JP2009223037A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain excellent image quality and stabilize the image quality over a long period of time, in an image forming system which multiplexes multi-color toner images on an image carrier having pixel electrodes arranged in a matrix, compared with a system using no pixel electrode. <P>SOLUTION: This image forming device includes: an image carrier 1 which has pixel electrodes 1b arranged in a matrix; an image write means 2 to write each color latent image pattern expressed by the latent image potential of each pixel electrode 1b on the image carrier 1 by applying each color latent image voltage based on each color image signal to each pixel electrode 1b; a plurality of developing means 3 (3a-3d) to visualize each color latent image pattern by using the corresponding color toner at the developing position facing the image carrier 1; and a latent image write controller 4 to decide each color latent image voltage based on the image signal in consideration of the voltage compensation based on the existing color toner image already formed on each pixel electrode 1b, when writing each color latent image pattern by using the image write means 2. <P>COPYRIGHT: (C)2010,JPO&INPIT

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). In Patent Document 1, thin film transistors (TFTs) that switch pixel electrodes are formed in a matrix, and storage capacitors are provided in the respective TFTs, so that stable development is performed by the charge storage effect in the storage capacitors. A device has been proposed. 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 no pixel electrode is used in an image forming method in which multicolor toner images are multiplexed on an image carrier having pixel electrodes arranged in a matrix in the vertical and horizontal directions in pixel units. Compared to the system, it is to obtain a good image quality and to stabilize the image quality over a long period of time.

  According to the first aspect of the present invention, the movable support and the support supported by the support are arranged vertically and horizontally with the direction along the moving direction of the support being the sub-scanning direction and the direction orthogonal to the direction being the main scanning direction. Each color latent image voltage based on an image signal for each color is applied to the image carrier having pixel electrodes and each color electrode, and each color latent image pattern represented by the latent image potential for each pixel electrode is applied to the image carrier. An image writing means for writing and the image holding member are arranged so as to face the image holding member along the moving direction of the image holding member, and each color latent image pattern is visualized with a corresponding color toner at a developing position facing the image holding member. In writing each color latent image pattern by a plurality of developing means and image writing means, each color latent image based on the image signal for each color is taken into consideration in consideration of voltage correction based on the presence of a color toner image already formed for each pixel electrode. After determining the image voltage, the image writing means An image forming apparatus and a latent image writing control means Gosuru.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the latent image writing control means is a magnitude obtained by accumulating the magnitude of the image signal up to the previous color and the magnitude of the image signal of the color. This is an image forming apparatus that determines each color latent image voltage so as to be equal.
According to a third aspect of the present invention, in the image forming apparatus according to the first aspect, in which the image holding member is a rotating member, the circumference of the image holding member is L0, and the minimum arc length between adjacent developing positions is set. This is an image forming apparatus in which the scanning speed S in the sub-scanning direction is set so as to satisfy the relationship S ≧ (L0 / L1) V, where L1 and the peripheral speed of the image carrier are V.
The invention according to claim 4 is the image forming apparatus according to claim 1, wherein the latent image writing means is configured to apply a latent image voltage to the pixel electrode using a thin film transistor. .

According to a fifth aspect of the present invention, in the image forming apparatus according to the first aspect, the developing unit is disposed opposite to the image holding body and holds the charged conductive toner to the developing position and conveys the toner holding body, A charge injection member disposed opposite to the toner holding body on a side different from the image holding body, and an uncharged electric field is applied between the charge injection member and the toner holding body by applying a charge injection electric field. An image forming apparatus includes charge injection means for injecting charge into conductive toner.
According to a sixth aspect of the present invention, in the image forming apparatus according to the fifth aspect, the toner holding member is rotatably provided facing the image holding member, and holds and conveys the conductive toner to the developing position. A developing toner holder that develops the latent image on the holder with conductive toner, and is provided to be opposed to the developing toner holder and can be rotated at a higher rotational speed than the developing toner holder. An intermediate toner holding body for holding and transporting the conductive toner charged by the charge injection means until reaching a position away from the developing position, and is provided between the developing toner holding body and the intermediate toner holding body. In the image forming apparatus, the moving electric field forming unit applies a moving electric field for moving the conductive toner from the intermediate toner holding member toward the developing toner holding member.

The invention according to claim 7 is the image forming apparatus according to claim 5, wherein the image holding member and the toner holding member are arranged in a non-contact manner.
According to an eighth aspect of the present invention, in the image forming apparatus according to the fifth or sixth aspect, the charge injecting means charges the conductive toner by sliding the conductive toner while the charge injection electric field is applied. The image forming apparatus is configured to perform injection.
According to a ninth aspect of the present invention, in the image forming apparatus according to the eighth aspect, the conductive toner changes to a high resistance so as to maintain the charge retention of the conductive toner at the development position, and a charge injection electric field. In the image forming apparatus, the image forming apparatus changes to a low resistance so as to facilitate the charge injection of the conductive toner.

  According to the tenth aspect of the present invention, the movable support and the support supported by the support are arranged vertically and horizontally with the direction along the moving direction of the support being the sub-scanning direction and the direction orthogonal to the direction being the main scanning direction. Each color latent image voltage based on an image signal for each color is applied to the image carrier having pixel electrodes and each color electrode, and each color latent image pattern represented by the latent image potential for each pixel electrode is applied to the image carrier. An image writing means for writing and the image holding member are arranged so as to face the image holding member along the moving direction of the image holding member, and each color latent image pattern is visualized with a corresponding color toner at a developing position facing the image holding member. In writing each color latent image pattern by a plurality of developing means and image writing means, each color latent image based on the image signal for each color is taken into consideration in consideration of voltage correction based on the presence of a color toner image already formed for each pixel electrode. Image writing means after determining image voltage A latent image writing control means for controlling an image forming apparatus including a transfer unit for transferring the transfer medium the color toner image formed on the image holding member by said plurality of developing means.

According to an eleventh aspect of the present invention, in the image forming apparatus according to the tenth aspect, the transfer unit is disposed to face the image carrier, and a predetermined transfer voltage is applied to the image carrier and a predetermined amount is provided between the transfer unit and the image carrier. An image forming apparatus having a transfer member for applying a transfer electric field.
According to a twelfth aspect of the present invention, in the image forming apparatus according to the tenth aspect, in addition to writing the latent image pattern, the image writing unit performs transfer based on each color toner image already formed for each pixel electrode. A voltage is applied, and a transfer image pattern as a transfer potential change for each pixel electrode by the transfer voltage is written on the image holding body, and the transfer means includes the image writing means for writing the transfer image pattern, and image holding An image forming apparatus including a counter electrode member disposed opposite to a body and applying a transfer electric field corresponding to a transfer image pattern by an image writing unit between each pixel electrode.
According to a thirteenth aspect of the present invention, in the image forming apparatus according to the twelfth aspect, each color toner image already formed for each pixel electrode by the plurality of developing units when the transfer image pattern is written by the image writing unit. The image forming apparatus includes a transfer image writing control unit that controls the image writing unit after determining a transfer voltage in consideration of the above.

  According to a fourteenth aspect of the invention, in the image forming apparatus according to the twelfth aspect, in which the image holding member is a rotating member, the circumference of the image holding member is L0, and the minimum arc length between adjacent development positions is set. L1, the length of the arc from the development position of the final color to the transfer position, which is the facing portion between the facing member and the image carrier, is L2, and the circumferential speed of the image carrier is V, the scanning speed in the sub-scanning direction In the image forming apparatus, S is set so as to satisfy the relationship of S ≧ (L0 / L1) V and S ≧ (L0 / L2) V.

According to the first aspect of the present invention, in the image forming method of multiplexing the multi-color toner images on the image carrier having the pixel electrodes arranged in a matrix in the vertical and horizontal directions in pixel units, Compared with a method that does not use it, it is possible to obtain a good image quality and to stabilize the image quality over a long period of time.
According to the second aspect of the invention, the second and subsequent toners can be multiplexed more favorably than those not having this configuration.
According to the third aspect of the present invention, the latent image voltage at the time of development is stabilized and toner multiplexing is performed by performing at least one sub-scan even at the minimum development position interval as compared with the case without this configuration. Will be made surely.
According to the fourth aspect of the invention, it is possible to stably apply a voltage to the pixel electrode as compared with the case without this configuration, and a desired voltage can be selectively and easily applied to the pixel electrode. Will be able to.

According to the fifth aspect of the present invention, the use of the conductive toner injected with a charge injection electric field can suppress environmental deterioration and deterioration over time, compared to the apparatus without this configuration. Miniaturization can be achieved.
According to the sixth aspect of the present invention, as compared with the case without the present configuration, a sufficiently high image density can be secured and environmental deterioration and deterioration with time can be suppressed while using conductive toner injected with a charge injection electric field. In addition, the apparatus can be miniaturized.
According to the seventh aspect of the present invention, it is possible to perform good multiplexing without damaging the preceding toner image at the time of development as compared with the case without this configuration.
According to the eighth aspect of the present invention, uniform and stable charge injection with respect to the conductive toner can be performed as compared with the case without this configuration.
According to the ninth aspect of the present invention, the charge retaining property is kept good at the developing position as compared with the case not having this configuration, while the charge injection is efficiently performed in the electric field region of charge injection. .

According to the tenth aspect of the present invention, in the image forming method of multiplexing the multi-color toner images on the image carrier having the pixel electrodes arranged in a matrix in the vertical and horizontal directions in pixel units, the pixel electrodes are Compared to a method that does not use it, it is possible to obtain a good image quality as a transfer image and to stabilize the image quality over a long period of time.
According to the invention of claim 11, specific transfer is performed by the transfer member.
According to the twelfth aspect of the present invention, transfer using the pixel electrode becomes possible, and the spread of the transfer electric field at the time of transfer can be suppressed, and the image quality is improved.
According to the thirteenth aspect of the present invention, compared to a case without this configuration, a transfer electric field can be formed in accordance with the toner image formed on the pixel electrode, and transfer with high image quality becomes possible.
According to the fourteenth aspect of the invention, the latent image voltage at the time of development is stabilized and toner multiplexing is ensured, and the transfer voltage at the time of transfer is set to the pixel electrode as compared with the case without this configuration. The transfer performance can be stabilized.

First, an outline of an embodiment model to which the present invention is applied will be described.
Outline of Embodiment Model FIGS. 1A and 1B show an outline of an image forming apparatus according to an embodiment model embodying the present invention. In the figure, as a representative model of the image forming apparatus, a movable support 1a and a direction supported by the support 1a and along the moving direction of the support 1a are the sub-scanning direction, and the direction orthogonal to the direction is the same. An image carrier 1 having pixel electrodes 1b arranged vertically and horizontally in the main scanning direction, and each color latent image voltage based on an image signal for each color is applied to each pixel electrode 1b, and the pixel electrode 1b is applied to the image carrier 1. Image writing means 2 for writing each color latent image pattern represented by each latent image potential, and a development position that is disposed opposite to the image carrier 1 along the moving direction of the image carrier 1 and faces the image carrier 1 In writing each color latent image pattern by the plurality of developing means 3 (3a to 3d) for visualizing each color latent image pattern with the corresponding color toner and the image writing means 2, each pixel electrode 1b has already been In the presence of the formed color toner image And a latent image writing control means 4 for controlling the image writing means 2 over the designated colors latent image voltage based on the image signal for each color in consideration of the voltage correction amount that brute.

  Here, the shape of the support 1a is not particularly limited as long as it can move the pixel electrode 1b and the like. However, from the viewpoint of downsizing the apparatus, 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. The number of the developing means 3 may be plural. For example, the developing means 3 may be provided with four-color modes for full color, special colors, or transparent colors. But it doesn't matter.

  Further, when writing each color latent image by the image writing means 2, the voltage correction amount considered by the latent image writing control means 4 is the number of colors before the previous color when developing each color by the plurality of developing means 3. It means a voltage component added as a latent image voltage in order to favorably attach a new color toner on the toner image formed on the pixel electrode 1b.

Next, in order to deepen the understanding of the present embodiment model, a so-called IOI (image on image) method in which multicolor toner images are superimposed on a photoreceptor in an electrophotographic method will be described as a comparative model.
As shown in FIG. 23, in this comparative model, a charging device 210 (210a to 210d) that charges the surface of the photoconductor 200 to form a four-color toner image on one photoconductor 200 (corresponding to an image carrier). ), An exposure device 220 (220a to 220d) that exposes the charged photoconductor 200 to form a latent image, and a developing device 230 (230a) that develops the formed latent image with toner to make the latent image visible. ˜230d), the four combinations are sequentially arranged along the rotation direction of the photosensitive member 200. In the figure, reference numeral 240 denotes a transfer device that collectively transfers the toner images multiplexed on the photoconductor 200 onto a recording material, and reference numeral 250 denotes a cleaning device that cleans the photoconductor 200 after transfer. .

In such an IOI method, in the process for the second and subsequent colors, a latent image is formed by charging and exposing the toner layer up to the previous color formed on the photoreceptor 200, and then the toner layer up to the previous color is applied to the toner layer. Since it is necessary to develop the next color so as to overlap, there is a problem that light scattering and absorption occur in the existing toner layer formed on the photoconductor 200 and the image quality of the next color is likely to be deteriorated. In addition, since the toner passes directly under the charging device 210, the charging device 210 itself is easily soiled. Further, since the toner receives a strong history by the charging device 210, a transfer failure is likely to occur during transfer in the transfer device 240. There's a problem.
On the other hand, the charging device 210 is not limited to a contact type that contacts the photoconductor 200, and the charging device 210, the exposure device 220, and the developing device 230 all need to be disposed around the photoconductor 200. There is a possibility that the device configuration becomes large.

  Further, since the charging device 210 is used, the charging potential on the side of the photoconductor 200 is also likely to vary, and due to such variation, image quality deterioration such as density unevenness, color unevenness, and streaks is not caused, and development with a desired toner amount is not performed. There is also a possibility that the color reproducibility is lowered. Furthermore, the charging device 210 is contaminated with toner, and the desired charging cannot be performed, or the generation of a discharge product due to the discharge of the charging device 210 (the discharge of the charging device 210 itself or the gap with the photosensitive member 200) is photosensitive. There is a possibility that the body 200 may be altered or the cleaning performance of the cleaning device 250 may be reduced.

  In contrast to such a comparison model, in the present embodiment model, as shown in FIGS. 1A and 1B, an image holding body 1 provided with pixel electrodes 1b arranged vertically and horizontally for each pixel is used. In particular, as the latent image voltage applied to the pixel electrode 1b, each color latent image voltage based on the image signal is applied in consideration of a voltage correction based on the presence of toner already formed on the pixel electrode 1b. Therefore, the charging device 210 and the exposure device 220 as in the comparative model shown in FIG. 23 are not required, and a predetermined latent image voltage is applied to each pixel electrode 1b of the image carrier 1, so that the development position Then, a desired toner amount can be attached to the pixel electrode 1b. Therefore, it is possible to improve image quality and obtain stable image quality over a long period of time.

  From the viewpoint of improving the color reproducibility for the second and subsequent colors, the latent image writing control unit 4 accumulates the magnitude of the image signal up to the previous color and the magnitude of the image signal of that color. It is preferable to determine each color latent image voltage so that According to this, for example, a larger latent image voltage can be applied to the pixel electrode 1b to which the toner has adhered by the previous color, and the toner has already adhered to the pixel electrode 1b at the time of subsequent development by the developing means 3. Even in such a state, desired development can be performed from above, and the image quality including color reproducibility is improved by good toner adhesion.

  Further, in the aspect in which the image carrier 1 is a rotating body, from the viewpoint of good development by the developing unit 3 during development by the developing unit 3, the circumferential length of the image carrier 1 is L0, and the adjacent development. When the length of the minimum arc between the positions is L1 and the peripheral speed of the image carrier 1 is V, the scanning speed S in the sub-scanning direction is set so as to satisfy the relationship of S ≧ (L0 / L1) V. It is preferable. As a result, when developing is performed by the developing unit 3, the latent image voltage corresponding to each color is surely applied to the pixel electrode 1b by the development position of each color, and good development at each development position is achieved. Will be made.

  In the present embodiment model, from the viewpoint of stably applying a voltage to the pixel electrode 1b, the image writing unit 2 is configured to apply a voltage to the pixel electrode 1b using a thin film transistor. Preferably, by using a thin film transistor as a switching element in this way, a large number of switching elements can be formed using a normal thin film technique, and stable switching performance can be secured.

  Further, from the viewpoint of improving the developing performance, the developing unit 3 includes a toner holding member that is disposed opposite to the image holding member 1 and holds and conveys the charged conductive toner to the developing position, and an image holding member of the toner holding member. A charge injection means for injecting charges into uncharged conductive toner by applying a charge injection electric field between the charge injection member and the toner holding member. It is preferable to comprise.

Furthermore, from the viewpoint of improving the toner density in the developing means 3, the toner holder is provided so as to be rotatable facing the image holder 1 and holds and conveys the conductive toner to the developing position. A developing toner holder that develops the latent image on the image holder 1 with conductive toner, and a developing toner holder that is opposed to the developing toner holder and is rotatable at a higher rotational speed than the developing toner holder. An intermediate toner holder for holding and transporting the conductive toner charged by the charge injection means until reaching a position away from the development position of the holder, and between the developing toner holder and the intermediate toner holder It is preferable to apply a moving electric field for moving the conductive toner from the intermediate toner holding member toward the developing toner holding member by the provided moving electric field forming means.
Further, from the viewpoint of satisfactorily developing with the plurality of developing units 3, it is preferable that the image carrier 1 and the toner carrier are arranged in a non-contact manner.

From the standpoint of uniform and stable charge injection when using conductive toner as the toner, the charge injection means rubs the conductive toner while sandwiching the conductive toner while applying a charge injection electric field. It is preferable to perform charge injection.
Further, the conductive toner changes to a high resistance so as to maintain the charge retention of the conductive toner at the development position, and facilitates the charge injection of the conductive toner in a region where a charge injection electric field acts. The resistance is preferably changed to a low resistance, and the conductive toner behaves in this manner, so that stabilization at the time of charge injection and development into the conductive toner can be achieved.

  Further, as the image forming apparatus of the second aspect in the present embodiment model, as shown in FIGS. 1A and 1B, a movable support 1a and a support supported by and supported by the support 1a. An image carrier 1 having pixel electrodes 1b arranged vertically and horizontally with the direction along the moving direction 1a as the sub-scanning direction and the direction orthogonal to the main scanning direction as the main scanning direction, and an image signal for each color for each pixel electrode 1b The image writing means 2 for applying each color latent image voltage based on the above and writing each color latent image pattern represented by the latent image potential for each pixel electrode 1b on the image holding body 1 along the moving direction of the image holding body 1 And a plurality of developing means 3 that visualize each color latent image pattern with a corresponding color toner at a development position opposite to the image holding body 1 and corresponding to each color. When writing a latent image pattern, it is already formed for each pixel electrode 1b. A latent image writing control means 4 for controlling the image writing means 2 after determining each color latent image voltage based on the image signal for each color in consideration of the voltage correction based on the presence of the color toner image thus obtained, and a plurality of latent image writing control means 4 Transfer means 6 for transferring each color toner image formed on the image carrier 1 by the developing means 3 to the transfer medium 5.

Here, “each color toner image formed on the image carrier 1 by a plurality of developing means 3” means a toner image formed on the same pixel electrode 1 b by all the developing means 3. From the non-adhering one to the one in which the toner images are multiplexed in all the developing means 3 is indicated.
Further, the transfer medium 5 onto which the toner image on the image carrier 1 is transferred by the transfer means 6 may be a recording material, or an intermediate transfer member in which the recording material is interposed. It does not matter even if it is designed to be transferred to. By providing the transfer means 6 in this way, the toner image on the image carrier 1 can be reliably transferred to the transfer medium 5, and good image quality on the transfer medium 5 is ensured. Further, the transfer unit 6 is not particularly limited, but from the viewpoint of simplifying the apparatus configuration, the transfer unit 6 is disposed opposite to the image carrier 1 and is applied with a predetermined transfer voltage and the image carrier. It is preferable to have a transfer member that applies a predetermined transfer electric field between the transfer member 1 and the transfer member 1. The transfer member may be of a type that contacts the image carrier 1 such as a transfer roll, or may be of a type that does not contact the image carrier 1 such as corotron.

From the viewpoint of using the pixel electrode 1b at the time of transfer, the image writing unit 2 applies a transfer voltage based on each color toner image already formed for each pixel electrode 1b in addition to writing the latent image pattern. A transfer image pattern as a transfer potential change for each pixel electrode 1b by the transfer voltage is written on the image carrier 1, and the transfer unit 6 includes an image writing unit 2 for writing the transfer image pattern, and an image carrier 1 And a counter electrode member that applies a transfer electric field according to a transfer image pattern by the image writing means 2 between the pixel electrode 1b and the pixel electrode 1b.
Here, from the viewpoint of performing transfer in accordance with the toner image on the pixel electrode 1b, when the transfer image pattern is written by the image writing unit 2, each of the pixel electrodes 1b has already been written by the plurality of developing units 3. It is preferable to have a transfer image writing control means 7 for controlling the image writing means 2 after determining a transfer voltage in consideration of each formed color toner image.

In particular, in such an embodiment in which the pixel electrode 1b is used even at the time of transfer, a desired transfer electric field can be applied to each pixel electrode 1b, the transfer conditions are stabilized, and the image quality is further improved. It becomes like this.
In such an image forming apparatus in which the image carrier 1 is a rotating member, the circumferential length of the image carrier 1 is L0, the minimum arc length between adjacent development positions is L1, and the development of the final color is performed. The scanning speed S in the sub-scanning direction is S, where L2 is the length of the arc from the position to the transfer position, which is the facing portion between the facing member and the image carrier 1, and the peripheral speed of the image carrier 1 is V. It is preferably set so as to satisfy the relationship of ≧ (L0 / L1) V and S ≧ (L0 / L2) V. As a result, a desired transfer voltage can be applied to the pixel electrode 1b even at the time of transfer by the transfer means 6, and good transfer can be performed.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
Embodiment 1
FIG. 2 shows Embodiment 1 of an image forming apparatus to which the above-described embodiment model is applied. In the figure, the color image forming apparatus according to the present embodiment uses each of the color toner images of each color component (for example, yellow (Y), magenta (M), cyan (C), and black (K)) by, for example, electrophotography. An image holding body 10 that is held in a multiplexed manner is provided. The image holding body 10 is arranged around the image holding body 10 so as to be separated from the image holding body 10. Four developing devices 30 (30a to 30d) to be imaged are sequentially arranged. The arrangement of each color component is not particularly limited, and may be appropriately selected. Also, if the quantity is a plurality of colors, it is not limited to four colors, and may be two or more colors. A transparent color or a special color may be used for a part, or a plurality of the same colors may be provided.

Further, around the image carrier 10, a transfer device that collectively transfers the multiple toner images multiplexed on the image carrier 10 by the developing devices 30 of the respective colors onto the recording material supplied from the recording material supply unit 50. 54 and a cleaning device 55 for cleaning residual toner on the image carrier 10 is provided. A predetermined developing bias acts between the developing device 30 and the image holding member 10, and a predetermined transfer bias acts between the transfer device 54 and the image holding member 10. It is like that.
Further, around the recording material supply unit 50 according to the present embodiment, a feeding roll 51 that feeds the recording material from the recording material supply unit 50 and a sheet of the recording material that has been fed are conveyed and conveyed. A separating mechanism 52 that conveys the recording material downstream is provided.

  Then, the recording material conveyed from the separating mechanism 52 is positioned by the positioning roll 53 and then conveyed at a predetermined timing, and the image is held at the transfer position that is the opposite portion between the image carrier 10 and the transfer unit 54. Multiple toner images on the image carrier 10 are collectively transferred onto the recording material by a transfer electric field acting between the body 10 and the transfer unit 54. The toner image transferred onto the recording material is fixed by the fixing device 56 and then discharged to a recording material discharge portion 57 provided on the side of the apparatus.

  As shown in FIG. 3, the image carrier 10 of the present embodiment winds a matrix panel 20 in which a large number of pixels are formed in a so-called matrix form on a film on a rigid drum 11 that is a rotatable support. It is fixed and supported. The matrix panel 20 is produced by using, for example, a thin film technology used in a so-called IC manufacturing process for a polyimide film, and a pixel (not shown) is sub-scanned in a direction along the rotation direction of the rigid drum 11. The main scanning direction is the direction along the rotation axis, and the vertical and horizontal directions are arranged in a matrix. The pixels arranged in a matrix form in this manner use the pixel arrangement along the main scanning direction as a scanning line and the pixel arrangement along the sub-scanning direction as a data line. For this reason, the data lines and scanning lines of the matrix panel 20 are each provided with an appropriate number of data drivers 21 and scanning drivers 22 connected to each pixel as an element of the image writing means. The input lines to 22 are further gathered so that when the number is reduced, the input lines are routed to the inner surface side of the rigid drum 11 through the matrix panel 20.

The rigid drum 11 is provided with an opening 11a along the rotational axis direction in a part of the outer peripheral surface thereof, and the shaft center portion of the rigid drum 11 is used for electrical connection between the matrix panel 20 and the outside. A so-called slip ring 14 is provided, and the rigid drum 11 rotates around the fixed slip ring 14.
On the inner peripheral surface side of the rigid drum 11, as shown in FIGS. 4A and 4B, an appropriate number of terminals 12 are provided along the rotation axis direction of the rigid drum 11. Are connected to the data driver 21 and the scanning driver 22 of the matrix panel 20, respectively. Further, these terminals 12 are provided with sliders 13 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 12. A current collecting ring 14a is attached. The current collecting ring 14a portion of the slip ring 14 is smaller in diameter than the insulating rings 14b on both sides, and the slider 13 is always in contact with the opposing current collecting ring 14a even when the rigid drum 11 rotates. It is like that. The opening 11a of the rigid drum 11 is closed with, for example, a seal tape so that the resistance of the air current when the image carrier 10 rotates is reduced and the influence of toner during development is prevented. It has become.

  Therefore, signal transmission between the matrix panel 20 and the outside is performed from the lead wire 15 wired in the slip ring 14 corresponding to the current collection ring 14 a of the slip ring 14 via the current collection ring 14 a and the slider 13. This is performed between the panel 20 and the signal transmission with the matrix panel 20 can be appropriately performed even when the rigid drum 11 rotates. The rotation method of the rigid drum 11 is not particularly limited. For example, the outer peripheral surface end portion of the rigid drum 11 may be pressed against the rotating roll to rotate, or may be different from the insertion side of the slip ring 14. A rotating shaft for rotating the rigid drum 11 itself may be provided on the side.

Next, the pixels of the matrix panel 20 will be described.
As shown in FIG. 5A, the matrix panel 20 of the present embodiment has pixels arranged vertically and horizontally, and each pixel has a pixel electrode 24 and a pixel electrode 24 as shown in FIG. A so-called active matrix system configured by switching elements or the like that individually switch applied voltages is employed. For example, a TFT (Thin Film Transistor) 23 is used as a switching element which is an element of the image writing means of the present embodiment. In addition, a storage capacitor 25 for maintaining the potential of the pixel electrode 24 and various wirings (source line, gate) Each line is formed. Each pixel and the connection between the pixels are grouped as a source line to which the source of the TFT 23 is connected for each data line and a gate line to which the gate of the TFT 23 is connected for each scanning line. Further, the pixel electrode 24 and the storage capacitor 25 are connected in parallel to the drain of the TFT 23, and one of the storage capacitors 25 is grouped for each scanning line (not shown), and exhibits an equivalent circuit as shown in FIG. It is configured.

Since the matrix panel 20 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 20, as shown in FIG. 6, a predetermined number of pixels are grouped for each data line and scanning line, and the source side of the TFT 23 is connected to the data driver 21 for each data line. The gate side is connected to the scanning driver 22 for each scanning line, and the data driver 21 and the scanning driver 22 are driven by the latent image writing control device 100. Therefore, by driving the data driver 21 and the scanning driver 22, a predetermined voltage can be applied to a predetermined pixel. The data driver 21 includes, for example, a shift register, a latch, and a buffer with sample and hold, and the scanning driver 22 includes, for example, a counter, latch, and buffer. In FIG. 6, the pixel electrode 24 is omitted, but it goes without saying that the pixel electrode 24 connected between the TFT 23 and the storage capacitor 25 is provided.

  Here, the switching operation of each pixel electrode 24 in the present embodiment will be described with reference to FIG. That is, in order to operate the pixel electrode 24, when an ON voltage is applied to the gate (gate line) connected to the scanning line side of the TFT 23, the source and drain of the TFT 23 become conductive and become equivalent to the source voltage. The storage capacitor 25 is charged. This charged charge becomes the potential of the pixel electrode 24, for example, a latent image potential for forming an electrostatic latent image. In this state, even if an OFF voltage is applied to the gate and the source-drain is cut off, the potential is maintained as it is due to the storage effect of the storage capacitor 25. Therefore, even if the source voltage subsequently changes, the ON voltage is applied to the gate. As long as is not applied, the potential of the pixel electrode 24 is maintained as it is.

  Therefore, by applying a signal voltage corresponding to, for example, image density to the source side of the TFT 23 of each pixel and applying an ON voltage to the gate side, a latent image voltage is applied to one line of scanning lines. The latent image pattern is formed. Then, a two-dimensional latent image pattern is formed by sequentially moving (scanning) the gate to which the ON voltage is applied in the direction opposite to the rotation direction of the image carrier 10, for example, and sequentially applying a new signal voltage to the data line. Will come to be.

  In this embodiment, a latent image writing control device 100 for controlling the data driver 21 and the scanning driver 22 is provided in order to apply a predetermined latent image voltage to the pixel electrode 24 as described above. As shown in FIG. 7, the latent image writing control device 100 transmits a voltage signal and a control signal based on the image signal to the data driver 21 and the scanning driver 22 of the matrix panel 20. Therefore, in the latent image writing control apparatus 100, a memory unit 101 that stores image data for at least one screen from an image signal, and a tone conversion unit that performs tone conversion of the image data from the memory unit 101 for each color. 103 (103a to 103d) and each color latent image writing unit 102 (specifically, Y color) including a latent image voltage setting unit 104 (104a to 104d) for setting a latent image voltage corresponding to the image data subjected to gradation conversion. Latent image writing unit 102a to K color latent image writing unit 102d) and a latent image voltage power supply unit for setting a latent image voltage in latent image voltage setting unit 104 of each color latent image writing unit 102 105, the timing control unit 106 that performs various timing controls in response to the control signal, and the information transmitted to the data driver 21 among the latent image voltages set by each color latent image writing unit 102 are branched. Bifurcation It is composed of 07 or the like.

In particular, in the present embodiment, as indicated by the dotted line in the figure, in each latent image voltage setting unit 104 (104a to 104d), the pixel electrode 24 is set according to the voltage set in the upstream latent image voltage setting unit 104. In consideration of the voltage correction based on the presence of the toner image adhering to the toner image, the downstream latent image voltage setting unit 104 adds the voltage correction to set a new latent image voltage. That is, the latent image voltage is obtained by accumulating the magnitude of the image signal up to the previous color for the pixel electrode 24 and the magnitude of the image signal of that color. This may be achieved by simply adding and accumulating the latent image voltage set by the upstream latent image voltage setting unit 104, or performing correction for each color according to the charge amount of each color toner. The values may be accumulated.
Then, by inputting an image signal or a control signal to the latent image writing control device 100, the latent image writing control device 100 controls the data driver 21 and the scanning driver 22, and the image signal is supplied to each pixel electrode 24. The latent image voltages of the respective colors based on the above are applied.

  In addition, the drive timing of the scanning driver 22 by the latent image writing control device 100 is devised, and the latent image of the pixel electrode 24 is developed at the development position that is the facing portion between the image carrier 10 and the developing device 30 of each color. Each parameter is set so that the potential corresponds to the development position.

In the present embodiment, as shown in FIG. 8, the circumference of the image carrier 10 is L 0, and the arc length (minimum) of each developing device 30 where the distance between adjacent developing devices 30 is the closest. Each parameter is set so as to satisfy the following relationship, where L1 is the arc length), V is the peripheral speed of the image carrier 10, and S is the scanning speed of the image carrier 10 in the sub-scanning direction. .
(Minimum arc length L1 / peripheral speed V) ≧ (peripheral length L0 / scanning speed S)
That is, the time required for one pixel electrode 24 of the image carrier 10 to pass through the minimum distance between the development positions is set to be longer than the time required for one round of sub-scanning, so that the distance between the development positions is the shortest. In this, the sub-scan of the pixel electrode 24 is surely performed at least once. This means that the upstream position including the developing position of the developing device 30 (the developing device 30 adjacent to the upstream side of the developing device 30 and the developing device 30). Means that the pixel electrode 24 is reliably scanned.
Therefore, the scanning speed S ≧ (peripheral length L0 / minimum arc length L1) × peripheral speed V may be satisfied. This is the same even if the scanning direction is reversed.

This will be described with reference to FIG. The timing of applying the latent image voltage of each color to the pixel electrode (not shown) is Y color in the α region when scanning is performed on the pixel electrodes in the α to δ regions in the figure. A latent image voltage of M color may be applied in the β region, C color in the γ region, and K color in the δ region. This can be achieved, for example, by determining the reference position of the pixel electrode of the image carrier 10 and determining where the reference position is currently located by the rotation of the image carrier 10.
At this time, in order to form a latent image of each color with respect to one rotation of the image holding body 10, assuming that the minimum arc length L1 is between C and K, the latent image voltage of K is Since only the δ region is applied, it is necessary to increase the scanning speed S. That is, since it is necessary to cover the entire circumference of the image carrier 10 in the δ region, the scanning speed S is equal to or higher than the value obtained by multiplying the circumferential speed V of the image carrier 10 by the value obtained by dividing the circumferential length L0 by the minimum arc length L1. By doing so, it is possible to form a latent image for one round of the image carrier 10 even when a K-color latent image voltage is applied in the δ region of the figure.
Further, by increasing the scanning speed S, the δ region can be set narrower, and in particular, the influence on the upstream C color can also be suppressed.

  This relationship is the same if the scanning speed when the pixel electrodes 24 are virtually arranged along the circumference of the image holding body 10 is used as the scanning speed even if the image holding body 10 has the opening 11a. It is clear that this is a relationship. In the present embodiment, it is needless to say that the opening 11a is much narrower than the interval between the developing devices 30.

  In the present embodiment, since the latent image voltage applied to the pixel electrode 24 is performed from the image signal via the gradation conversion unit 103, the latent image voltage is not simply binarized but more than that. In other words, the latent image voltage matching the image density can be applied to the pixel electrode 24. This will be described with reference to FIG. For example, for each color density of the image signal (image data), for example, three levels of threshold values (indicated by A, B, and C in the figure) are provided. If there is V / 3, B exceeds A and less than A, 2V / 3, and if A exceeds V, a latent image of four gradations is formed.

  Next, a method for applying the latent image voltage based on the image data classified into the four stages to the pixel electrode 24 will be described with reference to FIG. Now, the tone-converted signal is a signal as shown in FIG. 11A, and “... a, b, c, d...” Along the main scanning direction of the data line, and “ ..., B, a, d, c..., The latent image voltage setting unit 104 (see FIG. 7), for example, as shown in FIG. First, binarized data is generated in accordance with d. That is, a data signal such as “... 00011011 …… 01001110...” Is generated. Then, the voltage corresponding to “00” to “11” is selected from the generated signal from the latent image voltage power supply unit 105, thereby setting the latent image voltage waveform in four stages. By transmitting the set latent image voltage waveform to the data driver 21 and transmitting the timing control signal to the scanning driver 22, as shown in FIG. Thus, latent image potentials of respective colors having different densities are formed. That is, a latent image pattern is formed by the pixel electrode 24.

In this way, by converting the latent image voltage applied to the pixel electrode 24 to gradation, the amount of toner adhering to the pixel electrode 24 by development can be changed, and an image with higher image quality can be formed. Will be able to.
Here, 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 apply a binarized latent image voltage without performing gradation. Not too long. Furthermore, here, a gradation method used in the active matrix method as a method of applying a latent image voltage based on an image signal, that is, a voltage gradation method in which the voltage amplitude is a predetermined number of gradations is shown. Needless to say, a frame rate gradation method that performs gradation display at a rate may be used.

Furthermore, in the present embodiment, the following device is devised in order to more suitably multiplex the toner images of the respective colors on the image carrier 10. This will be described with reference to FIG.
For example, assuming that the first and second color development is performed by the pixel electrode 24, in this embodiment, as shown in FIG. 12A, the first color latent image voltage is applied to develop the first color. When completed, predetermined toner adheres to the pixel electrode 24. Next, as the latent image voltage for the second color, a larger latent image voltage is applied in consideration of the voltage correction based on the presence of the first color toner adhered on the pixel electrode 24. As a result, a desired amount of the second color toner adheres to the first color toner on the pixel electrode 24 after the second color development, and a good image can be obtained. Thereafter, the third and fourth colors are performed in the same manner.
On the other hand, when the voltage correction is not considered for the latent image voltage of the second color as in the comparative form shown in FIG. 12B, the one already attached on the pixel electrode 24 during the development of the second color. Due to the presence of the color toner, a sufficient electric field in the direction of attracting the second color toner onto the pixel electrode 24 cannot be formed, and the second color toner is not sufficiently adhered. Therefore, the image quality is deteriorated.

  That is, in this embodiment, as shown in FIG. 13, in the first color, toner is developed between the pixel electrode 24 and the developing device 30a (specifically, a developing roll 33 described later) based on the image signal. Development is performed by applying a potential difference V 1 necessary for the above, and the first Y color is deposited on the pixel electrode 24. In the second color, the potential difference ΔV1 for the Y-color toner is raised in order to secure the potential difference V2 necessary for developing the toner based on the image signal between the M-color toner and the developing device 30b. A potential difference of (V2 + ΔV1) is ensured between the pixel electrode 24 and the developing device 30b. Further, in the third color, in order to secure the potential difference V3 necessary for developing the toner based on the image signal between the C toner and the developing device 30c, the potential difference ΔV1 and the M color corresponding to the Y color toner are secured. The potential difference (V3 + ΔV1 + ΔV2) obtained by raising the potential difference ΔV2 corresponding to the toner is ensured between the pixel electrode 24 and the developing device 30c. Similarly, for the fourth color, a potential difference of (V4 + ΔV1 + ΔV2 + ΔV3) can be secured between the pixel electrode 24 and the developing device 30d. These ΔV1 to ΔV3 correspond to voltage correction. Here, as the voltage correction, the latent image voltages (values corresponding to V1 to V3) applied up to the previous color may be used, or may be selected separately according to the characteristics of the toner to be used. It is better to confirm a more appropriate value by experiment or the like.

  FIG. 14 shows an example to further explain this easily. Here, for the sake of easy understanding, the gradation conversion is assumed to be three gradations (for example, the latent image voltage is indicated by three gradations of 0V, 5V, and 10V), and the density is zero, light, and dark. It was made to correspond to. In the figure, the first example is that the first color (Y color) to the fourth color (K color) are all 10V (dense density). The latent image voltage (specifically, the signal voltage applied to the pixel electrode 24) is 10V, the latent image voltage is 20V in the second color development, the latent image voltage is 30V in the third color development, and the latent image voltage in the fourth color development. Is 40V.

In the second example, the first color (Y color) and the second color (M color) are 5V (light density), and the third color (C color) and the fourth color (K color) are 10V (dark density). For the pixel electrode 24, the first color is 5V, the second color is 10V, the third color is 20V, and the fourth color is 30V.
Further, the third example is all of a low density, with 5V for the first color, 10V for the second color, 15V for the third color, and 20V for the fourth color.
Furthermore, in the fourth example, there is no second color, and only the light colors of the third color (C color) and the fourth color (K color) are multiplexed. The third color is 5V and the fourth color is 10V. It has become.
Further, the fifth indicates a blank state without any color, and the latent image voltage of this portion is 0 V from the first color to the fourth color.

  In this way, considering the voltage correction due to the existing toner formed on the pixel electrode 24 by developing the image carrier 10, it is necessary to newly develop toner at each downstream development position. The voltage obtained by accumulating the voltage for applying the electric field and the voltage correction amount of the existing toner is applied to the corresponding pixel electrode 24 as a new latent image voltage. Even if the toners are multiplexed, a desired amount of toner can be formed on the image carrier 10 and an image with good image quality can be obtained. That is, the later development, the better the development is achieved by increasing the applied latent image voltage. However, since it is assumed that the development characteristics differ depending on the charge amount of the toner depending on each color, the voltage actually applied as the latent image voltage may be corrected through an experiment or the like. It is also preferable to consider the attenuation of the latent image potential to the development position after the latent image voltage is applied to the pixel electrode 24 due to the characteristics of the TFT 23 that drives the pixel electrode 24 and the like.

  As described above, in the present embodiment, the latent image voltage corresponding to the development position is applied to the pixel electrode 24, so that each developing device 30 performs good development, and desired toner is transferred to the image carrier 10. It will stick to the side. Thereafter, transfer is performed on the recording material at the transfer position. FIG. 15 shows a state at the time of transfer in the present embodiment, and a bias power source 54 a for applying a transfer electric field is provided between the image carrier 10 and the transfer unit 54. At this time, as the transfer electric field, for example, the electric field at the transfer position between the image carrier 10 and the transfer unit 54 is desired in a case where four color toners are multiplexed and the amount of adhesion is the largest. Thus, the entire amount of toner on the image carrier 10 can be transferred substantially.

  As described above, in this embodiment, the position and shape of the pixel are determined by the position and shape of the pixel electrode, and the latent image potential is determined by the voltage applied to the pixel electrode (latent image voltage). The stable element is eliminated, and the position, shape, and potential of the pixel are uniquely determined, and high image quality that does not cause density unevenness, color unevenness, streaks, color shift, and the like can be obtained. In addition, since there is no charger, the charger itself is contaminated with toner, resulting in poor charging, the discharge product generated from the charger alters the photoreceptor, and the discharge product reduces the cleaning performance. There is nothing to do. In addition, colorization can be realized by a very simple process. Unlike the conventional IOI method, a desired electrostatic latent image can be formed by controlling the electrode voltage without charging and exposing from the toner image. There is no fear.

  In the present embodiment, as shown in FIGS. 3 and 4, an opening 11a is provided in the image carrier 10, and the electrical connection from the matrix panel 20 to the slip ring 14 is via the opening 11a. For example, the connection from the matrix panel 20 is extended in the direction of the rotation axis of the rigid drum 11 from the matrix panel 20 and is connected to the terminal 12 through the end surface of the rigid drum 11. It is also possible to eliminate the opening 11a.

Embodiment 2
FIG. 16 shows a developing device 30 used in the image forming apparatus according to the second embodiment, and is specifically devised to use conductive toner as the toner. Since each developing device 30 (30a to 30d: see FIG. 2) is configured in substantially the same manner, only one developing device 30 will be described here.
The developing device 30 in the present embodiment has a developing housing 31 in which conductive toner (hereinafter abbreviated as toner as appropriate) is accommodated. The developing housing 31 has a developing opening 32 facing the image carrier 10. And a developing roll (corresponding to a developing toner holder) 33 that faces the developing opening 32 and is spaced apart from the image carrier 10 and rotates in the same direction (With) at the opposite portion. By applying a predetermined developing bias between the image carrier 10 and the developing roll 33 by a bias power source 42, a developing electric field is applied to a developing region (corresponding to a developing position) where the image carrier 10 and the developing roll 33 face each other. It is supposed to act. The developing roll 33 of the present embodiment is set to rotate at 1 to 2 times the peripheral speed of the image carrier 10.

Further, on the side of the developing roll 33 different from the image holding body 10, an intermediate roll 34 is provided as an intermediate toner holding body that holds and conveys charged conductive toner, facing the developing roll 33. .
The intermediate roll 34 in the present embodiment is configured substantially in the same manner as the outer diameter of the developing roll 33, rotates in different directions (Against) at a portion facing the developing roll 33, and its peripheral speed is the developing roll 33. Is set to be 1.2 to 2 times the peripheral speed. Further, by applying a predetermined moving bias between the intermediate roll 34 and the developing roll 33 by the bias power source 43, a moving electric field is applied to a moving area where the intermediate roll 34 and the developing roll 33 face each other, and the intermediate roll 34. The upper toner is easily moved to the developing roll 33.

Further, a charge injection roll 35 as a charge injection member capable of injecting charges into uncharged toner is provided at a position facing substantially above the intermediate roll 34.
The charge injection roll 35 according to the present embodiment is formed of a roll member made of metal such as aluminum or stainless steel, for example, and a predetermined charge injection bias is applied between the intermediate roll 34 and a bias power supply 44, thereby A charge injection electric field is applied to the charge injection region where the injection roll 35 and the intermediate roll 34 face each other. Further, the charge injection roll 35 rotates in the same direction (With) at a portion facing the intermediate roll 34, and its peripheral speed is 1.5 to 2.5 times the peripheral speed of the intermediate roll 34. It has become.

  Further, in the developing device 30 of the present embodiment, a toner supply roll 36 having a conductive foam roll configuration made of, for example, polyurethane resin is supplied from the charge injection roll 35 to the intermediate roll 34 in order to supply toner to the intermediate roll 34. Are arranged opposite to the intermediate roll 34 at positions upstream in the rotation direction, and are provided so as to rotate in different directions (Against) at portions facing the intermediate roll 34. Further, the toner supply roll 36 is set to rotate at a peripheral speed that is 0.3 to 1.0 times the peripheral speed of the intermediate roll 34. In this embodiment, the toner supply roll 36 and the intermediate roll 34 are electrically short-circuited. Therefore, even if the surface of the intermediate roll 34 is charged between the charge injection roll 35 and the intermediate roll 34, the action of making the potentials of the toner supply roll 36 and the intermediate roll 34 uniform works, and the surface of the intermediate roll 34 is charged. The effect of suppressing, that is, the effect of removing electricity, is activated, the toner adhering to the intermediate roll 34 can be cleaned, and the toner supply roll 36 performs the refresh function of the intermediate roll 34.

  Further, an agitator 41 that stirs and supplies toner to the toner supply roll 36 is provided behind the toner supply roll 36 so that the toner contained in this portion can be supplied to the toner supply roll 36 side.

  Further, a layer forming blade 37 that regulates the toner supplied from the toner supply roll 36 to the intermediate roll 34 to be layered is provided between the toner supply roll 36 and the charge injection roll 35 of the intermediate roll 34. . The layer forming blade 37 is made of a plate spring member such as stainless steel or phosphor bronze having a thickness of 0.05 to 0.2 mm, for example, and is fixed to the free end side of a support member 37a whose one end side is fixed to the developing housing 31. It has come to be supported. In particular, the layer forming blade 37 is provided so that the surface on the free end side is pressed against the intermediate roll 34 with a predetermined pressing force, and the layer forming blade 37 is layered without excessively scraping off the toner on the intermediate roll 34. The effect of arranging can be further demonstrated. The layer forming blade 37 is not particularly limited as long as the toner can be layered, and an elastic body may be provided on the surface of the plate spring member.

  On the other hand, a refresh roll 38 made of a metal roll made of aluminum, for example, is brought into contact with the developing roll 33 at a position facing the developing roll 33 between the intermediate roll 34 on the downstream side of the developing area of the developing roll 33. Is provided. Then, by grounding the refresh roll 38, the residual toner on the developing roll 33 is electrostatically removed, and the surface of the developing roll 33 is neutralized. The refresh roll 38 is provided with a metal blade (not shown) so as to collect the toner adhering to the refresh roll 38. The refresh roll 38 is not limited to a metal roll, and for example, a brush using conductive fibers may be used.

Further, the conductive toner used in the present embodiment has a conductive toner base (conductive core) made of a conductive material as shown in FIG. 17A, for example. The periphery is covered with an insulating coating layer (for example, an insulating resin layer), and the insulating coating layer is provided with an appropriate number of recesses so that a part of the conductive core is exposed.
In the present embodiment, the conductive toner can be produced by a polymerization method or various known encapsulation techniques. At this time, the conductive core is formed by dispersing a conductive agent such as conductive carbon or transparent conductive powder such as ITO in a polyester resin or a styrene-acrylic resin, or a particle surface made of a polyester resin or a styrene-acrylic resin. Is coated with the conductive agent.

  When a high electric field is applied to the conductive toner of such an aspect, the resistance tends to decrease. The magnitude of the electric field that lowers the resistance depends mainly on the occupation ratio of the concave portion of the toner or the thickness of the insulating coating layer. About this mechanism, since the conductive core is covered with the insulating coating layer, the conductive core itself does not contact the cores or directly contact the electrode member, etc. As a result, it is presumed that when a high electric field is applied, for example, the tunnel effect or the like is conducted.

  As another embodiment of the conductive toner, for example, as shown in FIG. 17B, the conductive core is covered with an insulating or semiconductive coating layer, and the thickness h of the coating layer is adjusted appropriately. By doing so, it is possible to appropriately select a mode in which the resistance of the toner can be adjusted. At this time, for the semiconductive coating layer, a semiconductive material itself may be used. For example, a trace amount of metal oxide such as titanium oxide or tin oxide or conductive carbon may be added to the insulating resin. You may make it use the semiconductive resin contained. As the conductive core, for example, a mode in which conductive fine particles adhere to the vicinity of the outer surface of an insulating toner base (insulating core) made of a normal insulating toner, or conductive fine particles are mixed inside the insulating core. You can choose what you want.

  An outline of the operation of the developing device 30 when such a conductive toner is used will be described. After the toner agitated by the agitator 41 is supplied to the toner supply roll 36 side, the toner supply roll 36 is rotated and is carried to a position facing the intermediate roll 34 to be supplied to the intermediate roll 34 side of Against rotation. The layer thickness of the toner supplied onto the intermediate roll 34 is regulated by the layer forming blade 37, and a substantially uniform toner layer is formed. The uniformly formed toner layer on the intermediate roll 34 is sandwiched and rubbed between the intermediate roll 34 and the charge injection roll 35 by the charge injection electric field provided by the bias power supply 44 while being sandwiched between the two. Charge is injected.

  In such a state, since the toner sandwiched between them is arranged to be equal to or less than a single layer, the contact probability between the toner and the charge injection roll 35 is increased, and the contact resistance of the toner can be reduced. Accordingly, the apparent resistance of the toner is reduced, and the toner is injected with a low resistance. For this reason, even when the electric charge injection field is relatively low, the electric charge is efficiently injected into the toner. In particular, the present embodiment has a feature that the charge injection function can be stably performed because the charge injection roll 35 can exclusively perform the charge injection function to the toner.

  In this way, by performing charge injection on the toner having a single layer or less, charge injection into the toner is effectively performed and generation of WST (Wrong Sign Toner) can be suppressed. Then, on the intermediate roll 34 that has passed through the portion facing the charge injection roll 35, a toner layer of a single layer or less in which uniform charge injection is performed is held and conveyed by the intermediate roll 34. At this time, since the toner is sandwiched between the charge injection roll 35 and the intermediate roll 34 and in particular, the charge is injected while being rubbed, the contact probability of the toner to the charge injection roll 35 is increased, and Since the contact resistance can be reduced, the toner can be efficiently injected in a single layer state with a low charge injection electric field. Further, since shear force is applied between the toner layers, it is possible to prevent the toners from overlapping in a polarized state, and it is possible to prevent the occurrence of WST even if the charge injection electric field is a high electric field.

  Next, the toner charged by the charge injection is conveyed to a portion where the intermediate roll 34 and the developing roll 33 are opposed to each other. Here, since the intermediate roll 34 and the developing roll 33 are rotated against each other and a moving electric field is applied by the bias power source 43, the toner does not pass through the nip between the intermediate roll 34 and the developing roll 33. The toner is electrostatically moved to the developing roll 33, and the toner charge amount is not changed at all. Further, since the peripheral speed of the intermediate roll 34 is increased by 1.2 to 2 times the peripheral speed of the developing roll 33, the amount of toner moving from the intermediate roll 34 to the developing roll 33 can be increased. Thus, the toner amount density on the developing roll 33 can be approximately 1.2 to 2 times the toner amount density on the intermediate roll 34, and the toner amount density on the developing roll 33 can be set on the intermediate roll 34. The toner amount density can be increased. At this time, the intermediate roll 34 and the developing roll 33 do not necessarily have to rotate Against, and may be rotated with. This is because the moving electric field is set to be smaller than the electric charge injection electric field, so that there is less possibility of changing the charged state of the toner during the movement.

  Then, the toner that has moved onto the developing roll 33 is conveyed on the developing roll 33 as it is, and proceeds to a position where the developing roll 33 and the image carrier 10 are opposed to each other. Here, the developing electric field by the bias power source 42 acts, so that the toner on the developing roll 33 develops the electrostatic latent image to become a visible image. At this time, since the toner amount density on the developing roll 33 is high, it is possible to realize an image density according to the electrostatic latent image. Further, since it is not necessary to increase the peripheral speed of the developing roll 33, the toner on the image holding member 10 is not scraped off by the rotation of the developing roll 33. Therefore, fine line reproducibility, graininess, etc. Therefore, it is possible to obtain a sufficient image density without deterioration of image quality. Since the development electric field is lower than the electric charge injection electric field, the electric charge injected into the conductive toner by the electric charge injection electric field does not escape from the electric development electric field, and good development is performed.

  FIG. 18 shows a developing device 30 ′ which is a modification of the developing device 30 (see FIG. 16). Such a developing device 30 ′ may be used. The developing device 30 ′ shown here is configured in substantially the same manner as the developing device 30 described above, but the charge injection roll 35 is not provided independently, but is provided between the intermediate roll 34 and the toner supply roll 36. On the other hand, the point that the layer forming blade 37 is provided so as to regulate the toner on the charge injection roll 35 is greatly different. Therefore, the toner is transported from the toner supply roll 36 to the charge injection roll 35, and is transported from the charge injection roll 35 to the developing roll 33 via the intermediate roll 34. Reference numeral 39 denotes a refresh roll provided on the intermediate roll 34.

  The operation of the developing device 30 'having such a configuration will be described. In the developing device 30 ′, the conductive toner is stirred by the agitator 41 in the developing housing 31, and the stirred toner is supplied to the toner supply roll 36 side. Since the toner supply roll 36 and the charge injection roll 35 rotate against each other, the toner supplied to the toner supply roll 36 moves toward the charge injection roll 35 at a portion facing the charge injection roll 35. The toner moved onto the charge injection roll 35 is regulated in layer thickness by the layer forming blade 37, and the toner conveyed by the charge injection roll 35 forms a predetermined toner layer.

  The toner layer formed by the layer forming blade 37 is charged by injecting electric charge by the electric charge injection electric field acting between the electric charge injection roll 35 and the intermediate roll 34 at an opposite portion. At this time, the toner is sandwiched between the charge injection roll 35 and the intermediate roll 34, and is charged into a single layer or less while being rubbed by the difference in peripheral speed between the two. Contact probability between the toner and the charge injection roll 35 and the contact resistance of the toner can be reduced, and the apparent resistance of the toner is reduced accordingly, and the toner is injected in a low resistance state. Is done.

  The charged and charged toner is held as a single or lower toner layer on the intermediate roll 34 and is conveyed as it is, and reaches a position where the intermediate roll 34 and the developing roll 33 face each other. Here, a moving electric field in a direction that facilitates the movement of the toner acts between the two, and further, Against rotation is performed so that the peripheral speed of the intermediate roll 34 is faster than the peripheral speed of the developing roll 33. A toner layer having a toner amount density higher than the toner amount density on the intermediate roll 34 is formed on the developing roll 33 and is held and conveyed on the developing roll 33. The toner conveyed by the developing roll 33 is developed into a visible image by developing the latent image on the image holding member 10 by a developing electric field in a developing region which is a portion facing the image holding member 10.

  As described above, even in the developing device 30 ′, the toner amount density on the developing roll 33 can be made larger than the toner amount density on the intermediate roll 34, and the image density can be increased accordingly. It becomes like this. In addition, low charge toner and reverse polarity toner are rarely generated in the development region, and fog and toner cloud can be effectively prevented.

In the present embodiment, the embodiment using the developing devices 30 and 30 ′ as described above is shown. However, the developing device 30 can visualize the latent image formed on the image carrier 10. It suffices that the developing rolls 30 and 30 ′ are integrated with the developing roll 33 and the intermediate roll 34.
Further, from the viewpoint of enabling development with a low electric field action on the image carrier 10, it is preferable to use conductive toner as the toner, but it is also possible to use normally used insulating toner. Not too long.

Embodiment 3
FIG. 19 shows a block diagram of a latent image writing control apparatus 100 ′ used in the image forming apparatus of the third embodiment. The latent image writing control apparatus 100 ′ of the present embodiment is configured in substantially the same manner as the latent image writing control apparatus 100 (see FIG. 7) of the first embodiment, but in this embodiment, the latent image writing control apparatus 100 ′ is configured. This is different from the first embodiment in that a transfer voltage is applied to the pixel electrode 24 even at the time of transfer by the embedding control device 100 ′. Components similar to those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted here.

  In FIG. 19, a latent image writing control apparatus 100 ′ according to the present embodiment has a memory unit 101 that stores image data for at least one screen from an image signal, and gradations image data from the memory unit 101 for each color. Each color latent image writing unit 102 (104) includes a tone conversion unit 103 (103a to 103d) for converting and a latent image voltage setting unit 104 (104a to 104d) for setting a latent image voltage corresponding to the tone-converted image data. Specifically, the Y-color latent image writing unit 102a to the K-color latent image writing unit 102d) and the latent image voltage setting unit 104 of each color latent image writing unit 102 set the latent image voltage. Based on the toner image formed for each pixel electrode 24 from the image data of each color from the memory unit 101, the timing control unit 106 that performs various timing control in response to the control signal, the latent image voltage power supply unit 105 The transfer voltage setting unit 108 for setting the transfer voltage, the transfer voltage power supply unit 109 for setting the transfer voltage in the transfer voltage setting unit 108, and the color latent image writing unit 102 and the transfer voltage setting unit 108 Of the latent image voltage and the transfer voltage, a branching unit 107 ′ for branching a signal transmitted to the data driver 21 is formed.

  That is, in the present embodiment, the latent image writing control device 100 ′ also performs transfer image writing control at the same time. Therefore, when the image signal and the control signal are input to the latent image writing control device 100 ′, the data driver 21 and the scanning driver 22 are driven, and the latent images of the respective colors are respectively applied to the pixel electrodes 24 at a predetermined timing. A voltage is applied or a transfer voltage is applied.

In this embodiment, the latent image voltage is determined in consideration of the voltage correction based on the toner already formed on the pixel electrode 24, and the toner (transfer image pattern) formed on the pixel electrode 24 by development. The transfer voltage is determined in consideration of the above.
Further, in the present embodiment, the drive timing of the scanning driver 22 by the latent image writing control device 100 ′ is devised, and at the development position that is the facing portion between the image carrier 10 and the developing device 30 of each color. The latent image potential of the pixel electrode 24 is set to the latent image potential corresponding to the development position, and is formed on the pixel electrode 24 at the transfer position that is the opposite portion between the image carrier 10 and the transfer unit 54. The transfer potential is such that the transferred toner is satisfactorily transferred.

Therefore, in the present embodiment, as shown in FIG. 20, the circumference of the image carrier 10 is L0, and the arc length (where the distance between adjacent developing devices 30 is the shortest among the developing devices 30 ( L1 is the minimum arc length), L2 is the arc length between the most downstream developing device 30d and the transfer device 54 adjacent to the developing device 30d, V is the peripheral speed of the image carrier 10, and the image carrier. When the scanning speed in the sub-scanning direction of 10 is S, each parameter is set so as to satisfy the following relationship.
(Minimum arc length L1 / peripheral speed V) ≧ (peripheral length L0 / scanning speed S)
That is, the time required for one pixel electrode 24 of the image carrier 10 to pass through the minimum distance between the development positions is set to be longer than the time required for one round of sub-scanning, so that the distance between the development positions is the shortest. In this, the sub-scan of the pixel electrode 24 is surely performed at least once. This means that the upstream position including the developing position of the developing device 30 (the developing device 30 adjacent to the upstream side of the developing device 30 and the developing device 30). Means that the pixel electrode 24 is reliably scanned.
Therefore, the scanning speed S ≧ (peripheral length L0 / minimum arc length L1) × peripheral speed V may be satisfied.

Furthermore, in this embodiment, each parameter is set so as to satisfy the following relationship.
(Developer and transfer unit arc length L2 / peripheral speed V) ≧ (peripheral length L0 / scanning speed S)
That is, the time required for one pixel electrode 24 of the image carrier 10 to pass through the interval between the most downstream developing device 30d and the transfer device 54 is set longer than the time required for one round of sub-scanning, so that the developing device 30d. Means that the sub-scan of the pixel electrode 24 is reliably performed at least once between the image transfer device 54 and the transfer device 54, and it is ensured that a transfer voltage is applied to the pixel electrode 24 at the time of transfer. .
Therefore, the scanning speed S ≧ (peripheral length L0 / arc length L2 of the developing device and the transfer device) × the peripheral speed V may be satisfied.

Next, the operation at the time of transfer in the present embodiment will be described.
In the present embodiment, as the transfer voltage to be applied to the pixel electrode 24, a voltage value considering the color toner images developed and formed on the pixel electrode 24 is selected. That is, as shown in FIGS. 21A and 21B, a transfer voltage is applied to the pixel electrode 24 in accordance with the amount of toner formed on the pixel electrode 24 after development, whereby the image is transferred onto the recording material. The toner amount depends on the toner amount formed on the pixel electrode 24. Note that (a) shows the toner in a large amount, and (b) shows the toner in a small amount.
However, here, the amount of charge and the like of each color toner may differ, and it is preferable to determine the transfer voltage in consideration of these factors.

This will be described in more detail. FIG. 22A shows a schematic diagram of a configuration between the image carrier 10 and the transfer unit 54 at the time of transfer. The pixel electrode 24 on the image carrier 10 is multiplexed, for example, by development. It is assumed that toner is attached, and the transfer unit 54 is grounded. Here, it is assumed that the toner to be used is a negatively charged toner.
In such a configuration, in the present embodiment, in order to improve the toner adhesion to the pixel electrode 24, the latent image voltage of, for example, 30 V for the pixel electrode (A) and 10 V for the pixel electrode (B), for example. Is applied corresponding to the development of the final color (K color in this example), so that a predetermined amount of toner is attached to the pixel electrodes (A) and (B), respectively.

  When such a pixel electrode 24 reaches the transfer position as it is, a force that keeps the toner on the pixel electrode 24 side acts on the toner at the time of transfer, and the transfer is not successful. For this reason, when the pixel electrode 24 reaches the transfer position, a transfer voltage corresponding to the amount of toner attached to each pixel electrode 24 is applied to the pixel electrode 24 so that the toner is transferred onto the recording material. become. At this time, as shown in FIG. 22B, since the toner amount is large in the pixel electrode (A) and the toner amount is small in the pixel electrode (B), the transfer electric field required for transfer is the pixel electrode ( A) needs to be larger than the pixel electrode (B).

  Therefore, in the present embodiment, a new transfer voltage different from the latent image voltage applied to the pixel electrode 24 is applied to the pixel electrode 24 based on the amount of toner adhered during development. As a result, between the pixel electrode 24 to which the transfer voltage is applied and the transfer unit 54, the transfer electric field of the pixel electrode (A) having a large amount of toner is made larger than the transfer electric field of the pixel electrode (B) having a small amount of toner. Thus, the toner adhering to the pixel electrode (A) is transferred by a large transfer electric field, while the toner adhering to the pixel electrode (B) is transferred by a small transfer electric field. Regardless of the case, the toner is properly transferred. Therefore, the image density and the like on the recording material can be realized more appropriately.

  Here, as the transfer voltage, for example, -30 V is applied as the transfer voltage to the pixel electrode (A) of 30 V (corresponding to the latent image voltage) in the state of FIG. Moreover, what is necessary is just to apply -10V as a transfer voltage with respect to what was 10V for the pixel electrode (B).

  As described above, in the present embodiment, it is possible to apply a predetermined voltage to each of the pixel electrodes 24 in the matrix panel 20 via the latent image writing control device 100 ′. The transfer process can be performed by applying different voltages for each pixel electrode 24, and the spread of the electric field at the development position and the transfer position can be suppressed, so that a good image can be formed. In addition, since the latent image voltage has been subjected to gradation conversion, the amount of toner formed on the pixel electrode 24 during development can be varied to form an image with better image quality.

In the above embodiment, the image holding body 10 is shown in the form in which the matrix panel 20 is wound around the rigid drum 11. However, as the image holding body 10, thin film technology is used on the rigid drum 11 made of, for example, an aluminum alloy. Alternatively, the matrix panel 20 may be directly formed. The image carrier 10 may be a flat plate, and the developing devices 30 may be arranged in parallel. In this case, the image carrier 10 may be moved.
Further, although the mode in which the multiplexed toner image on the image holding member 10 is directly transferred to the recording material at the transfer position is shown, it may be transferred once again to the recording material after being transferred to the intermediate transfer member. There is no problem.
Furthermore, for example, a two-color developing device 30 is provided on the image carrier 10, and the image carriers 10 are arranged side by side on two sets of intermediate transfer members so that the toner images superimposed on the respective image carriers 10 are intermediate. There is no problem even if it is further stacked on the transfer body.

(A) (b) is explanatory drawing which shows the outline | summary of the image forming apparatus which concerns on embodiment model which embodies this invention. 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. FIG. 3 is an explanatory diagram illustrating a latent image writing control device according to the first embodiment. FIG. 4 is an explanatory diagram illustrating speed-related parameters according to the first embodiment. FIG. 6 is an explanatory diagram illustrating scanning timing in the first embodiment. 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. (A) is explanatory drawing which shows the application method of the latent image voltage of Embodiment 1, (b) is explanatory drawing in a comparison model. FIG. 3 is an explanatory diagram illustrating the magnitude of a latent image voltage for each color in the first embodiment. FIG. 6 is an explanatory diagram showing changes in latent image voltage in each development of the first embodiment. 3 is an explanatory diagram illustrating a transfer method according to Embodiment 1. FIG. FIG. 6 is an explanatory diagram illustrating a developing device used in an image forming apparatus according to a second embodiment. (A) (b) is explanatory drawing which shows the conductive toner used in Embodiment 2. FIG. FIG. 10 is an explanatory diagram illustrating a modification of the developing device according to the second embodiment. FIG. 10 is an explanatory diagram showing a latent image writing control apparatus according to a third embodiment. FIG. 10 is an explanatory diagram illustrating speed-related parameters according to the third embodiment. (A) and (b) are explanatory drawings showing the transfer voltage application method of the third embodiment. (A) (b) is explanatory drawing which shows the effect | action at the time of transcription | transfer of Embodiment 3. FIG. It is explanatory drawing which shows the outline | summary of the image forming apparatus of the conventional IOI system as a comparison model.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Image holding body, 1a ... Support body, 1b ... Pixel electrode, 2 ... Image writing means, 3 (3a-3d) ... Developing means, 4 ... Latent image writing control means, 5 ... Transfer medium, 6 ... Transfer Means 7: Transfer image writing control means

Claims (14)

A movable support and an image carrier supported by the support and having pixel electrodes arranged vertically and horizontally with the direction along the direction of movement of the support as a sub-scanning direction and a direction orthogonal to the direction as a main scanning direction; ,
Image writing means for applying each color latent image voltage based on an image signal for each color to each pixel electrode, and writing each color latent image pattern represented by the latent image potential for each pixel electrode on the image carrier;
A plurality of developing means arranged to face the image holding body along the moving direction of the image holding body and visualize each color latent image pattern with a corresponding color toner at a developing position facing the image holding body;
In writing each color latent image pattern by the image writing means, each color latent image voltage based on the image signal for each color is determined in consideration of the voltage correction based on the presence of the color toner image already formed for each pixel electrode. And a latent image writing control means for controlling the image writing means. The image forming apparatus according to claim 1.
The latent image writing control means determines each color latent image voltage so that the magnitude of the image signal up to the previous color and the magnitude of the image signal of the color are accumulated. Forming equipment. The image forming apparatus according to claim 1, wherein the image holding body is a rotating body.
When the circumferential length of the image carrier is L0, the length of the minimum arc between adjacent development positions is L1, and the circumferential velocity of the image carrier is V, the scanning speed S in the sub-scanning direction is:
S ≧ (L0 / L1) V
An image forming apparatus that is set to satisfy the above relationship. The image forming apparatus according to claim 1.
The image forming apparatus, wherein the latent image writing unit is configured to apply a latent image voltage to the pixel electrode using a thin film transistor. The image forming apparatus according to claim 1.
The developing means includes
A toner holding member disposed opposite to the image holding member and holding and transporting the charged conductive toner to a developing position; and a charge injection member arranged opposite to the image holding member on a side different from the image holding member. Have
An image forming apparatus comprising: charge injection means for injecting charges into uncharged conductive toner by applying a charge injection electric field between the charge injection member and the toner holder. The image forming apparatus according to claim 5.
The toner holder is
A developing toner holder that is rotatably provided facing the image carrier, holds and conveys the conductive toner to a development position, and develops the latent image on the image carrier with the conductive toner;
A conductive member that is provided so as to be able to rotate at a higher rotational speed than the developing toner holding member so as to face the developing toner holding member, and has been charged by the charge injecting means until reaching a portion away from the developing position of the developing toner holding member. An intermediate toner holder for holding and transporting the functional toner,
The moving electric field forming means provided between the developing toner holding member and the intermediate toner holding member causes a moving electric field to move the conductive toner from the intermediate toner holding member to the developing toner holding member. An image forming apparatus. The image forming apparatus according to claim 5.
The image forming apparatus, wherein the image holding member and the toner holding member are arranged in a non-contact manner. The image forming apparatus according to claim 5 or 6,
The image forming apparatus according to claim 1, wherein the charge injection means performs charge injection on the conductive toner by rubbing and rubbing the conductive toner while applying a charge injection electric field. The image forming apparatus according to claim 8.
The conductive toner is changed to a high resistance so as to maintain the charge retention property of the conductive toner at the development position, and the charge injection of the conductive toner is facilitated in a region where a charge injection electric field acts. An image forming apparatus characterized by changing to a low resistance. A movable support and an image carrier supported by the support and having pixel electrodes arranged vertically and horizontally with the direction along the direction of movement of the support as a sub-scanning direction and a direction orthogonal to the direction as a main scanning direction; ,
Image writing means for applying each color latent image voltage based on an image signal for each color to each pixel electrode, and writing each color latent image pattern represented by the latent image potential for each pixel electrode on the image carrier;
A plurality of developing means arranged to face the image holding body along the moving direction of the image holding body and visualize each color latent image pattern with a corresponding color toner at a developing position facing the image holding body;
In writing each color latent image pattern by the image writing means, each color latent image voltage based on the image signal for each color is determined in consideration of the voltage correction based on the presence of the color toner image already formed for each pixel electrode. Latent image writing control means for controlling the image writing means at
An image forming apparatus comprising: transfer means for transferring each color toner image formed on the image carrier by the plurality of developing means to a transfer medium. The image forming apparatus according to claim 10.
The image forming apparatus according to claim 1, wherein the transfer unit includes a transfer member that is disposed to face the image carrier and to which a predetermined transfer voltage is applied and a predetermined transfer electric field acts between the transfer unit and the image carrier. The image forming apparatus according to claim 10.
In addition to writing the latent image pattern, the image writing unit applies a transfer voltage based on each color toner image already formed for each pixel electrode, and transfers the image for each pixel electrode based on the transfer voltage. Write the transferred image pattern as potential change,
The transfer means is a counter electrode that is placed opposite to the image writing means for writing the transfer image pattern and an image holding member and applies a transfer electric field according to the transfer image pattern by the image writing means between the pixel electrodes. And an image forming apparatus. The image forming apparatus according to claim 12.
Further, when writing the transfer image pattern by the image writing unit, the transfer for controlling the image writing unit after determining the transfer voltage in consideration of each color toner image already formed for each pixel electrode by the plurality of developing units. An image forming apparatus comprising an image writing control unit. The aspect of the image forming apparatus according to claim 12, wherein the image holding body is a rotating body.
The circumference of the image carrier is L0, the length of the minimum arc between adjacent development positions is L1, and the length of the arc from the development position of the final color to the transfer position which is the opposite part between the opposing member and the image carrier. When the peripheral speed of the image carrier is L2, the scanning speed S in the sub-scanning direction is
S ≧ (L0 / L1) V and S ≧ (L0 / L2) V
An image forming apparatus that is set to satisfy the above relationship.

Images