JPH10274885A - Liquid developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently remove toner remaining after development, which is stuck on a developing roller and to reduce the occurrence of a defect in an image such as a streaky noise by providing a fixed type toner scraping member arranged in contact with a cleaning member. SOLUTION: The toner D1 remaining without being stuck to an electrostatic latent image is transferred to a downstream side position P3 from a developing region P1, in the rotational direction a2 of the developing roller 41, in a state where the toner D1 is still stuck to the surface of the developing roller 41, so that the toner D1 reaches the proximity region P4 of the developing roller 41 and a cleaning roller 42. Since a bias voltage is applied to between the developing roller 41 and the cleaning roller 42 from the power source PW4 of a bias applying device 45, the residual toner D1 stuck on the developing roller 41 is stuck to the surface of the cleaning roller 42, together with the rotation in the direction a3 of the cleaning roller 42, in the proximity region P4. A scraper 43 is in linear or surface contact with the surface of the cleaning roller 42, to scrape the toner D2 stuck on the cleaning roller 42.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrophotographic copying machine or a printer for developing an electrostatic latent image formed on an electrostatic latent image carrier using a liquid developer. And a liquid developing device for electrophotography.

[0002]

2. Description of the Related Art In an image forming apparatus such as an electrophotographic copying machine or a printer, a surface of an electrostatic latent image carrier such as a photoconductor is generally charged, and an image is formed in the charged area based on image information. Exposure to form an electrostatic latent image, develop the latent image into a visible toner image, transfer this toner image to a recording material such as paper,
Fix it. A liquid developing device is employed to develop the latent image with a liquid developer to form a visible toner image.

[0003] The liquid developer used in the liquid developing apparatus contains a toner and a carrier liquid. Since the liquid developer contains finer toner than the dry developer, an image formed by the liquid developing device can have higher resolution than an image formed by the dry developing device.

[0004]

However, the liquid developing apparatus has the following problems. That is, a part of the liquid developer supplied to the developing area facing the electrostatic latent image carrier by the developing roller is consumed for developing the electrostatic latent image, and the remaining liquid developer is used as a residual developer, and Is returned into the developing device with the rotation of. At this time, the residual toner contained in the residual developer adheres to the developing roller, and if left as it is, it is carried to the developing area even at the next development,
This causes an image defect such as a so-called image memory. For this reason, in the liquid developing device, a cleaning device that removes residual toner adhering to the developing roller is usually provided at a position downstream of the developing region in the rotation direction of the developing roller. Generally, a cleaning member such as a rotary brush or a cleaning blade is used as the cleaning device.

However, the toner in the liquid developer has a small particle size, and the remaining toner corresponding to the non-image area on the electrostatic latent image carrier that does not require toner adhesion is removed from the electrostatic latent image carrier. The electric field heading to the developing roller is applied, and it may be in contact with the developing roller.
Large adhesive force such as van der Waals force and mirror image force acts, and strongly adheres to the developing roller surface.

On the other hand, as the cleaning member used in the cleaning device, a cleaning member which comes into contact with a developing roller is employed. However, the toner adhered in such a strong manner has a small particle diameter. Easy to slip through. If the cleaning member is strongly rubbed against the developing roller so as to improve the cleaning property, the surface of the developing roller is damaged. Further, in the case of using a brush-type cleaning member such as a rotating brush, there is a problem that the brush bristles come off or peel off, and a problem that the cleaned toner adheres to and accumulates on the brush bristles and the toner hardens (so-called blocking or the like). Easy to invite.

Due to the above, such a cleaning device is liable to cause image defects such as streak-like image noise. Some conventional liquid developing devices are provided with a high-concentration liquid developer layer forming device for efficiently developing with a liquid developer (a device using a so-called electrodeposition method). The high-concentration liquid developer layer forming apparatus includes an electrode along a developing roller surface provided at a position upstream of a developing region of an electrostatic latent image formed on the electrostatic latent image carrier in a rotating direction of the developing roller. Contains. A bias voltage that biases the toner floating in the carrier liquid toward the developing roller is applied to this electrode, so that the concentration of the toner in the liquid developer can be increased, and the development efficiency can be improved. it can.

In such a liquid developing device, the concentration of the toner in the developer that has passed through the developing region is high, and the above-mentioned problem caused by the cleaning device becomes remarkable. Therefore, the present invention
A liquid developing device that supplies a liquid developer containing toner by a developing roller that is driven to rotate to an electrostatic latent image formed on an electrostatic latent image carrier, and develops the latent image into a visible toner image. It is another object of the present invention to provide a liquid developing apparatus capable of efficiently removing residual toner adhered to the developing roller after development as compared with a conventional apparatus and reducing the occurrence of image defects such as streak noise.

[0009]

In order to solve the above-mentioned problems, the present invention supplies a liquid developer containing toner by a developing roller which is driven to rotate on an electrostatic latent image formed on an electrostatic latent image carrier. A liquid developing device that develops the latent image into a visible toner image, wherein the liquid developing device is disposed at a position downstream of the electrostatic latent image development area at a fixed distance from the developing roller in a rotation direction of the developing roller. A cleaning member that is rotated and driven; and a bias applying device that applies a bias voltage between the developing roller and the cleaning member to apply a bias voltage for sucking residual toner after development attached to the developing roller to the cleaning member. A fixed toner scraping member disposed in contact with the cleaning member to scrape toner adhered to the cleaning member by applying the bias voltage. To provide a liquid developing device is characterized in that is e.

According to the liquid developing apparatus of the present invention, the residual toner on the developing roller is removed by applying a bias voltage between the developing roller and the cleaning member to the cleaning member by a bias voltage applied by the bias applying device. Is performed by the toner suction action of the toner. The cleaning member is driven to rotate, and the fixed toner scraping member is disposed in contact with the cleaning member.
The toner adhered to the cleaning member is removed by the fixed toner scraping member as the cleaning member rotates. As a result, the cleaning performance of the cleaning member can be maintained, and the residual toner after the development, which has adhered to the developing roller, can be removed more smoothly and reliably than the conventional device.

The cleaning member is not in contact with the developing roller, but is arranged at a fixed distance from the electrostatic latent image carrier, and is disposed on the developing roller under application of a bias voltage by the bias applying device. Since the residual toner is adsorbed and removed, unlike the conventional liquid developing device using a cleaning member in contact with the developing roller, a load that damages the surface of the developing roller is not applied. In addition, since a brush-type cleaning member such as a conventional rotating brush that comes into contact with the developing roller is not used, problems such as detachment and peeling of brush bristles can be solved, and problems such as blocking can be reduced.

The contact portion between the fixed toner scraping member and the cleaning member is provided so that the toner removed from the cleaning member can be immediately returned to the liquid developer.
It can be set at a position submerged in the liquid developer. Further, by setting the position to be immersed in the developer in this way, the removed toner is easily dispersed in the developer, and the toner due to the pressure contact force between the fixed scraping member and the cleaning member is formed. Can be suppressed, and toner contamination such as toner adhering to the toner removing member and the cleaning member can be reduced. Further, when the cleaning member or the like becomes dirty with toner or the like, a preliminary operation such as operating the cleaning member in advance is usually required to clean the cleaning member. You can save time.

If the gap distance between the developing roller and the cleaning member is less than 50 μm, it is difficult to manufacture the apparatus, or the aggregated toner tends to clog in this gap, and if it exceeds 500 μm, the developing roller The cleaning performance of the residual toner adhered to the upper portion is liable to be reduced.
It can be exemplified that the distance is set in a range of up to 500 μm.

If the voltage applied between the developing roller and the cleaning member by the bias applying device is less than 50 V, the suction of the residual toner tends to decrease, and if it exceeds 2000 V, problems such as electric discharge occur. However, since the cleaning performance is apt to be lowered, the setting is not limited thereto, but it can be exemplified that the cleaning performance is set in the range of 50 V to 2000 V.

The cleaning member may be in the form of a roller or the like, and examples of the material include a material such as a metal and a resin which has a small change in shape due to an external load. The surface roughness is 10 μm (ten-point average roughness: R
z) The following are desirable. The rotation direction of the cleaning member may be the same as or opposite to the rotation direction of the developing roller. If the peripheral speed of the cleaning member is lower than the peripheral speed of the developing roller, the cleaning performance of the residual toner tends to be reduced. Therefore, it is desirable to make the peripheral speed higher than the peripheral speed of the developing roller.

Further, as a material of the fixed toner scraping member, for example, a material such as metal, resin, rubber, etc., which can uniformly contact the cleaning member by line contact or surface contact can be used. The liquid developing device according to the present invention includes a high-concentration liquid developer layer forming device at a position on the upstream side of the developing region in the rotation direction of the developing roller in order to efficiently perform development with the liquid developer. Can be.

In any case, in the rotation direction of the developing roller, at a position downstream of the developing area, a toner cleaning member for cleaning residual toner adhered to the developing roller after development is provided to the developing roller. It may be arranged in contact. In this case, the mutual contact portion between the toner cleaning member and the developing roller can be set at a position submerged in the liquid developer.
Further, the mutual contact portion can be located on the downstream side in the rotation direction of the developing roller from the mutually opposing portion of the developing roller and the cleaning member. In addition, when the high-concentration liquid developer forming device is present, it can be located upstream of the device. As the material of the toner cleaning member, a material such as rubber that can evenly contact the developing roller can be adopted.

By employing such a toner cleaning member,
In addition to the action of removing the toner from the developing roller by the cleaning member described above, the action of wiping the toner on the developing roller by the toner cleaning member is added, so that the residual toner adhering to the developing roller after development can be more efficiently removed than in the conventional apparatus. As described above, any of the liquid developing devices can remove the residual toner adhered onto the developing roller after development more efficiently than the conventional device, and can reduce the occurrence of image defects such as streak image noise.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of an image forming apparatus provided with an example of a liquid developing device according to the present invention. FIG. 2 is a side view of a main part of the liquid developing device shown in FIG. FIG. 3 is a side view of a main part of a developing device in which a high-concentration liquid developer layer forming device is provided in the liquid developing device shown in FIG. FIG. 4 is a side view of a main part of the developing device in which a toner cleaning member is arranged in contact with a developing roller of the liquid developing device shown in FIG.

First, the image forming apparatus shown in FIG. 1 will be described, and then each liquid developing apparatus will be described in detail with reference to FIGS. The image forming apparatus shown in FIG. 1 includes a photoconductor 1, a charging charger 2, a print head 3, a liquid developing device 4, a pre-transfer charger 5, a transfer roller 6, a cleaner 7, a fixing roller 8, and the like. .

In this image forming apparatus, the print head 3
Irradiates the charged area on the photoreceptor 1 uniformly charged by the charging charger 2 to form an electrostatic latent image corresponding to a document image on the photoreceptor based on image data. Form. This electrostatic latent image moves with the rotation of the photoconductor 1 in the a1 direction, and is developed by the liquid developer D contained in the liquid developing device 4 (details will be described later) to become a visible toner image. The surface of the photoconductor 1 holding the visible toner image containing the carrier liquid in the liquid developer D is squeezed by a squeeze roller 46 provided in the liquid developing device 4 and a power supply PW.
The carrier liquid is removed by the squeezing voltage supplied from 1 while holding the visible toner image on the photoreceptor 1, and further, the charger 5 is used to easily transfer the visible toner image to the recording sheet S. The charge of the toner of the visible toner image is increased, and the process proceeds to the transfer portion T.

The transfer section T is provided with a transfer roller 6 to which a transfer voltage is applied from a power supply PW2 for sucking the visible toner image. The image is transferred onto the recording sheet S. The recording sheet S is supplied from a recording material supply unit (not shown), and is sent to the transfer unit T in synchronization with the toner image on the photoconductor 1 by a pair of timing rollers (not shown). After the transfer of the toner image, the sheet S is conveyed to the fixing roller 8, where the toner image is fixed, and then discharged.

On the other hand, the recording sheet S
Remaining on the photosensitive member 1 is transferred to the cleaner 7 as the photosensitive member 1 rotates in the a1 direction. Excess toner remaining on the surface of the photoreceptor 1 is removed by a cleaning roller 71 and a cleaning blade 72 provided on the cleaner 7 to prepare for the next image formation.

Although the squeezing device such as the squeezing roller 46 is integrated into the developing device 4 here, the squeezing device may be provided at a similar position as a component different from the developing device. The image forming apparatus shown in FIG.
Although the toner image on the photoreceptor 1 is electrostatically transferred to the recording sheet S, the transfer roller 6 may be a heat roller and thermally transferred under an appropriate pressure. In addition, the charge of the toner contained in the liquid developer is determined by performing regular development or
The liquid developer may be charged positively or negatively by changing the properties of the liquid developer depending on whether reverse development is performed or not. The liquid developing device here is employed in an image forming apparatus for directly transferring a toner image on a photoreceptor to a recording sheet. However, the toner image is temporarily transferred to an intermediate transfer member such as an intermediate transfer belt. After that, it may be adopted in an image forming apparatus or the like that performs secondary transfer on a recording sheet.

Next, the liquid developing device 4 will be described in detail with reference to FIG. The liquid developing device 4 shown in FIG. 2 includes a developing roller 41, a cleaning roller 42, a scraper 43,
A support plate 44 for supporting the scraper 43 and a bias applying device 45 are provided, and the liquid developer D is contained therein. The developing device 4 applies a2 to the electrostatic latent image formed on the photoconductor 1.
A liquid developer D containing toner is supplied by a developing roller 41 driven to rotate in the direction, and the latent image is developed into a visible toner image.

A developing bias voltage is applied to the developing roller 41 by a power source PW3 so that toner adheres to the electrostatic latent image formed on the photosensitive member 1. The cleaning roller 42 is disposed at a position P3 on the downstream side of the electrostatic latent image development area P1 in the rotation direction a2 of the development roller 41 and at a constant distance from the development roller 41, and
It is driven to rotate in three directions.

The bias applying device 45 includes a developing roller 41
A bias voltage for attracting the residual toner D1 after the development to the cleaning roller 42 is applied to the developing roller 41.
And the cleaning roller 42. The scraper 43, which is an example of the fixed toner scraping member, is disposed in contact with the cleaning roller 42 in order to scrape the toner D2 adhered to the cleaning roller 41 by applying the bias voltage.

The mutual contact portion P5 between the scraper 43 and the cleaning roller 42 is set at a position where the scraper 43 is submerged in the liquid developer D. The liquid developer D contains a toner and a carrier liquid. The toner is pumped together with the carrier liquid by the developing roller 41 rotating in the direction a2 to a position P2 on the upstream side of the developing area P1. 41 moves to the opposing electrostatic latent image development area P <b> 1 and adheres to the electrostatic latent image on the photoconductor 1.

Toner D1 remaining without adhering to the electrostatic latent image
Are attached to the surface of the developing roller 41 and
In the first rotation direction a2, the position shifts to the position P3 on the downstream side of the developing region P1 and reaches the proximity region P4 between the developing roller 41 and the cleaning roller. Since a bias voltage is applied between the developing roller 41 and the cleaning roller 42 from the power supply PW4 of the bias applying device 45, the residual toner D1 adhering on the developing roller 41
With the rotation of the cleaning roller 42 in the direction a3, the cleaning roller 42 adheres to the surface of the cleaning roller 42. Thereby, the developing roller 41
The upper residual toner D1 can be removed smoothly and reliably.

The toner D2 coming from the developing roller 41 and adhering to the cleaning roller 42 moves to the scraper 43 with the rotation of the cleaning roller 42 in the direction a3. The scraper 43, which is disposed in contact with the cleaning roller 42 and is fixed to the support plate 44, is in line contact or surface contact with the surface of the cleaning roller 42, and scrapes off the toner D2 attached to the cleaning roller 42. Thereby, the cleaning roller 42 can maintain the force for sucking the residual toner D1 by the bias voltage between the cleaning roller 42 and the developing roller 41.

Therefore, the liquid developing device 4 includes the developing roller 4
After the development, the residual toner D1 adhered to the surface 1 can be efficiently removed, and the occurrence of image defects such as streak-like image noise can be reduced. Next, another embodiment of the liquid developing device according to the present invention will be sequentially described with reference to FIGS. The liquid developing device 4a shown in FIG. 3 is a device provided with a high-concentration liquid developer layer forming device 47 for efficiently developing the liquid developing device 4 shown in FIG.

This high-concentration liquid developer layer forming apparatus 47
In the rotation direction a2 of the developing roller 41, the developing roller 41 is provided at a position P2 upstream of the electrostatic latent image developing area P1.
It includes an electrode 47a along one surface. This electrode 47a
To the developing roller 41, a bias voltage is applied from a power supply PW5 that biases the toner floating in the carrier liquid contained in the developer D to the developing roller 41 side. Can be increased, and the efficiency of development can be improved.

After the electrostatic latent image is developed by the high-concentration liquid developer D3 formed by such a device, the toner D1 remaining on the developing roller 41 strongly adheres to the surface of the developing roller 41. However, like the liquid developing device 4 shown in FIG. 2, the cleaning roller 42 provided in the liquid developing device 4a also causes the residual toner D1 that strongly adheres to the surface of the developing roller 41 by the action of the cleaning roller 42 and the like. It can be effectively removed.

The liquid developing device 4b shown in FIG. 4 is a device in which a cleaning blade 48 is arranged in contact with the developing roller 41 of the liquid developing device 4a shown in FIG.
The cleaning blade 48 is fixed to the support plate 44 and is disposed in contact with the developing roller 41 at a position downstream of the proximity area P4 between the developing roller 41 and the cleaning roller 42 in the rotation direction a2 of the developing roller 41. The residual toner D1 adhering to the developing roller 41 without being attracted to the roller 42 is cleaned.

The contact portion P6 between the cleaning blade 48 and the developing roller 41 is set at a position submerged in the liquid developer D. Accordingly, the toner wiping effect of the cleaning blade 48 is added to the toner removing effect of the cleaning roller 42 and the like,
The residual toner D1 adhering to the developing roller 41 after the development can be more efficiently removed.

In the developing device 4 shown in FIG.
A similar cleaning blade 48 may be provided. As described above, any of the liquid developing devices 4, 4 a, and 4 b can efficiently remove the residual toner D <b> 1 after development, which adheres to the developing roller 41, and can reduce the occurrence of image defects such as streak noise as compared with the conventional device.

Next, an experiment for evaluating the performance of the developing apparatus shown in FIG. 4 will be described. In addition, a comparative experiment was also performed, and will be described together. Figure 4 shows the evaluation experiment.
1 is mounted on an image forming apparatus of the type shown in FIG. 1, and an IP solvent 1620 (Idemitsu Petrochemical Co., Ltd.) is used as a carrier liquid in the liquid developer.
And a dispersion of a polyester resin toner having an average particle size of 2 μm in the liquid. The experimental conditions are as follows.

Toner charge Negative charge Developing method Inverting developing method Toner density 3% by weight Surface potential of photoconductor 1 -700 V Gap distance between photoconductor 1 and developing roller 41 200 μm Gap distance between developing roller 41 and cleaning roller 42 100 μm Peripheral speed of photoconductor 1 163.5 mm / s Peripheral speed of developing roller 41 200 mm / s Peripheral speed of cleaning roller 42 200 mm / s Material of cleaning roller 42 SUS (stainless steel) Diameter of cleaning roller 42 φ20 mm Cleaning roller 42 Surface roughness (ten-point average roughness: Rz) of 0.5 μm Material of scraper 43 Phosphor bronze Material of cleaning blade 48 Polyurethane rubber Voltage value of power supply PW3 500V Voltage value of power supply PW5 1000V Voltage value of power supply PW4 500V In the experiment, the developing device shown in FIG. 4b was mounted on an image forming apparatus of the type shown in FIG. 1, and the operation was performed without supplying a voltage from the power supply PW4 between the developing roller 41 and the cleaning roller.

As a result, in the comparative experimental example to which the present invention was not applied, streak-like stains causing image defects such as streak-like noise occurred on the developing roller after the developing roller rotated about 100 times. On the other hand, when operated in an experimental example using the developing device 4b according to the present invention, the developing roller 41
Even after 0 rotation, no streak-like stain was generated. As a result, the occurrence of image defects such as streak noise can be reduced by the operation described above as compared with the conventional device.

[0040]

According to the present invention, a liquid developer containing toner is supplied to a latent image formed on an electrostatic latent image carrier by a developing roller which is driven to rotate, and the latent image is made visible toner. Provided is a liquid developing device for developing an image, which is capable of efficiently removing residual toner adhered to a developing roller after development as compared with a conventional device and reducing the occurrence of image defects such as streak noise. be able to.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of an image forming apparatus provided with an example of a liquid developing device according to the present invention.

FIG. 2 is a side view of a main part of the liquid developing device shown in FIG.

FIG. 3 is a side view of a main part of a developing device in which a high-concentration liquid developer layer forming device is provided in the liquid developing device shown in FIG. 2;

4 is a side view of a main part of the developing device in which a toner cleaning member is arranged in contact with a developing roller of the liquid developing device shown in FIG. 3;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charger 3 Laser printer head L Laser beam 4, 4a, 4b Liquid developing device 41 Developing roller 42 Cleaning roller 43 Scraper 44 Support plate 45 Bias applying device 46 Squeeze roller 47 High-concentration liquid developer layer forming device 47a Electrode 48 Cleaning blade D Liquid developer D1, D2 Toner D3 High-concentration liquid developer P1 Electrostatic latent image developing area P2 Position upstream from electrostatic latent image developing area in developing roller rotation direction P3 Electrostatic latent in developing roller rotating direction Downstream position from image development area P4 Proximity area between developing roller 41 and cleaning roller 42 P5 Mutual contact area between scraper 43 and cleaning roller 42 P6 Mutual contact area between cleaning blade 48 and developing roller 41 5 Charger before transfer 6 Transfer Roller 7 Lina 71 cleaning roller 72 cleaning blade 8 fixing roller T transfer unit S recording sheet PW1, PW2, PW3, PW4, PW5 power

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hidetoshi Miyamoto 2-3-13 Azuchicho, Chuo-ku, Osaka-shi Inside Osaka International Building Minolta Co., Ltd. (72) Toshimitsu Fujiwara 2-3-3 Azuchicho, Chuo-ku, Osaka-shi 13 Osaka International Building Minolta Co., Ltd. (72) Inventor Masaharu Kanazawa 2-3-13 Azuchicho, Chuo-ku, Osaka City Osaka International Building Minolta Co., Ltd.

Claims (5)

[Claims] A liquid for developing a latent image into a visible toner image by supplying a liquid developer containing toner by a developing roller that is driven to rotate to the electrostatic latent image formed on the electrostatic latent image carrier. A developing device, a cleaning member that is disposed at a fixed distance from the developing roller at a position downstream of the electrostatic latent image developing area in the rotation direction of the developing roller and is driven to rotate, A bias applying device for applying a bias voltage between the developing roller and the cleaning member for sucking the adhered residual toner after the development to the cleaning member; and applying the bias voltage to the cleaning member. A liquid developing device, comprising: a fixed toner scraping member disposed in contact with the cleaning member to scrape toner. 2. The liquid developing device according to claim 1, further comprising a high-concentration liquid developer layer forming device at a position upstream of the developing region in a rotation direction of the developing roller. 3. The liquid developing apparatus according to claim 1, wherein a contact portion between the fixed toner scraping member and the cleaning member is set at a position where the fixed toner scraping member is submerged in a liquid developer. 4. A toner cleaning member for cleaning residual toner after development adhering to the developing roller at a position downstream of the developing area in a rotation direction of the developing roller, and is arranged in contact with the developing roller. The liquid developing device according to claim 1, 2 or 3, wherein 5. The liquid developing apparatus according to claim 4, wherein a contact portion between said toner cleaning member and said developing roller is set at a position submerged in a liquid developer.