JP4733401B2 - Liquid image forming apparatus - Google Patents

Description

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

  In a liquid image forming apparatus using a liquid developing system, for example, the liquid developer in a developer storage tank is pumped up by a coating roller, the amount of liquid developer on the coating roller is regulated by a doctor blade, and then the developing roller is thinned. Layered and applied. The developing roller conveys the thin liquid developer to the nip portion with the photosensitive drum. In the nip portion, development based on the latent image on the photosensitive drum is performed by the thin layer of the liquid developer.

Conventionally, there has been described a technique for preventing permanent deformation of a developing roller whose surface is made of an elastic body and further preventing contamination of the surface of the latent image carrier (Patent Document). 1).
JP 2002-278293 A

  By the way, in the nip portion where the photosensitive drum and the developing roller are close to each other, if the thickness of the thin layer is larger than the distance between the photosensitive drum and the developing roller in the nip portion, a liquid developer pool is generated. This liquid developer pool causes the thickness of the thin layer of the liquid developer formed on the developing roller to be disturbed, and there is a problem that a clear image cannot be obtained.

  In the liquid image forming apparatus of the type in which the developing roller is separated from the image carrier (corresponding to the photosensitive drum) as in the configuration of Patent Document 1, the liquid developer pool is generated in the nip portion. For this reason, when the developing roller is separated from the photosensitive drum, the liquid developer pool moves along the peripheral surface of the photosensitive drum, moves below the photosensitive drum, and gradually drops downward. The liquid developer dripped in this manner contaminates the developing roller charging device disposed near the entrance of the nip portion and the exposure device disposed below the photosensitive drum. There is a problem that charging failure, leakage, etc. occur due to contamination of the charging device of the drum.

  It is an object of the present invention to clean a liquid developer reservoir, to avoid disturbing the thickness of a thin layer of liquid developer formed on a developing roller, and to obtain a clear image. It is an object of the present invention to provide a liquid image forming apparatus that can prevent contamination of a peripheral device disposed below the surface and prevent occurrence of problems due to contamination of the peripheral device.

In order to solve the above problems, an invention according to claim 1 is directed to an image carrier that carries an electrostatic latent image, a liquid developer carrier that supplies a liquid developer to the image carrier, and the image. In a liquid image forming apparatus provided with a cleaning device for cleaning a carrier, the liquid developer carrier is positioned at a proximal position close to the image carrier during development, and a distal position far from the image carrier during non-development The liquid developer carrier is distant from the image carrier by a first contact / separation mechanism for separating the liquid developer carrier, a rotational drive source for rotating the image carrier, and the first contact / separation mechanism. A control unit that controls the rotation drive source to control the rotation of the image carrier when separated to a position, and the rotation of the rotation drive source of the control unit causes the image carrier to be moved by a cleaning device. Before cleaning Γp the critical surface tension of the surface of the image bearing member, when said critical surface tension of the surface of the liquid developer carrier .gamma.d, [gamma] t the surface tension of the liquid developer, .gamma.d <[gamma] t <and γp are child satisfied A gist of a liquid image forming apparatus characterized by the above.

According to a second aspect of the present invention, in the first aspect, the surface layer of the liquid developer carrying member is made of a fluorine-based resin or a urethane-based resin.
According to a third aspect of the present invention, in the first or second aspect, the surface layer of the peripheral surface of the image carrier is formed of amorphous silicon.

According to a fourth aspect of the present invention, in any one of the first to third aspects, the transfer carrier that contacts and separates from the image carrier and the transfer carrier abuts against the image carrier during development. A second contact / separation mechanism that separates the transfer carrier from the image carrier during non-development, and when the liquid developer carrier is separated by the first contact / separation mechanism, The second contact / separation mechanism is controlled to separate the transfer carrier from the image carrier, and the rotation driving source is controlled to control the rotation of the image carrier.

  According to the first aspect, when the liquid developer carrier is separated from the image carrier by the first contact / separation mechanism, the control unit controls the rotation drive source to control the rotation of the image carrier. Therefore, the liquid developer pool generated in the nip portion between the image carrier and the liquid developer carrier due to the rotation of the image carrier is moved to the cleaning device side and cleaned by the cleaning device. As a result, since the liquid developer pool is removed, the thickness of the thin layer of the liquid developer formed on the developing roller is not disturbed after being cleaned by the cleaning device, and a clear image can be obtained. Can do. Further, the contamination of the peripheral device disposed below the photosensitive drum can be prevented, and the occurrence of problems due to the contamination of the peripheral device can be prevented.

When the critical surface tension γp of the surface of the image carrier, the critical surface tension γd of the surface of the liquid developer carrier, and the surface tension γt of the liquid developer are γd <γt <γp, The liquid developer pool generated in the nip portion of the liquid developer carrier is likely to adhere to the image carrier, and is moved to the cleaning device side with the rotation of the image carrier. As a result, the cleaning effect by the cleaning device can be enhanced.

According to the second aspect, the surface layer of the liquid developer carrying member is made of a fluororesin or a urethane resin, so that swelling of the inner layer liquid developer covered with the surface layer by the carrier liquid can be prevented.

According to the third aspect of the present invention, the surface layer on the peripheral surface of the image carrier is made of amorphous silicon, so that the solvent resistance is excellent and the durability against light irradiated to the image carrier is improved. Can do.

According to a fourth aspect of the present invention, in the liquid image forming apparatus including the transfer carrier, when the liquid developer carrier is separated by the first contact / separation mechanism, the control unit moves the second contact / separation mechanism. The transfer carrier is separated from the image carrier by performing separation control, and the rotation driving source is controlled to control the rotation of the image carrier. As a result, even in the liquid image forming apparatus including the transfer carrier, the effect described in any one of claims 1 to 3 can be achieved.

Hereinafter, an embodiment in which the present invention is embodied in a liquid image forming apparatus will be described with reference to FIGS. FIG. 1 shows a liquid image forming apparatus (hereinafter referred to as an image forming apparatus 10).
As shown in FIG. 1, the image forming apparatus 10 includes a photosensitive drum 20, a main charging device 30, an LPH (LED PRINT HEAD) 40, a cleaning device 60, a charge eliminating lamp 70, a liquid developing device 50, a transfer roller 100, and the like. ing.

  The photosensitive drum 20 uses a drum using amorphous silicon for the photosensitive layer (that is, the surface layer) on the peripheral surface, and is charged by the main charging device 30 so as to have a predetermined dark potential at the developing position. In the present embodiment, the critical surface tension γp of the surface of the photosensitive drum 20 and the surface tension γt of the liquid developer are adjusted in advance so that γt <γp. Amorphous silicon improves the durability characteristics against irradiated light and is excellent in the solvent resistance of the liquid developer to the carrier liquid. The LPH 40 irradiates light according to image information onto the surface of the charged photosensitive drum 20, thereby forming an electrostatic latent image on the surface of the photosensitive drum 20. The photosensitive drum 20 corresponds to an image carrier. The electrostatic latent image on the surface of the photosensitive drum 20 is developed with a liquid developer composed of toner and carrier liquid supplied from the developing roller 52 of the liquid developing device 50 to form a toner image. Examples of the carrier liquid and the non-volatile carrier liquid include silicon oil, but are not limited to this material. The developing roller 52 corresponds to a liquid developer carrier.

(Second contact / separation mechanism S2)
Here, the transfer roller 100 and the second contact / separation mechanism S2 will be described.
The transfer roller 100 is disposed so as to be movable between a transfer position and a retracted position separated from the transfer position. The transfer position is a position where the transfer roller 100 is pressed against the photosensitive drum 20 via an intermediate transfer belt 110 as a transfer carrier. The retracted position is a position where the transfer roller 100 has moved a predetermined amount from the transfer position in a direction away from the photosensitive drum 20. The intermediate transfer belt 110 is an endless belt, and maintains an appropriate tension with a tension roller (not shown). When the transfer roller 100 is released, the intermediate transfer belt 110 is separated from the photosensitive drum 20 by the tension. Have been to.

  As shown in FIG. 1, the transfer roller 100 is supported by the tip of an arm 101 that is swingably attached to a frame (not shown) of the apparatus main body. The base end of the arm 101 has a rotating shaft 102 that is swingably attached to the frame.

  The rotation shaft 102 is operatively connected to a transfer roller drive motor 310 (see FIG. 10), and the transfer roller drive motor 310 is rotationally driven to move the transfer roller 100 from the retracted position to the transfer position via the arm 101. Can be moved. Further, one end of the arm 101 is attached with a tension coil spring 104 as an urging means attached to the frame of the apparatus main body. When the transfer roller drive motor 310 is not driven to rotate, the tension coil spring 104 The transfer roller 100 can be positioned from the transfer position to the retracted position.

  The transfer roller drive motor 310, the arm 101, the rotating shaft 102, and the tension coil spring 104 constitute a second contact / separation mechanism S2 that makes the intermediate transfer belt 110 (transfer carrier) contact or separate from the photosensitive drum 20. ing.

  The toner image in which the electrostatic latent image formed as described above is developed is transferred to an endless intermediate transfer belt 110 located in the nip with the transfer roller 100. The intermediate transfer belt 110 is formed of a resin belt, and a resin film such as PVdF (polyvinylidene fluoride), nylon, PET (polyethylene terephthalate), or polycarbonate can be used as the material of the resin belt. The toner that has not been transferred onto the photosensitive drum 20 is scraped off by the cleaning device 60 in the next process. The photosensitive drum 20 is neutralized by a neutralizing lamp 70 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.

(Cleaning device 60)
The cleaning device 60 will be described. The cleaning device 60 includes a cleaning blade 62, a screw 64, a housing 66, and the like. The screw 64 is rotatably arranged in the housing 66, and is operatively connected to a drive system (not shown) so as to be rotated. Then, by the rotation of the screw 64, the collected developer (that is, the collected liquid developer) and paper dust in the bottom portion of the housing 66 are transferred to a waste liquid tank (both not shown) through the discharge path.

  The cleaning blade 62 is attached and fixed to the lower side surface of the housing 66 of the cleaning device 60 via a bracket 67. The tip (edge portion) of the cleaning blade 62 is in counter contact, that is, pressed against the photosensitive drum 20 (see FIG. 1). Note that the counter contact means that the counter contact is in the counter direction with respect to the rotation direction of the photosensitive drum 20. In this embodiment, the cleaning blade 62 is a plate having elasticity of polyurethane rubber, made of a plate material having an Asker C hardness of 60 to 80 degrees, a thickness of 1.5 to 2.5 mm, and an overall shape being a planar rectangle. It is formed in a shape. The cleaning blade 62 is in counter contact with the peripheral surface of the photosensitive drum 20 with a deflection of about 1 mm. The material of the cleaning blade 62 is not limited to polyurethane rubber, but may be synthetic resin having elasticity or synthetic rubber.

(Liquid developing device 50)
Next, the liquid developing device 50 will be described.
In the container 51 (see FIG. 8), the liquid developing device 50 includes a developing roller 52 whose surface is formed of an elastic body, an anilox roller 53 as a supply roller, a pumping roller 54, and a doctor blade 55 (see FIG. 8). 6 (b)) and a cleaning blade 56. The material of the developing roller 52 is preferably formed of an elastic material such as urethane rubber or nitrile rubber in order to prevent swelling due to the liquid developer (exactly carrier liquid). Further, the surface layer of the developing roller 52 may be formed by coating or tubing to prevent the carrier liquid from swelling. In this case, the developing roller 52 is formed of epichlorohydrin rubber or silicon rubber, and its surface is tubed with fluorine coating, polyurethane coating, fluorine resin, or polyurethane resin to prevent swelling. .

  As the fluororesin used in the fluorine coating, PTFE (polytetrafluoroethylene) or PFA (perfluoroalkoxyalkane) is preferably used, but is not limited thereto. The critical surface tension γd of the developing roller 52 is adjusted by the coating or tubing so that γd <γt (<γp) with respect to the surface tension γt of the liquid developer.

  The surface tension can be measured by the Wilhelmi (plate) method, and in this embodiment, the surface of the photosensitive drum 20 and the developing roller 52 are set by this measurement method so that the above γd <γt <γp is satisfied. It has been adjusted to be the surface of. In the present embodiment, the critical surface tension γp of the surface of the photosensitive drum 20 is 45 mN / m. The critical surface tension γd of the surface of the developing roller 52 is 6 to 24 mN / m. The surface tension γt of the liquid developer is about 30 mN / m.

  Due to this adjustment, the critical surface tension γd (6 to 24 mN / m) of the developing roller 52 is smaller than the surface tension γt (around 30 mN / m) of the liquid developer. It is made to repel. Further, since the critical surface tension γp (45 mN / m) of the photosensitive drum 20 is larger than the surface tension γt (around 30 mN / m) of the liquid developer, the liquid developer gets wet on the surface of the photosensitive drum 20. Has been.

  As a result, when the developing roller 52 is separated from the photosensitive drum 20, the liquid developer in the liquid developer pool in the nip portion N is attached to the photosensitive drum 20 side having better wettability than the developing roller 52. Has been.

The surface roughness of the developing roller 52 is preferably Rzjis (10-point average roughness, jis B0601 2001) 5-10.
As shown in FIG. 8, the photosensitive drum 20 has a rotating shaft 20 a that is rotatably supported with respect to the side wall 51 a of the container 51. Similarly, the anilox roller 53 and the pump-up roller 54 are rotatably supported so that the rotation shafts 53 a and 54 a are rotatable with respect to both side walls 51 a that are spaced apart in the longitudinal direction of the container 51. In FIG. 8, only one side wall 51a is shown.

  As shown in FIG. 9, the side wall 51a is formed with an arc-shaped long hole 51b having a radius of curvature centering on the axis O of the rotating shaft 53a of the anilox roller 53, and the long hole 51b is developed. The rotating shaft 52a of the roller 52 is penetrated and supported so as to be movable along the shape of the elongated hole 51b. Moreover, the movement range of the rotating shaft 52a is regulated at both ends in the longitudinal direction of the long hole 51b.

  In the present embodiment, as shown in FIG. 9, when the rotation shaft 52 a is locked to one end of the long hole 51 b, the developing roller 52 is referred to as a contact position P <b> 0 where it contacts the photosensitive drum 20. Further, when the rotation shaft 52a is locked to the other end of the long hole 51b, the developing roller 52 is referred to as a separation position P1 at which it is separated from the photosensitive drum 20. The contact position P0 of this embodiment corresponds to the proximal position of the present invention. The proximal position is not necessarily limited to the position where the developing roller 52 is in contact with the photosensitive drum 20. The proximal position includes a position where the developing roller 52 is separated from the photosensitive drum 20 so as to have a minute gap if the latent image on the photosensitive drum 20 can be developed by a thin layer of liquid developer. It is the purpose. Further, the separation position P1 of the present embodiment corresponds to the distal position of the present invention.

In this way, the rotation shaft 52a of the developing roller 52 can draw an arc-shaped movement locus around the axis of the rotation shaft 53a.
Gears 72, 73, and 74 are fixed to the rotary shafts 52a, 53a, and 54a protruding from the container 51, and a gear train that meshes with adjacent gears is formed by these gears.

  The gear 72 fixed to the rotating shaft 52a of the developing roller 52 is always meshed with the gear 73 regardless of the position of the developing roller 52 between the contact position P0 and the separation position P1. Yes.

  The drive transmission joint 80 is connected to the rotation shaft 53a, and can transmit the rotation torque of the developing roller drive motor 350 (see FIG. 10) to the rotation shaft 53a. The torque transmission system from the developing roller drive motor 350 to the gears 72 to 74 constitutes one drive transmission system. Further, on the outer side of the side wall 51a, the rotating shafts 52a and 53a are pivotally penetrated and attached to the plate-like connecting members 65, as shown in FIGS. .

  In the present embodiment, the gear 73 corresponds to a first sun gear, and the gear 72 corresponds to a first planetary gear. The connecting member 65 and the gears 72 and 73 constitute a first differential gear mechanism that is a planetary gear mechanism.

  The developing roller 52, the anilox roller 53, and the scooping roller 54 are rotationally driven by a developing roller driving motor 350 through the gears 72, 73, 74 and the drive transmission joint 80. A gear 71 is fixed to the rotary shaft 20a of the photosensitive drum 20, and the gear 71 is connected to the photosensitive drum via a drive transmission system different from the drive transmission system including the gears 72 to 74. It is rotationally driven by a drive motor 320 (see FIG. 10). The photosensitive drum drive motor 320 corresponds to a rotational drive source.

  The cleaning blade 56 is formed from a rubber or metal blade-like member. As shown in FIG. 8, the cleaning blade 56 is supported so as to be rotatable with respect to the rotation shaft 52 a via a bracket 68, and with respect to the surface (that is, the peripheral surface) of the developing roller 52. The surface of the developing roller 52 is cleaned by always abutting in the counter direction with respect to the rotation direction of the developing roller 52. 6A, 6B, 7A, and 7B, only the portion of the bracket 68 that is attached to the rotating shaft 52a of the bracket 68 is illustrated, and the cleaning blade 56 is attached. These portions are not shown for convenience of explanation.

  One end of a tension coil spring 82 as urging means is fixed to the bracket 68. The other end of the tension coil spring 82 is fixed to the wall surface of the container 51. The developing roller 52 is urged away from the photosensitive drum 20 by the elastic force (that is, urging force) of the tension coil spring 82 via the rotating shaft 52a. The biasing force is adjusted so as not to prevent the circumferential movement of the gear 72 relative to the gear 73 when the gears 72, 73, 74 are rotationally driven by the developing roller drive motor 350.

  Accordingly, when the photosensitive drum 20, the developing roller 52, the anilox roller 53, and the scooping roller 54 are rotationally driven by the developing roller drive motor 350 via the gears 72, 73, 74 and the drive transmission joint 80, The developing roller 52 can move to the photosensitive drum 20 side.

  A first contact / separation mechanism S1 is configured by using the tension coil spring 82 as an urging means and the connecting member 65 and the gears 72 and 73 as a first differential gear mechanism. The first contact / separation mechanism S1 may be configured by omitting the connecting member 65. In this case, a configuration including the side wall 51a having the long hole 51b and the gears 72 and 73 is defined as a first differential gear mechanism.

  The doctor blade 55 is attached to the side wall 51 a via a bracket (not shown), and the tip thereof is in contact with the rotation direction of the anilox roller 53 in the counter direction.

  Although not shown, the liquid developer stored in the lower portion of the container 51 is adjusted so that the toner is dispersed at a high concentration in a carrier liquid made of a nonpolar insulating liquid such as silicone oil. The pumping roller 54 is partially immersed in the liquid developer, and is not shown in FIG. 6A, but is spaced apart from the anilox roller 53 with a small gap. Then, the liquid developer pumped up at the time of rotation is applied to the anilox roller 53.

  The liquid developer pumped up by the pump-up roller 54 is transferred to the anilox roller 53, and the liquid developer on the surface of the anilox roller 53 is regulated (measured) by the doctor blade 55 after the excess developer is regulated (measured). It is supplied to the developing roller 52.

  The anilox roller 53 applies a liquid developer onto the developing roller 52 to form a thin layer of the liquid developer on the developing roller 52. In the developing area on the photosensitive drum 20, that is, in the nip portion N with the photosensitive drum 20, the latent image is developed by the liquid developer. Further, after the development, the liquid developer remaining on the developing roller 52 is removed from the developing roller 52 by the edge portion of the cleaning blade 56 in contact with the surface of the developing roller 52. On the other hand, the toner image developed on the photosensitive drum 20 is transferred to the intermediate transfer belt 110. Further, a part of the liquid developer remains on the photosensitive drum 20 in an untransferred state and is removed by the cleaning device 60.

(Electrical configuration)
Next, the electrical configuration of the image forming apparatus 10 will be described with reference to FIG.
A control device 200 as a control unit of the image forming apparatus includes a CPU 210, a ROM 220, a RAM 230, and the like. The ROM 220 stores a cleaning program. The CPU 210 can control the rotation of the transfer roller drive motor 310 via the drive motor control circuit 240. The CPU 210 can control the rotation of the photosensitive drum drive motor 320 via the drive motor control circuit 250. Further, the CPU 210 can perform on / off control of the main charging device 30 via the main charging device control circuit 260.

  The CPU 210 can perform on / off control of the developing bias applying unit 340 that applies the developing bias to the developing roller 52 via the developing bias control circuit 270. The CPU 210 can control the rotation of the developing roller drive motor 350 via the drive motor control circuit 280. Further, the CPU 210 can control the rotation of the intermediate transfer belt drive motor 360 via the drive motor control circuit 290. By the rotation of the intermediate transfer belt driving motor 360, the intermediate transfer belt 110 is driven so that the outer peripheral speed of the photosensitive drum 20 and the outer peripheral speed of the intermediate transfer belt 110 are equal. The CPU 210 can control the LPH 40 via the LED control circuit 300.

Now, the operation of the image forming apparatus 10 configured as described above will be described.
When printing is stopped, the transfer roller driving motor 310, the photosensitive drum driving motor 320, the developing roller driving motor 350, and the intermediate transfer belt driving motor 360 are stopped, and the main charging device 30 and the LPH 40 are turned off. It is controlled. In this case, in the liquid developing device 50, the developing roller driving motor 350 is stopped, and the developing roller 52 is moved to the separation position P1 via the bracket 68 and the rotating shaft 52a by the tension coil spring 82 of the first contact / separation mechanism S1. The developing roller 52 is located away from the photosensitive drum 20 (see FIGS. 7A and 7B). In this state, since the developing roller 52 is not in contact with the photosensitive drum 20, when the power is turned off, plastic deformation of the surface of the developing roller 52 is prevented.

  In the second contact / separation mechanism S <b> 2, the transfer roller 100 is positioned at the retracted position by the tension coil spring 104, and the intermediate transfer belt 110 is separated from the photosensitive drum 20.

  At the time of printing (development), the surface potential (that is, dark potential) of the photosensitive drum 20 in the main charging device 30 is set to a predetermined value by the main charging device 30 by the control through the main charging device control circuit 260 of the control device 200. The voltage is applied so that Further, the photosensitive drum drive motor 320 is rotationally controlled by the control via the drive motor control circuit 250 of the control device 200, whereby the photosensitive drum 20 is rotationally driven.

  Thereafter, a developing bias (for example, 250 V) lower than the surface potential is applied to the developing roller 52 by the developing bias applying means 340 under the control of the CPU 210 via the developing bias control circuit 270.

  Thereafter, the developing roller driving motor 350, the transfer roller driving motor 310, and the intermediate transfer belt driving motor 360 are turned on under the control of the control device 200. By driving the developing roller driving motor 350, each roller of the liquid developing device 50 is rotationally driven through the drive transmission joint 80 and the gears 72 to 74. By this rotation, the developing roller 52 is moved from the separation position P1 to the contact position P0, and the development roller 52 is in contact with the photosensitive drum 20 (see FIGS. 6A and 6B).

  Then, a developing electric field is generated between the developing roller 52 and the image portion (that is, the bright potential portion) of the photosensitive drum 20 where the surface of the photosensitive drum 20 is exposed by an exposure device (not shown) and has a bright potential of, for example, 20V. The toner charged to the positive potential of the liquid developer moves from the developing roller 52 to the photosensitive drum 20. On the other hand, in the photosensitive drum 20, the non-image portion (that is, the dark potential portion) that is not exposed is an electric field formed by the dark potential and the developing bias, and the toner particles do not adhere.

In this manner, each roller of the liquid developing device 50 and the photosensitive drum 20 are rotationally driven, and the latent image on the photosensitive drum 20 is developed.
On the other hand, the transfer roller driving motor 310 is driven to move the transfer roller 100 in the retracted position to the transfer position, and the transfer roller 100 presses the intermediate transfer belt 110 against the photosensitive drum 20. Further, the intermediate transfer belt 110 is moved by driving the intermediate transfer belt drive motor 360, and the toner image developed on the photosensitive drum 20 is transferred to the intermediate transfer belt 110 at the nip with the transfer roller 100. The toner image transferred to the intermediate transfer belt 110 is transferred by a recording medium such as recording paper (not shown).

  By the way, after the development is completed (that is, when it is not developed), in this embodiment, the CPU 210 of the control device 200 executes the cleaning program stored in the ROM 220.

  As shown in FIG. 2, in this program, at the time of development, at the nip portion N between the photosensitive drum 20 and the developing roller 52, the thickness of the thin layer of the liquid developer formed on the surface of the developing roller 52 is If it is thicker than the distance between the photosensitive drum 20 and the developing roller 52 in the nip portion N, a liquid developer pool T is generated, and this is for cleaning.

  When the cleaning program is executed, the CPU 210 first controls the main charging device 30, the developing bias applying unit 340, and the LPH 40 to be turned off, and the transfer roller driving motor 310, the developing roller driving motor 350, and the intermediate transfer belt driving motor 360. Stop drive control.

  When the rotation driving of the developing roller driving motor 350 is stopped, the developing roller 52 is moved to the separation position P1 via the bracket 68 and the rotating shaft 52a by the urging force of the tension coil spring 82, and from the photosensitive drum 20 They are separated (see FIGS. 7A, 7B, and 3).

  At this time, as shown in FIG. 3, the liquid developer reservoir T, that is, the liquid developer in the liquid developer reservoir in the nip portion N adheres to the photosensitive drum 20 side having better wettability than the developing roller 52. .

  When the rotation driving of the transfer roller drive motor 310 by the control is stopped, the transfer roller 100 is moved from the transfer position to the retracted position by the urging force of the tension coil spring 104. As a result, the pressure of the transfer roller 100 is released, and the intermediate transfer belt 110 is separated from the photosensitive drum 20 as shown by the solid line in FIG.

  After the intermediate transfer belt 110 is separated from the photosensitive drum 20, the photosensitive drum driving motor 320 is driven via the driving motor control circuit 250 as shown in FIG. 4 and FIG. The body drum 20 is rotated by a predetermined angle.

  This predetermined angle is a rotation angle until the liquid developer pool T in the nip portion N is moved by the rotation of the photosensitive drum 20 and cleaning is completed at the tip (edge portion) of the cleaning blade 62. Are set in advance. In the present embodiment, the predetermined angle is defined as described above, but is not limited to the above definition. For example, the predetermined angle may be an angle that exceeds at least the angle from the nip portion N to the upper vertex of the circumferential surface of the photosensitive drum 20 (see the position T of the liquid developer reservoir in FIG. 4). For example, if the liquid developer pool T in the nip portion N is moved to a position at least exceeding the angle to the upper vertex (see FIG. 4) of the circumferential surface of the photosensitive drum 20, the moved liquid developer The pool T can be expected to start dripping to the cleaning device 60 due to its own weight.

  As a result, the liquid developer reservoir T is cleaned by the tip (edge portion) of the cleaning blade 62. The collected developer and the like scraped off at the tip (edge portion) of the cleaning blade 62 is dropped onto the bottom of the housing 66. After completing the cleaning, the CPU 210 ends the cleaning program. Thereafter, when printing is started, the above-described processing at the time of printing (development) is started again.

  Thus, in the present embodiment, when the developing roller 52 is separated by the first contact / separation mechanism S1, the control device 200 controls the photosensitive drum drive motor 320 to control the rotation of the photosensitive drum 20. Therefore, the liquid developer pool generated in the nip N between the photosensitive drum 20 and the developing roller 52 due to the rotation of the photosensitive drum 20 is moved to the cleaning device 60 side and cleaned by the cleaning device 60. As a result, since the liquid developer reservoir T is removed, the thickness of the thin layer of the liquid developer formed on the developing roller is not disturbed after being cleaned by the cleaning device 60, and a clear image can be obtained. Obtainable. Further, the contamination of the peripheral device disposed below the photosensitive drum can be prevented, and the occurrence of problems due to the contamination of the peripheral device can be prevented.

  In this embodiment, the critical surface tension γp of the surface of the photosensitive drum 20, the critical surface tension γd of the surface of the developing roller 52, and the surface tension γt of the liquid developer satisfy γd <γt <γp. Therefore, the liquid developer pool T generated at the nip portion between the photosensitive drum 20 and the developing roller 52 is likely to adhere to the photosensitive drum 20 and is moved to the cleaning device side as the photosensitive drum 20 rotates. As a result, the cleaning effect by the cleaning device can be enhanced.

  Further, in this embodiment, the surface layer of the developing roller 52 is made of a fluorine resin or a urethane resin, so that swelling of the inner layer liquid developer covered with the surface layer due to the carrier liquid can be prevented.

  Further, in the present embodiment, by forming the surface layer on the peripheral surface of the photoconductive drum 20 with amorphous silicon, it is possible to improve durability characteristics against light irradiated on the photoconductive drum 20.

  In this embodiment, when the developing roller 52 is separated by the first contact / separation mechanism S1, the control device 200 controls the second contact / separation mechanism S2 to separate the intermediate transfer belt 110 from the photosensitive drum 20. The photosensitive drum 20 is rotationally controlled by controlling the rotational drive source while being separated. As a result, when the liquid developer reservoir T is cleaned, the liquid developer reservoir T can be moved to the cleaning device 60 without the intermediate transfer belt 110 being disturbed.

In addition, this invention is not limited to the said embodiment, You may change as follows.
In the configuration of the embodiment, the configuration of the first contact / separation mechanism S1 may be changed as follows. That is, a solenoid is connected to the bracket 68 instead of the tension coil spring 82, and the solenoid is excited and demagnetized under the control of the CPU 210. Then, by the excitation and demagnetization of the solenoid under the control of the CPU 210, the contact position P0 where the developing roller 52 contacts the photosensitive drum 20, and the developing roller 52 (liquid developer carrier) from the photosensitive drum 20 (image carrier). It is made to position in any one of the separation positions P1 which separate.

1 is a schematic configuration diagram of a liquid image forming apparatus according to an embodiment of the present invention. Explanatory drawing which similarly shows an effect | action. Explanatory drawing which similarly shows an effect | action. Explanatory drawing which similarly shows an effect | action. Explanatory drawing which similarly shows an effect | action. (A) is a schematic diagram of a liquid developing device, (b) is an explanatory diagram showing the position of a developing roller during development, and (c) is an explanatory diagram of a differential gear mechanism. (A), (b) is explanatory drawing of an effect | action of a liquid developing device similarly. Explanatory drawing which similarly shows the principal part of a liquid developing device. FIG. 6 is an explanatory diagram of a support structure for the developing roller 52 with respect to a side wall 51 a of the container 51. The block diagram which shows the electric constitution of a control part.

Explanation of symbols

20 ... Photosensitive drum (image carrier)
52. Developing roller (liquid developer carrier)
60 ... Cleaning device 110 ... Intermediate transfer belt (transfer carrier)
200: Control device (control unit)
320 ... Photoreceptor drum drive motor (rotation drive source)
S1 ... First contact / separation mechanism S2 ... Second contact / separation mechanism

Claims (4)

In a liquid image forming apparatus comprising: an image carrier that carries an electrostatic latent image; a liquid developer carrier that supplies a liquid developer to the image carrier; and a cleaning device that cleans the image carrier.
A first contact / separation mechanism for positioning the liquid developer carrier at a proximal position close to the image carrier during development and separating the liquid developer carrier at a distal position far from the image carrier during non-development; ,
A rotational drive source for rotating the image carrier;
A control unit that controls the rotation drive source to control the rotation of the image carrier when the liquid developer carrier is separated from the image carrier by the first contact / separation mechanism;
The image carrier is cleaned by a cleaning device by rotation control of a rotation drive source of the control unit,
When the critical surface tension of the surface of the image carrier is γp, the critical surface tension of the surface of the liquid developer carrier is γd, and the surface tension of the liquid developer is γt, γd <γt <γp is established. When
A liquid image forming apparatus.   2. The liquid image forming apparatus according to claim 1, wherein the surface layer of the liquid developer carrying member is made of a fluorine-based resin or a urethane-based resin.   3. The liquid image forming apparatus according to claim 1, wherein the surface layer of the peripheral surface of the image carrier is formed of amorphous silicon. A transfer carrier that contacts and separates from the image carrier;
  A second contact / separation mechanism for bringing the transfer carrier into contact with the image carrier during development and separating the transfer carrier from the image carrier during non-development;
  When the liquid developer carrier is separated by the first contact / separation mechanism, the control unit controls the second contact / separation mechanism to separate the transfer carrier from the image carrier, The liquid image forming apparatus according to claim 1, wherein the rotation driving source is controlled to control the rotation of the image carrier.

Images