Optical device, image formation device, and reading device

Abstract

To suppress variation in focal positions of a plurality of optical elements in a longitudinal direction to keep printing quality.SOLUTION: An LED head 16 includes: a substrate 55 to which a plurality of LED chips 76 is mounted in a longitudinal direction; a lens array 53 installed on an optical path for light between the LED chips 76 and a photoreceptor drum 35 and allowing light to pass therethrough; paste 80 provided between the substrate 55 and the LED chips 76 to bond the substrate 55 to the LED chips 76; and a curative agent pillar 70 provided between the substrate 55 and the LED chips 76 and made of a material different from that of the paste 80.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to an optical device, an image forming apparatus, and a reading apparatus, and is suitable for application to an exposure device mounted in an electrophotographic image forming apparatus, for example. [Background technology]

[0002] Conventionally, a widely used image forming apparatus prints an image by irradiating the surface of a photosensitive drum with light from an exposure device that emits light for exposure, forming an electrostatic latent image on the surface of the photosensitive drum, and then developing the toner image by attaching toner to the electrostatic latent image. An example of this exposure device is an LED head that uses light emitted from an LED (Light Emitting Diode) chip as an optical element that is a light-emitting element (see, for example, Patent Document 1).

[0003] An LED head may include, for example, a substrate on which an LED array in which multiple LED chips are arranged in a line is mounted, a lens unit in which multiple lenses are aligned to focus the light emitted from each LED chip, and a holder that holds the substrate and the lens unit.The light emitted from the LED array mounted on the substrate passes through the lens unit and is focused, and is exposed to the surface of a photosensitive drum disposed at the imaging position of the lens unit, thereby forming an electrostatic latent image.

[0004] In addition, conventionally, a reading device that reads an image on a document by irradiating the surface of the document with light from a lamp and receiving the light reflected by the surface of the document into a light receiving device has been widely used. An example of this light receiving device is a reading head that uses light incident on a CCD (Charge Coupled Device) sensor chip, which is an optical element serving as a light receiving element. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-183945 Summary of the Invention [Problem to be solved by the invention]

[0006] In such image forming apparatuses and reading devices, it is desirable to maintain quality by suppressing variations in focal positions of a plurality of optical elements in the longitudinal direction.

[0007] The present invention has been made in consideration of the above points, and aims to propose an optical device, an image forming device, and a reading device that can maintain quality. [Means for solving the problem]

[0008] In order to solve this problem, the optical device of the present invention comprises a substrate on which a plurality of optical elements are mounted in the longitudinal direction, a lens unit that is arranged on the optical path of light between the optical elements and the object and that allows the light to pass through, an adhesive member that is arranged between the substrate and the optical elements and that bonds the substrate and the optical elements, and a cured body that is arranged between the substrate and the optical elements and is made of a material different from the adhesive member.

[0009] The image forming apparatus of the present invention is also provided with an exposure device, which is the optical device described above.

[0010] Furthermore, the reading device of the present invention is provided with a light receiving device which is the optical device described above.

[0011] According to the present invention, unevenness on the surface of the substrate is absorbed by the cured body before the optical elements are mounted on the substrate, thereby making it possible to suppress variation in the focal positions of the plurality of optical elements in the longitudinal direction. [Effects of the Invention]

[0012] According to the present invention, by mounting light-emitting elements on a substrate after the unevenness of the surface of the substrate is absorbed by a cured body, it is possible to suppress variation in the focal positions of multiple light-emitting elements in the longitudinal direction, thereby realizing an optical device, an image forming device, and a reading device that can maintain print quality. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 2 is a left side view showing the configuration of the color printer. [Figure 2] FIG. 2 is a left side view showing the configuration of the image forming unit. [Figure 3] FIG. 2 is a cross-sectional view showing the configuration of the LED head. [Figure 4] FIG. 1 is a bottom view showing a configuration (1) of a part of a substrate, an LED array, and a hardener column according to the first embodiment. [Figure 5] 5 is a cross-sectional view taken along the line AA in FIG. 4, showing a configuration (2) of a part of the substrate, the LED array, and the hardener column according to the first embodiment. FIG. [Figure 6] 10A to 10C are cross-sectional views showing a method for forming a hardener pillar. [Figure 7] FIG. 2 is a vertical cross-sectional view showing the configuration of a substrate on which irregularities have occurred. [Figure 8] FIG. 1 is a vertical cross-sectional view showing the configuration of a substrate on which a thick paste is applied and an LED array. [Figure 9] 10 is a graph showing the focal position of an LED head. [Figure 10] FIG. 10 is a bottom view showing a configuration (1) of a part of a substrate, an LED array, and a hardener column according to the second embodiment. [Figure 11] 11 is a cross-sectional view taken along the line AA in FIG. 10, showing a configuration (2) of a part of the substrate, the LED array, and the hardener column according to the second embodiment. FIG. [Figure 12] FIG. 10 is a side view showing the configuration of a scanner according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, modes for carrying out the invention (hereinafter referred to as embodiments) will be described with reference to the drawings. 1. First Embodiment [1-1. Color printer configuration] As shown in FIG. 1, color printer 1 is a color electrophotographic printer that prints a desired color image on paper P, such as A3 or A4 size paper. Color printer 1 has various components arranged inside a roughly box-shaped printer housing 2. In the following description, the right-hand side of FIG. 1 is the front of color printer 1, and the up-down, left-right, and front-rear directions are defined when viewed from the front. Color printer 1 is controlled overall by a control unit 3. This control unit 3 is connected wirelessly or wired to a host device (not shown) such as a personal computer via a communications processing unit (not shown). When image data representing a color image to be printed is provided from the host device and a command to print the color image is received, the control unit 3 executes a printing process to form the print image on the surface of paper P.

[0015] At the bottom of the printer housing 2 are provided a paper storage cassette 4 that stores paper P, and a paper feed unit 5 that separates and feeds the paper P stored in a stacked state in the paper storage cassette 4 one sheet at a time. The paper feed unit 5 is located above the front end of the paper storage cassette 4, and is composed of multiple rollers such as a hopping roller 7 that is located above the front end of the paper storage cassette 4 and has its central axis facing left and right, and a registration roller 8 that is located above the hopping roller 7, as well as guides that guide the paper P.

[0016] Under the control of the control unit 3, the paper feed unit 5 rotates the hopping roller 7, registration roller 8, etc., to separate and take in the paper P stored in the paper storage cassette 4 one sheet at a time, and then advances the taken-in paper P forward and upward, and then folds it back at a position that is approximately centered vertically near the front end of the printer housing 2.

[0017] A transfer belt unit 10 is provided above the paper storage cassette 4 within the printer housing 2, spanning a large area across the printer housing 2 from front to back. The transfer belt unit 10 has two rollers 11, each of which is a long, thin cylinder with its central axis oriented in the left-right direction, arranged at the front and rear, and a transfer belt 12 is stretched around the front and rear rollers 11. The transfer belt 12 is formed as an endless belt that is wide in the left-right direction and moves in accordance with the rotation of the rollers 11. The transfer belt unit 10 rotates the rollers 11 under the control of the control unit 3, causing the transfer belt 12 to move, and the paper P delivered from the paper supply unit 5 is placed on the top surface of the transfer belt 12 and transported rearward.

[0018] Meanwhile, above the transfer belt unit 10, i.e., above the center of the printer housing 2, four image forming units 15C, 15M, 15Y, and 15K (hereinafter collectively referred to as image forming units 15) shown in FIG. 2 are arranged in order from rear to front. That is, the image forming units 15 for each color are arranged in tandem. The image forming units 15C, 15M, 15Y, and 15K correspond to the colors cyan (C), magenta (M), yellow (Y), and black (K), respectively. The image forming units 15C, 15M, 15Y, and 15K are configured identically, differing only in the color of the toner they use. Each image forming unit 15 is formed in a generally box-like shape that is relatively long in the left-right direction to accommodate the left-right width of the paper P.

[0019] Also provided within the printer housing 2 are LED heads 16C, 16M, 16Y, and 16K (hereinafter collectively referred to as LED heads 16) corresponding to the image forming units 15C, 15M, 15Y, and 15K, respectively. Each LED head 16 is configured as a rectangular parallelepiped elongated in the left-right direction, and has multiple LEDs (Light Emitting Diodes) arranged side by side within it, and each LED emits light in an illumination pattern corresponding to image data supplied from the control unit 3. When the image forming units 15 are attached to the printer housing 2, they are positioned very close to the LED heads 16, and exposure processing is performed using light from the LED heads 16.

[0020] Toner cartridges 18C, 18M, 18Y, and 18K (hereinafter collectively referred to as toner cartridges 18) are connected to the upper portions of the image forming units 15C, 15M, 15Y, and 15K, respectively. Each toner cartridge 18 is a hollow container elongated in the left-right direction, containing powdered toner of each color and incorporating a predetermined stirring mechanism. Transfer rollers 13C, 13M, 13Y, and 13K (hereinafter collectively referred to as transfer rollers 13) are provided in four locations directly below each image forming unit 15 between the front and rear rollers 11. Each image forming unit 15 sandwiches the upper portion of the transfer belt 12 between itself and the corresponding transfer roller 13. The transfer rollers 13 are configured to be electrically charged.

[0021] The control unit 3 supplies toner from the toner cartridges 18 to the image forming units 15. At the same time, the control unit 3 causes the LED heads 16 to emit light so as to form an emission pattern corresponding to image data supplied from a host device (not shown). In response, each image forming unit 15 uses the toner supplied from the toner cartridges 18 to form a toner image corresponding to the emission pattern of the LED heads 16, and transfers this toner image onto the paper P (details will be described later). As a result, four-color toner images corresponding to the image data are sequentially transferred onto the paper P being transported by the transfer belt unit 10.

[0022] A fixing unit 20 is provided behind the transfer belt unit 10, i.e., near the vertical center near the rear end of the printer housing 2. The fixing unit 20 is composed of a heating roller 21 and a pressure roller 22. The heating roller 21 is cylindrical with its central axis oriented in the left-right direction and has a heater installed inside. The pressure roller 22 is cylindrical like the heating roller 21 and presses its upper surface against the lower surface of the heating roller 21 with a predetermined pressure. Under the control of the control unit 3, the fixing unit 20 heats the heating roller 21 and rotates the heating roller 21 and pressure roller 22 in predetermined directions. As a result, the fixing unit 20 applies heat and pressure to the paper P delivered from the transfer belt unit 10, i.e., the paper P on which a four-color toner image is superimposed, to fix the toner, and then delivers the paper P upward and rearward.

[0023] A paper discharge section 24 is disposed above and rearward of the fixing unit 20. The paper discharge section 24 is composed of a combination of multiple rollers (not shown) with central axes oriented in the left-right direction, guides for guiding the paper P, and the like. By appropriately rotating each roller under the control of the control section 3, the paper discharge section 24 conveys the paper P handed over from the fixing unit 20 toward the upper rear, then turns it back toward the front, and discharges it onto a discharge tray 2T formed on the top surface of the printer housing 2.

[0024] In this way, when color printer 1 executes printing processing, LED head 16 is caused to emit light, causing image forming units 15 of each color to form toner images, which are then transferred onto paper P in sequence.

[0025] [1-2. Image Forming Unit Configuration] Next, we will explain the configuration of image forming unit 15. As shown in Fig. 2, most of the outer periphery of image forming unit 15 is enclosed by a frame 31, and a relatively large space is formed inside.

[0026] A photosensitive drum 35 is provided near the lower center of the image forming unit 15. The photosensitive drum 35 is formed in a cylindrical shape with its central axis facing in the left-right direction, and is supported by the frame 31 so as to be rotatable about this central axis. Incidentally, the photosensitive drum 35 rotates in the direction of arrow R1 by receiving a driving force from a motor (not shown).

[0027] The portion of the frame 31 that will become the underside of the photosensitive drum 35 is open over a relatively large area. Therefore, when the image forming unit 15 is installed in the printer housing 2 (FIG. 1), the underside of the photosensitive drum 35 comes into contact with the transfer belt 12 or the paper P placed on the transfer belt 12. Also, a long, narrow exposure hole is formed in the left-right direction in the portion of the frame 31 that will be directly above the photosensitive drum 35.

[0028] A cylindrical charging roller 36 having a smaller diameter than the photosensitive drum 35 is provided above and behind the photosensitive drum 35. The charging roller 36 is made of, for example, a semiconductive elastic material, and its peripheral surface is in contact with the peripheral surface 35S of the photosensitive drum 35, uniformly charging the contact area of the peripheral surface 35S.

[0029] A cylindrical developing roller 38 with a smaller diameter than the photosensitive drum 35 is provided above and in front of the photosensitive drum 35. The developing roller 38 is made of semiconductive urethane rubber, for example, urethane rubber to which a conductive substance such as carbon has been added to appropriately adjust the electrical resistance, and can be charged. The rear peripheral surface of the developing roller 38 abuts against the peripheral surface 35S of the photosensitive drum 35, and the front peripheral surface of the developing roller 38 abuts against a cylindrical supply roller 39 with a slightly smaller diameter than the developing roller 38. The supply roller 39 is made of, for example, semiconductive foamed silicone sponge.

[0030] A thin plate-shaped developing blade 40 is provided above and behind the developing roller 38. The developing blade 40 is made of metal such as stainless steel or phosphor bronze, or rubber such as silicone rubber. The upper rear end of this developing blade 40 is fixed inside the frame 31, and a small gap is formed between the lower front end and the peripheral side surface of the developing roller 38.

[0031] In this configuration, when the image forming unit 15 prints an image on paper P, it rotates the photosensitive drum 35 in the direction of arrow R1, and rotates the charging roller 36, developing roller 38, and supply roller 39 in the direction of arrow R2 based on the control of the control unit 3, and further charges the charging roller 36 and developing roller 38.

[0032] First, the upper rear portion of the peripheral side surface 35S of the photosensitive drum 35 is uniformly charged by the charging roller 36, and as the photosensitive drum 35 rotates in the direction of arrow R1, this charged portion reaches the vicinity of the upper end and faces the LED head 16. At this time, the peripheral side surface 35S of the photosensitive drum 35 is exposed to light emitted from the LED head 16 in an emission pattern according to image data, and an electrostatic latent image according to the image data is formed.

[0033] On the other hand, as the developing roller 38 rotates in the direction of arrow R2, toner supplied from the toner cartridge 18 adheres to the peripheral surface by the supply roller 39, and then excess toner is scraped off by the developing blade 40, so that the toner adheres to the peripheral surface in the form of a uniform thin film.

[0034] As the photosensitive drum 35 continues to rotate in the direction of arrow R1, the toner formed as a thin film on the circumferential side of the developing roller 38 near the front end where it abuts against the developing roller 38 adheres to the circumferential side 35S only in areas corresponding to the electrostatic latent image. As a result, a toner image corresponding to the image data is formed on the circumferential side 35S of the photosensitive drum 35. Incidentally, the toner image formed on the circumferential side 35S at this time is an image that represents only the components of one color (i.e., cyan, magenta, yellow, or black) that this image forming unit 15 is responsible for, out of the image that will ultimately be printed.

[0035] Thereafter, photosensitive drum 35 further rotates in the direction of arrow R1, causing the toner image to reach the vicinity of the bottom edge. At this time, control unit 3 causes transfer belt unit 10 (FIG. 1) to cause paper P to reach the bottom of image forming unit 15, and also charges transfer roller 13 to have the opposite characteristics to that of the toner. As a result, image forming unit 15 sandwiches paper P between the part of photosensitive drum 35 on which the toner image is formed and charged transfer roller 13, and transfers this toner image to paper P. Incidentally, if toner remains on circumferential surface 35S of photosensitive drum 35 after the toner image has been transferred to paper P, this toner is removed by a cleaning device (not shown).

[0036] In this manner, the image forming unit 15 has the LED head 16 facing the vicinity of the photosensitive drum 35, and forms a toner image on the peripheral side surface 35S by the exposure action of the LED head 16.

[0037] [1-3. LED head configuration] Next, the configuration of the LED head 16 will be described. As shown in Fig. 3, the LED head 16 is formed as a rectangular parallelepiped elongated in the left-right direction as a whole, and various components are attached to a holder 51. Hereinafter, the downward direction in Fig. 3 will be referred to as the irradiation direction, and the upward direction will be referred to as the counter-irradiation direction. Also, below, the left-right direction in which the LED array 56 is arranged will be referred to as the arrangement direction (longitudinal direction, main scanning direction), the front-rear direction intersecting with this left-right direction will be referred to as the sub-scanning direction, and the up-down direction in which the optical axis of the lens array 53 is arranged will be referred to as the optical axis direction.

[0038] [1-4.Holder configuration] The holder 51 is fabricated, for example, by sheet metal press processing, to have a predetermined thickness. Its overall shape resembles a hollow rectangular prism with a holder internal space 51IS extending in the left-right direction, with the side surface opposite the illumination direction (upper side) removed, resulting in a cross section resembling the capital letter "U." The holder 51 is centered around a plate-like bottom 51B that is elongated in the left-right direction and thin in the up-down direction. Furthermore, the holder 51 has plate-like side portions 51W that are elongated in the left-right direction and thin in the front-to-back direction extending parallel to each other from both front and rear sides of the bottom 51B upward and perpendicular to the bottom 51B. A holder opening 51A is formed at the upper end. A lens array hole 51H, elongated in the left-to-right direction and thin in the front-to-back direction, is drilled approximately in the center of the bottom 51B in the front-to-back direction, penetrating the bottom 51B in the up-to-down direction.

[0039] The surfaces of the pair of front and rear side portions 51W facing the holder internal space 51IS, i.e., the rear surface of the front side portion 51W and the front surface of the rear side portion 51W, have holder inner wall surfaces 51WS, which are flat surfaces extending in the vertical and horizontal directions.

[0040] Furthermore, a lens array 53 is inserted into the lens array hole 51H and attached. In this way, the lens array 53 is supported by the holder 51. The lens array 53 is formed as a rectangular parallelepiped that is elongated in the left-right direction as a whole, and holds a large number of tiny lenses aligned in the left-right direction. These lenses have optical properties that converge light emitted from an LED array 56, which will be described later. The lens array 53 is fixed to the holder 51 at a position where the emission distance Lo between the lower surface, which is the end surface from which light is emitted in the lens array 53, and the circumferential side surface 35S of the photosensitive drum 35 on which the light is imaged, is an optimum value in terms of the characteristics of the lens array 53.

[0041] The gap between the bottom 51B of the holder 51 and the lens array 53 is filled with adhesive 62. The adhesive 62 is an ultraviolet-curing adhesive that hardens when irradiated with ultraviolet light. This allows the LED head 16 to fix the lens array 53 to the holder 51, seal the gap between the holder 51 and the lens array 53, and almost completely seal the space surrounded by the bottom 51B and front and rear side portions 51W of the holder 51 and the LED array placement surface 55S of the substrate 55, preventing light and foreign matter from entering this space.

[0042] Furthermore, a substrate 55 is attached to the holder 51 above the lens array 53, with its longitudinal direction aligned in the left-right direction and in contact with the adhesive 60. The substrate 55 is made of a so-called glass epoxy substrate, and is formed in the shape of a plate that is elongated in the left-right direction and thin in the up-down direction, with multiple conductive layers, each having a predetermined wiring pattern, stacked in the up-down direction.

[0043] [1-5. Circuit board configuration] As shown in Figures 3, 4, and 5, an LED array 56 is mounted on the LED array mounting surface 55S, which is the underside of the substrate 55, in a COB (chip-on-board) configuration along the longitudinal direction of the substrate 55, approximately at the center in the front-to-rear direction, facing the lens array 53. This LED array 56 is configured by arranging multiple (e.g., 37) LED chips 76, which are light-emitting elements, along the left-to-right direction so that light-emitting points that emit light downward are aligned at predetermined small intervals along the left-to-right direction. Each LED chip 76 has, for example, 380 light-emitting points along the left-to-right direction. These LED chips 76 are bonded to the substrate 55 by adhesive paste 80 applied between the LED chips 76 and the LED array mounting surface 55S of the substrate 55. The thickness of this paste 80 is approximately 15 μm. Note that the paste 80 between the LED chips 76 and the hardener columns 70 (described below) is not shown in Figure 5.

[0044] This substrate 55 is fixed to the holder 51 so that the incident distance Li (Figure 3) between the lower surface, which is the surface of the LED array 56, and the upper surface, which is the end face into which light is incident in the lens array 53, is the same as the exit distance Lo.

[0045] A driver IC (Integrated Circuit) (not shown) is mounted on the LED array arrangement surface 55S of the substrate 55. The driver IC is connected to a plurality of bonding pads 66 formed on the upper surface of each LED chip 76 by bonding wires 68, and controls the lighting and extinguishing of the LED chips 76.

[0046] 7, during the production stage, the substrate 55 may develop an uneven portion 77, which is a localized unevenness having a height of about 100 μm from the flat LED array mounting surface 55S. Although the uneven portion 77 protrudes from the LED array mounting surface 55S in FIG. 7, the uneven portion 77 may also develop as a recess in the LED array mounting surface 55S. FIGS. 4 and 5 are partial enlarged views of the substrate 55, the LED array 56, and the hardener column 70, including a portion of the uneven portion 77 (FIG. 7).

[0047] The LED array 56 is fixed to the substrate 55 with the paste 80, with the bottom surfaces of multiple cylindrical or truncated cone-shaped hardener columns 70 abutting against the top surfaces of the multiple hardener columns 70. The hardener columns 70 are formed in the area of the LED array mounting surface 55S where the LED array 56 is mounted. The multiple hardener columns 70 are discretely arranged between the substrate 55 and the LED array 56 along the longitudinal direction (left-right direction) of the LED array 56. Each of the multiple hardener columns 70 is positioned at the same position as the bonding pad 66 in the front-rear and left-right directions so that the bonding pad 66 is contained within its outer shape when viewed from below in a direction perpendicular to the LED array mounting surface 55S. The bottom surfaces of the multiple hardener columns 70 are formed so as to lie along a virtual plane parallel to the flat surface portion of the LED array mounting surface 55S. This virtual plane has sufficient flatness, for example, a flatness of 30 μm or less. Furthermore, the hardener pillars 70 protrude downward, for example, by 200 μm, from the flat surface portion of the LED array mounting surface 55S. Therefore, when the hardener pillars 70 are provided in the LED array mounting surface 55S at locations where convex portions of the uneven portion 77 are formed, they protrude downward, for example, by less than 200 μm, from the flat surface portion of the LED array mounting surface 55S. On the other hand, when the hardener pillars 70 are provided in the LED array mounting surface 55S at locations where concave portions of the uneven portion 77 are formed, they protrude downward, for example, by more than 200 μm, from the concave portions. The hardener pillars 70 are ultraviolet-curable adhesive that is cured by irradiation with ultraviolet light.

[0048] In this way, the color printer 1 provides multiple hardener columns 70 along the left-right direction in the area on the LED array placement surface 55S of the substrate 55 where the LED array 56 is mounted, and the single imaginary plane along which the bottom surfaces of these multiple hardener columns 70 that face and abut against the LED array 56 is aligned has sufficient flatness. Also, the color printer 1 is configured so that the LED chips 76 (i.e., the LED array 56) are fixed to the substrate 55 with the paste 80 in a state where the bottom surfaces of the hardener columns 70 abut against the top surfaces. Therefore, even if the LED array 56 is mounted in a location where an uneven portion 77 occurs on the LED array placement surface 55S of the substrate 55, the color printer 1 can mount the LED array 56 on a plane parallel to the flat surface portion of the LED array placement surface 55S as originally designed, after the unevenness of the uneven portion 77 is absorbed by the hardener columns 70. This allows the color printer 1 to maintain a constant position (i.e., focal position) where the light emitted from the LED array 56 passes through the underside of the lens array 53 and forms an image from one end to the other end of the LED array 56 in the longitudinal direction.

[0049] A protective film (not shown) is attached to the upper surface of the substrate 55, and the entire upper surface is covered with the protective film, thereby preventing exposure to the outside.

[0050] 3, adhesive 60 is applied to the upper surface of the protective film (not shown), the short-side end faces of the substrate 55, and the holder inner wall surface 51WS of the holder 51. Therefore, adhesive 60 is applied between the upper surface of the protective film 58 and the holder inner wall surface 51WS, and adhesive 60 is filled in the gap between the short-side end faces of the substrate 55 and the holder inner wall surface 51WS so as to fill this gap. In this way, the LED head 16 adheres the substrate 55, to which the protective film is fixed, to the holder 51.

[0051] [1-6. Hardener pillar formation process] Next, the process of forming the curing agent pillars 70 will be described with reference to FIG. 6. First, as shown in FIG. 6(A), a pre-curing agent 72, which is a curing agent before hardening, is dripped onto an area of the LED array mounting surface 55S of the substrate 55 where the LED array 56 is to be mounted. The pre-curing agent 72 is an ultraviolet-curing adhesive that hardens when irradiated with ultraviolet light. Specifically, the pre-curing agent 72 is dripped onto positions that will be under the bonding pads 66 of each LED chip 76 when the LED array 56 is mounted on the substrate 55, with a diameter of approximately Φ360 to 500 μm when viewed from a direction perpendicular to the LED array mounting surface 55S.

[0052] Next, as shown in FIG. 6(B), a flatness jig 74, which is a plate-shaped member having at least a lower surface with a high degree of flatness (e.g., 10 μm or less), is stopped in a state where it is pressed against the substrate 55 so as to crush the pre-cured curing agent 72 with the lower surface of a flat plate portion 74a, which is a flat plate-shaped member. The flatness jig 74 is composed of a flat plate portion 74a and an abutment portion 74b protruding downward from an end of the flat plate portion 74a. The abutment portion 74b has a planar abutment surface 74bS formed on its lower surface, which is parallel to the lower surface of the flat plate portion 74a. The distance between the lower surface of the flat plate portion 74a and the abutment surface 74bS is set to, for example, 200 μm. That is, the abutment surface 74bS protrudes downward by 200 μm from the lower surface of the flat plate portion 74a. In this step, the contact surface 74bS comes into contact with the LED array arrangement surface 55S, and the process is stopped with a load of, for example, approximately 500 g force applied. The flatness jig 74 has a surface that is pre-coated with, for example, a silicone coating. This prevents the flatness jig 74 from adhering to the pre-curing agent 72 and the substrate 55 after the pre-curing agent 72 has cured.

[0053] Next, as shown in FIG. 6(C), ultraviolet light is irradiated from the side of the substrate 55 by an ultraviolet irradiator 78, thereby hardening the pre-hardening curing agent 72 and forming hardener pillars 70. Next, as shown in FIG. 6(D), the flatness jig 74 is lifted up and separated from the substrate 55. As described above, the surface of the flatness jig 74 is coated, so the hardened hardener pillars 70 are peeled off from the flatness jig 74. As a result, hardener pillars 70 with sufficient flatness are formed on the upper surface of the LED array placement surface 55S of the substrate 55. Next, the LED array 56 is fixed onto the hardener pillars 70 with paste 80.

[0054] [1-7. Comparative Example] When LED chips 76 are die-bonded to a substrate 55 having an uneven portion 77 as shown in FIG. 7 , the local unevenness of the LED array mounting surface 55S of the substrate 55 due to the uneven portion 77 is not absorbed, and the LED array 56 appears meandering when viewed along the LED array mounting surface 55S. When such a substrate 55 is incorporated into an LED head 16, the focal position (imaging position) of the LED head 16 varies in the longitudinal direction, as shown in FIG. 9 . In particular, as shown in FIG. 9 , the focal positions around LED chips 76 No. 10 and No. 32 are significantly deviated from the reference focal position as designed, assuming a reference focal position of 0 μm. When such an LED head 16 is incorporated into a color printer 1, the size of the electrostatic latent image formed on the photosensitive drum 35 varies in the areas where the focal position varies in the longitudinal direction of the LED head 16, resulting in reduced print quality.

[0055] To compensate for such localized unevenness on the substrate 55, it is conceivable to apply a thick layer of paste 80 and then mount the LED chip 76 to the substrate 55 by die bonding, as shown in Figure 8. However, in this case, the LED chip 76 would be tilted relative to the reference by the thickness of the paste 80, and when the substrate 55 was assembled into the LED head 16, the focal position of the LED head 16 could not be improved, resulting in a decrease in print quality. Furthermore, such a substrate 55 had to be discarded.

[0056] [1-8. Effects, etc.] In the color printer 1 configured as described above, a plurality of hardener pillars 70 are formed along the left-right direction in the region where the LED array 56 is mounted on the LED array arrangement surface 55S of the substrate 55, and the single imaginary plane along which the bottom surfaces of the plurality of hardener pillars 70 that face and abut against the LED array 56 are aligned has sufficient flatness. Also, in the color printer 1, the LED chip 76 (i.e., the LED array 56) is fixed to the substrate 55 with paste 80, with the bottom surface of the hardener pillars 70 abutting against the top surface.

[0057] Therefore, even if the LED array 56 is mounted at a location where an uneven portion 77 occurs on the LED array placement surface 55S of the substrate 55, the color printer 1 can absorb the unevenness of the uneven portion 77 with the hardener columns 70, and then support the LED array 56 with the hardener columns 70, thereby mounting the LED array 56 on a plane parallel to the flat surface portion of the LED array placement surface 55S as originally designed.

[0058] Therefore, color printer 1 can suppress tilting of LED chips 76 mounted on uneven portion 77. As a result, color printer 1 can keep the focal position of light that has passed through the lower surface of lens array 53 constant across the entire length of LED array 56, stabilizing the focal position and maintaining print quality.

[0059] Furthermore, in the color printer 1, the hardener columns 70 are arranged in the same positions as the bonding pads 66 of the LED chips 76 in the front-rear and left-right directions. Therefore, in comparison with a case where the hardener columns 70 are arranged in positions different from the bonding pads 66 of the LED chips 76 in the front-rear and left-right directions, the color printer 1 can prevent the substrate 55 from bending during wire bonding when the bonding wires 68 are connected to the bonding pads 66, even if the LED chips 76 are raised above the LED array arrangement surface 55S by the amount of the hardener columns 70.

[0060] Incidentally, in some LED heads, the LED array arrangement surface 55S of the substrate 55 is pressed against an abutment surface of the holder that is provided so as to face the LED array arrangement surface 55S, and adhesive is applied to fix the substrate 55 to the holder. In the case of such an LED head, even if the LED array arrangement surface 55S has an uneven portion 77, when the substrate 55 is pressed against the abutment surface of the holder in the assembling process of the substrate 55, the uneven portion 77 can be corrected to some extent so as to be nearly flat, and the substrate 55 can be fixed to the holder.

[0061] On the other hand, in the case where the substrate 55 is fixed only to the holder inner wall surface 51WS of the holder 51 with the adhesive 60, if there is an uneven portion 77 on the LED array arrangement surface 55S, it is impossible to correct the uneven portion 77 in the process of assembling the substrate 55. For this reason, the present invention is significantly effective when applied to an LED head 16 in which the substrate 55 is directly fixed only to the holder inner wall surface 51WS of the holder 51 with the adhesive 60, as in the LED head 16 of the present embodiment.

[0062] According to the above configuration, the LED head 16 as an optical device of the color printer 1 comprises a substrate 55 on which a plurality of LED chips 76 as optical elements are mounted in the longitudinal direction, a lens array 53 which is arranged on the optical path of light between the LED chips 76 and the photosensitive drum 35 as the object and which allows the light to pass through, a paste 80 which is arranged between the substrate 55 and the LED chips 76 and which bonds the substrate 55 and the LED chips 76 together, and a hardener column 70 which is arranged between the substrate 55 and the LED chips 76 and is made of a material different from the paste 80.

[0063] As a result, the LED head 16 of the color printer 1 can reduce variation in the focal position of the LED array 56 in the longitudinal direction by having the hardener column 70 absorb the unevenness of the uneven portion 77 on the LED array placement surface 55S of the substrate 55 and then mounting the LED array 56 on the substrate 55.

[0064] 2. Second Embodiment [2-1. Color printer configuration] As shown in Figures 1 and 2, color printer 101 according to the second embodiment differs from color printer 1 according to the first embodiment in that it has LED head 116 (LED heads 116C, 116M, 116Y and 116K) instead of LED head 16 (LED heads 16C, 16M, 16Y and 16K), but is otherwise configured similarly.

[0065] [2-2. LED head configuration] 10 and 11, in which the same reference numerals are used for the components corresponding to those in Fig. 4 and Fig. 5, the LED head 116 according to the second embodiment is different from the LED head 16 according to the first embodiment in that it has a hardener column 170 instead of the hardener column 70, but is otherwise configured similarly. Note that the paste 80 between the LED chip 76 and the hardener column 170 is not shown in Fig. 11.

[0066] [2-3. Circuit board configuration] The hardener pillars 170 are provided continuously between the substrate 55 and the LED array 56 along the longitudinal direction (left-right direction) of the LED array 56, from the left end to the right end of the LED array 56. The hardener pillars 170 are formed so that their lower surfaces, which face and abut against the LED array 56, lie along a virtual plane parallel to the flat surface portion of the LED array mounting surface 55S. The lower surface has sufficient flatness, for example, a flatness of 30 μm or less. The hardener pillars 170 protrude downward by, for example, 200 μm from the flat surface portion of the LED array mounting surface 55S.

[0067] The LED array 56 dissipates heat generated by the LED chips 76 to the substrate 55 via the paste 80, which has high thermal conductivity. Furthermore, the curing agent columns 170, which are ultraviolet-curing adhesives, generally have lower thermal conductivity than the paste 80. Therefore, in the case of the LED head 116 according to this embodiment, the curing agent columns 170 are disposed in the entire region between the LED array 56 and the substrate 55, and therefore the heat dissipation performance of the LED array 56 is worse than that of the LED head 16, in which the curing agent columns 70 are disposed in only a portion of the region between the LED array 56 and the substrate 55. However, since the curing agent columns 170 are disposed in the LED head 116 over a wider area than the LED head 16, the strength of the curing agent columns 170 can be made stronger than that of the curing agent columns 70.

[0068] Furthermore, in the color printer 101 according to this embodiment, even if the LED array 56 is mounted at a location where an uneven portion 77 occurs on the LED array placement surface 55S of the substrate 55, the unevenness of the uneven portion 77 is absorbed by the hardener columns 170, and the LED array 56 is supported by the hardener columns 170, so that the LED array 56 can be mounted on a plane parallel to the flat surface portion of the LED array placement surface 55S as originally designed.

[0069] Therefore, color printer 101 can suppress tilting of LED chips 76 mounted on uneven portion 77. As a result, color printer 101 can keep the focal position of light that has passed through the lower surface of lens array 53 constant across the entire length of LED array 56, stabilizing the focal position and maintaining print quality.

[0070] In other respects as well, color printer 101 having LED head 116 according to the second embodiment can achieve substantially the same effects as color printer 1 having LED head 16 according to the first embodiment.

[0071] 3. Third Embodiment [3-1. Scanner configuration] As shown in a side view in FIG. 12, the scanner 82 is a document reading device that reads a document M, such as an A3 or A4 size document, and generates electronic data. The scanner 82 as a reading device is composed of a reading head 83, a lamp 84, a document table 85, rails 86, a drive belt 87, and a motor 88. The lamp 84 is positioned so that the light it emits is reflected by the surface of the document M, which serves as a light source, and is captured into the reading head 83. The document table 85 is made of a material that transmits visible light, and the document M is placed on it. The rails 86 are positioned below the document table 85 and movably support the reading head 83. The reading head 83 as a light receiving device is partially connected to a drive belt 87 that is stretched by multiple pulleys 90, and is configured to be movable on the rails 86 by the drive belt 87 driven by a motor 88. The reading head 83 captures the light emitted by the lamp 84 and reflected by the surface of the document M and converts it into electronic data.

[0072] [3-2. Read head configuration] The reading head 83 is configured as a whole in such a way that a line sensor 94 serving as a detector is placed in place of the LED array 56 (FIGS. 3, 4, and 5) of the LED head 16, and an original document M serving as a subject is placed in place of the photosensitive drum 35 (FIG. 3). This reading head 83 is composed of a lens unit 92, a mirror 93, and the line sensor 94. The lens unit 92 is configured in the same manner as the lens array 53 (FIG. 3) according to the first embodiment. The mirror 93 bends the optical path of light reflected by the original document M so that it enters the lens unit 92. The line sensor 94 has a plurality of light-receiving elements, such as CCD sensor chips, arranged linearly at predetermined intervals in place of the LED chips 76 (FIGS. 4 and 5) serving as light-emitting elements, and converts the image of the original document formed by the lens unit 92 into an electrical signal. In this embodiment, the line sensor 94 has a resolution of 600 dpi, so 600 light receiving elements are arranged per inch (i.e., the light receiving elements are arranged at longitudinal intervals of 0.0423 mm). The line sensor 94 is adhered to the substrate by a paste provided between the substrate and the CCD sensor chip. A hardener pillar made of a material different from the paste is provided between the substrate and the CCD sensor chip.

[0073] In this configuration, the scanner 82 turns on the lamp 84 to irradiate the surface of the original M with light, and captures the light reflected from the surface of the original M into the reading head 83. The scanner 82 drives the drive belt 87 with the motor 88 to move the reading head 83 and the lamp 84 in the left-right direction of the paper in FIG.

[0074] At this time, the light reflected by the original M passes through the original table 85, has its optical path bent by a mirror 93, and enters a lens unit 92. The image of the original formed by the lens unit 92 is formed on a line sensor 94, which converts the formed image of the original into an electrical signal to generate electronic data.

[0075] In other respects as well, the scanner 82 having the reading head 83 according to the third embodiment can achieve substantially the same effects as the color printer 1 having the LED head 16 according to the first embodiment.

[0076] 4. Other Embodiments In the first or second embodiment described above, the color printer 1 or 101 has been described as comprising the hardener columns 70 or 170 of an ultraviolet-curing adhesive. However, the present invention is not limited to this, and the hardener columns 70 or 170 may be comprised of various other materials, such as an adhesive that hardens with an accelerator, an adhesive that hardens over time, an adhesive that hardens due to temperature changes, or a combination of these. The key point is that a high degree of flatness is achieved when the material hardens from an uncured state, so the hardener columns 70 or 170 may simply be comprised of a hardened material that hardens from an uncured state. The same is true for the third embodiment.

[0077] In the first embodiment described above, the color printer 1 is described as being arranged with the hardener column 70 positioned so as to accommodate the bonding pad 66 of the LED chip 76 within its outer shape in the front-rear and left-right directions. However, the present invention is not limited to this, and the color printer 1 may be arranged with the hardener column 70 positioned at a different position from the position at which the bonding pad 66 of the LED chip 76 is accommodated within its outer shape in the front-rear and left-right directions. The same applies to the third embodiment.

[0078] Furthermore, in the first or second embodiment described above, the color printer 1 or 101 has been described as arranging the hardener columns 70 or 170 linearly along the left-right direction. However, the present invention is not limited to this, and the color printer 1 or 101 may also arrange the hardener columns 70 or 170 in a direction that includes the front-rear direction in addition to the left-right direction.

[0079] Furthermore, in the first or second embodiment described above, the color printer 1 or 101 has been described as being equipped with LED chips 76 as light-emitting elements. However, the present invention is not limited to this, and the color printer 1 or 101 may be equipped with various other devices, such as light-emitting thyristors, as light-emitting elements.

[0080] Furthermore, in the above-described third embodiment, the present invention has been described as being applied to the scanner 82. However, the present invention is not limited to this, and may also be applied to sensors and switches that convert optical signals into electrical signals, as well as input / output devices, biometric authentication devices, communication devices, dimension measuring instruments, and the like that use these.

[0081] Furthermore, in the first and second embodiments described above, the present invention is described as being applied to the LED heads 16 or 116 of each color corresponding to the image forming units 15 of each color arranged in series along the front-to-rear direction in a tandem color printer 1 or 101. However, the present invention is not limited to this, and may be applied to LED heads mounted in color printers of various other types, such as a four-cycle type. The same applies to the second embodiment.

[0082] Furthermore, in the first and second embodiments described above, four LED heads 16 or 116 corresponding to the colors yellow, magenta, cyan, and black are attached to the printer housing 2 of the color printer 1 or 101 that performs color printing. The present invention is not limited to this, and for example, three or fewer or five or more LED heads 16 or 116 may be attached to the printer housing 2 depending on the number of toner colors used in the color printer, or one LED head 16 or 116 may be attached to a monochrome printer that performs monochrome printing.

[0083] Furthermore, in the first and second embodiments described above, the present invention has been described as being applied to color printer 1 or 101. However, the present invention is not limited to this, and the present invention may be applied to any device that has an LED head 16 similar to color printer 1 or 101, such as a facsimile, an MFP (Multifunction Printer), or a copying machine.

[0084] Furthermore, the present invention is not limited to the above-described embodiments and other embodiments. That is, the scope of application of the present invention also extends to embodiments in which the above-described embodiments are combined in part or in whole with any of the above-described other embodiments. The scope of application of the present invention also extends to embodiments in which part of the configuration described in any of the above-described embodiments and other embodiments is extracted and used as part of the configuration of any of the above-described embodiments and other embodiments, or in which part of the extracted configuration is added to any of the above-described embodiments.

[0085] Furthermore, in the first and second embodiments described above, the LED head 16 or 116 as an exposure device is configured using the substrate 55 as a substrate, the lens array 53 as a lens unit, the paste 80 as an adhesive member, and the hardener column 70 or 170 as a hardened body, and the color printer 1 or 101 as an image forming apparatus having the LED head 16 or 116 is described as being configured. However, the present invention is not limited to this, and the exposure device may be configured using a substrate, lens unit, adhesive member, and hardened body having various other configurations, and the image forming apparatus may be configured as being configured. [Industrial Applicability]

[0086] The present invention can be used in, for example, an LED head mounted on an electrophotographic printer. [Explanation of symbols]

[0087] 1, 101...color printer, 2...printer housing, 2T...output tray, 3...controller, 4...paper storage cassette, 5...paper feeder, 7...hopping roller, 8...registration roller, 10...transfer belt unit, 11...roller, 12...transfer belt, 13...transfer roller, 15...image forming unit, 16, 116...LED head, 18...toner cartridge, 20...fixing unit, 21...heating roller, 22...pressure roller, 24...paper output unit, 31...frame, 35...photosensitive drum, 35S...periphery, 36...charging roller, 38...developing roller, 39...supply roller, 40...developing blade, 51...holder, 51IS...holder internal space, 51B...bottom, 51W...side, 51WS... ...Holder inner wall surface, 51H...Lens array hole portion, 51A...Holder opening portion, 53...Lens array, 55...Substrate, 55S...LED array placement surface, 56...LED array, 60...Adhesive, 62...Adhesive, 66...Bonding pad, 68...Bonding wire, 70, 170...Hardener column, 72...Pre-hardened hardener, 74...Flatness jig, 74a...Flat portion, 74b...Abutment portion, 74bS...Abutment surface, 76...LED chip, 77...Uneven portion, 78...Ultraviolet irradiator, 80...Paste, 82...Scanner, M...Original, 83...Reading head, 84...Lamp, 85...Original table, 86...Rail, 87...Drive belt, 88...Motor, 92...Lens unit, 93...Mirror, 94...Line sensor.

Claims

1. a substrate on which a plurality of optical elements are mounted in the longitudinal direction; a lens unit that is provided on an optical path of light between the optical element and an object and that transmits the light; an adhesive member provided between the substrate and the optical element, and adhering the substrate and the optical element; a cured body that is provided between the substrate and the optical element and is made of a material different from that of the adhesive member; An optical device having:

2. The cured product is an adhesive after curing. The optical device according to claim 1 .

3. the optical element is electrically connected to the substrate by a wire connected to a pad disposed on a surface of the optical element that is away from the substrate; The hardened body is disposed at a position including at least the pad in the longitudinal direction. The optical device according to claim 1 .

4. The cured body is disposed at a position where the pad is included within the outer shape of the cured body when viewed from a direction perpendicular to the surface of the substrate.

4. The optical device according to claim 3.

5. The hardened body is arranged in a plurality of pieces discretely in the longitudinal direction. The optical device according to claim 1 .

6. The flatness of the surface of the cured body facing the optical element is 30 μm or less. The optical device according to claim 1 .

7. A plurality of the cured bodies are arranged, The flatness of the virtual surface along the surface of the plurality of cured bodies facing the optical element is 30 μm or less.

7. The optical device according to claim 6.

8. the optical element is a light-emitting element, the lens unit passes light from the light emitting element to the object; the adhesive member is provided between the substrate and the light-emitting element and bonds the substrate and the light-emitting element together; The cured body is provided between the substrate and the light-emitting element and is made of a different material from the adhesive member.

8. The optical device according to claim 1.

9. An image forming apparatus comprising the optical device according to claim 8.

10. the optical element is a light receiving element, the lens unit passes light from the object to the light receiving element; the adhesive member is provided between the substrate and the light-receiving element and bonds the substrate and the light-receiving element together; The cured body is provided between the substrate and the light-receiving element and is made of a different material from the adhesive member.

8. The optical device according to claim 1.

11. A reading device comprising an optical device according to claim 10.

Images