Optical print head and image forming apparatus

Abstract

To prevent a sealing agent applied to a gap between a lens array inserted into an opening and an enclosure from leaking out into an undesired position in the enclosure.SOLUTION: An optical print head, which is formed in a longitudinal shape extending in a rotational axis line direction of a photoreceptor and exposes the photoreceptor, comprises a substrate in which light-emitting elements are arranged in the rotational axis line direction, a lens array that concentrates light emitted from the light-emitting elements into the photoreceptor, and a holding member that holds the lens array and the substrate. The holding member is made of metal and has a flat surface part in which an opening into which the lens array is inserted is formed, and a damming part that dams a sealing agent applied to a gap between the lens array inserted into the opening and the flat surface part. The damming part, provided in the flat surface part, separates the flat surface part into a first flat surface part leading to an edge of the opening and a second flat surface part having the first flat surface part interposed between the edge of the opening and the part, in a traverse direction orthogonal to a longitudinal direction of the flat surface part.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present invention relates to an optical print head having a plurality of light-emitting elements that expose a photosensitive member, and an image forming apparatus having the optical print head. [Background technology]

[0002] Some image forming devices, such as printers and copiers, are equipped with optical print heads that have multiple light-emitting elements for exposing a photosensitive drum. Optical print heads have LEDs (Light Emitting Diodes) as light-emitting elements that emit light, and the photosensitive drum is exposed to the light emitted from these multiple LEDs. Some optical print heads also have organic electroluminescence (OLED) elements as light-emitting elements that emit light. Organic EL is sometimes called OLED (Organic Light Emitting Diode). The multiple LEDs are arranged on a substrate, and the light emitted from the LEDs is focused onto the photosensitive drum by a lens array.

[0003] The optical print head proposed in Patent Document 1 will be described with reference to FIG. 19. Optical print head 300 includes light-emitting substrate 301 on which a plurality of LED array chips 301a, each having a plurality of light-emitting elements, is mounted, lens array 302 for converging light emitted from light-emitting substrate 301, and housing 303 for holding light-emitting substrate 301 and lens array 302. Housing 303 has opening 303a for holding and fixing light-emitting substrate 301. Lens array 302 is fixed and held in opening 303a with adhesive. Then, sealant 304 is applied to the gap between lens array 302, which is fixed and held in opening 303a, and housing 303. This prevents foreign matter from entering the interior of optical print head 300. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5433541 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, there has been a demand for smaller image forming devices, necessitating designs with a shorter distance between photosensitive drums (hereinafter referred to as the drum pitch). As the drum pitch becomes shorter, the width of the optical print head placed between the photosensitive drums becomes narrower, and the width of the housing also becomes narrower. Furthermore, typical sealants require time for the surface to harden, and if the surface is still unhardened, the sealant may flow to unintended locations within the housing. Therefore, if the width of the housing becomes narrower, the sealant may flow to unintended locations within the housing and harden.

[0006] Therefore, an object of the present invention is to provide an optical print head and an image forming device that prevent the sealant applied to the gap between the lens array inserted into the opening and the housing from leaking to unintended locations in the housing. [Means for solving the problem]

[0007] A representative configuration of the present invention is an optical print head that exposes a photosensitive member, the optical print head comprising: a substrate provided with a plurality of light-emitting units that emit light to expose the photosensitive member; a lens array having a plurality of lenses that focus the light emitted from the light-emitting units onto the photosensitive member; and a holder that holds the substrate and the lens array, the holder having an opening into which the lens array is inserted and an opposing surface that faces the photosensitive member in the optical axis direction of the lenses; a groove formed in the opposing surface, the groove including a first region that overlaps with the lens array when viewed from a lateral direction perpendicular to the longitudinal direction and the optical axis direction of the holder and a second region that does not overlap with the lens array when viewed from the lateral direction; and a sealant that seals a gap between a sidewall of the lens array and an edge of the opening, the sealant being applied between the groove and the sidewall. the holder has a contact surface against which a cleaning rod for cleaning the light exit surface of the lens array comes into contact, and the groove is a groove for preventing the sealant applied between the groove and the side wall from flowing onto the contact surface. It is characterized by: [Effects of the Invention]

[0008] According to the present invention, the sealant applied to the gap between the lens array inserted into the opening and the flat portion is blocked by the blocking portion, preventing it from leaking to unintended locations in the holding member. [Brief explanation of the drawings]

[0009] [Figure 1] 1A and 1B are cross-sectional views showing a schematic configuration of an image forming apparatus. [Figure 2] (a) and (b) are diagrams for explaining the configuration of the drum unit and the developing unit and its surroundings. [Figure 3] Schematic perspective view of an exposure unit [Figure 4] (a), (b), and (c) are diagrams showing a substrate in an optical print head, and (d) and (e) are diagrams showing a lens array. [Figure 5] A diagram for explaining a substrate having an OLED [Figure 6] (a), (b), and (c) are diagrams for explaining the internal structure of a substrate having an OLED. [Figure 7] (a) and (b) are diagrams for explaining the light emitting surface and mounting surface of the board. [Figure 8] FIG. [Figure 9] FIG. 10 is a cross-sectional view of the optical print head showing the positional relationship between the holder and parts around the lens array. [Figure 10] FIG. 10 is a top view of the optical print head showing the positional relationship between the lens array and the sealant retaining portion. [Figure 11] FIG. 4 is a cross-sectional view of the optical print head showing the cross-sectional shape of the sealant retaining portion. [Figure 12] FIG. 4 is a cross-sectional view of the optical print head showing the cross-sectional shape of the sealant retaining portion. [Figure 13] 10A and 10B are top views of an optical print head showing examples of the shape of a sealant retaining portion. [Figure 14] 10A and 10B are top views of an optical print head showing examples of the shape of a sealant retaining portion. [Figure 15] FIG. [Figure 16] FIG. [Figure 17] FIG. 4 is a cross-sectional view showing the positional relationship between the cleaning rod and the optical print head during cleaning. [Figure 18] FIG. [Figure 19] FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] The following describes embodiments of the present invention with reference to the drawings. Note that the dimensions, materials, shapes, relative positions, etc. of the components described below are not intended to limit the scope of the present invention unless otherwise specified.

[0011] (Image forming device) First, a schematic configuration of an image forming apparatus 1 will be described using FIG. 1(a). FIG. 1(a) is a schematic cross-sectional view of the image forming apparatus 1. The image forming apparatus 1 shown in FIG. 1(a) is a color printer (SFP: Single Function Printer) that does not have a reading device, but the embodiment may also be a copier that has a reading device. Furthermore, the embodiment is not limited to a color image forming apparatus that has multiple photosensitive drums 103 as shown in FIG. 1(a), and may also be a color image forming apparatus that has one photosensitive drum 103 or an image forming apparatus that forms monochrome images.

[0012] The image forming apparatus 1 shown in FIG. 1(a) includes four image forming units 102Y, 102M, 102C, and 102K (hereinafter collectively referred to as "image forming units 102") that form toner images of yellow, magenta, cyan, and black, respectively. The image forming units 102Y, 102M, 102C, and 102K also include photosensitive drums 103Y, 103M, 103C, and 103K (hereinafter collectively referred to as "photosensitive drum 103"), which are examples of photosensitive bodies. The photosensitive drums 103 may be photosensitive belts. The image forming units 102Y, 102M, 102C, and 102K are also equipped with chargers 104Y, 104M, 104C, and 104K (hereinafter collectively referred to as "charger 104") as charging means for charging the photosensitive drums 103Y, 103M, 103C, and 103K, respectively. The image forming units 102Y, 102M, 102C, and 102K are also equipped with LED (Light Emitting Diode, hereinafter referred to as LED) exposure units 520Y, 520M, 520C, and 520K (hereinafter collectively referred to as "exposure unit 520") as exposure light sources that emit light to expose the photosensitive drums 103Y, 103M, 103C, and 103K. Furthermore, the image forming units 102Y, 102M, 102C, and 102K are equipped with developing units 106Y, 106M, 106C, and 106K (hereinafter collectively referred to as "developing units 106") that develop the electrostatic latent image on the photosensitive drum 103 with toner and develop toner images of each color on the photosensitive drum 103. The letters Y, M, C, and K attached to the reference numerals indicate the colors of the toner.

[0013] The image forming apparatus 1 shown in Figure 1(a) is an image forming apparatus that employs a so-called "bottom exposure method" in which the photosensitive drum 103 is exposed from below. The following description will be given on the assumption that the image forming apparatus employs a bottom exposure method, but an embodiment may also be an image forming apparatus that employs an "top exposure method" in which the photosensitive drum 103 is exposed from above, such as the image forming apparatus 2 shown in Figure 1(b). In Figure 1(b), parts that show the same configuration as in Figure 1(a) are designated by the same reference numerals.

[0014] The image forming apparatus 1 includes an intermediate transfer belt 107 onto which the toner image formed on the photosensitive drum 103 is transferred, and primary transfer rollers 108 (Y, M, C, K) that sequentially transfer the toner image formed on the photosensitive drum 103 onto the intermediate transfer belt 107. The image forming apparatus 1 also includes a secondary transfer roller 109 as a transfer means that transfers the toner image on the intermediate transfer belt 107 onto recording paper P transported from a paper feed unit 101, and a fixing device 100 that fixes the secondarily transferred image onto the recording paper P. Note that, in addition to the intermediate transfer method using the intermediate transfer belt 107 described above, a direct transfer method in which the image is directly transferred from the photosensitive drum 103 onto paper may also be used.

[0015] (Image formation process) Next, a brief description will be given of the image formation process of the image forming apparatus. The charger 104Y charges the surface of the photosensitive drum 103Y. The exposure unit 520Y exposes the surface of the photosensitive drum 103Y charged by the charger 104Y. As a result, an electrostatic latent image is formed on the photosensitive drum 103Y. Next, the developer 106Y develops the electrostatic latent image formed on the photosensitive drum 103Y with yellow toner. The yellow toner image developed on the surface of the photosensitive drum 103Y is transferred onto the intermediate transfer belt 107 by the primary transfer roller 108Y. Magenta, cyan, and black toner images are formed in a similar image formation process and transferred onto the intermediate transfer belt 107 so as to be superimposed on each other.

[0016] The toner images of each color transferred onto the intermediate transfer belt 107 are transported to a secondary transfer unit T2 by the intermediate transfer belt 107. A transfer bias is applied to a secondary transfer roller 109 disposed in the secondary transfer unit T2 to transfer the toner image onto the recording paper P. The toner image transported to the secondary transfer unit T2 is transferred onto the recording paper P transported from the paper feed unit 101 by the transfer bias of the secondary transfer roller 109. The recording paper P onto which the toner image has been transferred is transported to a fixing unit 100. The fixing unit 100 fixes the toner image onto the recording paper P by heat and pressure. The recording paper P that has been fixed by the fixing unit 100 is discharged to a paper discharge unit 111.

[0017] (Drum unit and developing unit) A replaceable drum unit in the image forming apparatus of this embodiment will be described below by way of example. The photosensitive drum 103 and charger 104 described above may be integrated into a unit (drum unit, drum cartridge) together with a cleaning device (not shown). An example of such a configuration will be described with reference to FIGS. 2(a) and 2(b). FIG. 2(a) is a perspective view showing the general structure of the drum unit 518 (Y, M, C, K) and the developing unit 641 (Y, M, C, K) provided in the image forming apparatus 1. FIG. 2(b) shows the drum unit 518 inserted into the image forming apparatus 1 from outside the apparatus main body.

[0018] Drum units 518Y, 518M, 518C, and 518K (hereinafter collectively referred to as "drum units 518") each having a photosensitive drum 103 are attached to the image forming apparatus 1. The drum unit 518 is a cartridge that is replaced by an operator such as a user or a maintenance technician. The drum unit 518 rotatably supports the photosensitive drum 103. Here, the drum unit 518 also functions as a drum support member that rotatably supports the photosensitive drum 103. In this embodiment, the drum support member is also referred to as the drum unit 518. Specifically, the photosensitive drum 103 is rotatably supported by a frame of the drum unit 518. The drum unit 518 may not be equipped with a charger 104 or a cleaning device.

[0019] The image forming apparatus 1 of this embodiment is also equipped with developing units 641Y, 641M, 641C, and 641K (hereinafter, collectively referred to as "developing units 641") that are separate from the drum unit 518. The developing unit 641 of this embodiment is a cartridge in which the developing device 106 shown in FIG. 1A and a toner storage unit are integrated. The developing device 106 includes a developing sleeve (not shown) that carries developer. The developing unit 641 is provided with multiple gears for rotating a screw that mixes the toner and carrier. When these gears deteriorate over time, an operator removes the developing unit 641 from the main body of the image forming apparatus 1 and replaces it. Note that the embodiment of the drum unit 518 and the developing unit 641 may also be a process cartridge in which the drum unit 518 and the developing unit 641 are integrated.

[0020] As shown in FIG. 2A, the image forming apparatus 1 includes a front panel 642 made of sheet metal and a rear panel 643 also made of sheet metal. The front panel 642 is a side wall provided on the front side of the image forming apparatus 1. The front panel 642 forms part of the housing of the apparatus body on the front side of the apparatus body of the image forming apparatus 1. The rear panel 643 is a side wall provided on the rear side of the image forming apparatus 1. The rear panel 643 forms part of the housing of the apparatus body on the rear side of the apparatus body of the image forming apparatus 1. As shown in FIG. 2A, the front panel 642 and the rear panel 643 are disposed facing each other, and a metal beam (not shown) bridges the two panels. The front panel 642, the rear panel 643, and the beam (not shown) each form part of the frame of the image forming apparatus 1. Here, with respect to the image forming apparatus 1 or its components in this embodiment, the front side or the front side refers to the side from which the drum unit 518 is inserted into or removed from the apparatus body.

[0021] An opening 644 is formed in the front side panel 642 so that the drum unit 518 and the developing unit 641 can be inserted and removed from the front side of the image forming apparatus 1. The drum unit 518 and the developing unit 641 are attached to a predetermined position (attachment position) in the main body of the image forming apparatus 1 through the opening 644. The image forming apparatus 1 also includes covers 558Y, 558M, 558C, and 558K (hereinafter collectively referred to as "cover 558") that cover the front sides of both the drum unit 518 and the developing unit 641 attached to the attachment position. One end of the cover 558 is fixed to the main body of the image forming apparatus 1 by a hinge, and the cover 558 is rotatable relative to the main body of the image forming apparatus 1 by the hinge. The replacement operation is completed when an operator opens the cover 558, removes the drum unit 518 or the developing unit 641 from the main body, inserts a new drum unit 518 or the developing unit 641, and closes the cover 558.

[0022] As shown in FIGS. 2(a) and 2(b), in the following description, the front side plate 642 side with respect to the device body is defined as the front side (near side or front side), and the rear side plate 643 side is defined as the rear side (rear side or back side). Furthermore, when the photosensitive drum 103K on which the electrostatic latent image for the black toner image is formed is used as a reference, the side on which the photosensitive drum 103Y on which the electrostatic latent image for the yellow toner image is formed is defined as the right side. When the photosensitive drum 103Y on which the electrostatic latent image for the yellow toner image is formed is used as a reference, the side on which the photosensitive drum 103K on which the electrostatic latent image for the black toner image is formed is defined as the left side. Furthermore, the direction perpendicular to the front-rear and left-right directions defined here and pointing vertically upward is defined as the up direction, and the direction perpendicular to the front-rear and left-right directions defined here and pointing vertically downward is defined as the down direction. The defined front, rear, right, left, up, and down directions are shown in FIGS. 2 and 3.

[0023] Furthermore, the rotational axis direction of the photosensitive drum 103 described below is the same as the front-to-rear direction shown in FIG. 2. The longitudinal direction of the optical print head 105 is also the same as the front-to-rear direction shown in FIG. 2. That is, the rotational axis direction of the photosensitive drum 103 and the longitudinal direction of the optical print head 105 are the same as each other. Furthermore, one end side in the rotational axis direction of the photosensitive drum 103 means the front side as defined here, and the other end side means the rear side as defined here. One end side and the other end side in the front-to-rear direction also correspond to the front side and rear side as defined here. One end side in the left-to-right direction means the right side as defined here, and the other end side means the left side as defined here.

[0024] (Exposure unit) Next, an exposure unit 520 including the optical print head 105 will be described with reference to Fig. 3. Fig. 3 is a schematic perspective view of the exposure unit 520 provided in the image forming apparatus 1 of this embodiment.

[0025] The optical print head 105 has an elongated shape (longitudinal shape) extending in the direction of the rotation axis of the photosensitive drum 103. The optical print head 105 also includes a holding member 505 (an example of a holder), a lens array 506, and a substrate 502 (see FIG. 4). The holding member 505 holds the lens array 506 and the substrate 502. In this embodiment, the holding member 505 is a metal member formed by bending a plated material such as a zinc-plated steel plate or a cold-rolled steel plate. Here, an example of an exposure method adopted in an electrophotographic image forming apparatus is a laser beam scanning exposure method in which a semiconductor laser irradiation beam is scanned by a rotating polygon mirror or the like and the photosensitive drum is exposed via an f-θ lens or the like. The "optical print head 105" described in this embodiment is used in an LED exposure method that exposes the photosensitive drum 103 using light-emitting elements such as LEDs arranged along the rotation axis direction of the photosensitive drum 103, and is not used in the laser beam scanning exposure method mentioned above.

[0026] The exposure unit 520 described in this embodiment is provided vertically below the rotation axis of the photosensitive drum 103. LEDs are provided as light-emitting elements on a substrate 502 of the holding member 505, and these light-emitting elements expose the photosensitive drum 103 from below. However, the exposure unit 520 may be provided vertically above the rotation axis of the photosensitive drum 103, and may expose the photosensitive drum 103 from above (see FIG. 1(b)).

[0027] 3, the exposure unit 520 includes the optical print head 105, a support member 526, a first link mechanism 530, and a second link mechanism 540. The support member 526, the first link mechanism 530, and the second link mechanism 540 constitute a movement mechanism 640 that moves the optical print head 105.

[0028] The holding member 505 of the optical print head 105 is provided with abutment pins 514 and 515. Both the abutment pins 514 and 515 are examples of metal pins. For example, the abutment pin 515 is provided on the holding member 505 on one side (rear side) of the lens array 506 in the direction of the rotation axis of the photosensitive drum 103, and protrudes from both sides of the holding member 505 in the optical axis direction of the lens array 506. The same is true for the abutment pin 514. When the abutment pins 514 and 515 abut against the drum unit 518, a gap is formed between the lens array 506 and the photosensitive drum 103. In this way, the position of the optical print head 105 relative to the photosensitive drum 103 is determined. In this embodiment, the abutment pins 514 and 515 are both metal straight pins. Furthermore, the abutment pins 514 and 515 are fixed to the metal holding member 505 by welding. In this manner, in this embodiment, the contact pins 514 and 515 are integrated with the holding member 505 .

[0029] The first link mechanism 530 includes a link member 535 and a link member 536. The second link mechanism 540 includes a link member 537 and a link member 538. The link member 535 is attached to the holding member 505 in front of the center in the direction of the rotation axis of the photosensitive drum 103, and the link member 537 is attached to the holding member 505 in rear of the center in the direction of the rotation axis of the photosensitive drum 103.

[0030] Sliding member 525 slides forward and backward in response to the opening and closing of cover 558 (see FIG. 2) provided on the front side of image forming apparatus 1. Linking members 535 to 538 rotate in conjunction with the sliding movement of sliding member 525, and optical print head 105 moves up and down.

[0031] In this embodiment, the optical print head 105 is provided vertically below the photosensitive drum 103. That is, in the image forming apparatus 1 in this embodiment, the optical print head 105 exposes the photosensitive drum 103 from below in the vertical direction.

[0032] 3, the exposure unit 520 also includes a support member 526. The support member 526 supports the optical print head 105 via a first link mechanism 530 and a second link mechanism 540. Specifically, a link member 535 of the first link mechanism 530 supports the holding member 505, and a link member 537 of the second link mechanism 540 supports the holding member 505.

[0033] The support member 526 is formed by bending a metal plate into a U-shape. The support member 526 is a longitudinal member extending in the direction of the rotation axis of the photosensitive drum 103. One end side (front side) of the support member 526 in the longitudinal direction of the support member 526 is fixed to the front side plate 642, and the other end side (rear side) of the support member 526 in the longitudinal direction of the support member 526 is fixed to the rear side plate 643. In this way, the position of the support member 526 with respect to the photosensitive drum 103 is fixed on the side opposite to the side on which the photosensitive drum 103 is disposed with respect to the holding member 505.

[0034] Support member 526 includes slide member 525 that is movable in the longitudinal direction of support member 526. As slide member 525 moves relative to support member 526, link members 535-538 rotate, and optical print head 105 moves relative to support member 526.

[0035] Furthermore, an insertion portion 550 into which a cleaning means (cleaning rod 900 shown in FIG. 15) described later is inserted is fixed to support member 526. Since support member 526 is fixed to the main body of image forming apparatus 1, insertion portion 550 is also fixed to the main body of image forming apparatus 1.

[0036] (Substrate and lens array) Next, the substrate 502 and lens array 506 held by the holding member 505 of the optical print head 105 will be described with reference to Figure 4. First, the substrate 502 will be described. Figure 4(a) is a schematic perspective view of the substrate 502. Figure 4(b) shows the arrangement of multiple LEDs 503 provided on the substrate 502, and Figure 4(c) shows an enlarged view of Figure 4(b).

[0037] An LED chip 639 is mounted on the substrate 502. As shown in FIG. 4A, the LED chip 639 is provided on one side of the substrate 502, and a connector 504 is provided on the back side. Here, "one side," i.e., the side on which the LED chip 639 is provided, is defined as the "light-emitting surface." In other words, of the front and back sides of the substrate 502, the side from which light is emitted toward the photosensitive drum 103 is the light-emitting surface. The substrate 502 is provided with wiring for supplying signals to each LED chip 639. One end of a flexible flat cable (FFC) (not shown) is connected to the connector 504. The image forming apparatus 1 has a main body provided with a substrate. The substrate includes a control unit and a connector. The other end of the FFC is connected to the connector. A control signal is input to the substrate 502 from the control unit of the main body of the image forming apparatus 1 via the FFC and the connector 504. The LED chip 639 is driven by the control signal input to the substrate 502.

[0038] The LED chip 639 mounted on the substrate 502 will be described in more detail. As shown in FIGS. 4(b) and 4(c), LED chips 639-1 to 639-29 (29 chips) each having a plurality of LEDs 503 arranged thereon are arranged on one surface of the substrate 502. Each of the LED chips 639-1 to 639-29 has 516 LEDs (light-emitting elements) arranged in its longitudinal direction. The center-to-center distance k2 between adjacent LEDs in the longitudinal direction of the LED chip 639 corresponds to the resolution of the image forming apparatus 1. Since the resolution of the image forming apparatus 1 in this embodiment is 1200 dpi, the LEDs are arranged so that the center-to-center distance between adjacent LEDs in the longitudinal direction of the LED chips 639-1 to 639-29 is 21.16 μm. Therefore, the exposure range of the optical print head 105 in this embodiment is approximately 316 mm. The photosensitive layer of the photosensitive drum 103 is formed with a width of 316 mm or more. Since the length of the long side of A4 size recording paper and the length of the short side of A3 size recording paper are 297 mm, the optical print head 105 in this embodiment has an exposure range that can form images on A4 size recording paper and A3 size recording paper.

[0039] A plurality of LED chips 639-1 to 639-29 are arranged in the rotational axis direction of the photosensitive drum 103. Specifically, the LED chips 639-1 to 639-29 are alternately arranged in two rows along the rotational axis direction of the photosensitive drum 103. That is, as shown in FIG. 4(b), counting from the left, the odd-numbered LED chips 639-1, 639-3, ... 639-29 are mounted in a row in the longitudinal direction of the substrate 502. Also, counting from the left, the even-numbered LED chips 639-2, 639-4, ... 639-28 are mounted in a row in the longitudinal direction of the substrate 502. The LED chips 639 are arranged in this manner. As a result, as shown in Figure 4(c), in the longitudinal direction of the LED chip 639, the center-to-center distance k1 between the LEDs 503 arranged between one end of one LED chip 639 and the other end of the other LED chip 639 in different adjacent LED chips 639 can be made equal to the center-to-center distance k2 between adjacent LEDs 503 on one LED chip 639.

[0040] In this embodiment, the light-emitting elements are semiconductor LEDs, which are light-emitting diodes, but they may also be, for example, OLEDs (Organic Light Emitting Diodes). OLEDs are also called organic ELs (Organic Electro-Luminescence) and are current-driven light-emitting elements. The OLEDs are arranged in a line along the main scanning direction (the direction of the rotation axis of the photosensitive drum 103) on a TFT (Thin Film Transistor) substrate, for example, and are electrically connected in parallel by power supply wiring that is also provided along the main scanning direction.

[0041] Next, the lens array 506 will be described. FIG. 4(d) is a schematic diagram of the lens array 506 as viewed from the photosensitive drum 103 side. FIG. 4(e) is a schematic perspective view of the lens array 506. As shown in FIG. 4(d), the lens array 506 focuses light emitted from the light-emitting elements onto the photosensitive drum 103. The lens array 506 has a plurality of lenses. These lenses are arranged in two rows along the arrangement direction of the plurality of LEDs 503. The lenses are alternately arranged such that one lens in one row is in contact with both of the adjacent lenses in the arrangement direction of the lenses in the other row. Each lens is a cylindrical glass rod lens and has an incident surface 506b onto which light emitted from the LEDs 503 enters and an exit surface 506a from which the light incident from the incident surface exits (see FIG. 9). The material of the lens is not limited to glass and may be plastic. The shape of the lens is also not limited to cylindrical and may be a polygonal prism such as a hexagonal prism.

[0042] The dotted line Z in Figure 4(e) indicates the optical axis of the lens. The optical print head 105 is moved by the aforementioned movement mechanism 640 (see Figure 3) in a direction generally along the optical axis of the lens indicated by the dotted line Z. The optical axis of the lens here refers to the line connecting the center of the lens's emission surface and the focal point of the lens. The lens array 506 serves to focus the light emitted from the LED 503 onto the surface of the photosensitive drum 103.

[0043] The plurality of LEDs 503 and the lens array 506 provided on the substrate 502 described above are held by a holding member 505 so as to face each other. As a result, light emitted from the plurality of LEDs 503 is condensed onto the photosensitive drum 103 by the lens array 506. In this embodiment, light emitted from three LEDs 503 (a plurality of LEDs 503) can pass through the same lens. Furthermore, even light emitted from a single LED 503 can pass through multiple lenses because the light travels radially. In other words, light emitted from the plurality of LEDs 503 passes through the lens array 506 (some of the multiple lenses included in the lens array 506) to expose the photosensitive drum 103.

[0044] Furthermore, an organic EL (also called an OLED) may be used as a light source that emits light to expose the photosensitive drum 103. A substrate using an organic EL as a light source will be described with reference to FIGS.

[0045] FIG. 5 is a diagram illustrating a substrate 502 when an OLED is used as a light-emitting element. This diagram shows the internal configuration of the substrate 502. As shown in FIG. 5, the longitudinal direction of the substrate 502 is the X direction, and the lateral direction is the Y direction. The Y direction is the rotation direction of the photosensitive drum 103, in other words, the movement direction of the photosensitive surface (photoconductor surface) of the rotating photosensitive drum 103. The X direction is a direction approximately perpendicular to the Y direction, i.e., the rotation direction of the photosensitive drum 103. It is also a direction approximately parallel to the rotation axis direction of the photosensitive drum 103. Note that approximately perpendicular allows a tilt of approximately ±1° relative to an angle of 90°, and approximately parallel allows a tilt of approximately ±1° relative to an angle of 0° between the two. That is, the longitudinal direction of the substrate 502 may be tilted by approximately ±1° relative to the rotation axis direction of the photosensitive drum 103. The lateral direction of the substrate 502 may also be tilted by approximately ±1° relative to the rotation direction of the photosensitive drum 103. The substrate 502 has wire bonding pads (hereinafter referred to as WB pads) 601-1, 601-2, 601-3, and 601-4 formed on the silicon substrate 402. The silicon substrate 402 has a built-in circuit section 602 (shown by a broken line). The circuit section 602 may be configured to include an analog drive circuit, a digital control circuit, or both. Power is supplied to the circuit section 602 and signals are input and output from outside the substrate 502 via the WB pads 601.

[0046] The substrate 502 having the OLED includes a linear light-emitting region 604 extending along the rotation axis direction of the photosensitive drum 103. The light-emitting region 604 includes an anode, a cathode, and a light-emitting layer 450 (see FIG. 6), which will be described later, and is a region that emits light when a potential difference occurs between the anode and the cathode.

[0047] Circuit section 602 is provided with a drive section that drives light emitting area 604 and a data transfer and light emitting signal generation section that generates a signal (hereinafter referred to as a light emitting signal) for causing light emitting area 604 to emit light. Circuit section 602 is formed on silicon substrate 402. This forms a circuit that is capable of high speed operation.

[0048] The substrate 502 when an OLED is used will be described in more detail with reference to FIG. 6. The X direction in FIG. 6 indicates the longitudinal direction of the substrate 502 (see FIG. 5). The Z direction is the direction in which each layer of the layer structure described below overlaps (stacking direction). FIG. 6(a) is an enlarged view of a main part of the schematic diagram of the AA cross section in FIG. 5. FIG. 6(a) is a schematic diagram of lower electrodes 410-1 to 410-748 described below as viewed from the Y direction. As shown in FIGS. 6(a) and 6(c), the substrate 502 includes a silicon substrate 402, lower electrodes 410-1 to 410-748, a light-emitting layer 450, and an upper electrode 460. The silicon substrate 402 is a driving substrate on which driving circuits including driving units corresponding to the lower electrodes 410-1 to 410-748 described below are formed during the manufacturing process.

[0049] As shown in Figures 6(a) and 6(c), lower electrodes 410-1 to 410-748 (cathodes) are multiple electrodes formed in layers (first electrode layers) on silicon substrate 402. Each of lower electrodes 410-1 to 410-748 is formed on multiple driving units built into silicon substrate 402 using Si integrated circuit processing technology in addition to the manufacturing process for silicon substrate 402. Lower electrodes 410-1 to 410-748 are preferably made of a metal with high reflectivity at the emission wavelength of light-emitting layer 450, which will be described later. Therefore, lower electrodes 410-1 to 410-748 preferably contain silver (Ag), aluminum (Al), or an alloy thereof, a silver-magnesium alloy, or the like.

[0050] As shown in Fig. 6, the lower electrodes 410-1 to 410-748 are electrodes provided corresponding to each pixel in the X direction. That is, the lower electrodes 410-1 to 410-748 are electrodes provided to form one pixel each. The lower electrodes 410-1 to 410-748 form a first electrode row. The lower electrodes 410-1 to 410-748 forming the first electrode row are aligned along the rotation axis of the photosensitive drum 103. Here, the lower electrodes 410-1 to 410-748 may be aligned at an angle of about ±1° with respect to the rotation axis of the photosensitive drum 103. They do not need to be aligned strictly parallel to the rotation axis of the photosensitive drum 103.

[0051] The width W of lower electrodes 410-1 to 410-748 in the X direction corresponds to the width of one pixel. Distance d is the distance between lower electrodes (arrangement interval) in the X direction. Because lower electrodes 410-1 to 410-748 are formed on silicon substrate 402 with distance d between them, multiple drive units formed on silicon substrate 402 can individually control the voltages of lower electrodes 410-1 to 410-748. The distance d is filled with an organic material for light-emitting layer 450, and the lower electrodes are partitioned by the organic material.

[0052] The shape of the lower electrode 410 is not limited to a square, and may be a polygon with more sides than a square, a circle, an ellipse, or the like, as long as it emits light of an exposure area size corresponding to the output resolution of the image forming device and the image quality of the output image produced by that light is at a level that satisfies the design specifications of the image forming device.

[0053] Next, the light-emitting layer 450 will be described. The light-emitting layer 450 is formed by being laminated on the silicon substrate 402 on which the lower electrodes 410-1 to 410-748 are formed. That is, the light-emitting layer 450 is laminated on the lower electrodes 410-1 to 410-748 in the portions where the lower electrodes 410-1 to 410-748 are formed. The light-emitting layer 450 is laminated on the silicon substrate 402 in the portions where the lower electrodes 410-1 to 410-748 are not formed. In this example, the light-emitting layer 450 is formed so as to span all of the lower electrodes 410-1 to 410-748, but the embodiment is not limited to this. For example, the light-emitting layer 450 may be formed so as to be separately laminated on each lower electrode, similar to the lower electrodes 410-1 to 410-748. Alternatively, the lower electrodes 410-1 to 410-748 may be divided into a plurality of groups, and one light-emitting layer may be laminated on each lower electrode belonging to each divided group.

[0054] For example, an organic material can be used for the light-emitting layer 450. The light-emitting layer 450, which is an organic EL film, is a laminated structure including functional layers such as an electron transport layer, a hole transport layer, an electron injection layer, a hole injection layer, an electron blocking layer, and a hole blocking layer. The light-emitting layer 450 may be made of an inorganic material other than an organic material.

[0055] An upper electrode 460 (anode) is laminated (second electrode layer) on the light-emitting layer 450. The upper electrode 460 is an electrode that can transmit (is transmissive to) light of the wavelength emitted by the light-emitting layer 450. For this reason, a material containing indium tin oxide (ITO) is used as a transparent electrode for the upper electrode 460 in this example. An indium tin oxide electrode has a transmittance of 80% or more for light in the visible light range, making it suitable as an electrode for organic EL.

[0056] The upper electrode 460 is formed on the opposite side of the lower electrodes 410-1 to 410-748, with at least the light-emitting layer 450 sandwiched between them. That is, in the Z direction, the light-emitting layer 450 is disposed between the upper electrode 460 and the lower electrodes 410-1 to 410-748. When the lower electrodes 410-1 to 410-748 are projected onto the upper electrode 460 in the Z direction, the region where the lower electrodes 410-1 to 410-748 are formed falls within the region where the upper electrode 460 is formed. Note that the transparent electrode does not need to be stacked over the entire light-emitting layer 450. However, in order to efficiently emit light from the light-emitting layer 450, it is preferable that the area occupied by the upper electrode 460 is 100% or more, and more preferably 120% or more, of the area occupied by one pixel. The upper limit of the area occupied by the upper electrode 460 can be arbitrarily designed depending on the areas of the silicon substrate 402 and the light-emitting layer 450. Wiring may be provided in the upper electrode 460 except for the portion that transmits light.

[0057] The drive circuit controls the potential of each of the lower electrodes 410-1 to 410-748 based on image data to generate a potential difference between the upper electrode 460 and any one of the lower electrodes 410-1 to 410-748.

[0058] The example of the substrate 502 having an OLED described so far is a so-called top-emission type emission device. When a voltage is applied to the upper electrode 460, which is an anode, and the lower electrode 410, which is a cathode, a potential difference is generated between them. Electrons flow from the cathode into the light-emitting layer 450, and holes flow from the anode into the light-emitting layer 450. The electrons and holes then recombine in the light-emitting layer 450, causing the light-emitting layer 450 to emit light. When the light-emitting layer 450 emits light, light directed toward the upper electrode 460 passes through the upper electrode 460 and is emitted from the substrate 502 in the direction of arrow A shown in FIG. 6 . Light directed from the light-emitting layer 450 toward the lower electrode 410 is reflected by the lower electrode 410 toward the upper electrode 460, and the reflected light also passes through the upper electrode 460 and is emitted from the substrate 502. There is a time difference between the timing of emission from the upper electrode 460 of the light emitted directly from the light-emitting layer 450 toward the upper electrode 460 and the light reflected by each lower electrode 410 and emitted from the upper electrode 460. However, because the thickness of the substrate 502 is extremely small, the two can be considered to be emitted almost simultaneously.

[0059] By using a transparent electrode such as indium tin oxide as the upper electrode 460, the aperture ratio, which indicates the light transmittance of the electrode, can be made substantially equal to the transmittance of the upper electrode 460. In other words, since there is substantially no portion other than the upper electrode 460 that attenuates or blocks light, the light emitted from the light-emitting layer 450 is attenuated as little as possible or becomes emitted light without being blocked.

[0060] When light-emitting layer 450 is made of a moisture-sensitive light-emitting material such as an organic EL layer or an inorganic EL layer, it is desirable to seal light-emitting region 604 to prevent moisture from entering. As a sealing method, for example, a sealing film is formed, which is a single or laminated thin film of silicon oxide, silicon nitride, aluminum oxide, or the like. A method that has excellent coating performance for structures such as steps is preferable as a method for forming the sealing film, and for example, atomic layer deposition (ALD) can be used.

[0061] As described above, when an OLED is used as a light source that emits light to expose the photosensitive drum 103, the upper electrode 460 is formed on the light-emitting layer 450. The "light emission surface" of the substrate 502 refers to the surface of the substrate 502 on which the upper electrode 460 is formed. In other words, the surface of the substrate 502 from which light is emitted from the OLED is defined as the "light emission surface."

[0062] The following description will be given again by taking as an example the substrate 502 that uses the LED 503, which is not an organic EL, as a light source. Figures 7(a) and 7(b) are diagrams for explaining the substrate 502 that uses the LED 503 as a light source.

[0063] 7(a) is a view of the light emitting surface 502T of the substrate 502 viewed in a direction perpendicular to the light emitting surface 502T. In the figure, the Y direction is the short-side direction of the substrate 502, and the X direction is the long-side direction of the substrate 502. The LED chips 639 are arranged along the long-side direction of the substrate 502.

[0064] The "light exit surface" is the side of the substrate 502 on which the photosensitive drum 103 is arranged, and can also be said to be the surface including the LED 503 (light emitting portion).

[0065] The width of the substrate 502 in the short direction is preferably 5 mm or more and 10 mm or less. In order to expose the photosensitive drum 103, the optical print head 105 needs to be placed close to the photosensitive drum 103. However, since the charger 104 and the developing unit 641 are located near the photosensitive drum 103, the image forming apparatus 1 itself needs to be enlarged to ensure sufficient space. Therefore, it is preferable to design the width of the substrate 502 to be 10 mm or less.

[0066] On the other hand, it is necessary to provide wiring for driving the LED chip 639 and space for mounting electronic components 950 and 951, which will be described later, on the substrate 502. Therefore, even if the width of the substrate 502 in the short direction is narrowed, a width of about 5 mm is still required.

[0067] FIG. 7(b) is a diagram illustrating the mounting surface 502B, which is the back surface of the substrate 502. Electronic components 950 and 951 for driving the LED chips 639 are provided on the mounting surface 502B. Examples of the electronic components 950 and 951 include driver integrated circuits (ICs). In this embodiment, a connector 504 is provided between the electronic components 950 and 951. Power is supplied to the electronic components 950 and 951 via the connector 504. Furthermore, locating the electronic components 950 (951) or wiring patterns close to the edge of the substrate 502 is undesirable in terms of stability and quality during mass production of the substrate 502. Therefore, it is preferable to provide a space of approximately 1 to 2 mm between the electronic components 950 (951) or wiring patterns and the edge of the substrate 502. Taking all of these factors into consideration, it is preferable that the width of the substrate 502 in the short direction be 5 mm or more.

[0068] (Optical print head detailed configuration) Next, we will explain the detailed configuration of optical print head 105. Figure 8 is a schematic perspective view of optical print head 105 provided in image forming apparatus 1 of this embodiment. Figure 9 is a cross-sectional view of optical print head 105 showing the positional relationship between holding member 505 and parts around lens array 506.

[0069] As described above, the optical print head 105 has an elongated shape (longitudinal shape) extending in the direction of the rotation axis of the photosensitive drum 103. The optical print head 105 also includes a holding member 505, a lens array 506, and a substrate 502.

[0070] As described above, the holding member 505 is made of metal. For example, the holding member 505 is formed into a U-shape by pressing a metal plate such as a thin iron plate. The shape of the holding member 505 will be described below.

[0071] (Shape of holding member) 8 and 9, the holding member 505 has a flat portion 802 in which a first opening 701 into which the lens array 506 is inserted is formed. The holding member 505 also has an extending portion 804R extending from one side in the short direction of the flat portion 802 in a direction away from the photosensitive drum 103. The holding member 505 also has an extending portion 804L extending from the other side in the short direction of the flat portion 802 in a direction away from the photosensitive drum 103. Furthermore, on the charger side (the other side in the short direction) of the holding member 505, the flat portion 802 and the extending portion 804L are connected by a connecting portion 808. The connecting portion 808 is an inclined surface between the flat portion 802 and the substrate support portion 804R that intersects with the flat portion 802 and the substrate support portion 804R and is provided in a direction away from the charger 104. The extending portions 804R and 804L form a substrate support portion 804 in the holding member 505 for supporting the substrate 502 inserted through the second opening 803. The flat portion 802, the substrate support portions 804 (804R, 804L), and the connecting portion 808 are integral with each other to form the holding member 505 that holds the lens array 506 and the substrate 502, and are formed in a substantially U-shape. By forming the holding member 505 in a substantially U-shape, a second opening 803 is formed on the opposite side to the flat portion 802. The second opening 803 is formed between the substrate support portions 804 (extending portions 804L, 804R) that extend from the flat portion 802 to the side away from the photosensitive drum.

[0072] Substrate 502 is inserted from second opening 803, that is, from the underside of U-shaped holding member 505, and is adhered with adhesive to the inside of each substrate support portion 804 (the inside of extension portion 804L and the inside of extension portion 804R). Note that the position of substrate 502 in the focal direction is determined by a jig (not shown), and therefore optical print head 105 does not include a positioning means for substrate 502 in the focal direction.

[0073] The lens array 506 is also inserted into the first opening 701 formed in the flat portion 802 and bonded to the flat portion 802 with an adhesive. The lens array 506 is fixed to the flat portion 802 (holding member 505) after its position and tilt in the focus direction are adjusted using a jig so that the distance in the focus direction between all of the LED chips 639 mounted on the substrate 502 and the lens array 506 is a predetermined value. The lens array 506 is also fixed to the flat portion 802 with an adhesive at multiple locations in the longitudinal direction. That is, the optical print head of this embodiment has multiple bonding locations in the longitudinal direction of the flat portion 802 where the lens array 506 inserted into the first opening 701 is bonded to the flat portion 802.

[0074] As described above, the substrate 502 and the lens array 506 are held by the holding member 505, so that the LEDs 503 face the incident surface 506b of the lens array 506. Light emitted from the LEDs 503 enters the incident surface 506b and is emitted from the exit surface 506a toward the photosensitive drum 103.

[0075] 9, the holding member 505 holds the substrate 502 inside the pair of substrate support portions 804, 804 (extension portions 804R, 804L). Therefore, as shown in FIG. 9, the interval W0 between the substrate support portion 804R and the substrate support portion 804L, in other words, the interval (distance) W0 between the pair of substrate support portions 804R, 804L, is wider than the width of the substrate 502 in the short-side direction of the substrate 502.

[0076] After the positions of the substrate 502 and the lens array 506 are adjusted and fixed to the holding member 505, a gap 723 between the substrate support portion 804 and the substrate 502 is sealed in the longitudinal direction with a sealant 805. Similarly, a sealant 800 is applied to a gap 724 between the lens array 506 inserted into the first opening 701 and the flat portion 802, and the gap 724 is sealed in the longitudinal direction with the sealant 800.

[0077] 9 and 10, the holding member 505 further has a blocking portion 801 for blocking the sealant 800 applied to the gap 724 between the lens array 506 inserted into the first opening 701 and the flat portion 802. FIG. 10 is a diagram showing the top surface of the optical print head 105, illustrating the positional relationship between the lens array 506 and the blocking portion 801. In FIG. 10, the X direction is the longitudinal direction of the flat portion 802, and the Y direction is the lateral direction perpendicular to the longitudinal direction of the flat portion 802. The blocking portion 801 is provided on the flat portion 802 and extends along the longitudinal direction of the first opening 701. The blocking portions 801 are provided on both sides of the first opening 701 in the lateral direction perpendicular to the longitudinal direction of the flat portion 802. The blocking portion 801 separates the flat portion 802 in the short direction of the flat portion 802 into a first flat portion 806 that is continuous with the edge of the first opening 701 and a second flat portion 807 that is interposed between the first flat portion 806 and the edge of the first opening 701. In other words, the first flat portion 802 forms the edge of the first opening 701. Furthermore, in the short direction of the flat portion 802, the first flat portion 806 is disposed between the first opening 701 and the second flat portion 806.

[0078] The damming portion 801 has a concave shape that forms a step between the first flat portion 806 and the flat portion 802 in the short direction. The concave shape of the damming portion 801 is formed by stamping. More specifically, the concave shape of the damming portion 801 is created by including a stamping process when the holding member 505 is press-formed.

[0079] As described above, the damming portions 801 are provided on both sides of the first opening 701 in the short-side direction perpendicular to the long-side direction of the flat portion 802. As shown in Fig. 9 , the damming portions 801 separate the flat portion 802 into the first flat portion 806 and the second flat portion 807 in the short-side direction of the flat portion 802, such that the first flat portion 806 is interposed between the first opening 701 and the second flat portion 807. Therefore, the sealant 800 applied to the gap 724 between the lens array 506 inserted in the first opening 701 and the flat portion 802 is blocked by the damming portions 801 in the following manner.

[0080] The applied sealant 800 flows from the side surface of the lens array 506 in the short-side direction of the flat portion 802 toward the outside in the short-side direction of the holding member 505 until the surface hardens. However, the sealant 800 is blocked by the first flat portion 806 and the concave-shaped blocking portion 801 provided between the first opening 701 and the blocking portion 801, and is prevented from flowing out to the second flat portion 807 provided outside the blocking portion 801. Specifically, a first blocking occurs due to the surface tension of the sealant 800 at the step between the first flat portion 806 and the blocking portion 801. Furthermore, if the sealant 800 cannot be blocked by the first blocking, the sealant 800 accumulates in the concave shape of the blocking portion 801, which functions as a second blocking.

[0081] The sealant 800 applied to the gap 724 flows from the longitudinal end face of the lens array 506 toward the longitudinal outside of the holding member 505 in the longitudinal direction of the flat portion 802 until the surface hardens. If the longitudinal length of the damming portion 801 is set equal to or shorter than that of the lens array 506, the sealant 800 flowing in the longitudinal direction may go around the damming portion 801 and flow out to the second flat portion 807. Therefore, in this embodiment, as shown in FIG. 10 , the damming portion 801 is set to be longer in the longitudinal direction of the flat portion 802, extending outward in the longitudinal direction than the first opening 701. As a result, the sealant 800 flowing in the longitudinal direction is blocked by the damming portion 801, and is prevented from flowing out to the second flat portion 807 provided outside the damming portion 801.

[0082] As described above, the blocking portion 801 configured as described above can be easily fabricated by incorporating a stamping process into the press working of the holding member 505. If a holding member 505 made of metal (e.g., steel plate) were to have a sloped shape around the lens array, as with a holding member made of resin, bending or drawing would be required in a narrow area, significantly degrading the dimensional accuracy of the holding member 505. In contrast, the blocking portion 801 of this embodiment can be sufficiently effective even with a shallow stamping depth of, for example, about 0.2 mm. Therefore, compared to the configuration with a sloped shape, the impact on the dimensional accuracy of the holding member 505 can be reduced. Furthermore, the width (length in the short direction) of the flat portion 802 of the blocking portion 801 is 0.5 mm or less. Because the blocking portion 801 functions satisfactorily even with a width of 0.5 mm or less, the width of the holding member 505 can be narrower than when the blocking portion is formed by bending or drawing, thereby enabling the image forming apparatus to be more compact.

[0083] 9 is rectangular, other shapes may be used as long as a step is formed between the first flat surface portion 806 and the damming portion 801 and the recessed shape functions as a depositing portion for the sealant. The recessed shape of the damming portion 801 may be, for example, a V-shape as shown in FIG. 11 or a trapezoidal shape as shown in FIG. 12. By configuring it in this way, the same effect can be obtained.

[0084] Furthermore, in this embodiment, the damming portions 801 are provided continuously in the longitudinal direction of the holding member 505 as shown in FIG. 10 , but the present invention is not limited to this. For example, the damming portions 801 may be provided intermittently as shown in FIG. 13 . In this case, in the region between the damming portions 801 in the longitudinal direction of the holding member 505, the flow rate of the sealant 800 flowing from the side surface of the lens array 506 toward the outside in the lateral direction of the holding member 505 is regulated to some extent by the damming action of the damming portions 801 on both longitudinal sides of the region and the surface tension of the sealant 800 in the region. There is no problem as long as the flow rate of the sealant is within the width of the damming portions 801.

[0085] In this embodiment, the blocking portion 801 is provided linearly in the longitudinal direction of the holding member 505, but this is not limiting. For example, if the flat portion 802 has a plurality of bonding locations along the longitudinal direction for bonding and fixing the lens array 506 to the holding member, it is expected that the sealant 800 applied to the bonding locations will protrude further in the lateral direction of the optical print head 105 than the areas other than the bonding locations. In such bonding locations, as long as the width of the second flat portion 807 can be ensured, the blocking portion 801 may be shaped to protrude in the lateral direction of the holding member 505 only at the bonding locations, as shown in FIG. 14 . In other words, the blocking portion 801 may have protruding portions 801a that are wider in the lateral direction of the flat portion 802 at the bonding locations than at the areas other than the bonding locations. By providing the protruding portion 801a in the region of the adhesive portion in this manner, the sealant 800 applied to the gap 724 can be prevented from flowing out onto the second flat portion 807 of the holding member 505, even in the region of the adhesive portion.

[0086] (Positional relationship between cleaning mechanism and optical print head) As mentioned above, if foreign matter such as toner adheres to the light-emitting surface of the lens array 506, it will partially block the light emitted from the light-emitting elements, resulting in a deterioration in the quality of the output image. Therefore, the light-emitting surface of the lens array 506 must be cleaned periodically. In this embodiment, the image forming apparatus has a cleaning rod 900 as cleaning means for cleaning the lens array 506 of the optical print head 105. The cleaning rod 900 for cleaning the lens array 506 will now be described in detail.

[0087] FIG. 15 is a perspective view of cleaning rod 900. Cleaning rod 900 is generally rod-shaped and elongated in the longitudinal direction. Cleaning rod 900 has a rod-shaped body 903 with a U-shaped cross section, and includes a handle 902 at one end and a cleaning part 901 at the other end. Note that while cleaning part 901, handle 902, and body 903 are illustrated as a single unit, they may alternatively be separate and detachable. Additionally, cleaning rod 900 may be provided on, for example, a cover member (not shown) within the image forming apparatus, or it may be provided outside the image forming apparatus and used when cleaning is required.

[0088] 16 is an enlarged perspective view of cleaning part 901. Cleaning rod 900 for cleaning optical print head 105 has cleaning part 901 that comes into contact with the surface of lens array 506 to clean it. In this example, cleaning part 901 has cleaning blade 906 that comes into contact with the surface of lens array 506 to clean that surface. Cleaning rod 900 also has seat 907, which is a contact part that comes into contact with second flat part 807 of holding member 505 to regulate the position (amount of penetration) of cleaning part 901 relative to the surface (emission surface) of lens array 506.

[0089] A magnet 904 is fixed to the tip of the body 903 of the cleaning rod 900, and yokes 905 for concentrating magnetic flux are fitted on both sides of the magnet. By concentrating the magnetic flux using the yokes 905, the magnetic flux density generated by the magnet 904 is effectively concentrated, thereby increasing the magnetic force. A cleaning blade 906 serving as the cleaning part 901 is provided between the two yokes 905 in a position facing the lens array 506 when the cleaning rod 900 is fitted into the optical print head 105. The cleaning blade 906 is a 0.5 mm thick urethane rubber blade, and one side of its L-shape is attached to the body 903 with double-sided tape. Note that the thickness and material of the cleaning blade 906 are merely examples, and other materials such as silicone rubber may also be used. The cleaning part 901 is not limited to a blade; it may be configured as a sponge with a nonwoven fabric attached to its surface.

[0090] The seating surface 907 is provided on the side surface of the yoke 905. As described above, the seating surface 907 is a contact portion that comes into contact with the second flat surface portion 807 of the holding member 505 in order to keep the penetration amount of the cleaning blade 906 into the lens array 506 constant.

[0091] FIG. 17 is a cross-sectional view showing the positional relationship between the cleaning rod 900 and the optical print head 105 during cleaning. The U-shaped cross section of the body 903 is designed so that the width of its recess fits perfectly into the holding member 505 of the optical print head 105. The cleaning rod 900 is attracted to the optical print head 105 by the magnetic force between the yoke 905 and the holding member 505, and the second flat portion 807 of the holding member 505 abuts against the seating surface 907 of the cleaning rod 900. This maintains a constant penetration depth (position) of the cleaning blade 906 relative to the lens array 506. The cleaning blade 906 is designed to interfere with the exit surface 506a of the lens array 506. Therefore, when the cleaning rod 900 slides along the optical print head 105, the tip of the cleaning blade 906 wipes the exit surface 506a of the lens array 506, removing any foreign matter. The penetration depth of the cleaning blade 906 relative to the lens array 506 is, for example, approximately 0.5 mm. To ensure stable sliding of the exit surface 506a of the lens array 506 despite the repulsive force caused by interference, it is desirable that the attractive force generated between the cleaning part 901 and the holding member 505 be at least 200 gf. In this embodiment, the magnet 904 is a ferrite magnet measuring 6 mm x 3 mm x 15 mm, and the yoke 905 is an electrogalvanized steel plate with a contact width of 14 mm and a thickness of 1 mm. This combination generates an attractive force of 500 gf or more in the vertical direction. It is important that the magnetic force between the yoke 901 and the holding member 505 generates an attractive force that attracts the cleaning rod 900 to the optical print head 105. Therefore, the magnet 904 in this embodiment is merely an example. For example, the magnet may be a neodymium magnet or a samarium-cobalt magnet, and the shapes and sizes of the magnet 904 and the yoke 905 are not limited to these.

[0092] The actual cleaning operation will be described with reference to Figure 18. When cover 558 (see Figure 2) provided on the front of image forming apparatus 1 is opened, optical print head 105 moves to the retracted position shown in Figure 18, and cleaning rod 900 is inserted into insertion portion 550 of exposure unit 500. Body portion 903 is guided and fitted into holding member 505 by insertion portion 550, and cleaning rod 900 is moved back and forth using holding member 505 as a rail to clean lens array 506. At this time, regardless of the position of cleaning rod 900 in the longitudinal direction of optical print head 105, seating surface 907 of cleaning rod 900 contacts second flat portion 807 of holding member 505, and seating surface 907 does not contact sealant 800.

[0093] As described above, according to this embodiment, the sealant 800 applied to the gap 724 between the lens array 506 inserted in the first opening 701 and the flat portion 802 is blocked by the blocking portion 801, preventing the sealant 800 from flowing to unintended locations in the holding member 505. Specifically, the sealant 800 can be prevented from flowing to the second flat portion 807 in the holding member 505. This allows the second flat portion 807 of the holding member 505 to be used as a location that comes into contact with the seating surface 907 of the cleaning rod 900 when cleaning the optical print head 105 with the cleaning rod 900.

[0094] In the above-described embodiment, four image forming units are used, but the number of units used is not limited to this and may be set appropriately as required.

[0095] In the above-described embodiment, a printer is used as an example of an image forming apparatus, but the present invention is not limited to this. For example, other image forming apparatuses such as a copier or facsimile machine, or other image forming apparatuses such as a multifunction peripheral that combines the functions of these, may also be used. Furthermore, while the present invention is exemplified as an image forming apparatus that uses an intermediate transfer member, sequentially transfers toner images of each color onto the intermediate transfer member in a superimposed manner, and then transfers the toner images carried on the intermediate transfer member to a recording material all at once, the present invention is not limited to this. It may also be an image forming apparatus that uses a recording material carrier, sequentially transfers toner images of each color onto a recording material carried on the recording material carrier in a superimposed manner. Similar effects can be achieved by applying the present invention to optical printheads used in these image forming apparatuses. [Explanation of symbols]

[0096] 1, 2...Image forming device 102...Image forming unit 103...Photosensitive drum 104...Charger 105...Optical print head 500...Exposure unit 502... Circuit board 504...Connector 505...Holding member 506...Lens array 506a...Emission surface 506b…Incidence surface 518...Drum unit 520...Exposure unit 641...Developing unit 701...First opening 723,724...Gap 800...Sealant 801...damming part 801a…Outcall Department 802…Plane part 803...Second opening 804...Substrate support part 804L, 804R…Extension part (board support part) 805...Sealant 806...First plane part 807…Second plane part 900…Cleaning rod 901...Cleaning Department 906...Cleaning blade 907…Seat

Claims

1. an optical print head for exposing a photoreceptor, a substrate provided with a plurality of light-emitting units that emit light to expose the photosensitive member; a lens array having a plurality of lenses that condense the light emitted from the light emitting unit onto the photosensitive member; a holder that holds the substrate and the lens array, The holder is an opposing surface formed with an opening into which the lens array is inserted, the opposing surface facing the photosensitive member in the optical axis direction of the lenses; a groove formed on the opposing surface, the groove including a first region that overlaps with the lens array when viewed from a short-side direction perpendicular to the longitudinal direction of the holder and the optical axis direction, and a second region that does not overlap with the lens array when viewed from the short-side direction; a sealant that seals a gap between a sidewall of the lens array and an edge of the opening, the sealant being applied between the groove and the sidewall; the holder has a contact surface against which a cleaning rod for cleaning the light exit surface of the lens array comes into contact, and the groove is a groove for preventing the sealant applied between the groove and the side wall from flowing onto the contact surface. An optical print head characterized by:

2. 2. The optical print head according to claim 1, wherein the opposing surface has a coating area between the opening and the groove where the sealant is applied.

3. 3. The optical print head according to claim 2, wherein the holder has a contact surface against which a cleaning rod that cleans the light exit surface of the lens array contacts, and the application area and the contact surface are flat surfaces that are on the same plane.

4. the sealant seals a gap between another side wall of the lens array opposite to the side wall and another edge of the opening facing the other side wall; 4. The optical print head according to claim 3, wherein the opposing surface has another abutment surface against which the cleaning rod abuts on the opposite side of the abutment surface with respect to the lens array, and another groove is formed between the opening and the other abutment surface.

5. 2. The optical print head according to claim 1, wherein the holder is made of metal.

6. 2. The optical print head according to claim 1, wherein the width of the groove is narrower than the width of the lens array in a direction perpendicular to the longitudinal direction and the optical axis direction of the lenses.

7. 2. The optical print head according to claim 1, wherein said lens array is fixed to the edge of said opening at a plurality of locations in said longitudinal direction with an adhesive.

8. 2. The optical print head according to claim 1, wherein the light-emitting portion is an organic electroluminescent layer.

9. 2. The optical print head according to claim 1, wherein the grooves are arranged along the longitudinal direction.

10. 10. The optical printhead of claim 9, wherein the groove is longer than the lens array in the longitudinal direction.

11. An image forming apparatus having a photoreceptor and an optical print head that exposes the photoreceptor, 11. An image forming apparatus comprising the optical print head according to claim 1 as the optical print head.

12. an optical print head for exposing a photoreceptor, a substrate provided with a plurality of light-emitting units that emit light to expose the photosensitive member; a lens array having a plurality of lenses that condense the light emitted from the light emitting unit onto the photosensitive member; a holder that holds the substrate and the lens array, The holder is an opposing surface formed with an opening into which the lens array is inserted, the opposing surface facing the photosensitive member in the optical axis direction of the lens array; a groove formed on the opposing surface, the groove at least partially overlapping with the lens array when viewed from a short side direction perpendicular to the longitudinal direction of the lens array and the optical axis direction; a sealant that seals a gap between a sidewall of the lens array and an edge of the opening, the sealant being applied between the groove and the sidewall; The groove is formed along the longitudinal direction, In the longitudinal direction, the length of the groove is longer than the length of the lens array, the holder has a contact surface against which a cleaning rod for cleaning the light exit surface of the lens array comes into contact, and the groove is a groove for preventing the sealant applied between the groove and the side wall from flowing onto the contact surface. An optical print head characterized by:

13. 13. The optical print head according to claim 12, wherein one end of the groove in the longitudinal direction extends to the outside of one end of the lens array, and the other end of the groove extends to the outside of the other end of the lens array.

14. 13. The optical printhead of claim 12, wherein the groove has a rectangular cross section.

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