Image forming apparatus

Abstract

To solve the problem that in the case of an exposure head in which a driving circuit is built in a light-emitting chip, it is necessary to provide electronic components near the light-emitting chip; in the exposure head, in a manufacturing step, if the height of the electronic component provided near the light-emitting chip from the substrate surface is higher than the height of the light-emitting surface of the light-emitting chip from the substrate surface, there is a risk that foreign matter attached to the surface of the light-emitting chip may not be sufficiently removed when cleaning is performed with a roller because the roller may not come into contact with the light-emitting surface of the light-emitting chip.SOLUTION: In an image forming apparatus provided with an exposure head having a substrate on which a light emitting chip having a light emitting part for emitting light for exposing a photoreceptor and electronic components are mounted, height of the light emitting chip from a surface of a printed circuit board is higher than that of the electronic components.SELECTED DRAWING: Figure 15

Description

[Technical field]

[0001] The present invention relates to an electrophotographic image forming apparatus using an exposure head. [Background technology]

[0002] In electrophotographic printers, a method is generally known in which a photosensitive drum is exposed to light using an exposure head using LEDs or organic EL to form a latent image on the surface of the photosensitive drum. Patent Document 1 discloses an optical print head in which a light-emitting element array chip having a plurality of light-emitting points is mounted on a long substrate. Furthermore, Patent Document 1 discloses that a driving IC for driving the light-emitting element array chip is mounted on the same surface of the substrate as the surface on which the light-emitting element array chip is mounted. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2009-96137 A Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, in the exposure head described in Patent Document 1, the amount of light reaching the photoconductor may be reduced due to foreign matter adhering to the exit surface during the manufacturing process. For this reason, it is necessary to remove the foreign matter adhering to the exit surface using a cleaning member. However, in an exposure head in which electronic components are mounted on the same surface as the light-emitting element as in Patent Document 1, for example, if the height of the electronic components from the substrate surface is higher than the height of the exit surface, there is a risk that the foreign matter adhering to the exit surface cannot be sufficiently removed.

[0005] In view of the above problems, the present invention aims to provide an exposure head in which a light-emitting chip and electronic components are mounted on the same surface of a substrate, in which foreign matter adhering to the light-emitting surface of the light-emitting chip is effectively removed, and to provide an image forming device having such an exposure head. [Means for solving the problem]

[0006] The image forming apparatus according to the present invention comprises: A photoconductor; a substrate having a light emitting chip having a plurality of light emitting units that emit light to expose the photoconductor and a light emitting surface from which the light is emitted, and electronic components mounted on one surface of the substrate; Equipped with In a vertical direction perpendicular to the one surface of the substrate, a first height, which is a height from the one surface of the light emitting chip to the light emitting surface, is higher than a second height, which is a height from the one surface to an end of the electronic component farthest from the one surface; It is characterized by: Effect of the Invention

[0007] According to the present invention, it is possible to provide an exposure head in which a light-emitting chip and electronic components are mounted on the same surface of a substrate, in which foreign matter adhering to the light-emitting surface of the light-emitting chip is effectively removed, and an image forming device using the exposure head. [Brief description of the drawings]

[0008] [Figure 1] 1 is a diagram showing a schematic configuration of an image forming apparatus according to an embodiment; [Diagram 2] FIG. 2 is an explanatory diagram of the configuration of a photoconductor drum and an exposure head according to the embodiment. [Diagram 3] FIG. 4 is an explanatory diagram of the configuration of a printed circuit board of an exposure head according to an embodiment. [Figure 4] 1A and 1B are explanatory diagrams of a light-emitting chip and a light-emitting element array in the light-emitting chip according to an embodiment. [Diagram 5] FIG. 2 is a plan view showing a schematic configuration of a light emitting chip and a part of a printed circuit board according to an embodiment. [Figure 6] FIG. 1 is a cross-sectional view showing a schematic configuration of a light-emitting chip according to an embodiment. [Figure 7] FIG. 4 is a circuit diagram showing a control configuration of an exposure apparatus according to an embodiment. [Figure 8] 6 is a signal chart related to access to a register of a light emitting chip according to an embodiment; [Figure 9] 11 is a signal chart related to the transmission of image data to a light-emitting chip according to an embodiment; [Figure 10] FIG. 2 is a functional block diagram showing a detailed configuration of a light-emitting chip according to an embodiment. [Figure 11] FIG. 13 is an explanatory diagram of multiple exposure using light-emitting elements arranged in a stepped pattern. [Figure 12A] 5 is an explanatory diagram of a procedure for light emission control based on input image data. [Figure 12B] 5 is an explanatory diagram of a procedure for light emission control based on input image data. [Figure 12C] 5 is an explanatory diagram of a procedure for light emission control based on input image data. [Figure 12D] 5 is an explanatory diagram of a procedure for light emission control based on input image data. [Figure 13A] FIG. 2 is an explanatory diagram illustrating a configuration of a printed circuit board before mounting a light emitting chip according to an embodiment. [Figure 13B] FIG. 2 is an explanatory diagram illustrating a configuration of a printed circuit board before mounting a light emitting chip according to an embodiment. [Figure 14] 5A to 5C are explanatory views of a mounting process of a light emitting chip according to an embodiment. [Figure 15] 5A to 5C are explanatory views of a light emitting element cleaning step according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, the embodiments will be described in detail with reference to the attached drawings. Note that the following embodiments do not limit the invention according to the claims. Although the embodiments describe a number of features, not all of these features are essential to the invention, and the features may be combined in any manner. Furthermore, in the attached drawings, the same reference numbers are used for the same or similar configurations, and duplicated descriptions are omitted.

[0010] <Configuration of Image Forming Apparatus> 1 shows an example of a schematic configuration of an image forming apparatus 1 according to an embodiment. The image forming apparatus 1 includes a reading unit 100, an image creating unit 103, a fixing unit 104, and a conveying unit 105. The reading unit 100 optically reads an original placed on a platen and generates read image data. The image creating unit 103 forms an image on a sheet based on the read image data generated by the reading unit 100, or based on print image data received from an external device via a network, for example.

[0011] The image forming unit 103 includes image forming units 101a, 101b, 101c, and 101d. The image forming units 101a, 101b, 101c, and 101d form black, yellow, magenta, and cyan toner images, respectively. The image forming units 101a, 101b, 101c, and 101d have the same configuration, and are collectively referred to as the image forming unit 101 below. The photosensitive drum 102 of the image forming unit 101 is rotated clockwise in the figure during image formation. The charger 107 charges the photosensitive drum 102. The exposure head 106 exposes the photosensitive drum 102 to light to form an electrostatic latent image on the surface of the photosensitive drum 102. The developer 108 develops the electrostatic latent image on the photosensitive drum 102 with toner to form a toner image. The toner image formed on the surface of the photoconductor drum 102 is transferred to a sheet transported on a transfer belt 111. By transferring the toner images of the four photoconductor drums 102 onto a sheet in a superimposed manner, a color image including four color components, namely black, yellow, magenta, and cyan, can be formed.

[0012] The conveying unit 105 controls the feeding and conveying of the sheet. Specifically, the conveying unit 105 feeds the sheet from a designated unit among the internal storage units 109a and 109b, the external storage unit 109c, and the manual feed unit 109d to the conveying path of the image forming apparatus 1. The fed sheet is conveyed to the registration roller 110. The registration roller 110 conveys the sheet onto the transfer belt 111 at an appropriate timing so that the toner image of each photoconductor drum 102 is transferred onto the sheet. As described above, the toner image is transferred onto the sheet while the sheet is being conveyed on the transfer belt 111. The fixing unit 104 fixes the toner image onto the sheet by heating and pressurizing the sheet onto which the toner image has been transferred. After the toner image is fixed, the sheet is discharged to the outside of the image forming apparatus 1 by the discharge roller 112. An optical sensor 113 is disposed at a position opposite the transfer belt 111. Optical sensor 113 optically reads a test chart formed on transfer belt 111 by image forming unit 101. When misregistration is detected in the test chart read by optical sensor 113, image controller 700 (described later) performs control to compensate for the misregistration when a subsequent job is executed.

[0013] Although an example in which a toner image is directly transferred from each photoconductor drum 102 to a sheet on transfer belt 111 has been described here, the toner image may be indirectly transferred from each photoconductor drum 102 to a sheet via an intermediate transfer body. Also, although an example in which a color image is formed using toners of multiple colors has been described here, the technology according to the present disclosure is also applicable to an image forming apparatus that forms a monochrome image using toners of a single color.

[0014] <Example of exposure head configuration> 2(A) and 2(B) show the photosensitive drum 102 and the exposure head 106. The exposure head 106 has a light emitting element array 201, a printed circuit board 202 on which the light emitting element array 201 is mounted, a rod lens array 203, and a housing 204 that holds 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 such 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 attached faces the surface of the photosensitive drum 102. While the photosensitive drum 102 rotates in the circumferential direction D2, the light emitting element array 201 of the exposure head 106 emits light from the light emission surface, and the rod lens array 203 focuses the light on the surface of the photosensitive drum 102. That is, the light emitting element 602 corresponds to a light emitting unit.

[0015] The configuration of the printed circuit board 202 will be described. Figures 3(A) and 3(B) show an example of the configuration of the printed circuit board 202. Note that Figure 3(A) shows the surface on which the light-emitting element array 201 is mounted, and Figure 3(B) shows the surface on which the connector 305 is mounted (the surface opposite to the surface on which the light-emitting element array 201 is mounted). In addition, for convenience of explanation, the longitudinal direction (X direction) of the printed circuit board 202 may be referred to as the "longitudinal direction", the lateral direction (Y direction) of the printed circuit board 202 may be referred to as the "lateral direction", and the height (thickness) direction (Z direction) of the printed circuit board 202 may be referred to as the "height direction" or "vertical direction".

[0016] In this embodiment, the light-emitting element array 201 has a plurality of light-emitting elements arranged two-dimensionally. The light-emitting element array 201 includes, as a whole, N columns of light-emitting elements in the axial direction D1 and M rows in the circumferential direction D2 of the photosensitive drum 102, where M and N are integers of 2 or more. In the example of FIG. 3(A), the light-emitting element array 201 is divided into 20 light-emitting chips 400-1 to 400-20, each of which includes a subset of the entire plurality of light-emitting elements, and the light-emitting chips 400-1 to 400-20 are arranged in a staggered manner along the axial direction D1. The light-emitting chips 400-1 to 400-20 are also collectively referred to as light-emitting chips 400. As shown in FIG. 3(A), the range occupied by all the light-emitting elements of the 20 light-emitting chips in the axial direction D1 is wider than the range occupied by the maximum width W0 of the input image data. Therefore, some light-emitting elements located at both ends in the axial direction D1 may not be used to expose the photosensitive drum 102 unless a positional deviation of the image is detected. Each light emitting chip 400 on the printed circuit board 202 is connected to the image controller 700 (FIG. 7) via a connector 305. In the following description, for convenience of explanation, the side of the light emitting chips 400-1 to 400-20 arranged along the axial direction D1 with a smaller branch number may be referred to as the "left" and the side with a larger branch number may be referred to as the "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. 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 group 307-1 is electrically connected to the light emitting chip 400-1, the printed circuit board electrode group 307-2 is electrically connected to the light emitting chip 400-2, and so on.

[0017] FIG. 4 is a schematic diagram showing a light-emitting chip 400 and an arrangement of the light-emitting elements 602 in the light-emitting chip 400. 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). Meanwhile, the number M 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). That is, in an exemplary embodiment, each light-emitting chip 400 has a total of 2992 (=748×4) light-emitting elements 602, with 748 in the axial direction D1 and 4 in the circumferential direction D2. The interval P between the center points of the light-emitting elements 602 adjacent to each other in the circumferential direction D2 is C may be, for example, about 21.16 μm corresponding to a resolution of 1200 dpi. The interval between the center points of adjacent light-emitting elements 602 in the axial direction D1 may also be about 21.16 μm, in which case 748 light-emitting elements 602 occupy a length of about 15.8 mm in the axial direction D1. Note that, for convenience of explanation, FIG. 4 shows an example in which the light-emitting elements 602 are completely arranged in a lattice in each light-emitting chip 400, but in reality, M (M=4) light-emitting elements 602 in each row are arranged in a staircase pattern.

[0018] FIG. 5 is a plan view showing a schematic configuration of the light emitting chip 400 and a part of the printed circuit board 202. The light emitting elements 602 of each light emitting chip 400 are formed on the light emitting substrate 402, which is, for example, a silicon substrate. The light emitting substrate 402 is provided with a circuit section 406 for driving the light emitting elements 602. The light emitting substrate electrodes 408-1 to 408-9 are electrodes for connecting the signal lines for communicating with the image controller 700 (see FIG. 7), the power lines for connecting to the power source, and the ground lines for connecting to the ground from the printed circuit board 202. The light emitting substrate electrodes 408-1 to 408-9 are also collectively referred to as the light emitting substrate electrodes 408. The printed circuit board electrode group 307 of the printed circuit board 202 is composed of the printed circuit board electrodes 308-1 to 308-9. The printed circuit board electrode units 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 a ground to the light emitting board electrode units 408-1 to 408-9. The printed circuit board electrode units 308-1 to 308-9 are also collectively referred to as the printed circuit board electrode units 308. The printed circuit board electrode unit 308-1 is electrically connected to the light emitting board 408-1, the printed circuit board electrode unit 308-2 is electrically connected to the light emitting chip 400-2, and so on. For example, a gold wire may be used for the electrical connection.

[0019] FIG. 6 shows a part of the cross section taken along line AA in FIG. 5. A plurality of lower electrodes 504 are formed on the light emitting substrate 402. A gap of length d is provided between two adjacent lower electrodes 504. A light emitting layer 506 is provided 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. Therefore, one lower electrode 504 and a partial region of the light emitting layer 506 and the upper electrode 508 corresponding to the lower electrode 504 constitute one light emitting element 602. That is, in this embodiment, the light emitting substrate 402 includes a plurality of light emitting elements 602.

[0020] The light-emitting layer 506 may be, for example, an organic EL film. The upper electrode 508 is made of, for example, a transparent electrode such as indium tin oxide (ITO) so as to transmit the emission wavelength of the light-emitting layer 506. In this embodiment, the entire upper electrode 508 transmits the emission wavelength of the light-emitting layer 506, but the entire upper electrode 508 does not need to transmit the emission wavelength. Specifically, it is sufficient that a partial region through which light from each light-emitting element 602 passes transmits the emission wavelength. In FIG. 6, one continuous light-emitting layer 506 is formed, but multiple light-emitting layers 506 each having a width equivalent to the width W of the lower electrode 504 may be formed on the lower electrode 504. In FIG. 6, the upper electrode 508 is one common electrode for multiple lower electrodes 504, but multiple upper electrodes 508 each having a width equivalent to the width W of the lower electrode 504 may be formed corresponding to each lower electrode 504. Moreover, among the lower electrodes 504 of each light-emitting chip 400, a first plurality of lower electrodes 504 may be covered with a first light-emitting layer 506, and a second plurality of lower electrodes 504 may be covered with a second light-emitting layer 506. Moreover, among the lower electrodes 504 of each light-emitting chip 400, a first upper electrode 508 may be commonly formed corresponding to the first plurality of lower electrodes 504, and a second upper electrode 508 may be commonly formed corresponding to the second plurality of lower electrodes 504. Even in such a configuration, one lower electrode 504 and a region of the light-emitting layer 506 and upper electrode 508 corresponding to the lower electrode 504 configure one light-emitting element 602.

[0021] FIG. 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 that communicates with the printed circuit board 202 via a plurality of signal lines (wires). The image controller 700 has a CPU 701, a clock generating 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 that configures an exposure device together with the exposure head 106. The light-emitting control unit 705 terminates a 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 a signal line DATAn and a signal line WRITEn. The signal line DATAn is used to transmit image data from the image controller 700 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.

[0022] One signal line CLK, one signal line SYNC, and one signal line EN are further 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 transmitting data 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 later.

[0023] The CPU 701 controls the entire image forming apparatus 1. The image data processing unit 703 performs image processing on image data received from the reading unit 100 or an external device to generate binary bitmap image data for controlling the on / off of the light emission of the light emitting element 602 of the light emitting chip 400 on the printed circuit board 202. The image processing here may include, for example, raster conversion, tone correction, color conversion, and halftone processing. The image data processing unit 703 transmits the generated image data to the light emission control unit 705 as input image data. 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 transmits it to the light emission control unit 705.

[0024] FIG. 8 shows the transition of the signal level of each signal line when control data is written to the register of the light-emitting chip 400. An enable signal that is at high level during communication and indicates that 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. Next, the light-emitting control unit 705 transmits a write identification bit indicating a write operation, and then transmits the address of the register to which the control data is to be written (4 bits in this example) and the control data (8 bits in this example). When writing to the register, the light-emitting control unit 705 sets the frequency of the clock signal transmitted to the signal line CLK to, for example, 3 MHz.

[0025] FIG. 9 shows the transition of the signal level of each signal line when image data is transmitted to each light-emitting chip 400. A periodic line synchronization signal indicating the exposure timing of each line on the photosensitive drum 102 is output to the signal line SYNC. If the circumferential speed of the photosensitive drum 102 is 200 mm / s and the resolution in the circumferential direction is 1200 dpi (approximately 21.16 μm), the line synchronization signal is output at a period of approximately 105.8 μs. The light-emitting control unit 705 transmits image data to the signal lines DATA1 to DATA20 in synchronization with the rising edge of the line synchronization signal. In this embodiment, since each light-emitting chip 400 has 2992 light-emitting elements 602, it is necessary to transmit image data indicating the light emission / non-light emission of each of the total 2992 light-emitting elements 602 to each light-emitting chip 400 within a period of approximately 105.8 μs. Therefore, in this example, as shown in FIG. 9, when transmitting image data, the light-emitting control unit 705 sets the frequency of the clock signal transmitted to the signal line CLK to 30 MHz.

[0026] FIG. 10 is a functional block diagram showing a detailed configuration of one light-emitting chip 400 (n-th light-emitting chip 400-n). As also shown in FIG. 5, the light-emitting chip 400 has nine pads 408-1 to 408-9. The pads 408-1 and 408-2 are connected to a power supply voltage VCC by a power supply line. Power is supplied from the power supply voltage VCC to each circuit of the circuit unit 406 of the light-emitting chip 400. The pads 408-3 and 408-4 are connected to the ground by a ground line. Each circuit of the circuit unit 406 and the upper electrode 508 are connected to the ground via the pads 408-3 and 408-4. The signal line CLK is connected to the transfer unit 1003, the register 1102, and the latch units 1004-001 to 748 via the pad 408-5. The signal lines SYNC and DATAn are connected to the transfer unit 1003 via the pads 408-6 and 408-7. The signal lines EN and WRITEn are connected via pads 408-8 and 408-9 to a register 1102. The register 1102 stores control data indicating a desired light emission intensity of the light emitting element 602, for example.

[0027] The transfer unit 1003 receives input image data including a series of pixel values ​​each indicating the emission or non-emission of one light emitting element 602 from a signal line DATAn in synchronization with a clock signal from a signal line CLK, starting from a line synchronization signal from a signal line SYNC. The transfer unit 1003 performs serial-to-parallel conversion on the series of pixel values ​​serially received from the signal line DATAn in units of M (for example, M=4) pixel values. For example, the transfer unit 1003 has four cascaded D flip-flops, and parallelizes pixel values ​​DATA-1, DATA-2, DATA-3, and DATA-4 input over four clocks, and outputs the parallelized pixel values ​​to the latch units 1004-0001 to 1004-748. The transfer unit 1003 further has four D flip-flops for delaying the line synchronization signal, and outputs a first latch signal to the latch unit 1004-001 via a signal line LAT1 at a timing delayed by four clocks from the input of the line synchronization signal.

[0028] The kth latch unit 1004-k (k is an integer from 1 to 748) holds 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 kth latch signal is input, by using a latch circuit. In addition, except for the last-stage latch unit 1004-748, the kth latch unit 1004-k delays the kth 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, the kth latch unit 1004-k continues to output a drive signal based on the four pixel values ​​held by the latch circuit to the current drive unit 1104 during the signal period of the kth latch signal. For example, there is a delay of 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. Therefore, the latch unit 1004-1 outputs drive signals based on the 1st, 2nd, 3rd and 4th pixel values ​​to the current driver 1104, whereas the latch unit 1004-2 outputs drive signals based on the 5th, 6th, 7th and 8th pixel values ​​to the current driver 1104. Generally speaking, the latch unit 1004-k outputs drive signals based on the (4k-3), (4k-2), (4k-1) and (4k)th pixel values ​​to the current driver 1104. Therefore, in the embodiment shown in FIG. 10, 748 latch units 1004-001 to 1004-748 output 2992 drive signals for controlling the driving of 2992 (=748×4) light emitting elements 602 in approximately parallel to the current driver 1104. Each drive signal is a binary signal indicating a high level or a low level.

[0029] The current driver 1104 has 2992 light emission driver circuits corresponding to the 2992 light emitting elements 602 each including a partial region of the light emitting layer 506. Each light emission driver circuit applies a drive voltage corresponding to the light emission intensity indicated by the control data in the register 1102 to the light emitting layer 506 of the corresponding light emitting element 602 while the corresponding drive signal indicates a high level indicating that light emission is on. This causes a current to flow through the light emitting layer 506, causing the light emitting element 602 to emit light. Note that the control data may indicate one individual light emission intensity for each light emitting element 602, may indicate one light emission intensity for each group of the light emitting elements 602, or may indicate one light emission intensity common to all the light emitting elements 602.

[0030] <Multiple exposure control> FIG. 4 shows an example in which the light-emitting elements 602 are completely arranged in a lattice pattern in each light-emitting chip 400, but in reality, in this embodiment, the M light-emitting elements 602 in each row can be arranged in a stepped pattern at a constant pitch. FIG. 11 is an explanatory diagram of multiple exposure using light-emitting elements arranged in a stepped pattern. Here, an example of the arrangement of light-emitting elements in the light-emitting chip 400-1 when M=4 is partially shown. R in the figure j_m (j={0,1,...,J-1}, m={0,1,2,3}) represents the light emitting element 602 in the j-th column from the left in the axial direction and in the m-th row from the top in the circumferential direction. C As described above, the axial spacing between two adjacent light-emitting elements among the M light-emitting elements in each row, i.e., the axial pitch P A may be approximately 5 μm, which corresponds to a resolution of 4800 dpi.

[0031] By arranging the four light-emitting elements in each row in a stepped manner in this manner, any two adjacent light-emitting elements among the four light-emitting elements occupy areas that partially overlap in the axial direction. Then, the four light-emitting elements in the row corresponding to each pixel position of the input image data sequentially emit light while the photoconductor drum 102 is rotating, forming spots corresponding to each pixel position on the surface of the photoconductor drum 102. In the example of FIG. 11, when the pixel value at the left end of the i-th line of the input image data indicates that light is on, the light-emitting element R 0_0 , R 0_1 , R 0_2 , R 0_3 is a line L on the surface of the photosensitive drum 102. i As a result, the line L i In the same manner, when the jth pixel value from the left of the i-th line of the input image data indicates that light is emitted, the light-emitting element R j_0 , R j_1 , R j_2 , R j_3 is a line L on the surface of the photosensitive drum 102. i As a result, the line L i The jth spot area from the left of is multiplexed and the corresponding spot SP j is formed.

[0032] 11, in this embodiment, the light-emitting elements in two axially adjacent rows also occupy a partially overlapping range in the axial direction. Similarly, of the two axially adjacent light-emitting chips 400, the light-emitting elements in the rightmost row of the left light-emitting chip 400 and the light-emitting elements in the leftmost row of the right light-emitting chip 400 also occupy a partially overlapping range in the axial direction. The axial pitch P of the light-emitting elements across all 20 light-emitting chips 400 is Ais constant at about 5 μm. By sequentially emitting light at appropriate times from the four light-emitting elements in each row of these light-emitting chips 400, a smooth line of an electrostatic latent image consisting of a series of spots that are partially overlapping each other and have a constant spot spacing can be formed on the surface of the photoconductor drum 102. Then, as a result of such lines being continuously formed in the circumferential direction, a two-dimensional electrostatic latent image is created.

[0033] 12A to 12D are explanatory diagrams of the procedure of light emission control based on input image data. When forming an image, the light emission control unit 705 receives input image data IM1 in a binary bitmap format from the image data processing unit 703. On the left side of FIG. 12A, the jth pixel value from the left of the i-th line from the top of the input image data IM1, which is a two-dimensional pixel value array, is represented as (j, i) (j={0, 1, 2, ...}, i={0, 1, 2, ...}). The light emission control unit 705 adds dummy pixel values ​​for (M-1) lines to the beginning of the input image data IM1. In the case of M=4, the range of the index i of the pixel value is {-3, -2, -1, 0, 1, 2, ...}, including the added dummy pixel values. The dummy pixel value may be, for example, zero, which means that light emission is off. The light emission control unit 705 may add dummy pixel values ​​to the left and right of the input image data IM1 so that the number of pixel values ​​in one line is equal to the number of light emitting elements in the axial direction, but for simplicity of explanation, only effective pixel values ​​are shown here in the axial direction.

[0034] In the first line period t0 of image formation, the light-emission control unit 705 reads out pixel values ​​of the top four lines of the input image data IM1, and outputs a subset of 2992 (=748×4) of the read pixel values ​​to the light-emitting chip 400-n via the signal line DATAn. Focusing on the light-emitting chip 400-1 shown on the right of FIG. 12A, image data within a read range RD including pixel values ​​from (0,-3) to (748,0) is input via the signal line DATA1 during the line period t0. The light-emitting chip 400-1 performs serial-to-parallel conversion of the input image data, and supplies drive signals based on these pixel values ​​to each of the 2992 light-emitting elements. For example, drive signals based on pixel values ​​(0,-3), (0,-2), (0,-1), (0,0), and (1,-3) are output to the light-emitting chip R. 0_0 , R 0_1 , R 0_2 , R 0_3 and R 1_0 In particular, as shown by the dashed line in the figure, the light emitting element R 0_3 A drive signal based on the effective pixel value of line DL0 of index i=0 of input image data IM1 is supplied to the light-emitting elements in the fourth row including line L0. As a result, line L0 on the surface of photoconductor drum 102 is exposed in accordance with the pixel value set of line DL0 of input image data IM1. However, at this point, multiple exposure is in progress and formation of electrostatic latent image line L0 is not completed.

[0035] FIG. 12B illustrates how the light-emitting chip 400-1 is driven during the next line period t0+1. In the line period t0+1, the light-emitting control unit 705 moves the readout range RD of the input image data IM1 down by one line, reads out pixel values ​​from (0,-2) to (748,1), and outputs the pixel values ​​to the light-emitting chip 400-1 via the signal line DATA1. The light-emitting chip 400-1 supplies drive signals based on the input pixel values ​​to the 2992 light-emitting elements. 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 element R. 0_0 , R 0_1 , R 0_2 , R 0_3 and R 1_0In the line period t0+1, the light-emitting element R 0_2 A driving signal based on the effective pixel value of the line DL0 of the input image data IM1 is supplied to the light-emitting elements in the third row including the light-emitting chip 400-1. At this time, since the photoconductor drum 102 is rotating in the circumferential direction, the line L0 on the surface of the photoconductor drum 102 faces the light-emitting elements in the third row of the light-emitting chip 400-1. As a result, the line L0 on the surface of the photoconductor drum 102 is exposed again according to the pixel value set of the line DL0 of the input image data IM1.

[0036] FIG. 12C illustrates the driving of the light-emitting chip 400-1 during the next line period t0+2. In the line period t0+2, the light-emitting control unit 705 moves the readout range RD of the input image data IM1 further down by one line, reads out pixel values ​​from (0,-1) to (748,2), and outputs the pixel values ​​to the light-emitting chip 400-1 via the signal line DATA1. The light-emitting chip 400-1 supplies drive signals based on the input pixel values ​​to the 2992 light-emitting elements. In the line period t0+2, the light-emitting elements R 0_1 A driving signal based on the effective pixel value of the line DL0 of the input image data IM1 is supplied to the light-emitting elements of the second row including the line L0 on the surface of the photoconductor drum 102. At this time, the line L0 on the surface of the photoconductor drum 102 faces the light-emitting elements of the second row of the light-emitting chip 400-1. As a result, the line L0 on the surface of the photoconductor drum 102 is exposed a third time according to the pixel value set of the line DL0 of the input image data IM1.

[0037] FIG. 12D illustrates the driving of the light-emitting chip 400-1 during the next line period t0+3. In the line period t0+3, the light-emitting control unit 705 moves the readout range RD of the input image data IM1 further down by one line, reads out pixel values ​​from (0,0) to (748,3), and outputs the pixel values ​​to the light-emitting chip 400-1 via the signal line DATA1. The light-emitting chip 400-1 supplies drive signals based on the input pixel values ​​to the 2992 light-emitting elements. In the line period t0+3, the light-emitting elements R 0_0A driving signal based on the effective pixel value of the line DL0 of the input image data IM1 is supplied to the light-emitting elements of the first row including the light-emitting elements of the first row of the light-emitting chip 400-1. At this time, the line L0 on the surface of the photoconductor drum 102 faces the light-emitting elements of the first row of the light-emitting chip 400-1. As a result, the line L0 on the surface of the photoconductor drum 102 is exposed a fourth time according to the pixel value set of the line DL0 of the input image data IM1. At this point, multiple exposure by the four light-emitting elements of each column of the light-emitting chip 400 is performed, and the formation of the line L0 of the electrostatic latent image is completed. Lines following the line L0 of the electrostatic latent image can also be formed on the surface of the photoconductor drum 102 in the same manner through the repetition of such line periods. In this way, in this embodiment, each pixel value from (0,0) to (748,3) is input to the four light-emitting elements 602. Specifically, for example, the pixel value of (0,0) is input to the four light-emitting elements R 0_0、 R 0_1 , R 0_2 , R 0_3 For example, the pixel value of (1,0) is input to the four light-emitting elements R 1_0、 R 1_1 , R 1_2 , R 1_3 That is, the spot on the photoconductor drum 102 corresponding to the pixel value of (0,0) is input to the four light-emitting elements R 0_0、 R 0_1 , R 0_2 , R 0_3 The spot on the photoconductor drum 102 corresponding to the pixel value of (1,0) is formed by the four light-emitting elements R 1_0、 R 1_1 , R 1_2 , R 1_3 is formed by.

[0038] As can be understood from the above description, the light emission control unit 705 causes the multiple light emitting elements 602 to emit light based on pixel values ​​read from a read range spanning M lines of the input image data IM1. The read range moves by one line for each line period.

[0039] <Printed circuit board configuration> The configuration of the printed circuit board 202 before the light emitting chip 400 is mounted will be described with reference to FIG. 13. FIGS. 13A and 13B show the printed circuit board 202 before the light emitting chip 400 is mounted. FIG. 13A shows the surface of the printed circuit board 202 on which the light emitting chip 400 is mounted. That is, the surface of the printed circuit board 202 on which the light emitting element arrangement 201 is mounted corresponds to the front surface. FIG. 13B shows the surface of the printed circuit board 202 on the opposite side to the surface on which the light emitting chip 400 is mounted, on which the connector 305 is mounted. That is, the surface of the printed circuit board 202 on the opposite side to the surface on which the light emitting chip 400 is mounted corresponds to the back surface. The assembly 800 includes printed circuit boards 202-1 to 202-6 before the light emitting chip 400 is mounted, a plurality of connecting parts 801, and a waste board 802. In this embodiment, the number of printed circuit boards 202 included in the assembly 800 is six, but the number is not limited to this as long as two or more printed circuit boards 202 are included.

[0040] As shown in FIG. 13A, the light emitting board electrode portion 408 provided on the light emitting chip 400, the printed board electrode portion 308 (not shown) for electrically connecting the printed board 202, and the electronic components 302, the details of which will be described later, are provided on the surface of the printed board 202. In this embodiment, the electronic components 302 refer to components that constitute an electronic circuit on the printed board 202. For example, the electronic components 302 include a capacitor, a diode, a resistor, and a thermistor that measures the temperature of the light emitting element 602. The electronic components 302 are provided on the same surface of the board 202 as the surface on which the light emitting chip 400 is provided. The number of electronic components 302 may be one or more. Furthermore, the number of electronic components 302 is not limited to one, and more than one may be provided.

[0041] An example of the electronic component 302 is a bypass capacitor. At least one bypass capacitor is provided for each light-emitting chip 400, one end of which is connected to a power line (not shown) supplied to the light-emitting chip 400, and the other end of which is connected to GND. The current consumption of the driving unit 1104 included in the light-emitting chip 400 changes depending on the driving state. When the current consumption increases, a voltage drop occurs in the power supply voltage, and the voltage supplied to the driving unit 1104 decreases, which may cause the driving unit 1104 to malfunction. When the current consumption of the driving unit 1104 decreases, the voltage supplied from the power supply increases, which may cause the driving unit 1104 to malfunction. When the bypass capacitor is provided between the power supply and the light-emitting chip 400, the charge stored in the bypass capacitor can be released when the voltage supplied from the power supply decreases, and the charge can be stored in the bypass capacitor when the voltage supplied from the power supply increases. As described above, the change in the voltage supplied to the light-emitting chip 400 can be reduced by the bypass capacitor.

[0042] In addition, since the impedance in the wiring also becomes a factor of the change in the voltage supplied to the light-emitting chip 400, it is preferable that the wiring length between the bypass capacitor and the light-emitting chip 400 is as short as possible. That is, in order to shorten the wiring length between the bypass capacitor and the light-emitting chip 400, it is preferable that the bypass capacitor is disposed on the same surface as the light-emitting chip 400 on the printed circuit board 202 and in the vicinity of the light-emitting chip 400. In this embodiment, the bypass capacitors corresponding to the light-emitting chips 400 are provided at positions overlapping the corresponding light-emitting chips 400 in the longitudinal direction of the board. When the bypass capacitors are provided at positions overlapping the light-emitting chips 400 in the longitudinal direction of the board, it is preferable that the distance between the bypass capacitors and the light-emitting chips 400 in the direction along the short side of the board 202 is 3 mm or less.

[0043] In addition, the current supplied from the power source to the light-emitting chip 400 may contain high-frequency noise components due to disturbances or the like. Since high-frequency noise components easily flow through the bypass capacitor, the noise components flowing through the light-emitting chip 400 can be reduced by discharging the high-frequency noise components to the ground. Noise components often have different frequencies, and the noise components that easily flow differ depending on the capacitance reactance of the bypass capacitor. For this reason, by using multiple bypass capacitors with different capacitance reactances, noise components with different frequencies can be removed. In this embodiment, three bypass capacitors with different capacitance reactances are provided on the surface of the printed circuit board 202. Note that the number of bypass capacitors is one example and may be any other number. In addition, the bypass capacitor is preferably disposed near the light-emitting chip 400 as described above, but may be disposed at other positions without being limited thereto.

[0044] <Light emitting chip mounting process> Next, a mounting process of the light emitting chip 400 will be described. Fig. 14(A) shows the printed circuit board 202 before the light emitting chip 400 is mounted thereon. The light emitting chip 400 is mounted in a light emitting chip mounting area 803 provided on the surface of the printed circuit board 202. When the light emitting chips 400-1 to 20 are mounted on the printed circuit board 202, each of the light emitting chip mounting areas 803 is provided corresponding to a different one of the light emitting chips 400, and the light emitting chip mounting area 803 is composed of 20 areas, the light emitting chip mounting areas 800-1 to 20.

[0045] FIG. 14(B) is a diagram showing a state in which the adhesive 304 is applied to each of the light emitting chip mounting areas 803-1 to 803-20 in the printed circuit board 202. The light emitting chip 400 is mounted on the printed circuit board 202 by arranging the light emitting chip 400 in each of the light emitting chip mounting areas 803 to which the adhesive 304 is applied. In this embodiment, an ultraviolet-curing adhesive is used as the adhesive base 304, but other adhesives may be used. For example, the adhesive 304 may be a thermosetting adhesive or a conductive adhesive. The area to which the adhesive 304 is applied may be either the entire part or a part of the light emitting chip mounting area 803. Furthermore, the adhesive 304 may be applied so as to protrude from the light emitting chip mounting area 803.

[0046] 14C shows the printed circuit board 202 after mounting the light emitting chip 400. The light emitting chip 400 is mounted and adhered to the light emitting chip mounting area 803 to which the adhesive 304 has been applied.

[0047] Although the details will be described later, after mounting the light emitting chip 400 on the printed circuit board 202, a cleaning process is performed to remove foreign matter adhering to the surface of the light emitting element 602 provided on the light emitting chip 400. Examples of foreign matter adhering to the surface of the light emitting element 602 include silicon fragments generated when the light emitting chip 400 is cut, and dust floating in the air. When the above-mentioned foreign matter adheres to the surface of the light emitting element 602, the light emitted by the light emitting element 602 is blocked by the foreign matter, and there is a risk that the amount of light reaching the photoconductor drum 102 will decrease. For this reason, it is desirable to remove the foreign matter adhering to the surface of the light emitting element 602.

[0048] After a cleaning process is performed to remove foreign matter from the surface of the light emitting element 602, the printed board electrode portion 308 provided on the printed board 202 is electrically connected to the light emitting board electrode portion 408 provided on the light emitting chip 400. In this embodiment, the connection is performed using wire bonding, which performs electrical connection using a wire, but other methods may be used to perform the electrical connection.

[0049] Finally, the multiple connecting portions 801 (see FIG. 13B ) are cut so that the multiple printed circuit boards 202 constituting the assembly 800 each become a single printed circuit board 202. In this embodiment, the connecting portions 801 are cut using a laser cutting process, but the connecting portions 801 may be cut using other methods. For example, the connecting portions 801 may be cut by machining or the like.

[0050] Through the above-mentioned steps, a single printed circuit board 202 (see FIG. 3) on which the light emitting chips 400 are mounted is obtained from the initial state assembly 800.

[0051] Next, foreign matter adhering to the light emitting elements 602 of the light emitting chips 400 mounted on each of the printed circuit boards 202 constituting the aggregate 800 is removed by an adhesive cleaning roller 900. The foreign matter adhering to the light emitting elements 602 includes silicon fragments generated when the light emitting chips 400 are cut, dust floating in the general environment, etc. That is, the light emitting element cleaning process is performed for the purpose of removing foreign matter adhering to the light emitting elements 602 of the light emitting chips 400 mounted on one side of each of the printed circuit boards 202 constituting the aggregate 800.

[0052] <How to clean the surface of the light-emitting element> The light-emitting element cleaning process in this embodiment will be described in detail with reference to Fig. 15. Note that the light-emitting chip 400, the electronic component 302, and the adhesive 304 are illustrated larger or smaller in size in order to make it easier to understand the height relationship between them, and may differ from the actual height ratio.

[0053] In this embodiment, foreign matter adhering to the surface of the light emitting element 602 is removed by bringing a cleaning roller 900, which is an adhesive roller, into contact with the surface of the light emitting element 602. Since the above-mentioned foreign matter may be adsorbed to the surface of the light emitting element 602 by electrostatic force, there is a risk that the foreign matter adhering to the surface of the light emitting element 602 cannot be removed by a cleaning method such as air blowing. For this reason, it is desirable to remove the foreign matter adhering to the surface of the light emitting element 602 by contacting the cleaning roller.

[0054] As shown in FIG. 15, the cleaning roller 900 is fixed at a predetermined position. The assembly 800 moves in a direction along the longitudinal direction of the substrate 202 from one end to the other end of the substrate 202 with the surface of the light emitting element 602 and the cleaning roller 900 in contact with each other. The cleaning roller 900 rotates about a rotation axis that is perpendicular to the longitudinal direction of the substrate 202 and parallel to the short side direction of the substrate 202. The cleaning roller 900 removes foreign matter attached to the surface of the light emitting element 602 by adhesive force while rotating due to frictional force generated between the surface of the light emitting element 602 and the cleaning roller 900. The direction in which the assembly 800 moves may be along the longitudinal direction of the substrate 202, and may be a direction from the light emitting chip 400-1 to the light emitting chip 400-20, or a direction from the light emitting chip 400-20 to the light emitting chip 400-1.

[0055] In this embodiment, the method of fixing the cleaning roller 900 and moving the assembly 800 has been described, but the assembly 800 may be fixed and the cleaning roller 900 may be moved to remove foreign matter adhering to the surface of the light-emitting element 602. Furthermore, both the assembly 800 and the cleaning roller 900 may be moved to remove foreign matter adhering to the surface of the light-emitting element 602.

[0056] In addition, in this embodiment, the cleaning roller 900 is used which rotates about an axis of rotation perpendicular to the longitudinal direction of the substrate 202 and parallel to the short-side direction of the substrate 202, but the direction of the axis of rotation is not limited to this. For example, foreign matter adhering to the surface of the light-emitting element 602 may be removed using the cleaning roller 900 which rotates about an axis of rotation perpendicular to the short-side direction of the substrate 202 and parallel to the longitudinal direction of the substrate 202.

[0057] Furthermore, in this embodiment, a method of using a cleaning roller has been described as a method of removing foreign matter adhering to the surface of the light emitting element 602, but this is not limiting and other methods may be used. That is, a cleaning method may be used in which a sticky cleaning member is brought into contact with the surface of the light emitting element 602 to remove foreign matter, without using a cleaning roller.

[0058] Furthermore, foreign matter may be removed by using airflow instead of a sticky cleaning member. In this case, the foreign matter attached to the light emitting element 602 may be charged, and may be adsorbed to the surface of the light emitting element 602 by electrostatic force. For this reason, an ionizer is used to neutralize either the surface of the light emitting element 602 or the foreign matter, allowing the foreign matter to be effectively removed by airflow.

[0059] 15(A) is a diagram showing a longitudinal cross section of the substrate 202 on whose surface only the light emitting chip 400 is mounted. Since only the light emitting chip 400 is mounted on the substrate 202 in FIG. 15(A), the cleaning roller 900 can be brought into contact with the surface of the light emitting element 602 reliably.

[0060] 15B is a diagram showing a cross section in the longitudinal direction of the substrate 202 on whose surface the light emitting chip 400 and the electronic component 302 are mounted. In FIG. 15B, in the height direction perpendicular to the longitudinal and lateral directions of the substrate 202, the height of the electronic component 302 from the surface of the substrate 202 is higher than the height of the light emitting chip 400 from the surface of the substrate 202. In this embodiment, the height of the electronic component 302 is defined as the distance from the surface of the substrate 202 facing the cleaning roller 900 to the end of the electronic component 302 that is the furthest in the height direction. In this embodiment, the height of the light emitting chip 400 is defined as the distance from the surface of the substrate 202 facing the cleaning roller 900 to the end of the light emitting chip 400 that is the furthest in the height direction.

[0061] If the height of the electronic component 302 is higher than the height of the light emitting chip 400, there is a risk that the cleaning roller 900 will come into contact with the electronic component 302 and will not come into contact with the surface of the light emitting element 602 of the light emitting chip 400. In this case, the cleaning roller 900 cannot sufficiently remove foreign matter adhering to the surface of the light emitting element 602.

[0062] Fig. 15(C) is a diagram showing a longitudinal cross section of the substrate 202 on whose surface the light emitting chip 400 and the electronic component 302 are mounted. In Fig. 15(C), unlike Fig. 15(B), the height of the electronic component 302 from the surface of the substrate 202 is lower than the height of the light emitting chip 400 from the surface of the substrate 202. By defining the height of the electronic component 302 and the height of the light emitting chip 400 as in Fig. 15(C), the cleaning roller 900 can contact the surface of the light emitting element 602 of the light emitting chip 400 without being obstructed by the electronic component 302, and foreign matter attached to the surface of the light emitting element 602 can be sufficiently removed.

[0063] As a configuration for reliably removing foreign matter adhering to the surface of the light-emitting element 602, a configuration in which the height of the electronic component 302 is lower than the height of the light-emitting chip 400 as shown in Figure 15 (C) is shown, but even if the heights of the electronic component 302 and the light-emitting chip 400 are the same, the cleaning roller 900 can be brought into contact with the surface of the light-emitting element 602.

[0064] Furthermore, the adhesive cleaning roller 900 may be made of a rubber material that is elastically deformable. When the cleaning roller 900 is made of a rubber material, even if an electronic component 302 that is taller than the light emitting chip 400 is provided on the substrate 202, the cleaning roller 900 can be brought into contact with the light emitting chip 400 even if the cleaning roller 900 comes into contact with the electronic component 302, as long as the electronic component 302 is provided at a position sufficiently farther away from the light emitting chip 400 in the short-side direction of the substrate 202. At this time, the electronic component 302 is separated from the light emitting chip 400 by 3 mm or more in the direction along the short-side direction of the substrate 202, and it is desirable that the difference in height between the light emitting chip 400 and the bypass capacitor is within 0.4 mm.

[0065] As described above, in this embodiment, in the substrate 202 on which the light-emitting chip is mounted, the height of the electronic component 302 from the surface of the substrate 202 is set to be lower than the height of the light-emitting chip 400. By setting the heights of the electronic component 302 and the light-emitting chip 400 as described above, foreign matter attached to the surface of the light-emitting element 602 can be reliably removed. [Explanation of symbols]

[0066] 1. Image forming device 101 Image forming section 102 Photoconductor drum 106 Exposure head 201 Light emitting element array 202 Printed circuit board 203 Rod Lens Array 204 Housing 302 Bypass capacitor 304 Adhesive 400 Light Emitting Chips 402 Light emitting substrate 602 Light emitting element

Claims

1. A photoconductor; a substrate having a light emitting chip having a plurality of light emitting units that emit light to expose the photoconductor and a light emitting surface from which the light is emitted, and electronic components mounted on one surface of the substrate; Equipped with In a vertical direction perpendicular to the one surface of the substrate, a first height, which is a height from the one surface of the light emitting chip to the light emitting surface, is higher than a second height, which is a height from the one surface to an end of the electronic component farthest from the one surface.

1. An image forming apparatus comprising:

2. a plurality of the light emitting chips and a plurality of the electronic components are mounted on the one surface of the substrate; In the vertical direction, each of the first heights of the light emitting chips mounted on the one surface is higher than the second height of the electronic component having the highest second height among the electronic components mounted on the one surface.

2. The image forming apparatus according to claim 1,

3. At least a portion of the electronic component overlaps with the light emitting chip in the longitudinal direction of the substrate.

2. The image forming apparatus according to claim 1,

4. The image forming apparatus includes: a power source for supplying a current to the light emitting chip via a power line; Equipped with The light emitting chip has a driving unit that drives the plurality of light emitting units, the electronic component includes a bypass capacitor having one end connected to the power supply line and the other end connected to the drive unit; 2. The image forming apparatus according to claim 1,

5. In the vertical direction, the first height of the light emitting chip is higher than a height from the one surface to an end of the bypass capacitor farthest from the one surface of the substrate; 5. The image forming apparatus according to claim 4.

6. the electronic component includes a thermistor for measuring a temperature of the light emitting chip; In the vertical direction, the first height is greater than a height from the one surface of the substrate to an end of the thermistor farthest from the one surface of the substrate.

2. The image forming apparatus according to claim 1,

7. The light emitting chip is mounted on the substrate using an adhesive; 2. The image forming apparatus according to claim 1, wherein the first height is a sum of a height of the adhesive and a height of the light emitting chip in the vertical direction.

8. a light-emitting chip having a plurality of light-emitting units that emit light to expose a photoconductor and a light-emitting surface from which the light is emitted; and an electronic component mounted on one surface of the substrate; In a vertical direction perpendicular to the one surface of the substrate, a first height, which is a height from the one surface to the light emitting surface of the light emitting chip, is higher than a second height, which is a height from the one surface to an end of the electronic component farthest from the one surface; An exposure head comprising:

9. a plurality of the light emitting chips and a plurality of the electronic components are mounted on the one surface of the substrate; In the vertical direction, each of the first heights of the light emitting chips mounted on the one surface is higher than the second height of the electronic component having the highest second height among the electronic components mounted on the one surface.

9. The exposure head according to claim 8.

10. At least a portion of the electronic component overlaps with the light emitting chip in the longitudinal direction of the substrate.

9. The exposure head according to claim 8.

11. The light emitting chip includes a driving unit that is supplied with current via a power line and drives the plurality of light emitting units, the electronic component includes a bypass capacitor having one end connected to the power supply line and the other end connected to the drive unit; 9. The exposure head according to claim 8.

12. In the vertical direction, the first height of the light emitting chip is higher than a height from the one surface to an end of the bypass capacitor farthest from the one surface of the substrate; 12. The exposure head according to claim 11.

13. the electronic component includes a thermistor that measures temperatures of the plurality of light-emitting units, In the vertical direction, the first height is greater than a height from the one surface to an end of the thermistor farthest from the one surface.

9. The exposure head according to claim 8.

14. The light emitting chip is mounted on the substrate using an adhesive; 9. The exposure head according to claim 8, wherein the first height is a sum of a height of the adhesive and a height of the light emitting chip in the vertical direction.

15. The difference between the first height and the second height is less than 0.4 mm.

2. The image forming apparatus according to claim 1,

16. Each of the plurality of light-emitting units is an organic electroluminescent (EL).

2. The image forming apparatus according to claim 1,

17. Each of the plurality of light-emitting units is an organic electroluminescent (EL).

9. The exposure head according to claim 8.

Images