Optical scanning apparatus, image forming apparatus, and method for manufacturing an optical scanning apparatus

Abstract

To provide an optical scanning device equipped with a reflective element having sufficient corrosion resistance. [Solution] The optical scanning device according to the present invention comprises a deflector that deflects a light beam from a light source to scan a surface to be scanned in the main scanning direction, an optical system that guides the light beam deflected by the deflector to the surface to be scanned, a reflective element having a reflective surface that reflects the light beam deflected by the deflector, and first and second surfaces that are non-parallel to the reflective surface, and a holding member that holds the reflective element, wherein the corrosion resistance of the second ridge between the reflective surface and the second surface is lower than the corrosion resistance of the first ridge between the reflective surface and the first surface, and the first region including at least a part of the second ridge is bonded to the holding member with a first adhesive.

Description

Technical Field

[0001] The present invention relates to an optical scanning device, and particularly to an optical scanning device suitably used in an image forming apparatus such as a laser beam printer (LBP) having an electrophotographic process, a digital copying machine, or a multifunction printer (all-in-one printer).

Background Art

[0002] Patent Document 1 discloses an optical scanning device provided with a reflective element having higher corrosion resistance on an end face along a sub-scanning direction than on an end face along a main scanning direction.

Prior Art Documents

Patent Documents

[0003] <S

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the optical scanning device disclosed in Patent Document 1, it is difficult to suppress a decrease in corrosion resistance due to the peeling up of a reflection film at a ridge portion between a reflection surface and an end face of a reflective element. [[ID=Q36]]

[0005] Therefore, an object of the present invention is to provide an optical scanning device provided with a reflective element having sufficient corrosion resistance.

Means for Solving the Problems

[0006] The optical scanning device according to the present invention comprises a deflector that deflects a light beam from a light source to scan a surface to be scanned in the main scanning direction, an optical system that guides the light beam deflected by the deflector to the surface to be scanned, a reflective element having a reflective surface that reflects the light beam deflected by the deflector, and first and second surfaces that are non-parallel to the reflective surface, and a holding member that holds the reflective element, wherein the corrosion resistance of the second ridge between the reflective surface and the second surface is lower than that of the first ridge between the reflective surface and the first surface, and the first region including at least a part of the second ridge is bonded to the holding member by a first adhesive. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an optical scanning device equipped with a reflective element having sufficient corrosion resistance. [Brief explanation of the drawing]

[0008] [Figure 1] A perspective view of the optical scanning device according to the first embodiment. [Figure 2] A perspective view and a cross-sectional view of a reflective mirror included in an optical scanning device according to the first embodiment. [Figure 3] A perspective view of each timing during the manufacturing of the reflective mirrors included in the optical scanning device according to the first embodiment. [Figure 4] An enlarged cross-sectional view of the optical scanning apparatus according to the first embodiment. [Figure 5] An enlarged cross-sectional view of the optical scanning apparatus according to the first embodiment. [Figure 6] A perspective view of each timing during the manufacturing of the reflective mirrors included in the optical scanning device according to the second embodiment. [Figure 7] An enlarged cross-sectional view of the optical scanning apparatus according to the second embodiment. [Figure 8] An enlarged cross-sectional view of the optical scanning apparatus according to the second embodiment. [Figure 9] A sub-scanning cross-sectional view of the main part of a color image forming apparatus according to an embodiment. [Figure 10] Cross-sectional views at various stages during the manufacturing of a reflective mirror. [Modes for carrying out the invention]

[0009] The optical scanning apparatus according to this embodiment will be described in detail below with reference to the attached drawings. Note that the drawings shown below may be drawn to a different scale than the actual dimensions in order to facilitate understanding of this embodiment. In the following explanation, the main scanning direction is the direction perpendicular to the rotation axis of the polygon mirror 5 and the optical axis of the imaging optical system 8 (the direction in which the polygon mirror 5 scans the surface to be scanned 11), and the secondary scanning direction is the direction parallel to the rotation axis of the polygon mirror 5.

[0010] Furthermore, the main scanning cross-section is a cross-section perpendicular to the sub-scanning direction, and the sub-scanning cross-section is a cross-section perpendicular to the main scanning direction. In the following, the main scanning direction is defined as the Y direction, the sub-scanning direction as the Z direction, and the direction parallel to the optical axis of the imaging optical system 8 as the X direction.

[0011] [First Embodiment] Various optical scanning devices have been proposed for use in image forming equipment such as laser beam printers (LBPs) with electrophotographic processes, digital copiers, and multifunction printers.

[0012] In an optical scanning device, the light beam emitted from the light source, which is modulated according to the image signal, is converted into a parallel light beam by a collimator lens, and then periodically deflected by a deflector formed from a rotating polyhedron mirror. The deflected light beam is then focused into a spot shape onto the photosensitive surface of a photosensitive recording medium (photosensitive drum) by an imaging optical system having fθ characteristics, and image recording is performed by scanning the photosensitive surface with the focused light beam.

[0013] Furthermore, there are also known optical scanning devices that are equipped with a reflective mirror to reflect the light beam deflected by the deflector toward the photosensitive surface of the photosensitive drum. Then, by folding back the optical path of the deflected light beam by the reflection mirror, the optical scanning device can be arranged at a suitable position in the image forming apparatus.

[0014] The reflection mirror used in such an optical scanning device is generally formed by a post-cutting method in which after depositing a reflection film on the surface of a large-sized mirror, the large-sized mirror is cut to a predetermined size in each of the longitudinal direction and the short-side direction so as to have a rectangular reflection surface. FIGS. 10(a), (b), and (c) respectively show schematic cross-sectional views of a large-sized mirror with a reflection film deposited on its surface, a plurality of reflection mirrors formed by cutting the large-sized mirror, and the formed single reflection mirror.

[0015] Specifically, when forming the reflection mirror, first, as shown in FIG. 10(a), after thoroughly cleaning the glass substrate 201, a reflection film 202, which is a metal thin film such as aluminum or an alloy containing aluminum, is deposited on the surface of the glass substrate 201 by a vacuum evaporator. Then, a protective film 203 mainly made of silicon dioxide or the like is deposited on the formed reflection film 202.

[0016] Next, as shown in FIG. 10(b), the glass substrate 201 on which the reflection film 202 and the protective film 203 are deposited is scribed and cut. Specifically, after scratching the glass substrate 201 with a diamond blade along a cutting line on the front or back surface, a stress is applied to bend it to the left and right of the cutting line, and then it is cut and separated by cracking on the cutting line.

[0017] At this time, since burrs are generally likely to be formed on the cross-section formed by scribing and cutting the glass substrate 201 as shown in FIG. 10(b), polishing or chamfering may be performed on the cross-section and its corners. Then, as shown in FIG. 10(c), in the reflection mirror formed by the above post-cutting method, a part of the reflection film 202 and the protective film 203 deposited at the end is curled up.

[0018] The reflective film 202, which is a thin metal film of aluminum or an aluminum-containing alloy that has been peeled up in this manner, is easily exposed to the outside air, such as moisture, and therefore corrosion occurs rapidly, especially in high-temperature and high-humidity environments, causing a decrease in reflectivity. Furthermore, since the corrosion gradually progresses toward the inner portion of the reflective film 202, it was necessary to define the effective area of ​​the reflective surface taking into account the area where the corrosion was progressing, which led to an increase in the size of the reflective mirror and, consequently, the optical scanning device mounted on it.

[0019] Therefore, conventional optical scanning devices have been proposed in which the corrosion resistance of the first end face along the main scanning direction and the second end face along the sub-scanning direction are different from each other, and which are equipped with a synchronization detection mirror that reflects the light beam deflected by the deflector toward a synchronization detection photodetector. However, in this conventional optical scanning device, corrosion still occurs in the portion of the reflective film that is curled up at the end face of the synchronization detection mirror, which has low corrosion resistance. Therefore, it is necessary to enlarge the synchronization detection mirror in proportion to the corrosion.

[0020] Therefore, the objective of this embodiment is to provide an optical scanning device that can be miniaturized and cost-effective while maintaining durability. Figure 1 shows a schematic perspective view of the optical scanning device 70 according to the first embodiment.

[0021] The optical scanning device 70 according to this embodiment includes a light source 1, a collimator lens 2, a cylinder lens 3, an aperture 4, a polygon mirror 5 (deflector), a first imaging lens 6, and a second imaging lens 7. Furthermore, the optical scanning device 70 according to this embodiment includes a reflective mirror 9 (reflective element), a synchronization detection reflective mirror 12a, a synchronization detection imaging lens 12b, and a synchronization detection light receiving element 12c.

[0022] In the optical scanning device 70 according to this embodiment, an incident optical system 13 is formed by a collimator lens 2, a cylinder lens 3, and an aperture 4, and an imaging optical system 8 (optical system) is formed by a first imaging lens 6 and a second imaging lens 7. Furthermore, in the optical scanning device 70 according to this embodiment, the synchronization detection optical system 12 is formed by the synchronization detection reflective mirror 12a and the synchronization detection imaging lens 12b. The imaging optical system 8 is not limited to the above; it may be formed by a single imaging lens or three or more imaging lenses.

[0023] Light source 1 is a multi-beam laser in which multiple light-emitting points are provided on a single chip, for example, in the form of an end-face emitting type or a surface emitting type (i.e., VCSEL). Furthermore, while light with a wavelength of 650 nm is primarily emitted from light source 1, it is not limited to this; infrared light with a wavelength of 850 nm or blue light with a wavelength of 430 nm may also be emitted.

[0024] The collimator lens 2 focuses the divergent light beam emitted from the light source 1 so as to convert it into a parallel light beam within the main scanning cross-section. In this context, the term "parallel beam" includes not only strictly parallel beams but also approximate parallel beams such as weakly converging beams and weakly diverging beams.

[0025] Specifically, the collimator lens 2 is formed by a single lens having a spherical optical surface, but is not limited to this. In other words, the collimator lens 2 may be formed from a bonded lens, a glass molded lens, or a plastic molded lens, in which multiple glass lenses, each having a spherical optical surface, are joined together.

[0026] The cylinder lens 3 focuses the light beam that has passed through the collimator lens 2 into a converged light beam within the sub-scanning cross-section, so as to form a line image near the deflection surface 5a of the polygon mirror 5. The aperture 4 restricts the beam width of the light beam emitted from the cylinder lens 3 in both the main scanning direction and the sub-scanning direction so that it becomes a predetermined beam width.

[0027] The aperture formed in the aperture 4 is shaped as an ellipse, rectangle, or oval depending on the wavelength of the light beam emitted from the light source 1 and the required size and shape of the beam spot. Furthermore, while aperture 4 is located between the cylinder lens 3 and the polygon mirror 5, it is not limited to this location; it may also be located between the light source 1 and the collimator lens 2, or between the collimator lens 2 and the cylinder lens 3.

[0028] Furthermore, the aperture 4 is not limited to the above, and may be formed by a slit member extending in the sub-scanning direction to restrict the beam width of the light passing through in the main scanning direction, and a slit member extending in the main scanning direction to restrict the beam width of the light passing through in the sub-scanning direction. In particular, when the light source 1 has multiple light-emitting points, jitter can be reduced by providing a slit member that restricts the width of the light beam in the main scanning direction of the passing light beam near the polygon mirror 5. Furthermore, if the light source 1 has multiple light-emitting points, the uniformity of the printing intervals of the multiple light beams can be improved by providing a slit member that restricts the width of the light beam in the sub-scanning direction of the passing light beam at a position optically conjugate to the imaging optical system 8, for example, between the light source 1 and the collimator lens 2.

[0029] The polygon mirror 5 has multiple deflection surfaces 5a and is configured to rotate at a constant angular velocity around a rotation axis by a drive system (not shown). As a result, the light beam emitted from the light source 1 and guided by the incident optical system 13 is deflected by the deflection surface 5a of the polygon mirror 5, causing it to be scanned at a constant speed on the scanning surface 11. In the optical scanning device 70 according to this embodiment, the principal ray of the light beam emitted from the light source 1 and guided by the incident optical system 13 is incident on the deflection surface 5a of the polygon mirror 5 parallel to the main scanning cross-section (perpendicular incidence) within the sub-scanning cross-section.

[0030] The first imaging lens 6 and the second imaging lens 7 are each made of plastic material and focus (guide) the light beam deflected by the polygon mirror 5 so that a beam spot is formed on the scanning surface 11. The first imaging lens 6 and the second imaging lens 7 are each manufactured using a known injection molding technique in which a resin material is filled into a mold, cooled, and then removed from the mold. This method allows for lower manufacturing costs compared to using glass materials.

[0031] In order to design the imaging optical system 8 with a predetermined power configuration, the first imaging lens 6 is formed, for example, as an aspherical lens having power mainly within the main scanning cross-section, that is, the optical surface has an aspherical shape expressed by a known function. In other words, in the first imaging lens 6 provided in the optical scanning device 70 according to this embodiment, the power in the main scanning cross-section is greater than the power in the sub-scanning cross-section. The first imaging lens 6 is a convex meniscus lens in which the incident and exit surfaces have a non-arc and concave shape toward the polygon mirror 5 side within the main scanning cross-section.

[0032] The shape of the first imaging lens 6 in the optical scanning device 70 according to this embodiment is symmetrical with respect to the optical axis of the imaging optical system 8 within the main scanning cross-section. Furthermore, the first imaging lens 6 may have an incident surface and an exit surface with the same curvature, such that it is substantially powerless within the sub-scanning cross-section.

[0033] Furthermore, the second imaging lens 7 is formed, for example, as an anamorphic lens that has power mainly within the sub-scanning cross-section, meaning that its optical surface has an aspherical shape expressed by a known function. In other words, in the second imaging lens 7 provided in the optical scanning device 70 according to this embodiment, the power in the sub-scanning cross-section is greater than the power in the main scanning cross-section.

[0034] The incident surface of the second imaging lens 7 has an arc shape and a non-arc shape in the main scanning cross-section and the sub-scanning cross-section, respectively. On the other hand, the emission surface of the second imaging lens 7 has a non-arc shape in both the main scanning cross-section and the sub-scanning cross-section.

[0035] The shape of the second imaging lens 7 provided in the optical scanning device 70 according to this embodiment within the main scanning cross-section is symmetrical with respect to the optical axis of the imaging optical system 8. Furthermore, the power of the second imaging lens 7 provided in the optical scanning device 70 according to this embodiment within the main scanning cross-section is approximately zero near the optical axis of the imaging optical system 8.

[0036] On the other hand, the second imaging lens 7 provided in the optical scanning device 70 according to this embodiment has, within the sub-scanning cross-section, an incident surface having a substantially planar shape with extremely gentle curvature, and an exit surface having a convex shape in which the curvature gradually changes from above the optical axis to off-optical axis of the imaging optical system 8. Furthermore, the shape of the second imaging lens 7 provided in the optical scanning device 70 according to this embodiment within the sub-scanning cross-section is symmetrical with respect to the optical axis of the imaging optical system 8. The second imaging lens 7 is primarily responsible for focusing the light beam within the sub-scanning plane and correcting some distortion within the main scanning plane.

[0037] The imaging optical system 8 is also called the Fθ optical system or scanning optical system, and it forms a so-called distortion correction optical system in which the deflection surface 5a of the polygon mirror 5 and the scanned surface 11 are set to be approximately conjugate to each other within the sub-scanning cross-section. Furthermore, the imaging optical system 8 is not limited to the above configuration; for example, it may have an asymmetrical shape with respect to the optical axis in order to improve imaging performance.

[0038] The reflective mirror 9 is positioned between the imaging optical system 8 and the scanned surface 11 so as to extend along the main scanning direction, and reflects the light beam guided by the imaging optical system 8. In other words, the reflective mirror 9 reflects the light beam that has been deflected by the polygon mirror 5 at a predetermined timing and then guided by the imaging optical system 8. To put it another way, the reflective mirror 9 reflects the light beam that is deflected by the polygon mirror 5 and reaches the scanned surface 11. The light beam reflected by the reflective mirror 9 then passes through a slit formed in the housing 30 (holding member) and reaches the surface to be scanned 11.

[0039] The synchronization detection optical system 12 guides the light beam deflected by the deflection surface 5a of the polygon mirror 5 to the synchronization detection photodetector 12c at a predetermined scanning angle different from the scanning angle corresponding to the effective area on the scanned surface 11, i.e., at a timing different from the predetermined timing. Specifically, the light beam deflected by the deflection surface 5a of the polygon mirror 5 at the predetermined scanning angle passes through the first imaging lens 6, is reflected by the synchronous detection reflection mirror 12a, and is then guided to the synchronous detection photodetector 12c by the synchronous detection imaging lens 12b. Then, when the synchronization detection light-receiving element 12c receives the light beam, the write timing on the scanned surface 11 is determined.

[0040] In the optical scanning device 70 according to this embodiment, the light source 1, collimator lens 2, cylinder lens 3, aperture 4, polygon mirror 5, first imaging lens 6, and second imaging lens 7 are each housed in a housing 30 (not shown) and attached to the side wall or bottom wall of the housing 30. Furthermore, the reflective mirror 9, the synchronous detection reflective mirror 12a, the synchronous detection imaging lens 12b, and the synchronous detection light receiving element 12c are each housed within a housing 30 (not shown) and attached to the side wall or bottom wall of the housing 30.

[0041] Figures 2(a) and 2(b) show a perspective view and a cross-sectional view, respectively, of the reflective mirror 9 provided in the optical scanning device 70 according to this embodiment. As shown in Figure 2(a), the reflective mirror 9 has longitudinally extending and opposing side faces 25 and 26 (first faces) and transversely extending and opposing end faces 27 and 28 (second faces).

[0042] Furthermore, as shown in Figure 2(a), the reflective mirror 9 has a reflective surface 20 on which a reflective film 18 is deposited. In other words, in the reflective mirror 9, the reflective surface 20 and the side surfaces 25 and 26 are non-parallel to each other, the reflective surface 20 and the end surfaces 27 and 28 are non-parallel to each other, and the side surfaces 25 and 26 and the end surfaces 27 and 28 are non-parallel to each other. Specifically, the reflective surface 20 is formed by depositing a metal thin film 16 and a protective thin film 17 in that order onto a float glass substrate 21, as shown in Figure 2(b).

[0043] As the metal thin film 16, for example, a low-cost aluminum-based material or a chromium-based material, or a metal base material including a silver-based material or a copper-based material having high reflectivity and non-polarizing properties can be used. Furthermore, as the protective thin film 17, a single-layer or multi-layer film of a titanium-based material or a silicon-based material is used to improve moisture resistance, abrasion resistance, chemical resistance, oxidation resistance, etc.

[0044] In addition, an undercoat layer may be formed to improve the adhesion between the metal thin film 16 and the float glass substrate 21. The reflective mirror 9 provided in the optical scanning device 70 according to this embodiment has a rectangular shape with a length L1 = 88 mm in the longitudinal direction and a width L2 = 8 mm in the short direction, within a cross section parallel to the longitudinal and short directions.

[0045] Figures 3(a), (b), and (c) show perspective views at various timings during the manufacturing of the reflective mirror 9 provided in the optical scanning device 70 according to this embodiment. Specifically, Figure 3(a) shows a perspective view of the float glass substrate 21 before the reflective film 18 is deposited. First, the float glass substrate 21, which is the base material of the reflective mirror 9, is formed by cutting a large sheet of glass to a length of L3 = 264 mm and a width of L2 = 8 mm (first step).

[0046] The length L3 = 264 mm in the longitudinal direction of the float glass substrate 21 is set to be three times the length L1 = 88 mm in the longitudinal direction of the reflective mirror 9. Large sheets of glass are also cut by scrape cutting. In other words, large sheets of glass are cut and separated by first creating a scratch along a cutting line on the surface or back surface with a diamond blade, and then applying bending stress on both sides of the scratch, causing the glass to break along the cutting line.

[0047] When large sheets of glass are cut using a scraper in this manner, burrs tend to form on the cut surface. Therefore, the cut surface and its corners are polished, or a chamfer is formed between the surface and the cut surface, in other words, a chamfer is created. In particular, as shown in Figure 3(a), a chamfered portion 22 (third surface) is provided between the surface and side surface that become the reflective surface 20, which is prone to degradation of optical performance due to burrs.

[0048] Furthermore, in order to suppress the occurrence of injuries when assembling the reflective mirror 9 to the housing 30, it is preferable to provide chamfering between the surface that becomes the reflective surface 20 and each side and end face. In the following, the ridges between the reflective surface 20 and each side and end face, and the surfaces formed by chamfering between the reflective surface 20 and each side and end face, will be collectively referred to as ridges.

[0049] Next, as shown in Figure 3(b), a reflective film 18 is deposited onto the surface of the float glass substrate 21 to form a long mirror 23 having a reflective surface 20 (second step). Specifically, after thoroughly cleaning and drying the surface of the float glass substrate 21, a metal thin film 16 and a protective thin film 17 are formed in that order using a vacuum deposition machine.

[0050] The formation of the reflective film 18 on the surface of the float glass substrate 21 is not limited to vacuum deposition; it may also be carried out using a coating method such as sputtering. Furthermore, since attaching the float glass substrate 21 in the vacuum deposition machine is easier than attaching the float glass substrate of the reflective mirror 9, costs can be reduced.

[0051] In addition, the float glass substrate 21 is heavier than the float glass substrate of the reflective mirror 9 because it is larger in size. In other words, compared to the case where a reflective mirror 9 is attached in a vacuum deposition machine, the float glass substrate 21 is less likely to shift position when shocks or vibrations occur, making it possible to stably form a homogeneous reflective film 18.

[0052] Next, as shown in Figure 3(c), three reflective mirrors 9 are formed by scraping the long mirror 23 along its short side at intervals of L1 = 88 mm along its longitudinal side (third step). In the manufacturing method of the reflective mirror 9 described above, at least one of the end faces 27 and 28 is formed by cutting the float glass substrate 21 after forming the reflective film 18 on it.

[0053] On the other hand, the sides 25 and 26 are formed by cutting a large sheet of glass before forming the reflective film 18 on the float glass substrate 21. In other words, the reflective film 18 near at least one edge of the end faces 27 and 28 is curled up, for example, as shown in Figure 4(a), when the reflective mirror 9 is formed by cutting the elongated mirror 23.

[0054] The portion of the reflective film 18 that has been peeled up in this manner, specifically the metal thin film 16 made of aluminum or an aluminum-containing alloy, is susceptible to rapid corrosion (oxidative corrosion) when exposed to the outside air, such as moisture, especially in high-temperature and high-humidity environments. As a result, the reflectivity of the corroded portion of the thin metal film 16 will decrease significantly.

[0055] On the other hand, on the sides 25 and 26, the reflective film 18 is not peeled up, and the reflective film 18 is in close contact with the float glass substrate 21 up to the chamfered portion 22 between the sides 25 and 26 and the reflective surface 20. Therefore, corrosion of the metal thin film 16 contained in the reflective film 18 at the chamfered portion 22 between the reflective surface 20 and the side surfaces 25 and 26 is suppressed, and thus the reflective performance can be maintained.

[0056] As described above, in the reflective mirror 9 provided in the optical scanning device 70 according to this embodiment, the side surfaces 25 and 26 are formed before the reflective film 18 is deposited, while at least one of the end surfaces 27 and 28 is formed after the reflective film 18 is deposited. Therefore, the corrosion resistance of the reflective film 18 near the ridge (second ridge) between the reflective surface 20 and at least one of the end faces 27 and 28 is lower than that of the reflective film 18 near the ridge (first ridge) between the reflective surface 20 and the side faces 25 and 26. In other words, the reflective film 18 near the edge between the reflective surface 20 and at least one of the end faces 27 and 28 is more susceptible to corrosion than the reflective film 18 near the edge between the reflective surface 20 and the side faces 25 and 26.

[0057] Next, the holding of the reflective mirror 9 in the optical scanning device 70 according to this embodiment will be described. Although the following describes the holding of one side of the reflective mirror 9 in the longitudinal direction by the housing 30, the configuration described below also applies to the holding of the other side of the reflective mirror 9 in the longitudinal direction by the housing 30.

[0058] Figures 4(a) and 4(b) show, respectively, an enlarged cross-sectional view and an enlarged sub-scanning cross-sectional view of the portion of the housing 30 holding the reflective mirror 9 in the optical scanning device 70 according to this embodiment, viewed from a predetermined direction perpendicular to the main scanning direction. Figure 4(c) also shows an enlarged cross-sectional view of the portion of the housing 30 holding the reflective mirror 9 in the optical scanning device 70 according to this embodiment, viewed from a direction perpendicular to the main scanning direction and the predetermined direction.

[0059] As described above, the housing 30 provided in the optical scanning device 70 according to this embodiment houses each optical element, and each optical element is held in place by the side walls and bottom walls of the housing 30. In the optical scanning device 70 according to this embodiment, in order to reduce the number of holding parts that hold each optical element in the housing 30, a portion of each optical element, including the reflective mirror 9, is held by being bonded to the housing 30 using an adhesive.

[0060] As shown in Figures 4(a) and (b), the housing 30 has a positioning portion 32 (projection) for determining the position and angle of the reflective mirror 9, which is formed integrally with the side wall portion 31. In the optical scanning device 70 according to this embodiment, after placing the reflective mirror 9 on the bottom wall portion 33, the orientation, i.e., position and angle of the reflective mirror 9 is determined by bringing the longitudinal end of the reflective surface 20 of the reflective mirror 9 into contact with the positioning portion 32.

[0061] As described above, in the optical scanning device 70 according to this embodiment, a part of the reflective mirror 9 is held in place by being bonded to the housing 30. Therefore, as shown in Figure 4(c), it is preferable that the following conditions (1) and (2) are satisfied at the ridge between the side surface 25 and the end surface 27 of the reflective mirror 9.

[0062] 0.05 ≤ L0 / L2 ≤ 0.20 ···(1) 5 ≤ θ ≤ 45 ···(2)

[0063] In condition (1), L0 is the length of the surface (fourth surface) formed between the side surface 25 and the end surface 27 of the reflective mirror 9 by chamfering, in a plane parallel to the side surface 25, and L2 is the distance between the side surface 25 and the side surface 26 (fifth surface). In condition (2), θ is the angle (°) (acute angle) formed between the surface 25 and the end face 27.

[0064] Conditional expressions (1) and (2) define the shape of the chamfer formed between the side surface 25 and the end surface 27 of the reflective mirror 9. If the value falls below the lower limit of condition (1), the adhesive used to hold the reflective mirror 9 to the housing 30 will not flow in easily, making it difficult to bond and hold the reflective mirror 9 with sufficient strength using the housing 30. On the other hand, if the upper limit of condition (1) is exceeded, the reflective mirror 9 must be made longer than the required length, which would result in the optical scanning device 70 according to this embodiment becoming larger.

[0065] Furthermore, if the value falls below the lower limit of condition (2), the length of the chamfered portion becomes smaller, making it difficult for the adhesive used to hold the reflective mirror 9 to the housing 30 to flow in, thus making it difficult to bond and hold the reflective mirror 9 with sufficient strength using the housing 30. On the other hand, if the upper limit of condition (2) is exceeded, the angle of the chamfered portion becomes shallower, making it difficult for the adhesive used to hold the reflective mirror 9 to the housing 30 to flow in, and thus making it difficult for the housing 30 to bond and hold the reflective mirror 9 with sufficient strength. In the optical scanning device 70 according to this embodiment, L0 = 1 mm, L2 = 8 mm, and θ = 30°, so conditions (1) and (2) are satisfied.

[0066] Furthermore, in the optical scanning device 70 according to this embodiment, as shown in Figure 4(c), the side wall portion 34 of the housing 30 facing the end face 27 of the reflective mirror 9 has a tapered shape such that the distance from the end face 27 decreases toward the bottom wall portion 33. In other words, the housing 30 has a bottom surface on which the reflective mirror 9 is placed, and a tapered side surface that moves further away from the end surface 27 as it moves away from the bottom surface. In the optical scanning device 70 according to this embodiment, by forming the side wall portion 34 of the housing 30 to have such a tapered shape, the adhesive can be easily poured into the side wall portion 34.

[0067] Furthermore, in the optical scanning device 70 according to this embodiment, when positioning the reflective mirror 9 relative to the housing 30, it is preferable to leave a gap between the side wall portion 34 of the housing 30 and the end face 27 of the reflective mirror 9. This is to adhere the reflective mirror 9 to the housing 30 by pouring adhesive into the gap. In other words, this is to facilitate the flow of adhesive between the side wall portion 34 of the housing 30 and the end face 27 of the reflective mirror 9, and to maintain the adhesive holding of the reflective mirror 9 by the housing 30 even if the length of the reflective mirror 9 in the longitudinal direction changes due to temperature changes.

[0068] Next, the adhesive locations for adhesively holding the reflective mirror 9 in the housing 30 of the optical scanning device 70 according to this embodiment will be described. Figures 5(a) and 5(b) show, respectively, an enlarged cross-sectional view of the portion of the housing 30 holding the reflective mirror 9 in the optical scanning device 70 according to this embodiment, viewed from a predetermined direction perpendicular to the main scanning direction, and an enlarged cross-sectional view viewed from a direction perpendicular to the main scanning direction and the predetermined direction.

[0069] As shown in Figure 5(a), in the optical scanning device 70 according to this embodiment, an adhesive portion 35 is provided between the side wall portion 34 of the housing 30 and the end face 27 of the reflective mirror 9, formed by an adhesive (first adhesive). In other words, the adhesive portion 35 is provided to cover a predetermined region (first region) that includes at least a part of the ridge formed between the reflective surface 20 and the end face 27 of the reflective mirror 9.

[0070] As described above, in the reflective mirror 9 provided in the optical scanning device 70 according to this embodiment, the reflective film 18 is peeled up near the edge formed between the reflective surface 20 and the end face 27, resulting in reduced corrosion resistance. Therefore, by covering the area near the ridge where the reflective film 18 is peeling up with the adhesive portion 35, the occurrence of corrosion near the ridge can be suppressed.

[0071] In this embodiment, the adhesive portion 35 of the housing 30 of the optical scanning device 70 has a moisture permeability of 50 g / m². 2 • Adhesives with low breathability (less than 24 hours) are used. By using an adhesive with low moisture permeability in the bonded portion 35 in this way, the resistance to humidity, which is a factor in causing corrosion near the edge between the reflective surface 20 and the end face 27 of the reflective mirror 9, can be improved, thereby suppressing the occurrence of corrosion. Specifically, as the low moisture permeability adhesive used in the adhesive portion 35 of the housing 30 in the optical scanning device 70 according to this embodiment, an ultraviolet curing adhesive that hardens when irradiated with ultraviolet light, such as Photorec® E (Sekisui Chemical Co., Ltd.), can be used.

[0072] Furthermore, in the adhesive portion 35 of the housing 30 of the optical scanning device 70 according to this embodiment, adhesive is applied over the entire ridge formed between the reflective surface 20 and the end face 27 of the reflective mirror 9. As a result, the entire portion of the reflective film 18 that is curled up near the edge between the reflective surface 20 and the end face 27 of the reflective mirror 9 is covered with adhesive, thereby suppressing the occurrence of corrosion in that portion.

[0073] As described above, in the optical scanning device 70 according to this embodiment, the reflective mirror 9 is bonded to the housing 30 by an adhesive applied to the bonding portion 35, which includes at least a part of the ridge between the reflective surface 20 and the end face 27. As a result, when the reflective film 18 is deposited on the reflective mirror 9 and then cut, the portion that curls up can be covered with the adhesive used to hold the reflective mirror 9 in place by the housing 30, thereby suppressing the occurrence of corrosion in the curled-up portion.

[0074] Furthermore, while maintaining the durability of the reflective mirror 9, it is possible to suppress an increase in the size of the reflective mirror 9, and consequently the optical scanning device 70 according to this embodiment. Although the above configuration has been described for holding the reflective mirror 9 in the optical scanning device 70 according to this embodiment, it is not limited to this, and the above configuration may also be applied to holding the synchronous detection reflective mirror 12a, for example.

[0075] Furthermore, the above describes a configuration in which a reflective mirror 9 is provided in the optical scanning device 70 according to this embodiment, in which the corrosion resistance of the reflective film 18 near the edge between the reflective surface 20 and at least one of the end faces 27 and 28 is lower than the corrosion resistance of the reflective film 18 near the edge between the reflective surface 20 and the side faces 25 and 26, but the invention is not limited to this configuration. In other words, the above configuration can also be applied to a reflective mirror 9 in the optical scanning device 70 according to this embodiment, where the corrosion resistance of the reflective film 18 near the edge between the reflective surface 20 and the end face 27 is lower than that of the reflective film 18 near the edge between the reflective surface 20 and the end face 28.

[0076] Furthermore, the above configuration can also be applied to a reflective mirror 9 in the optical scanning device 70 according to this embodiment, where the corrosion resistance of the reflective film 18 near the edge between the reflective surface 20 and the side surface 25 is lower than that of the reflective film 18 near the edge between the reflective surface 20 and the side surface 26. In other words, the above configuration can also be applied to a reflective mirror 9 in the optical scanning device 70 according to this embodiment, in which the corrosion resistance of the reflective film 18 near the edge between the reflective surface 20 and one of two surfaces perpendicular to the reflective surface 20 and parallel to each other is lower than the corrosion resistance of the reflective film 18 near the edge between the reflective surface 20 and the other of the two surfaces.

[0077] [Second Embodiment] Figures 6(a), (b), and (c) show perspective views at different timings during the manufacturing of the reflective mirror 19 provided in the optical scanning device according to the second embodiment. The optical scanning device according to this embodiment has the same configuration as the optical scanning device 70 according to the first embodiment, except that a reflective mirror 19 and a housing 50 are provided instead of the reflective mirror 9 and housing 30. Therefore, the same reference numerals are used for the same components, and their descriptions are omitted.

[0078] As shown in Figure 6(c), the reflective mirror 19 has longitudinally extending sides 25 and 26 that face each other, and transversely extending end faces 27 and 28 that face each other. The reflective mirror 19 has a rectangular shape with a length L1 = 88 mm in the longitudinal direction and a width L2 = 8 mm in the short direction, within a cross section parallel to the longitudinal and short directions.

[0079] Specifically, when manufacturing the reflective mirror 19, as shown in Figure 6(a), the float glass substrate 41, which is the base material of the reflective mirror 19, is first formed by cutting a large sheet of glass to a length of L4 = 176 mm and a width of L5 = 64 mm. The length L4 = 176 mm in the longitudinal direction of the float glass substrate 41 is set to be twice the length L1 = 88 mm in the longitudinal direction of the reflective mirror 9.

[0080] Furthermore, the width L5 = 64 mm in the short direction of the float glass substrate 41 is set to be eight times the width L2 = 8 mm in the short direction of the reflective mirror 9. Large sheets of glass are cut by scrape cutting. That is, large sheets of glass are cut and separated by first creating a scratch along a cutting line on the front or back surface with a diamond blade, and then applying bending stress on both sides of the scratch, causing the glass to break along the cutting line.

[0081] When large sheets of glass are cut using a scraper in this manner, burrs tend to form on the cut surface. Therefore, the cut surface and its corners are polished, or chamfers are formed on the edges. In particular, chamfered edges are provided on the edges of the surface that becomes the reflective surface 20, where burrs tend to degrade optical performance. Furthermore, in order to suppress the occurrence of injuries when assembling the reflective mirror 19 to the housing 50, it is preferable to provide chamfering on each edge.

[0082] Next, as shown in Figure 6(a), the surface of the float glass substrate 41 is thoroughly cleaned and dried, and then a metal thin film 16 and a protective thin film 17 are formed in that order using a vacuum deposition machine (fourth step). The formation of the reflective film 18 on the surface of the float glass substrate 41 is not limited to vacuum deposition; it may also be carried out using a coating method such as sputtering.

[0083] Furthermore, since attaching the float glass substrate 41 in the vacuum deposition machine is easier than attaching the float glass substrate of the reflective mirror 19, costs can be reduced. In this way, a medium-format mirror 40 can be manufactured in which a reflective film 18 is deposited on a float glass substrate 41.

[0084] Next, as shown in Figure 6(b), eight long mirrors 43 are formed by scraping the medium-format mirror 40 along its longitudinal direction at intervals of L2 = 8 mm in the short direction (fifth step). Furthermore, after the medium-format mirror 40 is scraped and cut to form the long mirror 43, it is preferable to chamfer the edges of the sides of each long mirror 43 in order to suppress the occurrence of injuries when handling them.

[0085] When the medium-format mirror 40 is scraped and cut to form a long mirror 43, the reflective film 18 is curled up near the edges of the sides. The portion of the reflective film 18 that has been peeled up in this manner, specifically the metal thin film 16 made of aluminum or an aluminum-containing alloy, is susceptible to rapid corrosion (oxidative corrosion) when exposed to the outside air, such as moisture, especially in high-temperature and high-humidity environments.

[0086] Therefore, in this embodiment, corrosion is suppressed near the edges of the side surfaces by applying a corrosion inhibitor 44 to the long mirror 43. Specifically, a corrosion inhibitor 44 is applied to the side surface of the long mirror 43 and to the chamfered portion between the reflective surface 20 and the side surface.

[0087] For example, Miratect (Tightly Co., Ltd.) can be used as the corrosion inhibitor 44. In this case, since the corrosion inhibitor 44 is applied to the long mirror 43, the number of steps can be reduced compared to the case where the corrosion inhibitor 44 is applied to each of the two reflective mirrors 19 formed from the long mirror 43, as will be described later.

[0088] Next, as shown in Figure 6(c), two reflective mirrors 19 are formed by scraping the long mirror 43 along its short side at intervals of L1 = 88 mm along its longitudinal side (fifth step). Furthermore, chamfering may be provided on the edges of the end faces 27 and 28 of the formed reflective mirror 19.

[0089] As described above, in the reflective mirror 19, the corrosion inhibitor 44 is applied near the edges of the sides 25 and 26, while the corrosion inhibitor 44 is not applied near the edges of the end faces 27 and 28. When the long mirror 43 is scraped and cut to form the reflective mirror 19, the reflective film 18 is curled up near at least one edge of the end faces 27 and 28.

[0090] Furthermore, the lifted portion of the metal thin film 16 of the reflective film 18, which is made of aluminum or an aluminum-containing alloy, becomes susceptible to rapid corrosion (oxidative corrosion) when exposed to the outside air, such as moisture, especially in high-temperature and high-humidity environments. As a result, the reflectivity of the corroded portion of the metal thin film 16 will decrease significantly.

[0091] On the other hand, since corrosion inhibitor 44 is applied near the edges of the sides 25 and 26 of the reflective mirror 19, the occurrence of corrosion (oxidative corrosion) in the portion of the reflective film 18 that is peeled up near the edges of the sides 25 and 26 is suppressed. Therefore, a decrease in reflectivity in that portion can be suppressed. As described above, in the reflective mirror 19, the portions of the reflective film 18 formed near the edges of the side surfaces 25 and 26 have higher corrosion resistance (are less susceptible to corrosion) than the portions of the reflective film 18 formed near at least one edge of the end faces 27 and 28.

[0092] Figures 7(a) and 7(b) show, respectively, an enlarged cross-sectional view and an enlarged sub-scanning cross-sectional view of the portion of the housing 50 holding the reflective mirror 19 in the optical scanning device according to this embodiment, viewed from a predetermined direction perpendicular to the main scanning direction. Figure 7(c) also shows an enlarged cross-sectional view of the portion of the housing 50 holding the reflective mirror 19 in the optical scanning device according to this embodiment, viewed from the main scanning direction and a direction perpendicular to the predetermined direction.

[0093] Although the following describes the holding of one side of the reflective mirror 19 in the longitudinal direction by the housing 50, the configuration described below also applies to the holding of the other side of the reflective mirror 19 in the longitudinal direction by the housing 50. As shown in Figures 7(a) and (b), in the housing 50 provided in the optical scanning device according to this embodiment, the positioning unit 52 for determining the position and angle of the reflective mirror 19 is formed to be integrated with the side wall 51.

[0094] In the optical scanning device according to this embodiment, after placing the reflective mirror 19 on the bottom wall portion 53, the orientation, i.e., position and angle of the reflective mirror 19 is determined by bringing the longitudinal end of the back surface (sixth surface) of the reflective mirror 19 into contact with the positioning portion 52. In other words, the back surface is the surface opposite to the reflective surface 20 of the reflective mirror 19.

[0095] In the optical scanning device according to this embodiment, the entire reflective surface 20 of the reflective mirror 19 can be used as an effective area by bringing the back surface of the reflective mirror 19 into contact with the positioning unit 52 when determining the orientation of the reflective mirror 19. Therefore, by reducing the size of the reflective mirror 19 in the longitudinal direction, the optical scanning device according to this embodiment can be miniaturized.

[0096] Furthermore, in the optical scanning device according to this embodiment, similar to the optical scanning device 70 according to the first embodiment, a portion of the reflective mirror 19 is held in place by being bonded to the housing 50 using an adhesive. Therefore, as shown in Figure 7(c), it is preferable that the above conditions (1) and (2) are satisfied at the ridge between the side surface 25 and the end surface 27 of the reflective mirror 19.

[0097] In the optical scanning device according to this embodiment, the reflective mirror 19 has L0 = 1.4 mm, L2 = 8 mm, and θ = 10°, so conditions (1) and (2) are satisfied. Furthermore, in the optical scanning device according to this embodiment, as shown in Figure 7(c), the side wall portion 54 of the housing 50 facing the end face 27 of the reflective mirror 19 has a tapered shape such that the distance from the end face 27 decreases toward the bottom wall portion 53.

[0098] Figures 8(a) and 8(b) show, respectively, an enlarged cross-sectional view of the portion of the housing 50 holding the reflective mirror 19 in the optical scanning device according to this embodiment, viewed from a predetermined direction perpendicular to the main scanning direction, and an enlarged cross-sectional view viewed from a direction perpendicular to the main scanning direction and the predetermined direction. As shown in Figure 8(a), in the optical scanning device according to this embodiment, similar to the optical scanning device 70 according to the first embodiment, an adhesive bonding portion 55 is provided between the side wall portion 54 of the housing 50 and the end face 27 of the reflective mirror 19. The adhesive portion 55 is provided to cover the ridge formed between the reflective surface 20 and the end face 27 of the reflective mirror 19.

[0099] As described above, in the reflective mirror 19 provided in the optical scanning device according to this embodiment, the reflective film 18 is peeled up near the ridge formed between the reflective surface 20 and the end face 27, resulting in reduced corrosion resistance. Therefore, by covering the area near the ridge where the reflective film 18 is peeling up with the adhesive portion 55, the occurrence of corrosion near the ridge can be suppressed.

[0100] In this embodiment, the adhesive portion 55 of the housing 50 of the optical scanning device has a moisture permeability of 50 g / m². 2 • Adhesives with low breathability (less than 24 hours) are used. By using an adhesive with low moisture permeability in the bonded portion 55 in this way, the resistance to humidity, which is a factor in causing corrosion near the edge between the reflective surface 20 and the end face 27 of the reflective mirror 19, can be improved, thereby suppressing the occurrence of corrosion. Specifically, as the low moisture permeability adhesive used in the adhesive portion 55 of the housing 50 in the optical scanning device according to this embodiment, an ultraviolet curing adhesive, such as Photorec® E (Sekisui Chemical Co., Ltd.), can be used.

[0101] Furthermore, in the optical scanning device according to this embodiment, as shown in Figure 8(a), an adhesive bonding portion 56 is also provided between both the side wall portion 54 and the side wall portion 51 of the housing 50 and the end face 27 of the reflective mirror 19. In other words, the reflective mirror 19 is bonded to the housing 50 by an adhesive (second adhesive) applied to a predetermined area (second area) that includes at least a portion of the ridge (third ridge) between the end face 27 and the back surface. In the optical scanning device 70 according to the first embodiment described above, as shown in Figures 4(a) and (b), a positioning portion 32 is provided in the housing 30 so as to abut the end of the reflective surface 20 of the reflective mirror 9 in the longitudinal direction.

[0102] Therefore, as shown in Figure 4(b), the positioning unit 32 presses against the reflective surface 20 of the reflective mirror 9 in accordance with the weight of the reflective mirror 9. On the other hand, in the optical scanning device according to this embodiment, as shown in Figure 7(b), the weight of the reflective mirror 19 is generated such that the positioning unit 52 and the reflective mirror 19 are separated from each other.

[0103] Therefore, in the optical scanning device according to this embodiment, an adhesive portion 56 is provided in the housing 50 to suppress the separation between the positioning portion 52 and the reflective mirror 19. Furthermore, it is preferable to use an adhesive with high adhesive strength for the adhesive portion 56 so that the housing 50 can adequately hold the reflective mirror 19. For example, an ultraviolet curing adhesive such as 3038C (ThreeBond Co., Ltd.) can be used.

[0104] In other words, it is preferable that the adhesive strength of the adhesive used in the adhesive portion 56 is greater than the adhesive strength of the adhesive used in the adhesive portion 55. Furthermore, the adhesive portion 55 and the adhesive portion 56 may be integrally bonded to each other.

[0105] Furthermore, in the adhesive portion 55 of the housing 50 in the optical scanning device according to this embodiment, adhesive is applied to the entire ridge formed between the reflective surface 20 and the end face 27 of the reflective mirror 19. As a result, the entire portion of the reflective film 18 that is curled up near the edge between the reflective surface 20 and the end face 27 of the reflective mirror 19 is covered with adhesive, thereby suppressing the occurrence of corrosion in that portion.

[0106] As described above, in the optical scanning device according to this embodiment, the reflective mirror 19 is bonded to the housing 50 by an adhesive applied to the bonding portion 55, which includes at least a part of the ridge between the reflective surface 20 and the end face 27. As a result, the portion of the reflective mirror 19 that curls up after the reflective film 18 is deposited and then cut can be covered with the adhesive used when the reflective mirror 19 is held in place by the housing 50, thereby suppressing the occurrence of corrosion in the curled-up portion. Furthermore, while maintaining the durability of the reflective mirror 19, it is possible to suppress the increase in size of the reflective mirror 19 and, consequently, the optical scanning device according to this embodiment.

[0107] This embodiment also includes a method for manufacturing an optical scanning apparatus according to the first or second embodiment. In other words, the method includes the step of applying an adhesive to a predetermined area that has lower corrosion resistance than the corrosion resistance of the ridge between the reflective surface and the end face of the reflective mirror provided in the optical scanning device. The method also includes the step of bonding the reflective mirror to the housing using an adhesive applied to the predetermined area.

[0108] [Image forming apparatus] Figure 9 shows a schematic sub-scanning cross-sectional view of a color image forming apparatus 100 equipped with an optical scanning device according to the first or second embodiment.

[0109] The color image forming apparatus 100 is a tandem-type color image forming apparatus in which four optical scanning devices according to the first or second embodiment each record image information on the photosensitive surface of four photosensitive drums, which are image carriers, in parallel. The color image forming apparatus 100 comprises optical scanning devices 101, 102, 103, and 104 according to the first or second embodiment, and photosensitive drums 121, 122, 123, and 124. The color image forming apparatus 100 also includes developer units 111, 112, 113, and 114, a transport belt 130, a printer controller 140, and a fuser 160.

[0110] As shown in Figure 9, the color image forming apparatus 100 receives R (red), G (green), and B (blue) color signals output from an external device 150 such as a personal computer. The input color signals are then converted into C (cyan), M (magenta), Y (yellow), and K (black) image data (dot data) by a printer controller 140 located within the color image forming apparatus 100.

[0111] Next, the image data is input to optical scanning devices 101, 102, 103, and 104, respectively, and optical scanning devices 101, 102, 103, and 104 emit modulated optical beams 131, 132, 133, and 134 according to the respective image data. The emitted light beams 131, 132, 133, and 134 then scan the photosensitive surfaces of the photosensitive drums 121, 122, 123, and 124 in the main scanning direction.

[0112] A charging roller (not shown) is provided in contact with the photosensitive surface of each of the photosensitive drums 121, 122, 123, and 124 to uniformly charge the respective photosensitive surfaces. The photosensitive surfaces of the photosensitive drums 121, 122, 123, and 124, which have been charged by the charging roller, are then illuminated by light scanning devices 101, 102, 103, and 104 with light beams 131, 132, 133, and 134.

[0113] As described above, the light beams 131, 132, 133, and 134 are modulated based on image data of each color, and by irradiating with the light beams 131, 132, 133, and 134, electrostatic latent images are formed on the photosensitive surfaces of the photosensitive drums 121, 122, 123, and 124. The formed electrostatic latent image is then developed as a toner image by developing units 111, 112, 113, and 114, which are arranged to contact the photosensitive drums 121, 122, 123, and 124.

[0114] Next, the toner images developed by the developing units 111 to 114 are transferred in multiple layers onto a sheet of paper (transfer material) (not shown) that is transported on a transport belt 130 by a transfer roller (transfer unit) (not shown) positioned opposite the photosensitive drums 121 to 124. This forms a single full-color image. The paper onto which the unfixed toner image has been transferred is then transported to the fuser 160, which is located behind the photosensitive drums 121, 122, 123, and 124 (on the left side in Figure 9).

[0115] The fuser 160 is formed by a fuser roller having a fuser heater (not shown) inside and a pressure roller disposed to press against the fuser roller. Then, the paper transported from the transfer roller is heated while being pressurized by the contact area between the fixing roller and the pressure roller, thereby fixing the unfixed toner image on the paper.

[0116] Furthermore, a paper discharge roller (not shown) is located behind the fuser 160, and this paper discharge roller ejects the fixed paper to the outside of the color image forming apparatus 100. Optical scanning devices 101, 102, 103, and 104 correspond to the colors C (cyan), M (magenta), Y (yellow), and K (black).

[0117] The optical scanning devices 101, 102, 103, and 104 each record image signals (image information) on the photosensitive surfaces of the photosensitive drums 121, 122, 123, and 124 in parallel, thereby printing color images at high speed. As the external device 150, for example, a color image reading device equipped with a CCD sensor or a CMOS sensor may be used.

[0118] In this case, a color digital copier is formed by the color image reading device and the color image forming device 100. Although preferred embodiments have been described above, the invention is not limited to these embodiments, and various modifications and changes are possible within the scope of its essence.

[0119] This embodiment includes the following configurations and methods. (Configuration 1) An optical scanning device comprising: a deflector that deflects a light beam from a light source to scan a surface to be scanned in the main scanning direction; an optical system that guides the light beam deflected by the deflector to the surface to be scanned; a reflective element having a reflective surface that reflects the light beam deflected by the deflector, and first and second surfaces that are non-parallel to the reflective surface; and a holding member that holds the reflective element, wherein in the reflective element, the corrosion resistance of the second ridge between the reflective surface and the second surface is lower than the corrosion resistance of the first ridge between the reflective surface and the first surface, and the first region including at least a part of the second ridge is bonded to the holding member by a first adhesive. (Configuration 2) The optical scanning apparatus according to Configuration 1, characterized in that the reflective surface reflects the light beam that is deflected by the deflector and reaches the scanning surface. (Configuration 3) The optical scanning apparatus according to Configuration 1 or 2, characterized in that the first and second surfaces are non-parallel to each other. (Configuration 4) The optical scanning apparatus according to any one of Configurations 1 to 3, characterized in that the reflective element extends in the main scanning direction and the second surface is perpendicular to the main scanning direction. (Configuration 5) The optical scanning apparatus according to any one of Configurations 1 to 4, characterized in that the holding member holds the deflector and the optical system. (Configuration 6) The optical scanning device according to any one of Configurations 1 to 5, characterized in that the first adhesive is an adhesive that hardens when irradiated with ultraviolet light. (Configuration 7) The optical scanning apparatus according to any one of Configurations 1 to 6, characterized in that the reflective element has a third surface located between the reflective surface and the first surface, and a reflective film is formed on the third surface and the reflective surface. (Configuration 8) An optical scanning device according to any one of Configurations 1 to 7, characterized in that when L0 is the length of the fourth surface located between the first surface and the second surface in a plane parallel to the first surface, L2 is the distance between the fifth surface on the opposite side of the first surface of the reflecting element and the first surface, and θ(°) is the angle between the second surface and the fourth surface, the conditions 0.05 ≤ L0 / L2 ≤ 0.2 and 5 ≤ θ ≤ 45 are satisfied. (Configuration 9) The optical scanning apparatus according to any one of Configurations 1 to 8, characterized in that the holding member includes a bottom surface on which a reflective element is placed and a side surface having a tapered shape that moves further away from the second surface as it moves away from the bottom surface. (Configuration 10) The optical scanning apparatus according to any one of Configurations 1 to 9, characterized in that the holding member has a protrusion that contacts the reflective surface. (Configuration 11) The optical scanning apparatus according to any one of Configurations 1 to 9, characterized in that the holding member has a projection that abuts against a sixth surface of the reflecting element opposite to the reflective surface, and the reflecting element is bonded to the holding member by a second adhesive applied to a second region including at least a part of the third edge between the second surface and the sixth surface. (Configuration 12) The optical scanning apparatus according to Configuration 11, characterized in that the adhesive strength of the second adhesive is greater than the adhesive strength of the first adhesive. (Configuration 13) An optical scanning apparatus according to any one of Configurations 1 to 12, characterized in that the first region includes the entire second ridge. (Composition 14) The moisture permeability of the first adhesive is 50 g / m 2 An optical scanning apparatus according to any one of configurations 1 to 13, characterized in that it operates for 24 hours or less. (Configuration 15) An image forming apparatus comprising an optical scanning device described in any one of Configurations 1 to 14, and a developer for developing an electrostatic latent image formed on a surface to be scanned by the optical scanning device. (Configuration 16) An image forming apparatus comprising an optical scanning device described in any one of Configurations 1 to 14, and a controller that converts a signal output from an external device into image data and inputs it to the optical scanning device. (Method 1) A method for manufacturing an optical scanning device, wherein the optical scanning device comprises a deflector that deflects a light beam from a light source to scan a surface to be scanned in the main scanning direction, an optical system that guides the light beam deflected by the deflector to the surface to be scanned, a reflective element having a reflective surface that reflects the light beam deflected by the deflector, and first and second surfaces that are non-parallel to the reflective surface, and a holding member that holds the reflective element, wherein in the reflective element, the corrosion resistance of the second ridge between the reflective surface and the second surface is lower than the corrosion resistance of the first ridge between the reflective surface and the first surface, and the method comprises the steps of applying a first adhesive to a first region including at least a part of the second ridge, and bonding the reflective element to the holding member with the first adhesive applied to the first region. (Method 2) The method according to Method 1, characterized by comprising: a first step of cutting a substrate so as to form a first surface; a second step of forming a reflective surface by forming a reflective film on the substrate after the first step; and a third step of manufacturing a reflective element by cutting the substrate so as to form a second surface after the second step. (Method 3) The method according to Method 1, characterized by comprising a fourth step of forming a reflective surface by forming a reflective film on a substrate, and a fifth step of manufacturing a reflective element by cutting the substrate after the fourth step so that the first and second surfaces are formed. (Method 4) The method according to Method 2 or 3, characterized in that the cutting of the substrate is performed by first forming a scratch on the substrate and then applying stress to both sides of the scratch. [Explanation of Symbols]

[0120] 1 light source 5. Polygon mirror (deflector) 8. Imaging optical system (optical system) 9. Reflective mirror (reflective element) 11 Scanned surface 20 reflective surface 25, 26 Side view (first side) 27, 28 End faces (second faces) 30 Housing (holding member) 35 Adhesive area (first region) 70 Optical scanning device

Claims

1. A deflector that deflects the light beam from the light source to scan the surface to be scanned in the main scanning direction, An optical system that guides the light beam deflected by the deflector to the surface to be scanned, A reflective element having a reflective surface that reflects the light beam deflected by the deflector, and first and second surfaces that are non-parallel to the reflective surface, The system comprises a holding member for holding the reflective element, In the reflective element, the corrosion resistance of the second edge between the reflective surface and the second surface is lower than the corrosion resistance of the first edge between the reflective surface and the first surface. An optical scanning device characterized in that the first region, including at least a portion of the second ridge, is bonded to the retaining member by a first adhesive.

2. The optical scanning apparatus according to claim 1, characterized in that the reflective surface reflects the light beam that is deflected by the deflector and reaches the surface to be scanned.

3. The optical scanning apparatus according to claim 1, characterized in that the first and second surfaces are non-parallel to each other.

4. The reflective element extends in the main scanning direction, The optical scanning apparatus according to claim 1, characterized in that the second surface is perpendicular to the main scanning direction.

5. The optical scanning apparatus according to claim 1, characterized in that the holding member holds the deflector and the optical system.

6. The optical scanning apparatus according to claim 1, characterized in that the first adhesive is an adhesive that hardens when irradiated with ultraviolet light.

7. The optical scanning apparatus according to claim 1, characterized in that the reflective element has a third surface located between the reflective surface and the first surface, and a reflective film is formed on the third surface and the reflective surface.

8. When L0 is the length of the fourth surface located between the first surface and the second surface in a plane parallel to the first surface, L2 is the distance between the fifth surface on the opposite side of the reflective element from the first surface and the first surface, and θ (°) is the angle between the second surface and the fourth surface, 0.05 ≤ L0 / L2 ≤ 0.2 5 ≤ θ ≤ 45 The optical scanning apparatus according to claim 1, characterized in that it satisfies the following conditions.

9. The optical scanning apparatus according to claim 1, characterized in that the holding member includes a bottom surface on which the reflective element is placed, and a side surface having a tapered shape that moves further away from the second surface as it moves away from the bottom surface.

10. The optical scanning apparatus according to claim 1, characterized in that the holding member has a protrusion that contacts the reflective surface.

11. The holding member has a projection that contacts the sixth surface of the reflecting element opposite to the reflective surface, The optical scanning apparatus according to claim 1, characterized in that the reflective element is bonded to the holding member by a second adhesive applied to a second region including at least a portion of the third edge between the second surface and the sixth surface.

12. The optical scanning apparatus according to claim 11, characterized in that the adhesive strength of the second adhesive is greater than the adhesive strength of the first adhesive.

13. The optical scanning apparatus according to claim 1, characterized in that the first region includes the entire area of ​​the second ridge.

14. The moisture permeability of the first adhesive is 50 g / m². ２ The optical scanning apparatus according to claim 1, characterized in that it is 24 hours or less.

15. An image forming apparatus comprising an optical scanning apparatus according to any one of claims 1 to 14, and a developer for developing an electrostatic latent image formed on the surface to be scanned by the optical scanning apparatus.

16. An image forming apparatus comprising an optical scanning device according to any one of claims 1 to 14, and a controller that converts a signal output from an external device into image data and inputs it to the optical scanning device.

17. A method for manufacturing an optical scanning device, The optical scanning device comprises a deflector that deflects a light beam from a light source to scan a surface to be scanned in the main scanning direction, an optical system that guides the light beam deflected by the deflector to the surface to be scanned, a reflective element having a reflective surface that reflects the light beam deflected by the deflector, and first and second surfaces that are non-parallel to the reflective surface, and a holding member that holds the reflective element. In the reflective element, the corrosion resistance of the second edge between the reflective surface and the second surface is lower than the corrosion resistance of the first edge between the reflective surface and the first surface. The aforementioned method, A step of applying a first adhesive to a first region including at least a portion of the second ridge, A method for manufacturing an optical scanning device, characterized by comprising the step of bonding the reflective element to the holding member with the first adhesive applied to the first region.

18. A first step of cutting the substrate so that the first surface is formed, A second step is to form the reflective surface by forming a reflective film on the substrate after the first step, The method according to 17, further comprising a third step of manufacturing the reflective element by cutting the substrate after the second step such that the second surface is formed.

19. A fourth step is to form the reflective surface by forming a reflective film on the substrate, The method according to 17, further comprising a fifth step of manufacturing the reflective element by cutting the substrate after the fourth step such that the first and second surfaces are formed.

20. The method according to 18 or 19, characterized in that the cutting of the substrate is performed by forming a scratch on the substrate and then applying stress to both sides of the scratch.

Images