Image formation apparatus

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, which forms an image on a sheet by using an electrophotographic image forming method. [Background technology]

[0002] When forming an image with an electrophotographic image forming apparatus, first, an electrostatic latent image is 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 includes a light-emitting unit using organic electroluminescence (EL) and an exposure head having a lens that forms an image of the light emitted from the light-emitting unit on the surface of the photoconductor by irradiating the photoconductor with light, and the image forming apparatus can be made smaller and the manufacturing costs can be reduced compared to a laser scanning type configuration in which a laser beam is deflected and scanned by a rotating polygon mirror to form an electrostatic latent image.

[0004] Also, the light quantity of one of the light-emitting parts using organic electroluminescence of the exposure head is not sufficiently high. Therefore, Patent Document 1 describes a configuration in which light is irradiated from a plurality of light-emitting parts to the same part of the surface of the photoconductor in order to supplement the light quantity for forming an electrostatic latent image on the surface of the photoconductor. Specifically, in the exposure head, light-emitting parts 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 parts adjacent to each other in the rotation direction of the photoconductor are caused to emit light at different timings according to the rotation speed of the photoconductor, so that light is irradiated from the plurality of light-emitting parts to the same part of the surface of the photoconductor. Hereinafter, the irradiation of light from the plurality of light-emitting parts to the same part of the surface of the photoconductor in this way is referred to as multiple exposure.

[0005] Furthermore, in the case of an exposure head, if there is a misalignment in the mounting position when mounting the light-emitting units on the board, the exposure position on the photoconductor may be misaligned, causing a misalignment of the image. In response to this, Patent Document 2 describes a configuration in which dithering processing is performed with image data with a higher resolution than the interval in the main scanning direction of the light-emitting units, the image data is shifted according to the amount of misalignment in the mounting positions of the light-emitting units, and then the image data is converted to match the pitch in the main scanning direction of the light-emitting units. This makes it possible to correct the misalignment of the image with a resolution higher than the pitch in the main scanning direction of the light-emitting units. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2018-134820 A [Patent Document 2] JP 2019-217653 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, in 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 of the sharpness of the image decreasing. This will be explained below with reference to the drawings.

[0008] Fig. 18(a) is a diagram showing an example of image data when dithering is performed with image data having a higher resolution than the pitch of the light-emitting unit in the main scanning direction, and the image data is shifted according to the amount of deviation in the mounting position of the light-emitting unit. 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 unit 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 unit in the main scanning direction, data of the edge part of the image becomes an intermediate value, and there is a risk of reducing the sharpness of the image.

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

[0010] A representative configuration of an image forming apparatus according to the present invention for achieving the above object is an image forming apparatus for forming an image by irradiating a surface of a photoconductor with light to form an electrostatic latent image and attaching toner to the electrostatic latent image, the image forming apparatus comprising: an exposure head for forming the electrostatic latent image by irradiating the surface of the photoconductor with light, the exposure head comprising a substrate; a first electrode layer including a plurality of electrodes arranged two-dimensionally in a rotation direction of the photoconductor and in a rotation axis direction of the photoconductor, the plurality of electrodes being separately arranged on the substrate; a light-emitting layer laminated on the first electrode layer and emitting light when a voltage is applied thereto; and a second electrode layer arranged on the opposite side of the light-emitting layer to the side on which the first electrode layer is arranged and through which light can pass; and a control unit for controlling application of a 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 controlling application of a voltage to each of the plurality of electrodes included in the first electrode layer based on image data so that one pixel ... and a control unit capable of controlling a voltage to each of the plurality of electrodes based on the image data so that a pixel is formed by controlling a voltage to a plurality of electrodes arranged at different positions in the rotation axis direction, the plurality of electrodes for forming the same pixel are arranged such that a portion of the electrodes overlaps with one another when viewed from the rotation direction, and such that a distance between the centers of gravity of the plurality of electrodes in the rotation axis direction is equally spaced in the rotation axis direction, wherein, when a width of the electrode in the rotation axis direction is W1 [mm], the number of the plurality of electrodes for forming the same pixel is n, and the distance between the centers of gravity of the electrodes at equal intervals in the rotation axis direction is d3 [mm], then d3 = W1 / n (n is a natural number of 2 or more), and the plurality of electrodes for forming the same pixel are arranged such that the centers of gravity of each electrode are spaced apart by d3 in the rotation axis direction. Effect of the Invention

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

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

[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, together with the 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. Note that in the following description, although components that use toner of each of the above colors are given the suffixes Y, M, C, and K, the configurations and operations of the components are essentially the same except for the color of the toner used, and therefore 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 section that forms an image. The image forming section 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 an 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 section, 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 the image data read by the image reading section 90 or the image data transmitted from an external device (not shown), and forms 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, and a yellow toner image is formed 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] By 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 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 heating and pressure treatment. This causes the toner image on the sheet S to be fixed to the sheet S. Thereafter, the sheet S with the toner image fixed thereto is discharged to 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 mounting surfaces on one side and the other side of a printed circuit board 22 provided in the exposure head 6. Fig. 3(c) is an enlarged view of an 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 (collects) 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 transmitted 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 in its longitudinal direction (arrow X direction) at a predetermined resolution pitch. Each light emitting element array chip 40 has four light emitting units 50 arranged in its lateral direction (arrow Y direction) at a predetermined pitch. That is, in each light emitting element array chip 40, the light emitting units 50 are two-dimensionally arranged in the arrow X direction and the arrow Y direction. The four light emitting units 50 arranged in the arrow Y direction 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 chip 40 is 1200 dpi (approximately 21.16 μm). The distance from one end to the other end of the light-emitting unit 50 of 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 14960 light-emitting units 50 in the direction of the arrow X, which allows exposure processing corresponding to an image width in the longitudinal direction of approximately 316 mm (≈ approximately 15.8 mm × 20 chips). In addition, in the short direction (arrow Y direction) of the light-emitting element array chip 40, the interval L1 between the light-emitting units 50 of adjacent light-emitting element array chips 40 is approximately 105 μm (5 pixels at 1200 dpi, 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 sections 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 causes 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 the formation of shading and image streaks. The amount of overlap is calculated from the maximum amount of mounting variation of the mounting device (die bonder) and is set to an amount that prevents gaps from being formed between the light emitting sections 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 during mounting 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 causes 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 described below, to suppress the occurrence of image streaks.

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

[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 such 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 described later, since the exposure head 6 is configured to expose in the direction of the arrow X at a resolution of 4800 dpi, the distance L2 is configured to be close to the interval of 4800 dpi, but the distance L2 is set according to the exposure resolution in the direction of the arrow X of the exposure head 6.

[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 transverse 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 section 50 having a layered structure described later overlaps. The longitudinal direction of the light-emitting element array chip 40 may be inclined by about ±1° with respect to the rotation axis direction of the photosensitive drum 1. The transverse direction of the light-emitting element array chip 40 may also be inclined by about ±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 cut 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 driving 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 electrode 54 (first electrode layer having a plurality of electrodes) is a plurality of electrodes formed in a layer shape and separated on the light emitting substrate 42, and is an electrode provided corresponding to each pixel. That is, each of the lower electrodes 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 (is transmissive 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 according to image data, 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 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 travels toward the upper electrode 58 and is emitted after passing through the upper electrode 58. Light 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 the reflected light also travels 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 emitted from the light-emitting layer 56 directly toward the upper electrode 58 and the light reflected by the lower electrode 54 and emitted from the upper electrode 58, the emission can be regarded as being 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 the light emitted by the light emitting layer 56 is directly emitted through the upper electrode 58. In this embodiment, the upper electrode 58 is an anode provided in common to each of the lower electrodes 54, but it may be configured to provide each of the lower electrodes 54 individually, 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, it is not necessarily required that the entire electrode is a transparent electrode, and only the openings for emitting light may be a transparent electrode, and the other parts may be wired with electrodes other than transparent electrodes, such as metal wires.

[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 necessary. The light-emitting layer 56 may be formed continuously in the direction of the arrow X, or may be divided into portions of the same size as the lower electrodes 54. Each lower electrode 54 may be divided into a plurality of groups, and one light-emitting layer 56 may be laminated on the upper portion of the lower electrodes 54 belonging to each divided 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 the region. As a sealing method, for example, a sealing film is formed by forming a single or laminated thin film of silicon oxide, silicon nitride, aluminum oxide, etc. As a method for forming the sealing film, a method that has excellent covering performance for structures such as steps is preferable, and for example, an atomic layer deposition method (ALD method) can be used. Note that the material, configuration, and forming method of the sealing film are merely examples and are not limited to the above examples, and appropriate methods may be selected.

[0042] The lower electrode 54 is preferably made of a metal having a high reflectance with respect to the wavelength of light emitted by the light-emitting layer 56. For example, Ag, Al, or an alloy of Ag and Al is used. The lower electrode 54 is formed by using a Si integrated circuit processing technique together with the formation of the circuit section 46, and is directly connected to the driving section of the circuit section 46. By forming the lower electrode 54 by the Si integrated circuit processing technique in this way, the process rule is about 0.2 μm, and high precision is achieved, so that the lower electrodes 54 can be arranged with high precision and high density. Furthermore, since the lower electrodes 54 can be arranged with high density, most of the light-emitting region 44 can be made to emit light, and the utilization efficiency of the light-emitting region 44 can be improved. The organic material of the light-emitting layer 56 is filled between each of the lower electrodes 54, and each of the lower electrodes 54 is partitioned by the organic material.

[0043] Moreover, when the voltage applied across both ends of the light-emitting unit 50 exceeds a predetermined value, a current starts to flow, and thereafter, the value of the current increases approximately in proportion to the value of the voltage. There is variation in the voltage at which a current starts to flow in each light-emitting unit 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 adjusted in light intensity as described above, but also adjusted in focus to adjust 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 at a predetermined interval in the arrow X direction and the arrow Y direction in the light-emitting region 44. In this embodiment, the width W1 of the light-emitting section 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. 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% with respect to the pitch of the light-emitting sections 50 in the arrow X direction in the design nominal. 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 in the shape of a square with one side measuring 19.80 μm. Although the light-emitting section 50 is in the shape of a square 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 the widths W1 and W2 is ±0.2 μm.

[0046] The interval d2 between the light emitting sections 50 adjacent in the arrow Y direction is 0.68 μm, similar to the interval d1, and the light emitting sections 50 are also arranged at a pitch of 21.16 μm (1200 dpi) in the arrow Y direction. The pitch of the light emitting sections 50 in the arrow Y direction may deviate within the tolerance range. The tolerance of the pitch of the light emitting sections 50 in the arrow Y direction is ±1% with respect to the pitch of the light emitting sections 50 in the arrow Y direction in the design nominal. That is, the tolerance of the pitch of the light emitting sections 50 in the arrow Y direction in this embodiment is ±0.21 μm. Here, the intervals d1 and d2 of the light emitting sections 50 are set wider than the interval dz (FIG. 6) between the upper electrode 58 and the lower electrode 54. With this configuration, it is possible to suppress the leakage current between the lower electrodes 54 adjacent in the arrow X direction and the arrow Y direction, and to suppress erroneous light emission of the light emitting sections 50.

[0047] Here, in this embodiment, the width, shape, arrangement, etc. of the light emitting section 50 are substantially determined by the width, shape, and arrangement of the lower electrode 54, and therefore can be rephrased as the width, shape, and arrangement of the lower electrode 54. Also, 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 position of the lower electrode 54 in the design nominal.

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

[0049] Here, the interval d3 is determined as follows in this embodiment. That is, the resolution in the main scanning direction (arrow X direction) of the image formed by the image forming device A is m [dpi], the number of light-emitting units 50 arranged in parallel in the arrow Y direction is n [pieces], and the reference value of the amount of deviation in the arrow X direction of the positions of the light-emitting units 50 arranged in parallel in the arrow Y direction is the interval d3 [mm] (reference value). In this case, the interval d3 is calculated 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 shifted from each other by an integer multiple of the interval d3. That is, in this embodiment, since m = 1200 and n = 4, d3 = 25.4 / 1200 × 1 / 4 = 0.00529 [mm] = 5.29 [μm].

[0050] The result is the same as the above calculation result of the interval d3 even if the interval d3 is determined as follows. That is, the pitch in the arrow X direction of the multiple light-emitting units 50 that are located at the same position in the arrow Y direction is q [mm], the number of light-emitting units 50 arranged in parallel in the arrow Y direction is n [pieces], and the reference value of the shift amount in the arrow X direction of the positions of the light-emitting units 50 arranged in parallel in the arrow Y direction is the interval d3 [mm] (reference value). In this case, the interval d3 is calculated from d3 = q / n, and the light-emitting units 50 arranged in parallel in the arrow Y direction are arranged so that their positions are shifted from each other by an integer multiple of the interval d3. That is, in this embodiment, q = 0.02116, n = 4, and therefore d3 = 0.02116 / 4 = 0.00529 [mm] = 5.29 [μm].

[0051] The interval d3 may be determined as follows instead of the above-mentioned method. That is, for the light-emitting units 50 arranged at different positions in the arrow Y direction to form the same pixel, the number of the light-emitting units 50 is n, and the width of the light-emitting units 50 in the arrow X direction is W1 [mm]. In this case, the interval d3 is obtained from d3=W1 / n (n is a natural number of 2 or more). The light-emitting units 50 arranged at different positions in the arrow Y direction to form the same pixel are arranged so that the center of gravity of each light-emitting unit 50 is located at an interval of d3 in the arrow X direction. That is, in order to form the same pixel by multiple exposure described later, the light-emitting units 50 are arranged so that the distance between the centers of gravity of the four light-emitting units 50 arranged at different positions in the arrow Y direction at equal intervals in the arrow X direction is d3. In this embodiment, W1=19.80 [μm]=0.01980 [mm], n=4. Therefore, d3=0.01980 / 4=0.00495 [mm]=4.95 [μm]. By setting the spacing d3 in this manner, the amount of overlap in the direction of the arrow X of the four light-emitting elements 50 arranged at different positions in the direction of the arrow Y to form the same pixel is made uniform, so that the amount of light of 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 section 50 is not limited to a square, and may be a polygon having more than a square, a circle, an ellipse, or the like, as long as the light is emitted in 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, since the amount of light emitted by an organic light-emitting material is smaller than that of an LED, it is preferable to make the light-emitting section 50 square and reduce the distance between adjacent light-emitting sections 50, thereby ensuring a light-emitting area for obtaining an amount of light sufficient to change the potential of the photosensitive drum 1. In addition, the number of light-emitting sections 50 arranged in parallel in the direction of the 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 the like.

[0053] As described above, the distance between the light-emitting sections 50, that is, the distance between the lower electrodes 54, is defined based on the center of gravity of the lower electrodes 54 in the design nominal. 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 is a perfect circle, and 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, a description will be given of the configuration of the exposure head 6 and the image controller section 70 (control section) which controls the exposure head 6. The image controller section 70 is provided on the main body side of the image forming apparatus A. Note that although the following describes the control performed when processing one piece of image data (monochrome), when performing image forming operations, similar processing is performed in parallel for four pieces of image data corresponding to yellow, magenta, cyan, and black.

[0055] Fig. 8 is a block diagram showing the system configuration of the image controller section 70 and the exposure head 6. As shown in Fig. 8, the image controller section 70 includes an image data generating section 71, a chip data converting section 72, a CPU 73, and a synchronization signal generating section 74. The image controller section 70 processes image data and image formation timing using these sections, and transmits control signals for controlling the exposure head 6 to the printed circuit board 22 of 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 generating unit 71 (image processing unit). The image data generating unit 71 performs dithering processing on the input image data at a resolution instructed by the CPU 73 to generate image data for outputting an image. In this embodiment, the image data generating unit 71 performs dithering processing at a resolution of 1200 dpi and with a binary number of gradations, 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 a binary number of gradations. In the high-resolution processing, the 1200 dpi data is simply copied.

[0057] Fig. 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 the exposure by the light emitting element array chip 40. At this time, the image data generation unit 71 generates binarized data, thereby enabling high definition image formation without losing the sharpness of the image.

[0058] In this embodiment, the resolution of the dithering process of the image data generating unit 71 is set to 1200 dpi, so that the image data after the dithering process is generated in units 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 row of light emitting units 50 and the second row of light emitting units 50 have different distances from the center of the rod lens array 23, so that a difference occurs in the amount of light irradiated from each row to the photosensitive drum 1. The same is true for the third and fourth rows of light emitting units 50. Therefore, by performing the dithering process to generate image data in units of four light emitting units 50 arranged in parallel in the direction of the arrow X, it is possible to suppress the occurrence of moire and banding due to the density difference of the generated dots. In addition, by shifting the image data so as to correct the image position with a resolution of 4800 dpi for the image data after dithering, it is possible to correct the image position with 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 according to the resolution in the sub-scanning direction of an image formed by the image forming apparatus A, as one line period, and instructs the synchronization signal generating unit 74 of the time interval of the signal period.

[0060] In this embodiment, the resolution in the sub-scanning direction of the image formed by the image forming apparatus A 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 a distance (10.58 um) corresponding to the pixel size of 2400 dpi is 52.92 us, and the period of the line synchronization signal is 52.92 us. The rotation speed of the photosensitive drum 1 is calculated by the CPU 73 based on a set value stored in a storage unit (not shown).

[0061] The chip data conversion unit 72 divides image data of one line×4 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 information on the amount of light emitted and mounting position 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 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 a clock signal is 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 composed of a 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 generating section 83, a line synchronization signal generating section 84, and a data holding section 85. The digital section 80 uses these sections to generate pulse signals for making the light-emitting sections 50 emit light based on preset values, image data signals, and line synchronization signals that are synchronized with a clock signal and are set 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, image data for four lines (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 image data for four lines 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, image data for four lines (D1[1] to D1[4]) is 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 a drive signal (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 the data latch signal we002.

[0070] Four lines of image data (D2[1] to D2[4]) are also input to the data holding unit 85-002 at the same time. 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 a drive signal (P002[1] to P002[4]). The data holding unit 85-002 also delays the data latch signal we002 by one clock and transmits it to the data holding unit 85-003 as the data latch signal we003.

[0071] In this manner, 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 composed of a drive circuit that is connected one-to-one to each light-emitting unit 50. For ease of explanation, one drive circuit will be explained below, 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 passed through 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 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 Pch MOSFET, the source terminal of which is connected to the drain terminal of the current control MOSFET 62, and the gate terminal of which 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 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 becomes the drive current for the light-emitting unit 50.

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

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

[0078] Next, the light emitting units 50 three positions downstream from the most upstream light emitting unit 50 in the rotation direction of the photosensitive drum 1 are made to emit light at a timing delayed by four lines of 2400 dpi from the light emitting unit 50 on the most upstream side in the rotation direction of the photosensitive drum 1. Similarly, the light emitting units 50 four positions downstream from the most upstream light emitting unit 50 are made to emit light at a timing delayed by six lines of 2400 dpi from the light emitting unit 50 on the most upstream side 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 irradiation position of light on the photosensitive drum 1 when the four light-emitting units 50 arranged in parallel in the Y direction are caused to emit light by the above-mentioned 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 above-mentioned timing, the light 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 and shifted in position by an interval d3 in the X direction. Here, since the interval d3 is set to d3=25.4 / m×1 / n, a portion where at least two or more of the light H1 to H4 overlap is formed on the photosensitive drum 1, thereby forming one pixel. Therefore, the amount of light when multiple exposure is performed on the photosensitive drum 1 to form an electrostatic latent image can be supplemented.

[0080] In this embodiment, the light-emitting units 50 arranged in parallel in the direction of the arrow Y are shifted from each other in the direction of the arrow X by 5.29 μm (=d3), which is equivalent to 4800 dpi. Therefore, the exposure process can be performed on the photosensitive drum 1 with a resolution of 4800 dpi without changing the data of the edge part of the image to an intermediate value. Therefore, the image position can be corrected with 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 in a configuration in which the interval d3 is 4.95 μm calculated from d3=W1 / n (n is a natural number of 2 or more), it is possible to obtain the effect of performing the exposure process on the photosensitive drum 1 with a resolution higher than the pitch of the light-emitting units 50 in the main scanning direction. In this case, the image data generating unit 71 performs the high-resolution process according to the value of the interval d3 calculated from d3=W1 / n (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 the arrow X is small, the amount of overlap of the light 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 multiple exposure to be poor or gaps to appear between the light H1 to H4, resulting in image streaks. Therefore, the width W1 is set to at least twice the interval d3. This allows the light emitted not only from the light-emitting units 50 adjacent 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 multiple exposure to be performed accurately and suppressing image streaks.

[0082] As described above, the interval L1 (shortest distance) between the light-emitting units 50 of two light-emitting element array chips 40 adjacent in the direction of the arrow Y shown in FIG. 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 sum of the interval L1 and 2 lines that are the light-emitting area of ​​a pixel, between the light-emitting unit 50 on the most downstream side of the first light-emitting element array chip 40 and the light-emitting unit 50 on the most upstream side of the second light-emitting element array chip 40 downstream of the first light-emitting element 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 units 50 of the staggered light-emitting element array chips 40.

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

[0084] In the present embodiment, the light-emitting element array chip 40 is configured such that the light-emitting units 50 adjacent in the arrow Y direction are shifted in the arrow X direction by an interval d3, but the present invention is not limited to this. That is, as shown in FIG. 16, for example, if the amount of shift in the arrow X direction between the light-emitting units 50 arranged in parallel in the arrow Y direction is an integer multiple of the interval d3, the amount of shift between the light-emitting units 50 adjacent in the arrow Y direction does not need to be the interval d3. As shown in FIG. 17, the light-emitting units 50 arranged in parallel in the arrow Y direction may include some of the light-emitting units 50 that are located at the same position in the arrow X direction. Even in the configuration shown in FIG. 16 or FIG. 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 including multiple electrodes) 56...Emitting layer 58...Top electrode (second electrode layer) 70...Image controller unit (control unit) 71...Image data generating unit (image processing unit) A: Image forming device

Claims

1. An image forming apparatus for forming an image on a recording material, A rotating photoconductor; 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 photoconductor, The n light emitting units are arranged so as to be shifted from each other by an integer multiple of an interval d3 in the direction of the rotation axis, the plurality of light-emitting units are arranged so as to satisfy d3 = q / n (n is a natural number greater than or equal to 2), where q is the pitch at which adjacent light-emitting units among the plurality of light-emitting units are arranged in the direction of the rotation axis.

2. 2. The image forming apparatus according to claim 1, wherein one pixel included in the image formed on the recording material is formed using the n light emitting portions.

3. The exposure head further includes a long substrate and a light-emitting chip having a silicon substrate mounted on the substrate, 3. The image forming apparatus according to claim 2, wherein the plurality of light emitting sections are formed on the silicon substrate.

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

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

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

7. 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.

8. The image forming apparatus according to claim 1 , further comprising a control unit that controls turning on the light emitting units based on image data.

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

Images