LED chip, exposure head, image forming apparatus, and method for manufacturing LED chip

Abstract

To provide an LED chip in which the ratio of stray light to normal light from a light emitting element is reduced without impairing the light emitting characteristics of the light emitting element, and a method for manufacturing the same.SOLUTION: An embodiment of the present disclosure relates to an LED chip having a light-emitting region in which a plurality of light-emitting elements are arranged two-dimensionally on a main surface of a substrate, and a contact region arranged outside the light-emitting region, the plurality of light-emitting elements have a second electrode that is continuous across the plurality of light-emitting elements, the light-emitting region has long sides extending in a first direction and short sides extending in a second direction intersecting the first direction, and an end of the second electrode in the first direction has a portion that is non-parallel to a third direction perpendicular to the first direction.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to, for example, an LED chip, an exposure head, an image forming apparatus, and a method for manufacturing an LED chip. [Background technology]

[0002] 2. Description of the Related Art Conventionally, the technology described in Patent Document 1 is known as a technology relating to an exposure head used in an electrophotographic image forming apparatus.

[0003] The exposure head described in Patent Document 1 includes a substrate on which a plurality of light-emitting elements are arranged along the axial direction of a photosensitive drum, and a lens that collects light emitted from the plurality of light-emitting elements. In the exposure head, the light emitted from the plurality of light-emitting elements is collected through the lens to expose the photosensitive drum.

[0004] Therefore, the exposure head described in Patent Document 1 is disposed close to the photosensitive drum together with a developing device that develops the latent image formed on the photosensitive drum with toner. Therefore, the exposure head is disposed close to the developing device. In addition, the exposure head includes an LED (Light Emitting Diode) as a light-emitting element. The light-emitting element may be an organic light-emitting element.

[0005] In the exposure head, ghost spots may occur on the photosensitive drum due to stray light, and if the ratio of stray light to normal light for exposure increases, print quality will deteriorate.

[0006] In an organic light-emitting element, the electrode on the light-emitting side of the electrodes arranged on either side of the organic light-emitting layer may be made of a metal with high reflectivity such as Al or Ag. When the light emitted from the organic light-emitting element becomes unintended stray light due to scattering in the light-emitting element substrate, the housing of the exposure head in which the organic light-emitting element is installed, or on the surface of the photosensitive drum, the electrode made of the highly reflective metal may reflect the stray light. Therefore, the stray light transmitted through the lens array generates ghost spots on the photosensitive drum.

[0007] The configuration described in Patent Document 1 includes an organic light-emitting element disposed on a glass substrate, and a second electrode disposed on the opposite side of a projection surface of the emitted light from the organic light-emitting element, i.e., a photosensitive drum. The second electrode is provided with anti-reflection means for preventing stray light. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2006-236727 A Summary of the Invention [Problem to be solved by the invention]

[0009] The stray light countermeasure configuration of Patent Document 1 requires roughness treatment of the second electrode of the organic light-emitting element and application of an anti-reflection layer between the organic light-emitting layer and the second electrode, which may impair the light-emitting characteristics of the organic light-emitting element itself.

[0010] One aspect of the present disclosure provides an LED chip in which the ratio of stray light to normal light from a light-emitting element is reduced without impairing the light-emitting characteristics of the light-emitting element, and a manufacturing method thereof. [Means for solving the problem]

[0011] One aspect of the present disclosure relates to an LED chip having a light-emitting region in which a plurality of light-emitting elements are arranged two-dimensionally on a main surface of a substrate, and a contact region arranged outside the light-emitting region, the plurality of light-emitting elements have a first electrode, an organic layer, and a second electrode on a light-emitting side, the second electrode being continuous across the plurality of light-emitting elements, and in a planar view with respect to the main surface, the light-emitting region has a long side extending in a first direction and a short side extending in a second direction intersecting the first direction, and in the planar view, an end of the second electrode in the first direction has a portion that is non-parallel to a third direction perpendicular to the first direction.

[0012] Another aspect of the present disclosure relates to a method for manufacturing an organic EL element including at least one organic layer between a first electrode and a second electrode, the method including the steps of: placing a deposition mask having a plurality of openings against a substrate on which the first electrode and the organic layer are disposed; aligning the substrate and the deposition mask; and forming the second electrode on the substrate by depositing a deposition material through the openings in the deposition mask, the openings in the deposition mask having long sides extending in a first direction, short sides extending in a second direction intersecting with the first direction, and a portion at an end in the first direction that is non-parallel to a third direction intersecting with the first direction. Effect of the Invention

[0013] According to one aspect of the present disclosure, it is possible to provide an LED chip in which the ratio of stray light to normal light from an organic light-emitting element is reduced without impairing the light-emitting characteristics of the organic light-emitting element, and a method for manufacturing the same. [Brief description of the drawings]

[0014] [Figure 1] (a) A schematic diagram of an example of a portion of an LED chip when viewed in plan, (b) A cross-sectional view of the LED chip in (a) taken along line A-A', (c) An enlarged view of a region R surrounded by a dashed dotted line in the LED chip in (a), (d) A diagram showing an example of the shape of the light-emitting region of the LED chip in (a), and (e) A cross-sectional view of the LED chip in (a) taken along line BB'. [Diagram 2] FIG. 1 is an enlarged view illustrating the shape of a second electrode; [Diagram 3] (a) and (b) Schematic diagrams of an example of a part of an LED chip when viewed from above [Figure 4] (a) and (b) Schematic diagrams of an example of a part of an LED chip when viewed from above [Diagram 5] (a) is a schematic diagram showing an example of a part of an LED chip having a color filter when viewed from above, and (b) is a cross-sectional view taken along line A-A' of the LED chip in (a). [Figure 6](a) is a schematic diagram showing an example of a part of an LED chip having a color filter when viewed from above, and (b) is a cross-sectional view taken along line A-A' of the LED chip in (a). [Figure 7] FIG. 1 is a cross-sectional view showing an example of an exposure head. [Figure 8] FIG. 1 is a schematic diagram for explaining a head substrate and a lens array in an exposure head; [Figure 9] Schematic diagram for explaining a part of the manufacturing method of an LED chip [Figure 10] FIG. 1 is a perspective view of an image forming apparatus; [Figure 11] 11 is a schematic cross-sectional view of the image forming apparatus in FIG. 10. [Figure 12] Schematic diagram of an example of a part of an LED chip DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, the embodiments of the present invention will be described with reference to the drawings. Note that the dimensions, materials, shapes, relative positions, and the like of the components described below are not intended to limit the scope of the present disclosure unless otherwise specified.

[0016] [First embodiment] An example of the LED chip of this embodiment will be described with reference to Figures 1 to 4. The light emitting element 69 of the LED chip 53 has a first electrode 63, a second electrode 67, and an organic layer 66 arranged between the first electrode and the second electrode on a substrate 61. A protective layer, a color filter, etc. may be provided on the second electrode 67. When a color filter is provided, a planarizing layer may be provided between the protective layer. The planarizing layer may be made of acrylic resin or the like.

[0017] A specific example of the LED chip configuration will be described with reference to the drawings. Fig. 1(a) is a schematic plan view showing an example of a portion of an LED chip 53 using the light-emitting element of this embodiment, and Fig. 1(b) is a schematic cross-sectional view taken along line A-A' in Fig. 1(a). A plan view refers to a plan view taken from a direction perpendicular to a certain surface (the normal direction of the surface).

[0018] As shown in FIG. 1(a), the LED chip 53 of this embodiment has a light-emitting region 60 in which a plurality of light-emitting elements 69 are arranged two-dimensionally on the main surface of a substrate 61, and a contact region 64a arranged outside the light-emitting region 60.

[0019] As shown in FIG. 1(b), the plurality of light-emitting elements 69 have a first electrode 63 arranged on the main surface of the substrate 61, an organic layer 66 including at least a light-emitting layer arranged thereon, and a second electrode 67 (upper electrode) arranged on the light-emitting side. The second electrode 67 is continuous across the plurality of light-emitting elements 69. In a plan view of the main surface, the light-emitting region 60 has a long side extending in a first direction X and a short side extending in a second direction Y' intersecting the first direction, and an example of a rectangle is shown here. In the plan view, an end of the second electrode 67 in the first direction X has a portion that is not parallel to a third direction Y perpendicular to the first direction X. Details will be described later.

[0020] Moreover, the LED chip 53 has an insulating layer 62 that covers the end of the first electrode 63 and has an opening 65 on the first electrode 63, and functions as a bank, and a protective layer 68 that is disposed on the second electrode 67. Furthermore, the LED chip 53 has wiring 64 disposed in the contact region 64a to apply a voltage to the second electrode 67. Also, the LED chip 53 has a pad section 70 for inputting a control signal from the image forming apparatus main body to each LED chip 53. The LED chip 53 has a moisture-resistant ring 116 disposed around the light-emitting region 60, the contact region 64a, and the pad section 70. The moisture-resistant ring 116 can suppress the intrusion of moisture into the light-emitting element.

[0021] In this specification, the light emitting region 60 of the LED chip refers to the entire element light emitting region of the plurality of light emitting elements arranged on the substrate of the LED chip in the plan view. Therefore, the shape of the light emitting region 60 of the LED chip is the shape of the outer edge when all the element light emitting regions of the plurality of light emitting elements are regarded as one light emitting region, and may include non-light emitting regions such as bank regions.

[0022] Specifically, the outer edge shape of the light-emitting region 60 is, for example, a region connecting the ends of the openings 65 of the insulating layer 62 of the outermost light-emitting elements. Therefore, as shown in FIG. 1(b), in the cross-sectional view of the LED chip taken along line A-A', the light-emitting region 60 is a region partitioned by dotted lines.

[0023] The outer edge shape of the light-emitting region will be described in more detail with reference to FIG. 1(c). FIG. 1(c) shows an enlarged view of the region R surrounded by the dashed line of the LED chip in (a). Here, the outermost corners of the opening 65 of the insulating layer 60 of the light-emitting element that is also outermost in the second direction Y among the four light-emitting elements that are outermost in the first direction X are defined as corners C1 and C2. Similarly, the outermost corners of the opening 65 of the insulating layer 60 of the light-emitting element that is also outermost in the second direction among the four light-emitting elements that are outermost on the opposite side of the first direction X are defined as corners C3 and C4.

[0024] At this time, as shown in FIG. 1(d), the shape formed by the lines connecting the corners C1, C2, C3, and C4 is the outer edge shape of the light-emitting region 60. For example, in FIG. 1, the light-emitting region 60 is a parallelogram having a long side extending in the first direction X and a short side extending in the second direction Y' intersecting with the first direction X. Note that the corners C1, C2, C3, and C4 may be rounded due to the processing accuracy and alignment accuracy in the manufacturing process. Even in such a case, the outer edge shape can be specified by taking the point where the two lines sandwiching these corners intersect as the tip of the corner.

[0025] Here, the element light-emitting regions of the multiple light-emitting elements may have discontinuous parts or misalignment on the long and short sides of the light-emitting region 60, but the outer edge of the light-emitting region 60 of the LED chip is defined by the approximation lines of the outer edges of these element light-emitting regions, as described above. For example, the first direction X and the second direction Y' are directions parallel to the approximation lines of the outermost light-emitting regions of the element light-emitting regions of the multiple light-emitting elements.

[0026] The element light-emitting region, which is the light-emitting region of each light-emitting element, refers to the portion where the first electrode 63, the organic layer 66, and the second electrode 67 are laminated in the opening 65 of the insulating layer 62. The non-light-emitting region refers to the portion other than the light-emitting region.

[0027] In a plan view, the length of the long side of the light-emitting region 60 in this embodiment is five times or more the length of the short side. The area occupied by the light-emitting region 60 is the largest in the LED chip 53. Therefore, the length of the long side of the LED chip 53 is also five times or more the length of the short side of the LED chip 53.

[0028] (Arrangement and shape of the second electrode) The shape of the second electrode 67 of the LED chip 53 will be described with reference to Fig. 1. In order to reduce stray light in the LED chip 53, it is preferable to make the area of ​​the second electrode 67, which generates unintended stray light due to reflection, as small as possible. On the other hand, the second electrode 67 has an area necessary for the light emitting element 69 to obtain its original function. Therefore, it is preferable to make the area of ​​the second electrode 67 as small as possible without impairing the light emitting characteristics of the light emitting element 69.

[0029] In this embodiment, as one aspect, an example will be described in which the contact regions 64a are located at both ends in the longitudinal direction of the light-emitting region 60 in which the light-emitting elements 69 are two-dimensionally arranged in the longitudinal and lateral directions. However, the contact regions 64a may be located at any position on the substrate 61.

[0030] Since the second electrode 67 is formed to extend to the contact region 64a, the area of ​​the second electrode increases if the contact region 64a is located away from the light-emitting region 60. Therefore, it is preferable that the contact region 64a is located close to the light-emitting region 60. Also, from the viewpoint of electrical resistance, it is preferable that the contact region 64a is located close to the light-emitting region 60.

[0031] The second electrode of this embodiment has a portion removed at an end in the first direction X, and as a result has a portion that is non-parallel to the third direction Y. By having a portion that is non-parallel to the third direction Y in this manner (having a cutout portion), the area of ​​the second electrode can be made smaller than when there is no cutout portion.

[0032] This will be described in detail. When the contact region 64a is outside the light emitting region 60, the area of ​​the second electrode 67 can be theoretically minimized by forming the second electrode 67 along the outermost periphery of the light emitting region 60 and the contact region 64a. For example, in the case of the structure of FIG. 1(a), the area of ​​the second electrode 67 can be minimized by setting a closed region 71 including a plurality of light emitting elements 69 represented by two-dot chain lines connecting the four corners of the contact region 64a as the film formation region of the second electrode 67.

[0033] However, for example, when the second electrode 67 is formed by vacuum deposition through an opening in a deposition mask, there is a gap between the deposition mask and the substrate on which the second electrode is formed by deposition, and the film formed by deposition has a deposition blurred portion. The thickness of the deposition blurred portion is thin, which is undesirable because it tends to increase the electrical resistance. Therefore, the shape of the second electrode 67 requires an isotropic margin width (M) that corresponds to the predetermined alignment accuracy of the deposition device used. Therefore, the area 72 indicated by the dashed line including the area 71 must be the film formation area of ​​the second electrode 67, and the area of ​​the second electrode 67 that contributes to unintended light reflection is larger than the area 71.

[0034] Fig. 1(e) shows a cross-sectional view of the LED chip of Fig. 1(a) taken along line BB'. A transistor 115 for driving a light-emitting element and an insulator 101 are arranged on the substrate 100. An insulating layer 102, a plug 111 arranged in the insulating layer 102, a conductive layer 107, an insulating layer 103, and a plug 112 arranged in the insulating layer 103 are arranged on the transistor 115 and the insulator 101 in this order from the substrate 100 side.

[0035] Furthermore, on the insulating layer 103, a conductive layer 108, an insulating layer 104, a plug 113 disposed in the insulating layer 104, a conductive layer 109 and a conductive layer 117 functioning as a pad electrode, the insulating layer 105, and a plug 114 disposed in the insulating layer 105 are disposed in this order from the substrate side. On the insulating layer 105, a conductive layer 110 functioning as a first electrode 63 of the light-emitting element is disposed, and an insulating layer 106 is disposed covering the insulating layer 105, the conductive layer 110, and the conductive layer 117.

[0036] The insulating layer 101 may be, for example, a silicon oxide film such as LOCOS. The insulating layers 102, 103, 104, and 105 can be formed of, for example, a film containing at least one of silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, and aluminum oxide, or a stack of these films. Here, an example is shown in which the insulating layers 102, 103, 104, and 105 are silicon oxide films.

[0037] The insulating layer 106 is preferably a film with low moisture permeability. The insulating layer 106 can be, for example, a silicon nitride film, an aluminum oxide film, or a laminate of these.

[0038] The conductive layers 107, 108, and 109 may be layers of metal such as copper, aluminum, or cobalt, and may further be laminated with a layer of titanium nitride or the like, and function as wiring, for example. The conductive layer 110 may be made of aluminum, an aluminum alloy, or a laminate of aluminum or an aluminum alloy and titanium nitride, etc. The first electrode 63 will be described in detail later.

[0039] The moisture-resistant ring 116 has, for example, conductive layers such as plug 111, conductive layer 107, plug 112, conductive layer 108, plug 113, conductive layer 109, plug 114, and insulating layer 106. By surrounding the light-emitting region with the moisture-resistant ring 116 composed of these layers with low moisture permeability, it is possible to suppress moisture from reaching the light-emitting element. Note that the moisture-resistant ring is not limited to this, and a portion of the conductive layer may be replaced with an insulating layer with low moisture permeability such as a nitride film, or may be a film having silicon oxide or the like in part. Even with such a configuration, moisture permeation can be suppressed in other parts, so that the moisture-resistant ring substantially functions as a moisture-resistant ring. Therefore, the moisture-resistant ring 116 of this embodiment includes a configuration in which a portion is not a layer that suppresses moisture permeation as described above, so long as it substantially functions as a moisture-resistant ring.

[0040] 2 is an enlarged view of the periphery of the contact region 64a. A circle 80 is an imaginary circle for the purpose of explanation, and has a radius equal to a margin width (M) corresponding to the alignment accuracy indicated by a dashed line with a center at a corner of the contact region 64a.

[0041] 2, by removing a part of the second electrode 67 outside the circle 80 (providing a cutout portion 81), the second electrode 67 has a shape in which an end in the first direction X has a part that is non-parallel to the third direction Y. This makes it possible to reduce the area of ​​the second electrode 67 formed compared to the case in which the second electrode 67 is formed in a region 72 having a long side that is a tangent to the circle 80 and a short side that extends in the third direction.

[0042] With this configuration, even if the alignment is shifted to the maximum, there is no area where the second electrode 67 cannot cover the contact region 64a, and it is possible to reduce the area of ​​the second electrode 67 that contributes to unintended light reflection while maintaining sufficient electrical contact. Note that, in this embodiment, the case where the contact region 64a is rectangular is illustrated, so the corner of the contact region 64a is set as the center of the circle 80, but the center of the circle 80 is not limited to this.

[0043] Even if the contact region 64a is not rectangular, it is sufficient to draw an arc locus in which the center of a circle 80 moves along the outermost periphery of the contact region 64a by connecting the points farthest from the light-emitting region 60. By removing at least a part of the second electrode 67 (providing a cutout portion 81) in the outer region 73 of the shape derived in this manner, it is possible to reduce the area of ​​the second electrode 67 without impairing the light-emitting characteristics of the light-emitting element 69.

[0044] 3(a), a corner may be cut off at the intersection of a line passing through the outermost parts of the light-emitting region 60 and the contact region 64a and parallel to the long side of the light-emitting region 60, and a line passing through the outermost parts of the light-emitting region 60 and the contact region 64a and parallel to the short side of the light-emitting region 60. As shown in Fig. 3(b), in the configuration of Fig. 3(a), a side of the second electrode 67 parallel to the third direction Y may be shifted toward the light-emitting region 60 in the first direction X.

[0045] As shown in Fig. 4(a), the end of the second electrode 67 in the first direction may have a shape with curvature. For example, the end of the second electrode 67 in the first direction has a curve, specifically, a shape in which a curve having a center of curvature on the light-emitting region 60 side continues. In this case, the area of ​​the second electrode 67 can be further reduced while the second electrode 67 covers the wiring 64. As shown in Fig. 4(b), only the corners of the second electrode 67 may be curved with curvature, and the center in the third direction Y (direction perpendicular to the long side of the light-emitting region) may be linear.

[0046] At the end of the second electrode 67 in the first direction, the length in the third direction of the portion non-parallel to the third direction Y is preferably longer than ⅓ of the distance L (FIG. 2) from the end of the second electrode 67 in the third direction to the portion where the second electrode 67 contacts the wiring 64. Furthermore, at the end of the second electrode 67 in the first direction, the length in the third direction of the portion non-parallel to the third direction Y may be longer than half of the distance L from the end of the second electrode 67 in the third direction to the portion where the second electrode 67 contacts the wiring 64. FIG. 2 shows an example in which the length in the third direction of the portion non-parallel to the third direction Y is approximately equal to the distance L from the end of the second electrode 67 in the third direction to the portion where the second electrode 67 contacts the wiring 64.

[0047] When forming a film by the vacuum deposition method, the shape of the second electrode 67 may vary depending on the distance between the deposition source and the substrate, the taper angle in the thickness direction of the opening of the deposition mask, whether the LED chip is formed near the center of the substrate or on the periphery, and the like. However, in a plan view of the main surface of the substrate 61, the end of the second electrode 67 in the first direction X has a portion that is non-parallel to the third direction Y perpendicular to the first direction X, so that the area of ​​the second electrode 67 can be reduced without impairing the light-emitting characteristics of the light-emitting element 69. Therefore, unintended reflection of light by the second electrode 67 can be reduced without impairing the light-emitting characteristics of the light-emitting element 69.

[0048] Furthermore, by providing the cutout portion, not only the area of ​​the second electrode can be reduced, but also the perimeter of the second electrode can be reduced. It is known that an organic EL element, which is an example of the light-emitting element of this embodiment, deteriorates due to water in the atmosphere. One of the places where water can enter the organic EL element is the periphery of the second electrode 67. Therefore, by reducing the perimeter of the second electrode 67, it is possible to suppress the penetration of water into the light-emitting element.

[0049] (substrate) The substrate 61 may be made of any material as long as it can support the first electrode 63, the organic layer 66, and the second electrode 67. Although omitted in Fig. 1(b), an active element such as a transistor may be disposed on the substrate 61. Furthermore, an interlayer insulating layer and a wiring layer may be disposed between the substrate 61 and the first electrode 63 in a single layer or in a multi-layered structure.

[0050] The substrate 61 may be made of, for example, glass, plastic, silicon, etc. In this embodiment, a silicon substrate is used as an example. The thermal conductivity of a glass substrate is approximately 0.55 to 1.1 W / m·K, whereas the thermal conductivity of a silicon substrate is approximately 162 W / m·K, making the silicon substrate very high in thermal conductivity.

[0051] It is known that organic light-emitting elements dissipate heat depending on the length of time that they emit light and the amount of light emitted, so it is preferable to efficiently dissipate the heat generated when the light-emitting element 69 is driven.

[0052] By using a silicon substrate as the substrate 61, even when the light emitting element 69 formed on the substrate 61 generates heat due to operation, the heat can be efficiently dissipated by utilizing the heat transfer of the substrate 61. Furthermore, when the substrate 61 is cooled from the back side by an air-cooling mechanism or the like, the light emitting element 69, which is a heat source, can be efficiently cooled.

[0053] Furthermore, from the viewpoint of the above-mentioned thermal conduction, it is preferable that the thickness of the substrate 61 is thin. For example, in the case of a silicon substrate, the standard thickness of an 8-inch wafer is 725 μm, but this may be thinned by a background process or the like. However, when mounting a plurality of LED chips 53 on other devices, the thinner the substrate 61, the more likely it is that the substrate 61 will crack or be damaged during handling, reducing the yield. To avoid this, it is preferable that the substrate 61 has a certain degree of thickness.

[0054] For example, the thickness of the substrate 61 can be set to 200 μm to 700 μm. The thickness of the silicon substrate is more preferably 378 μm to 408 μm. For example, a silicon substrate thinned by a back grinder to a thickness in the range of 378 μm to 408 μm can be used. Note that the substrate 61 may be provided with switching elements such as transistors, wiring layers, interlayer insulating layers (not shown), etc., and the thickness of the silicon substrate does not include these structures such as the wiring layers and interlayer insulating layers.

[0055] (1st electrode) The first electrode 63 may be transparent or opaque. If the first electrode 63 is opaque, the material of the first electrode 63 is preferably a metal material having a reflectance of 70% or more at the emission wavelength. The material of the first electrode 63 may be a metal such as Al or Ag, an alloy of these metals with Si, Cu, Ni, Nd, or the like added thereto, or ITO, IZO, AZO, IGZO, or the like. For example, the first electrode 63 may have a layered structure of Ti / TiN / AlCu (the sum of the film thicknesses is 65 nm).

[0056] The emission wavelength here refers to the spectral range of light emitted from the organic layer 66. The first electrode 63 may be a laminated electrode with a barrier electrode made of a metal such as Ti, W, Mo, or Au or an alloy thereof, or may be a laminated electrode with a transparent oxide film electrode such as ITO or IZO, so long as the reflectance is higher than the desired one.

[0057] On the other hand, when the first electrode 63 is a transparent electrode, a reflective layer may be further provided under the first electrode 63. Examples of materials that can be used for the transparent electrode include ITO, IZO, AZO, and IGZO. For the purpose of optimizing the optical path length, which will be described later, an insulating film may be further provided between the reflective layer and the transparent conductive film.

[0058] (2nd electrode) The light emitting element 69 of this embodiment emits light from the second electrode. Therefore, the second electrode 67 is disposed on the organic layer 66 and has semi-transparency. The second electrode 67 can be a semi-transparent conductive layer that transmits part of the light that reaches its surface and reflects the other part (i.e., semi-transmissive and reflective). The material of the second electrode 67 is preferably one with a small work function. For example, an alkali metal such as lithium, an alkaline earth metal such as calcium, aluminum, titanium, manganese, silver, lead, chromium, or other metal alone or a mixture containing these can be used.

[0059] Alternatively, an alloy combining these metal elements can be used as the material of the second electrode 67. For example, magnesium-silver, aluminum-lithium, aluminum-magnesium, silver-copper, zinc-silver, etc. may be used. One of these electrode materials may be used alone, or two or more types may be used. The second electrode may have a single layer structure or a multi-layer structure.

[0060] Among them, it is preferable to use silver, and it is more preferable to use a silver alloy in order to suppress the aggregation of silver. As long as the aggregation of silver can be suppressed, the alloy ratio is not important. For example, it may be 1:1. As the semi-transparent material, an alloy mainly composed of magnesium or silver is particularly preferable. Furthermore, the second electrode 67 may have a laminated structure of layers containing the above materials as long as it has a preferable transmittance and reflectance. Furthermore, the second electrode 67 may be shared by a plurality of light-emitting elements 69.

[0061] By using the second electrode 67 made of a semi-transparent material, a top emission element that satisfies the above interference conditions may be formed. The method for forming the electrode is not particularly limited, and may be a vacuum deposition method, but it is more preferable to use a DC or AC sputtering method, etc., since it provides good film coverage and makes it easier to reduce resistance.

[0062] For example, the second electrode 67 may have a laminated structure of magnesium and silver (total thickness: 15 nm).

[0063] Either the first electrode 63 or the second electrode 67 may be disposed individually for each of the plurality of light-emitting elements 69, and the other may be continuous across the plurality of light-emitting elements 69. Furthermore, the first electrode 63 and the second electrode 67 may be disposed individually in the plurality of light-emitting elements 69.

[0064] In this embodiment, an example is shown in which the second electrode 67 is common to the multiple light emitting elements 69. This makes it possible to reduce the number of wires connecting the power supply wire to the cathodes 67 of the multiple light emitting elements 69.

[0065] The second electrode 67 preferably has low resistance because it supplies current to the organic layer 66 via the wiring 64. If the resistance of the second electrode 67, which is a common electrode, is high, the driving voltage of the light-emitting element 69 may rise or uneven brightness may occur due to shading, which may impair the light-emitting characteristics. Therefore, the portion (cutout portion 81) to be removed to reduce the area of ​​the second electrode 67 is preferably the outer region rather than the inner region from the contact region 64 toward the light-emitting region 60, which may increase the resistance.

[0066] (organic layer) The organic layer 66 is disposed on the first electrode 63, and can be formed by a known technique such as vapor deposition or spin coating.

[0067] The organic layer 66 has at least a light-emitting layer, and may be composed of a plurality of layers. When the organic layer is an organic compound layer, the plurality of layers may include any one of a hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting layer, a hole blocking layer, an electron transport layer, and an electron injection layer, or a combination thereof.

[0068] The light-emitting layer emits light when holes injected from the anode and electrons injected from the cathode are recombined in the organic layer. The light-emitting layer may be a single layer or multiple layers. Any of the light-emitting layers may contain a red light-emitting material, a green light-emitting material, and a red light-emitting material, and white light can be obtained by mixing the respective colors of light emitted.

[0069] In addition, any of the light-emitting layers may contain light-emitting materials of complementary colors, such as a blue light-emitting material and a yellow light-emitting material. In any case, it is preferable to emit light of an emission wavelength according to the application, and by using an organic light-emitting element, the emission wavelength can be adjusted by the light-emitting material.

[0070] Also, different colors may be emitted by changing the material or configuration contained in the light-emitting layer for each light-emitting element 69. Also, a common light-emitting layer may be provided for a plurality of light-emitting elements 69, or a light-emitting layer may be provided for each light-emitting element 69. When a light-emitting layer is provided individually for each light-emitting element 69, the light-emitting layer may be patterned for each light-emitting element 69.

[0071] The light-emitting element 69 according to this embodiment may have a first reflecting surface, a second reflecting surface, and a light-emitting layer disposed between the first reflecting surface and the second reflecting surface. The first reflecting surface may be the first electrode 63, or a reflecting layer disposed between the first electrode 63 and an insulating layer.

[0072] In order to optimize the optical distance between the first reflecting surface and the light emitting position of the organic layer 66 including the light emitting layer, the optical path length from the upper surface of the first reflecting surface to the light emitting position of the organic layer 12 is Lr, and the phase shift in the reflecting layer is Φr. Lr=(2m-(Φr / π))×(λ / 4)···(1) m is an integer equal to or greater than 0. The thicknesses of the first electrode 63 or the first reflecting surface and the organic layer 66 may be optimized so as to approximately satisfy the above formula (1).

[0073] Furthermore, the optical distance Ls from the light emission position to the second reflecting surface approximately satisfies the following formula (2), where Φs is the phase shift that occurs when light of wavelength λ is reflected by the reflecting surface. In this embodiment, m′=0. Ls=(2m'-(Φs / π))×(λ / 4)=-(Φs / π)x(λ / 4)...(2)

[0074] Therefore, the total layer interference L approximately satisfies the following condition. L=Lr+Ls=(2m-Φ / π)×(λ / 4)...(3)

[0075] Here, Φ is the sum of phase shifts Φr+Φs when light of wavelength λ is reflected by the first electrode 63 or the reflective layer and the second electrode 67.

[0076] The above expression "approximately satisfy" means that the allowable range in formulas (1) to (3) is about λ / 8 or about 20 nm.

[0077] Since it may be difficult to specify the light-emitting position of the light-emitting layer, the light-emitting position is substituted with the interface on the first reflecting surface side or the interface on the second reflecting surface side of the functional layer in the above configuration. Taking the above-mentioned allowable range into consideration, even if substituted in this way, the effect of intensifying light can be achieved.

[0078] It is also well known that under interference conditions that intensify light, the distribution of light emitted from the light-emitting element is modulated from the Lambertian distribution, increasing the front component and decreasing the oblique component. Therefore, using a top-emission light-emitting element that satisfies the interference conditions is more preferable for suppressing stray light and improving print quality.

[0079] For example, on the first electrode 63, a hole injection layer (film thickness 8 nm), a hole transport layer (37 nm), a light emitting layer (20 nm), a hole blocking layer (34 nm), an electron transport layer (20 nm), and an electron injection layer (0.5 nm) may be stacked.

[0080] (Contact area and pad area) In the contact region 64a, the wiring 64 may be made of a metal material such as aluminum (Al), titanium (Ti), titanium nitride (TiN), etc., as long as it is in electrical contact with the second electrode 67. Also, a mixed material or a laminated structure of these may be used.

[0081] When the organic layer 66 is formed by deposition or the like, it is only necessary to ensure electrical continuity between the second electrode 67 and the wiring 64, so the organic layer 66 may partially cover the wiring 64. The pad section 70 also needs to be electrically connected to the head substrate 50 by wire bonding or the like, so it can be made of the same material as the wiring 64.

[0082] (protective layer) The protective layer 68 is an insulating layer, and preferably contains an inorganic material that is transparent and has low permeability to oxygen and moisture from the outside. For example, the protective layer 68 can be made of an inorganic material such as silicon nitride (SiN), silicon oxynitride (SiON), silicon oxide (SiOx), aluminum oxide (Al2O3), or titanium oxide (TiO2).

[0083] In particular, inorganic materials such as SiN, SiON, and Al2O3 are preferred in terms of protective performance. The protective layer 14 is preferably formed by chemical vapor deposition (CVD), atomic layer deposition (ALD), or sputtering. For example, after the second electrode is formed, the substrate may be transferred to another chamber without breaking the vacuum, and a silicon nitride film having a thickness of 2 μm may be formed by CVD to serve as the protective layer. A protective layer may be provided by atomic layer deposition (ALD) after the film is formed by CVD.

[0084] As long as the protective layer 68 has sufficient moisture blocking performance, it may be a single layer structure or a laminated structure combining the above materials and forming methods. For example, it may be a laminate of a silicon nitride layer and a high density layer formed by atomic deposition. Furthermore, the protective layer 68 may have an organic layer as long as it has moisture blocking performance. Examples of the organic layer include polyacrylate, polyimide, polyester, and epoxy. Furthermore, the protective layer 68 may be disposed across multiple light emitting elements 69.

[0085] For example, the protective layer 68 may be formed by transporting the element substrate to another chamber while maintaining the vacuum after the second electrode formation 67, and forming a silicon nitride film having a thickness of 2 μm by a CVD method.

[0086] An anti-reflection layer may be provided on the protective layer 68. The anti-reflection layer is formed so that the optical thickness (product of refractive index and thickness) of the film having a refractive index different from that of the protective layer 68 is λ / 4, where λ is the wavelength at which reflection is to be suppressed. However, the wavelength of the light emitted from the light emitting element 69 is generally broader and has a larger half-width than that of a semiconductor laser.

[0087] Therefore, in order to obtain a sufficient antireflection effect over a broad emission wavelength range, a multi-layer structure is preferable to a single-layer structure. The material of the antireflection layer may be magnesium fluoride, silicon oxide, or a polymer similar to the planarization layer. In consideration of the cost of the manufacturing process related to film formation, the material may be appropriately selected from the case of using a color filter described later.

[0088] (Color filter) In this embodiment, an example in which a color filter is not provided on the light emission side of the light emitting element is shown, but a color filter may be provided on the protective layer. For example, a color filter taking into consideration the size of the light emitting element 69 may be provided on a separate substrate and bonded to the substrate on which the light emitting element is provided, or a color filter may be patterned on the protective layer shown above using photolithography technology. The color filter may be made of a polymer. The color filter transmits the desired light from the light emitting element 69 and absorbs light of unnecessary wavelengths.

[0089] In display device applications, color filters can be provided for the red, green, and blue light-emitting elements to enhance color purity, or for separating light from a white light-emitting element into red, green, and blue colors.

[0090] When used in an exposure head of an image forming apparatus, the color filter can transmit light having a wavelength for exposing a photosensitive drum. On the other hand, to prevent stray light, the color filter needs to be arranged in a creative way. For example, by not providing a color filter on the light-emitting region and providing a color filter that absorbs light from the light-emitting element on the non-light-emitting region, the stray light can be absorbed without reducing the amount of light incident on the photosensitive drum.

[0091] Alternatively, a color filter that transmits light of the emission wavelength can be provided on the light-emitting region 60, and a color filter that absorbs light from the light-emitting element 69 can be provided on the non-light-emitting region. With this configuration, stray light can be absorbed without reducing the amount of light incident on the photosensitive drum. The color filter provided on the non-light-emitting region may be a black resist.

[0092] (flattening layer) A planarizing layer may be provided between the color filter and the protective layer. The planarizing layer may be made of an organic compound, and may be a low molecular weight or a high molecular weight compound, but is preferably a high molecular weight compound.

[0093] The planarization layer may be provided above and below the color filter, and may be made of the same or different materials. Specifically, polyvinylcarbazole resin, polycarbonate resin, polyester resin, ABS resin, acrylic resin, polyimide resin, phenol resin, epoxy resin, silicone resin, urea resin, etc. can be used. By providing a planarization layer on the color filter as well, it is possible to reduce the penetration of moisture and oxygen from the outside into the color filter and to protect it.

[0094] [Second embodiment] In this embodiment, a configuration example in which the LED chip 53 of the first embodiment has a color filter will be described. Since the configuration is the same as the first embodiment except for the color filter, the description will be omitted. Note that the color filter 91 can be created, for example, by forming a planarization layer 90 on the protective layer 68 to planarize the unevenness of the protective layer 68 caused by the light emitting element 69, and then using a photolithography technique.

[0095] Fig. 5 shows an example in which a first color filter 91 that absorbs light from a light emitting element 69 is provided in an area other than the light emitting region 60 and the pad portion 70. Fig. 5(a) is a plan view of the LED chip 53, and Fig. 5(b) is a schematic diagram of a cross section taken along line A-A' in Fig. 5(a). Since the pad portion 70 needs to be electrically connected, no color filter is provided on the pad portion 70.

[0096] Moreover, the first color filter 91 is not disposed on the light emitting element 69, but a transparent planarization layer 90 is provided thereon. Therefore, stray light from unintended directions can be absorbed without reducing the amount of light emitted from the LED chip 53. The first color filter 91 may be a black resist that absorbs light other than the emission wavelength from the light emitting element 69.

[0097] FIG. 6 shows an example in which a color filter is provided in an area other than the pad portion 70. FIG. 6(a) is a plan view of an example of a part of the LED chip 53, and FIG. 6(b) is a schematic diagram of a cross section along line A-A' of the configuration of FIG. 6(a). A second color filter 92 that transmits light of the emission wavelength is provided on the light emitting element 69, and a first color filter 91 that absorbs light from the light emitting element 69 is provided on the light emitting region 60 and in an area other than the pad portion 70. This makes it possible to absorb stray light from unintended directions without reducing the normal amount of light emitted from the LED chip. The first color filter 91 may be a black resist that absorbs light other than the wavelength corresponding to the light from the light emitting element 69.

[0098] [Third embodiment] Next, the exposure head 4 will be described with reference to Fig. 7. Fig. 7 is a schematic cross-sectional view of the exposure head 4 of the present embodiment. The exposure head 4 of the present embodiment has the LED chip 53 of the first or second embodiment.

[0099] The exposure head 4 has an elongated shape (longitudinal shape) extending in the axial direction of the photosensitive drum 2. The exposure head 4 includes a head substrate 50, a light-emitting element 69 mounted on the head substrate 50, a lens array 52, and a holding member that holds the head substrate 50 and the lens array 52. ​​The holding member includes a housing 54 (described later) and a housing support member 55 that supports the housing 54. Here, the exposure head 4 includes an LED (Light Emitting Diode) as a light-emitting element that emits light, and for example, an organic light-emitting element can be used.

[0100] (Housing) As shown in FIG. 7, the housing 54 holds the lens array 52 and the substrate 50. In this embodiment, the housing 54 is a metal member formed by bending a plate material that has been plated on a galvanized steel plate or a cold-rolled steel plate. Here, as an example of an exposure method adopted in an electrophotographic image forming apparatus, there is a laser beam scanning exposure method in which a semiconductor laser irradiation beam is scanned with a rotating polygon mirror or the like and a photosensitive drum is exposed through an f-θ lens or the like. The exposure head 4 described in this embodiment is disposed adjacent to the photosensitive drum 2 and is used in an LED exposure method in which the photosensitive drum 2 is exposed using light-emitting elements 69 arranged along the axial direction of the photosensitive drum 2.

[0101] The housing 54 may be made of, for example, metal. For example, the housing 54 is formed into a U-shape by pressing a metal plate such as a thin iron plate. The shape of the housing 54 will be described below.

[0102] The flat surface 54U faces the photosensitive drum 2 in the optical axis direction of the lenses of the lens array 52. ​​The flat surface 54U is not limited to a flat surface, and may be a slightly curved surface. The housing 54 also has an extension 54R extending from one side in the short side direction of the flat surface 54U in a direction away from the photosensitive drum 2. The housing 54 also has an extension 54L extending from the other side in the short side direction of the flat surface 54U in a direction away from the photosensitive drum 2.

[0103] The extending portions 54R and 54L form a substrate support portion for supporting the head substrate 50 inserted from the second opening 54b in the housing 54. The flat portion and the substrate support portion (extending portions 54R, 54L) are integral with each other to form the housing 54 that holds the lens array 52 and the head substrate 50, and are formed in a substantially U-shape. By forming the housing 54 in a substantially U-shape, the second opening 54b is formed on the opposite side to the flat portion 54U. The second opening 54b is formed between the substrate support portion (extending portions 54L, 54R) that extends from the flat portion 54U to the side away from the photosensitive drum.

[0104] The head substrate 50 is inserted from the second opening 54b, i.e., from the lower side of the U-shaped housing 54, and is adhered to the inside of each substrate support part (the inside of the extending part 54L and the inside of the extending part 54R) with an adhesive. Note that, since the position of the head substrate 50 in the focal direction is determined by a jig (not shown), the exposure head 4 does not include a positioning means for the head substrate 50 in the focal direction.

[0105] The lens array 52 is also bonded to the flat portion 54U with an adhesive while being inserted into the first opening 54a formed in the flat portion 54U. The lens array 52 is fixed to the flat portion 54U (housing 54) after adjusting the position and inclination in the focus direction with a jig so that the distance in the focus direction between all the LED chips 53 mounted on the head substrate 50 and the lens array 52 becomes a predetermined value. The lens array 52 is also fixed to the flat portion 54U with an adhesive at multiple points in the longitudinal direction. That is, the exposure head 4 of this embodiment has multiple bonding points in the longitudinal direction of the flat portion 54U for bonding and fixing the lens array 52 inserted into the first opening 54a to the flat portion 54U.

[0106] After the head substrate 50 and lens array 52 are positioned and fixed to the housing 54, the gap between the substrate 50 inserted into the second opening 54b and the housing 54 (extensions 54L, 54R) is sealed in the longitudinal direction with a sealant 59. This reduces contamination of the light emitting element 69 by toner or dust from the outside. Here, the sealant 59 only seals the gap (boundary) between the substrate 50 and the housing 54, and most of the FFC connector 57 and head substrate 50 are exposed.

[0107] Similarly, a sealant 59 is applied to the gap between the lens array 52 inserted into the first opening 54a and the housing 54 (flat surface portion 54U), and the gap is sealed in the longitudinal direction by the sealant 59. More specifically, as shown in Fig. 4, the sealant 59 seals the gap between the side wall of the lens array 52 along the longitudinal direction of the housing 54 and the edge of the first opening 54a. This reduces the possibility that dust such as toner will flow in through the gap between the side wall of the lens array 52 and the first opening 54a, causing the dust to block the light emitted from the light-emitting element 69.

[0108] The gap sealed by the sealant 59 is not only the gap between the sidewall on one side of the lens array 52 and the edge of the first opening 54a, but also the gap between the sidewall on the other side of the lens array 52 and the edge of the first opening 54a. The sidewall on the other side of the lens array 52 refers to the sidewall opposite to the sidewall on one side of the lens array 52. ​​Here too, the gap (boundary) between the housing 54 and the lens array 52 is sealed by the sealant 59. This reduces contamination of the light emitting elements 69 by toner and dust from the outside.

[0109] As described above, the head substrate 50 and the lens array 52 are held by the housing 54, so that the light emitting element 69 faces the incident surface of the lens. As a result, the light emitted from the light emitting element 69 is incident on the incident surface of the lens and is emitted from the exit surface of the lens towards the photosensitive drum 2, exposing the photosensitive drum 2.

[0110] Here, ideally, all the light emitted from the light emitting element 69 should be incident on the entrance surface of the lens, but some of the light from the light emitting element 69 is emitted obliquely due to the light radiation distribution. For example, oblique light that does not directly enter the lens array from the light emitting element 69 and is reflected by the inner wall of the housing of the exposure head is light that passes through an unintended path and can become stray light. In addition, light that normally enters the photosensitive drum 2 from the light emitting element 69 through the lens array 52 may be reflected on the surface of the photosensitive drum 2 or scattered by toner or dust that may be present in the light path. In addition, Fresnel reflection also occurs at the end surface of the lens array. If these lights pass through the lens array again and are further reflected by the second electrode 67 of the light emitting element 69, the light may become stray light.

[0111] When the light-emitting element 69 is an organic light-emitting element, in a top-emission configuration, what mainly contributes to reflection is the second electrode having high reflectivity that is located closest to the organic layer 66 and on the same side as the lens array. In order to suppress the above-mentioned stray light, it is preferable to make the area of ​​this second electrode as small as possible without impairing the light-emitting characteristics of the organic light-emitting element.

[0112] Therefore, by using the LED chip 53 described in the first or second embodiment in the exposure head 4 of this embodiment, the area of ​​the second electrode 67 can be reduced compared to when the second electrode does not have a cutout portion, and stray light can be suppressed. Furthermore, by suppressing stray light, when the exposure head 4 is used in an image forming apparatus, ghost spots caused by stray light can be reduced and printing quality can be improved.

[0113] (Housing support member) The housing support member 55 supports the housing 54 holding the head substrate 50 and the lens array 52 in the longitudinal direction, and is provided integrally with the housing 54. The housing support member 55 is a longitudinal member extending in the axial direction of the photosensitive drum 2. The housing support member 55 is formed in a U-shape as shown in FIG. 4. The housing support member 55 has a left side wall 55L which is a first side wall, a right side wall 55R which is a second side wall facing the left side wall 55L, and a bottom surface portion 55D which faces the flat surface portion 54U of the housing 54 between the left side wall 55L and the right side wall 55R. The bottom surface portion 55D of the housing support member 55 has a plurality of openings 55a provided in the longitudinal direction which is the axial direction of the photosensitive drum 2.

[0114] The opening 55a of the housing support member 55 is provided at a position facing the surface (the back surface of the head substrate 50) opposite to the mounting surface (the front surface of the head substrate 50) on which the light emitting elements 69 of the head substrate 50 are mounted. The opening 55a is provided between the left side wall 55L and the right side wall 55R in the short direction perpendicular to the long direction.

[0115] (Substrate and lens array) Here, the head substrate 50 and lens array 52 of the exposure head 4 will be described with reference to Fig. 8. First, the head substrate 50 will be described. Fig. 8(a) is a schematic perspective view of the head substrate 50. Fig. 8(b) shows an arrangement of a plurality of light-emitting elements 69 provided on the head substrate 50, and Fig. 8(c) shows an enlarged view of Fig. 8(b).

[0116] An LED chip 53 is mounted on the head substrate 50. As shown in Fig. 8(a), the LED chip 53 is provided on one surface of the head substrate 50, and a long flexible flat cable (FFC) connector 57 is provided on the other surface. The one surface of the head substrate 50 referred to here is the surface (upper surface, front surface) on which the LED chip 53 is provided. The other surface of the substrate is the surface (lower surface, back surface) opposite to the side on which the LED chip 53 is provided.

[0117] The FFC connector 57 is attached to the other surface (lower surface, back surface) of the head substrate 50 so that its longitudinal direction is aligned with the longitudinal direction of the head substrate 50. The long FFC connector 57 is provided to input a control signal (drive signal) from a control circuit section of the main body of the image forming apparatus, and the control signal is transferred to each LED chip 53. The LED chips 53 are driven (to emit light and turn off the light) by the control signal input to the head substrate 50.

[0118] The LED chips 53 mounted on the head substrate 50 will now be described. As shown in Fig. 8(b) and Fig. 8(c), a plurality of light-emitting elements 69 are arranged on one surface of the head substrate 50. For example, LED chips 53-1 to 53-29 (29 pieces) are arranged. Each of the LED chips 53-1 to 53-29 has a plurality of light-emitting elements 69 arranged in its longitudinal direction, and for example, 516 light-emitting elements 69 are arranged.

[0119] In the longitudinal direction of the LED chip 53, the center-to-center distance k2 between adjacent light-emitting elements 69 corresponds to the resolution of the image forming apparatus 100. For example, when the resolution of the image forming apparatus 100 of this embodiment is 1200 dpi, the light-emitting elements 69 are arranged in the longitudinal direction of the LED chips 53-1 to 53-29 such that the center-to-center distance k2 between adjacent light-emitting elements 69 is 21.16 μm. Therefore, the exposure range of the exposure head 4 of this embodiment is approximately 314 mm.

[0120] The photosensitive layer of the photosensitive drum 2 is formed with a width of 314 mm or more. Since the length of the long side of A4 size recording paper and the length of the short side of A3 size recording paper are 297 mm, the exposure head 4 of this embodiment has an exposure range capable of forming images on A4 size recording paper and A3 size recording paper. Note that, although an example in which a plurality of light emitting elements 69 are arranged in the longitudinal direction is shown in FIG. 8, the light emitting elements 69 may be arranged in the lateral direction in addition to the longitudinal direction.

[0121] A plurality of LED chips 53-1 to 53-29 are arranged in the axial direction of the photosensitive drum 2. Specifically, the LED chips 53-1 to 53-29 are alternately arranged in two rows along the axial direction of the photosensitive drum 2. That is, as shown in Fig. 5(b) , counting from the left side, the odd-numbered LED chips 53-1, 53-3, ... 53-29 are mounted in a row in the longitudinal direction of the substrate 50. Also, counting from the left side, the even-numbered LED chips 53-2, 53-4, ... 53-28 are mounted in a row in the longitudinal direction of the substrate 50. The LED chips 53 are arranged in this manner.

[0122] As a result, as shown in Figure 8 (c), in the longitudinal direction of the LED chip 53, the center-to-center distance k1 between the light-emitting elements 69 arranged between one end of one LED chip 53 and the other end of the other LED chip 53 in adjacent different LED chips 53 can be made equal to the center-to-center distance k2 between adjacent light-emitting elements 69 on one LED chip 53.

[0123] In this embodiment, the light-emitting element 69 is an organic light-emitting element, and is a current-driven light-emitting element. The organic light-emitting elements are arranged in a line along the main scanning direction (the axial direction of the photosensitive drum 2) on a TFT (Thin Film Transistor) substrate, for example, and are electrically connected in parallel by power supply wiring also provided along the main scanning direction.

[0124] Next, the lens array 52, which is a lens assembly, will be described. Fig. 8(d) is a schematic diagram of the lens array 52 as viewed from the photosensitive drum 2 side. Fig. 8(e) is a schematic perspective view of the lens array 52. ​​As shown in Fig. 8(d), the lens array 52 collects light emitted from the light-emitting element 69 onto the photosensitive drum 2. The lens array 52 is a lens assembly having a plurality of lenses.

[0125] These lenses are arranged in two rows along the arrangement direction of the light-emitting elements 69. The lenses are arranged alternately such that one lens in one row is arranged so as to be in contact with both of the lenses adjacent to the other row in the arrangement direction of the lenses. Each lens is a cylindrical glass rod lens, and has a light incident surface 52b into which the light emitted from the light-emitting elements 69 is incident, and a light exit surface 52a from which the light incident from the light incident surface exits (see FIG. 7). The material of the lens is not limited to glass, and may be plastic. The shape of the lens is also not limited to cylindrical, and may be a polygonal prism such as a hexagonal prism.

[0126] The dotted line Z in Figure 8(e) indicates the optical axis of the lens. The optical axis of the lens here means the line connecting the center of the light exit surface of the lens and the focal point of the lens. The lens array 52 is a lens assembly having multiple lenses, and the "optical axis" mentioned above is the optical axis of any of these multiple lenses. Strictly speaking, the multiple lenses in the lens array 52 may be slightly tilted from each other. This is due to the tolerances during assembly.

[0127] However, deviations of the order of tolerance mentioned here will not be taken into consideration when defining the direction of the optical axis. Therefore, the optical axes of the multiple lenses are considered to be in the same direction. The lens array 52 has the role of collecting light emitted from the light emitting element 69 onto the surface of the photosensitive drum 2.

[0128] When assembling the exposure head 4, the mounting position of the lens array 52 relative to the housing 54 is adjusted so that the distance between the light emitting surface of the light emitting element 69 and the light incident surface of the lens is approximately equal to the distance between the light exit surface of the lens and the surface of the photosensitive drum 2.

[0129] 8(b), in the exposure head 4, a plurality of LED chips 53 are arranged on the exposure head substrate 50. Therefore, by being able to reduce the area of ​​the second electrode 67 in the LED chip 53, the area contributing to unintended light reflection by the second electrode 67 of the entire exposure head 4 is reduced in proportion to the number of LED chips 53. Therefore, it is preferable that more than half of the LED chips 53 to be arranged are the LED chips 53 described in the first or second embodiment, and it is more preferable that all of the LED chips are the LED chips 53 described in the first or second embodiment.

[0130] In this embodiment, the LED chips 53 are alternately arranged in two rows, so-called a staggered arrangement, is shown. As shown in FIG. 8(c), there is a region where the ends of the two LED chips 53 overlap in the longitudinal direction. This region corresponds to the location where the ends of the second electrodes 67 of the LED chips are present, and therefore, when the exposure head 4 is viewed as a whole, this region becomes a portion where the reflection area is locally large. Therefore, by reducing the area of ​​the second electrodes 67 at the ends of the second electrodes 67, the reflection area in this overlapping region can be reduced, and therefore stray light due to unintended light reflection can be effectively reduced.

[0131] When the LED chip is used in the exposure head 4, exposure is performed in a line, so the ratio of the longitudinal direction (first direction X) to the lateral direction (second direction Y) of the shape of the light emitting region 60 is larger than when the LED chip is used in a display device, etc. Also, the ratio of the longitudinal direction (first direction X) to the lateral direction (third direction Y) of the shape of the substrate of the LED chip is larger.

[0132] Specifically, for example, the length of the long side of the LED chip (or the light-emitting region 60) is 5 times or more, and may be 10 times or more, the length of the short side of the LED chip (or the light-emitting region 60). For example, the length of the long side of the LED chip (or the light-emitting region 60) can be 20 times or more the length of the short side of the LED chip (or the light-emitting region 60).

[0133] The length of the long side of the LED chip is determined by the axial length of the photosensitive drum 2, the number of LED chips arranged in the axial direction, and the arrangement of the LED chips 53. The length of the short side of the LED chip 53 is determined by whether the light emitting element 69 is arranged in the light emitting region 60 in the direction perpendicular to the axis of the photosensitive drum 2, and by the arrangement of the pads 70 and the contact region 64a.

[0134] It is also known that organic light-emitting elements dissipate heat according to the length of their light-emitting time and the amount of light emitted. Such heat can cause thermal expansion of the circuit board on which the organic light-emitting elements are formed and the head substrate 50 on which multiple organic light-emitting elements are mounted, and can cause the relative positional relationship between the lens array and the light-emitting elements 69 to shift, resulting in a higher ratio of stray light to normal light.

[0135] When the amount of normal light, which is the main source of exposure, decreases, the proportion of stray light increases relative to the amount of normal light, which can lead to a deterioration in print quality.

[0136] Therefore, by using a silicon substrate as the substrate 61, in a configuration in which a plurality of LED chips 53 are mounted on the head substrate 50, even when the light-emitting elements 69 formed on the substrate 61 generate heat due to driving, heat is efficiently transferred to the head substrate 50 via the substrate 61. Conversely, when the head substrate 50 is cooled from the rear surface side by an air-cooling mechanism or the like, this is advantageous in that the light-emitting elements 69, which are the heat source, can be efficiently cooled.

[0137] Moreover, in consideration of the wavelength dependency of the photosensitive sensitivity of the photosensitive drum 2, the organic layer 66 may be configured to have a light emitting layer that emits red light.

[0138] The LED chip 53 may have a color filter as shown in the second embodiment. By having a color filter, the normal amount of light incident on the photosensitive drum 2 is not reduced, and stray light from unintended directions can be absorbed, thereby improving the print quality.

[0139] [Fourth embodiment] Next, a part of the manufacturing process of the LED chip 53 will be described with reference to FIG. 9, however, the present disclosure is not limited to this.

[0140] In a deposition chamber, for example, the second electrode 67 of the LED chip 53 of the first or second embodiment can be formed on the substrate 61 by the following configuration. Some manufacturing methods for the LED chip 53 include a step of placing a deposition mask having a plurality of openings against a substrate on which the first electrode and the organic layer are arranged, and a step of aligning the substrate with the deposition mask. Some manufacturing methods for the LED chip 53 further include a step of forming a second electrode on the substrate by depositing a deposition material through the openings of the deposition mask.

[0141] Here, the opening of the deposition mask has a long side extending in a first direction X, a short side extending in a second direction Y' intersecting with the first direction X, and a portion at an end of the first direction X that is non-parallel to a third direction Y intersecting with the first direction X.

[0142] 9(a), a substrate 61 held by a substrate holding arm 120 is opposed to a deposition mask 111 having a plurality of openings and disposed on a mask stage 200. Here, a first electrode 63, an insulating layer 62, and an organic layer 66 are formed on the substrate 61. Wiring 64, pads 70, and circuits for driving light-emitting elements 69 may also be formed.

[0143] 9(b), for example, one or both of the substrate 61 and the deposition mask 111 are moved to align the substrate 61 and the deposition mask 111. Thereafter, as shown in FIG. 9(c), a deposition material 300 is deposited on the substrate 61 through a plurality of openings in the deposition mask 111 to form a second electrode 67 on the substrate 61.

[0144] In the deposition mask 111, the multiple openings have long sides extending in a first direction X, short sides extending in a second direction Y' intersecting with the first direction X, and a portion non-parallel to the third direction Y intersecting with the first direction X at an end of the first direction X. Therefore, the second electrode 67 formed through the openings also has long sides extending in the first direction X, short sides extending in the second direction Y' intersecting with the first direction X, and a portion non-parallel to the third direction Y intersecting with the first direction X at an end of the first direction X.

[0145] Therefore, the area of ​​the second electrode 67 can be reduced compared to a case where the second electrode 67 does not have a portion at the end in the first direction X that is non-parallel to the third direction Y. This makes it possible to suppress unintended light from being reflected by the second electrode, affecting the light emission characteristics of the LED chip 53, and becoming stray light in the exposure head 4 having the LED chip 53. Therefore, when the exposure head 4 of this embodiment is used in an image forming apparatus, ghost spots caused by stray light can be reduced and printing quality can be improved.

[0146] The manufacturing device for the LED chip 53 here is an example, and the present disclosure is not limited thereto. The light emitting element 69 has a plurality of functional layers, and the deposition device, which is the manufacturing device, is composed of a number of deposition chambers corresponding to the plurality of functional layers. In addition to the deposition chambers, the device may also be provided with a plurality of process chambers such as a loading chamber, a pre-treatment chamber, a transfer chamber, a relay chamber, and a substrate stock chamber.

[0147] [Fifth embodiment] (Image forming device) First, a schematic configuration of an image forming apparatus 100 will be described with reference to Figs. 10 and 11. Fig. 10 is a perspective view of the image forming apparatus 100. Fig. 11 is a schematic cross-sectional view of the image forming apparatus in Fig. 10. The image forming apparatus 100 shown in Figs. 10 and 11 is a copying machine equipped with a reading device, but the embodiment may be another image forming apparatus such as a printer not equipped with a reading device. In addition, the embodiment is not limited to a color image forming apparatus equipped with a plurality of photosensitive drums 2 as shown in Fig. 11, and may be a color image forming apparatus equipped with one photosensitive drum 2 or an image forming apparatus that forms a monochrome image.

[0148] An image forming apparatus 100 shown in FIG. 11 includes four image forming units 1Y, 1M, 1C, and 1K (hereinafter collectively referred to simply as "image forming units 1") that form toner images of yellow, magenta, cyan, and black, respectively.

[0149] The image forming units 1Y, 1M, 1C, and 1K are provided with photosensitive drums 2Y, 2M, 2C, and 2K (hereinafter, collectively referred to simply as "photosensitive drums 2") that are examples of photosensitive members. The photosensitive drums 2 may be photosensitive belts.

[0150] The image forming units 1Y, 1M, 1C, and 1K are also provided with charging rollers 3Y, 3M, 3C, and 3K (hereinafter also collectively referred to simply as "charging rollers 3") as charging means for charging the photosensitive drums 2Y, 2M, 2C, and 2K, respectively.

[0151] In addition, the image forming units 1Y, 1M, 1C, and 1K are equipped with LED (Light Emitting Diode, hereinafter referred to as LED) exposure heads 4Y, 4M, 4C, and 4K (hereinafter collectively referred to as "exposure heads 4") as exposure means for exposing the photosensitive drums 2Y, 2M, 2C, and 2K.

[0152] Furthermore, the image forming sections 1Y, 1M, 1C, and 1K each include developing units 24Y, 24M, 24C, and 24K (hereinafter collectively referred to as "developing units 24") as developing means for developing the electrostatic latent image on the photosensitive drum 2 with toner and developing a toner image of each color on the photosensitive drum 2. The letters Y, M, C, and K attached to the reference characters indicate the colors of the toner.

[0153] The image forming apparatus 100 shown in Fig. 11 is an image forming apparatus that employs a so-called "bottom surface exposure method" in which the photosensitive drum 2 is exposed from below. The following description will be given on the premise that the image forming apparatus employs the bottom surface exposure method. Note that, although not shown, an embodiment may also employ an image forming apparatus that employs an "top surface exposure method" in which the photosensitive drum is exposed from above.

[0154] The image forming apparatus 100 includes an intermediate transfer belt 9 onto which the toner images formed on the photosensitive drums 2 are transferred, and primary transfer rollers 6 (Y, M, C, K) that sequentially transfer the toner images formed on the photosensitive drums 2 onto the intermediate transfer belt 9. The intermediate transfer belt 9 is disposed above the image forming unit 1. Note that, other than the intermediate transfer method using the intermediate transfer belt 9, a direct transfer method in which an image is directly transferred from the photosensitive drums 2 to paper may also be used.

[0155] The image forming apparatus 100 also includes a secondary transfer roller 16 as a transfer means for transferring the toner image on the intermediate transfer belt 9 onto the recording paper P transported from the feed section 11, and a fixing device 19 as a fixing means for fixing the secondarily transferred image onto the recording paper P.

[0156] Further, toner bottles 22Y, 22M, 22C, and 22K (hereinafter collectively referred to as "toner bottles 22") that accommodate replenishment toner of each color are units that can be detached and replaced with respect to image forming apparatus 100. Toner bottle 22 is disposed above intermediate transfer belt 9. Toner bottle 22 replenishes an appropriate amount of toner at an appropriate time to each of the development units provided in the four image forming sections from the corresponding toner bottles by a toner replenishing mechanism (not shown).

[0157] The image forming apparatus 100 also includes a feeding unit 11 that feeds the recording paper P. The feeding unit 11 has sheet cassettes 12a and 12b, feeding rollers 13a and 13b, and registration rollers 15. The sheet cassettes 12a and 12b are disposed below the image forming unit 1. The recording papers P stored in the sheet cassettes 12a and 12b are fed one by one by the feeding rollers 13a and 13b, and are transported to the secondary transfer unit T2 at a predetermined timing by the registration rollers 15.

[0158] (Image formation process) Next, a brief description will be given of the image forming process of the image forming apparatus 100. The charging roller 3Y charges the surface of the photosensitive drum 2Y. The exposure head 4Y exposes the surface of the photosensitive drum 2Y charged by the charging roller 3Y. As a result, an electrostatic latent image is formed on the photosensitive drum 2Y. Next, the developing unit 24Y develops the electrostatic latent image formed on the photosensitive drum 2Y with yellow toner.

[0159] The yellow toner image developed on the surface of the photosensitive drum 2Y is transferred by the primary transfer roller 6Y onto the intermediate transfer belt 9. Magenta, cyan and black toner images are also formed in a similar image forming process and transferred to the intermediate transfer belt 9 so as to be superimposed on each other.

[0160] The toner images of each color transferred onto the intermediate transfer belt 9 are transported by the intermediate transfer belt 9 to a secondary transfer section T2. ​​The toner images transported to the secondary transfer section T2 are transferred collectively by a secondary transfer roller 16 onto a recording paper P transported from a feed section 11. The recording paper P onto which the toner images have been transferred is transported to a fixing device 19. The fixing device 19 fixes the toner image to the recording paper P by heat and pressure. The recording paper P that has been fixed by the fixing device 19 is discharged by a discharge roller 20 onto a discharge tray 21 disposed above a toner bottle 22. The print quality of the print printed on the recording paper P can be evaluated by visual sensory evaluation.

[0161] [Sixth embodiment] In this embodiment, an example of a light emitting element 69 used in the LED chip of any of the first to fifth embodiments will be described.

[0162] [Structure of organic light-emitting element] An organic light-emitting element as an example of the light-emitting element 69 is provided by forming an insulating layer, a first electrode, an organic compound layer, and a second electrode on a substrate. A protective layer, a color filter, a microlens, etc. may be provided on the cathode. When a color filter is provided, a planarizing layer may be provided between the protective layer. The planarizing layer may be made of acrylic resin or the like. The same applies when a planarizing layer is provided between the color filter and the microlens.

[0163] [substrate] Examples of the substrate include quartz, glass, silicon wafer, resin, and metal. In addition, a switching element such as a transistor and wiring may be provided on the substrate, and an insulating layer may be provided thereon. As the insulating layer, any material can be used as long as a contact hole can be formed so that wiring can be formed between the first electrode and the insulating layer, and insulation from wiring that is not connected can be ensured. For example, resin such as polyimide, silicon oxide, silicon nitride, etc. can be used. By using a silicon substrate, heat generated from the light emitting element can be efficiently dissipated.

[0164] [electrode] A pair of electrodes can be used. The pair of electrodes may be an anode and a cathode. When an electric field is applied in the direction in which the organic light-emitting element emits light, the electrode with a higher potential is the anode, and the other is the cathode. It can also be said that the electrode that supplies holes to the light-emitting layer is the anode, and the electrode that supplies electrons is the cathode.

[0165] The material constituting the anode should have as large a work function as possible. For example, metals such as gold, platinum, silver, copper, nickel, palladium, cobalt, selenium, vanadium, tungsten, etc., mixtures containing these metals, alloys combining these metals, metal oxides such as tin oxide, zinc oxide, indium oxide, indium tin oxide (ITO), and indium zinc oxide can be used. Conductive polymers such as polyaniline, polypyrrole, and polythiophene can also be used.

[0166] These electrode materials may be used alone or in combination of two or more kinds. The anode may be composed of one layer or multiple layers.

[0167] When used as a reflective electrode, for example, chromium, aluminum, silver, titanium, tungsten, molybdenum, or alloys or laminates thereof can be used. The above materials can also function as a reflective film without serving as an electrode. When used as a transparent electrode, a transparent conductive layer of oxide such as indium tin oxide (ITO) or indium zinc oxide can be used, but is not limited to these. Photolithography technology can be used to form the electrode.

[0168] On the other hand, the material for the cathode should have a small work function. Examples of the material include alkali metals such as lithium, alkaline earth metals such as calcium, aluminum, titanium, manganese, silver, lead, chromium, and other metals or mixtures containing these metals. Alternatively, alloys combining these metals can be used. For example, magnesium-silver, aluminum-lithium, aluminum-magnesium, silver-copper, zinc-silver, and the like can be used. Metal oxides such as indium tin oxide (ITO) can also be used. These electrode materials may be used alone or in combination of two or more types. The cathode may have a single layer structure or a multi-layer structure. Among these, it is preferable to use silver, and it is even more preferable to use a silver alloy to reduce the aggregation of silver. As long as the aggregation of silver can be reduced, the ratio of the alloy is not important. For example, the ratio of silver to other metals may be 1:1, 3:1, and the like.

[0169] The cathode may be a top emission element using an oxide conductive layer such as ITO or silver having a thickness sufficient to provide semi-transparency, or a bottom emission element using a reflective electrode such as aluminum (Al), and is not particularly limited. The method of forming the cathode is not particularly limited, but it is more preferable to use a direct current or alternating current sputtering method, etc., since it provides good film coverage and makes it easier to reduce resistance. In both the top emission element and the bottom emission element, the area of ​​the second electrode, which has high reflectivity and serves as a common electrode, can be reduced by forming the second electrode into the shape of the first or second embodiment.

[0170] [Pixel isolation layer] The pixel separation layer is formed of a silicon nitride (SiN) film, a silicon oxynitride (SiON) film, or a silicon oxide (SiO) film formed by chemical vapor deposition (CVD). In order to increase the resistance in the in-plane direction of the organic compound layer, it is preferable that the organic compound layer, particularly the hole transport layer, is thinly formed on the sidewall of the pixel separation layer. Specifically, the thickness of the sidewall can be thinned by increasing the taper angle of the sidewall of the pixel separation layer or the thickness of the pixel separation layer to increase vignetting during deposition.

[0171] On the other hand, it is preferable to adjust the sidewall taper angle and film thickness of the pixel separation layer to such an extent that no voids are formed in the protective layer formed thereon. Since no voids are formed in the protective layer, the occurrence of defects in the protective layer can be reduced. Since the occurrence of defects in the protective layer is reduced, deterioration in reliability such as the occurrence of dark spots and poor conduction of the second electrode can be reduced.

[0172] According to this embodiment, even if the taper angle of the sidewall of the pixel separation layer is not steep, it is possible to effectively suppress charge leakage to adjacent pixels. As a result of this study, it was found that the charge leakage can be sufficiently reduced if the taper angle is in the range of 60 degrees or more and 90 degrees or less. The thickness of the pixel separation layer is preferably 10 nm or more and 150 nm or less. The same effect can be obtained even if the pixel separation layer is composed only of a pixel electrode without a pixel separation layer. However, in this case, it is preferable that the thickness of the pixel electrode is half or less than that of the organic layer, or the edge of the pixel electrode is forward tapered by less than 60 degrees, because this reduces short circuits of the organic light-emitting element.

[0173] [Organic compound layer] The organic compound layer may be formed as a single layer or as multiple layers. When the organic compound layer has multiple layers, it may be called a hole injection layer, a hole transport layer, an electron blocking layer, a light emitting layer, a hole blocking layer, an electron transport layer, an electron injection layer, etc., depending on its function. The organic compound layer is mainly composed of an organic compound, but may also contain inorganic atoms and inorganic compounds. For example, it may contain copper, lithium, magnesium, aluminum, iridium, platinum, molybdenum, zinc, etc. The organic compound layer may be disposed between the first electrode and the second electrode, or may be disposed in contact with the first electrode and the second electrode.

[0174] In the case where a plurality of light-emitting layers are provided, a charge generating portion may be provided between the first light-emitting layer and the second light-emitting layer. The charge generating portion may have an organic compound having a lowest unoccupied molecular orbital energy (LUMO) of -5.0 eV or less. The same applies when a charge generating portion is provided between the second light-emitting layer and the third light-emitting layer.

[0175] [Protective layer] A protective layer may be provided on the second electrode. For example, by bonding glass provided with a moisture absorbent on the second electrode, it is possible to reduce the intrusion of water and the like into the organic compound layer and reduce the occurrence of display defects. In another embodiment, a passivation film such as silicon nitride may be provided on the cathode to reduce the intrusion of water and the like into the organic compound layer. For example, after forming the cathode, the cathode may be transported to another chamber without breaking the vacuum, and a silicon nitride film having a thickness of 2 μm may be formed by the CVD method to form a protective layer. A protective layer may be provided using the atomic deposition method (ALD method) after the film formation by the CVD method. The material of the film by the ALD method is not limited, and may be silicon nitride, silicon oxide, aluminum oxide, etc. Silicon nitride may be further formed by the CVD method on the film formed by the ALD method. The film by the ALD method may have a smaller thickness than the film formed by the CVD method. Specifically, it may be 50% or less, or even 10% or less.

[0176] [Color Filter] A color filter may be provided on the protective layer. For example, a color filter taking into consideration the size of the organic light-emitting element may be provided on another substrate and then bonded to the substrate on which the organic light-emitting element is provided, or a color filter may be patterned on the protective layer described above using a photolithography technique. The color filter may be made of a polymer.

[0177] [Planarization layer] A planarization layer may be provided between the color filter and the protective layer. The planarization layer is provided for the purpose of reducing unevenness of the layer below. It may also be called a material resin layer without limiting the purpose. The planarization layer may be composed of an organic compound, and may be either a low molecular weight or a high molecular weight, but is preferably a high molecular weight.

[0178] The planarization layer may be provided above and below the color filter, and may be made of the same or different materials.Specific examples of the materials include polyvinylcarbazole resin, polycarbonate resin, polyester resin, ABS resin, acrylic resin, polyimide resin, phenol resin, epoxy resin, silicone resin, and urea resin.

[0179] [Microlens] The LED chip may have an optical member such as a microlens on its light-emitting side. The microlens may be made of acrylic resin, epoxy resin, or the like. The microlens may be intended to increase the amount of light extracted from the organic light-emitting device and control the direction of the extracted light. The microlens may have a hemispherical shape. When the microlens has a hemispherical shape, among the tangents to the hemisphere, there is a tangent that is parallel to the insulating layer, and the tangent and the hemisphere are the vertices of the microlens. The vertex of the microlens can be determined in the same manner in any cross-sectional view. In other words, among the tangents to the semicircle of the microlens in the cross-sectional view, there is a tangent that is parallel to the insulating layer, and the tangent and the semicircle are the vertices of the microlens.

[0180] It is also possible to define the midpoint of the microlens. In the cross section of the microlens, a line segment is imaginary from a point where an arc shape ends to a point where another arc shape ends, and the midpoint of the line segment can be called the midpoint of the microlens. The cross section for determining the vertex and midpoint may be a cross section perpendicular to the insulating layer.

[0181] The microlens has a first surface having a convex portion and a second surface opposite to the first surface. It is preferable that the second surface is disposed closer to the functional layer than the first surface. In order to adopt such a configuration, it is necessary to form a microlens on the light-emitting device. When the functional layer is an organic layer, it is preferable to avoid a process in which the manufacturing process becomes high temperature. In addition, when adopting a configuration in which the second surface is disposed closer to the functional layer than the first surface, it is preferable that the glass transition temperature of all the organic compounds constituting the organic layer is 100°C or higher, and more preferably 130°C or higher.

[0182] [Opposite substrate] A counter substrate may be provided on the planarization layer. The counter substrate is called a counter substrate because it is provided at a position corresponding to the aforementioned substrate. The material of the counter substrate may be the same as that of the aforementioned substrate. When the aforementioned substrate is a first substrate, the counter substrate may be a second substrate. The counter substrate may not be provided if it is not necessary.

[0183] [Organic layer] The organic compound layers (hole injection layer, hole transport layer, electron blocking layer, light emitting layer, hole blocking layer, electron transport layer, electron injection layer, etc.) constituting the organic light emitting element according to one embodiment of the present disclosure are formed by the method described below.

[0184] The organic compound layer constituting the organic light-emitting device according to one embodiment of the present invention can be formed by dry processes such as vacuum deposition, ionization deposition, sputtering, plasma, etc. Alternatively, instead of the dry process, a wet process can be used in which a layer is formed by dissolving the compound in an appropriate solvent and applying a known coating method (e.g., spin coating, dipping, casting, LB method, inkjet method, etc.).

[0185] Here, when the layer is formed by a vacuum deposition method or a solution coating method, crystallization is unlikely to occur and the layer has excellent stability over time. When the layer is formed by a coating method, the layer can be formed by combining with a suitable binder resin.

[0186] Examples of the binder resin include, but are not limited to, polyvinylcarbazole resin, polycarbonate resin, polyester resin, ABS resin, acrylic resin, polyimide resin, phenol resin, epoxy resin, silicone resin, and urea resin.

[0187] These binder resins may be used alone as homopolymers or copolymers, or in combination of two or more kinds. If necessary, known additives such as plasticizers, antioxidants, and ultraviolet absorbers may be used in combination.

[0188] [Pixel circuit] The LED chip may have a pixel circuit connected to the light-emitting element. The pixel circuit may be an active matrix type that controls the light emission of the first light-emitting element and the second light-emitting element independently. The active matrix type circuit may be voltage programming or current programming. The drive circuit has a pixel circuit for each pixel. The pixel circuit may have a light-emitting element, a transistor that controls the light emission luminance of the light-emitting element, a transistor that controls the light emission timing, a capacitance that holds the gate voltage of the transistor that controls the light emission luminance, and a transistor for connecting to GND without going through the light-emitting element.

[0189] The LED chip has a light-emitting region and a peripheral region disposed around the light-emitting region. The light-emitting region has a pixel circuit, and the peripheral region has a display control circuit. The mobility of a transistor constituting the pixel circuit may be smaller than the mobility of a transistor constituting the display control circuit.

[0190] The slope of the current-voltage characteristic of the transistor that constitutes the pixel circuit may be smaller than the slope of the current-voltage characteristic of the transistor that constitutes the display control circuit. The slope of the current-voltage characteristic can be measured by the so-called Vg-Ig characteristic.

[0191] The transistor that constitutes the pixel circuit is a transistor that is connected to a light-emitting element, such as the first light-emitting element.

[0192] Next, an example of a portion of the LED chip according to this embodiment will be described with reference to the drawings.

[0193] 12 is a schematic cross-sectional view showing an example of an LED chip having an organic light-emitting element as a light-emitting element and a transistor connected to the organic light-emitting element. The transistor is an example of an active element. The transistor may be a thin film transistor (TFT).

[0194] FIG. 12 is an example of a pixel that is a component of the LED chip according to this embodiment. The pixel has a subpixel 10. The subpixels are divided into 10R, 10G, and 10B according to their light emission. The emitted light color may be distinguished by the wavelength emitted from the light-emitting layer, or the light emitted from the subpixel may be selectively transmitted or color-converted by a color filter or the like. In this embodiment, three types of wavelengths are distinguished by the color filter and light emission, but if one or two types of wavelengths are required, the corresponding light-emitting layer or color filter may be one or two types, respectively. Each subpixel has a reflective electrode 2, which is a first electrode, on an interlayer insulating layer 1, an insulating layer 3 covering the end of the reflective electrode 2, an organic compound layer 4 covering the first electrode and the insulating layer, a transparent electrode 5, a protective layer 6, and a color filter 7.

[0195] A transistor and a capacitor may be disposed below or inside the interlayer insulating layer 1. The transistor and the first electrode may be electrically connected via a contact hole or the like (not shown).

[0196] The insulating layer 3 is also called a bank or a pixel separation film. It covers the edge of the first electrode and is disposed so as to surround the first electrode. The part where the insulating layer is not disposed contacts the organic compound layer 4 and becomes a light-emitting region.

[0197] The organic compound layer 4 has a hole injection layer 41 , a hole transport layer 42 , a first light emitting layer 43 , a second light emitting layer 44 , and an electron transport layer 45 .

[0198] The second electrode 5, whether a transparent electrode, a reflective electrode, or a semi-transparent electrode, is made of a material having high light reflectance and is disposed in common across a plurality of light emitting elements.

[0199] The protective layer 6 reduces the penetration of moisture into the organic compound layer. Although the protective layer is illustrated as being a single layer, it may be a multi-layer. Each layer may be an inorganic compound layer and an organic compound layer.

[0200] The color filters 7 are divided into 7R, 7G, and 7B according to their colors. The color filters may be formed on a planarization film (not shown). A resin protective layer (not shown) may be provided on the color filters. The color filters may be formed on a protective layer 6. Alternatively, the color filters may be provided on an opposing substrate such as a glass substrate and then bonded to each other.

[0201] The present disclosure includes, for example, the following configurations.

[0202] (Configuration 1) An LED chip comprising: a light-emitting region in which a plurality of light-emitting elements are arranged two-dimensionally on a main surface of a substrate; and a contact region arranged outside the light-emitting region, wherein the plurality of light-emitting elements have a first electrode, an organic layer, and a second electrode on the light-emitting side, the second electrode being continuous across the plurality of light-emitting elements, wherein, in a planar view of the main surface, the light-emitting region has a long side extending in a first direction and a short side extending in a second direction intersecting the first direction, and wherein, in the planar view, an end of the second electrode in the first direction has a portion that is non-parallel to a third direction perpendicular to the first direction.

[0203] (Configuration 2) 2. The LED chip according to claim 1, wherein, in the plan view, the length of a long side of the light emitting region is at least five times the length of the short side.

[0204] (Configuration 3) 3. The LED chip according to claim 1, wherein an end of the second electrode has a curved line in the plan view.

[0205] (Configuration 4) An LED chip described in any of configurations 1 to 3, wherein, in the planar view, the length in the third direction of the portion non-parallel to the third direction is longer than 1 / 3 of the distance from the end of the second electrode in the third direction to the portion where the second electrode contacts the wiring.

[0206] (Configuration 5) A color filter is disposed over the contact area; In the plan view, the color filter includes the contact region, 5. The LED chip according to any one of Configurations 1 to 4, having an opening at a position overlapping the light emitting region.

[0207] (Configuration 6) a first color filter overlapping the contact region in the plan view; a second color filter overlapping the light emitting region in the plan view; 6. The LED chip according to any one of configurations 1 to 5, wherein the second color filter transmits light of a color different from that of the first color filter.

[0208] (Configuration 7) 7. The LED chip according to configuration 6, wherein the first color filter has a lower transmittance for light from the plurality of light-emitting elements than the second color filter.

[0209] (Configuration 8) 8. The LED chip according to any one of configurations 1 to 7, wherein the substrate is a silicon substrate.

[0210] (Configuration 9) 9. The LED chip according to any one of configurations 1 to 8, wherein the substrate has a thickness of 200 μm to 700 μm.

[0211] (Configuration 10) 10. The LED chip according to any one of configurations 1 to 9, wherein the substrate has a thickness of 200 μm to 408 μm.

[0212] (Configuration 11) 11. The LED chip according to any one of configurations 1 to 10, wherein the substrate has a thickness of 378 μm to 408 μm.

[0213] (Configuration 12) An exposure head having a head substrate on which multiple LED chips having sides parallel to the longitudinal direction and sides parallel to the short direction are arranged in the longitudinal direction, and at least one of the LED chips is an LED chip described in any one of structures 1 to 11.

[0214] (Configuration 13) 12. The exposure head according to configuration 11, wherein, of the plurality of LED chips, two LED chips adjacent to each other in the longitudinal direction are shifted in the lateral direction.

[0215] (Configuration 14) An exposure head comprising a housing holding a head substrate on which multiple LED chips, each having a side parallel to the longitudinal direction and a side parallel to the lateral direction, are arranged in the longitudinal direction, and a lens array arranged opposite the head substrate, and at least one of the LED chips is an LED chip described in any one of structures 1 to 13.

[0216] (Configuration 15) 15. The exposure head according to configuration 14, wherein the LED chip is disposed so that the second electrode faces the lens array.

[0217] (Configuration 16) An image forming apparatus comprising: a photosensitive drum; an exposure head disposed opposite the photosensitive drum and configured to expose the photosensitive drum to form a latent image on the photosensitive drum; and a developing means configured to develop the latent image formed on the photosensitive drum with toner, wherein the exposure head is an exposure head as defined in any one of configurations 11 to 15.

[0218] (Method 1) A method for manufacturing an organic EL element including at least one organic layer between a first electrode and a second electrode, the method comprising the steps of: placing a deposition mask having a plurality of openings against a substrate on which the first electrode and the organic layer are arranged; aligning the substrate and the deposition mask; and forming the second electrode on the substrate by depositing a deposition material through the openings in the deposition mask, wherein the openings in the deposition mask have long sides extending in a first direction, short sides extending in a second direction intersecting with the first direction, and a portion at an end in the first direction that is non-parallel to a third direction perpendicular to the first direction. [Explanation of symbols]

[0219] 52a Light exit surface 53 LED chips 61 Substrate 63 1st electrode 64 Wiring 64a Contact Area 66 Organic layer 67 2nd electrode 69 Light emitting element

Claims

1. a light emitting region in which a plurality of light emitting elements are two-dimensionally arranged on a main surface of a substrate; a contact region disposed outside the light emitting region; The plurality of light-emitting elements each have a first electrode, an organic layer, and a second electrode on a light-emitting side; the second electrode is continuous across the plurality of light emitting elements; In a plan view of the main surface, the light emitting region has a long side extending in a first direction and a short side extending in a second direction intersecting the first direction, The LED chip is characterized in that, in the plan view, an end of the second electrode in the first direction has a portion that is non-parallel to a third direction perpendicular to the first direction.

2. The LED chip according to claim 1 , wherein the length of a long side of the light emitting region is at least five times the length of the short side in the plan view.

3. The LED chip according to claim 1 , wherein an end of the second electrode has a curved shape in the plan view.

4. 2. The LED chip of claim 1, wherein, in the planar view, the length in the third direction of the portion non-parallel to the third direction is longer than 1 / 3 of the distance from the end of the second electrode in the third direction to the portion where the second electrode contacts the wiring.

5. A color filter is disposed over the contact area; In the plan view, the color filter includes the contact region, The LED chip according to claim 1 , further comprising an opening at a position overlapping with the light emitting region.

6. a first color filter overlapping the contact region in the plan view; a second color filter overlapping the light emitting region in the plan view; The LED chip according to claim 1 , wherein the second color filter transmits light of a color different from that of the first color filter.

7. The LED chip according to claim 6 , wherein the first color filter has a lower transmittance for light from the plurality of light-emitting elements than the second color filter.

8. The LED chip of claim 1 , wherein the substrate is a silicon substrate.

9. The LED chip of claim 1 , wherein the substrate has a thickness of 200 μm to 700 μm.

10. 10. The LED chip of claim 1, wherein the substrate has a thickness of 200 to 408 μm.

11. 10. The LED chip of claim 1, wherein the substrate has a thickness of 378 μm to 408 μm.

12. A plurality of LED chips having sides parallel to a longitudinal direction and sides parallel to a lateral direction are arranged in the longitudinal direction on a head substrate, An exposure head, wherein at least one of the LED chips is the LED chip according to claim 1.

13. The exposure head according to claim 12 , wherein among the plurality of LED chips, two LED chips adjacent to each other in the longitudinal direction are shifted in the lateral direction.

14. a head substrate on which a plurality of LED chips, each having a side parallel to a longitudinal direction and a side parallel to a lateral direction, are arranged in the longitudinal direction; a lens array disposed at a position facing the head substrate; The housing holds the An exposure head, wherein at least one of the LED chips is the LED chip according to claim 1.

15. The exposure head according to claim 14 , wherein the LED chip is disposed so that the second electrode faces the lens array.

16. A photosensitive drum; an exposure head disposed opposite the photosensitive drum and exposing the photosensitive drum to light to form a latent image on the photosensitive drum; a developing means for developing the latent image formed on the photosensitive drum with toner; having 16. An image forming apparatus, wherein the exposure head is an exposure head according to any one of claims 11 to 15.

17. A method for manufacturing an organic EL element including at least one organic layer between a first electrode and a second electrode, comprising the steps of: a step of placing a deposition mask having a plurality of openings opposite a substrate on which the first electrode and the organic layer are disposed; aligning the substrate and the deposition mask; forming the second electrode on the substrate by depositing a deposition material through the opening of the deposition mask; a deposition mask having a long side extending in a first direction, a short side extending in a second direction intersecting the first direction, and a portion at an end in the first direction that is non-parallel to a third direction perpendicular to the first direction.

Images