However, for example, a roll type (cooling roll type) cooler may be used. Further, the cooling of the kneaded product extruded from the extrusion port K32 of the kneader is not limited to the one using the above-described cooler, and may be performed by, for example, air cooling.

(Coarse grinding process)
Next, the kneaded material K7 that has undergone the cooling step as described above is roughly pulverized to obtain a coarsely pulverized material. The coarsely pulverized product thus obtained can be used as a toner material. By using the coarsely pulverized product obtained by roughly pulverizing the kneaded material K7 as the toner material, the particle size of the toner particles can be reduced more effectively in the wet pulverization step described later.
The method of coarse pulverization is not particularly limited, and can be performed using, for example, various pulverizers and crushers such as a ball mill, a vibration mill, a jet mill, and a pin mill.
The coarse pulverization step may be performed in multiple steps.

<Preparation of liquid developer>
Next, a liquid developer is prepared using the toner material prepared as described above.
(Wet grinding process (fine grinding process))
First, the toner material obtained as described above is wet-pulverized to obtain a pulverized dispersion.
The present invention is characterized in that wet pulverization is performed using the first liquid having a low viscosity among the first liquid and the second liquid constituting the insulating liquid.

  Such a first liquid has a relatively low viscosity, a high degree of freedom of movement of the toner material in the first liquid, and a low resistance of the first liquid, so that the coarsely pulverized product is efficiently pulverized. be able to. In addition, since the first liquid has a relatively low viscosity, it can penetrate into cracks and the like of the toner material (coarse pulverized material) generated by pulverization and the like, and can be pulverized efficiently. As a result, it is possible to efficiently form toner particles having a small particle diameter. Further, the pulverization rate can be improved. Further, by pulverizing in the first liquid having a relatively low viscosity, the energy applied for pulverization can be efficiently used for pulverization of the toner material, so that the temperature of the first liquid rises. Can be prevented. As a result, even if the resin material constituting the toner material has a low melting point, it can be efficiently pulverized.

The viscosity of the first liquid at room temperature (20 ° C.) is preferably 1 to 10 mPa · s, more preferably 1 to 5 mPa · s, and further preferably 1 to 3 mPa · s. Thereby, toner particles having a sufficiently small particle diameter can be obtained more efficiently.
The first liquid is preferably composed of a nonpolar liquid. Thereby, the electrical resistance (insulating property) of the insulating liquid can be made higher.

The first liquid may be a liquid having a sufficiently high insulating property. Specifically, the electric resistance at room temperature (20 ° C.) is preferably 10 ⁹ Ωcm or more, and preferably 10 ¹¹ Ωcm or more. More preferably, it is more preferably 10 ¹³ Ωcm or more. Thereby, the electrical resistance (insulating property) of the insulating liquid can be made higher.

The relative dielectric constant of the first liquid is preferably 3.5 or less.
Examples of the liquid constituting the first liquid include Isopar E, Isopar G, Isopar H, Isopar L (Isopar; trade name of Exxon Chemical), Cielsol 70, Cielsol 71 (Cielsol; Product name), Amsco OMS, Amsco 460 solvent (Amsco; product name of Spirits), mineral oil such as low viscosity liquid paraffin (Wako Pure Chemical Industries), octane, isooctane, decane, isodecane, decalin, nonane, dodecane, isododecane , Cyclohexane, cyclooctane, cyclodecane, benzene, toluene, xylene, mesitylene and the like.

  Among the above, mineral oil easily penetrates into cracks and the like existing in the toner material, so that the toner material can be pulverized more efficiently. In addition, mineral oil has a high affinity with toner particles, and can suitably enclose toner particles when mixed with a second liquid described later. As a result, the dispersibility of the toner particles is further improved, and a liquid developer having higher storage stability can be obtained.

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.
A dispersant (surfactant) may be added to the first liquid before mixing the first liquid and the coarsely pulverized product. 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.
Further, by pulverizing the toner material in the state where the first liquid contains the dispersant, the dispersant adheres to the surface of the toner particles, thereby improving the charging characteristics of the finally obtained liquid developer. be able to.

  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 fatty acid condensation polymers, viscosity minerals, silica, tricalcium phosphate, metal tristearate (for example, aluminum salt), metal distearate (for example, aluminum salt, barium salt, etc.) ), Metal stearates (eg, 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.), 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 pulverized with the first liquid, the polymer dispersant can be suitably present (entangled) on the surface of the toner particles. When mixed with the first liquid, the first liquid can be more effectively held 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. In particular, among the polymer dispersants, when Solsperse is used, the above-described effects become more remarkable. The pulverization with the first liquid may be pulverization of the aggregate.

(Mixing process)
Next, a liquid developer is obtained by mixing the obtained pulverized material dispersion and the second liquid. Accordingly, the insulating liquid constituting the liquid developer includes the first liquid and the second liquid.
The second liquid has a higher viscosity than the first liquid described above.

Thus, the viscosity of the insulating liquid (liquid developer) can be adjusted by mixing the pulverized product dispersion obtained by wet pulverization using the first liquid and the second liquid.
Further, the obtained liquid developer has high dispersibility of the toner particles. This is considered to be due to the following reasons.
That is, when the coarsely pulverized product (toner material) is wet pulverized with the first liquid, the toner particles are encased in the first liquid in the obtained pulverized product dispersion. Since it is mixed with the second liquid in this state, the obtained liquid developer has high dispersibility of the toner particles.

Further, since the liquid developer obtained by such a manufacturing method has high dispersibility of toner particles and is adjusted to an appropriate viscosity, the liquid developer is applied to the application roller P12 in an image forming apparatus P1 as described later. The liquid developer can be supplied uniformly, and dripping of the liquid developer from the application roller P12 and the like can be effectively prevented.
In particular, when an epoxy resin or a polyester resin is used as the resin material constituting the coarsely pulverized product (toner material), the following effects can be obtained.

  That is, when the resin material includes at least one of an epoxy resin and a polyester resin, the epoxy resin and the polyester resin have a high affinity with the first liquid described above, and therefore, a crack in the toner material caused by pulverization or the like Therefore, the toner material can be crushed more efficiently. Further, when mixed with the second liquid, the toner particles can be more reliably wrapped with the first liquid, and the dispersibility of the toner particles in the liquid developer can be further increased.

  Although it will not specifically limit if a 2nd liquid is a thing higher than the viscosity of a 1st liquid, It is preferable that the viscosity in room temperature (20 degreeC) is 30-1000 mPa * s, 30-500 mPa -It is more preferable that it is s, and it is further more preferable that it is 30-200 mPa * s. When the viscosity of the second liquid is in such a range, the viscosity of the insulating liquid (liquid developer) can be more easily made suitable. As a result, the dispersibility of the toner particles can be made higher.

Further, when the viscosity of the first liquid is V ₁ [mPa · s] and the viscosity of the second liquid is V ₂ [mPa · s], the relationship of 0.0005 ≦ V ₁ / V ₂ ≦ 1 is satisfied. It is preferable to satisfy the relationship of 0.0005 ≦ V ₁ / V ₂ ≦ 0.1. Thereby, the toner material can be pulverized more efficiently and the dispersibility of the toner particles can be further increased.

When the content of the first liquid in the insulating liquid is A [wt%] and the content of the second liquid is B [wt%], the relationship of 0.1 ≦ A / B ≦ 9 is satisfied. It is preferable that the relationship 0.1 ≦ A / B ≦ 0.3 is satisfied. By satisfying such a relationship, the viscosity of the obtained liquid developer (insulating liquid) can be made more suitable.
The second liquid is preferably composed of a nonpolar liquid. Thereby, the electrical resistance (insulating property) of the insulating liquid can be made higher.

The second liquid may if sufficiently high insulating liquid, specifically, is preferably intended electric resistance of more than 10 ⁹ [Omega] cm at room temperature (20 ℃), 10 ¹¹ More preferably, it is Ωcm or more, more preferably 10 ¹³ Ωcm or more. Thereby, the electrical resistance (insulating property) of the insulating liquid can be made higher.
The relative dielectric constant of the second liquid is preferably 3.5 or less.

  Examples of the liquid constituting the second liquid include vegetable oils such as linseed oil and soybean oil, and mineral oils such as high viscosity liquid paraffin and silicone oil. In particular, when vegetable oil is used, an environmentally friendly liquid developer can be provided. Further, the dispersibility of the toner particles can be made higher, and the storage stability of the obtained liquid developer can be made higher.

Moreover, it is preferable that both the 1st liquid and the 2nd liquid are comprised with the nonpolar liquid. Thereby, the compatibility between the first liquid and the second liquid can be improved while further increasing the electrical resistance (insulating property) of the insulating liquid. As a result, the storage stability as a liquid developer is improved.
A liquid other than the first liquid and the second liquid described above may be added.

  The average particle diameter of the toner particles in the liquid developer obtained as described above is preferably 0.1 to 4 μm, more preferably 0.4 to 4 μm, and 0.5 to 3 μm. Is more preferable. When the average particle diameter of the toner particles is within the above range, the dispersion of characteristics such as charging characteristics and fixing characteristics among the toner particles is particularly small, and the reliability of the entire liquid developer is particularly high. In addition, the resolution of the image formed by the liquid developer (toner) can be made sufficiently high.

The standard deviation of the particle size between toner particles constituting the liquid developer is preferably 3.0 μm or less, more preferably 0.1 to 2.0 μm, and 0.1 to 1. More preferably, it is 0 μm. As a result, variations in characteristics such as charging characteristics and fixing characteristics among the toner particles are particularly reduced, and the reliability of the entire liquid developer is further improved.
The viscosity of the liquid developer obtained as described above at room temperature (20 ° C.) is preferably 50 to 500 mPa · s, more preferably 50 to 200 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.
In addition, the viscosity of the insulating liquid in the obtained liquid developer at room temperature (20 ° C.) is preferably 30 to 400 mPa · s, and more preferably 30 to 150 mPa · s. Thereby, the dispersibility of the toner particles can be made higher, and the viscosity of the liquid developer can be made more suitable.

Next, a preferred embodiment of the image forming apparatus to which the liquid developer of the present invention as described above is applied will be described.
FIG. 2 shows an example of a contact-type image forming apparatus to which the liquid developer of the present invention is applied. The image forming apparatus P1 includes 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. In particular, the liquid developer obtained by the method of the present invention has high dispersibility of toner particles, and the viscosity of the liquid developer is optimal. Thickness and toner particles are uniformly dispersed. As a result, a clear and uniform image can be suitably obtained.

  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, residual toner remaining on the intermediate transfer roller P18 after transfer from the intermediate transfer roller P18 to the information recording medium P20 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 information recording medium P20 such as paper passing between them. The toner image on the information recording medium P20 such as paper is fixed using the fixing device shown in FIG.

  FIG. 3 shows an example of a non-contact type image forming 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. Other than that, it is the same as the image forming apparatus described with reference to FIG.
In FIGS. 2 and 3, image formation using a single color liquid developer has been described. However, when forming an image using a plurality of color toners, an image of each color is formed using a plurality of color developers. Thus, a color image can be formed.

FIG. 4 is a cross-sectional view of the fixing device. F1 is a heat fixing roll, F1a is a columnar halogen lamp, F1b is a roll base, F1c is an elastic body, F2 is a pressure roll, F2a is a rotating shaft, and F2b is a roll base. F2c is an elastic body, F3 is a heat-resistant belt, F4 is a belt stretching member, F4a is a protruding wall, F5 is a sheet material, F5a is an unfixed toner image, F6 is a cleaning member, F7 is a frame, F9 is a spring, L is It is a pressing part tangent.
As shown in the figure, the fixing device F40 includes a heat fixing roll (hereinafter also referred to as a heating roll) F1, a pressure roll F2, a heat-resistant belt F3, a belt stretching member F4, and a cleaning member F6.

  The heat fixing roll F1 is formed by covering a pipe member having an outer diameter of about 25 mm and a wall thickness of about 0.7 mm with a roll base material F1b and an elastic body F1c having a thickness of about 0.4 mm on the outer periphery thereof. 1,050W as a heat source and two columnar halogen lamps F1a are built in and can be rotated counterclockwise as indicated by an arrow in the figure. Further, the pressure roll F2 has a pipe material having an outer diameter of about 25 mm and a wall thickness of about 0.7 mm as a roll base material F2b with a thickness of 0. The elastic body F2c having a thickness of about 2 mm is formed so as to cover the heat fixing roll F1 and the pressure roll F2 with a pressure contact force of 10 kg or less, a nip length of about 10 mm, and disposed opposite the heat fixing roll F1. It can be rotated in the clockwise direction indicated by an arrow.

  Thus, since the outer diameters of the heat fixing roll F1 and the pressure roll F2 are configured to be as small as about 25 mm, the sheet material F5 after fixing does not wrap around the heat fixing roll F1 or the heat-resistant belt F3. A means for forcibly removing the sheet material is not necessary. Further, by providing a PFA layer of about 30 μm on the surface layer of the elastic body F1c of the heat fixing roll F1, the rigidity is improved accordingly. Thereby, although the thicknesses of the elastic bodies F1c and 2c are different, 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 roll F1. Since there is no difference in the conveyance speed of the heat-resistant belt F3 or the sheet material F5, extremely stable image fixing is possible.

  In addition, two columnar halogen lamps F1a and F1a constituting a heat source are built in the heat fixing roll 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 the heat-resistant belt F3 is wound around the heat fixing roll F1 and a portion where the belt stretching member F4 is in sliding contact with the heat fixing roll F1 are formed. Temperature control can be easily performed under different conditions or different conditions between a wide sheet material and a narrow sheet material.

  The heat-resistant belt F3 is an endless annular belt which is stretched around the outer periphery of the pressure roll F2 and the belt tension member F4 and is movable, and is sandwiched between the heat fixing roll F1 and the pressure roll 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 sheet material F5 comes into contact) is formed of PFA, and the back surface (contacts with the pressure roll F2 and the belt stretching member F4). It is formed of a seamless tube having a two-layer structure in which the surface on the side to be formed is made 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 silicon.

  The belt stretching member F4 is disposed upstream of the fixing nip portion between the heat fixing roll F1 and the pressure roll F2 in the conveying direction of the sheet material F5, and has an arrow P around the rotation axis F2a of the pressure roll 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 roll F1 in a state where the sheet material F5 does not pass through the fixing nip portion. If the fixing pressure is large at the initial position where the sheet material F5 enters the fixing nip portion, the entry may not be smoothly performed and the sheet material F5 may be fixed with the leading end of the sheet material F5 broken. By adopting a configuration in which F3 is stretched in the tangential direction of the heat fixing roll F1, an introduction port portion of the sheet material F5 through which the sheet material F5 smoothly enters can be formed, and to the stable fixing nip portion of the sheet material F5. Can enter.

  The belt stretching member F4 is inserted into the inner periphery of the heat-resistant belt F3 and cooperates with the pressure roll F2 to apply a tension f to the heat-resistant belt F3 (the heat-resistant belt F3 is a belt). Sliding on the tension member F4). The belt stretching member F4 is disposed at a position where the heat-resistant belt F3 is wound around the heat fixing roll F1 side from the pressing portion tangent L between the heat fixing roll F1 and the pressure roll 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 roll F1 and the frame, and the protruding wall F4a of the belt stretching member F4 is lightly pressed by the heat fixing roll F1, so that the belt tension is increased. The frame member F4 is positioned in sliding contact with the heat fixing roll F1.

  In order to stretch the heat-resistant belt F3 with the pressure roll F2 and the belt stretching member F4 and drive it stably with the pressure roll F2, the friction coefficient between the pressure roll F2 and the heat-resistant belt F3 is changed to the belt stretching member. It is good to set larger than the friction coefficient of F4 and heat-resistant belt F3. However, the friction coefficient is such that foreign matter enters between the heat-resistant belt F3 and the pressure roll F2 or between the heat-resistant belt F3 and the belt stretching member F4, or the heat-resistant belt F3, the pressure roll 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 roll F2 and the heat-resistant belt F3, and the diameter of the belt stretching member F4 is smaller than the diameter of the pressure roll 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 stably driven by the pressure roll F2. Will be able to.

  Further, a cleaning member F6 is disposed between the pressure roll 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, and foreign matter on the inner peripheral surface of the heat-resistant belt F3. It cleans and wear powder. 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 tension member F4 is provided with a recess F4f, and the recess F4f is suitable for storing foreign matter, abrasion powder, and the like removed from the heat-resistant belt F3.

  The position where the belt tension member F4 is lightly pressed against the heat fixing roll F1 is the nip initial position, and the position where the pressure roll F2 is pressed against the heat fixing roll F1 is the nip end position. Then, the sheet material F5 enters the fixing nip portion from the initial nip position, passes between the heat-resistant belt F3 and the heat fixing roll F1, and exits from the nip end position, whereby an unfixed sheet formed on the sheet material F5. The toner image F5a is fixed, and then discharged in the tangential direction L of the pressing portion of the pressure roll F2 to the heat fixing roll F1.

As mentioned above, although this invention was demonstrated based on suitable embodiment, this invention is not limited to these.
For example, in the method for producing a liquid developer of the present invention, one or two or more optional steps may be added.
In the above-described embodiment, the liquid developer is manufactured using the kneaded material obtained by kneading the material constituting the toner particles. However, the toner particles are configured without using the kneaded material. You may use what mixed the material to do.

In the above-described embodiment, the wet pulverization is performed using the pulverized product of the kneaded product, but the coarse pulverization step of the kneaded product may be omitted.
In the above-described embodiment, the wet pulverization is performed using only the first liquid. However, the wet pulverization may be performed using a mixed liquid containing the first liquid and a relatively small amount of the second liquid. Good. By performing wet pulverization in this manner, the viscosity of the liquid used for wet pulverization can be optimized. As a result, sufficiently small toner particles can be obtained more efficiently.
Further, in the above-described embodiment, the wet liquid pulverization with the first liquid has been described as being mixed with the second liquid. However, a part of the first liquid may be removed after the wet pulverization.

In addition to the first liquid, the liquid used for wet pulverization may include a third liquid different from the first liquid and the second liquid. As such a third liquid, for example, a liquid having a viscosity lower than that of the first liquid can be used. Thereby, the efficiency of wet pulverization can be further improved, and sufficiently small toner particles can be obtained more efficiently. Examples of the third liquid include those having compatibility with the first liquid such as low-molecular mineral oil and silicone oil. In this case, the third liquid may or may not be removed before mixing with the second liquid.
Further, the liquid developer of the present invention is not limited to those applied to the image forming apparatus as described above.

[1] Production of liquid developer (Example 1)
[Kneaded product]
First, an epoxy resin (Epicoat 1004, softening temperature T _f : 128 ° C.) as a binder resin: 80 parts by weight and a cyan pigment as a colorant (Pigment Blue 15: 3, manufactured by Dainichi Seika Co., Ltd.): 20 weights And 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 as shown in FIG.
The total length of the process part of the biaxial kneading extruder was 160 cm.
Moreover, it set so that the temperature of the raw material in a process part might be 105-115 degreeC.
The screw rotation speed was 120 rpm, and the raw material charging speed was 20 kg / hour.

The time required for the raw material to pass through the process part, determined from such conditions, is about 4 minutes.
The kneading as described above was performed while degassing the inside of the process unit by operating a vacuum pump connected to the process unit via a degassing port.
The raw material (kneaded material) kneaded in the process part was extruded outside the biaxial kneading extruder through the head part. The temperature of the kneaded material in the head part was adjusted to 135 ° C.

Thus, the kneaded material extruded from the extrusion port of the biaxial kneading extruder was cooled using a cooling machine as shown in FIG. The temperature of the kneaded material immediately after the cooling step was about 45 ° C.
The cooling rate of the kneaded product was 9 ° C./second. In addition, the time required from the end of the kneading process to the end of the cooling process was 10 seconds.
The kneaded product cooled as described above was coarsely pulverized to obtain a powder having a mean particle size of 1.0 mm or less (pulverized product). 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, Isopar H as a first liquid (trade name of Exxon Chemical): 100 parts by weight, and polyamine fatty acid degenerate as a dispersant 10 parts by weight (manufactured by Nippon Lubrizol Corporation, trade name “Solsperse 11200”): 1.0 part by weight of magnesium stearate as a charge control agent was prepared. The electric resistance of the first liquid at room temperature (20 ° C.) is 1.6 × 10 ¹⁵ Ωcm, the dielectric constant of the first liquid is 2.5, and the viscosity at room temperature (20 ° C.) is 1.95 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 soybean oil as a second liquid (trade name “soybean oil” manufactured by Kanto Chemical Co., Ltd.): 400 parts by weight are mixed to obtain a liquid developer. It was. The viscosity of soybean oil at room temperature (20 ° C.) was 56 mPa · s.
The average particle size of the toner particles in the obtained liquid developer was 2.5 μm, and the standard deviation of the particle size between the toner particles was 0.48 μm. Further, the viscosity of the liquid developer at room temperature (20 ° C.) was 57 mPa · s.
When the insulating liquid contained in the liquid developer was centrifuged and the viscosity of the insulating liquid was measured, the viscosity was 42 mPa · s.

(Example 2)
A liquid developer was produced in the same manner as in Example 1, except that high-viscosity liquid paraffin (manufactured by Wako Pure Chemical Industries, Ltd., viscosity (20 ° C.): 171 mPa · s) was used as the second liquid.
(Example 3)
Example 1 except that low-viscosity liquid paraffin (manufactured by Wako Pure Chemical Industries, Ltd., viscosity (20 ° C.): 8.0 mPa · s) was used as the first liquid, and dehydrated castor oil was used as the second liquid. A liquid developer was produced in the same manner as described above.
(Examples 4 and 5)
A liquid developer was produced in the same manner as in Example 1 except that the binder resin shown in Table 1 was used.

(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, high viscosity liquid paraffin as an insulating liquid (manufactured by Wako Pure Chemical Industries, Ltd., viscosity (20 ° C.): 171 mPa · s): 100 parts by weight, dispersant As polyoxyethylene alkyl ether: 10 parts by weight and magnesium stearate as a charge control agent: 1.0 part by weight.
These components were put into a ball mill and wet-ground for 200 hours. However, the toner particles could not be made sufficiently large.

(Comparative Example 2)
A liquid developer was produced in the same manner as in Comparative Example 1 except that soybean oil (manufactured by Kanto Chemical Co., Inc., viscosity (20 ° C.): 56 mPa · s) was used as the insulating liquid. It could not be made into particles.
(Comparative Example 3)
A coarsely pulverized product was obtained in the same manner as in Example 1.

Next, the obtained coarsely pulverized product: 100 parts by weight, Isopar H as an insulating liquid (viscosity (20 ° C.): 1.95 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 200 hours to obtain a pulverized dispersion.
Thereafter, 100 parts by weight of the obtained pulverized dispersion liquid and 400 parts by weight of Isopar H were mixed to obtain a liquid developer.

(Comparative Example 4)
The same as Comparative Example 3 except that low-viscosity liquid paraffin (Chuo Kasei Co., Ltd., viscosity (20 ° C.): 8 mPa · s) was used as the insulating liquid instead of Isopar H, and wet pulverization was performed for 300 hours or more. Thus, a liquid developer was produced.
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 for dispersion stability, fixing strength, storage stability, and charging characteristics.
[2.1] 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 times with a carrier solvent (Isopar H) 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.
(Double-circle): Absorbance is 1.50 or more (precipitation is not seen at all).
○: Absorbance is 1.00 or more and less than 1.50 (almost no sedimentation is observed).
(Triangle | delta): Absorbance is 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 after being left to stand).

[2.2] Fixing Strength Using an image forming apparatus as shown in FIG. 2, an image of a predetermined pattern with 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 by "X-Rite model 404" manufactured by Rite Inc, and evaluated according to the following four-stage criteria.
A: Image density residual ratio is 90% or more.
○: 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 residual ratio is less than 70%.

[2.3] Storage Stability The liquid developers obtained in the above Examples and Comparative Examples were allowed to stand for 6 months in an environment at a temperature of 15 to 20 ° C. Thereafter, the state of the toner in the liquid developer was visually confirmed and evaluated according to the following four criteria.
A: No aggregation or sedimentation of toner particles is observed.
○: Almost no aggregation or sedimentation of toner particles is observed.
Δ: Slight aggregation and sedimentation of toner particles is observed.
X: Aggregation and sedimentation of toner particles are clearly recognized.

[2.4] Charging Characteristics The charging characteristics were evaluated using a “Laser Zeta Electrometer” ELS-6000 manufactured by Otsuka Electronics Co., Ltd. according to the following four-stage criteria.
A: Potential difference is +50 mV or more.
○: Potential difference is +45 mV or more and less than +50 mV.
Δ: Potential difference is +30 mV or more and less than +45 mV.
X: Potential difference is less than +30 mV.
These results are shown in Table 2 together with the volume-based average particle diameter and particle diameter standard deviation of the toner particles.

As is clear from Table 2, the liquid developer of the present invention was excellent in dispersion stability, fixing strength, storage stability, and charging characteristics. On the other hand, satisfactory results were not obtained with the liquid developers of the comparative examples.
Further, when an image of a predetermined pattern by the liquid developer obtained in each of the above examples was formed on a recording paper (quality paper LPCPPA4 manufactured by Seiko Epson Corporation) using an image forming apparatus as shown in FIG. A clear and uniform image was obtained. In contrast, in the liquid developers obtained in Comparative Example 3 and Comparative Example 4, unevenness was confirmed in the image. This is presumably because the liquid developer was not sufficiently uniformly supplied to the application roller of the image forming apparatus.
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.

It is a longitudinal cross-sectional view which shows typically an example of a structure of the kneading machine used for the manufacturing method of the liquid developer of this invention, and a cooler. 1 is a cross-sectional view illustrating an example of a contact-type image forming 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

K1 ... kneading machine K2 ... process part K21 ... barrel K22, K23 ... screw K24 ... fixing member K25 ... deaeration port K3 ... head part K31 ... internal space K32 ... extrusion port K33 ... cross-sectional area gradually decreasing part K4 ... feeder K5 ... raw material K6 ... Coolers K61, K62, K63, K64 ... Rolls K611, K621, K631, K641 ... Rotating shafts K65, K66 ... Belt K67 ... Discharge part K7 ... Kneaded material P1 ... Image forming device P2 ... Photoconductor P3 ... Chargeer 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 ... development roller cleaning blade P18 ... intermediate transfer roller P19 ... secondary Transfer roller P20 ... information recording medium P21 ... static elimination light P2 DESCRIPTION OF SYMBOLS 2 ... Cleaning blade P23 ... Cleaning blade P24 ... Charging blade F40 ... Fixing device F1 ... Heat fixing roll (heating roll) F1a ... Column-shaped halogen lamp F1b ... Roll base material F1c ... Elastic body F2 ... Pressure roll F2a ... Rotating shaft F2b ... Roll base material F2c ... Elastic body F3 ... Heat-resistant belt F4 ... Belt tension member F4a ... Projection wall F4f ... Recess F5 ... Sheet material F5a ... Unfixed toner image F6 ... Cleaning member F9 ... Spring

Claims (10)

A wet pulverization step of pulverizing the colorant and the resin material in the first liquid to obtain a pulverized dispersion;
A mixing step of mixing the pulverized dispersion obtained in the wet pulverization step with a second liquid having a higher viscosity than the first liquid;
A method for producing a liquid developer, comprising:   The method for producing a liquid developer according to claim 1, wherein the viscosity V1 of the first liquid is 0.5 to 30 mPa · s.   The method for producing a liquid developer according to claim 1, wherein the viscosity V2 of the second liquid is 30 to 1000 mPa · s. The V1 [mPa · s] and the V2 [mPa · s] are:
0.0005 ≦ V1 / V2 ≦ 1
The method for producing a liquid developer according to claim 1, wherein the liquid developer has the following relationship.   The method for producing a liquid developer according to claim 1, wherein the first liquid and the second liquid are nonpolar liquids.   6. The liquid developer according to claim 1, wherein, in the pulverization step, the colorant and the resin material are pulverized in a state where a dispersant is contained in the first liquid. Method.   The liquid developer according to any one of claims 1 to 6, wherein the first liquid and the dispersant are mixed before mixing the first liquid, the colorant, and the resin material. Production method.   The method for producing a liquid developer according to claim 1, wherein the first liquid is mineral oil.   The method for producing a liquid developer according to claim 1, wherein the second liquid is a vegetable oil.   The method for producing a liquid developer according to claim 1, wherein the resin material includes at least one of an epoxy resin and a polyester resin.

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