Light emitting device and image forming device

Abstract

To prevent a reduction in luminous efficiency of a light-emitting chip.SOLUTION: A light-emitting chip (400) comprises: a rectangular substrate (402) that has a first long side (402B) and a second long side (402B); a light-emitting area (404) that has a plurality of light-emitting parts, and has a third long side (404B) and a fourth long side (404T) farther from the first long side than the third long side in a short direction of the substrate; and a sealing area (409) that has a fifth long side (409B) and a sixth long side (409T) farther from the first long side than the fifth long side, and covers a light-emitting surface and side faces of the light-emitting area. The distance between the first long side and the third long side (wa2) is shorter than the distance between the second long side and the fourth long side (wa3). The distance between the first long side and the fifth long side (wa2-wb2) is shorter than the distance between the second long side and the sixth long side (wa3-wb3). The distance between the third long side and the fifth long side (wb2) is shorter than the distance between the fourth long side and the sixth long side (wb3).SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a light emitting Device And the present invention relates to an image forming apparatus. [Background technology]

[0002] An electrophotographic image forming apparatus includes a photoconductor that is rotated, an exposure unit that exposes the photoconductor to light to form an electrostatic latent image, a development unit that develops the electrostatic latent image on the photoconductor using a developer, and a transfer unit that transfers the image developed by the developer to a sheet. Here, a laser scanner, an exposure head, etc. are known as the exposure unit. A laser scanner is an exposure device that deflects light from a light source using a deflection member so that the light from the light source scans the surface of the photoconductor. On the other hand, an exposure head is an exposure device that does not include a deflection member and has multiple light sources arranged in a direction perpendicular to the direction in which the surface of the photoconductor moves. The exposure head includes a lens array that forms an image of light from multiple light-emitting elements on the photoconductor.

[0003] In the exposure head described in Patent Document 1, the organic EL is sealed by bonding the organic EL substrate and the driving IC substrate with metal bonding in order to prevent the multiple organic ELs serving as light sources from deteriorating due to moisture and oxygen. Furthermore, the exposure head described in Patent Document 1 has multiple organic EL substrates arranged in a staggered pattern. This is because the manufacturing cost can be reduced compared to an exposure head having a single long organic EL substrate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2015-162428 A Summary of the Invention [Problem to be solved by the invention]

[0005] In an exposure head in which light-emitting element array chips, each of which is made up of a plurality of light-emitting elements, are arranged in a staggered pattern on a substrate, it is desirable to shorten the distance between the light-emitting region of each light-emitting element array chip and the center of the lens array from the viewpoint of light utilization efficiency. However, since a sealant is required to seal the light-emitting region in order to prevent moisture and oxygen from entering from the ends of the light-emitting element array chip, the distance between the light-emitting region and the center of the lens array becomes large, which is a problem in that the light utilization efficiency decreases. SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to suppress the decrease in the light emitting efficiency of a light emitting chip. [Means for solving the problem]

[0006] In order to solve the above problems, a light emitting device according to one embodiment of the present invention is Device teeth, A rectangular shape having a first long side and a second long side aligned along the first long side. Light emitting chip and, A plurality of light emitting devices are provided along the first long side. With , a third long side along the first long side, and a fourth long side along the first long side. and , the above Light emitting chip In the short direction of The first long side and The third long side The distance between The first long side and the above The fourth long side and is shorter than the distance between , a light emitting region; A sealing region covering the light emitting region, a fifth long side along the first long side, and a sixth long side along the first long side and , in the short direction The first long side and The fifth long side The distance between The first long side and the above The sixth long side and is shorter than the distance between , a sealing region; a lens array that collects light emitted from the light emitting region; Equipped with In the short direction, between the first long side and the third long side The above the distance is less than the distance between the second long side and the fourth long side; In the short direction, between the first long side and the fifth long side The abovethe distance is less than the distance between the second long side and the sixth long side; In the short direction, The fifth long side is located between the first long side and the third long side. , It is characterized by: Effect of the Invention

[0007] According to the present invention, it is possible to suppress a decrease in the light emitting efficiency of the light emitting chip. [Brief description of the drawings]

[0008] [Figure 1] FIG. [Diagram 2] FIG. 2 is a diagram showing the arrangement of a photosensitive drum and an exposure head. [Diagram 3] FIG. [Figure 4] FIG. 2 is a diagram showing a light-emitting element array chip. [Diagram 5] FIG. 5 is a partially enlarged cross-sectional view of the light-emitting element array chip taken along line VV in FIG. [Figure 6] FIG. [Figure 7] FIG. 4 is a block diagram of an image controller and a printed circuit board. [Figure 8] FIG. 4 is a block diagram of a circuit section in the light-emitting element array chip. [Figure 9] Block diagram of the analog section. [Figure 10] FIG. 4 is a diagram showing a drive circuit of a drive unit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] (Image forming device) An electrophotographic image forming apparatus 1 in this embodiment will be described with reference to FIG. 1. FIG. 1 is a cross-sectional view of the image forming apparatus 1. The image forming apparatus 1 is a multifunction printer (MFP). The image forming apparatus 1 has a scanner unit 100, an image forming unit 103, a fixing unit 104, a feeding / conveying unit 105, and a printer control unit 115. The printer control unit 115 controls the scanner unit 100, the image forming unit 103, the fixing unit 104, and the feeding / conveying unit 105. The scanner unit 100 illuminates an original placed on an original table and optically reads reflected light from the original. The scanner unit 100 converts the read reflected light into an electrical signal to generate image data. The image forming unit 103 has four image forming units 120C, 120M, 120Y, and 120K that perform a series of electrophotographic processes (charging, exposure, development, and transfer). The four image forming units 120C, 120M, 120Y, and 120K are arranged in the order of cyan (C), magenta (M), yellow (Y), and black (K) to form a full-color image. After a predetermined time has elapsed from the start of image formation by the cyan image forming unit 120C, the four image forming units 120C, 120M, 120Y, and 120K sequentially perform image formation operations for magenta, yellow, and black. The suffixes C, M, Y, and K of the reference symbols represent cyan, magenta, yellow, and black, respectively. In the following description, the suffixes C, M, Y, and K of the reference symbols may be omitted unless particularly necessary.

[0010] The image forming unit 103 rotates the photosensitive drums 102C, 102M, 102Y, and 102K. The chargers 107C, 107M, 107Y, and 107K uniformly charge the surfaces of the photosensitive drums 102C, 102M, 102Y, and 102K. The exposure heads 106C, 106M, 106Y, and 106K emit light in accordance with image data to form electrostatic latent images on the surfaces of the photosensitive drums 102C, 102M, 102Y, and 102K. The developers 108C, 108M, 108Y, and 108K develop the electrostatic latent images formed on the surfaces of the photosensitive drums 102C, 102M, 102Y, and 102K with toner of each color to form cyan, magenta, yellow, and black toner images.

[0011] The image forming apparatus 1 has internal feeding units 109a and 109b, an external feeding unit 109c, and a manual feeding unit 109d. The feeding / conveying section 105 feeds a sheet as a recording medium on which an image is to be formed from a pre-designated feeding unit among the internal feeding units 109a and 109b, the external feeding unit 109c, and the manual feeding unit 109d. The fed sheet is conveyed to a registration roller 110. The registration roller 110 conveys the sheet onto a transfer belt 111 so that the toner image formed in the image forming section 103 is transferred to the sheet.

[0012] The cyan, magenta, yellow and black toner images on the surfaces of the photosensitive drums 102C, 102M, 102Y and 102K are sequentially transferred and superimposed on a sheet on a transfer belt 111 by transfer devices 114C, 114M, 114Y and 114K, respectively. The sheet on which the toner images have been transferred is transported to a fixing section (fixing device) 104. The fixing section 104 has a heating roller incorporating a halogen heater as a heat source, and a pressure roller that is in pressure contact with the heating roller. The fixing section 104 melts the toner image on the sheet by heat and pressure, and fixes it to the sheet. As a result, a full-color image is formed on the sheet. The sheet on which the image has been formed is discharged to the outside of the image forming apparatus 1 by discharge rollers 112.

[0013] An optical sensor 113 is disposed facing the transfer belt 111. The optical sensor 113 detects the position of the toner image of the test chart transferred onto the transfer belt 111. The amount of color shift of the toner image of each color is calculated based on the detection result of the optical sensor 113. The amount of color shift is input to an image controller unit 700 (FIG. 7). The image controller unit 700 corrects the image position of each color based on the amount of color shift. A full-color toner image without color shift is transferred onto the sheet by the color shift correction control by the image controller unit 700.

[0014] Printer control unit 115 communicates with an MFP control unit (not shown) that controls the entire image forming apparatus 1. Printer control unit 115 issues instructions to each unit in accordance with instructions from the MFP control unit (not shown) to ensure that the entire unit operates smoothly and in harmony while managing the reading of an image on a document, the formation and fixing of a toner image, and the state of sheet feeding / transportation.

[0015] (Exposure head) Next, the exposure head 106 that exposes the photosensitive drum 102 will be described with reference to FIG. 2. FIG. 2 is a diagram showing the arrangement of the photosensitive drum 102 and the exposure head 106. FIG. 2(a) is a diagram showing the arrangement of the exposure head 106 with respect to the photosensitive drum 102. FIG. 2(b) is a diagram showing a light beam 200 that is emitted from a light-emitting element group 201 and is condensed onto the photosensitive drum 102 by a rod lens array 203. The exposure head 106 and the photosensitive drum 102 are attached to the image forming apparatus 1 by an attachment member (not shown). The exposure head 106 includes the light-emitting element group 201, a printed circuit board 202 on which the light-emitting element group 201 is mounted, a rod lens array 203, and a housing 204 on which the rod lens array 203 and the printed circuit board 202 are attached. In the factory, an assembly adjustment work is performed on the exposure head 106 alone. In the assembly adjustment work, focus adjustment and light amount adjustment are performed to adjust the spot at the condensing position to a predetermined size. Here, the rod lens array 203 is disposed so that the distance between the photosensitive drum 102 and the rod lens array 203 and the distance between the rod lens array 203 and the light emitting element group 201 are predetermined distances. As a result, the light beam 200 emitted from the light emitting element group 201 is imaged on the photosensitive drum 102 by the rod lens array 203. In focus adjustment, the attachment position of the rod lens array 203 is adjusted so that the distance between the rod lens array 203 and the light emitting element group 201 is a predetermined value. In light amount adjustment, each light emitting element of the light emitting element group 201 is caused to emit light individually and sequentially, and the drive current of each light emitting element is adjusted so that the amount of light collected by the rod lens array 203 is a predetermined value.

[0016] (Printed circuit board) Next, the printed circuit board 202 on which the light emitting element group 201 is mounted will be described with reference to FIG. 3. FIG. 3 is a diagram showing the printed circuit board 202. The printed circuit board 202 has a surface 202a on which the light emitting element group 201 is mounted (hereinafter referred to as a light emitting element mounting surface) and a surface 202b opposite to the light emitting element mounting surface 202a (hereinafter referred to as a light emitting element non-mounting surface). FIG. 3(a) is a diagram showing the light emitting element non-mounting surface 202b of the printed circuit board 202. A connector 305 is disposed on the light emitting element non-mounting surface 202b. The connector 305 is connected to a control signal cable from the image controller unit 700 (FIG. 7) and a power cable from a power source (not shown). The control signal cable includes a chip select signal line 705, a clock signal line 706, an image data signal line 707, a line synchronization signal line 708, and a communication signal line 709, which will be described later with reference to FIG. 7. FIG. 3(b) is a diagram showing the light emitting element mounting surface 202a of the printed circuit board 202. The light emitting element group 201 is composed of 20 light emitting element array chips 400(1), 400(2), ..., 400(19) and 400(20) arranged alternately, i.e. in a staggered pattern. The light emitting element array chips 400(1) to 400(20) are driven by control signals input from the image controller unit 700 via the connector 305 and power supplied from a power source (not shown). The light emitting element array chip 400 has a rectangular shape.

[0017] FIG. 3(c) is a diagram showing a boundary between the light-emitting element array chip 400(2) and the light-emitting element array chip 400(3). In each of the light-emitting regions 404 of the light-emitting element array chips 400(1) to 400(20), a plurality of light-emitting units 602 are formed at a predetermined pitch LP in the longitudinal direction LD of the exposure head 106. The longitudinal direction LD is a direction perpendicular to the direction in which the surface of the photosensitive drum 102 moves. In this embodiment, 748 light-emitting units 602 are provided as light-emitting points in one light-emitting element array chip 400. The light-emitting units 602 may be surface-emitting elements such as surface-emitting lasers and surface-emitting diodes. The light-emitting units 602 may be bottom-emission organic EL or LEDs or top-emission organic EL or LEDs. In this embodiment, the predetermined pitch LP of the light-emitting units 602 adjacent to each other in the longitudinal direction LD is a pitch (about 21.16 μm) of a resolution of 1200 dpi. The distance from one end to the other of the 748 light emitting units 602 in the light emitting region 404 of the light emitting element array chip 400 is about 15.8 mm. The light emitting element group 201 has 20 light emitting element array chips 400 and 14,960 light emitting units 602, so that an image with a width of about 316 mm can be formed. The light emitting element array chips 400(1) to 400(20) are arranged in two rows in a staggered manner. Each of the light emitting element array chips 400(1) to 400(20) is arranged along the longitudinal direction LD of the exposure head 106. For example, the light emitting element array chip 400(1) and the light emitting element array chip 400(3) are arranged so as to be shifted from the light emitting element array chip 400(2) and the light emitting element array chip 400(4) in the direction in which the surface of the photosensitive drum 102Y moves. Furthermore, the light emitting element array chips 400(1) to 400(20) have a plurality of overlapping regions in the longitudinal direction LD of the exposure head 106.

[0018] 3(c), even at the boundary between the light-emitting element array chips 400 (between chips), the pitch LP0 between the light-emitting sections 602 (748) and 602 (1) in the longitudinal direction LD is the pitch at a resolution of 1200 dpi (about 21.16 μm) (LP0=LP). Moreover, the light-emitting element array chips 400 are arranged so that the interval S between the light-emitting sections 602 of the two rows of light-emitting element array chips 400 is about 105 μm (the interval of five pixels at 1200 dpi) in the direction perpendicular to the longitudinal direction LD.

[0019] (Light emitting element array chip) Next, the light emitting element array chip (light emitting chip) 400 will be described with reference to FIG. 4. FIG. 4 is a diagram showing the light emitting element array chip 400. In FIG. 4, the X direction is the longitudinal direction LD of the exposure head 106, and the Y direction is the rotation direction of the photosensitive drum 102. FIG. 4(a) is a plan view of the light emitting element array chip 400. The light emitting element array chip 400 includes a light emitting substrate 402, a light emitting region 404 including a plurality of light emitting units 602 arranged on the light emitting substrate 402, a plurality of wire bonding pads (WB pads) 408 formed on the light emitting substrate 402, and a sealing region 409. The wire bonding pads 408 are electrically connected to the printed circuit board 202 by metal wires. The light emitting substrate 402 includes a circuit unit 406 as a control circuit for controlling the driving of the light emitting region 404. The circuit unit 406 can be an analog driving circuit, a digital control circuit, or a circuit including both. Power supply to the circuit section 406 and input / output of signals to / from the outside of the light-emitting element array chip 400 are performed through wire bonding pads 408 .

[0020] The sealing region 409 is the light-emitting region 404 and its surrounding region. In the sealing region 409, a sealing layer 509 (FIG. 5) made of a sealant covers the light-emitting surface and side surfaces of the light-emitting region 404, as well as the upper surface (the surface on the light-emitting surface side that emits light) of the light-emitting substrate 402 around the light-emitting region 404. When viewed from the light-emitting surface side, the sealing region 409 to which the sealant is applied contains the light-emitting region 404. The sealing layer 509 will be described later. As shown in FIG. 4(a), the distance from the left side 404L of the light-emitting region 404 to the left side 409L of the sealing region 409 is wb0, and the distance from the left side 404L of the light-emitting region 404 to the left side 402L of the light-emitting substrate 402 is wa0. The distance from the right side 404R of the light-emitting region 404 to the right side 409R of the sealing region 409 is defined as wb1, and the distance from the right side 404R of the light-emitting region 404 to the right side 402R of the light-emitting substrate 402 is defined as wa1. The distance from the bottom side 404B of the light-emitting region 404 to the bottom side 409B of the sealing region 409 is defined as wb2, and the distance from the bottom side 404B of the light-emitting region 404 to the bottom side 402B of the light-emitting substrate 402 is defined as wa2. The distance from the top side 404T of the light-emitting region 404 to the top side 409T of the sealing region 409 is defined as wb3, and the distance from the top side 404T of the light-emitting region 404 to the top side 402T of the light-emitting substrate 402 is defined as wa3.

[0021] The distance from the lower side (first side) 402B, which is one of the two long sides of the light-emitting element array chip 400, to the lower side (one long side) 409B of the sealing region 409, which is parallel to the lower side 402B and closest to the lower side 402B, is defined as a first distance (wa2-wb2). The distance from the upper side (second side) 402T, which is the other of the two long sides of the light-emitting element array chip 400, to the upper side (other long side) 409T of the sealing region 409, which is parallel to the upper side 402T and closest to the upper side 402T, is defined as a second distance (wa3-wb3). The first distance (wa2-wb2) is preferably shorter than the second distance (wa3-wb3). The distance wa2 from the lower side (first side) 402B of the light-emitting element array chip 400 to the lower side (one long side) 404B of the light-emitting region 404, which is parallel to the lower side 402B and closest to the lower side 402B, is defined as a third distance wa2. A distance wa3 from the top side (second side) 402T of the light-emitting element array chip 400 to the top side (the other long side) 404T of the light-emitting region 404 that is parallel to and closest to the top side 402T is defined as a fourth distance wa3. The third distance wa2 is preferably shorter than the fourth distance wa3.

[0022] The distance from the left side (third side) 402L, which is one of the two short sides of the light-emitting element array chip 400, to the left side (one short side) 409L of the sealing region 409 that is parallel to and closest to the left side 402L, is defined as a fifth distance (wa0-wb0). The distance from the right side (fourth side) 402R, which is the other of the two short sides of the light-emitting element array chip 400, to the right side (other short side) 409R of the sealing region 409 that is parallel to and closest to the right side 402R, is defined as a sixth distance (wa1-wb1). The first distance (wa2-wb2) is preferably shorter than the fifth distance (wa0-wb0) and the sixth distance (wa1-wb1).

[0023] The seventh distance wa0 is the distance from the left side (third side) 402L, which is one of the two short sides of the light-emitting element array chip 400, to the left side (one short side) 404L of the light-emitting region 404 that is parallel to and closest to the left side 402L. The eighth distance wa1 is the distance from the right side (fourth side) 402R, which is the other of the two short sides of the light-emitting element array chip 400, to the right side (other short side) 404R of the light-emitting region 404 that is parallel to and closest to the right side 402R. The third distance wa2 is preferably shorter than the seventh distance wa0 and the eighth distance wa1.

[0024] In this embodiment, the position of the light emitting region 404 relative to the light emitting substrate 402 is determined so that the distance wa2 is the smallest among the distances wa0, wa1, wa2, and wa3. The sealing region 409 is formed so that the distance wb2 is the smallest among the distances wb0, wb1, wb2, and wb3. The distance wb2 has a length sufficient to seal the light emitting region 404. By minimizing the distance wb2 in this manner, the distance wa2 between one side along the longitudinal direction LD (the lower side 402B in FIG. 4(a)) and the lower side 404B of the light emitting region 404 can be minimized.

[0025] The boundary (seam) between adjacent light-emitting element array chips 400 will be described with reference to FIG. 4(b). In this embodiment, the light-emitting element array chips 400 are arranged in a staggered manner along a straight line 410 extending in the longitudinal direction LD so that the sides with the smallest distance from the light-emitting region 404 face each other. The straight line 410 is preferably the center line of the exposure head 106, but does not necessarily have to be the center line. FIG. 4(b) is a diagram showing the boundary between the light-emitting element array chip 400(2) and the light-emitting element array chip 400(3) as an example. The lower side 402B of the light-emitting element array chip 400(2) and the lower side 402B of the light-emitting element array chip 400(3) are arranged on the straight line 410 facing each other. In this way, the light-emitting element array chips 400 are arranged in a staggered manner along the straight line 410 so that the lower sides (first sides) 402B of the adjacent light-emitting element array chips 400 partially face each other. The distance between the light-emitting regions 404 of adjacent light-emitting element array chips 400 in the Y direction is twice the distance wa2. The distance between each light-emitting region 404 and the straight line 410 is minimized. When the rod lens array 203 is disposed on the straight line 410, the distance between the rod lens array 203 and the light-emitting region 404 is also minimized. This makes it possible to minimize the decrease in light utilization efficiency.

[0026] (Light emitting area) Next, the light emitting region 404 will be described with reference to FIG. 5. FIG. 5 is a partially enlarged cross-sectional view of the light emitting element array chip 400 taken along the line VV in FIG. 4(a). The Z direction in FIG. 5 is perpendicular to the X and Y directions and is the direction in which the emitted light 510 is emitted from the light emitting region 404. The light emitting region 404 has a plurality of lower electrodes 504, a light emitting layer 506, and an upper electrode 508. The sealing region 409 is provided with a sealing layer 509 that seals the light emitting region 404. The plurality of lower electrodes 504 are formed on the light emitting substrate 402. The light emitting layer 506 is formed on the plurality of lower electrodes 504 formed on the light emitting substrate 402. The upper electrode 508 is formed on the light emitting layer 506. The sealing layer 509 is formed on the light emitting layer 506.

[0027] The lower electrode 504 is an independent electrode. The upper electrode 508 is a common electrode. As shown in FIG. 5, the lower electrode 504 has a width W in the X direction parallel to the longitudinal direction LD. In the light-emitting region 404, a plurality of (748 in this embodiment) lower electrodes 504 are formed at intervals s in the X direction. The light-emitting layer 506 is formed between the lower electrode 504 and the upper electrode 508. The light-emitting layer 506 may be formed continuously or may be formed divided into portions having a size substantially equal to that of the lower electrode 504. By passing a current through a selected lower electrode 504 and the upper electrode 508 among the plurality of lower electrodes 504, the portion of the light-emitting layer 506 corresponding to the selected lower electrode 504 emits light, and emits outgoing light 510 through the upper electrode 508. The lower electrode 504 is formed of silver (Ag) having a high reflectance with respect to the emission wavelength of the light-emitting layer 506. However, the bottom electrode 504 may also be formed of a metal such as aluminum (Al) or an alloy thereof.

[0028] The upper electrode 508 is formed of a material transparent to the emission wavelength of the light emitting layer 506, so that the upper electrode 508 transmits the emitted light 510 emitted from the light emitting layer 506. In this embodiment, the upper electrode 508 is formed of indium tin oxide (ITO). The light emitting layer 506 is formed of, for example, an organic EL film. However, the light emitting layer 506 may be formed of an inorganic EL film other than the organic EL film. The sealing layer 509 is provided so as to cover the upper surface and side surfaces of the upper electrode 508, the side surfaces of the light emitting layer 506, the side surfaces of the lower electrode 504, and the upper surface of the light emitting substrate 402 around the light emitting region 404. The sealing layer 509 uses a sealing material that is impermeable to oxygen and moisture and transparent to the emission wavelength of the light emitting layer 506.

[0029] (Array of light-emitting elements) Hereinafter, the light-emitting portion 602 on the light-emitting region 404 will be described with reference to FIG. 6. FIG. 6 is a diagram showing the light-emitting portion 602. FIG. 6(a) is a diagram showing the light-emitting region 404 in which a plurality of light-emitting portions 602 are arranged in a row. A plurality of light-emitting portions 602(1), 602(2), 602(3), . . . , 602(n) are arranged at a predetermined pitch LP in the X direction to form a light-emitting array 604. For example, when the resolution is 1200 dpi, the predetermined pitch is 21.16 μm. The light-emitting portion 602 has a width W1 in the X direction. The adjacent light-emitting portions 602 have an interval s1 in the X direction. When the light-emitting layer 506 is sufficiently thin, the dimensions of the light-emitting portion 602 are substantially the same as the dimensions of the lower electrode 504. In this embodiment, the width W1 of the light-emitting portion 602 may be regarded as the width W of the lower electrode 504 shown in FIG. 5. The interval s1 between adjacent light emitting portions 602 may be regarded as the interval s between adjacent lower electrodes 504 shown in Fig. 5. In this embodiment, the width W1 of the light emitting portion 602 is 20.9 µm. The interval s1 between adjacent light emitting portions 602 is 0.26 µm.

[0030] Fig. 6(b) is a cross-sectional view of the light-emitting array 604. As shown in Fig. 6(b), each of the plurality of (748 in this embodiment) lower electrodes 504 has a width W1 in the X direction. The plurality of lower electrodes 504 are arranged at intervals s1 in the X direction to form the light-emitting array 604. Each of the light-emitting sections 602 is composed of the lower electrode 504, a portion of the upper electrode 508 facing the lower electrode 504, and a light-emitting layer 506 between the lower electrode 504 and the upper electrode 508. In Fig. 6(b), the light-emitting section 602 is indicated by the portion surrounded by a dotted line.

[0031] (Control unit) Next, the control unit 750 will be described with reference to FIG. 7. The control unit 750 includes an image controller unit 700 and a printed circuit board 202. FIG. 7 is a block diagram of the image controller unit 700 and the printed circuit board 202. Here, to simplify the description, a single-color process by the control unit 750 will be described, but the control unit 750 can perform similar processes simultaneously for four colors in parallel. The image controller unit 700 has an image data generation unit 701, a chip data conversion unit 702, a CPU 703, and a synchronization signal generation unit 704. The printed circuit board 202 has light-emitting element array chips 400(1), 400(2), 400(3), . . . , 400(20) and a head information storage unit 710.

[0032] (Image controller) The image controller unit 700 transmits a control signal for controlling the printed circuit board 202 to the printed circuit board 202. The control signal includes a chip select signal indicating the effective range of image data, a clock signal, image data, a signal indicating the division of the image data for each line (hereinafter referred to as a line synchronization signal), and a communication signal with the CPU 703. The chip select signal, the clock signal, and the image data are transmitted from the chip data conversion unit 702 of the image controller unit 700 to the light emitting element array chip 400 through a chip select signal line 705, a clock signal line 706, and an image data signal line 707. The line synchronization signal is transmitted from the synchronization signal generation unit 704 of the image controller unit 700 to the light emitting element array chip 400 through a line synchronization signal line 708. The communication signal is transmitted from the CPU 703 to the light emitting element array chip 400 and the head information storage unit 710 through a communication signal line 709.

[0033] The image controller unit 700 performs processing for image data and processing for print timing. The image data generating unit 701 performs dithering processing on image data (image signals) received from the scanner unit 100 or an external device at a resolution instructed by the CPU 703, and generates image data for print output. In this embodiment, the dithering processing is performed at a resolution of 1200 dpi.

[0034] The synchronization signal generating unit 704 generates a line synchronization signal. The CPU 703 determines the period during which the surface of the photosensitive drum 102 moves in the rotation direction (Y direction) by a pixel size of 1200 dpi (approximately 21.16 μm) at a predetermined rotation speed as one line period, and instructs the synchronization signal generating unit 704 on the time interval of the signal period. For example, when printing in the sheet transport direction (Y direction) at a speed of 200 mm / s, the CPU 703 determines the time interval as one line period of 105.8 μs (two decimal places and below are omitted) to the synchronization signal generating unit 704. The CPU 703 calculates the speed in the sheet transport direction using a setting value (fixed value) of the print speed set in a speed control means (not shown) of the photosensitive drum 102.

[0035] The chip data conversion unit 702 divides one line of image data for each light-emitting element array chip 400 in synchronization with a line synchronization signal generated by a synchronization signal generation unit 704. The chip data conversion unit 702 transmits the divided image data to the printed circuit board 202 together with a clock signal and a chip select signal.

[0036] (Printed circuit board) Next, the configuration of the printed circuit board 202 will be described. The head information storage unit 710 is a storage device that stores head information such as the amount of light emitted and mounting position information of each light-emitting element array chip 400. The head information storage unit 710 is connected to the CPU 703 via a communication signal line 709. The clock signal line 706, the image data signal line 707, the line synchronization signal line 708, and the communication signal line 709 are connected to all of the light-emitting element array chips 400. The chip select signal line 705 is connected to the input of the light-emitting element array chip 400(1). The output of the light-emitting element array chip 400(1) is connected to the input of the light-emitting element array chip 400(2) via a chip select signal line 711(1). The output of the light-emitting element array chip 400(2) is connected to the input of the light-emitting element array chip 400(3) via a chip select signal line 711(2). Similarly, the chip select signal lines are cascade-connected to each light-emitting element array chip 400. Each of the light-emitting element array chips 400 applies a current between the upper electrode 508 and the lower electrode 504 based on a set value set by the input chip select signal, clock signal, line synchronization signal, image data, and communication signal. This causes the light-emitting layer 506 (light-emitting portion 602) between the upper electrode 508 and the lower electrode 504 to emit light. In addition, each of the light-emitting element array chips 400 generates a chip select signal for the next light-emitting element array chip 400.

[0037] (Circuit section in light-emitting element array chip) FIG. 8 is a block diagram of the circuit section 406 in the light-emitting element array chip 400. The circuit section 406 in the light-emitting element array chip 400 is composed of a digital section 800 and an analog section 806. A clock signal, a communication signal, a chip select signal, image data, and a line synchronization signal are input to the digital section 800 through a clock signal line 706, a communication signal line 709, a chip select signal line 705, an image data signal line 707, and a line synchronization signal line 708. The digital section 800 has a function of generating a pulse signal for making the light-emitting section 602 emit light in synchronization with the clock signal based on a preset value, a chip select signal, image data, and a line synchronization signal that are preset by the communication signal. The digital section 800 transmits the pulse signal to the analog section 806. The digital section 800 also has a function of generating a chip select signal for the next light-emitting element array chip based on the input chip select signal.

[0038] The digital section 800 has a communication interface section (hereinafter referred to as a communication IF section) 801, a register section 802, a chip select signal generating section 803, an image data storage section 804, and pulse signal generating sections 805(1), 805(2), ..., 805(748). The communication IF section 801 controls writing and reading of setting values ​​to the register section 802 based on a communication signal input from the CPU 703 through a communication signal line 709. The register section 802 stores setting values ​​required for operation. The setting values ​​include exposure timing information used by the image data storage section 804, width and delay information of a pulse signal generated by the pulse signal generating section 805, and setting information of a drive current set by the analog section 806. The chip select signal generating section 803 delays the chip select signal input through the chip select signal line 705, and generates a chip select signal for the next light-emitting element array chip 400. The chip select signal generation unit 803 outputs a chip select signal for the next light-emitting element array chip 400 to the next light-emitting element array chip 400 through a chip select signal line 711 .

[0039] The image data storage unit 804 stores image data during the period when the input chip select signal is valid, and outputs the image data in synchronization with the line synchronization signal to the pulse signal generation unit 805. The pulse signal generation unit 805 generates a pulse signal based on the width information and phase information of the pulse signal set in the register unit 802 in accordance with the image data input from the image data storage unit 804, and outputs the pulse signal to the analog unit 806. The analog unit 806 supplies a drive current to the lower electrode 504 based on the pulse signal generated by the digital unit 800.

[0040] (Analog section) 9 is a block diagram of the analog unit 806. The analog unit 806 has driving units 1001(1), 1001(2), ..., 1001(748), a digital-to-analog converter (hereinafter referred to as DAC) 1002, and a driving unit selection unit 1007. The driving units 1001(1), 1001(2), ..., 1001(748) respectively drive the 748 lower electrodes 504. The pulse signal generation units 805(1), 805(2), ..., 805(748) generate pulse signals that control the ON timing of the lower electrodes 504(1) to 504(748). Pulse signal generating units 805(1), 805(2), ..., 805(748) input pulse signals to driving units 1001(1), 1001(2), ..., 1001(748) through signal lines 1006(1), 1006(2), ..., 1006(748).

[0041] The DAC 1002 sets an analog voltage that determines a drive current to the drive unit 1001 through a signal line 1003 based on the data set in the register unit 802. The drive unit selection unit 1007 transmits a drive unit select signal that selects the drive unit 1001 to the drive unit 1001 through signal lines 1004, 1005, ... based on the data set in the register unit 802. The drive unit select signal is generated so that only the signal connected to the selected drive unit 1001 is Hi (High). For example, when the drive unit 1001(1) is selected, Hi is supplied only to the signal line 1004. Low is supplied to other signal lines such as the signal lines 1005, ... connected to the unselected drive unit 1001(2) and the signal line 1748 connected to the unselected 1001(748). The driving units 1001 set an analog voltage through a signal line 1003 at the timing selected by the driving unit selection unit 1007 (the timing when the driving unit select signal becomes Hi). The CPU 703 sequentially selects the driving units 1001 through the register unit 802 and sets an analog voltage corresponding to the selected driving unit 1001, thereby setting analog voltages for all the driving units 1001 through one DAC 1002. By the above-mentioned operation, an analog voltage and a pulse signal that determine the driving current are input to the driving units 1001(1), ..., 1001(748), and the driving current and light emission time are independently controlled by a driving circuit described later.

[0042] (Drive circuit) 10 is a diagram showing a drive circuit of drive unit 1001(1). The drive circuits of drive units 1001(2),...,1001(748) that drive other lower electrodes 504(2),...,504(748) are similar. Drive unit 1001 has MOS type field effect transistors (hereinafter referred to as MOSFETs) 1102, 1103, 1104,1107, an inverter 1105, and a capacitor 1106.

[0043] The MOSFET 1102 supplies a driving current to the lower electrode 504(1) in accordance with the gate voltage value. The MOSFET 1102 controls the current so that the driving current is turned off (turned off) when the gate voltage is at a low level. A signal line 1006 that transmits a pulse signal from a pulse signal generating unit 805 is connected to the gate of the MOSFET 1104. When the pulse signal is Hi, the MOSFET 1104 passes the voltage charged in the capacitor 1106 to the MOSFET 1102. A signal line 1004 that transmits a driving unit select signal from a driving unit selecting unit 1007 is connected to the gate of the MOSFET 1107. When the driving unit select signal is Hi, the MOSFET 1107 turns on and charges the capacitor 1106 with an analog voltage supplied from the DAC 1002 through a signal line 1003. In this embodiment, the DAC 1002 sets an analog voltage to the capacitor 1106 at a timing before image formation, and the voltage level is maintained by turning off the MOSFET 1107 during the image formation period. In accordance with the analog voltage and pulse signal set by the above operations, the MOSFET 1102 supplies a driving current to the lower electrode 504(1).

[0044] If the input capacitance of lower electrode 504(1) is large and the response speed when turned off is slow, it is possible to speed up the turn-off speed by using MOSFET 1103. A signal that is a logical inversion of a pulse signal by inverter 1105 is input to the gate of MOSFET 1103. When the pulse signal is low, the gate of MOSFET 1103 becomes high, and the charge stored in the input capacitance between upper electrode 508 and lower electrode 504(1) is forcibly discharged.

[0045] As described above, the light emitting region 404 and the sealing region 409 are provided on the light emitting substrate 402 so that the distance between the lower side 402B of the longitudinal direction LD and the light emitting region 404 is minimized. The light emitting element array chips 400 are arranged in a staggered pattern on the printed circuit board 202 so that the lower sides 402B face each other. This makes it possible to minimize the distance between the light emitting region 404 and the rod lens array 203 and suppress a decrease in light utilization efficiency. [Explanation of symbols]

[0046] 400 Light-emitting element array chip 402 Light-emitting substrate 402B: Lower side (first long side) of light-emitting substrate 402T: Upper side of light-emitting board (second long side) 404...Light emitting area 404B: Lower side (third long side) of light-emitting area 404T: Top edge of light-emitting area (fourth long side) 409...Sealing area 409B... Bottom side of sealing area (fifth long side) 409T... Top edge of sealing area (sixth long side) 602 Light emitting part

Claims

1. a rectangular light emitting chip having a first long side and a second long side aligned along the first long side; a light-emitting region having a plurality of light-emitting elements provided along the first long side, a third long side along the first long side, and a fourth long side along the first long side, and a distance between the first long side and the third long side in a short-side direction of the light-emitting chip is shorter than a distance between the first long side and the fourth long side; a sealing region covering the light-emitting region, the sealing region having a fifth long side along the first long side and a sixth long side along the first long side, and a distance between the first long side and the fifth long side in the short direction is shorter than a distance between the first long side and the sixth long side; a lens array that collects light emitted from the light emitting region; Equipped with In the short-side direction, the distance between the first long side and the third long side is shorter than the distance between the second long side and the fourth long side; In the short-side direction, the distance between the first long side and the fifth long side is shorter than the distance between the second long side and the sixth long side; In the short-side direction, the fifth long side is located between the first long side and the third long side. A light emitting device characterized by:

2. In the short direction, the distance between the first long side and the fifth long side is shorter than the distance between the third long side and the fifth long side.

2. The light emitting device according to claim 1 .

3. a circuit unit provided in the light emitting chip and controlling turning on and off of the plurality of light emitting elements based on image data; 2. The light emitting device according to claim 1 .

4. The light emitting region and the circuit unit overlap when viewed in a vertical direction perpendicular to a surface of the light emitting chip.

4. The light emitting device according to claim 3.

5. A light-transmittable first electrode; a plurality of second electrodes provided between the first electrode and the substrate in a vertical direction perpendicular to a surface of the substrate; a light-emitting layer provided between the first electrode and the plurality of second electrodes in the vertical direction; Equipped with The light emitted from the light emitting layer is transmitted through the first electrode.

5. The light emitting device according to claim 4.

6. The circuit unit is built into the light-emitting chip.

4. The light emitting device according to claim 3.

7. In the short direction, a distance between the third long side and the fifth long side is shorter than a distance between the fourth long side and the sixth long side.

2. The light emitting device according to claim 1 .

8. The plurality of light-emitting elements are organic electroluminescent elements.

2. The light emitting device according to claim 1 .

9. An image forming apparatus for forming an image on a recording medium, comprising: A photosensitive drum; a light emitting device for exposing a surface of the photosensitive drum; Equipped with The light emitting device comprises: a rectangular light emitting chip having a first long side and a second long side aligned along the first long side; a light-emitting region having a plurality of light-emitting elements provided along the first long side, a third long side along the first long side, and a fourth long side along the first long side, and a distance between the first long side and the third long side in a short-side direction of the light-emitting chip is shorter than a distance between the first long side and the fourth long side; a sealing region covering the light-emitting region, the sealing region having a fifth long side along the first long side and a sixth long side along the first long side, and a distance between the first long side and the fifth long side in the short direction is shorter than a distance between the first long side and the sixth long side; a lens array that collects light emitted from the light emitting region; Equipped with In the short-side direction, the distance between the first long side and the third long side is shorter than the distance between the second long side and the fourth long side; In the short-side direction, the distance between the first long side and the fifth long side is shorter than the distance between the second long side and the sixth long side; In the short-side direction, the fifth long side is located between the first long side and the third long side.

1. An image forming apparatus comprising:

10. In the short direction, the distance between the first long side and the fifth long side is shorter than the distance between the third long side and the fifth long side.

10. The image forming apparatus according to claim 9,

11. A circuit unit is provided in the light-emitting chip and controls turning on and off the plurality of light-emitting elements based on image data.

10. The image forming apparatus according to claim 9,

12. The light emitting region and the circuit part overlap when viewed in a vertical direction perpendicular to a surface of the light emitting chip.

12. The image forming apparatus according to claim 11.

13. A light-transmittable first electrode; a plurality of second electrodes provided between the first electrode and the substrate in a vertical direction perpendicular to a surface of the substrate; a light-emitting layer provided between the first electrode and the plurality of second electrodes in the vertical direction; Equipped with The light emitted from the light emitting layer is transmitted through the first electrode.

13. The image forming apparatus according to claim 12.

14. The circuit unit is built into the light-emitting chip.

12. The image forming apparatus according to claim 11.

15. In the short direction, a distance between the third long side and the fifth long side is shorter than a distance between the fourth long side and the sixth long side.

10. The image forming apparatus according to claim 9,

16. The plurality of light-emitting elements are organic electroluminescent devices.

10. The image forming apparatus according to claim 9,

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