JPH08328392A - Liquid developing device for electrostatic latent image and method therefor - Google Patents

Abstract

PURPOSE: To provide an liquid developing device for an electrostatic latent image and the developing device therefor capable of uniformly supplying liquid developer on the latent image of the image supporting body. CONSTITUTION: The liquid developing device for the electrostatic latent image, developing the electrostatic latent image formed on a photoreceptor 10 by toner is provided with a developing roller 510, means for applying the liquid developer 508 of high density-high viscosity stored in a tank 502 to the developing roller 510 through the feeding roller 502a and the transporting roller 504, and applying rollers 506a and 506b, and power source devices 513, 511 and 531 for applying voltage to the feeding roller 502a, the transporting roller 504, and the the applying rollers 506a and 506b, and moreover provided with the developing device 50 for feeding the liquid developer 508 applied on the developing roller 510 to the latent image surface on the photoreceptor 10.

Description

Detailed Description of the Invention

[0001]

The present invention relates to electrophotography, electrostatic recording,
The present invention relates to a liquid developing apparatus and a liquid developing method for an electrostatic latent image, which visualizes an electrostatic latent image formed by a method such as ionography using a liquid developer.

[0002]

2. Description of the Related Art Conventionally, in a liquid developing device for an electrostatic latent image which develops an electrostatic latent image formed on an image support with toner which is charged developing particles, a latent image on the image support is used. As a method of supplying the liquid developer to the surface, a method of forming unevenness on the surface of the developing roller which is a developer support, holding the liquid developer in the recess and supplying the image support to the image support, and a sponge roller to the developer support Method of supplying the liquid developer absorbed by the sponge roller to the image support by pressing the sponge roller against the image support, or immersing the image support in a developer tank in which the liquid developer is stored. Therefore, a method of directly supplying the liquid developer to the image support without using the developer support is used.

[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. Therefore, when such a high-concentration and high-viscosity liquid developer is used, it is not clear what method is suitable for supplying the liquid developer to the latent image surface of the image support.

[0004]

The present invention has been made in view of the above circumstances, and provides a liquid developing apparatus and a liquid developing method for an electrostatic latent image capable of uniformly supplying a liquid developer to the latent image surface of an image support. The purpose is to do.

[0005]

In order to solve the above-mentioned problems, a liquid developing device for an electrostatic latent image of the present invention is visualized particles that are charged with the electrostatic latent image formed on an image support. A liquid developing device for an electrostatic latent image, which is developed with toner, comprising: a developer support; and 100 to 10,000 mPa · s in which the toner is dispersed in a high concentration in an insulating liquid on the developer support.
a high-viscosity liquid developer of No. s is applied through a plurality of rollers, and a voltage applying means for applying a voltage to at least one of the plurality of rollers. And a developing means for supplying the liquid developer coated on the latent image surface of the image support.

Further, another electrostatic latent image liquid developing apparatus of the present invention develops the electrostatic latent image formed on the image support with toner, which is charged image-forming particles. A liquid developing device, comprising a developer support and a toner dispersed in insulating liquid at a high concentration of 100 to 10,000 mPa.
a plurality of rollers for contacting the high-viscosity liquid developer of s to the developer support to apply the liquid developer onto the developer support, and the liquid developer applied onto the developer support. It is characterized by comprising a developing means for supplying the latent image surface of the image support.

[0007]

The liquid electrostatic latent image developing device of the present invention is provided with a coating means for coating a high-concentration and high-viscosity liquid developer on the developer support through a plurality of rollers. Since the layer thickness of the liquid developer is regulated thinly and uniformly at the contact portion with the adjacent roller, it is possible to apply the highly concentrated and highly viscous liquid developer thinly and uniformly on the developer support. Also,
By providing voltage applying means for applying a voltage to at least one of the plurality of rollers, the electrostatic force acting between the charged toner and the roller to which the voltage is applied causes the liquid developer to reach the developer support. Can be adjusted, that is, the layer thickness of the liquid developer on the developer support can be adjusted. Further, the electrostatic latent image liquid developing apparatus of the present invention develops the liquid developer in which the toner is dispersed in a high concentration into a thin layer to develop the liquid developer, so that the liquid amount is smaller than that of the 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, 1000
A liquid developer of 0 mPa · s or more becomes unrealistic in terms of cost and becomes unrealistic. On the other hand, when it is 100 mPa · s or less, the toner concentration becomes low and the dispersibility of the toner becomes poor, so that it becomes impossible to develop the developer in a thin layer. The layer thickness of the liquid developer layer on the developer support is
When the toner concentration is high, the thickness needs to be thin, and when the toner concentration is low, the thickness needs to be thick. In addition, the higher the viscosity, the thinner it needs to be. However, when the layer thickness is thicker than 40 μm, excessive adhesion of toner occurs and image noise occurs. On the other hand, the layer thickness is 5
If the thickness is less than μm, unevenness occurs when a solid black image is output.

Further, another electrostatic latent image liquid developing apparatus of the present invention is provided with a plurality of rollers for abutting a high-concentration and high-viscosity liquid developer on the developer support to apply the developer on the developer support. As a result, uneven coating (waviness) caused by the influence of the viscosity of the liquid developer and the dispersibility of the toner can be made dense to form a more uniform liquid developer layer on the developing belt. Further, by developing the liquid developer in which the toner is dispersed at a high concentration in a thin layer and developing the same, the liquid amount is the same as that of the conventional low concentration liquid developer as in the liquid latent image developing device of the present invention. By comparison, it can be much less.

In the above electrostatic latent image liquid developing apparatus, the insulating liquid has a viscosity of 0.5 to 1000 mPa · s, an electric resistance of 10 ¹² Ωcm or more, and a surface tension of 21 dyn / cm or less.
When a liquid developer having a boiling point of 100 ° C. or higher 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 increases, so
Not suitable because it is treated as dangerous goods. Insulating liquid has a boiling point of 10
If the temperature is 0 ° C. or lower, the amount of evaporation increases, which causes a problem in the method for storing the developer, the entire device must be hermetically sealed, and it is difficult to improve the working environment. When the electric resistance is 10 ¹² Ωcm or less, the insulation becomes poor,
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. 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.

[0011]

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. FIG. 1 is a schematic configuration diagram of an image forming apparatus according to 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 device shown in FIG. FIG. 4 is a diagram for explaining the operation, and FIG. 4 is a diagram for explaining the operation of the image forming apparatus shown in FIG.

In the image forming apparatus according to the first embodiment of the present invention, the image support is charged with a charge having a polarity opposite to that of the toner, and then the image support is exposed to light to expose a reverse image, This is what is called normal development in which an electrostatic latent image to be visualized is formed in a portion which is not exposed, that is, a portion which is not made conductive. Image forming apparatus 1 of this embodiment
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. Charging device 30, an exposure device 40 that exposes an image on the photoconductor 10, and a developing process that visualizes the electrostatic latent image by supplying toner to a portion of the photoconductor 10 where the electrostatic latent image is formed. A device 50, a transfer device 60 for transferring a toner image formed on the photoconductor 10 onto a predetermined paper, and a photoconductor 10
Cleaning device 70 for removing the toner remaining on the top
And a neutralization device 80 for neutralizing the charged photoconductor 10.
Although not shown, a fixing device for fixing the toner image transferred to the paper is provided. The charging device 30 is the static eliminator 8
In order to prevent the influence of 0, the light shielding plate 302 is attached to the side surface on the side where the static eliminator 80 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 220 is applied to the surface of the photoconductor 10.
In order to apply a thin and uniform coating, the supply roller 202a,
It is desirable to use those having good lipophilicity as the transport roller 204 and the coating roller 206. As a roller with good lipophilicity, a ceramic roller (manufactured by Nippon Steel Co., Ltd.) that has been subjected to a special surface treatment on ceramics containing alumina and titania as a main component, BEET (manufactured by Miyagawa Roller Co., Ltd.) formed of synthetic resin, etc. is there.

As shown in FIG. 2, the developing device 50 of this embodiment has a developing roller 510 as a developer support, and coating rollers 506a and 506b for coating a surface of the developing roller 510 with a liquid developer 508 described later. And liquid developer 508
And a supply roller 502a for pumping up the liquid developer 508 stored in the tank 502.
A transport roller 504 that transports the liquid developer 508 supplied by the supply roller 502a to the application rollers 506a and 506b, a back plate 503 formed of a conductive member, and a power supply device 513 that applies a voltage to the supply roller 502a. A power source device 511 for applying a voltage to the transport roller 504, a power source device 531 for applying a voltage to the coating rollers 506a and 506b, and a layer thickness measuring device 53 for measuring the layer thickness of the liquid developer 508 on the developing roller 510. And the power supply devices 511, 51 based on the result of the layer thickness measuring device 53.
3, 541, and a pre-wetting liquid 2 that has moved from the photoconductor 10 to the developing roller 510 during development.
A pre-wet liquid recovery device 51 for recovering 20 and a developer recovery device 52 for recovering the liquid developer 508 remaining on the developing roller 510 after development are provided.

The developing roller 510 is installed so as to come into contact with the photoconductor 10 and rotates in a direction opposite to the direction of rotation of the photoconductor 10 so that the latent image surface of the photoconductor 10 is coated by the coating 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, foam such as NBR (nitrile butylene rubber) or low hardness such as silicon rubber or urethane rubber is used. There is a rubber member. However, the rubber member
Generally, when it is used for a long time in a state of being elastically deformed, it may be permanently deformed and may not return to its original shape, that is, a roller shape. 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. Further, as the heat-shrinkable tube having conductivity, PFA,
A resin tube such as 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 be able 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 to obtain an electric resistance value. Should be set to a desired value, that is, about 10 ³ Ωcm. The developing bias voltage is the toner and the developing roller 5
The electrostatic force (attractive force) that acts between the toner and the photosensitive member 10 is weaker than the electrostatic force (attractive force) that acts between the toner and the portion of the photosensitive member 10 on which the electrostatic latent image is formed. It must be set to be stronger than the electrostatic force (attractive force) that acts between the part where the electrostatic latent image is not formed.
In this embodiment, a positively charged toner is used as the liquid developer, and the developing bias voltage is set to -150V.

As shown in FIG. 3, the supply roller 502a is installed so that a part thereof is immersed in the liquid developer 508 in the tank 502, and by rotating in the direction opposite to the rotation direction of the conveying roller 504, , The liquid developer 508 stored in the tank 502 is pumped up, and the transport roller 5
Supply to 04. The power supply device 513 supplies a predetermined bias voltage based on a signal from the control means 54 to the supply roller 502.
applied to a. The back plate 503 is the supply roller 5
It is provided so as to cover a part of 02a and is grounded. As a result, an electric field is generated between the supply roller 502a and the back plate 503, and the amount of the liquid developer 508 drawn up from the tank 502 is adjusted by the electrostatic force acting on the toner. The bias voltage need not always be applied. When applying the liquid developer 508 to the developing roller 510, the liquid developer 508 with a desired liquid amount is applied.
Need only be performed in advance, as if the application rollers 506a and 506b have already been supplied.

The carrying roller 504, as shown in FIG.
It is provided so as to contact the supply roller 502a,
The liquid developer 508 supplied by the supply roller 502a is caused to rotate in a direction opposite to the rotation direction of the coating rollers 506a, 506b.
Transport to b. The power supply device 511 applies a predetermined bias voltage to the transport roller 504 based on the signal from the control means 54. As a result, an electric field is generated between the transport roller 504 and the supply roller 502a, and the electrostatic force acting on the toner adjusts the transport amount of the liquid developer 508 from the supply roller 502a to the transport roller 504.

As shown in FIG. 3, the application rollers 506a and 506b are provided so as to come into contact with the conveying roller 504 and the developing roller 510, and by rotating in the direction opposite to the rotating direction of the developing roller 510, the developing roller 510 develops. Roller 5
The liquid developer 508 transported by the transport roller 504 is applied to the surface of 10. The power supply device 531 applies a predetermined bias voltage to the application rollers 506a and 506b based on the signal from the control means 54. As a result, an electric field is generated between the application rollers 506a and 506b and the transport roller 504, and the electrostatic force acting on the toner causes the liquid developer 508 to flow from the transport roller 504 to the application roller 506.
The amount of liquid developer 508 applied to the developing roller 510 is adjusted by generating an electric field between the applying rollers 506a and 506b and the developing roller 510 while adjusting the amount of conveyance to the developing roller 510.

The supply roller 502a, the conveying roller 504, and the coating rollers 506a and 506b are used to supply the liquid developer 508 to the developing roller 510 because the toner is dispersed in a high concentration in this embodiment as described later. This is because, since the high-viscosity liquid developer 508 is used, it is necessary to apply a small amount of the liquid developer on the developing roller 510 thinly and evenly. By applying the liquid developer on the developer support through a plurality of rollers, the layer thickness of the liquid developer on each roller is thinly and uniformly regulated at the contact portion with the adjacent roller. A high-concentration and high-viscosity liquid developer can be thinly and uniformly applied onto the agent support. Further, the two application rollers 506a and 506b are used because the liquid developer 5 is used.
This is because the uneven coating (waviness) caused by the effect of the viscosity of 08 and the dispersibility of the toner is made dense to form a more uniform liquid developer layer on the developing roller. The number of coating 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 supply roller 502a, the transport roller 504, and the coating rollers 506a and 506b must have high electric resistance values. Electric resistance is 10 ⁸ to 10 ¹³
Ωcm is desirable. Electric resistance of 10 ⁸ Ωc
When it is m or less, when a bias voltage is applied, the roller is rapidly discharged to the adjacent roller, and the amount of pumping up the liquid developer 508 and the amount of conveyance thereof cannot be adjusted sufficiently. Particularly, since the coating rollers 506a and 506b contact the developing roller 510, it is necessary to sufficiently increase the electric resistance value of the developing roller 510. On the other hand, the electric resistance value is 10 ¹³ Ωc
When it is m or more, the charging becomes insufficient when the bias voltage is applied, and the amount of pumping up and the amount of transport of the liquid developer 508 cannot be sufficiently adjusted.

Supply roller 502a and coating roller 506
When a hard roller having a hardness of 60 ° (JIS A) or more is used for a and 506b, the conveyance roller 504 has a hardness of 60 ° (J
IS A) It is desirable to use the following soft rollers. By alternately arranging the hard roller and the soft roller in contact with each other in this manner, the soft roller is elastically deformed by the pressing force applied to the hard roller, and a nip is formed at the contact portion with the hard roller. By this nip, the liquid developer layer on each roller can be made uniform. In order to elastically deform the soft roller, the harder the harder the better. The hardness of the hard roller is preferably 90 ° (JIS-A) or more. Further, if the pressing force of the soft roller to the hard roller is strong, a high torque is required to rotate each roller. Therefore, it is preferable that the soft roller is elastically deformed by a weak pressing force. Hardness of soft roller is 40 ° (JIS-A)
The following is desirable. However, when the hardness is 15 ° (JIS-A) or less, it becomes difficult to maintain a constant shape, and thus it becomes difficult to form a nip at the contact portion with the hard roller.

The layer thickness measuring device 53 measures the light reflectance of the liquid developer 508 applied on the developing roller 510, and calculates the layer thickness based on this light reflectance. The controller 54 is
The voltage values of the power supply device 511, the power supply device 513, and the power supply device 531 are adjusted based on the layer thickness calculated by the layer thickness measurement device 53. As a result, an appropriate amount of liquid developer 508 is supplied to the developing roller 510. The power supply devices 511, 51
It is desirable that the voltage values of 3,531 can be controlled manually. According to the experiments by the present inventors, when positively charged toner is used as the liquid developer and the developing bias voltage applied to the developing roller 510 is set to −150 V, the bias voltage applied to each roller and the liquid developer are set. It was confirmed that there is a relationship shown in Table 1 with the coating amount of. Here, V ₁ is the bias voltage applied to the coating rollers 506a and 506b, V ₂ is the bias voltage applied to the transport roller 504, V ₃ is the bias voltage applied to the supply roller 502a, and V _p is the back plate 503. Represents the voltage of.

[0027]

[Table 1]

The pre-wet liquid collecting device 51 includes 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. In addition, the pre-wet liquid recovery roller 512
2, a bias voltage is applied by the power supply device 517, as shown in FIG. The bias voltage is 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. Thereby, only the pre-wet liquid 220 can be attached to the pre-wet liquid recovery roller 512.
In this embodiment, when the developing bias voltage was set to -150V, the bias voltage applied to the pre-wet liquid collecting roller 512 was set to -100 to -50V.

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. Developer collecting roller 514
Rotates in the direction opposite to the rotating direction of the developing roller 510.
Further, the developer collecting roller 514, as shown in FIG.
A bias voltage is applied by the power supply device 519.
The bias voltage is 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, when the developing bias voltage is set to -150V, the bias voltage applied to the developer collecting roller 514 is set to -250 to -200V.

As shown in FIG. 2, the liquid developer 508 attached to the developer collecting roller 514 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 is a liquid developer 508.
Is measured, and the toner density is calculated based on this light transmittance. The concentration adjusting device 530 is the concentration measuring device 52.
The liquid developer 50 stored in the tank 526 is collected in the liquid developer 508 based on the toner concentration calculated in step S8.
9 is mixed to adjust the toner density. Concentration adjustment device 53
The liquid developer 508 whose toner density is adjusted by 0 is
It 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 capable of coming into contact with and separated 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. . The hardness of the intermediate transfer drum 602 is 5 to 50 degrees JIS-A, preferably 15 to 40 degrees J.
It is preferably IS-A. Hardness is 5 degrees JIS-A
When it is below, it is difficult to maintain a constant shape because it is too soft. On the other hand, when the hardness is 50 degrees JIS-A or more, it is too hard. Therefore, when the toner image formed on the photoconductor 10 and the intermediate transfer drum 602 are brought into contact with each other, the photoconductor 1
There is a risk that the toner image on 0 will be crushed.

As the member forming the elastic layer of the intermediate transfer drum 602, 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, when a rubber member is used for many years in a state of being elastically deformed, it may be permanently deformed and may not return to its original shape, that is, a cylindrical shape. 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 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. These tubes are preferably resin tubes which are so-called endless tubes without joints, for example, tubes made of polyimide, PET or the like. If the elastic layer is formed of a rubber member such as urethane rubber or fluorosilicone rubber that does not swell in silicone oil, 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 of a transparent material, 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 adhesiveness between the intermediate transfer body and the recording medium can be improved by the elastic layer of the intermediate transfer drum 602 and the electrostatic force of the secondary transfer roller 604, so that the adhesiveness can be excellent regardless of the unevenness of the surface of the recording medium. Can be transcribed.

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 capable of coming into contact with and detaching from the intermediate transfer member 2 and contacting at the time of cleaning, and rotates in a 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 the intermediate transfer drum 6 is removed.
Remove from 02.

The cleaning device 70 of this embodiment includes 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 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, according to experiments conducted by the inventors, when the surface tension is large, fogging and toner lumps may adhere. 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 becoming dirty, 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 to blur the image. 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, the reversal image is exposed on the charged photoconductor 10 by the exposure device 40. For example, a reverse 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. 4C, 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.

Then, 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 way, by applying the liquid developer 508 through the plurality of rollers,
A uniform and thin liquid developer layer is formed on the developing roller 510. A bias voltage is applied to the supply roller 502a, the transport roller 504, and the coating rollers 506a and 506b by the power supply device 513, the power supply device 511, and the power supply device 531, respectively. As a result, the liquid developer 508
The amount of toner supplied to the developing roller 510 is adjusted. 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 to 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 part, and FIG. 9 is a diagram showing a separation process of the image part. 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 to 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, a developing roller 510 having elasticity is used, and the pressing force of the developing roller 510 on the photoconductor 10 is adjusted to form a liquid developer layer formed on the developing roller 510 and the photoconductor 10. The liquid developer layer and the pre-wet liquid layer are kept in contact with each other while maintaining the two-layer state by dispersing the contact pressure when the pre-wet liquid layer is brought into contact with the liquid developer layer. 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 and the sharpness and the resolution are lowered. Further, the toner tends to flow during development and the image tends to be blurred.
In experiments using DC344, 30 μm or less, especially 20 μm
Good results were obtained with a thickness of less than μm. 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 gap, 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 and the liquid developer layer, the liquid developer layer and the pre-wet liquid layer, and the pre-wet liquid layer and the photoconductor 10 are in contact with each other. 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 2 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-wetting 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,
The thickness 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., but even if the various developing conditions are optimized, there is a general tendency as shown in Table 2. It was confirmed that the optimum area of the liquid developer falls within the range shown in Table 2. The silicone oil of the pre-wet solution is DC200 series manufactured by Dow Corning, and the carrier liquid of the developer is DC345 manufactured by the same company.
Was used.

[0066]

[Table 2]

According to the first embodiment of the present invention, the supply roller 502a, the transport roller 504 and the coating roller 506a,
Liquid developer 50 on the developing roller 510 via 506b.
By applying No. 8, since the layer thickness of the liquid developer on each roller is thinly and uniformly regulated at the contact portion with the adjacent roller, the high concentration and high viscosity liquid developer 5 on the developing roller 510.
08 can be applied thinly and uniformly.

Further, according to the first embodiment of the present invention, the power supply device 51 for applying the bias voltage to the supply roller 502a.
3 and the back plate 503, which is connected to the ground, is provided in the developing tank 502, an electric field is generated between the supply roller 502a and the back plate 503, and the liquid developer is generated by the electrostatic force acting on the toner. The pumping rate of 508 can be adjusted. Further, since the liquid developer 508 in the developing tank 502 is drawn up by the electrostatic force, there is no limitation on the installation position of the developing tank 502, and therefore the degree of freedom in designing the image forming apparatus can be improved. Further, the power supply device 511 for applying a bias voltage to the transport roller 504 and the coating roller 50.
6a, 506b is provided with a power supply device 531 for applying a voltage, so that the electrostatic force acting between the toner and the conveying roller 504 and the toner and the applying roller 506a, 506b.
The amount of the liquid developer 508 applied to the developing roller 510, that is, the layer thickness of the liquid developer on the developing roller 510 can be adjusted by the electrostatic force acting between the developing roller 510 and the developing roller 510.

Further, according to the first embodiment of the present invention, the layer thickness measuring device 53 for measuring the light reflectance of the liquid developer layer on the developing roller 510 and calculating the layer thickness based on this light reflectance.
And the control device 54 that adjusts the voltage values of the power supply device 511 and the power supply device 513 based on the layer thickness calculated by the layer thickness measuring device 53, so that an appropriate amount of the liquid developer 508 is always supplied to the developing roller 510. Can be supplied to.

Further, according to the first embodiment of the present invention, by providing the two coating rollers 506a and 506b for coating the liquid developer 508 on the developing roller 510, the viscosity of the liquid developer 508 and the toner It is possible to form a more uniform liquid developer layer on the developing roller 510 by making the coating unevenness (waviness) caused by the influence of the dispersibility dense.

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 one.

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 this embodiment has a sufficiently large resistance value, the toner concentration can be increased. Also,
Generally, in the case of Isopar, the toner is well dispersed, and therefore even if the toner concentration is 1 to 2%, the toners repel each other, so that the toner is uniformly dispersed. On the other hand, silicone oil has a toner concentration of 1 to 2%,
The dispersibility is not good and it will precipitate 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, the amount of the developing solution can be significantly reduced as compared with the conventional low-concentration liquid developer, and the developing device can be downsized. 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.

Further, according to the first embodiment of the present invention, the pre-wetting device 20 for applying the pre-wetting liquid 220, which is a dielectric liquid having releasability and chemically inert, onto the photoconductor 10.
By providing the toner, it is possible to prevent the toner from adhering to the non-image portion of the photoconductor 10.

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. It should be noted that, in the second embodiment, those having the same functions as those in the first embodiment will be designated by the same reference numerals or corresponding reference numerals, and detailed description thereof will be omitted.

The image forming apparatus according to the second embodiment of the present invention uses so-called regular development, as in the image forming apparatus according to the first embodiment. Image forming apparatus 2 of this embodiment
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.
An exposure device 40 that exposes an image on the photoconductor 10, and a developing device 55 that visualizes the electrostatic latent image by supplying toner to a portion of the photoconductor 10 where the electrostatic latent image is formed. A transfer device 60 that transfers the toner image formed on the photoconductor 10 to a predetermined paper, a cleaning device 70 that removes the toner remaining on the photoconductor 10, and a neutralization device 80 that neutralizes the charged photoconductor 10. And a fixing device (not shown) for fixing the toner transferred to the paper.

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 a prewetting device 25 is used instead of the prewetting device 20, and a 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 photoconductor 10. 562a, 562b
A developer supply device 57 for applying the liquid developer 508 to the surface of the developing belt 560, and power supply devices 511, 513.
531, a layer thickness measuring device 53 for measuring the layer thickness of the liquid developer 508 on the developing belt 560, a control device 54 for controlling the power supply devices 511, 513, 531 based on the result of the layer thickness measuring device 53, and a developing device. A pre-wet liquid collecting device 51 that collects the pre-wet liquid 220 that has sometimes moved from the photoconductor 10 to the developing belt 560, and a developing belt 560 after development.
And a developer recovery device 58 for recovering the liquid developer 508 remaining on the upper side. The power supply devices 511, 51
3, 531, the control device 54, and the pre-wet liquid recovery device 51 are the same as those in the first embodiment.

The developing belt 560 is driven by the driving roller 562.
The liquid developer 508 supplied by the developer supplying device 57 is supplied to the surface of the photoconductor 10 by rotating in the opposite 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 preferably has an electric resistance value of about 10 ³ Ωcm so that an electric developing bias can be applied. 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 has conductivity, a rubber roller having a low electric resistance value, to which conductive particles are added so that a developing bias can be applied, is used as the driving rollers 562a and 562b. 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 developer supplying device 57 includes four developing cartridges 57a, 57b, 57c and 57d (hereinafter, also simply referred to as developing cartridges) and a separating / connecting device (not shown). Each developing cartridge supplies application rollers 506a and 506b that apply the liquid developer 508 to the surface of the developing belt 560, a tank 552 that stores the liquid developer 508, and a supply that pumps up the liquid developer 508 stored in the tank 552. A roller 502a and a transport roller 504 that transports the liquid developer 508 supplied by the supply roller 502a to the application rollers 506a and 506b.
And a back plate 503 formed of a conductive member,
It has. The supply roller 502a and the transport roller 5
04, the application rollers 506a and 506b, and the back plate 503 are the same as those in the first embodiment, and thus detailed description thereof will be omitted.

The liquid developer 508a containing yellow toner is stored in the tank 552 of the developing cartridge 57a, and the liquid developer 508b containing magenta toner is stored in the tank 552 of the developing cartridge 57b.
The liquid developer 508c containing cyan toner is stored in the tank 552 of c, and the liquid developer 508d containing black toner is stored in the tank 552 of the developing cartridge 57d.
Are stored respectively (hereinafter, liquid developer 508
a, 508b, 508c, and 508d are simply liquid developers 5
08). A separation / contact device (not shown) causes the application rollers 556a and 556b of each developing cartridge to contact the developing belt 560.

In the developer supplying device 57 having the above-mentioned structure, the applying / detaching device (not shown) causes the applying rollers 506a and 506b of one of the developing cartridges to connect to the developing belt 56.
The liquid developer 508 containing the toner of a desired color is applied to the surface of the developing belt 560 by bringing it into contact with 0.

The developer collecting device 58 is constructed by attaching four developer collecting rollers 580a, 580b, 580c, 580d (hereinafter, also simply referred to as developer collecting rollers) to a rotating shaft 582. The rotating shaft 582 uses a driving device (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 580d is rotationally driven so as to be in 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. This bias voltage is applied to the developing belt 560 and the developing belt 56.
The toner is set to be attracted to the developer collecting roller by the electric field generated between the developer collecting roller and the developer collecting roller that is in contact with zero.

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.

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 reversal 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. Liquid developer 508 stored in tank 552
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 belt 560. In this way, by applying the liquid developer 508 through the plurality of rollers,
A uniform and thin liquid developer layer is formed on the developing belt 560. A bias voltage is applied to the supply roller 502a, the transport roller 504, and the coating rollers 506a and 506b by the power supply device 513, the power supply device 511, and the power supply device 531, respectively. As a result, the liquid developer 508
The amount of toner supplied to the developing belt 560 is adjusted. It should be noted that the developing belt 560 is applied to the applying rollers 506a, 50 of either of the developing cartridges by a separating / connecting device (not shown).
The liquid developer 508 containing any one of yellow, magenta, cyan, and black toners can be applied to the developing belt 560 by bringing 6b into contact with each other.

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 belt 560 during development is recovered by the pre-wet liquid recovery device 51. Also, after development, the development belt 56
Liquid developer 508 remaining on top of the developer
To collect each color.

Next, the toner image formed on the photoconductor 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, the application roller 506 that contacts the developing belt 560 by a separation / contact device (not shown).
By switching a and 506b and repeating the cycle from the charging to the discharging again, the toner images of yellow, magenta, cyan, and black are successively superposed on the intermediate transfer drum 602, and 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 recording medium, that is, paper. 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, the photoconductor 10
A toner image corresponding to colorization is formed on the intermediate transfer drum 602 by sequentially performing a process of primary transfer of the toner image formed on the intermediate transfer drum 602 for each color of yellow, magenta, cyan, and black. After that, since the toner image corresponding to colorization formed on the intermediate transfer drum 602 is secondarily transferred to the recording medium, compared to the case where the toner images formed on the photoconductor are sequentially transferred to paper directly. Therefore, it is not necessary to consider the misalignment of the paper, so that it becomes easy to match the registration of the color image transferred to the paper. Other effects are similar to those of the first embodiment.

In the first and second embodiments described above, the image support is charged with a charge having a polarity opposite to that of the toner, and then the image support is exposed to light to expose a reverse image, A description has been given of what uses so-called regular development, which forms an electrostatic latent image to be visualized in a portion that is not exposed to light, that is, a portion that is not made conductive, but the present invention is not limited to this. , The latent image to be visualized on the light-exposed portion of the image support by exposing the image support to light with an electric charge having the same polarity as the toner, and then exposing the image support to light It is also possible to use a so-called reversal development for forming. The inventors of the present invention set the developing bias voltage to 500 V by using positively charged toner in the apparatus to which the reversal development is applied, and find that the bias voltage applied to each roller is between the coating amount of the liquid developer. It was confirmed that the relationships shown in Table 3 exist. here,
V ₁ is the bias voltage applied to the coating rollers 506 a and 506 _b , V ₂ is the bias voltage applied to the transport roller 504, V ₃ is the bias voltage applied to the supply roller 502 a, and V _P is the voltage of the back plate 503. It represents.

[0096]

[Table 3]

Next, the third embodiment of the present invention will be described with reference to FIG.
And FIG. 18 will be described. FIG. 17 is a schematic configuration diagram of an image forming apparatus according to a third embodiment of the present invention, and FIG. 18 is a diagram showing timings of application of a developing bias voltage and contact / separation of a coating roller. Incidentally, in the third embodiment, those having the same functions as those in the second embodiment are designated by the same reference numerals or corresponding reference numerals, and detailed description thereof will be omitted.

In the image forming apparatus according to the third embodiment of the present invention, the image support is charged with a charge having the same polarity as the toner, and then the image support is exposed to light to expose a regular image,
The so-called reversal development is used to form an image to be visualized on the light-exposed portion of the image support. The image forming apparatus 3 of this embodiment differs from the image forming apparatus 2 of the second embodiment shown in FIG. 13 in that the photoconductor 10 is replaced with a charging device 30 that is charged with an electric charge having a polarity opposite to that of the toner. That is, the charging device 30a that charges 10 with the electric charge having the same polarity as the toner is used, and the developing device 55a is used instead of the developing device 55. The other structure is the same as that of the second embodiment, and the detailed description thereof is omitted.

The developing device 55a of this embodiment differs from the developing device 55 of the second embodiment in that, as shown in FIG. 17, from the contact point P of the developing belt 560 with the photosensitive member 10 to the coating roller of the developing cartridge 57d. The length L to the contact point Q with 506a is longer than the maximum value of the length of the latent image that can be formed on the photoconductor 10, and the developing bias voltage is applied to the developing belt 560 only at the time of developing. Is. In this embodiment, a positively charged toner is used as the liquid developer, and the developing bias voltage is set to 500V.

Timing of application of the developing bias voltage and separation / contact of the coating rollers 506a and 506b in the developing device 55a having the above structure will be described with reference to FIG.
Here, V _B is the developing bias voltage, R ₁ is the applying rollers 506a and 506b of the developing cartridge 57a, and R ₂ is the applying rollers 506a and 506 of the developing cartridge 57b.
b and R ₃ are coating rollers 506 of the developing cartridge 57c
a, 506b, and R ₄ are developing cartridges 57d
The coating rollers 506a and 506b of FIG. Also,
In R _{1 to} R ₄ , high represents a state of contact with the developing belt 560, and low represents a state of being separated from the developing belt 560. The developing device 55a of this embodiment is shown in FIG.
As shown in 8, the developing bias voltage (50
0 V) is applied and the application roller 506
a, 506b developing belt 56 of liquid developer 508
0 is supplied before the developing process, that is, the developing belt 5
This is performed when the developing bias voltage is not applied to 60. This is to prevent the application of the liquid developer 508 to the developing belt 560 from being disturbed by the developing bias voltage having the same polarity as the toner applied to the developing belt 560. In the developing device 55a of the present embodiment, as described above, the length L from the contact point P of the developing belt 560 with the photosensitive member 10 to the contact point Q of the developing cartridge 57d with the coating roller 506a is set to the photosensitive member 10a.
Is longer than the maximum value of the latent image that can be formed on the coating roller 506a, the application of the developing bias voltage and the coating roller 506a,
Even when the separation / contact timing of 506b is set as shown in FIG. 18, the amount of the liquid developer 508 necessary for the latent image surface of the photoconductor 10 is set.
Can be supplied.

Regarding the operation of the image forming apparatus 3 of this embodiment, the image forming apparatus 2 of the second embodiment uses normal development, whereas the image forming apparatus 3 of this embodiment uses reversal development. Except for the points, it is basically the same as the image forming apparatus 2 of the second embodiment. Therefore, detailed description of the operation of the image forming apparatus 3 of the present embodiment will be omitted.

According to the third embodiment of the present invention, the length L from the contact point P of the developing belt 560 with the photoconductor 10 to the contact point Q of the developing cartridge 57d with the coating roller 506a.
Is longer than the maximum value of the length of the latent image that can be formed on the photoconductor 10, and the developing bias voltage is applied only during development, so that the application of the liquid developer 508 to the developing belt 560 is prevented. It can be prevented from being disturbed by the developing bias voltage having the same polarity as the toner applied to 560. As a result, the absolute value of the bias voltage applied to the application rollers 506a and 506b, the transport roller 504, and the supply roller 502a can be reduced, so that the liquid developer 5 can be formed with a simple configuration.
The supply amount of 08 to the developing belt 560 can be adjusted. Other effects are similar to those of the second embodiment.

In the first to third embodiments described above, the bias voltage is applied to the supply roller 502a, the conveying roller 504 and the coating rollers 506a and 506b to supply the liquid developer 508 to the developer support. Although the adjustment of the amount has been described, the present invention is not limited thereto. It suffices that the amount of the liquid developer 508 supplied to the developer support is adjusted by applying a bias voltage to at least one of these rollers. For example, the bias voltage may be applied only to the supply roller 502a.

Next, a fourth embodiment of the present invention will be described with reference to FIG.
Will be described with reference to. FIG. 19 is a schematic configuration diagram of an image forming apparatus according to the fourth embodiment of the present invention. Incidentally, in the fourth embodiment, those having the same function as the second embodiment,
The detailed description will be omitted by giving the same reference numerals or corresponding reference numerals.

The image forming apparatus according to the fourth embodiment of the present invention uses so-called reversal development, like the image forming apparatus according to the third embodiment. The image forming apparatus 4 of the present embodiment is different from the image forming apparatus 2 of the second embodiment shown in FIG. That is, the charging device 30a that charges 10 with the electric charge having the same polarity as the toner is used, and the developing device 55b is used instead of the developing device 55. The other structure is the same as that of the second embodiment, and the detailed description thereof is omitted.

The developing device 55b of this embodiment is different from the developing device 55 of the second embodiment in that, as shown in FIG. 502a
That is, the ground terminal of the power supply device 513 for applying the bias voltage to the developing belt 560 is set to the same potential. This is to prevent the application of the liquid developer 508 to the developing belt 560 from being disturbed by the developing bias voltage having the same polarity as the toner applied to the developing belt 560. In this embodiment, similarly to the apparatus of the third embodiment, the positively charged toner is used as the liquid developer and the developing bias voltage is set to 500V.

Regarding the operation of the image forming apparatus 4 of this embodiment, the image forming apparatus 2 of the second embodiment uses normal development, whereas the image forming apparatus 4 of this embodiment uses reversal development. Except for the points, it is basically the same as the image forming apparatus 2 of the second embodiment. Therefore, detailed description of the operation of the image forming apparatus 4 according to the present exemplary embodiment will be omitted.

According to the fourth embodiment of the present invention, by applying the coating rollers 506a, 506b and the conveying roller 504 to the same potential as the developing belt 560, the developing belt 560 is coated with the liquid developer 508. It can be prevented from being disturbed by the developing bias voltage having the same polarity as the toner applied to 560. Other effects are similar to those of the second embodiment.

In the fourth embodiment described above, the coating roller 5
06a and 506b and the conveyance roller 504 are connected to the developing belt 5.
However, the present invention is not limited to this, and any roller to which a bias voltage is not applied may be made to have the same potential as the developing belt 560. For example, when applying a bias voltage to the transport roller 504, the application rollers 506a, 506
It is only necessary that b and the supply roller 502a have the same potential as the developing belt 560.

Further, in the above-described second to fourth embodiments, as the developer supplying device, the developing cartridge 57a for applying the liquid developer 508a containing the yellow toner onto the developing belt 560 and the magenta toner are used. A developing cartridge 57b for applying the liquid developer 508b containing the toner, a developing cartridge 57c for applying the liquid developer 508c containing the cyan toner, and a developing cartridge 57d for applying the liquid developer 508d containing the black toner are provided. However, the present invention is not limited to this. 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-mentioned embodiments, the case where the image is exposed on the image support by the exposure device and then the pre-wet liquid is applied on the image support by the pre-wet device has been described. Is not limited to this, and the application of the pre-wetting 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 liquid developer is applied to the developer support through the supply roller, the transport roller and the application roller in order to supply the liquid developer to the developer support in the developing device. However, the present invention is not limited to this, and the developing device may be any device that applies the liquid developer onto the developer support through at least two rollers. For example, two or more transport rollers may be provided between the supply roller and the application roller, or the liquid developer drawn up by the supply roller may be directly supplied to the application roller without providing the transport roller. It may be. Further, it is not always necessary to internally install the back plate in the tank that stores the liquid developer. Further, the developer support is not limited to the one used in each of the above-mentioned 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 the two-layer state, It is necessary to use a flexible belt-shaped member for the body or to install the developing roller so that a minute gap, that is, a space d is formed between the developing roller and the photosensitive drum. is there.

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

Further, in each of the above 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.

[0117]

As described above, according to the liquid electrostatic latent image developing device of the present invention, the coating means for coating the high density and high viscosity liquid developer on the developer support through the plurality of rollers. By providing the above, since the layer thickness of the liquid developer on each roller is regulated thinly and uniformly at the contact portion with the adjacent roller,
A high-concentration and high-viscosity liquid developer can be thinly and uniformly applied on a developer support, and a voltage applying means for applying a voltage to at least one roller among a plurality of rollers is provided to be charged. The amount of liquid developer conveyed to the developer support can be adjusted by the electrostatic force acting between the toner and the roller to which a voltage is applied. It can be uniformly supplied to the latent image surface of the support, and by developing the liquid developer in which the toner is dispersed in a high concentration in a thin layer, it is possible to achieve high resolution and easy downsizing, and to reduce the size. It is possible to provide a liquid developing device for an electrostatic latent image that can be made pollution.

According to another electrostatic latent image liquid developing apparatus of the present invention, a plurality of rollers for contacting a high-concentration and high-viscosity liquid developer to the developer support and applying it on the developer support are provided. As a result, it is possible to prevent unevenness in the density of the liquid developer layer on the developer support due to the influence of the viscosity of the liquid developer and the dispersibility of the toner. Can be thinly and uniformly applied with a high-concentration and high-viscosity liquid developer, and therefore, the liquid developer can be uniformly supplied to the latent image surface of the image support, and the toner can be dispersed in a high concentration. By developing the liquid developer in a thin layer and developing the liquid developer, it is possible to provide a liquid developing device for an electrostatic latent image, which has high resolution, can be easily downsized, and can reduce pollution.

[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 the operation of the developing device 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.

FIG. 17 is a schematic configuration diagram of an image forming apparatus that is a third embodiment of the present invention.

FIG. 18 is a diagram showing the timing of application of a developing bias voltage and separation / contact of a coating roller.

FIG. 19 is a schematic configuration diagram of an image forming apparatus that is a fourth embodiment of the present invention.

[Explanation of symbols]

1, 2, 3, 4 Image forming apparatus 10 Photoreceptor 20, 25 Pre-wet apparatus 30, 30a Charging apparatus 40 Exposure apparatus 50, 55, 55a, 55b Developing apparatus 51 Pre-wet liquid collecting apparatus 52, 58 Developer collecting apparatus 53 Layer thickness measuring device 54 Control device 57 Developer supply device 57a, 57b, 57c, 57d Development cartridge 60 Transfer device 70 Cleaning device 80 Static eliminator 202, 256, 502, 552 Tank 202a, 502a Supply roller 204, 504 Conveying roller 206, 506a, 506b 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 503 Back plate 508, 508a, 508b, 508c, 508d, 5
09 liquid developer 510 developing roller 512 pre-wet liquid collecting roller 511, 513, 515, 517, 519, 531, 5
83, 608, 612, 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 560 Developing belt 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 (13)

[Claims] 1. A liquid developing apparatus for an electrostatic latent image, which develops an electrostatic latent image formed on an image support with toner, which is a charged developing particle, comprising: a developer support; Toner having a high concentration dispersed in an insulating liquid on an agent support 100 to 10,000 mPa
A coating means for applying the high-viscosity liquid developer of s through a plurality of rollers, and a voltage applying means for applying a voltage to at least one of the plurality of rollers,
A liquid developing device for an electrostatic latent image, comprising: a developing means for supplying the liquid developer coated on the developer support to the latent image surface of the image support. 2. The developing means includes a layer thickness measuring means for measuring a layer thickness of the liquid developer applied on the developer support, and the layer thickness measuring means for measuring the layer thickness based on the layer thickness measured by the layer thickness measuring means. 2. A liquid developing device for an electrostatic latent image according to claim 1, further comprising control means for controlling a voltage applying means. 3. The coating means comprises a developer tank for storing the liquid developer and a conductive plate provided in the developer tank, wherein the first-stage roller among the plurality of rollers is Part is arranged so as to be immersed in the liquid developer stored in the developer tank, and the voltage applying means is
3. The liquid electrostatic latent image developing device according to claim 1, wherein a voltage is applied between the first-stage roller and the conductive plate. 4. A length from a contact position between the last roller of the plurality of rollers and the developer support to a contact position between the developer support and the image support is defined as the image support. The developer is made longer than the maximum value of the electrostatic latent image that can be formed on the developer, and the developer is applied only when the liquid developer coated on the developer support is supplied to the latent image surface of the image support. 4. A liquid developing device for an electrostatic latent image according to claim 1, wherein a developing bias voltage is applied to the support. 5. All of the plurality of rollers, except the roller to which the voltage is applied by the voltage applying means, are kept at substantially the same potential as the developing bias voltage applied to the developer support. Claim 1, characterized in that
2. A liquid developing device for an electrostatic latent image according to 2, 3 or 4. 6. A liquid developing apparatus 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, comprising: a developer support; A plurality of rollers for applying a high-viscosity liquid developer of 100 to 10000 mPa · s in which a toner is dispersed in a liquid at a high concentration to the developer support so as to be applied to the developer support; A liquid developing device for an electrostatic latent image, comprising: a developing means for supplying the liquid developer coated on the developer support to the latent image surface of the image support. 7. A pre-wetting means for applying a pre-wetting liquid, which is a dielectric liquid having releasability and chemically inert, to the image support. , 2, 3, 4, 5 or 6, the electrostatic latent image liquid developing device. 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 device for an electrostatic latent image according to claim 7, which has a surface tension of 21 dyn / cm or less at 00 to 250 ° C. 9. The liquid developing device for an electrostatic latent image according to claim 8, wherein the pre-wetting liquid contains silicon oil as a main component. 10. The liquid developer has an insulating liquid viscosity of 0.5 to 1000 mPa · s and an electric resistance of 10 ¹² Ωc.
m or more, surface tension 21 dyn / cm or less, boiling point 10
It is 0 degreeC or more, The claim 1, 2, 3,
4. A liquid developing device for an electrostatic latent image according to 4, 5, 6, 7, 8 or 9. 11. The liquid developing device for an electrostatic latent image according to claim 10, wherein the liquid developer uses silicon oil as an insulating liquid. 12. The liquid developer has an average particle size of 0.1 to 0.1.
5. A toner containing 5 .mu.m at a concentration of 5 to 40%, wherein the toner is 5 to 40%.
8. A liquid developing device for an electrostatic latent image according to 8, 9, 10 or 11. 13. A liquid developing method of an electrostatic latent image, which comprises developing a latent electrostatic image formed on an image support with toner, which is a charged image-forming particle, wherein the developer is formed through a plurality of rollers. 100 to 10 in which toner is dispersed in a high concentration in an insulating liquid applied on a support.
A liquid developer having a high-viscosity liquid developer of 000 mPa · s is supplied to the latent image surface of the image support, and a voltage is applied to at least one of the plurality of rollers to obtain the liquid. A liquid developing method for an electrostatic latent image, which comprises adjusting the amount of developer conveyed to the developer support.