JP5206401B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus.

  In general, an electrophotographic system is known as an image forming system used in an image forming apparatus such as a copying machine or a printer. This is because an electrostatic latent image is formed by irradiating a photoconductor charged with a charger such as a corona discharger or a charging roll with a light image using a laser or LED array. The electrostatic latent image is developed with a charged toner to form a visible image. An image forming apparatus using the electrophotographic method as described above is widely used mainly in offices because it has excellent on-demand characteristics and allows easy image formation on plain paper.

  On the other hand, in consideration of environmental influences in the electrophotographic system, an image forming apparatus of a system in which electrodes are arranged in a matrix and no charger is used has been proposed (see Patent Documents 1 to 5). In Patent Document 1 and Patent Document 2, image formation is performed in such a manner that thin film transistors (TFTs) are formed in a matrix and storage capacitors are provided in the respective TFTs, and stable development is performed by the charge storage effect in the storage capacitors. A device has been proposed. Japanese Patent Application Laid-Open No. 2004-228561 proposes a method of detecting the toner density on the surface of the image carrier after development and setting the voltage to be applied to the switching element based on the detected toner density. Further, Patent Document 4 proposes a configuration in which a storage capacitor divided into two layers is provided for each switching element arranged in a matrix and the potential of the image part / non-image part is adjusted. Patent Document 5 proposes a method of forming a latent image for each pixel using switching elements arranged in a matrix and using a pixel electrode at the time of transfer.

  On the other hand, an electrostatic cleaning system is known as a cleaning device that cleans residual toner on an image carrier. Patent Document 6 proposes a method using a magnetic brush, and Patent Document 7 proposes a method using an electrostatic brush.

Japanese Patent No. 3233463 (Example, FIG. 4) Japanese Patent Laying-Open No. 2005-331955 (Best Mode for Carrying Out the Invention, FIG. 4) Japanese Patent No. 3826013 (Embodiment 8, FIG. 9) Japanese Patent Laying-Open No. 2003-32440 (Embodiment of the Invention, FIG. 1) JP 2004-219635 A (Embodiment 1, FIG. 1) JP 58-59479 A (page 3, FIG. 3) Japanese Utility Model Publication No. 63-24570 (Example, Fig. 1)

  The technical problem of the present invention is that, when an image is formed using an image carrier having pixel electrodes arranged two-dimensionally in units of pixels, a good image quality is obtained as compared with a method using no pixel electrodes, and an image is obtained. It is to obtain a further improved image quality by purifying the holding body.

  The invention according to claim 1 is a support having a movable surface, and is supported on the surface of the support, and is arranged two-dimensionally in the moving direction of the support surface and in the intersecting direction intersecting the support surface. An image carrier having a plurality of pixel electrodes to which a latent image voltage for forming a toner image according to information can be applied, and a protective layer that insulates and coats these pixel electrodes, and disposed opposite to the image carrier And a rotatable conductive cleaning member that comes into contact with the surface of the image carrier and cleans the residual toner, and the image holding unit so as to form a cleaning electric field whose polarity changes between the cleaning member and the pixel electrode. The pixel electrodes arranged along the body movement direction are divided into a plurality of regions, and cleaning voltages having different cleaning electric fields with respect to the cleaning electric field formed between the pixel electrodes in the adjacent regions and the cleaning member are applied. Apply, cleaning member and image carrier , A cleaning device having a cleaning voltage application means for coexist an area in which at least polarities different cleaning electric field is formed within the contact area between an image forming apparatus having a.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the cleaning voltage applying unit further has a polarity between the cleaning member and the pixel electrode along the intersecting direction of the image carrier. The pixel electrodes arranged along the intersecting direction are divided into a plurality of regions so as to form a changing cleaning electric field, and are mutually polar with respect to the cleaning electric field formed between the pixel electrode in the adjacent region and the cleaning member. The image forming apparatus is configured to apply a cleaning voltage that provides a different cleaning electric field.
A third aspect of the present invention is the image forming apparatus according to the first or second aspect, wherein the cleaning member is a brush member.
According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect, the cleaning member rotates in the same direction as the moving direction of the image carrier at a portion facing the image carrier. .
According to a fifth aspect of the present invention, in the image forming apparatus according to the fourth aspect, the rotational speed of the cleaning member is set larger than the moving speed of the image carrier.
According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects, the cleaning device includes a toner recovery member that is disposed to face the cleaning member at a position separated from the image carrier. The image forming apparatus further includes a toner collecting unit that causes a toner collecting electric field to act between the toner collecting member and the cleaning member to collect the toner adhering to the cleaning member by the toner collecting member.
According to a seventh aspect of the present invention, in the image forming apparatus according to the sixth aspect, in which the toner whose resistance is changed by an action electric field is used, the toner recovery means has a toner recovery electric field larger than a cleaning electric field. And an image forming apparatus that changes the toner resistance in the toner recovery electric field to be lower than the resistance in the cleaning electric field.

According to the first aspect of the present invention, when forming an image using an image carrier having pixel electrodes arranged two-dimensionally in units of pixels, it is possible to obtain better image quality than a method using no pixel electrodes. Compared with the case without this configuration, the image carrier can be cleaned and further improved image quality can be obtained.
According to the invention which concerns on Claim 2, compared with what does not have this structure, the favorable cleaning by a cleaning member comes to be made. The residual toner can be more effectively cleaned while suppressing the reattachment of the toner adhering to the cleaning member to the image carrier.
According to the third aspect of the present invention, it is possible to more effectively clean the residual toner while suppressing the reattachment of the toner adhering to the cleaning member to the image holding member, as compared with the case without this configuration. .
According to the fourth aspect of the present invention, the load applied to the image holding member can be reduced and the image holding member and the cleaning member can be used for a long period of time as compared with the case without this configuration.
According to the fifth aspect of the present invention, the residual toner on the image holding member is guided to the contact area and the cleaning performance can be improved as compared with the case without this configuration.
According to the invention which concerns on Claim 6, compared with what does not have this structure, the cleaning performance by a cleaning member can be maintained for a long term.
According to the seventh aspect of the present invention, the toner adhering to the cleaning member can be recovered to the toner recovery member side better than that having no structure.

First, an outline of an embodiment model to which the present invention is applied will be described.
Outline of Embodiment Model FIG. 1 shows an outline of an image forming apparatus according to an embodiment model embodying the present invention. FIG. 1A shows the configuration and FIG. 1B shows the operation. In the figure, the image forming apparatus is a support 2 whose surface is movable, supported on the surface of the support 2, arranged in a two-dimensional manner in the moving direction of the surface of the support 2 and the crossing direction intersecting with the moving direction. An image carrier 1 having a plurality of pixel electrodes 3 to which a latent image voltage for forming a toner image corresponding to image information for each pixel can be applied, and a protective layer 4 for insulatingly covering these pixel electrodes 3; A rotatable conductive cleaning member 6 disposed opposite to the image carrier 1 and contacting the surface of the image carrier 1 to clean the residual toner T, and a polarity between the cleaning member 6 and the pixel electrode 3. The pixel electrodes 3 arranged along the moving direction of the image carrier 1 are divided into a plurality of regions and formed between the adjacent pixel electrodes 3 and the cleaning member 6 so as to form a changing cleaning electric field. A cleaning electric field with different polarities from each other A cleaning device 5 having a cleaning voltage applying means 7 for applying a voltage to coexist a region where at least a cleaning electric field having a different polarity is formed in a contact region m between the cleaning member 6 and the image carrier 1; It has.

  Here, the image information typically means an image signal corresponding to a toner image to be formed. In addition, as a region where a cleaning electric field having a different polarity formed in the contact region m between the cleaning member 6 and the image carrier 1 is formed, two or more regions are formed. For example, the cleaning voltage may be applied so that the polarity of the cleaning electric field is different for each pixel electrode 3, or the cleaning voltage is applied so that the polarity is different for each of the one or more pixel electrodes 3. It may come to be. At this time, the one or more pixel electrodes 3 are not fixed quantities but are regions having different polarities in the cleaning electric field acting between the pixel electrode 3 and the cleaning member 6 along the surface movement direction of the image carrier 1. Can be alternately formed, the number of pixel electrodes in each region can be any number.

Next, referring to FIG. 1B, the cleaning electric field applied between the cleaning member 6 and the pixel electrode 3 in the contact area m between the image carrier 1 and the cleaning member 6 by the cleaning voltage applying means 7. The cleaning action of the bipolar toner by changing the polarity will be described.
Here, it is assumed that the cleaning member 6 is grounded, and a region (A region) of the pixel electrode 3 to which a positive voltage (V (+)) is applied and a negative voltage (V (−)) are applied in the contact region m. Assuming that there is a region (B region) of the applied pixel electrode 3, a positive toner T (+) and a negative toner T (−) are mixed as the residual toner T on the image carrier 1. In the area A, the positive electric toner T (+) is electrostatically attracted to the cleaning member 6 by the action of the cleaning electric field E (+) from the pixel electrode 3 toward the cleaning member 6. When the cleaning electric field E (−) toward the electrode 3 acts, the negative toner T (−) is electrostatically attracted to the cleaning member 6. In this case, the number of regions that become cleaning electric fields having different polarities may be two or more regions (for example, A region and B region) with respect to the contact region m, and the number of pixel electrodes 3 in the A region and B region. Are not particularly limited, and may be the same or different quantities as long as both are one or more quantities.

  In such a cleaning electric field, the negative toner T (−) in the A region is not electrostatically attracted to the cleaning member 6 but is moved to a neighboring region by the rotating action of the cleaning member 6. The negative toner T (−) moved by moving to the region is electrostatically attracted to the cleaning member 6. Similarly, the positive toner T (+) in the B area is electrostatically attracted to the cleaning member 6 in the A area. Therefore, the cleaning member 6 is attracted regardless of the polarity of the toner T. The toner electrostatically attracted to the cleaning member 6 remains on the cleaning member 6 due to the toner holding force of the cleaning member 6. However, even if the toner is separated from the cleaning member 6, the same action is repeated to repeat the image holding member. The residual toner T on 1 is cleaned.

  In this way, by forming a region in which the polarity of the cleaning electric field is different from the contact region m, the cleaning member 6 side regardless of the polarity of the toner T, regardless of the polarity of the toner T, regardless of the direction of the toner T. Can be electrostatically attracted. Therefore, in order to reduce the load on the image carrier 1 due to the cleaning member 6, the cleaning member 6 is rotated when the cleaning member 6 is rotated so that the rotation direction of the cleaning member 6 is the same movement direction at the portion facing the image carrier 1. The rotational speed of the image holding member 1 can be made larger than that of the image holding member 1, and the load on the image holding member 1 can be further reduced, and a cleaning device having a cleaning effect can be realized.

  The shape of the support 2 is not particularly limited as long as it can support the pixel electrode 3 and the like and the surface is movable. However, from the viewpoint of downsizing the apparatus, a rotating body is preferable. . Furthermore, the pixel electrodes 3 only need to be arranged two-dimensionally along the moving direction and crossing direction of the image carrier 1 in units of pixels, and the number of pixel electrodes 3 is not particularly limited, but a normal image can be formed. It is preferable that the resolution can be realized. Furthermore, the polarity of the toner T used may be any. Further, as the protective layer 4, the surface of the image carrier 1 is mechanically protected, and an insulating layer is applied so as not to adversely affect the voltage applied to the pixel electrode 3.

  Further, the position where the cleaning voltage is applied to the pixel electrode 3 by the cleaning voltage applying means 7 can be any as long as a cleaning electric field can act between the cleaning member 6 and the region facing the cleaning member 6. However, the position near the upstream side in the moving direction of the image carrier 1 is usually selected from the area facing the cleaning member 6. Further, a means for applying a voltage to the pixel electrode 3 by the cleaning voltage applying means 7 may be provided exclusively. However, in order to make the pixel electrode 3 act effectively, for example, a latent image is formed on the pixel electrode 3. It is preferable to use a means to do this.

  Further, from the viewpoint of suppressing the spread of the toner T in the crossing direction of the image carrier 1, the cleaning voltage application unit 7 further includes the cleaning member 6, the pixel electrode 3, and the crossing direction of the image carrier 1. The pixel electrodes 3 arranged along the crossing direction are divided into a plurality of regions and formed between the adjacent pixel electrodes 3 and the cleaning member 6 so as to form a cleaning electric field whose polarity changes between them. It is preferable to apply a cleaning voltage that is a cleaning electric field having a different polarity with respect to the cleaning electric field. In this way, by providing regions with different polarities of the cleaning electric field for the pixel electrodes 3 in the intersecting direction, the spread of the toner T in the intersecting direction can be suppressed, and the toner T is more applied to the cleaning member 6. A lot will be sucked. At this time, from the viewpoint of more effectively suppressing the spread of the toner T as a region having a different polarity, it is preferable to make the polarity different for every one to several pixel electrodes 3.

The conductivity of the cleaning member 6 is not limited as long as it has a conductivity that allows an effective cleaning electric field to act on the image carrier 1 and electrostatically attracts toner. This is intended to include semiconductivity. The cleaning member 6 is not particularly limited as long as the cleaning member 6 can rotate by applying a cleaning electric field to the pixel electrode 3. For example, the cleaning member 6 may be an elastic roll or a brush. However, from the viewpoint of effectively cleaning the residual toner T on the image carrier 1 and reducing damage to the image carrier 1, the cleaning member 6 is a rotatable brush member. It is preferable. By using the brush member, the toner T once sucked can be easily held by the brush fiber, and the cleaning efficiency is further enhanced. The degree of conductivity of the brush member may be such that the volume resistivity of the brush fiber is about 10 ¹⁰ Ω · cm or less.

Further, when a brush member is used as the cleaning member 6, particularly from the viewpoint of reducing deterioration of the image carrier 1 and the cleaning member 6, the cleaning member 6 is opposed to the image carrier 1 (corresponding to the contact region m). The image carrier 1 is preferably rotated in the same direction as the moving direction. In this way, the load between the cleaning member 6 and the image carrier 1 is reduced by moving the image carrier 1 and the cleaning member 6 in the same direction at the opposing portions.
Furthermore, the rotational speed of the cleaning member 6 is preferably set to be higher than the moving speed of the image carrier 1. By increasing the rotational speed of the cleaning member 6, the rubbing force of the cleaning member 6 against the toner on the image holding body 1 can be maintained, and the cleaning member 6 remains without being sucked by the cleaning member 6 on the image holding body 1. The toner can be moved in the contact area m, and the cleaning property is improved. Needless to say, the rotational speed of the cleaning member 6 is such that the residual toner on the image carrier 1 can be cleaned.

Further, from the viewpoint of maintaining the cleaning efficiency of the cleaning member 6, the cleaning device 5 includes a toner recovery member 9 that is disposed to face the cleaning member 6 at a position separated from the image carrier 1, and this toner recovery member It is preferable to further include a toner collecting means 8 for collecting the toner T adhering to the cleaning member 6 by the toner collecting member 9 by applying a toner collecting electric field between 9 and the cleaning member 6.
From the viewpoint of further functioning the toner recovery means 8, in the embodiment using the toner T whose resistance is changed by the working electric field, the toner recovery means 8 has a toner recovery electric field larger than the cleaning electric field. 9 and the cleaning member 6, and the toner resistance in the toner recovery electric field is preferably changed to be lower than the resistance in the cleaning electric field. That is, the toner T has a resistance variable portion that changes to a high resistance in the cleaning electric field and changes to a low resistance compared to the resistance in the cleaning electric field in the toner recovery electric field having an electric field strength larger than the cleaning electric field. It is preferable to use it.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
Embodiment 1
-Overall configuration of image forming apparatus-
FIG. 2 shows Embodiment 1 of an image forming apparatus to which the above-described embodiment model is applied. In the figure, the image forming apparatus of the present embodiment is a so-called tandem type color image forming apparatus, and each color component (for example, yellow, magenta, cyan, black) is contained in the apparatus housing 15 by, for example, electrophotography. Image holders 20 (20a to 20d) on which toner images of the respective colors are formed are arranged side by side in a substantially vertical direction, and an intermediate transfer belt 50 that circulates and rotates against these image carriers 20 is applied in a substantially vertical direction. Then, the color toner images on the image carrier 20 are multiplexed on the intermediate transfer belt 50.

  Around the image carrier 20, a developing device 41 (100) that develops the electrostatic latent image formed on the image carrier 20 with toner to make a visible image, and residual toner on the image carrier 20 A cleaning device 42 (200) for cleaning the toner image is provided, and the developed toner image on the image carrier 20 is placed on the intermediate transfer belt 50 at a position facing the image carrier 20 with the intermediate transfer belt 50 interposed therebetween. A transfer device 43 for transferring is provided.

On the other hand, the intermediate transfer belt 50 is stretched around a plurality of stretch rolls 51 to 53 (three in this example), and circulates and rotates, for example, using the stretch roll 51 as a drive roll. On the surface side of the belt 50, a secondary transfer device 60 is provided at a position facing the stretch roll 53 and the intermediate transfer belt 50, and a recording material, which will be described later, receives a multiplexed toner image multiplexed on the intermediate transfer belt 50. Batch transfer is performed on the recording material supplied from the supply unit 70. At this time, the secondary transfer device 60 is configured such that a predetermined secondary transfer bias is applied between the tension rolls 53 as opposed members.
A recording material supply unit 70 for supplying a recording material is provided below the apparatus housing 15. For example, the recording material accommodated in the supply container 71 is supplied one by one by the supply roll 72 and the separating mechanism 73. Further, it is supplied toward the recording material conveyance path 74 on the downstream side.

  Further, the recording material conveyance system in the present embodiment is as follows. That is, the recording material supplied from the recording material supply unit 70 to the recording material conveyance path 74 is once positioned by a resist roll 75 disposed in the recording material conveyance path 74, and then is subjected to downstream secondary transfer at a predetermined timing. It is conveyed to the device 60 side. Thereafter, the multiple toner images on the intermediate transfer belt 50 are collectively transferred onto the recording material at the secondary transfer portion that is the opposite portion between the secondary transfer device 60 and the stretching roll 53, and the toner image is fixed by the fixing device 76. Then, the paper is discharged from the discharge roll 77 to the recording material discharge portion 16 constituted by a part of the apparatus housing 15. The recording material conveyance path 74 is appropriately provided with a conveyance member (for example, a conveyance roll or a guide member) for conveying the recording material so that the recording material can be conveyed satisfactorily.

-Configuration of image carrier-
Next, the image carrier 20 of the present embodiment will be described in detail. As shown in FIG. 3, the image carrier 20 in the present embodiment is fixedly supported by winding a matrix panel 30 in which a large number of pixels are formed in a so-called matrix shape on a rigid drum 21 that is a rotatable support. It has become. The matrix panel 30 is manufactured using, for example, a thin film technology used in a so-called IC manufacturing process or the like for a heat resistant film, and has pixels arranged in a matrix. In the pixels arranged in a matrix in this way, for example, data lines are provided in the direction along the rotation direction of the rigid drum 21, and scanning lines are provided in the direction along the rotation axis direction. Therefore, an appropriate number of data drivers 31 and scanning drivers 32 connected to each pixel are provided on the data lines and scanning lines of the matrix panel 30, and input lines to these drivers 31 and 32 are further summarized. When the number is reduced, wiring is made through the matrix panel 30 to the inner surface side of the rigid drum 21.

The rigid drum 21 is provided with a groove 21a along the direction of the rotation axis in a part of its outer peripheral surface, while the rigid drum 21 is so-called for electrical connection between the matrix panel 30 and the outside at the center of the shaft. A slip ring 24 is provided, and the rigid drum 21 rotates around a fixed slip ring 24.
On the inner peripheral surface side of the rigid drum 21, as shown in FIGS. 4A and 4B, an appropriate number of terminals 22 are provided along the rotational axis direction of the rigid drum 21, and these terminals are provided. 22 are connected to the data driver 31 and the scanning driver 32 of the matrix panel 30, respectively. Further, these terminals 22 are provided with sliders 23 extending in the direction of the center of the rotation axis and in the directions in which the respective end portions are separated from each other, and are connected to the terminals 22. A current collecting ring 24a is attached. The current collecting ring 24a portion of the slip ring 24 is smaller in diameter than the insulating rings 24b on both sides, and the slider 23 is always kept in contact with the opposing current collecting ring 24a by the rotation of the rigid drum 21. It is like that. The groove 21a of the rigid drum 21 is closed with, for example, a seal tape, so that the resistance of the air current when the image carrier 20 rotates is reduced and the influence of toner during development is prevented. ing.

  Therefore, signal transmission between the matrix panel 30 and the outside is performed from the lead wire 25 wired in the slip ring 24 corresponding to the current collection ring 24 a of the slip ring 24 via the current collection ring 24 a and the slider 23. It is performed between the panel 30 and the signal transmission with the matrix panel 30 can be appropriately performed even when the rigid drum 21 rotates. The rotation method of the rigid drum 21 is not particularly limited. For example, the outer peripheral surface end portion side of the rigid drum 21 may be pressed against the rotating roll to rotate, or may be different from the insertion side of the slip ring 24. A rotating shaft for rotating the rigid drum 21 itself may be provided on the side.

-Matrix panel configuration-
Next, the configuration of the matrix panel 30 will be described.
As shown in FIG. 5A, the matrix panel 30 of the present embodiment has a two-dimensional array of pixels, and each pixel is configured by a so-called active matrix system as shown in FIG. 5B. For example, a TFT (Thin Film Transistor) 33 is used as a switching element, and a pixel electrode 34, a storage capacitor 35, and wiring (source line, gate line, etc.) are formed. Each pixel and the connection between the pixels are a source line (data line) in which the source of each TFT 33 is connected along the rotation direction of the image carrier 20, and a gate of each TFT 33 along the rotation axis direction of the image carrier 20. They are collected as gate lines (scan lines) to be connected. Further, the pixel electrode 34 and the storage capacitor 35 are connected in parallel to the drain of the TFT 33, and one of the storage capacitors 35 is grouped for each scanning line (not shown). As a result, an equivalent circuit as shown in FIG. It is configured to present. A protective layer 36 (not shown) is provided on the entire surface of the matrix panel 30 so as to cover the TFT 33, the pixel electrode 34, and the storage capacitor 35.

Since the matrix panel 30 has a configuration in which a large number of pixels are arranged in this way, the drive method is performed as follows.
That is, in the matrix panel 30, as shown in FIG. 6, a predetermined number of pixels are grouped for each data line and scanning line, and the source side of the TFT 33 is connected to the data driver 31 for each data line. The gate side is connected to the scanning driver 32 for each scanning line, and the data driver 31 and the scanning driver 32 are driven by a pixel electrode driving device 80 provided in the image forming apparatus. . Therefore, by driving the data driver 31 and the scanning driver 32, a predetermined voltage can be applied to a predetermined pixel. The data driver 31 is composed of, for example, a shift register with a sample and hold, a latch, and a buffer, and the scanning driver 32 is composed of, for example, a counter, latch, and buffer. In FIG. 6, the pixel electrode 34 is omitted, but it goes without saying that the pixel electrode 34 connected between the TFT 33 and the storage capacitor 35 is provided.

-Pixel electrode drive system-
As shown in FIG. 7, the pixel electrode driving device 80 drives the data driver 31 and the scanning driver 32 of the matrix panel 30 from voltage signals and control signals based on image signals. In the pixel electrode driving device 80, a latent image voltage forming unit 81 for forming a latent image voltage applied to the data driver 31 for forming a latent image pattern by the pixel electrode 34, and residual toner on the pixel electrode 34 are cleaned. Formed by a cleaning voltage forming unit 85 that forms a cleaning voltage to be applied to the pixel electrode 34 when cleaning is performed by the device 42, a memory unit 88 that temporarily stores an image signal, a latent image voltage forming unit 81, and a cleaning voltage forming unit 85. Among the obtained latent image voltage and cleaning voltage, timing for performing various timing controls in order to synchronize with a switching unit 89 that switches a voltage to be transmitted to the data driver 31, for example, a control signal such as the rotational position of the image carrier 20. A control unit 90 and the like are provided. That is, in this example, the common image electrode 34 is applied to the formation of the latent image pattern and the cleaning pattern by applying the latent image formation and the cleaning voltage to the different data lines of the matrix panel 30 in a time-sharing manner. I have to.

  The latent image voltage forming unit 81 includes a gradation conversion unit 82 that performs gradation conversion in order to select an image density corresponding to each pixel electrode 34 from the image signal as a latent image pattern, and a gradation conversion unit. A latent image voltage setting unit 83 that sets a latent image voltage to be applied to the pixel electrode 34 in accordance with the value converted at 82, and a latent image for selecting various latent image voltages by the latent image voltage setting unit 83. A voltage power supply 84 and the like are included. Further, the cleaning voltage forming unit 85 applies a cleaning voltage to be applied to the pixel electrode 34 so that the polarity of the cleaning electric field (electric field acting between a cleaning member in a cleaning device described later) is reversed for each pixel electrode 34. A cleaning voltage setting unit 86 to be set, and a cleaning voltage power source 87 for selecting various cleaning voltages by the cleaning voltage setting unit 86 are configured. That is, in this embodiment, the cleaning voltage forming means and the cleaning voltage applying means are not provided exclusively in the cleaning device 42 described later, but are shared with those for forming a latent image.

  The latent image voltage or the cleaning voltage formed by the pixel electrode driving device 80 is supplied to the data driver 31, while the corresponding scanning line is activated in accordance with the supply timing of the voltage supplied to the data driver 31. A signal is also supplied to the scanning driver 32. Here, the method of switching and supplying the latent image voltage and the cleaning voltage to the data driver 31 is shown, but for example, the scanning line is continuously selected so that the latent image voltage is not formed during cleaning. It is also possible to apply a cleaning voltage.

  Here, a driving method of each pixel electrode 34 in the present embodiment will be described with reference to FIG. That is, in order to operate the pixel electrode 34, when an ON voltage is applied to the gate connected to the scanning line side of the TFT 33, the source-drain of the TFT 33 becomes conductive, and the storage capacitor 35 is made to be equivalent to the source voltage. Charged. The voltage applied to the pixel electrode 34 by this charging is maintained as it is by the storage capacitor 35 even if the OFF voltage is applied to the gate in that state, and the source-drain is cut off. As long as the ON voltage is not applied to the gate, the voltage of the pixel electrode 34 is maintained as it is.

  Therefore, by applying a latent image voltage or cleaning voltage to the source side of the TFT 33 of each pixel and applying an ON voltage to the gate side, a latent image pattern or cleaning pattern for one scanning line is formed. Become. Then, the two-dimensional latent image is obtained by sequentially moving the gate to which the ON voltage is applied in the direction opposite to the rotation direction of the image carrier 20 (moving the scanning line to be selected) and applying a new signal voltage to the data line. Patterns and cleaning patterns are formed.

-Developer-
As shown in FIG. 8, the developing device 41 (100) of the present embodiment is of a type that uses conductive toner as toner and injects charge into the conductive toner.
In FIG. 1, a developing device 100 has a developing container 101 that contains conductive toner (hereinafter referred to as toner as appropriate). A developing opening 102 is opened in the developing container 101 so as to face the image carrier 20. At the same time, a developing roll 103 that faces the developing opening 102 and is spaced apart from the image carrier 20 and rotates in different directions at opposite positions is provided.

  On the side of the developing roll 103 that is different from the image carrier 20, an intermediate roll 104 that holds and conveys charged toner is provided facing the developing roll 103. The intermediate roll 104 is rotated so as to move in different directions at a portion facing the developing roll 103, and the peripheral speed is set to be 1.2 to 2 times the peripheral speed of the developing roll 103. Has been. In addition, by applying a predetermined moving bias between the intermediate roll 104 and the developing roll 103 by the bias power source 112, a moving electric field is applied to a region where the intermediate roll 104 and the developing roll 103 face each other. The toner is easily moved to the developing roll 103.

  Further, a charge injection roll 105 for injecting electric charge into uncharged toner is disposed substantially opposite the upper position of the intermediate roll 104. The charge injection roll 105 is composed of, for example, a roll member made of an aluminum alloy, and a predetermined charge injection bias is applied between the charge injection roll 105 and the intermediate roll 104 by a bias power supply 113, whereby the charge injection roll 105 and the intermediate roll 104 are separated. A charge injection electric field is applied to the opposing regions. Further, the charge injection roll 105 rotates in the same direction at a portion facing the intermediate roll 104, and its peripheral speed is 1.5 to 2.5 times the peripheral speed of the intermediate roll 104. .

  Further, in the developing device 100 of this embodiment, in order to supply conductive toner to the intermediate roll 104, a toner supply roll 106 having a conductive foam roll configuration made of, for example, polyurethane resin or the like has an intermediate roll than the charge injection roll 105. It is arranged opposite to the intermediate roll 104 at a position upstream of the rotation direction 104, and rotates in different directions at a position facing the intermediate roll 104. Further, the toner supply roll 106 is set to rotate at a peripheral speed that is 0.3 to 1.0 times the peripheral speed of the intermediate roll 104. Since the toner supply roll 106 and the intermediate roll 104 are electrically short-circuited, even if the surface of the intermediate roll 104 is charged between the charge injection roll 105 and the intermediate roll 104, the toner supply roll 106 and the intermediate roll 104 are charged. The action of making the potential of the sheet 104 uniform works, and the effect of suppressing the charging of the surface of the intermediate roll 104, that is, the effect of neutralization, and the conductive toner adhering to the intermediate roll 104 can be cleaned. As a result, the toner supply roll 106 fulfills the refresh function of the intermediate roll 104.

  Further, an agitator 111 for stirring and supplying the toner to the toner supply roll 106 is provided behind the toner supply roll 106 so that the toner accommodated in this portion can be supplied to the toner supply roll 106 side.

  Further, a layer forming blade 107 that regulates the toner supplied from the toner supply roll 106 to the intermediate roll 104 and forms a layer is provided between the toner supply roll 106 and the charge injection roll 105 of the intermediate roll 104. . The layer forming blade 107 is made of a plate spring member such as stainless steel or phosphor bronze having a thickness of 0.05 to 0.2 mm, for example, and is fixed to the free end side of the support member 107a whose one end is fixed to the developing container 101. It has come to be supported. In particular, the layer forming blade 107 is provided such that the surface on the free end side is pressed against the intermediate roll 104 with a predetermined pressing force, and the layer forming blade 107 is layered without excessively scraping off the toner on the intermediate roll 104. The effect of arranging can be further demonstrated. The layer forming blade 107 is not particularly limited as long as the toner can be layered, and an elastic body may be provided on the surface of the plate spring member.

  On the other hand, a refresh roll 108 made of a metal roll made of, for example, an aluminum alloy so as to come into contact with the development roll 103 at a position facing the development roll 103 between the development roll 103 and the intermediate roll 104 on the downstream side of the development area. Is provided, and by grounding the refresh roll 108, residual toner on the developing roll 103 is electrostatically removed and the surface of the developing roll 103 is neutralized. Further, the refresh roll 108 is provided with a metal blade (not shown) so as to collect the toner adhering to the refresh roll 108. The refresh roll 108 is not limited to a metal roll, and for example, a brush member using conductive fibers may be used.

  A bias power source 114 is connected to the developing roll 103 so that a bias can be applied to the image carrier 20 (specifically, the pixel electrode 34), and a developing electric field added to the latent image potential of the pixel electrode 34. Can be supplied as appropriate.

-Toner used-
The toner (conductive toner) used in such a developing device 100 has a conductive toner base (conductive core) 130 made of a conductive material, as shown in FIG. 9A, for example. The periphery of the conductive core 130 is covered with an insulating coating layer (for example, an insulating resin layer) 140, and an appropriate number of recesses 150 are formed in the insulating coating layer 140 so that a part of the conductive core 130 is exposed on the surface. The provided one is used. The conductive toner can be prepared by a polymerization method or various known encapsulation techniques. As the conductive core 130, a polyester resin, a styrene-acrylic resin, a conductive carbon, a transparent conductive powder such as ITO, or the like can be used. It is produced by dispersing a conductive agent or coating the surface of particles made of polyester resin or styrene-acrylic resin with the conductive agent.

  When a high electric field is applied to such a conductive toner, a toner having a high resistance tends to decrease in resistance. The magnitude of the electric field that lowers the resistance in this way depends mainly on the occupation ratio of the concave portions 150 of the conductive toner or the thickness of the insulating coating layer 140. In such a mechanism, since the conductive core 130 is covered with the insulating coating layer 140, the conductive core 130 itself does not come into contact with each other and does not come into direct contact with the electrode member that acts on the electric field. Thus, a certain minute gap is maintained through the insulating coating layer 140. As a result, it is assumed that, for example, when a high electric field is applied, conduction is caused by a tunnel effect or the like.

  As another embodiment of the conductive toner, for example, as shown in FIG. 9B, the conductive core 130 is covered with an insulating or semiconductive coating layer 160, and the thickness h of the coating layer 160 is set. As a result, the resistance of the conductive toner can be adjusted. At this time, the semiconductive coating layer 160 may be made of a semiconductive material itself, for example, an insulating resin, a metal oxide such as titanium oxide or tin oxide, conductive carbon, or the like. A semiconductive resin containing a small amount of the conductive agent may be used. As the conductive core 130, for example, a mode in which conductive fine particles are attached to the vicinity of the outer surface of an insulating toner base (insulating core) made of a normal insulating toner, or conductive fine particles are provided inside the insulating core. You can select the one to be mixed as appropriate.

-Transfer device-
As shown in FIG. 2, the transfer device 43 of the present embodiment is disposed, for example, so as to face the image carrier 20 with the transfer roll sandwiching the intermediate transfer belt 50, and between the transfer roll and the image carrier 20. In addition, a transfer bias is applied so that a transfer electric field in a direction in which the toner image on the image carrier 20 is transferred onto the intermediate transfer belt 50 acts. In addition, a corona charger can be used as such a transfer device 43, but a transfer roll is more preferable than a corona charger in terms of suppressing the generation of discharge products. Further, for example, a voltage corresponding to an image signal may be applied to the pixel electrode 34 at the transfer site as the transfer device 43 so that a transfer electric field corresponding to the amount of toner attached on the pixel electrode 34 is applied. Absent.

-Cleaning device-
As shown in FIG. 10, the cleaning device 42 (200) of the present embodiment has an electrostatic brush 202 as a cleaning member disposed in the cleaning container 201 so as to face the image carrier 20. As a toner collecting member for collecting the toner adhering to the electric brush 202, one collecting roll 204 is provided so as to come into contact with the electrostatic brush 202. Further, in the present embodiment, a blade 206 that scrapes off the toner collected by the collecting roll 204 from the collecting roll 204 is provided, and a stirring and conveying member that conveys the waste toner scraped off by the blade 206 to the outside of the cleaning container 201. 207 is provided. In the figure, reference numeral 30a indicates a film which is a base material of the matrix panel 30, and reference numeral 36 indicates a protective layer.

For example, four pixel electrodes 34 are arranged in a contact area m where the image carrier 20 and the electrostatic brush 202 are in contact with each other. The cleaning electric field between them has different polarities between adjacent pixel electrodes 34. FIG. 11 is a schematic diagram illustrating a state in which the cleaning voltage is applied in the cleaning device 200. Here, for easy understanding, the image holding body 20 of the cleaning device 200 in FIG. 34 is shown.
In the figure, a voltage VC is applied to the electrostatic brush 202 from the bias power source 203, while the pixel electrode 34 (specifically P ₁₎ located in the contact area m between the image carrier 20 and the electrostatic brush 202 is applied. the pixel electrode) in a to P ₄ position, by the cleaning voltage formed by the cleaning voltage forming unit 85 (see FIG. 7), VA to _{P 1} position and _{P 3} position, the VB to _{P 2} position and _{P 4} positions It is to be applied. In this embodiment, for example, VA = 50V, VB = 0V, VC = 25V, and (VA + VB) / 2 = VC are set. The voltage applied to the pixel electrode 34 is such that the voltage VA or VB is applied to the corresponding pixel electrode 34 before reaching the contact area m between the image carrier 20 and the electrostatic brush 202. .
In the present embodiment, the mode in which the polarity is changed for each pixel electrode 34 has been described. However, the present invention is not limited to this, and one region may be configured by a plurality of pixel electrodes 34. Moreover, although the aspect provided with the four pixel electrodes 34 in the contact area m was shown, it is not restricted to this, The area | region of the cleaning electric field from which polarity differs in the contact area m should just be provided.

The electrostatic brush 202 is formed by winding a cloth around a shaft made of an aluminum alloy, for example, and raising the outer diameter 20-60 mm, pile height 3-20 mm, dispersing conductive carbon black in rayon, acrylic, nylon resin or the like. The volume resistivity was adjusted to 10 ⁶ to 10 ¹⁰ Ω · cm, the density was 20,000 to 100,000 / in ² , and the fiber diameter was 3 to 10 denier (about 12 to 20 μm). The rotational direction of the electrostatic brush 202 is rotated in the same direction in the opposing portion between the image carrier 20 in order to further reduce the load on the image carrier 20, its peripheral speed (rotational speed) v ₂ is the image holding It is set to be 1.5 to 3 times the moving speed (rotational speed) v ₁ of the body 20. Here, the rotation direction of the electrostatic brush 202 is rotated in the same direction at the portion facing the image carrier 20, but the rotation direction of the electrostatic brush 202 is mutually opposite at the portion facing the image carrier 20. It does not matter if it is designed to rotate in different directions.

  Further, the recovery roll 204 is subjected to a curing process after cast molding an elastic layer in which a conductive agent is kneaded into a resin such as silicone rubber, EPDM, SBR, or urethane elastomer on the surface of an aluminum alloy shaft, for example. Further, a coating solution prepared by adding a conductive agent to urethane resin, acrylic resin, polyamide resin or the like and applying resistance adjustment is applied to the surface of the elastic layer, and a high resistance layer is formed so as to be cured. It has become like this. Examples of the conductive agent include carbon black, graphite, and ionic conductive agent.

  The collection roll 204 rotates, for example, in different directions at a portion facing the electrostatic brush 202, and a bias power supply 205 is connected to the collection roll 204 so that a toner collection electric field acts between the collection roll 204 and the electrostatic brush 202. For example, + 250V is applied to the collection roll 204.

Functions required for the recovery roll 204 in such a configuration include low potential, self-discharge, non-charge injection, and the like. The low potential is based on the fact that it is necessary to reduce the electric voltage loss in the collecting roll 204 in order to obtain a sufficient toner collecting electric field. Therefore, the high resistance layer of the collection roll 204 is preferably as thin as possible, but is set to a thickness of about several tens of μm in consideration of preventing the generation of pinholes during production. The self-discharge property means that a discharge time constant of several hundreds ms or less, which is a time for one rotation of the collection roll 204, is obtained by setting a resistance so that electric charges are not accumulated in the collection roll 204. Based on this, the volume resistivity is set to 10 ¹¹ Ω · cm or less. Further, the non-charge injection property is necessary to suppress the toner that returns to the electrostatic brush 202 side when the reverse charge is injected into the toner collected from the collection roll 204. is there. In other words, in order to prevent the toner recovery electric field from injecting extra charge into the toner, it is necessary to prevent charge transfer or attenuation within the time during which the toner recovery electric field is applied. It is preferably 0.1 seconds or more, and therefore, the volume resistivity is ideally 10 ¹¹ Ω · cm or more.

However, actually, even if charge injection occurs in part and the toner on the collection roll 204 returns to the electrostatic brush 202 side, it can be actually used as the cleaning device 200 and has a volume resistivity of 10 ⁹ Ω · Even if it is cm, there is no practical problem. In addition to this, the volume resistivity of the recovery roll 204 is adjusted within the range of 10 ⁹ to 10 ¹¹ Ω · cm by considering self-discharge characteristics.

The operation of the image forming apparatus according to the present embodiment will be described below.
-Latent image formation-
As shown in FIG. 7, as the latent image voltage applied to the pixel electrode 34, the signal waveform of the image signal is subjected to gradation conversion by the gradation conversion unit 82, and the latent image voltage corresponding to the gradation-converted data. Is applied to the pixel electrode 34.
That is, as shown in FIG. 12, predetermined threshold values α, β, and γ are provided for the image signal, and gradation conversion is performed based on these threshold values. By applying and setting a latent image voltage of V3 to a portion exceeding V1, β2 to a portion exceeding γ, and V3 to a portion exceeding γ, conversion of four gradations is performed. Therefore, by applying a latent image voltage according to this gradation conversion, a potential potential corresponding to four gradations is formed on each pixel electrode 34.

-Development mechanism-
As shown in FIG. 8, after the toner (conductive toner) stirred by the agitator 111 is supplied to the toner supply roll 106 side, the toner supply roll 106 is rotated and conveyed to a position facing the intermediate roll 104, so It is supplied to an intermediate roll 104 that rotates in different directions at the site. The layer thickness of the toner supplied onto the intermediate roll 104 is regulated by the layer forming blade 107, and a substantially uniform toner layer is formed on the intermediate roll 104. The uniformly formed toner layer on the intermediate roll 104 is sandwiched and rubbed between the intermediate roll 104 and the charge injection roll 105 by the charge injection electric field provided by the bias power supply 113 while facing the intermediate roll 104 and the charge injection roll 105. Charge is injected.

  In such a state, since the toner layer sandwiched between the two layers is made equal to or less than a single layer, the contact probability between the toner and the charge injection roll 105 is increased, and the contact resistance of the toner can be reduced. As a result, the apparent resistance of the toner is reduced, and the toner is injected with a low resistance. For this reason, even if the electric charge injection field is relatively low, the electric charge can be efficiently injected into the toner. In particular, the present embodiment has a feature that the charge injection function can be stably performed because the charge injection roll 105 can perform a charge injection function to the toner exclusively.

  In this way, by performing charge injection on the toner layer having a single layer or less, charge injection into the toner is effectively performed, and generation of reverse polarity toner can be suppressed. In addition, since the toner is sandwiched between the intermediate roll 104 and the charge injection roll 105 and the charge is injected while being rubbed, a shear force is applied between the toner layers, so that the toner is prevented from overlapping in the polarization state. Therefore, even if the electric charge injection field is a high electric field, the generation of the reverse polarity toner is prevented. Then, on the intermediate roll 104 that has passed through the portion facing the charge injection roll 105, a toner layer of a single layer or less in which substantially uniform charge injection is performed is formed, and is held by the intermediate roll 104 and conveyed as it is. Become.

  Next, the toner charged by the charge injection is conveyed to a portion where the intermediate roll 104 and the developing roll 103 are opposed to each other. Here, since the intermediate roll 104 and the developing roll 103 are rotated in different directions and a moving electric field is applied by the bias power source 112, the toner passes through the nip between the intermediate roll 104 and the developing roll 103. Therefore, the toner moves to the developing roll 103 electrostatically, and the change in the toner charge amount can be suppressed. Furthermore, since the peripheral speed of the intermediate roll 104 is increased to 1.2 to 2 times the peripheral speed of the developing roll 103, the amount of toner moving from the intermediate roll 104 to the developing roll 103 can be increased. As a result, the toner amount density on the developing roll 103 can be approximately 1.2 to 2 times the toner amount density on the intermediate roll 104, and the toner amount density on the developing roll 103 can be increased. become able to. At this time, the intermediate roll 104 and the developing roll 103 do not necessarily have to be rotated in different directions at the facing portion, and may be rotated in the same direction at the facing portion. This is because the moving electric field is set to be smaller than the charge injection electric field, so that there is less possibility that the charged state of the toner changes during the movement.

  Then, the toner that has moved onto the developing roll 103 is conveyed on the developing roll 103 as it is and proceeds to a position where the developing roll 103 and the image holding body 20 face each other, and a pixel electrode 34 (not shown) on the image holding body 20. Development is performed corresponding to the latent image pattern by the latent image potential. At this time, since the toner amount density on the developing roll 103 is high, it is possible to realize a finer image density according to the latent image. Further, since it is not necessary to increase the peripheral speed of the developing roll 103, deterioration of image quality such as fine line reproducibility and graininess can be suppressed, and a sufficient image density can be obtained. That is, as shown in FIG. 13A, the latent image voltage is applied to the pixel electrode 34 to which the latent image voltages V0 to V3 formed by the latent image voltage forming unit 81 (see FIG. 7) are applied. The corresponding toner adhesion is made in a more faithful form. The bias power supply 114 may be grounded.

  Further, if a photoconductive layer is used as the protective layer 36 of the matrix panel 30 and light irradiation is performed corresponding to the development site, the dielectric thickness of the protective layer 36 is reduced as shown in FIG. Accordingly, the voltage drop due to the protective layer 36 during development can be suppressed to a low level, and a sufficiently large potential potential can be obtained even when the latent image potential is small, and the same latent image voltage as in FIG. In this case, more toner can be attached, and the latent image voltage itself can be reduced accordingly.

-Transcription-
As shown in FIG. 14A, during transfer, in order to transfer the toner on the image carrier 20 to the intermediate transfer belt 50 side between the rigid drum 21 of the image carrier 20 and the transfer device 43, for example, a bias A transfer electric field is applied by applying a transfer voltage VT from a power source 43a. Since the toner attached on the pixel electrode 34 is transferred by substantially the same amount for each pixel electrode 34 by such a transfer electric field, the toner is attached to each pixel electrode 34 for more faithful reproducibility of the transferred image. It is better to apply a transfer electric field having an electric field strength corresponding to the toner amount. In this embodiment, since the pixel electrode 34 is used, as shown in FIG. 14B, for example, a transfer voltage forming unit 43c is provided in the pixel electrode driving device 80 (see FIG. 7), and this transfer is performed. If a transfer voltage (for example, −V1 ′, −V2′−V3 ′) corresponding to the image signal formed by the voltage forming unit 43c is applied to the pixel electrode 34, a transfer electric field corresponding to the amount of attached toner is generated. It is also possible to change the pixel electrode 34 for each pixel electrode, and it is possible to improve the reproducibility of the transferred image by transferring substantially the entire amount of the adhering toner to the intermediate transfer belt 50. At this time, it is sufficient that the transfer device 43 is supplied with a voltage of VT ′, for example, from the bias power supply 43b, and the value of VT ′ may be appropriately selected.

-Cleaning mechanism for bipolar toner-
Next, a cleaning mechanism for cleaning residual toner on the image carrier 20 in the present embodiment will be described.
In general, in order to prevent a sudden failure and to prevent the image carrier 20 from being worn or damaged, a cleaning method using an electrostatic force is suitable. As a cleaning method using such an electrostatic force, a method using a photosensitive member as an image holding member and using an electrostatic brush or a magnetic brush for the photosensitive member is known. The cleaning electric field when using such an electrostatic force is uniquely determined by the potential relationship between the electrostatic brush or magnetic brush as a cleaning member and the photosensitive member. In contrast, in the present embodiment, as shown in FIG. 11, by applying a desired voltage to the electrostatic brush 202 and the pixel electrode 34, the contact area m between the image carrier 20 and the electrostatic brush 202 is within the contact area m. By forming a region of a cleaning electric field having a different polarity, a single electrostatic brush 202 is used to clean the bipolar toner.

In the present embodiment, the image carrier 20 and the electrostatic brush 202 are rotated so as to move in the same direction at the opposing portion, and the rotation speed v ₂ of the electrostatic brush 202 is further rotated. since it is larger than the speed v _1, the toner which has not been sucked to the electrostatic brush 202 is to be moved forward.
FIG. 15 explains this in an easy-to-understand manner. Now, as shown in FIG. 15A, a part (P) of the pixel electrode 34 is formed at a portion (contact area m) between the electrostatic brush 202 and the image carrier 20. ₁ position and the area _{P 3} position) with respect to the voltage of VA (pixel electrode 34 side positive and becomes direction of the cleaning electric field E (+) is applied), the voltage of VB for the remaining _{(P 2} position and _{P 4} position) ( The voltage formed by the cleaning voltage forming unit 85 (see FIG. 7) is applied so that the cleaning electric field E (−) acts in a direction in which the pixel electrode 34 is negative. The electrostatic brush 202 is connected to a VC voltage by a bias power source 203. Therefore, the electric field strength of the cleaning electric field E (+) is proportional to (VA−VC), and the electric field strength of the cleaning electric field E (−) is proportional to (VC−VB).

Here, for example, if the P ₂ position of the pixel electrode 34 is of positive polarity and negative polarity toner, the direction cleaning the pixel electrode 34 side is negative between the pixel electrode 34 and the electrostatic brush 202 with the P ₂ position When the electric field E (−) acts, the negative toner on the image carrier 20 is attracted to the electrostatic brush 202 side. At this time, the positive toner on the image carrier 20 moves along the rotational direction by the rubbing force of the electrostatic brush 202 without being attracted to the electrostatic brush 202. At this time, as shown in the (b) at P ₃ position of the pixel electrode 34, acting direction of the cleaning electric field E pixel electrode 34 side is positive (+) is between the pixel electrode 34 and the electrostatic brush 202 from the positive polarity toner moved is to be sucked to the electrostatic brush 202 side P ₃ position. The negative polarity toner is attracted to the previously electrostatic brush 202 to the cleaning electric field E (+) is the image carrier 20 side so as to act at P ₃ position by toner holding force of the electrostatic brush 202 There is almost no return. Even if a part of the toner adheres again to the image carrier 20, the residual toner on the image carrier 20 is cleaned by repeating the above-described operation.

FIGS. 16A and 16B are enlarged views of main parts of FIGS. 15A and 15B, and show specific brush fibers as the electrostatic brush 202. That is, the negative polarity toner is attracted to the electrostatic brush 202 (brush fiber) by the cleaning electric field E (−) at the P ₂ position, and the positive polarity toner is attracted to the electrostatic brush 202 by the cleaning electric field E (+) at the P ₃ position. To become sucked.
As described above, the electrostatic brush 202 is rotated in the same direction with respect to the image holding body 20 and the speed thereof is further increased, so that damage to the image holding body 20 by the electrostatic brush 202 can be suppressed to be small. Accordingly, it is possible to promote the long life of the image carrier 20. In addition, the toner is less likely to be scattered upstream of the contact area between the image carrier 20 and the electrostatic brush 202, and the occurrence of toner cloud can be suppressed.
Here, the mode in which the polarity of the cleaning electric field is changed pixel by pixel with respect to the pixel electrode 34 along the rotation direction of the image carrier 20 is shown, but different cleaning is performed in the contact area m between the image carrier 20 and the electrostatic brush 202. A region having an electric field may be provided.

Next, as a comparative example different from the present embodiment, a case where there is no region having a cleaning electric field having a different polarity in the contact region m between the image carrier 20 and the electrostatic brush 202 will be described. FIG. 17 shows the cleaning action of the bipolar toner in an image forming apparatus that does not have a cleaning electric field region having a different polarity with respect to the contact region m where the image carrier 20 and the electrostatic brush 202 face each other. Here, (a) shows that the image holding body 20 and the electrostatic brush 202 rotate in the same direction at the facing portion, and (b) shows directions in which the image holding body 20 and the electrostatic brush 202 are different at the facing portion. It is supposed to rotate. Here, the cleaning voltage formed by the cleaning voltage forming unit 85 ′ is applied to the pixel electrode 34 and the electrostatic brush 202 using the same drive system as in the embodiment. Then, (from P ₁ position to the P ₄ position) the pixel electrode 34 of the contact area m of the image carrier 20 and the electrostatic brush 202 A region in which the direction of the cleaning electric field E pixel electrode side is positive (+) is applied It is shown that there is a B region having a cleaning electric field having a polarity different from that of the A region on the upstream side in the rotation direction of the image carrier 20. Note that (b) will be described later.

  As shown in FIG. 17A, when the image carrier 20 and the electrostatic brush 202 rotate in the same direction at the opposing portion, the positive polarity toner among the bipolar toners in the area A is the cleaning electric field E (+). However, the negative toner tends to stay on the image carrier 20 due to the cleaning electric field E (+), and as a result, the toner passes through the contact area m with the electrostatic brush 202 and goes downstream as it is. It is sent or pushed downstream by the rubbing force of the electrostatic brush 202. Therefore, although the positive polarity toner is cleaned by the electrostatic brush 202 in this example, the negative polarity toner is not cleaned well and remains as residual toner on the image carrier 20, which may reduce the cleaning effect. is there. Therefore, it can be understood how large the cleaning effect is obtained by providing the cleaning area with different polarities in the contact area m.

Next, a case where the image holding body 20 and the electrostatic brush 202 rotate in different directions at the opposing portion will be described as a modification of the present embodiment.
As shown in FIG. 18 (a), if the electrostatic brush 202 the image carrier 20 rotates in different directions in the opposing site of bipolar toner in the P ₁ position, an electrostatic brush at P ₁ position The positive toner is sucked into 202 and the negative toner that has not been sucked is blocked by the sliding force of the electrostatic brush 202. The negative toner dammed, as (b), the so sucked to the electrostatic brush 202 by the polarity of the pixel electrode 34 after the P ₁ position. The negative polarity toner not attracted to the electrostatic brush 202 with P ₁ position can not be blocked in the P ₁ position, be moved while being adsorbed to the pixel electrode 34 of the P ₁ position, the contact area m Thus, the electrostatic brush 202 moves toward the front and rear pixel electrodes 34 due to the rubbing force, and is attracted to the electrostatic brush 202 by the cleaning electric field E (−) having a different polarity of the pixel electrode 34. For this reason, in such a rotation direction, the sliding force of the image carrier 20 by the electrostatic brush 202 is usually larger than that in the opposite portion rotating in the same direction, and there is a possibility that the image carrier 20 is likely to be damaged. However, the cleaning effect itself is good.

Here, as a comparative form, assuming that the image carrier 20 and the electrostatic brush 202 rotate in opposite directions at the opposite portion and there is no cleaning electric field region having a different polarity in the contact region m, the above-described figure. 17 (b), the positive polarity toner a region in the contact area m (corresponding to the pixel electrode 34 from the P ₁ position to the P ₄ position) is sucked to the electrostatic brush 202, the negative polarity toner Tends to stay on the image carrier 20. However, it is easily pushed to the upstream side in the rotation direction of the image carrier 20 by the rubbing force of the electrostatic brush 202, and scatters in the upstream direction indicated by the arrow in the figure from the upstream end of the contact area m with the electrostatic brush 202. It becomes easy to be done. Further, when it does not scatter, it is blocked by the upstream end of the contact area m, and the next B area reaches the contact area m and is attracted to the electrostatic brush 202. However, when the blocking amount increases, the cleaning electric field acting on the toner alone at this portion is apparently reduced, and sufficient electrostatic attraction to the electrostatic brush 202 does not occur, so that the cleaning is not performed well. The subsequent residual toner may also be prevented from entering the contact area m, and it may be difficult to achieve a sufficient cleaning effect. Further, an increase in the blocking amount causes an increase in the amount of toner scattered from there, which may cause a toner cloud problem.
Therefore, even when the image carrier 20 and the electrostatic brush 202 rotate in different directions from each other at the opposite portions as described above, it is understood that a cleaning electric field region having a different polarity with respect to the contact region m may be provided. Is done.

In this way, when the image carrier 20 and the electrostatic brush 202 rotate in different directions at the opposite part, the image carrier 20 and the electrostatic brush 202 rotate in the same direction at the opposite part. , the rotational speed _{v 2} of the electrostatic brush 202 is to be performed in the same manner when the rotational speed _{v 1} is less than the image carrier 20 (see FIG. 17 (a)). That is, when the rotation speed v ₂ of the electrostatic brush 202 is smaller than the rotation speed v ₁ of the image holding body 20, the brush fibers are apparently rotated in the reverse direction with respect to the image holding body 20. This is because it acts in the direction of blocking the toner.
Further, when the rotational speed v ₂ of the electrostatic brush 202 is equal to the rotational speed v ₁ of the image carrier 20 is reduced is rubbing force by the electrostatic brush 202, the tip of the brush fibers of the electrostatic brush 202 Since it slides somewhat by contact with the image carrier 20, a certain level of rubbing force can be obtained, and the toner on the image carrier 20 can be moved. Therefore, the cleaning effect by the electrostatic brush 202 is exhibited.

In this embodiment, when such a cleaning electric field is applied to the rotation direction of the image carrier 20, the same cleaning electric field is applied to the pixel electrode 34 in the rotation axis direction of the image carrier 20. However, since the rubbing direction by the electrostatic brush 202 is somewhat directed in the direction intersecting the rotation direction, the toner may move in the rotation axis direction of the image carrier 20. In order to suppress this, it is better to set the cleaning voltage to be applied to the pixel electrode 34 so that the regions of the cleaning electric field having different polarities are adjacent to each other in the rotation axis direction of the image carrier 20.
FIGS. 19A and 19B show an example in which the polarity of the cleaning electric field between the pixel electrode 34 and the electrostatic brush 202 is changed along the rotation axis direction of the image carrier 20. (a) is a view of the direction of the cleaning electric field for each pixel electrode 34 from the image carrier 20 surface, (b) the lateral one scan line (here, for example, P ₂ position) of (a) The image carrier 20 and the electrostatic brush 202 both move toward the back side of the sheet.
Here, in the direction along the rotation direction of the image carrier 20 to change the polarity of the cleaning electric field for each one of the pixel electrodes 34 in the P ₁ position to the P ₄ position, further rotation axis direction of the image carrier 20 from of an H ₁ position to H ₆ position represents that so as to vary the polarity of the cleaning electric field for each two pixel electrodes 34. The A region and the B region indicate cleaning electric field regions having different polarities, the A region is a cleaning electric field E (+) region in which the pixel electrode 34 is positive, and the B region is negative in the pixel electrode 34 side. Represents the region of the cleaning electric field E (−).

Now, paying attention to one of the brush fibers of the electrostatic brush 202, the positive polarity toner in H ₅ position of the pixel electrode 34 is made to be attracted to the electrostatic brush 202 by the cleaning electric field E (+), negative polarity The toner is moved by the electrostatic brush 202. At this time, cause a negative polarity toner is moved in the rotation axis direction of the image carrier 20 by the rotation of the electrostatic brush 202, for example, also so that the negative polarity toner in H ₅ position is pushed H ₄ position side Become. However, as shown in the figure, the pixel electrode 34 of the H ₄ position H ₅ positions and polarities different cleaning electric field E (-) because is adapted to act, a negative polarity toner repulsion shown in the figure F receiving, moving to H ₄ position side is suppressed, is easy to be moved downstream in the rotation direction of the electrostatic brush 202. As a result, the negative polarity toner that has been moved to the downstream side will be attracted to the electrostatic brush 202 side by the action of the pixel electrode 34 in the example P ₃ position.
As described above, the cleaning of the toner on the image carrier 20 can be further performed by applying the cleaning electric fields having different polarities between the pixel electrode 34 and the electrostatic brush 202 in the rotation axis direction of the image carrier 20. It will be done well. From the viewpoint of suppressing toner scattering with respect to the pixel electrode 34 in the rotation axis direction of the image carrier 20, it is preferable to switch the polarity corresponding to about one to several pixel electrodes 34.

  In the present embodiment, for example, as shown in FIG. 11, VC is applied from the bias power source 203 to the electrostatic brush 202 at the time of cleaning, so that the polarity differs as the cleaning voltage for the pixel electrode 34 at the time of cleaning. In order to form the region of the cleaning electric field, VA and VB are applied so that VC = (VA + VB) / 2. Therefore, for example, even if VB is grounded, two power sources VA and VC are required. However, for example, if the electrostatic brush 202 is grounded, for example, VA and VB (= −VA) may be applied to the pixel electrode 34. In this case, one of the power supplies is connected to the inverter from one side. It is also possible to supply the power via the power supply, and there is an advantage that the number of power supplies is reduced and control becomes easy.

-Bipolar toner recovery mechanism-
Next, the collecting mechanism of the bipolar toner from the electrostatic brush 202 by the collecting roll 204 will be described with reference to the schematic diagram of FIG.
In this embodiment, conductive toner is used as the toner, and the toner is collected from the electrostatic brush 202 because the conductive toner has a function (switching) that greatly changes electric resistance depending on the magnitude of an electric field acting on itself. In this case, a high electric field is applied to the toner to switch it to a low resistance, and desired charge injection is facilitated so that the charged polarity of the bipolar toner attracted to the electrostatic brush 202 is made uniform. Has been adopted. That is, the bipolar toner on the image carrier 20 is applied to the electrostatic brush 202 by the cleaning electric field between the image carrier 20 (specifically, determined by the cleaning voltage applied to the pixel electrode 34) and the electrostatic brush 202. It is sucked and further held by the electrostatic brush 202. For the bipolar toner held by the electrostatic brush 202, a toner recovery electric field larger than the cleaning electric field is applied to a portion where the electrostatic brush 202 and the recovery roll 204 face each other. The positive polarity toner is injected with electric charge by the toner recovery electric field and becomes negative polarity. As a result, the bipolar toner is collected on one collection roll 204. When cleaning, if the toner has a low resistance, electric charge is injected into the cleaned toner, and the injected toner comes to reattach to the image holding body 20. By performing the cleaning electric field to be lower than the toner recovery electric field, the toner is kept at a high resistance during cleaning, and efficient cleaning is performed.

  In other words, in the present embodiment, the conductive toner whose resistance is greatly reduced when the electric field strength acting on the toner is larger than a predetermined value (specified value) is used, and the residual toner on the image carrier 20 is statically removed. The electric field strength of the cleaning electric field at the time of cleaning sucked to the electric brush 202 is made smaller than the specified value, while the electric field strength of the toner collecting electric field at the time of collecting sucking the toner from the electrostatic brush 202 to the collecting roll 204 is less than the specified value. By increasing the size, charge is injected into the toner that has been cleaned from the image carrier 20 and adhered to the electrostatic brush 202, the polarity of the toner is aligned, and the collecting roller 204 for the bipolar toner that has adhered to the electrostatic brush 202. It is easy to recover the product.

  In order to collect the toner adhering to the electrostatic brush 202, instead of using the collecting roll 204, for example, a flicker may be used to mechanically scrape off the electrostatic brush 202, or electrostatic suction may be performed by air suction. The toner adhering to the brush 202 may be removed. However, in the former, the removability of the toner entangled with the fibers of the electrostatic brush 202 is low, and the removal effect may be reduced. It is necessary to consider that it is easy.

  In the present embodiment, the developing device 100 having the configuration shown in FIG. 8 is used. However, as a modification, the developing device 100 shown in FIG. 21 may be used, and electric field injection into the conductive toner is possible. Will be made effective. The developing device 100 is configured in substantially the same manner as the developing device 100 of FIG. 8, but the charge injection roll 105 is not provided independently, but is provided between the intermediate roll 104 and the toner supply roll 106, 8 differs from the developing device 100 of FIG. 8 in that the layer forming blade 107 is provided so as to regulate the toner on the charge injection roll 105. Therefore, the toner is supplied from the toner supply roll 106 to the charge injection roll 105 and is conveyed from the charge injection roll 105 to the developing roll 103 via the intermediate roll 104. Reference numeral 109 denotes a refresh roll that electrostatically removes residual toner on the intermediate roll 104 and performs a charge eliminating function on the surface thereof.

  The operation of the developing device 100 having such a configuration will be described. The toner stirred by the agitator 111 is supplied to the toner supply roll 106 side. The toner supplied to the toner supply roll 106 is supplied to the charge injection roll 105 at a portion facing the charge injection roll 105, and the layer thickness is regulated by the layer forming blade 107 on the charge injection roll 105 to form a predetermined toner layer. Is done.

  The toner layer formed by the layer forming blade 107 is charged by injecting electric charge by a charge injection electric field acting between the charge injection roll 105 and the intermediate roll 104 at an opposite portion. At this time, the toner is sandwiched between the charge injection roll 105 and the intermediate roll 104, and is charged into a single layer or less while being rubbed by the difference in peripheral speed between the two. The contact probability between the toner and the charge injection roll 105 is increased, and furthermore, the contact resistance of the toner can be reduced, and the apparent resistance of the toner is reduced accordingly, and the toner is injected in a low resistance state. Is done.

  The charged and charged toner is held on the intermediate roll 104 as a toner layer of a single layer or less and is conveyed as it is, and reaches the opposite portion between the intermediate roll 104 and the developing roll 103. Here, a moving electric field in a direction that facilitates the movement of the toner acts between them, and further, they rotate in different directions so that the peripheral speed of the intermediate roll 104 is faster than the peripheral speed of the developing roll 103. On the developing roll 103, a toner layer having a toner amount density higher than the toner amount density on the intermediate roll 104 is formed, held on the developing roll 103, and conveyed. The toner conveyed by the developing roller 103 visualizes the latent image pattern on the image carrier 20 in a development area that is a portion facing the image carrier 20.

  As described above, an embodiment in which the intermediate roll 104 is used as the developing device 100 in the present embodiment has been described. For example, the charge injection roll 105 is disposed directly opposite to the developing roll 103 without using the intermediate roll 104, and the developing roll is used. There is no problem even if charge is injected into the toner between 103 and the charge injection roll 105.

Embodiment 2
The image forming apparatus according to the present embodiment is configured in substantially the same manner as the image forming apparatus according to the first embodiment (see, for example, FIG. 2), but the toner that is usually used in, for example, an electrophotographic image forming apparatus is used. The developing device 41 and the cleaning device 42 are different from those of the first embodiment. The outline of them will be described below. Components similar to those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted here.

-Developer-
The developing device 41 according to the present embodiment is configured to perform development with normal toner on the pixel electrode 34 on which the latent image pattern is formed, and with respect to the developing roll disposed opposite to the image carrier 20. A predetermined amount of toner is supplied, and the toner on the developing roller is moved to the image holding member 20 side by the electric field action between the developing roller and the pixel electrode 34 at the developing portion which is the opposite portion between the image holding member 20 and the developing roller. Will be scattered. As the developing device 41, either a known one-component developing method or two-component developing method may be used.

-Cleaning device-
As shown in FIG. 22, the cleaning device 42 (200) of the present embodiment has an electrostatic brush 202 disposed opposite to the image carrier 20 in a cleaning container 201, and both electrodes attached to the electrostatic brush 202. Two recovery rolls 208 and 210 are provided for recovering the toner from the electrostatic brush 202. These collection rolls 208 and 210 rotate in a different direction, for example, at a position facing the electrostatic brush 202, and one collection roll 208 has a toner collection electric field between which the collection roll 208 is positive, for example, the collection roll 208 side is positive. A bias power source 209 is connected so as to operate, and a bias power source 211 is connected to the other recovery roll 210 so that a toner recovery electric field that becomes negative on the recovery roll 210 side, for example, is connected to the electrostatic brush 202. Yes. Further, blades 212 and 213 for scraping off toner from the collection rolls 208 and 210 are provided on the respective collection rolls 208 and 210.

  The electrostatic brush 202 and the collection rolls 208 and 210 have the same configuration as in the first embodiment. For example, VC is applied to the electrostatic brush 202 by a bias power source 203, while the collection roll 208 is configured by a bias power source 209, for example. VD is applied, and VE is applied to the collection roll 210 by a bias power source.

-Bipolar toner recovery mechanism-
Since the cleaning mechanism of the bipolar toner on the image carrier 20 by the electrostatic brush 202 in the cleaning device 200 is the same as that of the first embodiment, the bipolar toner recovery mechanism by the recovery rolls 208 and 210 is used here. Will be described.
Since the toner used in the present embodiment is a normal toner, the charge is not injected into the toner as in the first embodiment, and one of the collecting rolls 208 or 210 is used for each toner polarity. It comes to collect. That is, of the toner held on the electrostatic brush 202, the negative polarity toner is collected by the collection roll 208 by the toner collection electric field by the collection roll 208, while the positive polarity toner is collected by the toner collection electric field by the collection roll 210. To be recovered. Therefore, good recovery is performed regardless of the polarity of the toner adhered to the electrostatic brush 202, and the subsequent cleaning effect by the electrostatic brush 202 is maintained.

  In the first embodiment and the second embodiment described above, the color image forming apparatus including a plurality of image holding bodies 20 as the image forming apparatus has been described. However, in the monochrome image forming apparatus using one image holding body 20. There is no problem.

Embodiment 3
FIG. 23 shows an outline of the image forming apparatus according to the third embodiment. Unlike the image forming apparatus according to the first embodiment (see FIG. 2), the image forming apparatus according to the present embodiment is a single image carrier. A plurality of (four in this example) developing devices 410 are provided around 20.

  The image carrier 20 according to the present embodiment is configured in substantially the same manner as in the first embodiment, and is provided with pixel electrodes configured in a matrix. Around the image carrier 20, for example, developing devices 410 (410a to 410d) corresponding to colors of yellow, magenta, cyan, and black are arranged, and the latent image pattern formed on the image carrier 20 is transferred to each developing device. Development is performed at 410 to form a toner image. A transfer device 430 for transferring a toner image formed on the image holding member 20 onto the recording material is provided between the developing device 410d and the developing device 410a around the image holding member 20. A cleaning device 200 is provided between the transfer device 430 and the developing device 410a.

  As the developing device 410 in the present embodiment, a developing device 100 of a type using conductive toner (see, for example, FIG. 8) as in the first embodiment may be used, or development in the case of using normal toner. An apparatus (see Embodiment 2) may be used, and as the cleaning apparatus 200, when a conductive toner is used, the cleaning apparatus 200 used in Embodiment 1 (see FIG. 10). Or a cleaning device 200 (see FIG. 22) as used in the second embodiment may be used.

  In the image forming apparatus according to the present embodiment, first, for example, a yellow image signal is output from the pixel position of the image carrier 20 until a predetermined pixel position (scanning line) reaches the developing area of the developing device 410a. A latent image is formed by supplying a latent image voltage corresponding to the data line to a data line, and a latent image corresponding to a yellow image signal is sequentially formed on pixel electrodes (not shown) on the subsequent scanning lines. While developing these latent images on the image holding body 20 with the developing device 410a, the magenta image of the predetermined pixel position is reached until the predetermined pixel position reaches the developing area of the next developing device 410b. A latent image corresponding to the image signal is formed, and a latent image corresponding to the magenta image signal is sequentially formed on the pixel electrodes on the subsequent scanning lines, and developed by the developing device 410b. Similarly, cyan and black latent images are formed and developed, and as a result, a toner image in which each color toner image is multiplexed is formed on the image carrier 20 that has passed through the developing device 410d. become. That is, by sequentially forming latent images corresponding to the respective developing devices 410 by time-division driving, the color toner images are sequentially multiplexed on the image carrier 20.

  The toner images multiplexed on the image carrier 20 are transferred onto the recording material at a transfer portion where the image carrier 20 and the transfer device 430 face each other. Since the toner remaining on the image carrier 20 after the transfer includes reverse polarity toner, a predetermined cleaning electric field acts on the pixel electrode at the portion facing the cleaning device 100. By applying the cleaning voltage, the residual toner on the image carrier 20 can be cleaned well. The cleaning voltage may be applied by increasing the number of time divisions when forming the latent image. For example, after the multiplexed toner image on the image carrier 20 is transferred, the latent image is formed. For example, only the cleaning voltage may be applied to one rotation of the image carrier 20 by interrupting the operation.

  As described above, the method of multiplexing the color toner images formed on the image holding body 20 as they are on the image holding body 20 forms each color toner image on the plurality of image holding bodies 20 and each image holding body 20. Compared to the method of multiplexing the toner images transferred from the toner, the number of components can be reduced, and it is advantageous for miniaturization and cost reduction.

Reference form Next, in order to confirm the effect of applying the cleaning voltage to the pixel electrode, the cleaning action of the bipolar toner on the image carrier (here, the photosensitive member) when the pixel electrode is not used. explain.
FIG. 24 shows an outline of an electrostatic brush type cleaning device 600 in the case where no pixel electrode is used as a reference form, and the bipolar residual toner on the photosensitive member 500 as an image holding member is separated into two electrostatic brushes. At 602, 603, an attempt was made to clean. This cleaning device 600 is provided with two electrostatic brushes 602 and 603 that rotate in the same direction at a position opposite to the moving direction of the photosensitive member 500 in a cleaning container 601, and is connected to the photosensitive member 500 by bias power sources 604 and 605, respectively. The bipolar toners on the photoreceptor 500 are to be attracted by the electrostatic brushes 602 and 603 so that different electric fields act on each other.
Further, the electrostatic brushes 602 and 603 are provided with recovery rolls 606 and 607 for recovering the respective adhered toners so as to rotate in different directions from the electrostatic brushes 602 and 603, respectively. The electric field is activated. Reference numerals 610 and 611 denote blades for scraping the collected toner on the collecting rolls 606 and 607, and reference numerals 612 and 613 denote stirring and conveying members for conveying the scraped toner to the outside of the cleaning container 601. Yes.

In such a configuration, of the residual toner on the photoreceptor 500, the negative toner is attracted to the electrostatic brush 602 and adheres to the electrostatic brush 602. Further, since the bias power source 608 is made larger than the bias power source 604, the negative polarity toner attached to the electrostatic brush 602 due to the electric field action between the recovery roll 606 and the electrostatic brush 602 is recovered to the recovery roll 606 side. Become so. Similarly, the positive polarity toner is recovered by the recovery roll 607 via the electrostatic brush 605.
Bipolar toner is also cleaned by using such a cleaning device 600. However, since two electrostatic brushes 602 and 603 are required, the configuration of the device is likely to increase in size and complexity. ing.

In this example, in order to confirm the effectiveness of toner collection by the cleaning device (see FIG. 10) used in the first embodiment, the resistance change of the conductive toner was evaluated and confirmed.
The conductive toner was prepared as follows. For example, 15 wt% of ITO particles (manufactured by Sumitomo Metal Mining Co., Ltd.) are added to insulating toner (average particle diameter 6.5 μm) for general color toners, and sample mill (SK-M10 type: manufactured by Kyoritsu Riko Co.) After mixing, ITO particles were adhered to the surface of the insulating toner. The resistance measurement result at this time was 10 ⁴ Ω · cm, and it was found that sufficient electrical conductivity was possible.
Then, an insulating layer was formed on the surface by adding insulating fine particles made of polyester resin or styrene acrylic resin to the insulating toner to which the ITO particles were adhered, and mixing them. It has been found that a predetermined electrical resistance can be obtained by adjusting the surface coverage of the insulating layer. The surface coverage is adjusted by adjusting the mixing time, for example.

When the relationship between the volume resistivity of the conductive toner thus produced and the applied electric field was measured, the result shown in FIG. 25 was obtained. A region where the volume resistivity suddenly changes is confirmed around the applied electric field of 1 × 10 ⁵ V / cm. Before and after that, the applied electric field is about 5 × 10 ⁴ V / cm and the volume resistivity is 1 × 10 ¹³ Ω · cm. On the other hand, when the applied electric field was about 2 × 10 ⁵ V / cm, a value lower than 1 × 10 ⁹ Ω · cm was obtained.
For this reason, since the electrostatic brush is indefinite, it is difficult to specify the electric field actually applied to the conductive toner, but the cleaning electric field is around 3 × 10 ⁴ V / cm and the toner recovery electric field is 1 If it is about ˜3 × 10 ⁵ V / cm, good toner recovery is expected, and the cleanability of the image carrier is expected to be maintained. Practically, the electrical resistance of the conductive toner is effective by measuring the change in the charge amount of the conductive toner on the image carrier, electrostatic brush, and collection roll, and measuring the presence or absence of charge injection. It was confirmed that switching was performed.

(A) shows the outline | summary of the image forming apparatus which concerns on embodiment model which embodies this invention, (b) is explanatory drawing which shows the effect | action at the time of cleaning. 1 is an explanatory diagram showing an overview of an image forming apparatus according to Embodiment 1. FIG. FIG. 3 is a perspective view showing an image holding body according to the first embodiment. (A) and (b) are explanatory drawings showing the internal structure of the image carrier of the first embodiment. FIG. 2 is an explanatory diagram illustrating a pixel structure of Embodiment 1, where (a) shows a pixel group, (b) shows one pixel, and (c) shows a state of connection between pixels. 3 is an explanatory diagram illustrating a configuration of a matrix panel of the image carrier according to Embodiment 1. FIG. 1 is a block diagram illustrating a pixel electrode driving device according to a first embodiment. FIG. 2 is an explanatory diagram illustrating an outline of a developing device according to the first embodiment. (A) And (b) is explanatory drawing which shows the outline | summary of the electroconductive toner used in Embodiment 1. FIG. It is explanatory drawing which shows the outline | summary of the cleaning apparatus of Embodiment 1. FIG. It is explanatory drawing which shows the application condition of the cleaning voltage of a cleaning apparatus. It is explanatory drawing which shows the gradation conversion of a latent image voltage. (A) is explanatory drawing which shows the effect | action at the time of image development of Embodiment 1, (b) is the development at the time of light irradiation using a photoconductive layer for a protective layer as a modification of Embodiment 1. It is explanatory drawing which shows the effect | action of time. (A) is explanatory drawing which shows the effect | action at the time of transfer of Embodiment 1, (b) is explanatory drawing which shows the effect | action at the time of utilizing a pixel electrode at the time of transfer as a deformation | transformation form of Embodiment 1. FIG. (A) (b) is explanatory drawing which shows the cleaning effect | action of the bipolar toner in the cleaning apparatus in this Embodiment. (A) and (b) are the principal part enlarged views of FIG. (A) (b) is explanatory drawing which shows an effect | action when not having the area | region of the cleaning electric field from which polarity differs in a contact area as a comparison form of Embodiment 1. FIG. (A) and (b) are explanatory views showing the cleaning action of the bipolar toner when the rotation direction of the electrostatic brush is changed as a modification of the first embodiment. (A) (b) is explanatory drawing which shows the cleaning effect | action of a toner when the cleaning electric field from which polarity differs also acts with respect to the rotating shaft direction of an image holding body. 6 is an explanatory diagram illustrating a collecting operation of bipolar toner in Embodiment 1. FIG. FIG. 6 is an explanatory diagram illustrating a modification of the developing device according to the first embodiment. It is explanatory drawing which shows the outline | summary of the cleaning apparatus which concerns on Embodiment 2. FIG. FIG. 10 is an explanatory diagram illustrating an overview of an image forming apparatus according to a third embodiment. It is explanatory drawing which shows the outline | summary of the cleaning apparatus of a reference form. It is explanatory drawing which shows the result of an Example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Image holding body, 2 ... Support body, 3 ... Pixel electrode, 4 ... Protective layer, 5 ... Cleaning device, 6 ... Cleaning member, 7 ... Cleaning voltage application means, 8 ... Toner collection means, 9 ... Toner collection member, T ... toner, m ... contact area

Claims (7)

A support whose surface is movable;
Supported on the surface of the support, arranged in a two-dimensional manner in the direction of movement of the support and the direction intersecting the support, and a latent image voltage can be applied to form a toner image corresponding to image information for each pixel. A plurality of pixel electrodes,
An image carrier having a protective layer for insulatingly covering these pixel electrodes;
A rotatable conductive cleaning member disposed opposite to the image carrier and cleaning residual toner in contact with the surface of the image carrier;
The pixel electrodes arranged along the moving direction of the image carrier are divided into a plurality of regions and pixels in adjacent regions so as to form a cleaning electric field whose polarity changes between the cleaning member and the pixel electrodes. A cleaning voltage that is a cleaning electric field having a different polarity is applied to a cleaning electric field formed between the electrode and the cleaning member, and at least a cleaning electric field having a different polarity is present in the contact area between the cleaning member and the image carrier. A cleaning voltage applying means for coexisting the region to be formed, and a cleaning device,
An image forming apparatus comprising: The image forming apparatus according to claim 1.
The cleaning voltage applying means is further arranged along the intersecting direction so as to form a cleaning electric field whose polarity changes between the cleaning member and the pixel electrode along the intersecting direction of the image carrier. The pixel electrode is divided into a plurality of regions, and a cleaning voltage is applied to generate a cleaning electric field having a different polarity with respect to a cleaning electric field formed between the pixel electrode in the adjacent region and the cleaning member. Image forming apparatus. The image forming apparatus according to claim 1, wherein
The image forming apparatus, wherein the cleaning member is a brush member. The image forming apparatus according to claim 3.
The image forming apparatus according to claim 1, wherein the cleaning member rotates in the same direction as the moving direction of the image holding member at a portion facing the image holding member. The image forming apparatus according to claim 4.
The rotation speed of the cleaning member is set to be larger than the moving speed of the image carrier. The image forming apparatus according to claim 1,
The cleaning device includes a toner recovery member that is disposed opposite to the cleaning member at a position separated from the image holding member, and a cleaning member by applying a toner recovery electric field between the toner recovery member and the cleaning member. An image forming apparatus, further comprising: a toner collecting unit that collects toner adhering to the toner using a toner collecting member. The aspect of using the toner whose resistance is changed by an applied electric field in the image forming apparatus according to claim 6.
The toner collecting means applies a toner collecting electric field larger than the cleaning electric field between the toner collecting member and the cleaning member, and changes the toner resistance in the toner collecting electric field to be lower than the resistance in the cleaning electric field. What is claimed is: 1. An image forming apparatus comprising:

Images