JP2003005453A - Method of manufacturing liquid developer and liquid developer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a liquid developer which is free of fogging of images, image density unevenness, the defect on the images occurring in fine impurities, etc., and is capable of realizing high image quality and the liquid developer. SOLUTION: A predispersion (a dispersion of flocculated particles of pigments) obtained by feeding the pigments into a solvent containing a dispersion assistant and predispersing (coarsely dispersing) the pigments by a propeller stirring machine, etc., is supplied to a 'Crea Mix (R)' which is the stirring apparatus 12 and is subjected to dispersion treatment (fine dispersion treatment). The stirring apparatus has the structure to give rise to the effects of shearing force, collision force, pressure fluctuation, cavitation and potential core by a rotor (stirring vanes) 2 for rotating the liquid to be treated at a high velocity and a screen (a stationary ring) 1 fixed to this rotor to enclose the same and the liquid to be treated is subjected to emulsification and dispersion by the synergistic effects of these actions. As a result, the dispersion of the pigment particulates having an adequate volumetric grain size and sharp grain size distribution is obtained.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an electrostatic charge image (hereinafter,
The present invention relates to a liquid developer used for developing an electrostatic latent image) and a method for producing the liquid developer.

[0002]

2. Description of the Related Art Conventionally, as a liquid developer used for developing an electrostatic latent image formed on a photoconductor as a latent image carrier, a liquid developer having toner dispersed in an insulating liquid is known. Are known. Development of an electrostatic latent image using this liquid developer involves forming a thin layer of the liquid developer on the developer carrier of the developing device provided at a position facing the electrostatic latent image on the latent image carrier. The toner image is formed by electrostatically moving the toner toward the electrostatic latent image.

Here, the toner constituting the liquid developer is composed of a plurality of coloring agents and a binder resin, and the coloring agent is obtained by coating the surface of fine pigment particles with a resin (hereinafter referred to as a coating resin). Has become.

It is known that the flushing method is effective for improving the gradation and resolution of an image developed using this liquid developer and improving the image quality such as preventing unevenness in image density. (For example, JP-A-3-225354.
No.).

[0005]

However, in recent years, further improvement of image quality such as further improvement of image gradation and resolution and improvement of image density unevenness prevention has been demanded. In order to satisfy such requirements, it is desirable that the pigment fine particles are dispersed into so-called primary particles, which is the smallest order that can stably exist, and the surface is surely coated with the coating resin. .

In the conventional method for producing a liquid developer, there are cases where free pigment fine particles not covered with the coating resin are present in the liquid developer. In this case,
The pigment fine particles that are not controlled in charge lower the resistance of the liquid developer, and as a result, reduce the amount of charge on the surface of the latent image carrier, or the effect of imparting charge to the toner decreases and electrostatic movement of the toner occurs. This may cause problems and cause problems such as fogging in the formed image.

Further, in the conventional method for producing a liquid developer, when the dispersion of the pigment fine particles is not uniform, the content ratio of the colorant among the particles of the toner is different, which causes uneven image density. Sometimes.

As a result of repeated studies by the present inventors, it was found that the dispersion state (particle size distribution) in the solvent of the pigment fine particles used for association with the coating resin during flushing is important. Based on such knowledge, further studies were carried out on the method of dispersing pigment fine particles.

Here, as a disperser used to disperse the pigment fine particles in the solvent, an ultrasonic disperser, a pressure disperser such as a manton-goulin or a pressure homogenizer, a sand grinder, a Getzman mill, a diamond fine mill. Media type dispersers such as

However, in the dispersion treatment by the ultrasonic disperser, the state of application of the ultrasonic waves varies, so that the particle size distribution of the pigment fine particles becomes considerably wide.
Also, the dispersion treatment by the above-mentioned pressure type disperser causes variation in the particle size distribution, and it is not possible to obtain a dispersion liquid of pigment fine particles having a sharp particle size distribution. According to these, the dispersion state of the pigment fine particles becomes non-uniform, and the content ratio of the pigment fine particles among the colorants varies, which may cause image density unevenness.

Further, in the dispersion treatment by the above-mentioned medium type disperser, crushed pieces (fine impurities) generated by abrasion of the medium may remain in the dispersion liquid of fine pigment particles. When the toner obtained by using such a dispersion liquid is subjected to image formation, problems such as damage to the photoreceptor and the like due to the crushed pieces may occur, and image defects may occur.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a high-quality image without image fogging, image density unevenness, image defects caused by fine impurities, and the like. It is an object of the present invention to provide a liquid developer manufacturing method and a liquid developer capable of realizing quality.

[0013]

In order to achieve the above object, the method for producing a liquid developer according to claim 1 comprises a toner contained in an insulating liquid, and the toner has a concentration of 5% or more.
A liquid developer having a high concentration of 0% or less, in which the toner comprises a colorant comprising pigment fine particles and a coating resin coating the pigment fine particles and a binder resin for binding the colorant. In the method for producing the pigment fine particles, by stirring the pigment fine particles in a solvent containing a dispersion aid with a stirrer equipped with a screen for partitioning and forming a stirring chamber and a rotor rotating at high speed in the stirring chamber. The present invention is characterized by using fine pigment particles present as dispersed particles having a volume average particle diameter of 10 nm or more and 500 nm or less in the solvent.

The method for producing a liquid developer according to a second aspect is the method for producing a liquid developer according to the first aspect, in which the shearing force, the collision force, and the pressure fluctuation exerted by the screen and the rotor in the stirring device are exerted. , The cavitation and the action of the potential core stir the fine pigment particles in a solvent containing the dispersion aid.

In the method for producing a liquid developer according to claims 1 and 2, the agglomerated particles of the pigment are crushed by the action of the shearing force generated by the screen and the rotor, and the pigment fine particles have a volume average particle diameter of 10 nm to 500 nm. The following dispersed particles are present in the solvent. As a result, a dispersion liquid of pigment fine particles having a uniform particle size and a sharp distribution with a standard deviation (σ) of 30 or less is obtained. If such pigment fine particles are enclosed in the resin by, for example, flushing, the pigment fine particles can be surely introduced into the particles of the toner to be formed, and the generation of liberated pigment can be eliminated. Further, there is no variation in the content ratio of the colorant among the toner particles.

A method for producing a liquid developer according to a third aspect is the method for producing a liquid developer according to the first or second aspect, wherein the insulating liquid has a viscosity of 0.5 Pa · S or more and 1000 Pa or more.
・ S or less, electric resistance of 10 ¹² Ωm or more, surface tension of 3
It is characterized in that it has a dyn / cm of 0 dyn / cm or less and a boiling point of 100 ° C. or more.

In the method for producing a liquid developer according to claim 3, the lower limit of the viscosity of the insulating liquid is set to 0.5 Pa · S to prevent the occurrence of fixing offset, and the upper limit is set to 1000 Pa · S to set the insulating property during image transfer. A liquid developer capable of suppressing the amount of liquid absorbed by a transfer paper or the like to a small amount and avoiding adhesion of an insulating liquid to the transfer paper or the like. Furthermore, the lower limit of the electric resistance is set to 10 ¹² Ωm, and a liquid developer capable of obtaining stable chargeability by avoiding the problems of the deterioration of the insulating property and the conductivity of the toner which occur when the electric resistance is smaller than the lower limit. To manufacture. Furthermore, the upper limit of the surface tension is 30 dyn / c
A liquid developer capable of preventing the wettability that occurs when the surface tension is larger than m and preventing the occurrence of problems in image quality is manufactured. Further, the lower limit of the boiling point is 100
C. and a temperature equal to or higher than the boiling point of water.
As a result, the liquid developer can be maintained in a non-volatile state in the normal operation range, and various problems caused by the liquid developer starting to evaporate even at a temperature lower than the temperature at which water evaporates do not occur.

The method for producing a liquid developer according to a fourth aspect is characterized in that, in the method for producing a liquid developer according to the third aspect, silicon oil is used as the insulating liquid.

In the method for producing a liquid developer according to a fourth aspect, silicon oil having a resistance value larger than that of Isopar G (trademark: manufactured by EXXON) which has been generally used as an insulating liquid is used. Thereby, claim 3
The insulating liquid can be easily manufactured. Further, Isopar has good dispersibility of toner, and when the conventional toner concentration is as low as 1 to 2%, the toners repel each other to enable uniform toner dispersion, and the chargeability is also good. However, if Isopar is used in the liquid developer containing the toner to be produced in the present invention in a high concentration, the distance between the particles of the toner is reduced, and the charging property is deteriorated, which is not preferable. In the present invention, a liquid developer using silicon oil having a resistance value larger than that of Isopar as an insulating liquid while maintaining a stable toner dispersion state by densely packing the toner by containing the toner at a high concentration It is possible to maintain the chargeability of. In addition, since silicone oil is non-volatile and does not stick even when used in moving parts, it does not stick to the moving parts of means for applying pollution to the liquid developer or applying stress to the liquid developer. It can be prevented.
Therefore, it is highly useful for improving the working environment in manufacturing and using the liquid developing device, and the structure of the means for applying a stress load can be simplified, and the frequency of maintenance can be reduced.

The method for producing a liquid developer according to claim 5 is the method for producing a liquid developer according to any one of claims 1, 2, 3 or 4, wherein the toner has a volume average particle diameter of 0.1 μm or more and 5 or more.
It is characterized in that a film having a thickness of less than μm is used.

In the method for producing a liquid developer according to a fifth aspect of the present invention, the volume average particle diameter of the toner is set to 0.1 μm or more, and when the volume average particle diameter is less than 0.1 μm, the physical adhesive force becomes too large and the toner is transferred during transfer. Avoid making it difficult to peel off. Further, the volume average particle diameter of the toner is set to 5 μm or less to prevent the deterioration of resolution which occurs when the particle diameter is larger than that. Normally, the toner is 5 to 10 on the printed transfer paper.
It is known that the particles exist in the form of lumps, and the resolution is improved substantially in inverse proportion to the volume average particle diameter per toner. Then, the volume average particle size becomes large and becomes 5μ.
If it exceeds m, the resolution becomes poor. In the present invention, the volume average particle diameter is set to 5 μm or less to prevent deterioration of resolution. Then, by containing such a toner in the liquid developer in the range of 5% or more and 40% or less,
It constitutes a high-concentration liquid developer.

According to a sixth aspect of the liquid developer of the present invention, the insulating liquid contains a high concentration of toner, and the toner comprises a coloring agent composed of pigment fine particles and a coating resin for coating the pigment fine particles, and the coloring agent. A liquid developer comprising a binder resin that binds the agent, wherein the liquid developer is produced by the method for producing a liquid developer according to claim 1, 2, 3, 4, or 5. To do.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In recent years, there has been a demand for further improvement of image quality such as further improvement of image gradation and resolution and improvement of image density unevenness prevention performance. Then, the present inventor has invented a liquid developer effective for improving image quality and a manufacturing method thereof. Hereinafter, a method for producing a liquid developer according to the present invention and an embodiment to which the liquid developer can be applied will be described.

First, a method of manufacturing the liquid developer will be described. This liquid developer is obtained by dispersing toner in an insulating liquid at a high concentration. The toner is composed of a plurality of colorants and a binder resin, and the colorant is one in which the surface of dispersed pigment fine particles is coated with a coating resin.

As the insulating liquid, a petroleum hydrocarbon (such as cyclohexane, n-hexane, n-heptane, n-octane, n-nonane, isooctane, isododecane, ligroin and a mixture thereof as an aliphatic hydrocarbon solution ( As commercially available products, there are Isopar E, G, H, L, K and V manufactured by Exxon Chemical Co., Shelsol 71 manufactured by Shell Petroleum Co., and Solubbeso 150). Silicon-based solvents include KF96 (Shin-Etsu Silicon), SH200,
SH344 (Toray Silicon), TSF451 (Toshiba Silicon) and the like, and decamethyltetrasiloxane, octamethyltrisiloxane, phenylmethylsiloxane and the like can be used, and these can be appropriately mixed and used.

The insulating liquid of this embodiment has a viscosity of 0.5 Pa · S or more and 1000 Pa · S or less, an electric resistance of 10 ¹² Ωm or more, and a surface tension of 30 dyn / cm or less,
It has a boiling point of 100 ° C or higher. When this liquid developer is used for image formation by the printer, the developer is contained in the liquid developer attached to the latent image surface of the printer because the developer is carried in a thin layer on the developer support. The amount of the insulating liquid is also extremely small, and the amount of the insulating liquid adhered and absorbed on the transfer paper at the time of transfer is also extremely small, which causes no problem.

If a silicon-based solvent having a resistance value larger than that of Isopar is used as the insulating liquid, the chargeability of the toner can be maintained well even if the toner is contained in a high concentration. Further, when isoper is used, the dispersibility of the toner is improved, so it is effective in the case of a normal toner density, but in the case of a developer containing a high concentration of toner as in the present embodiment, silicone is used. Even in the solvent of the system, the toner can be in a state of being clogged with honey and can be uniformly dispersed. In addition, since silicone oil is non-volatile and does not stick even when used in moving parts, it does not stick to the moving parts of means for applying pollution to the liquid developer or applying stress to the liquid developer. It can be prevented. Therefore, it is highly useful for improving the working environment in manufacturing and using the liquid developing device, and the structure of the means for applying a stress load can be simplified, and the frequency of maintenance can be reduced.

The above-mentioned pigment fine particles are subjected to dispersion treatment of inorganic or organic pigment fine particles to primary particles, and then treated by the flushing method described below in order to further improve gradation, resolution, image density and the like.

In the flushing method, first, a pigment or a water-containing paste of a pigment is put together with a resin solution or a resin in a kneader called a flasher and mixed well at room temperature or under heating. By this process, water existing around the pigment is replaced by the resin solution or resin as the coating resin.
This is taken out from a kneader, the aqueous phase is discarded, and then the one obtained by continuing kneading and dispersion under heating or at room temperature is dried, the solvent is removed, and the obtained lump is crushed. The pigment fine particles thus obtained will be referred to as "flushing pigments" in the present invention.

As the coating resin for coating the dispersion-treated pigment fine particles, the acid-basic property and melt viscosity of the selected resin are appropriately selected according to the acid-basic property of the pigment. For example, polyolefin, or a polyolefin copolymer can be used, other general polyolefin, acrylic resin, rosin-modified resin, styrene-butadiene resin,
Natural resins, paraffin wax, and other resins can be mixed and used within a range satisfying various constituent requirements defined in the present invention. However, the usable resin is not limited to these examples.

The flushing pigment obtained as described above is a colorant, and the colorant and a binder resin form a toner, and the toner is dispersed in an insulating liquid to obtain a liquid developer.

FIG. 1 is a schematic view of a stirrer 12 used in the production of the liquid developer, which is a feature of this embodiment. This agitating device 12 is a screen 1 that defines a stirring chamber.
And a rotor 2 that rotates at high speed in the stirring chamber. The pigment fine particles used to obtain the toner of the present invention are sheared by the screen 1 and the rotor 2 of the stirrer by stirring in a solvent containing a dispersion aid, the collision force, the pressure fluctuation, and the cavitation. ,
And, it is finely dispersed by the action of the potential core to form fine particles.

Here, the step of dispersing the pigment in the form of fine particles will be described. The fine pigment particles used to obtain the toner of the present invention are preliminarily dispersed liquid (coagulated particles of pigment) obtained by introducing the pigment into a solvent containing a dispersion aid and preliminarily dispersing (coarsely dispersing) it with a propeller stirrer or the like. (Dispersion liquid) is supplied to the stirring device, and the dispersion process (fine dispersion process) is performed by the stirring device. In the present invention, as a stirring device that can be used in the dispersion treatment for obtaining pigment fine particles, there is used "CLEAMIX".
RMIX) ”(manufactured by M Technique Co., Ltd.). This "CLEAR MIX" consists of a rotor 2 (stirring blade) that rotates the liquid to be treated at high speed, and the rotor 2
With a fixed screen 1 (fixed ring) that surrounds, a structure that causes the action of shearing force, collision force, pressure fluctuation, cavitation and potential core, and emulsifies / disperses by the synergistic effect of these actions Is. That is, this “CLEARMIX” is used for the production of emulsion (dispersion of liquid fine particles), but the present inventors have used this device for dispersing pigment (solid) in an aqueous medium. It has been found that a dispersion liquid of pigment fine particles having a suitable volume average particle diameter and a sharp particle diameter distribution can be obtained by using it as a dispersing device.

A suitable volume average particle diameter (dispersed particle diameter) of fine pigment particles used as a component of the toner is 10 to 500 nm. The volume average particle diameter of the pigment fine particles is a value measured by using an electrophoretic light scattering photometer "Microtrac" (manufactured by Nikkiso Co., Ltd.). The particle size distribution of the fine pigment particles is preferably 30 or less in standard deviation, more preferably 2
It is set to 0 or less. When the particle size distribution of the pigment fine particles has a standard deviation of 30 or less, the distribution is sharp and the particle size is uniform, and the pigment fine particles can be reliably taken in,
It is possible to prevent the release of fine pigment particles. The "particle size distribution of fine pigment particles" means a particle size analyzer "Microtrac".
The standard deviation measured by "UPA" (manufactured by Nikkiso Co., Ltd.) is shown.

Then, in the stirring device 12, the rotor 2
The rotation speed is usually 4500 to 22000 rpm, preferably 10000 to 21500 rpm. The tip peripheral speed of the rotor 2 is usually 10 to 40 m / sec, preferably 15 to 30 m / sec. The screen 1 surrounding the rotor 2 is composed of a fixed ring in which a large number of slits (not shown) are formed. The width of the slit is 0.
It is 5 to 5 mm, preferably 0.8 to 2 mm. Also,
The number of slits is 10 to 50, preferably 15 to
The number is 30. The clearance between the rotor 2 and the screen 1 is usually 0.1 to 1.5 mm, preferably 0.2 to 1.0 mm.

In the stirrer 12 having the above-described structure, the average particle size and particle size distribution of the pigment fine particles can be adjusted by controlling the rotation speed of the rotor 2, and the shapes of the screen 1 and the rotor 2 can be adjusted. It can also be adjusted by selecting. Specifically, a screen (S1.0-2) attached to "Clear Mix"
4, S1.5-24, S1.5-18, S2.0-18,
The standard equipment such as S3.0-9) and the rotor 2 (R1 to R4) can be used in combination, but it is also possible to manufacture a desired shape.

FIG. 2 is a schematic diagram showing a continuous type processing apparatus (Clearmix) equipped with a stirring device having a rotor 2 and a screen 1. When the pigment is dispersed by this processing device, the dispersion liquid in which the pigment is preliminarily dispersed (preliminary dispersion liquid) is supplied from the preliminary dispersion liquid inlet 4 to the stirring chamber between the screen 1 and the rotor 2 (see FIG. 1). Supply to. The screen 1 and the rotor 2 have a pressurized vacuum attachment 3
The temperature sensor 6, the cooling jacket 7, and the cooling coil 8 are arranged. By this processing device, the aggregated particles of the pigment in the preliminary dispersion liquid are crushed (finely dispersed) by applying a shearing force generated by the rotor 2 and the screen 1 which rotate at high speed.

That is, the aggregated particles of the pigment in the pre-dispersion liquid supplied to the zone (stirring chamber) between the screen 1 and the rotor 2 are shearing forces generated by the screen 1 and the rotor 2 rotating at a high speed. (Mechanical energy)
By being subjected to the action of the shearing force and the action of the collision force, the pressure fluctuation, the cavitation and the potentiating core together with the action of the shearing force, the substance is crushed (finely dispersed), whereby fine pigment particles are formed. The dispersion liquid of the pigment fine particles is ejected from the slit of the screen 1 into the pressure vacuum attachment 3. As a result, fine pigment particles (dispersed particles) having a suitable average particle diameter and a sharp particle diameter distribution are formed. The dispersion liquid containing fine pigment particles is sent to the next step from the dispersion liquid outlet 5.

The mechanism by which the fine pigment particles (dispersed particles) are formed by the stirring device of the present embodiment is as follows. (1) A large velocity gradient exists near the surface of the rotor (stirring blade) 2 that rotates at a high speed, and a high shear velocity region is formed near the surface. Aggregated particles of the pigment that have been subjected to the shearing force are disintegrated into fine pigment particles having a sharp particle size distribution. (2) A vacuum portion (cavitation) is generated behind the rotor (stirring blade) 2 that rotates in the liquid when the rotation speed is high. The bubbles generated by this are destroyed when the flow velocity decreases, but at this time, an impact pressure is generated due to the compression of the bubbles, and the impact pressure crushes the aggregated particles of the pigment, resulting in a pigment having a sharp particle size distribution. It becomes fine particles. (3) When the pressure energy applied to the preliminary dispersion liquid by the rotor (stirring blade) 2 rotating at high speed is suddenly released, the kinetic energy increases. A pressure wave is generated when the preliminary dispersion liquid flowing by the rotor 2 repeatedly passes through the open portion (slit portion) and the closed portion (non-slit portion) of the screen 1. Due to this pressure wave (pressure fluctuation), the aggregated particles of the pigment are crushed to become fine pigment particles having a sharp particle size distribution. (4) When the pre-dispersion liquid having a large kinetic energy collides with the screen 1 and other walls, the agglomerated particles of the pigment subjected to the collision force are crushed to become pigment fine particles having a sharp particle size distribution. (5) When the dispersion liquid having velocity energy passes through the slit portion of the screen 1, it becomes a jet flow (jet flow).
In the potential core (velocity region not affected by viscous flow) in the jet, the surrounding fluid is sucked at a high velocity. Aggregated particles of the pigment that have received this energy are crushed to become pigment fine particles having a sharp particle size distribution.

As a modified example of the processing apparatus, it is also possible to use a batch type. FIG. 3 is a stirring device (Clearmix) equipped with a rotor 2 and a screen 1.
It is a schematic diagram which shows the processing apparatus which carries out batch type dispersion processing equipped with. This processing apparatus uses a dispersion container equipped with a stirrer equipped with a screen 1 and a rotor 2. In a solvent contained in the dispersion container, a pigment (an aqueous medium containing the pigment) is discharged from a stirring chamber of the stirrer. ) Is to eject.

In FIG. 3, 11 is a dispersion container, 12 is a stirrer, and 13 is a stirrer shaft for driving the stirrer 12. The stirrer 12 has the same configuration (screen 1 and rotor 2) as that shown in FIG.
In this processing device, the preliminary dispersion liquid (dispersion liquid of aggregated particles of pigment) is supplied from the upper part of the stirring device 12 to the stirring chamber, and a strong shearing force generated between the rotor 2 and the screen 1 rotating at high speed, Stirring by impact force and turbulent flow, pigment fine particles having a volume average particle diameter of 10 to 500 nm are formed. Then, from the slit of the screen 1 to the dispersion container 11
Gush out inside. In the dispersion process of the pigment fine particles, the dispersion container 1
1 may have a jacket structure, and hot water or steam, and if necessary, cold water may be flowed into the jacket to control the temperature in the dispersion container 11.

In the case of performing a batch type dispersion treatment using the dispersion container 11 shown in FIG. 3, as a jetting direction of the pigment from the stirring chamber of the stirrer 12 (a jetting direction of the pigment fine particles into the aqueous medium). Is preferably in the downward or horizontal direction. By jetting the pigment fine particles downward or horizontally, the aqueous medium in the dispersion container 11 flows as shown by the arrow F. As a result, the pigment itself is also jetted downward, and its flow rises along the wall and again. It is a system that circulates into the clear mix. By this, the dispersion process of the pigment fine particles can be surely repeated, and the dispersion energy can be uniformly applied. As a result, it is estimated that the particle size of the pigment can be made uniform. This makes it possible to efficiently form fine pigment particles having a sharp particle size distribution.

In the dispersion treatment apparatus having the above constitution, the dispersion time for obtaining the dispersion liquid of the pigment fine particles is not particularly limited. As a reference, in the case of the continuous method described above, by circulating 5 passes or more, and in the case of the batch method described later, by circulating for 5 to 30 minutes,
It is possible to disperse the pigment fine particles used in the production of the toner to a desired dispersion state. If the circulation time is too short, the desired dispersion cannot be obtained, and if it is too long, the dispersion becomes excessive and the abundance of fine particles increases, which is not preferable.

Next, a pigment suitable for obtaining fine pigment particles which is a constituent of the liquid developer produced by the method for producing a liquid developer of the present invention will be described. Examples of pigments that can be used include various inorganic pigments and organic pigments.

As the inorganic pigment, any pigment can be used as long as it is a conventionally known one. Among them, suitable inorganic pigments are exemplified below. As the black pigment, for example, carbon black such as furnace black, channel black, acetylene black, thermal black and lamp black, and magnetic powder such as magnetite and ferrite can be used. These inorganic pigments can be used alone or in combination of two or more as desired. The content ratio of the inorganic pigment in the toner in the liquid developer of the present invention is 10% by weight of the resin component (polymer).
It is preferably 2 to 20 parts by mass with respect to 0 parts by mass.

As the organic pigment, any conventionally known pigment can be used, and specific organic pigments are exemplified below. Examples of magenta or red pigments include CI pigment red 2, CI pigment red 3, CI pigment red 5, and CI pigment red.
Pigment Red 6, CI Pigment Red 7, C.I.
CI Pigment Red 15 and CI Pigment Red 1
6, CI Pigment Red 48: 1, CI Pigment Red 53: 1, CI Pigment Red 57: 1,
CI Pigment Red 122, CI Pigment Red 123, CI Pigment Red 139, CI Pigment Red 144, CI Pigment Red 149,
CI pigment red 166, CI pigment red 177, CI pigment red 178, CI pigment red 222 and the like. Pigments for orange or yellow include CI Pigment Orange 3
1, CI Pigment Orange 43, CI Pigment Yellow 12, CI Pigment Yellow 13, CI
Pigment Yellow 14 and CI Pigment Yellow 1
5, C. I. Pigment Yellow 17, C. I. Pigment Yellow 93, C. I. Pigment Yellow 94, C.I.
Pigment Yellow 138 and the like. As pigments for green or cyan, CI pigment blue 15, CI pigment blue 15: 2, CI pigment blue 15: 3, CI pigment blue 16,
CI pigment blue 60, CI pigment green 7, etc. are mentioned. These organic pigments can be used alone or in combination of two or more as desired.
The content ratio of the organic pigment in the toner of the present invention is preferably 2 to 20 parts by mass, and more preferably 3 to 15 parts by mass with respect to 100 parts by mass of the resin component (polymer).

The pigment fine particles constituting the toner of the present invention are
The surface may be modified. Here, as the surface modifier, conventionally known ones can be used, and specifically, a silane coupling agent, a titanium coupling agent, an aluminum coupling agent and the like can be preferably used. For example, as the silane coupling agent, alkoxysilanes such as methyltrimethoxysilane, phenyltrimethoxysilane, methylphenyldimethoxysilane and diphenyldimethoxysilane, siloxanes such as hexamethyldisiloxane, γ-chloropropyltrimethoxysilane and vinyltrichlorosilane. , Vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane,
γ-ureidopropyltriethoxysilane and the like can be mentioned.

The addition amount of these surface modifiers is preferably 0.01 to 20% by mass, more preferably 0.1 to 5% by mass, based on the pigment. As a method of modifying the surface of the pigment fine particles, a method of adding a surface modifier to the dispersion liquid of the pigment fine particles and heating the dispersion liquid to cause a reaction can be mentioned. The surface-modified pigment particles are
It is collected by filtration, and the washing treatment with the same solvent and the filtration treatment are repeated, followed by a drying treatment.

The pigment fine particles obtained as described above are treated by the above-mentioned flushing method to obtain a flushing pigment having the surface of the pigment fine particles coated with the coating resin. When performing the flushing treatment, it is possible to take a measure such as removing water and solvent by reducing the pressure while kneading with a kneader. In the flushing process, since not only the pigment but also the dye is kneaded together with water in a mud form to obtain almost the same result as the pigment, in the present embodiment, the dye to be flushed may be adopted as the toner component. It is possible. The proportion of the pigment and the coating resin when flushing is appropriately 10 to 60 parts by mass of the pigment with respect to 100 parts by mass of the coating resin. Also,
Flushing treatment is humic acid, humic acid salt (Na salt, NH4
It is particularly advantageous to work in the presence of a salt or the like) or a humic acid derivative. The amount of these humic acids added is suitably about 0.1 to 30% by mass of the pigment-containing water solution.

As the coating resin used for flushing, any resin which has been conventionally used as a binder resin for liquid development can be applied. In particular, the resin having the above characteristics (acid value of 0. A polyolefin having a melt viscosity of 5 to 50, 200 to 50 ° C. of 50 to 15,000 cp, or a polyolefin copolymer) is preferable.

Examples of the aqueous medium in which the fine pigment particles are dispersed include an aqueous solution in which the surfactant is dissolved at a concentration of the critical micelle concentration (CMC) or higher. The surfactant is emulsion polymerization. The same surfactant as that used in the process can be used. Aggregated particles of the pigment used in the dispersion step can be prepared by introducing the pigment into an aqueous medium containing a dispersion aid and preliminarily dispersing (coarsely dispersing) it with a propeller stirrer or the like. The dispersion treatment of the pigment fine particles may be carried out in a continuous manner by using an apparatus as shown in FIG. 2, or batchwise by using a dispersion container 11 equipped with an agitator 12 as shown in FIG. You may implement by a formula. The pigment dispersion step may be performed as a pretreatment for performing the flushing process, or may be included in the flushing process.

The flushing pigment is used as a colorant to form a toner together with a binder resin. Here, the particle diameter of the toner particles constituting the liquid developer of the exemplary embodiment is preferably 0.1 to 5 μm in terms of volume average particle diameter. The volume average particle diameter of the toner can be measured using Microtrac HRA (manufactured by Nikkiso Co., Ltd.). 5 to 4 of this toner in an insulating liquid
A liquid developer containing a high concentration of toner is obtained by dispersing in a range of 0%.

As described above, the particle size of the toner particles is set to 0.1.
When the thickness is not less than μm, it is possible to prevent the physical adhesion of the toner from becoming too large and the toner from becoming difficult to peel off during transfer. Further, when the thickness is 5 μm or less, deterioration of resolution can be prevented.

By producing the liquid developer as described above, the aggregated particles of the pigment are crushed by the action of the shearing force generated by the screen 1 and the rotor 2, and the volume average particle diameter is 10 nm or more and 500 nm or less. It is possible to coat pigment fine particles having a uniform particle size with a sharp particle size distribution having a standard deviation (σ) of 30 or less as a dispersed particle in a solvent and presenting a uniform particle size with a coating resin. it can. Therefore, it is possible to reliably introduce the colorant composed of the pigment fine particles and the coating resin into the toner particles, to eliminate the liberated pigment, and to prevent the content ratio of the colorant from varying among the toner particles.

Examples 1 and 2 to which the liquid developer manufacturing method of the present invention is applied will be described below. However, the present invention is not limited to these examples. [Example 1] 200 g of water and 20 g of ammonium humic acid salt were well dissolved in a gallon kneader, and 200 g of carbon black "Black Pearl 430 (manufactured by Cabot Corporation)" as a pigment was gradually added thereto, and the mixture was stirred for 30 minutes, Carbon black was predispersed.

Next, 800 g of ethylene-maleic acid copolymer was put into the resin container, and a stirrer 12 "CLEARMIX" (manufactured by M Technique Co., Ltd.) as shown in FIGS. 1 and 2 was used in the resin container. Then, the stirring device 12
Dispersion treatment (fine dispersion treatment) by the action of shearing force generated by the screen 1 and the rotor 2 constituting the above is performed to prepare a dispersion liquid of pigment fine particles (hereinafter, referred to as “pigment dispersion liquid (C-1)”). . Here, as the screen 1,
"S1.0-24 type" (slit width: 1.0MM, number of slits: 24) is used, and the rotor 2 is "R2
Type "was used. In this combination, the clearance between the screen 1 and the rotor 2 is 0.5 mm. The rotation speed of the rotor 2 was 21500 rpm (peripheral speed: 30 m / sec), and the processing time was 20 minutes.

The particle size of the pigment fine particles in this pigment dispersion (C-1) was measured by using a particle size analyzer "Microtrac UPA" (manufactured by Nikkiso Co., Ltd.).
51 nm, the standard deviation of the particles was 20.

Next, it was vacuum dried, cooled and pulverized to obtain a flushing pigment. After drying, the solid content concentration of the pigment dispersion liquid (C-1) measured by the mass method was 20 mass%. Further, when the above solid content was processed for TEM observation and the particle size was confirmed, it was a value almost close to the average particle size.

[Comparative Example 1] The pigment was replaced by C.V. instead of the carbon black "Black Pearl 430 (manufactured by Cabot Co.)" used in Example 1. I. Pigment Red 122 was used in the same manner as in Example 1 (C-1) except that 1.2 kg of Pigment Red 122 was used.
-1) ". ) Was prepared. This pigment dispersion (Z-
The particle size of the pigment fine particles in 1) was measured by a particle size analyzer "Microt
rac UPA "(manufactured by Nikkiso Co., Ltd.), the volume average particle diameter was 619 nm, and the standard deviation of the particles was 30.

[Example 2] The pigment was carbon black "Black Pearl 430 (manufactured by Cabot Corporation)", C.I. I. Pigment Blue 15: 3 was used in the same manner as in Example 1 (C-1) except that 1.2 g of Pigment Blue 15: 3 was used to prepare a dispersion liquid of pigment fine particles (hereinafter, referred to as "pigment dispersion liquid (C-2)"). . The particle size of the fine pigment particles in this pigment dispersion (C-2) was measured using a particle size analyzer "Microtrac UPA" (manufactured by Nikkiso Co., Ltd.), and the volume average particle size was 303 nm.
The standard deviation of the particles was 15. Further, the solid content concentration of the pigment dispersion liquid (C-2) measured by the mass method by static drying was 16.6 mass%.

Comparative Example 2 The dispersion process of the color pigment of Example 2 (C-2) was carried out by an ultrasonic disperser without using Clear Mix. The particle size of the pigment fine particles in this pigment dispersion liquid (Z-2) was measured with a particle size analyzer "Microtrac UPA".
The volume average particle diameter was 721 nm, and the standard deviation of the particles was 30, when measured using (manufactured by Nikkiso Co., Ltd.).

Using the fine pigment particles of Examples 1 and 2 and Comparative Examples 1 and 2, toners were prepared in the same manner as in Example 1 of JP-A-3-225354.

Pigment fine particles 50 parts by mass Lauryl methacrylate / methyl methacrylate / methacrylic acid / glycidyl methacrylate (80/10/5/5) copolymer Isopar H 20% solution 100 parts by mass Isopar H 200 parts by mass is ball milled. After dispersing for 24 hours, 300 parts of Isopar H was further added and dispersed for 1 hour to obtain a concentrated toner. 200 g of this was taken and diluted in 1 L of KF96 (manufactured by Shin-Etsu Silicone, viscosity 100 cSt) to obtain a liquid developer. <Live shooting test> For each of Examples 1 and 2 and Comparative Examples 1 and 2, under normal temperature and high humidity environment (temperature: 25 ° C, relative humidity: 50).
%) To evaluate the occurrence of fogging and image defects by conducting a real-life test for forming a copied image.

FIG. 4 is a main schematic configuration diagram of the printer according to the present embodiment. In FIG. 4, a charging unit 18, a developing unit, an intermediate transfer member 19, a photosensitive drum cleaning unit 20 and the like are arranged around the photosensitive drum 17 as a latent image carrier. In addition, the intermediate transfer member 19
The image formed on the intermediate transfer member is transferred onto the recording paper by a transfer roller which is disposed so as to face the sheet.

In the above structure, the photosensitive drum 17 is rotationally driven in the direction of the arrow at a constant speed during printing by a driving means such as a motor (not shown). Then, after being uniformly charged by the charging unit 18, the writing light LB is irradiated and image-formed by an optical writing unit (not shown) based on the image information, and an electrostatic latent image is formed on the photosensitive drum 17. Then, the electrostatic latent image is developed by the developing unit, and an image is formed on the photosensitive drum 17. The image formed on the photosensitive drum 17 is
Intermediate transfer member 19 driven at the same speed as the photosensitive drum 17.
Transcribed on. The image on the intermediate transfer member 19 is transferred onto a transfer sheet 16 conveyed from a sheet feeding cassette (not shown) to a transfer section.
It is transferred to the recording paper by the transfer roller.

After the transfer is completed, the transfer paper 16 is fixed by a fixing unit (not shown) and discharged. The liquid developer on the photoconductor drum 17 that has not been transferred onto the intermediate transfer body 19 is removed from the photoconductor drum 17 by the photoconductor drum cleaning unit 20. In addition, the intermediate transfer member 1
The transfer residual developer on 9 is removed by an intermediate transfer member cleaning unit (not shown). After that, the photosensitive drum 1
The surface of No. 7 is prepared for the next printing after the residual potential is removed by a charge eliminating lamp (not shown).

As shown in FIG. 4, the developing unit in the printer of this embodiment includes a developing section 21 and a developing roller 2
2, a developer collecting section 23, a developer accommodating section (hereinafter referred to as “developer adjusting section”), a toner bottle, and a carrier bottle. The liquid developer used in this embodiment has a viscosity of 100 to 10,000 mP.
A toner having a toner concentration in the range of 5 to 40% is used. More specifically, for example, the viscosity is 300 mPa
-Use a toner density of 15% for s.

In the developing section 21, a storage tank 24 in which the liquid developer is stored, an application roller 25 for applying the liquid developer to the developing roller 22, and a pair of screws 26a and 26b for supplying the liquid developer to the application roller. A regulating blade 27 for regulating the amount of the liquid developer 1 on the surface of the coating roller 25 is provided. Storage tank 24 is 100-150cc
The liquid developer can be stored. The liquid developer is transported from the developer adjusting unit into the storage tank by the transport pump. By driving the pair of screws 26a and 26b, the liquid surface of the liquid developer in the container rises, and the raised portion contacts the coating roller 25, whereby the liquid developer is supplied to the coating roller 25. . When the liquid developer transported by the transport pump is excessively supplied, it overflows into a developer recovery unit for recovering undeveloped toner on the developing roller, and the liquid developer is recovered by the developer adjusting unit. The amount of the liquid developer supplied to the coating roller 25 is regulated by the regulation blade 27, so that the developing roller 22 is coated with about 30 cc of the liquid developer per minute. Further, the developer collecting section 23 mainly includes a wiping roller 28 and a cleaning blade 29, and cleans the liquid developer remaining on the surface of the developing roller 22.

Sensory evaluations were carried out in the above-described printers in Examples 1 and 2 and Comparative Examples 1 and 2. As a result, the image of Example 1 is more uniform than that of Comparative Example 1, and the image of Example 2 is more uniform than that of Comparative Example 2.

From the above, a uniform image can be formed when the volume average particle size of the pigment fine particles is in the range of 10 nm or more and 500 nm or less as in Examples 1 and 2, and Comparative Example 1 It was found that when the average particle size exceeds 500 nm as in Nos. 2 and 3, the image becomes non-uniform, and the volume average particle size of the pigment fine particles affects the uniformity of the image.

Further, when an image is formed by using a liquid developer containing a high concentration of toner as in the present embodiment in a printer, the amount of the developer is higher than that in the case of using a conventional low concentration liquid developer. The amount of liquid can be greatly reduced, which is also effective for downsizing the printer.

[0072]

According to the method for producing a liquid developer of claims 1 and 2, it is possible to eliminate the presence of free pigments in the produced liquid developer. Without reducing the resistance of the developer, the charge amount on the surface of the latent image bearing member is not reduced, and the effect of imparting charge to the toner is not reduced.
A liquid developer capable of forming a fog-free image can be manufactured. Further, since the pigment fine particles are uniformly dispersed and the content ratio of the pigment does not vary among the toner particles, it is possible to manufacture a liquid developer capable of forming an image without image density unevenness. Furthermore, since the medium type disperser is not used, no impurities remain in the finally obtained toner, and a liquid developer can be produced without causing image defects due to fine impurities. From the above, there is an excellent effect that it is possible to manufacture a liquid developer capable of realizing high image quality without image fogging, image density unevenness, image defects caused by fine impurities, and the like. Further, since it is a liquid developer containing toner in a high concentration of 5% or more and 40% or less, there is also an excellent effect that the toner can be supplied at high speed and many images can be formed with a small developer consumption. .

According to the liquid developer manufacturing method of the third aspect, there is an excellent effect that a liquid developer capable of realizing better image quality can be manufactured.

According to the liquid developer manufacturing method of the fourth aspect, the insulating liquid of the third aspect can be easily manufactured by using the silicone oil as the insulating liquid.
There is an excellent effect that a liquid developer containing a high concentration of toner and capable of maintaining chargeability can be produced. Further, there are also excellent effects that the working environment in the production and use of the liquid developing device can be improved, the structure of means for applying a stress load can be simplified, and the maintenance can be simplified.

According to the method for producing a liquid developer of claim 5, there is an excellent effect that a liquid developer having a high concentration and capable of forming an image with high resolution can be produced.

According to the liquid developer of the sixth aspect, by performing image formation using this liquid developer, there are no image fog, image density unevenness, and image defects due to fine impurities. There is an excellent effect that high image quality can be realized.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a main part of an image forming apparatus according to an embodiment.

FIG. 2 is a schematic diagram showing a continuous processing apparatus equipped with a stirring device according to the present embodiment.

FIG. 3 is a schematic diagram showing a batch-type processing device equipped with the stirring device of the present embodiment.

FIG. 4 is a main schematic configuration diagram of a printer according to the present embodiment.

[Explanation of symbols]

1 screen 2 rotor 3 Pressurized vacuum attachment 4 Pre-dispersion liquid inlet 5 Dispersion liquid outlet 6 Humidity sensor 7 Cooling jacket 8 cooling coils 11 Dispersion container 12 Stirrer 13 Stirrer shaft 16 Transfer paper 17 Photosensitive drum 18 Charging unit 19 Intermediate transfer body 20 cleaning unit 21 Development Department 22 Developing roller 23 Developer Collection Department 24 storage tanks 25 coating roller 26a, b 1 pair of screws 27 Regulation blade 28 Wiping roller M stirring chamber

Claims (6)

[Claims] 1. An insulating liquid containing a toner, wherein the toner has a high concentration of 5% or more and 40% or less,
In the method for producing a liquid developer, wherein the toner comprises a colorant comprising pigment fine particles and a coating resin coating the pigment fine particles and a binder resin for binding the colorant, By agitating the pigment fine particles in a solvent containing a dispersion aid with an agitator equipped with a screen for partitioning and forming a agitating chamber and a rotor rotating at a high speed in the agitating chamber, a volume average particle diameter of 10 nm is obtained in the solvent. A method for producing a liquid developer, comprising using fine pigment particles present as dispersed particles having a particle size of 500 nm or less. 2. The method for producing a liquid developer according to claim 1, wherein the dispersion is performed by the action of shearing force, collision force, pressure fluctuation, cavitation, and potential core exerted by the screen and the rotor in the stirring device. A method for producing a liquid developer, which comprises stirring the pigment fine particles in a solvent containing an auxiliary agent. 3. The method for producing a liquid developer according to claim 1, wherein the insulating liquid has a viscosity of 0.5 Pa · S or more 10
A method for producing a liquid developer, which is characterized in that it has an electric resistance of 00 Pa · S or less, an electric resistance of 10 ¹² Ωm or more, a surface tension of 30 dyn / cm or less, and a boiling point of 100 ° C. or more. 4. The method for producing a liquid developer according to claim 3, wherein silicon oil is used as the insulating liquid. 5. The method for producing a liquid developer according to claim 1, 2, 3, or 4, wherein the toner has a volume average particle diameter of 0.1 μm or more and 5 μm or more.
The following items are used:
3. The method for producing a liquid developer according to 3 or 4. 6. A binder containing a high concentration of toner in an insulating liquid, wherein the toner binds the colorant composed of pigment fine particles and a coating resin coating the pigment fine particles with the colorant. A liquid developer comprising a resin, wherein the liquid developer is produced by the method for producing a liquid developer according to claim 1, 2, 3, 4, or 5.