JP2002268394A - Wet-type imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wet-type imaging device by which an image having a high quality is formed, without markedly lowering the developer concentration at reusing liquid developer and also by preventing fogging of the image. SOLUTION: In the wet-type imaging device, which possesses a latent image carrier to carry a latent image on a surface and a developer carrier for carrying a liquid developer 60, constituted by dispersing toner in carrier liquid on the surface and by which the latent image carried by the latent image carrier, is developed with the liquid developer 60 carried on the developer carrier; and a cleaning means for recovering excess toner on the latent image carrier is provided on a downstream side from an area at which developing is performed in the moving direction of the surface of the latent image carrier, and also the cleaning means mainly recovers the toner and also enables the carrier liquid to remain on the latent image carrier.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wet image forming apparatus used for an electrophotographic dry copying machine, a printer, a facsimile, and the like, and more particularly, to a high-viscosity, high-concentration liquid developer in which a toner is dispersed in a carrier liquid. And a coating member for applying the liquid developer to the developer carrying member, and the liquid developer carried on the developer carrying member is provided on the latent image carrying member. The present invention relates to a wet image forming apparatus for developing a latent image formed on a transfer member, transferring the developed image to a transfer member, transferring the transferred image to a recording member, and removing a developer remaining on the image support.

[0002]

2. Description of the Related Art Conventionally, Japanese Patent Application Laid-Open No. 7-295339 discloses a constitution in which an insulating liquid is applied (pre-wet) on a latent image carrier in advance of development, and at the same time, the latent image carrier is charged. An image forming method has been proposed. In this image forming method, a nip portion is formed by bringing a flexible developer carrier into contact with a latent image carrier. Then, a thin layer of liquid developer is formed on the developer carrier, and the insulating liquid, the carrier liquid and the toner in the thin layer form a latent image on the latent image carrier forming the nip portion. Is electrostatically transferred to the image area of FIG. On the other hand, the carrier liquid and the insulating liquid are slightly transferred to the background portion (non-image portion) on the latent image carrier passing through the nip portion without adhering toner.

[0003]

However, in the image forming method proposed in Japanese Patent Application Laid-Open No. 7-295339,
Since the insulating liquid to be pre-wetted is always positively supplied while performing the charging process, surplus insulating liquid is supplied as a result. For this reason, with the movement of the latent image carrier via the latent image carrier to which the insulating liquid has adhered, the insulating liquid tends to become excessive throughout the entire image forming process, and the insulating liquid becomes the developer. When the developer is reused, the concentration of the developer is significantly reduced.

The present invention has been made in view of the above background, and an object of the present invention is to provide a wet image forming apparatus capable of forming a high quality image while preventing image fogging. .

[0005]

In order to achieve the above object, a wet image forming apparatus according to claim 1 includes a latent image carrier for carrying a latent image on a surface thereof, and a toner in a carrier liquid on a surface thereof. A developer carrier carrying the dispersed liquid developer, and developing the latent image carried by the latent image carrier with the liquid developer carried on the developer carrier. In the wet-type image forming apparatus, a cleaning unit that collects excess toner on the latent image carrier is provided downstream of the developing area in the latent image carrier surface moving direction, and the cleaning unit includes:
The present invention is characterized in that the toner is mainly collected and the carrier liquid is left on the latent image carrier.

According to the first aspect of the present invention, the toner particles remaining on the photoreceptor serving as the latent image carrier are collected, and the carrier liquid is left on the photoreceptor, thereby pre-printing the photoreceptor. It is possible to keep it in a wet state. For this reason,
It is not necessary to apply an extra insulating liquid also serving as a carrier liquid to the photoreceptor, and it is possible to prevent the developer concentration from remarkably lowering when the developer is reused. In addition, prior to the developing process, the surface of the photoreceptor, which is a latent image carrier, can be maintained in a pre-wet state with a carrier liquid. There is sufficient carrier liquid between the developing roller and the photoreceptor as the latent image carrier, and the toner transfers according to the electric field formed by the latent image, so that excess toner adheres to the non-image area. Can be developed. Thus, fogging of the image due to the excess toner can be prevented.

[0007] In the wet image forming apparatus of the second aspect,
In the wet image forming apparatus according to claim 1, the liquid developer carried by the developer carrier is a toner in which charged toner particles, which are visualized particles, are dispersed at a high concentration in an insulating liquid that is a carrier liquid, 100 to 10000 mPa · s, preferably 10
It is a liquid developer having a high viscosity of 0 to 5000 mPa · s.

According to the second aspect of the present invention, even in a wet image forming apparatus using a high-viscosity, high-concentration liquid developer, as in the first aspect of the present invention, the surplus insulating liquid is transferred to the latent image carrier. Since it is not necessary to apply the liquid developer to the photoconductor, it is possible to prevent the high concentration of the liquid developer from being significantly reduced.

According to a third aspect of the present invention, there is provided a wet image forming apparatus.
Alternatively, in the wet image forming apparatus of the second aspect, the cleaning unit is configured to be capable of applying a voltage.

According to the third aspect of the present invention, the cleaning means can generate an electrostatic force by applying a voltage, and the charged residual toner particles can be efficiently removed from the photosensitive member as the latent image carrier. it can.

According to a fourth aspect of the present invention, there is provided a wet image forming apparatus.
The wet image forming apparatus according to any one of the first to third aspects, further comprising a transport unit that transports the liquid developer containing the toner collected by the cleaning unit to a developing device that includes the developing carrier.

According to the present invention, the developer containing the toner collected by the cleaning means can be returned to the developing device by the transport means, and the liquid developer can be collected and reused.

According to a fifth aspect of the present invention, there is provided a wet image forming apparatus.
In any of the wet image forming apparatuses according to any one of the first to fourth aspects, the cleaning unit is configured by a rotatable cylindrical member formed of an elastic body.

According to the fifth aspect of the present invention, a nip portion can be formed by pressing the cleaning means against the photoreceptor serving as a latent image carrier, and residual toner particles are passed while passing through the nip portion. Since the time for attaching to the cleaning means can be secured, the toner of the developer can be easily removed and collected from the photoreceptor. Further, since the shape of the cleaning unit is cylindrical, the configuration for pressing may be a simple configuration that only applies a pressing force to the rotating shaft, and furthermore, the toner is continuously removed only by rotating the cleaning unit. It becomes possible to collect.

According to a sixth aspect of the present invention, there is provided a wet image forming apparatus.
In any of the wet image forming apparatuses according to any one of the first to fifth aspects, a plate member is in contact with the cleaning unit in order to remove a liquid developer containing the collected toner adhered to the cleaning unit.

According to the present invention, the plate-like member removes the liquid developer containing the toner removed from the latent image carrier held by the cleaning means from the surface of the cleaning means. The agent can be collected more efficiently.

According to a seventh aspect of the present invention, there is provided a wet-type image forming apparatus.
In the wet image forming apparatus, the rotatable cylindrical member formed of the elastic body is constituted by a cored bar and one or more laminated structures.

According to the seventh aspect of the present invention, since the columnar member is constituted by a layer made of a plurality of materials, the elasticity and electric resistance of the entire columnar member can be optimized by the combination of the materials. This makes it possible to stably contact the columnar member with the photoconductor, which is a latent image carrier, and to exhibit appropriate electrical characteristics required for cleaning.

[0019] The wet image forming apparatus according to claim 8 is the fifth embodiment.
Alternatively, in the wet image forming apparatus according to 7, the volume resistance of the rotatable cylindrical member formed of the elastic body is 10 ⁹ Ωc.
m or less.

According to the present invention, when a voltage is applied to the cleaning means, it is possible to uniformly generate electric charges on the surface of the cleaning means. Thus, the toner can be efficiently adsorbed and removed from the latent image carrier.

According to a ninth aspect of the present invention, in the wet image forming apparatus of the fifth, seventh and eighth aspects, the hardness of the rotatable cylindrical member formed of the elastic body is 50 degrees (JI).
SA) It is characterized by the following.

According to the ninth aspect of the present invention, when the cylindrical member as the cleaning means is pressed against the photosensitive member as the latent image carrier, which occurs when the hardness is greater than 50 degrees (JIS-A). The carrier liquid can be prevented from passing through between the columnar member and the photoconductor, and the columnar member can stably contact the latent image carrier. Pre-wet of the photoconductor can be realized.

According to a tenth aspect of the present invention, there is provided the wet image forming apparatus according to any one of the fifth to ninth aspects, wherein the rotatable cylindrical member formed of the elastic body is made of a foam and has a hardness of 60 degrees. (ASKER-C).

According to the tenth aspect, when the rotatable columnar member formed of the elastic body is formed of a foam, the hardness is 60 degrees (ASKA-C) as in the ninth aspect.
In the following cases, the cylindrical member can stably contact the latent image carrier, so that the transfer of the residual toner to the cleaning unit and the pre-wetting of the photoconductor can be realized. .

The wet image forming apparatus according to claim 11 is the wet image forming apparatus according to any one of claims 5, 7 to 10,
The rotatable cylindrical member formed of the elastic body does not have the property of swelling or impregnating the carrier liquid of the developer.

According to the eleventh aspect of the present invention, the columnar member as the cleaning means swells in the carrier liquid of the developer,
Because it is not impregnated, deterioration of the cleaning means can be prevented,
A stable cleaning operation can be maintained.

[0027] According to a twelfth aspect of the present invention, there is provided a wet image forming apparatus according to any one of the fifth to seventh aspects,
A rotatable cylindrical member surface formed of the elastic body,
It is characterized by having a property as a release layer with respect to a carrier liquid of a developer.

According to the twelfth aspect of the invention, when the residual toner adheres to the columnar member as the cleaning means, the carrier liquid can be prevented from adhering to the surface of the columnar member, and the carrier liquid can be adhered to the surface of the latent image carrier. While efficiently recovering the toner.

A wet image forming apparatus according to a thirteenth aspect is the wet image forming apparatus according to any one of the fifth to seventh aspects,
The surface of the rotatable cylindrical member formed of the elastic body has a smoothness of Rz 3 μm or less.

According to the thirteenth aspect of the present invention, the cylindrical member serving as the cleaning means and the photosensitive member serving as the latent image carrier can be brought into more close contact with each other. The toner can be more efficiently transferred to the cleaning unit.

According to a fourteenth aspect of the present invention, there is provided a wet image forming apparatus as defined in any one of the fifth to seventh to thirteenth aspects.
The rotatable columnar member made of the elastic body is made of a material mainly composed of urethane resin.

According to the fourteenth aspect of the present invention, it is possible to easily achieve the elastic performance and the swelling resistance and impregnation resistance of the developer with respect to the carrier liquid, which are required for the cleaning means, and are efficient and deteriorated. Cleaning can be provided.

The wet image forming apparatus according to claim 15 is the wet image forming apparatus according to any one of claims 5, 7 to 14,
The surface layer of the rotatable columnar member formed of the elastic body is a film layer having a thickness of 100 μm or less.

According to the fifteenth aspect of the present invention, it is possible to easily achieve the elastic performance and the swelling resistance and impregnation resistance of the developer with respect to the carrier liquid, which are required for the cleaning means, and are efficient and deteriorated. Cleaning can be provided.

The wet image forming apparatus according to claim 16 is the wet image forming apparatus according to any one of claims 5, 7 to 15,
The surface layer of the rotatable columnar member made of the elastic body is a film layer having a volume resistance of 10 ⁹ Ωcm or less.

According to the sixteenth aspect of the present invention, when a voltage is applied to the cleaning means, it is possible to uniformly generate electric charges on the surface of the cleaning means. Thus, the toner can be efficiently adsorbed and removed from the latent image carrier.

According to a seventeenth aspect of the present invention, in the wet image forming apparatus according to any one of the first to sixteenth aspects, an insulating liquid serving as a carrier liquid is supplied to the cleaning means, and the latent liquid is supplied through the cleaning means. It is characterized in that the insulating liquid is applied on the image carrier.

According to the seventeenth aspect of the invention, the insulating liquid is supplied to the cleaning means and applied to the photosensitive member as the latent image carrier, thereby facilitating the transfer of the residual toner to the cleaning means. At the same time, it becomes possible to replenish the carrier liquid which is reduced in the transfer step or the like during the image forming process, and stable image formation can be achieved.

[0039]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to an electrophotographic image forming apparatus (hereinafter, simply referred to as an image forming apparatus) which is a wet image forming apparatus will be described below.

First, a schematic configuration of the image forming apparatus will be described. FIG. 1 is a schematic configuration diagram of a main part of an image forming apparatus according to the present embodiment. In the figure, the image forming apparatus includes a charger 20, an exposure device (not shown) for irradiating the photosensitive drum 1 with an exposure L, a wet developing device 100, an intermediate transfer belt 31 around a photosensitive drum 1 as a latent image carrier. And a transfer device including a transfer roller 32 and the like, a static elimination lamp 40, a cleaning device 50, and the like.

The material of the photosensitive drum 1 is amorphous silicon (a-Si), organic photosensitive member (OPC)
Etc. can be used.

The charger 20 may be of a type in which a charging roller to which a charging bias is applied is brought into contact with a photosensitive drum, in addition to the corona discharger as shown in FIG.

The exposure apparatus can use an array of LEDs or a laser having a scanning optical system, or a light image from an illuminated original of a copying machine.

The transfer device includes an intermediate transfer belt 31, a transfer roller 32 for stretching the belt, a plurality of stretch rollers 33, and a transfer bias having a polarity opposite to the charging polarity of the toner. And a power source (not shown) for applying the intermediate transfer belt 31. The endless movement of the intermediate transfer belt 31 is performed in the direction of the arrow in FIG. The intermediate transfer belt 31 is pressed by the transfer roller 32 toward the photosensitive drum 1 to form a transfer nip. A transfer electric field is formed in the transfer nip by a potential difference between the transfer roller 32 to which the transfer bias is applied and the surface of the photosensitive drum 1. The toner image that has entered the transfer nip with the rotation of the photosensitive drum 1 is primarily transferred onto the intermediate transfer belt 31 under the action of the transfer electric field and the nip pressure. Then, the toner image thus primarily transferred is secondarily transferred to transfer paper in a region (not shown).

The transfer device may be configured to transfer the toner image on the photosensitive drum 1 directly to the transfer paper from the photosensitive drum 1 without using the intermediate transfer belt. As a transfer method, a method using an electrostatic roller such as the transfer roller 32, a method using corona discharge,
An adhesive transfer method, a thermal transfer method, or the like can be used.

A case where an image is formed by reversal development in the image forming apparatus having the above configuration will be described. The photosensitive drum 1 is driven to rotate at a constant speed in the direction of the arrow at the time of copying by a driving means such as a motor (not shown). After being uniformly charged to about 600 V in the dark by the charger 20, a light image corresponding to the image is irradiated by the exposure device, and the electrostatic latent image is carried on the outer peripheral surface of the photosensitive drum 1.
Thereafter, while passing through the developing device 100, the electrostatic latent image is developed with the charged toner adhered thereto.

The toner image formed on the photosensitive drum 1 is transferred to transfer paper by a transfer device. Thereafter, the charge remaining on the surface of the photosensitive drum 1 is removed from the photosensitive drum 1 by the charge removing lamp 40. Then, the toner remaining on the surface of the photosensitive drum 1 is removed by the cleaning device 50. After that, before charging by the charger 20 in the next image forming step, the residual potential may be removed from the surface of the photosensitive drum 1 again by a not-shown discharging lamp, if necessary.

The transfer paper on which the toner image has been transferred passes through a fixing device (not shown) to fix the toner on the transfer paper. Then, the transfer paper on which the toner image has been fixed is discharged out of the apparatus from the fixing device via a paper discharge path. As the fixing device, for example, a fixing method such as heat and pressure fixing, solvent fixing, pressure fixing, and UV fixing can be used.

The developer used in the image forming apparatus of the present embodiment is a low-viscosity, low-concentration liquid developer generally used and commercially available, for example, an insulating material called Isopar (trade name: manufactured by Exxon). 1w in ionic liquid carrier
This is not a low-viscosity liquid developer of about 1 cSt containing a toner of about t% concentration, but a high-viscosity, high-concentration liquid developer. The high-viscosity, high-concentration liquid developer refers to a toner having a concentration of about 5 to 40 wt% in an insulating liquid carrier such as silicone oil, normal paraffin, IsoparM (trade name: manufactured by Exxon), vegetable oil, or mineral oil. Is a liquid developer having a viscosity of about 100 to 5000 cSt. The volatility and non-volatility of such a high-viscosity, high-concentration liquid developer used in the developing device 100 is adjusted in accordance with the developing performance of the developing device 100 and the image forming performance of the image forming apparatus. Further, the particle size of the toner is similarly adjusted from submicron to about 6 μm.

Next, the developing device 100, which is a feature of the present embodiment, will be described. The developing device 100 includes a tank unit 101, stirring screws 102 and 103, anilox roller 104, regulating blade 105, developing roller 106,
The developing unit 109 includes a cleaning blade 107, a return unit 108, and the like, and a sweep unit 112 including a sweep roller 110, a cleaning blade 111, and the like.

Development roller 106 and sweep roller 110
Are provided with cleaning blades 107 and 111 made of a metal blade or a rubber blade, respectively. Instead of each cleaning blade, a roller-type cleaning member may be used. Further, the anilox roller 104 is provided with a regulating blade 105.

Each of the developing roller 106 and the sweep roller 110 has an elastic layer having conductivity on the outer peripheral surface. Conductive urethane rubber can be used as the material of these elastic layers. The rubber hardness of each elastic layer is preferably 50 degrees or less in JIS-A hardness. The material of each elastic layer is not limited to urethane rubber, but may be any material that has conductivity and does not swell or dissolve in a solvent.

Further, instead of providing the elastic layer on the developing roller 106 and the sweep roller 110, an elastic layer may be provided on the photosensitive drum 1. Further, the photosensitive member may be constituted by an endless belt-shaped member instead of the drum.

The sweep roller 110 is formed by coating or a tube so that the surface thereof has a smoothness of Rz 3 μm or less.

When the developing roller 106 and the sweep roller 110 are respectively brought into contact with the photosensitive drum 1 with an appropriate pressure, the elastic layer of each roller is elastically deformed to form a developing nip and a removing nip. In particular, by forming the developing nip, it is possible to secure a certain developing time for the toner of the developer to move and adhere to the photosensitive drum 1 by the developing electric field in the developing area. Further, by using a contact / separation cam 113 provided on the sweep portion 112 as shown in FIG. 1, the entire sweep portion is moved toward and away in the direction of the photosensitive drum 1, the contact pressure is adjusted, and the surface at the nip portion is adjusted. The nip width, which is the size in the moving direction, can be adjusted. The means for adjusting the nip width provided in the sweep unit 112 includes a developing unit 109 including the developing roller 106.
Can also be provided.

Each nip width is set to be equal to or more than the product of the linear velocity of each roller and the development time constant. Here, the development time constant is
This is the time required until the development amount is saturated, and is obtained by dividing the nip width by the process speed. For example, if the nip width is 3 mm and the process speed is 300 mm / sec, the development time constant is 10 msec.

The thin layer of the developer formed on the surface of the developing roller 106 is
06 through the development nip formed. Generally, in an electrophotographic developing device, the surface moving speed of the developing roller is set to be faster than the surface moving speed of the photoconductor in order to send a sufficient amount of toner to an area between the photoconductor and the developing device. For this reason, since the toner has a high moving speed with respect to the surface of the photoreceptor, a positional shift occurs between the toner and the latent image. Phenomenon appears. This phenomenon is also observed in liquid development. In the image forming apparatus according to this embodiment, the surface of the developing roller 106 and the photosensitive drum 1
The surface of the photosensitive drum 1 moves at a substantially constant speed and does not have a velocity vector in the tangential direction of the photosensitive drum 1 relative to the toner, so that the above phenomenon does not occur.

A developing bias voltage (about 400 V) lower than the photoconductor surface potential (for example, about 600 V in the case of the charger 20) is applied to the developing roller 106. A developing electric field is generated between the developing roller and the image surface where the photoconductor surface potential has become 50 V or less. In the image portion of the photoconductor drum 1, the toner in the developer moves to the photoconductor drum 1 by the above-described developing electric field to visualize the latent image. On the other hand, in the background portion (non-image portion), the toner is moved to the surface side of the developing roller 106 by the electric field formed by the developing bias potential and the photoconductor surface potential so that the toner does not adhere to the background portion on the photoconductor drum. To do.

However, if a part of the toner in the background does not move to the surface of the developing roller 106 and remains on the photosensitive drum 1 side, it causes fogging. Therefore, the developing device 100 of the image forming apparatus according to the present embodiment is provided with the sweep roller 110 for sweeping (cleaning) toner causing the fog (hereinafter, referred to as excess toner). The sweep roller 110 is located on the downstream side in the rotation direction of the photosensitive drum 1 with respect to the developing roller 106, and sandwiches the developed toner layer so as to sandwich the developed toner layer.
It is installed by pressing. The surface of the sweep roller 110 moves at substantially the same speed as the surface of the photosensitive drum 1.

The sweep roller 110 applies a toner layer surface potential (100 to 2) on the photosensitive drum 1 so that toner from the toner layer after development is not returned to the sweep roller 110.
A bias voltage (250 V) close to 00 V) is applied. In the background portion, the surplus floating toner is removed by the sweep roller 110 by an electric field generated by a difference between the potential of the background portion of the photosensitive drum 1 and the potential due to the bias voltage.
Move to At this stage, the developer layer in the background portion is about half the thickness of the developing nip portion of the developing roller 106, and the toner density is reduced to about 20% of the density before development. Is easily done. This allows
Fog on the background can be completely prevented.

By installing the sweep roller 110, about half of the excess carrier liquid adhering to the background on the photosensitive drum 1 during development can be removed.

Further, since excess toner can be efficiently removed by the sweep roller 110, a small amount of excess toner may remain in the developing nip between the photosensitive drum 1 and the developing roller 106, and the fog removing electric field (developing electric field) Roller 106
(The potential difference between the developing bias applied to the photosensitive member and the charged potential of the photosensitive member) can be kept low. Therefore, the charging potential of the photosensitive drum 1 can be reduced. As a result, various advantages such as improvement of the durability of the photosensitive drum 1, reduction of the load on the charging roller 2, and reduction of the exposure power are obtained.

In the image forming method described in the prior art, it is possible to simultaneously perform the development and the removal of the excess toner on the background by the developer carrier. However, this requires a relatively long development time (for example, about 40 msec).
Needs to be secured, and it is necessary to increase the width of the developing nip formed between the latent image carrier and the developer carrier.
In addition, in this conventional image forming method, the nip portion is formed by bringing the developer carrier having the elastic layer into contact with the latent image carrier, so that the contact pressure is increased in order to increase the development nip width. Tends to be large. On the other hand, in the developing device 100 of the image forming apparatus according to the present embodiment, since the sweep roller 110 is provided, the functions of development and removal of excess toner can be separated in the development roller 106, and the development nip The width can be made smaller than before, and the contact pressure can be made smaller (for example, 0.3 kgf / mm or less). As a result, the photosensitive drum 1, the developing roller 10
6 and the sweep roller 110 can be reduced, and the durability of the entire apparatus can be improved.

In the above embodiment, the case where an image is formed by reversal development has been described. However, an image can be formed by regular development. In the case of regular development, the relationship between the potentials in the image forming apparatus is, for example, the photoconductor surface potential is 600 V, the toner layer potential is 200 to 300 V,
The potential between the photosensitive drum 1 and the sweep roller 110 is set to 200 V, the potential between the photosensitive drum 1 and the developing roller 106 is set to 100 V, and the non-image portion potential is set to 50 V.

The toner image visualized on the photosensitive drum 1 as described above is transferred to a transfer member such as an intermediate transfer belt in the transfer device. A transfer bias is applied to the transfer member, and the toner particles on the photosensitive drum 1 are transferred to the transfer member by electrostatic force. However, the residual toner remaining on the photoreceptor without being transferred is collected by the cleaning device 50 through the charge removing step of the charge removing lamp 40.

Hereinafter, the cleaning device 50 which is a feature of the image forming apparatus of the present invention will be described. As shown in FIG. 2, the cleaning device 50 according to the present invention is formed of a columnar member (hereinafter, referred to as a cleaning roller 51), and as shown in FIG. Have been. Further, the cleaning roller 51 adsorbs the residual toner by electrostatic force as described later, the adsorbed toner on the cleaning roller is removed by a cleaning blade 52, and a developer such as the removed toner is transported by a transport screw (not shown). Collected at. The collected developer is returned to the developing device 100 through a communication unit (not shown) and is reused.

The cleaning roller 51 cannot clean all of the developer adhering to the photosensitive member. That is,
The toner particles in the developer are collected by the cleaning roller 51 by the electrostatic force, but the carrier component remains on the photoreceptor substantially in half.

The carrier component remaining on the photoreceptor covers the photoreceptor as a pre-wet layer before development. That is,
Passes through the cleaning roller 51 in the cleaning process,
The carrier remaining on the photoreceptor functions as a release layer at the time of next development. Therefore, in order to suppress the toner from adhering to the background portion, which is a non-image portion, there is little background contamination,
In addition, since the pre-wet liquid such as the insulating liquid is not positively applied unlike the related art, the developer concentration can be controlled so that the developer concentration does not decrease.

In the present invention, it is also possible to use a charging roller capable of applying a pre-wet liquid described in JP-A-7-295339, which is a conventional technique. According to the method, the carrier and the like remain on the photoreceptor to form the pre-wet layer, so that a corona charger can be used for the charger 20 of the photoreceptor. This makes it possible to perform non-contact charging, so that the developing process can be started without disturbing the pre-wet layer. Further, by applying an insulating layer to the photoconductor, deterioration of the photoconductor due to charging and sparking can be prevented.

In the embodiment of the present invention, in order to match the peripheral speed between the photosensitive member and the cleaning roller 51, the driving force of the photosensitive member is particularly adjusted to be coaxial with the cleaning roller 51 via a drive transmission system (not shown). The driving force is transmitted to the fixed drive gear 53, and the cleaning roller 51 is driven to rotate. On the other hand, the cleaning roller 51 is pressed and deformed to form a nip portion between the photosensitive member and the cleaning roller 51 as shown in FIG. Therefore, when the cleaning roller 51 is pressed and deformed, the ratio between the peripheral speed of the photosensitive member surface and the peripheral speed of the cleaning roller 51 is 1: 1 or less, and the surface speed of the photosensitive member and the cleaning roller There is a difference in the surface speed of the surface 51. Since the cleaning roller 51 is deformed and rotated, the actual surface speed of the cleaning roller is slightly lower than the surface speed of the photoconductor. Therefore, in order to match the difference between the surface speed of the photoconductor and the surface speed of the cleaning roller 51 to the surface speed of the photoconductor,
When a one-way clutch is provided for the drive gear 53 and the surface speed of the cleaning roller 51 is low, the cleaning roller 51 rotates by contact with the surface of the photoconductor, and the drive gear 53 and the shaft of the cleaning roller 51 slide. Therefore, the surface speeds of the photoconductor and the cleaning roller 51 match. Naturally, the one-way clutch is disposed so as to slide in the rotation direction of the cleaning roller. The introduction of the one-way clutch allows the cleaning roller to rotate satisfactorily even when the frictional resistance between the photoconductor and the cleaning roller 51 is large, such as when the developer is not attached on the photoconductor. Can be.

The cleaning roller 51 has a length substantially equal to the width of the image drawn on the photoconductor, and as shown in FIG. 4, a core metal 51 made of a rigid material such as stainless steel.
a, an elastic layer 51b having elasticity formed around the cored bar 51a, and a surface layer 5 formed on the surface of the elastic layer 51b.
1c. As the elastic member forming the elastic layer 51b, polystyrene, polyethylene, polyurethane, polyvinyl chloride, NBR (nitrile / butylene rubber)
Or a low-hardness rubber member such as silicone rubber or urethane rubber. The surface layer 51c is formed of a conductive member that does not swell in silicon oil or the like which is a carrier liquid of a liquid developer described later, for example, a conductive urethane rubber material.

When a voltage for removing residual toner from the core metal 51a of the cleaning roller is applied to the cleaning roller, for example, an elastic layer made of a synthetic rubber-based binder in which conductive particles such as carbon black are dispersed is used. 51
b, comprising a surface layer 51c of a conductive film layer,
The electric resistance of the cleaning roller is desirably 10 ⁹ Ωcm or less. As a method of applying the voltage, as shown in FIG. 2, the end surface of the core metal which is also the shaft 56 of the cleaning roller is pressed by a leaf spring 55 such as a phosphor bronze plate,
By contact, a voltage for removing residual toner was applied. In particular, although a leaf spring has been described as a bias applying unit of the cleaning roller, the present embodiment is not limited to this.

Further, the elastic material having conductivity often increases in hardness due to dispersion of conductive particles such as carbon black, and a desired resistance value may not be obtained when importance is placed on elasticity. . In such a case, the cleaning roller surface layer 51c may be made of a material having a volume resistance of 10 ⁹ Ωcm or less, and a bias may be applied by directly contacting the electrode from the surface of the cleaning roller. It is also possible to apply a voltage for removing residual toner by pressing a leaf spring such as a phosphor bronze plate on the surface of the cleaning roller and making contact therewith, but the conductive cleaning blade 52 is used as a bias application electrode. They may be combined. In particular, although a leaf spring has been described as a bias applying unit of the cleaning roller, the present embodiment is not limited to this.

When a wearable copper material is provided on the plate spring of the electrode in contact with the end face of the core metal as the bias applying means, the contact between the core metal and the electrode affects the contamination of the core metal due to the wear of the copper material. Instead, stable contact is possible, and the voltage for removing residual toner can function stably.

As a method of forming the surface layer 51c on the surface of the elastic layer 51b of the cleaning roller, for example, a method of coating the surface of the cleaning roller 51b with a synthetic rubber-based composite in which conductive particles such as carbon black are dispersed. There is a method of covering the cleaning roller 51b with a heat-shrinkable tube having conductivity and applying heat to the heat-shrinkable tube. Further, the elastic layer 51b of the cleaning roller may be formed inside the surface layer 51c by injecting an elastic material into the inside of the tube having conductivity or foaming the injected elastic material. As the conductive tube, polyimide, polycarbonate,
A resin tube such as nylon or a metal tube such as nickel is used. As the heat-shrinkable tube having conductivity, a resin tube such as PFA or PTFE is used. In particular, the PFA and PTFE tubes having a volume resistance of about 10 ⁹ Ωcm in order to prevent the developer from adhering to the cleaning roller 51 exhibited a good effect.

Further, the surface layer 51 is applied to the cleaning roller.
By forming c, it is possible to suppress the increase in hardness due to the impregnation of the elastic material with the carrier liquid and the addition of the conductive additive. In particular, it is desirable that the tube forming the surface layer 51c be a seamless endless tube. The elastic layer 51b of the cleaning roller
May be formed of an elastic member such as urethane rubber which does not swell in silicone oil. In this case, it is not necessary to form the surface layer 51c on the surface of the elastic layer 51b of the cleaning roller. However, in this case, in order to apply an electrical bias to the cleaning roller, the surface of the elastic layer 51b of the cleaning roller is conductively processed, or conductive fine particles are formed on the elastic member forming the elastic layer 51b of the cleaning roller. , It is necessary to make the electric resistance value a desired value.

Further, as shown in FIG. 3, the cleaning roller 51 is disposed so as to contact the photosensitive member.
The photoconductor rotates in a direction opposite to the rotation direction of the photoconductor, that is, in a direction following the photoconductor. As shown in FIG. 3, the cleaning roller 51 has a nip width t formed by elastic deformation caused by the pressing force of the cleaning roller 51 against the photosensitive member. The hardness of the cleaning roller 51 is
It is preferable that the angle is 50 degrees or less (JIS-A) or less.
Good results were obtained below the degree (JIS-A). If the hardness of the cleaning roller 51 is 50 degrees or more (JIS-A) or more, the carrier liquid cannot pass between the cleaning roller 51 and the photosensitive member because it is too hard. Cannot be realized. As will be described later, conditions for obtaining a desired nip are determined by the diameter of the photoconductor, the diameter of the cleaning roller, and the hardness of the cleaning roller.

The cleaning roller 51 and the photosensitive member need to be installed so as to form a nip width t. Further, a nip width t generated by the elastic deformation of the cleaning roller 51.
Is set in relation to a movement time constant defined by an electric circuit including a capacitance and a resistance component formed by the cleaning roller 51, the developer layer, and the photoconductor.
In order to adjust the pressing force of the cleaning roller 51 against the photosensitive member, as shown in FIG. 2, abutting rollers 54 that contact the photosensitive member are disposed on both sides of the cleaning roller 51, and the abutting rollers having different outer diameters are arranged. 54. As shown in FIG. 5, when the outer diameter of the abutting roller 54 changes, the difference from the outer diameter of the cleaning roller 51 changes, and the contact amount s between the cleaning roller 51 and the photosensitive member changes. If an appropriate nip width t can be realized, the lower the pressing force between the photoconductor and the cleaning roller 51, the lower the carrier is, because the carrier easily passes through the cleaning process (between the photoconductor and the cleaning roll).

When the elastic material of the cleaning roller 51 is solid, the thickness of the film tube on the surface is 100 μm.
If it is larger than m, sufficient elasticity cannot be obtained. Therefore, the thickness of the film tube on the surface needs to be 100 μm or less. Further, the cleaning roller 5
When the outer diameter of No. 1 was 24φ, a good effect was obtained with a film layer having a thickness of 70 μm. Also, the cleaning roller 51
When the elastic material is a foam, the average pore diameter of the foam is desirably 300 μm or less.

Further, if a release layer capable of repelling the carrier liquid is provided on the surface of the cleaning roller 51, the carrier component further remains on the photoreceptor and functions well as a pre-wet layer in the developing step.

The cleaning roller 51 is moved to the photosensitive drum 1
When they are brought into contact with each other at an appropriate pressure, the elastic layer 51b of the roller is elastically deformed to form a cleaning nip. In particular, by forming the cleaning nip, a certain moving time for the residual toner in the developer to move from the photosensitive drum 1 to the cleaning roller 51 by the electric field in the cleaning area and adhere to the cleaning roller is secured. can do. Further, by adjusting the contact pressure of the cleaning roller 51 with the photosensitive drum 1, the nip width, which is the size of the nip portion in the surface movement direction, can be adjusted. The nip width is set to be equal to or more than the product of the linear speed of the roller and the movement time constant. Here, the moving time constant is a time required until the developing amount is saturated, and is obtained by dividing a nip width by a process speed. For example, if the nip width is 3 mm and the process speed is 300
If it is mm / sec, the moving time constant is 10 msec.

The cleaning roller 51 is provided with a conductive elastic layer 51b on the outer peripheral surface. Urethane rubber can be used as a material of these elastic layers 51b. As the rubber hardness of each elastic layer 51b,
The JIS-A hardness is desirably 50 degrees or less. The material of each elastic layer 51b is not limited to urethane rubber, but may be any material that has conductivity and does not swell or dissolve in a solvent. When the elastic layer is made of foam, the hardness is 60 degrees (ASKER-
C) By performing the following, stable contact between the cleaning roller 51 and the photoconductor becomes possible. Further, instead of providing the elastic layer on the cleaning roller 51, an elastic layer may be provided on the photoconductor side. further,
The photoconductor may be composed of an endless belt-shaped member. The cleaning roller 51 is formed by coating or a tube so that the surface thereof has a smoothness of Rz 3 μm or less.

Further, in this embodiment, the developer concentration detecting means
(Not shown) or a developer amount detecting means (not shown) measures the concentration and amount of the developer inside the developing device 100, and based on the amount and concentration value of the developer, additionally supplies the developer or the carrier liquid. are doing. Therefore, it is clear that the amount of the carrier adhered / remaining on the photoconductor before the cleaning varies depending on the configuration and use condition of the image forming apparatus. Moreover, when the amount of the carrier liquid is small, it tends to be difficult to clean the residual toner particles of the untransferred developer. Therefore, toner particles can be satisfactorily collected by separately applying the carrier liquid to the cleaning roller 51. Further, when the toner concentration of the developer increases, the carrier liquid is positively applied to the cleaning roller 51 to increase the amount of the carrier liquid remaining on the surface of the photoreceptor. Over time, the developer concentration can also be adjusted.

As a means for applying the carrier liquid, a porous body is impregnated with the carrier liquid and applied to the cleaning roller 51. As shown in FIG. 6, the function required of the carrier liquid application device 57 of the present embodiment is to apply a constant amount of the carrier liquid uniformly on the photoreceptor via the cleaning roller 51. For that purpose, a method of applying the carrier liquid by a sponge-like thing, a method of discharging the carrier liquid from a plurality of nozzles arranged in the width direction of the cleaning roller, a method of applying the carrier liquid by a sponge roller, and the like, Various methods for coating liquids on other surfaces can be used. The present inventors have tried various methods and confirmed that the above method is feasible. However, the simplest and most efficient method is to use a carrier liquid such as Belita (trade name: manufactured by Kanebo Co., Ltd.). Was applied. Bel eater is a continuous porous body having a three-dimensional network structure in which pores are continuous, can hold the carrier liquid by the volume of the pores, and when the carrier liquid exceeding the pore volume is supplied, the carrier liquid is removed. It can be released uniformly from the surface. FIG.
As shown in FIG. 7, the bell eater of this embodiment has a substantially semi-cylindrical contact surface with the cleaning roller 51.

It is preferable that the amount of the carrier liquid applied to the cleaning roller 51 is substantially equal to or less than the amount of the carrier adhering to the recording paper. The amount of the carrier liquid adhering to the photoconductor after passing through the sweep roller 110 is 0.2 mg / cm when the amount of the developer adhering on the developing roller 106 is 0.8 mg / cm ^2.
It was ² . Further, the carrier liquid on the photoconductor is transferred to the transfer belt 31. This transfer amount is estimated to be 0.1 mg / cm ² . Therefore, the amount of the carrier liquid applied to the cleaning roller is preferably equal to or less than the amount of the carrier liquid transferred to the transfer belt, for example, 0.1 mg / cm ² . The carrier transferred to the transfer belt 31 is transferred to a recording medium or collected by a transfer belt cleaning (not shown) and discarded or recycled. In the case of recycling, it is necessary to remove toner particles remaining in the carrier liquid. Therefore, the developer cannot be immediately fed back to the developing device 100 and must be temporarily stored in a buffer such as a tank.

[0086]

According to the first aspect of the present invention, the toner particles remaining on the photoreceptor, which is a latent image carrier, are collected, and the carrier liquid is left on the photoreceptor. Can be kept in a pre-wet state. For this reason, it is not necessary to apply an extra insulating liquid also serving as a carrier liquid to the photoreceptor, and it is possible to prevent a significant decrease in the developer concentration even when the developer is reused. In addition, prior to the developing process, the surface of the photoreceptor, which is a latent image carrier, can be maintained in a pre-wet state with a carrier liquid. There is sufficient carrier liquid between the developing roller and the photoreceptor as the latent image carrier, and the toner transfers according to the electric field formed by the latent image, so that excess toner adheres to the non-image area. Can be developed. This allows
Image fogging due to the excess toner can be prevented.

Further, according to the second aspect of the present invention, even in a wet image forming apparatus using a high-viscosity, high-concentration liquid developer, as in the first aspect of the present invention, surplus insulating liquid is latently discharged. Since there is no need to apply the liquid developer to the photoconductor, it is possible to prevent the high concentration of the liquid developer from being significantly reduced.

According to the third aspect of the present invention, the cleaning means can generate an electrostatic force by applying a voltage, and the charged residual toner particles can be efficiently removed from the photosensitive member as the latent image carrier. be able to.

According to the fourth aspect of the invention, the developer containing the toner collected by the cleaning means can be returned to the developing device by the transport means, and the liquid developer can be collected and reused. .

According to the fifth aspect of the present invention, the nip portion can be formed by pressing the cleaning means against the photosensitive member as the latent image carrier, and the residual toner is passed while passing through the nip portion. Since the time for the particles to adhere to the cleaning unit can be secured, the toner of the developer can be easily removed and collected from the photoreceptor. Further, since the shape of the cleaning unit is cylindrical, the configuration for pressing may be a simple configuration that only applies a pressing force to the rotating shaft, and furthermore, the toner is continuously removed only by rotating the cleaning unit.
It becomes possible to collect.

According to the sixth aspect of the present invention, the plate-like member removes the liquid developer containing the toner removed from the latent image carrier held by the cleaning means from the surface of the cleaning means. The liquid developer can be collected more efficiently.

According to the seventh aspect of the present invention, since the columnar member is constituted by a layer made of a plurality of materials, the elasticity and electric resistance characteristics of the entire columnar member can be changed depending on the combination of the materials. It is possible to set optimally, and it is possible to stably contact the columnar member with the photoconductor, which is a latent image carrier, and to exhibit appropriate electrical characteristics required for cleaning.

According to the eighth aspect of the present invention, when a voltage is applied to the cleaning means, it is possible to uniformly generate electric charges on the surface of the cleaning means. The resulting electric field makes it possible to efficiently adsorb and remove from the latent image carrier.

According to the ninth aspect of the present invention, the hardness is 5
When the cylindrical member serving as the cleaning means is pressed against the photosensitive member serving as the latent image carrier, the carrier liquid is not generated between the cylindrical member and the photosensitive member when the cylindrical member serving as the cleaning means is generated at a temperature larger than 0 degree (JIS-A). Since the passage can be prevented and the cylindrical member can stably contact the latent image carrier, the transfer of the residual toner to the cleaning unit and the pre-wetting of the photoconductor can be realized.

According to the tenth aspect of the present invention, when the rotatable cylindrical member formed of the elastic body is formed of a foam, the hardness is 60 degrees (ASKA) as in the ninth aspect.
-C) In the following cases, the cylindrical member can stably contact the latent image carrier, so that the transfer of the residual toner to the cleaning unit and the pre-wetting of the photoconductor can be realized.

According to the eleventh aspect of the present invention, since the cylindrical member as the cleaning means does not swell or impregnate with the carrier liquid of the developer, deterioration of the cleaning means can be prevented, and a stable cleaning operation can be maintained.

According to the twelfth aspect of the present invention, when the residual toner adheres to the cylindrical member as the cleaning means, it is possible to prevent the carrier liquid from adhering to the surface of the cylindrical member.
The toner can be efficiently collected while leaving the carrier liquid on the surface of the latent image carrier.

According to the thirteenth aspect of the present invention, the cylindrical member serving as the cleaning means and the photosensitive member serving as the latent image carrier can come into closer contact with each other.
The residual toner sandwiched between the two can be more efficiently transferred to the cleaning unit side.

According to the fourteenth aspect of the present invention, it is possible to easily achieve the elasticity and the swelling resistance and impregnation resistance of the developer with respect to the carrier liquid, which are required for the cleaning means. In addition, cleaning with less deterioration can be provided.

According to the fifteenth aspect of the present invention, it is possible to easily achieve the elasticity and the swelling resistance and impregnation resistance of the developer with respect to the carrier liquid, which are required for the cleaning means. In addition, cleaning with less deterioration can be provided.

According to the sixteenth aspect of the present invention, when a voltage is applied to the cleaning means, it is possible to uniformly generate electric charges on the surface of the cleaning means.
The charged residual toner is efficiently adsorbed by the electric field generated by the charge, and can be removed from the latent image carrier.

Further, according to the seventeenth aspect of the present invention, the insulating liquid is supplied to the cleaning means and applied to the photosensitive member which is a latent image carrier, thereby facilitating transfer of residual toner to the cleaning means side. At the same time, it becomes possible to replenish the carrier liquid that decreases in the transfer step and the like during the image forming process, and stable image formation can be achieved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a positional relationship between a member and a region arranged around a photoconductor drum with respect to a photoconductor surface.

FIG. 2 is a perspective view of a cleaning roller.

FIG. 3 is a diagram illustrating a positional relationship between a cleaning roller and a photoconductor.

FIG. 4A is a cross-sectional view of a cleaning roller having a surface layer. (B) is sectional drawing of the cleaning roller which does not have a surface layer.

FIG. 5 is a diagram illustrating a relationship between an outer diameter of a cleaning roller and an abutting roller.

FIG. 6 is a diagram in which a cleaning device having a carrier liquid application unit is arranged around a photosensitive drum.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photoconductor drum (latent image carrier) 20 charger 31 intermediate transfer belt 32 transfer roller 33 tension roller 40 static elimination lamp 50 cleaning device 51 cleaning roller 52 cleaning blade 53 drive gear 54 butting roller 55 leaf spring electrode 56 cleaning Roller shaft 100 Developing device 101 Tank unit 102, 103 Stirring screw 104 Anilox roller 105 Regulator blade 106 Developing roller (developer carrier) 107 Cleaning blade (developing unit) 110 Sweep roller 111 Cleaning blade (Sweeping unit) 112 Sweep Part 113 contact / separation cam 114 contact / separation cam follower 115 pressure biasing spring

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Mie Yoshino 1-3-6 Nakamagome, Ota-ku, Tokyo Stock inside Ricoh Company (72) Inventor Tsuneo Kurohtori 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company Ricoh F-term (reference) 2H074 AA03 AA06 AA09 BB42 BB50 BB54 BB58 BB60 BB72 3J103 AA02 AA14 BA41 FA07 GA02 GA52 GA57 GA58 GA60 HA04 HA05 HA11 HA12 HA20 HA33 HA48 HA53

Claims (17)

[Claims] 1. A developer comprising: a latent image carrier for carrying a latent image on a surface; and a developer carrier for carrying a liquid developer in which toner is dispersed in a carrier liquid on the surface. In a wet image forming apparatus for developing the latent image carried by the latent image carrier with a liquid developer carried on the carrier, the wet image forming apparatus is downstream from the developing area in the latent image carrier surface moving direction. Cleaning means for recovering excess toner on the latent image carrier, the cleaning means recovering mainly the toner and leaving the carrier liquid on the latent image carrier. Characteristic wet image forming apparatus. 2. A liquid image forming apparatus according to claim 1, wherein the liquid developer carried by said developer carrier is a toner which is a visualized particle charged in an insulating liquid which is a carrier liquid. A wet image forming apparatus, wherein the liquid developer is a high-viscosity liquid developer dispersed at a concentration of 100 to 10000 mPa · s. 3. The wet image forming apparatus according to claim 1, wherein said cleaning means is configured to be capable of applying a voltage. 4. The wet image forming apparatus according to claim 1, further comprising a transport unit that transports the liquid developer containing the toner collected by the cleaning unit to a developing device that includes the developing carrier. A wet image forming apparatus. 5. The wet image forming apparatus according to claim 1, wherein said cleaning means comprises a rotatable columnar member formed of an elastic body. 6. A wet image forming apparatus according to claim 1, wherein a plate-shaped member is brought into contact with said cleaning means in order to remove a liquid developer containing collected toner adhered on said cleaning means. A wet image forming apparatus. 7. A wet image forming apparatus according to claim 5, wherein said rotatable cylindrical member formed of said elastic body is composed of a core metal and one or more laminated structures. Image forming device. 8. The wet image forming apparatus according to claim 5, wherein a volume resistance value of the rotatable cylindrical member formed of the elastic body is one.
0 ⁹ wet image forming apparatus characterized by Ωcm or less. 9. The wet image forming apparatus according to claim 5, wherein a hardness of the rotatable columnar member formed of the elastic body is 50 degrees or less (JIS-A). Wet image forming apparatus. 10. A wet image forming apparatus according to claim 5, wherein said rotatable cylindrical member formed of said elastic body is a foamed body and has a hardness of 60 degrees (ASKER-C) or less. A wet image forming apparatus. 11. A wet image forming apparatus according to claim 5, wherein said rotatable cylindrical member formed of said elastic material has a property of swelling or impregnating with a carrier liquid of a developer. A wet image forming apparatus. 12. The wet image forming apparatus according to claim 5, wherein the surface of the rotatable cylindrical member formed of the elastic body is:
A wet image forming apparatus, which has a property as a release layer with respect to a carrier liquid of a developer. 13. The wet image forming apparatus according to claim 5, wherein the surface of the rotatable cylindrical member formed of the elastic body has a smoothness of Rz 3 μm or less. Forming equipment. 14. A wet image forming apparatus according to claim 5, wherein said rotatable cylindrical member made of said elastic body is made of a material mainly composed of urethane resin. Characteristic wet image forming apparatus. 15. The wet image forming apparatus according to claim 5, wherein the surface layer of the rotatable columnar member formed of the elastic body is a film layer having a thickness of 100 μm or less. Characteristic wet image forming apparatus. 16. The wet image forming apparatus according to claim 5, wherein the surface layer of the rotatable columnar member formed of the elastic body is a film layer having a volume resistivity of 10 ⁹ Ωcm or less. A wet image forming apparatus. 17. The wet image forming apparatus according to claim 1, wherein an insulating liquid serving as a carrier liquid is supplied to said cleaning means, and said insulating liquid is provided on said latent image carrier through said cleaning means. A wet-type image forming apparatus configured to apply an ionic liquid.