JP6341020B2 - Wet development apparatus and wet image forming apparatus - Google Patents

Description

  The present invention relates to a printer, a copier, a facsimile machine, and other electrophotographic image forming apparatuses, and more particularly to a wet developing apparatus and a wet image forming apparatus that employ wet development as a developing system.

  JP 2007-225893 A (Patent Document 1), JP 2007-17584 A (Patent Document 2), JP 2005-121816 A (Patent Document 3), and JP 2006-30719 A (Patent Document 1). Document 4) discloses a wet developing apparatus and a wet image forming apparatus employing wet development.

  In the wet developing device described in Patent Document 1, a charging device provided facing the developer carrying member, and a developer carrying member provided downstream of the developer carrying member in the rotation direction of the developer carrying member. A cleaning blade for removing residual wet developer on the body and an electric field removing unit are provided, and control means for controlling application of a bias potential of the electric field removing unit in synchronization with charging by the charging device.

  In the wet developing apparatus described in Patent Document 2, when the printing operation is stopped, a white image is uniformly formed on the photosensitive member, and the photosensitive member carrier liquid recovery member recovers the carrier liquid on the photosensitive member. A control device that executes a sequence for increasing the bias of the photosensitive member carrier liquid recovery member in comparison with that during the normal printing operation and then stops the printing operation.

  In the wet developing apparatus described in Patent Document 3, the toner particles contained in the wet developer on the photoconductor are provided between the cleaning position where the wet developer on the photoconductor is removed by the cleaning blade and the transfer position. Dispersion state adjusting means for adjusting the dispersion state is provided.

  In the wet developing apparatus described in Patent Document 4, a cleaning blade for removing the wet developer remaining after development is provided on the developer carrying member, and wet development on the developer carrying member is provided upstream of the cleaning blade. A removal assisting means for weakening the cohesive force of the agent is provided.

JP 2007-225893 A JP 2007-17484 A JP 2005-121816 A JP 2006-30719 A

  In wet development, a method is used in which a thin layer of a wet developer containing uncharged toner particles is formed on a developing roller, and then the toner particles on the developing roller are charged and developed by applying an external charge. . When the toner particles are charged from the outside, the toner particles are unevenly distributed in the vicinity of the surface of the developing roller, the adhesion force between the toner particles and the developing roller surface is increased, and cleaning becomes difficult with only the cleaning blade.

  Further, since the toner particles enter the cleaning blade in a state where the toner particles are unevenly distributed or adhered to the surface of the developing roller, the toner particles dammed up by the cleaning blade are formed between the cleaning blade and the developing roller, and / or Alternatively, it densely gathers on the upper surface of the cleaning blade and accumulates with time. This is called toner deposit.

  Since the toner deposit has a high toner particle concentration and a high viscosity, it is difficult to transport the toner deposit from the cleaning blade to the developer tank, and remains on the cleaning blade and the transport path. The remaining toner deposit is collected and discarded when the wet developing apparatus is cleaned, which causes a problem in terms of cost. Further, if the wet developing device is stopped without being cleaned, the carrier liquid in the toner deposit is dried to form a solid matter of toner particles, which causes a problem in the next use of the wet developing device.

  In order not to generate toner deposits, it is necessary to remove toner particles adhering to and / or unevenly distributed on the surface of the developing roller before entering the cleaning blade, and redisperse in the wet developer.

  When the toner particles are redispersed in the wet developer, the toner particles are also collected together with the carrier liquid, so that toner deposits on the cleaning blade are not generated. In order to re-disperse the toner particles, it is effective to form an AC electric field between the developing roller by bringing the AC bias application roller into contact with the developing roller at the upstream portion of the cleaning blade. By forming an alternating electric field, the toner particles adhering to the developing roller can be electrically separated and redispersed in the wet developer.

  The wet developer adheres to both rollers after passing through the nip portion of the contacted roller. If the toner particles are present in a dispersed state in the wet developer, the toner particles also adhere to both rollers. Accordingly, when an AC electric field is formed during image formation and the toner particles are redispersed in the wet developer, the toner particles also adhere to the AC bias application roller.

  If the wet developing apparatus is stopped and left in this state, the carrier liquid on the AC bias application roller volatilizes, and only the toner particles remain and solidify. The solidified toner particles act as an insulator. The AC bias requires high voltage and high frequency, and is easily affected by roller resistance. When the wet developing device is repeatedly operated and stopped, the toner particles solidified on the AC bias application roller increase, and there are places where the effect of AC bias cannot be obtained due to the increase in resistance, resulting in toner deposits. Become.

  When the AC bias application roller is provided with a cleaning blade, the toner particles on the AC bias application roller can be recovered, but there are problems such as restrictions on the installation position of the cleaning blade and the need to circulate the recovered wet developer.

  In order to solve the above problem, it is necessary to collect toner particles adhering to the AC bias application roller after image formation.

  An object of the present invention is to provide a wet developing apparatus and a wet image forming apparatus capable of recovering toner particles adhering to an AC bias application roller after image formation. It is in.

  In this wet developing apparatus, a developer carrier, a supply member that supplies a wet developer containing toner particles to the developer carrier, a toner charging member that charges the toner particles on the developer carrier, and A cleaning member for cleaning the toner particles on the developer carrier after development, and provided upstream of the cleaning member in the rotational direction of the developer carrier, and abuts on the developer carrier and An AC bias applying member that forms an AC electric field with the developer carrier, and a control device that controls the output of the toner charging member and the output of the AC bias to the AC bias applying member.

  The control device stops the output of the AC bias applied to the AC bias applying member at the time of image formation in a state where the output to the toner charging member is maintained after the image formation is completed. Control is performed to maintain a state where a DC bias is applied between the developer carrying member and the AC bias applying member in a direction in which the toner particles are pressed against the developer carrying member for a certain period of time.

  In another embodiment, the AC bias applying member and the developer carrying member are provided so as to be capable of being pressed and separated from each other, and the control device performs control for maintaining the DC bias applied state for a certain period of time. Then, the AC bias applying member and the developer carrying member are separated from each other, and thereafter, the control for maintaining the state where the output of the toner charging member is stopped for a predetermined time is further performed.

  In another embodiment, there is provided a charge eliminating member that applies a charge opposite in polarity to the polarity of the toner particles on the developer carrier on the upstream side of the cleaning member in the rotation direction of the developer carrier. The control device stops the output of the AC bias applied to the AC bias applying member during image formation while maintaining the output to the toner charging member, and carries the AC bias applying member and the developer carrying When performing control to maintain a state in which a DC bias is applied in a direction to press the toner particles from the AC bias applying member to the developer carrying body between the body and the body, the output of the static eliminating member is Control is performed to make the output smaller than the absolute value of the applied bias output during image formation.

  In another embodiment, the charge removal member is provided upstream of the nip between the developer carrier and the AC bias applying member in the rotation direction of the developer carrier.

  In another embodiment, the control device applies an absolute value of an output of the bias applied to the toner charging member when applying a DC bias in a direction in which the toner particles are pressed against the developer carrier from the AC bias applying member. Is controlled to be smaller than the absolute value of the applied bias output during image formation.

  In one aspect of the wet image forming apparatus of the present invention, an image carrier, an image forming device for forming an electrostatic latent image on the image carrier, and the image forming device formed on the image carrier. The wet developing apparatus according to any one of the above, which develops the electrostatic latent image.

  In another aspect of the wet image forming apparatus of the present invention, an image carrier, an image forming device for forming an electrostatic latent image on the image carrier, and the image forming device formed on the image carrier. A wet developing device for developing the electrostatic latent image, an image carrier, the image forming device, and a control device for controlling the wet developing device.

  The wet developing device includes a developer carrier, a supply member that supplies a wet developer containing toner particles to the developer carrier, a toner charging member that charges the toner particles on the developer carrier, A cleaning member for cleaning the toner particles on the developer carrier after development, and provided upstream of the cleaning member in the rotation direction of the developer carrier, and abuts on the developer carrier and develops the developer An AC bias applying member that forms an AC electric field with the agent carrier.

  The image carrier and the wet developing device are provided so that they can be pressed and separated, and the AC bias applying member and the developer carrier are provided so that they can be pressed and separated, and the control device finishes image formation. Thereafter, the AC bias applied to the AC bias applying member is stopped, and the image carrying is performed for a certain period of time in a state where a DC bias is applied from the AC bias applying member in a direction to press the toner particles against the developer carrier. After the image is printed on the body, the output of the toner charging member is stopped, and the AC bias applying member is kept away from the developer carrier for a certain period of time, and then the image carrier and the wet development are performed. Control is performed to maintain a state in which the apparatus is separated from the apparatus for a certain period of time.

  According to this wet developing apparatus and wet image forming apparatus, it is possible to provide a wet developing apparatus and a wet image forming apparatus that can collect toner particles adhering to an AC bias application roller after image formation. .

It is a figure which shows the whole structure of the wet image forming apparatus of related technology. It is a schematic diagram which shows the state of the wet developer before passing a charging charger. It is a schematic diagram which shows the state of the wet developer on the developing roller after passing through the developing unit. It is a schematic diagram showing a toner deposit on the developing roller. It is a figure which shows the structure of the wet developing apparatus of related technology. It is a schematic diagram which shows the state of the wet developing agent which rushes into the cleaning blade on the developing roller of related technology. It is a figure which shows a fixed alternating current bias application member in the wet developing apparatus of related technology. It is a figure which shows the state of the wet developing agent which passed the nip part of the developing roller of related technology, and an alternating current bias application roller. FIG. 3 is a diagram illustrating a configuration of a developing roller and an AC bias applying roller of the wet developing apparatus according to the first embodiment. It is a figure which shows the adhesion state of the toner particle on the developing roller at the time of image formation in related technology, and an alternating current bias application roller. FIG. 5 is a block diagram illustrating a control function when cleaning an AC bias application roller of the wet developing apparatus according to the first embodiment. The “developing roller” drive (ON), “development bias”, “toner charging charger bias”, “AC bias application roller drive”, and “AC bias application roller bias” in the wet development apparatus of the first embodiment It is a figure which shows the timing chart of ON / OFF at the time of a stop. FIG. 4 is a diagram illustrating an adhesion state of toner particles T in an “AC bias application roller cleaning” step in the wet developing apparatus according to the first embodiment. FIG. 5 is a diagram illustrating a toner particle adhesion state when the bias of the toner charging charger is turned off during cleaning of the AC bias application roller in the wet developing apparatus according to the first embodiment. FIG. 10 is a block diagram illustrating a control function when cleaning an AC bias application roller of the wet developing apparatus according to the second embodiment. In the wet developing apparatus of the second embodiment, “developing roller” driving (ON), “developing bias”, “toner charging charger bias”, “AC bias applying roller driving”, “AC bias applying roller bias”, and It is a figure which shows the ON / OFF timing chart at the time of the stop of "AC bias application roller press-contact / separation". FIG. 6 is a diagram illustrating a state in which an AC bias application roller is separated from a development roller in the wet development apparatus according to the second embodiment. FIG. 10 is a diagram illustrating a configuration of a developing roller and an AC bias applying roller in the wet developing apparatus according to the third embodiment. FIG. 10 is a block diagram illustrating a control function when cleaning an AC bias application roller of a wet developing apparatus according to a third embodiment. In the wet developing apparatus according to the third embodiment, “development roller” drive (ON), “development bias”, “toner charging charger bias”, “AC bias application roller drive”, “AC bias application roller bias”, and It is a figure which shows the timing chart of ON / OFF at the time of the stop of "static elimination charger bias". FIG. 10 is a diagram illustrating a configuration of another developing roller and an AC bias applying roller in the wet developing apparatus according to the third embodiment. FIG. 10 is a block diagram illustrating a control function when cleaning an AC bias application roller of a wet developing apparatus according to a fourth embodiment. In the wet-type image forming apparatus according to the fourth embodiment, “photosensitive member” driving, “photosensitive member charging charger bias”, “developing roller” driving (ON), “developing bias”, “wet developing device pressure contact / separation” ”,“ Toner charging charger bias ”,“ AC bias application roller driving ”,“ AC bias application roller bias ”, and“ AC bias application roller pressure contact / separation ”stop / on timing charts is there. FIG. 10 is a diagram illustrating a configuration of a wet image forming apparatus including a wet developing apparatus according to a fourth embodiment.

  A wet developing apparatus and a wet image forming apparatus according to an embodiment of the present invention will be described below with reference to the drawings. In each embodiment described below, when referring to the number, amount, and the like, the scope of the present invention is not necessarily limited to the number, amount, and the like unless otherwise specified. The same parts and corresponding parts are denoted by the same reference numerals, and redundant description may not be repeated. It is planned from the beginning to use a combination of the configurations in each embodiment as appropriate.

[Related technologies]
With reference to FIG. 1, as a related technique, a schematic configuration of a wet developing apparatus 100 employing a general electrophotographic process using a wet developer and a wet image forming apparatus 1000 including the wet developing apparatus 100 will be described. To do. FIG. 1 is a diagram showing an overall configuration of a wet image forming apparatus 1000 in the related art.

  The wet image forming apparatus 1000 has a photoreceptor 1. The photoconductor 1 rotates in the direction of arrow a in the figure with an axis extending in one direction as a rotation center. The photoreceptor 1 is charged to a uniform potential by the photoreceptor charging charger 2. After that, exposure is performed by an exposure device 3 as an image forming device that forms an electrostatic latent image, the potential of the image portion is attenuated, and an electrostatic latent image is formed on the photoreceptor 1. The photoreceptor 1 on which the electrostatic latent image is formed is conveyed to a developing unit n1 that is a portion facing the developing roller 4 as a developer carrying member.

  The developing roller 4 rotates in the direction b in the drawing with a rotation axis substantially parallel to the rotation axis of the photoconductor as a rotation center, and the wet developer 41 on the development roller 4 contacts the photoconductor 1 in the developing unit n1. . The wet developer 41 contains toner particles composed of a colorant and a resin, and a dispersion medium (carrier liquid) for dispersing the toner particles as main components.

  The toner particles on the developing roller 4 are charged, and the toner particles move to the photosensitive member 1 side in the developing portion n1 on the photosensitive member 1, and move to the developing roller 4 side in the background portion. The toner particles developed on the photoreceptor 1 are conveyed to a transfer portion n2 that is a portion facing the transfer roller 11. In the transfer unit n2, the transfer target (paper) 15 is conveyed in the direction of arrow e, and the toner particles on the photosensitive member 1 are transferred to the transfer target 15 by the voltage having the opposite polarity to the toner particles applied to the transfer roller 11. . The transferred object 15 to which the toner particles are transferred is conveyed to a fixing unit (not shown) and the toner image is fixed.

  On the other hand, a photoreceptor cleaning member 12 is provided on the photoreceptor 1 after passing through the transfer portion, and collects toner particles and carrier liquid remaining on the photoreceptor 1 remaining after the transfer. The photoreceptor 1 from which the toner particles and the carrier liquid are collected is exposed by the eraser lamp 13 and the latent image potential is cancelled.

  On the developing roller 4 after passing through the developing unit n1, toner particles and carrier liquid remaining without being developed are also present. In order to remove the toner particles and the carrier liquid, a cleaning blade 10 as a cleaning member is provided. By repeating the above steps, images are sequentially printed on the transfer medium 15.

[Wet development apparatus 100]
Next, the wet developing apparatus 100 will be described in detail. The wet developing apparatus 100 includes a developing roller 4 as a developer carrying member that supplies the wet developer 41 to the photosensitive member 1 as the image carrier and a supply member that supplies the wet developer 41 to the developing roller 4. Supply roller 5, toner charging charger 6 as a toner charging member for applying a charge to wet developer 41 on developing roller 4, and cleaning blade 10 as a cleaning means for cleaning wet developer 41 on developing roller 4, It is equipped with.

  A wet developer 41 having toner particles made of a colorant and a resin and a carrier liquid for dispersing the particles is stored in the developer tank 8. A part of the supply roller 5 is immersed in the wet developer 41 and rotates in the direction c in the drawing. The wet developer 41 is pumped up by the rotation of the supply roller 5, and the wet developer 41 is regulated to a constant film thickness by the regulation blade 7 provided in contact with the supply roller 5.

  After the wet developer 41 is regulated to a certain film thickness, the wet developer 41 is transported to the nip n3 with the developing roller 4 and delivered to the developing roller 4. The wet developer 41 delivered to the developing roller 4 is conveyed to the opposite portion of the toner charging charger 6 by the rotation of the developing roller 4, and the toner in the wet developer 41 by the current flowing from the toner charging charger 6 to the developing roller 4. The particles are charged. Thereafter, the wet developer 41 is conveyed to the developing unit n1 that is a nip with the photoreceptor 1, and the electrostatic latent image on the photoreceptor 1 is developed by the wet developer 41.

  The toner particles and the carrier liquid that are not used for development and remain on the developing roller 4 are conveyed to the opposite portion of the cleaning blade 10 by the rotation of the developing roller 4, and are dammed and collected by the cleaning blade 10.

  Since the wet developer collected by the cleaning blade 10 has a toner concentration different from that of the original wet developer 41, the wet developer is collected in a tank (not shown) different from the developer tank 8, and after adjusting the toner concentration, It is returned to the developer tank 8 again. The supply roller 5 may be urethane, a rubber roller made of NBR, or an anilox roller having a concave portion on the surface. As the developing roller 4, a rubber roller made of urethane or NBR can be used.

  Referring to FIG. 2, wet developer 41 stored in developer tank 8 and supplied onto developing roller 4 via supply roller 5 exists in a state where toner particles T are uniformly dispersed in carrier liquid C. doing. From this state, the toner particles T receive a force that is pressed against the developing roller 4 by being charged by the toner charging charger 6 or by an electric field at the developing unit n1 (an electric field applied to the background).

  As a result, as shown in FIG. 3, the toner particles T present at a location corresponding to the background portion of the image that has passed through the developing portion n <b> 1 are unevenly distributed near the surface of the developing roller 4. There will be adhering toner particles T.

  Referring to FIG. 4, when wet developer 41 enters the contact portion with cleaning blade 10 in this state, toner particles T are deposited on the wedge portion where cleaning blade 10 and developing roller 4 are in contact. In the vicinity of the surface of the wet developer 41, the carrier liquid C is rich, and more carrier liquid C flows down on the cleaning blade 10.

  As a result, toner deposits having a high concentration of toner particles T are generated. Further, the deposit of the toner particles T increases with time, and the toner particles T reach the upper part of the cleaning blade 10. Since the toner deposit has a high concentration of toner particles T, the fluidity of the toner deposit is poor, and it is difficult for the toner deposit to flow down on the cleaning blade 10, and the toner deposit is also generated on the cleaning blade 10.

  When toner deposits are generated in this way, it becomes difficult to transport the concentrated toner deposits to the developer tank, and the deposited toner particles T are collected and discarded during cleaning. As a result, the amount of toner particles consumed increases, leading to an increase in cost.

  Further, if the wet developing apparatus 100 (wet image forming apparatus 1000) is not cleaned when the wet developing apparatus 100 is stopped, the carrier liquid C in the toner deposit is dried and a solid body of toner particles T is formed. Therefore, the toner particles T unevenly distributed in the vicinity of the surface of the developing roller 4 before reaching the cleaning blade 10 are peeled off and redispersed in the carrier liquid C.

  Next, the configuration of the wet developing apparatus 100A as a related technique will be described with reference to FIGS. FIG. 5 is a diagram showing a configuration of the wet developing apparatus 100A, FIG. 6 is a schematic diagram showing a state of the wet developer 41 entering the cleaning blade 10 on the developing roller 4, and FIG. 7 is a fixed type in the wet developing apparatus 100A. FIG. 8 is a diagram showing the state of the wet developer that has passed through the nip portion between the developing roller and the AC bias applying roller.

  The basic structure of this wet developing apparatus 100A is the same as that of the above-described wet developing apparatus 100. The difference is that the developing roller 4 and the developing roller 4 are interposed between the developing unit n1 and the cleaning blade 10 via the wet developer 41. An AC bias applying roller 31 is provided as an AC bias applying member that abuts and forms an AC electric field with the developing roller 4. In the wet developing apparatus 100A shown in FIG. 5, a case where a conductive metal roller is used as the AC bias applying roller 31 will be described.

  The carrier liquid C and the toner particles T enter the nip n4 between the AC bias applying roller 31 and the developing roller 4 by the rotation of the developing roller 4 (b direction in the figure), and as the electric field becomes stronger, the vicinity of the surface of the developing roller 4 increases. The existing toner particles T start to move and reciprocate between the developing roller 4 and the AC bias applying roller 31. Thereafter, the toner particle T stops moving as it approaches the outlet of the nip n4 and gradually weakens, and the toner particles T are uniformly dispersed in the carrier liquid C as shown in FIG. It becomes.

  Referring to FIG. 6, when wet developer 41 in such a state enters cleaning blade 10, toner particles T are collected without being deposited in the vicinity of cleaning blade 10. The AC bias application roller 31 is rotated in the direction f in FIG. 5 and may be rotated at the same speed (linear speed) as the surface speed (linear speed) of the developing roller 4, but different speeds (linear speed). ) Is more preferable because a force for scraping off the toner particles T acts mechanically.

  Further, toner particles can be peeled even with an AC bias having a small amplitude, and an AC power source with a smaller capacity can be used, leading to cost reduction. Further, local overcurrent hardly occurs and damage to the developing roller 4 is small.

  Further, the metal roller brought into contact with the developing roller 4 as the AC bias applying roller 31 has been described, but the essence is that an AC electric field is applied to the toner particles T in the wet developer 41 to obtain a dispersing action.

  Therefore, as shown in FIG. 7, if the wet developer 41 is not dammed when entering the cleaning blade 10, it is not necessary to stick to the roller form, and a bowl-shaped conductive fixing member is used. The same effect can be obtained by using the AC bias applying member 31A. In addition, when a bowl-shaped conductive fixing member is used, a roller driving device is not required, which can lead to cost reduction.

  The material of the conductive roller as the AC bias applying roller 31 may be a metal such as aluminum, iron or stainless steel, or a roller in which an elastic member such as conductive resin or rubber is installed on the surface of the base of the metal. Furthermore, various conventionally known materials used for forming a bias electric field in an electrophotographic apparatus can be used up to those whose surfaces are coated with an insulating material that is thin enough to form an electric field. When an elastic member is used, the peak pressure between the AC bias applying roller 31 (AC bias applying member (31, 31A) 31A) and the developing roller 4 can be reduced, and the wet developer 41 is introduced at the entrance of the nip n4. There is little damming and the setting allowable range can be widened.

  Further, the same material can be adopted even in the case of the AC bias applying member (31, 31A) 31A using a fixed electrode instead of a roller. Hereinafter, when referring to the AC bias applying roller 31 (FIG. 5), the same applies to the AC bias applying member (31, 31A) 31A (FIG. 7).

  As the AC bias applied to the AC bias application roller 31, a waveform such as a rectangular wave, a sine wave, a triangular wave, a sawtooth wave, or a blank wave can be used. The frequency is preferably about 1,000 Hz to 100,000 Hz. If the frequency is 1,000 Hz or more, it is possible to suppress the occurrence of uneven location in an AC bias application state and an area with insufficient dispersion. When the frequency is 100,000 Hz or less, a good dispersion action is obtained by the toner particles following. Further, the amplitude is preferably 100 V (Peak-to-Peak 200 V) or more in order to facilitate the movement of toner particles and to obtain a high dispersion action.

  Referring to FIG. 8, generally, wet developer 41 after passing between the nips formed by the rollers adheres to the respective rollers. The wet developer 41 that has passed through the developing portion n1 between the developing roller 4 and the AC bias applying roller 31 also adheres to the AC bias applying roller 31 side. At this time, if the toner particles T exist in a dispersed state in the wet developer 41, the toner particles T also adhere to the AC bias applying roller 31. That is, when an AC bias is applied to the AC bias application roller 31 during image formation and the toner particles T are redispersed, the toner particles are also attached to the AC bias application roller 31.

  During the image formation, the adhesion of the toner particles T to the AC bias applying roller 31 is not a problem. However, when the image formation is completed and the toner particles T adhere to the AC bias application roller 31, the carrier liquid on the AC bias application roller 31 is volatilized, and only the toner particles T remain and solidify.

  When the toner particles T are solidified, the toner particles T act as an insulator, so that resistance unevenness occurs in the AC bias applying roller 31. When a portion with high roller resistance is generated in the AC bias application roller 31, the effect of the AC bias is reduced. As a result, the function of redispersing the toner particles T on the developing roller 4 in that portion is also reduced, and toner deposits are generated. In order to prevent this, it is necessary to collect the toner particles on the AC bias applying roller 31 before stopping the wet developing apparatus 100A.

[Embodiment 1: Wet development apparatus 100B]
Hereinafter, a specific configuration of the wet developing apparatus 100B in the present embodiment will be described with reference to FIGS. FIG. 9 is a diagram illustrating the configuration of the developing roller 4 and the AC bias applying roller 31 of the wet developing device 100B. FIG. 10 is a block diagram illustrating a control function when cleaning the AC bias applying roller 31 of the wet developing device 100B. 11 is a stop of “developing roller” driving (ON), “developing bias”, “toner charging charger bias”, “AC bias applying roller driving”, and “AC bias applying roller bias” in the wet developing apparatus 100B. FIG. 12 is a diagram showing an ON / OFF timing chart at the time, FIG. 12 is a diagram showing an adhesion state of the toner particles T during the “AC bias application roller cleaning” process in the wet developing device 100B, and FIG. 13 is a wet developing device 100B. Toner bias charger bias during AC bias application roller cleaning Is a diagram showing the state of adhesion of the toner particles in the case of to OFF.

  Other configurations not shown are the same as those of the wet developing apparatus 100A shown in FIG. Except for the configuration of the wet developing apparatus, the configuration of the wet image forming apparatus employing the wet developing apparatus 100B is the same as that of the wet image forming apparatus 1000 shown in FIG.

  With reference to FIG. 9, the adhesion state of the toner particles T on the developing roller 4 and the AC bias applying roller 31 during image formation will be described. In the wet developer 41 supplied to the developing roller 4, the toner particles are uniformly dispersed.

  Thereafter, the toner particles T are charged by the current flowing from the toner charging charger 6 to the developing roller 4 and are unevenly distributed near the surface of the developing roller 4. In the developing portion n1 (see FIG. 5) with the photosensitive member 1, the toner particles T in the printing portion are transferred to the photosensitive member 1, but the toner particles T in the background portion remain on the surface of the developing roller 4. At this time, the toner particles T in the background portion are further pressed against the surface side of the developing roller 4 by the electric field of the developing portion n1.

  Thereafter, the toner particles T unevenly distributed on the surface of the developing roller 4 are re-dispersed by the AC bias of the AC bias applying roller 31 and adhere to the AC bias applying roller 31 after passing through the nip n4. Therefore, the toner particles are also attached to the AC bias applying roller 31 during image formation.

  With reference to FIG. 10, the control flow in the case of cleaning the alternating current bias application roller 31 from the said state in this Embodiment is demonstrated.

  A toner charging charger bias power source 130 is connected to the toner charging charger 6. A toner charging charger bias controller 135 is connected to the toner charging charger bias power source 130. The toner charging charger bias control device 135 is connected to the CPU 100U. In response to the signal from CPU 100U, toner charging charger bias control device 135 controls the output of toner charging charger bias power supply 130.

  A developing roller driving device 140 is connected to the developing roller 4. A developing roller driving control device 145 is connected to the developing roller driving device 140. The CPU 100U is connected to the developing roller drive control device 145. In response to the signal from the CPU 100U, the developing roller driving control device 145 controls the developing roller driving device 140.

  A developing bias power source 150 is connected to the developing roller 4. A development bias controller 155 is connected to the development bias power supply 150. A CPU 100U is connected to the developing bias controller 155. In response to the signal from the CPU 100U, the development bias controller 155 controls the output of the development bias power supply 150.

  An AC bias application roller driving device 110 is connected to the AC bias application roller 31. An AC bias application roller drive control device 115 is connected to the AC bias application roller drive device 110. The AC bias application roller drive control device 115 is connected to the CPU 100U. In response to the signal from the CPU 100U, the AC bias application roller drive control device 115 controls the AC bias application roller drive device 110.

  An AC bias application roller bias power source 120 is connected to the AC bias application roller 31. An AC bias application roller controller 125 is connected to the AC bias application roller bias power source 120. The AC bias application roller control device 125 is connected to the CPU 100U. In response to the signal from the CPU 100U, the AC bias application roller controller 125 controls the output of the AC bias application roller bias power source 120.

  Referring to FIG. 11, “development roller 4” drive (ON), “development bias”, “toner charging charger bias”, “AC bias application roller 31 drive”, and “AC bias application roller bias” stop. An ON / OFF timing chart at the time will be described.

  During image formation, the developing roller 4 is driven, the developing bias is turned ON (400 V), the toner charging charger 6 is turned ON, and the AC bias applying roller 31 is driven (ON). Is applied. There is no potential difference in the DC bias component between the developing roller 4 and the AC bias applying roller 31. When a potential difference is generated, toner particles T adhere to either roller.

  When the image formation is completed, as an “AC bias application roller cleaning” step, the AC bias applied to the AC bias application roller 31 is turned OFF and the DC bias (500 V) is applied while the toner charging charger 6 is kept ON. To do. In the present embodiment, this DC bias has a higher DC value than the developing bias (in this embodiment, 400 V) so as to form an electric field in which the toner particles T move from the AC bias applying roller 31 to the developing roller 4. Apply a bias.

  As a result, a DC bias is applied between the AC bias applying roller 31 and the developing roller 4 in a direction in which the toner particles T are pressed against the developing roller 4 from the AC bias applying roller 31. In this state, the wet developing apparatus 100A is driven for a certain time.

  FIG. 12 shows the adhesion state of the toner particles T during the “AC bias applied roller cleaning” step. The toner particles T newly transported to the nip n4 of the AC bias applying roller 31 by the toner charging charger 6 are charged, and the electric field in which the toner particles T move from the AC bias applying roller 31 to the developing roller 4 is generated. By being formed, the newly carried toner particles T can be prevented from adhering to the AC bias application roller 31.

  Further, the toner particles T adhering to the AC bias applying roller 31 during image formation can be collected on the developing roller 4 by the electric field between the AC bias applying roller 31 and the developing roller 4. As a result, the toner particles T on the AC bias applying roller 31 can be eliminated.

  After driving in this state for a certain period of time, all of the driving of the developing roller 4, the developing bias, the toner charging charger bias, the driving of the AC bias applying roller 31, and the DC bias of the AC bias applying roller 31 are turned OFF, and the wet developing device 100B is stopped.

  Referring to FIG. 13, if the bias of toner charging charger 6 is turned OFF during AC bias application roller cleaning, toner particles T are not charged, and toner particles T are AC in a dispersed state in carrier liquid C. It is carried to the opposite part of the bias application roller 31. As a result, the toner particles T are not affected by the bias and adhere to the AC bias application roller 31, so that the AC bias application roller 31 is not clean.

  When the AC bias application roller 31 is cleaned, the toner charging charger 6 is biased ON so that the toner particles T are unevenly distributed near the surface of the developing roller 4 as shown in FIG. Things are generated, but this is not a problem amount due to short driving time. In order to reduce toner deposits at this time, it is also effective to lower the bias of the toner charging charger 6 as compared to the time of image formation and to reduce the uneven distribution of the toner particles T.

  In order to obtain a beautiful image in wet development, it is preferable to increase the output of the toner charging charger 6, but as a side effect, the adhesion between the toner particles T and the developing roller 4 becomes stronger and the toner deposit on the cleaning blade 10 is increased. Will occur. An AC bias application roller 31 is provided as a countermeasure against image formation. However, the toner particles T need only be charged when the AC bias application roller 31 is cleaned, and the output of the toner charging charger 6 during image formation is as follows. unnecessary.

  By setting the timing as described above, the apparatus can be stopped after the toner particles T attached to the AC bias applying roller 31 during the image formation are collected. Furthermore, the AC bias application roller 31 can be maintained clean even after the wet development apparatus 100B is stopped (after being left), and the AC bias of the AC bias application roller 31 can be stably formed during the next operation of the wet development apparatus 100B. Can do. Further, the AC bias is stopped first, which is advantageous for preventing leakage.

  Specifically, at the time of image formation, the photoreceptor 1 is uniformly charged to a surface potential of 500 V by the photoreceptor charge charger 2 (see FIG. 1). Thereafter, the printing unit is exposed by the exposure device 3, the surface potential is lowered to about 20V, and a latent image is formed. By setting the bias of the toner charging charger 6 to about 6 kV (the toner particles T are positively charged), and applying a developing bias of 400 V to the developing roller 4, there is no image noise with sufficient image density, and the background fogging. Can be obtained.

  After developing in this state, an AC bias having an amplitude of 300 V (peak to peak: 600 V), a frequency of 10 kHz, and an offset of 400 V is applied to the AC bias applying roller 31 in order to re-disperse the toner particles remaining on the developing roller 4. Yes. By applying such an AC bias to the AC bias application roller 31, the toner particles remaining on the developing roller 4 can be redispersed, and toner deposits are not generated on the cleaning blade 10.

  After the image formation is completed, the developing bias is kept at 400V, and the bias of the AC bias application roller 31 to which the AC bias was applied at the time of image formation is switched to a DC bias of 500V. By doing so, an electric field in which the toner particles move from the AC bias applying roller 31 to the developing roller 4 side is formed, and in this state for a certain time (approximately several seconds are possible. At least the time for one rotation of the AC bias applying roller 31 is necessary). By driving, the toner particles T adhering to the AC bias applying roller 31 during image formation are collected (pressed) on the developing roller 4 side. Further, the toner particles T in the wet developer 41 newly supplied by the developing roller 4 do not adhere to the AC bias applying roller 31.

  In the above description, the case where the developing bias is set to 400 V when the AC bias applying roller 31 is cleaned has been described. However, the developing bias is not necessarily limited to 400 V. It is only necessary to apply a DC bias in a direction in which the toner particles T are pressed against the developing roller 4 from the AC bias applying roller 31 between the AC bias applying roller 31 and the developing roller 4.

  Therefore, when the AC bias application roller 31 is cleaned, the developing bias may be turned OFF, and a 400 V DC bias that is the same DC bias component as that during image formation may be applied to the AC bias application roller 31.

  Further, the output of the bias applied to the toner charging charger 6 is about 6 kV during image formation, but the output of the bias applied to the toner charging charger 6 is lower than that during image formation when cleaning the AC bias application roller 31 ( For example, it is preferably about 5 kV. This is because by reducing the charge amount of the toner particles T, it can be expected to improve the cleaning characteristics of the cleaning blade 10 in a later step.

[Embodiment 2: Wet development apparatus 100C]
Next, a specific configuration of the wet developing apparatus 100C according to the second embodiment will be described with reference to FIGS. FIG. 14 is a block diagram showing a control function when cleaning the AC bias applying roller 31 of the wet developing apparatus 100C. FIG. 15 shows driving (ON) and “developing bias” of the “developing roller” in the wet developing apparatus 100C. , “ON / OFF timing chart” when stopping “toner charging charger bias”, “AC bias application roller driving”, “AC bias application roller bias”, and “AC bias application roller pressure contact / separation” 16 is a diagram illustrating a state in which the AC bias applying roller 31 is separated from the developing roller 4 in the wet developing apparatus 100C.

  Other configurations not shown are the same as those of the wet developing apparatus 100A shown in FIG. Except for the configuration of the wet developing apparatus, the configuration of the wet image forming apparatus employing the wet developing apparatus 100C is the same as that of the wet image forming apparatus 1000 shown in FIG.

  In the first embodiment, a deposit of toner particles T is formed at the contact portion between the developing roller 4 and the cleaning blade 10 when the AC bias applying roller 31 is cleaned, and is left in that state. The purpose of the present embodiment is to collect toner deposits generated during cleaning of the AC bias application roller 31. For this purpose, an AC bias application roller pressure contact / separation control device 235 is provided on the AC bias application roller 31.

  In the second embodiment, in addition to the configuration of the first embodiment, a case where a function of pressing and separating the AC bias applying roller 31 with respect to the developing roller 4 will be described. As shown in FIG. 14, an AC bias application roller pressure contact / separation driving device 230 is connected to the AC bias application roller 31. An AC bias application roller pressure contact / separation control device 235 is connected to the AC bias application roller pressure contact / separation driving device 230. The CPU 100U is connected to the AC bias application roller pressure contact / separation control device 235. In response to the signal from the CPU 100U, the AC bias application roller pressure contact / separation control device 235 controls the AC bias application roller pressure contact / separation drive device 230.

  The AC bias application roller 31 is held by a pressure contact / separation mechanism using an eccentric cam or the like, and performs a pressure contact / separation operation with respect to the developing roller 4 by a driving force from the AC bias application roller pressure contact / separation control device 235. The AC bias application roller pressure contact / separation control device 235 is controlled by the AC bias application roller pressure contact / separation control device 235 in response to a signal from the CPU 100U. The AC bias applying roller 31 may be fixed and the developing roller 4 may be provided with a pressure contact / separation mechanism.

  Referring to FIG. 15, the sequence from the image formation to the cleaning of AC bias applying roller 31 is the same as wet developing apparatus 100B of the first embodiment shown in FIG. After the image formation is completed, the AC bias application roller 31 is switched from the AC bias to the DC bias and driven for a certain time, and then the AC bias application roller 31 is separated from the developing roller 4.

  At that time, the developing bias, the toner charging charger bias, and the AC bias applying roller drive are controlled to be OFF, and only the developing roller 4 is driven. The adhesion state of the toner particles at this time is shown in FIG. By driving for a certain time in this state, the wet developer 41 in which the toner charger 6 does not act and the toner particles T are dispersed is supplied onto the developing roller 4 and also supplied to the cleaning blade 10. The wet developer 41 can collect toner deposits generated during cleaning of the AC bias application roller. Since the AC bias applying roller 31 is separated from the developing roller 4, it does not get dirty.

  As in the case of the first embodiment, it is also possible to reduce toner deposits by lowering the bias of the toner charging charger 6 when cleaning the AC bias application roller.

[Embodiment 3: Wet development apparatus 100D]
Hereinafter, a specific configuration of the wet developing apparatus 100D in the present embodiment will be described with reference to FIGS. FIG. 17 is a diagram showing the configuration of the developing roller 4 and the AC bias applying roller 31 of the wet developing apparatus 100D, and FIG. 18 is a block diagram showing the control function when cleaning the AC bias applying roller 31 of the wet developing apparatus 100D. 19, “Development roller” drive (ON), “Development bias”, “Toner charging charger bias”, “AC bias application roller drive”, “AC bias application roller bias”, and “Static elimination” in the wet developing apparatus 100D It is a figure which shows the timing chart of ON / OFF at the time of the stop of "charger bias".

  Other configurations not shown are the same as those of the wet developing apparatus 100A shown in FIG. Except for the configuration of the wet developing apparatus, the configuration of the wet image forming apparatus employing the wet developing apparatus 100D is the same as that of the wet image forming apparatus 1000 shown in FIG.

  The case where the wet developing apparatus 100D in the present embodiment neutralizes the toner particles T upstream of the AC bias applying roller 31 will be described. As shown in FIG. 17, the charge eliminating member that imparts a charge having a polarity opposite to that of the toner charging charger 6 to the toner particles T on the developing roller 4 between the developing unit n1 (see the drawing) and the AC bias applying roller 31. The static elimination charger 51 is provided.

  As shown in FIG. 18, a static elimination charger bias power source 330 is connected to the static elimination charger 51. A static elimination charger bias controller 335 is connected to the static elimination charger bias power source 330. The static elimination charger bias control device 335 is connected to the CPU 100U. In response to the signal from the CPU 100 </ b> U, the static elimination charger bias control device 335 controls the output of the static elimination charger bias power source 330.

  In the present embodiment, a corotron charger similar to the toner charging charger 6 is used as the charge eliminating charger 51. By applying a charge having a polarity opposite to the toner charging polarity from the charge eliminating charger 51, the charge amount of the toner particles T can be reduced.

  In wet development, if the toner charge amount is high, image characteristics such as fine line reproducibility and solid uniformity are good, but conversely, in the background portion, the adhesion between the developing roller 4 and the toner particles T becomes large and cleaning becomes difficult. Such as when the toner particles T are significantly deposited. Therefore, the toner charge amount needs to be determined in consideration of cleaning and toner particle T accumulation.

  As in the first and second embodiments, when the AC electric field is formed before the AC bias applying roller 31 is cleaned, the toner charge amount is high and the adhesion between the toner particles T and the developing roller 4 is increased. The toner particles T cannot be peeled off from the surface of the developing roller 4 by the force of the electric field, and toner deposits are generated.

  In the present embodiment, as described above, when the charge removal charger 51 is provided, the toner charge amount can be adjusted in front of the cleaning blade 10 (upstream side), and the cleaning blade 10 is independent of the output of the toner charging charger 6. The previous toner charge amount can be kept constant. As a result, even if the output of the toner charging charger 6 is increased, the adhesion between the toner particles in front of the cleaning blade 10 and the developing roller 4 can be kept constant, and can be peeled off by an AC electric field formed by the AC bias applying roller 31. It becomes possible and no toner deposit is generated.

  Accordingly, it is possible to increase the output of the toner charging charger 6 and to output a more excellent image. Conversely, if the charge eliminating charger 51 is provided without increasing the output of the toner charging charger 6, the toner charge amount becomes smaller and the adhesion between the toner particles T and the developing roller 4 becomes smaller, so that a smaller AC bias (amplitude). The toner particles T can be peeled off. Further, it is preferable that the charge amount of the toner after static elimination is close to 0 due to the cleaning property and the toner deposit.

  When the toner particles T are neutralized by the neutralization charger 51, the toner particles T are charged with a polarity opposite to the original polarity because the toner particles T vary in charge amount and also in the amount of charge with a reverse polarity. T (reversely charged toner particles) is generated. When an AC bias is applied to the AC bias application roller 31 to re-disperse the toner particles T, there is no effect even if reversely charged toner particles are mixed, but if a DC bias is applied during cleaning of the AC bias application roller 31, When reversely charged toner particles are present, the toner particles T adhere to the AC bias applying roller 31.

  For this reason, in the present embodiment, as shown in FIG. 19, the bias of the static elimination charger 51 is made lower when the AC bias applying member (31, 31A) after image output is cleaned than during image formation. Note that it may be OFF. By doing so, reversely charged toner particles are not generated, and toner adhesion to the AC bias applying roller 31 can be eliminated. At this time, as described in the first embodiment, the bias of the toner charging charger 6 may be made smaller than that during image formation.

  In addition, although demonstrated using the corotron charger as the static elimination charger 51, another structure may be sufficient. For example, a conductive roller may be provided in contact with or close to the developing roller 4, and discharge may be caused between the developing roller 4 by applying a high voltage. Furthermore, the same effect can be obtained by providing a mechanism for separating the AC bias applying roller 31 from the developing roller 4 as in the second embodiment and adopting the same control as in the second embodiment.

  In FIG. 16, a case has been described in which the charge removal charger 51 is provided upstream of the nip n4 between the developing roller 4 and the AC bias applying roller 31 as the front (upstream side) of the cleaning blade 10. As shown, a charge removal charger 51 may be provided between the cleaning blade 10 and the nip n4 in front of the cleaning blade 10 (upstream side).

[Embodiment 4: Wet Image Forming Apparatus 1000E / Wet Developing Apparatus 100E]
In the wet image forming apparatuses in the first to third embodiments, the case where the wet developing apparatuses 100B to 100D are driven to clean the AC bias applying member has been described. However, the present embodiment describes the photoreceptor 1 (see FIG. 1). ) Will also be described.

  FIG. 21 is a block diagram showing a control function when cleaning the AC bias application roller 31 of the wet image forming apparatus 1000E employing the wet developing apparatus 100D, and FIG. 22 shows “photosensitive member 1” in the wet image forming apparatus 1000E. , “Bias of photoconductor charging charger 2”, “Development roller” drive (ON), “Development bias”, “Press contact / separation of wet developing device 100E”, “Toner charging charger bias”, “AC bias application” FIG. 23 is a timing chart showing ON / OFF timing when the “roller driving”, “AC bias applying roller bias”, and “AC bias applying roller pressure contact / separation” stops, and FIG. 23 shows wet image formation including the wet developing device 100E. It is a figure which shows the structure of the apparatus 1000E.

  Other configurations not shown are the same as those of the wet developing apparatus 100A shown in FIG. Except for the configuration of the wet developing apparatus, the basic configuration of the wet image forming apparatus 1000E employing the wet developing apparatus 100E is the same as that of the wet image forming apparatus 1000 shown in FIG.

  A photoconductor driving device 485 is connected to the photoconductor 1. A photoconductor drive control device 480 is connected to the photoconductor drive device 485. The photoconductor drive control device 480 is connected to the CPU 100U. Upon receiving a signal from the CPU 100U, the photoconductor drive control device 480 controls the photoconductor drive device 485.

  A photosensitive member charging charger bias power source 495 is connected to the photosensitive member charging charger 2. A photoconductor charging charger bias control device 490 is connected to the photoconductor charging charger bias power source 495. A CPU 100U is connected to the photoconductor charging charger bias control device 490. Upon receiving a signal from the CPU 100U, the photoconductor charging charger bias control device 490 controls the output of the photoconductor charging charger bias power source 495.

  The wet developing device 100E is held by a wet developing device pressure contact / separation driving device 470 such as an eccentric cam, and the wet developing device 100E is connected to the photoreceptor 1 by the force from the wet developing device pressure contact / separation driving device 470. A pressure contact and separation operation is performed. A wet developing device pressure contact / separation control device 475 is connected to the wet developing device pressure contact / separation driving device 470. A CPU 100U is connected to the wet developing device pressure contact / separation control device 475. In response to the signal from the CPU 100U, the wet developing device pressure contact / separation control device 475 controls the wet developing device pressure contact / separation driving device 470.

  A timing chart for cleaning the AC bias applying roller 31 will be described with reference to FIG. When the image formation by the wet image forming apparatus 1000E is completed, the bias of the photosensitive member charging charger 2 is turned off, and the bias of the AC bias applying roller 31 is switched from the AC bias to the DC bias (500V). When the photoconductor charging charger 2 is turned off, the photoconductor 1 is not charged, so that the surface potential of the photoconductor 1 becomes about 0V.

  Referring to FIG. 23, if the same development bias (400 V) as that at the time of image formation is maintained in this state, a development potential difference is formed, and toner particles T on development roller 4 are developed (pressed) on photoreceptor 1. ). The toner particles T developed on the photoreceptor 1 are collected by the photoreceptor cleaning member 12 (see FIG. 1). At this time, the photosensitive member 1 and the transfer roller 11 (see FIG. 1) need to be separated from each other.

  On the other hand, the toner particles T are hardly present on the developing roller 4 after the toner particles T are developed on the photoreceptor 1, and the wet developer 41 rich in the carrier liquid C remains (a very small amount of toner). Particles T are present). Thus, the wet developer 41 rich in the carrier liquid C is also supplied to the nip n4 of the AC bias applying roller 31.

  In this state, the wet image forming apparatus 1000E is driven for a certain time, whereby the toner particles T attached to the AC bias applying roller 31 during image formation can be collected on the developing roller 4. Further, there are few toner particles T in the wet developer 41 newly supplied by the developing roller 4, and no new toner deposit is generated on the cleaning blade 10 when the AC bias applying roller 31 is cleaned.

  Thereafter, as in the case of the second embodiment, the AC bias application roller 31 is separated from the developing roller 4 and the drive of the AC bias application roller 31 of the AC bias application roller 31 is turned off. Thereby, the AC bias applying roller 31 can be stopped in a state where the toner particles T are not attached. The AC bias applying roller 31 is separated, the developing bias and the toner charging charger bias are turned off, and the developing roller 4 and the photosensitive member 1 are further pressed for a predetermined time.

  As a result, the wet developer 41 in which the toner particles T are dispersed on the photoreceptor 1 is supplied, and the toner particles deposited on the photoreceptor cleaning member 12 can be washed away when the AC bias application roller 31 is cleaned. Thereafter, the developing roller 4 is separated from the photoreceptor 1 and stopped.

  As a result, the wet image forming apparatus 1000E and the wet development are performed in a state where there is no toner particles on the AC bias applying roller 31 and there is no deposit of toner particles T on the cleaning blade 10 of the developing roller 4 and the photosensitive member cleaning member 12. The apparatus 100E can be stopped.

  As described above, according to the wet developing apparatus and the wet image forming apparatus in the present embodiment, the AC bias application roller 31 (hereinafter referred to as AC bias) is used for image formation in a state where the output to the toner charging charger 6 is maintained after the image formation is completed. The output of the AC bias applied to the application member 31 </ b> A) is stopped, and the toner particles T are pressed between the AC bias application roller 31 and the development roller 4 from the AC bias application roller 31 to the development roller 4. The state where the DC bias is applied is maintained for a certain period.

  Thus, the AC bias applying roller 31 is newly applied by the developing roller 4 by applying and driving a DC bias higher than the developing bias without applying the AC bias to the AC bias applying roller 31 while the toner particles T are charged. Is prevented from adhering to the AC bias application roller 31 (cleaning of the AC bias application roller 31).

  Further, the toner particles T attached to the AC bias applying roller 31 during image formation can be collected on the developing roller 4. Thereby, the toner particles T on the AC bias application roller 31 can be eliminated. Furthermore, the toner particles T can be prevented from solidifying on the AC bias applying roller 31 when the wet developing apparatus is left after being stopped. Further, since the toner particles T are not present on the AC bias applying roller 31 when the wet developing device is re-driven, caking can be prevented.

  In addition, after the AC bias application roller 31 is cleaned, the AC bias application roller 31 is separated from the developing roller 4, and the wet developing device is driven for a certain period of time with the output of the toner charging charger 6 stopped. The toner deposited on the cleaning blade 10 that is generated when the AC bias application roller 31 is cleaned can be collected.

  In addition, when the static elimination charger 51 is used during image formation, the output of the static elimination charger 51 is controlled to be lower (or stopped) than during image formation when the AC bias application roller 31 is cleaned. Thereby, when the AC bias application roller 31 is cleaned, the reversely charged toner particles T are not generated by the static elimination charger 51, and the adhesion of the toner particles T to the AC bias application roller 31 due to the DC bias can be prevented.

  Further, when the AC bias application roller 31 is cleaned, the bias of the toner charging charger 6 is lowered to reduce the toner charge amount. As a result, toner deposits on the cleaning blade 10 generated when the AC bias applying roller 31 is cleaned can be reduced. In addition, the AC bias is stopped first, thereby preventing leakage.

  Although the case where the conductive metal roller is used as the AC bias application roller 31 in each of the above embodiments has been described, a rubber roller having a conductive rubber on the surface may be used instead of the metal roller. . As a result, the peak pressure between the AC bias applying roller 31 and the developing roller 4 can be reduced, and it is possible to suppress damming the wet developer 41 at the nip n1.

  In each of the above-described embodiments, a device using a charger wire is generally used for the toner charging charger 6 and the charge eliminating charger 51. However, the charger wire may be cut by long-term use. Therefore, by adopting a roller-shaped charger, it can be used until the end of the machine life, maintenance is unnecessary, and a reduction in running cost can be expected.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 1 Photoconductor, 2 Photoconductor charging charger, 3 Exposure apparatus, 4 Developing roller, 5 Supply roller, 6 Toner charging charger, 7 Control blade, 8 Developer tank, 10 Cleaning blade, 11 Transfer roller, 12 Photoconductor cleaning means, 13 Eraser lamp, 15 Transfer object, 31 AC bias application roller, 31A AC bias application roller, 41 Wet developer, 51 Charger, 100, 100A, 100B, 100C, 100D, 100E Wet development device, 110 AC bias application roller Driving device, 115 AC bias application roller drive control device, 120 AC bias application roller bias power source, 125 AC bias application roller control device, 130 Toner charging charger bias power source, 135 Toner belt Charger bias control device, 140 Development roller drive device, 145 Development roller drive control device, 150 Development bias power supply, 155 Development bias control device, 230 AC bias application roller pressure contact / separation drive device, 235 AC bias application roller pressure contact / separation control device, 330 Neutralizing Charger Bias Power Supply, 335 Neutralizing Charger Bias Control Device, 470 Wet Development Device Pressure Contact / Separation Drive Device, 475 Wet Development Device Pressure Contact / Separation Control Device, 480 Photoconductor Drive Control Device, 485 Photoconductor Drive Device, 490 Photoconductor Charging Charger Bias Control Device, 495 photoconductor charging charger bias power source, 1000, 1000E wet image forming apparatus.

Claims (7)

A developer carrier;
A supply member for supplying a wet developer containing toner particles to the developer carrier;
A toner charging member for charging the toner particles on the developer carrier;
A cleaning member for cleaning the toner particles on the developer carrier after development;
An AC bias applying member provided on the upstream side of the cleaning member in the rotational direction of the developer carrier, and contacting the developer carrier to form an AC electric field with the developer carrier;
A controller for controlling the output of the toner charging member and the output of the AC bias to the AC bias applying member,
The controller is
After the image formation is completed, the output of the AC bias applied to the AC bias application member at the time of image formation is stopped while maintaining the output to the toner charging member, and the AC bias application member and the developer carrier A wet developing apparatus that performs control to maintain a state in which a DC bias is applied in a direction in which the toner particles are pressed against the developer carrier from the AC bias applying member. The AC bias applying member and the developer carrier are provided so as to be capable of being pressed and separated,
The control device performs control to maintain a state in which the DC bias is applied for a certain period, and then separates the AC bias application member and the developer carrier, and then stops output of the toner charging member. The wet developing apparatus according to claim 1, further performing control for maintaining the state for a predetermined time. In the rotation direction of the developer carrying member, a neutralizing member is provided on the upstream side of the cleaning member to give a charge of a polarity opposite to the polarity charged in the toner particles on the developer carrying member,
The controller is
While maintaining the output to the toner charging member, the output of the AC bias applied to the AC bias applying member during image formation is stopped, and between the AC bias applying member and the developer carrier, When performing control to maintain a state in which a DC bias is applied from the AC bias applying member in a direction in which the toner particles are pressed against the developer carrier, for a certain period of time,
The wet developing apparatus according to claim 1, wherein an output of the charge eliminating member is controlled to be an output smaller than an absolute value of an output of an applied bias at the time of image formation.   4. The wet developing apparatus according to claim 3, wherein the static eliminating member is provided upstream of a nip between the developer carrying member and the AC bias applying member in a rotation direction of the developer carrying member. The controller is
When applying a direct current bias in a direction in which the toner particles are pressed against the developer carrier from the alternating current bias application member, the absolute value of the applied bias output of the toner charging member is the absolute value of the applied bias output during image formation. The wet developing apparatus according to any one of claims 1 to 4, wherein the control is performed so as to be smaller than the value. An image carrier;
An image forming apparatus for forming an electrostatic latent image on the image carrier;
The wet developing apparatus according to claim 1, wherein the electrostatic latent image formed on the image carrier by the image forming apparatus is developed.
A wet image forming apparatus. An image carrier;
An image forming apparatus for forming an electrostatic latent image on the image carrier;
A wet developing device for developing the electrostatic latent image formed on the image carrier by the image forming device;
A controller for controlling the image carrier, the image forming apparatus, and the wet developing apparatus;
With
The wet developing apparatus is
A developer carrier;
A supply member for supplying a wet developer containing toner particles to the developer carrier;
A toner charging member for charging the toner particles on the developer carrier;
A cleaning member for cleaning the toner particles on the developer carrier after development;
An AC bias applying member provided on the upstream side of the cleaning member in the rotation direction of the developer carrier, and abutting on the developer carrier and forming an AC electric field with the developer carrier. ,
The image carrier and the wet developing device are provided so as to be capable of being pressed and separated,
The AC bias applying member and the developer carrier are provided so as to be capable of being pressed and separated,
The controller is
After completion of image formation, the AC bias applied to the AC bias applying member is stopped, and a DC bias is applied from the AC bias applying member in a direction to press the toner particles against the developer carrying member for a certain period of time. After printing an image on the image carrier, the output of the toner charging member is stopped, and the AC bias applying member is kept away from the developer carrier for a certain time, and then the image carrier and A wet image forming apparatus that performs control to maintain a state in which the wet developing apparatus is separated from the wet developing apparatus for a predetermined time.

Images