JP2006251253A - Method for manufacturing liquid developer and liquid developer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid developer which has a small width of a grain size distribution and a uniform shape, and in which the characteristics of each component constituting toner particles are sufficiently exhibited, to provide a method for manufacturing the liquid developer capable of efficiently manufacturing such liquid developer, more particularly to provide the liquid developer which is dispersed with the toner having a uniform shape and small width of the grain size distribution by an environmentally friendly method. <P>SOLUTION: The method for manufacturing the liquid developer is a method for manufacturing the liquid developer dispersed with the toner particles in an insulative liquid, and has a melt dispersion preparation process of using a kneaded mixture containing a colorant and a resin material and preparing a melt dispersion finely dispersed with the kneaded mixture in a molten state in the insulative liquid, and a cooling process of solidifying the kneaded mixture in the molten state by cooling the melt dispersion. The insulative liquid is mainly composed of non-volatile hydrocarbon. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

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

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.
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.

Conventionally, a liquid developer has conventionally been obtained by pulverizing a resin to produce a toner (see, for example, Patent Document 1), and polymerizing a monomer component in the electrically insulating liquid, thereby forming the electrically insulating liquid. It has been produced by a polymerization method for forming insoluble resin fine particles (for example, see Patent Document 2).
However, the conventional method for producing a liquid developer has the following problems.

  That is, in the pulverization method, it is difficult to pulverize the toner particles to a sufficiently small size (for example, 5 μm or less), and the effect of using the liquid developer as described above is sufficiently increased. In order to obtain a size that can be exhibited, a very long grinding energy was required for a very long time, and the productivity of the liquid developer was extremely low. Further, in the pulverization method, the particle size distribution of the toner particles tends to be wide (the variation in particle size is large), and the shape of the toner particles tends to be irregular and non-uniform. As a result, variation in characteristics (for example, charging characteristics) among the toner particles tends to increase.

  Also, in the polymerization method, it is difficult to make the conditions for the polymerization reaction suitable, so that a resin material having a suitable molecular weight can be formed, toner particles having a desired size can be formed, It is difficult to reduce the variation sufficiently. As a result, the stability and reliability of the toner quality tends to be low. Further, in the polymerization method, it takes a relatively long time to form toner particles, and the productivity of the liquid developer is poor.

JP-A-7-234551 Japanese Patent Publication No.8-7470

  It is an object of the present invention to provide a liquid developer having a small particle size distribution width, a uniform shape, and sufficiently exhibiting the characteristics of each component constituting the toner particles. An object of the present invention is to provide a method for producing a liquid developer capable of efficiently producing a developer. In particular, it is an object to provide a liquid developer in which a toner having a uniform shape and a small particle size distribution is dispersed by an environmentally friendly method.

Such an object is achieved by the present invention described below.
The method for producing a liquid developer of the present invention is a method for producing a liquid developer in which toner particles are dispersed in an insulating liquid,
Using a kneaded product containing a colorant and a resin material, a melt dispersion preparing step for preparing a melt dispersion in which the kneaded material in a molten state is finely dispersed in the insulating liquid;
Cooling the melt dispersion and solidifying the kneaded material in a molten state,
The insulating liquid is mainly composed of nonvolatile hydrocarbons.
Accordingly, it is possible to provide a liquid developer having a small particle size distribution width, a uniform shape, and sufficiently exhibiting the characteristics of each component constituting the toner particles. It is possible to provide a liquid developer in which a toner having a uniform shape and a small particle size distribution is dispersed by an environmentally friendly method.

In the method for producing a liquid developer of the present invention, in the liquid developer, the insulating liquid preferably includes a releasability improver that improves releasability at the time of fixing.
Accordingly, it is possible to effectively prevent the occurrence of offset when the toner particles are fixed on the recording medium. That is, the offset resistance is improved.
In the method for producing a liquid developer according to the present invention, it is preferable that the releasing agent is silicone oil.
Since the silicone oil has a high affinity with the material constituting the toner particles, it can be satisfactorily present in the vicinity of the surface of the toner particles when the toner particles are fixed on the recording medium. As a result, the occurrence of an offset can be prevented more effectively. In addition, since the silicone oil is highly compatible with the insulating liquid as described above, the dispersibility of the toner particles can be improved.

In the method for producing a liquid developer of the present invention, in the melt dispersion preparation step, a pulverized product obtained by pulverizing the solid kneaded product is put into the insulating liquid and applied at a predetermined temperature. It is preferable to prepare the melt dispersion by bringing the kneaded material into a molten state in the insulating liquid in a heated state.
Thereby, it is possible to efficiently prepare a melt dispersion in which a kneaded material (melt) in a molten state is uniformly finely dispersed in an insulating liquid. The melt (dispersoid) in the melt dispersion has a relatively uniform particle size. Further, since the heat history in the entire process can be reduced, the influence of heat on the material constituting the toner particles can be made sufficiently small. It is also advantageous in terms of energy.

In the method for producing a liquid developer of the present invention, when the predetermined temperature is Th [° C.], the softening point of the resin material is T _f [° C.], and the boiling point of the insulating liquid is Tb [° C.]
It is preferable that the relationship of T _1/2 ≦ Th ≦ Tb is satisfied.
By satisfying such a relationship, a melt dispersion in which a more uniformly shaped melt (dispersoid) is dispersed can be obtained.

In the method for producing a liquid developer of the present invention, the cooling rate in the cooling step is preferably 100 ° C./second or less.
As a result, it is possible to more efficiently form a liquid developer in which toner particles having a uniform shape and size are dispersed while preventing aggregation or the like of melts (dispersoids) finely dispersed in the melt dispersion. it can.

The liquid developer of the present invention is manufactured by the method of the present invention.
Accordingly, it is possible to provide a liquid developer having a small particle size distribution width, a uniform shape, and sufficiently exhibiting the characteristics of each component constituting the toner particles. In particular, it is possible to provide a liquid developer in which a toner having a uniform shape and a small particle size distribution is dispersed by an environmentally friendly method.

In the liquid developer of the present invention, the average particle size of the toner particles is preferably 0.1 to 5 μm.
As a result, variation in 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, and the liquid developer (toner) is formed. The resolution of the image can be made sufficiently high.
In the liquid developer of the present invention, it is preferable that the standard deviation of the particle diameter between the toner particles is 3.0 μm or less.
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.

In the liquid developer of the present invention, the average value (average circularity) of the circularity R represented by the following formula (I) for the toner particles is preferably 0.85 or more.
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)
Thereby, the transfer efficiency and mechanical strength of the toner particles can be made particularly excellent while the particle diameter of the toner particles is sufficiently small.
In the liquid developer of the present invention, the standard deviation of the average circularity between the particles is preferably 0.15 or less.
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.

Hereinafter, a preferred embodiment of a method for producing a liquid developer and a liquid developer according to the present invention will be described in detail with reference to the accompanying drawings.
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 preparing a melt dispersion. Hereinafter, in FIG. 1, the left side is assumed to be “base end” and the right side is assumed to be “tip”.

  The method for producing a liquid developer of the present invention uses a kneaded product containing a colorant and a resin material to prepare a melt dispersion in which the kneaded material in a molten state is finely dispersed in the insulating liquid. A solid dispersion preparation step, and a cooling step of cooling the melt dispersion and solidifying the kneaded material in a molten state, and the insulating liquid is mainly composed of nonvolatile hydrocarbons. It is characterized by.

<Constituent material of kneaded material>
The kneaded material can be obtained, for example, through a kneading step as described later, and includes components constituting the toner of the liquid developer, and includes at least a binder resin (resin material) and a colorant. .
First, the material used for preparation of a kneaded material is demonstrated.

1. Resin (binder resin)
The toner constituting the liquid developer is made of a material containing a resin (binder resin) 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, polyester resins, epoxy resins, styrene-acrylic acid ester copolymers and acrylics are particularly preferred because of their high dispersibility (affinity) for insulating liquids composed mainly of non-volatile hydrocarbons as described below. It is preferable to use a resin.
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 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 In addition, components other than those described above may be used for preparing the kneaded product. 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.
Moreover, as a constituent material (component) of the kneaded product, for example, a material used as a solvent such as an inorganic solvent or an organic solvent may be used. Thereby, for example, the efficiency of kneading can be improved, and a kneaded product in which the components are more uniformly mixed can be easily obtained.

<Kneaded material>
Next, an example of a method for obtaining the kneaded material K7 by kneading the raw material K5 containing the above components will be described.
The kneaded material K7 can be manufactured using, for example, an apparatus as shown in FIG.
[Kneading process]
The raw material K5 used for kneading contains the components as described above. In particular, since the raw material K5 contains a colorant, air contained in the raw material K5 in this step (especially, air entrapped by the colorant) can be efficiently removed, and bubbles are mixed inside the toner particles ( Remaining) can be effectively prevented. 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.

[Crushing process]
Next, the kneaded material K7 that has undergone the cooling process as described above is pulverized. Thus, by pulverizing the kneaded material K7, in the melt dispersion preparation step, the melt dispersion can be obtained as a dispersion of a finer dispersoid (melt) relatively easily. . As a result, the liquid developer finally obtained can also have a smaller toner particle size and can be suitably used for high-resolution image formation.

The pulverization method 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 pulverization process may be performed in multiple steps (for example, two stages of a coarse pulverization process and a fine pulverization process). In addition, after such a pulverization step, a classification process or the like may be performed as necessary. For the classification treatment, for example, a sieve, an airflow classifier or the like can be used.

By kneading the raw material K5 as described above, the air contained in the raw material K5 can be effectively removed. In other words, the kneaded material K7 obtained by kneading as described above contains almost no air (bubbles) inside. Thereby, it is possible to effectively prevent generation of irregularly shaped particles (hollow particles, missing particles, fused particles, etc.) in the obtained toner particles. As a result, in the finally obtained liquid developer, it is possible to effectively prevent problems such as a decrease in transferability and cleaning property due to irregularly shaped toner particles.
In the present invention, a melt dispersion is prepared using the kneaded material as described above.

  By using the kneaded material K7 for the preparation of the melt dispersion, the following effects can be obtained. That is, even when the toner constituent materials contain components that are difficult to disperse or compatible with each other, each component is sufficiently compatible and finely dispersed in the resulting kneaded product by kneading. State. In particular, pigments (colorants) usually have relatively low dispersibility in an insulating liquid as will be described later, but are kneaded in advance before being dispersed in the insulating liquid, so that the surroundings of the pigment particles are resinous. This effectively coats the components, etc., which improves the dispersibility of the pigment in the insulating liquid (particularly enables fine dispersion in the insulating liquid), and also provides the final color development of the toner. It becomes good. For this reason, even if the constituent material of the toner contains a component that is inferior in dispersibility in the insulating liquid described later (hereinafter also referred to as “hardly dispersible component”) or the like, the melt dispersion The dispersibility of the dispersoid (melt) in the liquid can be made particularly excellent. As a result, even in the finally obtained liquid developer, variations in composition and characteristics among the toner particles are reduced, and the overall characteristics are particularly excellent.

  On the other hand, when the raw material which has not been kneaded is used for the preparation of the melt dispersion, the hardly dispersible component and the like are likely to settle in the melt dispersion. In addition, since a hardly dispersible component generally tends to cause aggregation or the like, the tendency to settle out remarkably appears. And aggregation progresses further by settling. As a result, the toner particles obtained in the melt dispersion cooling step, which will be described in detail later, have a large composition variation among the particles. In addition, due to agglomeration, the variation in size and shape among the particles increases, and the characteristics of the entire toner (the entire liquid developer) deteriorate.

  In addition, in a melt dispersion as used in the present invention, the dispersoid (melt) is liquid (has fluidity and can be deformed relatively easily), so that the dispersoid depends on its surface tension. , Tend to be a shape with a large circularity (sphericity). Therefore, the liquid developer prepared using the melt dispersion is a dispersion of toner particles having a relatively high circularity (sphericity). In addition, in the case of a melt dispersion in which the dispersoid (melt) is liquid (has fluidity and can be deformed relatively easily), it can be dispersed relatively easily by stirring the melt dispersion. The uniformity of the quality size can be made sufficiently high.

<Preparation of melt dispersion>
Next, by using the kneaded material as described above, a melt dispersion in which the dispersoid (melt) composed of the toner material is dispersed in the insulating liquid is prepared (melt dispersion preparation step).
The method for preparing the melt dispersion is not particularly limited, but in this embodiment, the pulverized product of the kneaded material as described above is put into the insulating liquid heated to a predetermined temperature, and the insulating liquid is filled. A melt dispersion is prepared by bringing the pulverized product (kneaded product) into a molten state.

The insulating liquid (carrier liquid) used in the present invention is mainly composed of nonvolatile hydrocarbons.
In addition, “nonvolatile” in the present specification means that the vapor pressure at 20 ° C. is 0.3 kPa or less. More preferably, it refers to 0.2 kPa or less.
In this way, in the insulating liquid mainly composed of nonvolatile hydrocarbons, the toner material (kneaded material) is once melted (ie, subjected to a melting treatment), whereby the insulating liquid and the toner material are mixed. Affinity can be improved. As a result, the dispersion state of the toner particles can be improved over a long period of time. That is, the storage stability of the liquid developer can be increased.

However, such a melting process has not been performed in the conventional method for producing a liquid developer.
Moreover, the fact that the affinity is improved by the melting treatment is peculiar to the nonvolatile hydrocarbon, and such an effect cannot be obtained with the conventionally used insulating liquid.
Furthermore, in the insulating liquid that has been used in the past, the insulating liquid volatilizes during heating such as a melting process, which may cause problems such as a change in the liquid composition of the liquid developer and an influence on the environment. However, by using a non-volatile hydrocarbon as a component constituting the insulating liquid in this way, the change in the liquid composition of the liquid developer and the influence on the environment can be reduced even during heating such as melting processing. Can do. As a result, a liquid developer can be obtained by an environmentally friendly method.

In addition, by using non-volatile hydrocarbons, the impact of the insulating liquid on the environment (especially the impact on the office environment) can be achieved even when the liquid developer finally obtained is used or stored. Can be reduced. Therefore, an environmentally friendly liquid developer can be provided.
Further, when the insulating liquid is composed of a non-volatile hydrocarbon, the toner particles are sufficiently supplied to the application roller in the image forming apparatus as described later, and the wettability with respect to the material constituting the application roller. Insulating liquid itself can be made difficult to adhere.

As the nonvolatile hydrocarbon, an aliphatic saturated hydrocarbon, an alicyclic hydrocarbon, an aromatic hydrocarbon, or a halogenated hydrocarbon can be used. In particular, by using the aliphatic saturated hydrocarbon having a paraffinic or branched straight-chain, such as liquid paraffin (C ₈ or more isoparaffin), functions as an insulation liquid (carrier liquid) (viscosity and insulation, etc. ) And the effects of the present invention can be made more remarkable.

Moreover, it is preferable to use a C6-C20 thing as a non-volatile hydrocarbon, and it is more preferable to use a C8-C18 thing. Thereby, the effect of this invention becomes more remarkable.
Specific examples of the non-volatile hydrocarbon include liquid paraffin, isoper G, H, L, K, IP solvent 1620, 2028, isododecane, ligroin, and the like. Can be used in combination.

The insulating liquid may be any mainly composed of non-volatile hydrocarbons, but it is preferable that the non-volatile hydrocarbon content in the insulating liquid is 55 wt% or more. 60 wt% or more is more preferable, and 65 wt% or more is more preferable.
The electrical resistance of the insulating liquid as described above at room temperature (20 ° C.) is preferably 10 ⁹ Ωcm or more, more preferably 10 ¹¹ Ωcm or more, and even more preferably 10 ¹³ Ωcm or more. .
The dielectric constant of the insulating liquid is preferably 3.5 or less.

The heating temperature of the insulating liquid is not particularly limited as long as the charged pulverized material melts, but the heating temperature of the insulating liquid is Th [° C.], and the softening point of the resin material contained in the pulverized material is T _f. [° C.] When the boiling point of the insulating liquid is Tb [° C.], it is preferable to satisfy the relationship of T _f ≦ Th ≦ Tb, and more preferably to satisfy the relationship of T _f + 5 ≦ Th ≦ Tb−5. preferable. By satisfying such a relationship, a melt dispersion liquid in which a dispersoid (melt) having a more uniform shape and size is dispersed can be obtained.
The insulating liquid may contain a releasability improver that improves releasability during fixing. Thereby, it is possible to effectively prevent the occurrence of offset when the toner particles are fixed on the recording medium. That is, the offset resistance is improved.

By the way, it is conceivable to improve the releasability (offset resistance) by including wax in the toner particles without including a releasability improver in the insulating liquid. In order to obtain a sufficient improvement effect, if the wax content is increased, depending on the type of resin material etc. constituting the toner particles, the wax is liberated when the kneaded product is melted and dispersed in the insulating liquid. In some cases, the toner particles become coarse and it becomes difficult to form toner particles having a sufficiently uniform size and shape. On the other hand, if the wax content is reduced, sufficient releasability may not be obtained. However, by including a releasability improver in the insulating liquid as in this embodiment, the resulting liquid developer has excellent offset resistance while making the size and shape of the toner particles sufficiently uniform. It will have a sex.
Examples of such releasability improvers include silicone oils, modified silicone oils, vegetable oils, modified vegetable oils, etc., and one or more of these can be used in combination.

  Among the above, silicone oil has a high affinity with the material constituting the toner particles, and therefore can be well present near the surface of the toner particles when the toner particles are fixed on the recording medium. As a result, the occurrence of an offset can be prevented more effectively. In addition, since the silicone oil is highly compatible with the insulating liquid as described above, the dispersibility of the toner particles can be improved.

The content of the releasability improver in the insulating liquid is preferably 1 to 20 wt%, and more preferably 2 to 16 wt%. Thereby, the offset resistance can be improved efficiently while sufficiently maintaining the function as the insulating liquid.
Such a releasability improver may be contained in the insulating liquid in advance, or may be added after the cooling step described later.

  In preparing the melt dispersion, for example, a surfactant or the like may be used for the purpose of improving the dispersibility of the dispersoid (melt). Examples of the surfactant include inorganic mineral dispersants such as viscosity minerals, silica and tricalcium phosphate, nonionic organic dispersants such as polyvinyl alcohol, carboxymethyl cellulose, and polyethylene glycol, and tristearic acid metal salts (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 salts, lead) Salts, zinc salts, etc.), octanoic acid metal salts (eg, aluminum salts, calcium salts, cobalt salts, etc.), oleic acid metal salts (eg, calcium salts, cobalt salts, etc.), palmitic acid metal salts (eg, zinc salts, etc.) ), Metal salt of dodecylbenzenesulfonic acid (for example, sodium salt), metal salt of naphthenic acid ( For example, calcium salt, cobalt salt, 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) Salt), polymethacrylic acid metal salt (for example, sodium salt), polymaleic acid metal salt (for example, sodium salt), acrylic acid-maleic acid copolymer metal salt (for example, sodium salt), polystyrene sulfonic acid Anionic organic dispersants such as metal salts (for example, sodium salts) and the like, and cationic organic dispersants such as quaternary ammonium salts and the like. By using a dispersant as described above for the preparation of the melt dispersion, the dispersibility of the dispersoid is improved and the dispersion of the shape and size of the dispersoid in the melt dispersion is relatively easy. In particular, it can be made small, and the shape of the dispersoid can be made 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.

Although the content rate of the dispersoid (melt) in a melt dispersion liquid is not specifically limited, It is preferable that it is 1-30 wt%, and it is more preferable that it is 5-20 wt%.
The average particle size of the dispersoid in the melt dispersion is not particularly limited, but is preferably 0.01 to 5 μm, and more preferably 0.1 to 3 μm. As a result, it is possible to more reliably prevent the dispersoids from being bonded (aggregated) in the melt dispersion, and to optimize the size of the finally obtained toner particles. In the present specification, “average particle diameter” refers to an average particle diameter based on volume.

The melt dispersion may contain components other than those described above. Examples of such components include a charge control agent and magnetic powder.
Examples of the charge control agent include a metal salt of benzoic acid, a metal salt of salicylic acid, a metal salt of alkyl salicylic acid, a metal salt of catechol, a metal-containing bisazo dye, a nigrosine dye, a tetraphenylborate derivative, a quaternary ammonium salt, Examples thereof include alkyl pyridinium salts, chlorinated polyesters, and nitrohumic 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 such as Fe, Co, and Ni. The thing comprised with the magnetic material containing a magnetic metal etc. are mentioned.
In addition to the above materials, for example, zinc stearate, zinc oxide, cerium oxide or the like may be added to the melt dispersion.

<Cooling of melt dispersion>
Next, the melt dispersion obtained as described above is cooled to obtain a liquid developer (liquid developer of the present invention) (cooling step).
By cooling in this way, the molten dispersoid (melt) in the melt dispersion is solidified and becomes toner particles.

The cooling rate in the cooling step is preferably 100 ° C./second or less, and more preferably 0.1 to 50 ° C./second. This makes it possible to more efficiently form a liquid developer in which toner particles having a uniform shape and size are dispersed, while preventing aggregation of dispersoids in the melt dispersion.
In addition, after cooling, you may add an insulating liquid further as needed. That is, using only the insulating liquid necessary to disperse the kneaded material in the molten state, a melt dispersion is prepared, cooled, and then the insulating liquid is added to obtain a liquid developer. May be. By using such a method, the deterioration of the liquid developer due to heating or the like can be reduced, and as a result, the storage stability of the liquid developer can be further improved.

<Liquid developer>
The liquid developer obtained as described above has small variations in the shape and size of the toner particles. Therefore, such a liquid developer easily migrates in the insulating liquid (in the liquid developer) and is advantageous for high-speed development. In addition, since the toner particles have a small variation in shape and size, and because an insulating liquid containing a non-volatile hydrocarbon is used, the toner particles are excellent in dispersibility, and the toner particles in the liquid developer Sedimentation, floating, etc. are effectively prevented. Therefore, such a liquid developer is excellent in long-term stability.

  The average particle size of the toner particles in the liquid developer obtained as described above is preferably 0.1 to 5 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.
Further, 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 0.85 or more, and 0.90 to 0.00. 99 is more preferable, and 0.95-0.99 is even more preferable.

R = L ₀ / L ₁ (I)
(Where L ₁ [μm] is the circumference of the projected image of the toner particles to be measured, and L ₀ [μm] is 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)
Thereby, the transfer efficiency and mechanical strength of the toner particles can be made particularly excellent while the particle diameter of the toner particles is sufficiently small.

The standard deviation of the average circularity between the toner particles constituting the liquid developer is preferably 0.15 or less, more preferably 0.001 to 0.10, and 0.001 to 0. More preferably, .05. 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.
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.

  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, the liquid developer of the present invention is not limited to that applied to the image forming apparatus as described above.
Further, in the above-described embodiment, the case where the pulverized material is charged into the heated insulating liquid has been described. However, the present invention is not limited to this. For example, the pulverized material is charged into the insulating liquid and then heated. Also good.

In the above-described embodiment, the melt dispersion is prepared using the pulverized product of the kneaded product, but the pulverizing step of the kneaded product may be omitted.
In the above-described embodiment, the kneaded product is described as being melted by heating in an insulating liquid to obtain a melt dispersion. However, the present invention is not limited to this. For example, the kneaded product in a molten state is used. You may obtain a melt dispersion by throwing in an insulating liquid.

[1] Production of liquid developer (Example 1)
[Kneaded product]
First, an epoxy resin as a binder resin (softening temperature: 128 ° C.): 80 parts by weight and a cyan pigment as a colorant (Pigment Blue 15: 3 manufactured by Dainichi Seika Co., Ltd.): 20 parts by weight 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 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.

[Preparation of melt dispersion]
Non-volatile hydrocarbon (Isopar H: manufactured by Exxson, vapor pressure 0.104 kPa (at 20 ° C.): 360 parts by weight, polydimethylsiloxane as a mold release improver (manufactured by Toray Dow Corning Silicone Co., Ltd .: trade name “ SH200FLUID100CS "): 18 parts by weight of an insulating liquid was prepared. The boiling point of the insulating liquid was 176 ° C., and the electric resistance of the insulating liquid at room temperature (20 ° C.) was 1.5 × 10 ^15. The dielectric constant of Ωcm and the insulating liquid was 2.0.

To the insulating liquid, 1 part by weight of dodecyltrimethylammonium chloride as a surfactant and 1 part by weight of zirconium octylate as a charge control agent were added and mixed to obtain a mixed solution.
Next, this mixed liquid is heated to 130 ° C., 100 parts by weight of a coarsely pulverized kneaded product is added, and the mixture is stirred for 0.5 hour using a homomixer (made by Tokushu Kika Kogyo Co., Ltd.). A melt dispersion was obtained. The average particle size of the dispersoid in the melt dispersion was 1.42 μm.
Next, the melt dispersion was continuously cooled to room temperature while stirring to obtain a liquid developer. The cooling rate was 1.0 ° C./second.

(Examples 2 and 3)
A liquid developer was produced in the same manner as in Example 1 except that the binder resin shown in Table 1 was used, and the heating temperature of the mixed solution and the cooling rate of the melt dispersion were as shown in Table 1. .
(Examples 4 and 5)
The liquid developer was prepared in the same manner as in Example 1 except that the heating temperature of the mixed liquid and the cooling rate of the melt dispersion were as shown in Table 1 and the non-volatile hydrocarbons shown in Table 1 were used. Manufactured.

(Comparative Example 1)
A liquid developer was produced in the same manner as in Example 1 except that limonene (manufactured by Wako Pure Chemical Industries) having a vapor pressure of 0.4 kPa at 14.4 ° C. was used as the insulating liquid.
(Comparative Example 2)
A liquid developer was produced in the same manner as in Example 1 except that a silicone oil having a vapor pressure of 0.01 kPa at 20 ° C. (Toshiba Silicone: TSF451-100) was used as the insulating liquid.

(Comparative Example 3)
Not a kneaded product but a mixture of epoxy resin (softening temperature: 128 ° C.): 80 parts by weight and cyan pigment (manufactured by Dainichi Seika Co., Ltd., Pigment Blue 15: 3): 20 parts by weight for preparing the melt dispersion A liquid developer was produced in the same manner as in Example 1 except that a highly insulating liquid containing no polydimethylsiloxane was used.

(Comparative Example 4)
First, a coarsely pulverized kneaded product (average particle size: 1.0 mm or less) was obtained in the same manner as in Example 1.
100 parts by weight of the coarsely pulverized product, 360 parts by weight of an insulating liquid composed of the same non-volatile hydrocarbon as in Example 1, 1 part by weight of a surfactant (dodecyltrimethylammonium chloride), and octylic acid Zirconium was added to a mixture of 1 part by weight and dispersed (ground) for 5 days using a ball mill at room temperature to obtain a dispersion.
To the obtained dispersion, 180 parts by weight of the insulating liquid was added, and further mixed and dispersed at room temperature using a ball mill for 5 hours to obtain a liquid developer.

(Comparative Example 5)
A mixed solution of octadecyl methacrylate: 100 g, toluene: 150 g and isopropanol: 50 g was heated to a temperature of 75 ° C. with stirring under a nitrogen stream. 2,2′-Azobis (4-cyanovaleric acid): 30 g was added and reacted for 8 hours. After cooling, it was reprecipitated in 2 liters of methanol, and the white powder was agglomerated and dried. A mixture of the obtained white powder: 50 g, vinyl acetate: 3.3 g, hydroquinone: 0.2 g and toluene: 100 g was heated to a temperature of 40 ° C. and reacted for 2 hours. Next, the temperature was raised to 70 ° C., 100% sulfuric acid: 3.8 × 10 ⁻³ ml was added and reacted for 10 hours. After cooling to 25 ° C. and adding 0.02 g of sodium acetate trihydrate and stirring for 30 minutes, methanol was reprecipitated in 1 liter, agglomerated and dried to obtain a dispersion stabilizing resin.

Next, the obtained dispersion stabilizing resin: 12 g, vinyl acetate: 100 g, octadecyl methacrylate: 1.0 g and Isopar H: 384 g were heated to a temperature of 70 ° C. while stirring under a nitrogen stream. 2,2′-azobis (isovaleronitrile): 0.8 g was added and reacted for 6 hours. 20 minutes after the addition of the initiator, white turbidity occurred, and the reaction temperature rose to 88 ° C. The temperature was raised to 100 ° C. and stirred for 2 hours to distill off unreacted vinyl acetate. After cooling, white latex particles were obtained through a 200-mesh nylon cloth. The average particle size was 0.82 μm.
Further, 10 g of dodecyl methacrylate / acrylic acid copolymer, 10 g of nigrosine and 30 g of isopar G were placed in a paint shaker (manufactured by Tokyo Seiki Co., Ltd.) together with glass beads, and dispersed for 4 hours to obtain a fine dispersion of nigrosine.

A liquid developer was obtained by diluting 30 g of the above white latex particles, 2.5 g of the above nigrosine dispersion: 2.5 g, and octadecene / half-maleic acid octadecylamide copolymer: 0.07 g to 1 l of Isopar G.
The vapor pressure at 20 ° C. of the non-volatile hydrocarbon used in each example was 3.0 MPa or less.
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 image density, resolution, storage stability and offset resistance.
[2.1] Image Density Using the image forming apparatus as shown in FIG. 2 and the fixing device as shown in FIG. 4, an image of a predetermined pattern by the liquid developer obtained in each of the above examples and each of the comparative examples. Was formed on recording paper, and the image density on the recording paper was measured with a color difference meter manufactured by X-Rite.
[2.2] Resolving power Using the image forming apparatus as shown in FIG. 2 and the fixing device as shown in FIG. 4, an image of a predetermined pattern by the liquid developer obtained in each of the examples and the comparative examples was obtained. It was formed on a recording paper and the resolving power was examined visually.

[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 four criteria.
A: No floating or coagulation sedimentation of toner particles is observed.
○: Floating and coagulation sedimentation of toner particles are hardly observed.
Δ: Slight floating or coagulation sedimentation of toner particles is observed.
X: Floating toner particles and coagulation sedimentation are clearly recognized.

[2.4] Offset Resistance Using an image forming apparatus as shown in FIG. 4, an image of a predetermined pattern by the liquid developer obtained in each of the above examples and each of the comparative examples was recorded on a recording paper (manufactured by Seiko Epson Corporation). And 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 X -Measured by "X-Rite model 404" manufactured by Rite Inc, and evaluated according to the following four-stage criteria.
○: Image density residual ratio is 90% or more.
Δ: Image density remaining ratio is 70% or more and less than 90%.
X: Image density residual ratio is less than 70%.
These results are shown in Table 2 together with the average circularity R, circularity standard deviation, volume-based average particle diameter, and particle diameter standard deviation of the toner particles. The circularity was measured using a flow type particle image analyzer (FPIA-2000, manufactured by Toa Medical Electronics Co., Ltd.). However, the circularity R is represented by the following formula (I).
R = L ₀ / L ₁ (I)
(Wherein, L ₁ [μm] is the circumference of the projected image of the particle 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 particle to be measured. To express.)

As is clear from Table 2, in all of the liquid developers according to the present invention, the circularity of the toner particles is large and the width of the particle size distribution is small. Further, the variation in the shape of the toner particles (standard deviation of circularity) was small.
On the other hand, in the liquid developer of the comparative example, the variation in the shape and size of the toner particles was large. Further, in the liquid developer of the comparative example, the toner particles have an indefinite shape and the circularity is low.

Further, as apparent from Table 2, the liquid developer of the present invention was excellent in image density, resolution, storage stability and offset resistance. On the other hand, satisfactory results were not obtained with the liquid developers of the comparative examples.
In addition, the liquid developer of the present invention uses an image forming device as shown in FIG. 2 and a fixing device as shown in FIG. No off-flavor occurred. On the other hand, the liquid developer of Comparative Example 1 produced a strange odor.
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 for manufacturing the kneaded material used for preparation of a melt dispersion, 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 product 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 (11)

A method for producing a liquid developer in which toner particles are dispersed in an insulating liquid,
Using a kneaded product containing a colorant and a resin material, a melt dispersion preparing step for preparing a melt dispersion in which the kneaded material in a molten state is finely dispersed in the insulating liquid;
Cooling the melt dispersion and solidifying the kneaded material in a molten state,
The method for producing a liquid developer, wherein the insulating liquid is mainly composed of nonvolatile hydrocarbons.   The method for producing a liquid developer according to claim 1, wherein in the liquid developer, the insulating liquid includes a releasability improver that improves releasability during fixing.   The method for producing a liquid developer according to claim 2, wherein the releasability improver is silicone oil.   In the melt dispersion preparation step, a pulverized product obtained by pulverizing the solid kneaded product is put into the insulating liquid and heated at a predetermined temperature in the insulating liquid. 4. The method for producing a liquid developer according to claim 1, wherein the melt dispersion is prepared by bringing the kneaded material into a molten state. When the predetermined temperature is Th [° C.], the softening point of the resin material is T _f [° C.], and the boiling point of the insulating liquid is Tb [° C.]
The method for producing a liquid developer according to claim 4, wherein the relationship of T _1/2 ≦ Th ≦ Tb is satisfied.   The method for producing a liquid developer according to claim 1, wherein a cooling rate in the cooling step is 100 ° C./second or less.   A liquid developer produced by the method according to claim 1.   The liquid developer according to claim 7, wherein the toner particles have an average particle size of 0.1 to 5 μm.   The liquid developer according to claim 7 or 8, wherein the standard deviation of the particle diameter between the toner particles is 3.0 µm or less. 10. The liquid developer according to claim 7, wherein the toner particles have an average value (average circularity) of circularity R represented by the following formula (I) of 0.85 or more.
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) The liquid developer according to claim 7, wherein the standard deviation of the average circularity between the particles is 0.15 or less.

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