JPH08328388A - Liquid developing method for electrostatic latent image and device therefor - Google Patents

Abstract

PURPOSE: To provide a liquid developing method for an electrostatic latent image and a device therefor with use of liquid developer of high viscosity capable of excellently recovering the liquid developer remaining on the developer supporting body, and reusing the recovered liquid developer. CONSTITUTION: This device is provided with a pre-wet process for applying the pre-wet liquid on a photoreceptor 10, the developing process for feeding the liquid developer of the high density-high viscosity applied on a developing roller 510 to a latent image surface on the photoreceptor 10, the pre-wet liquid recovering process for recovering the pre-wet liquid on the developing roller 510 by the pre-wet liquid recovering roller 512 to which bias voltage is applied, so that repulsive force acts on the toner, by the electric field generated between the developing roller 510, and the developer recovering process for recovering the developer on the developing roller 510 by the developer recovering roller 514 to which the voltage is applied so that the attractive force acts corresponding to the toner by the electric field generated between the developing roller 510.

Description

Detailed Description of the Invention

[0001]

The present invention relates to electrophotography, electrostatic recording,
The present invention relates to an image forming apparatus in which an electrostatic latent image formed by a method such as ionography is visualized using a liquid developer and then transferred to a recording medium.

[0002]

2. Description of the Related Art Conventionally, in an electrostatic latent image liquid developing apparatus for developing an electrostatic latent image formed on an image support with toner which is a charged image-forming particle, a developer is developed after a developing process. As a method for recovering the liquid developer remaining on the support, a blade made of an elastic material such as rubber is brought into contact with the surface of the developer support to scrape off the liquid developer on the developer support. You are using the method.

[0003]

By the way, in a conventional electrostatic recording apparatus or the like, a low-viscosity toner obtained by mixing a toner with IsoparG (registered trademark: manufactured by Exxon) at a ratio of about 1 to 2% is generally used. You are using a liquid developer. However, in order to suppress the generation of solvent vapor and realize a safer and more compact liquid developing device, it is necessary to use a highly viscous liquid developer having a higher concentration than the liquid developer used in the conventional device. Desirably, no such device has previously been found. When such a high-concentration and high-viscosity liquid developer is used, in the above recovery method, the liquid developer adheres to the tip of the blade and the liquid developer remaining on the developer support is satisfactorily scratched. There is a problem that it cannot be taken. Further, the inventors of the present invention have provided a pre-wetting step of applying a pre-wet liquid on the image support prior to the developing step as a method for preventing the toner from adhering to the non-image portion of the image support. A liquid developing method for an electrostatic latent image was invented (Japanese Patent Application No. 5-259473). In this method, part of the pre-wetting liquid on the image support moves to the developer support in the developing step. Therefore, in the above recovery method, since the pre-wet liquid is scraped off together with the liquid developer,
The collected liquid developer cannot be reused as it is in the developing process.

[0004]

[Object] The present invention has been made based on the above circumstances, and it is possible to satisfactorily recover the liquid developer remaining on the developer support and to reuse the recovered liquid developer with a high viscosity. It is an object of the present invention to provide a liquid developing method of an electrostatic latent image and a liquid developing apparatus using the liquid developer of (1).

[0005]

In order to solve the above-mentioned problems, a liquid developing method for an electrostatic latent image of the present invention uses visualized particles obtained by charging the electrostatic latent image formed on an image support. A method of developing an electrostatic latent image by developing with a toner, wherein a pre-wetting liquid, which is a dielectric liquid having releasability and chemically inertness, is applied onto an image support prior to the developing process. Pre-wetting process and 100 to 1000 in which the toner is dispersed in high concentration in the insulating liquid applied on the developer support.
A bias voltage is applied so that a repulsive force acts on the toner due to an electric field generated between the developing step of supplying a high-viscosity liquid developer of 0 mPa · s to the latent image surface of the image support and the developer support. The pre-wet liquid recovery roller to which is applied is brought into contact with the developer support while rotating in the same direction as the rotation direction of the developer support, so that it adheres to the developer support during the developing step. A bias voltage is applied so that an attractive force acts on the toner by the electric field generated between the pre-wet liquid collecting step of collecting the pre-wet liquid on the pre-wet liquid collecting roller and the developer support. The developer recovery roller thus brought into contact with the developer support while rotating in a direction opposite to the rotation direction of the developer support causes the residual developer remaining on the developer support to be brought into contact with the developer support. A developer recovery step of recovering the body developer deposited on said developer collecting roller, and is characterized in that it comprises a.

[0006]

The electrostatic latent image liquid developing method of the present invention is provided with the pre-wet liquid collecting step and the developer collecting step having the above-mentioned constitutions, whereby electrostatic force and viscosity acting between the toner and the developer support can be reduced. A liquid developer attached to the developer support by
The adhesive force to the developer support is weaker than that of the liquid developer, and therefore the pre-wetting liquid that forms a layer on the liquid developer layer can be separated and recovered. For this reason, it is possible to prevent the pre-wet liquid from mixing with the collected liquid developer, so that the collected liquid developer can be reused in the developing process. Further, by collecting the liquid developer while rotating the developer collecting roller, the liquid developer can be collected well even when the highly viscous liquid developer is used. Further, in the liquid latent electrostatic image developing method of the present invention, a liquid developer in which toner is dispersed at a high concentration is formed into a thin layer and developed, so that the liquid amount is smaller than that of a conventional low concentration liquid developer. , Can be far less.
When the viscosity of the liquid developer is 10,000 mPa · s or more, it becomes difficult to stir the insulating liquid and the toner, and there is a problem in how to make the liquid developer. Therefore, a liquid developer of 10,000 mPa · s or more becomes unrealistic in terms of cost and becomes unrealistic. On the other hand, 100
Below mPa · s, the toner density becomes low and
Since the dispersibility of the toner deteriorates, it becomes impossible to develop the developer in a thin layer for development. The layer thickness of the liquid developer layer on the developer support needs to be thin when the toner concentration is high and thick when it is low. In addition, the higher the viscosity, the thinner it needs to be. However, if the layer thickness is thicker than 40 μm,
Toner excessively adheres, causing image noise. On the other hand, when the layer thickness is less than 5 μm, unevenness occurs when a solid black image is output.

In the liquid developing method for an electrostatic latent image of the present invention, the insulating liquid has a viscosity of 0.5 to 1000 mPa · s, an electric resistance of 10 ¹² Ωcm or more, a surface tension of 21 dyn / cm or less, and a boiling point of 100 ° C. When the above liquid developer is used, a highly viscous liquid developer can be obtained. Since the liquid developer formed on the developer support is formed in a thin layer, the insulating liquid contained in the liquid developer adhering to the latent image surface of the image support is extremely small. Therefore, the insulating liquid absorbed by the paper or the like at the time of transfer becomes extremely small, so that the problem of the insulating liquid adhering to the paper or the like does not occur if the viscosity is 1000 mPa · s or less. However, if the viscosity is 0.5 mPa · s or less, the volatility becomes high and it is not suitable as a hazardous material. When the boiling point of the insulating liquid is 100 ° C. or less, the amount of evaporation is large, so that there is a problem in the method of storing the developer, the entire device must have a closed structure, and it is difficult to improve the working environment. .
When the electric resistance is 10 ¹² Ωcm or less, the insulating property is deteriorated, and the toner has a problem of conductivity and cannot be used as a developer. Therefore, it is desirable that the electric resistance be as high as possible. When the surface tension is 21 dyn / cm or more, the wettability becomes poor and the compatibility with the pre-wet liquid becomes poor. Therefore, it is desirable that the surface tension be as low as possible.

The liquid developer has an average particle size of 0.1 to 5 μm.
When the m toner is contained at a concentration of 5 to 40%, it is possible to obtain a liquid developer in which the toner is dispersed in the insulating liquid at a high concentration. In addition, the resolution is improved in almost inverse proportion to the particle size of the toner. Normally, toner is
Since there are 5 to 10 lumps on the printed paper and they are present, when the average particle diameter of the toner is 5 μm or more, the resolution becomes poor. On the other hand, when the average particle diameter of the toner is 0.1 μm or less, the physical adhesive strength increases, and it becomes difficult to remove the toner during transfer.

The viscosity of the pre-wetting liquid used in the liquid developing method for the electrostatic latent image of the present invention is 0.5 to 5 mPa · s, the electric resistance is 10 ¹² Ωcm or more, the boiling point is 100 to 250 ° C., and the surface tension is 21 dyn /. When it is not more than cm, a pre-wetting liquid having releasability and good insulation can be obtained. Since the pre-wetting liquid is absorbed by the recording medium such as paper at the time of transfer, it needs to be evaporated at the time of fixing. Therefore, the viscosity is 0.5 to 5 in order to easily evaporate.
mPa · s is desirable. If the viscosity is 5 mPa · s or more, it becomes difficult to evaporate, and if it is 0.5 mPa · s or less, the volatility becomes high. If the boiling point is 100 ° C. or less, the amount of evaporation increases, which causes a problem in the method of storing the pre-wet liquid, the entire device must have a closed structure, and it is difficult to improve the working environment. On the other hand, when the boiling point is 250 ° C. or higher, the paper is curled at the time of fixing and cannot be used, and high energy for heating is required, resulting in high cost. When the electric resistance is 10 ¹² Ωcm or less, the insulating property is deteriorated and the prewetting liquid cannot be used. Therefore, it is desirable that the electric resistance be as high as possible. When the surface tension is 21 dyn / cm or more, the wettability deteriorates,
The compatibility with the liquid developer becomes poor. Therefore, it is desirable that the surface tension be as low as possible.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A first embodiment of the present invention will be described below with reference to FIGS.
Will be described with reference to. 1 is a schematic configuration diagram of an image forming apparatus which is a first embodiment of the present invention, FIG. 2 is a schematic configuration diagram of a developing device used in the image forming apparatus shown in FIG. 1, and FIG. 3 is a developing roller shown in FIG. FIG. 4 is a diagram for explaining the installation position of the pre-wet liquid collecting roller, and FIG. 4 is a diagram for explaining the operation of the image forming apparatus shown in FIG.

The image forming apparatus 1 according to the first embodiment of the present invention.
As shown in FIG. 1, a photoconductor drum (hereinafter also referred to as a photoconductor) 10 that is an image support, a pre-wetting device 20 that applies a prewetting liquid onto the photoconductor 10, and a photoconductor 10 are charged. The charging device 30, the exposure device 40 that exposes an image on the photoconductor 10, and the positively charged toner to the portion of the photoconductor 10 where the electrostatic latent image is formed to develop the electrostatic latent image. A developing device 50 for forming an image, and a transfer device 6 for transferring the toner image formed on the photoconductor 10 onto a predetermined paper.
0, a cleaning device 70 for removing the toner remaining on the photoconductor 10, a neutralization device 80 for neutralizing the charged photoconductor 10, and a fixing device (not shown) for fixing the toner image transferred to the paper. And are equipped with. Charging device 3
In order to prevent the influence of the static eliminator 80 from being 0, the static eliminator 80
A light shielding plate 302 is attached to the side surface on the side where the is installed.

Photoreceptor 10, charging device 30, exposure device 4
0, the static eliminator 80 and the fixing device can use the conventional technology used in the conventional electronic printer in most cases. Therefore, the description of each of the above devices is omitted, and the prewetting device 20, the developing device 50, the transfer device 60, and the cleaning device 70, which are the main parts of this embodiment, will be described below.

The pre-wetting device 20 of this embodiment is shown in FIG.
As shown in FIG. 5, a tank 202 for storing a pre-wet liquid 220 described later, and a supply roller 20 provided so that a part thereof is immersed in the pre-wet liquid 220 in the tank 202.
2a, a conveying roller 204 provided so as to contact the supply roller 202a, the conveying roller 204, and the photosensitive member 1
The coating roller 206 is provided so as to come into contact with 0.

The supply roller 202a is a conveyance roller 204.
By rotating in the opposite direction of the
The pre-wet liquid 220 stored in 02 is supplied to the transport roller 204. The transport roller 204 is the application roller 2
The pre-wetting liquid 220 supplied by the supply roller 202a by rotating in the direction opposite to the rotating direction of 06.
Are conveyed to the coating roller 206. The coating roller 206 is
The pre-wetting liquid 220 is applied to the surface of the photoconductor 10 by rotating the photoconductor 10 in a direction opposite to the rotation direction of the photoconductor 10. As a result, a thin pre-wet liquid layer is formed on the photoconductor 10. The roller is used to supply the pre-wet liquid 220 to the photoconductor 10, and even when the photoconductor 10 is rotated at a higher speed than before, a desired amount of the pre-wet liquid 220 can be obtained by increasing the rotation speed of the roller. This is because it can be supplied to the surface of the photoconductor 10. This allows
It can support high-speed image output. The supply roller 20
The conveyance roller 204 provided between the 2a and the application roller 206 is not limited to one, and a plurality of conveyance rollers 204 may be provided. In addition, the pre-wet liquid 2 is applied to the surface of the photoconductor 10.
When 20 can be applied thinly and uniformly, the transport roller 204 does not have to be separately provided.

The pre-wet liquid 2 is applied to the surface of the photoconductor 10.
In order to apply 20 thinly and uniformly, the supply roller 202
It is desirable to use a material having good lipophilicity as the a, the transport roller 204 and the coating roller 206. As a roller with good lipophilicity, a ceramic roller (manufactured by Nippon Steel Co., Ltd.) in which ceramics containing alumina and titania as main components are subjected to special surface treatment, or BEET formed of synthetic resin
(Miyakawa Laura) and so on.

As shown in FIG. 2, the developing device 50 of the present embodiment is a tank formed of a developing roller 510 as a developer support and a conductive member such as a metal for storing a liquid developer 508 described later. 502 and a supply roller 5 installed so that a part thereof is immersed in the liquid developer 508 in the tank 502.
02a, a transport roller 504 provided so as to contact the supply roller 502a, and an application roller 50 provided so as to contact the transport roller 504 and the developing roller 510.
6a and 506b, a pre-wet liquid collecting device 51 that collects the pre-wet liquid 220 that has moved from the photoconductor 10 to the developing roller 510 during development, and the developing roller 510 after development.
And a developer recovery device 52 for recovering the liquid developer 508 remaining on the upper side.

The supply roller 502a rotates in a direction opposite to the rotation direction of the conveying roller 504, so that the tank 50
The liquid developer 508 stored in the No. 2 is pumped up and supplied to the transport roller 504. A power supply device 513 is connected to the supply roller 502a, and the tank 502 is connected to the ground. Then, the liquid developer 508 is generated by the electric field generated between the supply roller 502a to which the bias voltage is applied by the power supply device 513 and the tank 502.
Is adjusting the pumping amount of.

The conveying roller 504 is a coating roller 506a,
By rotating in the opposite direction to the rotating direction of 506b,
Liquid developer 50 supplied by supply roller 502a
8 is conveyed to the application rollers 506a and 506b. By applying a bias voltage to the transport roller 504,
The amount of liquid developer 508 conveyed to the application rollers 506a and 506b may be adjusted.

By rotating the coating rollers 506a and 506b in the opposite direction to the rotation direction of the developing roller 510,
The liquid developer 508 carried by the carrying roller 504 is applied to the surface of the developing roller 510. The two application rollers 506a and 506b are used because the developing roller 510 is used.
This is to make the liquid developer layer formed thereon more uniform. Since the coating rollers 506a and 506b come into contact with the developing roller 510 to which the developing bias voltage is applied, it is desirable that the rollers themselves have high resistance. For example, when the electric resistance value of the developing roller 510 is set to about 10 ³ Ωcm, good results can be obtained by setting the electric resistance values of the coating rollers 506a and 506b to 10 ¹⁰ to 10 ¹³ Ωcm. The liquid developer 508 is applied by applying a bias voltage to the application rollers 506a and 506b.
The coating amount of the toner on the developing roller 510 may be adjusted. For example, in order to facilitate the movement of the liquid developer 508 on the application rollers 506a and 506b to the development roller 510 to some extent, the development roller 510 and the application roller 50
A bias voltage may be applied to the application rollers 506a and 506b so that the toner is attracted to the developing roller 510 by the electric field generated between the application rollers 6a and 506b. In the present embodiment, since positively charged toner is used as described later, the bias voltage applied to the application rollers 506a and 506b may be set higher than the developing bias voltage applied to the developing roller 510. Further, in order to make it difficult for the liquid developer 508 on the application rollers 506a and 506b to move to the developing roller 510 and to suppress the supply amount of the liquid developer to the developing roller 510, the developing roller 5
A bias voltage may be applied to the application rollers 506a and 506b so that the toner receives a repulsive force with respect to the developing roller 510 by the electric field generated between the image forming apparatus 10 and the application rollers 506a and 506b. In this embodiment, the coating roller 50
The bias voltage applied to 6a and 506b may be set lower than the developing bias voltage applied to the developing roller 510. Further, the number of application rollers is not limited to two, and one or three or more may be provided. That is, it is desirable to determine the number of application rollers according to the required accuracy such as image quality unevenness.

The developing roller 510 is installed so as to come into contact with the photoconductor 10, and by rotating in the opposite direction to the rotation direction of the photoconductor 10, the developing roller 510 is applied to the latent image surface of the photoconductor 10 by the application rollers 506a and 506b. The applied liquid developer 508 is supplied. The developing roller 510 has a cored bar formed of a rigid body such as stainless steel, an elastic layer formed around the cored bar, and a surface layer formed on the surface of the elastic layer. Therefore, when the pressing force of the developing roller 510 to the photoconductor 10 is adjusted, the liquid developer layer formed on the developing roller 510 and the pre-wet liquid layer formed on the photoconductor 10 come into contact with each other. When the pressure is dispersed, the photoconductor 10 and the developing roller 5 are intervened via the liquid developer layer and the pre-wet liquid layer.
It becomes as if a gap was formed between 10 and 10. As a result, the liquid developer layer formed on the developing roller 510 and the pre-wet liquid layer formed on the photoconductor 10 can be brought into contact while maintaining a two-layer state in which the layers can be distinguished from each other. The hardness of the developing roller 510 is 5 to
60 degrees JIS-A is desirable. Hardness is 5 degrees J
If it is IS-A or less, it is difficult to maintain a constant shape because it is too soft. On the other hand, when the hardness is 60 degrees JIS-A or more, it is too hard, so that the liquid developer layer on the developing roller 510 and the pre-wet liquid layer on the photoconductor 10 can be brought into contact with each other while maintaining the two-layer state. The developing roller 510 needs to be installed so that a space is formed between the developing roller 510 and the photoconductor 10 via the liquid developer layer and the pre-wet liquid layer.

As the member forming the elastic layer of the developing roller 510, polystyrene, polyethylene, polyurethane, polyvinyl chloride, NBR (nitrile butylene.
There are foams such as rubber) and low hardness rubber members such as silicone rubber and urethane rubber. However, in general, a rubber member may be permanently deformed and may not return to its original shape, that is, a roller shape, if it is used for many years in a state of being elastically deformed. Therefore, if possible, it is preferable to use a foamed material for the member forming the elastic layer. An elastic layer may be formed of foam around the cored bar, and a rubber member may be formed on the surface of the elastic layer. The surface layer of the developing roller 510 is formed of a conductive member that does not swell in the silicone oil that is the carrier liquid of the liquid developer 508. As shown in FIG. 2, the electric resistance value of the conductive member is preferably about 10 ³ Ωcm so that an electric developing bias can be applied to the developing roller 510 by the power supply device 515. As a method of forming the surface layer, for example, a method of coating a synthetic rubber-based binder in which conductive particles such as carbon black are dispersed on the surface of the elastic layer, the elastic layer is covered with a heat-shrinkable tube having conductivity, There is a method of applying heat to this to cause heat shrinkage. Alternatively, an elastic material may be injected into the tube having conductivity, or the injected elastic material may be foamed to form the elastic layer inside the surface layer. As the tube having conductivity, a resin tube made of polyimide, polycarbonate, nylon or the like or a metal tube made of nickel or the like is used.
In addition, as a heat-shrinkable tube having conductivity, PF
A resin tube such as A or PTFE is used. These tubes are preferably so-called endless tubes without joints. When the elastic layer is formed of an elastic member that does not swell in silicone oil such as urethane rubber,
It is not necessary to form a surface layer on the surface of the elastic layer. However, in order to apply an electric developing bias to the developing roller 510, the surface of the elastic layer is subjected to conductive processing, or conductive fine particles are added to a member forming the elastic layer.
It is necessary to set the electric resistance value to a desired value, that is, about 10 ³ Ωcm. The developing bias voltage is an electrostatic force (attractive force) that acts between the toner and the developing roller 510, and an electrostatic force (attractive force) that acts between the toner and a portion of the photoconductor 10 on which no electrostatic latent image is formed. Stronger and toner and photoconductor 1
It must be set to be weaker than the electrostatic force (attractive force) acting between the electrostatic latent image of 0 and the portion where the electrostatic latent image is formed. In the present embodiment, as described below, a positively charged toner was used and the developing bias voltage was set to -150V.

The pre-wet liquid collecting device 51 comprises a pre-wet liquid collecting roller 512 provided so as to contact the developing roller 510, and a scraping blade 520 provided so as to contact the pre-wet liquid collecting roller 512.
And a recovery tank 522.

The pre-wet liquid collecting roller 512 rotates in the same direction as the developing roller 510 rotates. A bias voltage is applied to the pre-wet liquid recovery roller 512 by a power supply device 517, as shown in FIG. This bias voltage must be set so that the positively charged toner receives a repulsive force with respect to the pre-wet liquid collecting roller 512 by the electric field generated between the pre-wet liquid collecting roller 512 and the developing roller 510. This is to prevent the liquid developer 508 from adhering to the pre-wet liquid recovery roller 512 by making the adhesive force of the toner to the developing roller 510 stronger than the adhesive force to the pre-wet liquid recovery roller 512. is there. As a result, the adhesive force to the developing roller 510 is weaker than that of the liquid developer 508, and therefore only the pre-wet liquid 220 that forms a layer on the liquid developer layer adheres to the pre-wet liquid collecting roller 512. In this embodiment, the developing bias voltage is set to −150V, so the bias voltage applied to the pre-wet liquid collecting roller 512 is −100 to −5.
It was set to 0V.

Further, the pre-wet liquid collecting roller 512
Is preferably installed in contact with the developing roller 510 via the liquid developer layer as shown in FIG.
This is because only the pre-wet liquid layer on the liquid developer layer is disturbed without disturbing the liquid developer layer.
This is because it is pulled up to 2. The pre-wet liquid 220 attached to the pre-wet liquid collecting roller 512 is scraped by the scraping blade 520 and collected in the collecting tank 522. The pre-wet liquid 220 recovered in the recovery tank 522 may be transported to the tank 202 of the pre-wetting device 20 for reuse.

The developer collecting device 52 includes a developing roller 510.
Developer collecting roller 514 provided so as to contact with
A recovery tank 524 for storing the recovered liquid developer 508, and a liquid developer 508 stored in the tank 502.
A tank 526 in which a liquid developer 509 having a toner concentration higher than that of the toner is stored, a concentration measuring device 528, and a concentration adjusting device 530 are provided.

The developer collecting roller 514 is the developing roller 51.
Rotate in the opposite direction of 0. A bias voltage is applied to the developer collecting roller 514 by a power supply device 519, as shown in FIG. This bias voltage must be set so that the positively charged toner is attracted to the developer collecting roller 514 by the electric field generated between the developer collecting roller 514 and the developing roller 510. This is to make the liquid developer 508 adhere to the surface of the developer recovery roller 514 by making the adhesion of the toner to the developer recovery roller 514 stronger than the adhesion to the developing roller 510. In this embodiment, since the developing bias voltage is set to -150V,
The bias voltage applied to the developer collecting roller 514 is set to -2.
It was set to 50 to -200V.

As shown in FIG. 2, the developer collecting roller 51.
The liquid developer 508 attached to the No. 4 is collected in the collecting tank 526, and then the toner concentration is measured by the concentration measuring device 528. The density measuring device 528 measures the light transmittance of the liquid developer 508, and calculates the toner density based on this light transmittance. The concentration adjusting device 530 is the concentration measuring device 528.
The liquid developer 509 stored in the tank 526 is collected in the liquid developer 508 based on the toner concentration calculated in
To adjust the toner concentration. Concentration adjusting device 530
The liquid developer 508 whose toner concentration has been adjusted by is transported to the tank 502 and reused.

As shown in FIG. 1, the transfer device 60 of this embodiment has an intermediate transfer drum 602 which is an intermediate transfer member and a secondary transfer member which is a secondary transfer member which is provided so as to be separable from the intermediate transfer drum 602. A transfer roller 604 and a removal roller 606 for removing the toner remaining on the intermediate transfer drum 602 are provided.

The intermediate transfer drum 602 is installed so as to come into contact with the photoconductor 10 and rotates in the direction opposite to the rotation direction of the photoconductor 10. In addition, the intermediate transfer drum 602 is
At the time of transfer, the power source device 608 as shown in FIG. 1 charges the toner with an electric charge having a polarity opposite to that of the toner. As a result, that is, the toner image on the photoconductor 10 is primarily transferred onto the intermediate transfer drum 602 by electrostatic force.

The intermediate transfer drum 602 has a cored bar formed of a rigid body such as stainless steel, an elastic layer formed around the cored bar, and a surface layer formed on the surface of the elastic layer. Therefore, the contact pressure when the toner image formed on the photoconductor 10 and the intermediate transfer drum 602 come into contact with each other can be dispersed, so that the toner image on the photoconductor 10 can be prevented from being disturbed. . Further, as in the case where a flexible belt is used as the intermediate transfer member, the problem such as meandering control does not occur even if the intermediate transfer member is rotated at a high speed. The hardness of the intermediate transfer drum 602 is preferably 5 to 50 degrees JIS-A, and preferably 15 to 40 degrees JIS-A. When the hardness is 5 degrees JIS-A or less, it is difficult to maintain a constant shape because it is too soft. On the other hand, hardness is 50 degrees J
If it is IS-A or more, the toner image on the photoconductor 10 may be crushed when the toner image formed on the photoconductor 10 and the intermediate transfer drum 602 are brought into contact with each other because the toner image is too hard.

As a member forming the elastic layer of the intermediate transfer drum 602, polystyrene, polyethylene, polyurethane, polyvinyl chloride, NBR (nitrile butylene rubber) or other foam, or silicone rubber, urethane rubber or the like is used. There is a low hardness rubber member. However, in general, a rubber member may be permanently deformed and may not return to its original shape, that is, a roller shape, if it is used for many years in a state of being elastically deformed. Therefore, the member forming the elastic layer,
If possible, it is preferable to use a foam. An elastic layer may be formed of a rubber member around the cored bar, and an elastic layer of foam may be formed on the surface of the elastic layer.

The surface layer of the intermediate transfer drum 602 is formed of a member that does not swell in the silicone oil that is the carrier liquid for the liquid developer 508. Examples of the method of forming the surface layer include a method of coating the surface of the elastic layer with a synthetic rubber-based binder, a method of coating the surface of the elastic layer with a tube, and the like. It is desirable that these tubes are resin tubes that are so-called endless tubes without joints, such as polyimide and PET tubes. still,
If the elastic layer is made of a rubber member that does not swell in silicone oil such as urethane rubber or fluorosilicone rubber, it is not necessary to cover the side surface of the intermediate transfer drum with a surface layer, but it swells in silicone oil such as foam. If the intermediate transfer drum is formed by (1), it is necessary to cover the side surface of the intermediate transfer drum with a surface layer.

The electric resistance value of the intermediate transfer drum 602 is 10
It is preferably ⁴ to 10 ¹¹ Ωcm, and preferably 10 ⁶ to 10 ⁹ Ωcm. When the electric resistance value is 10 ⁴ Ωcm or less, when the intermediate transfer drum 602 is charged, the intermediate transfer drum 602 is rapidly discharged to the photoconductor 10 and the photoconductor 10
To cause transfer failure. On the other hand, the electric resistance value is 1
When it is 0 ¹¹ Ωcm or more, the intermediate transfer drum 602 is not sufficiently charged, and the intermediate transfer drum 602 and the photoconductor 10 are not charged.
The electrostatic force between the toner image formed above and the toner image weakens, and the toner is not sufficiently moved. Intermediate transfer drum 60
In order to set 2 to the electric resistance value as described above, the surface of the intermediate transfer drum 602 is subjected to conductive processing, or conductive fine particles are added to the member forming the surface layer,
It is necessary to lower the electric resistance value.

The surface of the intermediate transfer drum 602 is preferably a glossy surface having releasability. This is because by improving the releasability from the toner, the intermediate transfer drum 602
This is to facilitate the removal of the toner attached to the. Therefore, as a member forming the surface layer of the intermediate transfer drum 602, a latex, a coated rubber member, a resin tube of polyimide or the like on which a release coating such as fluorine coating is applied, or P having a release effect on the surface.
It is desirable to use resin tubes such as FA, PTFE, ETFE, and FEP.

The secondary transfer roller 604 rotates in a direction opposite to the rotation direction of the intermediate transfer drum 602, thereby feeding the paper as a recording medium between the intermediate transfer drum 602 and the secondary transfer roller 604. At this time, the secondary transfer roller 6
04 is pressed against the intermediate transfer drum 602 through the paper.
Further, as shown in FIG. 1, the secondary transfer roller 604 is charged with a charge having a polarity opposite to that of the toner by the power supply device 612. Therefore, the electrostatic force of the secondary transfer roller 604 and the elastic layer of the intermediate transfer drum 602 improve the adhesion between the intermediate transfer body and the recording medium, and good transfer can be performed regardless of the unevenness of the surface of the recording medium. .

The surface of the secondary transfer roller 604 is coated with fluorine. This is because by improving the releasability from the toner, the toner adhering to the secondary transfer roller 604 can be easily removed and the secondary transfer roller 604 can be prevented from being soiled.

The removing roller 606 is the intermediate transfer drum 60.
It is installed so as to be able to come into contact with and separate from the intermediate transfer drum 2 and to contact the intermediate transfer drum 602 when the secondary transfer is completed, and rotates in the direction opposite to the rotating direction of the intermediate transfer drum 602. Further, as shown in FIG. 1, the removing roller 606 is charged by the power supply device 614 with an electric charge having a polarity opposite to that of the toner. As a result, the toner remaining on the intermediate transfer drum 602 after the secondary transfer process is attached to the surface of the removal roller 606 and removed from the intermediate transfer drum 602.

The cleaning device 70 of this embodiment comprises a removing roller 702 and a power supply device 704 connected to the removing roller 702. The removing roller 702 is provided so as to contact the photoconductor 10 and rotates in the direction opposite to the rotation direction of the photoconductor 10. The power supply device 704 applies a voltage to the removing roller 702 so that the removing roller 702 is charged with an electric charge having a polarity opposite to that of the toner. As a result, the toner remaining on the photoconductor 10 is removed.

Next, the image forming material used in this embodiment will be described. The liquid developer used in this embodiment is a resin that serves as a binder such as epoxy, a charge control agent that gives a predetermined charge to the toner, a positive charge in this embodiment, a color pigment, a dispersant that uniformly disperses the toner, and the like. And a carrier liquid. The toner composition is basically similar to that used in conventional liquid developers, but their formulation has been modified to be compatible with silicone oils for adjusting charging characteristics and dispersibility. The smaller the average particle size of the toner is, the better the resolution is. However, the smaller the particle size is, the larger the physical adhesive force is, and the more difficult it is to remove when transferring. Therefore, in this embodiment, the average particle diameter of the toner is adjusted so that the center is around 2 to 4 μm for the purpose of improving transferability.

The viscosity of the liquid developer depends on the carrier liquid used,
It depends on the resin, color pigment, charge control agent, etc. and their concentrations. In this example, the viscosity is 50 to 6000 m.
An experiment was conducted by changing the Pa · s and the toner concentration within the range of 5 to 40%.

As the carrier liquid, dimethylpolysiloxane oil, cyclic polydimethylsiloxane oil, or the like having a high electric resistance is used. Since the amount of carrier liquid contained in the liquid developer layer on the developing roller 510 is extremely small,
The amount of carrier liquid contained in the liquid developer supplied to the latent image surface of the photoconductor 10 is also extremely small. Therefore, the carrier liquid absorbed in the paper or the like during transfer is extremely small, and if the viscosity is 1000 mPa · s or less, almost no carrier liquid remains after fixing. According to experiments by the present inventors, the carrier liquid has a viscosity of 2.5 mPa.
Dow Corning DC 344 of the US and Dow Corning DC 3 of the viscosity of 6.5 mPa · s
When the image output experiment was carried out using No. 45, no carrier liquid remained on the paper after fixing was found. However, since the volatility is high, it is necessary to make the developing device have a closed structure. Further, when an image output experiment was conducted using KF-96-20 manufactured by Shin-Etsu Silicon Co., Ltd., which has a viscosity of 20 mPa · s, no carrier liquid remained on the paper after fixing. Further, since the volatility is not so high, it is not necessary to make the developing device have a closed structure. D
C344, DC345 and KF-96-20 are generally used in cosmetics and have high safety such as toxicity. There are many kinds of carrier liquids such as KF9937 manufactured by Shin-Etsu Silicon Co., Ltd., and any one may be selected as long as the electric resistance, the evaporation property, the surface tension, the safety and the like are satisfied.

Further, in experiments conducted by the inventors, when the surface tension is large, fog or toner lumps may adhere, and experimentally, when the surface tension is 21 dyn / cm or more, a problem occurs in image quality. I found it easy.

The electric resistance value is preferably 10 ¹⁴ Ωcm or more because of the problem of toner charging stability. At least 1
0 ¹² Ωcm or more is necessary. In the description of the present embodiment, in view of these experimental results, the DC3 is low in price and easily available.
An example using 45 is shown.

The pre-wetting liquid easily evaporates during fixing without disturbing the electrostatic latent image formed on the image support,
It is required that fogging and lumps of toner do not adhere. As an example, DC34 manufactured by Dow Corning, USA
4, DC200-0.65, -1.0, -2.0, KF96L-1, KF9937 manufactured by Shin-Etsu Silicon Co., and the like. Generally, it is preferable to select silicone oil having a high evaporation property.

In an experiment conducted by the inventors, the liquid viscosity was 0.
The liquid was dried by development, transfer, and fixing without problems in the range of 5 to 3 mPa · s, but from 5 mPa · s to 6 mPa · s
-At about s, there was a tendency that time and temperature were required for drying the liquid at the time of fixing. If it is 10 mPa · s, the energy required for drying becomes too large, which is not general. Also,
If it is 0.5 mPa · s or less, the volatility increases, so
It is not appropriate because it is subject to laws and regulations as a dangerous material. In addition, the boiling point is preferably 250 ° C. or lower because of the influence of heating the paper.

The surface tension is preferably as low as possible in order to eliminate the adhesive force between the developer and the image support, improve the releasability, prevent the image from being stained, and improve the resolution of the image quality. According to experiments by the present inventors, 20 to 21 dyn / c
The limit is about m, and it is necessary to select one lower than this.

When the electric resistance is low, the latent image charge leaks and the image is blurred. Therefore, it is necessary to use the highest possible one. Experimentally, about 10 ¹⁴ Ωcm or more is desirable. A minimum of 10 ¹² Ωcm is required.

Next, the operation of the image forming apparatus 1 of this embodiment will be described. First, as shown in FIG. 4A, the charging device 30 charges the surface of the photoconductor 10 with a charge having a polarity opposite to that of the toner, in the case of the present embodiment, a negative charge. Generally, a corona discharger is used for the charging device 30. Next, an image is exposed on the charged photoconductor 10 by the exposure device 40. For example, the image is exposed by a laser scanner to form an electrostatic latent image on the surface of the photoconductor 10. As shown in FIG. 4B, the portion of the laser scanner exposed to the light becomes conductive, so that the charge disappears, and the portion not exposed to the light remains as an electrostatic latent image which is an image of the charge.

Next, as shown in FIG. 4 (C), the pre-wetting liquid 22 is applied onto the photoconductor 10 by the pre-wetting device 20.
Apply 0. The pre-wetting liquid 220 stored in the tank 202 is pumped up by the supply roller 202a and supplied to the transport roller 204. The pre-wetting liquid 220 supplied to the transport roller 204 is transported to the coating roller 206 and then coated on the photoconductor 10. in this way,
By applying the pre-wet 220 through the roller, a thin pre-wet liquid layer is formed on the photoconductor 10.

Next, the developing device 50 visualizes the electrostatic latent image. Liquid developer 508 stored in tank 502
Is supplied to the transport roller 504 by the supply roller 502a. Liquid developer 50 supplied to the conveyance roller 504
8 is conveyed to the application rollers 506a and 506b,
It is applied to the developing roller 510. In this manner, by applying the liquid developer 508 via the roller, a thin liquid developer layer is formed on the developing roller 510. next,
As shown in FIG. 4D, the liquid developer layer on the developing roller 510 is brought into soft contact with the pre-wet liquid layer on the photoconductor 10 to form an electrostatic latent image on the surface of the photoconductor 10. The toner particles are brought close to each other and the charged toner is moved onto the photoconductor 10 by the electrostatic force to form a toner image on the photoconductor 10. The pre-wet liquid 220 that has moved from the photoconductor 10 to the developing roller 510 at the time of development is collected by the pre-wet liquid collecting device 51, and after the development, the developing roller 510.
The liquid developer 508 remaining on the top is collected by the developer collecting device 52.

Next, the transfer device 60 transfers the toner image formed on the photoconductor 10 onto a recording medium such as paper. First, as shown in FIG. 4E, the toner image formed on the photoconductor 10 is charged by the toner and the power supply device 608 with an electric charge having a polarity opposite to that of the toner.
By the electrostatic force generated between the intermediate transfer drum 6 and
02 primary transfer. Next, as shown in FIG. 4F, the toner image primarily transferred onto the intermediate transfer drum 602 is applied to the secondary transfer roller 604 with a pressing force applied to the intermediate transfer drum 602 and the secondary transfer roller 604. By the electrostatic force generated by the secondary transfer bias, secondary transfer is performed on the paper sent between the intermediate transfer drum 602 and the secondary transfer roller 604. On the other hand, the photoconductor 10 has the liquid developer 50 remaining on the photoconductor 10 by the cleaning device 70.
8 is removed, and then the charge is removed by the charge removing device 80.

Next, as shown in FIG. 4G, the toner image secondarily transferred onto the paper is fixed by the fixing device 620 not shown in FIG. The fixing heater 624 provided in the fixing roller 622 of the fixing device 620 thermally melts the toner. As a result, the toner image is fixed on the paper.

5 to 9 are diagrams for explaining the developing process of this embodiment in detail, FIG. 5 is a diagram for explaining the entire developing process, and FIG. 6 is a view of the approaching process. FIG. 7, FIG. 7 is a diagram showing a state of the toner movement process, FIG. 8 is a diagram showing a separation process of the non-image portion, and FIG. 9 is a diagram showing a separation process of the image portion. Unlike the conventional developing process, the developing process of the present embodiment is, as shown in FIG. 5, an approaching process in which the developing roller approaches the photoconductor and the liquid developer layer approaches the pre-wet liquid layer, and a liquid developer layer. And a pre-wet liquid layer are in soft contact with each other to move the toner, and a separation process in which the developing roller separates from the photoconductor and is separated into toner adhering to the developing roller and toner adhering to the photoconductor. It is thought to consist of three processes.

In the approaching process, as shown in FIG. 6, by using the developing roller 510 formed into a columnar shape having elasticity, the pressing force of the developing roller 510 on the photoconductor 10 is adjusted to adjust the developing roller. By dispersing the contact pressure when the liquid developer layer on 510 and the pre-wet liquid layer on the photoconductor 10 are dispersed, the high-viscosity liquid developer layer composed of carrier liquid and toner and the pre-wet liquid layer are separated. Soft contact. At this time, a minute gap, that is, a gap d is formed between the developing roller 510 and the photoconductor 10 via the liquid developer layer and the pre-wet liquid layer. In addition, the pre-wet liquid having a low viscosity is slightly extruded back and forth to cause a pool of the pre-wet liquid.

In the process of moving the toner, as shown in FIG. 7, in the image portion, the toner forms a pre-wet liquid layer mainly by the Coulomb force due to the electric field formed between the charge on the photoconductor 10 and the developing roller 510. It passes and moves to the latent image surface. On the other hand, the toner in the non-image area is basically the photosensitive member 10.
Since the surface of the liquid developer and the liquid developer layer are separated by the pre-wet liquid layer, unnecessary toner does not adhere to the surface of the photoconductor 10.

In the separation process, in the non-image part, as shown in FIG.
Basically, as shown in FIG.
Remains in. At the interface between the pre-wet liquid layer and the liquid developer layer, when the two layers are separated, a part of the pre-wet liquid layer having a low viscosity is transferred to the liquid developer layer and separated. Therefore, the separation point of the two layers is considered to be inside the pre-wet liquid layer. On the other hand, in the image area, as shown in FIG. 9, the toner that has moved to the surface of the photoconductor 10 pushes away the pre-wet liquid layer, so that the pre-wet liquid layer is located on the toner layer and is separated in that layer. On the developing roller 510, a part of the carrier liquid and a part of the pre-wetting liquid remaining after the toner moves form a layer. The pre-wetting liquid remaining on the photoconductor 10 facilitates the movement of the toner due to the electrostatic force in the subsequent transfer process.

FIG. 10 is a diagram for explaining the significance of thinning the liquid developer layer. If the liquid developer layer applied on the developing roller 510 is too thick, the liquid developer 50
Since the viscosity of No. 8 is high, the toner group that tries to move from the developing roller 510 to the surface of the photoconductor 10 by the electrostatic force forms a cluster with respect to the toner located around it and does not cut off the viscosity. To move to the surface of 10,
Toner excessively adheres, causing image noise. In order to suppress the generation of these clusters, it is necessary to control the layer thickness of the liquid developer layer to a minimum value that allows sufficient development.

FIG. 11 is a diagram showing a state in which the developing roller formed of a rigid body such as metal and the photoconductor are in hard contact, and FIG. 12 is a diagram for explaining the soft contact of this embodiment. As described above, the function of the pre-wet liquid layer for image formation is important in the developing process of this embodiment. Therefore, an important requirement in the developing process is to maintain the two-layer state of the pre-wet liquid layer and the liquid developer layer. As shown in FIG. 11, when the developing roller formed of a rigid body and the photosensitive body are in hard contact with each other, the two-layer state cannot be maintained. In this embodiment,
As shown in FIG. 12, the developing roller 510 having elasticity.
The contact between the liquid developer layer formed on the developing roller 510 and the pre-wet liquid layer formed on the photoreceptor 10 by adjusting the pressing force of the developing roller 510 on the photoreceptor 10 using By dispersing the pressure, the liquid developer layer and the pre-wet liquid layer are brought into contact with each other while maintaining the two-layer state. At this time, it is as if a minute gap, that is, an interval d is formed between the developing roller 510 and the photoconductor 10 via the liquid developer layer and the pre-wet liquid layer.

Next, optimization of the layer thickness of the liquid developer layer, the layer thickness of the pre-wet liquid layer and the developing gap, that is, the gap will be described. The layer thickness of the liquid developer layer is particularly 5 when the viscosity of the liquid developer is 50 to 100 mPa · s or more.
For those of 00 mPa · s or more, it is necessary to reduce the thickness. Ideally, it should be slightly thicker than the layer thickness that satisfies the toner development amount (that is, the density of the solid portion) required at the time of development. This is because when a high-viscosity liquid developer is used, electrostatically selected toner moves onto the photoconductor along with the excess toner due to the viscosity of the liquid during development, causing abnormal toner adhesion. This is because the image is smeared and the image is stained. In an experiment conducted by the inventors, a good image was obtained with a layer thickness of about 5 μm for liquid developers having a high toner concentration and about 40 μm for those having a low toner concentration. When a liquid developer having a toner concentration of 20 to 30% was used, good image quality was obtained when the layer thickness of the liquid developer was about 8 to 20 μm.

The layer thickness of the pre-wet liquid layer has an optimum value depending on the viscosity and surface tension of the selected pre-wet liquid. If it is too thin, the high-viscosity liquid developer irregularly adheres to the photoconductor to cause image contamination. As the amount of pre-wetting liquid is increased, image stains are improved,
The optimum value is confirmed. When the amount is further increased, the charge of the latent image flows, the sharpness and the resolution are deteriorated, and the toner flows during development, which also tends to blur the image. D
In experiments using C344, 30 μm or less, especially 20 μm
Good results were obtained with a thickness of m or less. For those having a lower viscosity than this, good results can be obtained with a thinner thickness or a thicker thickness. However, for high viscosity ones, the optimum value tends to have a narrow range.

As in the case of the conventional developing method, the narrower the gap between the photosensitive member and the developing roller, that is, the spacing, the better the resolution and the uniformity of the density of the solid portion in the image quality. In the high-viscosity liquid developer used in this example, since the cohesive force between the toners is strong, the toner released from the developer support or carrier particles by mechanical impact or electrostatic force is different from powder developer. The phenomenon used for development does not occur. That is, development is not performed with an air layer interposed between the liquid developer layer and the photoconductor. Therefore, it is essential that the developing roller 510 is in contact with the liquid developer layer, the liquid developer layer is in contact with the pre-wet liquid layer, and the pre-wet liquid layer is in contact with the photoconductor. Therefore, the minute gap, i.e., the distance d, must be a dimension that is equal to or less than the thickness of the liquid developer layer and the prewetting liquid layer and does not disturb the respective layers. In this embodiment, the pressing force of the developing roller 510 on the photoconductor 10 is adjusted so that the pre-wet liquid layer on the photoconductor 10 and the liquid on the developing roller 510 are adjusted according to the difference in the viscosity of the liquid developer and the toner concentration. The gap d was set to be between 8 μm and 50 μm when brought into contact with the developer layer.

Table 1 shows the results of the image forming experiment under the above-mentioned conditions. From these results, the optimum range of the developer and the viscosity of the pre-wet liquid for the developing method of this embodiment is 100 mPa · s to 6000 mPa · s for the developer.
s, pre-wetting liquid is 0.5 mPa · s to 5 mPa · s
It was found to be between s. Regarding image quality,
Although it varies depending on the thickness of the liquid developer layer on the developing belt, the thickness of the pre-wet liquid layer, the developing gap, that is, the gap, etc., even if the developing conditions are optimized, the tendency is as shown in Table 1. It was confirmed that the optimum area of the liquid developer falls within the range shown in Table 1. The silicone oil of the pre-wet liquid is DC200 series manufactured by Dow Corning, and the carrier liquid of the developing liquid is DC of the same company.
345 was used.

[0063]

[Table 1]

According to the first embodiment of the present invention, the pre-wet liquid collecting roller 512 to which the bias voltage is applied so that the repulsive force acts on the toner by the electric field generated between the developing roller 510 and the developing roller 510 is changed to the developing roller. By contacting with the developing roller 510 while rotating in the same direction as the rotating direction of 510, the pre-wetting liquid 220 that has moved from the photoconductor 10 to the developing roller 510 during development is a liquid developer that remains on the developing roller 510 after development. The developer collecting roller 514 to which the bias voltage is applied so as to exert an attractive force on the toner by the electric field generated between the developing roller 510 and the developing roller 510.
Developing roller 51 while rotating in a direction opposite to the rotating direction of
The liquid developer 508 remaining on the developing roller 510 after the pre-wet liquid 220 is collected by bringing the liquid developer 508 into contact with 0.
Collect. Therefore, it is possible to prevent the pre-wet liquid 220 from mixing with the collected liquid developer 508, and thus the collected liquid developer can be reused in the developing process. Further, since the liquid developer is collected while rotating the developer collecting roller 514, the liquid developer can be satisfactorily collected even when the highly viscous liquid developer is used.

Further, according to the first embodiment of the present invention, the liquid developer 508 collected by the developer collecting roller 514.
Density measuring device 528 for measuring the toner density of the toner, and based on the toner density measured by the density measuring device 528, the collected liquid developer 508 has a higher density.
By providing the concentration adjusting device 530 for adjusting the toner concentration by mixing the above, the toner concentration of the collected liquid developer can be adjusted to the concentration of the liquid developer stored in the tank 502, that is, the initial concentration.

Further, according to the first embodiment of the present invention, the pre-wet liquid recovery roller 512 is brought into contact with the developing roller 510 via the liquid developer layer, so that the pre-wet liquid 220 becomes the liquid developer 508. Compared with the developing roller 51
Since the adhesive force to 0 is weak, and therefore the pre-wet liquid layer is formed on the liquid developer layer, the developing roller 5 is electrostatically charged.
Only the pre-wet liquid layer on the liquid developer layer 10 can be drawn onto the pre-wet liquid collecting roller 512, whereby the pre-wet liquid 220 alone can be more favorably attached to the surface of the pre-wet liquid collecting roller 512. be able to.

Further, according to the first embodiment of the present invention, the use of silicon oil as the carrier liquid for the liquid developer has the following advantages over the conventional ones.

Conventional liquid developers generally use IsoparG (registered trademark: manufactured by Exxon) as a carrier liquid.
Since this Isopar has a resistance value not as high as that of silicone oil, when the toner concentration is increased, that is, when the distance between particles is reduced, the chargeability of the toner is deteriorated. Therefore, Isop
In the case of ar, the toner density is limited. On the contrary,
Since the silicone oil used in the first embodiment has a sufficiently large resistance value, the toner concentration can be increased. Further, in general, in the case of Isopar, the toner dispersion state is good, and therefore, even if the toner concentration is 1 to 2%, the toner particles repel each other, so that the toner particles are uniformly dispersed. On the other hand, when the toner concentration is 1 to 2%, the silicone oil has poor dispersibility and will be precipitated soon. However, when the toner concentration is set to 5 to 40%, the toner is densely packed and stably dispersed. Therefore, in this embodiment, a high-viscosity liquid developer in which toner is dispersed at high density is used. As a result, compared to the conventional low-concentration liquid developer, the amount of developer can be significantly reduced,
It is possible to reduce the size of the developing device. Furthermore, since the liquid developer of this embodiment is a high-viscosity liquid, it is easier to store and handle than the conventional low-viscosity liquid developer or powder developer.

Isopar used in the conventional liquid developer is
As mentioned above, it is highly volatile and emits a foul odor,
There is a problem that it not only deteriorates the work environment but also causes pollution. On the other hand, the silicone oil used in this example is a safe liquid and is odorless, as is clear from the fact that it is used for cosmetics. The environment can be improved and pollution problems do not occur.

Next, FIG. 13 shows the second embodiment of the present invention.
It will be described with reference to FIGS. 13 is a schematic configuration diagram of an image forming apparatus according to a second embodiment of the present invention, and FIG. 14 is FIG.
3 is a schematic perspective view of a pre-wetting device used in the image forming apparatus shown in FIG. 3, FIG. 15 is a diagram for explaining the operation of the pre-wetting device shown in FIG. 14, and FIG. It is a figure showing the flow of the pre-wet liquid when it was made to contact. Here, the same reference numerals are used for those having the same functions as those in the first embodiment.

Image forming apparatus 2 according to the second embodiment of the present invention
As shown in FIG. 13, the photoconductor 10 which is an image support.
A pre-wetting device 25 for applying a pre-wetting liquid onto the photoconductor 10 and a charging device 30 for charging the photoconductor 10.
And an exposure device 40 that exposes an image on the photoconductor 10, and a developing process that visualizes the electrostatic latent image by supplying positively charged toner to the portion of the photoconductor 10 where the electrostatic latent image is formed. A device 55, a transfer device 60 for transferring the toner image formed on the photoconductor 10 to a predetermined paper, a cleaning device 70 for removing the toner remaining on the photoconductor 10, and a charge removal for the charged photoconductor 10. A static eliminator 80, and a fixing device (not shown) for fixing the toner transferred to the paper,
It has.

The image forming apparatus 2 shown in FIG. 13 is different from the image forming apparatus 1 of the first embodiment shown in FIG. 1 in that the prewetting device 25 is used in place of the prewetting device 20, and the developing device 50. Instead, the developing device 55 is used. Therefore, in this embodiment, the pre-wetting device 25 and the developing device 55 will be described, and detailed description of the other devices will be omitted.

The pre-wetting device 25 of this embodiment is shown in FIG.
4, a plate-shaped pre-wet liquid supply body 252 having a length substantially the same as the image width drawn on the photoconductor 10,
Case 254 that houses the pre-wet liquid supply body 252
And a tank 256 for storing the pre-wet liquid 220,
A pump 258 for pumping up the pre-wet liquid 220 stored in the tank 256, and tubes 260a and 260b.
And a displacement device 262.

As the pre-wet liquid supply body 252, a continuous porous body having a three-dimensional network structure in which pores are continuous, for example, Beluita (registered trademark: Kanebo Co., Ltd.) is used.
The bell eater is pre-wet liquid 220 for the volume of the pores.
When the pre-wet liquid 220 exceeding the pore volume is supplied, the pre-wet liquid 220 can be uniformly discharged in the direction perpendicular to the flow direction of the pre-wet liquid 220. Case 25
As shown in FIG. 15, an opening 254 a is provided on the surface of No. 4 facing the photoconductor 10 so that the bottom surface of the pre-wet liquid supply body 252 can be brought into contact with the photoconductor 10. The tube 260 a conveys the pre-wet liquid 220 pumped up by the pump 258 to the supply side 252 a of the pre-wet liquid supply body 252. A space 254b is formed between the supply side 252a of the pre-wet liquid supply body 252 and the case 254. The pre-wet liquid 220 is stored in the space 254b and then supplied from the supply side 252a. It The tube 260b conveys the pre-wet liquid 220 discharged from the discharge side 252b of the pre-wet liquid supply body 252 to the tank 256. When a signal from the outside is not input, the displacement device 262 holds the pre-wet liquid supply body 252 at a position distant from the photoconductor 10 as shown in FIG. When the input is made, the pre-wet liquid supply body 252 is brought into contact with the photoconductor 10 as shown in FIG. 15 (B).

The developing device 55 of this embodiment includes a developing belt 560 which is a developer supporting member, and a driving roller which rotationally drives the developing belt 560 and holds a part of the developing belt 560 so as to abut on the photosensitive member 10. 562a, 562b
A developer supplying device 57 for applying a liquid developer to the surface of the developing belt 560, a pre-wet liquid collecting device 51 for collecting the pre-wet liquid that has moved from the photoconductor 10 to the developing belt 560 during development, and a developing device after development. A developer collecting device 5 for collecting the liquid developer 508 remaining on the belt 560.
8 and.

The developer supplying device 57 includes four developing cartridges 57a, 57b, 57c and 57d (hereinafter, also simply referred to as developing cartridges) and a contacting / disconnecting member which is not shown in the drawing and separates the developing cartridges from the surface of the developing belt 560. And a device. Each developing cartridge stores a liquid developer 508 and discharges it, and a bellows pump 552 is provided.
A coating roller 556 for coating the surface of the developing belt 560 with the liquid developer, transport rollers 554a, 554b for transporting the liquid developer discharged from the bellows pump 552 to the coating roller 556, and an adjusting roller 555. ing. Bellows pump 552 of the developing cartridge 57a
Is a liquid developer 508a containing yellow toner, the bellows pump 552 of the developing cartridge 57b is a liquid developer 508b containing magenta toner, and the bellows pump 552 of the developing cartridge 57c is a liquid developer containing cyan toner. Liquid developer 508d containing black toner is stored in the bellows pump 552 of the developing cartridge 57d (hereinafter, liquid developer 508a, 508b, 508c, 5).
08d is also simply referred to as liquid developer 508).

The carrying roller 554b is a carrying roller 554.
It is installed so as to come into contact with a.
The liquid developer 508 stored in the bellows pump 552 is transported to the transport roller 544a by rotating in the direction opposite to the rotational direction of a. The transport roller 554a is installed so as to contact the coating roller 556, and rotates in a direction opposite to the rotation direction of the coating roller 556, so that the liquid developer 5 transported by the transport roller 554b.
08 is conveyed to the coating roller 556. Coating roller 556
Is the developing belt 560 by a separating / connecting device (not shown).
The developing belt 510 is installed so that it can come in contact with the surface of the
By rotating in the direction opposite to the rotating direction of the developing roller 510, the liquid developer 508 carried by the carrying roller 554a is applied to the surface of the developing belt 510. The adjusting roller 555 is installed so as to be in contact with the carrying roller 554b, and adjusts the layer thickness of the liquid developer 508 on the carrying roller 554b by rotating in the direction opposite to the rotating direction of the carrying roller 554b. The number of transport rollers is not limited to two. Further, when the liquid developer 508 can be uniformly applied onto the developing belt 560, the carrying roller may not be provided.

The developer supplying device 57 having the above-described structure is provided on the surface of the developing belt 560 by bringing the applying roller 556 included in one of the developing cartridges into contact with the developing belt 560 by a separating / contacting device (not shown). The liquid developer 508 containing the toner of the color is applied.

The developing belt 560 is driven by the driving roller 562.
The liquid developer 508 applied to the surface of the photoconductor 10 by the application roller 556 is supplied by rotating the photoconductor 10 in the direction opposite to the rotation direction of the photoconductor 10 by a and 562b. As the developing belt 560, a flexible member such as a metal belt such as a seamless nickel belt or a resin belt such as a polyimide film belt is used.
Accordingly, when the tension of the developing belt 560 is adjusted to disperse the contact pressure when the liquid developer layer formed on the developing belt 560 and the pre-wet liquid layer formed on the photoconductor 10 are dispersed, It seems that a space is formed between the photoconductor 10 and the developing belt 560 via the liquid developer layer and the pre-wet liquid layer. Therefore, in the developing process, the liquid developer layer formed on the developing belt 560 and the pre-wet liquid layer formed on the photoconductor 10 are contacted while maintaining a two-layer state in which the layers can be distinguished from each other. be able to. The developing belt 560 must be capable of applying an electric developing bias. Therefore, when a resin belt is used, it is necessary to reduce the electric resistance value by conducting conductive processing on the surface of the belt or adding conductive fine particles to the material of the belt. When the belt itself is electrically conductive, the drive rollers 562a, 562
For b, a rubber roller having a low electric resistance value to which conductive fine particles are added so that a developing bias can be applied is used. When the surface of the belt is subjected to conductive processing, a conductor that comes into contact with the surface of the belt is provided, and a developing bias is applied to this conductor.

The pre-wet liquid recovery device 51 is the same as that used in the first embodiment. Therefore, detailed description thereof will be omitted.

The developer collecting device 58 is composed of four developer collecting rollers 580a, 580b, 580c and 580d (hereinafter, also simply referred to as developer collecting rollers) attached to a rotary shaft 582. The rotating shaft 582 uses a drive unit (not shown) to drive the developer collecting roller 580a when the liquid developer 508a containing yellow toner is applied onto the developing belt 560, and the liquid developer 508b containing magenta toner. Is applied, the developer recovery roller 580b is applied, the liquid developer 508c containing cyan toner is applied, the developer recovery roller 580c is applied, and the liquid developer 508d containing black toner is applied. When the developer is being collected, the developer collecting roller 5
The 80d are rotatably driven so as to come into contact with each other.

Each developer collecting roller rotates in the direction opposite to the rotating direction of the developing belt 560. Further, as shown in FIG. 13, a bias voltage is applied to each of the developer collecting rollers by a power supply device 583 via a rotating shaft 582. The bias voltage is generated by the electric field generated between the developing belt 560 and the developer collecting roller that is in contact with the developing belt 560.
The toner must be set to be attracted to the developer collection roller. This is because the liquid developer 508 is attached to the surface of the developer collecting roller 514 by making the adhesion of the toner to the developer collecting roller stronger than the adhesion to the developing belt 560.

In the developer collecting device 58 having the above-mentioned structure, the developer collecting roller to be contacted is switched according to the color of the liquid developer applied to the developing belt 560, and the liquid developer remaining on the developing belt 560 after development is changed. Collect. A concentration measuring device 528 and a concentration adjusting device 530 as shown in the developer collecting device 52 of the first embodiment are provided for each developer collecting roller, and the toner concentration of the collected liquid developer 508 is set for each color. It may be adjusted.

Next, the operation of the image forming apparatus 2 of this embodiment will be described. First, the charging device 30 charges the photoconductor 1
The surface of No. 0 is charged, and then the image is exposed on the charged photoconductor 10 by the exposure device 40.

Next, the pre-wetting device 25 applies the pre-wetting liquid 220 onto the photoconductor 10. The pre-wetting device 25 brings the pre-wetting liquid supply body 252 into contact with the photoconductor 10 when a signal is input from the outside. The pre-wet liquid 220 is constantly circulated by the pump 258 inside the pre-wet liquid supply body 252, and the pre-wet liquid 220 that exceeds the pore volume of the bell eater, which is the pre-wet liquid supply body 252, is shown in FIG. As described above, it is discharged from the discharge side 252b of the pre-wet liquid supply body 252 and is also discharged from the bottom surface of the pre-wet liquid supply body 252, and is uniformly applied onto the photoconductor 10 without damaging the photoconductor 10.

Next, the electrostatic latent image is visualized by the developing device 55. Adjusting roller 555 by bellows pump 552
The liquid developer 508 supplied to the contact start side of the conveying roller 554b and the conveying roller 554b is conveyed to the applying roller 556 via the conveying roller 554a and then applied to the developing belt 560. In this way, the developing belt 56 is passed through the plurality of rollers.
By applying the liquid developer 508 onto the developing belt 0, a thin liquid developer layer is formed on the developing belt 560. The liquid developer 508 containing any one of yellow, magenta, cyan, and black toners is brought into contact with the developing belt 560 by contacting the coating roller 556 included in one of the developing cartridges with a separating / contacting device (not shown). It can be applied to the developing belt 560.

Next, the liquid developer layer thus formed on the developing belt 560 is brought close to the electrostatic latent image formed on the surface of the photoconductor 10, and the charged toner is exposed by electrostatic force. It is moved onto the body 10 to form a toner image. The pre-wet liquid 220 that has moved from the photoconductor 10 to the developing roller 510 during development is collected by the pre-wet liquid collecting device 51. Further, after development, the developing roller 51
Liquid developer 508 remaining on top of the developer
To collect each color.

Next, the toner image formed on the photosensitive member 10 is primarily transferred onto the intermediate transfer drum 602 by the transfer device 60. The toner image formed on the photoconductor 10 is caused by an electrostatic force generated between the toner image formed on the photoconductor 10 and the intermediate transfer drum 602 charged with a charge having a polarity opposite to that of the toner by the power supply device 608. , Is transferred onto the intermediate transfer drum 602 and is primarily transferred. On the other hand, the photoconductor 10
The liquid developer 508 remaining on the photoconductor 10 is removed by the cleaning device 70, and then the static eliminator 80 is removed.
Is discharged by. Then, an application roller 556 that contacts the developing belt 560 by a separation / contact device (not shown).
By repeating the cycle from the charging to the discharging, the toner images of yellow, magenta, cyan, and black are successively superposed on the intermediate transfer drum 602, and the toner images are primarily transferred. As a result, a toner image corresponding to colorization is formed on the intermediate transfer drum 602.

Next, the transfer device 60 secondarily transfers the color-formed toner image formed on the intermediate transfer drum 602 to a paper as a recording medium. Intermediate transfer drum 602
The toner image corresponding to the color formed on the upper surface is intermediately transferred by the electrostatic force generated by the pressing force of the secondary transfer roller 604 to the intermediate transfer drum 602 and the secondary transfer bias applied to the secondary transfer roller 604. Secondary transfer is performed on the paper sent between the drum 602 and the secondary transfer roller 604. Then, by a fixing device (not shown),
Fix on paper. Thereby, a color image can be formed on the paper.

According to the second embodiment of the present invention, after development,
Liquid developers 508a-5 that remain on the developing belt 560
08d correspond to the corresponding developer collecting rollers 580a to 580a.
A developer collecting device 58 for collecting each color by 580d
By providing the, it is possible to prevent the collected liquid developer from being mixed with color. Other effects are similar to those of the first embodiment.

In the second embodiment described above, as the developer supply device, the developing cartridge 57 for applying the liquid developer 508a containing the yellow toner onto the developing belt 560.
a, a developing cartridge 57b for applying the liquid developer 508b containing magenta toner, and a developing cartridge 57 for applying the liquid developer 508c containing cyan toner.
However, the present invention is not limited to this, although the description has been given of the one in which the developer c and the developing cartridge 57d for applying the liquid developer 508d containing black toner are provided. The developer supply device may be one in which two or three developer cartridges for applying a liquid developer containing toner of a desired color to the developer support are provided as needed. In this case, the number of developer collecting rollers provided in the developer collecting device may be set according to the number of developing cartridges.

The present invention is not limited to the above embodiments, but various modifications can be made within the scope of the gist thereof. For example, in each of the above-described examples, the case where the organic photoconductor is used as the image support has been described, but the present invention is not limited to this, and the image support may be various photoconductors used in the Carlson method or It is also possible to use a recording medium in which an insulating layer is formed on a conductor that directly forms an electrostatic latent image such as ionography, or electrostatic recording paper used in an electrostatic plotter.

Further, in each of the above-described embodiments, a case where an image is exposed on an image support by an exposure device and then a prewetting liquid is applied on the image support by a prewetting device has been described. Is not limited to this, and the application of the pre-wet liquid may be performed before the developing step. For example, the pre-wetting device may apply the pre-wetting liquid on the image support, and then the exposure device may expose the image on the image support. Further, the pre-wetting device is not limited to the one used in each of the above-described embodiments, and may be any device that can uniformly apply a fixed amount of the pre-wetting liquid to the surface of the photoconductor. For example, it may be applied by ejecting the pre-wet liquid from a plurality of nozzles arranged in the axial direction, or applied by a sponge roller or the like. The viscosity of the pre-wet liquid is 0.5 to 5
mPa · s, electric resistance 10 ¹² Ωcm or more, boiling point 10
If the surface tension is 0 to 250 ° C. and the surface tension is 21 dyn / cm or less, the pre-wetting liquid may not contain silicon as a main component. Furthermore, when the surface of the image support is coated with a material having releasability, a pre-wetting device is not particularly required.

Further, in each of the above embodiments, the image support is charged by the charging device with a charge having the opposite polarity to that of the toner, and then the image support is exposed to light by the exposure device to emit light from the image support. Although a so-called normal development is used in which an electrostatic latent image to be visualized is formed on a portion which is not exposed, the present invention is not limited to this. The charging device charges the image support with an electric charge having the same polarity as the toner, and then the exposure device irradiates the image support with light to form an image to be visualized on the light-exposed portion of the image support. The so-called reversal development may be used. The present inventors have used positively charged toner in a device to which reversal development is applied,
When the developing bias voltage is set to 600V, the bias voltage of the pre-wet liquid collecting roller is set to 650 to 700V and the bias voltage of the developer collecting roller is set to 500 to 5V.
It was confirmed that when the voltage was set to 50 V, the liquid developer on the developer support and the pre-wet liquid could be well separated and collected.

In each of the above-described embodiments, the liquid developer is applied to the developer support in the developing device by applying the liquid developer to the developer support via the roller. The invention is not limited to this, and the developing device may be any device as long as it can apply the liquid developer thinly and evenly on the developer support. For example, the liquid developer may be directly coated on the developer support by a bellows pump, and then the layer thickness of the liquid developer layer on the developer support may be regulated by a layer forming roller or a layer forming blade. . Further, the developer support is not limited to the one used in each of the above examples, and may be a rigid body having conductivity such as metal. However, when a developing roller formed of a rigid body is used, since the liquid developer layer formed on the developing roller and the pre-wet liquid layer formed on the photoconductor are brought into contact with each other while maintaining a two-layer state,
It is necessary to use a photosensitive member formed of a flexible belt-shaped member, or install the developing roller so as to form a minute gap, that is, a space d between the developing roller and the photosensitive drum. There is.

Further, in each of the above-described embodiments, as the primary transfer in the transfer device, the intermediate transfer drum 602 is charged on the photoconductor 10 by the electric power having the opposite polarity to the toner by the power supply device 608. Although the primary transfer of the toner image onto the intermediate transfer drum 602 has been described, the present invention is not limited to this.
The transfer device may be, for example, a device in which the intermediate transfer drum 602 is charged with a charge having a polarity opposite to that of the toner by a corona discharger. Further, in each of the above-described embodiments, as the secondary transfer in the transfer device, an intermediate force is generated by the electrostatic force generated by the pressing force of the secondary transfer roller 604 to the intermediate transfer drum 602 and the bias voltage applied to the secondary transfer roller 604. Although the secondary transfer of the toner image on the transfer drum 602 to the paper has been described, the present invention is not limited to this. The transfer device may be any device that can secondarily transfer the toner image on the intermediate transfer drum 602 onto paper. For example, the secondary transfer roller 6
04 is provided with a fixing heater, and the intermediate transfer drum 602
When the upper toner is heated, the toner image on the intermediate transfer drum 602 can be secondarily transferred to the paper and fixed at the same time.

Further, in each of the above-described embodiments, the cleaning device using the removing roller 702 charged with the electric charge having the opposite polarity to the toner has been described, but the present invention is not limited to this. The cleaning device may be any device that can remove the toner remaining on the photoconductor, and may be, for example, a device that scrapes off the toner remaining on the photoconductor using a blade or the like.

The present invention is not limited to the above-mentioned embodiments, and the viscosity of the high-viscosity developer may be 10,000 mPa · s as long as the layer thickness of the liquid developer is 5 to 40 μm. .. At present, a developer with a high viscosity of 6000 mPa · s or more is difficult to agitate between the carrier liquid and the toner, so it is thought to be costly. However, if it becomes available at a low cost, it will be even at 6000 mPa · s or more. Good. If the viscosity exceeds 10,000 mPa · s, it becomes unrealistic. Further, the carrier liquid of the liquid developer is not limited to silicone oil.

[0099]

As described above, according to the present invention, by providing the pre-wet liquid collecting step and the developer collecting step having the above-described structure, the electrostatic force and the viscosity acting between the toner and the developer support can be reduced. The liquid developer that adheres to the developer support is separated and recovered from the pre-wet liquid that forms a layer on the liquid developer layer because the adhesive strength to the developer support is weaker than that of the liquid developer. As a result, it is possible to prevent the pre-wet liquid from mixing with the collected liquid developer, and therefore, it is possible to reuse the collected liquid developer in the developing process, and to increase the toner By developing a thin layer of liquid developer dispersed in a high density, it has high resolution, easy downsizing, and low pollution. Has releasability on the body Provided is a liquid developing method of an electrostatic latent image which can prevent toner from adhering to a non-image portion of an image support by providing a pre-wet process which is a chemically inert dielectric liquid. be able to.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus that is a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a developing device used in the image forming apparatus shown in FIG.

FIG. 3 is a diagram for explaining installation positions of a developing roller and a pre-wet liquid collecting roller shown in FIG.

FIG. 4 is a diagram for explaining the operation of the image forming apparatus shown in FIG.

FIG. 5 is a diagram for explaining the entire developing process.

FIG. 6 is a diagram showing a state of an approaching process.

FIG. 7 is a diagram showing a state of a toner movement process.

FIG. 8 is a diagram showing a separation process of a non-image portion.

FIG. 9 is a diagram showing a process of separating an image portion.

FIG. 10 is a diagram for explaining the significance of thinning the liquid developer.

FIG. 11 is a diagram showing a state in which a developing roller and a photoconductor are in hard contact.

FIG. 12 is a diagram for explaining a soft contact of the present invention.

FIG. 13 is a schematic configuration diagram of an image forming apparatus that is a second embodiment of the present invention.

14 is a schematic perspective view of a pre-wetting device used in the image forming apparatus shown in FIG.

FIG. 15 is a diagram for explaining the operation of the pre-wetting device shown in FIG.

FIG. 16 is a diagram showing the flow of the pre-wet liquid when the pre-wet liquid supply body is brought into contact with the photoconductor.

[Explanation of symbols]

1, 2 image forming apparatus 10 photoconductor 20, 25 pre-wet device 30 charging device 40 exposure device 50, 55 developing device 51 pre-wet liquid recovery device 52, 58 developer recovery device 57 developer supply device 57a, 57b, 57c, 57d Development cartridge 60 Transfer device 70 Cleaning device 80 Static eliminator 202, 256, 502, 526 Tank 202a, 502a Supply roller 204, 504, 554a, 554b Conveying roller 206, 506a, 506b, 556 Coating roller 220 Pre-wet liquid 252 Pre-wet Liquid supply body 254 Case 258 Pump 260a, 260b Tube 262 Displacement device 302 Light-shielding plate 508, 508a, 508b, 508c, 508d, 5
09 liquid developer 510 developing roller 512 pre-wet liquid recovery roller 513, 515, 517, 519, 583, 608, 6
12,614,704 Power supply device 514, 580a, 580b, 580c, 580d
Developer collecting roller 520 Scraping blade 522, 524 Collecting tank 528 Density measuring device 530 Density adjusting device 552 Bellows pump 555 Adjusting roller 560 Developing roller 562a, 562b Driving roller 582 Rotating shaft 602 Intermediate transfer drum 604 Secondary transfer roller 606, 702 Removal roller 620 Fixing device 622 Fixing roller 624 Fixing heater

Claims (10)

[Claims] 1. A liquid developing method for an electrostatic latent image, which comprises developing an electrostatic latent image formed on an image support with toner, which is a charged image-forming particle, wherein the image supporting is carried out prior to a developing step. A pre-wetting process that applies a pre-wetting liquid, which is a chemically inactive dielectric liquid that has releasability to the body, and a high concentration of toner in the insulating liquid that is coated on the developer support. A repulsive force is exerted on the toner by the developing step of supplying the dispersed high-viscosity liquid developer of 100 to 10,000 mPa · s to the latent image surface of the image support and the electric field generated between the developer support. The pre-wet liquid recovery roller, to which a bias voltage is applied so as to work, is brought into contact with the developer support while rotating in the same direction as the rotation direction of the developer support, so that the developer during the developing step The press attached to the support A bias voltage was applied so as to exert an attractive force on the toner by an electric field generated between the pre-wet liquid collecting step of collecting and collecting the re-wetting liquid on the pre-wet liquid collecting roller. The liquid developer remaining on the developer support is recovered by contacting the developer recovery roller while rotating the developer recovery roller in a direction opposite to the rotation direction of the developer support. A liquid developing method for an electrostatic latent image, comprising: a developer collecting step of collecting the developer by attaching it to a roller. 2. A concentration measuring step of measuring a concentration of the liquid developer collected in the developer collecting step, and the liquid developer collected in the developer collecting step based on a result of the concentration measuring step. The liquid developing method for an electrostatic latent image according to claim 1, further comprising: a density adjusting step of adding toner to the toner to adjust the density. 3. The developer collecting step has a plurality of developer collecting rollers according to the color of the liquid developer, and according to the color of the liquid developer applied on the developer support. 3. The liquid developing method for an electrostatic latent image according to claim 1, wherein the developer collecting roller that is brought into contact with the developer support is switched. 4. The pre-wet liquid recovery step comprises contacting the pre-wet liquid recovery roller with the developer support through a liquid developer layer on the developer support. 2. The liquid developing method for an electrostatic latent image according to 2 or 3. 5. The liquid developer has an insulating liquid having a viscosity of 0.5 to 1000 mPa · s and an electric resistance of 10 ¹² Ωcm.
As described above, the surface tension is 21 dyn / cm or less and the boiling point is 100.
5. The temperature is not less than 0 ° C, Claims 1, 2, 3 or 4
A liquid developing method for an electrostatic latent image as described above. 6. A liquid developing method for an electrostatic latent image according to claim 5, wherein the liquid developer utilizes silicon oil as an insulating liquid. 7. The liquid developer has an average particle diameter of 0.1 to 5
The liquid developing method for an electrostatic latent image according to claim 1, 2, 3, 4, 5 or 6, characterized in that it contains a toner of µm in a concentration of 5 to 40%. 8. The pre-wetting liquid has a viscosity of 0.5 to
5 mPa · s, electric resistance 10 ¹² Ωcm or more, boiling point 1
The liquid developing method for an electrostatic latent image according to claim 1, 2, 3, 4, 5, 6 or 7, wherein the surface tension is from 00 to 250 ° C and 21 dyn / cm or less. 9. The liquid developing method for an electrostatic latent image according to claim 8, wherein the pre-wetting liquid contains silicon oil as a main component. 10. A liquid developing device for an electrostatic latent image, which develops an electrostatic latent image formed on an image support with toner, which is a charged image-forming particle, and has releasability on the image support. Prewetting means for applying a prewetting liquid which is a chemically inactive dielectric liquid, and 100 to 10,000 mPa in which the toner is dispersed at a high concentration in the insulating liquid applied on the developer support. -S developing means for supplying a high-viscosity liquid developer to the latent image surface of the image support, a pre-wet liquid recovery roller installed so as to contact the developer support, and the pre-wet liquid recovery The rotation driving means for rotating the roller in the same direction as the rotation direction of the developer support, and the electric field generated between the pre-wet liquid recovery roller and the developer support cause toner on the pre-wet liquid recovery roller. for Prewetting liquid recovery means having a voltage application means for applying a bias voltage so that repulsive force acts, a developer recovery roller installed so as to contact the developer support, and the developer recovery roller An attraction force is exerted on the toner on the developer collecting roller by a rotation driving means for rotating the developer supporting body in a direction opposite to the rotating direction and an electric field generated between the developer collecting roller and the developer supporting body. And a developer recovering unit having a voltage applying unit for applying a bias voltage to the liquid developing unit for electrostatic latent image.