Image forming apparatus

Abstract

The present invention provides an image forming apparatus that can ensure sufficient light intensity through multiple exposures, suppress a decrease in image sharpness, and correct image position with high resolution. [Solution] The exposure head includes a plurality of light-emitting units 50, each comprising a plurality of lower electrodes arranged in two dimensions in the main scanning direction and the sub-scanning direction, a light-emitting layer stacked on the lower electrodes that emits light when a voltage is applied, and an upper electrode stacked on the light-emitting layer; and an image controller unit capable of controlling the voltage to each of the lower electrodes so that multiple exposures are performed by the light-emitting units. The plurality of lower electrodes for forming the same pixel are arranged such that a portion of them overlap when viewed from the sub-scanning direction, and the distance between the centroids in the main scanning direction is equally spaced in the main scanning direction. If the width in the main scanning direction is W1 [mm], the number of units for forming the same pixel is n, and the distance between the centroids at equal intervals in the main scanning direction is d3 [mm], then d3 = W1 / n (where n is a natural number of 2 or more).

Description

Technical Field

[0001] The present invention relates to an image forming apparatus such as an electrophotographic copying machine or an electrophotographic printer that forms an image on a sheet using an electrophotographic image forming method.

Background Art

[0002] When forming an image with an electrophotographic image forming apparatus, first, an electrostatic latent image is formed on the surface of a photoreceptor by irradiating light corresponding to image data onto the surface of the photoreceptor. Then, toner is attached to the electrostatic latent image on the surface of the photoreceptor by a developing device to form a toner image, the toner image is transferred to a sheet, and the toner image transferred to the sheet is heated by a fixing device and fixed on the sheet to form an image.

[0003] Here, in Patent Document 1, as an apparatus for irradiating light onto a photoreceptor to form an electrostatic latent image, an image forming apparatus is described that includes a light emitting portion using an organic EL and an exposure head having a lens that forms the light irradiated from this light emitting portion onto the surface of the photoreceptor. By using such an exposure head, it is possible to reduce the number of components compared to a configuration of a laser scanning method in which laser light is deflected and scanned by a rotating polygon mirror to form an electrostatic latent image, and it is possible to miniaturize the image forming apparatus and reduce the manufacturing cost.

[0004] Also, the light quantity of one light emitting portion of the light emitting portion using an organic EL of the exposure head cannot be said to be sufficiently high. Therefore, in Patent Document 1, a configuration is described in which light is irradiated from a plurality of light emitting portions onto the same portion of the surface of the photoreceptor in order to supplement the light quantity for forming an electrostatic latent image on the surface of the photoreceptor. Specifically, the light emitting portions are two-dimensionally arranged in the rotational axis direction (main scanning direction) and the rotational direction (sub-scanning direction) of the photoreceptor in the exposure head. Then, by shifting the timing of light emission of the light emitting portions adjacent in the rotational direction of the photoreceptor according to the rotational speed of the photoreceptor, light is irradiated from a plurality of light emitting portions onto the same portion of the surface of the photoreceptor. Hereinafter, irradiating light from a plurality of light emitting portions onto the same portion of the surface of the photoreceptor is referred to as multi-exposure.

[0005] Furthermore, in the exposure head, if there is a misalignment in the mounting position when the light-emitting unit is mounted on the substrate, the exposure position on the photoreceptor may shift, potentially causing image misalignment. In response to this, Patent Document 2 describes a configuration in which dithering is performed using image data with a higher resolution than the spacing in the main scanning direction of the light-emitting unit, the image data is shifted according to the amount of misalignment in the mounting position of the light-emitting unit, and then the image data is converted to match the pitch in the main scanning direction of the light-emitting unit. This makes it possible to correct image misalignment with a resolution higher than the pitch in the main scanning direction of the light-emitting unit. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2018-134820 [Patent Document 2] Japanese Patent Publication No. 2019-217653 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] However, while the configuration in Patent Document 2 can correct image misalignment with a resolution higher than the spacing in the main scanning direction of the light-emitting unit, there is a risk that the sharpness of the image may decrease. This will be explained below with reference to the figures.

[0008] Figure 18(a) shows an example of image data when dithering is performed using image data with a resolution higher than the pitch in the main scanning direction of the light-emitting unit, and the image data is shifted according to the amount of displacement of the mounting position of the light-emitting unit. Figure 18(b) shows the image data shown in Figure 18(a) converted to match the pitch in the main scanning direction of the light-emitting unit. As shown in Figure 18, in the configuration of Patent Document 2, when high-resolution image data is converted to match the pitch in the main scanning direction of the light-emitting unit, the data at the edges of the image becomes an intermediate value, which may reduce the sharpness of the image.

[0009] Therefore, the present invention aims to provide an image forming apparatus that can correct the image position with a resolution higher than the pitch in the main scanning direction of the light-emitting unit, while ensuring sufficient light intensity through multiple exposures in the exposure head and suppressing a decrease in image sharpness. [Means for solving the problem]

[0010] A typical configuration of an image forming apparatus according to the present invention for achieving the above objective is an image forming apparatus that irradiates light onto the surface of a photoreceptor to form an electrostatic latent image and deposits toner onto the electrostatic latent image to form an image, wherein the exposure head irradiates light onto the surface of the photoreceptor to form the electrostatic latent image, and comprises a substrate, a first electrode layer including a plurality of electrodes arranged in two dimensions in the rotational direction of the photoreceptor and in the rotational axis direction of the photoreceptor and separated and arranged on the substrate, an emission-emitting section comprising a substrate, an emission-emitting layer laminated on the first electrode layer and emitting light when a voltage is applied, and a second electrode layer arranged on the side opposite to the side on which the first electrode layer is arranged relative to the emission-emitting layer and through which light can pass, and a control unit that controls the application of voltage to each of the plurality of electrodes included in the first electrode layer based on image data so that the emission-emitting layer emits light, wherein one pixel is in the rotational direction The device comprises a control unit capable of controlling the voltage to each of the plurality of electrodes based on the image data, so as to be formed by controlling the voltage to a plurality of electrodes arranged at different positions, wherein the plurality of electrodes for forming the same pixel are arranged such that a portion of the electrodes overlap each other when viewed from the direction of rotation, and the distance between the centroids of the plurality of electrodes in the direction of rotation axis is equally spaced in the direction of rotation axis, and when the width of the electrodes in the direction of rotation axis is W1 [mm], the number of the plurality of electrodes for forming the same pixel is n, and the distance between the centroids of the equally spaced electrodes in the direction of rotation axis is d3 [mm], then d3 = W1 / n (where n is a natural number of 2 or more), and the plurality of electrodes for forming the same pixel are arranged such that the centroid positions of each electrode are located at intervals of d3 in the direction of rotation axis. [Effects of the Invention]

[0011] According to the present invention, in an exposure head of an image forming apparatus, it is possible to secure the amount of light by multiple exposure, suppress a decrease in the sharpness of an image, and correct the image position with a resolution higher than the pitch in the main scanning direction of a light emitting unit.

Brief Description of the Drawings

[0012] [Figure 1] It is a schematic cross-sectional view of an image forming apparatus. [Figure 2] It is a perspective view and a cross-sectional view of a photosensitive drum and an exposure head. [Figure 3] It is a diagram showing a mounting surface of a printed circuit board included in an exposure head. [Figure 4] It is a diagram showing the positional relationship between two light emitting element array chips and a light emitting unit to be used. [Figure 5] It is a schematic diagram of a light emitting element array chip. [Figure 6] It is a cross-sectional view of a light emitting element array chip [Figure 7] It is a schematic diagram for explaining the arrangement of light emitting units. [Figure 8] It is a block diagram showing a system configuration of an image controller unit and an exposure head. [Figure 9] It is a diagram showing an example of image data before and after high-resolution processing. [Figure 10] It is a block diagram showing a system configuration of a light emitting element array chip. [Figure 11] It is a circuit diagram of a data holding unit. [Figure 12] It is an operation timing chart of a data holding unit. [Figure 13] It is a circuit diagram of an analog unit. [Figure 14] It is a diagram showing image data sent to a light emitting unit of a light emitting element array chip. [Figure 15] It is a schematic diagram showing the position of light on a photosensitive drum when a light emitting unit emits light. [Figure 16] It is a schematic diagram for explaining the arrangement of light emitting units. [Figure 17]It is a schematic diagram for explaining the arrangement of the light emitting part. [Figure 18] It is an explanatory diagram for explaining a conventional configuration.

Embodiment for Carrying Out the Invention

[0013] <Image forming apparatus> Hereinafter, the overall configuration of the image forming apparatus A according to the present invention will be described with reference to the drawings together with the operation during image formation. Note that the dimensions, materials, shapes, relative arrangements, etc. of the components described below are not intended to limit the scope of the present invention only to these, unless specifically described.

[0014] The image forming apparatus A is a full-color image forming apparatus that forms an image by transferring four colors of toner, yellow (Y), magenta (M), cyan (C), and black (K), onto a sheet. In the following description, members using the above-mentioned toners of each color are appended with Y, M, C, and K as subscripts. However, since the configurations and operations of each member are substantially the same except for the color of the toner used, the subscripts are appropriately omitted unless distinction is required.

[0015] FIG. 1 is a schematic cross-sectional view of the image forming apparatus A. As shown in FIG. 1, the image forming apparatus A has an image forming unit for forming an image. The image forming unit includes a photosensitive drum 1 (1Y, 1M, 1C, 1K) as a photoreceptor, a charging device 2 (2Y, 2M, 2C, 2K), an exposure head 6 (6Y, 6M, 6C, 6K), a developing device 4 (4Y, 4M, 4C, 4K), and a transfer device 5 (5Y, 5M, 5C, 5K).

[0016] Next, the image forming operation by the image forming apparatus A will be described. When forming an image, first, a sheet S stored in the sheet cassette 99a or the sheet cassette 99b is sent to the registration roller 96 by the pickup rollers 91a, 91b, the feed rollers 92a, 92b, and the conveyance rollers 93a to 93c. Thereafter, the sheet S is sent onto the conveyance belt 11 by the registration roller 96 at a predetermined timing.

[0017] Meanwhile, in the image forming unit, the surface of the photosensitive drum 1Y is first charged by the charging device 2Y. Next, the exposure head 6Y irradiates light onto the surface of the photosensitive drum 10Y according to the image data read by the image reading unit 90 or image data transmitted from an external device (not shown), forming an electrostatic latent image on the surface of the photosensitive drum 10Y. Subsequently, the developing device 4Y deposits yellow toner onto the electrostatic latent image formed on the surface of the photosensitive drum 1Y, forming a yellow toner image on the surface of the photosensitive drum 1Y. The toner image formed on the surface of the photosensitive drum 1Y is transferred to the sheet S being transported by the transport belt 11 when a transfer bias is applied to the transfer device 5Y.

[0018] Through a similar process, light from exposure heads 6M, 6C, and 6K illuminates the photosensitive drums 1M, 1C, and 1K, forming an electrostatic latent image. The developing units 4M, 4C, and 4K then form magenta, cyan, and black toner images. A transfer bias is then applied to the transfer units 5M, 5C, and 5K, causing these toner images to be superimposed onto the yellow toner image on the sheet S. This forms a full-color toner image on the surface of the sheet S corresponding to the image data.

[0019] Subsequently, the sheet S carrying the toner image is transported by a conveyor belt 97 to a fixing device 94, where it is heated and pressurized. This fixes the toner image on the sheet S to the sheet S. After that, the sheet S with the fixed toner image is discharged into a discharge tray 95 by a discharge roller 98.

[0020] <Exposure head> Next, we will describe the configuration of the exposure head 6.

[0021] Figure 2(a) is a perspective view of the photosensitive drum 1 and exposure head 6. Figure 2(b) is a cross-sectional view of the photosensitive drum 1 and exposure head 6. Figures 3(a) and 3(b) show the mounting surfaces of one side and the other side of the printed circuit board 22 on which the exposure head 6 is located. Figure 3(c) is an enlarged view of the region V shown in Figure 3(b).

[0022] As shown in Figure 2, the exposure head 6 is fixed to the surface of the photosensitive drum 1 by a fixing member (not shown). The exposure head 6 has a light-emitting element array chip 40 that emits light and a printed circuit board 22 on which the light-emitting element array chip 40 is mounted. It also has a rod lens array 23 that focuses (concentrates) the light emitted from the light-emitting element array chip 40 onto the photosensitive drum 1, and a housing 24 to which the rod lens array 23 and the printed circuit board 22 are fixed.

[0023] Furthermore, a connector 21 is mounted on the printed circuit board 22 on the side opposite to the mounting surface of the light-emitting element array chip 40. The connector 21 is provided for transmitting control signals for the light-emitting element array chip 40 transmitted from the image controller unit 70 (Figure 8) and for connecting power lines. The light-emitting element array chip 40 is driven via the connector 21.

[0024] As shown in Figure 3, 20 light-emitting element array chips 40 are mounted on the printed circuit board 22 in a staggered arrangement in two rows. Within each light-emitting element array chip 40, 748 light-emitting units 50 are arranged in the longitudinal direction (arrow X direction) at a predetermined resolution pitch. Within each light-emitting element array chip 40, 4 light-emitting units 50 are arranged in the short direction (arrow Y direction) at a predetermined pitch. In other words, in each light-emitting element array chip 40, the light-emitting units 50 are arranged two-dimensionally in the arrow X direction and arrow Y direction. The four light-emitting units 50 arranged in the arrow Y direction form the same pixel through multiple exposure, which will be described later.

[0025] In this embodiment, the resolution pitch of the light-emitting element array chip 40 is 1200 dpi (approximately 21.16 μm). The distance from one end to the other in the longitudinal direction of the light-emitting section 50 of each light-emitting element array chip 40 is approximately 15.828 mm. That is, the exposure head 6 is equipped with a total of 14,960 light-emitting sections 50 in the direction of arrow X, which enables exposure processing corresponding to an image width in the longitudinal direction of approximately 316 mm (≒ approximately 15.8 mm × 20 chips). In the short direction (direction of arrow Y) of the light-emitting element array chip 40, the distance L1 between the light-emitting sections 50 of adjacent light-emitting element array chips 40 is approximately 105 μm (equivalent to 5 pixels at 1200 dpi, and 10 pixels at 2400 dpi).

[0026] Furthermore, adjacent light-emitting element array chips 40 in the direction of arrow Y are arranged so that their respective light-emitting sections 50 overlap in the direction of arrow X. This is to prevent positional misalignment during the mounting process of the light-emitting element array chips 40, which can cause the position of the light irradiated on the photosensitive drum 1 to shift at the boundary portion of each light-emitting element array chip 40, resulting in variations in density and the formation of image streaks. The amount of overlap is calculated from the maximum amount of mounting variation of the mounting device (die bonder) and set to an amount that prevents gaps from forming between the light-emitting sections 50 of adjacent light-emitting element array chips 40 in the direction of arrow Y.

[0027] Furthermore, the head information storage unit 171 (Figure 8) of the exposure head 6 stores the amount of misalignment of the light-emitting element array chip 40 during mounting, which is measured during the manufacturing process. During image formation, the image controller unit 70 (Figure 8) selectively emits light from the light-emitting unit 50 based on the misalignment information of the light-emitting element array chip 40 stored in the head information storage unit 171, as will be explained below, to suppress the occurrence of image streaks.

[0028] Figure 4 shows two adjacent light-emitting element array chips 40 in the direction of arrow Y. In Figure 4, the light-emitting parts 50 with diagonal lines are those used during exposure, and the light-emitting parts 50 without diagonal lines are those not used during exposure. Also, in Figure 4(a) and Figure 4(b), the relative positions of the two adjacent light-emitting element array chips 40 in the direction of arrow X are different.

[0029] As shown in Figure 4, the image controller unit 70 selects the light-emitting units 50 of two adjacent light-emitting element array chips 40 in the direction of arrow Y, such that the distance L2 between the light-emitting units 50 used during exposure in the direction of arrow X is closest to a 4800 dpi interval. In this embodiment, as will be described later, the exposure head 6 is configured to expose at a resolution of 4800 dpi in the direction of arrow X, so although the distance L2 is set to be as close to a 4800 dpi interval as possible, the distance L2 is set according to the exposure resolution of the exposure head 6 in the direction of arrow X.

[0030] In this embodiment, the direction of arrow X, which is the longitudinal direction of the light-emitting element array chip 40, is the rotation axis direction of the photosensitive drum 1 and is also the main scanning direction. The direction of arrow Y, which is the short direction of the light-emitting element array chip 40, is the rotation direction of the photosensitive drum 1 and is also the sub-scanning direction. The rotation direction of the photosensitive drum 1 is the tangential direction of the photosensitive drum 1 at the exposure position on the photosensitive drum 1 where light is focused by the exposure head 6. The direction of arrow Z is the stacking direction in which each layer of the light-emitting section 50, which will be described later, overlaps. The longitudinal direction of the light-emitting element array chip 40 may be tilted by approximately ±1° with respect to the rotation axis direction of the photosensitive drum 1. The short direction of the light-emitting element array chip 40 may also be tilted by approximately ±1° with respect to the rotation direction of the photosensitive drum 1.

[0031] <hibi array chip> Next, the configuration of the light-emitting element array chip 40 will be described.

[0032] Figure 5 is a schematic diagram of the light-emitting element array chip 40. Figure 6 is a cross-sectional view of the light-emitting element array chip 40 cut along the MM cross-section shown in Figure 5. Figure 7 is a schematic diagram illustrating the arrangement of the light-emitting section 50 of the light-emitting element array chip 40.

[0033] As shown in Figure 5, the light-emitting element array chip 40 includes a light-emitting substrate 42 (substrate) with a built-in circuit section 46 for controlling the light-emitting units 50, a light-emitting region 44 in which multiple light-emitting units 50 are regularly arranged on the light-emitting substrate 42, and wire bonding pads 48. Signal input and output between the external environment of the light-emitting element array chip 40 and the circuit section 46, as well as power supply to the circuit section 46, are performed through the wire bonding pads 48. The circuit section 46 can be an analog drive circuit, a digital control circuit, or a circuit including both.

[0034] As shown in Figure 6, the light-emitting section 50 consists of a light-emitting substrate 42, a plurality of lower electrodes 54 arranged in two dimensions on the light-emitting substrate 42 at regular intervals (intervals d1 and d2 shown in Figure 7) in the directions of arrows X and Y, a light-emitting layer 56, and an upper electrode 58.

[0035] The lower electrode 54 (the first electrode layer having multiple electrodes) consists of multiple electrodes formed in a layered and separate manner on the light-emitting substrate 42, and each electrode is provided corresponding to a pixel. In other words, each lower electrode 54 is provided to form one pixel.

[0036] The upper electrode 58 (second electrode layer) is laminated on the light-emitting layer 56 at a position opposite to the side on which the lower electrode 54 is positioned relative to the light-emitting layer 56. The upper electrode 58 is an electrode that can transmit (is capable of transmitting) light of the emission wavelength of the light-emitting layer 56.

[0037] The circuit unit 46 controls the potential of the selected lower electrode 54 based on a control signal generated according to the image data, creating a potential difference between the selected lower electrode 54 and the upper electrode 58. When a potential difference is created between the upper electrode 58, which is the anode, and the lower electrode 54, which is the cathode, electrons flow from the cathode into the light-emitting layer 56, and holes flow from the anode into the light-emitting layer 56. The light-emitting layer 56 emits light as electrons and holes recombine in the light-emitting layer 56.

[0038] When the light-emitting layer 56 emits light, the light directed toward the upper electrode 58 passes through the upper electrode 58 and is emitted. Also, the light directed from the light-emitting layer 56 toward the lower electrode 54 is reflected from the lower electrode 54 toward the upper electrode 58, and this reflected light also passes through the upper electrode 58 and is emitted. In this way, the light-emitting unit 50 emits light. Although there is a time difference in the emission timing between the light emitted directly from the light-emitting layer 56 toward the upper electrode 58 and the light reflected from the lower electrode 54 and emitted from the upper electrode 58, the thickness of the layers in the light-emitting unit 50 is extremely thin, so they can be considered to be almost simultaneous.

[0039] In this embodiment, the light-emitting substrate 42 is a silicon substrate. The upper electrode 58 is preferably transparent to the emission wavelength of the light-emitting layer 56. For example, by using a transparent electrode such as indium tin oxide (ITO), the aperture ratio becomes substantially 100%, and the light emitted by the light-emitting layer 56 passes through the upper electrode 58 and is emitted directly. In this embodiment, the upper electrode 58 is an anode commonly provided for each lower electrode 54, but it may also be configured to be provided individually for each lower electrode 54, or one upper electrode 58 may be provided for every multiple lower electrodes 54. Furthermore, when using a transparent electrode as the upper electrode 58, it is not necessarily required that the entire electrode be transparent; only the opening through which light is emitted may be transparent, and the rest may be wired with electrodes other than transparent electrodes, such as metal wires.

[0040] The light-emitting layer 56 can be an organic EL film or an inorganic EL layer. When an organic EL film is used as the light-emitting layer 56, the light-emitting layer 56 may be a laminated structure that includes functional layers such as an electron transport layer, a hole transport layer, an electron injection layer, a hole injection layer, an electron blocking layer, and a hole blocking layer as needed. The light-emitting layer 56 may be formed continuously in the direction of arrow X, or it may be divided into sections of the same size as the lower electrode 54. Alternatively, each lower electrode 54 may be divided into multiple groups, and one light-emitting layer 56 may be laminated on top of each lower electrode 54 belonging to that group.

[0041] Furthermore, when using a moisture-sensitive light-emitting material such as an organic EL layer or an inorganic EL layer as the light-emitting layer 56, it is desirable to seal it to prevent moisture from entering the light-emitting region 44. As a sealing method, for example, a sealing film can be formed by forming a single or stacked thin film of silicon oxide, silicon nitride, aluminum oxide, etc. As a method for forming the sealing film, a method that has excellent coverage performance for structures such as steps is preferred, and for example, atomic layer deposition (ALD) can be used. Note that the material, composition, and formation method of the sealing film are examples and are not limited to the examples described above, and suitable ones can be selected as appropriate.

[0042] Furthermore, the lower electrode 54 is preferably made of a metal with high reflectivity to the emission wavelength of the light-emitting layer 56. For example, Ag, Al, or an alloy of Ag and Al can be used. The lower electrode 54 is formed using Si integrated circuit processing technology along with the formation of the circuit section 46 and is directly connected to the drive section of the circuit section 46. By forming the lower electrode 54 using Si integrated circuit processing technology in this way, the process rule is approximately 0.2 μm, resulting in high precision, and the lower electrodes 54 can be arranged with high precision and density. Furthermore, because the lower electrodes 54 can be arranged at high density, almost the entire light-emitting region 44 can be made to emit light, thereby increasing the utilization efficiency of the light-emitting region 44. The organic material of the light-emitting layer 56 is filled between each lower electrode 54, and each lower electrode 54 is separated by the organic material.

[0043] Furthermore, when the voltage across both ends of the light-emitting section 50 exceeds a predetermined level, current begins to flow, and thereafter the value of the current increases approximately proportionally to the voltage. There is variation in the voltage at which current begins to flow in each light-emitting section 50. Therefore, before the product is shipped from the factory, the light-emitting sections 50 of the light-emitting element array chip 40 are individually and sequentially illuminated, and the current flowing to the light-emitting sections 50 is adjusted so that the light focused through the rod lens array 23 reaches a predetermined light intensity. In addition to the light intensity adjustment described above, the exposure head 6 is also focused before the product is shipped from the factory, adjusting the distance between the light-emitting element array chip 40 and the rod lens array 23.

[0044] As shown in Figure 7, the light-emitting units 50 are arranged in a matrix at predetermined intervals in the X-direction and Y-direction within the light-emitting region 44. In this embodiment, the width W1 of the light-emitting units 50 in the X-direction is 19.80 μm, and the spacing d1 between adjacent light-emitting units 50 in the X-direction is 0.68 μm. That is, the light-emitting units 50 are arranged at a pitch of 21.16 μm (1200 dpi) in the X-direction. Note that the pitch of the light-emitting units 50 in the X-direction may be shifted within a tolerance range. The tolerance for the pitch of the light-emitting units 50 in the X-direction is ±1% of the pitch of the light-emitting units 50 in the X-direction as specified in the design. In other words, the tolerance for the pitch of the light-emitting units 50 in the X-direction in this embodiment is ±0.21 μm.

[0045] Furthermore, the width W2 of the light-emitting section 50 in the direction of arrow Y is also 19.80 μm, similar to the width W1. That is, the light-emitting section 50 in this embodiment has a square shape with sides of 19.80 μm. Although the light-emitting section 50 has a square shape because its widths W1 and W2 are equal, the dimensions of these widths W1 and W2 may differ within the tolerance range. In this embodiment, the tolerance for both widths W1 and W2 is ±0.2 μm.

[0046] Furthermore, the spacing d2 between adjacent light-emitting units 50 in the direction of arrow Y is 0.68 μm, similar to spacing d1, and the light-emitting units 50 are arranged at a pitch of 21.16 μm (1200 dpi) in the direction of arrow Y. Note that the pitch of the light-emitting units 50 in the direction of arrow Y may be shifted within the tolerance range. The tolerance for the pitch of the light-emitting units 50 in the direction of arrow Y is ±1% of the pitch of the light-emitting units 50 in the direction of arrow Y as specified in the design. In other words, the tolerance for the pitch of the light-emitting units 50 in the direction of arrow Y in this embodiment is ±0.21 μm. Here, the spacings d1 and d2 of the light-emitting units 50 are set wider than the spacing dz (Figure 6) between the upper electrode 58 and the lower electrode 54. With this configuration, leakage current between adjacent lower electrodes 54 in the directions of arrow X and arrow Y can be suppressed, and false illumination of the light-emitting units 50 can be suppressed.

[0047] In this embodiment, the width, shape, and arrangement of the light-emitting section 50 are substantially determined by the width, shape, and arrangement of the lower electrode 54, and can therefore be rephrased as the width, shape, and arrangement of the lower electrode 54. In this embodiment, the distance between the light-emitting sections 50, i.e., the distance between the lower electrodes 54, means the distance between the centers of gravity defined based on the design designation of the center of gravity of the lower electrode 54.

[0048] Adjacent light-emitting units 50 in the direction of arrow Y are arranged such that their positions are offset by a gap d3 in the direction of arrow X. In this embodiment, the gap d3 is set to 5.29 μm (4800 dpi). Looking at the light-emitting units 50 as a whole, the positions of the four parallel light-emitting units 50 in the direction of arrow Y are offset from each other in the direction of arrow X by integer multiples of the gap d3. In other words, the four lower electrodes 54 provided in the direction of arrow Y to form the same pixel are arranged such that they partially overlap each other when viewed from the direction of arrow Y, and the distance between the centroids of the lower electrodes 54 is equal in the direction of arrow X.

[0049] In this embodiment, the interval d3 is determined as follows: m [dpi] is the resolution of the image formed by the image forming apparatus A in the main scanning direction (arrow X direction), n [units] is the number of light-emitting units 50 arranged in parallel in the arrow Y direction, and the reference value of the amount of displacement of the positions of the light-emitting units 50 arranged in parallel in the arrow Y direction toward the arrow X direction is the interval d3 [mm] (reference value). In this case, the interval d3 is obtained from d3 = 25.4 / m × 1 / n, and the light-emitting units 50 arranged in parallel in the arrow Y direction are arranged so that their positions are offset from each other by integer multiples of the interval d3. In other words, in this embodiment, m = 1200 and n = 4, so d3 = 25.4 / 1200 × 1 / 4 = 0.00529 [mm] = 5.29 [μm].

[0050] Alternatively, determining the interval d3 as follows will yield the same result as the above calculation for interval d3. That is, the pitch in the direction of arrow X of multiple light-emitting units 50 that are at the same position in the direction of arrow Y is q [mm], the number of light-emitting units 50 arranged in parallel in the direction of arrow Y is n [units], and the reference value of the amount of displacement of the positions of the light-emitting units 50 arranged in parallel in the direction of arrow Y towards the direction of arrow X is the interval d3 [mm] (reference value). In this case, the interval d3 can be obtained from d3 = q / n, and the light-emitting units 50 arranged in parallel in the direction of arrow Y are arranged so that their positions are offset from each other by integer multiples of the interval d3. In other words, in this embodiment, q = 0.02116 and n = 4, so d3 = 0.02116 / 4 = 0.00529 [mm] = 5.29 [μm].

[0051] Alternatively, the interval d3 may be determined in the following way, instead of the method described above. That is, with respect to light-emitting units 50 arranged at different positions in the direction of arrow Y to form the same pixel, let n be the number of light-emitting units 50 and W1 [mm] be the width of the light-emitting units 50 in the direction of arrow X. In this case, the interval d3 is calculated from d3 = W1 / n (where n is a natural number greater than or equal to 2). The light-emitting units 50 arranged at different positions in the direction of arrow Y to form the same pixel are positioned such that the centroid positions of each light-emitting unit 50 are spaced apart by d3 in the direction of arrow X. In other words, each light-emitting unit 50 is arranged such that the distance between the centroids of the four light-emitting units 50, which are arranged at different positions in the direction of arrow Y to form the same pixel by multiple exposure described later, is d3. In this embodiment, W1 = 19.80 [μm] = 0.01980 [mm] and n = 4. Therefore, d3 = 0.01980 / 4 = 0.00495 [mm] = 4.95 [μm]. By setting the interval d3 in this way, the overlap amount in the X direction of the four light-emitting units 50, which are positioned at different locations in the Y direction to form the same pixel, is made uniform. As a result, in the multiple exposure described later, the amount of light in each pixel is made uniform, and the density of each pixel is made uniform.

[0052] In this invention, the shape of the light-emitting unit 50 is not limited to a square. It can be a polygon with more than four sides, a circle, an ellipse, etc., as long as it emits light of an exposure area size corresponding to the output resolution of the image forming apparatus A and the image quality of the output image meets the design specifications of the image forming apparatus A. However, since organic light-emitting materials have less light output than LEDs, it is preferable to make the light-emitting unit 50 a square and reduce the distance between adjacent light-emitting units 50 so that it is possible to secure a light-emitting area that is sufficient to obtain a light output that changes the potential of the photosensitive drum 1. Also, the number of light-emitting units 50 arranged in parallel in the direction of arrow Y is not limited to four, as long as two or more are provided, and is determined based on the amount of light required for the exposure processing of the exposure head 6 and the resolution of the image formed by the image forming apparatus A.

[0053] As mentioned above, the distance between the light-emitting parts 50, that is, the distance between the lower electrodes 54, is defined based on the centroid position of the lower electrode 54 in the design designation. That is, if the shape of the lower electrode 54 is a regular polygon, the distance between the centroids is set based on the intersection of the diagonals; if it is a perfect circle, the center of the circle; and if it is an ellipse, the intersection of the major and minor axes. Note that if the shape of the lower electrode 54 is a regular polygon, the corners do not have to be perfect and may have a radius (R).

[0054] <System configuration of exposure head> Next, the configuration of the exposure head 6 and the image controller unit 70 (control unit) that controls the exposure head 6 will be described. The image controller unit 70 is located on the main body side of the image forming apparatus A. In the following description, the control performed when processing a single image data (monochromatic) will be explained, but when performing image forming operations, the same processing will be performed in parallel for four image data corresponding to yellow, magenta, cyan, and black.

[0055] Figure 8 is a block diagram showing the system configuration of the image controller unit 70 and the exposure head 6. As shown in Figure 8, the image controller unit 70 includes an image data generation unit 71, a chip data conversion unit 72, a CPU 73, and a synchronization signal generation unit 74. The image controller unit 70 processes image data and image formation timing using these components, and transmits control signals to the printed circuit board 22 of the exposure head 6 to control the exposure head 6.

[0056] The image data generation unit 71 (image processing unit) receives image data of a document read by the image reading unit 90 and image data transferred from an external device via a network. The image data generation unit 71 performs dithering on the input image data at a resolution instructed by the CPU 73 to generate image data for output. In this embodiment, the image data generation unit 71 performs dithering at a resolution of 1200 dpi and binary grayscale, and then generates data at 4800 dpi in the main scanning direction, 2400 dpi in the sub-scanning direction, and binary grayscale through a high-resolution processing. In the high-resolution processing, the 1200 dpi data is simply copied.

[0057] Figure 9(a) shows an example of image data D1 (first image data) before high-resolution processing by the image data generation unit 71. Figure 9(b) shows image data D2 (second image data) obtained by processing image data D1 with high resolution by the image data generation unit 71. As shown in Figure 20, the high-resolution processing generates image data D2 that matches the exposure resolution of the light-emitting element array chip 40. At this time, the image data generation unit 71 generates binarized data, enabling the formation of a high-definition image without losing image sharpness.

[0058] In this embodiment, the resolution of the dithering process of the image data generation unit 71 is set to 1200 dpi, so the image data after dithering is generated in units of four light-emitting units 50 arranged in parallel in the direction of arrow X on the photosensitive drum 1. Of the four rows of light-emitting units 50 extending in the direction of arrow X and arranged in parallel in the direction of arrow Y, the distance from the center of the rod lens array 23 differs between the first row of light-emitting units 50 and the second row of light-emitting units 50, resulting in a difference in the amount of light irradiated onto the photosensitive drum 1 from each row. The same applies to the third and fourth rows of light-emitting units 50. Therefore, by performing dithering on units of four light-emitting units 50 arranged in parallel in the direction of arrow X to generate image data, the occurrence of moiré and banding due to differences in density of the generated dots can be suppressed. Furthermore, by shifting the image data after dithering to correct the image position with a resolution of 4800 dpi, it becomes possible to correct the image position with a high resolution of 4800 dpi while suppressing moiré and banding.

[0059] The synchronization signal generation unit 74 periodically generates a line synchronization signal (control signal) indicating the start of image data acquisition and transmits it to the chip data conversion unit 72. The CPU 73 defines one line period as the period during which the surface of the photosensitive drum 1 moves in the rotational direction according to the resolution of the sub-scanning direction of the image formed by the image forming apparatus A, relative to a preset rotational speed of the photosensitive drum 1, and instructs the synchronization signal generation unit 74 on the time interval of the signal period.

[0060] In this embodiment, the resolution of the image formed by the image forming apparatus A in the sub-scanning direction is 2400 dpi, and the photosensitive drum 1 rotates at 200 mm / s. Therefore, the time it takes for the photosensitive drum 1 to travel a distance of 2400 dpi pixel size (10.58 μm) is 52.92 μs, and the period of the line synchronization signal is 52.92 μs. The rotation speed of the photosensitive drum 1 is calculated by the CPU 73 based on a setting value stored in a memory unit (not shown).

[0061] The chip data conversion unit 72, in synchronization with the line synchronization signal generated and input by the synchronization signal generation unit 74, divides the image data into four lines (the number of elements in the Y direction of the light-emitting unit 50) for each light-emitting element array chip 40. The chip data conversion unit 72 then transmits the image data along with the clock signal and line synchronization signal to each light-emitting element array chip 40 via the line synchronization signal line 75, the clock signal line 76, and the image data signal line 77. There are four image data signal lines 77, which is the same number as the number of elements in the Y direction of the light-emitting unit 50.

[0062] The head information storage unit 171 of the exposure head 6 is connected to the CPU 73 via a communication signal line 79. The head information storage unit 171 stores the light emission amount and mounting position information of each light-emitting element array chip 40 as head information. The light-emitting element array chip 40 causes the light-emitting unit 50 to emit light based on the set values ​​of the above signals input from the image controller unit 70. The light-emitting element array chip 40 also generates a line synchronization signal used by other light-emitting element array chips 40 connected via a line synchronization signal line 75. <System configuration of the light-emitting element array chip> Next, the system configuration of the light-emitting element array chip 40 will be described.

[0063] Figure 10 is a block diagram showing the system configuration of the light-emitting element array chip 40. In Figure 10, the connections are omitted because a clock signal is input to all blocks of the digital section 80. As shown in Figure 10, the circuit section 46 of the light-emitting element array chip 40 consists of a digital section 80 and an analog section 86.

[0064] The digital unit 80 comprises a communication IF unit 81, a register unit 82, an acquisition signal generation unit 83, a line synchronization signal generation unit 84, and a data holding unit 85. These units generate pulse signals to cause the light-emitting unit 50 to light up, synchronized with the clock signal and based on preset values ​​set by the communication signal, image data signals, and line synchronization signals, and transmit them to the analog unit 86. The data holding unit 85 is provided with 748 units (85-001 to 85-748), which is the number of light-emitting units 50 in the direction of arrow X on one light-emitting element array chip 40.

[0065] The line synchronization signal generation unit 84 delays the input line synchronization signal for a predetermined time and generates a line synchronization signal to be used by other light-emitting element array chips 40 connected via the line synchronization signal line 75. The acquisition signal generation unit 83 outputs a data latch signal we001 to the data holding unit 85-001 at a timing delayed by a predetermined set time input from the register unit 82 from the input line synchronization signal.

[0066] The register section 82 stores information such as the delay time of the signal acquisition generation section 83 and the drive current setting information set by the analog section 86. The communication IF section 81 controls the writing and reading of setting values ​​to the register section 82 based on the communication signal input from the CPU 73.

[0067] <Data storage section> Next, the configuration of the data storage unit 85 will be described.

[0068] Figure 11 is a circuit diagram of the data holding unit 85. As shown in Figure 11, the data holding unit 85 receives four lines of image data (image data 1 to 4), a clock signal, and a data latch signal wen (n=1 to 748). Each data holding unit 85 has four flip-flop circuits and four gate circuits to latch the four lines of image data that are input simultaneously when the data latch signal is input. Each data holding unit 85 also has one flip-flop circuit to output the data latch signal with a delay of one clock cycle.

[0069] Figure 12 is an operation timing chart for the data holding unit 85. As shown in Figure 12, four lines of image data (D1[1] to D1[4]) are simultaneously input to the data holding unit 85-001. The data holding unit 85-001 latches this image data when it receives the data latch signal we001 from the acquisition signal generation unit 83 and generates drive signals (P001[1] to P001[4]). The data holding unit 85-001 also delays the input data latch signal we001 by one clock cycle and transmits it as a data latch signal we002 to the next data holding unit 85-002.

[0070] Image data for four lines (D2[1]~D2[4]) is simultaneously input to the data holding unit 85-002. When the data latch signal we002 is input from the data holding unit 85-001, the data holding unit 85-002 latches this image data and generates drive signals (P002[1]~P002[4]). The data holding unit 85-002 also delays the data latch signal we002 by one clock cycle and transmits it to the data holding unit 85-003 as a data latch signal we003.

[0071] In this manner, the data holding units 85 (-001 to 748) sequentially latch image data while transmitting data latch signals up to the 748th data holding unit 85. Once a data holding unit 85 (-001 to 748) has latched an image data, it transmits the latched signal to the analog unit 86 as a drive signal. In this embodiment, since image data for 4 lines is latched with a single data latch signal, drive signals for 4 lines (4 pixels) are output simultaneously.

[0072] <Analog Section> Next, the configuration of the analog section 86 will be explained. The analog section 86 consists of drive circuits that are connected one-to-one with each light-emitting section 50. For the sake of explanation, although only one drive circuit will be described below, it will be assumed that there are the same number of similar drive circuits as there are light-emitting sections 50, i.e., 748 × 4 rows = 2992 circuits.

[0073] Figure 13 is a circuit diagram of the analog section 86. As shown in Figure 13, the analog section 86 consists of a DAC 61 for current setting, a MOSFET 62 for current control, and a MOSFET 63 for switching. The DAC 61 receives the current setting value to be flowed to the light-emitting section 50 from the register section 82 of the digital section 80 as a digital value, converts it to an analog voltage, and outputs it.

[0074] The MOSFET 62 used for current control is a P-channel MOSFET, with its source terminal connected to the power supply voltage VDD and its gate terminal connected to the output of the DAC 61. The higher the analog voltage input from the DAC 61, the greater the current flowing from the source to the drain.

[0075] The switching MOSFET 63 is a P-channel MOSFET, with its source terminal connected to the drain terminal of the current-controlling MOSFET 62, and its gate terminal receiving a drive signal output from the data-holding unit 85. The drive signal is a binary signal with high and low levels. When a high level signal is input, MOSFET 63 turns ON, and a current controlled by the current-controlling MOSFET 62 flows from the source to the drain. Since the drain terminal is connected to the anode terminal of the light-emitting unit 50, this current becomes the drive current for the light-emitting unit 50.

[0076] <Control of the light-emitting part during image formation> Next, the control of the light-emitting unit 50 during image formation will be explained. In the following explanation, light emission from the light-emitting unit 50 refers to the emission of light with an intensity that displaces the charge potential of the photosensitive drum 1 to the extent that toner is developed. In other words, light emission from the light-emitting unit 50 that displaces the charge potential of the photosensitive drum 1 to the extent that a toner image is not developed as a visible image is not included in the definition of light emission.

[0077] Figure 14 shows the image data sent to the light-emitting unit 50 of the light-emitting element array chip 40 when forming a single line image extending in the main scanning direction (arrow X direction). As shown in Figure 14, when forming the line image described above, first the upstream light-emitting unit 50 is made to emit light from the four light-emitting units 50 that are arranged in parallel in the rotation direction of the photosensitive drum 1 (arrow Y direction). Next, at a timing delayed by two lines of 2400 dpi, the light-emitting unit 50 immediately downstream of the first light-emitting unit 50 is made to emit light. The delay operation sets the image data readout position so that the image data at the corresponding position is read out in response to a common line synchronization signal. This makes it possible to match the exposure position (irradiation position) on the photosensitive drum 1 in the sub-scanning direction with the light emitted from the upstream light-emitting unit 50 in the rotation direction of the photosensitive drum 1 and the light emitted from the light-emitting unit 50 immediately downstream of this light-emitting unit 50.

[0078] Next, the light-emitting unit 50 located three positions downstream from the upstream light-emitting unit 50 in the rotational direction of the photosensitive drum 1 is made to emit light at a timing delayed by 4 lines at 2400 dpi. Similarly, the light-emitting unit 50 located four positions downstream from the upstream light-emitting unit 50 in the rotational direction of the photosensitive drum 1 is made to emit light at a timing delayed by 6 lines at 2400 dpi. This makes it possible to align the exposure positions in the sub-scanning direction on the photosensitive drum 1 with respect to the light emitted from the four light-emitting units 50 that are arranged in parallel in the rotational direction of the photosensitive drum 1.

[0079] Figure 15 is a schematic diagram showing the light irradiation position on the photosensitive drum 1 when four light-emitting units 50 arranged in parallel in the direction of arrow Y are emitted by the above control. As shown in Figure 15, when four light-emitting units 50 arranged in parallel in the direction Y are emitted at the timing described above, the light H1 to H4 emitted from the four light-emitting units 50 are irradiated on the photosensitive drum 1 at the same position in the direction of arrow Y, but with a position shift of the interval d3 in the direction of arrow X. Here, the interval d3 is set to d3 = 25.4 / m × 1 / n, so on the photosensitive drum 1, there is a portion where at least two or more of the light H1 to H4 overlap, thereby forming one pixel. Therefore, it is possible to supplement the amount of light when multiple exposure is performed on the photosensitive drum 1 to form an electrostatic latent image.

[0080] In this embodiment, the light-emitting units 50, which are arranged in parallel in the direction of arrow Y, are offset from each other by 5.29 μm (=d3) in the direction of arrow X, which corresponds to 4800 dpi. Therefore, exposure processing can be performed on the photosensitive drum 1 at a resolution of 4800 dpi without using intermediate values ​​for the data of the image edges. Thus, the image position can be corrected at a resolution higher than the pitch of the light-emitting units 50 in the main scanning direction while suppressing a decrease in the sharpness of the image. Even when the interval d3 is set to 4.95 [μm] calculated from d3 = W1 / n (where n is a natural number of 2 or more), the effect of performing exposure processing at a resolution higher than the pitch of the light-emitting units 50 in the main scanning direction on the photosensitive drum 1 can be obtained. In this case, the image data generation unit 71 performs high-resolution processing according to the value of the interval d3 calculated from d3 = W1 / n (where n is a natural number of 2 or more).

[0081] Furthermore, if the width W1 of the light-emitting unit 50 in the direction of arrow X is small, the amount of overlap of light H1 to H4 between parallel light-emitting units 50 in the direction of arrow Y will decrease, which may cause multiple exposures to not work properly or create gaps between each of the light H1 to H4, resulting in image streaks. Therefore, the width W1 is set to at least twice the spacing d3. This allows light emitted not only from adjacent light-emitting units 50 in the direction of arrow Y, but also from light-emitting units 50 two units away in the direction of arrow Y, to overlap on the photosensitive drum 1, enabling accurate multiple exposures and suppressing image streaks.

[0082] As mentioned above, the distance L1 (shortest distance) between the light-emitting sections 50 of two adjacent light-emitting array chips 40 in the direction of arrow Y, as shown in Figure 3(c), is set to 10 lines at 2400 dpi. Therefore, with respect to the rotation direction of the photosensitive drum 1, the light emission timing is delayed by 12 lines, which is the distance L1 plus the light-emitting area of ​​two lines of pixels, between the light-emitting section 50 furthest downstream of the first light-emitting array chip 40 and the light-emitting section 50 furthest upstream of the second light-emitting array chip 40 located downstream of the first light-emitting array chip 40. With this configuration, the exposure position in the sub-scanning direction on the photosensitive drum 1 can be aligned between the light-emitting sections 50 of each of the staggered-arranged light-emitting array chips 40.

[0083] In this embodiment, the light-emitting units 50 of the light-emitting element array chip 40 were described in a configuration in which the light-emitting units 50, which are arranged in parallel in the direction of arrow Y, are offset from each other by an integer multiple of the spacing d3 in the direction of arrow X. However, the present invention is not limited to this. That is, if the light-emitting element array chip 40 has a configuration in which a group of light-emitting units (electrode group) is included in which the light-emitting units 50, which are arranged in parallel in the direction of arrow Y, are offset from each other by an integer multiple of the spacing d3 in the direction of arrow X, the same effects as described above can be obtained.

[0084] Furthermore, although this embodiment describes a configuration in which adjacent light-emitting units 50 in the direction of arrow Y are arranged in the direction of arrow X with a position shifted by an interval d3, the present invention is not limited to this. That is, for example, as shown in Figure 16, if the amount of shift in the direction of arrow X between multiple light-emitting units 50 arranged in parallel in the direction of arrow Y is an integer multiple of the interval d3, the amount of shift between adjacent light-emitting units 50 in the direction of arrow Y does not need to be the interval d3. Also, as shown in Figure 17, a configuration may be used in which some of the multiple light-emitting units 50 arranged in parallel in the direction of arrow Y are located at the same position in the direction of arrow X. Even with the configurations shown in Figures 16 and 17, the same exposure as described above can be performed by adjusting the image data sent to the light-emitting units 50. [Explanation of Symbols]

[0085] 1…Photosensitive drum (photoconductor) 6… Exposure head 42…Light-emitting substrate (substrate) 50…Light-emitting part 54…Lower electrode (first electrode layer containing multiple electrodes) 56…Emitting layer 58...Top electrode (second electrode layer) 70…Image controller unit (control unit) 71…Image data generation unit (image processing unit) A...Image forming apparatus

Claims

1. In an image forming apparatus that forms an image by irradiating the surface of a photoreceptor with light to form an electrostatic latent image and then depositing toner onto the electrostatic latent image, An exposure head for irradiating light onto the surface of a photoreceptor to form an electrostatic latent image, comprising: a substrate; a first electrode layer including a plurality of electrodes arranged two-dimensionally in the rotational direction of the photoreceptor and in the rotational axis direction of the photoreceptor, and the plurality of electrodes being separately arranged on the substrate; a light-emitting section including a light-emitting section laminated on the first electrode layer and emitting light when a voltage is applied; and a second electrode layer arranged on the side opposite to the side on which the first electrode layer is arranged relative to the light-emitting layer and through which light can pass; A control unit that controls the application of voltage to each of the plurality of electrodes included in the first electrode layer based on image data so that the light-emitting layer emits light, the control unit that can control the voltage to each of the plurality of electrodes based on image data so that one pixel is formed by controlling the voltage to a plurality of electrodes arranged at different positions in the rotational direction, Equipped with, The plurality of electrodes for forming the same pixel are arranged such that when viewed from the direction of rotation, a portion of the electrodes overlap each other, and the distance between the centroids of the plurality of electrodes in the direction of the rotation axis is equally spaced in the direction of the rotation axis. An image forming apparatus characterized in that, when the width of the electrode in the direction of the rotation axis is W1 [mm], the number of the plurality of electrodes for forming the same pixel is n, and the distance between the equally spaced centroids in the direction of the rotation axis is d3 [mm], then d3 = W1 / n (where n is a natural number of 2 or more), and the plurality of electrodes for forming the same pixel are arranged such that the centroid positions of each electrode are located at intervals of d3 in the direction of the rotation axis.

2. The image forming apparatus according to claim 1, characterized in that, in the electrode group, the plurality of electrodes arranged in parallel in the rotational direction are positioned such that their positions are offset by d3 in the rotational axis direction from adjacent electrodes.

3. The image forming apparatus according to claim 1 or 2, characterized in that the width of each electrode constituting the plurality of electrodes in the direction of the rotation axis is at least twice the amount of d3.

4. The control unit includes an image processing unit that processes the image data, The image forming apparatus according to any one of claims 1 to 3, characterized in that the image processing unit generates first image data, then converts the first image data according to the arrangement of the plurality of electrodes contained in the first electrode layer to generate second image data with a higher resolution than the first image data, and corrects the second image data according to the image position.

5. The image forming apparatus according to any one of claims 1 to 4, characterized in that the control unit controls the voltage to each of the plurality of electrodes included in the first electrode layer according to binary image data.

Images