Image forming device

Abstract

To provide an image formation apparatus which can secure a light amount with multiple exposure and correct an image position with a high resolution while suppressing reduction in sharpness of the image.SOLUTION: An image formation apparatus comprises: an exposure head including a plurality of light emission parts that include a plurality of lower electrodes two-dimensionally arrayed in the main-scanning direction and the sub-scanning direction, a light emitting layer laminated on the lower electrode and emitting light by application with the voltage, and an upper electrode laminated on the light emitting layer; and an image controller part which can control voltage to each of the lower electrodes such that multiple exposure is performed by the light emission parts. The plurality of lower electrodes for forming the same pixel are arranged such that portions thereof overlap each other when viewed from the sub-scanning direction and their inter-gravity-center distances in the main-scanning direction become an equal interval in the main-scanning direction. When the width in the main-scanning direction is W1 [mm], and the number for forming the same pixel is n, and the inter-gravity-center distance at the equal interval in the main-scanning direction is d3 [mm], d3=W1 / n (n is a natural number being 2 or greater).SELECTED DRAWING: Figure 7

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 technology]

[0002] When forming an image using an electrophotographic image forming apparatus, an electrostatic latent image is first formed on the surface of a photoconductor by irradiating the surface of the photoconductor with light according to image data, then a developing device attaches toner to the electrostatic latent image on the surface of the photoconductor 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 to fix it to the sheet, thereby forming an image.

[0003] Here, Patent Document 1 describes an image forming apparatus that forms an electrostatic latent image by irradiating a photosensitive member with light, and that includes an exposure head having a light-emitting unit using organic electroluminescence (EL) and a lens that focuses the light irradiated from the light-emitting unit on the surface of the photosensitive member. By using an exposure head in this way, it is possible to reduce the number of parts compared to a laser scanning type configuration in which an electrostatic latent image is formed by deflecting and scanning a laser beam using a rotating polygonal mirror, thereby enabling the image forming apparatus to be made smaller and the manufacturing costs to be reduced.

[0004] Furthermore, the light intensity of each light-emitting element using organic electroluminescence in the exposure head is not sufficiently high. Therefore, Patent Document 1 describes a configuration in which multiple light-emitting elements irradiate the same portion of the surface of a photoconductor with light to supplement the light intensity required to form an electrostatic latent image on the surface of the photoconductor. Specifically, in the exposure head, light-emitting elements are two-dimensionally arranged in the direction of the rotation axis of the photoconductor (main scanning direction) and the rotation direction (sub-scanning direction). Then, light-emitting elements adjacent to each other in the rotation direction of the photoconductor emit light at different timings depending on the rotation speed of the photoconductor, thereby irradiating the same portion of the surface of the photoconductor with light from multiple light-emitting elements. Hereinafter, irradiating the same portion of the surface of the photoconductor with light from multiple light-emitting elements in this manner will be referred to as multiple exposure.

[0005] Furthermore, in an exposure head, if the mounting position of the light-emitting units is misaligned when they are mounted on a circuit board, the exposure position on the photosensitive member may be misaligned, resulting in misalignment of the image. Patent Document 2 describes a configuration in which dithering processing is performed using image data with a higher resolution than the spacing between the light-emitting units in the main scanning direction, shifting the image data according to the amount of misalignment in the mounting position of the light-emitting units, and then converting the image data to match the pitch of the light-emitting units in the main scanning direction. This makes it possible to correct image misalignment with a resolution higher than the pitch of the light-emitting units in the main scanning direction. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2018-134820 [Patent Document 2] Japanese Patent Application Publication No. 2019-217653 Summary of the Invention [Problem to be solved by the invention]

[0007] However, with the configuration of Patent Document 2, although the positional deviation of the image can be corrected with a resolution higher than the interval between the light-emitting elements in the main scanning direction, there is a risk that the sharpness of the image may decrease. This will be explained below with reference to the drawings.

[0008] Fig. 18(a) is a diagram showing an example of image data obtained when dithering is performed using image data with a resolution higher than the pitch of the light-emitting elements in the main scanning direction, and the image data is shifted according to the amount of deviation in the mounting positions of the light-emitting elements. Fig. 18(b) is a diagram showing the image data shown in Fig. 18(a) when converted to match the pitch of the light-emitting elements in the main scanning direction. As shown in Fig. 18, in the configuration of Patent Document 2, when high-resolution image data is converted to match the pitch of the light-emitting elements in the main scanning direction, the data of the edge portions of the image becomes intermediate values, which may reduce the sharpness of the image.

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

[0010] A representative configuration of the present invention is an image forming apparatus for forming an image on a recording material, the apparatus comprising: a rotating photosensitive member; and an exposure head having a plurality of light-emitting units arranged along the rotation axis direction of the photosensitive member; the plurality of light-emitting units include n light-emitting units arranged at different positions in the rotation direction of the photosensitive member; each of the n light-emitting units is arranged so that its position is shifted from one another in the rotation axis direction by an integer multiple of an interval d3; and the plurality of light-emitting units are arranged so as to satisfy d3=q / n (n is a natural number of 2 or more), where q is the pitch at which light-emitting units adjacent to one another in the rotation axis direction are arranged. the image forming apparatus forms one pixel included in the image formed on the recording material using the n light emitting units; It is characterized by: [Effects of the Invention]

[0011] According to the present invention, in the exposure head of an image forming device, the amount of light can be secured by multiple exposure, and the image position can be corrected with a resolution higher than the pitch of the light-emitting element in the main scanning direction while suppressing a decrease in image sharpness. [Brief explanation of the drawings]

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

[0013] <Image forming device> The overall configuration of the image forming apparatus A according to the present invention will be described below with reference to the drawings, along with its operation during image formation. Note that the dimensions, materials, shapes, relative positions, etc. of the components described below are not intended to limit the scope of the present invention unless otherwise specified.

[0014] Image forming apparatus A is a full-color image forming apparatus that forms an image by transferring toner of four colors, yellow Y, magenta M, cyan C, and black K, onto a sheet. In the following description, components that use toner of each color are given the suffixes Y, M, C, and K, but the configuration and operation of each component are essentially the same except for the color of the toner used, so the suffixes will be omitted as appropriate unless a distinction is required.

[0015] Fig. 1 is a schematic cross-sectional view of an image forming apparatus A. As shown in Fig. 1, the image forming apparatus A has an image forming unit that forms an image. The image forming unit has photosensitive drums 1 (1Y, 1M, 1C, 10K) as photosensitive members, charging devices 2 (2Y, 2M, 2C, 2K), exposure heads 6 (6Y, 6M, 6C, 6K), developing devices 4 (4Y, 4M, 4C, 4K), and transfer devices 5 (5Y, 5M, 5C, 5K).

[0016] Next, a description will be given of the image forming operation by the image forming apparatus A. When forming an image, first, a sheet S stored in a sheet cassette 99a or a sheet cassette 99b is sent to a registration roller 96 by pickup rollers 91a and 91b, feeding rollers 92a and 92b, and conveying rollers 93a to 93c. Thereafter, the sheet S is sent to the conveyor 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 the surface of the photosensitive drum 10Y with light in accordance with image data read by the image reading unit 90 or image data transmitted from an external device (not shown), thereby forming an electrostatic latent image on the surface of the photosensitive drum 10Y. Thereafter, the developing device 4Y causes yellow toner to adhere to the electrostatic latent image formed on the surface of the photosensitive drum 1Y, thereby 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 by applying a transfer bias to the transfer device 5Y.

[0018] Using a similar process, photosensitive drums 1M, 1C, and 1K are also irradiated with light from exposure heads 6M, 6C, and 6K to form electrostatic latent images, and magenta, cyan, and black toner images are then formed by developing devices 4M, 4C, and 4K. Then, by applying a transfer bias to transfer devices 5M, 5C, and 5K, these toner images are transferred and superimposed on the yellow toner image on sheet S. As a result, a full-color toner image corresponding to the image data is formed on the surface of sheet S.

[0019] Thereafter, the sheet S carrying the toner image is conveyed by a conveyor belt 97 to a fixing device 94, where it is subjected to a heat and pressure treatment. This fixes the toner image on the sheet S to the sheet S. Thereafter, the sheet S with the fixed toner image is discharged onto a discharge tray 95 by a discharge roller 98.

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

[0021] Fig. 2(a) is a perspective view of the photosensitive drum 1 and the exposure head 6. Fig. 2(b) is a cross-sectional view of the photosensitive drum 1 and the exposure head 6. Figs. 3(a) and 3(b) are diagrams showing the mounting surfaces on one side and the other side of the printed circuit board 22 provided in the exposure head 6. Fig. 3(c) is an enlarged view of area V shown in Fig. 3(b).

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

[0023] A connector 21 is mounted on the surface of the printed circuit board 22 opposite to the surface on which the light-emitting element array chip 40 is mounted. The connector 21 is provided for transmitting control signals for the light-emitting element array chip 40 sent from the image controller unit 70 (FIG. 8) and for connecting a power supply line. The light-emitting element array chip 40 is driven via the connector 21.

[0024] As shown in Fig. 3, 20 light-emitting element array chips 40 are mounted on the printed circuit board 22 in a staggered arrangement in two rows. Each light-emitting element array chip 40 has 748 light-emitting units 50 arranged at a predetermined resolution pitch in its longitudinal direction (arrow X direction). Each light-emitting element array chip 40 has four light-emitting units 50 arranged at a predetermined pitch in its lateral direction (arrow Y direction). That is, in each light-emitting element array chip 40, the light-emitting units 50 are two-dimensionally arranged in the directions of arrows X and Y. The four light-emitting units 50 arranged in the direction of arrow Y form the same pixel by multiple exposure, which will be described later.

[0025] In this embodiment, the resolution pitch of the light-emitting element array chips 40 is 1200 dpi (approximately 21.16 μm). The distance from one end to the other of the light-emitting elements 50 in each light-emitting element array chip 40 in the longitudinal direction is approximately 15.828 mm. That is, the exposure head 6 has a total of 14,960 light-emitting elements 50 in the direction of the arrow X, enabling 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 of the light-emitting element array chips 40 (direction of the arrow Y), the distance L1 between the light-emitting elements 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, the light-emitting element array chips 40 adjacent in the direction of the arrow Y are arranged so that their respective light-emitting units 50 overlap in the direction of the arrow X. The reason for this is to prevent 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 between the light-emitting element array chips 40, resulting in uneven shading and the formation of image stripes. The amount of overlap is calculated from the maximum amount of mounting variation in the mounting device (die bonder), and is set to an amount that prevents gaps from forming between the light-emitting units 50 of the light-emitting element array chips 40 adjacent in the direction of the arrow Y.

[0027] Further, the amount of misalignment of the light-emitting element array chip 40 when mounted is measured in the manufacturing process and stored in the head information storage unit 171 (FIG. 8) of the exposure head 6. During image formation, the image controller unit 70 (FIG. 8) selectively controls the light-emitting unit 50 to emit light based on the misalignment information of the light-emitting element array chip 40 stored in the head information storage unit 171, as will be described below, to suppress the occurrence of image streaks.

[0028] 4 is a diagram showing two light-emitting element array chips 40 adjacent to each other in the direction of the arrow Y. In FIG. 4, the hatched light-emitting sections 50 indicate the light-emitting sections 50 that are used during exposure, and the unshaded light-emitting sections 50 indicate the light-emitting sections 50 that are not used during exposure. In addition, the relative positions in the direction of the arrow X of the two light-emitting element array chips 40 adjacent to each other in the direction of the arrow Y are different between FIG. 4(a) and FIG. 4(b).

[0029] 4, the image controller unit 70 selects the light-emitting unit 50 to be used during exposure from among the light-emitting units 50 of two light-emitting element array chips 40 adjacent in the direction of the arrow Y so that the distance L2 in the direction of the arrow X between the light-emitting units 50 used during exposure is closest to the interval of 4800 dpi. Note that 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 the arrow X, so although the distance L2 is configured to be close to the interval of 4800 dpi, the distance L2 is set according to the exposure resolution of the exposure head 6 in the direction of the arrow X.

[0030] In this embodiment, the arrow X direction, which is the longitudinal direction of the light-emitting element array chip 40, is the direction of the rotation axis of the photosensitive drum 1 and is also the main scanning direction. The arrow Y direction, which is the lateral 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 collected by the exposure head 6. The arrow Z direction is the stacking direction in which each layer of the light-emitting unit 50 having a layered structure described below overlaps. The longitudinal direction of the light-emitting element array chip 40 may be inclined by approximately ±1° with respect to the rotation axis direction of the photosensitive drum 1. The lateral direction of the light-emitting element array chip 40 may also be inclined by approximately ±1° with respect to the rotation direction of the photosensitive drum 1.

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

[0032] Fig. 5 is a schematic diagram of the light-emitting element array chip 40. Fig. 6 is a cross-sectional view of the light-emitting element array chip 40 taken along the MM cross section shown in Fig. 5. Fig. 7 is a schematic diagram for explaining the arrangement of the light-emitting units 50 of the light-emitting element array chip 40.

[0033] 5, the light-emitting element array chip 40 has a light-emitting substrate 42 (substrate) incorporating a circuit section 46 for controlling the light-emitting sections 50, a light-emitting region 44 in which a plurality of light-emitting sections 50 are regularly arranged on the light-emitting substrate 42, and wire-bonding pads 48. Signals are input and output between the outside of the light-emitting element array chip 40 and the circuit section 46, and power is supplied to the circuit section 46 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 FIG. 6, the light-emitting section 50 is composed of a light-emitting substrate 42, a plurality of lower electrodes 54 two-dimensionally arranged on the light-emitting substrate 42 at regular intervals (intervals d1 and d2 shown in FIG. 7) in the directions of arrows X and Y, a light-emitting layer 56, and an upper electrode 58.

[0035] The lower electrodes 54 (first electrode layer having a plurality of electrodes) are a plurality of electrodes formed in a layered and separated manner on the light emitting substrate 42, and are electrodes provided corresponding to each 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 disposed with respect to the light-emitting layer 56. The upper electrode 58 is an electrode that can transmit (be transparent to) 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 in response to image data, thereby generating a potential difference between the selected lower electrode 54 and the upper electrode 58. When a potential difference is generated between the upper electrode 58, which is an anode, and the lower electrode 54, which is a 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 recombination of the electrons and holes in the light-emitting layer 56 causes the light-emitting layer 56 to emit light.

[0038] When the light-emitting layer 56 emits light, the light that travels toward the upper electrode 58 passes through the upper electrode 58 and is emitted. Light that travels from the light-emitting layer 56 toward the lower electrode 54 is reflected by 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 manner, the light-emitting section 50 emits light. Note that although there is a time difference in the emission timing between the light that is emitted from the light-emitting layer 56 directly toward the upper electrode 58 and the light that is reflected by the lower electrode 54 and emitted from the upper electrode 58, the emission can be considered to be nearly simultaneous because the layer thickness of the light-emitting section 50 is extremely thin.

[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 is substantially 100%, and light emitted by the light-emitting layer 56 passes through the upper electrode 58 and is emitted as is. In this embodiment, the upper electrode 58 is an anode provided in common to each of the lower electrodes 54. However, the upper electrode 58 may be provided individually for each of the lower electrodes 54, or one upper electrode 58 may be provided for each of the plurality of lower electrodes 54. In addition, when a transparent electrode is used as the upper electrode 58, the entire electrode does not necessarily have to be a transparent electrode; only the openings through which light is emitted may be transparent, and the area other than the openings may be wired with an electrode other than a transparent electrode, such as a metal wire.

[0040] The light-emitting layer 56 may 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 including 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 may be divided into segments of the same size as the lower electrodes 54. Alternatively, each lower electrode 54 may be divided into multiple groups, and one light-emitting layer 56 may be laminated on top of the lower electrodes 54 belonging to each group.

[0041] 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 the light-emitting region 44 to prevent moisture from entering. For example, a sealing film is formed by forming a thin film, either alone or in layers, of silicon oxide, silicon nitride, aluminum oxide, or the like. A method that excels in covering structures such as steps is preferred as a method for forming the sealing film, and atomic layer deposition (ALD) can be used, for example. The materials, configurations, and formation methods of the sealing film are merely examples, and are not limited to the above examples; any suitable method may be selected as appropriate.

[0042] The lower electrode 54 is preferably made of a metal having a high reflectivity at the wavelength of light emitted by the light-emitting layer 56. Examples of suitable materials include Ag, Al, or an alloy of Ag and Al. The lower electrode 54 is formed using Si integrated circuit processing technology together with the circuit section 46 and is directly connected to the drive section of the circuit section 46. Forming the lower electrode 54 using Si integrated circuit processing technology allows for high precision with a process rule of approximately 0.2 μm, allowing the lower electrodes 54 to be arranged with high precision and high density. Furthermore, because the lower electrodes 54 can be arranged with high density, most of the light-emitting region 44 can be made to emit light, thereby improving the utilization efficiency of the light-emitting region 44. The spaces between each lower electrode 54 are filled with the organic material of the light-emitting layer 56, and each lower electrode 54 is separated by the organic material.

[0043] Furthermore, when the voltage across both ends of the light-emitting unit 50 exceeds a predetermined value, a current begins to flow, and the value of the current then increases approximately in proportion to the voltage value. The voltage at which a current begins to flow varies among the light-emitting units 50. Therefore, before the product is shipped from the factory, the light-emitting units 50 of the light-emitting element array chip 40 are individually and sequentially made to emit light, and the current flowing through the light-emitting units 50 is adjusted so that the light focused through the rod lens array 23 has a predetermined light intensity. Note that, before the product is shipped from the factory, the exposure head 6 is not only subjected to the above-mentioned light intensity adjustment, but also to focus adjustment, which adjusts the distance between the light-emitting element array chip 40 and the rod lens array 23.

[0044] As shown in FIG. 7 , the light-emitting sections 50 are arranged in a matrix in the light-emitting region 44 at predetermined intervals in the arrow X and arrow Y directions. In this embodiment, the width W1 of the light-emitting sections 50 in the arrow X direction is 19.80 μm, and the interval d1 between adjacent light-emitting sections 50 in the arrow X direction is 0.68 μm. That is, the light-emitting sections 50 are arranged at a pitch of 21.16 μm (1200 dpi) in the arrow X direction. Note that the pitch of the light-emitting sections 50 in the arrow X direction may deviate within the tolerance range. The tolerance of the pitch of the light-emitting sections 50 in the arrow X direction is ±1% of the nominal design pitch of the light-emitting sections 50 in the arrow X direction. That is, the tolerance of the pitch of the light-emitting sections 50 in the arrow X direction in this embodiment is ±0.21 μm.

[0045] The width W2 of the light-emitting section 50 in the direction of the arrow Y is also 19.80 μm, the same as the width W1. That is, the light-emitting section 50 of this embodiment is square-shaped with one side measuring 19.80 μm. Note that although the light-emitting section 50 is square-shaped because the widths W1 and W2 are equal, the dimensions of these widths W1 and W2 may deviate within the tolerance range. In this embodiment, the tolerance of both widths W1 and W2 is ±0.2 μm.

[0046] The distance d2 between adjacent light-emitting sections 50 in the direction of arrow Y is also 0.68 μm, similar to the distance d1. The light-emitting sections 50 are also arranged at a pitch of 21.16 μm (1200 dpi) in the direction of arrow Y. The pitch of the light-emitting sections 50 in the direction of arrow Y may deviate within a tolerance range. The tolerance of the pitch of the light-emitting sections 50 in the direction of arrow Y is ±1% of the nominal design pitch of the light-emitting sections 50 in the direction of arrow Y. In other words, the tolerance of the pitch of the light-emitting sections 50 in the direction of arrow Y in this embodiment is ±0.21 μm. The distances d1 and d2 between the light-emitting sections 50 are set wider than the distance dz ( FIG. 6 ) between the upper electrode 58 and the lower electrode 54. This configuration can suppress leakage current between adjacent lower electrodes 54 in the directions of arrow X and arrow Y, thereby suppressing erroneous light emission by the light-emitting sections 50.

[0047] In this embodiment, the width, shape, arrangement, etc. of the light-emitting sections 50 are substantially determined by the width, shape, and arrangement of the lower electrodes 54, and therefore can also be rephrased as the width, shape, and arrangement of the lower electrodes 54. In addition, 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 center of gravity of the lower electrodes 54 in the design nominal form.

[0048] The light-emitting sections 50 adjacent to each other in the direction of arrow Y are arranged so that their positions are offset by a distance d3 in the direction of arrow X. In this embodiment, the distance d3 is set to 5.29 μm (4800 dpi). When viewed as a whole, the four light-emitting sections 50 arranged in parallel in the direction of arrow Y are arranged so that their positions are offset in the direction of arrow X by an integer multiple of the distance d3. In other words, the four lower electrodes 54 provided in the direction of arrow Y to form the same pixel are arranged so that they partially overlap each other when viewed in the direction of arrow Y and so that the distances between the centers of gravity of the lower electrodes 54 are equal in the direction of arrow X.

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

[0050] The same result as the above calculation of the distance d3 can also be obtained by determining the distance d3 as follows. That is, the pitch in the direction of the arrow X of multiple light-emitting units 50 that are located at the same position in the direction of the arrow Y is q (mm), the number of light-emitting units 50 arranged in a row in the direction of the arrow Y is n (units), and the distance d3 (mm) (reference value) is a reference value for the amount of deviation in the direction of the arrow X of the positions of the light-emitting units 50 arranged in a row in the direction of the arrow Y. In this case, the distance d3 is calculated from d3 = q / n, and the light-emitting units 50 arranged in a row in the direction of the arrow Y are positioned so that their positions are offset from each other by an integer multiple of the distance d3. In other words, in this embodiment, q = 0.02116 and n = 4, so that d3 = 0.02116 / 4 = 0.00529 (mm) = 5.29 (μm).

[0051] Alternatively, the spacing d3 may be determined as follows, rather than as described above. For light-emitting units 50 arranged at different positions in the arrow Y direction to form the same pixel, the number of light-emitting units 50 is n, and the width of each light-emitting unit 50 in the arrow X direction is W1 (mm). In this case, the spacing d3 is calculated as d3 = W1 / n (n is a natural number greater than or equal to 2). The light-emitting units 50 arranged at different positions in the arrow Y direction to form the same pixel are arranged so that the centers of gravity of each light-emitting unit 50 are spaced apart by d3 in the arrow X direction. In other words, to form the same pixel by multiple exposure (described later), four light-emitting units 50 arranged at different positions in the arrow Y direction are arranged so that the distance between the centers of gravity of the four light-emitting units 50 arranged at equal intervals in the arrow X direction 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 manner, the overlap amount in the direction of the arrow X of the four light-emitting units 50 arranged at different positions in the direction of the arrow Y to form the same pixel is made uniform, and therefore the amount of light for each pixel is made uniform in the multiple exposure described below, and the density of each pixel is made uniform.

[0052] In the present invention, the shape of the light-emitting unit 50 is not limited to a square, and may be a polygon with more sides than a square, a circle, an ellipse, or the like, as long as the light-emitting unit 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 satisfies the design specifications of the image forming apparatus A. However, because organic light-emitting materials emit less light than LEDs, it is preferable to form the light-emitting unit 50 in a square shape and reduce the distance between adjacent light-emitting units 50, thereby ensuring a light-emitting area sufficient to obtain a light amount sufficient to change the potential of the photosensitive drum 1. Furthermore, 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 process of the exposure head 6, the resolution of the image formed by the image forming apparatus A, and other factors.

[0053] As described above, the distance between the light-emitting sections 50, i.e., the distance between the lower electrodes 54, is defined based on the center of gravity of the nominal design lower electrodes 54. That is, the distance between the lower electrodes 54 is set as the distance between the centers of gravity based on the intersection of the diagonals if the shape of the lower electrodes 54 is a regular polygon, the center of the circle if the shape of the lower electrodes 54 is a perfect circle, or the intersection of the major and minor axes if the shape is an ellipse. Note that when the shape of the lower electrodes 54 is a regular polygon, the corners do not have to be perfect corners and may be rounded.

[0054] <Exposure head system configuration> Next, we will explain the configuration of the exposure head 6 and the image controller unit 70 (control unit) that controls the exposure head 6. The image controller unit 70 is provided on the main body side of the image forming apparatus A. Note that although the following explains the control performed when processing one image data (monochromatic), when performing image forming operations, similar processing is performed in parallel for four image data corresponding to yellow, magenta, cyan, and black.

[0055] Fig. 8 is a block diagram showing the system configuration of the image controller unit 70 and the exposure head 6. As shown in Fig. 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. Using these components, the image controller unit 70 processes image data and image formation timing, and sends control signals to the printed circuit board 22 of the exposure head 6 to control the exposure head 6.

[0056] Image data of a document read by the image reading unit 90 and image data transferred from an external device via a network are input to the image data generation unit 71 (image processing unit). The image data generation unit 71 performs dithering processing on the input image data at a resolution specified by the CPU 73 to generate image data for outputting an image. In this embodiment, the image data generation unit 71 performs dithering processing at a resolution of 1200 dpi and with binary gradation, and then performs high-resolution processing to generate data with a resolution of 4800 dpi in the main scanning direction and 2400 dpi in the sub-scanning direction and with binary gradation. The high-resolution processing simply copies the 1200 dpi data.

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

[0058] In this embodiment, the resolution of the dithering process of the image data generation unit 71 is set to 1200 dpi, and thus image data after dithering is generated for each of four light-emitting units 50 arranged in parallel in the direction of the arrow X on the photosensitive drum 1. Among the four rows of light-emitting units 50 extending in the direction of the arrow X and arranged in parallel in the direction of the arrow Y, the first and second rows of light-emitting units 50 are at different distances from the center of the rod lens array 23, resulting in differences in the amount of light irradiated onto the photosensitive drum 1 from each row. The same is true for the third and fourth rows of light-emitting units 50. Therefore, by generating image data by performing dithering for each of four light-emitting units 50 arranged in parallel in the direction of the arrow X, moire and banding due to differences in density of generated dots can be suppressed. Furthermore, by shifting the image data after dithering so as to correct the image position at a resolution of 4800 dpi, it is possible to correct the image position at a high resolution of 4800 dpi while suppressing moire and banding.

[0059] The synchronization signal generating unit 74 periodically generates a line synchronization signal (control signal) indicating the start of image data capture and transmits it to the chip data converting unit 72. The CPU 73 determines, for a preset rotation speed of the photosensitive drum 1, the period during which the surface of the photosensitive drum 1 moves in the rotation direction by a pixel size corresponding to the resolution in the sub-scanning direction of the image formed by the image forming apparatus A, as one line period, and instructs the synchronization signal generating 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 move the distance of a pixel size of 2400 dpi (10.58 μm) is 52.92 μs, and the period of the line synchronization signal is 52.92 μs. The rotational 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 divides image data of one line x four columns (the number of light-emitting units 50 in the direction of the arrow Y) into each light-emitting element array chip 40 in synchronization with the line synchronization signal generated and input by the synchronization signal generation unit 74. The chip data conversion unit 72 then transmits the image data together with the clock signal and line synchronization signal to each light-emitting element array chip 40 via a line synchronization signal line 75, a clock signal line 76, and an image data signal line 77. The number of image data signal lines 77 provided is four, which is the same as the number of light-emitting units 50 in the direction of the arrow Y.

[0062] The head information storage unit 171 provided in the exposure head 6 is connected to the CPU 73 via a communication signal line 79. The head information storage unit 171 stores, as head information, the light emission amount and mounting position information of each light-emitting element array chip 40. The light-emitting element array chip 40 causes the light-emitting unit 50 to emit light based on the setting values ​​of each 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 light-emitting element array chip> Next, the system configuration of the light-emitting element array chip 40 will be described.

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

[0064] The digital section 80 includes a communication IF section 81, a register section 82, a capture signal generation section 83, a line synchronization signal generation section 84, and a data holding section 85. Using these sections, the digital section 80 generates pulse signals for causing the light-emitting sections 50 to emit light based on preset settings, image data signals, and line synchronization signals that are synchronized with a clock signal by a communication signal, and transmits the pulse signals to the analog section 86. There are 748 data holding sections 85 (85-001 to 85-748), which is the number of light-emitting sections 50 in one light-emitting element array chip 40 in the direction of the arrow X.

[0065] The line synchronization signal generation unit 84 delays the input line synchronization signal by a predetermined time to generate a line synchronization signal to be used by other light-emitting element array chips 40 connected via the line synchronization signal line 75. The capture 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 unit 82 stores information on the delay time of the capture signal generation unit 83 described above, setting information on the drive current set by the analog unit 86, etc. The communication IF unit 81 controls writing and reading of setting values ​​to and from the register unit 82 based on a communication signal input from the CPU 73.

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

[0068] Fig. 11 is a circuit diagram of the data holding unit 85. As shown in Fig. 11, four lines of image data (image data 1 to 4), a clock signal, and a data latch signal wen (n = 1 to 748) are input to the data holding unit 85. Each data holding unit 85 has four flip-flop circuits and four gate circuits for latching the four lines of image data that are simultaneously input at the timing when the data latch signal is input. Each data holding unit 85 also has one flip-flop circuit for delaying the data latch signal by one clock and outputting it.

[0069] 12 is an operation timing chart of the data holding unit 85. As shown in FIG. 12, four lines of image data (D1[1] to D1[4]) are input simultaneously to the data holding unit 85-001. The data holding unit 85-001 latches this image data at the timing when the data latch signal we001 is input from the capture signal generating 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 and transmits it to the next data holding unit 85-002 as data latch signal we002.

[0070] Four lines of image data (D2[1] to D2[4]) are also input simultaneously to the data holding unit 85-002. The data holding unit 85-002 latches this image data at the timing when the data latch signal we002 is input from the data holding unit 85-001, and generates drive signals (P002[1] to P002[4]). The data holding unit 85-002 also delays the data latch signal we002 by one clock and sends it to the data holding unit 85-003 as data latch signal we003.

[0071] In this way, the data holding units 85 (-001 to 748) sequentially latch the image data while transmitting the data latch signal up to the 748th data holding unit 85. Then, when the data holding units 85 (-001 to 748) latch the image data, they transmit the latched signal as a drive signal to the analog unit 86. In this embodiment, four lines of image data are latched with one data latch signal, so drive signals for four lines (four pixels) are output simultaneously.

[0072] <Analog section> Next, we will explain the configuration of the analog unit 86. The analog unit 86 is made up of a drive circuit that is connected one-to-one to each light-emitting unit 50. For ease of explanation, the following will explain one drive circuit, but it is assumed that there are the same number of similar drive circuits as the number of light-emitting units 50, that is, 748 units x 4 columns = 2992 units.

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

[0074] The current control MOSFET 62 is a Pch 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 current flowing from the source to the drain increases as the analog voltage input from the DAC 61 increases.

[0075] The switching MOSFET 63 is a Pch MOSFET, and its source terminal is connected to the drain terminal of the current control MOSFET 62, and its gate terminal receives a drive signal output from the data holding unit 85. The drive signal is a binary signal of Hi level and Low level, and when a Hi level signal is input, the MOSFET 63 turns ON and a current controlled by the current control MOSFET 62 flows from the source to the drain. The drain terminal is connected to the anode terminal of the light-emitting unit 50, and this current serves as a drive current for the light-emitting unit 50.

[0076] <Lighting control of light-emitting units during image formation> Next, the lighting control of the light-emitting unit 50 during image formation will be described. In the following description, light emission by the light-emitting unit 50 refers to the light emitted by the light-emitting unit 50 being sufficient to change the charge potential of the photosensitive drum 1 to an extent that a toner image is not developed as a visible image. In other words, light emission does not include the light-emitting unit 50 emitting light having an amount sufficient to change the charge potential of the photosensitive drum 1 to an extent that a toner image is not developed as a visible image.

[0077] FIG. 14 shows image data sent to the light-emitting element array chip 40 when forming a line image extending in the main scanning direction (arrow X direction). As shown in FIG. 14, when forming the line image, the most upstream light-emitting element 50 of the four light-emitting elements 50 arranged in parallel in the rotation direction of the photosensitive drum 1 (arrow Y direction) is first activated. Next, with a delay of two lines (2400 dpi), the light-emitting element 50 one line downstream of the first activated light-emitting element 50 is activated. The delay operation sets the image data read position so that image data at a corresponding position is read in response to a common line synchronization signal. This allows the exposure positions (irradiation positions) in the sub-scanning direction on the photosensitive drum 1 of the light emitted from the most upstream light-emitting element 50 in the rotation direction of the photosensitive drum 1 and the light emitted from the light-emitting element 50 one line downstream from this light-emitting element 50 to be aligned.

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

[0079] FIG. 15 is a schematic diagram showing the light irradiation positions on the photosensitive drum 1 when four light-emitting units 50 arranged in parallel in the Y direction are caused to emit light according to the above-described control. As shown in FIG. 15, when the four light-emitting units 50 arranged in parallel in the Y direction are caused to emit light at the timing described above, the light beams H1 to H4 emitted from the four light-emitting units 50 are irradiated at the same position on the photosensitive drum 1 in the Y direction but at positions offset by a distance d3 in the X direction. Here, the distance d3 is set to d3 = 25.4 / m × 1 / n, so that at least two or more of the light beams H1 to H4 overlap on the photosensitive drum 1, thereby forming one pixel. Therefore, the amount of light can be compensated for 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 arranged in the direction of the arrow Y are offset from each other by 5.29 μm (= d3) in the direction of the arrow X, which corresponds to 4800 dpi. This allows exposure processing on the photosensitive drum 1 at a resolution of 4800 dpi without reducing the data of the edge portions of the image to intermediate values. This allows image position correction at a higher resolution than the pitch of the light-emitting units 50 in the main scanning direction while suppressing a decrease in image sharpness. Even when the spacing d3 is set to 4.95 μm, calculated from d3 = W1 / n (n is a natural number greater than or equal to 2), it is possible to achieve the effect of exposure processing on the photosensitive drum 1 at a higher resolution than the pitch of the light-emitting units 50 in the main scanning direction. In this case, the image data generation unit 71 performs high-resolution processing according to the value of the spacing d3 calculated from d3 = W1 / n (n is a natural number greater than or equal to 2).

[0081] Furthermore, if the width W1 of the light-emitting units 50 in the direction of the arrow X is small, the amount of overlap of the light beams H1 to H4 between the light-emitting units 50 arranged in parallel in the direction of the arrow Y will be small, which may cause poor multiple exposure or gaps to form between the light beams H1 to H4, resulting in image streaks. Therefore, the width W1 is set to be at least twice the distance d3. This allows the light emitted not only from adjacent light-emitting units 50 in the direction of the arrow Y, but also from the light-emitting units 50 two positions away in the direction of the arrow Y to overlap on the photosensitive drum 1, allowing for accurate multiple exposure and suppressing image streaks.

[0082] As described above, the interval L1 (shortest distance) shown in FIG. 3(c) between the light-emitting units 50 of two adjacent light-emitting element array chips 40 in the direction indicated by the arrow Y is set to 10 lines at 2400 dpi. Therefore, with respect to the rotation direction of the photosensitive drum 1, the light emission timing between the most downstream light-emitting unit 50 of the first light-emitting element array chip 40 and the most upstream light-emitting unit 50 of the second light-emitting element array chip 40 downstream of the first light-emitting element array chip 40 is delayed by 12 lines, which is the sum of the interval L1 and two lines representing the light-emitting area of ​​a pixel. This configuration allows the exposure positions in the sub-scanning direction on the photosensitive drum 1 to be aligned between the light-emitting units 50 of the staggered light-emitting element array chips 40.

[0083] In this embodiment, the configuration has been described in which all the light-emitting units 50 of the light-emitting element array chip 40 are arranged so that the light-emitting units 50 arranged in parallel in the direction of the arrow Y are shifted in position in the direction of the arrow X by an integer multiple of the interval d3. However, the present invention is not limited to this. In other words, the same effect as above can be obtained as long as the multiple light-emitting units 50 of the light-emitting element array chip 40 include a light-emitting unit group (electrode group) in which the light-emitting units 50 arranged in parallel in the direction of the arrow Y are shifted in position in the direction of the arrow X by an integer multiple of the interval d3.

[0084] Furthermore, in this embodiment, a configuration has been described in which adjacent light-emitting units 50 in the direction of the arrow Y in the light-emitting element array chip 40 are arranged so that their positions are shifted in the direction of the arrow X by a distance d3. However, the present invention is not limited to this. That is, for example, as shown in FIG. 16 , as long as the amount of shift in the direction of the arrow X between multiple light-emitting units 50 arranged in parallel in the direction of the arrow Y is an integer multiple of the distance d3, the amount of shift between adjacent light-emitting units 50 in the direction of the arrow Y does not have to be the distance d3. Furthermore, as shown in FIG. 17 , a configuration may be adopted in which some of the multiple light-emitting units 50 arranged in parallel in the direction of the arrow Y are located at the same position in the direction of the arrow X. Even with the configurations shown in FIGS. 16 and 17 , exposure similar to that 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 including 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 device

Claims

1. In an image forming apparatus for forming an image on a recording material, A rotating photoreceptor; an exposure head having a plurality of light-emitting units arranged along the rotation axis direction of the photosensitive member; Equipped with the plurality of light-emitting units include n light-emitting units arranged at different positions in a rotation direction of the photosensitive member, the n light-emitting units are arranged so as to be shifted from one another by an integral multiple of an interval d3 in the rotation axis direction, the plurality of light-emitting units are arranged so as to satisfy d3=q / n (n is a natural number of 2 or more), where q is a pitch at which adjacent light-emitting units among the plurality of light-emitting units are arranged in the rotation axis direction, The image forming apparatus is characterized in that one pixel included in the image formed on the recording material is formed using the n light emitting portions.

2. the exposure head further comprises a long substrate; and a light-emitting chip mounted on the substrate and having a silicon substrate; 2. The image forming apparatus according to claim 1, wherein the plurality of light emitting portions are formed on the silicon substrate.

3. 3. The image forming apparatus according to claim 2, wherein the plurality of light-emitting portions include a first electrode layer formed in a layered manner and transmitting light, a second electrode layer formed in a layered manner between the first electrode layer and the silicon substrate in a vertical direction perpendicular to the surface of the silicon substrate and including a plurality of electrodes arranged two-dimensionally in the rotation direction and the rotation axis direction, and a light-emitting layer formed between the first electrode layer and the second electrode layer in the vertical direction.

4. 4. The image forming apparatus according to claim 3, wherein the image forming apparatus comprises a plurality of the light emitting chips.

5. 5. The image forming apparatus according to claim 4, wherein the plurality of light emitting chips are arranged in a staggered pattern along the direction of the rotation axis.

6. 2. The image forming apparatus according to claim 1, wherein the n light emitting sections are not adjacent to each other in the direction of the rotation axis.

7. 2. The image forming apparatus according to claim 1, further comprising a control unit that controls lighting of the plurality of light emitting units based on image data.

8. 8. The image forming apparatus according to claim 7, wherein the image data is a set of binary bit data.

9. An image forming apparatus for forming an image on a recording material, A rotating photoreceptor; an exposure head having a plurality of light-emitting units arranged along the rotation axis direction of the photosensitive member; Equipped with the plurality of light-emitting units include n light-emitting units arranged at different positions in a rotation direction of the photosensitive member, the n light-emitting units are arranged so that their positions are shifted from one another by an integer multiple of the interval d3 in the rotation axis direction and so that at least a portion of each of the n light-emitting units overlaps with one another when viewed from the rotation direction, the plurality of light-emitting units are arranged so as to satisfy d3=q / n (n is a natural number of 2 or more), where q is a pitch at which adjacent light-emitting units among the plurality of light-emitting units are arranged in the rotation axis direction, The image forming apparatus is characterized in that one pixel included in the image formed on the recording material is formed using the n light emitting portions.

10. The exposure head further comprises an elongated substrate and a light-emitting chip mounted on the substrate and having a silicon substrate; 10. The image forming apparatus according to claim 9, wherein the plurality of light emitting portions are formed on the silicon substrate.

11. The image forming device described in Claim 10, characterized in that the multiple light-emitting portions include a first electrode layer formed in a layered manner and transmitting light, a second electrode layer formed in a layered manner between the first electrode layer and the silicon substrate in a vertical direction perpendicular to the surface of the silicon substrate and including multiple electrodes arranged two-dimensionally in the rotation direction and the rotation axis direction, and a light-emitting layer formed between the first electrode layer and the second electrode layer in the vertical direction.

12. The image forming device described in Claim 11, characterized in that the image forming device has a plurality of the light-emitting chips.

13. An image forming device as described in Claim 12, characterized in that the multiple light-emitting chips are arranged in a staggered pattern along the rotation axis direction.

Images