JP2007025028A - Image forming apparatus using liquid developer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To facilitate cleaning of liquid developer that is adhered to the surface of an intermediate transfer body. <P>SOLUTION: In an image forming apparatus having the intermediate transfer body and using liquid developer, an application member (42) for applying liquid onto the intermediate transfer body is disposed between a secondary transfer position, where an image is transferred from the intermediate transfer body (20) to a transfer medium (25) and a cleaning position which is downstream of the secondary transfer position, in the direction of rotation of the intermediate transfer body and in which a cleaning member (23) is abutted against the intermediate transfer body. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus using a liquid developer having an intermediate transfer member.

  Conventionally, an electrophotographic image forming apparatus (wet image forming apparatus) using a liquid developer is known. The developer used in the wet image forming apparatus is obtained by suspending solids (toner particles) in an electrically insulating organic solvent (carrier liquid). The particle diameter of the toner particles is 2 μm or less, usually Since it is extremely fine, about 1 μm or less, it is possible to achieve higher image quality than a dry image forming apparatus using powder toner particles of about 7 μm.

  The carrier liquid constituting the developer has a function of making the toner particles charged and further uniformly dispersed in addition to preventing the toner particles from scattering around 1 μm. It also has a role to make it easy to move by action. As described above, the carrier liquid is a component necessary for toner storage, toner conveyance, development, and transfer processes, but also adheres to non-image areas, and excessive carrier liquid after development causes transfer disturbance and the like. Therefore, the carrier liquid is usually removed (squeezed) from the developer on the photosensitive member and the intermediate transfer member.

In addition, when an intermediate transfer belt or a secondary transfer belt is used in a wet image forming apparatus, liquid developer (carrier liquid and solid content) adhering to the belt surface is removed by a cleaning blade. (Patent Document 1).
JP 2002-189354 A

  By the way, the deposit (liquid developer) to be cleaned in the intermediate transfer body is generally removed of the carrier as described above, so that the solid content is increased and the intermediate content like “wet powder” is increased. It adheres to the surface of the transfer body. Further, the developer remaining on the intermediate transfer member after being transferred to paper absorbs the carrier liquid on the paper, so that the solid content rate is further increased, requiring a force for cleaning, and the cleaning blade and the intermediate transfer member are worn. It will affect the life of parts such as deformation.

SUMMARY An advantage of some aspects of the invention is to facilitate cleaning of a liquid developer adhered on an intermediate transfer member in an image forming apparatus using the liquid developer.
Therefore, the present invention provides a secondary transfer position for transferring from an intermediate transfer body to a transfer medium in an image forming apparatus using a liquid developer having an intermediate transfer body, and rotation of the intermediate transfer body with respect to the secondary transfer position. A liquid application member for applying a liquid on the intermediate transfer member is disposed between the cleaning position where the cleaning member contacts the intermediate transfer member on the downstream side in the direction.
Further, the present invention is characterized in that a carrier liquid is applied onto the intermediate transfer member by the liquid application member.
Further, the invention is characterized in that a surfactant is applied onto the intermediate transfer member by the liquid application member.
The present invention is also characterized in that a component that lowers the viscosity of the carrier liquid is applied onto the intermediate transfer member by the liquid application member.
In the invention, it is preferable that a release material is applied onto the intermediate transfer member by the liquid application member.

  According to the present invention, it is possible to facilitate the cleaning of deposits having an increased solid content by applying a liquid onto the intermediate transfer member.

Embodiments of the present invention will be described below.
FIG. 1 is a diagram for explaining an example (Example 1) of an image forming apparatus according to an embodiment of the present invention. This image forming apparatus is an example in which images of Y, M, C, and K colors are formed on an intermediate transfer body and transferred onto a transfer medium at one time. Since development and primary transfer processes are the same for each color, These steps will be described on behalf of one color.

  The liquid developer container 1 contains a developer 2 in which solid contents (toner particles) are uniformly dispersed in a non-volatile carrier liquid. The developer 2 is pumped up by the supply roller 3 and comes into contact with the supply roller 3. Then, it is supplied to the developing roller 4 whose peripheral surface rotates in the same direction. A developing roller cleaner 5 is disposed on the developing roller 4 to clean the developer after development on the developing roller. In addition, the liquid developer container 1 is replenished by the gear pump 8 with the developer stirred by the stirring member 7 in the toner concentration adjusting tank 6.

  The photosensitive member 10 whose peripheral surface rotates in the same direction in contact with the developing roller 4 is uniformly charged by a charger 11, and then an electrostatic latent image is formed by exposure 12, and the formed electrostatic latent image is formed. Is developed with a liquid developer at a position facing the developing roller 4. After the development, excess carrier liquid is removed by the squeeze roller 13 and then transferred onto the intermediate transfer belt at the primary transfer position where the primary transfer roller 14 is opposed across the intermediate transfer belt. The developer remaining on the photoconductor after the transfer is cleaned by the photoconductor cleaner 15.

  The intermediate transfer belt 20 is stretched between a driving roller 21 and a driven roller 22 and is driven to rotate counterclockwise by the driving roller 21. The driving roller 21 and the secondary transfer roller 24 are transfer media such as paper. The position opposite to the surface 25 is the secondary transfer position. A belt cleaner 23 is arranged with the driven roller 22 as a backup roller, and the developer remaining on the intermediate transfer belt 20 after being collectively transferred to the transfer medium 25 at the secondary transfer position is cleaned. Further, squeeze rollers 30 are arranged between the Y, M, C, and K photoconductors and between the K photoconductor and the secondary transfer position, respectively, and the intermediate transfer belt after being transferred at the primary transfer positions of the respective colors. Excess carrier liquid on 20 is removed.

Next, the configuration of the intermediate transfer belt will be described with reference to FIG.
The intermediate transfer belt 20 includes a base material layer 20a (eg, thickness 100 μm) made of polyimide, an elastic layer 20b (eg, thickness 200 μm) made of urethane rubber (hardness JIS-A30 °), and a coating layer 20C made of fluororesin. The image is formed on the coat layer 20C by primary transfer. The width of the belt is 324 mm, and the volume resistance value of the belt is about log 10 Ωcm (resistance value of all layers).

Next, a squeeze roller that is provided in the subsequent stage of each color of the intermediate transfer belt and removes the carrier liquid will be described with reference to FIG.
The squeeze roller 30 is for removing the carrier liquid contained in the liquid developer on the intermediate transfer belt, and rotates at the same speed as the intermediate transfer belt. The squeeze roller is configured by winding a PFA tube 20 μm around a surface layer of urethane rubber (hardness JIS-A30 °) having a thickness of 2 mm (outside diameter φ14 mm) on a φ10 mm metal shaft, and has a roller width of 307 mm. Although not shown in FIG. 1, a squeeze backup roller 31 (φ10 mm metal shaft) is disposed opposite to the intermediate transfer belt 20 and is in contact with the intermediate transfer belt at a linear pressure of about 50 gf / cm. The actual resistance value of the roller is approximately Log 4Ω, and a bias voltage of +150 V is applied from the power source 32 between the squeeze roller 30 and the squeeze backup roller 31 so that the solid content in the developer is not removed. The squeeze roller 30 is cleaned by contact with a cleaning blade 33 made of urethane rubber (hardness JIS-A 70 °). With these configurations, the carrier liquid of the liquid developer is squeezed out and stored in the container 34 on the intermediate transfer belt.

  By the way, the adhering matter (liquid developer) remaining on the intermediate transfer belt after the secondary transfer is removed by the respective squeeze rollers after the primary transfer, and the carrier liquid is absorbed by the transfer medium during the secondary transfer. The solid content rises and requires force for cleaning. Therefore, in this embodiment, as shown in FIG. 1, after the secondary transfer, before the deposit is cleaned by the belt cleaner 23, the liquid is applied onto the intermediate transfer belt in order to reduce the solid content rate of the deposit. Apply. That is, in the rotational direction of the intermediate transfer belt 20, a sponge roller 42 as a liquid application member is disposed at an appropriate position on the downstream side of the secondary transfer position and on the upstream side of the position where the belt cleaner 23 contacts, and the intermediate transfer belt. The application backup roller 43 is arranged with 20 therebetween. Then, the liquid is supplied from the liquid container 40 to the sponge roller 42 by the gear pump 41 and applied onto the intermediate transfer belt. The liquid to be applied may be any liquid that can lower the solid content, such as water or a carrier liquid.

  In the case where the liquid container 40 is arranged at a position higher than the supply-destination sponge roller as in the configuration shown in FIG. 1, it may be dropped using gravity without using a gear pump. The supply amount is adjusted by a valve. As a piping member, a Tygon tube inner diameter of 5 mm was used. A sponge roller as a liquid application member is formed by winding a urethane sponge (Asker A hardness 40 °) having a thickness of 5 mm (outside diameter φ20 m) around a metal shaft φ10 mm. The sponge roller is the same as the rotational peripheral speed of the intermediate transfer belt 20, and the rotational direction is rotating. However, it is not limited to this. The roller width is 310 mm, and the roller is in contact with the intermediate transfer belt at a linear pressure of about 50 gf / cm.

  In the case of positively charged toner, a slight (−) electric field may be applied to the sponge roller for the purpose of floating the solid content adhering to the belt side. Of course, in the case of negatively charged toner, a (+) electric field may be applied similarly. Further, by setting the sponge roller about 1.2 times faster than the peripheral speed of the belt, the scraping effect by the sponge roller can be obtained, so that cleaning can be facilitated.

  The rubber blade constituting the belt cleaner 23 uses urethane rubber having a hardness of JIS-A 70 ° and a width of 317 mm and is brought into contact with the intermediate transfer belt at a linear pressure of 50 gf / cm. Normally, under this condition, the solid matter fixed on the belt slips through the blade. However, when the blade is brought into contact with a stronger force, problems such as destruction of the belt and an increase in torque at the time of driving the belt occur. In this embodiment, this problem can be avoided by applying a liquid with a sponge roller to lower the solid content rate of the deposit.

Next, another example (Example 2) of the embodiment of the image forming apparatus of the present invention will be described.
FIG. 4 is a diagram illustrating an example of an image forming apparatus that applies a carrier liquid or a recycled carrier liquid, and FIG. 5 is a diagram illustrating a recycling mechanism. In the first embodiment, the liquid to be applied is conveyed to the sponge roller. However, in the case where the recycled carrier liquid is applied in the second embodiment, the liquid developer collected (recycled) collected from each color station is used. A part of the agent (carrier liquid) is circulated through the sponge roller. The configuration of the sponge roller that applies the carrier liquid onto the intermediate transfer belt is the same as that of the first embodiment.

First, the recycling mechanism will be described with reference to FIG. Since the same numbers as those in FIG. 1 indicate the same contents, a detailed description thereof is omitted.
The developer 2 in the liquid developer container 1 is drawn up from the supply roller 3 and supplied to the developing roller 4 to develop the electrostatic latent image on the photoconductor 10 as in the case of FIG. In the toner concentration adjusting tank 6 for replenishing the developer into the liquid developer container 1, carrier liquid is supplied from the carrier tank 50 through the carrier supply path 51, and toner (solid content) is transferred from the toner tank 60 through the toner supply path 61. In addition, the recovered liquid from the developing roller cleaner 5 is dripped. The solid concentration in the liquid developer container 1 is about 25%. However, when the recovered liquid from the squeeze roller and the photoreceptor cleaner and the recovered liquid from the developing roller cleaner 5 are reused, a small amount of solid content is included. However, this does not affect the density adjustment. Concentration fluctuations in the concentration adjusting tank due to these are controlled to a predetermined solid content concentration by toner replenishment from the toner tank 60 (solid content concentration 25%) and carrier replenishment from the recovery carrier and carrier tank 50 tank. The developer container 1 is replenished with a liquid having a predetermined concentration in the concentration adjusting tank.

  In the second embodiment shown in FIG. 4, the development and transfer processes are the same as those in the first embodiment, and a detailed description thereof is omitted. In the example shown in FIG. 5, the carrier liquid in the carrier tank 50 is circulated through the sponge roller 42 to apply the carrier liquid onto the intermediate transfer belt. Further, since the carrier liquid is recovered through the recovery carrier transport path 52 described with reference to the recycling mechanism of FIG. 3, the recovered carrier liquid is temporarily returned to the carrier tank 50 or a tank provided separately from this, and the carrier tank The carrier liquid in 50 (or a separately provided tank) may be circulated through the sponge roller 42 to apply the carrier liquid onto the intermediate transfer belt.

  In normal solid printing, the carrier liquid is surplus, and the carrier is surplus in order to ensure a predetermined solid content concentration by the recycling mechanism. Therefore, the surplus carrier liquid is placed before the cleaning portion of the intermediate transfer belt. By supplying to the sponge roller 42 and applying onto the intermediate transfer belt, the solid content concentration on the intermediate transfer belt can be reduced to facilitate cleaning.

  In the third embodiment, the basic configuration of the apparatus is the same as that shown in FIG. 1, and a surfactant is applied onto the intermediate transfer belt through a sponge roller 42 disposed in front of the cleaning portion of the intermediate transfer belt 20. It may be. For example, by adding 10% of ether surfactant EE4210 (trade name), the resin of the deposit can be removed, and the cleaning of the deposit can be facilitated.

  In the fourth embodiment, the basic configuration of the apparatus is the same as that shown in FIG. 1, and a component for decreasing the carrier viscosity is applied onto the intermediate transfer belt through a sponge roller 42 disposed in front of the cleaning portion of the intermediate transfer belt 20. You may make it do. For example, a low molecular weight liquid paraffin having a kinematic viscosity of 4.4 CSt is applied to a carrier oil constituting the liquid developer (a kinematic viscosity of liquid paraffin of about 20 CSt). By applying the component that lowers the carrier viscosity on the intermediate transfer belt in this way, it is possible to easily clean the deposits.

  In the fifth embodiment, the basic configuration of the apparatus is the same as that shown in FIG. 1, and a component that becomes a mold release material is applied through a sponge roller 42 disposed in front of the cleaning portion of the intermediate transfer belt 20. Good. For example, fluorine surfactant (10% NOVECFC4430 manufactured by 3M Co., Ltd. is added. Not all developer can be removed by belt cleaning, but a coating layer with good peelability is formed on the belt, so cleaning becomes easy. .

  According to the present invention, since the deposits on the intermediate transfer member can be easily cleaned, the industrial utility value is great.

It is a figure explaining an example of an embodiment of an image forming device of the present invention. FIG. 4 is a diagram illustrating a configuration of an intermediate transfer belt. It is a figure explaining a squeeze roller. It is a figure explaining the example of the apparatus which apply | coats the recycled carrier liquid. It is a figure explaining a recycling mechanism.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Liquid developer container, 2 ... Developer, 3 ... Supply roller, 4 ... Developing roller, 5 ... Developing roller cleaner, 6 ... Toner density adjustment tank, 7 ... Stirring member, 8 ... Gear pump, 10 ... Photoconductor, 13 Squeeze roller, 15 photosensitive drum cleaner, 20 intermediate transfer belt, 21 drive roller, 22 driven roller, 23 belt cleaner, 30 squeeze roller, 40 liquid container, 41 gear pump, 42 sponge roller

Claims (5)

In an image forming apparatus using a liquid developer having an intermediate transfer body, a secondary transfer position for transferring from the intermediate transfer body to a transfer medium, and an intermediate transfer on the downstream side of the secondary transfer position in the rotation direction of the intermediate transfer body An image forming apparatus using a liquid developer, wherein a liquid applying member for applying a liquid on an intermediate transfer member is disposed between a cleaning position where the cleaning member contacts the body. 2. The image forming apparatus according to claim 1, wherein a carrier liquid is applied onto the intermediate transfer member by the liquid applying member. The image forming apparatus according to claim 1, wherein a surfactant is applied onto the intermediate transfer member by the liquid application member. 2. The image forming apparatus according to claim 1, wherein a component that lowers the viscosity of the carrier liquid is applied onto the intermediate transfer member by the liquid application member. The image forming apparatus according to claim 1, wherein a release material is applied onto the intermediate transfer member by the liquid application member.

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