JP5163066B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus.

  Generally, an electrophotographic method is used as an image forming method 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 laser or LED array to form an electrostatic latent image. The electrostatic latent image is developed with a charged toner so as to be visualized. An image forming apparatus using an electrophotographic method as described above is widely used mainly in offices because it has excellent on-demand characteristics and can form images on plain paper.

  On the other hand, an image forming apparatus of a system in which electrodes are arranged in a matrix and does not use a charger has been proposed in consideration of environmental influences in the electrophotographic system (see Patent Documents 1 to 4). Patent Document 1 proposes an image forming apparatus of a type in which thin film transistors (TFTs) are formed in a matrix and storage capacitors are provided in the respective TFTs, and stable development is performed by a charge storage effect in the storage capacitors. Yes. Patent Document 2 proposes an image forming apparatus of a type in which switching elements are configured in a matrix and a surface potential generated for each pixel is changed by laser irradiation. Further, Patent Document 3 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 4 proposes an image forming apparatus that forms a latent image for each pixel using switching elements arranged in a matrix.

Japanese Patent No. 3233463 (Example, FIG. 4) JP 2002-326382 A (Embodiment 1, FIG. 1) Japanese Patent Laying-Open No. 2003-32440 (Embodiment of the Invention, FIG. 1) JP 2004-219635 A (Embodiment 1, FIG. 1)

  The technical problem of the present invention is that, when an image is formed using an image carrier having pixel electrodes arranged vertically and horizontally in units of pixels, a good image quality is obtained and a long period of time is obtained as compared with a method using no pixel electrodes. The purpose is to stabilize the image quality.

The invention according to claim 1 is based on an image signal for each of the pixel electrodes, and an image holding body having a movable support and pixel electrodes supported by the support and arranged vertically and horizontally in pixel units. A latent image forming unit that forms a latent image on the image carrier by applying a latent image voltage, a developing unit that develops the latent image formed by the latent image forming unit with toner, and the pixel electrode, respectively. A transfer voltage is applied to the toner image developed by the developing unit by applying a transfer voltage based on an image signal to the transfer unit, and a transfer voltage to be applied to the transfer unit is adjusted. A transfer voltage adjusting means, wherein the transfer voltage adjusting means extracts a feature of the image from the image signal, and a transfer voltage based on the feature of the image extracted by the feature extracting portion. To determine A transfer control signal generating means for generating a control signal, which is an image forming apparatus having a transfer voltage setting means for setting a transfer voltage that is determined by the transfer control signal generating means.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the feature extraction unit extracts whether a high density area that is a high image density area or a low density area that is a low image density area, The transfer control signal generation unit generates the transfer control signal so that the transfer electric field acting on the high density region is larger than the transfer electric field acting on the low density region based on the determination result of the feature extraction unit. Forming device.
According to a third aspect of the present invention, in the image forming apparatus according to the second aspect , the transfer control signal generating unit is adjacent to the high density region of the low density region when the high density region and the low density region are adjacent to each other. In the image forming apparatus, the transfer control signal is generated so that the transfer electric field acting on the boundary portion is larger than the other low density regions.

According to a fourth aspect of the present invention, in the image forming apparatus according to the first aspect, the feature extraction unit extracts whether or not the background part region is a background part other than the image part, and the transfer control signal generation unit includes: In the image forming apparatus, the transfer control signal is generated so that the direction of the transfer electric field acting on the background area is different from the direction of the transfer electric field acting on the image area based on the extraction result of the feature extraction section. .
According to a fifth aspect of the present invention, in the image forming apparatus according to the first aspect, the feature extraction unit extracts whether or not the background part region is a background part other than the image part, and the transfer control signal generation unit includes: In the image forming apparatus, the transfer control signal is generated so that the transfer electric field acting on the background area is substantially zero based on the extraction result of the feature extraction unit.
According to a sixth aspect of the present invention, in the image forming apparatus according to the first aspect, the feature extraction unit extracts a line image area where a line image is formed or a solid image area where a solid image is formed, and the transfer The control signal generation unit generates the transfer control signal so that the transfer electric field acting on the line image region is larger than the transfer electric field acting on the solid image region based on the extraction result of the feature extraction unit. It is.

The invention according to claim 7 is based on an image signal for each of the pixel electrodes, and an image holding body having a movable support and pixel electrodes supported by the support and arranged vertically and horizontally in pixel units. A latent image forming unit that forms a latent image on the image carrier by applying a latent image voltage, a developing unit that develops the latent image formed by the latent image forming unit with toner, and the pixel electrode, respectively. A transfer unit that applies a transfer voltage based on an image signal to apply a transfer electric field to the toner image developed by the developing unit to a transfer medium, and a cleaning based on the image signal for each of the pixel electrodes. The image forming apparatus includes: a cleaning unit that applies a cleaning electric field for cleaning the surface of the image carrier that has been transferred by applying a voltage.

The invention according to claim 8 is based on an image signal for each of the pixel electrodes, and an image carrier having a movable support and pixel electrodes supported by the support and arranged vertically and horizontally in pixel units. A latent image forming unit that forms a latent image on the image carrier by applying a latent image voltage; a developing unit that develops the latent image formed by the latent image forming unit with toner; and the image carrier. And a transfer means for transferring a toner image on the image carrier developed by the developing means to a transfer medium, and applying a cleaning voltage based on an image signal to each of the pixel electrodes. The image forming apparatus includes a cleaning unit that applies a cleaning electric field for cleaning the surface of the image carrier that has been transferred.
The invention according to claim 9, in the image forming apparatus according to claim 7 or 8, the cleaning voltage to be applied to said cleaning means comprises a adjustable cleaning voltage regulating means, the cleaning voltage regulating means, the toner A cleaning control signal generating unit that generates a cleaning control signal for determining a cleaning voltage to be applied to each pixel electrode in a direction of peeling from the pixel electrode, and a cleaning voltage determined by the cleaning control signal generating unit are set. An image forming apparatus having a cleaning voltage setting unit.

The invention according to claim 10, in the image forming apparatus according to claim 7 or 8, the cleaning voltage to be applied to said cleaning means comprises a adjustable cleaning voltage regulating means, the cleaning voltage adjusting means, the image signal A feature extraction unit that extracts image features from the image, a cleaning control signal generation unit that generates a cleaning control signal for determining a cleaning voltage based on the image features extracted by the feature extraction unit, and the cleaning control The image forming apparatus includes a cleaning voltage setting unit that sets a cleaning voltage determined by the signal generation unit.
According to an eleventh aspect of the present invention, in the image forming apparatus according to the tenth aspect, the feature extraction unit extracts whether a high density area that is a high image density area or a low density area that is a low image density area, The cleaning control signal generation unit generates the cleaning control signal based on the extraction result of the feature extraction unit so that the cleaning electric field acting on the high concentration region is larger than the cleaning electric field acting on the low concentration region. Forming device.
According to a twelfth aspect of the present invention, in the image forming apparatus according to the tenth aspect, the feature extraction unit extracts whether or not the background part region is a background part other than the image part, and the cleaning control signal generation unit includes: In the image forming apparatus, the cleaning control signal is generated so that the direction of the cleaning electric field acting on the background area is different from the direction of the cleaning electric field acting on the image area based on the extraction result of the feature extraction section. .

According to the first aspect of the present invention, when an image is formed using an image carrier having pixel electrodes arranged vertically and horizontally in pixel units, it is possible to obtain better image quality than a method using no pixel electrodes. It becomes possible to stabilize the image quality over a long period of time. Furthermore, according to the present invention , it is possible to apply a transfer voltage suitable for the characteristics of an image per image, and it is possible to form an image with improved image quality on a transfer medium. Become.
According to the second aspect of the present invention, the transfer electric field acting on the high density area can be made larger than that of the low density area, and effective even from the high density area where the amount of adhering toner is large, compared to the case without this configuration. By transferring, the image reproducibility after transfer is improved.
According to the third aspect of the present invention, image omission at the boundary between the high density region and the low density region can be prevented, and the image quality can be improved, as compared with the case without this configuration.
According to the fourth aspect of the invention, as compared with the case without this configuration, it is possible to suppress the transfer of the toner adhering to the background area on the image carrier and to improve the image reproducibility after the transfer. Become.
According to the invention which concerns on Claim 5 , generation | occurrence | production of a ghost can be suppressed compared with the thing which does not have this structure.
According to the sixth aspect of the present invention, the line image region can be transferred effectively compared to the case without this configuration, and the image reproducibility after transfer is improved.

According to the seventh aspect of the present invention, when an image is formed using an image carrier having pixel electrodes arranged vertically and horizontally in pixel units, a better image quality can be obtained compared to a method using no pixel electrodes. By applying a cleaning voltage based on the image signal, the image carrier after the transfer is well cleaned. As a result, the image carrier surface can be kept clean, and the image quality can be stabilized over a long period of time. It becomes possible to plan.
According to the eighth aspect of the invention, when image formation is performed using an image carrier having pixel electrodes arranged vertically and horizontally in pixel units, it is possible to obtain better image quality than a method using no pixel electrodes. By applying the cleaning voltage based on the image signal, the image carrier after the transfer is cleaned well, and the surface of the image carrier can be kept clean.
According to the ninth aspect of the present invention, the residual toner on the image holding member can be easily cleaned and removed as compared with the case without this configuration.
According to the tenth aspect of the present invention, the residual toner on the image carrier can be controlled more finely in accordance with the image, and can be suitably cleaned and removed as compared with the case without this configuration.
According to the eleventh aspect of the present invention, the residual toner on the image holding member can be cleaned and removed better regardless of the amount of residual toner based on the image density, as compared with the case without this configuration. Become.
According to the twelfth aspect of the present invention, it is easier to remove and remove the reverse polarity toner as compared with the one not having this configuration.

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 a first embodiment model embodying the present invention. In the figure, the basic structure of the image forming apparatus is that an image carrier 1 having a movable support 1a and a pixel electrode 1b supported by the support 1a and arranged vertically and horizontally in pixel units, and a pixel electrode. A latent image forming unit 2 that forms a latent image on the image carrier 1 by applying a latent image voltage based on the image signal to each of the image signals 1b, and the latent image formed by the latent image forming unit 2 is used as toner. The developing means 3 for developing and a transfer means for applying a transfer electric field to the transfer medium 5 to the toner image developed by the developing means 3 by applying a transfer voltage based on the image signal to each of the pixel electrodes 1b. 4 is provided.

  Here, the shape of the support 1a is not particularly limited as long as the support 1a can move the pixel electrode 1b and the like, but from the viewpoint of downsizing the device, a rotatable mode is preferable. The pixel electrodes 1b only have to be arranged vertically and horizontally in pixel units, and the number of pixel electrodes 1b is not particularly limited, but it is preferable that the pixel electrodes 1b have a resolution that can form a normal image. Further, the latent image forming means 2 may be any device that can form a latent image on each pixel electrode 1b of the image carrier 1 based on the image signal of the image to be formed. The transfer method of the transfer means 4 may be a non-contact type such as a corotron or a contact type such as a transfer roll, but the transfer operation is performed for each pixel electrode 1b. From the viewpoint of controlling the thickness, it is preferable to use a transfer roll. The transfer medium 5 onto which the toner image on the image carrier 1 is transferred by the transfer unit 4 may be an intermediate transfer member or a recording material.

Next, in order to deepen the understanding of the present embodiment model, a method usually used in an electrophotographic method as a comparison model will be described.
As shown in FIG. 23, in this comparative model, after forming an electrostatic latent image by exposing a photosensitive member (corresponding to an image holding member) charged using a charging device by laser irradiation or the like from an exposure device, The electrostatic latent image is developed with toner using a developing device so as to be visualized. In such a system, the latent image potential on the photosensitive member and the photosensitive member whose pixel position rotates and the photosensitive member are easily varied by charging with the charging device, and if there is such variation, density unevenness, color unevenness, Image quality degradation such as streaks is likely to occur. In addition, such variations tend to cause toner scattering and fogging during development. Further, when the toner image on the photosensitive member is transferred to a transfer medium (for example, an intermediate transfer member or a recording material), a transfer electric field generated by the transfer device during transfer is applied only uniformly between the photosensitive member and the transfer device. Therefore, the amount of toner to be transferred onto the transfer medium is not properly transferred, and unnecessary transfer may occur.

  Turning to the change over time in such a system, the charging device is contaminated with toner, and the desired charging cannot be performed, or the charging device discharges (discharge of the charging device itself or contact with the photoreceptor). The generation of discharge products due to the discharge due to the gap changes the quality of the photoconductor, and further reduces the cleaning performance on the photoconductor. If the cleaning member is brought into strong contact with the photoconductor in order to suppress the deterioration of the cleaning performance on the photoconductor in such a situation, the photoconductor and the cleaning member may be accelerated.

  On the other hand, in the present embodiment model, as shown in FIG. 1, pixel electrodes 1b arranged vertically and horizontally for each pixel are provided as an image carrier 1, and in particular, a latent image based on an image signal is applied to each pixel electrode 1b. Since the latent image forming means 2 to be formed and the transfer means 4 for applying a transfer voltage based on the image signal to each of the pixel electrodes 1b are provided, a desired latent image is formed for each pixel electrode 1b, and the desired transfer is performed. Will be made.

From the viewpoint of improving the image quality of the image formed on the transfer medium 5, as shown in FIGS. 2 (a) and 2 (b), the transfer voltage adjustment capable of adjusting the transfer voltage to be applied to the transfer means 4 is possible. The transfer voltage adjusting unit 6 includes a feature extraction unit 7 that extracts image features from the image signal, and determines a transfer voltage based on the image features extracted by the feature extraction unit 7. It is necessary to have a transfer control signal generating means 8 for generating a transfer control signal of the above and a transfer voltage setting means 9 for setting a transfer voltage determined by the transfer control signal generating means 8. Here, “image characteristics” means the characteristics of an image on a recording material on which an image is finally formed (the transfer medium 5 may be a recording material). Area / low density area, image area / background area, line image area / solid image area, and the like. 2A is a process block diagram of the image forming apparatus, and FIG. 2B is a schematic diagram of the process.

  Further, from the viewpoint of improving the image reproducibility for such an image, the feature extraction unit 7 extracts whether it is a high density area that is a high image density area or a low density area that is a low image density area, It is preferable that the transfer control signal generation unit 8 generates the transfer control signal so that the transfer electric field acting on the high density region is larger than the transfer electric field acting on the low density region based on the extraction result of the feature extraction unit 7. Further, if attention is paid to the boundary between the high density area and the low density area, the transfer control signal generating means 8 is adjacent to the high density area of the low density area when the high density area and the low density area are adjacent to each other. It is preferable to generate the transfer control signal so that the transfer electric field acting on the boundary portion is larger than the other low density regions.

From another viewpoint of improving the image reproducibility, the feature extraction unit 7 extracts whether or not the background region is a background portion other than the image portion, and the transfer control signal generation unit 8 includes the feature extraction unit. It is preferable to generate the transfer control signal based on the extraction result 7 so that the direction of the transfer electric field acting on the background area is different from the direction of the transfer electric field acting on the image area.
Further, from the viewpoint of suppressing the generation of ghost images, the feature extraction unit 7 extracts whether or not the background region is a background portion other than the image portion, and the transfer control signal generation means 8 It is preferable to generate the transfer control signal so that the transfer electric field acting on the background area is substantially zero based on the determination result.

  In addition, from the viewpoint of improving the image quality in an image including a line image or a solid image, the feature extraction unit 7 extracts whether the line image area in which the line image is formed or the solid image area in which the solid image is formed, The transfer control signal generation means 8 preferably generates a transfer control signal so that the transfer electric field acting on the line image area is larger than the transfer electric field acting on the solid image area based on the extraction result of the feature extraction unit 7.

  As shown in FIG. 1, the image forming apparatus according to the second embodiment model embodying the present invention includes a movable support 1a and a support supported by the support 1a and vertically and horizontally in units of pixels. An image holding body 1 having pixel electrodes 1b arranged in a row, and a latent image forming means 2 for forming a latent image on the image holding body 1 by applying a latent image voltage based on an image signal to each of the pixel electrodes 1b. The latent image formed by the latent image forming unit 2 is developed by the developing unit 3 by developing with toner, and the developing unit 3 is developed by applying a transfer voltage based on the image signal to each of the pixel electrodes 1b. The transfer unit 4 that applies a transfer electric field to the transfer medium 5 to the toner image, and the surface of the image carrier 1 that has been transferred by applying a cleaning voltage based on the image signal to each of the pixel electrodes 1b. Apply a cleaning electric field to clean the And a cleaning means 10.

  The image forming apparatus according to the third embodiment model is as follows. That is, an image carrier 1 having a movable support 1a and pixel electrodes 1b supported by the support 1a and arranged in vertical and horizontal directions in units of pixels, and a latent image based on an image signal for each of the pixel electrodes 1b. A latent image forming means 2 for forming a latent image on the image holding body 1 by applying a voltage, a developing means 3 for developing the latent image formed by the latent image forming means 2 with toner, and an image holding body A transfer unit 4 that applies a transfer electric field to the transfer unit 1 and transfers a toner image on the image carrier 1 developed by the developing unit 3 to a transfer medium 5 and cleaning based on an image signal for each of the pixel electrodes 1b. A cleaning means 10 is provided for applying a cleaning electric field for cleaning the surface of the image carrier 1 that has been transferred by applying a voltage.

Here, the cleaning means 10 in the image forming apparatus of the second aspect or the third aspect is not particularly limited as long as a cleaning voltage corresponding to the image signal can be applied to each pixel electrode 1b, and after the transfer. The shape of the cleaning member 10a for removing the residue (residual toner or the like) on the image carrier 1 may be any of an aspect using a roll member, an aspect using a brush member, and an aspect using a blade.
Further, as shown in FIGS. 2A and 2B, a cleaning voltage adjusting unit 11 capable of adjusting a cleaning voltage to be applied to the cleaning unit 10 is provided. The cleaning voltage adjusting unit 11 removes toner from the pixel electrode 1b. A cleaning control signal generating unit 13 that generates a cleaning control signal for determining a cleaning voltage to be applied to each pixel electrode 1b in the peeling direction, and a cleaning voltage determined by the cleaning control signal generating unit 13 are set. The cleaning voltage setting unit 14 is preferably included, and according to this, toner adhesion to the image carrier 1 side can be suppressed, and toner removal by the cleaning member 10a can be more easily performed.
From the viewpoint of further enhancing the cleaning effect on the surface of the image carrier 1, the cleaning voltage adjusting unit 11 that can adjust the cleaning voltage to be applied to the cleaning unit 10 is provided. A feature extraction unit 12 that extracts the features of the image, a cleaning control signal generation unit 13 that generates a cleaning control signal for determining a cleaning voltage based on the features of the image extracted by the feature extraction unit 12, and It is preferable to have a cleaning voltage setting unit 14 that sets the cleaning voltage determined by the cleaning control signal generation unit 13. The feature extracting unit 12 of the cleaning voltage adjusting unit 11 may be used as the feature extracting unit 7 of the transfer voltage adjusting unit 6 described above.

Further, from the viewpoint of better cleaning and removing the residue on the image carrier 1 in such an image part, the feature extraction unit 12 is a high density area that is a high image density area or a low image density area. The cleaning control signal generation means 13 extracts the cleaning electric field acting on the high concentration area based on the extraction result of the feature extraction unit 12 so that the cleaning electric field acting on the low concentration area becomes larger than the cleaning electric field acting on the low concentration area. Preferably, a cleaning control signal is generated.
Further, from the viewpoint of cleaning and removing the toner whose polarity is reversed, the feature extraction unit 12 extracts whether or not the background region is a background portion other than the image portion, and the cleaning control signal generation unit 13 extracts the feature. It is preferable that the cleaning control signal is generated so that the direction of the cleaning electric field acting on the background area is different from the direction of the cleaning electric field acting on the image area based on the extraction result of the section 12.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
Embodiment 1
FIG. 3 shows a first embodiment 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 (Y), magenta (M)) is formed in the apparatus housing 15 by, for example, electrophotography. , Cyan (C), and black (BK) toner images 20 are formed in parallel in a substantially vertical direction, and circulate and rotate in opposition to these image carriers 20. An intermediate transfer belt 50 serving as a transfer medium is stretched in a substantially vertical direction, and 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 that develops the electrostatic latent image formed on the image carrier 20 with toner and visualizes it, and residual toner on the image carrier 20 are cleaned. A cleaning member 42 is provided, and a transfer device 43 that transfers the developed toner image on the image holding member 20 to the intermediate transfer belt 50 is located at a position facing the image holding member 20 and the intermediate transfer belt 50 with the cleaning member 42 therebetween. Is provided. Reference numeral 41 a denotes a developing roll that supplies toner directly to the image carrier 20 in the developing device 41.
On the other hand, the intermediate transfer belt 50 is stretched around a plurality of stretching rolls 51 to 53 (three in this example), and circulates and rotates using, for example, the stretching roll 51 as a driving roll. On the surface side of the belt 50, a secondary transfer device 60 is provided at a position opposed to the tension roll 53 and the intermediate transfer belt 50, and a recording material to be described later is used to multiplex toner images 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 roll 53 as a backup roll.

A recording material supply unit 70 for supplying a recording material is provided below the apparatus housing 15. For example, one recording material accommodated in a supply container 71 is supplied by a supply roll 72 and a separating mechanism 73. It is supplied to the recording material conveyance path 74 on the downstream side every time.
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 the resist roll 75 disposed on the downstream side, and then the secondary transfer device 60 on the downstream side at a predetermined timing. Conveyed to the 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. After that, the paper is discharged from the discharge roll 77 to the recording material discharge receiver 16 constituted by a part of the apparatus housing 15. Needless to say, the recording material conveyance path 74 is appropriately provided with a conveyance member (for example, a conveyance roll) for conveying the recording material.

Next, the image carrier 20 of the present embodiment will be described in detail.
As shown in FIG. 4, the image carrier 20 in the present embodiment winds a matrix panel 30 in which a large number of pixels are formed in a so-called matrix on a film on a rigid drum 21 that is a rotatable support. It is fixed and supported. The matrix panel 30 is manufactured using, for example, a thin film technology used in a so-called IC manufacturing process for a heat-resistant PET (polyester resin) film, and the pixels are arranged in a matrix form vertically and horizontally. Yes. For example, the pixels arranged in a matrix form have data lines (main scanning direction) as the direction along the rotation axis direction of the rigid drum 21, and scan lines (sub-scanning direction) as the direction along the rotation direction. It is said. 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.
Further, as shown in FIGS. 5A and 5B, an appropriate number of terminals 22 are provided on the inner peripheral surface side of the rigid drum 21 along the rotation 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.

Next, the pixels of the matrix panel 30 will be described.
As shown in FIG. 6A, the matrix panel 30 of the present embodiment has pixels arranged vertically and horizontally, and each pixel is configured by a so-called active matrix system as shown in FIG. For example, a TFT (Thin Film Transistor) 33 is used as an 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 grouped as a source line to which the source of the TFT 33 is connected for each data line, and a gate line to which the gate of the TFT 33 is connected for each scanning line. Further, a pixel electrode 34 and a 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), and exhibits an equivalent circuit as shown in (c). It is configured.

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. 7, 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. Although the pixel electrode 34 is omitted in FIG. 7, it goes without saying that the pixel electrode 34 connected between the TFT 33 and the storage capacitor 35 is provided.

On the other hand, as shown in FIG. 8, the pixel electrode driving device 80 transmits voltage signals and control signals based on image signals to the data driver 31 and the scanning driver 32 of the matrix panel 30. In the pixel electrode driving device 80, a control unit that generates control signals for generating various voltages (specifically, a latent image voltage, a transfer voltage, and a cleaning voltage) to be applied to the pixel electrode 34 based on the image signal. 90 and a drive unit 110 that sets a voltage to be applied to each pixel electrode 34 from each of the generated control signals.
The control unit 90 includes a memory unit 91 that stores image data for at least one image from the image signal, a latent image control unit 92 that controls a latent image voltage based on the image signal, and a transfer control unit that controls a transfer voltage based on the image signal. 95, a cleaning control unit 98 that controls a cleaning voltage based on an image signal, a timing controller 101 that performs various timing controls, and the like.

  The latent image control unit 92 has a gradation conversion unit 93 that performs gradation conversion on the image data from the memory unit 91, and latent image control for determining a latent image voltage level for each pixel electrode 34 from the gradation converted data. And a latent image control signal generation unit 94 for generating a signal. Further, the transfer control unit 95 extracts a feature of the image from the image data from the memory unit 91, and sets the transfer voltage level for each pixel electrode 34 based on the result extracted by the feature extraction unit 96. The transfer control signal generation unit 97 generates a transfer control signal for determination. Further, the cleaning control unit 98 extracts the feature of the image from the image data from the memory unit 91, and sets the cleaning voltage level for each pixel electrode 34 based on the result extracted by the feature extraction unit 99. The cleaning control signal generation unit 100 generates a cleaning control signal for determination.

  On the other hand, the driving unit 110 sets each voltage (specifically, a latent image voltage, a transfer voltage, and a cleaning voltage) to be applied to the pixel electrode 34 based on each control signal from the control unit 90. A latent image voltage setting unit 111, a transfer voltage setting unit 113, a cleaning voltage setting unit 115, and a timing controller 118 for controlling these timings are provided. The latent image voltage setting unit 111 is connected to a latent image voltage power source 112 having a plurality of voltage sources so that various types of latent image voltages can be supplied, and is based on a signal from the latent image control signal generation unit 94. Thus, a voltage waveform is generated. Further, a transfer voltage power source 114 is connected to the transfer voltage setting unit 113, and a cleaning voltage power source 116 is connected to the cleaning voltage setting unit 115. Here, as the transfer voltage power source 114, a polarity opposite to that of the latent image voltage is mainly used, and a voltage having the same polarity as that of the latent image voltage is included. As the cleaning voltage power supply 116, a voltage having a polarity opposite to that of the latent image voltage is mainly used as in the case of the transfer voltage power supply 114, and a voltage having the same polarity as that of the latent image voltage is included.

Further, among the various voltages set by the latent image voltage setting unit 111, the transfer voltage setting unit 113, and the cleaning voltage setting unit 115, the drive unit 110 is selectively transmitted to the data driver 31 of the matrix panel 30. Therefore, a switching unit 117 is provided, and the switching unit 117 transmits one type of latent image voltage, transfer voltage, and cleaning voltage to the data driver 31.
In addition, a control signal is transmitted from the driving unit 110 to the scanning driver 32 of the matrix panel 30.

  In the present example, the feature extraction units 96 and 99 are provided in the transfer control unit 95 and the cleaning control unit 98, respectively. However, the extraction result from the feature extraction unit 96 of the transfer control unit 95 is also used in the cleaning control unit 98, for example. Therefore, the feature extraction unit 96 may be directly guided to the cleaning control signal generation unit 100. In addition, the image data from the memory unit 91 is input to the feature extraction units 96 and 99. However, the present invention is not limited to this. For example, the tone extraction data from the tone conversion unit 93 is used as the feature extraction unit. 96, 99 may be input.

  As described above, a predetermined voltage can be applied to each of the pixel electrodes 34 in the matrix panel 30 via the pixel electrode driving device 80, and each process of forming, transferring, and cleaning the latent image is performed in the pixel electrode 34. By applying a different voltage for each step, the spread of each electric field acting between the pixel electrode 34 and the opposing member in each step can be suppressed, and good image formation can be performed. That is, between the pixel electrode 34 when developing the latent image formed by forming the latent image and the developing roll 41a, between the pixel electrode 34 when transferring, and the transfer device 43, when cleaning the pixel electrode 34. Spread of the electric field acting between the cleaning member 42 and the cleaning member 42 is suppressed. Further, since the latent image voltage has been subjected to gradation conversion, the amount of toner adhering to the pixel electrode 34 during development is different, and an image with better image quality can be formed.

  In the present embodiment, it is easy to form a latent image voltage based on an image signal in each of the pixel electrodes 34 by the gradation conversion unit 93. This will be described with reference to FIG. Now, for example, three levels of threshold values (indicated by A, B, and C in the figure) are provided for the density of the image signal (image data). For example, if V / 3 is greater than B and less than or equal to A but 2V / 3, and V is greater than A, then a four-gradation latent image is formed.

Next, a method for applying the image data classified into four stages to the pixel electrode 34 as described above will be described with reference to FIG.
The tone-converted signal is a signal as shown in FIG. 10A, and “... A, b, c, d... B, a, d, c. Is obtained, the latent image control signal generation unit 94 generates binarized data in accordance with a, b, c, and d, for example, as shown in (b). That is, a data signal such as “... 00011011 …… 01001110...” Is generated. Then, from this generated signal, the latent image voltage setting unit 111 selects four voltages corresponding to “00” to “11” from the latent image voltage power source 112, thereby setting a latent image voltage waveform in four stages. Is done. By transmitting the latent image voltage waveform set in this way to the data driver 31 and transmitting a control signal for timing control to the scanning driver 32, as shown in FIG. Thus, images having different densities are formed.

  It should be noted that the number of gradations is not particularly limited, and may be in a range that does not cause a problem in practice. It is also possible to simply use a latent image voltage that is binarized without performing gradation. Nor. Here, the gradation method used in the active matrix method, that is, the voltage gradation method in which the voltage amplitude is a predetermined number of gradations is shown as a method for applying the latent image voltage based on the image signal. It goes without saying that a frame rate gradation method that performs gradation display at a rate can also be used.

Here, the transfer voltage based on the image signal will be described.
Now, assuming that a latent image as shown in FIG. 10 is formed and a low density area and a high density area are extracted by the feature extraction unit 96, the “a” level shown in FIG. 11 is extracted as a low density region, and “c” and “d” levels are extracted as a high density region, the transfer control signal generation unit 97, for example, as shown in FIG. , A, b, c, and d are generated. That is, a data signal such as “... 00011010... 01001010...” Is generated. Then, from this generated signal, the transfer voltage setting unit 113 selects voltages corresponding to “00”, “01”, and “10” from the transfer voltage power supply 114, respectively, as shown in FIG. Three stages of transfer voltage waveforms (in this case, for example, represented as 0V, -XV, -YV) are set. By transmitting the waveform set in this way to the data driver 31, a desired transfer voltage can be applied to each pixel electrode 34, and a transfer electric field between the pixel electrode 34 and the transfer device 43 is preferably applied. Will be able to. This means that it is easy to apply a transfer electric field according to the amount of toner attached to the pixel electrode 34. The same operation as that at the time of transfer is performed during cleaning.

  Next, the 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. This charged electric charge becomes a latent image voltage for forming an electrostatic latent image. In this state, an OFF voltage is applied to the gate, and even if the source-drain is cut off, the latent image voltage is maintained as it is by the storage capacitor 35, so that the gate is not changed even if the source voltage subsequently changes. As long as the ON voltage is not applied, the latent image voltage is maintained as it is.

  Therefore, an electrostatic latent image for one data line is formed by applying a signal voltage corresponding to the image density to the source side of the TFT 33 of each pixel and applying an ON voltage to the gate side. . Then, the gate to which the ON voltage is applied is sequentially moved (scanned) in the direction opposite to the rotation direction of the image carrier 20, and a new signal voltage is applied to the data line so that a two-dimensional latent image is formed. become.

  In the present embodiment, the developing roller 41 a of the developing device 41 and the latent image are developed in the developing area, which is a region where the image holding body 20 and the developing device 41 are opposed to the electrostatic latent image formed on the image holding member 20. Due to the developing bias applied to the pixel electrode 34 to which the voltage is applied, toner adhesion is performed on the surface of the image carrier 20 according to the latent image voltage for each pixel, and the electrostatic latent image is developed. A visible toner image can be obtained. At this time, as the developing device 41, either a known one-component developing method or a two-component developing method may be used.

  Then, when the transfer region passes through the development region and reaches the transfer region facing the transfer unit 43, a transfer voltage based on the image signal (an electric field in the direction opposite to the development electric field is applied to the pixel electrode 34, as in the electrostatic latent image formation). The toner image on the image holding member 20 is transferred to the recording material by a transfer electric field acting between the pixel electrode 34 and the transfer unit 43. At this time, a corona discharger such as a corotron may be used as the transfer unit 43. However, in order to finely control the transfer electric field for each pixel, as shown in FIG. The type of transfer roll 43 is preferred. Further, although a voltage may be applied to the transfer roll 43, it may be simply grounded.

  In particular, in the present embodiment, as shown in FIG. 8, the feature extraction unit 96 extracts the low concentration region and the high concentration region, and the transfer control signal generation unit 97 performs the transfer electric field acting on the high concentration region. The potential of the pixel electrode 34 is set so as to be larger than the transfer electric field acting on the low density region. For this reason, the amount of toner transferred from the image carrier 20 to the intermediate transfer belt 50 has the same electric field strength per unit toner amount in both the high density region where the toner amount is large and the low density region where the toner amount is small. The toner can be transferred in a portion where the amount of toner is large, while the toner is transferred as it is in a portion where the amount of toner is small, and the reproducibility of the toner image formed on the intermediate transfer belt 50 is good. Things can be obtained.

  In this way, the toner images sequentially transferred and multiplexed from the respective image carriers 20 to the intermediate transfer belt 50 are secondary transfer portions which are regions where the intermediate transfer belt 50 and the secondary transfer device 60 are opposed to each other. The recording material that has been collectively transferred onto the recording material supplied from the recording material supply unit 70 and to which the multiplexed toner images have been collectively transferred is fixed by the fixing device 76, and then is discharged from the discharge roll 77 to the recording material discharge receiver 16. It will be discharged.

  Further, in the present embodiment, the toner remaining on the image carrier 20 after the toner image is transferred to the intermediate transfer belt 50 is in a region where the image carrier 20 and the cleaning member 42 are located downstream of the transfer region. By applying a cleaning voltage based on the image signal to the pixel electrode 34, the image electrode 20 is electrostatically attracted toward the cleaning member 42 and can be cleaned. As the cleaning member 42, a known member such as a conductive or semiconductive roll shape, a brush shape, a blade shape, or the like may be used. Further, a voltage may be applied to the cleaning member 42. It's good or just grounding.

  In particular, in the present embodiment, as shown in FIG. 8, the cleaning control unit 98 performs the same control as the transfer control unit 95, and the feature extraction unit 99 of the cleaning control unit 98 performs low density. The region and the high concentration region are extracted, and the cleaning control signal generation unit 100 sets the cleaning voltage applied to the pixel electrode 34 so that the cleaning electric field acting on the high concentration region is larger than the cleaning electric field acting on the low concentration region. It is like that. For this reason, even if a large amount of residual toner on the image carrier 20 remains in a portion (corresponding to a high density area) where the amount of adhered toner is large due to development, the high density area where the residual toner quantity is large during cleaning is also the amount of toner. Even in a low density region where the amount of toner is small, the cleaning electric field per unit toner amount can be set to the same electric field strength, so that a large amount of toner is sucked at a portion where the toner amount is large, while a portion where the toner amount is small As a result, the cleaning effect on the image carrier 20 is improved.

Here, the outline of the image forming process in the present embodiment will be described in detail with reference to FIG. Here, an example using negatively charged toner is shown, and a comparison with a process based on a comparative model using the photosensitive member of FIG. 23 is also added as appropriate.
-Latent image formation-
As shown in FIG. 12 (a), the latent image voltage in this example is a voltage based on an image signal (here, three levels of V, 2V / 3, and V / 3 are applied) for each pixel of the image carrier. Therefore, it is difficult to be affected between adjacent pixel electrodes. On the other hand, in the comparative model, the photosensitive member is once charged to a large negative value uniformly, and then the charged potential of the image portion is brought to the positive direction by light attenuation. It is difficult to say that the potential at is uniform across the entire pixel. Further, in this example, there is no need to worry about the rotation unevenness of the image carrier, whereas in the comparative model, there is a possibility that the rotation unevenness of the photoconductor may result in a light and dark stripe pattern (banding) of the image formed as it is. . Furthermore, in this example, the voltage difference between the pixels can be easily realized, so that the image density can be easily changed, but it is difficult in the comparative model.

-Development-
As shown in FIG. 12B, the development process itself is the same in this example and the comparative example, but in this example, the amount of toner adhered to each pixel changes due to the difference in the formed latent image potential. In contrast, in the comparative model, the pixel sharpness of the image is increased because the density of the image is easily expressed and the development electric field is easily concentrated between each pixel and the development roll. It is difficult to shade each image, and the developing electric field is easy to spread, so that the sharpness of the image is lowered.

-Transcription-
As shown in FIGS. 12C and 12D, in this example, a voltage based on the image signal is applied to the pixels to form a selective transfer electric field between the image carrier and the intermediate transfer belt. As a result, the toner on the image carrier is transferred to the intermediate transfer belt almost as it is. On the other hand, in the comparative model, a uniform electric field acts between the photosensitive member and the intermediate transfer belt regardless of the pixels, and when the toner on the photosensitive member is transferred to the intermediate transfer belt, It becomes easy to spread.
In particular, in this example, by using the same gradation method as the latent image formation, a transfer electric field corresponding to the toner adhesion amount on the pixel can be formed, and transfer according to the image density can be performed. It can also be realized easily.

  As in this example, the advantage that the transfer voltage can be changed for each pixel electrode is, for example, that the sharpness of the transferred image is kept good. FIG. 13A is a model of the potential distribution during transfer in this example, and as shown by the thickness of the white arrow in the figure by increasing the image carrier potential around the image more deeply. The transfer electric field around the image can be made larger than the transfer electric field at the image position. In addition, a large electric field works in an oblique direction at the boundary. For this reason, the toner has a relatively large force for pulling the toner inward as indicated by the arrows A and A ′, and the toner is pulled toward the transfer medium as indicated by the arrows B and B ′. A large force acts, and the toner during transfer can be prevented from scattering around the image.

On the other hand, in the comparative model shown in (b), the peripheral transfer electric field is slightly larger than the transfer electric field at the image position due to the absence of toner, but cannot be increased as shown in (a). For this reason, the force of the arrow C and the arrow C ′ for pulling the toner inward is smaller than in this example, and the inclination of the force of the arrow D and the arrow D ′ for the toner around the image to spread outward becomes gentle. In addition, the effect of suppressing the spread of the toner is small, and as a result, the toner is easily scattered.
Thus, by changing the voltage applied to the pixel electrode, the spread of the image at the time of transfer can be suppressed, and the sharpness of the image can be maintained.

Further, by using the pixel electrode, the following can be achieved.
FIG. 14A shows a transfer electric field at the time of transfer in this example, and there is a portion with a different amount of toner adhering along the electrostatic latent image on the image holding member. A transfer electric field corresponding to the image density (toner adhesion amount) is applied. In other words, the transfer electric field is large at the part where the toner adhesion amount is large and the transfer electric field is small at the part where the toner adhesion amount is small. In a portion where the toner adhesion amount is large, a large amount of toner is transferred, while in a region where the toner adhesion amount is small, the toner is transferred little. Therefore, an image that is more faithful to the image on the image carrier can be formed on the intermediate transfer belt (corresponding to a transfer medium).
On the other hand, in the comparative model, as shown in FIG. 14B, the transfer electric field between the photoconductor and the transfer medium acts between the photoconductor and the transfer medium regardless of the toner adhesion amount. Therefore, the transfer electric field becomes smaller in the part where the toner amount is large. For this reason, transfer from a portion having a particularly large amount of toner is reduced, and as a result, the amount of transferred toner cannot be correlated with the amount of toner attached on the photosensitive member.

Next, cleaning will be described.
−Cleaning−
As shown in FIG. 12E, at the time of cleaning, a voltage based on the image signal is applied to the pixels, so that both the pixels with a large amount of residual toner and the pixels with a small amount can be efficiently cleaned. On the other hand, in the comparative model, even when a voltage is applied to the cleaning member, a uniform electric field is formed between the photosensitive member and the cleaning member. is there.

  Further, in this embodiment, transfer and cleaning are also controlled in accordance with the characteristics of the image. That is, as shown in FIG. 15A, at the time of transfer, the feature extraction unit (see FIG. 8) extracts whether the image portion is a high density region or a low density region, and based on this extraction result, the high density region The transfer electric field acting on the transfer region is made larger than the transfer electric field acting on the low concentration region. That is, as a result, the transfer electric field in the high concentration region is made larger than the transfer electric field in the low concentration region. Further, when the high concentration region and the low concentration region are adjacent to each other, the transfer electric field acting on the boundary portion of the low concentration region is made larger than that of other portions. That is, as shown in (b), at the boundary between the high concentration region and the low concentration region, the transfer electric field is increased at the boundary portion on the low concentration region side (the portion where the transfer electric field is in the middle in the figure), Both the high density area and the low density area can be transferred uniformly.

  This is because the amount of toner is large in the high density region, so the amount of toner charge per unit area is large, and it is necessary to generate a high transfer electric field by applying a high voltage to the pixel electrode. However, when such a high voltage is applied to the low density region, an excessive electric field is generated, and for example, Paschen discharge is generated between the intermediate transfer belt, causing image unevenness and density reduction. Become. In addition, in a region where the high density region and the low density region are adjacent to each other, a gap between the toner and the intermediate transfer belt is generated at the boundary portion on the low density region side, and an effective transfer electric field applied to this region is generated. Get smaller. For this reason, if the low density region is made to have uniform electric field strength, the amount of transfer toner at the boundary portion is also reduced. Therefore, by increasing the electric field strength at the boundary, the transferred toner amount is adjusted in a uniform direction throughout the low density region.

  On the other hand, when cleaning the residual toner on the image holding member, it is as shown in FIG. That is, as shown in FIGS. 16A and 16B, at the time of cleaning, the feature extraction unit (see FIG. 8) extracts whether the image is a high density region or a low density region, and based on the extraction result, The cleaning electric field acting on the concentration region is made larger than the cleaning electric field acting on the low concentration region. By doing so, both the high density region and the low density region can be cleaned uniformly. In other words, since the cleaning member is conductive or semiconductive so that the member itself is not charged, when the electric field is high, the toner is charged and the cleaning efficiency is lowered. For this reason, the controllable electric field region is narrow and such control is effective even though the amount of toner is small because the toner is residual toner after transfer.

As described above, according to the image forming apparatus of the present embodiment, the pixel electrodes 34 are provided in a matrix on the surface side of the image carrier 20, and a voltage based on the image signal is applied to each pixel electrode 34 to form a latent image. Since the transfer and the cleaning are performed, the position and shape of the pixel are the same as the position and shape of the pixel electrode 34, and the latent image voltage is determined by the voltage applied to the pixel electrode 34. In addition, the potential is uniquely determined, and a high-quality image in which occurrence of image defects such as density unevenness, color unevenness, and streaks is suppressed can be obtained. Furthermore, since a transfer electric field or the like suitable for each image can be selected depending on the type of image, it is possible to suppress the occurrence of uneven transfer, toner scattering, and fogging.
Further, in such a system, since a charger is not used, the charger itself is contaminated with toner and causes a charging failure, or a discharge product generated from the charger alters the surface of the image carrier 20, or The cleaning performance is not deteriorated by the discharge product. Furthermore, by applying a cleaning voltage corresponding to the type of image to the pixel electrode 34, the cleaning efficiency can be improved, and the contact pressure between the image carrier 20 and the cleaning member 42 can be reduced. Damage to the cleaning member 42 itself is also reduced.

In the present embodiment, an image forming apparatus that performs transfer from the image carrier 20 to the intermediate transfer belt 50 has been described. However, the present invention is not limited to this, and the image carrier 20 may be directly transferred onto a recording material. Absent. Further, the cleaning voltage may not be applied to the pixel electrodes 34 at the time of cleaning by the cleaning member 42. In this case, for example, residual toner on the image holding body 20 is interposed between the image holding body 20 and the cleaning member 42. An electric field in the direction of electrostatic attraction may be applied to the cleaning member 42 side.
Further, the pixel electrode 34 is used for cleaning by the cleaning member 42, and a cleaning voltage is applied to each pixel electrode 34, while the pixel electrode 34 is not used for transfer, and the image electrode 20 and the transfer device 43 are not used. It is also possible to transfer by applying a transfer electric field.

Further, as the matrix panel 30, a dielectric film may be formed on the surface side as a protective layer, or the TFT 33 may be formed by a thin film technique on a cylindrical base material. .
In this embodiment, the method of providing the storage capacitor 35 for each pixel is shown. However, writing is performed on the pixel electrode in the vicinity of the facing region between the image carrier 20 and the developing device 41 (the ON voltage is applied to the gate side). If this is done, it is possible to form a toner image by utilizing the capacitance of the TFT 33 itself even when the storage capacitor 35 is not provided.

  Further, in the present embodiment, the full-color correspondence is shown in which the number of image carriers 20 is four, but the number of image carriers 20 is not limited to this, and for example, special color toner or transparent toner is applied. It is safe to add. Furthermore, in the present embodiment, a color-compatible image forming apparatus has been described, but it is needless to say that a monochrome-compatible image forming apparatus may be used. In particular, in the present embodiment, the image carrier 20 is rotated. However, the image carrier 20 is provided in a flat plate shape, and at least one of the image carrier 20 and the developing device 41 or the transfer device 43 is moved. In addition, although the speed at which image formation is repeated may be reduced as compared with the case where the image carrier 20 is a rotating body, an image similar to that of the rotating body can be formed. In this case, the cleaning member 42 may be moved similarly to the developing device 41 or the transfer device 43.

In this embodiment, as described above, the feature extraction unit has extracted the high density region and the low concentration region. However, the feature extraction unit performs the following extraction at the time of transfer or cleaning. You may make it perform.
For example, FIGS. 17A and 17B show modified embodiment 1 at the time of transfer, where FIG. 17A shows a flow at the time of transfer, and FIG. 17B shows a transfer electric field at the time of transfer. That is, the feature extraction unit extracts whether the image is an image area or a background area, and if there is a background area, a normal transfer electric field is applied to the image area and toner is applied to the background area. An electric field that prevents transfer of toner charged to a polarity different from the original polarity (reverse polarity toner) may be applied.
This is intended to prevent the toner from being fogged onto the background area. That is, in many cases where fog becomes a problem, reverse polarity toner is generated in the toner (or developer) due to deterioration of the toner (or developer), environmental fluctuation, and the like, and this reverse polarity toner is transferred to the background area. It is to adhere. Therefore, it is possible to prevent fogging by applying a transfer voltage to the pixel electrode so that a transfer electric field that prevents adhesion of reverse polarity toner to the background area acts. Furthermore, with such a potential configuration, an electric field in the direction of confining the toner in the image area to the image area acts from the potential relationship between the image area and the background area, and the toner scatters. It also works effectively to prevent this. On the other hand, in the comparative model, the relationship between the photosensitive member potential in the background area and the transfer voltage is affected by an electric field in a direction that hinders the transfer of reverse polarity toner, but the adhesion between the toner and the intermediate transfer belt is high. For this reason, it is difficult to say that the electric field is sufficient to prevent fogging.

18 (a) and 18 (b) show a deformation mode 2 at the time of transfer, (a) shows a flow at the time of transfer, and (b) shows a transfer electric field at the time of transfer. In other words, the feature extraction unit extracts whether the image is an image part region or a background part region, and if there is a background part region, a normal transfer electric field is applied to the image part region and the background part region The transfer electric field may be substantially zero.
This is intended to suppress the occurrence of ghosts in which this charging pattern affects the next image due to the transfer current charged through the intermediate transfer belt by the transfer current during transfer. That is, usually, the image area and the background area are more likely to be charged due to the high insulation of the toner. Therefore, by applying a voltage that causes the transfer electric field to be substantially zero to the pixel electrode in the background area, the influence of charging in the background area can be removed. On the other hand, in the comparative model, since the transfer electric field is applied to the entire image including the background area, such ghost prevention cannot be performed.

Further, FIGS. 19A and 19B show modified embodiment 3 at the time of transfer. FIG. 19A shows a flow at the time of transfer, and FIG. 19B shows a transfer electric field at the time of transfer. That is, the feature extraction unit may extract whether the image is a line image area or a solid image area, and the transfer electric field acting on the line image area may be made larger than the transfer electric field acting on the solid image area.
This is because the line image area is difficult to transfer because of its strong adhesion to the image carrier, but a high voltage is applied to the pixel electrode so that the transfer electric field in the line image area is larger than the transfer electric field in the solid image area. Thus, the transfer rate of the line image area can be improved, and the fine line reproducibility as an image can be improved.

Moreover, as an example applied at the time of cleaning, FIGS. 20 (a) and 20 (b) show a modified form at the time of cleaning, (a) shows a flow at the time of cleaning, and (b) shows a cleaning electric field at the time of cleaning. Yes. That is, the feature extraction unit extracts whether the image is an image part region or a background part region, and if there is a background part region, a normal cleaning electric field is applied to the image part region and toner is applied to the background part region. An electric field in the direction of cleaning toner charged to a polarity different from the original polarity (reverse polarity toner) may be applied.
Usually, toner (residual toner) adhering to the background area is often charged with a reverse polarity. Therefore, if a reverse cleaning electric field is applied to the background area in this way, the background area Can be effectively cleaned. On the other hand, in the comparative model, it was necessary to align the charging polarity of the toner with a charger before cleaning, but the charging device has a low ability to adjust the charging polarity in this way, and it is difficult to obtain sufficient cleaning efficiency. It was. In addition, the provision of such a charger itself has been a major negative factor in terms of its size and cost, and has prevented its spread.

  Furthermore, by using a pixel electrode, effective cleaning is performed not only in the case of cleaning using such an electric field (electrostatic suction) but also in the case of using, for example, a blade method using mechanical force. Is possible. In this case, the polarity of the cleaning voltage applied to the pixel electrode is set to the same polarity as that of the toner, that is, the image area is positive and the background area is reverse polarity, and the toner charge is repelled to the pixel electrode. The adhesion force of the toner to the holding body is reduced. As a result, the cleaning efficiency can be improved and the contact pressure between the image carrier and the cleaning member can be weakened, so that the image carrier and the cleaning member can be prevented from being worn.

Further, FIG. 21 shows a pixel electrode driving device 80 that is partially different from the pixel electrode driving device 80 described in the above embodiment. Even if such a pixel electrode driving device 80 is used, comparison is made. Compared with the model (for example, shown in FIG. 23), the image quality can be improved.
In this figure, the difference from the pixel electrode driving device 80 shown in FIG. 8 is that here, binarization conversion that simply binarizes the image data from the memory unit 91 without using the feature extraction units 96 and 99. The portions 102 and 103 are provided in the transfer control unit 95 and the cleaning control unit 98. That is, for the pixel electrode 34, the transfer voltage is set to a level of “1” or “0” during transfer, or the cleaning voltage is set to a level of “1” during cleaning, or “0”. The choice of whether to be the level of is made. Even in this case, at the time of transfer or cleaning, the transfer electric field or the cleaning electric field effectively acts between the intermediate transfer belt 50 and the pixel electrode 34 or between the cleaning member 42 and the pixel electrode 34, which is favorable. An image is formed.

Embodiment 2
FIG. 22 shows a schematic configuration of the image forming apparatus of the second embodiment. The image forming apparatus according to the present embodiment is different from the image forming apparatus according to the first embodiment in that a plurality of developing devices are provided around one image carrier.

  That is, similar to the image carrier 20 of the first embodiment, the image carrier 200 of the present embodiment also has a pixel electrode group configured in a matrix, and a static voltage can be applied by applying a signal voltage to the pixel electrode. An electrostatic latent image can be formed. Around the image holding body 200, for example, developing units 410 (410a to 410d) corresponding to the respective colors of yellow (Y), magenta (M), cyan (C), and black (BK) are arranged. The electrostatic latent image formed on the body 200 is developed by each developing device 410 to form a toner image. A transfer unit 430 is provided around the image carrier 200 to transfer the toner image formed on the image carrier 200 onto the recording material between the developing unit 410d and the developing unit 410a. A cleaning member 420 is provided between the transfer device 430 and the developing device 410a.

  In such an image forming apparatus, first, a latent image corresponding to a yellow image signal is formed on the image carrier 200 before reaching the developing area of the developing device 410a. After the electrostatic latent image on the image carrier 200 is developed by the developing device 410a, a latent image corresponding to the magenta image signal is formed before reaching the developing area of the next developing device 410b. Development is performed at 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 200 that has passed through the developing device 410d. become.

The toner images multiplexed on the image carrier 200 are transferred onto a recording material at a transfer portion where the image carrier 200 and the transfer device 430 face each other. At this time, a transfer voltage corresponding to the image signal is applied to the pixel electrode of the image carrier 200 that has passed through the developing device 410d until reaching the transfer site, while the transfer device 430 is grounded and transferred between the two. Good transfer is performed by the electric field. At this time, it goes without saying that the transfer voltage corresponding to the image signal is a voltage corresponding to the multiplexed toner image.
Then, a cleaning voltage corresponding to an image signal is applied to the pixel electrode of the image carrier 200 after the transfer until the cleaning member 420 is reached, and the cleaning member 420 is grounded, so that an effective cleaning electric field is established therebetween. And the residual toner on the image carrier 200 is cleaned.

  As described above, the method of multiplexing the color toner images on the image carrier 200 can reduce the number of components, and is advantageous for miniaturization and cost reduction. Here, the color-compatible image forming apparatus has been described, but it is needless to say that it may be a monochrome-compatible image forming apparatus.

Example 1
In this embodiment, in order to confirm the effectiveness of the image forming method of the present case, the effect at the time of transfer when the image density is different is evaluated. Usually, when the low density area with low density and the high density area with high density coexist in the pre-transfer image, the low density area and the high density area have different transfer rates for the applied transfer voltage. It shows a changing tendency.
FIG. 24 shows the relationship between the transfer voltage applied in the low density region and the high density region and the transfer rate. In the low density region, the transfer rate tends to be higher at the same transfer voltage than in the high density region. Is shown. However, the relationship between the two is reversed at a certain transfer voltage, and the transfer rate is higher in the high density region than in the low density region. In other words, in order to transfer the low density region, it is necessary to reduce the transfer voltage. If it is too large, good transfer cannot be performed due to discharge (discharge mark is generated), and the transfer rate is also reduced (discharge discharge region in the figure). ). Moreover, when too small, it will lead to generation | occurrence | production of density nonuniformity (density nonuniformity area | region in a figure). On the other hand, in the high density region, it is necessary to increase the transfer voltage in order to perform good transfer. If it is too small, density unevenness will occur (density unevenness region in the figure). Furthermore, if the same transfer voltage is applied to the low density region and the high density region, the color reproducibility in the color image tends to be lowered.
Therefore, when a low density region and a high density region coexist, it is difficult to apply a transfer voltage that satisfies the relationship between the two.
In contrast, in this example, since the transfer voltage applied to each pixel can be made different, transfer can be performed according to the amount of toner adhering to the pixel, and reproduction of the low density region and the high density region can be performed. The performance is greatly improved. In the figure, DMA is an abbreviation of development toner area.

◎ Comparative Example 1
In this example, since there is no discharge for charging the image carrier, the structure of a comparative model using the photoconductor of FIG. 23 was used as a comparative example, and it was confirmed how the photoconductor was abraded by discharge. In the evaluation, an AC voltage was applied to the charging roll, the frequency and the peak voltage were changed, and the amount of wear of the photoconductor itself after a predetermined time was measured.
The results showed a tendency for the amount of wear to increase in proportion to the AC voltage.
From this, it has been found that the discharge amount increases by increasing the AC voltage, whereby the surface of the photoreceptor tends to be accelerated by the discharge. That is, the photoreceptor wear is promoted by the discharge, which results in promoting the roughening of the photoreceptor surface. For this reason, the toner adhesion to the photosensitive member is greatly changed or the cleaning property is lowered, and the resulting image quality tends to be lowered.
On the other hand, in this example, since such charging itself is not performed, such image quality deterioration can be suppressed.

◎ Comparative Example 2
Next, in order to confirm the relationship between the amount of discharge generated and the amount of discharge products generated on the photosensitive member, the same configuration as in Comparative Example 1 was used, and conditions under which many discharges were generated (AC voltage was large). When the discharge condition is low (AC voltage is small), the amount of discharge product deposited on the surface of the photoreceptor was measured as the detected amount of ammonium ions by ion chromatography with respect to the image forming cycle.
The result shows that the more the discharge is, the more the ammonium ion tends to increase, which means that the amount of discharge products deposited on the surface of the photoreceptor increases in proportion to the discharge amount. ing. Such a discharge product inhibits uniform charging at the time of charging, lowers resistance due to moisture absorption, and causes image quality defects such as image flow.
In this example, since it is not necessary to worry about the discharge with respect to such a discharge product, deposition of the discharge product on the image carrier may be almost ignored.

◎ Comparative Example 3
Further, the same configuration as in Comparative Example 1 was used, and the frictional force between the photosensitive member and the blade when the blade was used as a cleaning member due to the discharge product was evaluated as the rotational torque of the photosensitive member. A comparison was made between a case where white paper was passed as the recording material and an AC voltage was applied to the charging roll as a discharge state, and a case where the AC voltage was zero.
As a result, it was found that the torque (static torque) tended to increase greatly in a short run when the discharge was large, whereas the increase in torque tended to be suppressed small when the discharge was small. From this, it has been found that the surface of the photoreceptor is roughened by the discharge, and the blade is easily caught and the torque is increased.
Therefore, as in this example, when there is no discharge, the rotational torque is also stable over a long period of time. For example, the occurrence of banding can be suppressed, and stable image quality can be maintained over a long period of time. become.

1 is an explanatory diagram showing an overview of an image forming apparatus according to an embodiment model embodying the present invention. (A) is a process block diagram of an embodiment model, (b) shows a mimetic diagram of a process. 1 is an explanatory diagram illustrating 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. 2 is an explanatory diagram illustrating a pixel electrode driving device according to Embodiment 1. FIG. FIG. 3 is an explanatory diagram showing a gradation method in the first embodiment. FIG. 2 is an explanatory diagram illustrating the action of a latent image voltage as a specific example of the first embodiment, where (a) is a signal obtained by performing gradation conversion on an image signal, and (b) is a latent image as a generation signal for setting a latent image voltage. A control signal generated by the control signal generator, (c) shows a state in which the set latent image voltage is assigned to the pixel electrode. It is explanatory drawing which shows the effect | action of a transfer voltage, (a) is the control signal produced | generated in the transfer control signal production | generation part as a production | generation signal for a transfer voltage setting, (b) shows a transfer voltage waveform. (A)-(e) is explanatory drawing which shows the effect | action in an image formation process. (A) shows the potential distribution that prevents toner scattering during transfer in Embodiment 1, and (b) is an explanatory diagram showing the potential distribution in the comparative model. (A) shows the transfer electric field at the time of transfer of Embodiment 1, and (b) is an explanatory view showing the transfer electric field in the comparative model. FIG. 5A is a diagram illustrating a transfer state when feature extraction at the time of transfer according to the first embodiment is performed, FIG. 9A is an explanatory diagram illustrating a flow at the time of transfer, and FIG. The cleaning state at the time of performing the feature extraction at the time of cleaning of Embodiment 1 is shown, (a) is the flow at the time of cleaning, (b) is explanatory drawing which shows the cleaning electric field at the time of cleaning. FIG. 2 shows a first modified example at the time of transfer, (a) is a flow at the time of transfer, and (b) is an explanatory view showing a transfer electric field at the time of transfer. FIG. 9 shows a second modified example at the time of transfer, (a) is a flow at the time of transfer, and (b) is an explanatory view showing a transfer electric field at the time of transfer. FIG. 9 shows a third modified example at the time of transfer, (a) is a flow at the time of transfer, and (b) is an explanatory view showing a transfer electric field at the time of transfer. The deformation | transformation form at the time of cleaning is shown, (a) is the flow at the time of cleaning, (b) is explanatory drawing which shows the cleaning electric field at the time of cleaning. It is explanatory drawing which shows the modification of a pixel electrode drive device. FIG. 6 is an explanatory diagram illustrating an overview of an image forming apparatus according to a second embodiment. 1 is an explanatory diagram showing an outline of a normal image forming apparatus as a comparison model. FIG. 3 is a graph showing the results of Example 1.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Image holding body, 1a ... Support body, 1b ... Pixel electrode, 2 ... Latent image formation means, 3 ... Development means, 4 ... Transfer means, 5 ... Transfer medium, 6 ... Transfer voltage adjustment means, 7 ... Feature extraction part , 8 ... transfer control signal generation means, 9 ... transfer voltage setting means, 10 ... cleaning means, 10a ... cleaning member, 11 ... cleaning voltage adjustment means, 12 ... feature extraction unit, 13 ... cleaning control signal generation means, 14 ... cleaning Voltage setting means

Claims (12)

An image carrier having a movable support and pixel electrodes supported by the support and arranged vertically and horizontally in pixel units;
Latent image forming means for forming a latent image on the image carrier by applying a latent image voltage based on an image signal to each of the pixel electrodes;
Developing means for developing the latent image formed by the latent image forming means with toner;
A transfer unit that applies a transfer voltage based on an image signal to each of the pixel electrodes to cause a transfer electric field to be transferred to a transfer medium on the toner image developed by the developing unit ;
A transfer voltage adjusting means capable of adjusting a transfer voltage to be applied to the transfer means,
The transfer voltage adjusting unit generates a feature extraction unit that extracts an image feature from the image signal and a transfer control signal for determining a transfer voltage based on the image feature extracted by the feature extraction unit. An image forming apparatus comprising: a transfer control signal generation unit; and a transfer voltage setting unit that sets a transfer voltage determined by the transfer control signal generation unit . The image forming apparatus according to claim 1 .
The feature extraction unit extracts a high density area that is a high image density area or a low density area that is a low image density area,
The transfer control signal generating means generates the transfer control signal so that the transfer electric field acting on the high concentration region is larger than the transfer electric field acting on the low concentration region based on the determination result of the feature extraction unit. An image forming apparatus. The image forming apparatus according to claim 2 .
In the transfer control signal generating means, when the high density region and the low density region are adjacent to each other, the transfer electric field acting on the boundary portion adjacent to the high density region of the low density region becomes larger than that of the other low density regions. An image forming apparatus characterized in that a transfer control signal is generated as described above. The image forming apparatus according to claim 1 .
The feature extraction unit extracts whether or not the background part region is a background part other than the image part,
The transfer control signal generation means generates a transfer control signal based on the extraction result of the feature extraction unit so that the direction of the transfer electric field acting on the background area is different from the direction of the transfer electric field acting on the image area. An image forming apparatus characterized by being configured as described above. The image forming apparatus according to claim 1 .
The feature extraction unit extracts whether or not the background part region is a background part other than the image part,
The image forming apparatus, wherein the transfer control signal generating means generates a transfer control signal so that a transfer electric field acting on a background area is substantially zero based on an extraction result of the feature extraction unit. . The image forming apparatus according to claim 1 .
The feature extraction unit extracts whether a line image area where a line image is formed or a solid image area where a solid image is formed;
The transfer control signal generation means generates the transfer control signal so that the transfer electric field acting on the line image area is larger than the transfer electric field acting on the solid image area based on the extraction result of the feature extraction unit. An image forming apparatus. An image carrier having a movable support and pixel electrodes supported by the support and arranged vertically and horizontally in pixel units;
Latent image forming means for forming a latent image on the image carrier by applying a latent image voltage based on an image signal to each of the pixel electrodes;
Developing means for developing the latent image formed by the latent image forming means with toner;
A transfer unit that applies a transfer voltage based on an image signal to each of the pixel electrodes to cause a transfer electric field to be transferred to a transfer medium on the toner image developed by the developing unit;
Image forming, characterized in that it comprises a cleaning means for applying a cleaning electric field for cleaning the surface to the surface of the image holding member having been subjected to transfer by applying the cleaning voltage based on the image signal s to the pixel electrode husband apparatus. An image carrier having a movable support and pixel electrodes supported by the support and arranged vertically and horizontally in pixel units;
Latent image forming means for forming a latent image on the image carrier by applying a latent image voltage based on an image signal to each of the pixel electrodes;
Developing means for developing the latent image formed by the latent image forming means with toner;
A transfer unit that applies a transfer electric field to the image carrier and transfers the toner image on the image carrier developed by the developing unit to a transfer medium;
Image forming, characterized in that it comprises a cleaning means for applying a cleaning electric field for cleaning the surface to the surface of the image holding member having been subjected to transfer by applying the cleaning voltage based on the image signal s to the pixel electrode husband apparatus. The image forming apparatus according to claim 7 or 8 ,
Cleaning voltage to be applied to said cleaning means comprises a cleaning voltage adjusting means capable of adjusting,
The cleaning voltage adjusting unit generates a cleaning control signal for generating a cleaning control signal for determining a cleaning voltage to be applied to each pixel electrode in a direction in which the toner is peeled off from the pixel electrode, and generates the cleaning control signal. An image forming apparatus comprising: a cleaning voltage setting unit that sets a cleaning voltage determined by the unit. The image forming apparatus according to claim 7 or 8 ,
Cleaning voltage to be applied to said cleaning means comprises a cleaning voltage adjusting means capable of adjusting,
The cleaning voltage adjusting unit generates a feature extraction unit that extracts an image feature from the image signal, and a cleaning control signal for determining a cleaning voltage based on the image feature extracted by the feature extraction unit. An image forming apparatus comprising: a cleaning control signal generation unit; and a cleaning voltage setting unit that sets a cleaning voltage determined by the cleaning control signal generation unit. The image forming apparatus according to claim 10 .
The feature extraction unit extracts a high density area that is a high image density area or a low density area that is a low image density area,
The cleaning control signal generation means generates the cleaning control signal so that the cleaning electric field acting on the high concentration region is larger than the cleaning electric field acting on the low concentration region based on the extraction result of the feature extraction unit. An image forming apparatus. The image forming apparatus according to claim 10 .
The feature extraction unit extracts whether or not the background part region is a background part other than the image part,
The cleaning control signal generation unit generates a cleaning control signal based on the extraction result of the feature extraction unit so that the direction of the cleaning electric field acting on the background area is different from the direction of the cleaning electric field acting on the image area. An image forming apparatus characterized by being configured as described above.

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