Patent Application
20240290929
This application claims the benefit of priority from Japanese Patent Application No. 2023-030286 filed on Feb. 28, 2023, the entire contents of which are incorporated herein by reference.
The present disclosure relates to a display apparatus and a method for manufacturing the display apparatus.
Display apparatuses with micro-sized light-emitting diodes (micro LEDs) are provided with a reflective structure to improve the efficiency of light extraction to the display surface side. For example, Japanese Patent Application Laid-open Publication No. 2020-205417 (JP-A-2020-205417) describes a configuration in which a partition wall is provided between a plurality of micro LEDs, and a reflective part is provided on the side surface of the partition wall to reflect light emitted in the direction toward the partition wall. Japanese Patent Application Laid-open Publication No. 2011-166140 (JP-A-2011-166140) describes a light-emitting element package including a light-emitting element chip disposed in a cavity and a reflective layer formed on the surface of the cavity.
Widely known are various configurations for coupling light-emitting diodes to a drive circuit. In U.S. Pat. No. 10,937,815, for example, light-emitting diodes are fixed on an array substrate including thin-film transistors (TFTs) by an adhesive layer. The display apparatus described in U.S. Patent Application Publication No. 2018/0191978 has a module structure in which one pixel includes three light-emitting diodes and a pixel circuit (micro integrated circuit (IC)) coupled to the three light-emitting diodes.
The configurations described in JP-A-2020-205417 and JP-A-2011-166140 have no reflective layer on the back surface side of the light-emitting diodes (side opposite to the display surface). Therefore, it is difficult to extract light output to the back surface side to the display surface side. If the mounting structure of the light-emitting diodes or the coupling configuration with the pixel circuit is different as described in U.S. Pat. No. 10,937,815 and U.S. Patent Application Publication No. 2018/0191978, the reflective structures described in JP-A-2020-205417 and JP-A-2011-166140 may possibly be inapplicable without any change.
A display apparatus according to an embodiment of the present disclosure includes a translucent substrate having a first main surface serving as a display surface and a second main surface opposite to the first main surface, a plurality of light-emitting elements provided to the second main surface of the substrate with an adhesive layer interposed between the light-emitting elements and the second main surface, a first terminal and a second terminal provided on a side of each of the light-emitting elements opposite to the substrate, a first protective film covering the light-emitting elements and having a groove between the light-emitting elements adjacent to each other, and a first reflective layer provided to cover the first protective film and having an overlapping portion overlapping the light-emitting element and a side portion provided to a side surface of the groove. The first reflective layer is electrically coupled to the first terminal through a first contact hole formed in the first protective film.
A display apparatus according to an embodiment of the present disclosure includes a translucent substrate having a first main surface serving as a display surface and a second main surface opposite to the first main surface, a plurality of light-emitting elements provided to the second main surface of the substrate, a first terminal and a second terminal provided on a side of each of the light-emitting elements opposite to the substrate, a first reflective layer having an overlapping portion and a side portion, the overlapping portion being provided on the side of the light-emitting element opposite to the substrate and having an opening in a part overlapping the second terminal of the light-emitting element, the side portion facing a side surface of the light-emitting element, a first protective film provided between the light-emitting elements and the first reflective layer, and a second reflective layer overlapping the opening of the first reflective layer. The first reflective layer is electrically coupled to the first terminal through a first contact hole formed in the first protective film, and the second reflective layer is electrically coupled to the second terminal through the opening.
A method for manufacturing a display apparatus according to an embodiment of the present disclosure includes mounting a plurality of light-emitting element on a second main surface of a translucent substrate having a first main surface serving as a display surface and the second main surface opposite to the first main surface with an adhesive layer interposed between the light-emitting elements and the second main surface, forming a first protective film covering the light-emitting elements and forming a groove in the first protective film between the light-emitting elements adjacent to each other, and providing a metal film covering the first protective film, forming a first reflective layer having an overlapping portion overlapping the light-emitting element and a side portion provided to a side surface of the groove, and electrically coupling a first terminal of the light-emitting element to the first reflective layer through a first contact hole formed in the first protective film.
Exemplary aspects (embodiments) to embody the present disclosure are described below in greater detail with reference to the accompanying drawings. The contents described in the embodiments below are not intended to limit the present disclosure. Components described below include components easily conceivable by those skilled in the art and components substantially identical therewith. Furthermore, the components described below may be appropriately combined. What is disclosed herein is given by way of example only, and appropriate modifications made without departing from the spirit of the present disclosure and easily conceivable by those skilled in the art naturally fall within the scope of the present disclosure. To simplify the explanation, the drawings may illustrate the width, the thickness, the shape, and other elements of each unit more schematically than an actual aspect. These elements, however, are given by way of example only and are not intended to limit interpretation of the present disclosure. In the present disclosure and the drawings, components similar to those previously described with reference to previous drawings are denoted by like reference numerals, and detailed explanation thereof may be appropriately omitted.
To describe an aspect where a first structure is disposed on a second structure in the present specification and the claims, the term “on” includes both of the following cases unless otherwise noted: a case where the first structure is disposed directly on the second structure in contact with the second structure, and a case where the first structure is disposed on the second structure with another structure interposed therebetween.
As illustrated in
The pixels Pix are arrayed in a first direction Dx and a second direction Dy in the display region AA of the substrate 21. The first direction Dx and the second direction Dy are parallel to the surface of the substrate 21. The first direction Dx is orthogonal to the second direction Dy. The first direction Dx may intersect the second direction Dy without being orthogonal thereto. A third direction Dz is orthogonal to the first direction Dx and the second direction Dy. The third direction Dz corresponds to the normal direction of the substrate 21, for example. In the following description, plan view refers to the positional relation when viewed from the third direction Dz.
The scanning circuit 12 is a circuit that sequentially selects, row by row, drive circuits 201 (refer to
The drive IC 210 is a circuit that controls display on the display apparatus 1. A plurality of wires (not illustrated) extend from the drive IC 210 toward the drive circuits 201 included in the pixels Pix. The drive IC 210 supplies control signals (pixel signals) to the drive circuits 201 of the respective pixels Pix selected by the scanning circuit 12. The drive circuit 201 supplies drive signals (current) to each light-emitting element 3 due to the control signals from the drive IC 210 and causes the light-emitting element 3 to emit light. The drive IC 210 is mounted in the peripheral region GA of the substrate 21. The present embodiment is not limited thereto, and the drive IC 210 may be mounted on a flexible printed circuit board or a rigid board coupled to the peripheral region GA of the substrate 21.
The cathode wiring 60 is provided to the peripheral region GA of the substrate 21. The cathode wiring 60 is provided surrounding the pixels Pix in the display region AA and the scanning circuit 12 in the peripheral region GA. The cathodes of the light-emitting elements 3 are electrically coupled to the common cathode wiring 60 and are supplied with a fixed potential (e.g., a ground potential). More specifically, a cathode terminal 32 (refer to
The pixels SPX each include the light-emitting element 3 and a reflective layer 37. The display apparatus 1 displays an image by causing a light-emitting element 3R, a light-emitting element 3G, and a light-emitting element 3B in the pixel SPX-R, the pixel SPX-G, and the pixel SPX-B, respectively, to output different light. The light-emitting element 3 is an inorganic light-emitting diode (LED) chip having a size of approximately 3 μ m to 300 μ m in plan view and is called a micro LED. The display apparatus 1 including the micro LEDs in the respective pixels is also called a micro LED display apparatus. The term “micro” of the micro LED is not intended to limit the size of the light-emitting element 3.
The light-emitting elements 3 may output light in four or more different colors. The arrangement of the pixels
SPX is not limited to the configuration illustrated in
The drive circuit 201 is composed of a micro IC, for example, and is provided to each pixel Pix. In the example illustrated in
While
Next, the configuration of the display apparatus 1 is described in detail.
As illustrated in
The reflective layer 37 is formed in a cavity shape (recessed shape) when viewed from the display surface (first main surface S1 of the substrate 21 (refer to
As illustrated in
An anode terminal 33 (second terminal) of the light-emitting element 3 is electrically coupled to the coupling electrode 35c through a second contact hole CH2. The coupling electrode 35c is electrically coupled to the anode electrode 35 through a third contact hole CH3 (refer to
As illustrated in
While
In the present specification, a direction from the substrate 21 toward the light-emitting element 3 in a direction perpendicular to the surface of the substrate 21 is referred to as an “upper side” or simply as “top”. A direction from the light-emitting element 3 to the substrate 21 is referred to as a “lower side” or simply as “bottom”.
The light-shielding layer 39 is provided on the second main surface S2 of the substrate 21. The light-shielding layer 39 is made of black resin material or a light-blocking metal or alloy film, for example. As described above, the light-shielding layer 39 has the openings 39a in the regions provided with the respective light-emitting elements 3.
An adhesive layer 22 is provided on the second main surface S2 of the substrate 21 to cover the light-shielding layer 39. The adhesive layer 22 is made of optical clear resin (OCR) or an optical clear adhesive film (OCA), for example. The adhesive layer 22 is provided covering the entire second main surface S2 of the substrate 21. The present embodiment is not limited thereto, and the adhesive layer 22 simply needs to be provided at least in the regions provided with the light-emitting elements 3. A plurality of adhesive layers 22 may be separately disposed for the respective openings 39a of the light-shielding layer 39.
A plurality of light-emitting elements 3 are provided on the second main surface S2 of the substrate 21 with the adhesive layer 22 interposed therebetween. While the light-emitting elements 3 may have any desired configuration, they can be each composed of an n-type semiconductor layer, an active layer, and a p-type semiconductor layer stacked in this order. The semiconductor layer is made of compound semiconductor, such as gallium nitride (GaN), aluminum indium phosphorous (AlInP), and indium gallium nitride (InGaN). The semiconductor layer may be made of different materials for the respective light-emitting elements 3R, 3G, and 3B. The active layer may have a multi-quantum well structure (MQW structure) in which well layers and barrier layers composed of several atomic layers are cyclically stacked for higher efficiency.
The cathode terminal 32 and the anode terminal 33 are provided on the side of the light-emitting element 3 opposite to the substrate 21. More specifically, the cathode terminal 32 and the anode terminal 33 are provided on the same surface of the light-emitting element 3, which is the surface opposite to the surface facing the second main surface S2 of the substrate 21. In other words, the light-emitting elements 3 are each disposed such that the surface not provided with the cathode terminal 32 or the anode terminal 33 faces the second main surface S2 of the substrate 21 and are provided on the second main surface S2 with the adhesive layer 22 interposed therebetween.
A first protective film 23 is provided covering the light-emitting elements 3. More specifically, the first protective film 23 is provided covering at least part of the upper surface and the side surfaces of the light-emitting elements 3 and has the first contact hole CH1 and the second contact hole CH2 in the regions overlapping the cathode terminal 32 and the anode terminal 33, respectively. The first protective film 23 is an organic insulating film and is made of organic material, such as photosensitive acrylic. The organic material, such as photosensitive acrylic, is excellent in coverability for level difference caused by the light-emitting elements 3 and in surface flatness compared with inorganic insulating material formed by CVD, for example.
The first protective film 23 has grooves GV formed between the light-emitting elements 3 adjacent to each other. The groove GV passes through the upper and lower surfaces of the first protective film 23 and has a tapered shape that decreases in width as closer to the second main surface S2 of the substrate 21. The bottom of the groove GV is disposed at the position overlapping the light-shielding layer 39. While
In other words, the first protective film 23 is formed in an island shape for each of the light-emitting elements 3 with the grooves GV interposed therebetween. The first protective film 23 covering each of the light-emitting elements 3 has a tapered shape that increases in width as closer to the second main surface S2 of the substrate 21. The side surfaces of the first protective film 23 are inclined in a direction of widening toward the second main surface S2 of the substrate 21.
The cathode electrode 34 (first reflective layer) and the coupling electrode 35c are provided covering the first protective film 23. The cathode electrode 34 includes the overlapping portion 34a that overlaps the light-emitting element 3 and the side portion 34b provided on the side surfaces of the grooves GV. The slit SP (refer to
The overlapping portion 34a of the cathode electrode 34 has an opening 34c in the region overlapping the anode terminal 33. The coupling electrode 35c is provided in the region overlapping the opening 34c on the first protective film 23. The coupling electrode 35c is provided in the same layer as that of the overlapping portion 34a of the cathode electrode 34 in a manner separated from the overlapping portion 34a of the cathode electrode 34 with a gap interposed therebetween. The coupling electrode 35c is coupled to the anode terminal 33 through the second contact hole CH2 formed in the first protective film 23.
A second protective film 24 is provided on the first protective film 23 to cover the cathode electrodes 34 (first reflective layer) and the coupling electrodes 35c. The second protective film 24 is made of an organic insulating film. The second protective film 24 is provided to fill the inside of the grooves GV and has a flat upper surface.
The anode electrode 35 (second reflective layer) is provided on the second protective film 24 and is coupled to the coupling electrode 35c through the third contact hole CH3 formed in the second protective film 24. The anode electrode 35 has a larger area than the opening 34c of the cathode electrode 34 in plan view and is provided in the region overlapping the opening 34c of the cathode electrode 34. In other words, the anode electrode 35 is provided in the region overlapping the gap between the cathode electrode 34 and the coupling electrode 35c.
The cathode electrode 34, the anode electrode 35, and the coupling electrode 35c are made of metal material, such as titanium (Ti) and aluminum (Al). The cathode electrode 34, the anode electrode 35, and the coupling electrode 35c may be a multilayered film of Ti/Al/Ti, for example. The cathode electrode 34 and the coupling electrode 35c are formed in the same process and made of the same material. The cathode electrode 34 and the anode electrode 35 may be made of the same material or different materials.
A third protective film 25 is provided on the second protective film 24 to covers the anode electrodes 35. The third protective film 25 is made of an organic insulating film like the first protective film 23 and the second protective film 24. The third protective film 25, however, may be an inorganic insulating film. At least one of the first protective film 23, the second protective film 24, and the third protective film 25 may be a multilayered film composed of an organic insulating film and an inorganic insulating film.
With this configuration, the reflective layer 37 is composed of the cathode electrode 34, the anode electrode 35, and the coupling electrode 35c. The reflective layer 37 is formed in a cavity shape when viewed from the first main surface S1 of the substrate 21, and each light-emitting element 3 is disposed in a manner surrounded by the cavity-shaped cathode electrode 34. Light L1 output from the light-emitting element 3 toward the substrate 21 is transmitted through the first main surface S1 of the substrate 21 and is visually recognized as a display image.
Light L2 output from the light-emitting element 3 toward the side is reflected by the side portion 34b of the cathode electrode 34 (first reflective layer) and is output toward the first main surface S1 of the substrate 21. Light L3 output from the light-emitting element 3 toward the back surface side is reflected by the overlapping portion 34a of the cathode electrode 34 (first reflective layer) and is output toward the first main surface S1 of the substrate 21. Light that has passed through the opening 34c of the cathode electrode 34 (gap between the cathode electrode 34 and the coupling electrode 35c) in the light L3 output from the light-emitting element 3 toward the back surface side is reflected by the anode electrode 35 (second reflective layer). Part of the reflected light passes through the opening 34c of the cathode electrode 34 and returns to the first main surface S1 side of the substrate 21. With this configuration, the display apparatus 1 according to the present embodiment can improve the light extraction efficiency.
The light-shielding layer 39 is provided between the end of the side portion 34b of the cathode electrode 34 on the second main surface S2 side and the second main surface S2 of the substrate 21 in the third direction Dz and between the side portions 34b of the cathode electrodes 34 adjacent to each other in plan view. With this configuration, part of light reflected in an oblique direction by the reflective layer 37 and traveling toward an adjacent pixel SPX is absorbed by the light-shielding layer 39. Therefore, the display apparatus 1 according to the present embodiment can improve the light extraction efficiency and suppress color mixture between the pixels SPX adjacent to each other.
The cathode electrode 34, the anode electrode 35, and the coupling electrode 35c serve not only as the electrodes that electrically couple the light-emitting element 3 to the drive circuit 201 (refer to
The configuration of the electrodes (reflective layer 37) illustrated in
As illustrated in
Subsequently, the light-emitting elements 3R, 3G, and 3B arrayed on a transfer substrate 101 with an adhesive layer 102 interposed therebetween are prepared. The light-emitting elements 3R, 3G, and 3B are formed on different sapphire substrates and are transferred from the respective sapphire substrates onto the common transfer substrate 101 by a laser lift-off method, for example. The light-emitting elements 3R, 3G, and 3B on the transfer substrate 101 are disposed corresponding to the array of the pixels SPX. The light-emitting elements 3R, 3G, and 3B are disposed such that the surface not provided with the cathode terminal 32 or the anode terminal 33 faces the second main surface S2 of the substrate 21, and the light-emitting elements 3R, 3G, and 3B are temporarily bonded to the adhesive layer 22 (Step ST2).
The adhesive layer 22 is cured by ultraviolet irradiation or other methods, and the light-emitting elements 3R, 3G, and 3B are fixed to the second main surface S2 of the substrate 21. Subsequently, the transfer substrate 101 is peeled off. Thus, the light-emitting elements 3R, 3G, and 3B are mounted on the second main surface S2 of the substrate 21 with the adhesive layer 22 interposed therebetween (Step ST3).
Subsequently, the first protective film 23 is applied and formed to cover the light-emitting elements 3 (Step ST4). The first protective film 23 is made of photosensitive material, such as acrylic resin. The first protective film 23 is formed to cover the upper surface (the cathode terminal 32 and the anode terminal 33) and the side surfaces of the light-emitting elements 3 and to flatten the unevenness of the light-emitting elements 3.
Subsequently, the first contact holes CH1, the second contact holes CH2, and the grooves GV are formed in the first protective film 23 by photolithography and etching (Step ST5). The first contact hole CH1 and the second contact hole CH2 are formed in the regions overlapping the cathode terminal 32 and the anode terminal 33, respectively, of the light-emitting element 3. The groove GV is formed in the first protective film 23 between the light-emitting elements 3 adjacent to each other. In other words, the groove GV is formed in the region overlapping the light-shielding layer 39.
Subsequently, a metal film is formed to cover the first protective film 23 and the grooves GV and is subjected to patterning. Thus, the cathode electrodes 34 (first reflective layer) each having the overlapping portion 34a overlapping the light-emitting element 3 and the side portion 34b provided on the side surfaces of the grooves GV are formed (Step ST6). In the process of patterning the metal film, the coupling electrodes 35c are formed in the same layer as that of the overlapping portions 34a of the cathode electrodes 34. The overlapping portion 34a of the cathode electrode 34 is electrically coupled to the cathode terminal 32 through the first contact hole CH1 formed in the first protective film 23. The coupling electrode 35c is electrically coupled to the anode terminal 33 through the second contact hole CH2 formed in the first protective film 23.
Subsequently, the second protective film 24 and the anode electrodes 35 (second reflective layer) are formed (Step ST7). More specifically, the second protective film 24 is made of photosensitive material, such as acrylic resin. The second protective film 24 is provided to cover the cathode electrodes 34, the coupling electrodes 35c, and the first protective films 23 and is formed to flatten the grooves GV. Subsequently, the third contact holes CH3 are formed in the regions overlapping the respective coupling electrodes 35c in the second protective film 24 by photolithography and etching.
A metal film is formed to cover the first protective film 23 and the third contact holes CH3 and is subjected to patterning. Thus, the anode electrodes 35 are formed in the regions overlapping the respective openings 34c of the cathode electrodes 34. The anode electrode 35 is electrically coupled to the coupling electrode 35c through the third contact hole CH3 formed in the second protective film 24.
Subsequently, the third protective film 25 is formed on the second protective film 24 to cover the anode electrodes 35 (Step ST8). The third protective film 25 is made of an organic insulating film like the first protective film 23 and the second protective film 24. The third protective film 25 may be made of an inorganic insulating film or a multilayered film composed of an organic insulating film and an inorganic insulating film.
As described above, the method for manufacturing the display apparatus 1 according to the present embodiment mounts the light-emitting elements 3 on the substrate 21 serving as the display substrate with the adhesive layer 22 interposed therebetween. In the display apparatus 1, the cathode electrode 34, the anode electrode 35, and the coupling electrode 35c are formed in a cavity shape to cover the light-emitting element 3 and also satisfactorily function as the reflective layer 37.
While exemplary embodiments according to the present disclosure have been described, the embodiments are not intended to limit the present disclosure. The contents disclosed in the embodiments are given by way of example only, and various modifications may be made without departing from the spirit of the present disclosure. Appropriate modifications made without departing from the spirit of the present disclosure naturally fall within the technical scope of the present disclosure. At least one of various omissions, substitutions, and modifications of the components may be made without departing from the gist of the embodiments above and the modifications thereof.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-030286 | Feb 2023 | JP | national |
