JP5030636B2 - Wet image forming device - Google Patents

Description

  The present invention relates to a wet image forming apparatus employed in a copying machine, a facsimile machine, a printer, and the like.

  In general, in a wet image forming apparatus, a charge is placed on a photoreceptor drum (image carrier) by a charger, and light corresponding to image information is irradiated onto the photoreceptor drum on which the charge is placed, whereby the photoreceptor drum An electrostatic latent image is formed on the surface, and a developer composed of toner and carrier liquid is attached to the electrostatic latent image by a developing roller (developer carrying member), whereby the toner image is formed on the surface of the photosensitive drum. Forming.

  In JP-A-9-185265 and JP-A-9-185266, the toner in the developer on the developing roller is attracted to the developing roller side so that the developer on the developing roller is divided into two layers. A configuration is disclosed in which an electric field application roller (developing solution double layering means) is disposed in the vicinity of the developing roller on the near side of the developing position. The electric field application roller is applied with a voltage for attracting toner in the developer on the developing roller to the developing roller side. In this way, by making the developer on the developing roller into two layers, the squeeze process is unnecessary and the developability is improved.

  In Japanese Patent Laid-Open No. 2004-258154, in order to eliminate image fogging, a bias voltage having the same polarity as the charged charge of toner in the developer is applied to the developer on the developing roller before entering the developing section. Thus, there is disclosed a configuration in which a bias blade electrode (developing solution double layering means) for making the developing solution on the developing roller into two layers is provided.

  Japanese Patent Laid-Open No. 2005-196191 discloses a deposit roller for adhering ink to the surface of the developing roller when the non-image area on the photosensitive drum and the developing roller come into contact with each other in order to reduce the consumed carrier solution. A technique for turning off the voltage applied to each developing roller is disclosed.

  As disclosed in the prior art, the developer on the developing roller is made into two layers by the developer two-layering means on the front side of the development position, thereby improving the developability and eliminating the image fogging. It has been found that it can be done. However, when a voltage is applied to the developing solution on the developing roller by the developing solution double-layering means, electric charge is injected into the toner itself, so that the toner electric field at the developing position causes the toner particles to be more firmly formed on the photosensitive drum. Developed.

  A wet image forming apparatus for forming a color image, which includes a plurality of image forming means (process units) for forming different color toner images and one intermediate transfer belt, is well known. Assume an arbitrary process unit of such a wet image forming apparatus for color image formation. On the photosensitive drum surface at the time when the photosensitive drum starts to rotate (when the drum is activated), the photosensitive drum surface is located on the front side of the photosensitive drum in the rotational direction from the position facing the charger. The region on the side passes through the development position without being charged by the charger immediately after the drum is started, and therefore is not used for image formation. This area is called a non-image forming area. In addition, an area where charges are placed by the charger is referred to as a charging area.

  In the process in which the non-image forming area passes through the development position after the drum is activated, the surface potential of the non-image forming area is 0 V, and therefore, unnecessary toner is developed in the non-image forming area. After the drum is started, until the non-image forming area where unnecessary toner is developed passes through the primary transfer position, that is, until the charged area on the surface of the photosensitive drum reaches the primary transfer position, the intermediate transfer belt is Since it is separated from the drum, the unnecessary toner developed in the non-image forming area is not transferred to the intermediate transfer belt. Therefore, the unnecessary toner developed in the non-image forming area is not transferred at the primary transfer position, but is removed by the cleaning blade disposed around the photosensitive drum and downstream of the primary transfer position.

However, as described above, when a voltage is applied to the developer on the developing roller by the developer double layering means, the toner particles are strongly developed even in the non-image forming area on the photosensitive drum. Therefore, there is a problem that unnecessary toner on the non-image forming area cannot be sufficiently removed by the cleaning blade.
JP-A-9-185265 JP-A-9-185266 JP 2004-258154 A JP 2005-196191 A

  The present invention provides a region on the surface of the image carrier at the time of starting the image carrier that is on the front side in the rotational direction of the image carrier from the position facing the charging unit and on the rear side in the rotational direction of the image carrier from the development position. Is defined as a non-image forming area on the surface of the image bearing member, an object of the present invention is to provide a wet image forming apparatus that can efficiently remove the developer adhering to the non-image forming area by a cleaning means.

  Another object of the present invention is to provide a wet image forming apparatus capable of efficiently removing a developer developed on an image carrier by a cleaning means when performing a refresh process of a liquid developing device.

According to the first aspect of the present invention, there is provided a charging means for placing an electric charge on the image carrier, an exposure means for forming an electrostatic latent image on the image carrier on which the electric charge is placed, and toner particles electrically A liquid developing device for forming a toner image on an image carrier by supplying a developer dispersed in a neutral solvent to the image carrier, and a toner image formed on the image carrier. The liquid developing device includes a transfer unit for transferring the image to the transfer medium or the recording medium at the transfer position, and a cleaning unit for removing the developer on the image carrier downstream from the transfer position. A developer carrier to be supplied to the carrier, a developer supply means for forming a thin film of the developer on the developer carrier, the periphery of the developer carrier, from the developer supply position by the developer supply means Downstream And a developer double layering means for making the developer on the developer carrying member into a toner particle layer on the surface of the developer carrying member and a solvent layer on the toner particle layer upstream of the developing position. A developing bias is applied to the developer carrying member at the time of image formation, and a bias is applied to the developer two-layering means in order to make the developer on the developer carrying member into two layers. Wet image formation in which the toner image on the image carrier is not transferred to the transfer medium or the recording medium during the period from the starting time until the charged area on the surface of the image carrier reaches the transfer position. In the apparatus, the bias applied to the developer carrier and the developer double layering unit is turned off until the charged area on the surface of the image carrier reaches the development position from the time when the image carrier is activated. To charge the surface of the image carrier Range is when it reaches the development position, characterized in that it comprises means for turning on the bias applied to the developer carrying member and the developer 2-layered unit.

According to a second aspect of the present invention, there is provided a charging means for placing a charge on the image carrier, an exposure means for forming an electrostatic latent image on the image carrier on which the charge is placed, and toner particles electrically A liquid developing device for forming a toner image on an image carrier by supplying a developer dispersed in a neutral solvent to the image carrier, and a toner image formed on the image carrier. The liquid developing device includes a transfer unit for transferring the image to the transfer medium or the recording medium at the transfer position, and a cleaning unit for removing the developer on the image carrier downstream from the transfer position. A developer carrier to be supplied to the carrier, a developer supply means for forming a thin film of the developer on the developer carrier, the periphery of the developer carrier, from the developer supply position by the developer supply means Downstream And a developer double layering means for making the developer on the developer carrying member into a toner particle layer on the surface of the developer carrying member and a solvent layer on the toner particle layer upstream of the developing position. A developing bias is applied to the developer carrying member at the time of image formation, and a bias is applied to the developer two-layering means in order to make the developer on the developer carrying member into two layers. Wet image formation in which the toner image on the image carrier is not transferred to the transfer medium or the recording medium during the period from the starting time until the charged area on the surface of the image carrier reaches the transfer position. In the apparatus, the bias applied to the developing solution double layering unit is turned off until the charged area on the surface of the image carrier reaches the development position from the time when the image carrier starts, and the surface of the image carrier from the time when the image carrier starts. The charged area reaches the development position. When, characterized in that it comprises means for turning on the bias applied to the developing solution 2-layered unit.

  According to a third aspect of the present invention, there is provided a charging means for placing a charge on the image carrier, an exposure means for forming an electrostatic latent image on the image carrier on which the charge is placed, and toner particles electrically A liquid developing device for forming a toner image on an image carrier by supplying a developer dispersed in a neutral solvent to the image carrier, and a toner image formed on the image carrier. The liquid developing device includes a transfer unit for transferring the image to the transfer medium or the recording medium at the transfer position, and a cleaning unit for removing the developer on the image carrier downstream from the transfer position. A developer carrier to be supplied to the carrier, a developer supply means for forming a thin film of the developer on the developer carrier, the periphery of the developer carrier, from the developer supply position by the developer supply means Downstream And a developer double layering means for making the developer on the developer carrying member into a toner particle layer on the surface of the developer carrying member and a solvent layer on the toner particle layer upstream of the developing position. In addition, a developing bias is applied to the developer carrying member during image formation, and a wet image formation in which a bias is applied to the developer double layering means in order to make the developer on the developer carrying member into two layers. In the apparatus, in order to forcibly discard the old developer in the liquid developing device, the developer is forcibly developed on the image carrier, and the developed developer is not transferred to the transfer medium or the recording medium. A refresh means for performing a refresh process to be collected by the cleaning means, and a bias applied to the developer two-layering means when the refresh process is being performed by the refresh means. Characterized in that it comprises means to keep off.

  According to the present invention, the region from the position facing the charging unit to the developing position on the surface of the image carrier at the time of starting the machine and the state where no charge is placed by the charging unit immediately after starting the machine. If an area that can pass through the development position is defined as an uncharged area, the developer attached to the uncharged area can be efficiently removed by the cleaning means.

  According to the present invention, the developer developed on the image carrier can be efficiently removed by the cleaning means when performing the refresh process of the liquid developing device.

  Hereinafter, with reference to the drawings, an embodiment in which the present invention is applied to a tandem color image forming apparatus (hereinafter simply referred to as a wet image forming apparatus) will be described.

[1] Description of schematic configuration of wet image forming apparatus

  FIG. 1 shows a schematic configuration of a wet image forming apparatus.

  The wet image forming apparatus includes a paper feeding unit 1, a vertical conveying path 2, a registration roller pair 3, a belt conveying unit 4, a first image forming unit 5, a second image forming unit 6, a third image forming unit 7, A fourth image forming unit 8, a secondary transfer roller 9, a fixing unit 10, a carry-out conveyance path 11, a belt cleaning device 12, a discharge tray 14 and the like are provided.

  The paper feed means 1 includes a paper feed cassette 1a and a pickup roller 1b, and transports the recording paper P in the paper feed cassette 1a to the vertical transport path 2 by the pickup roller 1b. The vertical conveyance path 2 conveys the conveyed recording paper P to the secondary transfer roller 9 through the registration roller pair 3.

  The belt conveying unit 4 includes a driving roller 41, a driven roller 42, and an endless intermediate transfer belt (transfer medium) 43 that is stretched between the two rollers. The intermediate transfer belt 43 maintains an appropriate tension by the tension roller 44. In this state, the drive roller 41 is rotationally driven by a drive motor (not shown) so that the outer peripheral speed of the photosensitive drum 51 of each image forming unit and the outer peripheral speed of the intermediate transfer belt 43 are equal. .

  The first to fourth image forming units 5 to 8 are for black (BK), magenta (M), cyan (C), and yellow (Y) from the left side in the drawing. Since the image forming units 5 to 8 have almost the same configuration, only the configuration of the first image forming unit 5 will be described. The constituent elements of the other image forming units 6 to 8 are denoted by the same reference numerals as the corresponding elements of the first image forming unit 5.

  The first image forming means 5 includes a photosensitive drum (image carrier) 51, a main charging device (charging means) 52, an LPH (LED PRINT HEAD) 53, a liquid developing device 54, and a primary transfer roller (transfer means) 55. The drum cleaning device 56 and the static elimination lamp 57 are combined into a housing made of resin to form one unit, which is attached to a device body (not shown). Here, it is assumed that the toner of the developer is positively charged.

  The photosensitive drum 51 is an amorphous silicon drum, and is charged by the main charging device 52 so that the dark potential at the developing position becomes + 300V to + 800V. The LPH 53 irradiates the surface of the charged photoconductive drum 51 with light corresponding to image information, whereby an electrostatic latent image is formed on the surface of the photoconductive drum 51.

  The liquid developing device 54 stirs and mixes a developer composed of toner and carrier liquid so as to have a predetermined concentration, and supplies the developer to the photosensitive drum 51 with a developing roller. The upper electrostatic latent image is developed to form a toner image. The dark potential of the photosensitive drum 51 is +300 V to +800 V, the developing bias is +200 V to +600 V, and the post-exposure potential is set to 0 to +200 V. That is, the dark potential corresponds to the white portion of the image, the post-exposure potential corresponds to the black portion of the image, and this difference is a so-called contrast potential. The toner image formed on the photosensitive drum 51 is transferred to the intermediate transfer belt 43 of the belt conveying unit 4 at the nip with the primary transfer roller 55. A voltage (-100 V to -1 kV) having a polarity opposite to the surface potential of the photosensitive drum 51 is applied to the primary transfer roller 55.

  The residual developer that has not been transferred onto the photosensitive drum 51 is removed by a drum cleaning device (cleaning means) 56. Further, the photosensitive drum 51 is neutralized by a neutralizing lamp 57 in order to lower the residual potential on the surface and make it uniform, and thereafter, it is prepared for the next series of processes. In this wet image forming apparatus, images corresponding to magenta, cyan, and yellow are developed on the photosensitive drum by the second to fourth image forming units 6 to 8 in the same manner as the first image forming unit 5. Then, a full-color image is formed by being sequentially and repeatedly transferred onto the intermediate transfer belt 43 without deviation.

  The secondary transfer roller 9 is arranged in a state of being pressed against the intermediate transfer belt 43 at a position facing the driving roller 41 on the vertical conveyance path 2. A secondary transfer bias is applied to the secondary transfer roller 9, and the recording paper conveyed by the secondary transfer roller 9 from the intermediate transfer belt 43 through the vertical conveyance path 2 and the registration roller pair 3. A full color image is secondarily transferred to P. The paper P onto which the full-color image has been secondarily transferred is separated from the intermediate transfer belt 43 and conveyed to the fixing unit 10. The fixing unit 10 includes a first fixing roller 10a and a second fixing roller 10b. Each fixing roller includes a fixing heater (not shown), and each fixing roller is heated to a predetermined temperature by the fixing heater. A full color image is fixed on the recording paper P while the recording paper P passes through both the fixing rollers 10a and 10b. Then, the recording paper P is discharged to the discharge tray 14 via the discharge conveyance path 11 after being fixed by the fixing means 10.

  The residual developer that has not been transferred onto the intermediate transfer belt 43 is removed by the belt cleaning device 12. The belt cleaning device 12 includes a cleaning roller 12a, a cleaning blade 12b, and a conveying screw 12d in a cleaning case 12c. The cleaning roller 12a is in pressure contact with the intermediate transfer belt 43 and is driven to rotate in the same direction as the rotation direction of the intermediate transfer belt 43 by a drive motor (not shown). The cleaning blade 12b is in pressure contact with the intermediate transfer belt 43 on the downstream side of the cleaning roller 12a, and removes the residual developer on the intermediate transfer belt 43. The conveying screw 12d collects the transfer residual developer scraped by the intermediate transfer cleaning blade 12b.

[2] Configuration of the liquid developing device 54

  FIG. 2 shows the configuration of the liquid developing device 54.

  The liquid developing device 54 includes a developer storage container 71 that stores the developer 70. Inside the developer storage container 71, there are a developing roller (developer carrier) 72, a coating roller (developer supplying means) 73, a pumping roller 74, a doctor blade 75, a cleaning blade 76, and a pair of stirring screws 77 a and 77 b. Is provided. The developing roller 72, the application roller 73, the pumping roller 74, and the stirring screws 77a and 77b are rotationally driven by a drive motor (both not shown) through a drive transmission mechanism including a gear train and the like.

  A developing corona charge (developing solution double layering means) 78 for making the developing solution on the developing roller 72 into two layers is located around the developing roller 72 and upstream of the developing position. Are arranged. A bias of about +3.5 kV to +7 kV at which discharge starts is applied to the development corona charge 78.

  The developer 70 is adjusted so that charged toner (hereinafter simply referred to as toner) is dispersed at a high concentration in a carrier liquid that is a nonpolar, ie, electrically neutral solvent, such as silicone oil.

  The toner contains a colorant, a resin (binder), and, if necessary, a charge control agent. The resin (binder) is adsorbed on the colorant, and is well dispersed in the carrier liquid to impart a positive or negative charge to the adsorbed colorant. In this embodiment, toner that is charged to a positive potential (positive) by a resin (binder) is used. That is, positively charged toner is used. Examples of the carrier liquid include isoparaffinic solvents (for example, Isopar G (manufactured by Exxon)), higher fatty acid esters, silicon oil, and the like. The agitation screws 77a and 77b circulate and agitate the developer 70. A part of the pumping roller 74 is immersed in the developer 70, and the developer 70 that has been pumped is rotated in contact with the application roller 73 to apply the developer 70 to the application roller 73.

  The application roller 73 forms a thin layer (liquid toner layer) of the developing solution 70 on the developing roller 72 by applying the developing solution 70 on the developing roller 72. When an electric field is generated by the developing corona charge 78, the liquid toner layer on the developing roller 72 is made into two layers. That is, the liquid toner layer on the developing roller 72 is divided into two layers: a toner particle layer on the surface of the developing roller 72 and a solvent layer on the toner particle layer. At the developing position, the liquid toner layer on the developing roller 72 is brought into contact with the surface of the photosensitive drum 51 in a state where the two layers are formed.

  The toner particles in the liquid toner layer on the developing roller 72 are compressed on the surface of the developing roller 72 by the developing corona charge 78 before the development. Since the toner does not come into contact with the drum surface, a fogged image can be prevented. Further, since electric charge is injected into the toner itself in the liquid toner layer on the developing roller 72 by forming the electric field of the developing corona charge 78, the toner is responsive to the electrostatic latent image on the photosensitive drum 51 by the developing electric field. While being developed, the toner adheres firmly on the surface of the photoreceptor.

  The toner image formed on the photosensitive drum 51 in this way is transferred to the intermediate transfer belt 43 by a bias applied to the primary transfer roller 55.

  After the development, the developer remaining on the developing roller 72 is removed from the developing roller 72 by the cleaning blade 76 and returned to the developer storage container 71.

  The drum cleaning device 56 includes a cleaning case 61 that stores the collected residual developer. Inside the cleaning case 61, a cleaning blade 62 for removing the residual developer on the photosensitive drum 51 is provided.

[3] Explanation of operation at drum startup

  In each of the image forming units 5 to 8, the photosensitive drum 51 rotates in front of the photosensitive drum 51 from the position facing the main charging device 52 on the surface of the photosensitive drum 51 when the photosensitive drum 51 starts to be driven (drum activation time). The region located behind the developing position in the rotation direction of the photosensitive drum passes through the developing position without being charged by the main charging device 52 immediately after the drum is started, and is used for image formation. Absent. This area is called a non-image forming area. In the process in which the non-image forming area passes through the development position after the drum is activated, the surface potential of the non-image forming area is 0 V, so that the toner is developed in the non-image forming area. That is, immediately after the drum is activated, unnecessary toner adheres to the non-image forming area.

  In this embodiment, in order to prevent unnecessary toner adhering to the non-image forming area from being transferred to the intermediate transfer belt 43, the photosensitive drum 51 and the intermediate transfer belt 43 are moved at the primary transfer position when the drum is activated. It is in a separated state (transfer prohibited state). Then, after the non-image forming area has passed the primary transfer position (when the charged area on the surface of the photosensitive drum 51 has reached the primary transfer position), the photosensitive drum 51 and the intermediate transfer belt 43 are close to each other. (Transferable state).

  Therefore, unnecessary toner adhering to the non-image forming area is conveyed to the drum cleaning device 56 without being transferred to the intermediate transfer belt 43 at the primary transfer position, and is removed by the cleaning blade 62 of the drum cleaning device 56.

  However, as described above, the electric field is injected into the toner in the liquid toner layer on the developing roller 72 due to the formation of the electric field of the developing corona charge 78, so the toner is electrostatically latent on the photosensitive drum 51 by the developing electric field. The image is developed with good reactivity on the image, and the toner adheres firmly on the surface of the photoreceptor. Therefore, the unnecessary toner attached to the non-image forming area cannot be sufficiently removed by the drum cleaning device 56.

  Therefore, in this embodiment, until the non-image forming area passes through the developing position after the photosensitive drum 51 is activated (until the charged area reaches the developing position), toner is not applied to the non-image forming area. The voltage (development bias) applied to the developing roller 72 and the bias voltage applied to the development corona charge 78 are turned off so as not to adhere firmly.

  FIG. 3 shows a control example of the bias voltage applied to the developing roller and the bias voltage applied to the developing corona charge 78.

  When the drum is activated, the photosensitive drum 51 is driven to rotate and a bias voltage is applied to the main charging device 52 at time t1. As a result, the photosensitive drum 51 is rotated and the surface of the photosensitive drum 51 is charged by the main charging device 52.

  When a time ΔT from the time point t1 until the non-image forming area on the surface of the photosensitive drum 51 finishes passing through the developing position has elapsed (time point t2), a bias voltage is applied to the developing roller 72 and the developing corona charge 78 is biased. A voltage is applied.

  That is, since the bias voltage is not applied to the developing roller 72 and the developing corona charge 78 during the period from the time when the drum is activated until the charged area on the surface of the photosensitive drum 21 reaches the developing position (the period from t1 to t2). It is possible to prevent the toner from firmly adhering to the non-image forming area on the body drum 21. Therefore, the unnecessary toner adhering to the non-image forming area is sufficiently removed by the drum cleaning device 56.

  In FIG. 3, both the voltage applied to the developing roller 72 and the bias voltage applied to the developing corona charge 78 are turned off during the period from the time point t1 to the time point t2. As shown, a bias voltage may be applied to the developing roller 72 from time t1 and only the bias voltage applied to the developing corona charge 78 may be turned off during the period from time t1 to time t2.

[4] Refresh operation of the liquid developing device 54

  There is a case where a refresh mode for forcibly discarding the old developer in the liquid developing device 54 is prepared. The refresh mode is set automatically based on the machine drive time up to now and the number of prints up to now, or manually by a user or the like.

  In the refresh mode, the developer is forced on the photosensitive drum 51 by driving the main charging device 52 and applying a developing bias to the developing roller 72 to expose an arbitrary pattern for refreshing on the surface of the photosensitive drum 51. The drum cleaning device 56 collects the toner without developing the toner image to the intermediate transfer belt 43. Even in the refresh mode, it is preferable to turn off the bias voltage applied to the developing corona charge 78 so that the developer does not adhere firmly to the photosensitive drum 51.

[5] Others The embodiment in which the present invention is applied to the wet image forming apparatus in which the developing corona charge 78 is used as the developing solution double layering means has been described. As shown in FIG. The present invention can also be applied to a wet image forming apparatus in which a developing electric field applying roller 79 is used in place of the developing corona charge 78 as the liquid double layering means. In the case where the developing electric field applying roller 79 is used as the developing solution double layering means, when the developing solution on the developing roller 72 is made into two layers, a bias of about 100V to 500V higher than the developing bias is applied.

It is a block diagram which shows schematic structure of a wet image forming apparatus. 3 is a configuration diagram showing a configuration of a liquid developing device 54. FIG. 6 is a time chart showing an example of control of the voltage applied to the developing roller and developing corona charge 78; 10 is a time chart showing another example of control of voltages applied to the developing roller and developing corona charge 78; FIG. 6 is a configuration diagram showing a configuration of a liquid developing apparatus in which a developing electric field applying roller 79 is used as a developing solution double layering unit.

Explanation of symbols

43 Intermediate transfer belt (transfer medium)
51 Photosensitive drum (image carrier)
54 Liquid developing device 56 Drum cleaning device 72 Developing roller (developer carrying member)
73 Coating roller (developer supply means)
78 Development corona charge 79 Development electric field application roller

Claims (3)

The toner particles are dispersed in an electrically neutral solvent at a charging means for placing a charge on the image carrier, an exposure means for forming an electrostatic latent image on the image carrier on which the charge is placed, and a developing position. The liquid developer for forming a toner image on the image carrier by supplying the developing solution to the image carrier, and the toner image formed on the image carrier on the transfer medium or recording medium at the transfer position A developing means for supplying the developer to the image carrier at the developing position, the transfer means for transferring, and a cleaning means for removing the developer on the image carrier downstream from the transfer position; A developer supply means for forming a developer thin film on the developer carrier, and around the developer carrier, downstream from the developer supply position by the developer supply means and upstream from the development position. And a developer double layering means for forming the developer on the developer carrier into a toner particle layer on the developer carrier surface and a solvent layer on the toner particle layer. A developing bias is applied to the liquid carrier, and a bias is applied to the developer double layering means in order to make the developer on the developer carrier into two layers. In the wet image forming apparatus in which the toner image on the image carrier is not transferred to the transfer medium or the recording medium in a period until the charged area reaches the transfer position.
The bias applied to the developer carrier and the developer double layering unit is turned off until the charged area on the surface of the image carrier reaches the development position from the time of starting the image carrier , and the image carrier is started from the time of starting the image carrier. Means for turning on a bias applied to the developer carrying member and the developer double layering means when the charged area on the body surface reaches the developing position ;
A wet-type image forming apparatus comprising: The toner particles are dispersed in an electrically neutral solvent at a charging means for placing a charge on the image carrier, an exposure means for forming an electrostatic latent image on the image carrier on which the charge is placed, and a developing position. The liquid developer for forming a toner image on the image carrier by supplying the developing solution to the image carrier, and the toner image formed on the image carrier on the transfer medium or recording medium at the transfer position A developing means for supplying the developer to the image carrier at the developing position, the transfer means for transferring, and a cleaning means for removing the developer on the image carrier downstream from the transfer position; A developer supply means for forming a developer thin film on the developer carrier, and around the developer carrier, downstream from the developer supply position by the developer supply means and upstream from the development position. And a developer double layering means for forming the developer on the developer carrier into a toner particle layer on the developer carrier surface and a solvent layer on the toner particle layer. A developing bias is applied to the liquid carrier, and a bias is applied to the developer double layering means in order to make the developer on the developer carrier into two layers. In the wet image forming apparatus in which the toner image on the image carrier is not transferred to the transfer medium or the recording medium in a period until the charged area reaches the transfer position.
From the time when the image carrier is activated until the charged area on the surface of the image carrier reaches the development position, the bias applied to the developer bilayering means is turned off, and the charged area on the surface of the image carrier from the time when the image carrier is activated Means for turning on the bias applied to the developer double layering means when the toner reaches the developing position ;
A wet-type image forming apparatus comprising: The toner particles are dispersed in an electrically neutral solvent at a charging means for placing a charge on the image carrier, an exposure means for forming an electrostatic latent image on the image carrier on which the charge is placed, and a developing position. The liquid developer for forming a toner image on the image carrier by supplying the developing solution to the image carrier, and the toner image formed on the image carrier on the transfer medium or recording medium at the transfer position A developing means for supplying the developer to the image carrier at the developing position, the transfer means for transferring, and a cleaning means for removing the developer on the image carrier downstream from the transfer position; A developer supply means for forming a developer thin film on the developer carrier, and around the developer carrier, downstream from the developer supply position by the developer supply means and upstream from the development position. And a developer double layering means for forming the developer on the developer carrier into a toner particle layer on the developer carrier surface and a solvent layer on the toner particle layer. In a wet image forming apparatus in which a developing bias is applied to the liquid carrier and a bias is applied to the developer double layering means in order to make the developer on the developer carrier two layers.
In order to forcibly discard the old developer in the liquid developing device, the developer is forcibly developed on the image carrier, and the developing means is not transferred to the transfer medium or the recording medium without cleaning. A refresh means for performing a refresh process collected by the means, and a means for turning off the bias applied to the developer double layering means when the refresh process is being performed by the refresh means,
A wet-type image forming apparatus comprising:

Images