Image forming apparatus and exposure head

Abstract

The invention discloses an image forming apparatus and an exposure head. An exposure head includes at least one light emitting chip and a plate. The at least one light emitting chip includes a plurality of light emitting portions for emitting light for exposing the photosensitive member from a light emitting surface. The at least one light emitting chip is supplied with power from a power source via a power line. At least one bypass capacitor connected to a power supply line and ground and the at least one light emitting chip are mounted on one surface of the board. In a vertical direction perpendicular to the one surface of the plate, a first height, which is a height from the one surface of the plate to the light emitting surface, is higher than a second height, which is a height from the one surface of the plate to an end portion of the at least one bypass capacitor farthest from the one surface of the plate.

Description

Technical Field

[0001] The present invention relates to an electrophotographic image forming apparatus using an exposure head and an exposure head used for the electrophotographic image forming apparatus. Background Art

[0002] It is generally known that an electrophotographic printer exposes a photosensitive drum by using an exposure head using a light emitting diode (LED) or an organic electroluminescent (EL) device to form a latent image on the surface of the photosensitive drum. U.S. Patent No. 8,345,074 discloses an optical print head, which includes a plurality of light emitting chips provided with light emitting points on the front surface of a long board. In the manufacturing process of the exposure head discussed in U.S. Patent No. 8,345,074, foreign matter may fall on the light emitting surface of the light emitting chip. It is necessary to remove the fallen foreign matter by bringing a cleaning member into contact with the light emitting surface. However, if electronic components are disposed on the front surface of the board in addition to the light emitting chip, the foreign matter on the light emitting surface of the light emitting chip may not be sufficiently removed. Summary of the invention

[0003] The present invention is directed to providing an exposure head including a light emitting chip and an electronic component mounted on a surface of a board, thereby allowing effective removal of foreign matter on a light emitting surface of the light emitting chip, and an image forming apparatus including the exposure head.

[0004] According to an aspect of the present invention, an exposure head comprises: at least one light-emitting chip, the at least one light-emitting chip comprising a plurality of light-emitting portions, the plurality of light-emitting portions being used to emit light for exposing a photosensitive member from a light-emitting surface, wherein the at least one light-emitting chip is configured to be supplied with power from a power supply via a power line; and a board, at least one bypass capacitor connected to the power line and ground and the at least one light-emitting chip being mounted on one surface of the board, wherein, in a vertical direction perpendicular to the one surface of the board, a first height is higher than a second height, the first height being the height from the one surface of the board to the light-emitting surface, and the second height being the height from the one surface of the board to an end of the at least one bypass capacitor farthest from the one surface of the board.

[0005] Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 The configuration of an image forming apparatus according to an exemplary embodiment is schematically illustrated.

[0007] Figure 2A and Figure 2B Configurations of a photosensitive drum and an exposure head according to an exemplary embodiment are illustrated respectively.

[0008] Figure 3A and Figure 3B A configuration of a printed circuit board of an exposure head according to an exemplary embodiment is illustrated.

[0009] Figure 4 A light emitting chip and a light emitting element array in the light emitting chip according to exemplary embodiments are illustrated.

[0010] Figure 5 is a plan view schematically illustrating a partial configuration of each light emitting chip and a printed circuit board according to an exemplary embodiment.

[0011] Figure 6 is a cross-sectional view schematically illustrating a configuration of each light emitting chip according to an exemplary embodiment.

[0012] Figure 7 is a circuit diagram illustrating a control configuration of an exposure apparatus according to an exemplary embodiment.

[0013] Figure 8 is a diagram of signals related to accessing a register of each light-emitting chip according to an exemplary embodiment.

[0014] Fig. 9 is a diagram of signals related to image data transmission to each light emitting chip according to an exemplary embodiment.

[0015] Fig.10 is a functional block diagram illustrating a detailed configuration of each light emitting chip according to an exemplary embodiment.

[0016] Fig.11 Multiple exposures by light emitting elements arranged in a staircase pattern are illustrated.

[0017] Fig. 12A The process of light emission control based on input image data is illustrated.

[0018] Fig. 12B The process of light emission control based on input image data is illustrated.

[0019] Fig. 12C The process of light emission control based on input image data is still illustrated.

[0020] Fig.12D The process of light emission control based on input image data is still illustrated.

[0021] Fig.13A A configuration of a printed circuit board before a light emitting chip is mounted according to an exemplary embodiment is illustrated.

[0022] Fig. 13BA configuration of a printed circuit board before a light emitting chip is mounted according to an exemplary embodiment is illustrated.

[0023] FIG. 14A to FIG. 14C A light emitting chip mounting process according to an exemplary embodiment is illustrated.

[0024] FIG. 15A to FIG. 15C A light emitting element cleaning process according to an exemplary embodiment is illustrated. DETAILED DESCRIPTION

[0025] Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The following exemplary embodiments do not limit the present invention to the scope of the appended claims. Although multiple features are described in the exemplary embodiments, all of the multiple features are not used in the present invention, and any combination of multiple features can be used. In the accompanying drawings, the same number refers to the same or similar components, and their redundant description will be omitted.

[0026] <Configuration of Image Forming Apparatus>

[0027] Figure 1 An example of a configuration of an image forming apparatus 1 according to an exemplary embodiment is schematically illustrated. The image forming apparatus 1 includes a reading unit 100, an image forming unit 103, a fixing unit 104, and a conveying unit 105. The reading unit 100 optically reads a document placed on a platen to generate read image data. The image forming unit 103 forms an image on a sheet based on the read image data generated by the reading unit 100 or print image data received from an external device via a network, for example.

[0028] The image forming unit 103 includes image forming units 101a, 101b, 101c, and 101d for forming black, yellow, magenta, and cyan toner images, respectively. The image forming units 101a, 101b, 101c, and 101d have similar configurations, and hereinafter these units are collectively referred to as the image forming unit 101. During image formation, Figure 1 The photosensitive drum 102 of the image forming unit 101 is rotatably driven in the clockwise direction of the image forming unit 101. The charging device 107 charges the photosensitive drum 102. The exposure head 106 exposes the photosensitive drum 102 to form an electrostatic latent image on the surface of the photosensitive drum 102. The developing device 108 develops the electrostatic latent image on the photosensitive drum 102 with a toner to form a toner image. The toner image formed on the surface of the photosensitive drum 102 is transferred to a sheet conveyed on a transfer belt 111. Transferring the respective toner images on four different photosensitive drums 102 to a sheet allows the formation of a color image composed of four different color components (black, yellow, magenta, cyan).

[0029] The conveying unit 105 controls sheet feeding and conveying. More specifically, the conveying unit 105 feeds sheets from the units specified by the internal storage units 109a and 109b, the external storage unit 109c, and the manual feeding unit 109d to the conveying path of the image forming device 1. The fed sheets are conveyed to the alignment rollers 110, which convey the sheets to the transfer belt 111 at appropriate timing so that the toner images on the respective photosensitive drums 102 are transferred to the sheets. As described above, while the sheets are being conveyed on the transfer belt 111, the toner images are transferred to the sheets. The fixing unit 104 heats and pressurizes the sheets to which the toner images are transferred so as to fix the toner images to the sheets. After the toner images are fixed, the sheets are discharged to the outside of the image forming device 1 by the discharge rollers 112. The optical sensor 113 is disposed at a relative position of the transfer belt 111.

[0030] The optical sensor 113 optically reads a test pattern formed on the transfer belt 111 by the image forming unit 101. If positional deviation is detected in the test pattern read by the optical sensor 113, the image controller 700 (described below) performs control for compensating for the positional deviation during execution of a subsequent job.

[0031] Although in the above-described examples, the toner images are directly transferred from the respective photosensitive drums 102 to the sheet on the transfer belt 111, the toner images may be indirectly transferred from the photosensitive drums 102 to the sheet via an intermediate transfer member. Although in the above-described examples, a color image is formed using toners of a plurality of colors, the technology according to the present disclosure may also be applied to an image forming apparatus for forming a monochrome image by using a monochrome toner.

[0032] <Configuration example of exposure head>

[0033] Figure 2A and Figure 2B The photosensitive drum 102 and the exposure head 106 are illustrated. The exposure head 106 includes: a light emitting element array 201 including a plurality of light emitting elements 602, a printed circuit board 202 including the light emitting element array 201, a rod lens array 203, and a housing 204 for holding the rod lens array 203 and the printed circuit board 202. The photosensitive drum 102 has a cylindrical shape. The exposure head 106 is disposed so that its longitudinal direction is parallel to the axial direction D1 of the photosensitive drum 102, and the surface on which the rod lens array 203 is mounted faces the surface of the photosensitive drum 102. When the photosensitive drum 102 rotates in the circumferential direction D2, the light emitting element 602 of the exposure head 106 emits light from the light emitting surface, and the rod lens array 203 converges the light on the surface of the photosensitive drum 102. This means that the light emitting element 602 corresponds to a light emitting portion.

[0034] Next, the configuration of the printed circuit board 202 will be described. Figure 3A and Figure 3B An example of the configuration of the printed circuit board 202 is illustrated. Figure 3A The figure shows a surface on which the light emitting element array 201 is mounted. Figure 3B The surface on which the connector 305 is mounted (the surface on the opposite side of the surface on which the light emitting element array 201 is mounted) is illustrated. In the following description, in some cases, for convenience of description, the longitudinal direction (X direction) of the printed circuit board 202 is referred to as the "longitudinal direction", the lateral direction (Y direction) of the printed circuit board 202 is referred to as the "lateral direction", and the height or thickness direction (Z direction) of the printed circuit board 202 is referred to as the "height direction" or "vertical direction".

[0035] According to the present exemplary embodiment, the light emitting element array 201 includes a plurality of light emitting elements arranged two-dimensionally. The light emitting element array 201 includes N columns of light emitting elements in the axial direction D1 of the photosensitive drum 102 and M rows of light emitting elements in the circumferential direction D2 of the photosensitive drum 102, where M and N are integers greater than or equal to 2. Figure 3A In the example of FIG. 2 , the light emitting element array 201 includes 20 light emitting chips 400-1 to 400-20, each light emitting chip including a subset of multiple light emitting elements. The light emitting chips 400-1 to 400-20 are arranged in a zigzag pattern in the axial direction D1. The light emitting chips 400-1 to 400-20 are collectively referred to as light emitting chips 400. Figure 3A As shown in , the range occupied by all the light emitting elements in the 20 light emitting chips in the axial direction D1 is larger than the range occupied by the maximum width W0 of the input image data. Therefore, if the image position deviation is not detected, the light emitting elements located at both ends of the axial direction D1 may not be used to expose the photosensitive drum 102. Each of the light emitting chips 400 on the printed circuit board 202 is connected to the image controller 700 ( Figure 7 ). In the following description, among the light-emitting chips 400-1 to 400-20 arranged in the axial direction D1, for the convenience of description, the light-emitting chip with a smaller sub-number may be referred to as "left", and the light-emitting chip with a larger sub-number may be referred to as "right". For example, the light-emitting chip 400-1 is the leftmost light-emitting chip 400, and the light-emitting chip 400-20 is the rightmost light-emitting chip 400. The printed circuit board electrode group 307 is a collection of electrodes for electrically connecting to the light-emitting chip 400. The printed circuit board electrode groups 307-1 to 307-20 are each electrically connected to a corresponding light-emitting chip among the light-emitting chips 400-1 to 400-20. More specifically, the printed circuit board electrode group 307-1 is connected to the light-emitting chip 400-1, the printed circuit board electrode 307-2 is connected to the light-emitting chip 400-2, and so on.

[0036] Figure 4The light emitting chip 400 and the light emitting elements 602 in the array in the light emitting chip 400 are schematically illustrated. The number J (J=N / 20) of the light emitting elements 602 arranged in each row of one light emitting chip 400 may be equal to, for example, 748 (J=748). On the other hand, the number of the light emitting elements 602 arranged in each column of one light emitting chip 400 may be equal to, for example, 4 (M=4). More specifically, according to an exemplary embodiment, each light emitting chip 400 includes 748 light emitting elements 602 in the axial direction D1 and 4 light emitting elements 602 in the circumferential direction D2, i.e., a total of 2992 (=748×4) light emitting elements 602.

[0037] The interval P between the center points of adjacent light emitting elements 602 in the circumferential direction D2 is C For example, it may be about 21.16 μm, corresponding to a resolution of 1200 dots per inch (dpi). The spacing between the center points of adjacent light emitting elements 602 in the axial direction D1 may also be about 21.16 μm. In this case, 748 light emitting elements 602 occupy a length of about 15.8 mm in the axial direction D1. Figure 4 In the example of , for convenience of description, the light emitting elements 602 are arranged in a complete lattice pattern, but the M light emitting elements 602 (M=4) in each column are actually arranged in a staircase pattern.

[0038] Figure 5 4 is a plan view schematically illustrating a partial configuration of the light emitting chip 400 and the printed circuit board 202. For example, a plurality of light emitting elements 602 in each light emitting chip 400 are formed on the light emitting substrate 402 which is a silicon substrate. The light emitting substrate 402 is provided with a circuit unit 406 for driving the plurality of light emitting elements 602. The light emitting substrate electrodes 408-1 to 408-9 are for connecting from the printed circuit board 202 to the image controller 700 (see Figure 7 )A signal line for communication, a power line for connecting to a power source, and an electrode for connecting to a ground line which is a ground potential.

[0039] The light-emitting substrate electrodes 408-1 to 408-9 are collectively referred to as light-emitting substrate electrodes 408. The printed circuit board electrode group 307 of the printed circuit board 202 includes printed circuit board electrodes 308-1 to 308-9. The printed circuit board electrodes 308-1 to 308-9 are electrodes for connecting a signal line for communicating with the image controller 700, a power line for connecting to a power source, and a ground line for connecting to the ground to the light-emitting substrate electrodes 408-1 to 408-9. The printed circuit board electrodes 308-1 to 308-9 are collectively referred to as printed circuit board electrodes 308. The printed circuit board electrodes 308-1 to 308-9 are each electrically connected to a corresponding light-emitting substrate electrode in the light-emitting substrate electrodes 408-1 to 408-9. More specifically, the printed circuit board electrode 308-1 is connected to the light-emitting substrate electrode 408-1, the printed circuit board electrode 308-2 is connected to the light-emitting substrate electrode 408-2, and so on. For example, a gold wire can be used for electrical connection.

[0040] Figure 6 is along Figure 5 A partial cross-sectional view taken along line AA of FIG. A plurality of lower electrodes 504 are formed on the light emitting substrate 402. A gap having a length d is provided between two adjacent lower electrodes 504. A light emitting layer 506 is disposed on the lower electrode 504, and an upper electrode 508 is provided on the light emitting layer 506. The upper electrode 508 is a common electrode for the plurality of lower electrodes 504. When a voltage is applied between the lower electrode 504 and the upper electrode 508, a current flows from the lower electrode 504 to the upper electrode 508, causing the light emitting layer 506 to emit light. One lower electrode 504 and partial regions of the light emitting layer 506 and the upper electrode 508 corresponding to the corresponding lower electrode 504 constitute one light emitting element 602. In other words, according to this exemplary embodiment, the light emitting substrate 402 includes a plurality of light emitting elements 602.

[0041] For example, an organic electroluminescent (EL) film may be used as the light emitting layer 506. For example, the upper electrode 508 is formed of a transparent electrode made of indium tin oxide (ITO) to transmit the emission wavelength of the light emitting layer 506. Although according to the present exemplary embodiment, the entire upper electrode 508 transmits the emission wavelength of the light emitting layer 506, the entire upper electrode 508 does not necessarily need to transmit the emission wavelength. More specifically, it is sufficient that a portion of the area through which light from each light emitting element 602 passes transmits the emission wavelength. Although in Figure 6504, a continuous light emitting layer 506 is formed in the lower electrode 504, but a plurality of light emitting layers 506 having the same width W as the width of each lower electrode 504 may be formed on the lower electrode 504. Although the upper electrode 508 is a common electrode for the plurality of lower electrodes 504, a plurality of upper electrodes 508 having the same width W as the width of each lower electrode 504 may be formed for the corresponding lower electrodes of the plurality of lower electrodes 504. In the lower electrodes 504 in each light emitting chip 400, the first plurality of lower electrodes 504 may be covered by the first light emitting layer 506, and the second plurality of lower electrodes 504 may be covered by the second light emitting layer 506. In the lower electrodes 504 in each light emitting chip 400, the first upper electrode 508 may be formed in common for the first plurality of lower electrodes 504, and the second upper electrode 508 may be formed in common for the second plurality of lower electrodes 504. In these configurations, one lower electrode 504 and the regions of the light emitting layer 506 and the upper electrode 508 corresponding to the corresponding lower electrode 504 constitute one light emitting element 602. With the light emitting portion according to this exemplary embodiment, as described above, the light emitting layer 506 may be formed commonly for all lower electrodes 504 , may be formed independently for each lower electrode 504 , or may be formed commonly for a plurality of lower electrodes 504 .

[0042] Figure 7 7 is a circuit diagram related to a control configuration for controlling the light emitting chip 400. The image controller 700 is a control circuit for communicating with the printed circuit board 202 via a plurality of signal lines (wiring). The image controller 700 includes a central processing unit (CPU) 701, a clock generation unit 702, an image data processing unit 703, a register access unit 704, and a light emitting control unit 705. The light emitting control unit 705 is a component included in the exposure device together with the exposure head 106. The light emitting control unit 705 terminates the signal line between the light emitting control unit 705 and the printed circuit board 202. The N-th light emitting chip 400-n (n is an integer from 1 to 20) on the printed circuit board 202 is connected to the light emitting control unit 705 via signal lines DATAn and WRITEn. The signal line DATAn is used for the image controller 700 to transmit image data to the light emitting chip 400-n. The signal line WRITEn is used for the image controller 700 to write control data to the register of the light emitting chip 400-n.

[0043] In addition, a signal line CLK, a signal line SYNC, and a signal line EN are provided between the light emitting control unit 705 and each light emitting chip 400. The signal line CLK is used to transmit a clock signal for data transmission on the signal lines DATAn and WRITEn. The light emitting control unit 705 outputs a clock signal generated based on a reference clock signal from the clock generating unit 702 to the signal line CLK. The signals transmitted to the signal lines SYNC and EN will be described below.

[0044] The CPU 701 controls the image forming apparatus 1 as a whole. The image data processing unit 703 performs image processing on the image data received from the reading unit 100 or the external device to generate image data in a binary bitmap format for on / off control of light emitted by the light emitting element 602 of the light emitting chip 400 on the printed circuit board 202. Examples of image processing include raster conversion, grayscale correction, color conversion, and halftone processing. The image data processing unit 703 transmits the generated image data as input image data to the light emitting control unit 705. The register access unit 704 receives control data to be written to the register in each light emitting chip 400 from the CPU 701, and then transmits the data to the light emitting control unit 705.

[0045] Figure 8 The diagram illustrates the transition of the signal levels of the respective signal lines when the control data is written to the register of each light-emitting chip 400. During the communication, a high-level enable signal indicating that the communication is in progress is output to the signal line EN. The light-emitting control unit 705 transmits a start bit to the signal line WRITEn in synchronization with the rising edge of the enable signal. Subsequently, the light-emitting control unit 705 transmits a write identification bit indicating a write operation, and then transmits the address (4 bits according to the present exemplary embodiment) and the control data (8 bits according to the present exemplary embodiment) of the register to which the control data is to be written. When the control data is written to the register, for example, the light-emitting control unit 705 sets the frequency of the clock signal to be transmitted to the signal line CLK to 3 megahertz (MHz).

[0046] Fig. 9 The diagram illustrates the transition of the signal levels of the respective signal lines when the image data is transmitted to the light-emitting chip 400. A periodic line synchronization signal indicating the exposure timing of each line of the photosensitive drum 102 is output to the signal line SYNC. At a circumferential speed of the photosensitive drum 102 of 200 mm / s and a circumferential resolution of 1200 dpi (approximately 21.16 μm), the line synchronization signal is output at intervals of approximately 105.8 μs. The light-emitting control unit 705 transmits the image data to the signal lines DATA1 to DATA20 in synchronization with the rising edge of the line synchronization signal. According to the present exemplary embodiment, since each light-emitting chip 400 includes 2992 light-emitting elements 602, the light-emitting control unit 705 transmits image data indicating the power on / off of each of the 2992 light-emitting elements 602 to each light-emitting chip 400 at intervals of approximately 105.8 μs. According to the present exemplary embodiment, as Fig. 9 As shown in , the light emission control unit 705 sets the frequency of the clock signal to be transmitted to the signal line CLK to 30 MHz when transmitting image data.

[0047] Fig.10 4 is a functional block diagram illustrating a detailed configuration of one light emitting chip 400 (the nth light emitting chip 400-n). Figure 5 As shown in FIG. 4 , each light emitting chip 400 includes nine pads 408-1 to 408-9. Pads 408-1 and 408-2 are connected to a power supply voltage VCC via a power supply line. The power of this power supply voltage VCC is supplied to each circuit in the circuit unit 406 of the light emitting chip 400. Pads 408-3 and 408-4 are connected to the ground via a ground line. Each circuit in the circuit unit 406 and the upper electrode 508 are connected to the ground via pads 408-3 and 408-4. The signal line CLK is connected to the transmission unit 1003, the register 1102, and the latch unit 1004-001 to 1004-748 via pads 408-5. The signal lines SYNC and DATAn are connected to the transmission unit 1003 via pads 408-6 and 408-7, respectively. The signal lines EN and WRITEn are connected to the register 1102 via pads 408-8 and 408-9, respectively. For example, control data indicating a desired emission intensity of the light emitting element 602 is stored in the register 1102. A bypass capacitor 302 (described below) is disposed near the light emitting chip 400. One terminal of the bypass capacitor 302 is connected to a power line, and the other terminal thereof is connected to ground.

[0048] Starting with the row synchronization signal from the signal line SYNC and in synchronization with the clock signal from the signal line CLK, the transmission unit 1003 receives input image data including a series of pixel values ​​indicating the power on / off of each light emitting element 602 from the signal line DATAn. The transmission unit 1003 performs serial-to-parallel conversion on a series of pixel values ​​serially received from the signal line DATAn in units of M pixel values ​​(e.g., M=4). For example, the transmission unit 1003 includes four D flip-flops connected in cascade. The transmission unit 1003 parallelizes the pixel values ​​DATA-1, DATA-2, DATA-3, and DATA-4 input on four clocks, and then outputs the data to the latch units 1004-0001 to 1004-748. The transmission unit 1003 also includes four D flip-flops for delaying the row synchronization signal. The transmission unit 1003 outputs the first latch signal to the latch unit 1004-001 via the signal line LAT1 at a timing delayed by four clocks from the input of the self-synchronization signal.

[0049] The k-th latch unit 1004-k (k is an integer from 1 to 748) uses a latch circuit to latch the four pixel values ​​DATA-1, DATA-2, DATA-3, and DATA-4 input from the transfer unit 1003 at the same time as the timing when the k-th latch signal is input. The k-th latch unit 1004-k except the last latch unit 1004-748 delays the k-th latch signal by four clocks and outputs the (k+1)-th latch signal to the latch unit 1004-(k+1) via the signal line LAT(k+1). Then, during the signal cycle of the k-th latch signal, the k-th latch unit 1004-k continuously outputs the driving signal based on the four pixel values ​​latched by the latch circuit to the current driving unit 1104. For example, there is a delay corresponding to four clocks between the timing when the first latch signal is input to the latch unit 1004-1 and the timing when the second latch signal is input to the latch unit 1004-2. The latch unit 1004-1 outputs a driving signal based on the first pixel value, the second pixel value, the third pixel value, and the fourth pixel value to the current driving unit 1104, and the latch unit 1004-2 outputs a driving signal based on the fifth pixel value, the sixth pixel value, the seventh pixel value, and the eighth pixel value to the current driving unit 1104. Generally speaking, the latch unit 1004-k outputs a driving signal based on the (4k-3)th pixel value, the (4k-2)th pixel value, the (4k-1)th pixel value, and the (4k)th pixel value to the current driving unit 1104. Fig.10 In the exemplary embodiment shown, 748 latch units 1004-001 to 1004-748 substantially parallelly output 2992 drive signals for controlling the driving of 2992 (=748×4) light emitting elements 602 to the current driving unit 1104. Each drive signal is a binary signal indicating a high level or a low level.

[0050] The current driving unit 1104 includes 2992 light-emitting driving circuits corresponding to 2992 light-emitting elements 602, each of which includes a partial area of ​​the light-emitting layer 506. When the corresponding driving signal indicates a high level (which is light-emitting on), each light-emitting driving circuit applies a driving voltage corresponding to the light-emitting intensity indicated by the control data in the register 1102 to the light-emitting layer 506 of the corresponding light-emitting element of the light-emitting element 602. Therefore, the current flows through the light-emitting layer 506, so that the corresponding light-emitting element 602 emits light. The control data may indicate the light-emitting intensity of each individual light-emitting element 602, the light-emitting intensity of each group of light-emitting elements 602, or the light-emitting intensity common to all light-emitting elements 602.

[0051] <Multiple Exposure Control>

[0052] Figure 4An example is illustrated in which the light emitting elements 602 are arranged in a complete lattice pattern in each light emitting chip 400. However, according to the present exemplary embodiment, the M light emitting elements 602 in each column may actually be arranged in a staircase pattern at fixed intervals. Fig.11 Multiple exposure using light emitting elements 602 arranged in a staircase pattern is illustrated. Fig.11 An example of arrangement of the light emitting elements 602 in the light emitting chip 400 - 1 when M=4 is partially illustrated. Fig.11 R j_m (j={0, 1, ..., J-1}, m={0, 1, 2, 3}) represents the light emitting element 602 in the jth column from the left in the axial direction and the mth row from the top in the circumferential direction. As described above, the axial spacing P between the light emitting elements 602 is C The axial spacing between two adjacent light emitting elements 602 in each column of the M light emitting elements 602 (ie, the axial spacing P between the light emitting elements 602) is about 21.16 μm. A ) can be about 5 μm, which corresponds to a resolution of 4800 dpi.

[0053] When the four light emitting elements 602 in each column are arranged in a staircase pattern in this manner, any two adjacent light emitting elements 602 among the four elements 602 occupy a range that partially overlaps in the axial direction. When the four light emitting elements 602 in each row corresponding to different pixel positions in the input image data successively emit light during the rotation of the photosensitive drum 102, light spots corresponding to the different pixel positions are formed on the surface of the photosensitive drum 102. Fig.11 In the example in FIG. 1 , when the leftmost pixel value of the i-th row in the input image data indicates that light emission is on, the light emitting element R 0_0 , R 0_1 , R 0_2 and R 0_3 Each of the rows L on its surface facing the photosensitive drum 102 i As a result, the row L i The leftmost spot area in is exposed in an overlapping manner to form spot SP0. Similarly, when the j-th pixel value (starting from the left) in the i-th row in the input image data indicates that light emission is on, the light emitting element R j_0 , R j_1 , R j_2 and R j_3 Each of the rows L facing the surface of the photosensitive drum 102 i As a result, the row L i The j-th spot area in (starting from the left) is exposed in an overlapping manner to form a spot SP j .

[0054] According to this exemplary embodiment, Fig.11 As understood in the above, two axially adjacent light emitting elements 602 also occupy a range that partially overlaps in the axial direction. Similarly, in two axially adjacent light emitting chips 400, the light emitting elements in the rightmost column of the left-hand light emitting chip 400 and the light emitting elements in the leftmost column of the right-hand light emitting chip 400 also occupy a range that partially overlaps in the axial direction. The axial spacing P between the light emitting elements 602 is A It is constant (about 5 μm) on all 20 light-emitting chips 400. When the four light-emitting elements 602 in each column of these light-emitting chips 400 emit light successively at appropriate timing, a smooth line of an electrostatic latent image is formed on the surface of the photosensitive drum 102. This line includes a series of points that partially overlap each other at fixed point intervals. This line formed continuously in the circumferential direction results in a two-dimensional electrostatic latent image.

[0055] FIG. 12A to FIG. 12D The light emission control process based on the input image data is illustrated. When forming an image, the light emission control unit 705 receives the input image data IM1 in a binary bitmap format from the image data processing unit 703. Fig. 12A On the left-hand side, in the input image data IM1 in the two-dimensional pixel value array, the j-th pixel value from the left in the i-th row from the top is called (j, i) (j={0,1,2,...} and i={1,2,3,...}). The light-emitting control unit 705 adds a dummy pixel value corresponding to the (M-1) row at the top of the input image data IM1. When M=4, if the dummy pixel value to be added is included, the range of the index i of the pixel value is {-3,-2,-1,0,1,2,...}. The dummy pixel value can be zero, for example, which means that the light emission is turned off. The light-emitting control unit 705 can also add dummy pixel values ​​to the right-hand and left-hand sides of the input image data IM1 so that the number of pixel values ​​in a row is equal to the number of light-emitting elements 602 in the axial direction. However, in this example, for the sake of simplicity of description, only the valid pixel values ​​are described in the axial direction.

[0056] The light emitting control unit 705 reads the pixel values ​​of the first four lines in the input image data IM1 during the initial line period t0 of image formation, and outputs a subset of 2992 (=748×4) read pixel values ​​to the light emitting chip 400-n via the signal line DATAn. Fig. 12AIn the light emitting chip 400-1 shown on the right hand side of FIG, during the row period t0, image data in the readout range RD including pixel values ​​(0, -3) to (748, 0) is input via the signal line DATA1. On the light emitting chip 400-1, the input image data is serial-to-parallel converted, and then drive signals based on these pixel values ​​are supplied to the 2992 light emitting elements 602. For example, drive signals based on pixel values ​​(0, -3), (0, -2), (0, -1), (0, 0), and (1, -3) are supplied to the light emitting elements R, ... 0_0 , R 0_1 , R 0_2 , R 0_3 and R 1_0 In particular, Fig. 12A As shown by the dotted line in FIG. 1 , a driving signal based on the effective pixel value of the row DL0 having the index i=0 in the input image data IM1 is supplied to the light emitting element R . 0_3 As a result, the row L on the surface of the photosensitive drum 102 is exposed according to the pixel value group of the row DL0 in the input image data IM1. 0。 However, this timing is in the middle of the multiple exposures, so that the formation of the line L0 of the electrostatic latent image is not completed at this timing.

[0057] Fig. 12B The diagram shows a state in which the light emitting chip 400-1 is driven during the next row period t0+1. During the row period t0+1, the light emitting control unit 705 moves the readout range RD in the input image data IM1 downward by one row, reads pixel values ​​(0, -2) to (748, 1), and outputs them to the light emitting chip 400-1 via the signal line DATA1. On the light emitting chip 400-1, drive signals based on these input pixel values ​​are supplied to 2992 light emitting elements 602. For example, drive signals based on pixel values ​​(0, -2), (0, -1), (0, 0), (0, 1), and (1, -2) are supplied to the light emitting elements R, ... 0_0 ,、R 0_1 , R 0_2 , R 0_3 and R 1_0 During the line period t0+1, a driving signal based on the effective pixel value of the line DL0 in the input image data IM1 is supplied to the light emitting element R 0_2 At this timing, since the photosensitive drum 102 rotates in the circumferential direction, the row L0 on the surface of the photosensitive drum 102 faces the light emitting elements in the third row of the light emitting chip 400-1. As a result, the row L0 on the surface of the photosensitive drum 102 is exposed again according to the pixel value group of the row DL0 in the input image data IM1.

[0058] Fig. 12C The diagram shows the state of driving the light emitting chip 400-1 during the next row period t0+2. During the row period t0+2, the light emitting control unit 705 further shifts the readout range RD in the input image data IM1 downward by one row, reads pixel values ​​(0, -1) to (748, 2), and outputs them to the light emitting chip 400-1 via the signal line DATA1.

[0059] The light emitting chip 400-1 supplies driving signals based on these input pixel values ​​to the 2992 light emitting elements 602. During the line period t0+2, driving signals based on the effective pixel values ​​of the line DL0 in the input image data IM1 are supplied to the light emitting elements R1 and R2. 0_1 At this timing, row L0 on the surface of the photosensitive drum 102 faces the light emitting elements in the second row of the light emitting chip 400-1. As a result, row L0 on the surface of the photosensitive drum 102 is exposed three times according to the pixel value group of row DL0 in the input image data IM1.

[0060] Fig.12D The state of driving the light emitting chip 400-1 during the next row period t0+3 is illustrated. During the row period t0+3, the light emitting control unit 705 further moves the readout range RD in the input image data IM1 downward by one row, reads pixel values ​​(0, 0) to (748, 3), and outputs them to the light emitting chip 400-1 via the signal line DATA1. On the light emitting chip 400-1, drive signals based on these input pixel values ​​are supplied to 2992 light emitting elements 602. During the row period t0+3, drive signals based on the effective pixel values ​​of the row DL0 in the input image data IM1 are supplied to the light emitting elements R 0_0 At this timing, row L0 on the surface of the photosensitive drum 102 faces the light-emitting elements in the first row of the light-emitting chip 400-1. As a result, row L0 on the surface of the photosensitive drum 102 is exposed four times according to the pixel value group of row DL0 in the input image data IM1. Until this timing, multiple exposure of the four light-emitting elements 602 in each column of the light-emitting chip 400 has been performed, and the formation of row L0 of the electrostatic latent image is completed. By repeating the above-mentioned row cycle, rows after row L0 of the electrostatic latent image can also be formed on the surface of the photosensitive drum 102 in a similar manner. According to the present exemplary embodiment, each of the pixel values ​​(0,0) to (748,3) is input to the four light-emitting elements 602 in this manner. More specifically, for example, the pixel value (0,0) is input to the four light-emitting elements R 0_0 , R 0_1 , R 0_2 , and R 0_3 , and the pixel value (1,0) is input to the four light emitting elements R 1_0 , R1_1 , R 1_2 and R 1_3 More specifically, the light spot on the photosensitive drum 102 corresponding to the pixel value (0,0) is composed of four light emitting elements R 0_0 , R 0_1 , R 0_2 , and R 0_3 The light spot on the photosensitive drum 102 corresponding to the pixel value (1, 0) is formed by four light emitting elements R 1_0 , R 1_1 , R 1_2 and R 1_3 form.

[0061] As understood from the above description, the light emission control unit 705 generates light emission of the plurality of light emitting elements 602 based on pixel values ​​read from the readout range on M rows in the input image data IM1. The readout range moves by one row for each column period.

[0062] <Printed Circuit Board Configuration>

[0063] The following will refer to Fig.13A and Fig. 13B The configuration of the printed circuit board 202 before the light emitting chip 400 is mounted is described. Fig.13A and Fig. 13B The printed circuit board 202 is illustrated before the light emitting chip 400 is mounted. Fig.13A There are illustrated surfaces of the printed circuit boards 202-1 to 202-6 on which the light emitting chips 400 are mounted. The surface of the printed circuit board 202 on which the light emitting element array 201 is mounted corresponds to the front surface. Fig. 13B The printed circuit boards 202-1 to 202-6 are illustrated with respect to surfaces on which the light emitting chips 400 are mounted, ie, surfaces on which the connectors 305 are mounted. The surface on which the printed circuit board 202 is mounted with respect to the light emitting chips 400 corresponds to a rear surface.

[0064] The assembly 800 includes printed circuit boards 202-1 to 202-6 before mounting the light emitting chip 400, a plurality of joints 801, and a dummy board 802. Although the assembly 800 includes six printed circuit boards 202 according to the present exemplary embodiment, the number of printed circuit boards 202 is not limited thereto as long as at least two printed circuit boards 202 are included.

[0065] like Fig.13AAs shown, the front surface of the printed circuit board 202 is provided with a light-emitting board electrode 408 disposed on the light-emitting chip 400, a printed circuit board electrode 308 (not shown) for electrically connecting the printed circuit board 202, and an electronic component (described below). According to the present exemplary embodiment, the electronic component refers to a component included in the electronic circuit on the printed circuit board 202. Examples of electronic components include capacitors, diodes, resistors, and thermistors for measuring the temperature of the light-emitting element 602. The electronic component is disposed on the same surface as the surface of the printed circuit board 202 on which the light-emitting chip 400 is mounted. One electronic component or multiple electronic components may be installed. In addition, one electronic component or multiple electronic components may be deployed.

[0066] Examples of electronic components also include a bypass capacitor 302. At least one bypass capacitor 302 is provided for each light emitting chip 400. One terminal of the bypass capacitor 302 is connected to a power line for supplying power to the light emitting chip 400, and the other terminal thereof is connected to the ground (GND). The driving unit 1104 included in each light emitting chip 400 changes the current consumption depending on the driving state. If the current consumption of the driving unit 1104 increases, the power supply voltage supplied to the driving unit 1104 decreases, which may cause a failure of the driving unit 1104. If the current consumption of the driving unit 1104 decreases, the voltage supplied from the power supply increases, which may cause a failure of the driving unit 1104. In the case where the bypass capacitor 302 is disposed between the power supply and the light emitting chip 400, if the voltage supplied from the power supply decreases, the charge accumulated in the bypass capacitor 302 may be discharged, and if the voltage supplied from the power supply increases, the charge may be accumulated in the bypass capacitor 302. As described above, by reducing the variation of the voltage supplied to the light emitting chip 400 using the bypass capacitor 302 , the variation of the voltage supplied to the light emitting chip 400 may be reduced.

[0067] The impedance of the wiring may also cause a change in the voltage supplied to the light emitting chip 400. Desirably, the wiring length between the bypass capacitor 302 and the light emitting chip 400 is as short as possible. More specifically, in order to shorten the wiring length between the bypass capacitor 302 and the light emitting chip 400, desirably, the bypass capacitor 302 is disposed on the same surface of the printed circuit board 202 as the light emitting chip 400 and in the vicinity of the light emitting chip 400. According to the present exemplary embodiment, the bypass capacitor 302 corresponding to each light emitting chip 400 is disposed at a position where the bypass capacitor 302 overlaps with the corresponding light emitting chip 400 in the longitudinal direction of the board. If the bypass capacitor 302 is disposed at a position where the bypass capacitor 302 overlaps with the light emitting chip 400 in the longitudinal direction of the board, desirably, the distance between the bypass capacitor 302 and the light emitting chip 400 in the transverse direction of the board 202 is 3 mm or less.

[0068] The current supplied from the power supply to the light emitting chip 400 may include high-frequency noise components due to interference. The high-frequency noise components tend to flow through the bypass capacitor 302, so that the noise components flowing in the light emitting chip 400 can be reduced by discharging the high-frequency noise components to the ground. The noise components generally have different frequencies, and the noise components that tend to flow depend on the capacitive reactance of the bypass capacitor 302. Therefore, the use of a plurality of bypass capacitors 302 with different capacitive reactances enables the elimination of noise components with different frequencies. According to the present exemplary embodiment, three different bypass capacitors 302 with different capacitive reactances are disposed on the front surface of the printed circuit board 202. The number of bypass capacitors 302 is only an example and is not limited thereto. Desirably, as described above, the bypass capacitor 302 is disposed near the light emitting chip 400. However, the position of the bypass capacitor 302 is not limited thereto, but may be other positions.

[0069] <Light Emitting Chip Mounting Process>

[0070] A process of mounting the light emitting chip 400 will be described. Fig.14A The printed circuit board 202 before mounting the light emitting chip 400 is illustrated. The light emitting chip 400 is disposed in the light emitting chip mounting area 803 on the front surface of the printed circuit board 202. When the light emitting chips 400-1 to 400-20 are mounted on the printed circuit board 202, each light emitting chip mounting area 803 is disposed in a corresponding light emitting chip of the light emitting chip 400, and each light emitting chip mounting area 803 has 20 light emitting chip mounting areas 800-1 to 800-20.

[0071] Fig. 14B The diagram illustrates a state in which the adhesive 304 is applied to each of the light emitting chip mounting regions 803-1 to 803-20 on the printed circuit board 202. By disposing one light emitting chip 400 in each of the light emitting chip mounting regions 803 to which the adhesive 304 is applied, the light emitting chip 400 is mounted on the printed circuit board 202. Although the present exemplary embodiment uses ultraviolet curing as the adhesive 304, other adhesives may also be applied. For example, the adhesive 304 may be a thermal curing adhesive or a conductive adhesive. The adhesive 304 may be applied to all or part of the light emitting chip mounting region 803. In addition, the adhesive 304 may be applied protruding from the light emitting chip mounting region 803.

[0072] Fig. 14C The printed circuit board 202 is illustrated after mounting the light emitting chip 400. The light emitting chip 400 is mounted and bonded to the light emitting chip mounting region 803 to which the adhesive 304 is applied.

[0073] After the light emitting chip 400 has been mounted on the printed circuit board 202, a cleaning process is performed to remove foreign matter on the surface of the light emitting element 602 on the light emitting chip 400. Examples of foreign matter on the surface of the light emitting element 602 include silicon fragments generated during cutting of the light emitting chip 400 and dust floating in the air. Any of the above foreign matter on the surface of the light emitting element 602 blocks the light emitted by the light emitting element 602, possibly reducing the amount of light reaching the photosensitive drum 102. Therefore, the foreign matter on the surface of the light emitting element 602 is desirably removed.

[0074] After the cleaning process for removing foreign matter from the surface of the light emitting element 602 is completed, the printed circuit board electrode 308 disposed on the printed circuit board 202 is electrically connected to the light emitting board electrode 408 disposed on the light emitting chip 400. Although in the present exemplary embodiment, the electrical connection is performed by using wire bonding (wired electrical connection), other methods may also be applicable.

[0075] Multiple connectors 801 (see Fig. 13B ) is cut so that each of the plurality of printed circuit boards 202 forming the aggregate 800 becomes a single printed circuit board 202. Although in the present exemplary embodiment, the joint 801 is cut by a laser cutting process, other methods may also be applied. For example, the joint 801 may be cut by a mechanical process.

[0076] Through the above-mentioned process, a single printed circuit board 202 (see FIG. 2 ) on which the light-emitting chip 400 is mounted can be produced from the aggregate 800 in the initial state. Figure 3A and Figure 3B ).

[0077] Then, foreign matters on the plurality of light emitting elements 602 of the plurality of light emitting chips 400 mounted on each of the printed circuit boards 202 forming the aggregate 800 are removed by using the adhesive cleaning roller 900. The foreign matters on the light emitting elements 602 include silicon fragments generated during the cutting of the light emitting chips 400 and dust floating in the general environment. More specifically, in order to remove foreign matters on the light emitting elements 602 of the plurality of light emitting chips 400 mounted on one surface of each of the printed circuit boards 202 forming the aggregate 800, a light emitting element cleaning process is performed.

[0078] <Cleaning the surface of the light-emitting element>

[0079] Set reference 15A to Fig. 15C The light emitting element cleaning process according to the present exemplary embodiment is described in detail. To make height relationships easier to understand, the light emitting chip 400, bypass capacitor 302 and adhesive 304 in the drawings are larger or smaller than actual components, and therefore, the height ratios therein may differ from the actual height ratios.

[0080] According to an exemplary embodiment, foreign matter on the light emitting surface of the light emitting element 602 is removed by bringing the cleaning roller 900 as an adhesive roller into contact with the surface of the light emitting element 602. The above foreign matter may adhere to the surface of the light emitting element 602 by electrostatic force. In this case, the foreign matter on the surface of the light emitting element 602 may not be removed by a cleaning method using air blowing. It is desirable to remove the foreign matter on the surface of the light emitting element 602 by bringing the cleaning roller 900 into contact with the surface of the light emitting element 602.

[0081] like FIG. 15A to FIG. 15C As shown, the cleaning roller 900 is fixed at a predetermined position. The aggregate 800 moves from one end of each plate 202 to the other end in the longitudinal direction of the plate 202 when the surface of the light emitting element 602 contacts the cleaning roller 900. The cleaning roller 900 rotates around a rotation axis that intersects perpendicularly with the longitudinal direction of the plate 202 and is parallel to the transverse direction of the plate 202. The cleaning roller 900 removes foreign matter on the surface of the light emitting element 602 while rotating by the friction between the surface of the light emitting element 602 and the cleaning roller 900. The aggregate 800 moves in the longitudinal direction of the plate 202 (for example, in the direction from the light emitting chip 400-1 to the light emitting chip 400-20 or in the direction from the light emitting chip 400-20 to the light emitting chip 400-1).

[0082] Although the cleaning method according to the present exemplary embodiment removes foreign matter on the surface of the light emitting element 602 by moving the aggregate 800 while the cleaning roller 900 is fixed, the foreign matter may be removed by moving the cleaning roller 900 while the aggregate 800 is fixed. In addition, the foreign matter on the surface of the light emitting element 602 may be removed by moving both the aggregate 800 and the cleaning roller 900.

[0083] Although in the present exemplary embodiment, the cleaning roller 900 is used to rotate about a rotation axis that intersects perpendicularly with the longitudinal direction of the plate 202 and is parallel to the transverse direction of the plate 202, the direction of the rotation axis is not limited thereto. For example, foreign matter on the surface of the light emitting element 602 can be removed by using the cleaning roller 900 to rotate about a rotation axis that intersects perpendicularly with the transverse direction of the plate 202 and is parallel to the longitudinal direction of the plate 202.

[0084] Although in the present exemplary embodiment, a method of using a cleaning roller 900 to remove foreign matter on the light emitting surface of the light emitting element 602 is used, other methods may also be applied. More specifically, other applicable methods include a cleaning method of removing foreign matter by contacting an adhesive cleaning member with the surface of the light emitting element 602 without using a cleaning roller 900.

[0085] Furthermore, foreign matter can be removed by using an air flow without using an adhesive cleaning member.

[0086] In this case, since the foreign matter on the light emitting surface of the light emitting element 602 is charged, the foreign matter may adhere to the light emitting surface of the light emitting element 602 by electrostatic force. Therefore, by eliminating the charge on the surface of the light emitting element 602 or on the foreign matter using an ionizer, the foreign matter can be effectively removed by airflow.

[0087] Fig.15A 2 is a cross-sectional view illustrating each board 202 on the front surface on which the light emitting chip 400 is individually mounted in the longitudinal direction. Fig.15A Since the light emitting chip 400 is mounted separately on the board 202 , the cleaning roller 900 can be reliably brought into contact with the light emitting surface of the light emitting element 602 .

[0088] Fig. 15B 2 is a cross-sectional view illustrating each board 202 on the front surface on which the light emitting chip 400 and the bypass capacitor 302 are mounted in the longitudinal direction. Fig. 15B , in the vertical direction perpendicular to the front surface of the board 202, the height of each bypass capacitor 302 from the front surface of the board 202 is higher than the height of the light emitting chip 400 from the front surface of the board 202. According to the present exemplary embodiment, the height of the bypass capacitor 302 is defined as the distance from the front surface of the board 202 to the farthest end of the bypass capacitor 302 in the vertical direction. According to the exemplary embodiment, the height of the light emitting chip 400 is defined as the distance from the surface of the board 202 facing the cleaning roller 900 to the farthest light emitting surface of the light emitting chip 400 in the vertical direction. The light emitting surface of the light emitting chip 400 refers to the surface from which the light emitting element 602 as the light emitting portion mounted on the light emitting chip 400 emits light.

[0089] If the height of the bypass capacitor 302 is higher than the height of the light emitting chip 400, when the cleaning roller 900 contacts the bypass capacitor 302, the cleaning roller 900 may not contact the light emitting surface of the light emitting element 602 included in the light emitting chip 400. In this case, the cleaning roller 900 cannot sufficiently remove foreign matter on the light emitting surface of the light emitting element 602.

[0090] Fig. 15C 2 is a cross-sectional view illustrating each board 202 on the front surface on which the light emitting chip 400 and the bypass capacitor 302 are mounted in the longitudinal direction. Fig. 15C ,and Fig. 15B Different from the board 202 in the embodiment, the height of each bypass capacitor 302 from the front surface of the board 202 is lower than the height of the light emitting chip 400 from the front surface of the board 202. Fig. 15CAs shown in , when the height of the bypass capacitor 302 and the height of the light-emitting chip 400 are defined, the cleaning roller 900 can contact the surface of the light-emitting element 602 of the light-emitting chip 400, and at the same time, the cleaning roller 900 is not interfered by the bypass capacitor 302, so that the cleaning roller 900 can fully remove foreign matter on the surface of the light-emitting element 602.

[0091] As a configuration for reliably removing foreign matter on the surface of the light emitting element 602, Fig. 15C As shown in FIG. 4 , the height of the bypass capacitor 302 is lower than the height of the light emitting chip 400 . However, even if the height of the bypass capacitor 302 is the same as the height of the light emitting chip 400 , the cleaning roller 900 can be brought into contact with the surface of the light emitting element 602 .

[0092] The adhesive cleaning roller 900 may be made of an elastic rubber material. Assume that the cleaning roller 900 is made of a rubber material and the bypass capacitor 302, which is higher than the light emitting chip 400, is disposed at a position sufficiently far from the light emitting chip 400 in the lateral direction of the board 202. In this case, even if the cleaning roller 900 is in contact with the bypass capacitor 302, the cleaning roller 900 may be brought into contact with the light emitting chip 400. In this case, desirably, in the lateral direction of the board 202, the bypass capacitor 302 is 3 mm or more away from the light emitting chip 400, and the height difference between the bypass capacitor 302 and the light emitting chip 400 is 0.4 mm or less.

[0093] As described above, according to the present exemplary embodiment, on the circuit board 202 on which the light emitting chip 400 is mounted, the height of the bypass capacitor 302 from the front surface of the board 202 is made lower than the height of the light emitting chip 400. As described above, the heights of the bypass capacitor 302 and the light emitting chip 400 set in this manner allow foreign matter on the surface of the light emitting element 602 to be reliably removed.

[0094] Although the bypass capacitor 302 is used as an example of an electronic component in the present exemplary embodiment, any member other than the bypass capacitor 302 may be mounted on the board 202. More specifically, a thermistor for measuring the temperature of the light emitting chip 400 may be disposed on the board 202. Even with the thermistor disposed on the front surface of the board 202, the height of the thermistor from the front surface of the board 202 is desirably lower than the height of the light emitting chip 400. The height of the thermistor being lower than the height of the light emitting chip 400 allows the cleaning roller 900 to contact the light emitting chip 400 without being obstructed, thereby making it possible to reliably clean the surface of the light emitting chip 400.

[0095] According to the present invention, an exposure head having a light emitting chip and an electronic component mounted on the same surface of a board can be provided, which allows efficient removal of foreign matter on the light emitting surface of the light emitting chip, and an image forming apparatus using the exposure head can be provided.

[0096] While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments.The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

Claims

1. An exposure head, comprising: at least one light-emitting chip including a plurality of light-emitting portions for emitting light for exposing a photosensitive member from a light-emitting surface, wherein the at least one light-emitting chip is configured to be supplied with power from a power source via a power supply line; as well as board, at least one bypass capacitor connected to the power line and ground and the at least one light emitting chip are mounted on one surface of the board, Wherein, in the vertical direction perpendicular to the one surface of the board, the first height is higher than the second height, the first height being the height from the one surface of the board to the light-emitting surface, and the second height being the height from the one surface of the board to the end of the at least one bypass capacitor farthest from the one surface of the board.

2. The exposure head according to claim 1, wherein the at least one light-emitting chip is a plurality of light-emitting chips, wherein the plurality of light emitting chips are mounted on the one surface of the board, and Each of the first heights of the plurality of light emitting chips is higher than the second height in the vertical direction. 3 . The exposure head according to claim 1 , wherein at least a portion of the at least one bypass capacitor overlaps the at least one light emitting chip in a longitudinal direction of the board.

4. The exposure head according to claim 3, wherein the at least one light-emitting chip is a plurality of light-emitting chips, wherein the plurality of light emitting chips are mounted on the one surface of the board, and Each of the plurality of light emitting chips is arranged in a zigzag pattern in the longitudinal direction.

5. The exposure head according to claim 4, wherein the at least one bypass capacitor is a plurality of bypass capacitors, wherein the plurality of bypass capacitors are mounted on the one surface of the board, and Each of the plurality of bypass capacitors is disposed for a corresponding light emitting chip among the plurality of light emitting chips. 6 . The exposure head according to claim 5 , wherein each of the plurality of bypass capacitors is disposed in a zigzag pattern in the longitudinal direction.

7. The exposure head according to claim 1, wherein the exposure head comprises a thermistor for measuring the temperature of the at least one light emitting chip, and The first height is higher than a third height in the vertical direction, and the third height is a height from the one surface of the board to an end of the thermistor farthest from the one surface of the board.

8. The exposure head according to claim 1, wherein the at least one light emitting chip is mounted on the board using an adhesive, and The first height is the sum of the height of the adhesive and the height of the at least one light-emitting chip in the vertical direction.

9. The exposure head according to claim 1, wherein a pad electrically connected to the at least one light emitting chip is disposed on the one surface of the board, and The plurality of light emitting sections emit light by power supplied via the pad. 10 . The exposure head according to claim 9 , wherein the pad does not overlap with the at least one light emitting chip in a longitudinal direction of the board.

11. The exposure head of claim 1, wherein a difference between the first height and the second height is less than 0.4 mm. 12 . The exposure head according to claim 1 , wherein each of the plurality of light emitting sections is an organic electroluminescent device.

13. An image forming device comprising: The exposure head according to claim 1; as well as Photosensitive components. 14 . The image forming apparatus according to claim 13 , wherein each of the plurality of light emitting sections is an organic electroluminescent device.

Images