JP2005049709A - Liquid developing device and cleaning device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively reduce the accumulation of toner particles on a cleaning member for clearing away liquid developer regardless of the viscosity and the toner concentration or the like of the liquid developer. <P>SOLUTION: The developing device has constitution where DC electric field or electric field obtained by superposing AC electric field on DC electric field is applied to or near a cleaning blade provided to abut on a developing roller 11 or a photoreceptor drum so as to remove the liquid developer remaining on the roller 11 after development or on the photoreceptor drum after transfer, and is constituted so that the insulation resistance value of the material of the cleaning blade may be 10<SP>7</SP>to 10<SP>10</SP>Ω, desirably, 10<SP>9</SP>to 10<SP>10</SP>Ω. Then, the DC electric field having the same potential as developing bias potential applied to the roller 11 is applied to or near the cleaning blade at the developing time, and the DC electric field or the electric field obtained by superposing the AC electric field on the DC electric field is applied to or near the cleaning blade at the non-developing time. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a liquid developing device and a cleaning device used for an image forming apparatus, and more particularly to a liquid developing device and a cleaning device used for image forming processing such as a copying machine, a printer, and a printing machine.

Conventionally, a liquid image using a liquid developer in which toner particles are dispersed in an insulating solvent (liquid carrier) as an electrophotographic image forming method such as a copying machine, a printer, or a printing machine that forms an image on a recording paper or the like. A forming method (wet image forming method) is known. In this image forming method, toner particles charged to a predetermined polarity are electrostatically attached to an electrostatic latent image forming unit formed on an image carrier such as a photosensitive drum, and the electrostatic latent image is developed. To do.
The liquid developing device includes a cleaning member such as a cleaning blade that removes the liquid developer remaining on the developer carrier such as a developing roller without being used during development. When the remaining liquid developer is removed using such a cleaning blade, the removed liquid developer moves on the cleaning blade and is finally returned to the developer container in the liquid developing device. In this case, the removed liquid developer adheres to the cleaning blade, and may be condensed and dried to deposit toner particles on the cleaning blade. This volume of toner particles not only prevents the liquid developer from moving on the cleaning blade, but also when the toner particle lump falls into the developer container during mechanical impact. This density change may cause image fogging and density unevenness.
There exists a cleaning blade of patent document 1 as what solves this problem. This effectively reduces toner particle accumulation on the cleaning blade by keeping the cleaning blade in contact with the developing roller in the same polarity as the developing toner particles. Further, toner particle accumulation is prevented by immersing the cleaning blade in a liquid developer. Note that the liquid developing device described in Patent Document 2 applies two layers of liquid developer remaining in a toner layer and a carrier layer by applying an electric field to the liquid developer remaining on the surface of the developing roller after development. In this way, the liquid developer is removed from the surface of the developing roller, whereby the remaining liquid developer can be reliably removed from the surface of the developing roller. In addition, the image forming apparatus described in Patent Document 3 applies a DC electric field to the liquid developer remaining on the surface of the developing roller before removing the liquid developer remaining on the surface of the developing roller after development by the cleaning member. By applying an electric field on which an alternating electric field is superimposed, the remaining liquid developer can be easily removed and the cleaning performance is improved.
JP 09-258550 A Japanese Patent Application Laid-Open No. 09-211993 JP 2003-91222 A

However, the removal method described in Patent Document 1 is effective for a low-viscosity or low-concentration liquid developer, but a liquid developer composed of a high-viscosity carrier liquid or a liquid developer with a high toner concentration is used. When used, toner particles cannot be sufficiently prevented from being deposited on the cleaning blade. In particular, when a liquid developer having a viscosity exceeding 1000 cSt is used, toner particles are significantly deposited on the cleaning blade. In this case, it is possible to reduce toner particle accumulation by immersing the cleaning blade in the liquid developer. However, in such a configuration, the layout of members such as the cleaning blade and the developing roller is limited. In addition, the cleaning blade may be exposed due to fluctuations in the liquid developer level, and toner particles may or may not be deposited.
Accordingly, the present invention has been made in view of the above circumstances, and its object is to effectively deposit toner particles on a liquid developer cleaning member regardless of the viscosity, toner concentration, etc. of the liquid developer. An object of the present invention is to provide a liquid developing device, a cleaning device, and an image forming apparatus using these that can reduce, prevent image fogging and density unevenness, and form a high-quality and high-quality image.

In order to achieve the above object, the present invention provides a developer carrier that carries a liquid developer in which toner particles are dispersed in an insulating solvent, and a development bias that applies a predetermined development bias potential to the developer carrier. An application means; a developer cleaning member that contacts the developer carrier and removes the liquid developer remaining on the developer carrier after development; and the liquid developer scraped by the developer cleaning member In the liquid developing apparatus comprising: a first developer moving member that moves the toner; or a developing cleaning electric field applying unit that applies a DC electric field or an electric field in which an AC electric field is superimposed on the DC electric field in the vicinity thereof. insulation resistance 10 ⁷ to 10 ¹⁰ Omega material of the developer moving member is constituted as a liquid developing device which is a preferably 10 ⁹ to 10 ¹⁰ Omega As a result, for example, current can be prevented from flowing into the photosensitive drum or the developing roller, and even when a high voltage (high electric field) is applied to the developing cleaning blade, voltage leakage to the photosensitive drum or the developing roller is prevented. Even when using a high-viscosity liquid developer, it is possible to apply a high voltage sufficient to form a two-layered toner, so that toner particles are deposited on the development cleaning blade. There is no longer to do. In this case, it is desirable that the first developer moving member is a developing cleaning blade provided with the developing cleaning member.

  Further, the developing cleaning electric field applying means applies a DC electric field having the same potential as the developing bias potential applied to the developer carrier during the development, and a DC electric field or an electric field obtained by superimposing an AC electric field on the DC electric field when not developing. , One applied to the first developer moving member or the vicinity thereof is conceivable. In this way, by switching the electric field applied between development and non-development, image fog and density unevenness can be prevented and toner accumulation on the development cleaning blade can be more effectively prevented. Can do.

  Further, the AC electric field applied by the developing cleaning electric field applying means has such a magnitude that the toner particles in the liquid developer are slightly vibrated to improve the mobility of the toner particles, and the developing cleaning electric field is It is conceivable that the DC electric field applied by the applying means has a direction in which the toner particles in the liquid developer are separated from the first development moving member. As a result, regardless of the toner concentration and viscosity of the liquid developer, it is possible to prevent image fogging and density unevenness and to form a high-quality and high-quality image.

  Further, if the AC electric field applied by the developing cleaning electric field applying means is an electric field generated by applying a rectangular wave AC voltage, an alternating electric field of a DC component is generated unlike a sinusoidal AC. , It becomes possible to finely vibrate the toner particles more effectively. In the case of rectangular wave alternating current, by changing the duty ratio, it becomes possible to supply a rectangular wave alternating voltage according to the concentration, viscosity, etc. of the liquid developer, and further supply a sine wave alternating voltage. Compared to the case, it is possible to apply a voltage near the limit voltage value at which voltage leakage to the image carrier or developer carrier occurs for a long time per unit time. Further improving effect

In the present invention, the technique used in the liquid developing device may be applied to a cleaning device that removes the liquid developer remaining on the image carrier such as a photosensitive drum. That is, a predetermined image carrier potential is applied, and the toner image is brought into contact with an image carrier carrying a toner image made of a liquid developer in which toner particles are dispersed in an insulating solvent. An image carrier cleaning member for removing the liquid developer remaining on the image carrier after the transfer, and a second developer moving member from which the liquid developer scraped by the image carrier cleaning member flows down Or an image carrier cleaning electric field applying means that applies a DC electric field or an electric field in which an AC electric field is superimposed on the DC electric field in the vicinity thereof. It may be configured as a cleaning device characterized in that the insulation resistance value of the material is 10 ⁷ to 10 ¹⁰ Ω, preferably 10 ⁹ to 10 ¹⁰ Ω. In this case, it is desirable that the second developer moving member is an image carrier cleaning blade provided with the image carrier cleaning member.

  Further, the image carrier cleaning electric field applying means superimposes a DC electric field having the same potential as the image carrier potential applied to the image carrier during the transfer, and a DC electric field or a DC electric field superimposed on an AC electric field when not developing. An electric field may be applied to the second developer moving member or the vicinity thereof.

  Further, the AC electric field applied by the image carrier cleaning electric field applying means has such a magnitude that the toner particles in the liquid developer are slightly vibrated to improve the mobility of the toner particles, and the image The DC electric field applied by the carrier cleaning electric field applying means may have a direction in which the toner particles in the liquid developer are separated from the second development moving member.

  Further, the AC electric field applied by the image carrier cleaning electric field applying means may be an electric field generated by applying a rectangular wave AC voltage.

  Further, even the image forming apparatus such as a copying machine, a printer, or a printing machine using one or both of the liquid developing device and the cleaning device can solve the above-described problem.

As described above, according to the present invention, the developer carrying member carrying the liquid developer, the developing bias applying means for applying a predetermined developing bias potential to the developer carrying member, and the developer after development. A developing cleaning member that removes the liquid developer remaining on the carrier, a first developer moving member to which the liquid developer scraped by the developing cleaning member moves, or a DC electric field or a direct current in the vicinity thereof. A developing cleaning electric field applying means for applying an electric field in which an AC electric field is superimposed on the field, and the insulation resistance value of the material of the first developer moving member is 10 ⁷ to 10 ¹⁰ Ω, preferably 10 ⁹ to 10 ^10. For example, current is prevented from flowing into the photosensitive drum or the developing roller, and a high voltage (high electric field) is applied to the developing cleaning blade. Even if it is added, it is possible to prevent the occurrence of voltage leakage to the photosensitive drum or the developing roller, and even when a high-viscosity liquid developer is used, it is sufficient to make this into two layers. Since a high voltage can be applied, toner particles do not accumulate on the development cleaning blade.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings so that the present invention can be understood. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.
FIG. 1 is a schematic sectional view of an image forming portion X of an image forming apparatus provided with a liquid developing device 16 according to an embodiment of the present invention. FIG. 2 is a liquid developer to which an electric field is applied by an electric field applying roller 10. FIG. 3 is a diagram showing a state where the liquid developer is removed by the first cleaning blade 14, and FIG. 4 is a diagram showing a state where the liquid developer is removed by the conventional first cleaning blade. FIG. 4 is a timing chart of switching of a voltage applied to the first cleaning blade.

First, a schematic configuration and an image forming operation of an image forming unit X of an image forming apparatus including a liquid developing device 16 and a cleaning device 3 according to an embodiment of the present invention will be briefly described with reference to FIG. The liquid developing device 16 can also be applied to an image forming apparatus such as a copying machine, a FAX device, and a printer device.
The image forming unit X is roughly divided into a photosensitive drum 4 (an example of an image carrier) that carries an electrostatic latent image, and a charging device that uniformly charges the surface on the photosensitive drum 4 around the photosensitive drum 4. 6, an exposure device 7 for forming an electrostatic latent image by irradiating the photosensitive drum 4 with a laser beam, a liquid developing device 16 for developing the electrostatic latent image, and a developed toner image conveyed by a transfer belt 9 A transfer device 8 for transferring to the recorded paper, a cleaning device for removing the liquid developer remaining on the surface of the photosensitive drum 4 after the transfer, and a static elimination lamp 5 for removing the potential remaining on the photosensitive drum 4 after the transfer. Etc. are arranged.

The photosensitive drum 4 is driven to rotate clockwise in FIG. 1, and the charging device 6 charges the surface of the rotating photosensitive drum 4 to several hundreds V (for example, +600 V) by corona discharge or the like. The surface potential of the photosensitive drum 4 downstream of the charging device 6 in the rotation direction of the photosensitive drum 4 is irradiated with the laser beam emitted from the exposure device 7, thereby reducing the surface potential to about 50V. A formed electrostatic latent image is formed.
A liquid developing device 16 according to an embodiment of the present invention is disposed further downstream in the rotation direction of the exposure device 7. A developing bias (for example, +300 V) is applied to the developing roller 11 constituting the liquid developing device 16 by a developing bias power supply device 23 (see FIG. 2), and the surface potential is increased to about 50 V by the developing roller 11 and the exposing device 7. The toner particles in the thin layer 24 (FIG. 2) of the liquid developer carried on the developing roller 11 move to the electrostatic latent image due to the potential difference generated with the lowered electrostatic latent image. Then, the electrostatic latent image is developed.
In the transfer device 8, the recording paper conveyed from a recording paper storage unit (not shown) is charged while being conveyed while being sandwiched between the photosensitive drum 4 and the transfer belt 9 moving at the same speed as the peripheral speed. As a result, the toner image developed on the photosensitive drum 4 is transferred onto the recording paper.
A cleaning device 3 for removing the liquid developer remaining on the surface of the photosensitive drum 4 is disposed downstream of the transfer device 8 in the rotation direction. The liquid developer removed by the cleaning device 3 is stored in a collection tank (not shown) provided in the cleaning device.
On the downstream side of the cleaning device 3 in the rotation direction, a static elimination lamp 5 is disposed. The charge removal lamp 5 removes the potential remaining on the photosensitive drum 4 after the transfer. Thereafter, the surface of the photosensitive drum 4 is uniformly charged by the charging device 6 and the next image forming process is executed.
The recording paper onto which the toner image has been transferred by the transfer device 8 is conveyed to a fixing device (not shown) provided on the downstream side in the conveyance direction. The recording paper is pressed and conveyed by a heating roller provided in the fixing device and a pressure roller facing the heating roller, so that the toner on the recording paper is melted and fixed by the heat of the heating roller, and at the same time by the pressure roller. The recording paper is pressed against the heating roller to fix the toner. Thereafter, the recording paper having the image fixed on a discharge tray (not shown) is discharged.

Here, the liquid developing device 16 will be described in detail with reference to FIGS. As shown in FIG. 1, a liquid developing device 16 according to an embodiment of the present invention disposed downstream in the rotation direction of the exposure device 7 includes a supply roller 13, an anilox roller 12, and a developing roller 11 ( An example of a developer carrying member) and an electric field application roller 10 (an example of an electric field application unit) are provided.
In such a liquid developing device, when the image forming process is started, the developing bias potential applied to the developing roller 11 by the developing bias power source device 23 (see FIG. 2) is, for example, about + 300V. The developing bias potential is set lower than the surface potential (for example, +600 V) of the photosensitive drum 4 charged by the charging device 6.
The liquid developer stored in the liquid developing device 16 is supplied by the supply roller 13 to the anilox roller 12 that rotates in contact with the supply roller 13. On the surface of the anilox roller 12, concave concave grooves are formed in a lattice pattern, and the liquid developer supplied by the supply roller 13 flows into the grooves. Excess liquid developer adhering to the surface of the anilox roller 12 other than the groove is scraped off by a doctor blade 15 provided in contact with the anilox roller 12, and only the liquid developer flowing into the groove is obtained. Is supplied to the developing roller 11 which rotates in contact with the anilox roller 12. A thin layer 24 of the liquid developer supplied from the anilox roller 12 is formed on the surface of the developing roller 11 as shown in FIG. The thickness of the thin layer 24 is about 5 μm to 30 μm, and the depth, width, angle, etc. of the groove or grating formed on the surface of the anilox roller 12 can form the thin layer. It is set to a value that can carry a liquid developer of a degree. In the liquid developer used in the present embodiment, silicon oil, normal paraffin, vegetable oil, mineral oil, or the like having high insulating properties is used as an insulating solvent. Further, the liquid developing device 16 according to the present embodiment is a liquid developer in which toner having a particle diameter of submicron (1 μm or less) to 6 μm is mixed in the insulating solvent, and the toner concentration is 1% to 30%. %, And the liquid developer having a viscosity of 1000 cSt to 5000 cSt is preferable.

  As shown in FIG. 2, the thin layer 24 of the liquid developer carried on the developing roller 11 has a rotating direction of the developing roller 11 opposite to the developing roller 11 and the photosensitive drum 4, that is, the developing portion. A DC electric field is applied by the electric field applying roller 10 provided on the upstream side as in the conventional apparatus, and an electric field on which an AC electric field that is a feature of the present invention is superimposed is applied. Specifically, when the toner particles q in the liquid developer are charged to the positive electrode, the DC voltage of the positive electrode having the same polarity as the toner particles q is applied to the electric field by the DC voltage source 21 which is an example of a voltage applying unit. The AC voltage is supplied to the application roller 10 and further supplied to the electric field application roller 10 by an AC voltage source 22 which is an example of an electric field application means, whereby the electric field application roller 10 and the surface of the developing roller 11 are An electric field is generated between them, and an electric field in which an AC electric field is superimposed on a DC electric field is applied to the thin layer 24 of the liquid developer. As a result, a DC electric field is generated in the direction in which the toner particles q move toward the developing roller 11, and an alternating electric field is generated by an AC voltage superimposed on the DC voltage. As a result, the toner particles q are slightly vibrated to increase the mobility of the toner particles q, and the toner particles q are moved toward the developing roller 11 so that the liquid developer can be made into two layers. Become.

Thus, by making the liquid developer into two layers, the contact on the photosensitive drum 4 is eliminated, and unnecessary toner particles adhere to suppress the occurrence of image fogging or density unevenness. However, even in this case, the electric field applied to the thin layer 24 of the liquid developer by the electric field applying roller 10 must be an appropriate value. That is, if the electric field of the electric field applying roller 10 with respect to the thin layer 24 of the liquid developer on the developing roller 11 is too strong, the charge of the toner particles q increases too much, and the developing efficiency from the developing roller 11 to the photosensitive drum 4 The primary transfer efficiency from the photosensitive drum 4 to the transfer belt 9 and the secondary transfer efficiency from the transfer belt 9 to the recording paper are reduced. On the other hand, if the electric field of the electric field applying roller 10 with respect to the thin layer 24 of the liquid developer on the developing roller 11 is too weak, the toner layer and the carrier layer are not sufficiently doubled, and the electrostatic latent image non-forming portion is not formed. There is a risk of image fogging and density unevenness. Therefore, the electric field applied by the electric field applying roller 10 needs to be set within an appropriate range. Specifically, when the developing bias potential charged to the developing roller 11 is +300 V and the surface potential charged to the photosensitive drum 4 by the charging device 6 is +600 V, the electric field applying roller 10 has +400 V to +800 V. And a DC voltage of 1000 Hz to 2000 Hz and an AC voltage of 2000 V to 4000 V are supplied.
In this case, it is possible to use a photosensitive drum 4 having an insulation resistance value of 10 ⁷ Ω or more, preferably 10 ⁹ to 10 ¹⁰ Ω, on the surface of the roller serving as an electrode of the electric field applying roller 10. Alternatively, it is possible to prevent current from flowing into the developing roller 11 and to prevent voltage leakage to the photosensitive drum 4 or the developing roller 11 even when a high voltage (high electric field) is applied to the electric field applying roller 10. It becomes possible.
Further, the AC voltage supplied to the electric field applying roller 10 is not limited to a sine wave AC voltage, but may be a rectangular wave AC voltage. Unlike a sinusoidal alternating current, an alternating electric field of a direct current component is generated, so that it is possible to more effectively vibrate toner particles more effectively. Further, in the case of rectangular wave alternating current, the duty ratio (ON / OFF time ratio) can be easily changed. By changing the duty ratio, a rectangular shape corresponding to the concentration, viscosity, etc. of the liquid developer can be obtained. Since a wave AC voltage can be supplied, and a voltage in the vicinity of a limit voltage value at which a leakage voltage to the developing roller 11 is generated can be applied per unit time longer than the sine wave AC voltage. There is an effect that the efficiency of the two-layered developer is further improved.

  As described above, in the conventional liquid developing apparatus, the thin layer 24 of the liquid developer is divided into a toner layer on the developing roller 11 side and a carrier layer on the outer side of the developing roller 11 by applying only a DC electric field. However, in the liquid developing device 16 according to the present invention, as described above, the electric field applying roller 10 applies an electric field in which an AC electric field is superimposed on a DC electric field, so that the toner particles q in the liquid developer are removed. The mobility of the toner particles q can be improved by slight vibration. As a result, even when a high-concentration liquid developer with a toner concentration of 30% or a high-viscosity liquid developer, particularly a high-viscosity liquid developer of 1000 cSt to 5000 cSt, is used, the above-described liquid developer is efficiently used. It becomes possible to make two layers well, and it is possible to prevent image fogging and density unevenness and to form a high-quality and high-quality image.

As shown in the enlarged view of FIG. 3, the liquid developer remaining on the developing roller 11 after development is provided in contact with the developing roller 11 at an appropriate pressure on the downstream side in the rotation direction of the developing roller 11 from the developing portion. The first cleaning blade 14 (an example of a first developer moving member) is scraped off. The first cleaning blade 14 has copper, phosphor bronze, stainless steel, aluminum or the like coated with urethane or fluorine, or carbon or an ionic conductive agent dispersed in urethane or the like so as not to damage the developing roller 11. It is made of
The liquid developer scraped off by the first cleaning blade 14 moves along the first cleaning blade 14 and is finally returned to the developer reservoir in the liquid developing device 16. An electric field in which an AC electric field is superimposed on a DC electric field is also applied to the first cleaning blade 14. Specifically, when the toner particles q in the liquid developer remaining on the developing roller 11 are charged to the positive electrode by the DC voltage source 31 which is an example of the developing cleaning electric field applying means, the DC voltage source 31 A positive DC voltage having the same polarity as the toner particles q is supplied to the first cleaning blade 14, and an AC voltage is supplied to the first cleaning blade 14 by an AC voltage source 32 which is an example of a developing cleaning electric field applying unit. By supplying, an electric field in which an AC electric field is superimposed on a DC electric field is applied. As a result, a constant electric field is generated around the first cleaning blade 14. That is, an electric field is generated between the toner particles q and the first cleaning blade 14 in a direction to move the toner particles q away from the first cleaning blade 14, and alternating current is generated by the AC voltage superimposed on the DC voltage. An electric field is generated. Due to the direct current electric field and the alternating electric field, the toner particles q in the liquid developer are slightly vibrated to increase the mobility of the toner particles q, and not only the toner particles q are easily separated from the developing roller 11 but also the above-mentioned. The liquid developer moving along the first cleaning blade 14 can be divided into two layers: a carrier layer on the first cleaning blade side and a toner layer on the outside of the first cleaning blade. As a result, the liquid developer moving along the first cleaning blade 14 moves in contact with only the carrier liquid on the surface of the first cleaning blade 14, so that the liquid developer after being scraped off is moved. The agent smoothly moves on the first cleaning blade 14, so that the liquid developer can be easily collected, and the toner particles q are less likely to be deposited on the first cleaning blade 14. The electric field obtained by superimposing the AC electric field on the DC electric field may not be applied directly to the first cleaning blade 14, but may be applied to an electrode provided in the vicinity thereof. Even in this case, a constant electric field is generated around the first cleaning blade 14 as in the case of direct application.

In this way, by separating the liquid developer moving along the first cleaning blade 14 into two layers, the scraped liquid developer can be easily collected, and the toner particles q are transferred to the first cleaning blade 14. However, in this case as well, the electric field applied roller 10 applies an electric field applied to the thin layer 24 of the liquid developer, as in the case of the first cleaning blade 14. The electric field applied to must be an appropriate value. If the electric field applied to the first cleaning blade 14 is too strong, unnecessary toner particles q may adhere to the photosensitive drum 4, and the electric field applied to the first cleaning blade 14 is weak. If it is too large, the liquid developer moving on the first cleaning blade 14 is not sufficiently two-layered, and the accumulation of toner particles q cannot be prevented. Therefore, the electric field applied to the first cleaning blade 14 needs to be set within an appropriate range. Specifically, when the developing bias potential charged to the developing roller 11 is +300 V and the surface potential charged to the photosensitive drum 4 by the charging device 6 is +600 V, the first cleaning blade 14 is charged. A DC voltage of + 300V to + 800V is supplied, and an AC voltage of 1000V to 2000Hz and 2000V to 4000V is supplied.
In this case, when the first cleaning blade 14 has an insulation resistance value of 10 ⁷ to 10 ¹⁰ Ω, preferably 10 ⁹ to 10 ¹⁰ Ω, a current is supplied to the photosensitive drum 4 or the developing roller 11. Even if a high voltage (high electric field) is applied to the first cleaning blade 14, it is possible to prevent voltage leakage to the photosensitive drum 4 or the developing roller 11. As a result, even when a liquid developer having a high viscosity of about 1000 cSt to 5000 cSt is used, a voltage sufficient to form a two-layered developer can be applied. The toner particles q are not deposited.
Further, the AC voltage supplied to the first cleaning blade 14 is not limited to a sine wave AC voltage but may be a rectangular wave AC voltage for the same reason as the AC voltage supplied to the electric field applying roller 10. .

  When an electric field is applied to the first cleaning blade 14, a developing bias potential is applied to the developing roller 11 to develop the photosensitive drum 4 as shown in the timing chart of FIG. When (development), a DC electric field having the same potential as the development bias potential is applied to the first cleaning blade 14. That is, a DC electric field is generated in the first cleaning blade 14 by supplying a DC voltage having the same potential as the developing bias potential. When the developing bias potential is not applied to the developing roller 11 and the photosensitive drum 4 is not developed (during non-development), the first cleaning blade 14 is moved to the developing roller 11. A DC high electric field higher than the developing bias potential or an electric field in which an AC electric field is superimposed on the DC high electric field is applied. That is, a high DC voltage higher than the development bias potential or a voltage obtained by superimposing an AC voltage on the DC high voltage is supplied to the first cleaning blade 14 so that the DC high electric field or the DC high electric field is applied. An electric field is generated by superimposing an alternating electric field. The stronger the electric field applied to the first cleaning blade 14, the more easily the liquid developer moving on the surface of the first cleaning blade is divided into two layers, but an electric field stronger than the developing bias potential is applied during development. As a result, the potential of the developing bias of the developing roller 11 is not stabilized, and the fogging and density unevenness of the image occur due to the influence of the developing process. On the other hand, at the time of non-development, the developing bias potential is not applied to the developing roller 11, and even if a high electric field is applied, the developing process is not affected. Even if an electric field stronger than the bias potential is applied, no problem occurs. Therefore, as described above, by switching the electric field applied during development and during non-development, the occurrence of image fogging and density unevenness can be prevented, and toner accumulation on the first cleaning blade 14 can be further prevented. It can be effectively prevented. Accordingly, the DC voltage source 31 or the AC voltage source 32 is provided with means for switching the electric field or voltage applied to the first cleaning blade 14 in accordance with the potential of the developing bias applied to the developing roller 11. It is desirable that

Next, the cleaning device 3 for removing the liquid developer remaining on the surface of the photosensitive drum 4 will be described with reference to FIG. The cleaning device 3 includes a cleaning roller 2 and a second cleaning blade 1 (an example of a second developer moving member) provided in contact with the photosensitive member 4 with an appropriate pressure. The liquid developer remaining on the photosensitive drum 4 after the toner image is transferred to the recording paper is first scraped off by the cleaning roller and further scraped off by the second cleaning blade 1. Similar to the first cleaning blade 14, an electric field in which an AC electric field is superimposed on a DC electric field is applied to the second cleaning blade 1. As a result, a constant electric field is generated around the second cleaning blade 1. That is, an electric field is generated between the toner particles q and the second cleaning blade 1 in a direction to move the toner particles q away from the second cleaning blade 1, and an AC voltage superimposed on the DC voltage is generated. An alternating electric field is generated. As described above, the second cleaning blade 1 moves on the second cleaning blade 1 by applying an electric field obtained by superimposing an AC electric field on the DC electric field, similarly to the first cleaning blade 14. The liquid developer to be recovered can be made into two layers, so that the toner particles q do not contact the first cleaning blade 14 and the carrier liquid contacts and moves, so that the liquid developer after scraping is recovered. Is performed smoothly, and toner particles q are not deposited on the second cleaning blade 1. The second cleaning blade 1 should have an insulation resistance value of 10 ⁷ to 10 ¹⁰ Ω, preferably 10 ⁹ to 10 ¹⁰ Ω, and a rectangular wave AC voltage can be applied to the second cleaning blade 1. Or by switching the electric field or voltage applied to the second cleaning blade 1 in accordance with the potential of the developing bias applied to the developing roller 11, and the case of the first cleaning blade 14. The same effect is produced.

FIG. 3 is a schematic cross-sectional view of an image forming unit X of an image forming apparatus including a liquid developing device. The figure which shows the state of the liquid developer to which the electric field was applied by the electric field application roller. FIG. 4 is a diagram illustrating a state in which the liquid developer is removed by a first cleaning blade. The figure which shows the state which removes a liquid developer with the conventional 1st cleaning blade. Voltage switching timing chart.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... 1st cleaning blade 2 ... Cleaning roller 3 ... Cleaning device 4 ... Photoconductor drum 5 ... Static elimination lamp 6 ... Charging device 7 ... Exposure device 8 ... Transfer device 9 ... Transfer belt 10 ... Electric field application roller 11 ... Developing roller 12 ... anilox roller 13 ... supply roller 14 ... first cleaning blade 15 ... doctor blade 16 ... liquid developing devices 21 and 31 ... DC voltage sources 22 and 32 ... AC voltage source 23 ... developing bias power supply device q ... toner particles

Claims (2)

A developer carrying member carrying a liquid developer in which toner particles are dispersed in an insulating solvent; development bias applying means for applying a predetermined developing bias potential to the developer carrying member; A developer cleaning member that contacts and removes the liquid developer remaining on the developer carrier after development; a first developer moving member that moves the liquid developer scraped by the developer cleaning member; Or a liquid developing device comprising a developing cleaning electric field applying means for applying a DC electric field or an electric field in which an AC electric field is superimposed on the DC electric field in the vicinity thereof,
A liquid developing apparatus, wherein an insulation resistance value of a material of the first developer moving member is 10 ⁷ to 10 ¹⁰ Ω, preferably 10 ⁹ to 10 ¹⁰ Ω. A predetermined image carrier potential is applied, and the toner image is transferred to a predetermined recording paper in contact with an image carrier carrying a toner image made of a liquid developer in which toner particles are dispersed in an insulating solvent. An image carrier cleaning member that removes the liquid developer remaining on the image carrier, and a second developer moving member from which the liquid developer scraped by the image carrier cleaning member flows down, or In an image carrier cleaning device comprising a DC electric field or an image carrier cleaning electric field applying means for applying an electric field in which an AC electric field is superimposed on a DC electric field in the vicinity thereof,
A cleaning device, wherein an insulation resistance value of a material of the second developer moving member is 10 ⁷ to 10 ¹⁰ Ω, preferably 10 ⁹ to 10 ¹⁰ Ω.

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